Clinicopathological correlation of Krüppel-like factor 5 and matrix metalloproteinase-9 expression and cartilage degeneration in human osteoarthritis

The present study was designed to investigate the clinicopathological correlation between the expression of KLF5 and MMP-9, which are associated with extracellular matrix degradation and cartilage degeneration in human knee osteoarthritis (OA). Tibiofemoral joint samples from 20 patients with OA, treated with surgery alone, were divided into two groups: 0 = no change (NC, n = 17), and severe changes with a higher mean score (≥3) (SC, n = 29). The latter group contains samples with severe damages in cartilages and subchondral bones at medial tibial plateaux. The expression of the proteins was detected by immunofluorescence and quantitative RT-PCR, respectively. Neurovascular invasion was evaluated by protein gene product (PGP) 9.5 and CD34-positive staining and scanning electron microscopy, respectively. Safranin O staining showed that the sections from the SC group had increased cartilage degeneration. The number of vascular invasions in the SC group (16/29, 55.2%) was higher than that in NC controls (2/17, 11.7%, P < 0.05). The expression of KLF5 and MMP-9 increased, and was co-localized in the same cells of SC cartilages. The severity of cartilage degeneration and vascular invasion was associated with upregulation of the two protein expressions and was significantly different between SC and NC samples (P < 0.05). Taken together, the expression of KLF5 and MMP-9 may be involved in cartilage degeneration, contributing to human OA.