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Badali, Matthew, i Anton Zilman. "Effects of niche overlap on coexistence, fixation and invasion in a population of two interacting species". Royal Society Open Science 7, nr 2 (luty 2020): 192181. http://dx.doi.org/10.1098/rsos.192181.
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Synergistic and antagonistic interactions in multi-species populations—such as resource sharing and competition—result in remarkably diverse behaviours in populations of interacting cells, such as in soil or human microbiomes, or clonal competition in cancer. The degree of inter- and intra-specific interaction can often be quantified through the notion of an ecological ‘niche’. Typically, weakly interacting species that occupy largely distinct niches result in stable mixed populations, while strong interactions and competition for the same niche result in rapid extinctions of some species and fixations of others. We investigate the transition of a deterministically stable mixed population to a stochasticity-induced fixation as a function of the niche overlap between the two species. We also investigate the effect of the niche overlap on the population stability with respect to external invasions. Our results have important implications for a number of experimental systems.
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Allgeier, Jacob E., Thomas C. Adam i Deron E. Burkepile. "The importance of individual and species-level traits for trophic niches among herbivorous coral reef fishes". Proceedings of the Royal Society B: Biological Sciences 284, nr 1856 (14.06.2017): 20170307. http://dx.doi.org/10.1098/rspb.2017.0307.
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Resolving how species compete and coexist within ecological communities represents a long-standing challenge in ecology. Research efforts have focused on two predominant mechanisms of species coexistence: complementarity and redundancy. But findings also support an alternative hypothesis that within-species variation may be critical for coexistence. Our study focuses on nine closely related and ecologically similar coral reef fish species to test the importance of individual- versus species-level traits in determining the size of dietary, foraging substrate, and behavioural interaction niches. Specifically, we asked: (i) what level of biological organization best describes individual-level niches? and (ii) how are herbivore community niches partitioned among species, and are niche widths driven by species- or individual-level traits? Dietary and foraging substrate niche widths were best described by species identity, but no level of taxonomy explained behavioural interactions. All three niches were dominated by only a few species, contrasting expectations of niche complementarity. Species- and individual-level traits strongly drove foraging substrate and behavioural niches, respectively, whereas the dietary niche was described by both. Our findings underscored the importance of species-level traits for community-level niches, but highlight that individual-level trait variation within a select few species may be a key driver of the overall size of niches.
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Mauretti, Arianna, Sergio Spaans, Noortje A. M. Bax, Cecilia Sahlgren i Carlijn V. C. Bouten. "Cardiac Progenitor Cells and the Interplay with Their Microenvironment". Stem Cells International 2017 (2017): 1–20. http://dx.doi.org/10.1155/2017/7471582.
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The microenvironment plays a crucial role in the behavior of stem and progenitor cells. In the heart, cardiac progenitor cells (CPCs) reside in specific niches, characterized by key components that are altered in response to a myocardial infarction. To date, there is a lack of knowledge on these niches and on the CPC interplay with the niche components. Insight into these complex interactions and into the influence of microenvironmental factors on CPCs can be used to promote the regenerative potential of these cells. In this review, we discuss cardiac resident progenitor cells and their regenerative potential and provide an overview of the interactions of CPCs with the key elements of their niche. We focus on the interaction between CPCs and supporting cells, extracellular matrix, mechanical stimuli, and soluble factors. Finally, we describe novel approaches to modulate the CPC niche that can represent the next step in recreating an optimal CPC microenvironment and thereby improve their regeneration capacity.
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Schirmer, Annika, Julia Hoffmann, Jana A. Eccard i Melanie Dammhahn. "My niche: individual spatial niche specialization affects within- and between-species interactions". Proceedings of the Royal Society B: Biological Sciences 287, nr 1918 (15.01.2020): 20192211. http://dx.doi.org/10.1098/rspb.2019.2211.
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Intraspecific trait variation is an important determinant of fundamental ecological interactions. Many of these interactions are mediated by behaviour. Therefore, interindividual differences in behaviour should contribute to individual niche specialization. Comparable with variation in morphological traits, behavioural differentiation between individuals should limit similarity among competitors and thus act as a mechanism maintaining within-species variation in ecological niches and facilitating species coexistence. Here, we aimed to test whether interindividual differences in boldness covary with spatial interactions within and between two ecologically similar, co-occurring rodent species ( Myodes glareolus , Apodemus agrarius ). In five subpopulations in northeast Germany, we quantified individual differences in boldness via repeated standardized tests and spatial interaction patterns via capture–mark–recapture ( n = 126) and automated VHF telemetry ( n = 36). We found that boldness varied with space use in both species. Individuals of the same population occupied different spatial niches, which resulted in non-random patterns of within- and between-species spatial interactions. Behavioural types mainly differed in the relative importance of intra- versus interspecific competition. Within-species variation along this competition gradient could contribute to maintaining individual niche specialization. Moreover, behavioural differentiation between individuals limits similarity among competitors, which might facilitate the coexistence of functionally equivalent species and, thus, affect community dynamics and local biodiversity.
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Costa-Pereira, Raul, Márcio S. Araújo, Franco L. Souza i Travis Ingram. "Competition and resource breadth shape niche variation and overlap in multiple trophic dimensions". Proceedings of the Royal Society B: Biological Sciences 286, nr 1902 (maj 2019): 20190369. http://dx.doi.org/10.1098/rspb.2019.0369.
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Competition plays a central role in the maintenance of biodiversity. A backbone of classic niche theory is that local coexistence of competitors is favoured by the contraction or divergence of species' niches. However, this effect should depend on the diversity of resources available in the local environment, particularly when resources vary in multiple ecological dimensions. Here, we investigated how available resource breadth (i.e. prey diversity) and competition together shape multidimensional niche variation (between and within individuals) and interspecific niche overlap in 42 populations of congeneric tropical frog species. We modelled realized niches in two key trophic dimensions (prey size and carbon stable isotopes) and sampled available food resources to quantify two-dimensional resource breadth. We found a 14-fold variation in multidimensional population niche width across populations, most of which was accounted for by within-individual diet variation. This striking variation was predicted by an interaction whereby individual niche breadth increased with resource breadth and decreased with the number of congeneric competitors. These ecological gradients also interact to influence the degree of niche overlap between species, which surprisingly decreased with population total niche width, providing novel insights on how similar species can coexist in local communities. Together, our results emphasize that patterns of exploitation of resources in multiple dimensions are driven by both competitive interactions and extrinsic factors such as local resource breadth.
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Richards, Greg. "Rethinking niche tourism: The example of backpacking". Croatian Regional Development Journal 2, nr 1 (1.06.2021): 1–10. http://dx.doi.org/10.2478/crdj-2021-0004.
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Abstract This conceptual paper re-evaluates the concept of niches in tourism markets. As many regions are now attempting to address niche markets in tourism as a development strategy, understanding of the dynamics of niche markets is crucial. Current approaches are often limited to seeing niche markets as simple subsectors of larger consumer markets. We argue for a broader view of market niches as forms of social rituals involving both consumers and producers with a mutual focus of attention. Based on the work of Randall Collins we examine how interaction rituals are produced and maintained, and how these are also reflected in niche markets, such as backpacking. We illustrate the how backpacking produces a mutual focus of attention and boundaries to outsiders, helping to sustain the niche over the longer term. This analysis has implications for producers hoping to tap into niche markets, as they too need to become part of the niche community.
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Adiloglu, Ali Kudret. "The Interaction of Diet, Microbiota, and Antimicrobial Peptides in the Gastrointestinal Ecosystem". Niche Journal 3, nr 2 (22.02.2016): 28–32. http://dx.doi.org/10.5152/niche.2016.218.
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Khattab, Shaimaa, Manal El Sorady, Ashraf El-Ghandour, Giuseppe Visani i Pier Paolo Piccaluga. "Hematopoietic and leukemic stem cells homeostasis: the role of bone marrow niche". Exploration of Targeted Anti-tumor Therapy 5, nr 5 (15.08.2024): 1027–55. http://dx.doi.org/10.37349/etat.2024.00262.
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The bone marrow microenvironment (BMM) has highly specialized anatomical characteristics that provide a sanctuary place for hematopoietic stem cells (HSCs) that allow appropriate proliferation, maintenance, and self-renewal capacity. Several cell types contribute to the constitution and function of the bone marrow niche. Interestingly, uncovering the secrets of BMM and its interaction with HSCs in health paved the road for research aiming at better understanding the concept of leukemic stem cells (LSCs) and their altered niche. In fact, they share many signals that are responsible for interactions between LSCs and the bone marrow niche, due to several biological similarities between LSCs and HSCs. On the other hand, LSCs differ from HSCs in their abnormal activation of important signaling pathways that regulate survival, proliferation, drug resistance, invasion, and spread. Targeting these altered niches can help in better treatment choices for hematological malignancies and bone marrow disorders in general and acute myeloid leukemia (AML) in particular. Moreover, targeting those niches may help in decreasing the emergence of drug resistance and lower the relapse rate. In this article, the authors reviewed the most recent literature on bone marrow niches and their relations with either normal HSCs and AML cells/LSC, by focusing on pathogenetic and therapeutic implications.
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Kuek, Vincent, Anastasia M. Hughes, Rishi S. Kotecha i Laurence C. Cheung. "Therapeutic Targeting of the Leukaemia Microenvironment". International Journal of Molecular Sciences 22, nr 13 (26.06.2021): 6888. http://dx.doi.org/10.3390/ijms22136888.
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In recent decades, the conduct of uniform prospective clinical trials has led to improved remission rates and survival for patients with acute myeloid leukaemia and acute lymphoblastic leukaemia. However, high-risk patients continue to have inferior outcomes, where chemoresistance and relapse are common due to the survival mechanisms utilised by leukaemic cells. One such mechanism is through hijacking of the bone marrow microenvironment, where healthy haematopoietic machinery is transformed or remodelled into a hiding ground or “sanctuary” where leukaemic cells can escape chemotherapy-induced cytotoxicity. The bone marrow microenvironment, which consists of endosteal and vascular niches, can support leukaemogenesis through intercellular “crosstalk” with niche cells, including mesenchymal stem cells, endothelial cells, osteoblasts, and osteoclasts. Here, we summarise the regulatory mechanisms associated with leukaemia–bone marrow niche interaction and provide a comprehensive review of the key therapeutics that target CXCL12/CXCR4, Notch, Wnt/b-catenin, and hypoxia-related signalling pathways within the leukaemic niches and agents involved in remodelling of niche bone and vasculature. From a therapeutic perspective, targeting these cellular interactions is an exciting novel strategy for enhancing treatment efficacy, and further clinical application has significant potential to improve the outcome of patients with leukaemia.
