Prepubertal heifers versus cows-The differences in the follicular environment

Effects of donor age and reproductive history on developmental potential of ovum pickup oocytes in Japanese Black cattle (Wagyu)

The objectives of this study were to analyze the (1) effects of donor age and multiparity on development of in vitro fertilization (IVF) embryos after ovum pickup (OPU), (2) effects of repeated and consecutive OPU-IVF procedures on embryo development, and (3) embryo production from OPU-IVF in donors with differing embryo yields after multiple ovulation and embryo transfer technology (MOET) in Japanese Black cattle (Wagyu). Donors were pre-treated with low-dosage follicle-stimulating hormone (FSH; 200 IU total), and oocytes were collected via OPU and fertilized by IVF to generate blastocysts. The number of oocytes collected per OPU session per donor was lower in heifers (2-4 years old, 5.3 oocytes) than in primiparous and pluriparous cows (2-10 years old, 13.6-19.1 oocytes; P < 0.05). Rates of blastocyst development for oocytes from heifers (33.1%) were lower than for those from cows (2-10 years old, 44.1-54.3%; P < 0.05), and average blastocyst yield/OPU/animal was lower in heifers (3.7) than in 5-6 years old cows (10.1; P < 0.05). Donors undergoing five consecutive OPU-IVF sessions after low-dosage FSH showed similar oocyte retrieval (12.2-15.1 oocytes per OPU/animal), blastocyst development rates (35.6-45.0%), and embryo yield/OPU/animal (4.8-5.8; P > 0.05) across sessions. Additionally, embryo yield from OPU-IVF was significantly improved in animals with previous low embryo yield from MOET (5.9 vs. 2.6, respectively, P < 0.05). These results indicate that Wagyu cows with previous births can be more productive as OPU-IVF donors than heifers, and oocytes from donors undergoing to five consecutive OPU-IVF cycles are competent for embryo development without loss of embryo yield/OPU/animal. Moreover, OPU-IVF can be used for embryo production and breeding from all elite Japanese Black cattle, regardless of previous low embryo yield in routine MOET.

The effect of age and FSH stimulation on the ovarian follicular response, nuclear maturation, and gene expression of cumulus-oocyte complexes in prepubertal gilts

This study investigated the effects of age and FSH treatment on the ovarian response, follicular fluid (FF) biochemical composition, nuclear maturation, and molecular profile of cumulus-oocytes complexes (COCs) recovered from prepubertal gilts. Thirty-five prepubertal gilts were separated according to age [140 (n = 20) or 160 (n = 15) days], and within each age, the gilts were allotted to receive either 100 mg of FSH [treated; G140+FSH (n = 10) and G160+FSH (n = 7)] or saline solution [control; G140+control (n = 10) and G160+control (n = 8)]. Thus, four experimental groups were included in this study. In the FSH-treated gilts, the percentage of medium follicles increased (P < 0.0001) in the same proportion with which the percentage of small follicles decreased (P < 0.0001). In addition, the glucose concentration in the FF obtained from medium follicles increased (P < 0.05), while that of triglycerides decreased (P < 0.05) in the FSH-treated gilts. The FSH stimulation also improved (P < 0.05) the number of grade I COCs obtained from medium follicles and the meiotic maturation and BCB + rates. FSH treatment only upregulated (P < 0.05) HMGCR expression in immature COCs from prepubertal gilts. The metaphase II and BCB + rates, FF glucose and plasma IGF-1 levels were greater (P < 0.05) in prepubertal gilts at 160 than at 140 days of age. Age had no effect (P > 0.05) on the transcript abundance of the target genes in immature COCs. Hence, oocytes obtained from 140-day-old prepubertal gilts appeared less meiotically competent than those of 160-day-old prepubertal gilts. Our study suggests a possible strategy of using FSH treatment to improve oocyte quantity, quality, and nuclear maturation in 140 and 160-day-old prepubertal gilts.

