Dissertations / Theses on the topic 'Stem growth'
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1
Amarachintha, Surya P. "Optimal Growth Conditions for Tracheal Epithelial Stem Cells." Bowling Green State University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1187395530.
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Ringstedt, Thomas. "Neurotrophins during development : overexpression in neural stem cells /." Stockholm, 1998. http://diss.kib.ki.se/search/diss.se.cfm?19980605ring.
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Culme-Seymour, E. J. "Engineering the growth substrate for embryonic stem cell processing." Thesis, University College London (University of London), 2010. http://discovery.ucl.ac.uk/20449/.
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Embryonic stem cells (ESCs) are pluripotent cells that represent a potentially unlimited supply of specialised cells for drug testing and cell therapy. However, a more robust, reproducible and efficient process is required for successful expansion and differentiation of these cells. One variable that exhibits a large effect on ESC culture is the growth substrate. Modifications to the currently accepted standard culture system have been made and a novel feeder layer system for human (h) ESC maintenance has been created in the research presented here. Standard hESC culture involves maintenance on supportive feeder layers of mitotically inactivated mouse embryonic fibroblasts (mEFs). The presence of these cocultured cells in pluripotent hESC cultures and during differentiation does pose technical challenges to large-scale production, thus there is a need for biphasic scalable coculture systems. Here, alginate modified with the RGD peptide sequence (commonly utilised for stimulated cell adhesion onto synthetic surfaces) has been used to immobilise mEFs into a biphasic culture system as a possible replacement to the traditional feeder layer. Analysis of proliferation, viability and ECM production of mEFs within alginate is described in this project, as well as results from both short- and long-term maintenance of hESCs on the modified layer. Apart from the choice of substrate, there are other variables within the culture system that affect ESC growth and lineage specification. Upon characterisation of the Young’s modulus (E) of an elastically tuneable glutaraldehyde cross-linked gelatin culture system, mouse (m) ESCs have been cultured on surfaces exhibiting varying degrees of stiffness. Investigations into the effect of E on the expression of pluripotency markers, regulation of spontaneous differentiation and efficiency of directed neuronal differentiation have been carried out. The results strongly suggest that adequate control of E may be critical in order to increase the yield of stem cell bioprocesses.
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Anilkumar, Thapasimuthu Vijayamma. "The pathobiology of hepatic stem cells (oval cells)." Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244072.
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Yeoh, Joyce Siew Gaik. "Regulatory role of fibroblast growth factors on hematopoietic stem cells." [S.l. : [Groningen : s.n.] ; University Library Groningen] [Host], 2007. http://irs.ub.rug.nl/ppn/299000842.
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Houlihan, Diarmaid Dominic. "Growth factors direct mesenchymal stem cell fate and therapeutic potential." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/5551/.
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Murine mesenchymal stem cells (MSCs) isolated by plastic adherence contain contaminating cells and have poor growth and differentiation. I report a detailed protocol outlining the steps to prospectively isolate a pure and potent MSC population from murine bone marrow based on their expression of stem cell antigen-1 (Sca-1) and platelet derived growth factor- alpha (PDGFRα) (PαS cells) using flow cytometry. PαS MSCs have augmented growth potential and robust tri-lineage differentiation compared to plastic adherent cells. They exert potent immunosuppressive effects on proliferating naive CD4+ T cells, which is mediated via the production of nitric oxide (NO). Nevertheless, prolonged culture results in cellular senescence, loss of adipogenic differentiation and reduced immunosuppressive properties. Addition of growth factors to standard media (SM) produced significant genotypic and phenotypic changes. Cells cultured in SM supplemented with basic fibroblast growth factor (bFGF) and platelet derived growth factor-BB (PDGF-BB) were primed towards fat and cartilage, but had reduced immunosuppressive potential. In contrast, cells cultured with transforming growth factor-beta (TGF-β) had reduced tri-lineage potential but potent immunosuppressive properties that endured despite long term culture. I demonstrate using novel tissue engineering techniques that bFGF PαS MSCs generate substantial 3-D cartilage pellets. These data have implications for MSC therapy in humans.
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Jennings, Adam Edward. "Control of growth and differentiation of human liver stem cells." Thesis, University of Birmingham, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.403607.
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Ham, Trevor Richard. "Covalent Growth Factor Tethering to Guide Neural Stem Cell Behavior." University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1555347467862553.
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Benjamin, Corey Antonio. "Growth Factors and Chondrogenic Differentiation of Adipose-Derived Stem Cells." Thesis, The University of Arizona, 2015. http://hdl.handle.net/10150/578983.
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Osteoarthritis is the result of the breakdown of articular cartilage, which often begins
with a traumatic injury to the joint. The loss of cartilage leads to joint pain, stiffness, and reduced
physical mobility and activity. Although joint replacement with artificial joints is currently the
standard of care for osteoarthritis, there are drawbacks that limit the types of activity the patient
can be involved in after surgery and other side effects that can lead to failure of the artificial
joint. Infection following surgery, loss of proprioception (the ability to know where the joint is in
space), and the possibility of a failure of parts of the synthetic joint that requires additional
surgeries are all risks that this treatment presents.One possible alternative to total joint replacement is tissue engineering that can be used
to regenerate the damaged joint. Stem cells that are differentiated into cartilage cells and reintroduced
into the area or areas with cartilage defects will form cartilage tissue. The conversion
of stem cells into cartilage cells (chondrocytes) can be induced through the use of growth factors,
including TGF-β3, TGF-β1, BMP-2, and BMP-6. [4, 10] The differentiation of stem cells into
chondrocytes will be examined with each growth factor separately as well as in combination.
Safranin-O staining results will be compared to determine which growth factor or combination of
growth factors most effectively converts stem cells into chondrocytes.
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Neumann, John A. P. "Variability in the relationship between leaf area and selected stem measures in Douglas fir." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/28819.
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Variability in the relationship between tree leaf area (TLA) and selected stem measurements was examined in three Douglas-fir stands (Pseudotsuga menziesii (Mirb.) Franco, var. menziesii) that were less than 50 years-old, spaced to approximately 550 to 650 stems/ha, and differed in soil moisture and nutrients. Attention was given to the effect of mean annual ring width (MARW), cross-sectional area of the live bark (ALB - a surrogate measure of relative nutrient storage in the stem), and cross-sectional area of the most recent annual rings equal in number to the number of whorls in the live crown (ALC), on variability in the relationship between TLA and cross-sectional area of sapwood (ASW).
At breast height, basal area, ASW, and cross-sectional area of sapwood plus live bark (ASWLB) were not linearly related to TLA, and linear regression equations using log transformed variables varied significantly between sites. Nonlinear regression equation for ASW at breast height was: TLA = 0.064ASẆ¹•³³ (I² = 0.856). Including D (the distance between breast height and the center of the live crown) in the nonlinear equation, did not significantly improve the regression.
Tree leaf area prediction models using stem measures from the base of live crown (blc) had higher adjusted R² values than models using stem measures from breast height.
At the blc, basal area, ASW, and ASWLB were linearly related to TLA (adjusted R² = 0.926, 0.908, and 0.934, respectively).
Multiplying ASW by MARW did not improve the fit of the regression models. Multiplying ASW by ALB improved the linearity of the relationship of ASW at breast height to TLA. The best fitting TLA model overall used the product of ASW at blc and ALB at blc as the independent variable (adjusted R² = 0.967).
The results indicate that research into the allometric relationship of TLA to stem measures should give consideration to more than hydraulic measures and include measures of bark function. At breast height and the blc, the independent variable ALC was linearly related to tree leaf area and had higher adjusted R² values than did ASW. In most trees the ALC stem measure was found to include a portion of heartwood area. The strong relationship between TLA and ALC suggests that a given transpiring leaf mass or area is related to a proportional amount of conducting stemwood and physical support stemwood.
A quick alternative approach for estimating individual tree leaf area using photographs taken at fixed distance and angle from the target tree did not result in a reliable tree leaf area prediction technique. The difficulty of obtaining views of the tree crown which were not obstructed by adjacent tree crowns was the major obstacle. Using a fixed distance and camera angle was a problem because of variable
tree heights. However, altering these fixed positions introduced additional variation into the tree leaf area estimation.