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Gottfried, Iwona, Bartosz Borczyk i Tomasz Gottfried. "Snakes use microhabitats created by the great capricorn beetle Cerambyx cerdo in southwest Poland". Herpetozoa 32 (12.06.2019): 133–35. http://dx.doi.org/10.3897/herpetozoa.32.e35824.
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Niche engineering is considered one of the most important interspecific interactions that shape ecosystems, but this kind of interaction network has not been sufficiently studied so far. Here we present the first observation of grass snake Natrixnatrix in the galleries of Cerambyxcerdo. We recorded three grass snake individuals basking and hiding inside the C.cerdo galleries. We suggest the presence of this beetle species may create new environmental niches and improve habitat quality for snakes and other vertebrates.
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Moncayo-Estrada, Rodrigo, Owen T. Lind i Carlos Escalera-Gallardo. "Trophic interactions among sympatric zooplanktivorous fish species in volume change conditions in a large, shallow, tropical lake". Neotropical Ichthyology 9, nr 1 (4.02.2011): 169–76. http://dx.doi.org/10.1590/s1679-62252011005000003.
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Significant reductions in the water volume of shallow lakes impose a restriction on species segregation promoting more interactions in the trophic relationships. The diets of three closely related zooplanktivorous silversides belonging to the Atherinopsidae species flock of lake Chapala , Mexico, were analyzed at two sites (Chirostoma jordani, C. labarcae, and C. consocium). Diets were described in critical shallow (August 2000) and volume recovery conditions (August 2005). Diets included mainly cladocerans (Bosmina, Ceriodaphnia, and Daphnia) and copepods (Cyclops). A significant difference in diets was detected when comparing years (MRPP analysis, A = 0.22, p < 0.0001) and sites at different years (MRPP analysis, A = 0.17, p = 0.004). According to niche breadth mean values, species were classified as specialized and intermediate feeders. In shallow conditions, the small range of niche breadth (1.72 to 3.64) and high diet overlap values (D = 0.64, L = 8.62) indicated a high potential for interspecific exploitative interaction. When the lake volume recovered, an increase in the niche breadth range (1.04 to 4.96) and low niche overlap values (D = 0.53, L = 2.32) indicated a reduction of the species interaction. The Mann-Whitney U-test supported this pattern by showing a significant difference between years for niche overlap (p = 0.006). The increased interaction during the low volume suggests alternative segregation in life-history variations and other niche dimensions such as spatial or temporal distribution.
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NOWNES, ANTHONY J. "Policy Conflict and the Structure of Interest Communities". American Politics Quarterly 28, nr 3 (lipiec 2000): 309–27. http://dx.doi.org/10.1177/1532673x00028003002.
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Drawing on data from a survey of 595 state interest representatives this article asks: Is policy conflict widespread in state interest communities or is it rare due to the isolation of interest organizations in relatively placid niches? Two contending perspectives frame the current debate on this issue. Whereas Browne maintains that balkanization characterizes interest communities, Salisbury and his colleagues suggest that many policy domains feature substantial intergroup interaction, conflict, and cooperation. In all, the data witness relatively high levels of conflict among groups and between groups and other political actors and thus confound the expectations of Browne's niche theory. Nevertheless, the data do not invalidate niche theory. Rather, they suggest that some policy domains are more likely to be characterized by niche politics than others and that the federal government provides more incentives than state governments for groups to seek niches.
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Bueno, Raquel de Oliveira, Thais Bastos Zanata i Isabela Galarda Varassin. "Niche partitioning between hummingbirds and well-matched flowers is independent of hummingbird traits". Journal of Tropical Ecology 37, nr 4 (lipiec 2021): 193–99. http://dx.doi.org/10.1017/s026646742100033x.
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AbstractAmong nectarivorous birds, the highest niche partitioning occurs between hummingbirds and plants. Although hummingbirds tend to visit morphologically well-matched resources, as ornithophilous species, they can also visit flowers with other traits. Here, we investigated whether the niche partitioning in hummingbird-plant interactions is also observed with ornithophilous species only. We also explored if hummingbird traits predicted resources use. We recorded a plant-ornithophilous species network in a semi-deciduous forest in Brazil. We quantified interaction partitioning through network connectance, complementary specialisation, and modularity. The influence of hummingbirds’ traits into their visits was investigated through methods of functional ecology and ecological networks. We recorded 948 interactions between nine hummingbirds and seven ornithophilous plants. We detected similar patterns of niche partitioning between hummingbirds and ornithophilous plants in comparison to networks considering the entire plant community. However, hummingbird species with the most specialised interactions are different from those when the whole system is evaluated. Therefore, we cannot downscale the patterns from one scale to the other. The pattern of interaction with ornithophilous plants was not related to hummingbirds’ traits. Therefore, the coexistence of species with shared traits might be occurring through facilitative and competitive processes, leading to trait mismatching and maintaining niche partitioning among ornithophilous plants.
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Hosokawa, Kentaro, Fumio Arai, Hiroki Yoshihara, Keiyo Takubo, Keisuke Ito, Sahoko Matsuoka i Toshio Suda. "Reactive Oxygen Species Control Hematopoietic Stem Cell-Niche Interaction through the Regulation of N-Cadherin." Blood 108, nr 11 (16.11.2006): 86. http://dx.doi.org/10.1182/blood.v108.11.86.86.
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Abstract Interaction of tissue stem cells with their particular microenvironments, known as stem cell niches, is critical for maintaining the stem cell properties, including self-renewal capacity and the ability of differentiation into single or multiple lineages. We previously reported that the regulation of reactive oxygen species (ROS) is critical for the self-renewal activity of HSCs (Ito et al., Nature 2004, Ito et al., Nat Med 2006). Accumulation of ROS in HSCs induced defects in repopulating ability and in maintenance of quiescence through the activation of p38MAPK and p16Ink4a, indicating that the oxidative stress contributes to exhaustion of the stem cell population. From these findings, we hypothesized that loss of quiescence was associated with the impaired HSC-niche interaction. Oxidative stress may affect not only intrinsic function of HSC but the interaction between HSCs and their niche. In this study, we investigated the effects of ROS in the interaction of HSC with osteoblastic niche. We have found that the side-population (SP) in c-Kit+Sca-1+ Lin− (KSL) fraction was the quiescent HSCs in the osteoblastic niche and KSL-SP cells expressed N-cadherin (NCAD) (Arai et al., Cell 2004), and NCAD mediated cell adhesion induced quiescence of HSCs. Then we analyzed the role of ROS in the maintenance of NCAD-mediated cell-cell adhesion and detachment of HSCs from the niche under the myelosuppressive condition. Administration of 5-FU to mice decreases the dividing cells (non-SP fraction), but not quiescent cells (SP fraction) in BM on day 2. On day 6, HSC population was shifted from SP to non-SP fraction. This event might be associated with the cell cycle activation and detachment of HSCs from the niche. We found that 5-FU treatment transiently increased a level of intracellular ROS in HSCs and downregulated the expression of NCAD in HSCs. Administration of anti-oxidant, N-Acetyl Cysteine (NAC), in 5-FU treated mice maintained NCAD expression in HSCs, suggesting that increased ROS suppressed the expression of NCAD in HSCs. In addition, NAC treatment inhibited the transition of HSCs from SP to non-SP fraction on day 6. Moreover, 5-FU induced upregulation of G-CSFR and Flt3 expression in HSCs on day 2, while NAC treatment inhibited the expressions of growth factor receptors. These data indicated that intracellular ROS was a trigger for the detachment of HSCs from the niche, and inhibition of oxidative stress in HSCs by ant-oxidant preserved NCAD-mediated cell adhesion and blocked cell cycle activation after myelosuppression. Furthermore, these data led us the possibility that normal quiescent HSCs maintains low oxidative stress by existing in the low oxygen environment. To confirm this hypothesis, we evaluated the redox status of fractionated hematopoietic cells (Lin+, Lin−, KSL-non SP, and KSL-SP) by hypoxic marker pimonidazole. And we confirmed that >80 % of KSL-SP cells were pimonidazole positive, suggesting that quiescent HSCs resided in the hypoxic niche. Altogether, our data suggest that regulation of oxidative stress is critical for the interaction between HSCs and BM niche. And osteoblastic niche maintains HSCs in low oxidative stress.
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Nicol, Jason M., i George G. Ganf. "Water regimes, seedling recruitment and establishment in three wetland plant species". Marine and Freshwater Research 51, nr 4 (2000): 305. http://dx.doi.org/10.1071/mf99147.
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The regeneration niche of three wetland species that co-occur at Bool Lagoon, South Australia, was investigated under nine hydrologic conditions. Typha domingensis grown from seed had the broadest niche requirements; seeds germinated and seedlings were established in all 9 hydrologic regimes, and asexual reproduction occurred in 5 of the 9 regimes. Whether asexual reproduction occurred was dependent upon an interaction between the rate of leaf elongation, the rate of drawdown and whether the leaf was able to broach the water surface. The buoyant nature of seeds and seedlings ofTriglochin procerum allowed it to avoid unfavourable regeneration niches. Melaleuca halmaturorum had a narrow regeneration niche that was confined to wet mud flats. The results are consistent with the changes in the floristic composition of the lagoon.
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Choi, Inpyo, Mira Jeong i Suk Ran Yoon. "Regulation of hematopoietic stem cell quiescence by TXNIP (36.1)". Journal of Immunology 184, nr 1_Supplement (1.04.2010): 36.1. http://dx.doi.org/10.4049/jimmunol.184.supp.36.1.
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Abstract Hematopoietic stem cells (HSCs) are distinct cells that are predominantly located in the bone marrow microenvironment, which is referred to as the niche. HSC quiescence, activation, and mobilization are coordinately regulated in their niche by intrinsic and extrinsic mechanisms. Several genes, including those that encode transcriptional regulators, cell cycle regulatory proteins, tumor suppressors, and proto-oncogenes, intrinsically regulate the balance between HSC quiescence and activation. The vitamin D3 up-regulated protein 1 (VDUP1) is a 397 amino acid residue, 50-kDa protein that belongs to the arrestin family. We hypothesized that VDUP1 plays a pivotal role in controlling HSC cell cycle, migration, and BM niche interactions. The expression of VDUP1 is decreased during HSC activation. In VDUP1-/- mice, the LT-HSC population is decreased and exhausted, and its capacity to repopulate is rapidly lost. The VDUP1 deficiency reduced the osteopontin/integrin β1-mediated interaction between HSCs and the bone marrow niche and impaired homing and retention in the osteoblastic niche, resulting in mobilized HSCs. Thus, we propose that VDUP1 is essential for maintaining HSC quiescence and interactions with the BM niche.
