Project description:Pericytes (PC) are abundant yet remain the most enigmatic and ill-defined cell population in the heart. Here, we investigated whether PC can be reprogrammed to aid neovascularisation of the heart post-myocardial infarction. We discovered that culture of human cardiac PC for 10 days in the presence of an inhibitor of ERK1/2 signalling (PD0325901, specific MEK1/2 inhibitor) induces the PC switch towards a vascular smooth muscle cells (VSMC)-like phenotype. Differentiated PC became more proangiogenic, more responsive to vasoactive agents, and insensitive to chemoattractants. RNA-Sequencing revealed transcripts marking the PD0325901-induced transition into proangiogenic, stationary VSMC-like cells.
Project description:Background. Ageing is one of the main risk factors of cardiovascular disease. Pericytes are capillary-associated mural cells involved in the maintenance and stability of the vascular network. In the heart, the consequences of ageing on cardiac pericytes are unknown. Methods. In this study, we have combined single nucleus RNA sequencing and histological analysis to determine the effects of ageing on cardiac pericytes. Furthermore, we have conducted in vivo and in vitro analysis of RGS5 loss of function and finally have perfomed pericytes-fibroblasts co-culture studies to understand the effect of RGS5 loss of function in pericytes on the neighbouring fibroblasts. Results. We showed that ageing reduces the pericyte area and coverage. Single nucleus RNA sequencing analysis further revealed that the expression of the Regulator of G protein signalling 5 (Rgs5) is reduced in old cardiac pericytes. In vivo and in vitro studies showed that the deletion of RGS5 induces morphological changes and a pro-fibrotic gene expression signature characterized by the expression of different extracellular matrix components and growth factors like TGFB2 and PDGFB in pericytes. Indeed, the culture of fibroblasts with the supernatant of RGS5 deficient pericytes induced their activation characterized by the increased expression of α smooth muscle actin in a TFGβ2 dependent mechanism. Conclusions. Our results identify RGS5 as a crucial regulator of pericyte function during cardiac ageing. The deletion of RGS5 causes cardiac dysfunction and induces myocardial fibrosis, one of the hallmarks of cardiac ageing.
Project description:Ischemic injury leads to irreversible loss of neurons and cardiomyocytes in the brain and heart, respectively which ultimately results in fibrotic scar formation. Despite recent advances in tissue fibrosis, cellular mediators of scar formation in the heart and brain remain elusive. Pericytes are a heterogeneous population of mural cells that surround microvessels in various organs including the brain and heart. Their function beyond vascular integrity and contractility is poorly understood, although recent studies have suggested they may be a major contributor to tissue fibrosis. In both the heart and brain, differences in injury models, lack of proper transgenic mouse models for lineage tracing and absence of pericyte-specific markers have contributed to discrepancies in the literature regarding their direct contributions to fibrosis. Here, by performing a set of complementary experiments using a common pericyte transgenic model and clinically-relevant ischemic injury models of stroke and myocardial infarction, we demonstrated the parallel pro-fibrotic response of pericyte after vascular injury.
Project description:Pericytes/vascular smooth muscle cells (VSMCs), regulated by platelet-derived growth factor receptor β (PDGFRβ) signaling, play important roles in endothelial survival and vascular stability. Here we report that treatment with imatinib, an inhibitor of PDGFRβ, led to significant tumor growth impairment associated with increased apoptosis in human lymphoma xenografts including Farage, Karpas422 and OCI-Ly7 in SCID mice. Confocal analysis of the tumor tissue showed decreased microvessel density, decreased vascular flow, and increased vascular leak in the imatinib-treated cohorts. Imatinib targeted tumor-associated PDGFRβ+ pericytes in vivo by inducing apoptosis and disruption of the PDGFRβ+ perivascular network, and PDGFRβ+ VSMC in vitro by inhibition of proliferation. FACS analysis of mononuclear cell suspension of tumor tissues revealed decreased mature pericytes and endothelial cells, as well as their progenitors with imatinib treatment. Compared to imatinib, treatment with anti-PDGFRβ monoclonal antibody partially inhibited the growth of Farage lymphomas. Lastly, microarray analysis of differentially expressed genes in PDGFRβ+ VSMC following imatinib treatment showed significant down-regulation of genes implicated in proliferation, survival and angiogenesis, including those within PI3K/AKT and MAPK/ERK1/2 pathways downstream of PDGFRβ signaling. Taken together, targeting PDGFRβ+ pericytes in lymphoma presents a novel and complementary target to endothelial cells for efficacious antiangiogenic therapy. PDGFRb+ murine vascular smooth muscle cells (VSMCs) were treated in 10 uM imatinib for 24 or 48 hours. Gene expression changes in response to imatinib treatment were examined using NimbleGen MM8_60mer gene expression microarrays by comparing expression patterns at 24- and 48-hours treatment to the baseline level (0 hours).
