Cytokines in recurrent miscarriage : Genetic and molecular studies.

Recurrent miscarriage, is defined as three or more consecutive pregnancy losses before 20 weeks of gestation. It affects 0.5-2% of pregnant women. A great variety of aetiologic factors has been identified, but a specific cause is still unknown in 50% of cases. It has been suggested that immune causes, including abnormalities in either cytokine production or immune cell populations may be the reason for some of these cases. It is also known that some women with recurrent miscarriage have an endometrial defect, which may lead to abnormal development of the feto-placental unit and subsequent miscarriage. Cytokines are known to be important in the control of embryo implantation and therefore it is possible that abnormalities in endometrial cytokine expression could provide an explanation for unexplained recurrent miscarriages. This study has therefore focused on the possible role of some pro-inflammatory cytokines and leptin in recurrent miscarriage. In the first part of the study, polymerase chain reaction (PCR) was used to establish the frequency of alleles of IL1RN, IL1beta and leptin receptor genes in the DNA extracted from peripheral blood from women who suffer recurrent miscarriage and compared to that seen in controls. The results for both IL1RN tandem repeat polymorphism and IL1beta-511 polymorphism showed that there was no significant difference between the genotype distribution or allele frequency in recurrent miscarriage women and the control population. For IL1beta-511 this was true whether the analysis was carried out on data obtained from the recurrent miscarriage group as a whole or when the women were divided according to the cause of the miscarriage. In the case of IL1RN polymorphism, an increased frequency of 2,2 genotype was seen in recurrent miscarriage women with PCOS, but the numbers in this group were very small.The GLN223ARG leptin receptor polymorphism investigated in this study results in the substitution of amino acids glutamine to arginine in the transmembrane section of the receptor. The results showed no significant difference between the distribution of GLN223ARG leptin receptor genotypes in the recurrent miscarriage women as a whole group compared to the control group.when divided according to the cause of recurrent miscarriage there was a significant increase in the AA genotype in women with secondary recurrent miscarriage and those whose aetiology is unknown.In the second part of the study, expression of IL-11 and IL-11Ralpha in endometrium of recurrent miscarriage and control women were compared using RT-PCR and immunocytochemistry. The results showed that IL-11 and IL-11 Ralpha mRNA and protein were expressed in the endometrium throughout the menstrual cycle by both stromal and epithelial cells. IL-11 and IL-11 Ralpha protein expression was greater in epithelial cells than stromal cells. IL-11 and IL-11Ralpha mRNA and protein were significantly higher in the late secretory phase compared to the proliferative phase of the menstrual cycle. The high levels of IL-11 and IL-11Ralpha mRNA and protein in the late secretory phase suggest that IL-11 may play a role in the functional differentiation that occurs during decidualization of human endometrial stromal cells. IL-11 and IL-11Ralpha were also expressed in the endometrium of women with recurrent miscarriage. There was no significant difference in amounts of IL-11 Ralpha mRNA and protein in the endometrium obtained from normal fertile women or recurrent miscarriage women during the peri-implantation period. However, IL-11 protein expression was decreased in endometrial epithelial cells in the recurrent miscarriage women compared to that seen in normal fertile women. Taken together these results, show decrease endometrial IL-11 production by women with recurrent miscarriage. They also suggest that leptin may be important in preventing miscarriage in some groups of recurrent miscarriage. However, further studies on large groups of recurrent miscarriage women need to be carried out in order to define the importance of this polymorphism. Although, the IL-1RN tandem repeat and IL-1beta-511 polymorphisms appear not to be associated with recurrent miscarriage, this does not mean that the IL-1 system is not involved in causing recurrent miscarriage, as plasma levels of IL-1 did not appear to be different in women with different genotypes.