TET1 may contribute to hypoxia-induced epithelial to mesenchymal transition of endometrial epithelial cells in endometriosis

Jingni Wu; Xidie Li; Hongyan Huang; Xiaomeng Xia; Mengmeng Zhang; Xiaoling Fang

doi:10.7717/peerj.9950

TET1 may contribute to hypoxia-induced epithelial to mesenchymal transition of endometrial epithelial cells in endometriosis

PeerJ. 2020 Sep 15:8:e9950. doi: 10.7717/peerj.9950. eCollection 2020.

Authors

Jingni Wu¹, Xidie Li¹, Hongyan Huang¹, Xiaomeng Xia¹, Mengmeng Zhang¹, Xiaoling Fang¹

Affiliation

¹ Department of Obstetrics and Gynecology, The Second Xiangya Hospital, Central South University, Changsha, Hunan, China.

Abstract

Background: Endometriosis (EMs) is a non-malignant gynecological disease, whose pathogenesis remains to be clarified. Recent studies have found that hypoxia induces epithelial-mesenchymal transition (EMT) as well as epigenetic modification in EMs. However, the relationship between EMT and demethylation modification under hypoxia status in EMs remains unknown.

Methods: The expression of N-cadherin, E-cadherin and TET1 in normal endometria, eutopic endometria and ovarian endometriomas was assessed by immunohistochemistry and immunofluorescence double staining. 5-hmC was detected by fluorescence-based ELISA kit using a specific 5-hmC antibody. Overexpression and inhibition of TET1 or hypoxia-inducible factor 2α (HIF-2α) were performed by plasmid and siRNA transfection. The expression of HIF-2α, TET1 and EMT markers in Ishikawa (ISK) cells (widely used as endometrial epithelial cells) was evaluated by western blotting. The interaction of HIF-2α and TET1 was analyzed by chromatin immunoprecipitation.

Results: Demethylation enzyme TET1 (ten-eleven translocation1) was elevated in glandular epithelium of ovarian endometrioma, along with the activation of EMT (increased expression of N-cadherin, and decreased expression of E-cadherin) and global increase of epigenetic modification marker 5-hmC(5-hydroxymethylcytosine). Besides, endometriosis lesions had more TET1 and N-cadherin co-localized cells. Further study showed that ISK cells exhibited enhanced EMT, and increased expression of TET1 and HIF-2α under hypoxic condition. Hypoxia-induced EMT was partly regulated by TET1 and HIF-2α. HIF-2α inhibition mitigated TET1 expression changes provoked by hypoxia.

Conclusions: Hypoxia induces the expression of TET1 regulated by HIF-2α, thus may promote EMT in endometriosis.

Keywords: EMT; Endometriosis; HIF-2α; TET1.

Grants and funding

This work was supported by the National Natural Science Foundation of China (grant number 81671437, 81771558), the Natural Science Foundation of Hunan Province (grant number 2020JJ4814), and the Postgraduate Independent Exploration and Innovation Project of Central South University, China (grant number 2020zzts285). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.