Ambivalent properties of hyaluronate and hylan during post-traumatic OA in the rat knee.

Aim: To determine whether viscosupplementation with intra-articular (i.a.) low- or high-molecular-weight hyaluronate (HA) injections influenced both chondral and synovial lesions in rats with surgically-induced OA knee.

Methods: On D0, rats underwent anterior cruciate ligament transection (ACLX) and were divided in 4 groups: sham group, ACLX-saline control group, ACLX-hyaluronate group, ACLX-hylan group. IA injections were performed on D7, D14 and D21. Histological grading of chondral and synovial lesions were performed on D28. Concomitant immunostainings of Caspase3a and Hsp70 were also performed.

Results: Articular damages were significantly reduced in both HAs-treated knee joints. In contrast, a significant increase of histological score of synovial inflammation was noted in both ACLX + HAs groups. Apoptotic events significantly decreased as anti-apoptotic Hsp70 expression increased significantly in both HAs groups.

Conclusion: HAs may exert, independently of its molecular weight, ambivalent properties on articular structures, simultaneously exerting chondroprotective properties and promoting long-term subacute synovitis.