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STUDY QUESTION Could epidermal growth factor-like domain 7 (EGFL7) be a factor involved in the preparation of the endometrium for implantation and could its dysregulation be implicated in poor reproductive outcomes? SUMMARY ANSWER EGFL7 is highly expressed in the endothelium and glandular epithelium throughout the menstrual cycle; it is upregulated by stromal cells in secretory phase and appears strongly reduced in endometrial biopsies and isolated stromal cells of women with unexplained recurrent pregnancy loss (uRPL) and recurrent implantation failure (RIF). WHAT IS KNOWN ALREADY The secreted factor EGFL7, originally identified as a gene primarily expressed in endothelial cells, is also expressed by the mouse blastocyst and by mouse and human trophoblast cells. It regulates trophoblast migration and invasion by activating NOTCH1 signaling. NOTCH1 has been demonstrated to play a fundamental role in endometrial receptivity and its dysregulation may be involved in selected pregnancy complications characterized by altered endometrial receptivity, such as uRPL. STUDY DESIGN, SIZE, DURATION This is an exploratory study for which 84 endometrial biopsies were collected from normally fertile women, as well as from women with uRPL and RIF. PARTICIPANTS/MATERIALS, SETTING, METHODS Samples were collected from women in both the proliferative and secretory phases of the menstrual cycle and stratified into three sub-groups according to the patient clinical history: 20 fertile women (8 in proliferative and 12 in secretory phase), 41 women with uRPL (6 in proliferative and 35 in secretory phase), and 27 women with RIF (8 in proliferative and 19 in secretory phase). Immunohistochemistry, real-time PCR, and western blot analyses were performed to study the expression of EGFL7 and NOTCH1, as well as the NOTCH target genes. MAIN RESULTS AND THE ROLE OF CHANCE Analysis of spatial and temporal distribution of EGFL7 in endometrial biopsies from fertile women revealed higher levels of EGFL7 in samples from the secretory phase compared to proliferative phase. The expected expression of EGFL7 in endothelial cells was shown as well as the novel, not previously reported, expression in endometrial glands and stromal cells. EGFL7 was significantly reduced in the endometrium of women with uRPL and RIF in the secretory phases and this was associated with a downregulation of the NOTCH1 signaling pathway. Human recombinant EGFL7 was able to activate the NOTCH1 signaling pathway in endometrial stromal cells (EndSCs) obtained from fertile women but not in cells from uRPL or RIF patients. EndSCs from fertile women and decidualized in vitro for three days showed an upregulation of EGFL7 expression, whereas cells obtained from women with uRPL and RIF and decidualized in vitro did not. LIMITATIONS, REASONS FOR CAUTION This study was conducted with a relatively small number of patient samples. Although results are highly reproducible and consistent, additional observations from multicentric cohorts would strengthen the relevance of the data. Moreover, this is an in vitro study, which might only partially represent the in vivo conditions. WIDER IMPLICATIONS OF THE FINDINGS Our results demonstrate for the first time that EGFL7 is new player involved in decidualization and provide new insights into the pathophysiology of selected implantation defects and early pregnancy complications. Our studies have revealed that alterations in EGFL7 expression and the consequent dysregulation of NOTCH signaling are potential underlying causes of RIF and uRPL. Our results might have therapeutic relevance, as the EGFL7/NOTCH pathway may represent a potential target for medical intervention. STUDY FUNDING/COMPETING INTEREST(S) This study has been supported by the Grant for Fertility Innovation 2017 (Merck KGaA). There are no competing interests to disclose. TRIAL REGISTRATION NUMBER Not applicable. [ABSTRACT FROM AUTHOR]

Unexplained recurrent pregnancy loss is a clinical condition for which there is a lack of evidenced-based therapies. However, in clinical practice, low molecular weight heparin has been widely used as an empirical therapy since immune effects have been hypothesized in modulating immune tolerance at the fetal-maternal interface. Epigenetic mechanisms are involved in establishing of immune tolerance, at fetal-maternal interface. To investigate potential induced immune-epigenetic changes at maternal periphery level, which could reflect the maternal-fetal interface condition, seems to open up new therapeutical strategies, since microRNAs circulating in maternal plasma and in peripheral blood mononuclear cells (PBMCs) may be specific and sensitive immunological markers/predictors of adverse pregnancy outcomes such as RPL. Our aim in this pilot study is to evaluate potential LMWH effects on genes regulating immunological response key mechanisms related to maternal-fetal tolerance processes, by studying circulating miRNAs in maternal peripheral blood. We tested a panel of selected miRNAs on three groups: 18 healthy pregnant women, 20 pregnant women affected by uRPL, 18 pregnant women affected by uRPL, treated with LMWH. The majority of differentially expressed miRNAs (miR 374a-5p, 19a-3p, 30e-5p, 128-3p, 155-5p and 200c-3p) were found to be modulated by LMWH, which seems to have a positive function in RPL patients, by bringing patients' values back to those comparable to the control ones. Selected microRNA panels would appear to be an effective clinical tool for uRPL diagnosis and management. LMWH-modified miRNA expression levels could be targets for immunotherapy, as LMWH would appear to restore physiological miRNA levels, which are dysregulated in uRPL. [ABSTRACT FROM AUTHOR]

Unexplained recurrent pregnancy loss (uRPL) is a clinical condition for which there is a lack of evidenced-based therapies. However, in clinical practice, low molecular weight heparin (LMWH) has been widely used as an empirical therapy since immune effects have been hypothesized in modulating immune tolerance at the fetal-maternal interface. Epigenetic mechanisms are involved in establishing of immune tolerance, at fetal-maternal interface. To investigate potential induced immune-epigenetic changes at maternal periphery level, which could reflect the maternal-fetal interface condition, seems to open up new therapeutical strategies, since microRNAs circulating in maternal plasma and in peripheral blood mononuclear cells (PBMCs) may be specific and sensitive immunological markers/predictors of adverse pregnancy outcomes such as RPL. Our aim in this pilot study is to evaluate potential LMWH effects on genes regulating immunological response key mechanisms related to maternal-fetal tolerance processes, by studying circulating miRNAs in maternal peripheral blood. We tested a panel of selected miRNAs on three groups: 18 healthy pregnant women, 20 pregnant women affected by uRPL, 18 pregnant women affected by uRPL, treated with LMWH. The majority of differentially expressed miRNAs (miR 374a-5p, 19a-3p, 30e-5p, 128–3p, 155–5p and 200c-3p) were found to be modulated by LMWH, which seems to have a positive function in RPL patients, by bringing patients' values back to those comparable to the control ones. Selected microRNA panels would appear to be an effective clinical tool for uRPL diagnosis and management. LMWH-modified miRNA expression levels could be targets for immunotherapy, as LMWH would appear to restore physiological miRNA levels, which are dysregulated in uRPL. • miRNAs are involved in immune tolerance establishing and its disruptions in RPL. • LMWH seems to be involved in modifying miRNA expression levels. • LMWH appears to restore physiological miRNA levels, which are dysregulated in uRPL. [ABSTRACT FROM AUTHOR]