Optimization of gonadotropin stimulation protocols for in vitro embryo production in prepubertal Mediterranean water buffalo

Embryos can be produced from prepubertal donor animals using laparoscopic ovum pickup and in vitro embryo production technologies (LOPU-IVEP). Together, these tools can shorten the interval between generations, rapidly accelerating the rate of genetic gain. Here, we assessed the impact of different gonadotropin stimulation protocols in Mediterranean water buffalo heifer calves aged between 2 and 6 months old. Following gonadotropin stimulation, LOPU was performed at two-week intervals, with animals receiving different protocols on subsequent LOPUs. After collection, the cumulus-oocyte complexes (COCs) were matured and fertilized in vitro, and embryos were cultured to the blastocyst stage followed by transfer into synchronized adult recipients. The number and size of follicles aspirated during LOPU, the number and quality of COCs recovered, as well as cleavage, embryo development and pregnancy rates were assessed. First, we evaluated the impact of using FSH with and without eCG (administered 24-h prior to LOPU) and found that a combination of FSH and eCG was able to significantly improve embryo development rates (20.6 ± 2.0% vs. 9.0 ± 3.6%; P < 0.05). Second, we compared this protocol to a slow-release formulation of FSH reconstituted in hyaluronan. In addition to requiring less work to prepare the animals for LOPU, this slow-release formulation yielded numerically higher, but not statistically different, average number of recovered COCs (14.4 ± 2.1 vs. 10.3 ± 2.0; P > 0.05) and embryo development rates (22.9 ± 4.7% vs. 14.1 ± 5.2%; P > 0.05) compared to FSH given every 12 h. Next, we compared the length of gonadotropin treatment over 3-, 4- and 5-days prior to LOPU and found that as the length of gonadotropin treatment increased, although the number of COCs recovered steadily decreased (14.1 ± 2.4 vs. 8.7 ± 1.0 vs. 6.9 ± 0.7; P < 0.05), the embryo development rates steadily increased (14.4 ± 3.9 vs. 27.3 ± 4.4 vs. 35.9 ± 7.0; P < 0.05), presumably due to an increase in the proportion of large follicles at the time of LOPU. Numerically, the 4-day treatment yielded more transferrable embryos per donor per LOPU (2.70 ± 0.5) than 3-day (1.94 ± 0.6) and 5-day (2.25 ± 0.5) treatments. Finally, following embryo transfer, 26 of 90 recipient females became pregnant (28.9%). Pregnancies were established from all treatments, which suggests that post-implantation development was not affected among the gonadotropin treatments assessed.

In vitro embryo production from ewes at different physiological stages

BACKGROUND

The collection of ovaries from slaughterhouses is an important source of oocytes for in vitro embryo production. On the other hand, the physiological stage of slaughtered females varies and influences embryo production.

OBJECTIVES

The study examined the in vitro efficiency of embryos and demi-embryos from young, non-pregnant adult, and pregnant adult ewes from a local slaughterhouse.

METHODS

One thousand three hundred ovaries were collected from August to October 2020. The recovered oocytes were matured, fertilized, and cultured at 5% CO₂, 38.5°C, and 100% humidity. Embryo bisection was performed in 96 blastocysts (n = 32 per treatment). The demi-embryo pairs were incubated for their reconstitution for 12 h. SAS was used for data analysis.

RESULTS

The number of oocytes collected from the experimental group of non-pregnant adult ewes was higher (p ≤ 0.007) than those collected from the group of pregnant adult ewes (2.67 ± 0.19 vs. 2.18 ± 0.15 oocytes/group, respectively). The blastocyst rate was higher (p ≤ 0.0001) in the non-pregnant adult group (36.39%) than in the young (17.96%). The ratio of demi-embryos that recovered the blastocoelic cavity was higher (p < 0.05) in the young group (81.25%) than in the pregnant adult group (59.38%). The diameter of the demi-embryos was higher (p < 0.05) in the non-pregnant adult group (186.54 ± 8.70 μm) than those in the young and pregnant adult groups.

CONCLUSIONS

In conclusion, the in vitro embryo production efficiency was highest when using oocytes from non-pregnant adult ewes under the conditions of this study.