Mean specific leaf area (SLA) varied significantly by site, needle age class, and crown position. Mean SLA per needle age class per branch can be predicted with 95% confidence and a 10% allowable error using six 10-needle samples.Forestry, Faculty of
Graduate
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Jia, Dan. "Roles of growth hormone in liver growth and mesenchymal stem cell myogenic and adipogenic lineage commitment." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/23924.
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Growth hormone (GH) has growth-stimulating effects on skeletal muscle and liver but a growth-inhibitory effect on adipose tissue. The mechanisms underlying these actions of GH are not fully understood. Two studies were conducted to achieve the following objectives: 1) to determine the cellular mechanism by which GH stimulates liver growth; 2) to determine the effects of GH on the commitment of mesenchymal stem cells (MSCs) to myogenic and adipogenic lineages. In the first study, the GH-deficient lit/lit male mice were injected (s.c.) daily with rbGH or vehicle for two weeks. GH-injected lit/lit mice tended to have a greater liver/body weight percentage than lit/lit control mice. GH injection did not alter the percentage of proliferating cells in the liver. However, GH-injected lit/lit mice had 18% larger hepatocytes and 16% less DNA per unit liver weight than those of lit/lit control mice. These data together indicate that GH stimulates liver growth in mice by increasing the size, not by increasing the number of hepatocytes. In the second study, we treated the MSC cell line C3H10T1/2 cells with or without 5'-azacytidine and rbGH for 4 days. We assessed the myogenic or adipogenic potential by determining the ability of these cells to differentiate into myotubes or adipocytes, respectively. C3H10T1/2 cells treated with 5'-azacytidine and GH formed more myotubes, myoblasts, and fewer adipocytes compared to cells treated with 5'-azacytidine alone. Taken together, these results suggest that GH enhances 5'-azacytidine-induced myogenic commitment but inhibits 5'-azacytidine-induced adipogenic commitment in C3H10T1/2 cells.Master of Science
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Ebong, Ima Mbodie. "Three-dimensional Extracellular Matrix Hydrogel Environments for Embryonic Stem Cell Growth." Thesis, Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16172.
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Embryonic stem cells (ESCs) are pluripotent cells derived from the inner cell mass of the blastocyst that can give rise to cells of the ectoderm, endoderm and mesoderm lineages. Once isolated from the blastocyst, ESCs can be cultured indefinitely in vitro in an undifferentiated state or can be induced to differentiate. In the case of mouse ESCs (mESCs), the cytokine leukemia inhibitory factor (LIF) is added to culture media to maintain pluripotency and is removed to induce differentiation. Although it is known that extracellular matrix (ECM) components influence stem cell maintenance, proliferation and differentiation, the precise effects of ECM environments on embryonic stem cell behavior have not been systematically studied. The main purpose of this thesis project was to investigate the behavior of undifferentiated mESCs cultured in different 3D hydrogel matrices and to determine whether viscoelastic and biochemical variations in the matrices differentially affect the ability of stem cells to self-renew; that is, retain their pluripotency or undifferentiated phenotype. Their behavior in 3D environments was compared to mESC behavior in traditional 2D culture. In addition, a new method of casting hydrogels in polydimethylsiloxane (PDMS) molds was developed in order to efficiently cast multiple hydrogels of varying sizes and shapes.
The findings of this thesis project will benefit both the scientific and engineering community as it encourages researchers to re-evaluate the quality of standard 2D embryonic stem cell culture methods versus potentially novel and advantageous 3D hydrogel culture methods.
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Murray, Helen. "Role of Grb2 in growth and differentiation of embryonic stem cells." Thesis, University of Edinburgh, 2011. http://hdl.handle.net/1842/5894.
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Embryonic stem (ES) cells are derived from the inner cell mass of the blastocyst stage embryo. They exhibit unlimited proliferation in culture and have the ability to differentiate into all three germ layers of the developing organism, a property defined as pluripotency. Previously it was reported that growth factor-bound protein 2 (Grb2) is required for differentiation of the epiblast, the embryonic tissue that harbours the pluripotent founder cells of the foetus. GRB2 is an adapter protein involved in the activation of the mitogen-activated protein kinase (MAPK) pathway in response to extracellular signals. It has also been implicated in the activation of the phosphoinositol-3-kinase (PI3K) pathway in response to fibroblast growth factor (FGF) signaling. The work presented in this thesis examines the role of Grb2 in ES cells and describes previously unreported contributions of this adaptor protein in regulating ES cell growth and differentiation. It has been previously been shown by others that Grb2 deficient (Grb2-/-) cells grow relatively normally in ES growth medium containing serum. However, in serum free conditions (N2B27 medium) in this project, proliferation of Grb2-/- cells is reduced compared with wild type and “restored” Grb2-/- cells stably expressing a Grb2 cDNA mini gene. Under serum free conditions, Grb2-/- cells grow in tight, refractive colonies. Nanog expression was uniformly upregulated, in contrast to the heterogeneous pattern reported in serum-based medium. Colony expansion on the substratum appears to be compromised, although there is no apparent defect in the initial attachment of Grb2-/- cells. Cell cycle analysis indicates that the slower growth of Grb2-/- cells in serum free medium could be due to lengthening of the G1 phase of the ES cell cycle. In an attempt to identify the signalling deficiency responsible for the growth defect of Grb2-/- cells, MAPK activation was restored by two methods, PMA a ligand that bypasses the requirement for Grb2, and Raf-ER, a conditionally regulated component of the MAPK pathway that acts downstream of Grb2 in the MAPK pathway. Although both approaches increased MAPK signalling they were unable to rescue the growth defect. This suggests that MAPK is not required or alone is not sufficient. Inhibition of Glycogen synthase kinase 3 β (GSK3 β ) is known to augment growth of ES cells under MAPK inhibition. Surprisingly, GSK3 β inhibition did not enhance Grb2-/- cell growth. Under GSK3 β inhibition, Grb2-/- ES cells fail to thrive. It is hypothesised that under these conditions cells undergo hyper-self-renewal at the cost of growth. Grb2-/- ES cells are reported to exhibit limited differentiation potential. To examine the potency of Grb2-/- cells, these cells were subjected to embryoid body (EB) and monolayer differentiation. Analysis of EBs showed a loss of Gata4, Gata6 and endoderm marker gene expression. However, markers of ectoderm (Sox1, Pax6, MAP2), the late epiblast/nascent mesoderm (Brachyury) and markers associated with gastrulation (Twist and Snail) were expressed. Outgrowths of morphologically and immunohistochemically identifiable neuronal cells confirmed differentiation of ectodermal cell types, indicating Grb2 is not required for neuronal differentiation. However, beating cardiomyocytes could not be identified in Grb2-/- EBs, though readily found in restored Grb2-/- cells expressing the Grb2 cDNA. This suggests that there is an essential role for Grb2 in the mesoderm/cardiomyocyte differentiation pathway. This may be due to a defect in GATA factor expression since these factors are essential for cardiogenesis. In serum-free monolayer differentiation, Grb2-/- cells formed neuronal cells. Additional inhibition of the MAPK pathway using a small chemical inhibitor failed to prevent this differentiation. However, biochemical analysis of the cells indicates that this occurs when ERK activation is very low, indicating differentiation was not MAPK-independent. Grb2 mediates FGF-MAPK induced exit from the naïve ground state. These data suggest a Grb2-independent pathway can also facilitate this transition. Grb2 is dispensable for differentiation in to some lineages. However as differentiation of Grb2-/- ES cells is restricted, this indicates Grb2 is required for true pluripotency.
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Mooney, Ciarán James. "Expression of growth factor receptors by haematopoietic stem and progenitor cells." Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7332/.
