Suppression of bone resorption by Mori Radicis Cortex through NFATc1 and c-Fos signaling-mediated inhibition of osteoclast differentiation

Background: Mori Radicis Cortex (MRC) is the root bark of the mulberry family as Morus alba L. In Korea, it is known as "Sangbaegpi”. While MRC has demonstrated anti-inflammatory and antioxidant effects, its specific mechanisms of action and impact on osteoporosis remain poorly understood. Methods: To investigate the anti-osteoporosis effect of MRC, we examined the level of osteoclast differentiation inhibition in receptor activator of nuclear factor kappa-Β ligand (RANKL)-induced-RAW 264.7 cells and animal models of ovariectomy (OVX) with MRC. Serum analysis in OVX animals was investigated by enzyme-linked immunosorbent assay (ELISA), and bone density analysis was confirmed by micro-computed tomography (micro-CT). The expression analysis of NFATc1 was confirmed by immunohistochemistry (IHC) in femur tissue. In addition, osteoclast differentiation inhibition was measured using tartrate-resistant acid phosphatase (TRAP). mRNA analysis was performed using reverse transcription polymerase chain reaction (RT-PCR), and the protein expression analysis was investigated by western blot. Results: Micro-CT analysis showed that MRC effectively inhibited bone loss in the OVX-induced rat model. MRC also inhibited the expression of alkaline phosphatase (ALP) and TRAP in serum. Histological analysis showed that MRC treatment increased bone density and IHC analysis showed that MRC significantly inhibited the expression of NFATc1. In RANKL-induced-RAW 264.7 cells, MRC significantly reduced TRAP activity and actin ring formation. In addition, MRC significantly inhibited the expression of nuclear factor of activated T cells 1 (NFATc1)/ and c-Fos, and suppressed the mRNA expression. Conclusion: Based on micro-CT, serum and histological analysis, MRC effectively inhibited bone loss in an OVX-induced rat model. In addition, MRC treatment suppressed the expression of osteoclast differentiation, fusion, and bone resorption markers through inhibition of NFATc1/c-Fos expression in RANKL-induced RAW 264.7 cells, ultimately resulting in a decrease in osteoclast activity. These results demonstrate that MRC is effective in preventing bone loss through inhibiting osteoclast differentiation and activity.