H3K4 Methyltransferase Smyd3 Mediates Vascular Smooth Muscle Cell Proliferation, Migration, and Neointima Formation.

Objective Smyd3 (SET and MYND domain-containing protein 3) is an H3K4 (histone H3 lysine 4) dimethyltransferase and trimethyltransferase that activates the transcription of oncogenes and cell cycle genes in human cancer cells. We discovered its overexpression in proliferative vascular smooth muscle cells (VSMCs). However, whether Smyd3 plays a role in vascular remodeling remains unanswered. The objective of this study is to investigate the role and underlying mechanism of Smyd3 in phenotypic transition of VSMCs (such as proliferation and migration) and vascular remodeling (such as neointima formation). Approach and Results: We discovered upregulation of Smyd3 in both PDGF (platelet-derived growth factor) BB-induced vascular cell proliferation model and balloon injury-induced neointima formation model. Knockdown of Smyd3 or blockade of its enzymatic activity suppressed VSMCs proliferation and migration ability, whereas Smyd3 overexpression promoted VSMC migration and proliferation. Mechanistically, RNA-seq and ChIP-seq analysis revealed Smyd3 promoted neointimal formation by directly binding and increasing H3K4me3 to the promoter regions of target genes that are associated with cell proliferation and migration, cell cycle control. Furthermore, knockout of Smyd3 in mice profoundly suppressed carotid artery ligation-induced neointimal hyperplasia, consistently, local knocking down Smyd3 in rats relieved balloon injury-induced neointimal formation, while restored VSMC contractile protein expression, suggesting that Smyd3 plays a critical role in vivo. Conclusions Our results demonstrate that Smyd3 promotes VSMC proliferation and migration during injury-induced vascular remodeling, which provide a potential therapeutic target for preventing neointimal hyperplasia in proliferative vascular diseases.