Excess genistein suppresses the synthesis of extracellular matrix in female rat mandibular condylar cartilage

Aim： To investigate the effect of excess genistein on the extracellular matrix in mandibular condylar cartilage of female rats in vivo. Methods： Female SD rats were administered through oral gavage with genistein （50 mg/kg） or placebo daily for 6 weeks. The morpho- logical changes of temporomandibularjoints were studied with HE staining. The expression of cartilage matrix compounds （aggrecan and collagen type Ⅱ）, estrogen-related molecules （aromatase, estradiol, ERα and ERβ） and proliferating cell nuclear antigen （PCNA） in mandibular condylar cartilage was detected using immunohistochemistry, ELISA and real-time PCR. Results： The genistein treatment significantly reduced the thickness of the posterior and middle regions of mandibular condylar cartilage, and decreased the expression of collagen type Ⅱ, aggrecan and PCNA. Compared with the control group, the estradiol content and expression levels of the key estradiol-synthesizing enzyme aromatase in the genistein-treatment group were significantly decreased. The genistein treatment significantly increased the expression of ERβ, but decreased the expression of ERα. Conclusion： Excess genistein suppresses extracellular matrix synthesis and chondrocytes proliferation, resulting in thinner mandibular condylar cartilage. These effects may be detrimental to the ability of mandibular condylar cartilage to adapt to mechanical loads.