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Open Access Research article

Induction of superficial zone protein (SZP)/lubricin/PRG 4 in muscle-derived mesenchymal stem/progenitor cells by transforming growth factor-β1 and bone morphogenetic protein-7

José A Andrades1*, Shirley C Motaung2, Pedro Jiménez-Palomo1, Silvia Claros1, José M López-Puerta3, José Becerra1, Thomas M Schmid4 and A Hari Reddi15

Author Affiliations

1 Department of Cell Biology, Genetic and Physiology, Faculty of Sciences, Networking Biomedical Research Center in Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), University of Málaga, 29071-Málaga, Spain

2 Department of Biomedical Sciences, Tshwane University of Technology, Faculty of Sciences, Private Bag X680, Pretoria 0001, South Africa

3 Department of Orthopaedic Surgery and Traumatology, Universitary Hospital Virgen del Rocío, 41013-Sevilla, Spain

4 Department of Biochemistry, Rush University Medical Center, Chicago, IL 60612, USA

5 Lawrence Ellison Center for Tissue Regeneration and Repair, Department of Orthopaedic Surgery, University of California, Davis, Sacramento, CA 95817, USA

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Arthritis Research & Therapy 2012, 14:R72  doi:10.1186/ar3793

Published: 10 April 2012

Abstract

Introduction

Articular cartilage (AC) is an avascular tissue with precise polarity and organization. The three distinct zones are: surface, middle and deep. The production and accumulation of the superficial zone protein (SZP), also known as lubricin, by the surface zone is a characteristic feature of AC. To date, there is a wealth of evidence showing differentiation of AC from mesenchymal stem cells. Most studies that described chondrogenic differentiation did not focus on AC with characteristic surface marker SZP/lubricin. The present investigation was initiated to determine the induction of SZP/lubricin in skeletal muscle-derived mesenchymal stem/progenitor cells (MDMSCs) by transforming growth factor-β1 (TGF-β1) and bone morphogenetic protein-7 (BMP-7).

Methods

MDMSCs were cultured as a monolayer at a density of 1 × 105 cells/well in 12-well tissue culture plates. Cell cultures were treated for 3, 7 and 10 days with TGF-β1 and BMP-7. The medium was analyzed for SZP. The cells were used to isolate RNA for RT-PCR assays for SZP expression.

Results

The SZP/lubricin increased in a time-dependent manner on Days 3, 7 and 10 in the medium. As early as Day 3, there was a three-fold increase in response to 3 ng/ml of TGF-β1 and 300 ng/ml of BMP-7. This was confirmed by immunochemical localization of SZP as early as Day 3 after treatment with TGF-β1. The expression of SZP mRNA was enhanced by TGF-β1.

Conclusions

The present investigation demonstrated the efficient and reproducible induction of SZP/lubricin accumulation by TGF-β1 and BMP-7 in skeletal MDMSCs. Optimization of the experimental conditions may permit the utility of MDMSCs in generating surface zone-like cells with phenotypic markers of AC and, therefore, constitute a promising cell source for tissue engineering approaches of superficial zone cartilage.