Predictors of the ovarian superstimulatory response and oocyte collection in prepubertal heifers

The objectives were to investigate the relationships between antral follicle counts and plasma AMH and FSH at the time of follicular wave emergence in prepubertal calves, and to determine the effects of age and duration of gonadotropin treatment on the ovarian superstimulatory response in pre- and post-pubertal heifers. Hereford crossbred prepubertal (Replicate 1 and 2, n = 20) and post-pubertal heifers (Replicates 1, n = 8; Replicate 2, n = 8) were assigned randomly to 2 treatment groups and given FSH for either 4 or 7 d (25 mg pFSH im at 12-h intervals). Prepubertal heifers were first treated at 4 mo and again at 7 mo of age. Blood samples were collected immediately before the first FSH administration, that was initiated 36 h after follicular ablation. An LH treatment (12.5 mg im) was given 12 h after the last FSH injection. Follicular fluid and cumulus-oocyte complexes (COC) were collected 24 h after LH treatment. At wave emergence, the number of follicles ≥1 mm (AFC, 31.1 ± 4.0 vs 16.2 ± 1.8; P < 0.001) and the plasma concentrations of AMH (606.4 ± 90.5 vs 279.6 ± 28.3 pg/mL; P = 0.001) were higher at 4 than at 7 mo of age, while plasma FSH concentrations did not differ between ages. At oocyte collection, a higher number of follicles ≥6 mm were observed in prepubertal calves at 4 mo of age and post-pubertal heifers than in calves at 7 mo of age (32.4 ± 5.4 and 22.0 ± 2.3 vs 14.9 ± 2.0, respectively; P = 0.003). Intrafollicular concentrations of estradiol were lower (23.7 ± 4.5 vs 144.0 ± 29.5 ng/mL; P < 0.0001) and of progesterone tended to be higher (217.5 ± 29.3 vs 157.0 ± 33.9 ng/mL; P = 0.07) in the 7- than in the 4-d groups. A greater number of COC was collected from calves at 4 mo of age and heifers than the 7-mo-old calves (13.4 ± 2.6 and 6.0 ± 1.0 vs 5.8 ± 1.1, respectively; P = 0.008). Overall, the 7-d FSH treatment tended to result in a greater proportion of expanded COC than the 4-d treatment in calves (50.1 ± 7.7 vs 31.9 ± 6.8%; P = 0.07). In summary, there was a positive relationship between AFC and plasma AMH concentrations at the time of wave emergence. A higher AFC was observed in calves at 4- than 7-mo of age, which resulted in greater ovarian response to gonadotropin treatment. Following an exogenous LH stimulus, COC maturation rates were greater in the 7-d than in the 4-d FSH treatment groups, resulting in collection of a higher proportion of fully expanded COC.

IGF2R, KCNQ1, PLAGL1, and SNRPN DNA methylation is completed in bovine by the early antral follicle stage

Imprinted genes are inherited with different DNA methylation patterns depending on the maternal or paternal origin of the allele. In cattle (Bos taurus), abnormal methylation of these genes is linked to the large offspring syndrome, a neonatal overgrowth phenotype analogous to the human Beckwith-Wiedemann syndrome. We hypothesized that in bovine oocytes, some of the methylation patterns on maternally imprinted genes are acquired in the last phase of folliculogenesis. The pyrosequencing analysis of IGF2R, KCNQ1, PLAGL1, and SNRPN imprinted genes showed no clear progression of methylation in oocytes from follicles 1-2 mm (late pre antral/early antral) and up. Instead, these oocytes displayed complete methylation at the imprinted differentially methylated regions (>80%). Other mechanisms related to imprint maintenance should be investigated to explain the hypomethylation at IGF2R, KCNQ1, PLAGL1, and SNRPN maternally imprinted sites observed in some bovine embryos.

Effect of Nellore (Bos indicus) donor age on in vitro embryo production and pregnancy rate

