Epigenetic modification of long interspersed elements-1 in cumulus cells of mature and immature oocytes from patients with polycystic ovary syndrome

Abstract

ObjectiveThe long interspersed elements (LINE-1, L1s) are a group of genetic elements found in large numbers in the human genome that can translate into phenotype by controlling genes. Growing evidence supports the role of epigenetic in polycystic ovary syndrome (PCOS). The purpose of this study is to evaluate the DNA methylation levels in LINE-1 in a tissue-specific manner using cumulus cells from patients with PCOS compared with normal controls.MethodsThe study included 19 patients with PCOS and 22 control patients who were undergoing controlled ovarian hyperstimulation. After oocyte retrieval, cumulus cells were extracted. LINE-1 DNA methylation levels were analysed by bisulfite treatment, polymerase chain reaction, and restriction enzyme digestion. The Connection Up- and Down-Regulation Expression Analysis of Microarrays software package was used to compare the gene regulatory functions of intragenic LINE-1.ResultsThe results showed higher LINE-1 DNA methylation levels in the cumulus cells of mature oocytes in PCOS patients, 79.14 (±2.66) vs. 75.40 (±4.92); p=0.004, but no difference in the methylation of cumulus cells in immature oocytes between PCOS and control patients, 70.33 (±4.79) vs. 67.79 (±5.17); p=0.155. However, LINE-1 DNA methylation levels were found to be higher in the cumulus cells of mature oocytes than in those of immature oocytes in both PCOS and control patients.ConclusionThese findings suggest that the epigenetic modification of LINE-1 DNA may play a role in regulating multiple gene expression that affects the pathophysiology and development of mature oocytes in PCOS.

Pathomechanisms of polycystic ovary syndrome Multidimensional approaches

“…We also noted that CGCs exhibited a hypomethylated status relative to PBLs (global as well as CpG-site specific hypomethylation), perhaps to facilitate the expression of ovary-specific genes that are otherwise not functional in PBLs. In contrast to our observations on global methylation levels in CGCs of mature follicles, the studies by Pruksananondaet al, report higher L1 methylation in women with PCOS (n = 19), as compared to controls (n = 22) although their studies in CGCs from immature oocytes show no difference between these groups (156). Also, an ELISA based global DNA methylation analysis between floating granulosa cells (GCs) performed by Xuet al alongside a genome-wide methylation study showed hypermethylation in GCs of PCOS women compared to controls (n = 9, per group) (157).…”

Influence of follicular fluid and cumulus cells on oocyte quality: clinical implications

“…Altered expressions of various transcripts, such as those encoding insulin receptors [175], IGF-binding proteins and receptors [184], and genes related to meiotic cell cycle regulation [185] have been observed in CCs from women with PCOS, suggesting that these women experience disturbances or delays in CC maturation and differentiation [185] and/or compromises in CC function [175]. Other studies focusing on CCs from these women found changes in long noncoding RNAs (lncRNAs; e.g., XLOC_011402, ENST00000454271, ENST00000433673, ENST00000450294, and ENST00000432431) [7], miRNAs (17 were differentially expressed; hsa-miRNA-135b-5p was the most highly upregulated and hsa-miRNA-3940-5p was the only example of downregulation) [186,187], and the methylation patterns of specific gene [188] when compared to controls, indicating that these cells undergo epigenetic deregulation. Together, the data indicate that the CCs from women with PCOS exhibit various alterations that are likely to negatively affect oocyte development.…”

DNA methylation in the pathogenesis of polycystic ovary syndrome

“…Most studies focusing on DNA methylation and PCOS have been conducted in granulosa cells, which play a fundamental role in steroidogenesis and ovarian folliculogenesis and whose dysfunction correlates with the pathogenesis of the disease (Pellatt et al 2007;Lan et al 2015). Some studies have reported differences in the global content of DNA methylation in granulosa cells of women with PCOS compared with controls (Pruksananonda et al 2016, Xu et al 2016, Sagvekar et al 2017, Pan et al 2018. In particular, a global hypomethylated state of the genome in granulosa cells of women with PCOS (evidenced by a decline in the DNA methylation levels of L-1) correlated with the hormonal alterations of the disease (Sagvekar et al 2017).…”