Inhibition of piR48444 promotes osteogenesis via METTL7A-mediated BMP2 mRNA m6A 1 methylation

Non-coding RNAs, including piwi-interacting RNAs (piRNAs), regulate the osteogenic 33 differentiation of bone marrow-derived MSCs (BMSCs). However, the role and mechanism of 34 piRNAs in the osteogenic differentiation of stem cells from human exfoliated deciduous teeth 35 (SHED) are unknown. Here, the piRNA/mRNA-seq revealed that piR48444 downregulation is 36 critically related to the upregulated osteogenic genes METTL7A, BMP2, and FOXO1 in SHED. 37 PiR48444 overexpression inhibited, and piR48444 knockdown promoted osteogenesis by targeting 38 METTL7A to regulate BMP2 mRNA m6A methylation, increasing BMP2 mRNA stability and 39 translation. Furthermore, METTL7A-eIF4E complex binds with BMP2 mRNA, further facilitating 40 the translation. BMP2 promoted FOXO1 expression, which induced the expression of ALP and 41 RUNX2. Moreover, piR48444 knockdown increased the osteogenic differentiation of MSCs from 42 various sources via the METTL7A/BMP2 axis. The treatment with piR48444 antagomir protected 43 bone loss in lipopolysaccharide-treated and aging mice. In conclusion, piR48444 inhibits 44 osteogenic differentiation of MSCs via METTL7A-mediated regulation of BMP2 mRNA m6A 45 methylation, suggesting bioengineering of piR48444 inhibitors to promote MSCs-based bone 46 regeneration.