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1
Thomas, GP, SU Baker, JA Eisman, and EM Gardiner. "Changing RANKL/OPG mRNA expression in differentiating murine primary osteoblasts." Journal of Endocrinology 170, no. 2 (August 1, 2001): 451–60. http://dx.doi.org/10.1677/joe.0.1700451.
Повний текст джерелаАнотація:
Osteoblast-osteoclast coordination is critical in the maintenance of skeletal integrity. The modulation of osteoclastogenesis by immature cells of the osteoblastic lineage is mediated through receptor activator of NF kappa B (RANK), its ligand RANKL, and osteoprotegerin (OPG), a natural decoy receptor for RANKL. Here, the expression of OPG and RANKL in primary mouse osteoblastic cultures was investigated to determine whether the osteoclastogenic stimulus depended on the stage of osteoblastic differentiation and the presence of the calciotrophic hormone 1,25-dihydroxyvitamin D(3) (1,25-(OH)(2)D(3)). OPG mRNA expression was increased in osteoblastic cultures after the onset of mineralisation relative to less mature cultures, but did not alter in response to 1,25-(OH)(2)D(3) treatment. In contrast, basal RANK L mRNA expression did not change during differentiation but was significantly enhanced by 1,25-(OH)(2)D(3) treatment at all times. The stimulatory effects of 1,25-(OH)(2)D(3) on RANKL were lessened in more mature cultures, however. The RANKL/OPG ratio, an index of osteoclastogenic stimulus, was therefore increased by 1,25-(OH)(2)D(3) treatment at all stages of osteoblastic differentiation, but to a lesser degree in cultures after the onset of mineralisation. Thus the 1,25-(OH)(2)D(3)-driven increase in osteoclastogenic potential of immature osteoblasts appears to be mediated by increased RANKL mRNA expression, with mature osteoblasts having relatively decreased osteoclastogenic activity due to increased OPG mRNA expression. These findings suggest a possible mechanism for the recently proposed negative regulatory role of mature osteoblasts on osteoclastogenesis and indicate that the relative proportions of immature and mature osteoblasts in the local microenvironment may control the degree of resorption at each specific bone site.
2
Mahalingam, Chandrika D., Bharat Reddy Sampathi, Sonali Sharma, Tanuka Datta, Varsha Das, Abdul B. Abou-Samra, and Nabanita S. Datta. "MKP1-dependent PTH modulation of bone matrix mineralization in female mice is osteoblast maturation stage specific and involves P-ERK and P-p38 MAPKs." Journal of Endocrinology 216, no. 3 (November 29, 2012): 315–29. http://dx.doi.org/10.1530/joe-12-0372.
Повний текст джерелаАнотація:
Limited information is available on the role of MAPK phosphatase 1 (MKP1) signaling in osteoblasts. We have recently reported distinct roles for MKP1 during osteoblast proliferation, differentiation, and skeletal responsiveness to parathyroid hormone (PTH). As MKP1 regulates the phosphorylation status of MAPKs, we investigated the involvement of P-ERK and P-p38 MAPKs in MKP1 knockout (KO) early and mature osteoblasts with respect to mineralization and PTH response. Calvarial osteoblasts from 9–14-week-old WT and MKP1 KO male and female mice were examined. Western blot analysis revealed downregulation and sustained expressions of P-ERK and P-p38 with PTH treatment in differentiated osteoblasts derived from KO males and females respectively. Exposure of early osteoblasts to p38 inhibitor, SB203580 (S), markedly inhibited mineralization in WT and KO osteoblasts from both genders as determined by von Kossa assay. In osteoblasts from males, ERK inhibitor U0126 (U), not p38 inhibitor (S), prevented the inhibitory effects of PTH on mineralization in early or mature osteoblasts. In osteoblasts from KO females, PTH sustained mineralization in early osteoblasts and decreased mineralization in mature cells. This effect of PTH was attenuated by S in early osteoblasts and by U in mature KO cells. Changes in matrix Gla protein expression with PTH in KO osteoblasts did not correlate with mineralization, indicative of MKP1-dependent additional mechanisms essential for PTH action on osteoblast mineralization. We conclude that PTH regulation of osteoblast mineralization in female mice is maturation stage specific and involves MKP1 modulation of P-ERK and P-p38 MAPKs.
3
Fulzele, Keertik, Cristina Panaroni, Kenta Mukaihara, Tomoaki Mori, Shrikanta Chattopadhyay, and Noopur S. Raje. "Mature Osteoblasts Promote Multiple Myeloma Survival through Cell-Cell Contact and Immune Modulation Mechanisms." Blood 134, Supplement_1 (November 13, 2019): 1802. http://dx.doi.org/10.1182/blood-2019-131213.
Повний текст джерелаАнотація:
The bone marrow (BM) microenvironment (TME) is a complex mix of cellular and non-cellular components that has a profound effect on hematopoiesis and hematological malignancies. Multiple myeloma (MM), a tumor of plasma cells that originates in the BM is highly influenced by TME components including stromal cells, osteoclasts, and immune cells. Among these cells, osteoblasts are the most versatile regulators of hematopoiesis and also play an integral role in malignant transformations of leukemia and lung cancer. MM is characterized by osteolytic bone lesions partly due to decreased numbers of osteoblasts. Therapies such as denosumab and zoledronic acid aim to restore bone health by inhibiting osteoclastogenesis. However, the contribution of osteoblasts to the initiation and progression of MM is not well understood. We previously demonstrated that increased osteoblast numbers using Activin A inhibition in an in vivo humanized myeloma model resulted in inhibition of MM growth (Vallet et al., 2010). Given that osteoblast numbers are on the decline in a typical MM patient, we hypothesized that the loss of osteoblasts contributes to the initiation and progression of MM. To assess the effects of osteoblasts on MM cells, MC3T3 murine pre-osteoblasts were differentiated into mature osteoblasts by supplementing media with ascorbic acid and β-glycerophosphate. Co-culture of 5TGM1 murine MM cells with the osteoblasts showed a significant decrease in the proliferation of MM cells by 40% (N=4). Osteoblasts go through distinct stages of maturation i.e., pre-osteoblasts, committed osteoblasts, and mature osteoblasts. These individual osteoblast populations were FACS sorted from mice to isolate pre-osteoblasts from the long bones of Osterix-GFP+ (Osx+) mice, committed osteoblasts from Collagen 2.3-GFP+ (Col2.3+) mice, and mature osteoblasts from Osteocalcin-YFP+ (OCN+) mice. Each of the osteoblast populations was co-cultured with 5TGM1 MM cells. Although all the osteoblast populationssignificantly suppressed MM proliferation, the OCN+ mature osteoblasts suppressed MM proliferation the most (N=3). Therefore, we focused our studies on the role of mature osteoblasts in MM progression. We generated mice in which mature osteoblasts could be postnatally deleted in an inducible and reversible manner. To achieve this, mice carrying floxed diphtheria toxin receptor (DTR) alleles were mated with mice expressing Cre-recombinase driven by the osteocalcin promoter (OC-Cre) to generate OC-Cre/iDTR mice. The control mice were littermates lacking the OC-Cre allele. The OC-Cre/iDTR mice were indistinguishable from the controls until treated with diphtheria toxin (DT). To induce postnatal deletion of mature osteoblasts, the OC-Cre/iDTR and control mice both were treatedwith 50 µg/Kg DT once a week beginning at 8-weeks of age. To study MM engraftment and progression, 3x1065TGM1-Luciferase MM cells were injected into the tibia of OC-Cre/iDTR and control mice followed by weeklyinjection of DT for 8-weeks. Bioluminescence imaging (BLI) showed that 4-weeks onwards the OC-iDTR mice, but not the control mice, continued to express and increase the BLI signal (N=6). This data suggeststhatunder physiological conditions, mature osteoblasts activelysuppress MM engraftment and progression. We hypothesized that osteoblasts provide niche support to MM cells via direct cell-to-cell contact. To begin to identify the molecular mechanisms, we compared gene expression changes in primary murine osteoblasts between the undifferentiated and 30-day osteogenic differentiation time points. We also examined the BM TME by quantitative protein antibody arrays at 2-weeks following 5TGM1MM intratibial injection into OC-Cre/iDTR and control mice. The mature osteoblasts showed a significant increase in the expression of integrins, including integrin α4, and several immunomodulatory markers. The cytokine array analysis showed altered expressions of cell-cell communication proteins MAdCAM1, BAFF-R, TACI, and immunomodulatory factors IL-33, IL-17F, and IL-13. Taken together, using in vivo and in vitro models, we show that mature osteoblasts may have a negative regulatory impact on MM cells through cell-cell communication or immunomodulatory mechanisms. Expanding the osteoblast niche may provide novel therapeutic avenues to reduce disease burden and create an environment for long term tumor control. Disclosures Raje: Merck: Consultancy; Amgen Inc.: Consultancy; Bristol-Myers Squibb: Consultancy; Celgene Corporation: Consultancy; Takeda: Consultancy; Janssen: Consultancy.
4
Zhu, Jiang, Yi Zhang, Nacksung Kim, Yongwon Choi, Gerard Joe, Russell Taichman, and Stephen G. Emerson. "Osteoblasts Support Early B Lymphoiesis as well as Stem Cell Proliferation and Myelopoiesis: Identification of the Mammalian Cellular Analog of the Bursa of Fabricius." Blood 104, no. 11 (November 16, 2004): 508. http://dx.doi.org/10.1182/blood.v104.11.508.508.
Повний текст джерелаАнотація:
Abstract The self-renewal, survival and differentiation of hematopoietic stem cells (HSC) are greatly influenced by the activities of neighboring osteoblasts and non-osteogenic bone marrow (BM) stromal cells such as fibroblasts, endothelial cells and adipocytes. Previously, we showed that osteoblasts from human long bones support the in vitro self-renewal as well as myeloid differentiation of human CD34+ cord blood cells. Recently, Li’s and Scadden’s groups provided in vivo evidence indicating a primary role of trabecular osteoblasts as a major component of HSC niche and of stromal osteoblastic cells in facilitating the self-renewal of HSCs. We have now asked whether osteoblasts contribute to early lymphopoiesis as well as myelopoiesis, by measuring the cellular outpout of purified HSCs on isolated osteoblasts alone, or with added non-osteoblast stromal cytokines as well. We prepared mature osteoblasts, as monitored and confirmed by homogeneous OPN and CD61 expression, by pretreating osteoblastic cells isolated from neonatal calvaria of C57BL/6 mice (CD45.2) with 1X10−7 M PTH. Purified OB were then co-cultured for 6 days with Lin− BM cells (CD45.1+) isolated from congenic B6 mice(CD45.1) and labeled with CFSE. Osteoblast coculture stimulated the proliferation of Lin− CD45.1+ BM cells 50-fold during culture, with most cells (87%) remaining tightly adherent to the osteoblast monolayer; no live cells were recovered from Lin− BM cell culture without osteoblasts. In addition to mature granulocytes/monocytes, a substantial amount of CD45.1+B220+ B lymphocytes (about 10% of small size cells gated by forward and side scatter), were detected. In contrast, very few CD45.1+Lin-Sca-1+c-Kit+ (LSK) cells or CD45.1+Lin−Sca-1−c-Kit+ (CMP) cells were detected under these conditions. Most B220+ cells attached to osteoblasts were found to be CD43+CD24+ pre-B cells undergoing division. In contrast to the cells recovered attached to the osteoblasts, the pre-B lymphocytes found in suspension were more mature with phenotype of B220+CD43−CD24+. Prevention of direct contact of Lin− BM cells with osteoblasts by Transwell co-culture abrogated the production of pre-B cells in both adherent and suspension compartments, indicating that physical contact is required for the interaction. Interestingly, when 20ng/ml of SCF, 6ng/ml of IL-3, 10ng/ml of IL-6 and 25ng/ml TPO were added to osteoblast/Lin− cell co-culture, B lymphpoiesis was repressed, while the production of CD45.1+LSK HSCs and CMPs was significantly enhanced. These data demonstrate a direct role of osteoblasts in inducing and supporting the early development of B lymphocytes from HSCs or/and common lymphoid progenitors. Additional cytokines, perhaps provided in specific in vivo niches by non-osteogenic stromal cells, cooperate with the stimulatory signals from osteoblasts to promote the survival and expansion of HSCs. Taken together, these results suggest that osteoblasts may be the mammalian analog of the avian Bursa of Fabricius, and that their local degree of proximity to non-osteogenic stromal cells may define specific microniches for stem cell survival, myelopoiesis and/or B lymphopoiesis.
5
Giuliani, Nicola, Francesca Morandi, Sara Tagliaferri, Mirca Lazzaretti, Sabrina Bonomini, Monica Crugnola, Cristina Mancini, et al. "The proteasome inhibitor bortezomib affects osteoblast differentiation in vitro and in vivo in multiple myeloma patients." Blood 110, no. 1 (July 1, 2007): 334–38. http://dx.doi.org/10.1182/blood-2006-11-059188.
