Comparative analysis of human bone marrow mesenchymal stem cells, articular cartilage derived chondroprogenitors and chondrocytes to determine cell superiority for cartilage regeneration.

INTRODUCTION

Chondroprogenitors, a promising therapeutic modality in cell-based therapy, are routinely isolated from articular cartilage by fibronectin differential adhesion assay. However, there is paucity of information regarding their biological profile and the lack of a marker that can reliably distinguish them from cultured chondrocytes due to possible dedifferentiation. Since chondroprogenitors have been classified as mesenchymal stem cells(MSCs), the aim of our study was to compare bone marrow-MSCs, chondroprogenitors and chondrocytes, and assess superiority for cartilage repair. An additional objective was to also compare CD49b as a differentiating marker for isolating chondroprogenitors as a recent report demonstrated significantly high expression in the surfaceome of migratory articular chondroprogenitors.

METHODS

Bone marrow aspirate and articular cartilage was obtained from three osteoarthritic knee joints. Study arms included a) bone marrow-MSCs, b) chondroprogenitors, c) cultured chondrocytes, d) chondrocytes cultured with additional growth factors and e) CD49b + sorted chondroprogenitors. Assessment parameters included population doubling, surface expression for positive, negative MSC markers and potential markers of chondrogenesis (CD29, CD49e, CD49b, CD166 and CD146), RT-PCR for markers of chondrogenesis and hypertrophy and trilineage differentiation.

RESULTS AND CONCLUSION

Chondroprogenitors exhibited efficient chondrogenesis (SOX-9 and COL2A1) and significantly lower tendency for hypertrophy (RUNX2), which was also reflected in trilineage differentiation where progenitors displayed minimal calcified matrix, efficient glycosaminoglycan deposition and high collagen type II uptake. CD49b did not serve as a marker for isolation as sorted chondroprogenitors performed significantly poorer when compared to fibronectin assay derived cells. Emphasis on preclinical studies utilizing progenitors of higher purity is the future direction.