Myostatin (GDF-8) inhibits chondrogenesis and chondrocyte proliferation in vitro by suppressing Sox-9 expression

Abstract

Here, we investigate a possible direct role for myostatin in chondrogenesis. First, we examined the effects of myostatin on the proliferation of bone marrow stromal cells (BMSCs) and epiphyseal growth plate (EGP) chondrocytes (EGPCs) isolated from myostatin-deficient mice. Results show that myostatin deficiency is associated with a significant (P < 0.001) increase in proliferation of both BMSCs (+25%) and EGPCs (+35%) compared with wild-type cells. Next, we examined the effects of myostatin treatment on chondrogenic differentiation of BMSCs. These experiments show that myostatin treatment starting at either 0 or 48 h induces a significant decrease in collagen type II protein synthesis by 31% (P < 0.001) and 25% (P < 0.05), respectively. Real-time PCR reveals significant (P < 0.01) down regulation of Sox9 mRNA expression with 10 and 100 ng/ml treatments. Together, these findings suggest that myostatin has direct effects on chondrogenesis, and may, therefore, represent a potential therapeutic target for improving bone repair.

Keywords::

• TGF-beta
• endochondral ossification
• bone marrow stem cells

Acknowledgments

We are grateful to Drs Xingming Shi and William Hill for their assistance with the isolation and culture of BMSCs, to Donna Kumiski and Penny Roon for their expertise in sectioning of the cartilage aggregates, and to Matthew Bowser and Phonepasong Arounleut for their assistance in the laboratory.

Declaration of interest: Funding for this study was provided by the National Institutes of Health (AR049717), the Office of Naval Research (N000140810197), and the Department of Army (USAMRMC PR093619). Dr William A. Horton generously provided the col2-eGFP mice utilized in this study, and Drs Alexandra McPherron and Se-Jin Lee provided the myostatin-deficient mice. The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.