Повний текст джерелаАнотація:
The proteasome inhibitor bortezomib may increase osteoblast-related markers in multiple myeloma (MM) patients; however, its potential osteoblastic stimulatory effect is not known. In this study, we show that bortezomib significantly induced a stimulatory effect on osteoblast markers in human mesenchymal cells without affecting the number of osteoblast progenitors in bone marrow cultures or the viability of mature osteoblasts. Consistently we found that bortezomib significantly increased the transcription factor Runx2/Cbfa1 activity in human osteoblast progenitors and osteoblasts without affecting nuclear and cytoplasmatic active β-catenin levels. Consequently a stimulatory effect of bortezomib on bone nodule formation was also demonstrated in osteoblast progenitors. These in vitro observations were confirmed in vivo by the finding of a significant increase in the number of osteoblastic cells × mm2 of bone tissue and in the number of Runx2/Cbfa1-positive osteoblastic cells that was observed in MM patients who responded to bortezomib. Our in vitro and in vivo observations support the hypothesis that a direct stimulatory effect on bone formation process could occur during bortezomib treatment.
6
Aubin, Jane E. "Advances in the osteoblast lineage." Biochemistry and Cell Biology 76, no. 6 (December 1, 1998): 899–910. http://dx.doi.org/10.1139/o99-005.
Повний текст джерелаАнотація:
Osteoblasts are the skeletal cells responsible for synthesis, deposition and mineralization of the extracellular matrix of bone. By mechanisms that are only beginning to be understood, stem and primitive osteoprogenitors and related mesenchymal precursors arise in the embryo and at least some appear to persist in the adult organism, where they contribute to replacement of osteoblasts in bone turnover and in fracture healing. In this review, we describe the morphological, molecular, and biochemical criteria by which osteoblasts are defined and cell culture approaches that have helped to clarify transitional stages in osteoblast differentiation. Current understanding of differential expression of osteoblast-associated genes during osteoprogenitor proliferation and differentiation to mature matrix synthesizing osteoblasts is summarized. Evidence is provided to support the hypothesis that the mature osteoblast phenotype is heterogeneous with subpopulations of osteoblasts expressing only subsets of the known osteoblast markers. Throughout this paper, outstanding uncertainties and areas for future investigation are also identified.Key words: skeletal development, differential gene expression, heterogeneity.
7
Panaroni, Cristina, Keertik Fulzele, Tomoaki Mori, Chukwuamaka Onyewadume, and Noopur S. Raje. "A Novel in-Vivo Model to Examine Homing of Multiple Myeloma Cells in Postnatal, Inducible, and Reversible Loss of Mature Osteoblasts." Blood 136, Supplement 1 (November 5, 2020): 50. http://dx.doi.org/10.1182/blood-2020-143182.
Повний текст джерелаАнотація:
The initiation of Multiple myeloma (MM) coincides with a decrease in osteoblasts and an increase in osteoclasts and adipocytes. However, the contribution of osteoblasts to the initiation and progression of MM remains mostly unknown. In-vitro studies have shown that co-cultures with MC3T3 murine osteoblast cell-line induced quiescence in 5TGM1 murine myeloma cells. In SCID or C57BL/KaLwRijHsd mice, the fluorescently labeled MM cell lines, injected through tail-vein, co-localized with endosteal osteoblasts and were found to be quiescent. We previously demonstrated that increased osteoblast numbers using Activin A inhibition in SCID mice with human-origin MM.1S cells resulted in inhibition of MM growth (Vallet et al., PNAS 2010). Here we aimed to develop a genetic in-vivo model for a better understanding of the interactions between osteoblasts and MM cells. Osteolineage cells develop through the stages of pre-osteoblasts, committed osteoblasts, mature osteoblasts, and osteocytes; each stage governed by a distinct molecular signature and function. To delineate these differences, individual osteoblast populations were FACS-sorted from long bones of Osterix-GFP+ (Osx+) mice (pre-osteoblasts), Collagen 2.3-GFP+ (Col2.3+) mice (committed osteoblasts), and Osteocalcin-YFP+ (OCN+) mice (mature osteoblasts). Co-cultured of these osteoblast populations with 5TGM1 MM cells showed that the OCN+ mature osteoblasts suppressed MM proliferation the most. Therefore, we focused our studies on the role of mature osteoblasts in MM homing and engraftment. We next generated mice in which mature osteoblasts were postnatally deleted in an inducible and reversible manner to better understand the molecular mechanisms of engraftment, proliferation, and migration of 5TGM1 injected intra-tibialy. To achieve this, mice carrying floxed diphtheria toxin receptor (DTR) alleles were mated with mice expressing Cre-recombinase driven by the osteocalcin promoter (OC-Cre). This led to the expression of DTR in mature osteoblasts (OC-Cre/iDTR) only. The control mice were littermates lacking the OC-Cre allele (iDTR). The OC-Cre/iDTR mice were indistinguishable from the controls until treated with diphtheria toxin (DT). We chose to induce mature osteoblast-deficiency at 8-weeks to allow skeletal maturation which is assumed to be completed by 6-7weeks of age. To induce postnatal deletion of mature osteoblasts, the OC-Cre/iDTR and control mice both were treated with 50 µg/Kg DT once a week, beginning at 8-weeks of age. Micro-CT analysis showed a significant increase in cortical porosity within 1-week after DT injection. 8-weeks of DT treatment significantly reduced trabecular bone fraction (BV/TV), trabecular numbers (Tb.N), and bone mineral density (BMD) with a significant increase in trabecular spacing (Tb.Sp). Immunohistochemistry for osteocalcin showed rapid loss of mature and endosteal osteoblasts (N.Ob/T.Ar). This was accompanied with a marked decreased in serum sclerostin and serum osteocalcin levels suggesting reduced osteocytes and mature osteoblasts, respectively. Importantly, serum CTX levels or numbers of osteoclasts (N.Oc/T.Ar) were unchanged. To study MM engraftment and progression, 3x106 5TGM1 luciferase eGFP positive (5TGM1-Luc-GFP) MM cells were injected into the tibia of OC-Cre/iDTR and control iDTR mice followed by weekly injection of DT for 8-weeks. Flow cytometry analysis showed a 4-fold increase in the 5TGM1-GFP cells in the BM from OC-Cre/iDTR mice compared to controls. Bioluminescence imaging (BLI) for 5TGM1-Luc-GFP cells at 4-weeks showed 600-fold increase in the OC-Cre/iDTR mice compared to controls. Interestingly, by 8-weeks, the BLI imaging showed 5TGM1-Luc-GFP cells in other long-bones of OC-Cre/iDTR mice but not the controls. These data show that MM cells engraft and proliferate rapidly in the absence of mature osteoblasts in-vivo. Moreover, in the absence of mature osteoblasts, MM cells have a propensity to migrate to other long bones. These data further suggest that expanding the mature osteoblast niche may provide novel therapeutic avenues and reduce disease burden and create an environment for long term tumor control. Importantly, this model will allow us to follow and analyze the sequential engraftment, dormancy, reactivation, proliferation, and migration of myeloma cells, and evaluate the effects of osteoanabolic and anti-myeloma therapies. Disclosures Fulzele: FORMA Therapeutics, Inc: Current Employment, Other: Shareholder of Forma Therapeutics. Raje:BMS: Consultancy; Amgen: Consultancy; Janssen: Consultancy; Karyopharm: Consultancy; Astrazeneca: Consultancy; Bluebird, Bio: Consultancy, Research Funding; Takeda: Consultancy; Immuneel: Membership on an entity's Board of Directors or advisory committees; Caribou: Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy.
8
Hernández-Tapia, Laura G., Zdenka Fohlerová, Jan Žídek, Marco A. Alvarez-Perez, Ladislav Čelko, Jozef Kaiser, and Edgar B. Montufar. "Effects of Cryopreservation on Cell Metabolic Activity and Function of Biofabricated Structures Laden with Osteoblasts." Materials 13, no. 8 (April 22, 2020): 1966. http://dx.doi.org/10.3390/ma13081966.
Повний текст джерелаАнотація:
Biofabrication and maturation of bone constructs is a long-term task that requires a high degree of specialization. This specialization falls onto the hierarchy complexity of the bone tissue that limits the transfer of this technology to the clinic. This work studied the effects of the short-term cryopreservation on biofabricated osteoblast-containing structures, with the final aim to make them steadily available in biobanks. The biological responses studied include the osteoblast post-thawing metabolic activity and the recovery of the osteoblastic function of 3D-bioprinted osteoblastic structures and beta tricalcium phosphate (β-TCP) scaffolds infiltrated with osteoblasts encapsulated in a hydrogel. The obtained structures were cryopreserved at −80 °C for 7 days using dimethyl sulfoxide (DMSO) as cryoprotectant additive. After thawing the structures were cultured up to 14 days. The results revealed fundamental biological aspects for the successful cryopreservation of osteoblast constructs. In summary, immature osteoblasts take longer to recover than mature osteoblasts. The pre-cryopreservation culture period had an important effect on the metabolic activity and function maintain, faster recovering normal values when cryopreserved after longer-term culture (7 days). The use of β-TCP scaffolds further improved the osteoblast survival after cryopreservation, resulting in similar levels of alkaline phosphatase activity in comparison with the non-preserved structures. These results contribute to the understanding of the biology of cryopreserved osteoblast constructs, approaching biofabrication to the clinical practice.
9
Fulzele, Keertik, Cristina Panaroni, Rosemary Soucy, Ka Tat Siu, Kenta Mukaihara, and Noopur Raje. "Mature Osteoblasts Provide a Protective Niche Against Multiple Myeloma Growth and Survival within the Tumor Microenvironment." Blood 132, Supplement 1 (November 29, 2018): 4476. http://dx.doi.org/10.1182/blood-2018-99-118377.
Повний текст джерелаАнотація:
Abstract Multiple myeloma (MM), a tumor of B-lymphocyte lineage cells, originates in the bone marrow (BM) and is highly influenced by the BM tumor microenvironment (TME). Among cells of the TME, osteoblasts are the most versatile regulators of many hematopoietic lineage cells through either direct cell-cell communication or secreted factors. Specifically relevant to MM, G-protein coupled receptor signaling in pre-osteoblasts is essential for the differentiation, maturation, and egress of B-cells (Panaroni et al., 2015). Despite these key roles, the contribution of osteoblasts to the initiation and progression of MM is not well understood. MM is characterized by osteolytic bone lesions partly due to decreased numbers of osteoblasts. Here, we hypothesize that osteoblasts provide niche support to maintain myeloma cells in a quiescent stage and that the loss of the osteoblastic niche leads to the progression of MM. As a proof of concept, we previously showed that increasing osteoblastogenesis by inhibiting Activin A led to inhibition of MM growth in an in vivo humanized myeloma model (Vallet et al., 2010). We generated mice in which mature osteoblasts could be postnatally deleted in an inducible and reversible manner. Diphtheria toxin receptor floxed mice were mated with mice expressing Cre-recombinase driven by the osteocalcin promoter to generate OC-Cre/iDTR mice. Littermates heterozygous for DTR but lacking the OC-Cre expression were used as controls. The OC-Cre/iDTR mice were indistinguishable from the controls until treated with diphtheria toxin (DT). To induce postnatal deletion of mature osteoblasts, the OC-Cre/iDTR and control mice both were treated with 50 µg/Kg DT beginning at 8-weeks of age. Osteocalcin immunohistochemistry of trabecular bone showed that the DT treated OC-Cre/iDTR mice were completely devoid of endosteal osteoblasts and young osteocytes. Consequently, serum levels of sclerostin were also significantly reduced in OC-Cre/iDTR mice compared to the controls. To study MM engraftment and progression, 3x106 5TGM1-Luciferase MM cells were inject into tibia of OC-Cre/iDTR and control mice followed by a weekly injection of DT for 8-weeks. Bioluminescence imaging (BLI) was used to assess tumor progression. Both the control and OC-Cre/iDTR mice started with similar BLI signal at 1-week. Interestingly, 4-weeks onwards only the OC-iDTR mice continued to express and increase the BLI signal indicating that the MM cells engrafted and continued to proliferate only in the OC-Cre/iDTR mice. This data suggests that under physiological conditions mature osteoblasts actively suppress MM engraftment and progression. To determine the direct effects of osteoblasts on MM cells, we established co-cultures of osteoblasts with MM cells. FACS sorting was used to isolate pre-osteoblasts from the long bones of Osterix-GFP+ (Osx+) mice, committed osteoblasts from Collagen 2.3-GFP+ (Col2.3+) mice, and mature osteoblasts from Osteocalcin-YFP+ (OCN+) mice. 5TGM1 MM cells were co-cultured along with 10,000 cells from each of the osteoblast populations. Although all three populations of osteoblasts significantly suppressed MM proliferation, the OCN+ mature osteoblasts suppressed MM proliferation the most. The mature osteoblastic niche may regulate MM cells via a) direct cell-to-cell contact, b) secreted factors, and/or c) other intermediary cells. To identify these possibilities, the BM TME was examined at 2-weeks following the 5TGM1 intratibia injection into the OC-Cre/iDTR and control mice. Quantitative protein antibody arrays analysis on the BM supernatant identified numerous key factors involved in cell-cell communication and immunomodulation in MM. These factors included BAFF-R, TACI, IL-33, IL-3, IL-21, and IL-17F. Gene expression analysis of the sorted 5TGM1 cells from the injected tibia indicated increased expression of genes involved in mitochondrial metabolism. Taken together, using in vivo and in vitro models, we show that mature osteoblasts offer specialized niches for MM cells where tumor cells are maintained in quiescence. The loss of the niche support allows the reactivation and progression of MM through the loss of cell-cell communication or through activation of immunomodulatory intermediary cells. Normalizing osteoblasts, such as through Activin A treatment, could provide novel avenues to reduce disease burden and long term tumor control. Disclosures No relevant conflicts of interest to declare.
