Distinctive Dna Methylome Changes In Human Ovarian Granulosa Cells Are Associated With Diminished Ovarian Function

Diminished ovarian function is a primary cause for age-related decline in female fertility; however, its underlying mechanism remains unclear. This study investigated whether epigenetic mechanisms may underlie the ovarian aging process. Translational research. Genomic DNA methylation patterns in ovarian granulosa cells were compared between two groups of women with differences in age and ovarian function. Group A consisted of young oocyte donors (mean age=26 years) with a robust response to ovarian stimulation during ART (mean number of oocytes retrieved=25). Group B comprised poor responders who were older (mean age =40 years) and responded poorly to ovarian stimulation during ART (oocytes retrieved ≤4 and peak estradiol level ≤ 1000 pg/ml). Methylated DNA Capture followed by Next Generation Sequencing (MethylCap-seq) was used to compare DNA methylomes between the two groups. Two sets of experiments using ovarian granulosa cells from 20 individuals in each group revealed highly consistent differences in DNA methylome patterns between groups A and B. Compared to young women, ovarian granulosa cells from older women with diminished ovarian function showed reproducible focal hyper-methylation. Over 97% of regions that exhibited at least 5-fold enrichment and 2-fold change were more highly methylated in group B. These DNA methylation changes were selectively localized to the X chromosome, and this preferential localization became more striking in proximity (≤1kb) to transcription start sites. Whole genome searches revealed focal hyper-methylation, especially on the X chromosome, in older women with diminished ovarian function, compared to young oocyte donors. Consistent differences in DNA methylation profiles between these two groups indicate that epigenetic changes in ovarian granulosa cells are associated with the age-related decline in ovarian function.