Oocyte quality and in vivo embryo survival after ovarian stimulation in nulliparous and multiparous rabbit does

Microencapsulated rrBNGF as an alternative ovulation induction method in rabbits

BACKGROUND

Rabbits are an induced-ovulatory species such that exogenous hormone factors are needed to induce ovulation. Traditionally, intramuscular injections of gonadotropin-releasing hormone (GnRH) analogues are given at the time of artificial insemination (AI). To avoid the need for injections, the intravaginal delivery of molecules naturally present in seminal plasma has been explored. Here, we examined the possibility of using nerve growth factor (NGF) microencapsulated with chitosan to induce ovulation. First, the biological activity of these NGF microcapsules was assessed in pheochromocytoma of rat adrenal medulla cell (PC12) cultures, along with their effects on semen. Next, we examined the ability of the intravaginal NGF-chitosan delivery system administered at AI (NGFch-0) or 30 min before AI (NGFch-30) to elicit ovulation. To this end, progesterone concentrations on Day 7 post AI, pregnancy rates and prolificacy (kits born alive and stillbirths per doe) were determined in nulliparous and multiparous rabbit does and then compared amongst treatments: intravaginal NGFch-0 and NGFch-30, intramuscular injection of GnRH analogue, intravaginal empty-catheter (C-e) or intravaginal semen-containing catheter (C-s).

RESULTS

NGF-chitosan promoted similar PC12 differentiation to free NGF without impairing cell viability. The presence of the NGF-containing microcapsules did not interfere with semen motility, viability or capacitation status. In our in vivo experiments, nulliparous rabbits showed similar rates of ovulating females across treatments (GnRH 90%, NGFch-30 100%, NGFch-0 66.7%, C-e 83.3%), yet higher pregnancy rates were observed in response to GnRH and NGFch-30 (90% and 100%, respectively) than to NGFch-0 (60%). Prolificacy results in these does were similar across treatments. In multiparous does, GnRH treatment gave rise to the highest rate of ovulating female and pregnancy rates (100 and 90%, respectively). In contrast, the NGF-chitosan groups showed the lowest ovulating female and pregnancy rates (NGFch-30 50% and 25%, NGFch-0 41.7% and 21%, respectively). An intermediate ovulatory response was obtained in does stimulated with the catheter (C-e 70%, C-s 57.1%), and a pregnancy rate of 20% was obtained if the catheter contained diluted semen (C-s).

CONCLUSIONS

Intravaginal NGF-chitosan administered 30 min before AI induced ovulation at a similar rate to GnRH injection in nulliparous, but not multiparous, rabbit females. A better receptivity status of nulliparous females could be a determining factor for this response. However, mechanical stimulation gave rise to a high ovulation rate, so this could be masking or, in some cases, directly replacing the NGF-chitosan effect.

Integrated TWAS, GWAS, and RNAseq results identify candidate genes associated with reproductive traits in cows

Low fertility in cows leads to early removal from herds. Since reproductive traits are complex and have low heritability, genetic analysis can aid in improving reproduction. This study identified key genes linked to fertility by conducting genome- and transcriptome-wide association studies, RNA-seq analysis, meta-analysis, weighted gene co-expression network analysis, and functional enrichment analysis. Through these methods, we identified candidate genes related to Cow conception rate (CCR), Daughter pregnancy rate (DPR), Heifer conception rate (HCR), and overall fertility traits, helping to improve genetic selection for reproductive success in cows. The identified genes include RPL12, FKBP1B, FZD10, COX10, COX7A2, GAA, ETFBKMT, ACSM5, NUDT9, TIGAR, PAIP2, and PSMB5. Notably, GAA, ETFBKMT, COX10, and COX7A2 are involved in the "generation of precursor metabolites and energy" process. COX10, GAA, ETFBKMT, ACSM5, NUDT9, and TIGAR exhibit significant impacts on CCR, DPR, and HCR. COX7A2, PAIP2, and PSMB5 have been identified as hub genes related to fertility traits. RPL12 plays a role in protein synthesis, essential for gametogenesis and embryo development, while FKBP1B regulates calcium signaling, particularly in oocyte aging and fertility decline, and FZD10 is crucial in Wnt signaling. The identified genes serve as markers for genomic selection aimed at enhancing reproductive traits in cow.

Why choose the rabbit to work in reproductive technology?

