Cuscuta chinensis Lam. extract alleviates ovariectomy-induced osteoporosis by inhibiting VCP-mediated METTL3 protein degradation.

To investigate the therapeutic effects of Cuscuta chinensis Lam. (CCL) on ovariectomy (OVX)-induced osteoporosis (OP) and elucidate the underlying molecular mechanisms, focusing on the VCP-METTL3 axis. The bioactive components of CCL were identified using liquid chromatography-mass spectrometry. An OVX-induced OP mouse model was established and treated with CCL. Bone microarchitecture was assessed by micro-CT, and bone metabolism markers were measured by ELISA. In vitro, bone marrow-derived mesenchymal stem cells (BMSCs) were used to assess osteogenic differentiation (alkaline phosphatase and alizarin red S staining). N6-methyladenosine (m6A) levels were quantified colorimetrically. Protein expression and interactions were analyzed by Western blot, co-immunoprecipitation, and immunohistochemistry. Protein stability and ubiquitination levels were assessed following cycloheximide (CHX) and MG132 treatments. Potential targets were screened via bioinformatics. CCL alleviated bone loss in OVX mice, improving bone volume/total volume (BV/TV), trabecular number (Tb.N), and trabecular thickness (Tb.Th), while reducing trabecular separation/spacing (Tb.Sp). It also restored the balance between bone formation and resorption. In BMSCs, CCL enhanced osteogenic differentiation and increased m6A levels by stabilizing METTL3, extending its half-life. Mechanistically, CCL targeted VCP, inhibiting its interaction with METTL3. VCP, in concert with the E3 ligase BARD1, promoted METTL3 ubiquitination and proteasomal degradation. Knockdown of METTL3 attenuated the pro-osteogenic effects of CCL. Conversely, METTL3 overexpression rescued the inhibitory effects of VCP overexpression on osteogenesis. CCL alleviates OP by targeting VCP to inhibit BARD1-mediated METTL3 ubiquitination and degradation, thereby promoting osteogenic differentiation. These findings highlight the VCP/METTL3 axis as a potential therapeutic target for OP.