Intervention On Cartilage Cell Apoptosis By Intra-articular Injection Of Hyaluronic Acid (HA) After Total Medial Meniscectomy In Rabbits

OBJECTIVE: To investigate the effects of intra-articular injection of HA on cartilage degeneration, and its intervention on cartilage cell apoptosis and protein expression level of iNOS in cartilage cell of OA induced by total medial meniscectomy in rabbits.METHOD: Thirty healthy New Zealand white rabbits were randomly divided into 3 group: Group A (sham operation group, n=6), Group B (HA injection group, n=12) and Group C (OA model group, n=12). Each rabbit was underwent total medial meniscectomy of the right knee except the rabbits in Group A who were only underwent articular capsule discission of both posterior knees. 4 weeks after meniscectomy, the rabbits in Group C were treated with 0.5mL of intra-articular HA injection, once a week for 5 weeks. Animals in the other two groups were treated with normal sodium of the same volume at the same time. The animals were sacrificed two weeks later after last dosage of intra-articular injection(week 11 post-operation), general morphology and histopathological changes of articular cartilage degeneration of medial femoral condyle were evaluated, the apoptosis of cartilage cell was detected with TUNEL method, and the protein level of iNOS in cartilages was examined with western-blot method.RESULTS: (1) Observation of articular cartilage degeneration of medial femoral condyle: The cartilage score was gradually increased from Group A to Group C. The cartilage scored (1.25±0.45) in Group B, while (3.08±0.29) in Group C. The rabbits treated with HA presented a significant reduction in the severity of cartilage degradation. (2) Histological changes of articular cartilage degeneration of medial femoral condyle at light microscopic level: In the Group C, Chondrocytes of superficial zone presented disorder, fibrous degeneration, anabrosis, ulceration, the number of cell obviously decreased. In the middle zone of the cartilage, marked cluster-shaped cell alignment was observed. In the Group B, less disorder, fibrous degeneration and marked cluster-shaped cell alignment were observed.The rate of empty lacuna was (15.91±3.036)%, lower than the those of Group C(22.75±2.70)%,(P<0.01). (3)The analyse of cell apoptosis by TUNEL: The Apoptosis Index(AI) was gradually increased from Group A to Group C, the AI was (13.42±2.57)% in Group B, which was lower than in the Group C (21.83±2.12)%(P<0.01). (4) Protein level of iNOS in cartilages: the number of chondrocytes with immunohistochemistry positive iNOS in the Group A was rare. The rate of iNOS immunohistochemistry positive in Group B was (26.83±6.69)%, while (41.83±4.17)% in Group C. The relative protein expression level of iNOS with western-blot method in cartilage of Group B was (2.69±0.23), while (3.60±0.18) in Group C. Both significant differences of iNOS protein level detected by immunohistochemistry and western-blot method were found between the two groups (P<0.05).CONCLUSION: A total medial meniscectomy is effective on building an OA model. It can completely reflect pathological process of degeneration of OA cartilage resulted from clinical post-meniscectomy surgery. High protein expression level of iNOS is closely linked to OA cartilage abnormal cell apoptosis, both may contribute to OA pathophysiology. Intra-articular injection of HA may decrease cartilage cell apoptosis and down-regulate the protein level of iNOS in cartilage. It has protective and repairing effect on OA cartilage and can significantly reduce the severity of cartilage degradation of rabbit knee after total medial meniscectomy.