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Results for “Vascular niche”

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At least 19 recordsLinked to original sources
PubMed2006

The vascular niche and its basement membrane.

Over the past few years, scientists have realized that many cellular and developmental processes, including pancreatic beta-cell growth and differentiation, stem cell and progenitor cell proliferation and cancer cell metastasis, occur in what are known as 'vascular niches'. Despite increasing numbers of reports on these niches, few common mechanisms have been identified to explain their various effects. Here, we define the term 'vascular niche' and suggest that a common and conserved feature of this niche is to provide a basement membrane to cells that are unable to form their own. We further propose that these cells require a vascular niche when they retain a high degree of plasticity.

Animals↗
PubMed2003

Chemokine-mediated interaction of hematopoietic progenitors with the bone marrow vascular niche is required for thrombopoiesis.

The molecular pathways involved in the differentiation of hematopoietic progenitors are unknown. Here we report that chemokine-mediated interactions of megakaryocyte progenitors with sinusoidal bone marrow endothelial cells (BMECs) promote thrombopoietin (TPO)-independent platelet production. Megakaryocyte-active cytokines, including interleukin-6 (IL-6) and IL-11, did not induce platelet production in thrombocytopenic, TPO-deficient (Thpo(-/-)) or TPO receptor-deficient (Mpl(-/-)) mice. In contrast, megakaryocyte-active chemokines, including stromal-derived factor-1 (SDF-1) and fibroblast growth factor-4 (FGF-4), restored thrombopoiesis in Thpo(-/-) and Mpl(-/-) mice. FGF-4 and SDF-1 enhanced vascular cell adhesion molecule-1 (VCAM-1)- and very late antigen-4 (VLA-4)-mediated localization of CXCR4(+) megakaryocyte progenitors to the vascular niche, promoting survival, maturation and platelet release. Disruption of the vascular niche or interference with megakaryocyte motility inhibited thrombopoiesis under physiological conditions and after myelosuppression. SDF-1 and FGF-4 diminished thrombocytopenia after myelosuppression. These data suggest that TPO supports progenitor cell expansion, whereas chemokine-mediated interaction of progenitors with the bone marrow vascular niche allows the progenitors to relocate to a microenvironment that is permissive and instructive for megakaryocyte maturation and thrombopoiesis. Progenitor-active chemokines offer a new strategy to restore hematopoiesis in a clinical setting.

Animals↗
PubMed2005

The bone marrow vascular niche: home of HSC differentiation and mobilization.

The bone marrow vascular niche consists of a network of thin-walled and fenestrated sinusoidal vessels whose integrity is maintained and supported by surrounding hematopoietic cells. However, this dependence is highly reciprocal in that the bone marrow vasculature provides not only a conduit for mature hematopoietic cells to the peripheral circulation but also a site where hematopoietic progenitors, especially megakaryocytes, differentiate and set the stage for full reconstitution of hematopoiesis.

Animals↗
PubMed2003

Specific induction of tie1 promoter by disturbed flow in atherosclerosis-prone vascular niches and flow-obstructing pathologies.

Nonlaminar flow is a major predisposing factor to atherosclerosis. Yet little is known regarding hemodynamic gene regulation in disease-prone areas of the vascular tree in vivo. We have determined spatial patterns of expression of endothelial cell receptors in the arterial tree and of reporter gene constructs in transgenic animals. In this study we show that the endothelial cell-specific receptor Tie1 is induced by disturbed flow in atherogenic vascular niches. Specifically, tie1 expression in the adult is upregulated in vascular bifurcations and branching points along the arterial tree. It is often confined to a single ring of endothelial cells functioning as sphincters and hence experiencing the steepest gradient in shear stress. In aortic valves, tie1 is asymmetrically induced only in endothelial cells encountering changes in flow direction. Disturbance of laminar flow by a surgical interposition of a vein into an artery led to induction of tie1, specifically in the region where the differently sized vessels adjoin. In pathological settings, tie1 expression is specifically induced in areas of disturbed flow because of the emergence of aneurysms and, importantly, in endothelial cells precisely overlying atherosclerotic plaques. Hemodynamic features of atherosclerotic lesion-prone regions, recreated in vitro with the aid of a flow chamber with a built-in step, corroborated an upregulated tie1 promoter activity only in cells residing where flow separation and recirculation take place. These defined promoter elements might be harnessed for targeting gene expression to atherosclerotic lesions.

Animals↗
PubMed2006

Maintaining hematopoietic stem cells in the vascular niche.

In this issue of Immunity, Sugiyama et al. (2006) provide evidence that most bone-marrow hematopoietic stem cells (HSCs) reside in vascular niches containing reticular cells that secrete CXCL12, a chemokine that promotes HSC maintenance.

Animals↗
PubMed2000

Vascular niche for adult hippocampal neurogenesis.