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The mechanisms that govern the lineage commitment of haematopoietic stem and progenitor cells (HSPCs) have been a topic of debate since the 1960s. Two models of lineage commitment have been described; a permissive model, in which haematopoietic growth factors (HGFs) stimulate proliferation and survival of distinct HSPC subpopulations to permit stochastic lineage-specification, and a deterministic model, which proposes that HGFs instruct HSPCs to differentiate towards a specific cell lineage. To provide further insight into whether HGFs provide instructive cues or act in a selective manner, this study has investigated the expression of fms-like tyrosine kinase 3 (Flt3), and the receptors for erythropoietin (EpoR) and macrophage-colony stimulating factor (M-CSFR) by single HSPCs within the bone marrow. Using single-cell qRT-PCR and flow cytometry, a large number of novel HSPC subpopulations have been identified based on receptor expression. Importantly, multiplex analysis of protein and mRNA expression revealed that the above receptors are rarely co-expressed during the early stages of haematopoiesis. Furthermore, Flt3 expression was identified within the haematopoietic stem cell compartment and in vitro analysis demonstrated that Flt3 ligand primarily acts on a subpopulation of downstream progenitors. These findings suggest that Flt3, EpoR and M-CSFR differentially regulate distinct early HSPC subpopulations.
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Tan, Hiang Boon. "Systemic stimulation of mesenchymal stem cell and growth factors following trauma." Thesis, University of Leeds, 2013. http://etheses.whiterose.ac.uk/4968/.
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Bone healing following trauma is known to be associated with an early increase in serum concentrations of several pro-inflammatory and angiogenic growth factors. However, the temporal pattern of growth factors (GFs) involved in bone formation and their relationship with trauma severity has not been explored. Furthermore, to what extent osteogenic progenitors, including mesenchymal stem cells (MSCs) are ‘mobilized’ following trauma is unknown. This study investigated the systemic levels of four GFs (PDGF-AA, TGF-β2, follistatin and angiogenin) over the first two weeks following trauma in three groups of patients with increasing severity (Isolated trauma (n=15), Polytrauma (n=15), and Head injury (n=14)) and compared to Healthy Controls (n=9). The dynamics of GF release measured by ELISA was correlated with clinical and biochemical inflammatory parameters and the healing outcome assessed by clinical and radiological parameters as well as requirement of surgical re-interventions. Potential MSC mobilization from their iliac crest bone marrow (ICBMA) niches into peripheral circulation was measured by standard colony-forming assay-fibroblast, at least twice following trauma. Further correlations were sought with circulating levels of platelets, PDFG-BB and PDGF-AA. Growth factors described as anabolic for bone (PDGF-AA and angiogenin) had an initial suppression following trauma (50% and 80% by day 1, respectively), whereas inhibitory GF follistatin was upregulated compared to control (1.5-fold by day 1). This effect was more pronounced with increasing trauma severity. The variability of TGF-β2 was too high to allow differences between trauma groups to be detected. The dynamics of all GFs were not correlated with the inflammatory state of the patients, assessed both clinically (Systemic Inflammatory Response Syndrome score) and biochemically (total white cell count, C-reactive protein and platelet levels). However, there was a significant correlation between levels of time-matched PDGF-AA and platelets (p<0.01, r=+0.61), independent of trauma severity. A marked suppression of TGF-β2 throughout the time course which reached statistical significance in the first week following trauma (5-fold, p<0.05) was observed in patients identified as ‘poor healers’; the same group additionally displayed an altered dynamics of follistatin release compared to patients who healed normally. The numbers of ICBMA MSCs were dynamic over time in the same patient, but did not correlate with trauma severity or patients’ inflammatory state. Instead, significant correlations were observed between the changes in ICBMA MSC numbers and changes the levels of PDGF-AA (p<0.01, r=+0.55), and PDGF-BB (p=0.03, r=+0.38) and circulating platelets (p=0.02, r=+0.44). No MSCs were found in patients’ peripheral blood at any time point studied. These data indicated that measuring GFs implicated in BMP signalling pathway may lead to the discovery of novel biomarkers of fracture non union. Measuring patient’s inflammatory response following fracture did not correlate with the release of growth factors studied suggesting that these phenomena were independent. Limited MSC mobilization in the bone marrow (but not into PB) did take place but appeared to be related to platelet counts and a possible release of PDGF-AA and PDGF-BB GFs, which are known to be mitogenic for MSCs. It was not linked to trauma severity or predictive of the healing outcome. Further research is needed to investigate the predictive value of TGF-β2 and follistatin in a larger cohort of patients. Whilst this is the first study showing a ‘dynamic’ nature of the MSC pool in human BM, further work should determine whether the influence of platelets is due to enhanced MSC migration or their proliferation in situ.
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Woodhouse, Samuel. "The role of Ezh2 in adult muscle stem cell fate." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610201.
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Murphy, Megan K. "Fibrin microthreads promote stem cell growth for localized delivery in regenerative therapy." Worcester, Mass. : Worcester Polytechnic Institute, 2008. http://www.wpi.edu/Pubs/ETD/Available/etd-090208-143505/.
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Li, Jing. "Effects of intrinsic & extrinsic factors on the growth and differentiation of human mesenchymal stem cells." View the Table of Contents & Abstract, 2006. http://sunzi.lib.hku.hk/hkuto/record/B36434450.
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Chang, Su-Ping. "Growth and maintenance of the mouse adrenal cortex." Thesis, University of Edinburgh, 2008. http://hdl.handle.net/1842/4145.
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The adrenal cortex is classically divided into three morphologically and biochemically distinct zones, covered by a thin, cellular capsule. The adult adrenal cortex is a dynamic tissue in which distinct regions of cell proliferation, movement and death have been identified. Several models for stem cell maintenance of the adult adrenal cortex have been proposed, but adrenocortical stem cells have not yet been identified. Adrenal cortices of 21OH/LacZ transgenic mice show similar mosaic patterns of β-galactosidase staining to X- inactivation mosaics and LacZ ↔ wildtype chimeras. 21OH/LacZ mice provide a tool for lineage analysis, which may help to i) identify clones of cells produced by stem cells in the adult, ii) determine when stem cells begin to function and iii) evaluate different models of how stem cells maintain the adrenal cortex. Analysis of 21OH/LacZ transgenic adrenal cortices showed that the randomly orientated clusters of fetal patches change progressively during the perinatal period to adult radial stripes. Correlation of changes in mosaic patterns and the locations of cell proliferation suggests that the stripes arise by edge-biased growth during the perinatal growth period. Although stem cells may not be involved in the initial formation of stripes, it seems likely that stem cells later maintain the stripes by producing clones of cells that move centripetally to displace the earlier fetal patterns and later replace aging cells. Various combinations of BrdU labelling and chase periods demonstrated that most cell division occurred in the outer 40% of the adrenal cortex, confirmed that cells moved towards the medulla and identified a population of label-retaining cells near the capsule, which could include stem cells. (Stem cells have been recognised as BrdU label-retaining cells in other tissues because they divide less frequently than their daughter cells so dilute the incorporated BrdU more slowly.) Stripe patterns in adult 21OH/LacZ transgenic adrenal cortices were examined to try to distinguish between various models proposed for stem cell maintenance of the adrenal cortex. The observed continuous radial stripe pattern favours the general hypothesis that a single population of stem cells in the periphery maintains the entire adrenal cortex, although other explanations are possible. Quantitative analysis of adult stripe patterns did not show the reduction in stripe number that might be predicted if an age-related decline in adrenocortical stem cell function occurs, as may happen in some other tissues.
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McConkie, Thomas O. "Curious Growth of a Buried SiO2 Layer." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3755.
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Initial investigation of Moxtek wire grid polarizers composed of Al and coated with SiO2 - SiX - SiO2 (where SiX is used to indicate a Si rich layer whose complete composition is not to be disclosed for proprietary reasons) showed a growth of 3x in the inner (closest to Al) SiO2 layer after baking. Upon removing the X and varying rib composition and layering composition and geometries in 12 sets of before and after samples, no obvious growth was observed. Even baking the original unbaked sample yielded no growth. Our data suggest that the initial conclusion of buried oxide growth was flawed and that the observed changes in optical properties upon baking are either very sensitive to layer thicknesses (smaller than we can confidently observe) or due to some other mechanism. Here we present our sample preparation and analysis using the Focused Ion Beam (FIB), Scanning Transmission Electron Microscopy (STEM), and Energy Dispersive Xray Spectroscopy (EDXS).
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Poon, Chin-ho, and 潘展豪. "Pushing stem cells toward bone lineage through ultrasound stimulation." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B47849824.
