Thyroid Hormone Profile In Offspring After High Estrogen Exposure During Early Pregnancy And Underlying Epigenetic Mechanisms

Part â…  Altered thyroid hormone profile in offspring after exposure to high estradiol environment during the first trimester of pregnancy:a cross-sectional studyObjective:To investigate whether the high E2 maternal environment in the first trimester increases the risk of thyroid dysfunction in children born following IVF-ET.Materials and methods:A cross-sectional survey design was used to carry out face-to-face interviews with consecutive children attending the hospital. A total of 949 singletons born after fresh embryo transfer (ET) (n= 357), frozen ET (n= 212),and natural conception (NC) (n= 380), aged 3 to 10 years old, were included. All children were thoroughly examined. Meanwhile, another 183 newborns, including 55 fresh ET, 48 frozen ET, and 80 NC were studied. Levels of serum T3, FT3, T4, FT4, and TSH and levels of maternal E2 at different stages of the first trimester were examined.Result(s):The mean serum E2 levels of women undergoing fresh ET during the first trimester of pregnancy were significantly higher than those of the women undergoing frozen ET or following NC. The thyroid hormone profile, especially the levels of T4, FT4, and TSH, were significantly increased in 3-to 10-year-old children conceived by fresh ET compared to NC. The same tendency was confirmed in newborns. However, levels of T4 and TSH in the frozen ET group were nearer to that of the NC group. Furthermore, levels of T4 and FT4 in fresh ET were positively correlated with maternal serum levels of E2 during early pregnancy.Conclusion(s):The maternal high E2 environment in the first trimester is correlated with increased risk of thyroid dysfunction. Frozen ET could reduce risks of thyroid damage in children conceived by IVF. Further studies are needed to confirm these findings and to better determine the underlying molecular mechanisms and clinical significance.Part â…¡ Establishment of intrauterine hyperestrogenemia mouse models and methylation status of pupsObjective:To evaluate the thyroid function of mouse offspring after high E2 exposure and to explore the underlying mechanism.Materials and methods:We established a high E2 mouse model of early pregnancy, and detected thyroid hormones of their offspring as well as expression of Tg, Nis, Tpo, Pax8, and Titf1 in thyroids of pups. Additionally, the CpG islands methylation status of Pax8 and the genes involved in methylation in thyroids of offspring were analyzed.Result(s):The birth weight and live birth rate were significantly decreased, while T4 and FT4 levels of offspring were obviously increased in the high E2 group, especially in female pups. In both 3-and 8-week-old pups of the high E2 group, the expression of Pax8 was up-regulated in thyroid glands, accompanied by the abnormal CpG islands methylation status in the promoter region, which may be responsible for the increased Tpo expression and abnormal secretion of thyroid hormones. Furthermore, altered gene expression of Dnmt3a and Mbd1 was found in thyroids of 3-or 8-week-old pups, indicating that the changes of methylation-related enzymes contributed to epigenetic alteration in thyroid glands and ultimately transformed the thyroid hormone profile in offspring. Besides, the disturbance of thyroid function in females was more severe than that in males, indicating that the effects were related to gender.Conclusion(s):Maternal high E2 exposure disturbs the thyroid function of offspring, especially in females, which was caused by the dysregulation and abnormal DNA methylation of Pax8.Part â…¢ Long non-coding RNA is involved in epigenetic regulation of thyroid cells exposed to high estrogenObjective:To explore the long non-coding RNA (lncRNA) expression profiles on the thyroid cells after exposure to high estrogen. The lncRNAs associated with thyroid function were screened, so as to verify its biological function, to explore its underlying molecular mechanisms, and to predict its role in the altered thyroid hormone profile in offspring exposed to high estrogen in uterus.Materials and Methods:Both high estradiol treated and normal thyroid cells were collected, and microarray analysis was performed to detect the lncRNAs expression. Six lncRNAs significantly differentially expressed between two groups were validated using real-time quantitative PCR. Bioinformatics analysis was carried out on the results of the chip to screen target lncRNAs, and then using real-time quantitative PCR method to verify the expression of these lncRNAs in Nthy ori3-1 with estrogen treatment. Mdm2 and cell proliferation were detected after using specific RNA interference to reduce the expression of lnc DSG1.Results:There were 188 lncRNAs differentially expressed in thyroid cells after exposure to high estradiol environment, including 111 lncRNAs up-regulated and 78 lncRNAs down-regulated. In accordance with the results of the chip, we verified 6 lncRNAs significantly differentially expressed in nthy ori3-1 cells. CNC network diagram indicated that lnc DSG1 might affect thyroid hormone signaling pathways. RIP experiments indicated that lnc DSG1 binded to Mdm2. Invitro experiments showed that estrogen could up-regulate the expression of lnc DSG1 and Mdm2, and interfering with lncDSG1 could down-regulate the expression of Mdm2 and inhibit cell proliferation.Conclusion:Exposure to high estrogen environment changes the expression of lncRNAs spectrum in thyroid cells. Furthermore, estrogen increases the expression of lnc DSG1 and Mdm2 in vitro. Interfering with lnc DSG1 can down-regulate the expression of Mdm2 and inhibit cell proliferation. LncRNA DSG1 may be one of the crucial epigenetic regulation mechanisms involved in high estradiol exposure induced thyroid dysfunction.