Osteoporosis (OP), characterized by reduced bone mineral density and degraded bone microarchitecture, significantly increases the risk of fractures(Johnston and Dagar, 2020). This condition affects millions globally, particularly postmenopausal women and elderly populations. Epidemiological studies demonstrate that OP is a major public health concern, with an estimated 200 million individuals affected worldwide(Tanski et al., 2021). The incidence of osteoporotic fractures escalates exponentially with age, resulting in substantial morbidity, mortality, and healthcare expenditures(Amin et al., 2023). Several risk factors contribute to the pathogenesis of OP. Age-related bone loss, hormonal alterations (notably estrogen deficiency in postmenopausal women), genetic susceptibility, and modifiable lifestyle factors—including low calcium intake, vitamin D insufficiency, physical inactivity, and tobacco use—serve as key contributors(Tanski et al., 2021). Furthermore, prolonged exposure to certain medications, particularly glucocorticoids, accelerates pathological bone resorption(Compston, 2018). Current therapeutic strategies for OP focus on preventing further bone degradation and mitigating fracture risk(Munoz et al., 2020). Pharmacological interventions such as bisphosphonates, denosumab, teriparatide, and selective estrogen receptor modulators are widely employed(Johnston and Dagar, 2020). Non-pharmacological approaches encompass calcium and vitamin D supplementation, weight-bearing exercise regimens, and fall prevention measures. However, these modalities often face challenges, including adverse effects, adherence difficulties, and insufficient recovery of bone structural integrity.

In OP, impaired osteoblast differentiation plays a critical role in disease progression(Lee et al., 2017). Osteoblasts are responsible for new bone formation, and their diminished activity disrupts the balance between bone resorption and deposition. Targeting molecular mechanisms to enhance osteoblast differentiation—such as modulating signaling pathways or regulating epigenetic factors—may represent innovative therapeutic strategies(Hu et al., 2022; Huang et al., 2021). For example, upregulation of osteogenic markers, including Runt-related transcription factor 2 (RUNX2), osteocalcin (OCN), and collagen type I alpha 1 (COL1A1), could restore bone mass and structural integrity(Qiu et al., 2023). Addressing these cellular mechanisms is essential for advancing more effective OP therapies.

A key pathogenic mechanism in OP involves DNA damage in bone cells, which compromises their functional capacity and viability(Chandra and Rajawat, 2021). Such damage arises from diverse sources, including reactive oxygen species (ROS), ionizing radiation, and genotoxic agents. RAD51, a central recombinase enzyme in the RecA family, is critical for homologous recombination repair of DNA double-strand breaks(Cruz et al., 2018). By facilitating homology search and strand exchange, RAD51 ensures genomic stability during DNA repair processes(Mu et al., 2023). Dysfunctional RAD51 activity has been implicated in malignancies such as breast and pancreatic cancers(Cruz et al., 2018; Nagathihalli and Nagaraju, 2011). However, its role in OP remains poorly characterized. Our previous findings revealed that RAD51 overexpression promotes osteogenic differentiation by activating the insulin-like growth factor 1 receptor (IGF1R)/phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) signaling axis in osteoblasts, suggesting its potential as a biomarker for OP(Qiu et al., 2023).

N6-methyladenosine (m6A) is the most abundant internal RNA modification in eukaryotic mRNAs and select non-coding RNAs(An and Duan, 2022). This reversible epigenetic modification involves the methylation of adenosine at the N6 position, regulating diverse aspects of RNA metabolism. m6A plays a pivotal role in post-transcriptional regulation, influencing mRNA stability, splicing, nuclear export, translation efficiency, and degradation. The m6A modification is dynamically regulated by a tripartite system of "writers," "readers," and "erasers"(Feng et al., 2023) Writers, such as methyltransferase-like (METTL)3 and METTL14, catalyze m6A deposition on RNA substrates. Readers, including YTH domain-containing proteins (YTHDCs), YTH domain family (YTHDF) members, and insulin-like growth factor 2 mRNA-binding protein (IGF2BP) family members, recognize and bind m6A-modified RNAs to mediate functional outcomes. Erasers, such as AlkB Homolog 5 (ALKBH5), remove m6A marks, thereby modulating RNA activity. ALKBH5 has been implicated in critical biological processes, including stem cell maintenance and neural function(Qiu et al., 2024; Shen et al., 2020). Dysregulation of ALKBH5 has been linked to pathological conditions, notably OP(Huang et al., 2024; Wang et al., 2020).

Our previous studies demonstrated that RAD51 contributed to OP progression by modulating key signaling pathways. In this study, we aimed to investigate whether RAD51 influences osteogenic differentiation and DNA damage in OP through RNA methylation regulation. This investigation may provide novel insights into the pathophysiological mechanisms of OP and identify potential therapeutic targets.