10
Guo, Ying, Nicole Pischon, Amitha H. Palamakumbura, and Philip C. Trackman. "Intracellular distribution of the lysyl oxidase propeptide in osteoblastic cells." American Journal of Physiology-Cell Physiology 292, no. 6 (June 2007): C2095—C2102. http://dx.doi.org/10.1152/ajpcell.00613.2006.
Повний текст джерелаАнотація:
Lysyl oxidase plays a critical role in the formation of the extracellular matrix, and its activity is required for the normal maturation and cross-linking of collagen and elastin. An 18-kDa lysyl oxidase propeptide (LOPP) is generated from 50-kDa prolysyl oxidase by extracellular proteolytic cleavage during the biosynthesis of active 30-kDa lysyl oxidase enzyme. The fate and the functions of the LOPP are largely unknown, although intact LOPP was previously observed in osteoblast cultures. We investigated the spatial localization of molecular forms of lysyl oxidase, including LOPP in proliferating and differentiating osteoblasts, by using confocal immunofluorescence microscopy and Western blots of cytoplasmic and nuclear extracts. In the present study, a stage-dependent intracellular distribution of LOPP in the osteoblastic cell was observed. In proliferating osteoblasts, LOPP epitopes were principally associated with the Golgi and endoplasmic reticulum, and mature lysyl oxidase epitopes were found principally in the nucleus and perinuclear region. In differentiating cells, LOPP and mature lysyl oxidase immunostaining showed clear colocalization with the microtubule network. The subcellular distribution of LOPP and its temporal and physical association with microtubules were confirmed by Western blot and far Western blot studies. We also report that N-glycosylated and nonglycosylated LOPP are present in MC3T3-E1 cell cultures. We conclude that LOPP has a stage-dependent intracellular distribution in osteoblastic cells. Future studies are needed to investigate whether the LOPP associations with microtubules or the osteoblast nucleus have functional effects for osteoblast differentiation and bone formation.
11
Bonnelye, E., L. Merdad, V. Kung та J. E. Aubin. "The Orphan Nuclear Estrogen Receptor–Related Receptor α (Errα) Is Expressed Throughout Osteoblast Differentiation and Regulates Bone Formation in Vitro". Journal of Cell Biology 153, № 5 (21 травня 2001): 971–84. http://dx.doi.org/10.1083/jcb.153.5.971.
Повний текст джерелаАнотація:
The orphan nuclear estrogen receptor–related receptor α (ERRα), is expressed by many cell types, but is very highly expressed by osteoblastic cells in which it transactivates at least one osteoblast-associated gene, osteopontin. To study the putative involvement of ERRα in bone, we first assessed its expression in rat calvaria (RC) in vivo and in RC cells in vitro. ERRα mRNA and protein were expressed at all developmental stages from early osteoprogenitors to bone-forming osteoblasts, but protein was most abundant in mature cuboidal osteoblasts. To assess a functional role for ERRα in osteoblast differentiation and bone formation, we blocked its expression by antisense oligonucleotides in either proliferating or differentiating RC cell cultures and found inhibition of cell growth and a proliferation-independent inhibition of differentiation. On the other hand, ERRα overexpression in RC cells increased differentiation and maturation of progenitors to mature bone-forming cells. Our findings show that ERRα is highly expressed throughout the osteoblast developmental sequence and plays a physiological role in differentiation and bone formation at both proliferation and differentiation stages. In addition, we found that manipulation of receptor levels in the absence of known ligand is a fruitful approach for functional analysis of this orphan receptor and identification of potential target genes.
12
Filvaroff, E., A. Erlebacher, J. Ye, S. E. Gitelman, J. Lotz, M. Heillman, and R. Derynck. "Inhibition of TGF-beta receptor signaling in osteoblasts leads to decreased bone remodeling and increased trabecular bone mass." Development 126, no. 19 (October 1, 1999): 4267–79. http://dx.doi.org/10.1242/dev.126.19.4267.
Повний текст джерелаАнотація:
Transforming growth factor-beta (TGF-beta) is abundant in bone matrix and has been shown to regulate the activity of osteoblasts and osteoclasts in vitro. To explore the role of endogenous TGF-(beta) in osteoblast function in vivo, we have inhibited osteoblastic responsiveness to TGF-beta in transgenic mice by expressing a cytoplasmically truncated type II TGF-beta receptor from the osteocalcin promoter. These transgenic mice develop an age-dependent increase in trabecular bone mass, which progresses up to the age of 6 months, due to an imbalance between bone formation and resorption during bone remodeling. Since the rate of osteoblastic bone formation was not altered, their increased trabecular bone mass is likely due to decreased bone resorption by osteoclasts. Accordingly, direct evidence of reduced osteoclast activity was found in transgenic mouse skulls, which had less cavitation and fewer mature osteoclasts relative to skulls of wild-type mice. These bone remodeling defects resulted in altered biomechanical properties. The femurs of transgenic mice were tougher, and their vertebral bodies were stiffer and stronger than those of wild-type mice. Lastly, osteocyte density was decreased in transgenic mice, suggesting that TGF-beta signaling in osteoblasts is required for normal osteoblast differentiation in vivo. Our results demonstrate that endogenous TGF-beta acts directly on osteoblasts to regulate bone remodeling, structure and biomechanical properties.
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Nakamura, Miho, Akiko Nagai, and Kimihiro Yamashita. "Surface Electric Fields of Apatite Electret Promote Osteoblastic Responses." Key Engineering Materials 529-530 (November 2012): 357–60. http://dx.doi.org/10.4028/www.scientific.net/kem.529-530.357.
Повний текст джерелаАнотація:
The osteoblast behaviors on the biomaterial substrates are recognized to play a fundamental role in osteoconduction process. The purpose of this study was to evaluate the in vitro behaviors of osteoblasts cultured on electrically polarized hydroxyapatite (HA), having the enhanced osteobonding abilities. Osteoblasts derived from mouse bone marrow were seeded onto the polarized HA and investigated the proliferation and differentiation. The polarization had effects on the proliferation of osteoblast precursor cells based on the MTT assay. The acceleration was emerged as the early achievement to the confluence on the N-HA and P-HA. The quantitative analysis of the results of ALP and AR-S staining, the charges induced on the HA surface accelerated the differentiation from the osteoblast precursor cells to mature osteoblasts.
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Globus, R. K., S. B. Doty, J. C. Lull, E. Holmuhamedov, M. J. Humphries, and C. H. Damsky. "Fibronectin is a survival factor for differentiated osteoblasts." Journal of Cell Science 111, no. 10 (May 15, 1998): 1385–93. http://dx.doi.org/10.1242/jcs.111.10.1385.
Повний текст джерелаАнотація:
The skeletal extracellular matrix produced by osteoblasts contains the glycoprotein fibronectin, which regulates the adhesion, differentiation and function of various adherent cells. Interactions with fibronectin are required for osteoblast differentiation in vitro, since fibronectin antagonists added to cultures of immature fetal calvarial osteoblasts inhibit their progressive differentiation. To determine if fibronectin plays a unique role in fully differentiated osteoblasts, cultures that had already formed mineralized nodules in vitro were treated with fibronectin antagonists. Fibronectin antibodies caused >95% of the cells in the mature cultures to display characteristic features of apoptosis (nuclear condensation, apoptotic body formation, DNA laddering) within 24 hours. Cells appeared to acquire sensitivity to fibronectin antibody-induced apoptosis as a consequence of differentiation, since antibodies failed to kill immature cells and the first cells killed were those associated with mature nodules. Intact plasma fibronectin, as well as fragments corresponding to the amino-terminal, cell-binding, and carboxy-terminal domains of fibronectin, independently induced apoptosis of mature (day-13), but not immature (day-4), osteoblasts. Finally, transforming growth factor-beta1 partially protected cells from the apoptotic effects of fibronectin antagonists. Thus, in the course of maturation cultured osteoblasts switch from depending on fibronectin for differentiation to depending on fibronectin for survival. These data suggest that fibronectin, together with transforming growth factor-beta1, may affect bone formation, in part by regulating the survival of osteoblasts.
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Panaroni, Cristina, Keertik Fulzele, Rie Nakamoto-Matsubara, Allison Maebius, Chukwuamaka Onyewadume, Tomoaki Mori, and Noopur S. Raje. "Mature Osteoblasts Are Critical Bone Marrow Niche Cells Regulating Multiple Myeloma Cell Growth, at Least in Part, By Affecting the Local Immune Microenvironment." Blood 138, Supplement 1 (November 5, 2021): 74. http://dx.doi.org/10.1182/blood-2021-154057.
Повний текст джерелаАнотація:
Abstract Despite high response rates to new therapies, most multiple myeloma (MM) patients relapse and become refractory to treatment. This is likely because MM cells enter dormancy and reactivate only under permissive conditions. Cellular dormancy is ubiquitous in normal tissues as well as in malignant, non-malignant, and metastasizing tumors. Dormant tumor cells (DTC) are protected from therapies which can reactivate later at the time of disease progression, resulting in relapsed refractory MM (RRMM). The tumor microenvironment (TME) is a key determinant of tumor dormancy and reactivation. We have previously shown that inhibition of Activin A in SCID mice transplanted with human MM.1S increased osteoblast numbers and resulted in inhibition of MM growth (Vallet et al., PNAS). We hypothesize that MM-DTCs reside in osteoblastic niche in the BM TME. Our long-term goal is to identify factors regulating DTCs in MM and develop strategies for long term disease control. We have generated mice in which mature osteoblasts can be postnatally deleted in an inducible and reversible manner. To achieve this, mice carrying floxed diphtheria toxin receptor (DTR) alleles were mated with mice expressing Cre-recombinase driven by the osteocalcin promoter (OC-Cre). This led to the expression of DTR in mature osteoblasts (OC-Cre/iDTR) only. The control mice were littermates lacking the OC-Cre allele (iDTR). Until the treatment with diphtheria toxin (DT), the OC-Cre/iDTR mice were immunocompetent compared to iDTR mice, as they did not show any differences in immune cell populations by flow cytometry, and did not show any skeletal phenotype, as measured by micro-computed CT (micro-CT). We chose to induce mature osteoblast-deficiency at 8-weeks of age to allow skeletal maturation which is assumed to be completed by 6-7weeks of age. To induce postnatal deletion of mature osteoblasts, the OC-Cre/iDTR and control mice both were treated with 50 µg/kg DT once a week, beginning at 8-weeks of age. Micro-CT analysis showed a significant increase in cortical porosity within 1-week after DT injection. 8-weeks of DT treatment significantly reduced trabecular bone fraction (BV/TV), trabecular numbers (Tb.N), and bone mineral density (BMD) with a significant increase in trabecular spacing (Tb.Sp). Immunohistochemistry for osteocalcin showed rapid loss of mature and endosteal osteoblasts (N.Ob/T.Ar). This was accompanied with a marked decreased in serum sclerostin and serum osteocalcin levels suggesting reduced osteocytes and mature osteoblasts, respectively. Importantly, serum CTX levels or numbers of osteoclasts (N.Oc/T.Ar) were unchanged. To study MM engraftment and progression, 3x10 6 5TGM1 luciferase tdTomato positive (5TGM1-Luc-Tom) MM cells were injected into the tibia of OC-Cre/iDTR and control iDTR mice followed by weekly injection of DT for 8-weeks. Flow cytometry analysis showed a 4-fold increase in the 5TGM1-Tom cells in the BM from OC-Cre/iDTR mice compared to controls. Bioluminescence imaging (BLI) for 5TGM1-Luc-Tom cells at 4-weeks showed dramatic increase in the OC-Cre/iDTR mice compared to controls. Interestingly, by 8-weeks, the BLI imaging showed 5TGM1-Luc-Tom cells in other long-bones of OC-Cre/iDTR mice but not the controls. To identify local BM TME changes, we assessed the levels of 200 cytokines and growth factors in the BM from these mice. The levels of immune regulatory cytokines, such as IL-17F and IL-21, were found to be decreased in the OC-Cre/iDTR mice compared to control iDTR mice, both after 4-weeks from intratibial 5TGM1 cell injection. This was accompanied by significant decrease in the fraction of CD4+ T-helper and Th17+ cells in the OC-Cre/iDTR mice compared to controls, as assessed by flow cytometry. These data show that MM cells engraft and proliferate rapidly within the BM in the absence of mature osteoblasts and have a propensity to migrate to other long bones with time. This may be partially mediated by the altered immune cell profile in the BM in the absence of mature osteoblasts. These data further suggest that expanding the mature osteoblast niche may provide novel therapeutic avenues and reduce disease burden creating an environment for long term tumor control. Importantly, this model will allow us to understand the osteoblastic niche for MM and the mechanisms of activation and dormancy, at least in part, via a role of the immune cells. Disclosures Fulzele: Constellation Pharma: Current Employment, Current equity holder in publicly-traded company, Current holder of individual stocks in a privately-held company. Raje: Celgene, Amgen, Bluebird Bio, Janssen, Caribou, and BMS: Other.
