[Diacetylrhein on a postcontusion model of experimental osteoarthritis in the rabbit].

The "chondroprotective" activity of a drug must be tested not only in vitro but also in vivo. Because this would require several years in humans, animal models of osteoarthritis are used. A closed contusion of the patella caused by the impact of a 1-kg weight dropped from a height of one meter results in osteoarthritis. Twenty-three adult New Zealand rabbits were sacrificed 49 days after the contusion. Cartilages of both condyles and the patella were studied on 6-mu hematoxylin-eosin-stained serial sections. The morphologic osteoarthritis score (sum of gross and microscopic scores) was determined. Mean score was the mean value of scores for both condyles and the patella, whereas total score was the sum of scores at the three sites. The 23 rabbits were divided into four groups: controls (n = 6), controls + diacerhein (n = 5), contusion (n = 6), and contusion + diacerhein (n = 6). Diacetylrhein was given orally (3.5 mg/kg/d) throughout the 49-day interval between contusion and sacrifice. Mean and total scores showed no significant differences between the control, diacerhein, and diacerhein + contusion groups. Scores were significantly lower in the control group as compared with the contusion group (p < 0.03) and in the diacerhein + contusion group as compared with the contusion group (p < 0.05). Diacetylrhein given in as prophylactic treatment under the experimental conditions used prevented contusion-induced cartilage destruction and exhibited a "chondro-protective" effect.