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Robertson, Sarah Y. T., JoAnn S. Roberts i Sophie X. Deng. "Regulation of Limbal Epithelial Stem Cells: Importance of the Niche". International Journal of Molecular Sciences 22, nr 21 (5.11.2021): 11975. http://dx.doi.org/10.3390/ijms222111975.
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Limbal epithelial stem/progenitor cells (LSCs) reside in a niche that contains finely tuned balances of various signaling pathways including Wnt, Notch, BMP, Shh, YAP, and TGFβ. The activation or inhibition of these pathways is frequently dependent on the interactions of LSCs with various niche cell types and extracellular substrates. In addition to receiving molecular signals from growth factors, cytokines, and other soluble molecules, LSCs also respond to their surrounding physical structure via mechanotransduction, interaction with the ECM, and interactions with other cell types. Damage to LSCs or their niche leads to limbal stem cell deficiency (LSCD). The field of LSCD treatment would greatly benefit from an understanding of the molecular regulation of LSCs in vitro and in vivo. This review synthesizes current literature around the niche factors and signaling pathways that influence LSC function. Future development of LSCD therapies should consider all these niche factors to achieve improved long-term restoration of the LSC population.
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Ji, Yue, Paul Kwong-Hang Tam i Clara Sze-Man Tang. "Roles of Enteric Neural Stem Cell Niche and Enteric Nervous System Development in Hirschsprung Disease". International Journal of Molecular Sciences 22, nr 18 (7.09.2021): 9659. http://dx.doi.org/10.3390/ijms22189659.
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The development of the enteric nervous system (ENS) is highly modulated by the synchronized interaction between the enteric neural crest cells (ENCCs) and the neural stem cell niche comprising the gut microenvironment. Genetic defects dysregulating the cellular behaviour(s) of the ENCCs result in incomplete innervation and hence ENS dysfunction. Hirschsprung disease (HSCR) is a rare complex neurocristopathy in which the enteric neural crest-derived cells fail to colonize the distal colon. In addition to ENS defects, increasing evidence suggests that HSCR patients may have intrinsic defects in the niche impairing the extracellular matrix (ECM)-cell interaction and/or dysregulating the cellular niche factors necessary for controlling stem cell behaviour. The niche defects in patients may compromise the regenerative capacity of the stem cell-based therapy and advocate for drug- and niche-based therapies as complementary therapeutic strategies to alleviate/enhance niche-cell interaction. Here, we provide a summary of the current understandings of the role of the enteric neural stem cell niche in modulating the development of the ENS and in the pathogenesis of HSCR. Deciphering the contribution of the niche to HSCR may provide important implications to the development of regenerative medicine for HSCR.
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Wang, Chaoyu, Chen Tian i Yizhuo Zhang. "The Interaction Between Niche and Hematopoietic Stem Cells". Indian Journal of Hematology and Blood Transfusion 32, nr 4 (12.01.2016): 377–82. http://dx.doi.org/10.1007/s12288-016-0639-1.
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Ho, Ivy A. W., i Winston S. N. Shim. "Contribution of the Microenvironmental Niche to Glioblastoma Heterogeneity". BioMed Research International 2017 (2017): 1–13. http://dx.doi.org/10.1155/2017/9634172.
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Glioblastoma is the most aggressive cancer of the brain. The dismal prognosis is largely attributed to the heterogeneous nature of the tumor, which in addition to intrinsic molecular and genetic changes is also influenced by the microenvironmental niche in which the glioma cells reside. The cancer stem cells (CSCs) hypothesis suggests that all cancers arise from CSCs that possess the ability to self-renew and initiate tumor formation. CSCs reside in specialized niches where interaction with the microenvironment regulates their stem cell behavior. The reciprocal interaction between glioma stem cells (GSCs) and cells from the microenvironment, such as endothelial cells, immune cells, and other parenchymal cells, may also promote angiogenesis, invasion, proliferation, and stemness of the GSCs and be likely to have an underappreciated role in their responsiveness to therapy. This crosstalk may also promote molecular transition of GSCs. Hence the inherent plasticity of GSCs can be seen as an adaptive response, changing according to the signaling cue from the niche. Given the association of GSCs with tumor recurrence and treatment sensitivity, understanding this bidirectional crosstalk between GSCs and its niche may provide a framework to identify more effective therapeutic targets and improve treatment outcome.
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Harutyunyan, Karine G., Felix Nwajei, M. Anna Zal, David A. Fruman, Saradhi Mallampati, Xiaoping Sun, Tomasz Zal i Marina Konopleva. "The Dynamics of Stroma-Leukemia Interaction in the Hypoxic BM Niches in Vivo". Blood 124, nr 21 (6.12.2014): 2396. http://dx.doi.org/10.1182/blood.v124.21.2396.2396.
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Abstract We and others have previously reported that leukemia progression is associated with vast expansion of the hypoxic niches and stabilization of hypoxia-inducible factor 1 alpha (HIF-1α) in leukemic cells (Frolova et al. Cancer Biol Ther. 2012, 10:858; Benito et al. PLoS One 2011, 6(8); e23108:1). Interactions of leukemia and the bone marrow (BM) microenvironment are known to play a key role in the survival and growth of leukemic cells, and we have shown that HIF-1α stabilization in stromal cells of the microenvironment facilitates leukemia homing and progression (Chen et al. Blood 2012, 119:4971). In this study, we aimed to characterize the time-dependent progression of BM hypoxia involving both leukemia cells and components of the BM niche, using the multiphoton intravital microscopy (MP-IVM) technique. We first generated a transplantable, imageable leukemia model by retrovirally transducing C57Bl6-Ai14 murine BM cells that express red fluorescing tdTomato with the p190-Bcr/Abl oncogene. The resulting p190-Bcr/Abl tdTomato cells caused rapid development of acute lymphocytic leukemia (ALL) in un-irradiated C57Bl6 immunocompetent mice, manifested by infiltration of the spleen, liver, BM within long bones, skull, and central nervous system followed by death within 28 days. Leukemia cells collected from the BM (LBC) of these animals were transplantable into secondary recipients and triggered accelerated ALL development (14-16 days). Time-course analysis of skull and femur bones in the secondary recipients by MP-IVM demonstrated LBC lodging on day 1 after ALL cell injection, followed by rapid accumulation of leukemia cells localized predominantly within the sinusoidal spaces, which were visualized by injecting the vascular fluorescent dye BSA-647 (Fig. 1a). To detect in vivo hypoxia development, we utilized HS680 (HypoxiSense 680), a carbonic anhydrase IX (CAIX)–targeted fluorescent agent that can be used to image overexpression of CAIX, a direct HIF-1α target, in tumors in response to regional hypoxia. C57Bl6 mice were engrafted with 2 x 105 LBC , and HS680 was injected intravenously at serial intervals followed by MP-IVM. In two separate experiments, increased HS680 fluorescence was detected in bone-lining cells in the BM niches of mice harboring ALL on days 8 and 13, but not in their healthy littermates (Fig 1b). To obtain an independent confirmation of hypoxia, additional mice (n=3) at the same stage (day 14) of leukemia development were sacrificed 3 hr after injection of chemical hypoxia probe pimonidazole (Pimo), and hypoxic BM cells that bound the hypoxia probe were detected by immunohistochemistry. Pimo staining demonstrated vastly spread areas of hypoxia that enclosed both leukemia cells and BM niche cells (Fig 1c), consistent with our previously published observations in different leukemia models. In summary, these findings demonstrate rapid development of intra-BM hypoxia that parallels leukemia progression and involves not only leukemia cells, but also BM niche cells. The HS680 probe can detect hypoxia in vivo within niche cells but not in leukemia cells, likely because of differential expression of CAIX. Our ongoing studies will characterize the cellular origin of hypoxic niche cells by utilizing immunohistochemical techniques and Col2.3-GFPemd transgenic mice to visualize osteoblasts. We postulate that the tumor microenvironment altered with hypoxic niche cells will influence leukemia development or responses to therapy. To this end, we have generated mice with conditionally deleted HIF-1α within BM stromal cells and are investigating the differences in leukemia homing, progression, and chemoresistance between these mice and mice whose BM stromal cells express HIF-1a. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.
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Yu, Zhuo, Wenqian Yang, Xiaoxiao He, Chiqi Chen, Wenrui Li, Limin Zhao, Ligen Liu i in. "Endothelial cell-derived angiopoietin-like protein 2 supports hematopoietic stem cell activities in bone marrow niches". Blood 139, nr 10 (10.03.2022): 1529–40. http://dx.doi.org/10.1182/blood.2021011644.
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Abstract Bone marrow niche cells have been reported to fine-tune hematopoietic stem cell (HSC) stemness via direct interaction or secreted components. Nevertheless, how niche cells control HSC activities remains largely unknown. We previously showed that angiopoietin-like protein 2 (ANGPTL2) can support the ex vivo expansion of HSCs by binding to human leukocyte immunoglobulin-like receptor B2. However, how ANGPTL2 from specific niche cell types regulates HSC activities under physiological conditions is still not clear. Herein, we generated an Angptl2-flox/flox transgenic mouse line and conditionally deleted Angptl2 expression in several niche cells, including Cdh5+ or Tie2+ endothelial cells, Prx1+ mesenchymal stem cells, and Pf4+ megakaryocytes, to evaluate its role in the regulation of HSC fate. Interestingly, we demonstrated that only endothelial cell-derived ANGPTL2 and not ANGPTL2 from other niche cell types plays important roles in supporting repopulation capacity, quiescent status, and niche localization. Mechanistically, ANGPTL2 enhances peroxisome-proliferator-activated receptor D (PPARD) expression to transactivate G0s2 to sustain the perinuclear localization of nucleolin to prevent HSCs from entering the cell cycle. These findings reveal that endothelial cell-derived ANGPTL2 serves as a critical niche component to maintain HSC stemness, which may benefit the understanding of stem cell biology in bone marrow niches and the development of a unique strategy for the ex vivo expansion of HSCs.
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Malara, Alessandro, Cristian Gruppi, Paola Rebuzzini, Maria Enrica Tira i Alessandra Balduini. "New Mechanisms of Megakaryocyte-Matrix Interaction within Bone Marrow Environment." Blood 116, nr 21 (19.11.2010): 2626. http://dx.doi.org/10.1182/blood.v116.21.2626.2626.
