Osteoactivin Induces Transdifferentiation of C2C12 Myoblasts Into Osteoblasts

Abstract

Osteoactivin (OA) is a novel osteogenic factor important for osteoblast differentiation and function. Previous studies showed that OA stimulates matrix mineralization and transcription of osteoblast specific genes required for differentiation. OA plays a role in wound healing and its expression was shown to increase in post fracture calluses. OA expression was reported in muscle as OA is upregulated in cases of denervation and unloading stress. The regulatory mechanisms of OA in muscle and bone have not yet been determined. In this study, we examined whether OA plays a role in transdifferentiation of C2C12 myoblast into osteoblasts. Infected C2C12 with a retroviral vector overexpressing OA under the CMV promoter were able to transdifferentiate from myoblasts into osteoblasts. Immunofluorescence analysis showed that skeletal muscle marker MF-20 was severely downregulated in cells overexpressing OA and contained significantly less myotubes compared to uninfected control. C2C12 myoblasts overexpressing OA showed an increase in expression of bone specific markers such as alkaline phosphatase and alizarin red staining, and also showed an increase in Runx2 protein expression. We also detected increased levels of phosphorylated focal adhesion kinase (FAK) in C2C12 myoblasts overexpressing OA compared to control. Taken together, our results suggest that OA is able to induce transdifferentiation of myoblasts into osteoblasts through increasing levels of phosphorylated FAK.

Transgenic Expression of Osteoactivin/gpnmb Enhances Bone Formation In Vivo and Osteoprogenitor Differentiation Ex Vivo

“…These observations confirm our previous published findings that OA/gpnmb over‐expression in osteoblasts in vitro stimulated their differentiation (Abdelmagid et al, ). We have also shown that OA increases osteoblast markers and decreases myoblast markers in vitro (Sondag et al, ). These data combined suggest that OA/gpnmb promotes osteoprogenitor differentiation primarily through up‐regulation of osteoblast differentiation markers.…”

Bone extracellular matrix hydrogel enhances osteogenic differentiation of C2C12 myoblasts and mouse primary calvarial cells

“…52 Previous studies have shown that the presence of specific factors can stimulate transdifferentiation of C2C12 myoblasts into osteoblasts. [53][54][55] The osteogenic capability of bECM hydrogels was measured in vitro with the myoblastic C2C12 cell line, by co-incubation of bECM and type I collagen with C2C12 cells with low and rich serum mediums. Differentiation was assessed by expression of ALP.…”

Interrelationship between bone substitution materials and skeletal muscle tissue

“…Furthermore, the involvement of BMP9 in the pathogenesis of heterotopic ossification was demonstrated (Kaji, 2014). Recently, a parathormone responsive local factor, Tmem119 as well as oeteoactivin were found to promote and induce the differentiation of myoblasts into osteoblasts (Tanaka et al, 2012;Kaji, 2014;Sondag et al, 2014).…”