Alteration of ERβ gene RsaI polymorphism may contribute to reduced fertilization rate and embryonic developmental competence

Molecular Clues to Understanding Causes of Human-Assisted Reproduction Treatment Failures and Possible Treatment Options

More than forty years after the first birth following in vitro fertilization (IVF), the success rates of IVF and of IVF-derived assisted reproduction techniques (ART) still remain relatively low. Interindividual differences between infertile couples and the nature of the problems underlying their infertility appear to be underestimated nowadays. Consequently, the molecular basis of each couple's reproductive function and of its disturbances is needed to offer an individualized diagnostic and therapeutic approaches to each couple, instead of applying a standard or minimally adapted protocols to everybody. Interindividual differences include sperm and oocyte function and health status, early (preimplantation) embryonic development, the optimal window of uterine receptivity for the implanting embryo, the function of the corpus luteum as the main source of progesterone production during the first days of pregnancy, the timing of the subsequent luteoplacental shift in progesterone production, and aberrant reactions of the uterine immune cells to the implanting and recently implanted embryos. In this article, the molecular basis that underlies each of these abnormalities is reviewed and discussed, with the aim to design specific treatment options to be used for each of them.

Molecular Drivers of Developmental Arrest in the Human Preimplantation Embryo: A Systematic Review and Critical Analysis Leading to Mapping Future Research

Developmental arrest of the preimplantation embryo is a multifactorial condition, characterized by lack of cellular division for at least 24 hours, hindering the in vitro fertilization cycle outcome. This systematic review aims to present the molecular drivers of developmental arrest, focusing on embryonic and parental factors. A systematic search in PubMed/Medline, Embase and Cochrane-Central-Database was performed in January 2021. A total of 76 studies were included. The identified embryonic factors associated with arrest included gene variations, mitochondrial DNA copy number, methylation patterns, chromosomal abnormalities, metabolic profile and morphological features. Parental factors included, gene variation, protein expression levels and infertility etiology. A valuable conclusion emerging through critical analysis indicated that genetic origins of developmental arrest analyzed from the perspective of parental infertility etiology and the embryo itself, share common ground. This is a unique and long-overdue contribution to literature that for the first time presents an all-inclusive methodological report on the molecular drivers leading to preimplantation embryos’ arrested development. The variety and heterogeneity of developmental arrest drivers, along with their inevitable intertwining relationships does not allow for prioritization on the factors playing a more definitive role in arrested development. This systematic review provides the basis for further research in the field.

A Potential Relationship Between Estrogen Receptors Polymorphisms, Sperm Function and in vitro Fertilization Success: A Preliminary Study*

Background: Estrogen receptor 1 (ESR1) and 2 (ESR2) play an important role in regulating fertility in the human reproductive system. Polymorphisms of these receptor genes have been implicated in male infertility in both Chinese and Caucasian populations. However, studies have produced inconsistent results. Spermatozoa defects that result in conception deficiencies could be related to estrogens, their receptors, or genes involved in estrogen-related pathways. This study aims to explore the potential association between the ESR1 and the ESR2 polymorphisms in relation to semen parameters of Caucasian males as well as fertilization success. Materials/Methods: A total of 116 males were included in this study. Forty couples underwent conventional in vitro fertilization, while 76 couples were treated by intracytoplasmic sperm injection. Standard semen analyses were performed according to the World Health Organization criteria. Polymerase chain reaction and restriction fragment length polymorphisms were used to determine genotype and allele distributions. Results: A strong association between the ESR1 rs2234693 recognized by PvuII enzyme, genotype/allele distribution and fertilization success was shown. The T allele occurrence was significantly lower in the case of fertilization failure (p = 0.02). Additionally, the TT genotype was absent in the same group (p=0.02). In the case of the remaining analyzed polymorphisms, little to no interdependence of genotype/allele distribution and fertilization success was noted. Conclusions: Apart from ESR1 rs2234693, the study failed to demonstrate that fertilization success was associated with the selected polymorphisms. In most cases, we did not discover a relationship between both estrogen receptors polymorphisms and sperm function.

Oestrogen receptors beta genotype in infertile Egyptian men with nonobstructive azoospermia

In a prospective study, the polymorphism of oestrogen receptor β gene was investigated in nonobstructive azoospermia patients. Ninety infertile patients with nonobstructive azoospermia diagnosed after two semen analysis, 2 weeks apart and negative testicular sperm extraction during intracytoplasmic sperm injection, and 60 fertile men as controls were enrolled in the study. Semen analysis, hormonal profile and allele-specific PCR reaction were performed to detect variants of the RsaI polymorphism of the oestrogen receptor β gene for all patients and controls. The mean patient's age was significantly lower than the mean age of the controls (P < 0.05). There was a significant increase in the mean serum levels of FSH, LH, free testosterone and E2 and significant decrease in total testosterone in patients than controls (P < 0.05). In the patients, the frequency of the homozygous GG, heterozygous AG and homozygous AA genotype was 83.3%, 14.3% and 3.3% respectively, whereas their frequencies in the controls were 95%, 5% and 0% respectively (odds ratio 3.8). There is no significant correlation between ERß polymorphisms and patient's age or pituitary and sex hormones (P > 0.05). Our findings suggested that in Egyptian population, genetic mutation in ERß is associated with the risk of nonobstructive azoospermia.