The aim of this study was to evaluate the effect of age of Nellore (Bos indicus) donors on the efficiency of in vitro embryo production (IVEP) and pregnancy rate. Thirty-six donors, including 11 female calves (13±0.61 months), 17 prepubertal heifers (25±0.78 months) and 8 cows (83±28 months), were submitted to 3 procedures of ovum pick up (OPU) on random days of the estrous cycle at intervals of 21 days. Caspase-3 and IGFBP2 were quantified in oocytes and blastocysts for the evaluation of oocyte and embryo quality. The produced embryos were vitrified (n=445) and transferred to synchronized recipients. Cows produced a larger number of follicles (cows: 54.5±6.2; calves: 20.0±0.57; prepubertal heifers: 20.8±0.46), total oocytes (cows: 45.97±7.22; calves: 28.93±6.14; prepubertal heifers: 27.21±4.94), and cleaved oocytes (cows: 21.14±4.22; calves: 13.09±3.72; prepubertal heifers: 12.4±3.19). The cleavage rate was similar between age categories; however, cows tended (p<0.07) to produce a larger number of blastocysts (9.74±2.26) per OPU than calves (5.57±1.99) and prepubertal heifers tended to have a higher blastocyst yield (35.4%) than calves (27.1%) (p<0.07). The expression levels of IGFBP2 and caspase-3 were higher in oocytes derived from calves compared to the other two categories. The pregnancy rate was higher in calves (43.1%) and cows (40.4%) than in prepubertal heifers (33.8%) (p=0.03). Despite the larger numbers of follicles and viable oocytes in cows, the blastocyst production results and pregnancy rates obtained indicate that the use of young females as oocyte donors in IVEP is feasible and may contribute to reduce the generation interval.

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.

Metabolic exchanges between the oocyte and its environment: focus on lipids

Finely regulated fatty acid (FA) metabolism within ovarian follicles is crucial to follicular development and influences the quality of the enclosed oocyte, which relies on the surrounding intra-follicular environment for its growth and maturation. A growing number of studies have examined the association between the lipid composition of follicular compartments and oocyte quality. In this review, we focus on lipids, their possible exchanges between compartments within the ovarian follicle and their involvement in different pathways during oocyte final growth and maturation. Lipidomics provides a detailed snapshot of the global lipid profiles and identified lipids, clearly discriminating the cells or fluid from follicles at distinct physiological stages. Follicular fluid appears as a main mediator of lipid exchanges between follicular somatic cells and the oocyte, through vesicle-mediated and non-vesicular transport of esterified and free FA. A variety of expression data allowed the identification of common and cell-type-specific actors of lipid metabolism in theca cells, granulosa cells, cumulus cells and oocytes, including key regulators of FA uptake, FA transport, lipid transformation, lipoprotein synthesis and protein palmitoylation. They act in harmony to accompany follicular development, and maintain intra-follicular homeostasis to allow the oocyte to accumulate energy and membrane lipids for subsequent meiotic divisions and first embryo cleavages.

Impact of oocyte donor age and breed on in vitro embryo production in cattle, and relationship of dairy and beef embryo recipients on pregnancy and the subsequent performance of offspring: A review

Genomic selection combined with in vitro embryo production (IVEP) with oocytes from heifer calves provides a powerful technology platform to reduce generation interval and significantly increase the rate of genetic gain in cattle. The ability to obtain oocytes with developmental competence from calves has been recognised for more than 60years. There is renewed interest in the potential of this reproductive technology as the beef and dairy industries seek to identify and multiply animals that satisfy consumer demand for efficient utilisation of natural resources, with minimal environmental impact and high product quality. Heifer calves show a good follicular response to FSH stimulation and oocytes can be recovered by ovum pick-up (OPU). However, the efficiency of OPU/IVEP remains lower for calves compared with peripubertal heifers and cows, in both indicus (Zebu, Bos indicus ) and taurus (Bos taurus ) breeds. Indicus cattle generally have more follicles, yield a greater number of oocytes, and have a better IVEP outcome, compared with taurus cattle. The treatment of prepubertal heifers with bovine somatotrophin (bST) and propylene glycol before OPU/IVEP has yet to show a major improvement in embryo production. Holstein (taurus) dairy heifers derived from different reproductive technologies (AI, MOET, OPU/IVEP) showed a similar age at puberty and first-lactation milk production. OPU/IVEP Holstein embryos transferred to beef or dairy cows likewise yielded heifers with the same performance. The gains in productivity that can be achieved with strategic use of OPU/IVEP in heifer calves make this a relevant and highly important reproductive technology in cattle breeding. Ongoing optimisation of the technology is needed for the potential of OPU/IVEP in young donors to be fully realised.

