This study aims to investigate the effects of intra-articular botulinum toxin.
Osteoarthritis was induced in both knees of 20 rabbits by transecting the anterior cruciate ligament under intramuscular anesthesia with ketamine and xylazine. Botulinum toxin, at a dose of 2.5 microg/ml (0.6 ml) and physiologic saline solution (0.6 ml) were injected into the right and left knees, respectively, three times with a 1week interval between each injection. The rabbits were sacrificed in the 12th week via high dose anesthesia to remove the distal femora for histological evaluation using the Mankin scale and Safranin O.
The mean cartilage areas calculated in toxin- and saline-injected knees differed significantly (1.097 mm(2) and 0.477 mm(2), respectively; P<0.05). The overall mean Mankin score was significantly lower in toxin-injected knees (3.57 versus11.14; P<0.05). Although there were no significant differences between the two groups with respect to cellular abnormality, matrix staining, and tidemark continuity (P>0.05), the mean scores for the structure of the cartilage were significantly different (0.86 versus 4.43; P<0.05). The integrity of the tidemark was preserved in all the toxin-administered knees, though a notable disruption was observed in four control knees.
Our results suggest that botulinum toxin delays the development of osteoarthritis at early stages through exerting a chondroprotective effect.