Endometrial factors in the implantation failure spectrum: protocol of a MUltidisciplinary observational cohort study in women with Repeated Implantation failure and recurrent Miscarriage (MURIM Study)

Altered Endometrial Microbiota Profile Is Associated With Poor Endometrial Receptivity of Repeated Implantation Failure

PURPOSE

To gain insight into the endometrial pathophysiology of unexplained repeated implantation failure (RIF), we examined the characteristics of genital tract microbiota and explored the correlation between the microbiota and endometrial receptivity.

METHODS

Vaginal secretion (VS) and endometrial biopsy (EB) samples were collected from patients with RIF (RIF group, n = 32) and those with infertility who had achieved pregnancy during their initial embryo transfer cycle (control group, n = 18). 16S ribosomal RNA sequencing and quantitative PCR were performed to characterize the microbiota of the two groups. Spearman's correlation analysis was performed to determine the relationship between endometrial receptivity markers and endometrial microbiota.

RESULTS

Endometrial microbiota exhibited distinct characteristics from vaginal microbiota, with a higher alpha-diversity. Alpha-diversity of the endometrial microbiota was higher in the RIF group than in the control group. Compared with the control group, the RIF group had a significant decrease in endometrial Lactobacillus abundance and an increase in Gardnerella and Acinetobacter abundances. The expression levels of endometrial receptivity markers, including homeobox A11, integrin αvβ3, leukemia inhibitor factor, matrix metalloproteinase-9, and vascular endothelial growth factor, were lower in the RIF group than in the control group. Moreover, the expression levels of these markers were correlated with endometrial Lactobacillus, Gardnerella, and Acinetobacter abundances.

CONCLUSION

RIF is characterized by endometrial microbiota dysbiosis and poor endometrial receptivity. Moreover, abnormal endometrial microbiota is associated with impaired endometrial receptivity, which may be a potential cause of unexplained RIF.

Local production of 17β-oestradiol in the endometrium during the implantation window: a pilot study

Abstract

Sex steroids are converted to bioactive metabolites and vice versa by endometrial steroid-metabolising enzymes. Studies indicate that alterations in this metabolism might affect endometrial receptivity. This pilot study determined whether the endometrial formation and inactivation of 17β-oestradiol differed between the supposedly embryo-receptive endometrium and non-receptive endometrium of women undergoing IVF/intracytoplasmic sperm injection (ICSI). Endometrial biopsies were obtained from IVF/ICSI patients 5-8 days after ovulation in a natural cycle, prior to their second IVF/ICSI cycle with fresh embryo transfer (ET). Endometrial biopsies from patients who achieved clinical pregnancy after fresh ET (n = 15) were compared with endometrial biopsies from patients that did not conceive after fresh ET (n = 15). Formation of 17β-oestradiol (oxidative 17β-hydroxysteroid dehydrogenases (HSDs)), oestrone (reductive HSD17Bs) and inhibition of HSD17B1 activity were determined by high-performance liquid chromatography. The endometrial transcriptome was profiled using RNA sequencing followed by principal component analysis and differentially expressed gene analysis. The false discovery rate-adjusted P < 0.05 and log fold change >0.5 were selected as the screening threshold. Formation and inactivation of 17β-oestradiol resulted similar between groups. Inhibition of HSD17B1 activity was significantly higher in the non-pregnant group when only primary infertile women (n = 12) were considered (27.1%, n = 5 vs 16.2%, n = 7, P = 0.04). Gene expression analysis confirmed the presence of HSD17B1 (encoding HSD17B1), HSD17B2 (encoding HSD17B2) and 33 of 46 analysed steroid metabolising enzymes in the endometrium. In the primary infertile subgroup (n = 10) 12 DEGs were found including LINC02349 which has been linked to implantation. However, the exact relationship between steroid-metabolising enzyme activity, expression and implantation outcome requires further investigation in larger, well-defined patient groups.

Lay summary

Sex hormones are produced and broken down by enzymes that can be found in the endometrium (the inner lining of the womb). This enzyme activity might influence the chances of becoming pregnant. We compared (i) enzyme activity in the endometrium of 15 women who did and 15 women who did not become pregnant in their second in vitro fertilisation attempt, (ii) how enzyme activity can be blocked by an inhibitor, and (iii) differences in gene expression (the process by which instructions in our DNA are converted into a product). Enzyme activity was similar between groups. We found that in women who have never been pregnant in the past, inhibition of enzyme activity was higher and found differences in a gene that has been linked to the implantation of the embryo, but future studies should be performed in larger, well-defined patient groups to confirm these findings.

Abnormal expression of galectin-1, -3 leading to unexplained infertility by decreasing endometrial receptivity: a retrospective analysis

OBJECTIVE

To explore the relationship between galectin-1, -3 and unexplained infertility and the effect on endometrial receptivity.

METHODS

The clinical data of 100 female patients at childbearing age coming to Xingtai People's Hospital from February 2019 to February 2021 were collected retrospectively. Based on normal pregnancy or not, 50 infertility patients were placed into an infertility group, and 50 patients with normal pregnancy history were placed into a normal group. The mRNA and protein levels of galectin-1, -3, endometrial wave-like activity, endometrial thickness, uterine artery pulsatility index (PI), resistance index (RI), end diastolic velocity (EDV) and peak systolic velocity (PSV) ratio (S/D = PSV/EDV) were compared between the two groups of patients.

RESULTS

The mRNA and protein levels of galectin-1, -3 in the infertile group were lower than those in the normal group (P<0.05). In addition, the endometrial wave-like activity in the infertile group was more than that in the normal group (P<0.05). The endometrial thickness was less, while PI, RI and S/D were higher in the infertile group than those in the normal group (P<0.05).

CONCLUSION

The low mRNA and protein expressions of galectin-1, -3 in unexplained infertility can affect endometrial receptivity, which may be closely related to unexplained infertility.

Correlation between Endometrial Vascular Endothelial Growth Factor Expression and Pregnancy Outcome of Frozen-Thawed Embryo Transfer in Patients with Repeated Implantation Failure

Objective

Vascular endothelial growth factor (VEGF) is a well-known angiogenic factor that is essential to numerous physiological and pathological processes. VEGF also contributes to embryo implantation by promoting embryo development, enhancing endometrial receptivity (ER), and promoting interactions between the endometrium and developing embryo. Changes in VEGF expression are linked to repeated implantation failure (RIF). Control endometrial tissues demonstrated an increase in VEGF expression during the implant window period, which promoted early villous vascularization and embryo implantation. The purpose of this study is to investigate the relationship between RIF and the expression of ER markers, such as VEGF during the implantation window stage.

Methods

The Yinchuan Maternal and Child Health Hospital collected 192 cases of FET endometrial tissues in the implantation window stage between January 2019 and December 2021. Immunohistochemistry was utilized to measure the levels of VEGF expression in patients with RIF (RIF group, n = 82) and patients with a successful pregnancy (control group, n = 110). The relationship between VEGF and the RIF group was analyzed using Spearman's correlation coefficient.

Results

VEGF levels were significantly lower during the implantation window stage (P < 0.05).

Conclusion

VEGF was expressed in planting window stage. The decrease of VEGF during the implantation window was correlated with RIF.