The time interval between FSH-P administration and slaughter can influence the developmental competence of beef heifer oocytes

Effect of use and dosage of p-follicle-stimulating hormone for ovarian superstimulation before ovum pick-up and in vitro embryo production in pregnant Holstein heifers

The benefit of ovarian superstimulation using exogenous FSH before ovum pick-up (OPU) and in vitro embryo production (IVEP) has been the subject of conflicting results. The objective of the present study, therefore, was to evaluate the effect of use and dose of porcine FSH (p-FSH) before OPU/IVEP on ovarian response and embryo production in pregnant heifers. Pregnant Holstein heifers (n = 48) were randomly assigned to receive 0, 160, or 300 mg NIH-FSH-P1 in a crossover design. Ovum pick-up was performed at 49, 63, and 77 d of gestation with a 14 d "washout" between OPU sessions. Follicle ablation was performed on D 0 (p.m.) and p-FSH treatments, consisting of 4 decreasing dose injections administered 12 h apart, were initiated 36 h after follicle ablation (d 2 a.m.). Heifers underwent OPU on D 5 (a.m.), 40 h after the last p-FSH treatment, and cumulus oocyte complexes (COC) were subjected to IVEP procedures. Differences between treatment groups were evaluated using generalized linear mixed models. There were quadratic effects of treatment on both number and percentage of small (<6 mm), medium (6-10 mm), and large (>10 mm) follicles. Number and percentage of medium follicles increased with increasing p-FSH dosages, although the magnitude of the change was greater between 0 and 160 mg, than between 160 and 300 mg of p-FSH. Total number of follicles, number of COC recovered and number of viable COC increased linearly with increasing p-FSH dose. Conversely, there was no evidence for an effect of p-FSH dose on COC recovery percentage nor the percentage of viable COC. Cleavage percentage, number of cleaved oocytes, blastocyst percentage, and number of blastocysts increased linearly with increasing p-FSH dose. In conclusion, use of p-FSH before OPU resulted in greater superstimulatory response and oocyte competence which in turn increased IVEP. Furthermore, these effects were dose dependent such that use of a greater dose of p-FSH up to 300 mg progressively increased embryo yield.

The coasting time affects the quality of cumulus-oocyte complexes in superstimulated ewes

We hypothesized that the coasting time may be beneficial to the quality of cumulus-oocyte complexes recovered from live ewes, as reported in cattle. The present study assessed the effect of coasting times on the quantity and quality of cumulus-oocyte complexes (COCs) in sheep. All ewes were subjected to the "Day 0 protocol", followed by an ovarian stimulation (80 mg of pFSH in three decreasing doses), varying only the coasting time [12 (G12), 36 (G36), or 60 h (G60]. In Experiment 1, data regarding follicular population was assessed. In Experiment 2, the COC quality was checked by their morphology, brilliant cresyl blue (BCB) test, evaluation of chromatin condensation pattern, and oocyte diameter. In Experiment 3, genes related to oocyte developmental competence were evaluated in BCB + COCs. The oocytes in the G60 group had more (P < 0.05) large follicles than the other groups and oocytes with a greater diameter than the G12. Oocyte morphology was similar (P > 0.05) among groups, as well as the BCB + COCs quantity. The G60-oocytes presented a better (P < 0.05) configuration of chromatin condensation compared with the other groups and a greater (P < 0.05) gene expression of BMP15, MATER, ZAR1, and PTGS2 compared with G12, and PTGS2 and HAS2 compared with G36 group. In conclusion, 60 h of coasting time positively affects the quality of COCs recovered after subjecting ewes to the "Day 0 protocol" and ovarian superstimulation. Implementing the appropriate coasting time to a given protocol can positively impact the in vitro embryo production outcomes in sheep.

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.

