MSX2 Stimulates Osteoblastic Differentiation

Objectives:Msx2 is a family member of homeobox genes. Mice deficient in Msx2 gene manifested persistent calvarial foramen and defects of skull ossification with marked reduction in bone formation of both cortical and cancellous bones and decreases in osteoblast numbers. In human, heterozygous mutations of Msx2 cause enlarged parietal foramina (PFM) characterized by oval defects of parietal bones. These results demonstrate that Msx2 plays a role in osteogenesis. Methods:To understand the mechanism by which Msx2 contributes to osteogenesis, we examined the effects of Msx2 on osteoblastic differentiation using the multipotent mesenchymal cell lines, C3H10T1/2 and C2C12. We next evaluated whether Msx2 was involved in the control of terminal differentiation of osteoblasts, since the mutations of Msx2 cause impaired ossification in human and mice. To address this, we overexpressed Msx2 into primary osteoblasts isolated from neonatal mice calvariae and examined the capacity of these cells to mineralize by the alizarin red staining. Results:Overexpression of Msx2 using adenovirus system promoted the osteoblastic differentiation of C3H10T1/2 and C2C12 cells, which was enhanced in the presence of BMP2 Overexpression of Msx2 increased the calcification of primary calvarial osteoblasts in the presence of BMP2. In addition, overexpression of mutant Msx2, which is shown to causes PFM in human, inhibited BMP2-induced calcification of these cells. Conclusions:In conclusion, our results suggest that Msx2 promotes the early and late stages of osteoblastic differentiation.