SOX trio decrease in the articular cartilage with the advancement of osteoarthritis

SOX trio (SOX-5, SOX-6, and SOX-9) maintain the chondrocytic phenotypes and are vital for chondrogenesis in embryonic development. The purpose of this study is to investigate the change in the expression of SOX trio with the advancement of osteoarthritis (OA) in human articular cartilage (AC). Human OA samples from eight patients were obtained from the distal femoral condyles during total knee arthroplasty. Minimally OA cartilage taken from areas with no obvious surface defects on lateral condyles was compared with advanced OA cartilage obtained from areas within 1 cm of overt lesion located on medial condyle surface. SOX-5, SOX-6, and SOX-9 gene expressions significantly decreased by 41% (p = 0.047), 46% (p = 0.047), and 56% (p = 0.029) in advanced OA area compared with the minimally OA area. There was a significant decrease in aggrecan and type II collagen (COL2A1) gene expressions by 73% (p = 0.029) and 65% (p = 0.029), respectively, in advanced OA area compared with the minimally OA area. From Western blotting and immunohistochemistry, SOX-5, SOX-6, SOX-9, type II collagen, and aggrecan protein expressions also significantly decreased in advanced OA cartilage compared with minimally OA cartilage. DNA methylation study of SOX-9 promoter regions revealed no difference in the epigenetic status between the two areas. It is concluded that SOX trio gene and protein decreased with advancement of OA in human articular cartilage.