Follicle priming by FSH and pre-maturation culture to improve oocyte quality in vivo and in vitro

Nowadays there is strong demand to produce embryos from premium quality cattle, and we can produce embryos using oocytes collected from living premium animals by ovum-pick up (OPU) followed by in vitro fertilization (IVF). However, the developmental competence of IVF oocytes to form blastocysts is variable. The developmental competence of oocytes depends on the size and stages of follicles, and follicle-stimulating hormone priming (FSH-priming) prior to OPU can promote follicular growth and improve the developmental competence of oocytes. Furthermore, following the induction of ovulation using an injection of luteinizing hormone or gonadotropin-releasing hormone after FSH-priming, we can collect in vivo matured oocytes from ovulatory follicles, which show higher developmental competence than oocytes matured in vitro. However, the conventional protocols for FSH-priming consist of multiple FSH injection for 3-4 days, which is stressful for the animal and labor-intensive for the veterinarian. In addition, these techniques cannot be applied to IVF of oocytes collected from bovine ovaries derived from slaughterhouses, which are important sources of oocytes. Here, we review previous research focused on FSH-priming, especially for collecting in vivo matured oocytes and a simplified method for superstimulation using a single injection of FSH. We also introduce the previous achievements using in vitro pre-maturation culture, which can improve the developmental competence of oocytes derived from non-stimulated animals.

Folliculogenesis and acquisition of oocyte competence in cows

IVF success depends on hundreds of factors and details but the oocyte quality remains the most important and problematic issue. All antral follicles contain oocytes and all of them have that have reached their full size, can be aspirated, can mature and can be fertilized in vitro. But only a few will make it to embryo unless harvested at a very specific time/status. The conditions impacting the oocyte competence are essentially dependant on the follicular status. Growing follicles contains oocytes that have not completed their preparation, as they are still writing information (RNA), later, dominant follicles or follicles at the plateau phase, stop transcription and become candidates for development. Once in transcriptional arrest, the oocytes, if not ovulated in a short amount of time, do not always make good embryos. This window is affected by time and follicle size and looks like a bell curve. The following review further explain the physiological and molecular evidences that we have to illustrate the competence window and provides clues on how to optimize ovarian stimulation to maximise oocyte quality.

40 years of bovine IVF in the new genomic selection context

The development of a complex technology such as in vitro fertilization (IVF) requires years of experimentation, sometimes comparing several species to learn how to create the right in vitro environment for oocytes, spermatozoa and early embryos. At the same time, individual species characteristics such as gamete physiology and gamete interaction are recently evolved traits and must be analysed within the context of each species. In the last 40 years since the birth of Louise Brown, IVF techniques progressed and are now used in multiple domestic and non-domestic animal species around the world. This does not mean that the technology is completely matured or satisfactory; a number of problems remain to be solved and several procedures still need to be optimized. The development of IVF in cattle is particularly interesting since agriculture practices permitted the commercial development of the procedure and it is now used at a scale comparable to human IVF (millions of newborns). The genomic selection of young animals or even embryos combined with sexing and freezing technologies is driving a new era of IVF in the dairy sector. The time has come for a retrospective analysis of the success and pitfalls of the last 40 years of bovine IVF and for the description of the challenges to overcome in the years to come.

In vitro-production of embryos using immature oocytes collected transvaginally from superstimulated wood bison (Bison bison athabascae)

