HISTOMORPHOLOGICAL AND IMMUNOHISTOCHEMICAL EVALUATION OF JOINT CHANGES IN A MODEL OF OSTEOARTHRITIS INDUCED BY LATERAL MENISCECTOMY IN SHEEP

Objective, To evaluate the histomorphological and immunohistochemical changes induced in cartilages of ovine stifle (knee) joints 6 months a fter unilateral lateral meniscectomy. Methods. Osteochondral sections were obtained from 8 distinct regions of knee joints of 6 adult Merino wethers that 6 months earlier had undergone lateral meniscectomy. Joi nt regions of 6 age matched sheep housed under identical conditions we re used for controls. Serial sections were stained with toluidine blue or immunolocalized with monoclonal antibodies (Mab) 3B3(-), 7D4, and 5B10, which recognize epitopes on proteoglycans. Results, In control j oints the cartilage from the region of the tibial plateau not protecte d by the meniscus had significantly (p < 0.005) more structural abnorm alities than other joint regions. After meniscectomy, only cartilages in the lateral femorotibial compartment showed histomorphological chan ges consistent with osteoarthritis (OA). The nature and severity of th e lesions differed between the topographical regions within the joint, The most severe were found on the lateral femoral condyles and tibial plateaus. Reactivity with Mab 3B3(-), 7D4, and 5B10 was increased onl y in the lateral compartment cartilages, and was stronger in mild rath er than moderate OA, Conclusion. Six month lateral meniscectomy in she ep produces histomorphological and immunohistochemical cartilage chang es analogous to those described for early human OA and in other animal models. The severity and type of lesions obtained were dependent on t he topographical joint location, but were most evident in cartilages f rom the lateral compartment.