Abstract
There is a statistically significant difference in the frequency of implantation in the group of patients with endometriosis associated with infertility compared with the control group. This has been confirmed by a number of different studies. The aim of the study to expand the understanding of the pathogenesis of implantation failures in patients with infertility associated with endometriosis
Materials and research methods: The present study included 83 women aged 29 to 43 years (the average age was 33 ± 3.2 years) with a diagnosis of endometriosis (ICD10 code N80.9 Endometriosis, unspecified), as well as infertility (ICD10 code N 97.8, Female infertility of other origin) and repeated implantation failures. All patients of the studied cohort underwent an immunohistochemical study of endometrial biopsy samples taken by the pipel-biopsy of the endometrium during the period of the supposed “implantation window”.
Research results: Significant decrease in the immunological labeling of VEGF-A in samples from the ERIF group by ∼2.7 times in comparison with EF group (p < .05), the indices of expression of the proapoptotic protein CASP3 are increased in the samples of the ERIF group in comparison with the EF group (by ∼2.7 times, p < .05) and significant decrease in the expression of HOXA10 in the stromal and glandular compartments (2.4 times; 57.2 vs. 23.5%, p < .05).
Conclusion: On the basis of the obtained results of the study, it should be concluded that the basis of implantation impairment in patients with repeated implantation failures associated with endometriosis lies in angiogenetic and apoptotic disorders and leads to implantation failure in the eutopic endometrium due to desynchronous transformation of the epithelial-mesenchymal compartment and disruption of endometrial trophism.
There is a statistically significant difference in the frequency of implantation in the group of patients with endometriosis associated with infertility compared with the control group (15.8 vs. 24.0% p < .005) [Citation1]. This has been confirmed by a number of different studies [Citation2,Citation3]. Thus, the leading cause of implantation failure is both morphologically and functionally defective endometrium. When using immunohistochemical studies, polymerase chain reaction and other modern methods of molecular biology, significant differences are found that cause functional changes in this unique tissue [Citation4].
One of the important factors of receptivity is the HOXA10 gene, which encodes transcription factors involved in the growth, differentiation, and receptivity of the endometrium, which responds to signals from steroid receptors [Citation5]. Interestingly, laparoscopic endometrioma resection increased the expression of HOXA10 in the eutopic endometrium, which may indicate an improved susceptibility of the endometrium to implantation [Citation6].
Abnormal angiogenesis also may lead to reproductive failure, particularly in women with infertility and recurrent implantation failure (RIF) associated with endometriosis after IVF-ET treatment [Citation7]. Vascular endothelial growth factor (VEGF-A) produced by fibroblasts, macrophages, some glandular epithelial cells and, finally, endothelial cells plays a significant role in neovasculogenesis in endometriosis-associated infertility [Citation8].
A mandatory pathogenetic component characterizing the proliferative activity of the endometrium in infertility associated with endometriosis is a decrease in apoptosis. A striking marker of apoptosis is effector caspase-3, which causes the cleavage of key proteins (ICAD → DNase CAD, ROCK), leading to self-destruction of cells (apoptosis), including the glandular epithelium [Citation9].
Thus, the eutopic endometrium in women suffering from infertility associated with endometriosis differs in both functional and structural characteristics, and its molecular genetic features play an important role in the pathogenesis of endometriosis-associated infertility and the etiology of implantation failures.
The aim of the study
To expand the understanding of the pathogenesis of implantation failures in patients with infertility associated with endometriosis
Materials and research methods
The present study included 83 women aged 29 to 43 years (the average age was 33 ± 3.2 years) with a diagnosis of endometriosis (ICD10 code N80.9 Endometriosis, unspecified), as well as infertility (ICD10 code N 97.8, Female infertility of other origin) and repeated implantation failures.
The main group (n = 41) consisted of patients with endometriosis and infertility caused by the endometrial factor (mean duration of infertility 3.4 ± 0.8), with a history of 3 or more (2 or more in patients over 35 years old) unsuccessful attempts to transfer 1 embryo of good quality into the uterine cavity during IVF programs (ERIF group – patients with repeated implantation failures due to endometriosis).
