microRNA-21 ameliorates the impairment of autophagy in palatal wound healing.

Fibroblast injury and autophagy dysfunction have been shown to contribute to the persistence of oral wounds. Recently, microRNAs have emerged as vital regulators and fine tuners of various pathophysiological cellular processes that influence the wound healing process. This study explored the biological function and regulatory mechanism of miRNA-21 (miR-21) in the healing of oral wounds by interfering with autophagy. Healthy gingival cells derived from wild-type (WT) and from miR-21KO mice were characterized by immunocytofluorescence, and changes in wound healing were subsequently assessed using an in vitro scratch wound healing assay. The roles of critical proteins required for autophagy, autophagy related 5 (ATG5) and Bcl-2 interacting coiled-coil protein 1 (Beclin1) were evaluated by immunohistochemistry. Human gingival fibroblasts (HGFs) were transfected with a miR-21 mimic and a miR-negative control, and the relative expression of miR-21, ATG5, Beclin1 and LC3-I/II was characterized by qRT-PCR and Western blot. Pathological changes were observed in a palatal wound healing model using WT and miR-21KO mice. Immunohistochemistry was used to examine extracellular matrix (ECM) proteins and autophagy markers. Cell migration was delayed in gingiva-derived mesenchymal stem cells (GMSCs) from miR-21KO mice compared with WT mice. The expression of ATG5 and Beclin1 was significantly up-regulated in miR-21KO gingiva. Transfection of a miR-21 mimic into HGFs inhibited autophagy and up-regulated miR-21 expression. Knockdown of miR-21 suppressed the expression of fibronectin and CTGF, enhanced the autophagy effect of fibroblasts, suggesting that autophagy is involved in miR-21 regulated palatal wound healing. Taken together, these results suggest that miR-21 promotes oral wound healing by increasing ECM production through the inhibition of autophagy and facilitates clinical management of wound healing.