In Vitro Production of Embryos from Prepubertal Holstein Cattle and Mediterranean Water Buffalo: Problems, Progress and Potential

Laparoscopic ovum pick-up (LOPU) coupled with in vitro embryo production (IVEP) in prepubertal cattle and buffalo accelerates genetic gain. This article reviews LOPU-IVEP technology in prepubertal Holstein Cattle and Mediterranean Water Buffalo. The recent expansion of genomic-assisted selection has renewed interest and demand for prepubertal LOPU-IVEP schemes; however, low blastocyst development rates has constrained its widespread implementation. Here, we present an overview of the current state of the technology, limitations that persist and suggest possible solutions to improve its efficiency, with a focus on gonadotropin stimulations strategies to prime oocytes prior to follicular aspiration, and IVEP procedures promoting growth factor metabolism and limiting oxidative and endoplasmic reticulum stress.

Expression of the developmental important candidate genes in oocytes, embryos, embryonic stem cells, cumulus cells, and fibroblast cells of buffalo (Bubalus bubalis)

The present study was undertaken to study the expression of the developmental important gene transcripts in immature oocytes, mature oocytes, different stages of IVF produced embryos, embryonic stem (ES), cumulus (BCC), fetal fibroblast (BFF), newborn fibroblast (NBF) and adult fibroblast (BAF) cells of buffalo by semi-quantitative RT-PCR. The expression of GLUT1, HSP70.1, POL A Polymerase, GDF9, BMP15, and SURVIVIN transcripts was found in immature oocytes, mature oocytes, 2-cell, 4-cell, 8-16 cell, morula, and the blastocyst. Interestingly, the CX43 expression was found in oocytes, embryos, and other cell types, but it was not detected in the blastocyst. However, the IFNT expression was found in the blastocyst only, but not in other cells. The buffalo ES cells showed the expression of intracellular and cell surface markers (NANOG, OCT4, SOX2, FOXD3, SSEA-3, SSEA-4, TRA-1-60, and TRA-1-81) and alkaline phosphatase activity. Two ES cell lines (S-line and M-line-II) were continued to survive up to 98th passages (~630 days) and 97th passages (~624 days), respectively. It was interesting to note that GLUT1, CX43, HSP70.1, POL A Polymerase, GDF9, BMP15, and SURVIVIN transcripts (except the IFNT) were expressed in buffalo ES, BCC, BFF, NBF and BAF cells. This is the first preliminary report that the buffalo ES, BCC, BFF, NBF, and BAF cells expressed the several developmental important candidate genes. It is concluded that the expression of the major developmental important genes was not only expressed in the oocytes and embryos but also expressed in the ES, BCC, BFF, NBF, and BAF cells of buffalo.

Response of Bovine Cumulus-Oocytes Complexes to Energy Pathway Inhibition during In Vitro Maturation

Glucose or fatty acids (FAs) metabolisms may alter the ovarian follicle environment and thus determine oocyte and the nascent embryo quality. The aim of the experiment was to investigate the effect of selective inhibition of glucose (iodoacetate + DHEA) or FA (etomoxir) metabolism on in vitro maturation (IVM) of bovine COCs (cumulus-oocyte complexes) to investigate oocyte's development, quality, and energy metabolism. After in vitro fertilization, embryos were cultured to the blastocyst stage. Lipid droplets, metabolome, and lipidome were analyzed in oocytes and cumulus cells. mRNA expression of the selected genes was measured in the cumulus cells. ATP and glutathione relative levels were measured in oocytes. Changes in FA content in the maturation medium were evaluated by mass spectrometry. Our results indicate that only glucose metabolism is substantial to the oocyte during IVM since only glucose inhibition decreased embryo culture efficiency. The most noteworthy differences in the reaction to the applied inhibition systems were observed in cumulus cells. The upregulation of ketone body metabolism in the cumulus cells of the glucose inhibition group suggest possibly failed attempts of cells to switch into lipid consumption. On the contrary, etomoxir treatment of the oocytes did not affect embryo development, probably due to undisturbed metabolism in cumulus cells. Therefore, we suggest that the energy pathways analyzed in this experiment are not interchangeable alternatives in bovine COCs.

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.

