iTRAQ-based proteomic profiling of granulosa cells from lamb and ewe after superstimulation

Use of assisted reproductive technologies (ARTs) to shorten the generational interval in ruminants: current status and perspectives

The challenges posed by climate change and increasing world population are stimulating renewed efforts for improving the sustainability of animal production. To meet such challenges, the contribution of genomic selection approaches, in combination with assisted reproductive technologies (ARTs), to spreading and preserving animal genetics is essential. The largest increase in genetic gain can be achieved by shortening the generation interval. This review provides an overview of the current status and progress of advanced ARTs that could be applied to reduce the generation time in both female and male of domestic ruminants. In females, the use of juvenile in vitro embryo transfer (JIVET) enables to generate offspring after the transfer of in vitro produced embryos derived from oocytes of prepubertal genetically superior donors reducing the generational interval and acceleration genetic gain. The current challenge is increasing in vitro embryo production (IVEP) from prepubertal derived oocytes which is still low and variable. The two main factors limiting IVEP success are the intrinsic quality of prepubertal oocytes and the culture systems for in vitro maturation (IVM). In males, advancements in ARTs are providing new strategies to in vitro propagate spermatogonia and differentiate them into mature sperm or even to recapitulate the whole process of spermatogenesis from embryonic stem cells. Moreover, the successful use of immature cells, such as round spermatids, for intracytoplasmic injection (ROSI) and IVEP could allow to complete the entire process in few months. However, these approaches have been successfully applied to human and mouse whereas only a few studies have been published in ruminants and results are still controversial. This is also dependent on the efficiency of ROSI that is limited by the current isolation and selection protocols of round spermatids. In conclusion, the current efforts for improving these reproductive methodologies could lead toward a significant reduction of the generational interval in livestock animals that could have a considerable impact on agriculture sustainability.

Growth hormone treatment improves the development of follicles and oocytes in prepubertal lambs

BACKGROUND

When prepubertal lambs are superovulated, the ovarian response to gonadotropin stimulation has great individual difference and the collected oocytes have lower developmental ability than that of adult ewes. Over the years, growth hormone (GH) has been used in assisted reproduction because it can improve the reproductive performance in humans and animals. However, the effect of GH on ovaries and oocytes of prepubertal lambs remains unclear.

METHODS

Before and during follicle-stimulating hormone (FSH) superovulation of prepubertal lambs (4‒6-week-old), the lambs were treated with high (50 mg) or low dose (25 mg) of ovine GH in a long (5 days) or short (2 days) period. The recovered oocytes were used for in vitro maturation and fertilization, and several parameters of oocyte quality and development capacity were evaluated. The possible underlying mechanisms of GH action were explored by analysis of granulosa cell (GC) transcriptome, ovarian proteome and follicular fluid metabolome.

RESULTS

Treatment of lambs with 50 mg GH over 5 days (long treatment) potentially promoted the response of lambs to superovulation and improved the development capacity of retrieved oocytes, consequently increasing the high quality embryo yield from lambs. A number of differently expressed genes or proteins were found in ovaries between GH-treated and untreated lambs. Cellular experiments revealed that GH reduced the oxidative stress of GCs and promoted the GC proliferation probably through activation of the PI3K/Akt signaling pathway. Finally, analysis of follicular fluid metabolome indicated that GH treatment altered the abundance of many metabolites in follicular fluid, such as antioxidants and fatty acids.