The thin lamina between the hippocampal hilus and granule cell layer, or subgranule zone (SGZ), is an area of active proliferation within the adult hippocampus known to generate new neurons throughout adult life. Although the neuronal fate of many dividing cells is well documented, little information is available about the phenotypes of cells in S-phase or how the dividing cells might interact with neighboring cells in the process of neurogenesis. Here, we make the unexpected observation that dividing cells are found in dense clusters associated with the vasculature and roughly 37% of all dividing cells are immunoreactive for endothelial markers. Most of the newborn endothelial cells disappear over several weeks, suggesting that neurogenesis is intimately associated with a process of active vascular recruitment and subsequent remodeling. The present data provide the first evidence that adult neurogenesis occurs within an angiogenic niche. This environment may provide a novel interface where mesenchyme-derived cells and circulating factors influence plasticity in the adult central nervous system.

Aging↗
PubMed2006

The stem cell niches in bone.

The stem cell niche is composed of a specialized population of cells that plays an essential role in regulating adult stem cell self-renewal and differentiation. In adults, osteoblasts, responsible for osteogenesis, and hematopoietic cells, responsible for hematopoiesis, are closely associated in the bone marrow, suggesting a reciprocal relationship between the two. It was recently discovered that a subset of osteoblasts functions as a key component of the HSC niche (namely, the osteoblastic niche), controlling HSC numbers. HSCs interact not only with osteoblasts but also with other stromal cells, including endothelial cells. Sinusoidal endothelial cells in bone marrow have been revealed as an alternative HSC niche called the vascular niche. In this Review we compare the architecture of these 2 HSC niches in bone marrow. We also highlight the function of osteoblasts in maintaining a quiescent HSC microenvironment and the likely role of the vascular niche in regulating stem cell proliferation, differentiation, and mobilization. In addition, we focus on studies of animal models and in vitro assays that have provided direct insights into the actions of these osteoblastic and vascular niches, revealing central roles for numerous signaling and adhesion molecules. Many of the discoveries described herein may contribute to future clinical treatments for hematopoietic and bone-related disorders, including cancer.

Animals↗
PubMed2006

Vascular-adrenal niche--endothelial cell-mediated sensitization of human adrenocortical cells to angiotensin II.

Alterations in both vasculature and renin-angiotensin-aldosterone system are a consistent finding in the metabolic syndrome. Adrenal tissue is highly vascularized and encounters blood flow, exceeding by far the volume expected for its size. Endothelial cells in the adrenal vasculature are therefore a major cellular component of adrenocortical tissue. The aim of the study was to analyze the cellular interaction between endothelial and steroid producing cells, focusing on endothelial cell-factor-mediated activation of aldosterone synthesis. The interaction between human endothelial (HUVECs) cell-conditioned medium and human adrenocortical (NCI-H295R) cells IN VITRO induced a significant surge in aldosterone secretion. The endothelial cell-conditioned medium together with angiotensin II and forskolin also potentiated aldosterone release by 1.5-fold and 2.6-fold, respectively, while preincubation of NCI-H295R cells for 24 h with endothelial cell-conditioned medium enhanced and sensitized the response of NCI-H295R to subsequent angiotensin II and forskolin stimuli by 2.5-fold and 2.2-fold, respectively. The increase in aldosterone release after preincubation with endothelial cell-conditioned medium was sensitive to cycloheximide and KN-93. Cellular conditioning with endothelial-cell factors exerts a hitherto unknown paracrine regulation of aldosterone production in human adrenocortical cells. This interaction may contribute to altered basal aldosterone release and have a role in patients with hypertension.

Adrenal Cortex↗
PubMed2006

Understanding hematopoietic stem-cell microenvironments.

The hematopoietic system is the paradigm for adult mammalian stem-cell research. Recent advances have improved our understanding of the cellular and molecular components of the microenvironment - or niche - that regulates hematopoietic stem cells (HSCs). Here, we summarize the molecular and cellular properties of two types of niche, namely the osteoblastic and the vascular niche, in homeostatic regulation of HSC behavior, including its maintenance, proliferation, differentiation, mobilization and homing. We highlight the most recent findings and point to an important trend to the study of niche activity in cancers. Knowledge of the basic features of the HSC niches, including physical location, cell type and various signaling pathways, should provide insights into other stem-cell systems and benefit clinical applications.

Animals↗
PubMed2026

Integrative transcriptomic, spatial and functional-genomic analysis identifies a UFMylation-related vascular-stromal program and prioritizes WWTR1 in glioblastoma.

