Repairing effects of hyaluronate on cartilage impact injury of the knee

Abstract

Objective To investigate the role and mechanism of hyaluronate (HA) repairing impact injury to the knee articular cartilage.Methods We established animal models of impact injury to the knee cartilage on both femoral condyles in a total of 20 rabbits.Immediately and every week after surgery,each left knee joint received an intra-articular injection of 0.5 mL HA (treatment group) while an equal volume of physiological saline was injected into each right knee joint (control group).At 8 weeks after the surgery,type Ⅱ collagen (Col-Ⅱ),glycosaminoglycan (GAG) and tumor necrosis factor-α (TNF-α) levels in the joint fluid were determined using enzyme linked immunosor bent assay.The cellular organization in the zone of cartilage was histologically observed with microscopy.The expression of Col-Ⅱ in femoral condyles was also analyzed by immunohistochemistry.In addition,cells that underwent apoptosis in cartilage and subchondral bone were detected by Tunel assay.Results Few proliferating cells were found in the superficial and intermediate zones of cartilage in the control group at 8 weeks.The number of proliferating cartilage cells was significantly increased in the treatment group.However,the growing cartilage cells did not organize normally and failed to migrate to the injured area.Immunohistochemistry staining showed that the control group had 26 ±8/mm2 of Col-Ⅱ positive cells and 137 ± 26/mm2 of the apoptotic cells in subchondral bone while the treatment group had 183 ±37/mm2 and 14 ±6/mm2 respectively,showing significant differences between groups (P ＜0.05).On the other hand,Col-Ⅱ and GAG levels in the articular fluid were significantly increased and TNF-α level was decreased in the treatment group compared to the control group at 8 weeks (P ＜ 0.05).Conclusions Intra-articular injection of HA may stable the articular cartilage after impact injury by increasing the secretion of Col-Ⅱ and GAG and reducing apoptotic cells.HA treatment may increase the proliferative cells but fail to repair the damaged cartilage probably due to limited capacity of the proliferative cells migrating to the injured area. Key words: Hyaluronic acid; Knee joint; Cartilage injury; Rabbits