CONCLUSIONS

GH treatment has a beneficial role on function of lamb ovaries, which supports the development of follicles and oocytes and improves the efficiency of embryo production from prepubertal lambs.

miRNA expression analysis of the sheep follicle during the prerecruitment, dominant, and mature stages of development under FSH stimulation

Follicle stimulating hormone (FSH) has been widely reported to influence ovarian follicular development, and miRNAs play a significant role in mammalian follicular development by regulating their target genes. Therefore, it is of interest to explore the roles of miRNAs in sheep follicular development during FSH stimulation. In the current study, we constructed miRNA expression profiles of small follicles (SFs, prerecruitment stage), medium follicles (MFs, dominance stage), and large follicles (LFs, maturation stage). Three and 50 significant differentially expressed miRNAs (DEMs) were identified in the MF vs. SF and LF vs. SF comparisons, respectively, and none were identified in the LF vs. MF comparison. Oar-miR-10a was significantly downregulated in MFs compared with SFs. In LFs compared with SFs, miR-212-3p, miR-212-5p and miR-202-5p were significantly upregulated, and miR-27a-3p, miR-181a-5p, miR-204-5p, and miR-182-5p were significantly downregulated. Furthermore, we predicted the target genes of significant DEMs and performed functional enrichment analyses of these target genes. Analyses of KEGG pathways and GO terms showed that the putative target genes were significantly enriched in ovarian steroidogenesis, glutathione metabolism, positive regulation of cell differentiation, positive regulation of cell development, and cellular response to oxygen-containing compounds. Analyses of miRNA-gene regulatory networks suggested that miR-181a-5p-CYP11A1, (miR-27a-3p and miR-129-5p)-LDLR, (miR-212-3p and miR-212-5p)-EFNA5, (miR-181a-5p, miR-182-5p, and miR-27a-3p)-INHBA, and miR-182-5p-SOD2 might be involved in follicular development. The present study provides basic data and suggests research directions for further exploration of the roles of miRNAs in sheep follicular development under FSH stimulation.

Transcriptomic comparison of ovarian granulosa cells between adult sheep and prepubertal lambs

BACKGROUND

The oocyte development ability of prepubertal animals is significantly lower than that of adult animals. Granulosa cells (GCs) have an important function on regulation of follicular and oocyte development. Therefore, analysis of GC characteristics can be used to explore the developmental mechanism of follicles and oocytes.

RESULTS

In order to understand the possible reasons for the differences in follicle and oocyte development between lambs and adult sheep, we utilized high-throughput sequencing technique to analyze the transcriptome of GCs from follicle-stimulating hormone (FSH) superstimulated adult ewes and prepubertal lambs. Adult ewes were treated with FSH for 3 days (group A) and lambs were FSH-treated for 2 days (group B) or 3 days (group C). Transcriptome analysis of GCs showed that there were 405 and 159 differentially expressed genes from A vs. B and A vs. C, respectively. The results indicated that prolonging the FSH-treatment of lambs made the GC state of lambs more similar to the adult ewes, but there were still a large number of differentially expressed genes between adult ewes and lambs. Further analysis showed that many differently expressed genes were implicated in cell proliferation and apoptosis, oocyte development and follicular ovulation. Cellular examination demonstrated that fatty acid binding protein 4 (FABP4), which was highly expressed in lamb GCs, had a potential of promoting cell apoptosis. Cytoplasmic phospholipase A2 (PLA2G4A), which was expressed lowly in lamb GCs, may be responsible for reduced synthesis of prostaglandins in cells and impaired follicle/oocyte development. In contrast, glutathione S-transferase β-1 (GSTT2B) and forkhead boxO6 (FOXO6) had no apparent effect on the proliferation and apoptosis of GCs.

CONCLUSIONS

Our study found dramatic transcriptomic differences in GCs between lambs and adult sheep, which may explain the possible reasons for the defects of follicle and oocyte development in lambs compared to adult sheep. Our data provides important information for further understanding the mechanism of follicular development in prepubertal animals and improving their oocyte developmental competence.

The Roles of the miRNAome and Transcriptome in the Ovine Ovary Reveal Poor Efficiency in Juvenile Superovulation

Simple Summary

Using 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.

Abstract

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.

