Effect of hyaluronan on chondrocyte apoptosis and nitric oxide production in experimentally induced osteoarthritis

Objective. Nitric oxide (NO) plays an important role in cartilage degenerat ion, and NO donors induce chondrocyte apoptosis. This study evaluated the e ffect of intraarticular injections of hyaluronan (HA) on chondrocyte apopto sis and NO production using an experimental osteoarthritis (OA) model. Methods. Thirty-six New Zealand white rabbits underwent unilateral anterior cruciate ligament transection (ACLT), and were divided into 3 groups. Four weeks after ACLT, the HA group started intraarticular HA injections once a week for 5 weeks; the vehicle group started to receive the carrier of HA; the no injection group received no treatment. All ACLT knees were harvested at Week 9 and evaluated for OA severity. Culture supernatants of the carti lage were analyzed for nitrite concentration. Cartilage sections were analy zed by TUNEL for apoptosis rand by immunohistochemistry for nitrotyrosine. Results. OA in the HA group was less severe than the other 2 groups. The nu mber of apoptotic chondrocytes was significantly lower in the HA group. HA injection did not influence NO production in cartilage. Conclusion. HA protects against chondrocyte apoptosis during the developmen t of OA, while it may not have definite effects on NO production in the joi nts. These inhibitory effects of HA on chondrocyte apoptosis may play a rol e in its mechanism of action in chondroprotection.