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Kassem, Moustapha, Leif Mosekilde, and Erik F. Eriksen. "Effects of fluoride on human bone cells in vitro: differences in responsiveness between stromal osteoblast precursors and mature osteoblasts." European Journal of Endocrinology 130, no. 4 (April 1994): 381–86. http://dx.doi.org/10.1530/eje.0.1300381.
Повний текст джерелаАнотація:
Kassem M, Mosekilde L, Eriksen EF. Effects of fluoride on human bone cells in vitro: differences in responsiveness between stromal osteoblast precursors and mature osteoblasts. Eur J Endocrinol 1994;130:381–6. ISSN 0804–4643 The cellular effects of sodium fluoride (NaF) on human bone cells in vitro have been variable and dependent on the culture system used. Variability could be attributed to differences in responsiveness to NaF among different populations of cells at various stages of differentiation in the osteoblastic lineage. In this study we compared the effects of NaF in serum-free medium on cultures of more differentiated human osteoblast-like (hOB) cells derived from trabecular bone explants and on osteoblast committed precursors derived from human bone marrow, i.e. human marrow stromal osteoblast-like (hMS(OB)) cells. Sodium fluoride (10−5 mol/l) increased proliferation of hMS(OB) cells (p<0.05, N = 10) but was not mitogenic to hOB cells (p>0.05, N= 10). Alkaline phosphatase (AP) production increased in both hMS(OB) (p<0.05, N=9) and hOB cells (p<0.05, N=9). No significant effects on procollagen type I propeptide production were obtained in either culture. In the presence of 1,25-dihydroxycholecalciferol (10−9 mol/l), NaF enhanced alkaline phosphatase (p<0.05, N=8), procollagen type I propeptide (p<0.05, N=7) and osteocalcin (p<0.05, N=7) production by hMS(OB) cells but not by hOB cells. Our results suggest that osteoblast precursors are more sensitive to NaF action than mature osteoblasts and that the in vivo effects of NaF on bone formation may be mediated by stimulating proliferation and differentiation of committed osteoblast precursors in bone marrow. M Kassem, Mayo Clinic, Endocrine Research Unit, W-Joseph 5-164, Rochester, MN 55904, USA
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Komarova, Svetlana V., Fasoil I. Ataullakhanov, and Ruth K. Globus. "Bioenergetics and mitochondrial transmembrane potential during differentiation of cultured osteoblasts." American Journal of Physiology-Cell Physiology 279, no. 4 (October 1, 2000): C1220—C1229. http://dx.doi.org/10.1152/ajpcell.2000.279.4.c1220.
Повний текст джерелаАнотація:
To evaluate the relationship between osteoblast differentiation and bioenergetics, cultured primary osteoblasts from fetal rat calvaria were grown in medium supplemented with ascorbate to induce differentiation. Before ascorbate treatment, the rate of glucose consumption was 320 nmol · h−1· 106cells−1, respiration was 40 nmol · h−1· 106cells−1, and the ratio of lactate production to glucose consumption was ∼2, indicating that glycolysis was the main energy source for immature osteoblasts. Ascorbate treatment for 14 days led to a fourfold increase in respiration, a threefold increase in ATP production, and a fivefold increase in ATP content compared with that shown in immature cells. Confocal imaging of mitochondria stained with a transmembrane potential-sensitive vital dye showed that mature cells possessed abundant amounts of high-transmembrane-potential mitochondria, which were concentrated near the culture medium-facing surface. Acute treatment of mature osteoblasts with metabolic inhibitors showed that the rate of glycolysis rose to maintain the cellular energy supply constant. Thus progressive differentiation coincided with changes in cellular metabolism and mitochondrial activity, which are likely to play key roles in osteoblast function.
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Chow, J. W. M., J. M. Lean, T. Abe та T. J. Chambers. "The anabolic effect of 17β-oestradiol on the trabecular bone of adult rats is suppressed by indomethacin". Journal of Endocrinology 133, № 2 (травень 1992): 189–95. http://dx.doi.org/10.1677/joe.0.1330189.
Повний текст джерелаАнотація:
ABSTRACT We have previously demonstrated that administration of oestrogen, at doses sufficient to raise serum concentrations to those seen in late pregnancy, increases trabecular bone formation in the metaphysis of adult rats. To determine whether prostaglandins (PGs), which have been shown to induce osteogenesis in vivo, play a role in the induction of bone formation by oestrogen, 13-week-old female rats were given daily doses of 4 mg 17β-oestradiol (OE2)/kg for 17 days, alone or with indomethacin (1 mg/kg). The rats were also given double fluorochrome labels and at the end of the experiment tibias were subjected to histomorphometric assessment. Treatment with OE2 suppressed longitudinal bone growth and increased uterine wet weight, as expected, and neither response was affected by indomethacin. Oestrogen also induced a threefold increase in trabecular bone formation in the proximal tibial metaphysis, which resulted in a substantial increase in trabecular bone volume. As previously observed, the increase in bone formation was predominantly due to an increase in osteoblast recruitment (as judged by an increase in the percentage of bone surface showing double fluorochrome labels), with only a minor increase in the activity of mature osteoblasts (as judged by the mineral apposition rate). Indomethacin abolished the increase in osteoblastic recruitment, but the activity of mature osteoblastic cells remained high. The bone formation rate and bone volume remained similar to controls. The results suggest that PG production may be necessary for the increased osteoblastic recruitment induced by oestrogen, but not to mediate the effects of oestrogen on the activity of mature osteoblasts. Journal of Endocrinology (1992) 133, 189–195
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Komori, Toshihisa. "Regulation of Proliferation, Differentiation and Functions of Osteoblasts by Runx2." International Journal of Molecular Sciences 20, no. 7 (April 4, 2019): 1694. http://dx.doi.org/10.3390/ijms20071694.
Повний текст джерелаАнотація:
Runx2 is essential for osteoblast differentiation and chondrocyte maturation. During osteoblast differentiation, Runx2 is weakly expressed in uncommitted mesenchymal cells, and its expression is upregulated in preosteoblasts, reaches the maximal level in immature osteoblasts, and is down-regulated in mature osteoblasts. Runx2 enhances the proliferation of osteoblast progenitors by directly regulating Fgfr2 and Fgfr3. Runx2 enhances the proliferation of suture mesenchymal cells and induces their commitment into osteoblast lineage cells through the direct regulation of hedgehog (Ihh, Gli1, and Ptch1), Fgf (Fgfr2 and Fgfr3), Wnt (Tcf7, Wnt10b, and Wnt1), and Pthlh (Pthr1) signaling pathway genes, and Dlx5. Runx2 heterozygous mutation causes open fontanelle and sutures because more than half of the Runx2 gene dosage is required for the induction of these genes in suture mesenchymal cells. Runx2 regulates the proliferation of osteoblast progenitors and their differentiation into osteoblasts via reciprocal regulation with hedgehog, Fgf, Wnt, and Pthlh signaling molecules, and transcription factors, including Dlx5 and Sp7. Runx2 induces the expression of major bone matrix protein genes, including Col1a1, Spp1, Ibsp, Bglap2, and Fn1, in vitro. However, the functions of Runx2 in differentiated osteoblasts in the expression of these genes in vivo require further investigation.
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Liu, Wenguang, Satoru Toyosawa, Tatsuya Furuichi, Naoko Kanatani, Carolina Yoshida, Yang Liu, Miki Himeno, Satoru Narai, Akira Yamaguchi, and Toshihisa Komori. "Overexpression of Cbfa1 in osteoblasts inhibits osteoblast maturation and causes osteopenia with multiple fractures." Journal of Cell Biology 155, no. 1 (October 1, 2001): 157–66. http://dx.doi.org/10.1083/jcb.200105052.
Повний текст джерелаАнотація:
Targeted disruption of core binding factor α1 (Cbfa1) showed that Cbfa1 is an essential transcription factor in osteoblast differentiation and bone formation. Furthermore, both in vitro and in vivo studies showed that Cbfa1 plays important roles in matrix production and mineralization. However, it remains to be clarified how Cbfa1 controls osteoblast differentiation, bone formation, and bone remodelling. To understand fully the physiological functions of Cbfa1, we generated transgenic mice that overexpressed Cbfa1 in osteoblasts using type I collagen promoter. Unexpectedly, Cbfa1 transgenic mice showed osteopenia with multiple fractures. Cortical bone, which was thin, porous, and enriched with osteopontin, was invaded by osteoclasts, despite the absence of acceleration of osteoclastogenesis. Although the number of neonatal osteoblasts was increased, their function was impaired in matrix production and mineralization. Furthermore, terminally differentiated osteoblasts, which strongly express osteocalcin, and osteocytes were diminished greatly, whereas less mature osteoblasts expressing osteopontin accumulated in adult bone. These data indicate that immature organization of cortical bone, which was caused by the maturational blockage of osteoblasts, led to osteopenia and fragility in transgenic mice, demonstrating that Cbfa1 inhibits osteoblast differentiation at a late stage.
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Guntur, Anyonya R., Phuong T. Le, Charles R. Farber, and Clifford J. Rosen. "Bioenergetics During Calvarial Osteoblast Differentiation Reflect Strain Differences in Bone Mass." Endocrinology 155, no. 5 (May 1, 2014): 1589–95. http://dx.doi.org/10.1210/en.2013-1974.
Повний текст джерелаАнотація:
Osteoblastogenesis is the process by which mesenchymal stem cells differentiate into osteoblasts that synthesize collagen and mineralize matrix. The pace and magnitude of this process are determined by multiple genetic and environmental factors. Two inbred strains of mice, C3H/HeJ and C57BL/6J, exhibit differences in peak bone mass and bone formation. Although all the heritable factors that differ between these strains have not been elucidated, a recent F1 hybrid expression panel (C3H × B6) revealed major genotypic differences in osteoblastic genes related to cellular respiration and oxidative phosphorylation. Thus, we hypothesized that the metabolic rate of energy utilization by osteoblasts differed by strain and would ultimately contribute to differences in bone formation. In order to study the bioenergetic profile of osteoblasts, we measured oxygen consumption rates (OCR) and extracellular acidification rates (ECAR) first in a preosteoblastic cell line MC3T3-E1C4 and subsequently in primary calvarial osteoblasts from C3H and B6 mice at days 7, 14, and 21 of differentiation. During osteoblast differentiation in media containing ascorbic acid and β-glycerophosphate, all 3 cell types increased their oxygen consumption and extracellular acidification rates compared with the same cells grown in regular media. These increases are sustained throughout differentiation. Importantly, C3H calvarial osteoblasts had greater oxygen consumption rates than B6 consistent with their in vivo phenotype of higher bone formation. Interestingly, osteoblasts utilized both oxidative phosphorylation and glycolysis during the differentiation process although mature osteoblasts were more dependent on glycolysis at the 21-day time point than oxidative phosphorylation. Thus, determinants of oxygen consumption reflect strain differences in bone mass and provide the first evidence that during collagen synthesis osteoblasts use both glycolysis and oxidative phosphorylation to synthesize and mineralize matrix.
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Lin, Jian-Ming, Karen E. Callon, Jun-Sheng Lin, Maureen Watson, Victoria Empson, Pak C. Tong, Andrew Grey, et al. "Actions of fibroblast growth factor-8 in bone cells in vitro." American Journal of Physiology-Endocrinology and Metabolism 297, no. 1 (July 2009): E142—E150. http://dx.doi.org/10.1152/ajpendo.90743.2008.