The Effect of Stress on Reproduction and Reproductive Technologies in Beef Cattle-A Review

Researchers have contributed by increasing our understanding of the factors affecting reproduction in beef, mainly physical health and nutrition aspects, which have been main concerns during decades. Animal welfare is of outmost relevance in all animal production systems and it is strongly associated to stress. Stress responses involve endocrine, paracrine and neural systems and the consequences of this stress on the reproductive efficiency of specifically, beef cattle and bulls, need to be highlighted. We, therefore, describe the fundamentals of stress and its quantification, focusing in beef herds, reviewing the highly valuable pieces of research, already implemented in this field. We examine major factors (stressors) contributing to stress in beef cattle and their effects on the animals, their reproductive performance and the success of reproductive biotechnologies. We include terms such as acclimatization, acclimation or temperament, very relevant in beef systems. We examine specifically the management stress due to handling, social environment and hierarchy or weaning effects; nutritional stress; and thermal stress (not only heat stress) and also review the influence of these stressors on reproductive performance and effectiveness of reproductive biotechnologies in beef herds. A final message on the attention that should be devoted to these factors is highlighted.

Energy metabolism of follicular environment during oocyte growth and maturation

Oocyte quality is affected by many factors, among which the environment of growth and maturation seems to be crucial. Studies show that well balanced oocyte energy metabolism has a significant impact on several elements of cytoplasmic and nuclear maturation as well as further embryo developmental competence. Therefore homeostasis between metabolism of glucose and fatty acids in the oocyte is being widely described nowadays. This review aims to discuss the follicular (in vivo) or maturation media (in vitro) environments with regard to glucose and fatty acid metabolism, as the main sources of the energy for the oocyte. A great emphasis is given on the balance between those two metabolic pathways and its further impact on female fertility.

The dynamics of gene expression, lipid composition and DNA methylation reprogramming are different during in vitro maturation of pig oocytes obtained from prepubertal gilts and cycling sows

This study aimed to characterize the gene expression, lipid composition and DNA methylation reprogramming during in vitro maturation (IVM) of pig oocytes with different developmental competencies. We used prepubertal gilts and cycling sows as a model to obtain oocytes with different levels of competency. We found that genes involved in lipid metabolism, SLC27A4, CPT2 and PLIN2, and DNA methylation, DNMT3A, TET1 and TET3, possessed altered transcript expression levels during IVM. Specifically, SLC27A4 mRNA (p = 0.05) increased in oocytes from cycling females, whereas CPT2 (p = 0.05), PLIN2 (p = 0.02) and DNMT3A (p = 0.02) increased in oocytes from prepubertal females during IVM. Additionally, TET3 mRNA increased during IVM in oocytes from prepubertal (p = 0.0005) and cycling females (p = 0.02). The TET1 transcript decreased (p = 0.05) during IVM in oocytes from cycling sows. Regarding lipid composition, mass spectrometry revealed a cluster of ions, with molecular masses higher than m/z 700, which comprises a group of complex phospholipids, was identified in all groups of oocytes, except in those from prepubertal gilts. With respect to DNA methylation reprogramming, it was noted that the less competent oocytes were not able to reprogramme the XIST gene during IVM. We conclude that the maternal mRNA store, lipid composition and epigenetic reprogramming are still being established during maturation and are related to oocyte competence. In addition, we propose that the methylation pattern of the XIST may be used as molecular marker for oocyte competence in pigs.

Adult follicular fluid supplementation during in vitro maturation improves the developmental competence of prepubertal lamb oocytes

Oocytes from prepubertal lambs have lower developmental ability than that from adult ewes. Follicular fluid (FF) provides an important microenvironment for oocyte development and maturation in vivo. The aim of this study was to examine the effects of FF supplemented during in vitro maturation (IVM) on the developmental competence of prepubertal lamb oocytes. FF was collected from follicle-stimulating hormone (FSH) stimulated adult ewes or 4‒6-week-old lambs or abattoir-derived adult ovaries. The FF was supplemented to the control IVM medium, TCM199 containing 20% estrus sheep serum and hormones. It was found that the lamb oocytes matured in medium supplemented with 20% or 30% adult FF from FSH-stimulated ewes yielded significantly higher blastocyst rates than that from the control medium, or medium supplemented with 10% adult FF or 20% lamb FF (43.5%, 37.9% vs. 28.4%, 29.7%, 27.6%, P < 0.05). However, when adult oocytes were matured in medium supplemented with 20% adult FF, their cleavage and blastocyst development were similar to that of those matured in control medium. Addition of 20% adult FF from abattoir-derived ovaries to IVM medium also significantly increased the blastocyst formation of lamb oocytes when compared to that from the medium without FF supplementation. The blastocyst development did not differ between the groups of FF from abattoir-derived ovaries and from FSH-stimulated ewes (38.2% vs 43.1%, P > 0.05). A total of 146 blastocysts derived from different groups of lamb oocytes were transferred into 76 synchronized recipients, of which 50% were pregnant and 38.2% lambed. These results suggest that supplementing IVM medium with adult FF has beneficial roles on the developmental competence of prepubertal lamb oocytes.