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Abstract Abstract 2626 Background. The mechanisms by which megakaryocytes (Mks) proliferate, differentiate, and release platelets into circulation are not well understood. Mk maturation and platelet generation occur in the bone marrow and is consequent to Mk migration from the osteoblastic to the vascular niche, where Mks extend proplatelets and newly generated platelets can be released into the bloodstream. Growing evidence indicate that a complex regulatory mechanism, involving megakaryocyte-matrix interactions, may contribute to the quiescent or permissive microenvironment related to Mk differentiation and maturation within the bone marrow. It has been demonstrated that interactions of primary human Mks with matrices supposed to fill the vascular niche, such as fibrinogen or von Willebrand factor, is able to sustain Mk maturation and proplatelet formation, while type I collagen, in the osteoblastic niche, totally suppresses these events and prevents premature platelet release. The negative regulation of proplatelet formation by type I collagen is mediated by the interaction with integrin alpha2beta1, and involves the Rho/ROCK pathway. Hypothesis. The dynamic interaction of Mks with different extra-cellular matrices, that fill the bone marrow spaces, may orchestrate their maturation in specific sites. Despite the improvement in knowledge of biochemical niche, little is known about the mechanical force that regulate Mk-niche interactions. Therefore, in this work, we correlated activation of signaling cascade with generation of contractile force to understand the influences of bone marrow environment on Mk function. Methodology/Principal Findings. To address this hypothesis, we first demonstrated that human Mks express and synthesize cellular fibronectin (cFN), with a predominance of the EDA isoform, and transglutaminase FXIII-A. Thereafter, we proposed that these two molecules are involved in a new regulatory mechanism of Mk-type I collagen interaction in the osteoblastic niche. We propose that Mk adhesion on type I collagen promotes Mk spreading through a mechanism that involves FN, membrane receptors and FXIII-A activity. This mechanism seemed to be mediated by the exposure of cFN to the cell membrane and maintained by FN polymerization catalyzed by FXIII-A. These data address a new role to FN that, upon specific activation, could be released and thereby modulate Mk interaction with extracellular matrices. In this context FXIII-A catalyzes FN cross-linking at cellular sites, stabilizes FN assembly and promotes the organization of extracellular matrix. Consistently, the same mechanism regulated the assembly of plasma FN (pFN) by adherent Mks to type I collagen. Most importantly, our results demonstrated that only Mks adherent to type I collagen, and not to fibrinogen, were able to promote FN assembly. As a result, we observed that Mk adhesion to type I collagen promoted Mk spreading overtime, while Mks on fibrinogen showed a shortened spreading that was replaced by proplatelet formation in sixteen hours of adhesion. Thus, FN assembly regulate the anchoring of Mks to type I collagen with consequent activation of biochemical signalling and generation of contractile force that may prevent proplatelet formation. Conclusions/Significance. In conclusion, this study provides important new elements in the understanding of the regulatory pathways for Mk-matrix interactions within bone marrow environment. In particular, our results demonstrate that fibronectins and FXIII-A modulate Mk spreading on type I collagen by promoting matrix assembly. This work opens new prospective in the study of illnesses, such as primary myelofibrosis or MYH9-related thrombocytopenia, related to defect of Mk-matrix interactions within the bone marrow environment, whose origin is still matter of debate. Disclosures: No relevant conflicts of interest to declare.
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Miscopein Saler, Laurine, Virginie Hauser, Mathieu Bartoletti, Charlotte Mallart, Marianne Malartre, Laura Lebrun, Anne-Marie Pret, Laurent Théodore, Fabienne Chalvet i Sophie Netter. "The Bric-à-Brac BTB/POZ transcription factors are necessary in niche cells for germline stem cells establishment and homeostasis through control of BMP/DPP signaling in the Drosophila melanogaster ovary". PLOS Genetics 16, nr 11 (5.11.2020): e1009128. http://dx.doi.org/10.1371/journal.pgen.1009128.
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Many studies have focused on the mechanisms of stem cell maintenance via their interaction with a particular niche or microenvironment in adult tissues, but how formation of a functional niche is initiated, including how stem cells within a niche are established, is less well understood. Adult Drosophila melanogaster ovary Germline Stem Cell (GSC) niches are comprised of somatic cells forming a stack called a Terminal Filament (TF) and associated Cap and Escort Cells (CCs and ECs, respectively), which are in direct contact with GSCs. In the adult ovary, the transcription factor Engrailed is specifically expressed in niche cells where it directly controls expression of the decapentaplegic (dpp) gene encoding a member of the Bone Morphogenetic Protein (BMP) family of secreted signaling molecules, which are key factors for GSC maintenance. In larval ovaries, in response to BMP signaling from newly formed niches, adjacent primordial germ cells become GSCs. The bric-à-brac paralogs (bab1 and bab2) encode BTB/POZ domain-containing transcription factors that are expressed in developing niches of larval ovaries. We show here that their functions are necessary specifically within precursor cells for TF formation during these stages. We also identify a new function for Bab1 and Bab2 within developing niches for GSC establishment in the larval ovary and for robust GSC maintenance in the adult. Moreover, we show that the presence of Bab proteins in niche cells is necessary for activation of transgenes reporting dpp expression as of larval stages in otherwise correctly specified Cap Cells, independently of Engrailed and its paralog Invected (En/Inv). Moreover, strong reduction of engrailed/invected expression during larval stages does not impair TF formation and only partially reduces GSC numbers. In the adult ovary, Bab proteins are also required for dpp reporter expression in CCs. Finally, when bab2 was overexpressed at this stage in somatic cells outside of the niche, there were no detectable levels of ectopic En/Inv, but ectopic expression of a dpp transgene was found in these cells and BMP signaling activation was induced in adjacent germ cells, which produced GSC-like tumors. Together, these results indicate that Bab transcription factors are positive regulators of BMP signaling in niche cells for establishment and homeostasis of GSCs in the Drosophila ovary.
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Souza, Franco, João Rodrigues, Miguel Olalla-Tárraga, José Diniz-Filho, Pablo Martinez i Ricardo J. Sawaya. "Niche divergence and diversification in South American freshwater turtles of the genus Acanthochelys (Chelidae)". Amphibia-Reptilia 40, nr 4 (2019): 475–85. http://dx.doi.org/10.1163/15685381-20191211.
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Abstract Species distribution models (SDMs) are increasingly used to assess how ecological factors shape species distributions and diversification. Chelid turtles represent the richest family of chelonians in South America. Given the distributional disjunction and distinct habitats of four Acanthochelys species, we explored SDMs and niche overlap metrics between species pairs to evaluate the extent to which niche divergence or conservatism may have contributed to their geographic distribution patterns. None of the species pairs presented patterns consistent with niche conservatism suggesting that these species have different environmental requirements. However, when comparing species pairs co-occurring in the same watershed, results were conflicting. Niche divergence detected among Acanthochelys species indicate an interaction between ecological niche preference and geographical barriers for allopatric speciation. This interaction implies that ecological differentiation contributed to the diversification of Acanthochelys side-necked turtles that occur in South American freshwater environments.
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Iwasaki, Hiroko, Fumio Arai, Yoshiaki Kubota, Maria Dahl i Toshio Suda. "Endothelial protein C receptor–expressing hematopoietic stem cells reside in the perisinusoidal niche in fetal liver". Blood 116, nr 4 (29.07.2010): 544–53. http://dx.doi.org/10.1182/blood-2009-08-240903.
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Abstract Hematopoietic stem cells (HSCs) are maintained in specialized niches in adult bone marrow. However, niche and HSC maintenance mechanism in fetal liver (FL) still remains unclear. Here, we investigated the niche and the molecular mechanism of HSC maintenance in mouse FL using HSCs expressing endothelial protein C receptor (EPCR). The antiapoptotic effect of activated protein C (APC) on EPCR+ HSCs and the expression of protease-activated receptor 1 (Par-1) mRNA in these cells suggested the involvement of the cytoprotective APC/EPCR/Par-1 pathway in HSC maintenance. Immunohistochemistry revealed that EPCR+ cells were localized adjacent to, or integrated in, the Lyve-1+ sinusoidal network, where APC and extracellular matrix (ECM) are abundant, suggesting that HSCs in FL were maintained in the APC- and ECM-rich perisinusoidal niche. EPCR+ HSCs were in a relatively slow cycling state, consistent with their high expression levels of p57 and p18. Furthermore, the long-term reconstitution activity of EPCR+ HSCs decreased significantly after short culture but not when cocultured with feeder layer of FL-derived Lyve-1+ cells, which suggests that the maintenance of the self-renewal activity of FL HSCs largely depended on the interaction with the perisinusoidal niche. In conclusion, EPCR+ HSCs resided in the perisinusoidal niche in mouse FL.
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Koyanagi, Anri, Iichiroh Onishi, Karin Muraoka, Ikue Sato, Shingo Sato, Tsuyoshi Kimura, Akio Kishida, Kouhei Yamamoto, Masanobu Kitagawa i Morito Kurata. "Identification of the Factor that Leads Human Mesenchymal Stem Cell Lines into Decellularized Bone". Bioengineering 9, nr 10 (21.09.2022): 490. http://dx.doi.org/10.3390/bioengineering9100490.
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Hematopoiesis is maintained by the interaction of hematopoietic stem cells (HSCs) and bone marrow mesenchymal stem cells (MSCs) in bone marrow microenvironments, called niches. Certain genetic mutations in MSCs, not HSCs, provoke some hematopoietic neoplasms, such as myelodysplastic syndrome. An in vivo bone marrow niche model using human MSC cell lines with specific genetic mutations and bone scaffolds is necessary to elucidate these interactions and the disease onset. We focused on decellularized bone (DCB) as a useful bone scaffold and attempted to induce human MSCs (UE7T-9 cells) into the DCB. Using the CRISPR activation library, we identified SHC4 upregulation as a candidate factor, with the SHC4 overexpression in UE7T-9 cells activating their migratory ability and upregulating genes to promote hematopoietic cell migration. This is the first study to apply the CRISPR library to engraft cells into decellularized biomaterials. SHC4 overexpression is essential for engrafting UE7T-9 cells into DCB, and it might be the first step toward creating an in vivo human–mouse hybrid bone marrow niche model.
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Smutin, Daniil, Egor Lebedev, Maxim Selitskiy, Nick Panyushev i Leonid Adonin. "Micro”bee”ota: Honey Bee Normal Microbiota as a Part of Superorganism". Microorganisms 10, nr 12 (29.11.2022): 2359. http://dx.doi.org/10.3390/microorganisms10122359.