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When human mesenchymal stem cells (hMSCs) are cultured inside a 3D collagen meshwork, they become a potential tissue engineering bone graft alternative. However, the in vitro osteogenesis rate of hMSCs is slow, leading to a low mineral deposition.
To enhance the osteogenic differentiation of hMSCs, low intensity pulsed ultrasound (LIPUS) was employed as an external stumulus. The present study demonstrated the feasibility of employing daily LIPUS exposure for enhancing osteogenesis in vitro. Exposure of seven consecutive days LIPUS, each of 30 minutes duration, did not affect the cell viability, and the organization of hMSCs within the collagen meshwork was not disturbed. The calcium deposition within the collagen meshwork was enhanced after seven days of exposure. The osteoinductivity was also upregulated at the early period of culture.
In order to optimizing the enhancement effects of LIPUS, various ultrasound parameters, including intensity, exposure duration and exposure repetition were investigated. Results showed the LIPUS enhancement effects are dose dependent, LIPUS exposure should be longer than 10 minutes/day in order to elicit a significant effect. Calcium deposition was higher when LIPUS exposure was done twice per day instead of one. Although individual variation exists, optimal LIPUS intensity range was between 60-120 mW/cm2 ISATA (Spatial Average Temporal Average Intensity).
The interaction mechanism between LIPUS and cells was also investigated. Microbubbles were added to the culture during LIPUS exposure to find out whether cavitation is involved in the interaction. Flow sensor primary cilium was also studied in order to verify that ultrasound is transduced through fluid flow. Results showed cavitation may not be a contributing factor to osteogenesis, and primary may be involved in the transduction of LIPUS stimulation.
This study demonstrated that osteogenesis of hMSCs encapsulated in collagen constructs could be enhanced by LIPUS. The LIPUS parameters were also optimized. The LIPUS interaction pathways were also being better understood. This thesis study will be a paradigm for cellular mechanotransduction studies and put an important step forward for therapeutic ultrasound.published_or_final_version
Electrical and Electronic Engineering
Master
Master of Philosophy
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Dause, Tyler. "Investigating Neural Stem and Progenitor Cell Intracrine Signaling." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1555618643450352.
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Chen, Ketian. "Regulation of Human Bone Marrow-Derived Stem Cells by Hepatocyte Growth Factor." Scholarly Repository, 2009. http://scholarlyrepository.miami.edu/oa_dissertations/334.
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Bone formation and remodeling require continuous generation of osteoprogenitors from bone marrow stromal cells (MSC), which are regulated by local growth factors and hormones with putative roles in mesenchymal proliferation and differentiation. Hepatocyte growth factor (HGF) and its receptor c-Met are widely expressed in MSC and are thought to play a key role in the interactions between cells. 1,25-dihydroxyvitamin D (1,25OHD) is the most active metabolite of vitamin D. 1,25OHD binds to its nuclear/membrane vitamin D receptor (VDR) and generates appropriate biological responses. The purpose of this study was to investigate the regulation of proliferation and differentiation by HGF in human bone marrow-derived stromal cells (hMSC). We examined the impact of HGF on hMSC cell-cycle regulation and the combination effects of HGF and 1,25OHD on hMSC osteogenic differentiation to enhance our knowledge of hMSC regulation. hMSC isolated from bone marrow were plated and grown in DMEM supplemented with 3% FBS incubated at 37C with 5% CO2 in air. HGF treatment of hMSCs reduced the rate of cell proliferation and this result was not due to apoptosis or cell senescence. Real-time RT-PCR and Western blot analysis showed increased gene and protein expression of the cell-cycle inhibitors p53, p21, and p27 after HGF treatment. These results appear to be specific because HGF did not significantly alter the gene expression level of other cell-cycle mediators such as RB, cyclin D1, CDK2, CDK4, or CDK6. Transfection of siRNA specific for cMet, the HGF receptor, eliminated the HGF anti-proliferation effect. cMet siRNA also eliminated the increase in p53, p21, and p27, further supporting a role for these cell-cycle inhibitors in HGF¡¯s regulation of hMSC. These results suggest that treatment of hMSC with HGF slows cell proliferation by increasing the expression of p53, p21, and p27. The reduced rate of cell proliferation did not appear to be due to cell differentiation, because treatment of hMSC with HGF alone did not induce cell differentiation. However, HGF in combination with a known osteogenic differentiation activator, 1,25OHD, significantly increased cell maturation/differentiation compared to 1,25D alone, as indicated by an increase in osteocalcin mRNA (a marker for osteogenic differentiation). Whereas HGF had no effect on 1,25OHD synthesis per se, HGF did induce 1,26OHD receptor (VDR) gene expression. HGF up-regulated the expression of the p63 gene, a member of the p53 family. Knocking down the p63 gene reduced the HGF effect on VDR expression and eliminated the HGF-induced up-regulation of the osteogenic differentiation markers osteopontin (OPN) and bone sialoprotein (BSP). Moreover, the ChIP assay shows that p63 was able to bind to the VDR promoter, possibly explaining the mechanism of p63-mediated VDR up-regulation. These results indicate that HGF can also induce hMSC osteogenic differentiation when combined with 1,25OHD by up-regulating 1,25OHD receptor VDR expression.
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Suresh, Shankar. "Growth factor priming of murine mesenchymal stem cells critically determines their functionality." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/5834/.
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Mesenchymal stem cells (MSCs) are a subset of multipotent cells with a variety of trophic and immunosuppressive functions. Isolation of murine MSCs has traditionally been hampered by the presence of contaminating cells in culture. In this study, I prospectively isolate murine MSCs based on the co-expression of platelet-derived growth factor (PDGF) receptor alpha and stem cell antigen‐1 (PαS MSCs) and present novel data regarding their in vitro phenotype, karyotype and immunomodulatory functions. However, PαS MSCs undergo senescence after extended culture, resulting in a loss of function. Addition of fibroblast growth factor 2 (FGF2), PDGF‐BB or transforming growth factor-beta 1 (TGF-β1) was able to overcome senescence in MSC cultures. These factors also ‘lineage primed’ MSCs down specific fates at the genetic and phenotypic levels, with un‐supplemented MSCs primed towards bone, FGF2 or PDGF‐BB supplemented cells primed towards fat, and FGF2 supplemented cells primed towards cartilage. TGF‐β1 supplementation attenuated tri‐lineage differentiation of PαS MSCs but maintained their immunosuppressive functions. These findings were confirmed in a mouse model of inflammatory liver injury, with late‐passage TGF‐β1 MSCs improving liver injury compared to controls. In summary, these results have significant translational relevance as I reveal that culture conditions can functionally ‘prime’ MSCs down specific fates.
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St, Laurent Daryl 1979. "Murine embryonic stem cells and hypoxia : growth kinetics, metabolism, and plating efficiency." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/28528.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Biological Engineering Division, 2004."June 2004."
Includes bibliographical references (p. 75-79).
There is reason to believe that embryonic stem cells would grow favorably in a hypoxic environment. These cells come from the pre-implantation embryo, whose native environment is the hypoxic mammalian reproductive tract. Growing stem cells in an environment with higher oxygen levels (i.e. the atmospheric oxygen levels that are normally used to cultivate stem cells) could be bad for the cells, as oxygen is toxic due to its powerful oxidative capacity. In this experiment, J1 murine embryonic stem cells were grown at 0%, 2%, 5%, 10%, and 20% oxygen by volume to assess the effects that lower oxygen levels have on stem cell growth, plating efficiency, and metabolism. Two reaction vessels were built so that the cells could be grown in a controlled environment. Premixed gas cylinders were used to flush the vessels and an optical probe was used to measure the headspace oxygen concentration. Cells were found to grow faster than atmospheric conditions when in a moderately hypoxic environment where the oxygen concentration was between 2% and 10%, and considerably slower than atmospheric conditions as the headspace oxygen concentration approached zero. Maximum cell density decreased, glucose-lactate yield increased, glucose-cell yield decreased, and glutamine-cell yield decreased as headspace oxygen decreased. There were no strong correlations between oxygen concentration and glutamine-ammonia yield or plating efficiency. From the results of this study, it appears that it may be preferable to grow murine embryonic stem cells in a moderately hypoxic environment around 10% oxygen to increase the growth rate while minimizing the maximum cell density and metabolic inefficiency compromises.
by Daryl St. Laurent.
