Kaempferol binds with NSUN2 to mediate RNA 5-methylcytosine modification of BMP2 in osteogenic differentiation.

PURPOSE This study aimed to investigate the effects and underlying mechanism of kaempferol (Kae) on osteogenic differentiation through 5-methylcytosine (m5C) modification in bone metabolism.

MATERIALS AND METHODS Dexamethasone (DEX, 1 μM) was used to inhibit the differentiation of MC3T3-E1 cells to mimic osteoporosis in vitro. The effects of Kae (5, 10, and 20 μM) on osteogenic differentiation were evaluated. m5C levels in MC3T3-E1 cells were measured by m5C dot blot assay, and the expression of several m5C-related genes was detected. The binding between Kae and an m5C-related gene was examined, and the interaction between NSUN2 andBMP2 was assessed. To investigate the regulatory role of Kae in osteoporosis, an ovariectomy (OVX)-induced osteoporotic mouse model was established.

RESULTS Kae at 5-20 μM promoted osteogenic differentiation of MC3T3-E1 cells. Kae treatment increased m5C levels and NSUN2 expression in MC3T3-E1 cells. Kae bound to NSUN2, and inhibition of NSUN2 partially attenuated the pro-osteogenic effects of Kae. Furthermore, NSUN2 inhibition promoted BMP2 mRNA degradation. Inhibition of BMP2 significantly reversed the effect of NSUN2 overexpression on osteogenic differentiation. In vivo, Kae alleviated OVX-induced osteoporosis by reducing bone loss.

CONCLUSIONS Kae promotes osteogenic differentiation of osteoblasts in vitro and ameliorates bone loss in OVX-induced osteoporotic mice. Kae binds to NSUN2 to mediate RNA m5C modification of BMP2 during osteogenic differentiation. Kae may be a promising therapeutic agent for osteoporosis.