The BMP signaling pathway enhances the osteoblastic differentiation of bone marrow mesenchymal stem cells in rats with osteoporosis

Background: This study was conducted with the aim of exploring the effect of the BMP signaling pathway on osteoblastic differentiation in rat bone marrow mesenchymal stem cells (rBMSCs) in rats with osteoporosis (OP). Methods: The bilateral ovaries of female SD rats were resected for the establishment of a rat OP model. The osteoblastic differentiation of isolated rBMSCs was identified through osteogenic induction. Adipogenetic induction and flow cytometry (FCM) were used to detect adipogenic differentiation and the expression of rBMSC surface markers. The rBMSCs were grouped into the blank group, NC group, si-BMP2 group, and oe-BMP2 group. The expression levels of key factors and osteogenesis-related factors were determined by Western blot and quantitative real-time polymerase chain reaction (qRT-PCR). The formation of calcified nodules was observed by alizarin red staining. ALP activity was measured by alkaline phosphatase staining. Results: The rats with OP had greater weight but decreased bone mineral density (BMD) than normal rats (all P < 0.01). The rBMSCs from rats with OP were capable of osteoblastic differentiation and adipogenic differentiation and showed high expression of CD44 (91.3 ± 2.9%) and CD105 (94.8 ± 2.1%). Compared with the blank group, the oe-BMP2 group had elevated BMP-2 and Smad1 levels and an increase in calcified nodules and ALP-positive staining areas (all P < 0.05). Moreover, the expression levels of Runx2, OC, and OPN in the oe-BMP2 group were relatively higher than those in the blank group (all P < 0.05). The findings in the si-BMP2 group were opposite to those in the oe-BMP2 group. Conclusion: BMP signaling pathways activated by BMP-2 can promote the osteoblastic differentiation of rBMSCs from rats with OP.