Qiang Yan

Background:Endometriosis is a chronic, estrogen-dependent, immune-modulated disorder with unclear causal contributions from circulating sex hormones. Understanding whether hormone levels directly influence risk may guide prevention and targeted therapies. To evaluate the causal effects of circulating sex hormones—estradiol (E2), total testosterone (TT), free testosterone (FT), estrone (E1), and sex hormone–binding globulin (SHBG)—on the risk of endometriosis using a two-sample Mendelian randomization (MR) framework, with clinical contextualization from a tertiary-care cohort.Methods:A two-sample MR study was performed using large, sex-stratified, European-ancestry genome-wide association studies (GWAS) summary statistics for hormones and endometriosis harmonized via MR-Base/OpenGWAS. Independent genome-wide significant Single Nucleotide Polymorphisms (SNPs) served as instruments, with multiple sensitivity and pleiotropy-robust estimators (MR-Egger, weighted median/mode, MR-PRESSO, radial MR). Multivariable MR accounted for SHBG and body mass index (BMI). A local cohort of 50 reproductive-age women with surgically or histologically confirmed endometriosis was analyzed descriptively (IBM SPSS Statistics 26.0) for phenotype benchmarking.Results:In primary analyses, higher genetically proxied estradiol (E2) increased endometriosis risk (IVW OR 1.18), while total testosterone (TT) and free/bioavailable testosterone (FT) were protective. SHBG showed a modest association that attenuated in multivariable models. Estrone (E1), evaluated as an exploratory exposure, was not statistically significant. E1 was not significant (OR 1.10, p = 0.100). Sensitivity analyses showed no major directional pleiotropy; >98% of SNPs satisfied Steiger directionality. Reverse MR found no evidence for endometriosis affecting hormone levels. The tertiary-care cohort reflected the typical clinical spectrum, reinforcing generalizability.Conclusions:This MR analysis supports a causal role for higher estradiol in increasing, and higher testosterone in reducing, endometriosis risk, with SHBG acting indirectly via steroid modulation. Findings were robust across sensitivity checks and integrated with clinical and mechanistic evidence, suggesting endocrine-targeted strategies may have preventive or risk-stratification potential.

Impaired decidualization has been considered a major cause of infertility in adenomyosis. However, the mechanism remains poorly understood. Recent studies suggest that micro RNAs (miR) play a crucial role in embryo implantation. The aim of the present study was to identify the role of miR-21 in human endometrial stromal cell (hESC) decidualization in vitro. To explore the roles of miR-21 in decidualization, we detected the expression of miR-21 in the endometrium of fertile control and adenomyosis patients, and analyzed the effects of miR-21 on the biological behaviors of hESC decidualization. The results demonstrated that miR-21 was downregulated in the endometrium of adenomyosis patients compared with the control endometrium. miR-21 effectively promoted the expression of the 8Br-cAMP plus MPA-induced hESC decidualization marker genes PRL and IGFBP-1 and morphological transformation through the modulation of KLF12 and NR4A1 expression; conversely, inhibition of miR-21 expression compromised hESC decidualization in vitro. In addition, Luciferase reporter, Western blotting and quantitative real-time PCR (qRT-PCR) assays confirmed that miR-21 interacted with the 3′ untranslated region of the transcription factor KLF12 and downregulated KLF12 at the transcriptional and translational levels. KLF12 overexpression abolished miR-21-enhanced 8Br-cAMP plus MPA-induced decidualization. Taken together, these results illustrate that miR-21 promotes endometrial decidualization by inhibiting KLF12, and miR-21 overexpression reverses the poor decidual response of hESCs in patients with adenomyosis in vitro.

Decidualization is a prerequisite for successful implantation and the establishment of pregnancy. A critical role of impaired decidualization in subfertility has been established. In human endometrial stromal cells (hESCs), Krüppel-like factor 12 (KLF12) and Nur77 are novel regulators of decidualization. We investigated whether KLF12 impaired the decidualization of hESCs in recurrent implantation failure (RIF) patients. Endometrial tissues and hESCs were collected from RIF patients (n = 34) and fertile controls (n = 30) for in vitro analysis. Primary hESCs isolated from RIF endometrial tissues were used to evaluate the biological functions of KLF12 and Nur77. In addition, their molecular mechanisms were investigated by adenovirus-mediated overexpression. Gene expression regulation was examined by real-time-quantitative PCR (qRT-PCR), immunostaining and luciferase reporter assay. Further, blastocyst-like spheroid (BLS) and blastocyst implantation models were performed to examine the roles of KLF12 and Nur77 during embryo expansion on hESCs. hESCs from the RIF patients showed a poor decidual response, mainly characterized by decreased decidual prolactin (dPRL) secretion, impaired transformation and limited BLS expansion. In addition, KLF12 expression was increased in endometrial tissues from the RIF patients compared with those from the fertile controls, especially in stromal compartments. The opposite results were observed for Nur77 expression in these tissues. KLF12 repressed hESC decidualization by decreasing Nur77 expression. Mechanistically, KLF12 bound to a conserved site in the Nur77 promoter region. Nur77 overexpression significantly reversed the KLF12-mediated repression of dPRL expression, decidual transformation and BLS/blastocyst expansion. KLF12 impairs endometrial decidualization by transcriptionally repressing Nur77, and Nur77 overexpression reverses the poor decidual response of hESCs in RIF patients.