Project description:Background. Ageing is one of the main risk factors of cardiovascular disease. Pericytes are capillary-associated mural cells involved in the maintenance and stability of the vascular network. In the heart, the consequences of ageing on cardiac pericytes are unknown. Methods. In this study, we have combined single nucleus RNA sequencing and histological analysis to determine the effects of ageing on cardiac pericytes. Furthermore, we have conducted in vivo and in vitro analysis of RGS5 loss of function and finally have perfomed pericytes-fibroblasts co-culture studies to understand the effect of RGS5 loss of function in pericytes on the neighbouring fibroblasts. Results. We showed that ageing reduces the pericyte area and coverage. Single nucleus RNA sequencing analysis further revealed that the expression of the Regulator of G protein signalling 5 (Rgs5) is reduced in old cardiac pericytes. In vivo and in vitro studies showed that the deletion of RGS5 induces morphological changes and a pro-fibrotic gene expression signature characterized by the expression of different extracellular matrix components and growth factors like TGFB2 and PDGFB in pericytes. Indeed, the culture of fibroblasts with the supernatant of RGS5 deficient pericytes induced their activation characterized by the increased expression of α smooth muscle actin in a TFGβ2 dependent mechanism. Conclusions. Our results identify RGS5 as a crucial regulator of pericyte function during cardiac ageing. The deletion of RGS5 causes cardiac dysfunction and induces myocardial fibrosis, one of the hallmarks of cardiac ageing.
Project description:Pericytes/vascular smooth muscle cells (VSMCs), regulated by platelet-derived growth factor receptor β (PDGFRβ) signaling, play important roles in endothelial survival and vascular stability. Here we report that treatment with imatinib, an inhibitor of PDGFRβ, led to significant tumor growth impairment associated with increased apoptosis in human lymphoma xenografts including Farage, Karpas422 and OCI-Ly7 in SCID mice. Confocal analysis of the tumor tissue showed decreased microvessel density, decreased vascular flow, and increased vascular leak in the imatinib-treated cohorts. Imatinib targeted tumor-associated PDGFRβ+ pericytes in vivo by inducing apoptosis and disruption of the PDGFRβ+ perivascular network, and PDGFRβ+ VSMC in vitro by inhibition of proliferation. FACS analysis of mononuclear cell suspension of tumor tissues revealed decreased mature pericytes and endothelial cells, as well as their progenitors with imatinib treatment. Compared to imatinib, treatment with anti-PDGFRβ monoclonal antibody partially inhibited the growth of Farage lymphomas. Lastly, microarray analysis of differentially expressed genes in PDGFRβ+ VSMC following imatinib treatment showed significant down-regulation of genes implicated in proliferation, survival and angiogenesis, including those within PI3K/AKT and MAPK/ERK1/2 pathways downstream of PDGFRβ signaling. Taken together, targeting PDGFRβ+ pericytes in lymphoma presents a novel and complementary target to endothelial cells for efficacious antiangiogenic therapy.
Project description:Humanized mouse models and mouse-adapted SARS-CoV-2 virus are increasingly used to study COVID-19 pathogenesis, and it is therefore important to learn where the SARS-CoV-2 receptor ACE2 is expressed. Here we mapped ACE2 expression during mouse postnatal development and in adulthood. Pericytes in the central nervous system, heart and pancreas express ACE2 strongly, as do perineurial and adrenal fibroblasts, whereas endothelial cells do not at any location analyzed. In a number of other organs pericytes do not express ACE2, including in the lung where ACE2 instead is expressed in bronchial epithelium and alveolar type-II cells. The onset of ACE2 expression is organ-specific: in bronchial epithelium already at birth, in brain pericytes before and in heart pericytes after postnatal day 10.5. Establishing the vascular localization of ACE2 expression is central to correctly interpret data from modelling COVID-19 in the mouse and may shed light on the cause of vascular COVID-19 complications.
