The IL-6 -634C/G polymorphism: a candidate genetic marker for the prediction of idiopathic recurrent pregnancy loss

Association between cytokine polymorphisms and recurrent pregnancy loss: A review of current evidence

Cytokines are a type of protein that play an important role in the immune response and can also affect many physiological processes in the body. Cytokine polymorphisms refer to genetic variations or mutations that occur within the genes that code for cytokines, which may affect the level of cytokine production and function. Some cytokine polymorphisms have been associated with an increased risk of developing certain diseases, while others may be protective or have no significant effect on health. In recent years, the role of cytokine polymorphisms in the development of recurrent pregnancy loss (RPL) has been studied. RPL or miscarriage is defined as the occurrence of two or more consecutive pregnancy losses before the 20th week of gestation. There are diverse causes leading to RPL, including genetic, anatomical, hormonal, and immunological factors. With regard to cytokine polymorphisms, a few of them have been found to be associated with an increased risk of RPL, for instance, variations in the genes that code for interleukin-6, tumor necrosis factor-alpha, and interleukin-10. The exact mechanisms by which cytokine polymorphisms affect the risk of recurrent miscarriage are still being studied, and further research is essential to fully understand this complex condition. This brief review aims to summarize the recent literature on the association between cytokine polymorphisms and RPL.

Understanding recurrent pregnancy loss: recent advances on its etiology, clinical diagnosis, and management

Recurrent pregnancy loss (RPL) has become an important reproductive health issue worldwide. RPL affects about 2%-3% of reproductive-aged women, and makes serious threats to women's physical and mental health. However, the etiology of approximately 50% of RPL cases remains unknown (unexplained RPL), which poses a big challenge for clinical management of these patients. RPL has been widely regarded as a complex disease where its etiology has been attributed to numerous factors. Heretofore, various risk factors for RPL have been identified, such as maternal ages, genetic factors, anatomical structural abnormalities, endocrine dysfunction, prethrombotic state, immunological factors, and infection. More importantly, development and applications of next generation sequencing technology have significantly expanded opportunities to discover chromosomal aberrations and single gene variants responsible for RPL, which provides new insight into its pathogenic mechanisms. Furthermore, based upon patients' diagnostic evaluation and etiologic diagnosis, specific therapeutic recommendations have been established. This review will highlight current understanding and recent advances on RPL, with a special focus on the immunological and genetic etiologies, clinical diagnosis and therapeutic management.

Genetics of recurrent pregnancy loss among Iranian population

Background

Recurrent pregnancy loss (RPL) is one of the most common reproductive disorders which is defined as the occurrence of recurrent miscarriage before 24 weeks of gestation and is observed among 1%–5% of women.

Methods

Various factors are associated with RPL such as immunological disorders, maternal age, obesity, alcohol, chromosomal abnormality, endocrine disorders, and uterine abnormalities. About half of the RPL cases are related with chromosomal abnormalities. Therefore, RPL genetic tests are mainly limited to karyotyping. However, there is a significant proportion of RPL cases without any chromosomal abnormalities that can be related to the single‐gene aberrations. Therefore, it is required to prepare a diagnostic panel of genetic markers besides karyotyping.

Results

In the present review, we have summarized all the significant reported genes until now which are associated with RPL among Iranian women. We categorized all the reported genes based on their cellular and molecular functions in order to determine the molecular bases of RPL in this population.

Conclusion

This review paves the way of introducing a population‐based diagnostic panel of genetic markers for the first time among Iranian RPL cases. Moreover, this review clarifies the genetic and molecular bases of RPL in this population.

Interleukin-6 Gene Polymorphism and the Risk of Systemic Inflammatory Response Syndrome Caused by Wasp Sting Injury

Previous studies have shown that serum levels of interleukin-6 (IL-6), which plays an important role in the development of systemic inflammatory response syndrome (SIRS), is significantly increased in wasp sting patients. However, the association between IL-6 gene variants and the risk of SIRS development in these patients is not clearly understood. In this study, we investigated the association between IL-6 gene polymorphism in the promoter region and the risk of SIRS in wasp sting patients. A total of 160 patients were divided into SIRS group and non-SIRS group (control), and evaluated for polymorphisms in IL-6 (-174G/C, -572G/C, -597G/A, and -634C/G), using DNA sequencing. The IL-6 serum levels were assessed using an enzyme-linked immunosorbent assay. Risk factors were analyzed by logistic regression analysis. We found that the IL-6 serum level was significantly higher in the SIRS group than in the control group (p < 0.001). A significant association was observed in the genotypic distribution of the IL-6 - 572G allele in the SIRS group, when compared with the control group [OR = 3.909 (1.906-8.019), p < 0.001], and SIRS is more likely to occur in wasp sting patients with more than 10 stings. Thus, the IL-6 - 572G allele and more than 10 stings can be used as predictors of risk of SIRS development in wasp sting patients.

Genetic and epigenetic variations associated with idiopathic recurrent pregnancy loss

Recurrent pregnancy loss (RPL) is a reproductive disorder defined as two or more successive and spontaneous pregnancy losses (before 20 weeks of gestation), which affects approximately 1-2% of couples. At present, the causes of RPL remain unknown in a considerable number of cases, leading to complications in treatment and high levels of stress in couples. Idiopathic recurrent pregnancy loss (iRPL) has become one of the more complicated reproductive problems worldwide due to the lack of information about its etiology, which limits the counseling and treatment of patients. For that reason, iRPL requires further study of novel factors to provide scientific information for determining clinical prevention and targeted strategies. The aim of this study is to describe the most recent and promising progress in the identification of potential genetic and epigenetic risk factors for iRPL, expanding the genetic etiology of the disease.

Genetics of recurrent miscarriage and fetal loss

Despite years of research, miscarriage, particularly when recurrent, continues to pose a medical challenge. An embryo chromosomal error is responsible for 50-60% of recurrent cases; however, up to 30-50% remains an enigma. Successful pregnancy involves different maternal physiologic changes and certain complex interactions between the fetus and the mother by cytokines, angiogenic mediators and hormones. To date, research lines have focused on genetic and epigenetic polymorphisms related mainly to immune response and inflammatory mediators, and have yielded a significant relationship between recurrent miscarriage and immune mechanisms. Thus, unknown causes of miscarriage could be due to an immune imbalance induced by T-helper Th1/Th2/Th17 cytokines and regulatory T cells. Furthermore, these genes and mediators have long been suspected of being blood markers for the clinical diagnosis and management of miscarriage; however, more evidence is required for them to be included in medical practice and obstetric guidelines.