Повний текст джерелаАнотація:
The fibroblast growth factors (FGFs) are a group of at least 25 structurally related peptides that are involved in many biological processes. Some FGFs are active in bone, including FGF-1, FGF-2, and FGF-18, and recent evidence indicates that FGF-8 is osteogenic, particularly in mesenchymal stem cells. In the current study, we found that FGF-8 was expressed in rat primary osteoblasts and in osteoblastic UMR-106 and MC3T3-E1 cells. Both FGF-8a and FGF-8b potently stimulated the proliferation of osteoblastic cells, whereas they inhibited the formation of mineralized bone nodules in long-term cultures of osteoblasts and reduced the levels of osteoblast differentiation markers, osteocalcin, and bone sialoprotein. FGF-8a induced the phosphorylation of p42/p44 mitogen-activated protein kinase (MAPK) in osteoblastic cells; however, its mitogenic actions were not blocked by either the MAPK kinase (MEK) inhibitor U-0126 or the PI 3-kinase (PI3K) inhibitor LY-294002. Interestingly, FGF-8a, unlike FGF-8b and other members of the family, inhibited osteoclastogenesis in mouse bone marrow cultures, and this was via a receptor activator of NF-κB ligand (RANKL)/osteoprotegerin (OPG)-independendent manner. However, FGF-8a did not affect osteoclastogenesis in RAW 264.7 cells (a macrophage cell line devoid of stromal cells) exogenously stimulated by RANKL, nor did it affect mature osteoclast function as assessed in rat calvarial organ cultures and isolated mature osteoclasts. In summary, we have demonstrated that FGF-8 is active in bone cells, stimulating osteoblast proliferation in a MAPK-independent pathway and inhibiting osteoclastogenesis via a RANKL/OPG-independent mechanism. These data suggest that FGF-8 may have a physiological role in bone acting in an autocrine/paracrine manner.
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Skottke, Gelinsky, and Bernhardt. "In Vitro Co-culture Model of Primary Human Osteoblasts and Osteocytes in Collagen Gels." International Journal of Molecular Sciences 20, no. 8 (April 23, 2019): 1998. http://dx.doi.org/10.3390/ijms20081998.
Повний текст джерелаАнотація:
Background: Osteocytes are the key regulator cells in bone tissue, affecting activity of both osteoblasts and osteoclasts. Current in vitro studies on osteocyte-osteoblast interaction are invariably performed with rodent cells, mostly murine cell lines, which diminishes the clinical relevance of the data. Objective: The objective of the present study was to establish an in vitro co-culture system of osteoblasts and osteocytes, which is based solely on human primary cells. Methods: Three different approaches for the generation of human primary osteocytes were compared: direct isolation of osteocytes from bone tissue by multistep digestion, long-time differentiation of human pre-osteoblasts embedded in collagen gels, and short time differentiation of mature human osteoblasts in collagen gels. Co-cultivation of mature osteoblasts with osteocytes, derived from the three different approaches was performed in a transwell system, with osteocytes, embedded in collagen gels at the apical side and osteoblasts on the basal side of a porous membrane, which allowed the separate gene expression analysis for osteocytes and osteoblasts. Fluorescence microscopic imaging and gene expression analysis were performed separately for osteocytes and osteoblasts. Results: All examined approaches provided cells with typical osteocytic morphology, which expressed osteocyte markers E11, osteocalcin, phosphate regulating endopeptidase homolog, X-linked (PHEX), matrix extracellular phosphoglycoprotein (MEPE), sclerostin, and receptor activator of NF-κB Ligand (RANKL). Expression of osteocyte markers was not significantly changed in the presence of osteoblasts. In contrast, osteocalcin gene expression of osteoblasts was significantly upregulated in all examined co-cultures with differentiated osteocytes. Alkaline phosphatase (ALPL), bone sialoprotein II (BSPII), and RANKL expression of osteoblasts was not significantly changed in the co-culture. Conclusion: Interaction of osteoblasts and osteocytes can be monitored in an in vitro model, comprising solely primary human cells.
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Christopher, Matthew J., Fulu Liu, Brenton Short, Paul J. Simmons, Ingrid Winkler, Jean-Pierre Levesque, and Daniel C. Link. "G-CSF Potently Suppresses Osteoblast Activity in the Bone Marrow." Blood 106, no. 11 (November 16, 2005): 591. http://dx.doi.org/10.1182/blood.v106.11.591.591.
Повний текст джерелаАнотація:
Abstract There is accumulating evidence that interaction of stromal cell derived factor-1 (SDF-1/CXCL12) with its cognate receptor, CXCR4, generates signals that regulate hematopoietic progenitor cell (HPC) trafficking in the bone marrow. During G-CSF induced HPC mobilization, SDF-1 protein expression in the bone marrow decreases, thereby attenuating CXCR4 signaling. We recently reported that G-CSF treatment induced a decrease in bone marrow SDF-1 mRNA that closely mirrored the fall in SDF-1 protein, suggesting that G-CSF targets one or more SDF-1 producing cell population in the bone marrow. However, the identity of cell populations in the bone marrow that express SDF-1 is controversial. In the present study, we address this issue by sorting cells into mature hematopoietic, hematopoietic progenitor, endothelial, and osteoblast cell populations. Real time RT-PCR analyses showed that osteoblasts and to a lesser degree endothelial cells are the major sources of SDF-1 production in the bone marrow. Surprisingly, on a per cell basis, SDF-1 expression per osteoblast was only modestly (less than two-fold) reduced in mice treated with G-CSF. These data raised the possibility that, rather than affecting SDF-1 expression per osteoblast, G-CSF regulated the number of osteoblasts in the bone marrow. To explore this possibility, osteoblast number in the bone marrow was measured by histomorphometry. Indeed, after 5 days of G-CSF treatment, a significant reduction in the number of endosteal osteoblasts was observed [number of osteoblasts per mm bone perimeter ± SEM: 74.8 ± 13.5 (untreated) versus 33.3 ± 3.8 (G-CSF)]. Moreover, expression of osteocalcin (a specific marker of mature osteoblasts) in the bone marrow was sharply reduced during G-CSF treatment: a 47 ± 12 fold reduction in osteocalcin mRNA (relative to b-actin mRNA) was observed in the bone marrow of G-CSF-treated mice compared with untreated mice. Finally, calcein double-labeling experiments showed that the mineral apposition rate was significantly reduced in G-CSF-treated mice. However, RT-PCR analyses showed that the G-CSF receptor is not expressed on osteoblasts. Accordingly, G-CSF had no direct effect on osteoblast activity in vitro. Collectively, these data show that G-CSF potently suppresses osteoblast number/activity in the bone marrow through an indirect mechanism. Since osteoblasts are thought to play a key role in establishing and maintaining the stem cell niche in the bone marrow, these data raise the possibility that G-CSF, by regulating osteoblast function (including SDF-1 expression), may have profound effects on the stem cell niche that ultimately contribute to HPC mobilization.
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Na, Woojin, Min-Kyung Kang, Sin-Hye Park, Dong Yeon Kim, Su Yeon Oh, Moon-Sik Oh, Sohyun Park, II-Jun Kang, and Young-Hee Kang. "Aesculetin Accelerates Osteoblast Differentiation and Matrix-Vesicle-Mediated Mineralization." International Journal of Molecular Sciences 22, no. 22 (November 17, 2021): 12391. http://dx.doi.org/10.3390/ijms222212391.
Повний текст джерелаАнотація:
The imbalance between bone resorption and bone formation in favor of resorption results in bone loss and deterioration of bone architecture. Osteoblast differentiation is a sequential event accompanying biogenesis of matrix vesicles and mineralization of collagen matrix with hydroxyapatite crystals. Considerable efforts have been made in developing naturally-occurring plant compounds, preventing bone pathologies, or enhancing bone regeneration. Coumarin aesculetin inhibits osteoporosis through hampering the ruffled border formation of mature osteoclasts. However, little is known regarding the effects of aesculetin on the impairment of matrix vesicle biogenesis. MC3T3-E1 cells were cultured in differentiation media with 1–10 μM aesculetin for up to 21 days. Aesculetin boosted the bone morphogenetic protein-2 expression, and alkaline phosphatase activation of differentiating MC3T3-E1 cells. The presence of aesculetin strengthened the expression of collagen type 1 and osteoprotegerin and transcription of Runt-related transcription factor 2 in differentiating osteoblasts for 9 days. When ≥1–5 μM aesculetin was added to differentiating cells for 15–18 days, the induction of non-collagenous proteins of bone sialoprotein II, osteopontin, osteocalcin, and osteonectin was markedly enhanced, facilitating the formation of hydroxyapatite crystals and mineralized collagen matrix. The induction of annexin V and PHOSPHO 1 was further augmented in ≥5 μM aesculetin-treated differentiating osteoblasts for 21 days. In addition, the levels of tissue-nonspecific alkaline phosphatase and collagen type 1 were further enhanced within the extracellular space and on matrix vesicles of mature osteoblasts treated with aesculetin, indicating matrix vesicle-mediated bone mineralization. Finally, aesculetin markedly accelerated the production of thrombospondin-1 and tenascin C in mature osteoblasts, leading to their adhesion to preformed collagen matrix. Therefore, aesculetin enhanced osteoblast differentiation, and matrix vesicle biogenesis and mineralization. These findings suggest that aesculetin may be a potential osteo-inductive agent preventing bone pathologies or enhancing bone regeneration.
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Levesque, Jean-Pierre, Ingrid G. Winkler, Natalie Sims, Howard Morris, Paul J. Simmons, and Yasushi Takamatsu. "The Inhibition of the Osteoblast Niche during Hematopoietic Stem Cell Mobilization Is an Indirect Effect Involving Mature Bone Marrow Leukocytes, IL6 and Soluble IL6 Receptor." Blood 106, no. 11 (November 16, 2005): 1966. http://dx.doi.org/10.1182/blood.v106.11.1966.1966.
Повний текст джерелаАнотація:
Abstract Mobilization of hematopoietic stem cells (HSC) involves the disruption of 1) the adhesive interaction between VCAM-1 and α4-integrins and 2) the chemotactic interaction between CXCL12 and CXCR4, interactions which are both required for the retention of HSC within the bone marrow (BM). Experiments in mice deficient in neutrophil proteases have shown that while the disruption of the VCAM-1/α4 integrin interaction is entirely due to the proteolytic cleavage of VCAM-1 by proteases released from neutrophils accumulating in mobilized BM, the down-regulation of CXCL12 involves protease-independent mechanisms. We have recently shown that osteoblasts are the main source of CXCL12 in the BM and that both the number of osteoblasts lining the endosteum and bone formation are dramatically reduced during G-CSF administration as reflected by bone pain often experienced by mobilized donors. Consequently, the decreased level of CXCL12 levels in mobilized BM could be due to inhibition of osteoblasts, an essential component of the hematopoietic niche. Quantitative real-time RT-PCR were performed on mouse BM cells to follow osteocalcin mRNA levels. Osteocalcin mRNA dropped 2–3 logs during mobilization induced by either G-CSF or cyclophosphamide showing that the inhibition of osteoblast function is not restricted to G-CSF-induced mobilization. Morphometric analyses of tibia sections showed a quasi disappearance of osteoblasts and osteoid as early as day 2 of G-CSF injection. In humans, we observed a significant reduction of osteocalcin protein concentration in the plasma during mobilization induced by either G-CSF alone, G-CSF+ KIT ligand or IL3+GM-CSF, showing that in both humans and mice this effect is not restricted to G-CSF. In cultures of purified human osteoblasts, neither G-CSF, KIT ligand, IL3 nor GM-CSF inhibited osteocalcin production demonstrating that inhibition of osteoblast function is not a direct effect of these cytokines. In parallel experiments, addition of differentiated BM CD34− leukocytes to osteoblast cultures, resulted in a dose-dependant inhibition of osteocalcin production showing that the effect is mediated by mature leukocytes. Since IL6 and soluble IL6 receptor (sIL6R) are important mediators of bone formation, we tested these two cytokines on purified osteoblasts and found that the combination of IL6+sIL6R was a potent inhibitor of osteocalcin production while these cytokines had no effect when used alone. Furthermore, we find cocultures of osteoblasts and BM leukocytes results in a 30-fold increase in IL6 production compared to monocultures of osteoblasts or BM leukocytes. Finally, in humans, plasma concentration of sIL6R is significantly increased during HSC mobilization and this increase is significantly correlated with the number of circulating CFU-GM. Taken together, these data indicate that the inhibition of osteoblast function during HSC mobilization is an indirect effect involving mature BM leukocytes, IL6 and sIL6R.
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McMahon, Mark S. "Developing and Fractured Bones Are Invaded by Osteoblast Precursors, not Mature Osteoblasts." Orthopedics 34, no. 6 (June 1, 2011): 415. http://dx.doi.org/10.3928/01477447-20110427-01.
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Fuller, Karen, Brian Wong, Simon Fox, Yongwon Choi, and Tim J. Chambers. "TRANCE Is Necessary and Sufficient for Osteoblast-mediated Activation of Bone Resorption in Osteoclasts." Journal of Experimental Medicine 188, no. 5 (September 7, 1998): 997–1001. http://dx.doi.org/10.1084/jem.188.5.997.
