Chordin knockdown enhances the osteogenic differentiation of human mesenchymal stem cells

Francois NK Kwong¹ , Stephen M Richardson² and Christopher H Evans¹

¹Center for Molecular Orthopaedics, Harvard Medical School, Longwood Avenue, Boston, Massachusetts 02115, USA

²Tissue Injury and Repair Group, The University of Manchester, Oxford Road, Manchester, M13 9PT, UK

author email corresponding author email

Arthritis Research & Therapy 2008, 10:R65doi:10.1186/ar2436


Published:	4 June 2008

See related editorial by Tsiridis and Heliotis, http://arthritis-research.com/content/10/4/115

Abstract

Introduction

Bone morphogenetic proteins (BMPs) are critical growth factors in the osteogenic differentiation of progenitor cells during development in embryos and fracture repair in adults. Although recombinant BMPs are in use clinically, their clinical efficiency needs to be improved. The biological activities of BMPs are naturally regulated by extracellular binding proteins. The specific hypotheses tested in this study were as follows: the BMP inhibitor chordin is produced endogenously during the osteogenic differentiation of human mesenchymal stem cells (MSCs); and blockade of the activity of the BMP inhibitor increases the rate of osteogenic differentiation of human MSCs in vitro.

Methods

Human MSCs were derived from bone marrow from an iliac crest aspirate and from patients undergoing hip hemiarthroplasty. The MSCs were induced down the osteogenic pathway using standard osteogenic differentiation media, and expressions of BMP-2 and chordin were determined by gene expression analysis. During osteogenic differentiation, chordin knockdown was induced using RNA interference. Osteogenic differentiation was assessed by measuring the expression of alkaline phosphatase and calcium deposition. The differences in expression of osteogenic makers between groups were compared by analysis of variance, followed by Gabriel post hoc test.

Results

We demonstrate the expression of BMP-2 and chordin in human MSCs during osteogenic differentiation. Knockdown of chordin by RNA interference in vitro resulted in a significant increase in the expression of the osteogenic marker alkaline phosphatase and the deposition of extracellular mineral, in response to osteogenic stimulation.

Conclusion

We conclude that endogenously produced chordin constrains the osteogenic differentiation of human MSCs. The targeting of BMP inhibitors, such as chordin, may provide a novel strategy for enhancing bone regeneration.