pericyteについて
Pericyte（ペリサイト）は、血管壁に存在する細胞の一種です。主に血管内皮細胞の周りに位置し、血管の安定性や修復に重要な役割を果たしています。Pericyteは血管の形成や機能維持に関与し、血管の透過性を調節することで血液の流れを制御します。
さらに、Pericyteは炎症反応やがん細胞の浸潤にも関与しており、最近の研究では、Pericyteの機能が病気の進行にどのように影響するかが注目されています。
Cerebral pericytes are perivascular cells that stabilize blood vessels. Little is known about the plasticity of pericytes in the adult brain in vivo. Recently, using state-of-the-art technologies, including two-photon microscopy in combination with sophisticated Cre/loxP in vivo tracing techniques, a novel role of pericytes was revealed in vascular remodeling in the adult brain. Strikingly, after pericyte ablation, neighboring pericytes expand their processes and prevent vascular dilatation. This new knowledge provides insights into pericyte plasticity in the adult brain.
Rationale: Pericytes are capillary mural cells playing a role in stabilizing newly formed blood vessels during development and tissue repair. Loss of pericytes has been described in several brain disorders, and genetically induced pericyte deficiency in the brain leads to increased macromolecular leakage across the blood-brain barrier (BBB). However, the molecular details of the endothelial response to pericyte deficiency remain elusive.
Objective: To map the transcriptional changes in brain endothelial cells resulting from lack of pericyte contact at single-cell level and to correlate them with regional heterogeneities in BBB function and vascular phenotype.
Methods and results: We reveal transcriptional, morphological, and functional consequences of pericyte absence for brain endothelial cells using a combination of methodologies, including single-cell RNA sequencing, tracer analyses, and immunofluorescent detection of protein expression in pericyte-deficient adult Pdgfbret/ret mice. We find that endothelial cells without pericyte contact retain a general BBB-specific gene expression profile, however, they acquire a venous-shifted molecular pattern and become transformed regarding the expression of numerous growth factors and regulatory proteins. Adult Pdgfbret/ret brains display ongoing angiogenic sprouting without concomitant cell proliferation providing unique insights into the endothelial tip cell transcriptome. We also reveal heterogeneous modes of pericyte-deficient BBB impairment, where hotspot leakage sites display arteriolar-shifted identity and pinpoint putative BBB regulators. By testing the causal involvement of some of these using reverse genetics, we uncover a reinforcing role for angiopoietin 2 at the BBB.
Conclusions: By elucidating the complexity of endothelial response to pericyte deficiency at cellular resolution, our study provides insight into the importance of brain pericytes for endothelial arterio-venous zonation, angiogenic quiescence, and a limited set of BBB functions. The BBB-reinforcing role of ANGPT2 (angiopoietin 2) is paradoxical given its wider role as TIE2 (TEK receptor tyrosine kinase) receptor antagonist and may suggest a unique and context-dependent function of ANGPT2 in the brain.
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Targeting pericytes for therapeutic approaches to neurological disorders
Many central nervous system diseases currently lack effective treatment and are often associated with defects in microvascular function, including a failure to match the energy supplied by the blood to the energy used on neuronal computation, or a breakdown of the blood-brain barrier.
Pericytes, an under-studied cell type located on capillaries, are of crucial importance in regulating diverse microvascular functions, such as angiogenesis, the blood-brain barrier, capillary blood flow and the movement of immune cells into the brain.
They also form part of the "glial" scar isolating damaged parts of the CNS, and may have stem cell-like properties.
Recent studies have suggested that pericytes play a crucial role in neurological diseases, and are thus a therapeutic target in disorders as diverse as stroke, traumatic brain injury, migraine, epilepsy, spinal cord injury, diabetes, Huntington's disease, Alzheimer's disease, diabetes, multiple sclerosis, glioma, radiation necrosis and amyotrophic lateral sclerosis. Here we report recent advances in our understanding of pericyte biology and discuss how pericytes could be targeted to develop novel therapeutic approaches to neurological disorders, by increasing blood flow, preserving blood-brain barrier function, regulating immune cell entry to the CNS, and modulating formation of blood vessels in, and the glial scar around, damaged regions.
