The histone methyltransferase Whsc1 regulates TGFβ-driven macrophage to myofibroblast transition

Abstract

Abstract In normal wound healing, macrophages regulate early and late inflammation, allowing for resolution of tissue injury and subsequent healing. During normal tissue repair, macrophages undergo transition to myofibroblasts, which promote wound healing. While this critical transition is impaired in diabetic wounds, the underlying mechanisms responsible are unknown. Our group and others have identified that epigenetic regulation of macrophages controls their phenotype in wounds. Since TGFβ drives macrophage to myofibroblast transition, we performed an epigenetic superarray to identify key chromatin modifying enzymes in macrophages (CD11b+CD3− CD19-NK1.1-Ly6G-) from normal diet (ND) and diabetic-induced obese (DIO) murine wounds treated ex vivo with TGFβ. The histone methyltransferase Whsc1, which mediates di- and tri-methylation at H3K36, was significantly increased in DIO macrophages with TGFβ treatment compared to ND macrophages (p<0.05). siRNA knockdown of Whsc1 in BMDMs decreased TGFβ-dependent expression of fibrotic (Acta2, Col1a1, Col3a1) and inflammatory genes (IL-1b, IL-6, and IL-12) (p<0.05). In ChIP experiments, Whsc1 was enriched at Col1a1 and Col3a1 promoters in ND but not DIO BMDMs, and TGFβ inhibited Whsc1 binding as well as H3K36me2 and H3K36me3 at fibrotic gene promoters. Additionally, H3K36me2 and H3K36me3 were decreased in Whsc1-knockdown BMDMs at Col1a1 and Col3a1, validating Whsc1 as an H3K36 methyltransferase that regulates myofibroblast gene expression. These results suggest that TGFβ regulates macrophage to myofibroblast conversion via Whsc1, which we identify as a critical epigenetic switch in tissue repair and potentially an important therapeutic target in diabetic wounds. F32 DK131799-01, 2022 American College of Surgeons Resident Research Scholarship, 2022 VESS/Medtronic Resident Research Award