Epigenetic regulation of the PGE(2) pathway modulates macrophage phenotype in normal and pathologic wound repair

Macrophages are a primary immune cell involved in inflammation, and their cell plasticity allows for transition from an inflammatory to a reparative phenotype and is critical for normal tissue repair following injury. Evidence suggests that epigenetic alterations play a critical role in establishing macrophage phenotype and function during normal and pathologic wound repair. Here, we find in human and murine wound macrophages that cyclooxygenase 2/prostaglandin E(2) (COX-2/PGE(2)) is elevated in diabetes and regulates downstream macrophage-mediated inflammation and host defense. Using single-cell RNA sequencing of human wound tissue, we identify increased NF-κB–mediated inflammation in diabetic wounds and show increased COX-2/PGE(2) in diabetic macrophages. Further, we identify that COX-2/PGE(2) production in wound macrophages requires epigenetic regulation of 2 key enzymes in the cytosolic phospholipase A(2)/COX-2/PGE(2) (cPLA(2)/COX-2/PGE(2)) pathway. We demonstrate that TGF-β–induced miRNA29b increases COX-2/PGE(2) production via inhibition of DNA methyltransferase 3b–mediated hypermethylation of the Cox-2 promoter. Further, we find mixed-lineage leukemia 1 (MLL1) upregulates cPLA(2) expression and drives COX-2/PGE(2). Inhibition of the COX-2/PGE(2) pathway genetically (Cox2(fl/fl) Lyz2(Cre+)) or with a macrophage-specific nanotherapy targeting COX-2 in tissue macrophages reverses the inflammatory macrophage phenotype and improves diabetic tissue repair. Our results indicate the epigenetically regulated PGE(2) pathway controls wound macrophage function, and cell-targeted manipulation of this pathway is feasible to improve diabetic wound repair.