The effects of intraarticular hyaluronan on cartilage and subchondral bone changes in an ovine model of early osteoarthritis.

OBJECTIVE: Intraarticular (ia) hyaluronan (HA) is reported to provide symptomatic relief in osteoarthritis (OA); however, there is limited information on the effects that this treatment may have on joint articular cartilage or subchondral bone. Our objective was to address this issue using an ovine model of early OA. METHODS: Unilateral medial meniscectomy was performed in 10 adult merino sheep, and 5 unoperated animals were used as controls (UOC). Sixteen weeks postmeniscectomy, joints of 5 operated animals were injected with 2 ml of HA (Artz, 10 mg/ml, M(r) = 0.9 x 10(6) Da) ia while the remaining 5 operated animals received 2 ml of sterile saline ia. This protocol was continued for a further 4 weeks. All animals were sacrificed 5 weeks after the last injection; however 3 weeks before sacrifice they were given tetracycline (20 mg/kg intravenously) weekly. Bone slabs, including articular cartilage, were cut from the medial tibial plateaux and femoral condyles, processed for histology, histomorphometry and fluorescence microscopy to assess articular cartilage and subchondral bone pathology. RESULTS: Meniscectomy and saline treatment increased osteoid volume and surfaces as well as increased the extent of tetracycline labelling of the subchondral bone relative to UOC. The articular cartilage also exhibited a significantly higher modified Mankin's score than UOC. In the HA injected group the aforementioned articular cartilage and subchondral bone changes were modified such that the observed variables were indistinguishable from UOC. CONCLUSION: Using this animal model intraarticular HA appeared to limit the development of articular cartilage and subchondral bone changes characteristic of early OA.