BACH1 deficiency impedes differentiation of vascular smooth muscle cell from hESCs via reducing the CARM1-catalyzed H3R17me2
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ABSTRACT: Vascular smooth muscle cells (VSMCs) derived from human embryonic stem cells (hESCs) have been considered as a potential therapeutic application in vascular diseases. The transcription factor BTB and CNC homology 1 (BACH1) participates in stem cell development and has an increased expression during the VSMCs differentiation process. Knockout of BACH1 inhibits the differentiation of hESCs into VSMCs, whereas overexpression of BACH1 promotes VSMCs differentiation after the mesoderm stage. Mechanistically, BACH1 interacts with Coactivator-associated arginine methyltransferase 1 (CARM1) in a bZIP domain-dependent manner. BACH1 recruits CARM1 and its specific histone mark H3R17me2 to VSMC marker genes promoters, thus up-regulating target gene expression. BACH1-induced promotion of VSMC marker genes was partially abolished by the knockdown of CARM1 or H3R17me2. Thus, our results demonstrate the regulatory role of BACH1 and CARM1 in VSMCs differentiation.
Project description:Loss of contractility and acquisition of an epithelial phenotype of vascular smooth muscle cells (VSMCs) are key events in proliferative vascular pathologies such as atherosclerosis and post-angioplastic restenosis. There is no proper cell culture system allowing VSMC differentiation so that it is difficult to delineate the molecular mechanism responsible for proliferative vasculopathy. We investigated whether a micro-patterned substrate could restore the contractile phenotype of VSMCs in vitro. To induce and maintain the differentiated VSMC phenotype in vitro, we introduced a micro-patterned groove substrate to modulate the morphology and function of VSMCs.
Project description:Vascular smooth muscle cells (VSMCs) show pronounced heterogeneity across and within vascular beds, with direct implications for their function in injury response and atherosclerosis. Here we combine single-cell transcriptomics with lineage tracing to examine VSMC heterogeneity in healthy mouse vessels. The transcriptional profiles of single VSMCs consistently reflect their region-specific developmental history and show heterogeneous expression of vascular disease-associated genes involved in inflammation, adhesion and migration. We detect a rare population of VSMC-lineage cells that express the multipotent progenitor marker Sca1, progressively downregulate contractile VSMC genes and upregulate genes associated with VSMC response to inflammation and growth factors. We find that Sca1 upregulation is a hallmark of VSMCs undergoing phenotypic switching in vitro and in vivo, and reveal an equivalent population of Sca1-positive VSMC-lineage cells in atherosclerotic plaques. Together, our analyses identify disease-relevant transcriptional signatures in VSMC-lineage cells in healthy blood vessels, with implications for disease susceptibility, diagnosis and prevention.
Project description:Chromatin accessibility is important for cell fate determination in differentiation and multiple pathophysiological processes. Here, we report a transcription factor BACH1, facilitates the recruitment of G9a and YAP, maintains the state of H3K9me2 and decreases the chromatin accessibility at the promoter of VSMC marker genes, thereby repressing their expression and contributing to dedifferentiated VSMC phenotype. Moreover, VSMC-specific loss of BACH1 in mice inhibited the transformation of VSMC from contractile to synthetic phenotype and VSMC proliferation and attenuated the neointimal hyperplasia in wire-injured femoral arteries.
Project description:We applied RNA-Seq to analyze the effects of silencing of Thoc2 or Thoc5, two components of the THO complex, in cultured VSMC. The result revealed that Thoc5 silencing closely resembled the gene expression changes induced upon PDGF-BB/PDGF-DD treatments in cultured VSMCs. Mechanistically, our RIP-Seq data revealed both Thoc2 and Thoc5 preferentially interacted with VSMC marker gene mRNAs and mediated their expression. Interestingly, mRNAs that lost Thoc2 or Thoc5 binding during VSMC dedifferentiation were enriched for genes important for VSMC identity. In addition, silencing of Thoc2 or Thoc5 led to dedifferentiation of VSMCs in vitro, characterized by decreased VSMC marker gene expression and increased migration and proliferation. Furthermore, we performed immuno-histochemical staining against Thoc2 and Thoc5, and found a dramatic reduction in their expression in human arteries undergoing carotid endarterectomy (CEA) compared to normal internal mammary arteries (IMA). Notably, Thoc5 overexpression in injured rat carotid arteries significantly repressed loss of VSMC marker gene expression and neointima formation. Together, our data introduce dynamic binding of THO to VSMC marker gene mRNAs as a novel mechanism contributing to VSMC fate decisions, and imply Thoc5 as a potential intervention node for vascular diseases.
