| Objective To investigate the association between slit guidance ligand 3 (SLIT3) protein and the development of postmenopausal osteoporosis (PMOP), to assess its predictive value as a diagnostic biomarker, and to validate its effects on bone metabolism through the construction of osteoblast-specific SLIT3 gene knockout mouse model. Methods This study employed a combination of a prospective case-control design and animal model experiments. Clinical data and serum samples were collected from 294 postmenopausal women. Based on bone mineral density (BMD) results, participants were divided into the PMOP group (232 cases) and the non-osteoporotic (NOP) group (62 cases). Serum levels of SLIT3, Osterix (OSX), RUNX2, β-CTX, TP1NP, and N-MID OC were measured. Baseline characteristics and the expression levels of these biomarkers were compared between the two groups. Correlations between SLIT3 and BMD, OSX, RUNX2, and bone turnover markers (β-CTX, TP1NP, N-MID OC) were analyzed. Multivariate analyses were performed to identify risk factors for PMOP. The predictive performance of SLIT3 was evaluated using random forest algorithms and receiver operating characteristic (ROC) curves. To further explore the role of SLIT3 in the bone metabolism, an osteoblast-specific SLIT3 gene knockout mouse model (SLIT3flox/flox, BGLAP-cre) was constructed, and ovariectomized (OVX) model was used to analyze the impact of SLIT3 on bone microarchitecture. Results Clinical results showed that compared to PMOP patients, the NOP group had higher body weight, lumbar spine BMD, and serum levels of SLIT3, OSX, and RUNX2, with statistically significant differences. Spearman correlation analysis revealed that SLIT3 levels were positively correlated with BMD, RUNX2, and OSX protein levels (P<0.001). Logistic regression analysis indicated that SLIT3 was an independent risk factor for PMOP. Random forest algorithms demonstrated the significance of SLIT3 levels in PMOP occurrence. The ROC curve confirmed the predictive value of SLIT3 for PMOP (AUC = 0.857, 95% CI : 0.794–0.920, P<0.001). Animal experiments showed that, compared to the Sham SLIT3fl/fl group, the OVX SLIT3fl/fl group exhibited lower BV/TV and Tb.N, and increased Tb.Sp and SMI indices (P<0.05). In both sham operation group and the ovariectomized model group, SLIT3fl/fl;BGLAP-cre mice showed significantly reduced total BMD and BV/TV compared to SLIT3fl/fl controls (P< 0.05). Conclusion Serum SLIT3 protein level serves as an indicator of bone formation status and is an independent risk factor for PMOP, with substantial predictive value. SLIT3 provides a clinical basis for PMOP prevention and treatment. A serum SLIT3 concentration below 2.32 ng/mL should alert clinicians to the potential risk of PMOP. Osteoblast-derived SLIT3 plays a crucial role in maintaining bone mass. |