Glioblastoma (GBM) contains spatially organized stress-adaptive and vascular niches. Because transcript abundance does not measure UFM1 conjugation, we asked whether a UFMylation-related transcriptional axis identifies a reproducible tissue program and alters candidate prioritization. In 518 unique primary TCGA-GBM tumors profiled on the Affymetrix HT Human Genome U133A array, weighted gene co-expression network analysis of 8,000 variable genes yielded 12 modules. The 278-gene green module ranked first across nine prespecified traits (mean |r|=0.637). Direct overlap comprised 1/3 measurable UFMylation-core, 5/19 ER-stress/UPR, and 2/15 proteostasis genes; after excluding overlapping genes, correlations with the green eigengene remained significant (r = 0.373, 0.831, 0.639, and 0.699 for UFMylation-core, ER-stress/UPR, proteostasis, and composite scores, respectively). The green score was associated with overall survival per standard-deviation increase (HR 1.17, 95% CI 1.07-1.28), although clinical adjustment attenuated the estimate. In a 10-sample single-cell dataset, sample-level scores were higher in pericytes and endothelial cells than in malignant cells. Donor-aware IvyGAP analysis supported regional organization, whereas one Visium section showed stronger concordance with ER-stress/UPR and mesenchymal scores than with the UFMylation-core score. CellChat indicated pathway-selective rather than global remodeling of inferred vascular communication. Layer ablation moved WWTR1 from rank 48 using WGCNA alone to rank 4 overall and rank 1 among non-common-essential genes after cross-platform integration. These findings define an ER-stress/mesenchymal-weighted, UFMylation-related vascular-stromal transcriptional association and nominate WWTR1 for experimental testing.

Humans↗
PubMed2006

Modeling the neurovascular niche: VEGF- and BDNF-mediated cross-talk between neural stem cells and endothelial cells: an in vitro study.

Neural stem cells (NSCs) exist in vascularized niches. Although there has been ample evidence supporting a role for endothelial cell-derived soluble factors as modulators of neural stem cell self-renewal and neuronal differentiation there is a paucity of data reported on neural stem cell modulation of endothelial cell behavior. We show that co-culture of NSCs with brain-derived endothelial cells (BECs) either in direct contact or separated by a porous membrane elicited robust vascular tube formation and maintenance, mediated by induction of vascular vascular endothelial growth factor (VEGF) and brain-derived neurotrophic factor (BDNF) and activation of vascular VEGFR2 and TrkB by NSC NO. Nitric oxide (NO) scavengers and sequestration of VEGF and BDNF blunted this induction of tube formation, whereas addition of exogenous NO donor, rBDNF and rVEGF rescued the induction of tube formation. Further, rBDNF enhanced NSC eNOS activation and NO generation, suggesting an inducible positive feed-back signaling loop between NSCs and BECs, providing for homeostasis and responsiveness of the resident NSCs and BECs comprising the neurovascular niche. These findings show the importance of reciprocal modulation of NSCs and BECs in induction and maintenance of the neurovascular niche and underscores their dynamic interactions.

Analysis of Variance↗
PubMed2004

The neurovascular unit and its growth factors: coordinated response in the vascular and nervous systems.

The nervous and vascular systems contain many common organizational features and develop similarly in terms of anatomical patterning. During embryogenesis and in regions of the brain undergoing postnatal neurogenesis, neural stem cells and endothelial cells are found in close proximity, or within a so-called vascular niche. The similarities in patterning and proximity may reflect coordinated development based on responsiveness to similar growth factors such as vascular endothelial growth factor, semaphorin, and ephrins/Ephs: molecules involved in the development and maintenance of both the nervous and vascular systems. Despite the blatant similarities between the vascular and nervous systems, little is still known about the co-dependence and/or interactions between the two systems during development and following alterations in metabolic demand as seen during aging, exercise, and disease processes. The interactions between the two systems involving common growth factors suggest these two systems have evolved in an interconnected way.

Animals↗
PubMed2026

Spatially defined microenvironmental niches are associated with clinical outcome and tumor ecosystem diversity in head and neck cancer.

BACKGROUND: Head and neck squamous cell carcinoma (HNSCC) exhibits substantial biological heterogeneity that is not fully explained by human papillomavirus (HPV) status. The spatial organization of tumor, immune, and stromal cell populations and its relationship to clinical outcome remain incompletely understood. METHODS: We performed single-cell spatial transcriptomic and proteomic profiling of 44 primary HNSCC tumors, generating a spatial atlas of 19,471,501 cells across whole-slide tissue sections. Spatial niches and ecosystem states were identified through integrated computational analyses and evaluated for associations with tumor programs, clinicopathologic features, and patient outcomes. FINDINGS: HPV-negative tumors were enriched for fibroblast-rich, immune-poor niches associated with epithelial-mesenchymal transition and hypometabolic tumor programs, whereas HPV-positive tumors displayed more diverse immune, stromal, and vascular niche combinations and were enriched for immunogenic ecosystem states. Approximately 20% of HPV-positive tumors exhibited fibroblast-rich ecosystem architectures resembling HPV-negative disease and were associated with less favorable outcomes than other HPV-positive tumors of similar stage. In patient-derived co-culture models, extracellular matrix-associated fibroblasts were associated with epithelial-mesenchymal transition (EMT)-like tumor states, CD8+ T cell dysfunction, and chemotherapy resistance-associated phenotypes. CONCLUSIONS: Spatial ecosystem architecture is associated with clinically relevant heterogeneity beyond conventional HPV-based classification. Fibroblast-rich, immune-poor ecosystem states characterize a high-risk subset of HPV-positive tumors and may provide a framework for improved biological classification and risk stratification in HNSCC. FUNDING: This work was supported by the National Institutes of Health (R01CA291607 and R21CA267527-01) and the Feldstein Medical Foundation.

