Project description:Cardiovascular disease is the leading cause of death in developed countries and there is compelling evidence that the majority of these fatalities are secondary to rupture of unstable atherosclerotic plaques. However, the mechanisms that control plaque stability are poorly understood, although it is widely believed that plaques having a decreased ratio of cells positive for smooth muscle cell (SMC) markers such as ACTA2 relative to macrophage markers are more likely to rupture. Herein we employMyh11-CreERT2 ROSA floxed STOP eYFP Apoe-/- mice to trace SMC lineage and show that traditional methods for detecting SMCs based on immunostaining for SMC markers like ACTA2 are unable to detect 82% of SMC-derived cells within advanced atherosclerotic lesions. Moreover, we show that these SMC-derived cells within advanced lesions exhibit multiple phenotypes including activation of multiple markers of macrophages, mesenchymal stem cells (MSC), and myofibroblasts (MF). Importantly, we show that SMC-derived macrophage like cells are phagocytic based on electron microscope YFP immunolabeling. In addition, results of single cell epigenetic assays developed in our lab shows that nearly 20% of macrophage-like cells within human lesions are of SMC not myeloid origin. These phenotypic transitions appear to be critical in lesion pathogenesis, in that we show that SMC-specific conditional knockout (KO) of the pluripotency factor, Krüppel-like factor 4 (KLF4), resulted in marked reductions in lesion size, increases in multiple indices of plaque stability, and reduced numbers of SMC-derived MSC- and macrophage-like cells. Finally, we show that cholesterol loading of cultured SMC is associated with activation of multiple markers of macrophages and MSC, secretion of pro-inflammatory cytokines, and increased phagocytosis, all of which are Klf4 dependent. Taken together, results indicate that the contribution of SMCs within atherosclerotic plaques has been greatly underestimated, and that loss of Klf4 within SMC result in major changes in SMC phenotype and function that play a major role in lesion pathogenesis. Examination of KLF4 transcription factor in an atherosclerosis setting

Project description:Cardiovascular disease is the leading cause of death in developed countries and there is compelling evidence that the majority of these fatalities are secondary to rupture of unstable atherosclerotic plaques. However, the mechanisms that control plaque stability are poorly understood, although it is widely believed that plaques having a decreased ratio of cells positive for smooth muscle cell (SMC) markers such as ACTA2 relative to macrophage markers are more likely to rupture. Herein we employMyh11-CreERT2 ROSA floxed STOP eYFP Apoe-/- mice to trace SMC lineage and show that traditional methods for detecting SMCs based on immunostaining for SMC markers like ACTA2 are unable to detect 82% of SMC-derived cells within advanced atherosclerotic lesions. Moreover, we show that these SMC-derived cells within advanced lesions exhibit multiple phenotypes including activation of multiple markers of macrophages, mesenchymal stem cells (MSC), and myofibroblasts (MF). Importantly, we show that SMC-derived macrophage like cells are phagocytic based on electron microscope YFP immunolabeling. In addition, results of single cell epigenetic assays developed in our lab shows that nearly 20% of macrophage-like cells within human lesions are of SMC not myeloid origin. These phenotypic transitions appear to be critical in lesion pathogenesis, in that we show that SMC-specific conditional knockout (KO) of the pluripotency factor, Krüppel-like factor 4 (KLF4), resulted in marked reductions in lesion size, increases in multiple indices of plaque stability, and reduced numbers of SMC-derived MSC- and macrophage-like cells. Finally, we show that cholesterol loading of cultured SMC is associated with activation of multiple markers of macrophages and MSC, secretion of pro-inflammatory cytokines, and increased phagocytosis, all of which are Klf4 dependent. Taken together, results indicate that the contribution of SMCs within atherosclerotic plaques has been greatly underestimated, and that loss of Klf4 within SMC result in major changes in SMC phenotype and function that play a major role in lesion pathogenesis.

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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Smooth muscle-derived adventitial progenitor cells direct atherosclerotic plaque composition complexity in a Klf4-dependent manner

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