Activation of β-catenin in Col2-expressing chondrocytes leads to osteoarthritis-like defects in hip joint.

Although osteoarthritis (OA) in the hip joint is a common and debilitating degenerative disease, the precise molecular mechanisms underlying its pathological process remains unclear. This study sets out to investigate whether β-catenin plays a critical role in hip OA pathogenesis. Here, we showed overexpressed β-catenin protein in human OA cartilage tissues. Then, we analyzed β-cat(ex3)Col2ER mice, in which β-catenin gene was conditionally activated in femoral head chondrocytes. At 2 months of age, β-cat(ex3)Col2ER mice already showed a phenotype of severe cartilage degeneration in the femoral head. More changes observed in β-cat(ex3)Col2ER mice with age included subchondral sclerosis and osteophyte formation along joint margins, resembling a hip OA phenotype in humans. In addition, cartilage degradation and chondrocyte apoptosis as the results of β-catenin activation possibly contributed to this hip OA-like phenotype. Overall our findings provide direct evidence about the importance of β-catenin in hip OA pathogenesis.