Combination of hyperlipidemia and 17β‐Estradiol induces TMJOA‐like pathological changes in rats

Abstract Objective We explored whether hyperlipidemia or combination of hyperlipidemia and E2 could induce TMJOA. Materials and Methods Four groups of female rats were treated with normal diet, normal diet with E2, high‐fat diet, and high‐fat diet with E2 (HFD/E2), respectively, to induce TMJOA till 8 weeks. Another three groups were then used for COX2 inhibitor celecoxib to block the induction of TMJOA. Primary condylar chondrocytes were treated with combination of E2, ox‐LDL, and corresponding inhibitors for evaluating expressions of related molecules. Results Condylar cartilage proliferation with plenty of chondrocyte apoptosis and increased staining for LOX1, nuclear NF‐κB, IL‐1β, and COX2 at 4 weeks and decreased condylar cartilage and increased subchondral bone density at 8 weeks were observed only in the HFD/E2 group. Celecoxib significantly alleviated the cartilage proliferation and apoptosis in the HFD/E2 group. Serum ox‐LDL increased in both high‐fat diet groups, while serum IL‐1β increased only in the HFD/E2 group. Combination of E2 and ox‐LDL synergistically induced expressions of LOX1, phosphorylated NF‐κB, IL‐1β, and COX2, while LOX1 inhibitor blocked the induction of phosphorylated NF‐κB, and NF‐κB inhibitor the induction of IL‐1β, and IL‐1β inhibitor the induction of COX2. Conclusion Combination of hyperlipidemia and E2‐induced TMJOA‐like pathological changes through LOX1/NF‐κB/IL‐1β/COX2‐signaling pathway.