Effects of Silkworm (Bombyx mori) Pupa Extract on the Function of Osteoblastic MC3T3-E1 Cells

Osteoporosis is recognized as one of the major hormonal deficiency diseases, especially in menopausal women and the elderly. When the estrogen level is reduced in the body, local factors, which are known to be related with bone resorption, are increased and promote osteoclastogenesis. In our previous study, we validated the estrogenicity of silkworm pupa. In this study, we investigated the effect of silkworm pupa extract (SPE) on the function of osteoblastic MC3T3-E1 cells. SPE (10 and $50\;{\mu}g/mL$) significantly elevated cell viability, alkaline phosphatase (ALP) activity, and collagen content in the cells. The effect of SPE ($50\;{\mu}g/mL$) in increasing cell viability, ALP activity, and collagen content was completely inhibited by the presence of $10^{-6}\;M$ of cycloheximide and $10^{-6}\;M$ of tamoxifen, suggesting that SPE's effect results from a newly synthesized, protein component and that it might be partly involved in estrogen action. Furthermore, we examined the effect of SPE on the $H_2O_2-induced$ apoptosis and production of local factors in osteoblasts. Treatment with SPE ($50\;{\mu}g/mL$) decreased the 0.2 mM $H_2O_2-induced$ apoptosis and the production of tumor necrosis factor (TNF)-${\alpha}$, interleukin (IL)-6 and nitric oxide (NO) in osteoblasts. Our data indicate that the enhancement of osteoblast function by silkworm pupa may prevent osteoporosis and inflammatory bone diseases.