Humans↗
PubMed2004

Endothelial cells stimulate self-renewal and expand neurogenesis of neural stem cells.

Neural stem cells are reported to lie in a vascular niche, but there is no direct evidence for a functional relationship between the stem cells and blood vessel component cells. We show that endothelial cells but not vascular smooth muscle cells release soluble factors that stimulate the self-renewal of neural stem cells, inhibit their differentiation, and enhance their neuron production. Both embryonic and adult neural stem cells respond, allowing extensive production of both projection neuron and interneuron types in vitro. Endothelial coculture stimulates neuroepithelial cell contact, activating Notch and Hes 1 to promote self-renewal. These findings identify endothelial cells as a critical component of the neural stem cell niche.

Animals↗
PubMed2007

Hit 'em where they live: targeting the cancer stem cell niche.

Cancer stem cells (CSCs) are thought to be critical for initiation and propagation of many types of cancer. Because these cells are resistant to conventional therapies, they have been very difficult to eliminate. A study in this issue of Cancer Cell suggests that brain tumor CSCs live in a "vascular niche" that promotes their long-term growth and self-renewal. Disrupting this niche impairs CSC self-renewal and thereby significantly inhibits the growth of tumors. Targeting the unique microenvironment of CSCs may be the key to effective cancer therapy.

Animals↗
PubMed2002

Recruitment of stem and progenitor cells from the bone marrow niche requires MMP-9 mediated release of kit-ligand.

Stem cells within the bone marrow (BM) exist in a quiescent state or are instructed to differentiate and mobilize to circulation following specific signals. Matrix metalloproteinase-9 (MMP-9), induced in BM cells, releases soluble Kit-ligand (sKitL), permitting the transfer of endothelial and hematopoietic stem cells (HSCs) from the quiescent to proliferative niche. BM ablation induces SDF-1, which upregulates MMP-9 expression, and causes shedding of sKitL and recruitment of c-Kit+ stem/progenitors. In MMP-9-/- mice, release of sKitL and HSC motility are impaired, resulting in failure of hematopoietic recovery and increased mortality, while exogenous sKitL restores hematopoiesis and survival after BM ablation. Release of sKitL by MMP-9 enables BM repopulating cells to translocate to a permissive vascular niche favoring differentiation and reconstitution of the stem/progenitor cell pool.

Animals↗
PubMed2007

A perivascular niche for brain tumor stem cells.

Cancers are believed to arise from cancer stem cells (CSCs), but it is not known if these cells remain dependent upon the niche microenvironments that regulate normal stem cells. We show that endothelial cells interact closely with self-renewing brain tumor cells and secrete factors that maintain these cells in a stem cell-like state. Increasing the number of endothelial cells or blood vessels in orthotopic brain tumor xenografts expanded the fraction of self-renewing cells and accelerated the initiation and growth of tumors. Conversely, depletion of blood vessels from xenografts ablated self-renewing cells from tumors and arrested tumor growth. We propose that brain CSCs are maintained within vascular niches that are important targets for therapeutic approaches.

AC133 Antigen↗
PubMed2005

Isolectin-IB 4 as a vascular stain for the study of adult neurogenesis.

It has been proposed that new neurons in the adult brain might preferentially develop in the immediate vicinity of existing vasculature, an area that has been referred to as a "vascular niche". The most common method for identifying neurons that arise as the result of mitotic activity is to label them with the thymidine analogue bromodeoxyuridine (BrdU), and a nuclear marker for mature neurons (NeuN). Unfortunately, commercially available forms of NeuN and the vasculature stain, RECA-1, are incompatible, as both antibodies are raised in the same species. This technical limitation has impeded the analysis of the relationship between new neurons and existing vasculature. In the present work we show that Isolectin-IB 4, a 114 k Da protein isolated from the seeds of the African legume, Griffonia simplicifolia, can be used to identify vasculature in conjunction with both NeuN and BrdU immunohistochemistry. Isolectin-IB 4 serves as an easy to use and robust marker for obtaining spatial information regarding the proximity of new neurons to vasculature in the mammalian brain.

Age Factors↗