M.Eng.
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Kelly, John. "Mathematical modelling of cancer growth and development : adhesion, stem cells and structure." Thesis, University of Dundee, 2014. https://discovery.dundee.ac.uk/en/studentTheses/94ea4aba-556e-4b08-a62e-a5000ce8bfe3.
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This thesis has investigated some of the intricacies of the growth and development of a solid tumour. Mathematical models and biological experimentation were used to gain a better understanding of the dual roles that the proto-oncogenic protein β-catenin has in adhesion and transcription, as well as its involvement in the epithelial-mesenchymal transition. Emphasis was placed on the spatial location of β-catenin within cells to determine what function it is performing. A model was also created to explore the hypothesis that multiple forms of β-catenin exist within cells to perform separate functions. The cancer stem cell hypothesis was explored in solid tumour growth, without necrosis and angiogenesis, by the use of a discrete, cell-based model created with the software package CompuCell3D. This was compared to a novel continuum model, which can be used to perform in silico experiments of solid tumours with a stem-progenitor-mature cell structure for a biologically relevant number of cells. Lastly, a cell-based model of a solid, vascularised tumour was created in CompuCell3D to investigate how an age- and size-structured population of cells can affect the overall growth of the tumour. This model was also used to show how the age structure of cells in a solid tumour can affect the efficacy of chemotherapeutic treatments.
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Logan, Suzanna J. "Optimization of Stem Cell Therapies for Coronary Collateral Growth in Cardiovascular Disease." NEOMED Integrated Pharmaceutical Medicine / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ne2mh1401096082.
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Collart, Dutilleul Pierre-Yves. "Dental pulp stem cells adhesion, growth and differentiation on porous silicon scaffolds." Thesis, Montpellier 1, 2013. http://www.theses.fr/2013MON12203/document.
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Le silicium poreux est un biomatériau prometteur pour l'ingénierie tissulaire car il est non toxique et biorésorbable. Des modifications de surface permettent de contrôler sa vitesse de dégradation et peuvent favoriser l'adhésion cellulaire. Les cellules souches de la pulpe dentaire (DPSC) sont des cellules souches mésenchymateuses retrouvées dans la pulpe dentaire, à l'intérieur des dents, et constituent une source accessible de cellules souches. Regrouper les capacités de prolifération et différenciation des DPSC avec les propriétés morphologiques et biochimiques du pSi représente une approche intéressante pour des applications thérapeutiques de médecine régénératrice. Dans cette thèse, nous avons étudié le comportement de DPSC humaines sur des supports de pSi, avec des pores variant de quelques nanomètres à plusieurs centaines de nanomètres. Nous avons travaillé sur différentes fonctionnalisations chimiques afin d'optimiser l'adhésion cellulaire et de stabiliser le matériau : oxydation thermique, silanisation et hydrosilylation. L'adhésion, la prolifération et la différenciation osseuse ont été évaluées par microscopie à fluorescence, microscopie électronique à balayage, activité enzymatique, tests de prolifération (activité mitotique), immunofluorescence et spectroscopie FTIR. Le pSi avec des pores de 30 à 40 nm de diamètre s'est révélé être le plus approprié pour l'adhésion, la prolifération cellulaire et la différenciation ostéoblastique. De plus, la structure nanométrique et le relargage d'acide silicique par le pSi a démontré un effet positif sur l'induction osseuse et la formation d'une matrice minéralisée. Le pSi est donc apparu comme un matériau prometteur pour l'adhésion de cellules souches mésenchymateuses, que ce soit pour une transplantation immédiate in vivo ou pour expansion et différenciation in vitroPorous silicon (pSi) is a promising biomaterial for tissue engineering as it is both non-toxic and bioresorbable. Moreover, surface modification can offer control over the degradation rate of pSi and can also promote cell adhesion. Dental pulp stem cells (DPSC) are mesenchymal stem cells found within the teeth and constitute a readily source of stem cells. Coupling the good proliferation and differentiation capacities of DPSC with the textural and chemical properties of the pSi substrates provides an interesting approach for therapeutic use. In this thesis, the behavior of human DPSC is analyzed on pSi substrates presenting pore of various sizes, from few to hundreds nanometers. We investigated different chemical surface treatments, in order to enhance cell adhesion and stabilize the material: thermal oxidation, silanization and hydrosilylation. DPSC adhesion, proliferation and further osteodifferentiation were followed for up to 3 weeks by fluorescence microscopy, scanning electron microscopy (SEM), enzymatic activity assay, BrdU assay for mitotic activity, immunostaining and FTIR spectroscopy. Porous Silicon with pore size ranging from 30 to 40 nm was found to offer the best adhesion, the fastest growth rate for DPSC and the highest osteoinductive effect. Moreover, the pSi nanostructure and the release of silicic acid had a positive effect on precursor cells osteodifferentiation and mineralized matrix formation. Porous silicon appeared to be an appropriate biomaterial for mesenchymal stem cells adhesion and immediate in vivo transplantation, or for long term in vitro culture, for stem cells proliferation and differentiation
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Stewart, Shelley Leigh. "Adipose-Derived Adult Stem Cells as Trophic Mediators of Tendon Regeneration." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/43702.
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The adipose-derived stromal vascular fraction (SVF) is a promising new therapy for equine flexor tendonitis. This heterogeneous population of cells may improve tendon healing via the production of growth and chemotactic factors capable of recruiting endogenous stem cells and increasing extracellular matrix production by tendon fibroblasts (TFBL). The purpose of this study was to evaluate the ability of adipose-derived cells (ADC) culture expanded from the SVF to act as trophic mediators in vitro. We hypothesized that ADCs would produce growth and chemotactic factors important in tendon healing and capable of inducing cell migration and matrix protein gene expression. Superficial digital flexor tendons and adipose tissue were harvested from eight adult horses and processed to obtain SVF cells, ADCs and TFBLs. Adipose-derived cells and TFBLs were grown in monolayer culture for growth factor quantification, to produce conditioned media for microchemotaxis, and in co-culture for quantification of matrix protein gene expression by TFBLs. Growth factor gene expression by SVF cells was significantly greater than in ADCs or TFBLs. Co-culture of TFBLs and ADCs resulted in modest up-regulation of matrix protein expression (collagen types I and III, decorin, and cartilage oligomeric matrix protein) by TFBLs. Media conditioned by ADCs induced ADC migration in a dose dependent manner. These findings support the role of both SVF and ADCs as trophic mediators in tendon regeneration. The differences detected in gene expression between SVF cells and ADCs indicate that additional studies are needed to evaluate the changes that occur during culture of these cells.Master of Science
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Zachos, Terri A. "Gene-augmented mesenchymal stem cells in bone repair." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1146076285.
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Gentry, Paula C. "Stem cell factor and c-kit in the ovine ovary /." free to MU campus, to others for purchase, 1996. http://wwwlib.umi.com/cr/mo/fullcit?p9713220.
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Abraham, Samuel D. M. "Activation of multiple hemopoietic growth factor genes in Abelson virus transformed myeloid cells." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/27786.
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The stringent requirement for hemopoietic growth factors (HGF) in the induction of hemopoiesis in vitro has raised questions as to their possible role(s) in leukemogenesis. Several recent clinical studies have shown aberrant cell growth factor gene activation in patient derived leukemic cells. Assessment of growth factor activity is often based on in vitro bioactivity assays of conditioned media or body fluids. The specificity of this type of endpoint is, however, open to question due to the overlap in biological activities of many HGFs.
