SIRT2 suppressed osteogenesis via transcriptionally regulation of SLC31A1-meidated cuproptosis in a crotonylation manner

Osteoporosis (OP), a systemic disorder of bone metabolism characterized by impaired osteogenesis and excessive skeletal resorption, is increasingly linked to epigenetic regulation. Among these, histone crotonylation (Kcr) has emerged as a key determinant of gene expression and cellular differentiation, yet the role of histone H3 lysine 4 crotonylation (H3K4cr) in osteogenesis remains unclear. In this study, analysis of OP-related GEO datasets combined with validation in patient serum samples and an OP cell model identified Sirtuin (Sirt) 2, a histone deacetylase, as a central regulator of H3K4cr during bone formation. Functional assays, including Reverse Transcription Quantitative Real-Time Polymerase Chain Reaction (RT-qPCR), western blotting, Chromatin immunoprecipitation followed by quantitative PCR (ChIP-qPCR), luciferase reporter analyses, and in vivo studies using ovariectomized (OVX) rats, demonstrated that SIRT2 expression was elevated in OP and negatively correlated with osteogenic markers. Knockdown of SIRT2 increased H3K4cr levels, thereby enhancing osteogenic differentiation in vitro and promoting bone regeneration in OVX rats. Mechanistically, SIRT2-mediated H3K4 decrotonylation facilitated SLC31A1 transcription by alleviating the inhibitory effect of H3K4cr on E74-like factor 3 (ELF3) binding to the promoter. Elevated Copper transporter 1 (CTR1/SLC31A1) expression impaired osteogenesis by increasing intracellular copper accumulation and triggering cuproptosis, whereas copper chelation or SLC31A1 inhibition restored osteogenic potential both in vitro and in vivo. Collectively, these findings define a previously unrecognized SIRT2–H3K4cr–SLC31A1 axis that integrates epigenetic regulation with copper metabolism to modulate osteogenic differentiation, highlighting a promising therapeutic target for osteoporosis.