Changes in the femoral trochlear induced with estradiol exposure, an experimental study on rats

Abstract

Abstract Background: It is well known that estrogen is closely related to bone and joint tissue. Findings indicate that estradiol, injected during pregnancy, passes through the placental barrier and reaches the fetuses in utero where it exerts its action. Since trochlea appears well established in the prenatal period, however, whether trochlear dysplasia is related to estradiol exposure has not been confirmed, and the pathological process of estradiol exposure-induced trochlear dysplasia remains unclear. This study aimed to establish an estradiol exposure animal model in fetuses and to analyze the morphology of the femoral trochlear in neonatal rats. Methods: 30 pregnant Wistar rats provided by the local Animal Center were assigned randomly into 3 groups, a high dose estradiol injection group, a low dose estradiol injection group and a blank control group. The pregnant rats in high dose group were intramuscular injected with estradiol benzoate, 200 μg/kg body weight, intramuscularly injected until the neonatal rats were born, and low dose group with 100 μg/kg body weight. Gross, cross-sectional observation and histological staining measurement of the rat offspring were conducted to evaluate the morphological changes of the femoral trochlea. Results: The incidence of trochlear dysplasia increased with the concentration of estradiol injection. Neonatal rats in the high dose group had the high prevalence of trochlea dysplasia (53 of 60), followed by low dose of trochlea dysplasia (49 of 60). Gross and cross-sectional observation showed a shallower trochlea groove in two groups with estradiol injection. Histological staining measurement indicated that the trochlear sulcus angle and trochlear sulcus depth were significantly different between the two groups with estradiol injection and the blank control group at 0,5 and 10 days after birth. Conclusion: In this study, estradiol exposure in fetuses had an adverse effect on intrauterine development and could induce trochlear dysplasia in rat offspring. In addition, this study also showed that the higher concentration of estradiol injection in pregnant rats, the more incidence of trochlear dysplasia in rat offspring.