METTL3-modified exosomes from adipose-derived stem cells enhance the proliferation and migration of dermal fibroblasts by mediating m6A modification of CCNB1 mRNA.

Skin scalded injury is a devastating condition. Exosomes derived from adipose-derived mesenchymal stem cells (ASC-exos) have been shown encouraging therapeutic potential in wound healing. Here, we explored the activity and mechanism of methyltransferase-like 3 (METTL3)-modified ASC-exos in the migration and proliferation of dermal fibroblasts. ASC-exos were isolated from mouse ASCs, characterized, and used to incubate mouse dermal fibroblasts. Fluorescence microscopy was used to analyze the transfer of ASC-exos into fibroblasts. Cell migration, invasion, proliferation, and viability were assessed by wound healing, transwell, 5-Ethynyl-2'-deoxyuridine (EdU), and Cell Counting Kit-8 (CCK-8) assays, respectively. Protein expression was tested by western blotting. The influence of METTL3 in cyclin B1 (CCNB1) was evaluated by methylated RNA immunoprecipitation (MeRIP), actinomycin D treatment and quantitative PCR assays. ASC-exos significantly increased the proliferative, invasive, and migratory potentials of dermal fibroblasts. Overexpression of METTL3 resulted in elevated proliferation, invasiveness, and migratory capacity in dermal fibroblasts. Furthermore, METTL3-modified ASC-exos derived from METTL3-increased ASCs exerted more significantly promoting effects on fibroblast proliferation and migration than ASC-exos. Mechanistically, METTL3 upregulated CCNB1 by affecting its mRNA m6A modification. Additionally, reduction of CCNB1 had a counteracting impact on the effects of METTL3-modified ASC-exos in dermal fibroblasts. Our study shows that METTL3-modified ASC-exos enhance the migration and invasion of dermal fibroblasts by mediating CCNB1 mRNA m6A modification, raising hopes that these exosomes might serve as a therapeutic option for scalded skin wound repair.