Age-related changes in gene expression patterns of immature and aged rat primordial follicles

Women are born with millions of primordial follicles which gradually decrease with increasing age and this irreversible supply of follicles completely exhausts at menopause. The fertility capacity of women diminishes in parallel with aging. The mechanisms for reproductive aging are not fully understood. In our recent work we observed a decline in BRCA1 mediated DNA repair in aging rat primordial follicles. To further understand the age-related molecular changes, we performed microarray gene expression analysis using total RNA extracted from immature (18–20 days) and aged (400–450 days) rat primordial follicles. The results of current microarray study revealed that there were 1011 (>1.5 fold, p<0.05) genes differentially expressed between two groups in which 422 genes were up-regulated and 589 genes were down-regulated in aged rat primordial follicles compared to immature. The gene ontology and pathway analysis of differentially expressed genes revealed a critical biological function such as cell cycle, oocyte meiosis, chromosomal stability, transcriptional activity, DNA replication and DNA repair were affected by age and this considerable difference in gene expression profiles may have adverse influence on oocyte quality. Our data provide information on the processes that may contribute to aging and age-related decline in fertility. In total of 6 samples, 3 replicate samples were from immature rat primordial follicles and 3 replicate samples were from aged rat primordial follicles. For each replicate sample, the primordial follicles isolated from multiple isolations (each time 10-20 rat ovaries) were finally pooled in order to get required quantity of RNA.