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Honey bees are model organisms for microbiota research. Gut microbiomes are very interesting for surveys due to their simple structure and relationship with hive production. Long-term studies reveal the gut microbiota patterns of various hive members, as well as the functions, sources, and interactions of the majority of its bacteria. But the fungal non-pathogenic part of gut microbiota is almost unexplored, likewise some other related microbiota. Honey bees, as superorganisms, interact with their own microorganisms, the microbial communities of food stores, hive surfaces, and other environments. Understanding microbiota diversity, its transition ways, and hive niche colonization control are necessary for understanding any separate microbiota niche because of their interplay. The long coevolution of bees with the microorganisms populating these niches makes these systems co-dependent, integrated, and stable. Interaction with the environment, hive, and other bees determines caste lifestyle as well as individual microbiota. In this article, we bring together studies on the microbiota of the western honey bee. We show a possible relationship between caste determination and microbiota composition. And what is primary: caste differentiation or microbiota composition?
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Bernasconi, Paolo, i Oscar Borsani. "Targeting Leukemia Stem Cell-Niche Dynamics: A New Challenge in AML Treatment". Journal of Oncology 2019 (7.08.2019): 1–12. http://dx.doi.org/10.1155/2019/8323592.
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One of the most urgent needs in AML is to improve the disease cure rate as relapse still occurs in 60–80% of patients. Recent evidence suggests that dismal clinical outcomes may be improved by a better definition of the tight interaction between the AML cell population and the bone marrow (BM) microenvironment (“the niche”); the latter has been progressively highlighted to have an active role in the disease process. It has now been well established that the leukemic population may misinterpret niche-derived signals and remodel the niche, providing a shelter to AML cells and protecting them from the cytotoxic effects of chemoradiotherapy. Novel imaging technological advances and preclinical disease models have revealed that, due to the finite number of BM niches, leukemic stem cells (LSCs) and normal hematopoietic stem cells (HSCs) compete for the same functional areas. Thus, the removal of LSCs from the BM niche and the promotion of normal HSC engraftment should be the primary goals in antileukemic research. In addition, it is now becoming increasingly clear that AML-niche dynamics are disease stage specific. In AML, the niche has been linked to disease pathogenesis in the preleukemic stage, the niche becomes permissive once leukemic cells are established, and the niche is transformed into a self-reinforcing structure at a later disease stage. These concepts have been fostered by the demonstration that, in unrelated AML types, endosteal vessel loss occurs as a primary AML-induced niche alteration, and additional AML-induced alterations of the niche and normal hematopoiesis evolve focally and in parallel. Obviously, this endosteal vessel loss plays a fundamental role in AML pathogenesis by causing excessive vascular permeability, hypoxia, altered perfusion, and reduced drug delivery. Each of these alterations may be effectively targeted by various therapeutic procedures, but preservation of endosteal vessel integrity might be the best option for any future antileukemic treatment.
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Dorn, David C. "Stem cell autotomy and niche interaction in different systems". World Journal of Stem Cells 7, nr 6 (2015): 922. http://dx.doi.org/10.4252/wjsc.v7.i6.922.
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Yu, Qianqian, Hongyu Li, Bing Zhang, Yun Song, Yueying Sun i Zhaojun Ding. "ATP Hydrolases Superfamily Protein 1 (ASP1) Maintains Root Stem Cell Niche Identity through Regulating Reactive Oxygen Species Signaling in Arabidopsis". Plants 13, nr 11 (26.05.2024): 1469. http://dx.doi.org/10.3390/plants13111469.
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The maintenance of the root stem cell niche identity in Arabidopsis relies on the delicate balance of reactive oxygen species (ROS) levels in root tips; however, the intricate molecular mechanisms governing ROS homeostasis within the root stem cell niche remain unclear. In this study, we unveil the role of ATP hydrolase superfamily protein 1 (ASP1) in orchestrating root stem cell niche maintenance through its interaction with the redox regulator cystathionine β-synthase domain-containing protein 3 (CBSX3). ASP1 is exclusively expressed in the quiescent center (QC) cells and governs the integrity of the root stem cell niche. Loss of ASP1 function leads to enhanced QC cell division and distal stem cell differentiation, attributable to reduced ROS levels and diminished expression of SCARECROW and SHORT ROOT in root tips. Our findings illuminate the pivotal role of ASP1 in regulating ROS signaling to maintain root stem cell niche homeostasis, achieved through direct interaction with CBSX3.
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Zhang, Qing, Ruwang Jiao, Sanyou Zeng i Zhigao Zeng. "Balancing Exploration and Exploitation With Decomposition-Based Dynamic Multi-Objective Evolutionary Algorithm". International Journal of Cognitive Informatics and Natural Intelligence 15, nr 4 (październik 2021): 1–23. http://dx.doi.org/10.4018/ijcini.20211001.oa25.
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Balancing exploration and exploitation is a crucial issue in evolutionary global optimization. This paper proposes a decomposition-based dynamic multi-objective evolutionary algorithm for addressing global optimization problems. In the proposed method, the niche count function is regarded as a helper objective to maintain the population diversity, which converts a global optimization problem to a multi-objective optimization problem (MOP). The niche-count value is controlled by the niche radius. In the early stage of evolution, a large niche radius promotes the population diversity for better exploration; in the later stage of evolution, a niche radius close to 0 focuses on convergence for better exploitation. Through the whole evolution process, the niche radius is dynamically decreased from a large value to zero, which can provide a sound balance between the exploration and exploitation. Experimental results on CEC 2014 benchmark problems reveal that the proposed algorithm is capable of offering high-quality solutions, in comparison with four state-of-the-art algorithms.
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Korneva, Yulia S., i Roman V. Ukrainets. "Principles of premetastatic niche formation". Journal of Modern Oncology 21, nr 4 (7.05.2020): 6–9. http://dx.doi.org/10.26442/18151434.2019.4.190715.
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The article is devoted to premetastatic niche as a complex term, including stromal cells, vessels, extracellular matrix and their changes during interaction with the primary tumor. On example of different malignant tumors authors describe as primary tumor through tumor exosomes prepares certain organs-recipients to metastatic clone implantation. In the area of premetastatic niche under the influence of tumorous exosomes polarization of macrophages towards M2 type takes place. The cells are the main agents, providing survival as well as migration of tumorous cells. Affecting extracellular matrix, macrophages change the microcirculatory bed permeability. This mechanism is directed towards increase of its permeability to entrance of metastatic clone cells form vessels into premetastatic niche. Besides macrophages fibroblasts and polypotent bone marrow stem cells are also reprogrammed, that results in metabolism and local immunity changes at the place of future implantation. As a result, only when tissue of recipient-organ is prepared for contact with metastatic clone, their interaction take place with consequent formation of secondary tumor metastatic niche. Thus, this review describes pathogenesis of metastasis, different from its early understanding as spread of metastatic clone with lymph and blood.
These peculiarities may in future have significant impact in practical medicine, Blockage of signal spread from primary tumor through exosomes is one of the promising directions in pathogenetic therapy of malignant tumors. Investigation of principles of premetastatic niche formation may become a theoretical substantiation for prophylaxis of metastatic disease and inhibition of micrometastasis to macrometastasis transformation.
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Sentosa, Agus Arifin, Astri Suryandari i Amula Nurfiarini. "TROPHIC INTERACTIONS OF THE FISH COMMUNITIES IN CIRATA RESERVOIR, WEST JAVA". Indonesian Fisheries Research Journal 27, nr 2 (20.09.2021): 79. http://dx.doi.org/10.15578/ifrj.27.2.2021.79-90.
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The utilization of food resources by the fish communities in the Cirata Reservoir depends on the environmental conditions of the reservoir. Eutrophication and the presence of potentially invasive alien fishes could affect the trophic interactions of food utilization by the fish communities in the Cirata reservoir. This study aimed to analyze the trophic interactions of the fish communities in the Cirata Reservoir, West Java. The samplings were conducted in October, December 2018, and April 2019. The fish samples were collected using experimental gill nets with different mesh sizes. The stomach contents were dissected to study their food habits under a stereoscopic microscope. Data analysis was performed using the index of preponderance, niche breadth, trophic level, and index Schoener. A total of 21 species of fishes in the Cirata Reservoir utilized food resources, including phytoplankton, zooplankton, aquatic plants/macrophytes, molluscs, insects (adult and larvae), worms, a body part of fishes and crustaceans, pellets and detritus. The fish communities had a wide range of niche between 0.00-0.32 and trophic levels between 2.00-3.63. The non-native fishes in the Cirata Reservoir had the food overlapping potential with native fishes, from low to high categories, especially from the Cichlidae. Trophic interaction of fish communities in the Cirata reservoir was still relatively stable, characterized by overlapping food niche in the low to medium categories. The fish stock enhancement effort such as fish introduction or restocking in the Cirata Reservoir could still be carried out with a precautionary approach to filling empty niches and avoiding the potential for invasive alien fish species.
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Petrova, Tatiana V., Irina N. Nifontova, Daria A. Svinareva, Maria A. Vinogradova, Elena A. Michaylova i Nina J. Drize. "Improvement of Hematopoietic and Stromal Cells Interaction after PTH Treatment of Long-Term Bone Marrow Cultures from Patients with Aplastic Anemia." Blood 108, nr 11 (16.11.2006): 1401. http://dx.doi.org/10.1182/blood.v108.11.1401.1401.
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Abstract Alterations in hematopoietic and stromal cells interactions could be one of the causes of aplastic anemia (AA). Assuming the existence of two types of stromal niches where hematopoietic stem cells (HSC) reside, - osteoblastic niche that regulates survival, self-maintenance abilities, adhesion, homing and quiescence, and vascular niche controlling proliferation and differentiation, - one could suggest an impairment of regulation in both of them in AA patients. As parathyroid hormone (PTH) activates osteoblasts it could potentially improve the survival of HSC in patients with various hematopoietic disorders. The aim of this study was to compare several functional characteristics of stromal cells from healthy donors and AA patients. In order to study stromal microenvironment capable to maintain hematopoiesis, long-term bone marrow cultures were established from 19 patients with AA and 24 healthy donors as a control group. PTH was added for 3 and 6 weeks of cultivation in concentration 10−8, 5x10−8 and 10−7 M once a week while changing half of the media. The proportion of CAFC 7 and CAFC 28–35 from the donor bone marrow survived cocultivation for 2–5 days with irradiated adherent cell layers (ACLs) of AA patients was estimated by limiting dilution assay. To characterize alterations in the expression of several genes in ACLs semi-quantitative analysis of RT-PCR products was performed using PhosphoImager Cyclone, Packard Bell (USA), after Southern blot hybridization with appropriate sequences. The level of b-actin expression was used as a normalization factor. All data from the patients was compared with corresponding gene’s expression level in donors ACLs. Among studied signaling molecules involved in niche regulation Ang-1 expression was significantly decreased (2.3-fold) in ACLs of patients after 3 weeks in culture. Further cultivation led to normalization of Ang-1 expression. Another difference in osteoblastic niche regulating genes was revealed in Notch 1 signaling. While in ACLs from donor bone marrow it increased 2-fold during cultivation, it was stable in ACLs from the patients. Expression level of ICAM-1 responsible for adhesion of HSC to osteoblasts in niche also increased (4-fold) during cultivation in ACLs from donors and did not change in AA patients. Expression level of all other studied genes of osteoblastic niche signaling pathways was not altered in ACLs of AA patients. Analysis of genes regulating stromal cells in vascular niche revealed increased level of VEGF (2-fold) accompanied with 2-fold decreased expression of VCAM-1 in ACLs of the patients. Expression level of both genes normalized with further cultivation. The data suggest the functional inhibition of stromal microenvironment in patients with aplastic anemia that could be overcomed by cultivation ex vivo. PTH treatment activating gene expression in ACLs of donors did not affect universally the same genes in patients. Nevertheless treatment with PTH improved survival (2–3-fold) of long-term repopulating HSC (CAFC 28–35) from donors bone marrow explanted on irradiated ACLs of AA patients. The survival rate of short-repopulating HSC (CAFC 7) was not sensitive to PTH treatment. So, in patients with aplastic anemia the impairment of stromal regulation of HSC was observed both in osteoblastic and vascular niches. PTH being the osteoblasts activator could partially improve functioning of stromal microenvironment and hence the HSC survival.
