Association of synovial expression of growth and differentiation factor 5 (GDF5) with radiographic severity of knee osteoarthritis.

Objectives: The growth and differentiation factor 5 (GDF5) gene plays a significant role in facilitating chondrogenesis, and GDF5 polymorphism is a genetic factor contributing to osteoarthritis (OA). However, the role of GDF5 expression in the synovial membrane remains unclear. The aim of this study was to determine the expression of GDF5 in the synovium in patients with primary knee OA. Materials and methods: Thirty patients scheduled for total knee arthroplasty were enrolled. Patients were grouped according to the Kellgren and Lawrence classification (KL) as grade 3 (15 patients) and grade 4 (15 patients). Synovial tissue was collected, and the GDF5 expression level was determined by real-time PCR. Ten synovial samples were randomly selected to evaluate the degree of synovitis. Results: Baseline characteristics did not differ between the two groups. The expression of GDF5 was significantly higher in the KL4 group (median expression 3.50, range 1.45-13.62) than in the KL3 group (median expression 1.81, range 0-9.46) (p value = 0.02). Histological staining of the synovium indicated low-grade synovitis in both groups. Conclusions: GDF5 expression in the synovium was positively associated with the radiographic severity of knee OA. The difference in GDF5 expression between the KL3 and KL4 groups supports the hypothesis that, through GDF5, the synovium may have important roles in cartilage maintenance and homeostasis in primary knee OA.