Aqueous extract of Rehmanniae Radix Praeparata improves bone health in ovariectomized rats by modulating the miR-29a-3p/NFIA/Wnt signaling pathway axis

Ethnopharmacological relevance

Rehmanniae Radix Praeparata (RRP), a widely used traditional Chinese medicine and a processed form of Rehmannia glutinosa, is primarily utilized to supplement kidney function and promote bone health. Clinical evidence suggests that RRP exhibits significant efficacy in the treatment of osteoporosis (OP). However, the precise mechanisms underlying its therapeutic effects remain incompletely understood.

Aim of the study

OP is a systemic skeletal disorder characterized by reduced bone density and quality, leading to an increased risk of fractures. The aim of this study is to evaluate the effectiveness and underlying mechanisms of RRP in treating OP.

Materials and methods

Ovariectomized (OVX) rats were administered RRP aqueous extract via gavage for three months. After the treatment period, femoral microstructure and osteogenic protein levels were assessed to evaluate the efficacy of RRP. Serum exosomes (Exos) derived from different groups of rats were isolated and characterized. The levels of miR-29a-3p in serum-derived Exos and femoral tissue were quantified. Subsequently, Exos were co-cultured with rat bone marrow mesenchymal stem cells (rBMSCs) to investigate their role in promoting osteogenic differentiation and explore the molecular mechanisms underlying this process, particularly through the miR-29a-3p/NFIA/Wnt signaling pathway axis.

Results

OVX rats exhibited significant bone microdamage. In contrast, the RRP-treated OVX rats showed marked improvements in femoral bone microstructure and increased osteogenic protein expression. MiR-29a-3p levels were elevated in serum-derived Exos from the RRP-treated rats. Furthermore, rBMSCs treated with these Exos displayed an increase in miR-29a-3p expression. Further investigations revealed that miR-29a-3p promoted osteogenesis by inhibiting NFIA expression in both bone tissue and rBMSCs. Overexpression of NFIA reversed the osteogenic effects of miR-29a-3p, confirming NFIA as its direct target and suggesting that miR-29a-3p enhances osteogenesis by inhibiting NFIA. Additionally, NFIA was found to promote the transcription of SFRP1, an inhibitor of the Wnt signaling pathway. Our findings suggest that the RRP aqueous extract increases miR-29a-3p levels in serum Exos, which in turn inhibits NFIA and activates the Wnt signaling pathway, thereby promoting osteogenesis.

Conclusion

These findings suggest that the RRP aqueous extract improves bone health and mitigates bone microstructural damage caused by OP through the regulation of the miR-29a-3p/NFIA/Wnt signaling pathway axis.