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:Atherosclerosis represents an age-related disease, which remains one of the leading cause of deaths in developed countries. It begins with a local deposition of lipid in the innermost part of the artery – intima. Thereafter a number of immune cells are attracted and infiltrate into the artery wall, where, together with endothelia and smooth muscle cells, form an atherosclerotic plaque (Libby, 2008). Thus, atherosclerosis is considered as an inflammatory disease, characterized by intense immunological activity (Libby P, 2012). One of the main risk factor for atherosclerosis is aging. It was demonstrated that there is an accumulation of senescent cells within atherosclerotic plaque (..). Accordingly, vascular smooth muscle cells (VSMCs) derived from the lesion demonstrate a phenotype characteristic for senescent cells: diminished proliferative potential, shorter telomeres, increased number of DNA damage and upregulation of SA-β-gal activity (Gorenne, 2006; Matthes, 2006, Mahomoudi, 2008). Accumulation of senescent VSMCs within the area of plaque development promotes its instability due to lack of proliferation and impaired production of extracellular matrix, both leading to weakening of fibrous cap (Gorenne, 2006). This has been further confirmed by the observation, that elimination of senescent cells in the atherosclerosis-prone low-density lipoprotein receptor-deficient (Ldlr-/-) mice slowed down the disease progression (27789842). One of the most important feature of senescent cells, that has the biggest impact on tissue microenvironment, is their ability to secrete a number of cytokines, chemokines, matrix metalloproteinases and growth factors collectively known as the Senescence Associated Secretory Phenotype (SASP) (20078217, 28165648). Apart from soluble factors, senescent cells secret also an increased number of extracellular vesicles (EVs), research of which has only recently begun (32461143). EVs are small membranous vesicles that can be categorized based on their size and origin, into: exosomes, microvesicles and apoptotic bodies. EVs play crucial role as carriers of proteins, different types of RNA and DNA, lipids and metabolites that, take part in intercellular communication (23420871). They were shown to participate in many physiological but also pathological conditions. Studies performed over the last decade proved that EVs affect atherosclerosis progression at different stages by several distinct mechanisms (as reviewed by Knokhot, 2020, 33261815). The increased concentrations of EVs have been found in plasma of patients suffering from cardiovascular diseases as well as in atherosclerotic plaque itself (Yin, 2015, 26142082; Rautou, 2011, 21852557). However, the role of EVs derived from senescent cells in atherosclerosis, particularly in the context of the plaque development, remains unknown. The functioning of immune cells within atherosclerotic plaque is modulated by local milieu. Thus, senescent cells present in the lesion can influence plaque development by non-cell autonomous mechanism. Indeed, recently it was demonstrated that SASP factors secreted by senescent VSMCs promote recruitment of monocytes, induce expression of adhesion receptors on endothelial cells and activate adjacent normal VSMCs, promoting inflammation in the plaque (Gardner, 2015). However, the role of EVs in this context has not been studied. Thus, we have undertaken research aimed at investigating the role of senescent cell derived EVs on immune cells activity. To this end, we isolated and characterized the EVs secreted by human VSMCs undergoing senescence. We performed unbiased quantitative proteomic analysis of both soluble and insoluble SASP components. Moreover, we analyzed the influence of EVs derived from senescent and non-senescent cells on T lymphocytes and monocytes. Altogether our studies revealed that EVs produced by senescent VSMCs strengthen inflammatory response of the immune cells, what would have a tremendous significance in atherosclerotic plaque development.

Project description:Atherosclerosis is a chronic inflammatory disease of the blood vessels, characterized by atherosclerotic lesions. Early vascular injury initiates excessive inflammatory and immune responses, communicated by blood leukocytes and cells from the vasculature. Key factors contributing to early stages of atherosclerosis and plaque development include the pro-inflammatory cytokine IFNγ, which is vital for both innate and adaptive immunity and is also expressed at high levels in atherosclerotic lesions. Recent discoveries provide novel evidence to suggest that IFNγ-activated STAT1 orchestrates a platform of cell-type common and specific inflammatory responses in Vascular Smooth Muscle Cells (VSMC) and macrophages (MΦ) that are instrumental in the onset and progression of atherosclerotic plaque formation. Therefore, we compared genome-wide transcriptional responses of mouse VSMCs and bone marrow-derived macrophages (BMDMs) in time-dependent IFNγ response using RNA-seq. We identified genes upregulated both in a common and cell-type-specific manner. Next, comparative analysis with RNAseq data from aortic plaques from HFD-treated ApoEKO mice identified 225 differentially expressed genes with a BMDM-specific character. These included many known IFNγ target genes containing putative GAS and ISRE sites in their promoters. Likewise, using a scRNAseq data set obtained from human coronary atherosclerotic plaques, identified 98 pro-inflammatory and pro-atherogenic genes that were characterized as BMDM-specific and exclusively expressed in foamy, inflammatory, monocytes and tissue-resident BMDM subtypes. Finally, we identified a 25 BMDM-specific gene subset commonly expressed in mouse and human plaques, over-representing STAT1-binding sites and predominantly associated with Leukocyte Chemotaxis and Migration. These results provide strong evidence for a BMDM-specific role of STAT1 in coronary artery plaque development and identify a BMDM-specific STAT1-dependent pro-inflammatory gene signature that could serve to monitor and diagnose plaque progression in human atherosclerosis.

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CMKLR1 in Vascular Smooth Muscle Cells: A Therapeutic Focus for Cardiovascular and Cerebrovascular Diseases

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