In assessing the role of growth factor gene expression in a murine myeloid leukemia model I have used a sensitive RNA detection procedure coupled with a vector-probe system that enables the synthesis of uniformly labelled radioactive DNA probes to detect unambiguously the expression of particular growth factor genes. The Abelson murine leukemia virus (A-MuLV) derived myeloid transformants used in this study had previously been shown to produce a multi-lineage colony stimulating activity (CSA). While these A-MuLV transformants were shown to produce GM-CSF, it seemed likely that the multi-lineage CSA was due to another factor. In addition to confirming the expression of GM-CSF mRNA, I was able to show that the cells of all four A-MuLV transformed lines tested also expressed interleukin-3 mRNA. This finding was strongly corroborated by bio-activity data obtained using the CM from the A-MuLV myeloid transformants. Additional preliminary analysis by bioactivity assays have also shown the possible presence of interleukin-6 (IL-6) and a recently described pre-B cell factor suggesting perhaps a common mechanism underlying the activation of these various growth factor genes.Medicine, Faculty of
Medical Genetics, Department of
Graduate
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Nottingham, Wade. "Transcriptional regulation of Runx1 in the developing haematopoietic system." Thesis, University of Oxford, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.670091.
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Rickels, Heather Anne. "Predicting college readiness in STEM: a longitudinal study of Iowa students." Diss., University of Iowa, 2017. https://ir.uiowa.edu/etd/5612.
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The demand for STEM college graduates is increasing. However, recent studies show there are not enough STEM majors to fulfill this need. This deficiency can be partially attributed to a gender discrepancy in the number of female STEM graduates and to the high rate of attrition of STEM majors. As STEM attrition has been associated with students being unprepared for STEM coursework, it is important to understand how STEM graduates change in achievement levels from middle school through high school and to have accurate readiness indicators for first-year STEM coursework. This study aimed to address these issues by comparing the achievement growth of STEM majors to non-STEM majors by gender in Science, Math, and Reading from Grade 6 to Grade 11 through latent growth models (LGMs). Then STEM Readiness Benchmarks were established in Science and Math on the Iowas (IAs) for typical first-year STEM courses and validity evidence was provided for the benchmarks.
Results from the LGM analyses indicated that STEM graduates start at higher achievement levels in Grade 6 and maintain higher achievement levels through Grade 11 in all subjects. In addition, gender differences were examined. The findings indicate that students with high achievement levels self-select as STEM majors, regardless of gender. In addition, they suggest that students who are not on-track for a STEM degree may need to begin remediation prior to high school. Results from the benchmark analyses indicate that STEM coursework is more demanding and that students need to be better prepared academically in science and math if planning to pursue a STEM degree. In addition, the STEM Readiness Benchmarks were more accurate in predicting success in STEM courses than if general college readiness benchmarks were utilized. Also, students who met the STEM Readiness Benchmarks were more likely to graduate with a STEM degree.
This study provides valuable information on STEM readiness to students, educators, and college admissions officers. Findings from this study can be used to better understand the level of academic achievement necessary to be successful as a STEM major and to provide guidance for students considering STEM majors in college. If students are being encouraged to purse STEM majors, it is important they have accurate information regarding their chances of success in STEM coursework.
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Sun, Zhao. "New molecular mechanisms controlling dental epithelial stem cell maintenance, growth and craniofacial morphogenesis." Diss., University of Iowa, 2016. https://ir.uiowa.edu/etd/5652.
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The regenerative tissues such as hair follicles, intestine and teeth have a particular microenvironment known as “stem cell niche” which houses stem cells and act as a signaling center to control stem cell fate. The precise and timely regulation of stem cell renewal and differentiation is essential for tissue formation, growth and homeostasis over the course of a lifetime. However, the molecular underpinning to control this regulation is poorly understood. To address this issue, we use the continuously growing mouse incisor as a model to study the gene regulatory network which controls dental epithelial stem cell (DESC) maintenance, growth and craniofacial morphogenesis.
We found FoxO6, a transcription factor mainly expressed in the brain and craniofacial region, control DESC proliferation by regulating Hippo signaling. FoxO6 loss-of-function mice undergo increases in cell proliferation which finally leads to lengthening of the incisors, expansion of the face and skull and enlargement of the mandible and maxilla. We have screened three human FOXO6 single nucleotide polymorphisms which are associated with facial morphology ranging from retrognathism to prognathism.
Our study also reveals that Sox2 and Lef-1, two markers for early craniofacial development, are regulated by Pitx2 to control DESC maintenance, differentiation and craniofacial development. Conditional Sox2 deletion in the oral and dental epithelia results in severe craniofacial defects, including ankyloglossia, cleft palate, arrested incisor development and abnormal molar development. The loss of Sox2 in DESCs leads to impaired stem cell proliferation, migration and subsequent dissolution of the tooth germ. On the other hand, conditional overexpression of Lef-1 in oral and dental epithelial region increases DESC proliferation and creates a new labial cervical loop stem cell compartment in dental epithelial stem cell niche, which produces rapidly growing long “tusk-like” incisors. Interestingly, Lef-1 overexpression rescues the tooth arrest defects but not the ankyloglossia or cleft palate in Sox2 conditional deletion mice.
Our data also reveal that miRNA and histone remodeler are involved in regulating DESC proliferation and craniofacial morphogenesis. We describe a miR-23a/b:Hmgn2:Pitx2 signaling pathway in regulating dental epithelial cell growth and differentiation. Pitx2 activates expression of amelogenin which is the major protein component for enamel deposition. This activation can be repressed by the chromatin-associated factor Hmgn2. miR-23a and miR-23b directly target Hmgn2, leading to the release of the Hmgn2 inhibition of Pitx2 transcriptional activity and thus enhance Amelogenin production. Phenotypically, ablation of Hmgn2 in mice results in an overgrowth of incisors with increased Amelogenin expression.
The findings in this study increase our current understanding of the molecular regulation of dental epithelial stem cell fate. It not only highlights new gene regulatory network that controls dental stem cell maintenance, growth and craniofacial morphogenesis, but also sheds new light on developing novel stem cell therapy or gene therapy for tooth regeneration and dental diseases.
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Nilsson, Ola. "The role of estrogen in growth plate chondrogenesis /." Stockholm, 2002. http://diss.kib.ki.se/2002/91-7349-410-0/.
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Rajpar, Ibtesam Mohamed Husein. "Tendon Regeneration: Roles of Growth Factors and Phenotypic Diversity in Tendon Stem Cells." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/88070.
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Tendon injuries significantly impact quality of life and are often career ending. Mesenchymal stem cell (MSC) therapy is known to augment intrinsic tendon healing, however, little is known of the stem cells endogenous to tendon, the microenvironmental cues that induce tendon differentiation, and whether individual cells in an inflammatory milieu respond differently to these cues. To address these questions, a three-dimensional tenogenesis assay was developed as an efficient and reproducible metric of cellular capacity to differentiate toward tendon. In contrast to more complex assays of tenogenesis, this design incorporates a simple apparatus using commercially available plasticware for the application of uniaxial static strain in in a type I collagen cell-seeded hydrogel construct. Tendon-related gene expression, glycosaminoglycan levels, elongated cell morphologies and parallel cell alignments are enhanced with BMP-12 induction over ten days of culture. This dissertation provides novel insight to the roles of growth factors in MSC tenogenesis.
Tendon healing in vivo is dependent on endogenous tendon stem cells (TSC) that mediate the inflammatory response to injury and promote synthesis of collagen and matrix remodeling, among other extracellular processes. Recent evidence suggests that these cells exist on a spectrum of differentiation potencies, and may be differently committed to the tendon fate. Individual stem cells were isolated from the tendon, and their capacities for proliferation, tri-lineage differentiation and tenogenesis were evaluated. Three distinct TSC phenotypes were revealed, and significant, positive correlations were found in quadra-differentiation potency (toward four lineages) and the expression of a strong, composite tendon phenotype.
These studies have important implications in the current standard-of-care in regenerative therapies for tendon. Our benchtop tenogenesis assay can be used to determine the therapeutic potential of allogeneic MSC lines and MSCs from novel sources for 'off-the-shelf' treatments. Our study of TSCs lends valuable insight to the diversity of cell phenotypes found in tendon, and the potential contributions of each phenotype to tendon healing and homeostasis. These results further strengthen the status of tendon as a superior source of stem cells for tendon repair.Ph. D.
