Abstract
Simple SummaryUsing the technology of juvenile superovulation, more follicles can be acquired in juvenile animals than in adult animals. However, oocytes derived from the follicles of juvenile animals are usually of poor quality, meaning that they have lower levels of subsequent maturation and embryonic development. In the present study, we used an exogenous hormone treatment to stimulate Hu sheep in order to compare the differences in ovarian superovulation effects and serum hormone secretion in juvenile and adult sheep. Differentially expressed microRNA (miRNA) and messenger RNA (mRNA) from the ovaries of juvenile and adult Hu sheep were then investigated using high-throughput sequencing technology to reveal the formation mechanism of large numbers of follicles and poor oocyte quality in juvenile ovaries under superovulation treatment. We found that molecules of oar-miR-143 and follicle-stimulating hormone receptor (FSHR), among others, might regulate follicle formation, while oar-miR-485-3p, oar-miR-377-3p, and pentraxin 3 (PTX3), among others, may be associated with oocyte quality. The results will help us to identify miRNAs and mRNAs that could be used to predict ovarian superovulation potential and oocyte quality in the future.Juvenile superovulation can provide a wealth of oocyte material for embryo production, animal cloning, and genetic modification research, but embryos derived from juvenile oocytes show poor efficiency in subsequent developmental capacity. In order to reveal the formation mechanism of large numbers of follicles and poor oocyte quality in juvenile ovaries under superovulation treatment, differentially expressed microRNAs (miRNAs) and messenger RNAs (mRNAs) were characterized and investigated in the ovaries of lambs and adult sheep using high-throughput sequencing technology. The majority of differentially expressed miRNAs (337/358) were upregulated in lamb libraries. The expression levels of mRNAs related to hormone receptors (follicle-stimulating hormone receptor, FSHR; luteinizing hormone/choriogonadotropin receptor, LHCGR; estrogen receptor 1, ESR1), steroid hormone secretion (cytochrome P450 family 11 subfamily A member 1, CYP11A1; cytochrome P450 family 17 subfamily A member 1, CYP17A1; cytochrome P450 family 19 subfamily A member 1, CYP19A1), and oocyte quality (pentraxin 3, PTX3; BCL2 apoptosis regulator, BCL2; caspase 3, CASP3) were significantly different between the lamb and adult libraries. The miRNA aor-miR-143, which targets FSHR, was highly and differentially expressed, and PTX3 was predicted to be targeted by oar-miR-485-3p and oar-miR-377-3p in the ovine ovary. A considerable number of miRNAs were predicted to inhibit ESR1 expression in lamb ovaries. In conclusion, oar-miR-143 and FSHR molecules, among others, might regulate follicle formation, and oar-miR-485-3p, oar-miR-377-3p, and PTX3, among others, may be associated with oocyte quality. These identified miRNAs and mRNAs will be beneficial for the prediction of ovarian superovulation potential and screening of oocytes.
Highlights
In the breeding of domestic animals, limiting factors such as the reproductive cycle and generation interval affect their genetic progress
juvenile in vitro embryo transfer (JIVET) technology can be used to shorten the generation interval and accelerate the progress of genetic selection, and it can provide a wealth of materials for research on embryonic stem cells, animal cloning, and genetic modification [3,22,38]
We focused on the initial stage of JIVET: ovaries under the treatment of superovulation; the miRNAome and transcriptome were compared between juvenile and adult ovaries to identify the mechanism of inferior oocyte capture by JIVET
Summary
In the breeding of domestic animals (sheep, cattle, pigs, etc.), limiting factors such as the reproductive cycle and generation interval affect their genetic progress. Exploring the reproductive potential of juvenile animals can provide an exciting shortcut to solve the above-mentioned limiting factors [1,2]. Under the stimulation of superovulation hormones, prepubertal females of a suitable age can produce considerably more antral follicles than adult females [1]. For unknown physiological reasons, these antral follicles from prepubertal females cannot ovulate normally, and follicular aspiration on the juvenile ovary is necessary for oocyte collection [4]. Compared with the technique of multiple ovulation and embryo transfer (MOET) applied in adult females, the above process, so-called juvenile in vitro embryo transfer (JIVET), is not smooth, and it has been found that embryos derived from juvenile oocytes show lower rates of development [5]. We suspected that the level of ovarian development in juvenile animals may be related to miRNA and mRNA expression levels, which contribute to limit its application on a large scale
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