Повний текст джерелаАнотація:
TRANCE (tumor necrosis factor–related activation-induced cytokine) is a recently described member of the tumor necrosis factor superfamily that stimulates dendritic cell survival and has also been found to induce osteoclastic differentiation from hemopoietic precursors. However, its effects on mature osteoclasts have not been defined. It has long been recognized that stimulation of osteoclasts by agents such as parathyroid hormone (PTH) occurs through a hormonal interaction with osteoblastic cells, which are thereby induced to activate osteoclasts. To determine whether TRANCE accounts for this activity, we tested its effects on mature osteoclasts. TRANCE rapidly induced a dramatic change in osteoclast motility and spreading and inhibited apoptosis. In populations of osteoclasts that were unresponsive to PTH, TRANCE caused activation of bone resorption equivalent to that induced by PTH in the presence of osteoblastic cells. Moreover, osteoblast-mediated stimulation of bone resorption was abrogated by soluble TRANCE receptor and by the soluble decoy receptor osteoprotegerin (OPG), and stimulation of isolated osteoclasts by TRANCE was neutralized by OPG. Thus, TRANCE expression by osteoblasts appears to be both necessary and sufficient for hormone-mediated activation of mature osteoclasts, and TRANCE-R is likely to be a receptor for signal transduction for activation of the osteoclast and its survival.
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Baek, Jong Min, Ju-Young Kim, Yoon-Hee Cheon, Sun-Hyang Park, Sung-Jun Ahn, Kwon-Ha Yoon, Jaemin Oh, and Myeung Su Lee. "Dual Effect ofChrysanthemum indicumExtract to Stimulate Osteoblast Differentiation and Inhibit Osteoclast Formation and ResorptionIn Vitro." Evidence-Based Complementary and Alternative Medicine 2014 (2014): 1–13. http://dx.doi.org/10.1155/2014/176049.
Повний текст джерелаАнотація:
The risk of bone-related diseases increases due to the imbalance between bone resorption and bone formation by osteoclasts and osteoblasts, respectively. The goal in the development of antiosteoporotic treatments is an agent that will improve bone through simultaneous osteoblast stimulation and osteoclast inhibition without undesirable side effects. To achieve this goal, numerous studies have been performed to identify novel approaches using natural oriental herbs to treat bone metabolic diseases. In the present study, we investigated the effect ofChrysanthemum indicumextract (CIE) on the differentiation of osteoclastic and osteoblastic cells. CIE inhibited the formation of TRAP-positive mature osteoclasts and of filamentous-actin rings and disrupted the bone-resorbing activity of mature osteoclasts in a dose-dependent manner. CIE strongly inhibited Akt, GSK3β, and IκB phosphorylation in RANKL-stimulated bone marrow macrophages and did not show any effects on MAP kinases, including p38, ERK, and JNK. Interestingly, CIE also enhanced primary osteoblast differentiation via upregulation of the expression of alkaline phosphatase and the level of extracellular calcium concentrations during the early and terminal stages of differentiation, respectively. Our results revealed that CIE could have a potential therapeutic role in bone-related disorders through its dual effects on osteoclast and osteoblast differentiation.
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Mackie, E. J., and R. P. Tucker. "Tenascin in bone morphogenesis: expression by osteoblasts and cell type-specific expression of splice variants." Journal of Cell Science 103, no. 3 (November 1, 1992): 765–71. http://dx.doi.org/10.1242/jcs.103.3.765.
Повний текст джерелаАнотація:
The extracellular matrix glycoprotein, tenascin, is associated in vivo with mesenchyme undergoing osteogenesis and chondrogenesis, but is absent from mature bone and cartilage matrix. The expression of tenascin by osteoblastic cells in vitro has been investigated by immunoblotting and immunocytochemistry. Tenascin was secreted into the medium and deposited in the matrix by human and rat osteoblast-like cell lines, as well as by primary osteoblast-enriched cultures from chick embryo calvarial bones. In primary osteoblast-enriched cultures, extracellular tenascin was found only in cell aggregates expressing the osteoblast marker alkaline phosphatase. Chicken osteoblast cultures synthesized almost exclusively the largest tenascin subunit, whereas fibroblast cultures from periostea of chicken calvariae synthesized approximately equal amounts of all three subunits. In situ hybridization studies of developing chicken bones, using a cDNA probe that hybridizes to all chicken tenascin splice variants, showed specific labelling of both osteogenic and chondrogenic regions of developing endochondral bones. In contrast, a cDNA probe specific for the large tenascin splice variant showed specific hybridization in osteogenic but not chondrogenic regions. Within osteogenic regions, tenascin mRNA was expressed by osteoblasts. A comparison of in situ hybridization and immunohistochemical studies demonstrated that tenascin mRNA and protein were codistributed in osteogenic regions of endochondral and membrane bones, whereas protein was retained in regions of differentiating cartilage where mRNA was no longer detectable. The results presented here demonstrate that tenascin is synthesized by osteoblasts. Moreover, within developing bones, there are at least three different cell type-specific patterns of expression of tenascin splice variants.
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Yamamoto, T., and C. V. Gay. "Ultrastructural localization of adenylate cyclase in chicken bone cells." Journal of Histochemistry & Cytochemistry 37, no. 11 (November 1989): 1705–9. http://dx.doi.org/10.1177/37.11.2553803.
Повний текст джерелаАнотація:
We investigated adenylate cyclase distribution in 6-day-and 3-week-old calvariae and in 6-day-old long bone metaphyses from chickens. Reaction product distribution was on the plasma membrane of osteoblasts, pre-osteoblasts, and forming osteocytes which contacted one another. Osteoclasts and mature osteocytes lacked reaction product. Six-day calvariae reacted less intensely than the other two tissues. In controls, reaction product was markedly diminished or eliminated by removal of forskolin or substrates, or by addition of the inhibitor 2',5'-dideoxyadenosine. The results indicate the importance of cyclic AMP in osteoblast regulation. Osteocytes and osteoclasts may involve alternate mechanisms as major regulatory systems.
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Lieben, Liesbet. "Direct contact between mature osteoblasts and osteoclasts." Nature Reviews Rheumatology 14, no. 4 (February 15, 2018): 183. http://dx.doi.org/10.1038/nrrheum.2018.16.
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Neag, Georgiana, Melissa Finlay, and Amy J. Naylor. "The Cellular Choreography of Osteoblast Angiotropism in Bone Development and Homeostasis." International Journal of Molecular Sciences 22, no. 14 (July 6, 2021): 7253. http://dx.doi.org/10.3390/ijms22147253.
Повний текст джерелаАнотація:
Interaction between endothelial cells and osteoblasts is essential for bone development and homeostasis. This process is mediated in large part by osteoblast angiotropism, the migration of osteoblasts alongside blood vessels, which is crucial for the homing of osteoblasts to sites of bone formation during embryogenesis and in mature bones during remodeling and repair. Specialized bone endothelial cells that form “type H” capillaries have emerged as key interaction partners of osteoblasts, regulating osteoblast differentiation and maturation and ensuring their migration towards newly forming trabecular bone areas. Recent revolutions in high-resolution imaging methodologies for bone as well as single cell and RNA sequencing technologies have enabled the identification of some of the signaling pathways and molecular interactions that underpin this regulatory relationship. Similarly, the intercellular cross talk between endothelial cells and entombed osteocytes that is essential for bone formation, repair, and maintenance are beginning to be uncovered. This is a relatively new area of research that has, until recently, been hampered by a lack of appropriate analysis tools. Now that these tools are available, greater understanding of the molecular relationships between these key cell types is expected to facilitate identification of new drug targets for diseases of bone formation and remodeling.
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Yamamoto, Ryoko, Tomoko Minamizaki, Yuji Yoshiko, Hirotaka Yoshioka, Kazuo Tanne, Jane E. Aubin та Norihiko Maeda. "1α,25-dihydroxyvitamin D3 acts predominately in mature osteoblasts under conditions of high extracellular phosphate to increase fibroblast growth factor 23 production in vitro". Journal of Endocrinology 206, № 3 (8 червня 2010): 279–86. http://dx.doi.org/10.1677/joe-10-0058.
Повний текст джерелаАнотація:
Osteoblasts/osteocytes are the principle sources of fibroblast growth factor 23 (FGF23), a phosphaturic hormone, but the regulation of FGF23 expression during osteoblast development remains uncertain. Because 1α,25-dihydroxyvitamin D3 (1,25(OH)2D3) and inorganic phosphate (Pi) may act as potent activators of FGF23 expression, we estimated how these molecules regulate FGF23 expression during rat osteoblast development in vitro. 1,25(OH)2D3-dependent FGF23 production was restricted largely to mature cells in correlation with increased vitamin D receptor (VDR) mRNA levels, in particular, when Pi was present. Pi alone and more so in combination with 1,25(OH)2D3 increased FGF23 production and VDR mRNA expression. Parathyroid hormone, stanniocalcin 1, prostaglandin E2, FGF2, and foscarnet did not increase FGF23 mRNA expression. Thus, these results suggest that 1,25(OH)2D3 may exert its largest effect on FGF23 expression/production when exposed to high levels of extracellular Pi in osteoblasts/osteocytes.
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Kenner, Lukas, Astrid Hoebertz, F. Timo Beil, Niamh Keon, Florian Karreth, Robert Eferl, Harald Scheuch, et al. "Mice lacking JunB are osteopenic due to cell-autonomous osteoblast and osteoclast defects." Journal of Cell Biology 164, no. 4 (February 9, 2004): 613–23. http://dx.doi.org/10.1083/jcb.200308155.
Повний текст джерелаАнотація:
Because JunB is an essential gene for placentation, it was conditionally deleted in the embryo proper. JunBΔ/Δ mice are born viable, but develop severe low turnover osteopenia caused by apparent cell-autonomous osteoblast and osteoclast defects before a chronic myeloid leukemia-like disease. Although JunB was reported to be a negative regulator of cell proliferation, junBΔ/Δ osteoclast precursors and osteoblasts show reduced proliferation along with a differentiation defect in vivo and in vitro. Mutant osteoblasts express elevated p16INK4a levels, but exhibit decreased cyclin D1 and cyclin A expression. Runx2 is transiently increased during osteoblast differentiation in vitro, whereas mature osteoblast markers such as osteocalcin and bone sialoprotein are strongly reduced. To support a cell-autonomous function of JunB in osteoclasts, junB was inactivated specifically in the macrophage–osteoclast lineage. Mutant mice develop an osteopetrosis-like phenotype with increased bone mass and reduced numbers of osteoclasts. Thus, these data reveal a novel function of JunB as a positive regulator controlling primarily osteoblast as well as osteoclast activity.
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Tang, Jun, Jing Xie, Wei Chen, Chenyi Tang, Jinjin Wu, Yiping Wang, Xue-Dong Zhou, Hou-De Zhou, and Yi-Ping Li. "Runt-related transcription factor 1 is required for murine osteoblast differentiation and bone formation." Journal of Biological Chemistry 295, no. 33 (June 22, 2020): 11669–81. http://dx.doi.org/10.1074/jbc.ra119.007896.
Повний текст джерелаАнотація:
Despite years of research investigating osteoblast differentiation, the mechanisms by which transcription factors regulate osteoblast maturation, bone formation, and bone homeostasis is still unclear. It has been reported that runt-related transcription factor 1 (Runx1) is expressed in osteoblast progenitors, pre-osteoblasts, and mature osteoblasts; yet, surprisingly, the exact function of RUNX1 in osteoblast maturation and bone formation remains unknown. Here, we generated and characterized a pre-osteoblast and differentiating chondrocyte-specific Runx1 conditional knockout mouse model to study RUNX1's function in bone formation. Runx1 ablation in osteoblast precursors and differentiating chondrocytes via osterix-Cre (Osx-Cre) resulted in an osteoporotic phenotype and decreased bone density in the long bones and skulls of Runx1f/fOsx-Cre mice compared with Runx1f/f and Osx-Cre mice. RUNX1 deficiency reduced the expression of SRY-box transcription factor 9 (SOX9), Indian hedgehog signaling molecule (IHH), Patched (PTC), and cyclin D1 in the growth plate, and also reduced the expression of osteocalcin (OCN), OSX, activating transcription factor 4 (ATF4), and RUNX2 in osteoblasts. ChIP assays and promoter activity mapping revealed that RUNX1 directly associates with the Runx2 gene promoter and up-regulates Runx2 expression. Furthermore, the ChIP data also showed that RUNX1 associates with the Ocn promoter. In conclusion, RUNX1 up-regulates the expression of Runx2 and multiple bone-specific genes, and plays an indispensable role in bone formation and homeostasis in both trabecular and cortical bone. We propose that stimulating Runx1 activity may be useful in therapeutic approaches for managing some bone diseases such as osteoporosis.
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Mandal, Chandi C., Suthakar Ganapathy, Yves Gorin, Kalyankar Mahadev, Karen Block, Hanna E. Abboud, Stephen E. Harris, Goutam Ghosh-Choudhury, and Nandini Ghosh-Choudhury. "Reactive oxygen species derived from Nox4 mediate BMP2 gene transcription and osteoblast differentiation." Biochemical Journal 433, no. 2 (December 22, 2010): 393–402. http://dx.doi.org/10.1042/bj20100357.