Two experiments were done to test the hypothesis that morphologic characteristics of wood bison cumulus-oocyte complexes (COC) are reflective of the ability of the oocyte to develop to an advanced embryonic stage after in vitro maturation, fertilization and culture, and to determine the effect of prolonging the interval from the end of superstimulation treatment to oocyte collection (FSH starvation period). Experiments were done during the anovulatory season. In Experiment 1, ovarian superstimulation was induced in 10 bison with two doses of FSH given at 48 h intervals beginning at the time of follicular wave emergence. COC were collected 3 days (72 h) after the last dose of FSH by follicular aspiration and classified as compact, expanded or denuded. The COC were matured in vitro for 24 h before fertilization in vitro (Day 0). Embryo development was assessed on Days 3, 7 and 8. The blastocyst rate was 7/34, 2/10 and 0/3 in COC classified as compact, expanded and denuded, respectively; however, only compact COC resulted in embryos that reached the expanded blastocyst stage. In Experiment 2, COC were collected at either 3 or 4 days (72 or 96 h) after the last dose of FSH (n = 16 bison/group) to determine the effect of the duration of FSH starvation on oocyte competence. The COC were classified as compact good (>3 layers of cumulus cells), compact regular (1-3 layers of cumulus cells), expanded or denuded, and then matured, fertilized and cultured in vitro. Although follicles were larger (P < 0.05) in the 4-day FSH starvation group, there was no effect of starvation period on the distribution of COC morphology; overall, 112/194 (57.7%) were compact, 29/194 (26.3%) were expanded, 39/194 (20.1%) were denuded, and 14/194 (7.2%) were degenerated (P < 0.05). Similarly, there was no effect of starvation period on embryo development. Compact good COC had the highest cleavage (88%) and blastocyst rates (54%; P < 0.05), followed by compact regular COC at 73% and 25%, respectively. Expanded and denuded COC had low cleavage (40% vs. 59%, respectively) and blastocyst rates (5% vs. 8%, respectively). We conclude that morphologic characteristics of wood bison COC are reflective of the ability of the oocyte to develop into an embryo in vitro. Importantly, oocytes collected from superstimulated bison during the anovulatory season were competent to develop to the blastocyst stage following in vitro maturation, fertilization and culture.

Effect of insulin-transferrin-selenium (ITS) and l-ascorbic acid (AA) during in vitro maturation on in vitro bovine embryo development

The aim of this study was to evaluate the effect of adding a combination of insulin, transferrin and selenium (ITS) and l-ascorbic acid (AA) during in vitro maturation (IVM) and in vitro culture (IVC) on in vitro embryo production. To verify the effect of the supplements, cleavage and blastocyst rates, embryo size and total cell number were performed. Embryonic development data, embryo size categorization and kinetics of maturation were analyzed by chi-squared test, while the total cell number was analyzed by a Kruskal-Wallis test (P < 0.05). When ITS was present during IVM, IVC or the entire culture, all treatments had a cleavage and blastocyst rates and embryo quality, similar to those of the control group (P < 0.05). Supplementation of IVM medium with ITS and AA for 12 h or 24 h showed that the last 12 h increased embryo production (51.6%; n = 220) on D7 compared with the control (39.5%; n = 213). However, no improvement was observed in blastocyst rate when less competent oocytes, obtained from 1-3 mm follicles, were exposed to ITS + AA for the last 12 h of IVM, with a blastocyst rate of 14.9% (n = 47) compared with 61.0% (n = 141) in the control group. The results suggest that the addition of ITS alone did not affect embryo production; however, when combined with AA in the last 12 h of maturation, there was improvement in the quantity and quality of embryos produced. Furthermore, the use of ITS and AA during IVM did not improve the competence of oocytes obtained from small follicles.

Short communication: Follicle superstimulation before ovum pick-up for in vitro embryo production in Holstein cows

The objective was to evaluate in vitro embryo production (IVEP) in nonlactating Holstein cows after ovarian superstimulation. Cows were randomly assigned in a crossover design to 1 of 2 groups: control (n=35), which was not synchronized and not treated with hormones before ovum pick-up (OPU), or hormone-treated (n=35), in which wave emergence was synchronized and animals treated with porcine (p)-FSH in the presence of norgestomet before OPU. In the hormone-treated group, all follicles ≥7mm in diameter were aspirated for synchronization of wave emergence and cows received a norgestomet ear implant. After 36h, treatment with p-FSH (6 doses of 40mg each, 12h apart, i.m.) started. Ovum pick-up from follicles >2mm in diameter was performed 44h after the last p-FSH (coasting). Then, IVEP was performed. The total number of cumulus-oocyte complexes recovered (16.0 vs. 20.5±2.2) and number of grades I to III (viable) oocytes (10.7 vs. 12.3±1.6) did not differ between hormone-treated and control groups Additionally, no differences were found in the number of blastocysts per cow per OPU (3.0 vs. 2.6±0.5) or in blastocyst rates (17.1 vs. 12.2±2.4%) between hormone-treated and control, respectively. Thus, in this study, ovarian follicle superstimulation with p-FSH followed by coasting in nonlactating Holstein cows that had synchronization of wave emergence and progestin supplementation did not improve oocyte quality or IVEP compared to no hormonal treatment.

