Expression Analysis of Mesenchymal Stem/Progenitor Cell Markers on Chondrocytes in Ossification of the Posterior Longitudinal Ligament.

INTRODUCTION

One hypothesis of ossification of the posterior longitudinal ligament (OPLL) pathogenesis is that pluripotent mesenchymal stem/progenitor cells (MSCs) differentiate into chondrocytes and that heterotopic ossification occurs via endochondral ossification. However, studies on the origin and characteristics of these ectopically appearing chondrocytes are limited. The purpose of this study was to investigate the characteristics of chondrocytes in human OPLL tissue, with a particular focus on MSC markers.

METHODS

OPLL samples were collected during surgery from four patients with cervical or lumbar OPLL. We investigated the expression of cell surface markers of MSC by reverse transcription-polymerase chain reaction (RT-PCR) and immunostaining.

RESULTS

RT-PCR analysis revealed the expression of CD73, CD90, CD105, and platelet-derived growth factor receptor α (PDGFRα) in OPLL tissue. Immunostaining analysis also demonstrated that the chondrocytes in ossified tissue co-expressed CD73, CD90, CD105, and PDGFRα.

CONCLUSIONS

Chondrocytes in the interstitium of the ossified tissue co-expressed MSC markers CD73, CD90, CD105, and PDGFRα, suggesting that ectopically appearing chondrocytes were derived from MSCs. These results indicated that MSCs are deeply involved in the pathogenesis of endochondral ossification in OPLL.