Ovarian Circular RNAs Associated with High and Low Fertility in Large White Sows during the Follicular and Luteal Phases of the Estrous Cycle

In this study, the ovarian tissues of Large White pigs were mined for novel circular RNAs (circRNAs), following which, their molecular characteristics and potential mechanisms for fertility regulation were examined. RNA sequencing was used for transcriptome analysis of ovarian follicles and corpora lutea in Large White sows with high (H) and low (L) fertility during the follicular (F) and luteal (L) phases of the estrous cycle. In total, 21,386 circRNA derived from 4535 host genes were identified. Differentially expressed circRNAs were detected in the LH vs. LL (1079) and in the FH vs. FL (1077) comparisons, and their host genes were enriched in steroid biosynthesis and forkhead box O (FOXO), thyroid hormone, cell cycle, and tumor growth factor (TGF)-beta signaling pathways. Protein–protein interaction networks were constructed on the basis of the host genes that were significantly enriched in pathways related to reproductive processes, with AKT3 and PP2CB serving as the hub genes in the networks of the LH vs. LL and FH vs. FL comparisons, respectively. The microRNA (miRNA) binding sites of the differentially expressed circRNAs were predicted, and 128 (LH vs. LL) and 113 (FH vs. FL) circRNA–miRNA pairs were identified. Finally, circRNA–miRNA negative regulatory networks were established on the basis of the gene expression profiles and bioinformatic analyses. In the current study, differentially expressed circRNAs were observed in ovarian tissues between the H and L fertility groups in both F and L phases of the estrous cycle, which suggested roles in pig fertility regulation. These findings provide new clues for elucidating fertility differences in pigs.

Fertility regulation

Ovarian cells or the number of incompetent ovarian cells that may lead to pregnancy is reduced. At a certain age, for example, after 40 years of age, naturally reduces the possibility of conception also the possibilities of spontaneous abortion and anomalies. Fertility of men and women also depends on life habits, the presence of certain illnesses, the enjoyment of various opiates, etc. Unhealthy lifestyle, poor nutrition and obesity are also factors that reduce fertility in men and women. An average, healthy couple it is necessary six to Fertility of men and women depends primarily on their age. In women, for example, the number of twelve months of active endeavours to conceive of pregnancy. If pregnancy does not occur during this period, it is necessary to seek medical help.