Effect of superstimulation protocols on nuclear maturation and distribution of lipid droplets in bovine oocytes

Our objective was to study the effect of superstimulation protocols on nuclear maturation of the oocyte and the distribution of lipid droplets in the ooplasm. Heifers (n = 4 each group) during the luteal phase were either treated with FSH for 4 days (Short FSH), FSH for 4 days followed by 84 h of gonadotropin free period (FSH Starvation) or for 7 days (Long FSH) starting from the day of wave emergence. In all groups, LH was given 24 h after induced luteolysis (penultimate day of FSH) and cumulus–oocyte complexes were collected 24 h later. Oocytes were stained for nuclear maturation (Lamin/chromatin) and lipid droplets (Nile red). The Long FSH group had a greater proportion of mature oocytes (metaphase II) compared with heifers in the Short FSH and FSH Starvation groups (59/100 vs 5/23 and 2/25, respectively; P < 0.01). On average across all groups, oocytes contained 22 pL of lipids (3.3% of ooplasm volume) distributed as 3000 droplets. Average volume of individual lipid droplets was higher in the FSH Starvation (11.5 ± 1.5 10–3 pL, P = 0.03) compared with the Short and Long FSH groups (7.2 ± 0.6 10–3 and 8.0 ± 0.8 10–3 pL, respectively). In conclusion, both FSH Starvation and Short FSH treatments yielded a lower proportion of mature oocytes compared with the Long FSH treatment. Furthermore, FSH starvation led to an accumulation of larger lipid droplets in the ooplasm, indicating atresia. Our results indicate that a longer superstimulation period in beef cattle yields higher numbers and better-quality oocytes.

In vivo embryo production in cows superovulated 1 or 2 days after ovum pick-up

The present study evaluated superovulatory responses and in vivo embryo production in cows treated with FSH starting 1 or 2 days after ovum pick-up (OPU). Thirty-three non-lactating Nelore cows were subjected to aspiration of all follicles ≥3mm for OPU. After OPU, cows were randomly divided into two groups in which the follicle superstimulatory treatments with FSH started 1 or 2 days after OPU (Groups D1 and D2, respectively). Data are presented as the least squares mean±s.e.m. The number of follicles ≥3mm before OPU was similar between groups (~34); however, cows in Group D2 had more follicles ≥3mm on the first day of FSH (15.2±2.3 vs 7.6±1.7; P=0.04) and a higher ratio of the number of follicles at first FSH/number of follicles before OPU (0.41±0.04 vs 0.24±0.02; P=0.01). In addition, Group D2 cows had a greater superovulatory response than did cows in Group D1 (18.9±2.8 vs 9.1±1.9 corpora lutea, respectively; P<0.03). However, there was no difference in the total number of recovered ova and embryos from cows in Groups D2 and D1 (5.1±1.4 vs 4.9±1.3, respectively; P>0.10). Nevertheless Group D2 cows had more freezable embryos than Group D1 cows (3.2±1.1 vs 1.3±0.5, respectively; P<0.05). Cows from Group D2 had a much higher proportion (P<0.001) of follicles ≥8mm compared with follicles ≥6mm and <8mm at the time of the last treatment with FSH. In conclusion, to obtain a greater production of viable embryos in superovulated cows after OPU, it is recommended to wait at least 2 days before starting FSH treatment.