Project description:Background: Ectopic vascular calcifications represent a major clinical problem associated with cardiovascular disease and mortality. However, the mechanisms underlying pathological vascular calcifications are largely unknown hampering the development of therapies to tackle this life threatening medical condition. Results: In order to gain insight into the genes and mechanisms driving this pathological calcification process we analyzed the transcriptional profile of calcifying vascular smooth muscle cells (C-VSMCs). These profiles were compared to differentiating osteoblasts, cells that constitute their physiological calcification counterparts in the body. Overall the transcriptional program of C-VSMC and osteoblasts did not overlap. Several genes, some of them relevant for bone formation, were distinctly modulated by C-VSMCs which did not necessarily lose their smooth muscle cell markers while calcifying. Bioinformatics gene clustering and correlation analysis disclosed limited bone-related mechanisms being shared by two cell types. Extracellular matrix (ECM) and biomineralization genes represented common denominators between pathological vascular and physiological bone calcifications. These genes constitute the strongest link between these cells and represent potential drivers for their shared end-point phenotype. Conclusions: the analyses support the hypothesis that VSMC trans-differentiate into C-VSMCs keeping their own identity while using mechanisms that osteoblasts use to mineralize. The data provide novel insights into groups of genes and biological processes shared in MSC and VSMC osteogenic differentiation. The distinct gene regulation between C-VSMC and osteoblasts might hold clues to find cell-specific pathway modulations, opening the possibility to tackle undesired vascular calcifications without disturbing physiologic bone formation and vice versa. Total RNA obtained from hMSC and hVSMC cultured in osteogenic differentiation medium supplemented with 1.8 mM Ca2+ for 0, 2, 8, 12 or 25 days respectively. For each timepoint 3 replicates were used, with exception for day 0 where 4 replicates were collected.
Project description:Vascular smooth muscle cell (VSMC) subpopulations relevant to vascular disease and injury repair have been depicted in healthy vessels and atherosclerosis profiles. However, whether VSMC subpopulation associated with vascular homeostasis exists in the healthy artery and how are their nature and fate in vascular remodeling remains elusive. Here, using single-cell RNA-sequencing (scRNA-seq) to detect VSMC functional heterogeneity in an unbiased manner, we showed that VSMC subpopulations in healthy artery presented transcriptome diversity and that there was significant heterogeneity in differentiation state and development within each subpopulation. Notably, we detected an independent subpopulation of VSMCs that highly expressed regulator of G protein signaling 5 (Rgs5), upregulated the genes associated with inhibition of cell proliferation and construction of cytoskeleton compared with the general subpopulation, and mainly enriched in descending aorta. Additionally, the proportion of Rgs5+ VSMCs was markedly decreased or almost disappeared in the vascular tissues of neointimal formation, abdominal aortic aneurysm and atherosclerosis. Specific spatiotemporal characterization of Rgs5+ VSMC subpopulation suggested that this subpopulation was implicated in vascular homeostasis. Together, our analyses identify homeostasis-relevant transcriptional signatures of VSMC subpopulations in healthy artery, which may explain the regional vascular resistance to atherosclerosis at some extent.
Project description:Vascular smooth muscle cells (VSMCs) play a central role in the development of atherosclerosis due in part to their capability to phenotypically transition into either a protective or harmful state. However, the ability to identify and trace VSMCs and their progeny in vivo is limited due to the lack of well-defined VSMC cell surface markers. Therefore, investigations into VSMC fate must utilize lineage-tracing mouse models, which are time-consuming and challenging to generate and not feasible in humans. Here, we employed CITE-seq to characterize the phenotypic expression of 119 cell surface proteins in mouse atherosclerosis. We found that CD200 is a highly expressed and specific marker of VSMCs, which persists even with phenotypic modulation. We validated our findings using a combination of flow cytometry, qPCR, and immunohistochemistry, all confirming that CD200 can identify and mark VSMCs and their derived cells in early to advanced mouse atherosclerotic lesions. Additionally, we describe a similar expression pattern of CD200 in human coronary and carotid atherosclerosis. Thus, our data support the use of CD200 as a lineage marker for VSMCs and VSMC-derived cells in mouse and human atherosclerosis.
