Investigating the prevalence of 5G / 4G polymorphisms in PAI-I gene in women with recurrent abortion

Abstract

Abortion means loss of pregnancy and is divided into unintentional, intentional, forgotten and therapeutic types. Environmental factors such as smoking, alcohol consumption and regular coffee drinking, pathological factors such as autoimmune, anatomical, infectious and endocrine factors, infectious factors including Chlamydia trachomatis, and genetic factors such as chromosomal and structural abnormalities are reasons for abortion. Based on the scientific studies, there is a direct relationship between 4G / 5G polymorphism of PAI-I gene and venous thrombosis. Since it has been shown that 4G allele compare to 5G allele increases the level of PAI-I protein, which inhibits t-PA and u-PA, to a greater extent, this polymorphism can lead to impaired fetal nutrition and eventually abortion. Thus, this study aimed to examine the relationship between 4G / 5G polymorphism and recurrent abortion.

Method: Blood samples of 83 patients with a history of recurrent abortion who did not suffer other factors involved in abortion, such as chromosomal abnormalities in fetus, urine anatomical problems, hormone disorders, and infections related to abortion, and 102 healthy individuals in Ahwaz, in 2020-2021 were collected. After extracting DNA by salting-out method, and then primary PCR with common upstream and downstream primers for 4G and 5G alleles, DNAs were run on agarose gel and subsequently gel documentation was performed. Then, pre-sequencing PCR was performed with forward-specific labelled primers 4G and 5G and a common downstream primer. Finally, the samples underwent capillary electrophoresis to perform sequencing for statistical analysis.

Results: 5G / 5G, 4G / 4G and 4G / 5G genotypes were found in 14 (17%), 28 (34%) and 41(49%) individuals respectively, in the patient population, and 16 (16%), 28 (27%) and 58 (57%) individuals in the order given, in the control group. 4G and 5G alleles were found in 97 (58%) and 69 (42%) patients, respectively, and 114 (56%) and 90 (44%) individuals, respectively, in healthy population. P-value was 0.57 between genotype and the number of observed subjects in both groups, and 0.62 between allele and the number of patients and controls. P-value was 0.3 for the difference of allele frequencies in patients, and 0.09 in the control group subjects.

Results: Although the difference between frequencies of 4G and 5G alleles in the patient population is significant, there is no significant relationship between 4G / 5G polymorphism and recurrent abortion in comparison with the control group subjects.

Discussion: In addition to environmental factors, diet and other unknown factors affecting recurrent abortion, the number of studied people is a reason for the discrepancy between the results of this study and a few numbers of previous studies. Also, 4G allele thrombosis does not necessarily lead to recurrent abortion.