Maternal age affects oocyte developmental potential at both ends of the age spectrum

Maternal age has a significant effect on oocyte developmental competence. Overall, evidence suggests that oocytes from both prepubertal females and reproductively aged females are inherently less competent. Reduced oocyte quality in both age groups is problematic for human medicine and agriculture. Some of the cellular mechanisms implicated in poor oocyte quality associated with maternal age are mitochondrial function and location, reduction of oxygen radicals, balance of metabolic pathways, regulation of maternal mRNAs and appropriate communication between the oocyte and cumulus cells. However, additional knowledge must be gained about the deficiencies present in prepubertal and reproductively aged oocytes that result in poor developmental potential before significant improvement can be achieved. This review discusses the evidence currently available regarding oocyte quality at both ends of the maternal age spectrum, what we know, or hypothesise, about the mechanisms involved and current thoughts regarding potential treatment for improvement.

Lipid Identification and Transcriptional Analysis of Controlling Enzymes in Bovine Ovarian Follicle

Ovarian follicle provides a favorable environment for enclosed oocytes, which acquire their competence in supporting embryo development in tight communications with somatic follicular cells and follicular fluid (FF). Although steroidogenesis in theca (TH) and granulosa cells (GC) is largely studied, and the molecular mechanisms of fatty acid (FA) metabolism in cumulus cells (CC) and oocytes are emerging, little data is available regarding lipid metabolism regulation within ovarian follicles. In this study, we investigated lipid composition and the transcriptional regulation of FA metabolism in 3–8 mm ovarian follicles in bovine. Using liquid chromatography and mass spectrometry (MS), 438 and 439 lipids were identified in FF and follicular cells, respectively. From the MALDI-TOF MS lipid fingerprints of FF, TH, GC, CC, and oocytes, and the MS imaging of ovarian sections, we identified 197 peaks and determined more abundant lipids in each compartment. Transcriptomics revealed lipid metabolism-related genes, which were expressed constitutively or more specifically in TH, GC, CC, or oocytes. Coupled with differential lipid composition, these data suggest that the ovarian follicle contains the metabolic machinery that is potentially capable of metabolizing FA from nutrient uptake, degrading and producing lipoproteins, performing de novo lipogenesis, and accumulating lipid reserves, thus assuring oocyte energy supply, membrane synthesis, and lipid-mediated signaling to maintain follicular homeostasis.

Oleic acid in the modulation of oocyte and preimplantation embryo development

Potential reproductive effects are considered as the major aspect of biomolecules functionality in an organism. The recent identification of differential patterns of fatty acids across ovarian follicles and their association with levels of sexual maturity highlights the importance of these biomolecules. It is well known that fatty acids are highly diverse in terms of their functional properties. Oleic acid is chemically classified as an unsaturated omega-9 fatty acid. Besides serving as an important energy source, oleic acid is involved in metabolic and structural roles. Free and esterified oleic acids are compartmentalized into discrete extracellular fluids, cell organelles and found within the cytosol. This review summarizes the current knowledge on the contribution of oleic acid in regulating female fertility, particularly its involvement in female germ cell growth and development. Oleic acid has been identified as a blastomeric and post-cryopreservation survival biomarker in bovine. Several related studies have shown the critical role of oleic acid in counteracting the detrimental effects of saturated fatty acids and in paracrine support of oocyte development. Although available data are not ideally detailed, most data suggest that oleic acid can contribute to normal oocyte and preimplantation embryo development via mechanisms involving metabolic partitioning of fatty acids, change in the membrane structural organization, attenuation of oxidative stress and regulation of intracellular signalling. Thus, oleic acid may play a significant role in oocyte and early embryo development, suggesting that future studies should explore in more detail its potential effects on the physiopathology of female reproduction.

