Expression of Klf5 and MMP9 is associated with cartilage degradation and vascular invasion in human osteoarthritis

The present study was designed to investigate the association between the expression of Kruppel‐like factor (KLF) 5, and matrix metalloproteinase (MMP)‐9 and vascular invasion in human knee osteoarthritis (OA). Each tibiofemoral joint sample was divided into two groups, no change (NC, n=17) and severe change (SC, n=29) that were severe damages in cartilages and subchondral bones at medial tibial plateaux. The expression of the proteins was detected by immunohistochemistry and RT‐PCR, respectively. Neurovascular invasion was evaluated by protein gene product (PGP) 9.5 and CD34 positive staining and scanning electron microscopy, respectively. Vascular invasions were observed in both NC and SC sections. In SC sections, 16/29 (55.2%) sections displayed vessels entering the articular cartilage, which was more than that in NC group (2/17, 11.7%, P<0.05), with an increased collagen degradation. The number of vascular invasion was significantly different between SC and NC (P<0.05). The expression of MMP‐9 in SC cartilages increased with increasing of KLF5, and the severity of neurovascular invasion was positively correlated with the two protein expression that was significantly different between SC and NC samples (P<0.05). Taken together, KLF5 and MMP‐9 expression may be involved in neurovascular invasion via cartilage degradation, contributing to OA pain.