Abstract

Human umbilical cord mesenchymal stem cells-derived exosomes (UC-MSCs-exos) have demonstrated considerable potential in osteoporosis treatment. This study explored the underlying mechanisms of UC-MSCs-exos in this context. Osteoporosis cell models were established by treating RAW264.7 cells with RANKL, followed by incubation with UC-MSCs-exos. The effects on osteoclast differentiation were assessed via Western blot and TRAP staining. Transfection of HECTD4, METTL3, and RANK was performed to investigate the regulatory mechanism of UC-MSCs-exos on osteoclast differentiation. MeRIP-qPCR analyzed the impact of METTL3 on RANK m6A modification, and ubiquitination assays examined the influence of HECTD4 on METTL3 ubiquitination. Treatment with UC-MSCs-exos inhibited osteoclast differentiation in the osteoporosis models by decreasing the number of mature osteoclasts and markers such as RANK, ACP5, and CTSK. UC-MSCs-exos also reduced METTL3 levels in these models. When METTL3 was overexpressed in the presence of UC-MSCs-exos, osteoclast differentiation was enhanced. METTL3 promoted RANK protein stability by facilitating its m6A modification. In UC-MSCs-exos-treated models, RANK silencing reversed the effect of METTL3 overexpression on osteoclast differentiation. UC-MSCs-exos were found to contain abundant HECTD4, which promoted METTL3 degradation via ubiquitination. Silencing of HECTD4 promoted osteoclast differentiation in the presence of UC-MSCs-exos, but this was reversed by METTL3 silencing. HECTD4 from UC-MSCs-exos attenuated osteoclast differentiation in osteoporosis by inhibiting RANK m6A modification through METTL3 ubiquitination. These findings suggest that UC-MSCs-exos offer a promising strategy for osteoporosis treatment.