Sambucusformosana stimulates differentiation of MC3T3-E1 osteoblasts through BMP-2 and ß-catenin pathways

Sambucus formosana Nakai is used as a folk medicine in Taiwan to remedy bone fracture. Here we examined the effects of S. formosana on the differentiation and mineralization of MC3T3-E1 osteoblasts. Then, the impact of S. formosana on signaling pathways known to be implicated in osteoblastogenesis was explored. Results showed the chloroform soluble fraction prepared from the ethanol extract of S. formosana (defined as SF-C) concentration-dependently increased in alkaline phosphatase (ALP) activity, levels of osteopontin, osteocalcin and bone morphogenetic proteins-2 (BMP-2), and calcium nodules formation. SF-C evoked differentiation was significantly abrogated by noggin, wortmannin and SB2003580 treatment. SF-C also induced Smad1/5/8, Akt and p38 phosphorylation suggesting that these signal pathways were probably involved. β-catenin plays a pivotal role in regulating bone mass formation. The results further showed that transfection with β-catenin siRNA significantly attenuated SF-C induced ALP activity. Considering the indirect effect on the regulation of osteoclastogenesis, we found SF-E could stimulate osteoprotegerin (OPG) production although have no effect on RANKL synthesis from MC3T3-E1 preosteoblasts. In summary, our results proved the clinical application of S. formosana and indicated that SF-C has bone anabolic effect being probably through BMP-2- and β-catenin-dependant signal pathways. Further, repression of bone catabolism via up-regulation of OPG/RANKL ratio may also participate in cure bone fracture by S. formosana.