Methylation analysis of plasminogen activator inhibitor-1 (PAI-1) gene in ovarian and peritoneal endometriosis

Abstract

Endometriosis, defined as the growth of endometrial-like tissue outside the uterus, leads to the emergence of chronic inflammatory reactions, which are influenced by the plasminogen activator systems that are known to play a role in fibrinolysis. Hypofibrinolysis due to the excessive expression of the plasminogen activator inhibitor-1 (PAI-1) gene occurs in endometriotic cells. It has been known that the PAI-1 level is lower in normal endometrial cells than in endometriotic cells. The aim of this study is to assess the methylation level of PAI-1 in association with ovarian and peritoneal endometriosis tissues. This was a comparative cross-sectional study conducted on 13 women with ovarian endometriosis, 5 with peritoneal endometriosis, and 8 without endometriosis. DNA from the patient samples was isolated and subjected to bisulfite conversion. DNA methylation was observed by performing the methylation-specific polymerase chain reaction (MSP) method, followed by electrophoresis. The methylation level of PAI-1 was determined by measuring the band intensity using the ImageJ software. The results were statistically analyzed using the Kruskal–Wallis test. A twotailed p value of <0.05 was considered to be statistically significant. Statistically significant difference was noted in the methylation levels of PAI-1 in ovarian endometriosis and peritoneal endometriosis samples compared with those noted in control samples (p = 0.006 and p = 0.003, respectively). The methylation levels in both sample types were lower than those in the control samples. However, the difference between the methylation levels of PAI-1 in peritoneal endometriosis and ovarian endometriosis were not statistically significant (p > 0.05). We found a low methylation level in the promoter region of PAI-1 gene, which led to an increase in the gene expression that may contribute as a risk factor in ovarian endometriosis and peritoneum endometriosis.