RESUMO
BACKGROUND:Osteoarthritis animal models induced by papain are commonly used for studying osteoarthritis. OBJECTIVE:To observe the morphology of articular cartilage surface during early osteoarthritis process in rats induced by papain and L-cysteine under scanning electron microscope. METHODS:The right knees of Sprague-Dawley rats were given 0.15 mL mixed solution of 2%papain and 0.03 mol/L L-cysteine in the ratio of 2:1. The left knees were given injections of 0.15 mL 0.9%NaCl, as the control group. Another two rats (four knees) maintained untreated, as the normal control group. Al the rats were observed with scanning electron microscope at 2, 4, 6 weeks after injection, to explore the surface morphology of medial condyle of femur. RESULTS AND CONCLUSION:The condyles of normal and control groups revealed numerous shal ow pits on the surface of articular cartilage. At 2 weeks after injection, the surfaces of condyles were unsmooth, presenting the shrinkage and distortion. The thinner articular cartilage and local tiny cracks were seen at 4 weeks. The deep and great cracks and cartilage defect were observed on the surface of cartilage at 6 weeks. The time of 4-6 weeks is a reference point for establishing early osteoarthritis model in rats through injections of 2%papain and 0.03 mol/L L-cysteine.