Age-associated changes in miRNA profile of bovine follicular fluid

Abstract

We examined age-associated changes in microRNA (miRNA) profiles in the follicular fluid (FF) of cows. The role of miR-19b, which is abundant in the FF of young cows, in in vitro growth of early antral follicles (EAFs)-derived oocytes was assessed. FF was collected from the antral follicles of young (20–40 months) and aged (>120 months) cows. The miRNA profiles were similar between the FF of both age groups, whereas the abundance of some miRNAs differed between these samples. The miRNA profiles in granulosa cells (GCs) and the spent culture medium of oocyte–GC complexes (OGCs) derived from EAFs were distinct. Some miRNA groups overlapped among the GCs, culture media, and FFs. miR-19b was highly abundant in the FF of young cows, GCs and culture medium. The supplementation of OGC culture medium with miR-19b increased the diameter, acetylation levels, and fertilisation ability of the oocytes. To assess whether miR-19b was functional in the GCs, a dual-luciferase assay, suppression of target protein, and RNA-sequencing of the GCs followed by functional annotation of the differentially expressed genes (DEGs) were conducted. Functional annotation of the DEGs suggested that miR-19b influences genes associated with FoxO signalling, endocytosis, and NR3C1 in GCs. These results suggest that in FFs, aging affects the abundance of miRNAs that have important roles in oocyte development.

microRNAs associated with the quality of follicular fluids affect oocyte and early embryonic development

“…The miRNA profiles of the FFs found in the present study also overlapped with those reported in cows. 21 , 24 Furthermore, many miRNAs found in human FFs overlap with the miRNAs found in this study. 32 Based on these reports, the top miRNAs in the EVs of FF are conserved among cows and resemble those in humans.…”

“…Furthermore, we previously showed that miRNA profiles in GCs differ from the profiles in the spent culture medium of GCs. 21 These results suggest that certain groups of miRNAs are selectively packaged into the EV for secretion.…”

“…miRNAs in EVs of FF are pivotal for oocyte growth because supplementation of the culture medium with miRNAs improves oocyte growth in cows and pigs. 16 , 21 Based on these reports, we speculated that miRNA profiles might differ between Good and Poor FF. Small RNA‐seq of the FF‐EV showed that the top 10 miRNAs in EVs both Good and Poor FF groups overlapped.…”

“… 19 We previously reported that lipofection of 8‐cell stage embryos with miRNAs detected in EV of OF around ovulation improved the blastulation rate to blastocyst, 20 and the miRNA was found in FF at high frequencies. 21 A report demonstrated that in vitro developing bovine embryos could take up EVs, and a greater fraction of the embryos reached the blastocyst stage with the upregulation of gene expression associated with metabolism and development, 7 suggesting that EVs derived from FF affect early embryo development. Based on these reports, we hypothesized that miRNAs in FF determine not only the quality of oocytes but also the development of embryos, which is the underlying background of differences in donors.…”

Beneficial Effect of Polysaccharide Gel Made of Xanthan Gum and Locust Bean Gum on Bovine Oocytes

“…Herein, the gel culture system activated genes associated with the focal adhesion and actine-mediated signal transduction; however, the key factors causing these changes are yet to be defined. RNA-sequencing (RNA-seq) technology combined with ingenuity upstream regulator analysis (IPA) is useful for identifying the molecules that cause the differential expression of genes in granulosa cells, embryos, and uterine epithelial cells [ 7 , 8 , 9 ].…”