Tendons are fibrous, elastic bands of collagen that connect muscles to bones and are essential to movement and proper functioning of the skeletal system. Weight-bearing tendons like the Achilles in humans and superficial digital flexor tendons in horses are particularly prone to damage and degeneration with overuse and/or aging. Bone marrow-derived stem cell treatments have shown promise in the reduction of pain and inflammation, and restoration of native tendon structure and function in cases of severe tendon injuries. However, the roles of stem cells in tendon healing, particularly their ability to transition to cell types native to tendon and integrate with an environment distinct from their own is unknown. Culturing of stem cells in three dimensional (3D) environments has enabled us to identify and understand the biochemical and mechanical signals that trigger stem cell transitions to tendon cells in tendons, but currently available 3D culture systems are complex and inefficient. In this dissertation we have developed a cost-effective and high throughput 3D culture system to assay the potential of stem cells to form tendon cells and composite tendon-like tissues. Toward this, we have also optimized the effects of known tendon proteins on the tendon fate in 3D culture of stem cells. Like most adult tissues, the tendon encompasses an in-house repository of stem cells. Tendon stem cells (TSCs) are primarily responsible for the inflammatory and reparative responses to tendon injury. Recent evidence suggests that TSCs are diverse in character, and differ from each other in their ability to form cells and tissues of fat, bone and cartilage. In this work, we provide evidence that TSCs are also differently committed to forming tendon tissue, and moreover that significant inter-relationships among gene expression patterns in these cells directly contribute to cultural diversity. In sum, our results provide novel insight to the roles of stem cells in tendon healing, particularly their response to subtle changes in their biochemical environment, and the contributions of individual cells in a milieu to a holistic reparative response.
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Freile, Vinuela Paz. "Role of fibroblast growth factor signalling on the regulation of embryonic stem cells." Thesis, University of Edinburgh, 2008. http://hdl.handle.net/1842/4281.
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Fibroblast growth factor (FGF) signalling plays many fundamentally important roles during the development of the mammalian embryo. However, its effects on pluripotent stem cells derived from mouse and human embryos appear to be markedly different. FGF2 is routinely added to culture medium for propagating undifferentiated human (hES) cells, whereas in mouse (mES) cell cultures FGFs have been described as regulators of their differentiated progeny. To assess the effect of FGF signalling on undifferentiated mES cells, the effects of FGF2 and 4 were analysed in the presence of saturating and sub-saturating levels of the inhibitor of differentiation, leukaemia inhibitory factor (LIF). Mouse ES cell self-renewal was quantified by measuring the expression of the stem cell specific reporter Oct4-LacZ in biochemical and fluorometric assays. Treatment with FGF reduced the expression of the OCT4-LacZ reporter, even under saturating concentrations of LIF and this was mirrored by decreased levels of OCT4 protein. Furthermore, treatment with FGF leads to upregulation of the ectodermal differentiation marker Pax6. These results suggest that FGF signalling has a direct impact on undifferentiated mES cells, and actively promotes their differentiation. To asses the effect of FGF signalling on hES cells without the influence of undefined factors, a feeder and serum free system was developed. Cells growing in this conditions for >20 passages maintained expression of surface (SSEA3 and TRA1-60 and 81) and internal (OCT4) markers specific for undifferentiated hES cells. Expression of these markers was dependant on the continuous presence of FGF2. Indeed, withdrawal of FGF2 resulted in a rapid decrease of in hES cell growth and of the emergence of cell flattened morphology and of the surface marker SSEA1, changes typically associated with differentiation. Two important signals activated by FGF in hES cells are the ERK/MAPK and PI3K pathways. To assess their functional relevance, hES cell cultures were treated with the drugs UO126 and LY294002, inhibitors of the MAPK and PI3K pathways respectively. Drug mediated suppression of the phosphorylation of these pathways, correlated with a reduction in cell growth, flattening of the colonies and reduction in SSEA4 expression. Use of SB431542, specific inhibitor of TGFβ/activin type I receptor kinase (Alk5) also resulted in the flattening of the colonies and the appearance of dispersed cells. Therefore, inhibition of MAPK and PI3K appears to impair growth and self-renewal in hES cells and this may be happening in conjunction with TGFβ/Activin pathway. Taken together, these results suggest that FGF signalling has opposite effects in mouse and human ES cells: inducing differentiation in mES and sustaining self-renewal in hES.
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Bray, Elen. "Analysis of mesenchymal stem cell properties in three dimensional in vitro growth environments." Thesis, University of York, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.516629.
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Olaye, Eghosa Omoregie Andrew. "Differentiation of embryonic stem cells through controlled release of growth factors from microspheres." Thesis, University of Nottingham, 2009. http://eprints.nottingham.ac.uk/10825/.
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The development of microspheres for the sustained delivery of protein and small drug delivery has been utilised in tissue engineering and drug delivery applications. However problems exist in obtaining a controlled and predictable release pattern of the encapsulated molecules from these materials. In this study, microspheres with a zero order release kinetic profile and no lag phase were developed from a novel PLGA based polymer blend. The novel PLGA based polymer blend was made from blending PLGA with varying compositions of the triblock co-polymer PLGA-PEG-PLGA. These blends were subsequently used in the fabrication of lysozyme and dexamethasone loaded microspheres. Blending of the triblock copolymer with PLGA resulted in a reduction of the glass transition temperature (36.1ºC against 59.7ºC) and an increased mechanical strength (25.25 ± 1.26MPa against 0.26 ± 0.05MPa) for PLGA and 30% triblock w/w microspheres respectively. An incremental increase in the triblock composition within the Triblock/PLGA blends resulted in a corresponding reduction in glass transition temperature of the microspheres. Varying the triblock composition within the microspheres showed no significant effect on entrapment efficiency (EE) of lysozyme (protein) and dexamethasone (drug) within fabricated microspheres (EE ~ 60% for and 75% for loading weight 5% w/w for lysozyme and dexamethasone microspheres respectively). Controlled release experiments showed incorporation of the triblock increased the burst release of the protein and drug molecules from the microspheres and improved their release kinetics, with zero-order release profile (post burst phase) observed at a triblock composition of 30% w/w. A positive correlation between the amount of triblock within the triblock / PLGA blend and the rate of protein and drug release was also observed. The induction of osteogenesis and chondrogenesis within stem cells seeded on dexamethasone and ascorbate phosphate, and TGF-β3 loaded scaffolds was successfully demonstrated. Zonal release of TGF-β3 and BMP4 proteins from a bilayered scaffold was also demonstrated. However experiments conducted to demonstrate the tissue zonation within a bone cartilage bilayered construct developed from embryonic stem cell seeded TGF-β3 and BMP4 loaded bilayered scaffolds yielded inconclusive data. These results suggests that protein and drug loaded injectable microspheres for tissue engineering applications can be formed from triblock/PLGA blends, and that by varying the triblock composition, the temperature at which the microspheres form scaffolds, the release kinetics and the mechanical strength of the resulting scaffolds can be controlled.
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Liu, Ziyan. "Induction of glioma stem cells by interleukin-1beta and transforming growth factor-beta." Thesis, Kansas State University, 2011. http://hdl.handle.net/2097/8572.
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Master of ScienceDepartment of Anatomy and Physiology
Lei Wang
Jishu Shi
Transforming growth factor beta (TGF-β) and interleukin-1β (IL-1β) are both up-regulated in high grade gliomas and their elevated activities have been associated with prognosis in glioma patients. It is known that TGF-β is involved in proliferation and maintenance of glioma stem cells. In this study, I evaluated whether IL-1β also plays an important role in glioma stem cell development. Glioma stem cells are usually identified by using a sphere assay where glioma stem cells proliferate as neurospheres in serum free medium (SFM) in the presence of two growth factors: EGF and bFGF. However, LN229, a human glioblastoma cell line does not form neurospheres in SFM, suggesting that LN229 cells contain very few stem cells. I found that combination of IL-1β and TGF-β, but not IL-1β or TGF-β alone induced LN229 cells to grow as neurospheres in SFM. Furthermore, quantitative RT-PCR analyses show that the expression of stem cell markers (Nestin, Bmi1, Notch2, and LIF), cytokines (IL-1β, IL-6 and IL-8) and invasive genes (SIP1, β-integrin and N-Cadherin) are significantly enhanced in IL-1β /TGF-β induced spheres compared to the control. Using an invasion assay, drug resistance test, and colony assay, I found that LN229 sphere cells induced by IL-1β and TGF-β are more invasive, have increased drug resistant ability, and are more oncogenic in comparison to the control. Together, these results suggest that IL-1β cooperates with TGF-β to induce glioma stem-like cell phenotype.
