Comprehensive molecular expression profiling of SARS-CoV-associated factors in the endometrium across the menstrual cycle and elevated susceptibility in women with recurrent pregnancy loss.

Objective: To evaluate the dynamic expression profiling alterations of SARS-CoV-2-associated molecules within the fertile human endometrium throughout the menstrual cycle. Furthermore, to explore the inherent vulnerability of the endometrium to SARS-CoV-2 infection among women experiencing recurrent pregnancy failure, including both recurrent implantation failures (RIF) and recurrent pregnancy losses (RPL). Method: The present study employed multiple datasets to investigate the expression patterns of SARS-CoV-2-associated genes. Firstly, a single-cell RNA-sequencing dataset comprising endometrial samples from 19 healthy women across the menstrual cycle was utilized. Additionally, two microarray datasets encompassing 24 women with RIF, and 24 women with RPL during the peri-implantation phase were included. To complement these analyses, immunohistochemical (IHC) staining was performed on endometrial samples collected from 30 women with RIF, 30 women with RPL, and 20 fertile controls recruited specifically during the implantation period. Results: The investigation revealed a moderate expression percentage of CTSL (22%), TMPRSS4 (15%), FURIN (16%) and MX1 (9%) in endometrium. Conversely, the expression percentages of ACE2 (1%) and TMPRSS2 (4%) were relatively low. Notably, the expression of BSG exhibited an increment towards the window of implantation, reaching its peak during the middle secretary phase. Furthermore, a significant reduction (p < 0.05) in TMPRSS2 expression was observed in the RIF group compared to the control group. While the expression of BSG was significantly increased (p < 0.05) in the RPL group, findings that were corroborated by the IHC staining results. Conclusion: The findings of this study indicate a noteworthy upregulation of BSG expression in the endometrium of women with RPL. These results suggest an augmented susceptibility of endometrium to SARS-CoV-2 infection, potentially contributing to unfavorable pregnancy outcomes.

Association of angiotensin II and receptors in peri-implantation endometrium with microvessel density and pregnancy outcomes of women with recurrent implantation failure after embryo transfer.

Purpose: Investigate whether local angiotensin II (AngII) and its AngII type 1 and 2 receptors (AT1R, AT2R) in the endometrium are different and correlate with microvessel density in women with reproductive failure and pregnancy outcomes. Methods: Endometrium during the window of implantation from 40 women with recurrent miscarriage (RM) and 40 with recurrent implantation failure (RIF) were compared with 27 fertile women. Peri-implantation endometrium from 54 women prior to euploid embryo transfer were collected and compared in women with successful pregnancy and unsuccessful pregnancy. Results: Compared with fertile women, expression of AT2R was significantly lower, while AT1R/AT2R expression ratio was significantly higher in the stroma of the RIF group. Endometrium arteriole MVD was significantly lower and negatively correlated with the AT1R/AT2R expression ratio in the stroma of the RIF group. No significant differences and correlations were found in the RM group. Compared with the pregnancy group, expression of AT1R and AT2R were significantly lower in all compartments, but only AT1R/AT2R ratio was significantly higher in the stroma of the non-pregnancy group. Similarly, endometrium arteriole MVD was also significantly lower and negatively correlated with the AT1R/AT2R ratio in the stroma of the non-pregnancy group. Conclusion: Local renin-angiotensin system is dysregulated in peri-implantation endometrium and associated with abnormal angiogenesis in RIF and poor implantation outcome after embryo transfer.

The role of the renin-angiotensin system in regulating endometrial neovascularization during the peri-implantation period: literature review and preliminary data.

BACKGROUND: Implantation is initiated when the blastocyst attaches to the endometrium during the peri-implantation period, and appropriate neovascularization is a prerequisite for the success of the subsequent process. The role of the renin-angiotensin system (RAS) in regulation of blood pressure and hydro-electrolyte balance has long been recognized, while its role in the peri-implantation endometrium remains unclear. This manuscript discusses endometrial RAS and its possible pathways in regulating endometrial angiogenesis and its influence on subsequent pregnancy outcomes. METHODS: A comprehensive search of electronic databases was carried out to identify relevant published articles, and a literature review was then performed. Using immunohistochemistry, we also performed a pilot study to examine expression of angiotensin II receptors, including angiotensin II type 1 (AT1) receptor (AT1-R) and angiotensin II type 2 (AT2) receptor (AT2-R) in the human endometrium around the time of implantation. RESULTS: The results of the pilot study showed expression of AT1-R and AT2-R in all endometrial compartments (luminal epithelium, glandular epithelium, stroma cells, and blood vessels), and altered expression was witnessed in women with recurrent miscarriage when compared with fertile control women from our preliminary result. CONCLUSION: Altered vasculature of the endometrium in the peri-implantation period is detrimental to implantation and may lead to recurrent miscarriage. Being an angiogenic mediators, endometrial RAS may play a role around the time of embryo implantation, affecting subsequent pregnancy outcomes.

