Alendronate enhances osteoblastic differentiation with increased expression of Id-1 and Id-2 in pre-osteoblast cell line, MC3T3-E1

Objective: Alendronate, a widely used bisphosphonates, acts to inhibit bone resorption by interfering with the activity of osteoclasts.Recently, it has been reported that alendronate also may increase bone proliferation and osteoblastic differentiation.However, little is known about mechanism of the action of alendronate on osteoblast differentiation, especially in transcription level.Inhibitors of DNA binding/ differentiation (Ids) are helix-loop-helix (HLH) transcription factors and play an important role in BMP-induced osteoblast lineage-specific differentiation.Therefore, this study was aimed to investigate the effect of alendronate on osteoblast differentiation and expression of Id-1 and Id-2.Methods: MC3T3-E1, pre-osteoblast cell line, were treated with alendronate of various concentrations (10 -9 M-10 -4 M) and time periods (24, 48 and 72 hours).And then, the effect of alendronate on osteoblast differentiation was examined by alkaline phosphatase (ALP) activity and RT-PCR for osteoblast differentiation markers such as ALP, type 1 collagen (Col 1), and osteocalcin (OCN).The expressions of Id-1 and Id-2 were measured by RT-PCR.Results: Alendronate treatment increased not only ALP activity, but also expressions of ALP, Col 1, and OCN.Also, alendronate treatment up-regulated the mRNA levels of Id-1 and Id-2 genes.This alendronate-induced osteoblastic differentiation is more effective in lower doses rather than high doses.Conclusion: This study shows that the expression of transcription factor Id-1 and Id-2 was increased in a dose-dependent manner during alendronate-induced osteoblast differentiation.