Effect of intraarticular hyaluronan injection in experimental canine osteoarthritis

Objective. To determine if intraarticular injections of hyaluronan (HA) protect against the early stages of joint damage in a canine model of osteoarthritis (OA), Methods. OA was induced in adult mongrel dogs by transection of the anterior cruciate ligament of the left knee. One group of dogs (n = 7) was treated with 5 weekly injections of HA (MW 1,500,000) into the operated knee beginning 1 day after ligament transection. The control group (n = 6) was injected with saline on the same schedule. Twelve weeks after surgery, all dogs were killed, the severity of pathologic changes of OA was graded, and composition of the cartilage and extent of aggregation of proteoglycans (PGs) synthesized in vitro by cartilage slices were determined. Results. All dogs showed gross morphologic changes typical of OA in the unstable knee. The severity of joint pathology in HA-treated dogs was comparable with that in the saline-injected controls. In OA cartilage from the saline-treated group, the mean uronic acid concentration was 30-60% greater than that in the contralateral knee. In sharp contrast, the uronic acid concentration in OA cartilage from the HA-treated dogs was 10-30% lower than that in cartilage from the contralateral knee (P = 0.02 and P = 0.03, respectively, for samples from the medial and lateral femoral condyle), The extent of aggregation of PG synthesized in vitro by cartilage from HA-injected animals was similar to that synthesized by cartilage from the saline-injected dogs. Conclusion. In this canine model of OA, the series of intraarticular injections of HA did not alter development of osteophytosis or fibrillation. However, the PG concentration of cartilage in the OA knee was significantly reduced by this treatment, suggesting that HA therapy might adversely affect the biomechanical properties of the cartilage.