Abstract:

BACKGROUND: The effects of testosterone on osteoarthritis (OA) remain controversial. The regulatory effects of testosterone on cartilage metabolism have been rarely reported.
OBJECTIVE: To investigate the effects of testosterone on insulin-like growth factor 1 (IGF-1) expression in cartilage of knee joints with osteoarthritis in male rabbits.
METHODS: Twenty-four male rabbits were established into OA models with Hulth method on the right knee joints and then randomly divided into four groups: non-castrated, castrated, testosterone and model. In the non-castrated group, testis was not removed. In the other three groups, bilateral testes were removed. At the end of the 8th week, rabbits in the non-castrated group and castrated for 8 weeks group were sacrificed for sample harvesting. From the 9th week, physiological dose of testosterone undecanoate (6 mg/kg, once every 2 weeks) was intramuscularly injected into the rabbits from the testosterone group. The castrated for 16 weeks group rabbits were normally raised. At the end of 16th week, rabbits from the testosterone and castrated for 16 weeks groups were sacrificed for sample harvesting.
RESULTS AND CONCLUSION: Gross and histological observation results showed that the lesion degree of knee joint cartilage was more severe in the non-castrated group than in the castrated group, in the testosterone group than in the castrated for 16 weeks group, but there was no obvious difference between castrated for 8 weeks group and castrated for 16 weeks group. Immunohistochemistry results showed that IGF-1 expression was observed in the knee joint cartilage of all rabbits. IGF-1-positive cells were significantly more in the non-castrated group than in the castrated for 8 weeks group (P < 0.05), and they were also significantly more in the testosterone group than in the castrated for 16 weeks group (P < 0.05) , and there was no significant difference between castrated for 8 weeks group and castrated for 16 weeks group (P > 0.05). These findings suggest that testosterone can postpone cartilage degeneration by up-regulating IGF-1 expression in knee joint cartilage of castrated male rabbits.