[Impact of GOLPH3 expression in cumulus granulosa cells on outcomes of intracytoplasmic sperm injection]

OBJECTIVE

To evaluate the impact of GOLPH3 expression in cumulus granulosa cells on the outcomes of intracytoplasmic sperm injection (ICSI).

METHODS

A total of 119 women receiving ICSI due to male infertility at our center between April, 2012 and June, 2014 were enrolled in the study. Cumulus granulosa cells were collected from the women for detection of GOLPH3 expressions using immunocytochemistry, Western blotting, and real-time PCR. GOLPH3 expression rate was compared between women with and without clinical pregnancy following ICSI, and the associations of GOLPH3 expression with the laboratory indicators of ICSI outcomes were assessed.

RESULTS

Immunocytochemistry showed that GOLPH3 expression was located mainly in in the plasma of the cumulus granulosa cells. The rate and intensity of GOLPH3 expression in the cumulus granulosa cells differed significantly between women with and without clinical pregnancy following ICSI (P<0.05). GOLPH3 expression was found to positively correlate with the numbers of punctured follicles, grade III oocyte cumulus complex, ICSI oocytes, fertilized oocytes, cleavage, high quality embryos, blastocysts, high quality blastocysts, and frozen embryos (all P<0.01). The results of RTPCR and Western blotting revealed significant differences in GOLPH3 expressions at both the mRNA and protein levels in the cumulus granulosa cells between the pregnant and non-pregnant groups after ICSI (t=14.560, P=0.000). Western blot analysis revealed significant difference of GOLPH3 protein expression in cumulus granulosa cells between women with and without clinical pregnancy following ICSI.

CONCLUSION

GOLPH3 expression in the cumulus granulosa cells plays an important role in the development of oocytes and promotion of conception to affect the outcomes of ICSI.

The Role of Oocyte Organelles in Determining Developmental Competence

The ability of an oocyte to undergo successful cytoplasmic and nuclear maturation, fertilization and embryo development is referred to as the oocyte’s quality or developmental competence. Quality is dependent on the accumulation of organelles, metabolites and maternal RNAs during the growth and maturation of the oocyte. Various models of good and poor oocyte quality have been used to understand the essential contributors to developmental success. This review covers the current knowledge of how oocyte organelle quantity, distribution and morphology differ between good and poor quality oocytes. The models of oocyte quality are also described and their usefulness for studying the intrinsic quality of an oocyte discussed. Understanding the key critical features of cytoplasmic organelles and metabolites driving oocyte quality will lead to methods for identifying high quality oocytes and improving oocyte competence, both in vitro and in vivo.

Interactions of bovine oocytes with follicular elements with respect to lipid metabolism

Among many factors, lipid metabolism within the follicular environment emerges as an important indicator of oocyte quality. In the literature a crucial significance is described concerning follicular fluid (FF) composition as well as messenger RNA (mRNA) expression in follicular cells. The aim of this study was to describe the relationship between oocyte, FF and follicular cells with regard to lipid metabolism. The set of data originating from individual follicles comprised: lipid droplets (LD) number in oocytes (BODIPY staining), mRNA expression of seven genes in cumulus and granulosa cells (SCD, FADS2, ELOVL2, ELOVL5, GLUT1, GLUT3, GLUT8; real time polymerase chain reaction) and fatty acid (FA) composition in FF (gas chromatography). Obtained results demonstrate significant correlation between oocyte lipid droplets number and FA composition in FF. However, gene expression studies show significant correlation between LD number and GLUT1 gene only. Moreover, the present experiment revealed correlations between FA content in FF and expression of several genes (SCD, FADS2, ELOVL5, GLUT8) in granulosa cells, whereas only the SCD gene in cumulus cells. We suggest that the results of our experiment indicate the importance of glucose : lipid metabolism balance, which contributes to better understanding of energy metabolism conversion between oocytes and the maternal environment.