| Objective Idiopathic condylar resorption(ICR) also known as progressive condylar absorption, is rare in clinic, mainly involving the change of the size and shape of the condyle, resuting in the height of unilateral or bilateral mandible ramus reduced, bone absorption, mandibular retraction, Class Ⅱ malocclusion and mirognathia. ICR often occurs in young women and its etiology and pathogenesis is not clear. Related studies about the relationship between estrogen/ estrogen receptors and ICR has found that estrogen receptors exists in both human and animal temporomandibular joints(TMJ). TMJ is the target organ of estrogen. Our previous study demonstrated that oral contraceptives and premature ovarian failure in rats induced lowered serum levels of estrogen, and interfered with the osteoblastic efficency of condylar cartilage, leading to certain condyle degeneration. It is speculated that changes of serum estrogen may effect and induce condylar degeneration and resorption through the ER pathway. This study aims to discuss the influence of change of serum estrogen on the morphology of rat condylar cartilage and the expression of ERα/ ERβand the possible role of change of estrogen in ICR to provid experimental basis and guidance for ICR in clinical treatment and prevention.Methods Forty healthy non-pregnant female 6-week-old SD rats were randomly divided into control group, contraceptive group(intragastric administration with contraceptive), contraceptive + saline(intragastric administration with contraceptive and saline) and contraceptive + estradiol group(intragastric administration with contraceptive and estradiol). Animal models with lowered and raised serum estrogen level were established by gastric gavage with oral contraceptives pills and Estradiol Valerate tablets respectively. The serum levels of estradiol were detected respectively before the experiment, on the twelfth week and sixteenth week. The rats were sacrified after the experiment and the expression of ERα, ERβof condyle was detected by immunohistochemistry and the morphology change of condylar was observed by hematoxylin eosin staining. SPSS11.0 software package was used for statistical data analysis.Results 1.The serum estradiol concentration of the other three was significantly lower than control group on twelveth week(P< 0.05); the serum estradiol concentration of contraceptive + estradiol group was significantly higher than contraceptive + saline group on sixteenth week(P< 0.05). 2. Immunohistochemical results showed that ERα and ERβ are expressed in the condylar cartilage in each group. Compared with control group, the expression of ERα and ERβ of contraceptive group was decreased(P< 0.05) and compared with the contraceptive + saline group, the ERα expression was increased(P< 0.05) while ERβexpression was not increased(P> 0.05) in contraceptive + estradiol group. 3.HE staining showed that compared with control group, retrogression occurred in rat condylar cartilage in contraceptive group and compared with the contraceptive + saline group, the retrogression was repaired to some extent in contraceptive + estradiol group. Conclusions 1.The lowered serum estrogen concentrations decreased the expression of ERα and ERβ, regulated and mediated condylar cartilage degeneration and the subchondral bone pathological remoulding process. 2.The exogenous Estradiol Valerate may raise estrogen level, increase the expression of ER α in rats and slow down the process of condylar cartilage degeneration or repair condylar cartilage to some extent through ER way. |
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