Повний текст джерелаАнотація:
BMP-2 (bone morphogenetic protein-2) promotes differentiation of osteoblast precursor cells to mature osteoblasts that form healthy bone. In the present study, we demonstrate a novel mechanism of BMP-2-induced osteoblast differentiation. The antioxidant NAC (N-acetyl-L-cysteine) and the flavoprotein enzyme NAD(P)H oxidase inhibitor DPI (diphenyleneiodonium) prevented BMP-2-stimulated alkaline phosphatase expression and mineralized bone nodule formation in mouse 2T3 pre-osteoblasts. BMP-2 elicited a rapid generation of ROS (reactive oxygen species) concomitant with increased activation of NAD(P)H oxidase. NAC and DPI inhibited BMP-2-induced ROS production and NAD(P)H oxidase activity respectively. NAD(P)H oxidases display structurally similar catalytic subunits (Nox1–5) with differential expression in various cells. We demonstrate that 2T3 pre-osteoblasts predominantly express the Nox4 isotype of NAD(P)H oxidase. To extend this finding, we tested the functional effects of Nox4. Adenovirus-mediated expression of dominant-negative Nox4 inhibited BMP-2-induced alkaline phosphatase expression. BMP-2 promotes expression of BMP-2 for maintenance of the osteoblast phenotype. NAC and DPI significantly blocked BMP-2-stimulated expression of BMP2 mRNA and protein due to a decrease in BMP2 gene transcription. Dominant-negative Nox4 also mimicked this effect of NAC and DPI. Our results provide the first evidence for a new signalling pathway linking BMP-2-stimulated Nox4-derived physiological ROS to BMP-2 expression and osteoblast differentiation.
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Saleh, Hasnawati, Damien Eeles, Jason M. Hodge, Geoffrey C. Nicholson, Ran Gu, Sueli Pompolo, Matthew T. Gillespie, and Julian M. W. Quinn. "Interleukin-33, a Target of Parathyroid Hormone and Oncostatin M, Increases Osteoblastic Matrix Mineral Deposition and Inhibits Osteoclast Formation in Vitro." Endocrinology 152, no. 5 (March 1, 2011): 1911–22. http://dx.doi.org/10.1210/en.2010-1268.
Повний текст джерелаАнотація:
IL-33 is an important inflammatory mediator in allergy, asthma, and joint inflammation, acting via its receptor, ST2L, to elicit Th2 cell cytokine secretion. IL-33 is related to IL-1 and IL-18, which both influence bone metabolism, IL-18 in particular inhibiting osteoclast formation and contributing to PTH bone anabolic actions. We found IL-33 immunostaining in osteoblasts in mouse bone and IL-33 mRNA expression in cultured calvarial osteoblasts, which was elevated by treatment with the bone anabolic factors oncostatin M and PTH. IL-33 treatment strongly inhibited osteoclast formation in bone marrow and spleen cell cultures but had no effect on osteoclast formation in receptor activator of nuclear factor-κB ligand/macrophage colony-stimulating factor-treated bone marrow macrophage (BMM) or RAW264.7 cultures, suggesting a lack of direct action on immature osteoclast progenitors. However, osteoclast formation from BMM was inhibited by IL-33 in the presence of osteoblasts, T cells, or mature macrophages, suggesting these cell types may mediate some actions of IL-33. In bone marrow cultures, IL-33 induced mRNA expression of granulocyte macrophage colony-stimulating factor, IL-4, IL-13, and IL-10; osteoclast inhibitory actions of IL-33 were rescued only by combined antibody ablation of these factors. In contrast to osteoclasts, IL-33 promoted matrix mineral deposition by long-term ascorbate treated primary osteoblasts and reduced sclerostin mRNA levels in such cultures after 6 and 24 h of treatment; sclerostin mRNA was also suppressed in IL-33-treated calvarial organ cultures. In summary, IL-33 stimulates osteoblastic function in vitro but inhibits osteoclast formation through at least three separate mechanisms. Autocrine and paracrine actions of osteoblast IL-33 may thus influence bone metabolism.
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Yadav, Avinash M., Manali M. Bagade, Soni Ghumnani, Sujatha Raman, Bhaskar Saha, Katharina F. Kubatzky, and Richa Ashma. "The phytochemical plumbagin reciprocally modulates osteoblasts and osteoclasts." Biological Chemistry 403, no. 2 (December 10, 2021): 211–29. http://dx.doi.org/10.1515/hsz-2021-0290.
Повний текст джерелаАнотація:
Abstract Bone metabolism is essential for maintaining bone mineral density and bone strength through a balance between bone formation and bone resorption. Bone formation is associated with osteoblast activity whereas bone resorption is linked to osteoclast differentiation. Osteoblast progenitors give rise to the formation of mature osteoblasts whereas monocytes are the precursors for multi-nucleated osteoclasts. Chronic inflammation, auto-inflammation, hormonal changes or adiposity have the potential to disturb the balance between bone formation and bone loss. Several plant-derived components are described to modulate bone metabolism and alleviate osteoporosis by enhancing bone formation and inhibiting bone resorption. The plant-derived naphthoquinone plumbagin is a bioactive compound that can be isolated from the roots of the Plumbago genus. It has been used as traditional medicine for treating infectious diseases, rheumatoid arthritis and dermatological diseases. Reportedly, plumbagin exerts its biological activities primarily through induction of reactive oxygen species and triggers osteoblast-mediated bone formation. It is plausible that plumbagin’s reciprocal actions – inhibiting or inducing death in osteoclasts but promoting survival or growth of osteoblasts – are a function of the synergy with bone-metabolizing hormones calcitonin, Parathormone and vitamin D. Herein, we develop a framework for plausible molecular modus operandi of plumbagin in bone metabolism.
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Aubin, Jane E., and Johan N. M. Heersche. "Osteoprogenitor cell differentiation to mature bone-forming osteoblasts." Drug Development Research 49, no. 3 (March 2000): 206–15. http://dx.doi.org/10.1002/(sici)1098-2299(200003)49:3<206::aid-ddr11>3.0.co;2-g.
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Yu, X., S. C. Hsieh, W. Bao, and D. T. Graves. "Temporal expression of PDGF receptors and PDGF regulatory effects on osteoblastic cells in mineralizing cultures." American Journal of Physiology-Cell Physiology 272, no. 5 (May 1, 1997): C1709—C1716. http://dx.doi.org/10.1152/ajpcell.1997.272.5.c1709.
Повний текст джерелаАнотація:
Platelet-derived growth factor (PDGF) is mitogenic and chemotactic for osteoblastic cells in vitro. It is expressed during osseous wound healing and stimulates formation of new bone in vivo. PDGF stimulates cells by binding to specific cell surface receptors. The purpose of this study was to examine the effects of PDGF on osteoblastic proliferation and differentiation in long-term mineralizing cultures. Utilizing Northern blot analysis, we found that continuous PDGF treatment increased histone expression, indicative of enhanced proliferation, but suppressed osteoblast differentiation, demonstrated by inhibition of alkaline phosphatase, type I collagen, and osteocalcin expression. The inhibitory effect of PDGF on the differentiated function of osteoblasts was further established by findings that PDGF significantly inhibited nodule formation. The expression of PDGF receptors varied at different stages of culture. PDGF receptor mRNA expression increased when the cells had achieved a mature phenotype, during the stage of matrix maturation, and then decreased. However, as demonstrated by thymidine incorporation assays, the capacity of PDGF to stimulate DNA synthesis actually decreased during osteoblast maturation, as receptor expression increased. To investigate this apparent contradiction, tyrosyl phosphorylation and immunoblot assays were performed to assess changes in PDGF activation of their cognate receptors. The pattern of PDGF-induced tyrosyl phosphorylation remained relatively constant. This suggests that the diminished mitogenic activity of PDGF that occurs after osteoblast differentiation is regulated at a postreceptor level.
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Giuliani, Nicola, Francesca Morandi, Sara Tagliaferri, Mirca Lazzaretti, Sabrina Bonomini, Monica Crugnola, Daniela Petrò, Cristina Mancini, Eugenia Martella, and Vittorio Rizzoli. "The Proteasome Inhibitor Bortezomib Affects Osteoblastogenesis and Bone Formation In Vitro and In Vivo in Multiple Myeloma Patients." Blood 108, no. 11 (November 16, 2006): 508. http://dx.doi.org/10.1182/blood.v108.11.508.508.
Повний текст джерелаАнотація:
Abstract It is well established that osteoblast formation and function are profoundly impaired in multiple myeloma (MM) patients. Osteoblastic cells also regulate myeloma cell growth and increasing bone formation result in a reduction of tumoral burden in mice. Recent data suggest that ubiquitin-proteasome pathway, the major cellular degradative system and therapeutic target in myeloma cells, also regulates osteoblast differentiation. Further it has been demonstrated that different proteasome inhibitors may stimulate bone formation in mice. Finally, preliminary observations obtained in MM patients treated with the proteasome inhibitor Bortezomib show an increase of bone specific alkaline phosphatase in responder patients as compared to non-responder ones. Currently it is not know whether the proteasome inhibitor Bortezomib may have a direct effect on osteoblast and bone formation in vitro human cultures and in vivo in MM patients. To clarify this issue first we checked the effect of Bortezomib either on osteoblast differentiation and formation or on osteoblast proliferation, survival and function. In long-term human BM cultures we found that Bortezomib did not reduce the number of both early bone marrow (BM) osteoblast progenitors Colony Forming Unit-Fibroblast (CFU-F) and late ones Colony Forming Bone nodules (CFU-OB). On the other hand we found that Bortezomib (2–3 nM) significantly induced osteoblast phenotype in human mesenchymal cells incubated in presence of osteogenic factors. A stimulatory effect on osteoblast markers was observed after 24 hours of Bortezomib treatment. Consistently we found that Bortezomib significantly increased the activity of the transcription factor Runx2/Cbfa1 in human osteoblast progenitors without affecting the canonical WNT signaling pathway checked by the evaluation of nuclear and cytoplasmatic active beta-catenin levels. Using the human osteoblast like cells MG-63 and immortalized normal osteoblasts (HOBIT) we found that Bortezomib at concentration ranging between 2nM and 5nM did not inhibit osteoblast proliferation or induce osteoblast apoptosis. Similarly, Bortezomib did not affect the expression of osteoblast markers, Runx2/Cbfa1 activity and WNT signaling in both MG-63 and HOBIT cells. To extent our in vitro observation we have evaluated the potential effect of Bortezomib in vivo in MM patients. Bone histomorphometry as well as immunostainig for Runx2/Cbfa1 and beta-catenin was performed on BM biopsies obtained from 15 MM patients before and after 6–8 cycles of Bortezomib administrated in mono-therapy. A significant increase in the number of osteoblastic cells X mm2 of bone tissue and in the number of Runx2/Cbfa1 positive osteoblastic cells was observed only in responder patients showing an early increase of the serum alkaline phosphatase. In conclusion our data indicate that Bortezomib may increase osteoblast differentiation in human mesenchymal cells without affecting the proliferation, survival and function of mature osteoblasts. In vivo and in vitro observations support the hypothesis that both direct and indirect effects on bone formation process could occur during Bortezomib treatment.
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Geoffroy, Valérie, Michaela Kneissel, Brigitte Fournier, Alan Boyde, and Patrick Matthias. "High Bone Resorption in Adult Aging Transgenic Mice Overexpressing Cbfa1/Runx2 in Cells of the Osteoblastic Lineage." Molecular and Cellular Biology 22, no. 17 (September 1, 2002): 6222–33. http://dx.doi.org/10.1128/mcb.22.17.6222-6233.2002.
Повний текст джерелаАнотація:
ABSTRACT The runt family transcription factor core-binding factor α1 (Cbfa1) is essential for bone formation during development. Surprisingly, transgenic mice overexpressing Cbfa1 under the control of the 2.3-kb collagen type I promoter developed severe osteopenia that increased progressively with age and presented multiple fractures. Analysis of skeletally mature transgenic mice showed that osteoblast maturation was affected and that specifically in cortical bone, bone resorption as well as bone formation was increased, inducing high bone turnover rates and a decreased degree of mineralization. To understand the origin of the increased bone resorption, we developed bone marrow stromal cell cultures and reciprocal coculture of primary osteoblasts and spleen cells from wild-type or transgenic mice. We showed that transgenic cells of the osteoblastic lineage induced an increased number of tartrate-resistant acid phosphatase-positive multinucleated cells, suggesting that primary osteoblasts as well as bone marrow stromal cells from transgenic mice have stronger osteoclastogenic properties than cells derived from wild-type animals. We investigated the candidate genes whose altered expression could trigger this increase in bone resorption, and we found that the expression of receptor activator of NF-κB ligand (RANKL) and collagenase 3, two factors involved in bone formation-resorption coupling, was markedly increased in transgenic cells. Our data thus suggest that overexpression of Cbfa1 in cells of the osteoblastic lineage does not necessarily induce a substantial increase in bone formation in the adult skeleton but has a positive effect on osteoclast differentiation in vitro and can also dramatically enhance bone resorption in vivo, possibly through increased RANKL expression.