Project description:Vascular remodeling is the process of structural alteration and cell rearrangement of blood vessels in response to injury and is the cause of many of the world's most afflicted cardiovascular conditions, including pulmonary arterial hypertension(PAH). Many studies have focused on the effects of vascular endothelial cells and smooth muscle cells(SMCs) during vascular remodeling, but pericytes, an indispensable cell population residing largely in capillaries, are ignored in this maladaptive process. Here we report that hypoxia-inducible factor 2α(HIF2α) expression is increased in human PAH patient lung tissues and HIF2α overexpressed pericytes result in greater contractility and an impaired endothelial-pericyte interaction. Using single-cell RNAseq and hypoxia-induced pulmonary hypertension(PH) models, we show HIF2α as a major molecular regulator for pericytes’ transformation into SMC-like cells. HIF2α overexpression in pericyte-selective mice exacerbate PH and right ventricular hypertrophy. Temporal cellular lineage tracing shows that HIF2α overexpressing reporter NG2+ cells (pericyte-selective) relocate from capillaries to arterioles and co-express SMA. This novel insight into the potential role of NG2+ pericytes in pulmonary vascular remodeling via HIF2α signaling suggests a potential drug target for PH.
Project description:Pericytes have been implicated in regulation of inflammatory, reparative, fibrogenic and angiogenic responses in several different organs and pathologic conditions. Although the adult mammalian heart contains abundant pericytes, their fate and involvement in myocardial disease remains unknown. We used NG2Dsred;PDGFRaEGFP pericyte-fibroblast dual reporter mice and inducible NG2CreER mice to study the fate and phenotypic modulation of pericytes in a model of myocardial infarction. The transcriptomic profile of pericyte-derived fibroblasts was studied using PCR arrays. The transcriptomic profile of NG2 lineage cells (pericytes) was studied in control and infarcted hearts using single cell RNA-sequencing analysis. The role of TGF-b signaling in regulation of pericyte phenotype in vivo was investigated using pericyte-specific Tgfbr2 knockout mice. In vitro, the effects of TGF-b were studied in cultured human placental pericytes.In normal mouse hearts, NG2 and PDGFRa identified distinct non-overlapping populations of pericytes and fibroblasts respectively. Following myocardial infarction, a population of cells expressing both pericyte and fibroblast markers emerged. These cells expressed large amounts of extracellular matrix (ECM) genes. Lineage tracing demonstrated that in the infarcted region, a subpopulation of pericytes underwent fibroblast conversion. Single cell RNA-seq experiments demonstrated expansion and diversification of pericyte-derived cells in the infarct, associated with emergence of subpopulations exhibiting accentuated matrix gene synthesis. In vitro studies and the profile of pericyte-derived fibroblasts identified TGF-b as a potentially causative mediator in fibrogenic activation of infarct pericytes. However, pericyte-specific Tgfbr2 disruption had no significant effects on myofibroblast infiltration and collagen deposition in the infarct. Pericyte-specific TGF-b signaling was involved in vascular maturation, mediating formation of a mural cell coat investing infarct neovessels. These reparative effects of infarct pericytes protected the infarcted heart from dilative remodeling.
Project description:Tumor necrosis factor alpha induces vascular permeability, playing an important role in inflammation. Also, TNF-induced vascular leakage is involved in the increased extravasation of nanoparticle formulated chemotherapeutics improving drug delivery and subsequently tumor response, and we found a positive correlation between the presence of pericytes in the tumor-associated vasculature and TNF-induced leakage. RNA sequencing and pathway analysis of TNF-stimulated versus non-stimulated pericytes and endothelial cells show significant upregulation of several pathways involving interferon regulating pathways with a high expression of CXCL10, also known as Interferon gamma-inducible protein 10 (IP-10) in TNF-stimulated pericytes. In addition, CXCL10 protein production was significantly increased in conditioned medium from TNF-exposed pericytes compared to the other conditions. In our animal studies, we observed that tumor types with high pericyte covered vessels show enhanced permeability when exposed to TNF, which can be blocked with a neutralizing CXCL10 antibody. Vice versa, tumors with vessels low in pericyte number do not respond to TNF, i.e., do not express elevated permeability. Importantly, this lack of pericyte coverage can be compensated by co-administration of CXCL10. Our finding reveals a mechanism where TNF induces CXCL10 release from pericytes, being at the basis of increased permeability and thus vascular leakage.