The Double Engines and Single Checkpoint Theory of Endometriosis

Peripheral blood leukocyte Telomere length and endometriosis: A Mendelian randomization study

Background

The link between peripheral blood leukocyte telomere length (LTL) and endometriosis has remained uncertain. In order to investigate this association, a two-sample Mendelian randomization(MR) analysis was performed.

Methods

We extracted Single-nucleotide polymorphisms (SNPs) associated with LTL from a published genome-wide association study (GWAS) comprising 472,174 individuals. Data on endometriosis, including its seven subtypes, were sourced from the iue open gwas project. Four methods were employed for MR: Inverse-variance weighted analysis (IVW), Mendelian randomization-Egger regression (MR Egger), weighted-median analysis, and Weighted Mode.

Results

Genetically determined LTL was identified as a factor that can promote the occurrence of endometriosis. With every 1-SD increase in LTL, the risk of endometriosis increased by 26 % (OR = 1.260, 95 % CI = 1.073 to 1.479; P = 0.005). Genetically determined LTL also contributed to endometriosis subtypes: intestine (OR = 3.584, 95 % CI = 1.597 to 8.041; P = 0.002), ovary (OR = 1.308, 95 % CI = 1.033 to 1.655; P = 0.026), rectovaginal septum and vagina (OR = 1.360, 95 % CI = 1.000 to 1.851; P = 0.049). There was no observed causal relationship between LTL and the other four subtypes.

Conclusion

This study, utilizing genetic data, offers evidence that longer LTL may cause increased risks of endometriosis, specifically endometriosis of the intestine, ovary, rectovaginal septum and vagina. These findings not only suggest that LTL may serve as a predictive factor for assessing the prevalence of three endometriosis subtypes but also provide new insights into the study of endometriosis pathogenesis.

Heme induced progesterone-resistant profiling and promotion of endometriosis in vitro and in vivo

Endometriosis is an estrogen-dependent, progesterone-resistant gynecological disease with an unknown pathogenesis. Compared to women without endometriosis, women with endometriosis have a remarkably high heme level in the peritoneal fluid. To further investigate the pathomechanisms of heme in endometriosis, we aimed to identify the dysregulated expression of heme-trafficking proteins, such as PGRMC1/2 that are also receptors that mediate the non-genomic responses to progesterone, and heme-degrading enzymes between ectopic endometrial stromal cells and their normal counterparts. We found that heme could regulate progesterone receptor-related gene expression. Functional human endometrial stromal cell experiments showed that heme promotes cell proliferation and migration in a heme oxygenase-1-independent manner; moreover, blocking oxidative phosphorylation/ATP generation could abolish these effects of heme in vitro, whereas intraperitoneal hemopexin administration could alleviate heme-triggered ectopic lesions in vivo. Therefore, heme likely mediates the induction of progesterone resistance and simultaneously induces endometriosis via the mitochondrial oxidative phosphorylation pathway.

Epigenetic regulation and T-cell responses in endometriosis – something other than autoimmunity

Endometriosis is defined as the presence of endometrial-like glands and stroma located outside the uterine cavity. This common, estrogen dependent, inflammatory condition affects up to 15% of reproductive-aged women and is a well-recognized cause of chronic pelvic pain and infertility. Despite the still unknown etiology of endometriosis, much evidence suggests the participation of epigenetic mechanisms in the disease etiopathogenesis. The main rationale is based on the fact that heritable phenotype changes that do not involve alterations in the DNA sequence are common triggers for hormonal, immunological, and inflammatory disorders, which play a key role in the formation of endometriotic foci. Epigenetic mechanisms regulating T-cell responses, including DNA methylation and posttranslational histone modifications, deserve attention because tissue-resident T lymphocytes work in concert with organ structural cells to generate appropriate immune responses and are functionally shaped by organ-specific environmental conditions. Thus, a failure to precisely regulate immune cell transcription may result in compromised immunological integrity of the organ with an increased risk of inflammatory disorders. The coexistence of endometriosis and autoimmunity is a well-known occurrence. Recent research results indicate regulatory T-cell (Treg) alterations in endometriosis, and an increased number of highly active Tregs and macrophages have been found in peritoneal fluid from women with endometriosis. Elimination of the regulatory function of T cells and an imbalance between T helper cells of the Th1 and Th2 types have been reported in the endometria of women with endometriosis-associated infertility. This review aims to present the state of the art in recognition epigenetic reprogramming of T cells as the key factor in the pathophysiology of endometriosis in the context of T-cell-related autoimmunity. The new potential therapeutic approaches based on epigenetic modulation and/or adoptive transfer of T cells will also be outlined.