Association between chronic endometritis and uterine natural killer cell density in women with recurrent miscarriage: clinical implications.

AIM: This aim of this study was to determine the association between uterine natural killer (uNK) cell density and chronic endometritis (CE). METHODS: Endometrial biopsies from 135 women with recurrent miscarriage were obtained precisely 7 days after luteinizing hormone surge in natural cycles. Endometrial sections were immunostained for CD56 for uNK cells and CD138 for plasma cells, respectively. Uterine NK cell counting was performed according to a standardized protocol and results were expressed as percentage of CD56+ cells/ total stromal cells. High uNK cell density was defined as >4.5% and CE was diagnosed when the plasma cell density > 5.15 cells/ 10 mm2 . RESULTS: The uNK cells density in women with CE (median, 5.1%; range, 3.4-8.8%) was significantly (P < 0.05) higher than that of those without CE (median, 3.8%; range, 1.2%-7.3%). The prevalence of high uNK cell density in women with CE (11/29, 37.9%) was significantly (P < 0.05) higher than that of women without CE (8/106, 7.5%). CONCLUSION: To conclude, there was a significant association between high uNK cell density and CE. In women with high uNK cell density, plasma cell should be examined to determine if the underlying cause is associated with CE.

Aberrant Overexpression of RNA-Editing Enzyme ADAR1 Promotes the Progression of Endometriosis.

Considerable efforts have been invested to elucidate the potential mechanisms involved in the physiopathology of endometriosis. However, to date, prior research has not been conclusive. This research has examined one particular mechanism, i.e., the effect of ADAR1 on endometriosis lesions. Eutopic endometrium was collected from women with (n = 25) and without endometriosis (n = 25), respectively. The expression of ADAR1 mRNA was measured based on quantitative real-time polymerase chain reactions (RT-qPCR). Both Western blot and immunohistochemistry were performed to establish ADAR1 protein expression levels. The results indicated that ADAR1 mRNA and proteins were significantly greater in the eutopic endometrium of the women with endometriosis, compared to the women without (P < 0.05). The Cell Counting Kit-8 (CCK-8) and EdU method were conducted to examine the effect of ADAR1 on cell viability and proliferation in eutopic endometriosis cells. A transwell assay was also used to detect the role of ADAR1 in the invasion of endometrial cells. The results obtained showed that ADAR1 promoted endometrial cell viability, proliferation, and invasion (P < 0.05). This informed our conclusion that the ADAR1 gene is upregulated in endometriosis, potentially paying a pivotal role in the physiopathology of endometriosis.

RNA Editing, ADAR1, and the Innate Immune Response.

RNA editing, particularly A-to-I RNA editing, has been shown to play an essential role in mammalian embryonic development and tissue homeostasis, and is implicated in the pathogenesis of many diseases including skin pigmentation disorder, autoimmune and inflammatory tissue injury, neuron degeneration, and various malignancies. A-to-I RNA editing is carried out by a small group of enzymes, the adenosine deaminase acting on RNAs (ADARs). Only three members of this protein family, ADAR1-3, exist in mammalian cells. ADAR3 is a catalytically null enzyme and the most significant function of ADAR2 was found to be in editing on the neuron receptor GluR-B mRNA. ADAR1, however, has been shown to play more significant roles in biological and pathological conditions. Although there remains much that is not known about how ADAR1 regulates cellular function, recent findings point to regulation of the innate immune response as an important function of ADAR1. Without appropriate RNA editing by ADAR1, endogenous RNA transcripts stimulate cytosolic RNA sensing receptors and therefore activate the IFN-inducing signaling pathways. Overactivation of innate immune pathways can lead to tissue injury and dysfunction. However, obvious gaps in our knowledge persist as to how ADAR1 regulates innate immune responses through RNA editing. Here, we review critical findings from ADAR1 mechanistic studies focusing on its regulatory function in innate immune responses and identify some of the important unanswered questions in the field.