Alendronate induces mineralization in mouse osteoblastic MC3T3-E1 cells: regulation of mineralization-related genes.

Alendronate, an aminobisphosphonate, is an effective reagent to reduce fracture risk in osteoporotic patients. Although several studies suggest that bisphosphonates affect osteoblast differentiation, how they affect the genes relating to the mineralization step remains unknown. The present study was performed to clarify the effects of alendronate on mineralization and its related genes in mouse osteoblastic MC3T3-E1 cells. Alendronate at 10 (-8) and 10 (-7) M induced mineralization in MC3T3-E1 cells. As for the genes that suppress mineralization, alendronate enhanced the level of PC-1 mRNA in a dose-dependent manner in 7-day cultures in semiquantitative RT-PCR, although it reduced the levels of PC-1 mRNA in 21-day cultures. On the other hand, alendronate did not affect the levels of ANK, osteopontin and matrix Gla protein mRNA in both 7- and 21-day cultures. Moreover, alendronate reduced the level of osteocalcin mRNA at 10 (-7) and 10 (-6) M in 14-day cultures of these cells. As for the expression of alkaline phosphatase (ALP), an important positive regulator of mineralization in osteoblasts, alendronate enhanced the levels of ALP mRNA and protein at 10 (-7)-10 (-5) M. In conclusion, low-dose alendronate induced mineralization in mouse osteoblastic cells. The regulation of PC-1, osteocalcin and ALP by alendronate might play some role in these effects.