Granulosa cell function and oocyte competence: Super-follicles, super-moms and super-stimulation in cattle

The review presents an overview of studies that examined the effects of follicular aging and maternal aging in the bovine model. The first of three main sections is a discussion of the developmental competence of oocytes from (1) the ovulatory follicle of 2-wave and 3-wave estrous cycles, (2) dominant follicles that develop under high or low LH pulse frequency, and (3) natural versus FSH-stimulated ovulatory follicles. The second section highlights the effects of maternal aging. Maternal aging in cattle is associated with (1) elevated circulating FSH concentrations, (2) reduced response to superstimulatory treatment, and (3) markedly decreased early embryonic development in cows >12 year of age. The third and final section on superstimulation protocols addresses the effects of the duration of FSH stimulation and withdrawal (i.e., FSH "starvation" or "coasting") on oocyte competence. Ovarian superstimulation for 4 days altered the expression of genes related to angiogenesis, and activated oxidative stress-response genes. Extending the duration of FSH stimulation from 4 to 7 days resulted in a greater and more synchronous ovulatory response and optimal oocyte maturation. The highest rates of blastocyst development in vitro were obtained when FSH support was discontinued for 44 to 68h and granulosa cell SMAD7 mRNA was predictive of this period. Longer periods of FSH starvation resulted in a loss of oocyte competence or ovulatory capability. By extending the bovine model to the transcriptome level, new approaches and treatments may be devised to resolve subfertility in women and animals.

Mild/minimal stimulation protocol for ovarian stimulation of patients at high risk of developing ovarian hyperstimulation syndrome

BACKGROUND

Recently, an increased scientific interest was focused on mild approaches for ovarian stimulation in clinical practice. Milder stimulation aims to develop safer and more patient-friendly protocols which are more physiological, less drug use, less expensive and the risks of treatment are highly minimized.

AIM

To investigate the efficacy and safety of a mild ovarian stimulation protocol in patients at high risk of developing ovarian hyperstimulation syndrome (OHSS), compared to conventional long down-regulation protocol.

SUBJECTS AND METHODS

This a prospective, open, randomized study, included 349 infertile patients considered at high risk of developing OHSS, undergoing in vitro fertilization treatment in two private assisted reproduction centers. The patients were randomized into two groups: group A (n = 148) had a mild/minimal stimulation protocol of recombinant FSH (rFSH) combined with GnRH antagonist. Group B (n = 201) (control group) had a standard long protocol of rFSH combined with GnRH agonist.

RESULTS

There was no significant difference observed between the two groups regarding the mean number of oocytes retrieved per patient, mature metaphase II oocytes, fertilization rate, and embryo cleavage rate. Significantly higher implantation rate (21.5 vs 14.5 %) (p < 0.05), pregnancy rate (37.7 vs 23.4 %) (p < 0.05), and delivery rate (32.8 vs 20.1 %) (p < 0.05) were observed in favor of groups A compared to group B. Lower proportion of patients (4.7 %), though not statistically significant, has developed OHSS in group A compared to group B (8.4 %).

CONCLUSION

Our study shows that mild stimulation regimen is highly effective for ovarian stimulation of patients who have experienced OHSS complication without increasing the risk of OHSS.

In vivo and in vitro environmental effects on mammalian oocyte quality

The oocyte is at the center of the equation that results in female fertility. Many factors influence oocyte quality, including external factors such as maternal nutrition, stress, and environmental exposures, as well as ovarian factors such as steroids, intercellular communication, antral follicle count, and follicular fluid composition. These influences are interconnected; changes in the external environment of the female translate into ovarian changes that affect the oocyte. The lengthy period during which the oocyte remains arrested in the ovary provides ample time and opportunity for environmental factors to take their toll. An appropriate environment for growth and maturation of the oocyte, in vivo and in vitro, is critical to ensure optimal oocyte quality, which determines the success of fertilization and preimplantation embryo development, and has long-term implications for implantation, fetal growth, and offspring health.