Transcriptome analysis of sheep follicular development during prerecruitment, dominant, and mature stages after FSH superstimulation

Sheep is usually a monovular animal; superovulation technology is used to increase the number of offspring per individual and shorten generation intervals. To date, mature FSH superstimulatory treatments have been successfully used in sheep breeding, but much remains unknown about genes, pathways, and biological functions involved in follicular development. Therefore, in this study, we performed transcriptome profiling of small follicles (SFs; 2-2.5 mm), medium follicles (MFs; 3.5-4.5 mm), and large follicles (LFs; > 6 mm) in Mongolian ewes after FSH superstimulation. Furthermore, we identified differentially expressed genes and performed Kyoto Encyclopedia of Genes and Genomes pathway and Gene Ontology enrichment analyses in 3 separate pairwise comparisons. We found that ovarian steroidogenesis was significantly enriched in the SFs versus MFs analysis; the associated genes, cytochrome P450 family 19 (CYP19) and Hydroxy-delta-5-steroid dehydrogenase 3 beta- and steroid delta-isomerase 1 (HSD3B1), were significantly upregulated. Moreover, proline metabolism, glutathione metabolism, and PPAR signaling pathways were significantly enriched in the LFs versus SFs analysis; the associated genes, glutamate-cysteine ligase modifier subunit (GCLM) and cystathionine gamma-lyase (CTH), were significantly upregulated, whereas peroxisome proliferator-activated receptor gamma (PPARγ) was significantly downregulated. In summary, our study provides basic data and possible biological direction to further explore the molecular mechanism of sheep follicular development after FSH superstimulation.

TMT-based quantitative proteomic analysis of cumulus cells derived from vitrified porcine immature oocytes following in vitro maturation

As the immature oocytes are submitted to cryopreservation, their surrounding cumulus cells (CCs) will inevitably suffer, which may have some adverse effects on subsequent oocyte maturation and development. So far, little is known about the molecular differences in CCs of immature oocytes after vitrification. The aim of this study therefore was to analyze the protein profile of CCs derived from vitrified porcine immature oocytes following in vitro maturation, using TMT-based quantitative proteomic approach. A total of 5910 proteins were identified, and 88 of them presented significant difference, with 46 up-regulated and 42 down-regulated proteins. Gene Ontology enrichment analysis revealed that cell cycle phase transition, mitotic cell cycle phase transition, positive regulation of cell differentiation and regulation of oogenesis were significantly down-regulated within the biological process. After Kyoto Encyclopedia of Genes and Genomes pathway analysis, some up-regulated proteins were significantly enriched in TGF-beta signaling pathway and 4 pathways related to steroid hormones. Furthermore, 10 selected proteins were quantified and verified by a parallel reaction monitoring technique, indicating a high reliability of the TMT results. In conclusion, vitrification affects protein profile of CCs as well as their biological functions, which will offer a new perspective to understand the reasons for decline in maturation quality of vitrified immature oocytes.

Comparative proteomic analysis of hypothalamus tissue from Huoyan geese between pre-laying period and laying period using an iTRAQ-based approach

The hypothalamus plays a central role in controlling poultry endocrine and reproductive activities. So far there is limited information focused on the proteome profiles of the hypothalamus from geese during different stages of the egg-laying cycle. In order to identify proteins regulating the egg-laying process of Huoyan geese, we investigated the proteome profiles of the hypothalamus from Huoyan geese during the laying period and pre-laying period by applying an isobaric tags for relative and absolute quantitation (iTRAQ)-based proteomic technology. A total number of 3,337 were identified and quantified, of which 18 were significantly up-regulated and 16 were significantly down-regulated. These differentially expressed proteins were subjected to bioinformatics analyses based on the Gene Ontology annotation and Kyoto Encyclopedia of Genes and Genomes pathway. Some of these were revealed to be involved in hormone and neurotransmitter secretion, exocytosis, calcium ion transport and synaptic transmission. Subsequently, excitatory amino acid transporter 2, complexin-1 and inositol 1,4,5-trisphosphate receptor, type 3 were confirmed at the messenger RNA level using quantitative real-time RT-PCR. Then, the abundance change of these proteins was verified further using Western blotting analysis. These data may aid in elucidating the molecular mechanism of higher laying performance in Huoyan geese.