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Zohora, Fatema Tuj. "Effect of Dimensionality on In Vitro Growth Environment and Mesenchymal Stem Cell Function." Wright State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=wright1535328622898468.
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Sharma, Karan, and Xuejun Wen. "ENGINEERING SURFACES TO SUPPORT NEURAL STEM CELLS (HNSC’S) AND HEPATOCYTES ADHESION AND GROWTH." VCU Scholars Compass, 2016. http://scholarscompass.vcu.edu/etd/4492.
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In a 2D cell culture, the cells are mainly grown on flat surfaces which are usually made of polystyrene plastic. Cells are able to attach to these surfaces, forming individual cell formations or colonies. In this study, we have been looked at many different platforms to improve cell growth, adhesion, attachment and proliferation on two different promising cell lines. These cell lines are the human neural stem cells (hNSCs) and human liver hepatocellular carcinoma cells (HepG2). Researchers have been very interested in studying these cell lines in the recent years as they have very useful potentials in the long run to aid and cure many of the disorders, diseases and possibly replace infected or injured organs as well. This can be done using actual clinical applications for cell therapies and tissue transplantation. Based on the studies conducted for this thesis, we have been able to show that cells can be maintained in a 2D culture setting with increasing growth and adhesion factors. The conditions used for these studies were a way to not use the traditional materials for cell attachment and growth. This was pursued due to the fact that most stem cells for their continuity require a microenvironment that will support their physical and chemical properties of an effective extra cellular matrix (ECM). To reiterate, presently most ECM molecules are human or animal derived for effective cell culture applications but not clinical. This is a major problem as each batch varies, they are difficult to isolate and most contain biological components that have been known to limit their use in clinical applications. Hence, this study concentrated on developing synthetic polymer based ECMs as they do not have the problems of the human or animal derived ECMs, but also as they are relatively low-cost, reliable and easily fabricated. Through many experimental trials we have successfully developed synthetic polymer based ECM molecules that sustain stem cell growth for HepG2 liver hepatocellular carcinoma and hNSC human neural stem cell lines. The different substrates developed were a peptide fabricated in our lab; different concentrations and solutions of Poly 4-vinylphenol (P4VP) that were used on a flat hollow fiber membrane made using Polyacrylonitrile (PAN) doped in a solution containing PAN/N, N-dimethylformamide (DMF) having a high biocompatibility. This hollow fiber membrane study was maintained with eight different conditions over a period of 6 weeks.
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Dougher, Tracy A. O. "Effect of Blue Light and Temperature on Leaf Expansion, Stem Elongation, and Growth." DigitalCommons@USU, 1999. https://digitalcommons.usu.edu/etd/6750.
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Short height and high yield per unit energy in controlled environments are essential to the success of a food production system for spaceflight. Temperature and light quality can be manipulated in controlled environments to reduce plant height and increase yield. Although the effects of temperature on height and yield are well studied at ambient CO2, temperature effects at elevated CO2 with a hydroponic root zone are not well characterized. We studied soybean yield and height under two lamp types over a broad range of temperatures. Temperature had little effect on yield or height, but lamp type had a significant effect on canopy height. This first study highlighted the importance of understanding spectral quality in controlling plant growth, especially canopy height.
Numerous studies have compared lamp types and suggested that profound differences in leaf area, canopy height, yield, and total dry mass responses were due to blue light differences. Unfortunately, the most energy-efficient light sources have the least blue light. We have a poor understanding of the specific morphological and histological effects of blue light on leaves and stems. Three species, soybeans, wheat, and lettuce, were grown at five blue light fractions (0, 2, 6, 12, and 26%) and two light levels (200 and 500 μmol m-2 s-1). Phytochrome photoequilibria were constant among treatments. Blue light responses were species dependent. Wheat leaf area, dry mass, and stem length were insensitive to blue light fraction. Increasing blue light to 26% decreased soybean stem length, but leaf area was greatest at 6% blue. Lettuce leaf area, stem length, and dry mass were highly sensitive to blue light fraction between 0% and 6% under high pressure sodium lamps, but were insensitive between 6% and 26% under metal halide lamps. These results may be complicated by sensitivity to other wavelengths . The decrease in soybean stem length with increasing blue light was caused by an inhibition of cell division, while the decrease in leaf area was caused primarily by a decrease in cell expansion. Increased lettuce leaf area with increasing blue light fraction was caused by both cell division and expansion. This research indicates that lamps high in blue photons are not only energetically wasteful, but do not benefit, and in some cases reduce, plant growth. However, some blue light is necessary for controlling plant height in soybean and even required for proper growth and development in lettuce.
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Barrett, Andrea Lynn. "A FGF-Hh feedback loop controls stem cell proliferation in the developing larval brain of drosophila melanogaster." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-2017.
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Rao, Rajesh Chalamalasetty. "Platelet-Derived Growth Factor Enables Direct Derivation of Oligodendrocyte Progenitors from CNS Stem Cells." Yale University, 2008. http://ymtdl.med.yale.edu/theses/available/etd-08242007-114313/.
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Oligodendrocytes derived in the laboratory from stem cells have been proposed as a treatment for acute and chronic injury to the central nervous system (CNS). Platelet-derived growth factor-receptor alpha (PDGFRÑ)w signaling is known to play an important role for regulation of oligodendrocyte progenitor cell numbers both during development and adulthood. Here, we analyze the effect of PDGFRÑ signaling on CNS stem cells derived from embryonic day 13.5 murine cortex and cultured in monolayer. Fetal and adult CNS stem cells express PDGFRÑ, and PDGF-AA treatment increases viability and proliferation of these cells. In the absence of insulin, this effect of PDGF-AA is very clear. Consistent with this result, PDGF-AA strongly stimulates glycolytic rate. PDGF-AA treatment rapidly induces morphological changes in the cells although the cells maintain expression of a wide range of precursor markers. We show that a brief exposure to PDGF-AA rapidly and efficiently induces oligodendrocytes from CNS stem cells. Our data suggest that phosphoinositide kinase-3 (PI3K)/Akt, mitogen-activated protein/extracellular signal-regulated kinase kinase/extracellular signal-related kinase (MEK/Erk), mammalian target of rapamycin (mTOR) regulate survival, proliferation, glycolytic rate, and oligodendrogliogenesis induced by PDGF-AA. By treating with PDGF-AA, progenitor cells directly from embryonic cortex can be expanded and differentiated into oligodendrocytes with high efficiency. Our results show that PDGF-AA promotes oligodendrocyte progenitor generation from CNS stem cells and supports their survival and proliferation. The derivation of oligodendrocytes demonstrated here may support the safe and effective use of stem cells in the development of new therapies targeting this cell type.
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Ang, Main-fong, and 洪明楓. "Ex vivo expansion of hematopoietic stem cells: preclinical studies and clinical application." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B3122815X.
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Husman, S. H., and M. J. Ottman. "Nitrogen Fertilization of Durum Based on Stem Nitrate, Buckeye, 1996." College of Agriculture, University of Arizona (Tucson, AZ), 1996. http://hdl.handle.net/10150/202441.
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Mansouri, Katayoun. "The influence of plant growth regulators on bud break and shoot growth from large stem segments of Acer saccharinum L /." Available to subscribers only, 2007. http://proquest.umi.com/pqdweb?did=1324375491&sid=5&Fmt=2&clientId=1509&RQT=309&VName=PQD.
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Thesis (M.S.)--Southern Illinois University Carbondale, 2007."Department of Plant, Soil Science and Agricultural Systems." Includes bibliographical references (leaves 58-62). Also available online.
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Mills, Jason Adam. "Cytokine and growth factor networks associated with epidermal-mesenchymal cell interactions during keratinocyte-stem cell growth in the bovine claw." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 278 p, 2008. http://proquest.umi.com/pqdweb?did=1459902991&sid=1&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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