METTL3-mediated m 6A modification of pri-miRNA-31 promotes hypertrophic scar progression.

Hypertrophic scar (HS) is a pathological scar characterized by excessive dermal fibrosis. Aberrant m ⁶A modification patterns have been identified in HS; however, the expression of the methyltransferase, along with its function and molecular mechanisms in HS, remains unclear. In this study, we find that both the protein level of METTL3 and the level of m6A methylation are upregulated in HS compared with normal skin. To investigate the role of METTL3 in HS, we knock down METTL3 in HS-derived fibroblasts (HSFBs) via shRNA. METTL3 knockdown reduces the expressions of collagen types I and III (COL I/III) and α-SMA, inhibits cell proliferation and migration, and induces cell cycle arrest in the G1 phase. MeRIP-seq analysis reveals m ⁶A modification sites on pri-miR-31. Our data indicate that the expression level of pri-miR-31 is elevated in METTL3-knockdown HSFBs, whereas the level of mature miR-31-5p is reduced. Notably, transfection of a miR-31-5p mimic into HSFBs partially counteracts the inhibitory effects of the m ⁶A methylation inhibitors cycloleucine and STM2457 (a specific inhibitor of METTL3) on fibrosis and cellular proliferation. Additionally, we confirm that ZBTB20 is a downstream target of miR-31-5p and that knockdown of ZBTB20 inhibits fibroblast fibrosis. Collectively, our findings elucidate the epigenetic mechanism of METTL3/m ⁶A/pri-miR-31/ZBTB20 in HS fibrosis, providing a potential therapeutic target for HS.