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Thomas, Zachary, Bowen Wang i Rong Lu. "Heterogeneous Intercellular Communication of Hematopoietic Stem Cells in the Mouse Bone Marrow". Blood 142, Supplement 1 (28.11.2023): 5617. http://dx.doi.org/10.1182/blood-2023-188073.
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Introduction.Hematopoietic stem cells (HSCs) are responsible for maintaining the homeostasis of the blood and immune systems. This process must rapidly adapt to bleeding, infection, injury, and disease. HSCs reside in specialized microenvironments in the bone marrow, called “niche”. Several bone marrow cell types have been proposed as the key components of the niche. It is well established that HSCs rely on molecular signals from the niche cells to survive, migrate, proliferate, and differentiate. Recent studies suggest that HSCs differentiate heterogeneously. Additionally, the bone marrow is a heterogeneous environment consisting of more than thirty cell types. This study will test the hypothesis that individual HSCs are engaged in heterogeneous intercellular signaling in the bone marrow. Materials and Methods.We utilized CellChat (Jin et al., 2021), a database for ligand-receptor pairs and associated pathways, to predict cell-cell signaling at the single cell level. We used single cell RNA sequencing data from mouse hematopoietic stem and progenitor cells, blood and immune cells, and non-hematopoietic cells from the bone marrow to determine putative cell-cell interactions. The predicted signaling interactions were then adjusted based on the cell-cell spatial interaction revealed by PhenoCycler measurement (Akoya Biosciences). Mouse bone marrow transplantation experiments were performed to test the functional significance of the identified signaling pathway interactions. Results.We found that individual HSCs send and receive different levels of molecular signals across various signaling pathways. In addition to the expected interactions with the known HSC niche cells, we also found new interactions between HSCs and their progeny cells including myeloid progenitors and immune cells. These cell-cell signaling interactions are consistent with the spatial interaction frequencies of the corresponding cell types as revealed by our imaging data from the PhenoCycler analysis. Further, we found that some signaling pathways are positively or negatively correlated across individual HSCs, indicating complex intercellular signaling networks. The most significant negative correlation was found between HSCs sending MHC-I signals and sending PARs signals (Figure). Moreover, this MHC-I/PARs signaling correlation network also involves signaling from the HSC niche, including those that are known to play roles in HSC homing such as ESAM and VCAM. Therefore, we tested the engraftment efficiency of HSCs that receive PARs and those that do not using the HSC mouse transplantation model. We found that PAR1 + HSCs engraft much less efficiently. Finally, we present the HSC Interaction Data Explorer (HIDE), a database that comprehensively depicts the interactions between HSCs and other bone marrow cells including the involved signaling pathways, ligands and receptors of the pathways, and the pathway correlations. Conclusion.Our study uncovered novel interactions of HSCs with myeloid progenitor cells and immune cells, which were validated by spatial interaction data. These interactions indicate feedback signaling in regulating blood cell regeneration. Our findings further revealed signaling pathway correlation networks across individual HSCs, and we showed their functional significance using transplantation experiments. Finally, we present HIDE as a resource that informs the interactions between HSCs and various bone marrow cells, the relevant signaling pathways, and the pathway correlations. Figure Legend. HSC signaling correlation networks. Each node shows a signaling pathway and direction (e.g., HSCs sending MHC-I). The edges represent the spearman correlation score.
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Haas, Simon, Chiara Baccin, Jude Al-Sabah, Lars Velten, Steinmetz Lars i Andreas Trumpp. "Combined Single-Cell and Spatial Transcriptomics to Deconvolute the Hematopoietic Stem Cell Niche". Blood 132, Supplement 1 (29.11.2018): 876. http://dx.doi.org/10.1182/blood-2018-99-118479.
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Abstract Coordinated interaction of many cell types is required to facilitate hematopoietic and mesenchymal stem cell maintenance and differentiation in the bone marrow. However, the molecular factors and cell types involved in this complex interplay remain poorly understood. Here we developed a combined single cell and spatial transcriptomics approach to address this problem. Large-scale single-cell transcriptional profiling in conjunction with a multi-layered sorting approach allowed us to generate a complete and evenly sampled transcriptional map of all major bone and bone marrow populations. Our dataset covers all cell types or differentiation trajectories involved in mesenchymal and hematopoietic stem cell differentiation, osteogenesis, adipogenesis, myelopoiesis, erythropoiesis, lymphopoiesis, memory T cell formation as well as bone marrow neural innervation and vascularization at the single cell level. Using this data, we derive fundamental properties of the described cell types, clarify the cellular source of signals affecting stem cell differentiation processes and provide a systems view on putative intercellular interactions. Systematic spatial transcriptomics, using laser-capture microdissection of selected bone marrow niches followed by transcriptional profiling and bioinformatic cellular deconvolution, allowed us to confirm predicted interactions and map the cellular composition of distinct bone marrow niches. Our analyses highlight the importance of pre-adipogenic CXCL12 abundant reticular cells as key niche cells for stem cell maintenance, provides a holistic systems view of the hematopoietic stem cell niche and offers a novel approach to systematically deconvolute the molecular, cellular and spatial composition of complex tissues. Disclosures No relevant conflicts of interest to declare.
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Medyouf, Hind. "The microenvironment in human myeloid malignancies: emerging concepts and therapeutic implications". Blood 129, nr 12 (23.03.2017): 1617–26. http://dx.doi.org/10.1182/blood-2016-11-696070.
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Abstract Similar to their healthy counterpart, malignant hematopoietic stem cells in myeloid malignancies, such as myeloproliferative neoplasms, myelodysplastic syndromes, and acute myeloid leukemia, reside in a highly complex and dynamic cellular microenvironment in the bone marrow. This environment provides key regulatory signals for and tightly controls cardinal features of hematopoietic stem cells (HSCs), including self-renewal, quiescence, differentiation, and migration. These features are essential to maintaining cellular homeostasis and blood regeneration throughout life. A large number of studies have extensively addressed the composition of the bone marrow niche in mouse models, as well as the cellular and molecular communication modalities at play under both normal and pathogenic situations. Although instrumental to interrogating the complex composition of the HSC niche and dissecting the niche remodeling processes that appear to actively contribute to leukemogenesis, these models may not fully recapitulate the human system due to immunophenotypic, architectural, and functional inter-species variability. This review summarizes several aspects related to the human hematopoietic niche: (1) its anatomical structure, composition, and function in normal hematopoiesis; (2) its alteration and functional relevance in the context of chronic and acute myeloid malignancies; (3) age-related niche changes and their suspected impact on hematopoiesis; (4) ongoing efforts to develop new models to study niche-leukemic cell interaction in human myeloid malignancies; and finally, (5) how the knowledge gained into leukemic stem cell (LSC) niche dependencies might be exploited to devise novel therapeutic strategies that aim at disrupting essential niche-LSC interactions or improve the regenerative ability of the disease-associated hematopoietic niche.
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Rhodes, Katherine A., Man Cheong Ma, María A. Rendón i Magdalene So. "Neisseria genes required for persistence identified via in vivo screening of a transposon mutant library". PLOS Pathogens 18, nr 5 (17.05.2022): e1010497. http://dx.doi.org/10.1371/journal.ppat.1010497.
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The mechanisms used by human adapted commensal Neisseria to shape and maintain a niche in their host are poorly defined. These organisms are common members of the mucosal microbiota and share many putative host interaction factors with Neisseria meningitidis and Neisseria gonorrhoeae. Evaluating the role of these shared factors during host carriage may provide insight into bacterial mechanisms driving both commensalism and asymptomatic infection across the genus. We identified host interaction factors required for niche development and maintenance through in vivo screening of a transposon mutant library of Neisseria musculi, a commensal of wild-caught mice which persistently and asymptomatically colonizes the oral cavity and gut of CAST/EiJ and A/J mice. Approximately 500 candidate genes involved in long-term host interaction were identified. These included homologs of putative N. meningitidis and N. gonorrhoeae virulence factors which have been shown to modulate host interactions in vitro. Importantly, many candidate genes have no assigned function, illustrating how much remains to be learned about Neisseria persistence. Many genes of unknown function are conserved in human adapted Neisseria species; they are likely to provide a gateway for understanding the mechanisms allowing pathogenic and commensal Neisseria to establish and maintain a niche in their natural hosts. Validation of a subset of candidate genes confirmed a role for a polysaccharide capsule in N. musculi persistence but not colonization. Our findings highlight the potential utility of the Neisseria musculi-mouse model as a tool for studying the pathogenic Neisseria; our work represents a first step towards the identification of novel host interaction factors conserved across the genus.
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Chen, Shuying, Qing Rao, Haiyan Xing, Jing Yu, Huan Li, Min Wang i Jianxiang Wang. "Rac1 Gtpase Promotes Hematopoietic Stem Cell Migration, Self-Renewal and Participates in Leukemia Initiation and Maintenance". Blood 124, nr 21 (6.12.2014): 2923. http://dx.doi.org/10.1182/blood.v124.21.2923.2923.