The comparison group (n = 42) consisted of patients with endometriosis with a history of childbirth and had no history of infertility, who applied for the treatment of menstrual irregularities associated with endometriosis (EF group – fertile patients with endometriosis).
The morphological control group (n = 40) consisted of fertile women without endometriosis, with a history of 2 or more deliveries of full-term healthy children, who gave voluntary informed consent to participate in the study.
All patients of the studied cohort underwent an immunohistochemical study of endometrial biopsy samples taken by the pipel-biopsy of the endometrium during the period of the supposed “implantation window” – on the 7th day after the peak of luteinizing hormone determined in blood serum during a dynamic study in the periovulatory period (usually this period corresponds to 20-22 days of the menstrual cycle) – was carried out using a two-stage streptavidin-biotin-peroxidase method with antigen unmasking and using standard polyclonal antibody kits from “Ventana”, “Cell Marque” and “Diagnostic BioSystems” USA. Immunohistochemical staining was performed in a Ventana BenchMark ULTRA IHC/ISH immunostainer (USA), markers were detected on paraffin sections according to the standard using of the appropriate standard antibodies.
Statistical processing of the obtained results was carried out by methods of nonparametric statistics. The critical level of reliability of the null statistical hypothesis was taken equal to 0.05. To assess the differences between groups of feature values, the nonparametric Mann-Whitney U-test was used. This criterion is used when the sample size is small, and if nothing is known about the distribution of the sample. This method determines a sufficiently small area of intersection of values between two series (a ranged series of parameter values in the first sample and the same in the second sample). The lower the criterion value, the more likely it is that the differences between the parameter values in the samples are reliable.
Research results
Comparative analysis by age qualification showed that the average age of the studied patients, as well as women of the control group, were statistically insignificant (p = 0.328), which indicated the representativeness, statistical homogeneity and comparability of the studied groups.
In the course of this study, it was important to evaluate the immunohistochemical parameters of endometrial biopsy specimens from patients in the study cohort ().
Table 1. The proportion of IHC-positive structures in endometrial biopsies in the ERIF, EF and Morphological control groups.
The results of the study indicate that there are reliable immunohistochemical proliferative, apoptotic and angiogenetic determinants in the endometrium during the "window of implantation" in patients with RIF associated with endometriosis (ERIF group) in comparison with biopsies of women with endometriosis and preserved fertile function (EF group). Significant decrease in the immunological labeling of VEGF-A in samples from the ERIF group by ∼2.7 times in comparison with EF group (p < .05) indicates a general inhibition of the natural process of angiogenesis in the endometrium due to endometriosis. Negative dynamics of staining for VEGF-A indicates inhibition of endothelial proliferation. The data obtained indirectly indicate the disconnection between the cellular and molecular processes of maintaining local homeostasis, including the inferior recovery in the proliferative phase with subsequent disruption of endometrial trophism.
The indices of expression of the proapoptotic protein CASP3 are increased in the samples of the ERIF group in comparison with the EF group (by ∼2.7 times, p < .05), which indicates the intensification of apoptosis, which is also one of the mechanisms involved in the development of local dystrophic processes of the functional layer of the endometrium in endometriosis and contributes to a decrease in the implantation potential, leading to infertility and RIF.
In addition, an impairment of the receptive consistency was determined in the endometrium of women of the studied cohort due to a statistically significant decrease in the expression of HOXA10 in the stromal and glandular compartments (2.4 times; 57.2 vs. 23.5%, p < .05).
Conclusion
On the basis of the obtained results of the study, it should be concluded that the basis of implantation impairment in patients with repeated implantation failures associated with endometriosis lies in angiogenetic and apoptotic disorders and leads to implantation failure in the eutopic endometrium due to desynchronous transformation of the epithelial-mesenchymal compartment and disruption of endometrial trophism.
Disclosure statement
The authors declare that there is no potential conflict of interest.
Additional information
Funding
References
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