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Liu, Yan, Ramesh A. Bhat, Laura M. Seestaller-Wehr, Shoichi Fukayama, Annamarie Mangine, Robert A. Moran, Barry S. Komm, Peter V. N. Bodine, and Julia Billiard. "The Orphan Receptor Tyrosine Kinase Ror2 Promotes Osteoblast Differentiation and Enhances ex Vivo Bone Formation." Molecular Endocrinology 21, no. 2 (February 1, 2007): 376–87. http://dx.doi.org/10.1210/me.2006-0342.
Повний текст джерелаАнотація:
Abstract Ror2 is a receptor tyrosine kinase, the expression of which increases during differentiation of pluripotent stem cells to osteoblasts and then declines as cells progress to osteocytes. To test whether Ror2 plays a role in osteoblastogenesis, we investigated the effects of Ror2 overexpression and down-regulation on osteoblastic lineage commitment and differentiation. Expression of Ror2 in pluripotent human mesenchymal stem cells (hMSCs) by adenoviral infection caused formation of mineralized extracellular matrix, which is the ultimate phenotype of an osteogenic tissue. Concomitantly, Ror2 over-expression inhibited adipogenic differentiation of hMSCs as monitored by lipid formation. Ror2 shifted hMSC fate toward osteoblastogenesis by inducing osteogenic transcription factor osterix and suppressing adipogenic transcription factors CCAAT/enhancer-binding protein α and peroxisome proliferator activated receptor γ. Infection with Ror2 virus also strongly promoted matrix mineralization in committed osteoblast-like MC3T3-E1 cells. Expression of Ror2 in a human preosteocytic cell line by stable transfection also promoted further differentiation, as judged by inhibited alkaline phosphatase activity, potentiated osteocalcin secretion, and increased cellular apoptosis. In contrast, down-regulation of Ror2 expression by short hairpin RNA essentially abrogated dexamethasone-induced mineralization of hMSCs. Furthermore, down-regulation of Ror2 expression in fully differentiated SaOS-2 osteosarcoma cells inhibited alkaline phosphatase activity. We conclude that Ror2 initiates commitment of MSCs to osteoblastic lineage and promotes differentiation at early and late stages of osteoblastogenesis. Finally, using a mouse calvariae ex vivo organ culture model, we demonstrate that these effects of Ror2 result in increased bone formation, suggesting that it may also activate mature osteoblasts.
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Kato, Hiroshi, Hiromi Ochiai-Shino, Shoko Onodera, Akiko Saito, Takahiko Shibahara, and Toshifumi Azuma. "Promoting effect of 1,25(OH) 2 vitamin D 3 in osteogenic differentiation from induced pluripotent stem cells to osteocyte-like cells." Open Biology 5, no. 2 (February 2015): 140201. http://dx.doi.org/10.1098/rsob.140201.
Повний текст джерелаАнотація:
We recently reported a new method to purify the induced pluripotent stem (iPS)-derived osteoprogenitors (iPSop). In this paper, we optimized the procedure and characterized cells at each process step. We observed that 10 days of treatment with FGF-2, IGF-1 and TGF-β (FIT) resulted in early-phase osteoblasts and 14 days of treatment resulted in late-phase osteoblasts. We found that treatment with 1,25(OH) 2 vitamin D 3 increased expression of osteocalcin and decreased expression of tissue-non-specific alkaline phosphatase and runt-related transcription factor 2 (RUNX2) in iPSop-day14 cells (cells treated with FIT for 14 days). Therefore, iPSop-day14 cells were promoted to mature osteoblasts by 1,25(OH) 2 vitamin D 3 treatment. In addition, we found that 1,25(OH) 2 vitamin D 3 treatment for 14 days enhanced not only mineralization but also expression of osteocyte markers, including dentin matrix protein-1 and fibroblast growth factor-23, in iPSop cells. Therefore, 1,25(OH) 2 vitamin D 3 is a potent promoter of osteoblast–osteocyte transition. The results of this study suggest that it is possible to evaluate both early- and late-phase osteoblasts and to apply cells to drug screening for anabolic drugs that stimulate bone formation.
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Hassan, Mohammad Q., Amjad Javed, Maria I. Morasso, Jeremy Karlin, Martin Montecino, Andre J. van Wijnen, Gary S. Stein, Janet L. Stein, and Jane B. Lian. "Dlx3 Transcriptional Regulation of Osteoblast Differentiation: Temporal Recruitment of Msx2, Dlx3, and Dlx5 Homeodomain Proteins to Chromatin of the Osteocalcin Gene." Molecular and Cellular Biology 24, no. 20 (October 15, 2004): 9248–61. http://dx.doi.org/10.1128/mcb.24.20.9248-9261.2004.
Повний текст джерелаАнотація:
ABSTRACT Genetic studies show that Msx2 and Dlx5 homeodomain (HD) proteins support skeletal development, but null mutation of the closely related Dlx3 gene results in early embryonic lethality. Here we find that expression of Dlx3 in the mouse embryo is associated with new bone formation and regulation of osteoblast differentiation. Dlx3 is expressed in osteoblasts, and overexpression of Dlx3 in osteoprogenitor cells promotes, while specific knock-down of Dlx3 by RNA interference inhibits, induction of osteogenic markers. We characterized gene regulation by Dlx3 in relation to that of Msx2 and Dlx5 during osteoblast differentiation. Chromatin immunoprecipitation assays revealed a molecular switch in HD protein association with the bone-specific osteocalcin (OC) gene. The transcriptionally repressed OC gene was occupied by Msx2 in proliferating osteoblasts, while Dlx3, Dlx5, and Runx2 were recruited postproliferatively to initiate transcription. Dlx5 occupancy increased over Dlx3 in mature osteoblasts at the mineralization stage of differentiation, coincident with increased RNA polymerase II occupancy. Dlx3 protein-DNA interactions stimulated OC promoter activity, while Dlx3-Runx2 protein-protein interaction reduced Runx2-mediated transcription. Deletion analysis showed that the Dlx3 interacting domain of Runx2 is from amino acids 376 to 432, which also include the transcriptionally active subnuclear targeting sequence (376 to 432). Thus, we provide cellular and molecular evidence for Dlx3 in regulating osteoprogenitor cell differentiation and for both positive and negative regulation of gene transcription. We propose that multiple HD proteins in osteoblasts constitute a regulatory network that mediates development of the bone phenotype through the sequential association of distinct HD proteins with promoter regulatory elements.
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Evans, Jodi F., James K. Yeh, and John F. Aloia. "Osteoblast-like cells of the hypophysectomized rat: a model of aberrant osteoblast development." American Journal of Physiology-Endocrinology and Metabolism 278, no. 5 (May 1, 2000): E832—E838. http://dx.doi.org/10.1152/ajpendo.2000.278.5.e832.
Повний текст джерелаАнотація:
In a previous work, we demonstrated that the osteoprogenitors derived from the marrow stroma of the hypophysectomized (HX) rat demonstrate enhanced proliferative and differentiation capacities when placed in an optimal microenvironment. In this study, we sought to investigate the potential of the trabecular osteoblast-like cells of the HX rat. These cells represent a more mature pool of osteoblasts than the progenitors derived from the marrow stroma. We examined all three stages of osteoblast development using trabecular osteoblast-like cells derived from age-matched intact rats as a control. Using thymidine incorporation and cell number as indicators of proliferation, we found that these cells, like the osteoprogenitors derived from the HX rat, demonstrate augmented proliferation when placed in culture. Additionally, type I collagen expression remained at significant levels past the end stages of proliferation, at which point it is expected to be downregulated. Matrix maturation markers, such as alkaline phosphatase activity and bone sialoprotein expression, however, were significantly lower than in the controls. Mineralization potential, as measured by mineralized nodule formation, Ca2+ content, and OPN and OCN expression, was also significantly reduced. Our results have uncovered an aberrant model of osteoblast development in which proliferation is deregulated, resulting in a minimal capacity of these cells to develop into fully differentiated mineralizing osteoblasts.
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Qin, Xin, Qing Jiang, Kenichi Nagano, Takeshi Moriishi, Toshihiro Miyazaki, Hisato Komori, Kosei Ito, et al. "Runx2 is essential for the transdifferentiation of chondrocytes into osteoblasts." PLOS Genetics 16, no. 11 (November 30, 2020): e1009169. http://dx.doi.org/10.1371/journal.pgen.1009169.
Повний текст джерелаАнотація:
Chondrocytes proliferate and mature into hypertrophic chondrocytes. Vascular invasion into the cartilage occurs in the terminal hypertrophic chondrocyte layer, and terminal hypertrophic chondrocytes die by apoptosis or transdifferentiate into osteoblasts. Runx2 is essential for osteoblast differentiation and chondrocyte maturation. Runx2-deficient mice are composed of cartilaginous skeletons and lack the vascular invasion into the cartilage. However, the requirement of Runx2 in the vascular invasion into the cartilage, mechanism of chondrocyte transdifferentiation to osteoblasts, and its significance in bone development remain to be elucidated. To investigate these points, we generated Runx2fl/flCre mice, in which Runx2 was deleted in hypertrophic chondrocytes using Col10a1 Cre. Vascular invasion into the cartilage was similarly observed in Runx2fl/fl and Runx2fl/flCre mice. Vegfa expression was reduced in the terminal hypertrophic chondrocytes in Runx2fl/flCre mice, but Vegfa was strongly expressed in osteoblasts in the bone collar, suggesting that Vegfa expression in bone collar osteoblasts is sufficient for vascular invasion into the cartilage. The apoptosis of terminal hypertrophic chondrocytes was increased and their transdifferentiation was interrupted in Runx2fl/flCre mice, leading to lack of primary spongiosa and osteoblasts in the region at E16.5. The osteoblasts appeared in this region at E17.5 in the absence of transdifferentiation, and the number of osteoblasts and the formation of primary spongiosa, but not secondary spongiosa, reached to levels similar those in Runx2fl/fl mice at birth. The bone structure and volume and all bone histomophometric parameters were similar between Runx2fl/fl and Runx2fl/flCre mice after 6 weeks of age. These findings indicate that Runx2 expression in terminal hypertrophic chondrocytes is not required for vascular invasion into the cartilage, but is for their survival and transdifferentiation into osteoblasts, and that the transdifferentiation is necessary for trabecular bone formation in embryonic and neonatal stages, but not for acquiring normal bone structure and volume in young and adult mice.
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Kim, Nacksung, Masamichi Takami, Jaerang Rho, Regis Josien, and Yongwon Choi. "A Novel Member of the Leukocyte Receptor Complex Regulates Osteoclast Differentiation." Journal of Experimental Medicine 195, no. 2 (January 14, 2002): 201–9. http://dx.doi.org/10.1084/jem.20011681.
Повний текст джерелаАнотація:
Osteoclasts (OCs) are multinucleated cells that resorb bone and are essential for bone homeostasis. They develop from hematopoietic cells of the myelomonocytic lineage. OC formation requires cell-to-cell interactions with osteoblasts and can be achieved by coculturing bone marrow precursor cells with osteoblasts/stromal cells. Two of the key factors mediating the osteoblast-induced osteoclastogenesis are macrophage–colony stimulating factor (M-CSF) and the tumor necrosis factor (TNF) family member TNF–related activation-induced cytokine (TRANCE) that are produced by osteoblasts/stromal cells in response to various bone resorbing hormones. In addition, other factors produced by osteoblasts/stromal cells further influence osteoclastogenesis. Here we report the identification and characterization of OC-associated receptor (OSCAR), a novel member of the leukocyte receptor complex (LRC)-encoded family expressed specifically in OCs. Genes in the LRC produce immunoglobulin (Ig)-like surface receptors and play critical roles in the regulation of both innate and adaptive immune responses. Different from the previously characterized members of the LRC complex, OSCAR expression is detected specifically in preosteoclasts or mature OCs. Its putative–ligand (OSCAR-L) is expressed primarily in osteoblasts/stromal cells. Moreover, addition of a soluble form of OSCAR in coculture with osteoblasts inhibits the formation of OCs from bone marrow precursor cells in the presence of bone-resorbing factors, indicating that OSCAR may be an important bone-specific regulator of OC differentiation. In addition, this study suggests that LRC-encoded genes may have evolved to regulate the physiology of cells beyond those of the immune system.
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Zouani, Omar F., Lila Rami, Yifeng Lei, and Marie-Christine Durrieu. "Insights into the osteoblast precursor differentiation towards mature osteoblasts induced by continuous BMP-2 signaling." Biology Open 2, no. 9 (July 12, 2013): 872–81. http://dx.doi.org/10.1242/bio.20134986.
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