Project description:Vascular smooth muscle cell (VSMC) dysregulation is a hallmark of vascular disease, including atherosclerosis. In particular, the majority of cells within atherosclerotic lesions are generated from pre-existing VSMCs and a clonal nature has been documented for VSMC-derived cells in multiple disease models. However, the mechanisms underlying the generation of oligoclonal lesions and the phenotype of proliferating VSMCs are unknown.Here we analyse clonal dynamics in multi-color lineage-traced animals over time after vessel injury to understand the cellular mechanisms underlying clonal VSMC expansion in disease.We demonstrate that VSMC proliferation is initiated in a small fraction of VSMCs that initially expand clonally in the medial layer and then migrate to form the oligoclonal neointima. Selective activation of VSMC proliferation also occurs in vitro, suggesting that this is a cell-autonomous feature. Mapping of VSMC trajectories using single-cell RNA-sequencing reveals a continuum of cellular states after injury and suggests that VSMC proliferation initiates in cells that have downregulated the contractile phenotype and show evidence of pronounced phenotypic switching. We show that proliferation is associated with induced expression of stem cell antigen 1 (SCA1) and the expression signature previously identified in SCA1+ VSMCs in healthy arteries. A remarkably increased proliferation of SCA1+ VSMCs, directly validated in functional assays, indicates that SCA1+ VSMCs act as "first responders" in vascular injury. Early atherosclerotic lesions also had clonal VSMC contribution and we show that the proliferation-associated injury response is conserved in plaque VSMCs, extending these findings to atherosclerosis. Finally, we identify VSMCs in healthy human arteries that correspond to the SCA1+ state in mouse VSMCs and show that genes identified as differentially expressed in this human VSMC subpopulation are enriched for genes showing genetic association with cardiovascular disease. We show that cell-intrinsic, selective VSMC activation drives clonal proliferation after injury and in atherosclerosis. Our study suggests that healthy mouse and human arteries contain VSMCs characterised by expression of disease-associated genes that are predisposed for proliferation. Targeting such "first responder" cells in patients undergoing vascular surgery could effectively prevent injury-associated VSMC activation and neoatherosclerosis.
Project description:Vascular calcification and increased extracellular matrix (ECM) stiffness are hallmarks of vascular ageing. Sox9 (SRY-Box Transcription Factor 9) is a master regulator of chondrogenesis, also expressed in the vasculature, that has been implicated in vascular smooth muscle cell (VSMC) osteo-chondrogenic conversion. Here, we investigated the relationship between vascular ageing, calcification and Sox9-driven ECM regulation in VSMCs. Immunohistochemistry in human aortic samples showed that Sox9 was not spatially associated with vascular calcification but correlated with the senescence marker p16. Analysis of Sox9 expression in vitro showed it was mechanosensitive with increased expression and nuclear translocation in senescent cells and on stiff matrices. Manipulation of Sox9 via overexpression and depletion, combined with atomic force microscopy (AFM) and proteomics, revealed that Sox9 regulates ECM stiffness and organisation by orchestrating changes in collagen expression and reducing VSMC contractility, leading to the formation of an ECM that mirrored that of senescent cells. These ECM changes promoted phenotypic modulation of VSMCs whereby senescent cells plated onto ECM synthesized from cells depleted of Sox9 returned to a proliferative state, while proliferating cells on a matrix produced by Sox9 expressing cells showed reduced proliferation and increased DNA damage, reiterating features of senescent cells. Procollagen-lysine, 2-oxoglutarate 5-dioxygenase 3 (LH3) was identified as a Sox9 target, and key regulator of ECM stiffness. LH3 is packaged into extracellular vesicles (EVs) and Sox9 promoted EV secretion, leading to increased LH3 deposition within the ECM. These findings identify cellular senescence and Sox9 as a key regulators of ECM stiffness during VSMC ageing and highlight a crucial role for ECM structure and composition in regulating VSMC phenotype. We identify a positive feedback cycle whereby cellular senescence and increased ECM stiffening promote Sox9 expression which drives further ECM modifications that act to accelerate vascular stiffening and cellular senescence.