Abstract 2121: SUV39H1 Mediated Regulation Of KLF4 And KDM4a Coordinate Smooth Muscle Cell Phenotypic Plasticity

Abstract

Background: The phenotypic plasticity of vascular smooth muscle cells is central to growth and remodeling processes, but also underlies many cardiovascular pathologies, including atherosclerosis, restenosis, and intimal hyperplasia. This ability of VSMCs to reversibly differentiate and dedifferentiate is incompletely understood. SUV39H1, a histone methyltransferase, that generates the H3K9Me3 mark results in epigenetic transcriptional repression. We hypothesized that SUV39H1 plays a key role in VSMC plasticity. Methods: We applied knockdown, qPCR, western blotting, chromatin immunoprecipitation (ChIP) assays, RNA-Seq, and murine vascular injury to determine the role of SUV39H1 in VSMC plasticity. Results: A qPCR array screen of epigenetic regulators revealed that SUV39H1 is upregulated with PDGF-induced dedifferentiation but downregulated with rapamycin-induced differentiation in hCASMCs. Knockdown of SUV39H1 induces differentiation-specific hCASMC contractile genes and functional contractility while decreased hCASMC migration, proliferation, and de-differentiation-associated gene expression. RNA-seq transcriptomics confirmed changes in multiple pathways consistent with a role for SUV39H1 in promoting hCASMC dedifferentiation. Mechanistically, SUV39H1 knockdown suppressed expression of KLF4, a master dedifferentiation factor, decreasing KLF4 mRNA stability and upregulating miRNA143. SUV39H1 knockdown also increased expression of KDM4a, an enzyme that removes H3K9me3 marks. In vivo, we noted a significant increase in SUV39H1 and H3K9me3 expression in murine carotid artery ligation-induced intimal hyperplasia compared to uninjured vessels. Conclusion: We identify SUV39H1 as an epigenetic regulator of VSMC phenotype whose expression and activity increase with dedifferentiation in vitro and in vivo . PDGF promotes H3K9me3 repressive marks at contractile genes by promoting expression of SUV39H1 (writer), which also inhibits the KDM4a (eraser) and SUV39H1 also regulates KLF4 expression. Understanding the role of SUV39H1 in VSMC plasticity may reveal new therapeutic strategies for treating vascular diseases.