Saponins from the Sea Cucumber Promote the Osteoblast Differentiation in MC3T3-E1 Cells through the Activation of the BMP2/ Smads Pathway

Background: Several studies have shown that plant saponins promoted osteoblast differentiation and improved osteoporosis. In the current study, Sea Cucumber Saponin (SCS) with a purity of 80% was extracted from Filipino sea cucumber, with a similar structure to plant saponins. Objective: This study aims to investigate the effects of SCS on bone formation in vitro and ex vivo. Results: SCS significantly promoted osteogenic differentiation and mineralization of MC3T3-E1 cells, as well as new osteoid formation in neonatal mouse calvarias ex vivo. qRT-PCR results indicated that SCS markedly down-regulated the expression of C/EBPα* and PPARγ at the levels of transcription, which demonstrate that SCS inhibits the trans-differentiation of MC3T3-E1 cells to an adipocytic phenotype. Moreover, further studies revealed that SCS increased the expression levels of Runx2 and OSX. The mechanism revealed that SCS induced the expression of BMP2 and p-Smad1/5, which indicated that SCS facilitated osteogenesis via activating the BMP2/Smads signaling pathway. Conclusion: SCS promoted osteogenic differentiation of pre-osteoblasts by activating the BMP2/ Smads molecular pathway, providing a theoretical basis for the development of sea cucumber saponins for the treatment to bone loss diseases such as osteoporosis.