Rabbits have played a significant role in both livestock production and the advancement of reproductive scientific research. Their unique biological traits, including induced ovulation and a reproductive process that closely mirrors that of humans, have been pivotal in their use as a model. Moreover, their body size is perfectly aligned with the 3Rs principles: Replacement, Reduction, and Refinement. Consequently, techniques for gamete collection and embryo recovery, followed by their use in artificial insemination or embryo transfer, are characterized by being minimally invasive. However, refining in vitro fertilization and embryo culture techniques continues to present challenges. The incorporation of cutting-edge genomic editing tools, such as CRISPR/Cas9, has reestablished rabbits as essential models in genetic and biomedical research, driving scientific progress. This review aims to describe the most effective reproductive biotechnologies for both male and female rabbits and how these methodologies are in line with the 3Rs principles-Replacement, Reduction, and Refinement-highlighting their significance in conducting ethical research.

Transcriptome profiling reveals superovulation with the gonadotropin-releasing hormone agonist trigger impaired embryo implantation in mice

Introduction

Superovulation is a critical step in assisted reproductive technology, but the use of human chorionic gonadotropin (hCG) as a trigger for superovulation can result in ovarian hyperstimulation. Thus, the use of Gonadotropin-releasing hormone agonist (GnRHa) trigger has been increasingly adopted, although it has been associated with a higher rate of pregnancy failure compared to natural cycles. This study aimed to investigate the effect of GnRHa trigger on embryo implantation in a mouse model.

Methods

Mice in the superovulation (PG) group were administered 7.5 IU of PMSG, followed by the injection of 3.5 μg of GnRHa (Leuprorelin) 48 h later, while mice in the control group (CTR) mated naturally. We compared the number of oocytes, blastocysts, and corpus luteum between the two groups and the implantation sites after the transfer of natural blastocysts. Ovaries, uterus, and serum 2 and 4 days after mating were collected for qRT-PCR, transcriptome sequencing, and hormone assays.

Results

The PG group had more oocytes, blastocysts, and corpus luteum after superovulation than the CTR group. However, the mRNA expression of leukemia inhibitory factor (Lif) and the number of implantation sites were reduced in the PG group. The ELISA assay revealed that superovulation increased ovarian estrogen secretion. The transcriptome analysis showed that superphysiological estrogen led to a response of the uterus to a high estrogen signal, resulting in abnormal endometrium and extracellular matrix remodeling and up-regulation of ion transport and inflammation-related genes.

Conclusion

Our findings suggest that a combination of PMSG and GnRHa trigger impaired embryo implantation in mice, as the excessive uterine response to superphysiological estrogen levels can lead to the change of gene expression related to endometrial remodeling, abnormal expression of uterine ion transport genes and excessive immune-related genes.

Comparative Transcriptomics Identify Key Pituitary Circular RNAs That Participate in Sheep (Ovis aries) Reproduction

CircRNAs have been found to play key roles in many biological processes and have diverse biological functions. There have been studies on circRNAs in sheep pituitary, and some important circRNAs have been found. But there are still few studies on circRNAs in sheep pituitary with different fecundity. In this study, we obtained the circRNAs expression profiles in the pituitary of FecB ++ genotype Small Tail Han sheep with different fecundity and estrous phases. A total of 34,878 circRNAs were identified in 12 pituitary samples, 300 differentially expressed circRNAs (DE circRNAs) (down: 104; up: 196) were identified in polytocous sheep in the follicular phase (PF) and monotocous sheep in the follicular phase (MF) (PF vs. MF), and 347 DE circRNAs (down: 162; up: 185) were identified in polytocous sheep in the luteal phase (PL) and monotocous sheep in the luteal phase (ML) (PL vs. ML). Cortisol synthesis and secretion pathway (follicular phase) and estrogen signaling pathway (luteal phase) were obtained by functional enrichment analysis of circRNAs source genes. Competing endogenous RNA (ceRNA) network analysis of key DE circRNAs revealed that oar-circ-0022776 (source gene ITPR2, follicular phase) targeted oar-miR-432, oar-circ-0009003 (source gene ITPR1, luteal phase) and oar-circ-0003113 (source gene PLCB1, luteal phase) targeted oar-miR-370-3p. We also explored the coding ability of DE circRNAs. In conclusion, our study shows that changes in the pituitary circRNAs may be related to the response of the pituitary to steroid hormones and regulate the reproductive process of sheep by affecting the pituitary function. Results of this study provide some new information for understanding the functions of circRNAs and the fecundity of FecB ++ genotype sheep.