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Abstract Acute myeloid leukemia (AML) is a hematological malignancy resulting from the transformation of normal hematopoietic stem cell (HSC). Except for the intrinsic factors, it is acceptable that some extrinsic events from microenvironment could be the important co-factors in the development of leukemia. In addition to the specific component, as an extrinsic factor, interaction between HSC and bone marrow niche regulates HSCs fate. Disruption on the interactions also influences hematopoiesis. It has become evident that Rac members of Rho GTPases family are important molecules regulating HSCs interactions with hematopoietic microenvironment and activation of Rac1 are observed in a serials of leukemia cells. We previously reported that Rac1 is highly expressed in leukemia cells and found that activation of Rac1 GTPase lead to an increase in leukemia cells migration, chemotherapy resistance, quiescence and trafficking to bone marrow niche. Furthermore, we showed that Rac1 mediated the localization in niche is further attributable to the maintenance of LSC quiescence. In this study, we investigated the effects of active Rac1 GTPase in the transformation of HSC and determined if the activation of Rac1GTPase could promote the interaction of HSC with osteoblastic niche and further contribute to the leukomogenesis. By forced expression of a constitutively active form of Rac1 GTPase (Rac1 V12）in c-Kit+ hematopoietic stem/progenitor cell, we show that activation of Rac1 GTPase promotes cell migration, adhesion and colony formation, and also lead to an increase in the frequency of cells in quiescent state. Gene expression analysis shows that activation of Rac1 up-regulates the expression of several molecules that mediated the interaction of LSC with osteoblastic niche, as well as the cell cycle inhibitors such as p21, p27, and p57. Furthermore, we established a mouse model of acute myeloid leukemia by transduction murine c-kit+HSPC with Rac1 V12 combined with AML1-ETO9a, followed by transplantation into lethally irradiated mice. To investigate the role of Rac1 activation in leukemogenesis in vivo, we treated the AML1-ETO-Rac1 leukemia cells with Rac1 GTPase inhibitor EHT1846 and then transplanted into recipient mice. After 40 μM EHT1846 treatment, no engraftment of AML cells in recipient mice was observed. Kaplan-Meier analyses indicate that treatment with EHT1846 significantly prolongs survival of the transplanted mice. 20μM dose of EHT1846 was less effective. These data indicated that active Rac1 might be an important contributing factor to leukemogenesis. In addition, short-term homing assays showed that EHT 1846 treatment causes a marked inhibition of AML cell homing into both bone marrow and spleen as compared with controls, indicating that Rac1 mediated homing could be an important step and participated in the leukemogensis. Altogether, our data suggest that activation of Rac1 GTPase is critical for the interaction between HSCs with BM niche and even be contributed to leukemia development. Disclosures Wang: Novartis: Consultancy; Bristol Myers Squibb: Consultancy.
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Yang, Ruiqi, Tony Haykal, Celine Tohme, Ronghua Wang, Christof Kaltenmeier, David Geller, Hamza Yazdani i Samer Tohme. "Abstract 1317: Exercise training prevents exosome mediated pre-metastatic niche formation in the liver". Cancer Research 83, nr 7_Supplement (4.04.2023): 1317. http://dx.doi.org/10.1158/1538-7445.am2023-1317.
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Abstract Introduction: Primary tumor cells release exosomes facilitating pre-metastatic niche formation in distant organs, initiating the process of metastasis. As metastasis is the main prognostic factor for patients, it is essential to understand the pre-metastatic niches and develop therapies to target them. It has been shown that Kupffer cells play an crucial role in the formation of pre-metastatic niche in the liver. We have recently shown that exercise training (ExT) alters the phenotype of Kupffer cells and attenuates tumor metastasis after surgery. Here, we hypothesize that ExT can interfere with exosome mediated pre-metastatic niches, hence decreasing metastasis. Methods: Eight-week-old male mice were randomized into sedentary and ExT group. Mice were pre-educated with cancer exosomes for 4 weeks to induce pre-metastatic niche and intra-splenically injected with murine colorectal cancer (MC38) cells. Tumor metastasis and growth was followed by 3 weeks. Results: Compared to the sedentary group, there was a significant decrease in metastatic nodules and hepatic tumor replacement in the ExT mice liver. To further study the effects of ExT, livers from both groups were harvested 4 weeks after exosome pre-education. We observed decrease in the uptake of tumor exosome, immune cells infiltration and fibronectin deposition in the ExT livers, which demonstrates less pre-metastatic niche formation. Bulk RNA sequencing was performed on Kupffer cells isolated from both groups. Ingenuity pathway analysis shows that Triggering Receptor Expressed on Myeloid cells 1 (TREM1) signaling pathway was downregulated in EXT group, indicating less activation of Kupffer cells. Conclusions: These results indicate that exercise reduces pre-metastatic niche formation and tumor metastasis by affecting the interaction between cancer exosomes and Kupffer cells. In light of these findings, potential may exist to reduce exosome-induced liver pre-metastatic niches through the use of ExT as a nonpharmacologic therapy in patients with cancer. Citation Format: Ruiqi Yang, Tony Haykal, Celine Tohme, Ronghua Wang, Christof Kaltenmeier, David Geller, Hamza Yazdani, Samer Tohme. Exercise training prevents exosome mediated pre-metastatic niche formation in the liver [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1317.
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Ran, Dan, Isabel Taubert, Larissa Pietsch, Patrick Wuchter, Isabelle Hellwig, Rainer Saffrich, Volker Eckstein, Anthony D. Ho i Mario Schubert. "Molecular Determinants and Functional Characteristics of Leukemic Stem Cells and Their Interaction with the Niche." Blood 114, nr 22 (20.11.2009): 1427. http://dx.doi.org/10.1182/blood.v114.22.1427.1427.
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Abstract Abstract 1427 Poster Board I-450 Introduction We have recently described a subset of leukemic stem cells (LSC) with a high activity of aldehyde dehydrogenase (ALDHbr) that was prospectively isolated from the bone marrow of patients with newly diagnosed AML. These cells, among other features, were characterized by their increased affinity to the stem cell niche. We therefore hypothesized that the niche interaction may be a regulatory and protective factor for LSC. Hence, in the current study, we further characterized the LSC-niche interaction on single cell level, identified molecules that propagated LSC adhesion to the niche, and have correlated those features to functional characteristics like cell proliferation, chemotherapy resistance, and clinical outcome. Material & Methods Mononuclear cells from the bone marrow or peripheral blood of patients with primary AML were obtained and LSC candidates were freshly isolated by Aldeflour staining followed by flow cytometry sorting based on their side scatter characteristics (SSC) and high ALDH activity (ALDHbr); cells from the same SSC-region with low ALDH activity (ALDHdim) served as a control population. Subpopulations were further narrowed down by additional staining for CD34, CD133, or CD38. Expression of adhesion molecules like CXCR4, Cdh2, or CD44 was comparatively measured by quantitative real-time PCR and flow cytometry. The influence of the niche interaction on adhesion molecule expression was evaluated by co-cultures with mesenchymal stromal cells (MSCs) which served as a surrogate niche model. Cell fate, divisional kinetics, and clonal evolution of LSC candidates - both with and without contact to the stromal niche - were evaluated on a single cell level. Additionally, leukemic subsets were treated with chemotherapeutic agents, with and without MSC co-cultures, and vital cells were quantified by PI-/AxV-staining followed by flow cytometry. Co-incubation with novel CXCR4-antagonists and functional in vivo assays are currently underway. Results Adhesion molecules, such as CD44s, Cdh2, and CXCR4, were consistently increased in the LSC subpopulations - both on mRNA and protein level (n=30; p<0.05). Their expression was further upregulated upon niche interaction in a time-dependent manner. For instance, the CXCR4 expression was elevated 3- to 6-fold within 24 hours cultivation with MSCs in our in vitro culture system, then gradually decreased, and was even downregulated at later timepoints. After chemotherapy treatment, significantly more vital cells were found in the ALDHbr subset as compared to ALDHdim cells; even more leukemic cells survived upon co-culture with MSC. The descendants of single LSC clones expressed the original aberrations that were present at diagnosis. Conclusion Our current data confirmed that a LSC subset can be isolated based on a high ALDH activity. The increased expression of adhesion molecules in this subset mediates a close affinity to the marrow niche, which, in turn, protects LSC against proapoptotic stimuli and helps them maintain their stem cell features. Our present study and our ongoing research will help in developing novel therapeutic methods, i.e. interfering with the niche interaction and, thus, render LSC susceptible to conventional chemotherapy treatment. Disclosures No relevant conflicts of interest to declare.
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Wang, Lingjun, i Yuanyuan Li. "Research on Niche Improvement Path of Photovoltaic Agriculture in China". International Journal of Environmental Research and Public Health 19, nr 20 (12.10.2022): 13087. http://dx.doi.org/10.3390/ijerph192013087.
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To explore the niche improvement path of photovoltaic agriculture in China, a niche influencing factor system was constructed first. Then, this study innovatively combined the DEMATEL and analytic network process (DANP) method and the NK model, which can correct the defects of the traditional NK model. Based on the above method, the influence coefficients and index weight of each niche factor were calculated, and the niche fitness landscape of photovoltaic agriculture was constructed. Finally, according to the fitness landscape map of each combination state, the optimal configuration state of niche influencing factors of photovoltaic agriculture and the optimal niche improvement path of photovoltaic agriculture were explored. We found that the interaction between the six niche influencing factors determines the niche fitness of photovoltaic agriculture, and the changes in the niche fitness and the niche improvement of photovoltaic agriculture are coordinated. It was proposed that the optimal niche improvement path of photovoltaic agriculture in China is “technological innovation → policy formulation → resource allocation → economic improvement → social recognition → environmental protection”, and the research conclusions were further explained and discussed.
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Aprile, Annamaria, Alessandro Gulino, Mariangela Storto, Isabella Villa, Stefano Beretta, Ivan Merelli, Alessandro Rubinacci i in. "Hematopoietic stem cell function in β-thalassemia is impaired and is rescued by targeting the bone marrow niche". Blood 136, nr 5 (30.07.2020): 610–22. http://dx.doi.org/10.1182/blood.2019002721.
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Abstract Hematopoietic stem cells (HSCs) are regulated by signals from the bone marrow (BM) niche that tune hematopoiesis at steady state and in hematologic disorders. To understand HSC-niche interactions in altered nonmalignant homeostasis, we selected β-thalassemia, a hemoglobin disorder, as a paradigm. In this severe congenital anemia, alterations secondary to the primary hemoglobin defect have a potential impact on HSC-niche cross talk. We report that HSCs in thalassemic mice (th3) have an impaired function, caused by the interaction with an altered BM niche. The HSC self-renewal defect is rescued after cell transplantation into a normal microenvironment, thus proving the active role of the BM stroma. Consistent with the common finding of osteoporosis in patients, we found reduced bone deposition with decreased levels of parathyroid hormone (PTH), which is a key regulator of bone metabolism but also of HSC activity. In vivo activation of PTH signaling through the reestablished Jagged1 and osteopontin levels correlated with the rescue of the functional pool of th3 HSCs by correcting HSC-niche cross talk. Reduced HSC quiescence was confirmed in thalassemic patients, along with altered features of the BM stromal niche. Our findings reveal a defect in HSCs in β-thalassemia induced by an altered BM microenvironment and provide novel and relevant insight for improving transplantation and gene therapy approaches.