Bone marrow pericyte dysfunction in individuals with type 2 diabetes
Aims/hypothesis: Previous studies have shown that diabetes mellitus destabilises the integrity of the microvasculature in different organs by damaging the interaction between pericytes and endothelial cells. In bone marrow, pericytes exert trophic functions on endothelial cells and haematopoietic cells through paracrine mechanisms. However, whether bone marrow pericytes are a target of diabetes-induced damage remains unknown. Here, we investigated whether type 2 diabetes can affect the abundance and function of bone marrow pericytes.
Methods: We conducted an observational clinical study comparing the abundance and molecular/functional characteristics of CD146+ pericytes isolated from the bone marrow of 25 individuals without diabetes and 14 individuals with uncomplicated type 2 diabetes, referring to our Musculoskeletal Research Unit for hip reconstructive surgery.
Results: Immunohistochemistry revealed that diabetes causes capillary rarefaction and compression of arteriole size in bone marrow, without changing CD146+ pericyte counts. These data were confirmed by flow cytometry on freshly isolated bone marrow cells. We then performed an extensive functional and molecular characterisation of immunosorted CD146+ pericytes. Type 2 diabetes caused a reduction in pericyte proliferation, viability, migration and capacity to support in vitro angiogenesis, while inducing apoptosis. AKT is a key regulator of the above functions and its phosphorylation state is reportedly reduced in the bone marrow endothelium of individuals with diabetes. Surprisingly, we could not find a difference in AKT phosphorylation (at either Ser473 or Thr308) in bone marrow pericytes from individuals with and without diabetes. Nonetheless, the angiocrine signalling reportedly associated with AKT was found to be significantly downregulated, with lower levels of fibroblast growth factor-2 (FGF2) and C-X-C motif chemokine ligand 12 (CXCL12), and activation of the angiogenesis inhibitor angiopoietin 2 (ANGPT2). Transfection with the adenoviral vector carrying the coding sequence for constitutively active myristoylated AKT rescued functional defects and angiocrine signalling in bone marrow pericytes from diabetic individuals. Furthermore, an ANGPT2 blocking antibody restored the capacity of pericytes to promote endothelial networking.
Bone marrow environments are composed of multiple cell types, most of which are thought to be derived from mesenchymal stem cells. In mouse bone marrow, stromal cells with CD45- Tie2- CD90- CD51+ CD105+ phenotype, Nestin-GFP+, CXCL12-abundant reticular (CAR) cells, PDGFRα+ Sca-1+ or CD51+ PDGFRα+, and Prx-1-derived CD45- Ter119- PDGFRα+ Sca-1+ populations select for MSC activity. There is evidence that these stromal cell populations display some significant overlap with each other and comprise important cellular constituents of the hematopoietic stem cell niche. Moreover, these mesenchymal cell populations share characteristics in their location as they all are found around bone marrow vessels (can be called "pericytes"). In this chapter, with reviewing the recent literatures, how the pericytes relate to physiological and pathological hematopoiesis is argued.
Pericyte-myofibroblast transition in the human lung
Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive interstitial lung disease that includes fibroblastic foci (FF). It has been increasingly appreciated that the origin of collagen-overproducing cells such as pathological myofibroblasts in FF is pericytes. However, neither pericytes derived from the lung nor FF in the IPF lung have not been fully characterized. Human lung pericytes (HuL-P) examined in this study expressed two representative pericyte markers; platelet-derived growth factor receptor β (PDGFRB) and chondroitin sulfate proteoglycan 4 (CSPG4), and were able to migrate and cover endothelial tubes in 3D conditions, indicating that they retain characteristics of pericytes. Moreover HuL-P cells transitioned to myofibroblast-like cells in the presence of transforming growth factor (TGF)-β signaling or to pericyte-like cells in the absence of TGF-β signaling (pericyte-myofibroblast transition). On the other hand, the FF detected in this study were invariably localized between peripheral lung epithelia and capillary endothelia, the basement membranes of which are physiologically fused. The localization is highly specific in that the only cells that exist between the gap are pericytes. As expected, FF were immunohistochemically positive for PDGFRB and CSPG4, suggesting that pericytes are activated to form FF. We also found that HuL-P cells were difficult to eradicate by dual silencing of Bcl-xL plus MCL1. It would be more sensible to suppress pericyte-myofibroblast transition than to kill activated myofibroblasts for the treatment of IPF.
2025年1月16日 | カテゴリー：骨代謝と整形外科的疾患, 各種病因学, 癌の病態生理と治療学, 基礎知識/物理学、統計学、有機化学、数学、英語 |
