Protective Effect of Genistein on Condylar Cartilage through Downregulating NF- κ B Expression in Experimentally Created Osteoarthritis Rats

Abstract

Temporomandibular joint osteoarthrosis (TMJOA) is characterised by chronic inflammatory changes, with subsequent gradual loss of joint cartilage. NF-κB is a crucial transcription factor in the course of inflammatory and immune responses, which are involved in OA pathology activated by proinflammatory cytokines. Genistein is known to have anti-inflammation and modulation of metabolic pathways through repression of the NF-κB signaling pathway in inflammatory disease. But so far, studies on the effects of genistein on TMJOA are very limited. So, the purpose of this study is to investigate the protective effect of genistein against experimentally induced condylar cartilage degradation through downregulating NF-κB expression in created osteoarthritis rats in vivo. Male SD rats were created as temporomandibular joint osteoarthritis models and administered through oral gavage with low and high dosage genistein (30 mg/kg and 180 mg/kg, respectively) daily for 4 weeks. The morphological changes of the condylar cartilage were studied with HE and Masson staining. The expressions of p65 and inflammatory cytokines (IL-1β and TNFα) were detected using immunohistochemistry and real-time PCR. The results showed that experimentally created osteoarthritis reduced the condylar cartilage thickness of rats and increased the gene expression of cytokines (IL-1β and TNFα) and positive cells of p65. Genistein treatment had positive effects on the condylar cartilage renovation, while high dose genistein treatment had more significant effects on the reversing of OA changes and reduction of the expression of p65 and inflammatory cytokines (IL-1β and TNFα). The results indicated that high dose genistein treatment had obvious therapeutic effects on condyle cartilage damages of OA rats. The mechanism may be that genistein suppresses the NF-κB expression activated by inflammatory cytokines.

Figure 1

Chemical structure of genistein.

Figure 2

Treatment effects of GE on condyle cartilage changes in the rat model of TMJOA. (a) Representative histology changes in the condyle cartilage for the OA and GE treatment animals at 4 weeks after injection by HE staining. (b) Demonstration of matrix changes by Masson staining. (c) Quantitation of histology changes by the modified Mankin score system. The histological evaluation included 4 aspects. HE staining for the evaluation of structural integrity, cellularity, and tidemark integrity and Masson-stained sections for the evaluation of the cartilage matrix. Quantitative data are shown as means ± SD. ^∗p < 0.05, ^∗∗p < 0.01, significantly different when compared with NC and OA groups, respectively, n = 6.

Figure 3

Effects of GE on P65 immunoreactivity in TMJOA rats. (a) GE inhibits p65 immunoreactivity in the condylar cartilage of OA rats. (b) Comparative intensity of p65 in various groups. Quantitative data are shown as means ± SD. ^∗p < 0.05, ^∗∗p < 0.01, ^∗∗∗p < 0.001, ^∗∗∗∗p < 0.0001, significantly different when compared with NC and OA groups, respectively, n = 6.

Figure 4

Effects of GE on the gene expression of IL-1β and TNF-α. (a) IL-1β expression in OA animals increased significantly compared with the NC group, while high dose of GE could significantly inhibit IL-1β expression. (b) TNF-α expression increased significantly in OA animals, and high dose of GE treatment could significantly inhibit TNF-α expression. Quantitative data are shown as means ± SD. ^∗p < 0.05, ^∗∗p < 0.01, ^∗∗∗p < 0.001, significantly different when compared with NC and OA groups, respectively, n = 6.