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Kléparski, Loïck, Grégory Beaugrand, Martin Edwards, François G. Schmitt, Richard R. Kirby, Elsa Breton, François Gevaert i Emeline Maniez. "Morphological traits, niche-environment interaction and temporal changes in diatoms". Progress in Oceanography 201 (luty 2022): 102747. http://dx.doi.org/10.1016/j.pocean.2022.102747.
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Arai, Fumio, Atsushi Hirao, Kentaroh Hosokawa i Toshio Suda. "Role of Cell Adhesion in the Maintenance of Hematopoietic Stem Cells in the Bone Marrow Niche." Blood 104, nr 11 (16.11.2004): 669. http://dx.doi.org/10.1182/blood.v104.11.669.669.
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Abstract Interaction of HSCs with their particular microenvironments, known as the stem cell niches, is critical for adult hematopoiesis in the bone marrow (BM). HSCs are keeping the balance of the quiescence and the self-renewal in the stem cell niche, and are maintaining long-term hematopoiesis. We have demonstrated that HSCs expressing the receptor tyrosine kinase Tie2 are quiescent and anti-apoptotic, transplantable and comprise a side-population (SP) of HSCs, which contact closely to angiopoietin-1, a ligand for Tie2, expressing osteoblasts (OBs) in the BM niche. Tie2 and Ang-1 are part of a key signaling interaction between HSCs and niche cells. This signaling pathway regulates the feature of HSCs in the BM niche. The interaction of Tie2 with Ang-1 in vitro is sufficient to maintain the long-term blood-repopulating (LTR) activity of HSCs in vivo by preventing cell division. In addition, Ang-1 enhanced the ability of HSCs to become quiescent and also induced their adhesion to bone surface, resulting protection of HSC compartment from stresses which suppress hematopoiesis (Arai et al., Cell, 2004). In this study, we focused on the role of cell adhesion molecule on the maintenance of HSCs in BM niche. A previous paper reported that both quiescent HSCs and some of osteoblasts express N-cadherin. We found that Tie2+ HSC expressed N- and VE-cadherin, and OBs expressed N-, P-, and OB-cadherin. This suggests that an adherens junction between HSCs and OBs created via N-cadherin may contribute to HSC maintenance. Furthermore, N-cadherin overexpressing OP9 stromal cells (OP9/N-cadherin) maintained LTC-IC more than control OP9 cells did. Overexpression of N-cadherin in HSCs also maintained colony formation. In addition, in the presence of Ang-1 in coculture of OP9/N-cadherin and HSCs facilitated the maintenance of CFU-C and HPP-CFC formation after long-term culture. Furthermore, Ang-1 treatment upregulated the expression of N-cadherin in Tie2+ HSCs as well as β1-integrin. It suggests that Tie2/Ang-1 signaling enhanced cell-cell adhesion between HSCs and OBs. Altogether, these observations led us to the novel model that the localization of HSCs on bone surface is regulated by stem cell specific adhesion molecules such as N-cadherin. Once the HSCs adjacently localize to OBs, Ang-1 produced by OBs may activate Tie2 on the HSCs and promote tight adhesion of HSCs in the niche, resulting in quiescence and enhanced survival of HSCs.
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Yin, Tong, Yucai Xie, Winfried Wiegraebe, Xi He i Linheng Li. "Detection of Functional Hematopoietic Stem Cell Niche Using Real-Time Imaging". Blood 112, nr 11 (16.11.2008): 550. http://dx.doi.org/10.1182/blood.v112.11.550.550.
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Abstract Hematopoietic stem cell (HSC) niches play an essential role in regulating adult stem cell self-renewal and differentiation. HSC niches have only recently been identified based on genetic models that showed a parallel increase in the numbers of both HSCs and osteoblasts, or by static immunolabeling of putative HSCs and the adjacent locations. However, osteoblasts and vasculature were viewed as separate niches with distinctive roles, their interrelationships and interactions with HSCs in vivo remain largely undefined. To study the dynamic interaction between the HSC and its niche, we developed a method of ex vivo imaging stem cells (EVISC) using two-photon microscopy. This method combined the technology of real-time imaging and the functional feature that Flk2−LSK HSCs can be prospectively isolated with high purity and can home to their niche upon transplantation into irradiated recipient mice. Using EVISC in combination with immunoassaying, we found that transplanted HSCs tended to home to the endosteal region predominantly in the trabecular bone area (TBA) compared to compact bone area (CBA) under irradiated conditions, but were randomly distributed and unstable under non-irradiated conditions. Mechanistically, we found that the ratio of expression level of SDF-1 between TBA and CBA was significantly increased in response to irradiation. By monitoring individual HSC behavior using EVISC ranging from minutes to 16-hours, we found that a small portion of the homed HSCs underwent active division in the irradiated mice, coinciding with their initial expansion as measured by flow assay and immunoassay. Our findings suggest that the endosteal region in the trabecular bone area formed a special zone, which normally maintains HSCs but promotes their expansion in response to irradiation. This zone includes both osteoblastic and vascular components and signals, which both underwent dynamic changes from homeostatic to stressed conditions.
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Wang, Xiangping, Tong Zeng, Mingsong Wu i Dianxiang Zhang. "Seasonal dynamic variation of pollination network is associated with the number of species in flower in an oceanic island community". Journal of Plant Ecology 13, nr 5 (11.08.2020): 657–66. http://dx.doi.org/10.1093/jpe/rtaa054.
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Abstract Aims Plant–pollinator interaction networks are dynamic entities, and seasonal variation in plant phenology can reshape their structure on both short and long timescales. However, such seasonal dynamics are rarely considered, especially for oceanic island pollination networks. Here, we assess changes in the temporal dynamics of plant–pollinator interactions in response to seasonal variation in floral resource richness in oceanic island communities. Methods We evaluated seasonal variations of pollination networks in the Yongxing Island community. Four temporal qualitative pollination networks were analyzed using plant–pollinator interaction data of the four seasons. We collected data on plant–pollinator interactions during two consecutive months in each of the four seasons. Four network-level indices were calculated to characterize the overall structure of the networks. Statistical analyses of community dissimilarity were used to compare this community across four seasons to explore the underlying factors driving these patterns. We also evaluated the temporal variation in two species-level indices of plant and pollinator functional groups. Important Findings Both network-level specialization and modularity showed a significantly opposite trend compared with plant species richness across four seasons. Increased numbers of plant species might promote greater competition among pollinators, leading to increased niche overlap and causing decreased specialization and modularity and vice versa. Further analyses suggested that the season-to-season turnover of interactions was dominated by interaction rewiring. Thus, the seasonal changes in niche overlap among pollinators lead to interaction rewiring, which drives interaction turnover in this community. Hawkmoths had higher values of specialization and Apidae had higher values of species strength compared with other pollinator functional groups. These findings should be considered when exploring plant–pollinator interactions in ecosystems of isolated oceanic islands and in other ecosystems.
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Verma, Sanjeev. "Niche level segmentation of green consumers". South Asian Journal of Business Studies 6, nr 3 (2.10.2017): 274–90. http://dx.doi.org/10.1108/sajbs-05-2016-0040.
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Purpose The purpose of this paper is to find the niche segmentation of green consumers as a solution to psychographic or demographic predicament. Age cohort and generational cohort (Gen Y and Gen Z) of young consumers are studied for individualization and customization. Design/methodology/approach Age cohorts (Gen Z and Gen Y customers) have their unique needs. Both Gen Y (1981-1995) and Gen Z (post-1995) belong to the young consumer segment in the age group of 20-30 years but their generational cohorts are different. Strategic marketing advocates both generational marketing based on age cohorts and segmented marketing for young consumers. Strategic marketing faces cross-road between youth segmentation and generational cohort (Gen Z and Gen Y) due to intersection between the two during the 20-30 age group. Primary data using the ecological conscious consumer behavior (ECCB) scale was collected and analyzed for understanding the individual and relative importance of psychographic and demographic factors in influencing green behavior. The traditional youth segment is sliced into four sub-groups (Young Nest 1-4), and their interaction effect with post hoc analysis was done for the identification of sources of difference between different age cohorts. The findings of the study were compared with previous studies and unique contributions of this study were identified. Findings The findings indicate multiple niche young segments with demographic as the primary criterion and psychographic as the building block. Niche level and individual level segments emerge due to the interaction of various factors within a given age cohort. The findings confirm the identity development process which considered age as an important factor that affects varying choices throughout life from adolescence to adulthood. Practical implications The findings of this study may be used for effective targeting and positioning strategy of green marketing. In the time of analytics, age cohorts and generational cohort of young consumers can be approached differently for yielding better environmental results. The magnified niche level segmentation of young consumers may be used to develop individualized and customized promotions for young customers in Young Nest 1-4 for an enhanced ECCB. Originality/value Previous studies have focused more on consumer characteristics (demographic or psychographic) and their relative importance but niche level segmentation within given demographic segment was not attempted before. This study is unique in offering microscopic analysis of age cohorts of young consumers (Young Nest 1-4) and their interaction with other demographic variables (gender and income) for niche level segmentation.
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Rosa, Giacomo, Sebastiano Salvidio i Andrea Costa. "Disentangling Exploitative and Interference Competition on Forest Dwelling Salamanders". Animals 13, nr 12 (15.06.2023): 2003. http://dx.doi.org/10.3390/ani13122003.
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Exploitative competition and interference competition differ in the way access to resources is modulated by a competitor. Exploitative competition implies resource depletion and usually produces spatial segregation, while interference competition is independent from resource availability and can result in temporal niche partitioning. Our aim is to infer the presence of spatial or temporal niche partitioning on a two-species system of terrestrial salamanders in Northern Italy: Speleomantes strinatii and Salamandrina perspicillata. We conducted 3 repeated surveys on 26 plots in spring 2018, on a sampling site where both species are present. We modelled count data with N-mixture models accounting for directional interactions on both abundance and detection process. In this way we were able to disentangle the effect of competitive interaction on the spatial scale, i.e., local abundance, and from the temporal scale, i.e., surface activity. We found strong evidence supporting the presence of temporal niche partitioning, consistent with interference competition. At the same time, no evidence of spatial segregation has been observed.