METTL14 Promotes the Osteogenic Differentiation of Human Bone Marrow Stromal Cells via m6A-Dependent Stabilization of USP7 mRNA.

Osteoporosis (OP) is a common clinical bone disease that can cause a high incidence of non-stress fractures and is one of the main degenerative diseases that endangers the health and life of middle-aged and older women. The mechanism underlying the abnormal differentiation and function of human bone marrow stem cells (hBMSCs) remains to be elucidated. Cell proliferation and differentiation were determined using 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di-phenytetrazoliumromide (MTT) assay, alkaline phosphatase (ALP) staining, and Alizarin Red Staining. The interaction between insulin-like growth factor 2 mRNA-binding protein 2 (IGF2BP2) and ubiquitin-specific protease 7 (USP7) was predicted and validated using bioinformatics approaches, luciferase assays, RNA immunoprecipitation (RIP), and immunoprecipitation (IP). Actinomycin D treatment was used to test the stability of mRNA in the various groups. Methyltransferase-like 14 (METTL14) expression was increased in osteogenic differentiation medium-induced hBSMCs and was associated with enhanced osteogenic differentiation. METTL14 regulated the expression USP7 by modulating its N⁶-methyladenosine (m6A) level. IGF2BP2 exerted an m6A-dependent effect on USP7 mRNA stability and USP7 increased sirtuin 1 (SIRT1) expression in hBMSCs by enhancing SIRT1 deubiquitination. METTL14 stimulated the osteogenic differentiation of hBMSCs through the m6A-IGF2BP2-USP7 pathway and promoted hBMSCs osteogenic development via SIRT1-Bmi1 signaling. METTL14 stimulated the osteogenic differentiation of hBMSCs by stabilizing USP7 mRNA in an m6A-dependent manner. USP7 was also stabilized by IGF2BP2 and it regulated downstream SIRT1-Bmi1 signaling.