Large-scale chromatin morpho-functional changes during mammalian oocyte growth and differentiation

Mammalian oocyte development is characterized by impressive changes in chromatin structure and function within the germinal vesicle (GV). These changes are crucial to confer the oocyte with meiotic and developmental competencies. In cow, oocytes collected from early and middle antral follicles present four patterns of chromatin configuration, from GV0 to GV3, and its progressive condensation has been related to the achievement of developmental potential. During oogenesis, follicular cells are essential for the acquisition of meiotic and developmental competencies and communicate with the oocyte by paracrine and gap junction mediated mechanisms. We recently analyzed the role of gap junction communications (GJC) on chromatin remodeling process during the specific phase of folliculogenesis that coincides with the transcriptional silencing and sequential acquisition of meiotic and developmental capabilities. Our studies demonstrated that GJC between germinal and somatic compartments plays a fundamental role in the regulation of chromatin remodeling and transcription activities during the final oocyte differentiation, throughout cAMP dependent mechanism(s).

Influence of superovulatory protocols on in vitro production of Nellore (Bos indicus) embryos

There are indications in the literature that delaying the period between ovarian superestimulation and ovum pick up (OPU) would induce follicles to a condition of initial atresia, which could be beneficial to oocyte development. In this work, we compared three protocols for OPU and in vitro production (IVP) of embryos, in Nellore cattle. Nellore cows (n = 18) were randomly allocated in three groups: Group 1 (OPU), Group 2 [Follicle stimulating hormone (FSH) and OPU] and Group 3 (FSH deprivation and OPU). Three OPUs were performed, and the animals were switched to a different group each time (crossover), in such a way that at the end of the experiment all cows received the 3 protocols. At random stage of the oestrous cycle (D-2), all follicles ≥ 6 mm were aspirated to induce a new follicular wave 2 days afterwards (D0). In Group 1, OPU was performed on D2 and oocytes were processed to IVP. In Group 2, starting on D0, cows were superstimulated (FSH, Folltropin(®), 30 mg administered daily, i.m., during three consecutive days, total dose = 180 mg), and 6 h after the last FSH dose, they received exogenous luteinizing hormone (LH) (12.5 mg, i.m., Lutropin(®), D3). The OPU was performed 6 h after LH administration, i.e. 12 h after the last dose of FSH. Animals in Group 3 received the same treatment as those in Group 2, except that LH was administered 42 h after the last dose of FSH, and OPU occurred 6 h later. Therefore, in this group, follicles were deprived of FSH at 48 h. Both cleavage and blastocyst rates were similar (p > 0.05, anova) among oocytes from Groups 1, 2 and 3, respectively: 77.4% (144/185) and 42.70% (79/185); 75.54% (105/139) and 31.65% (44/139); 63.52% (101/159) and 33.33% (53/159). However, hatched blastocyst rate was higher (p < 0.01) in Group 1 (30.27%, 56/185) when compared with Group 2 (11.51%, 16/139) or 3 (15.72%, 25/159). It is concluded that, contrary to previous work on European breeds (Bos taurus), ovarian superstimulation associated with deprivation of FSH and OPU (Group 3) did not increase IVP of Nellore embryos (Bos indicus). On the contrary, the highest hatched blastocyst rates were observed in oocytes from non-superstimulated cows.

In vitro-produced bovine embryos: dealing with the warts

Bovine in vitro embryo production is an inefficient process; while maturation and fertilization proceed apparently normally, the proportion of embryos reaching the transferable (blastocyst) stage is rarely over 40% and those that do reach this stage are often compromised in quality and competence. There is considerable evidence of a significant influence of follicular origin on oocyte developmental potential and it appears that once the oocyte is removed from the follicle its developmental capacity is capped. Evidence suggests that while culture conditions during bovine in vitro embryo production can impact somewhat the developmental potential of the early embryo, the intrinsic quality of the oocyte is the key factor determining the proportion of oocytes developing to the blastocyst stage. This paper highlights some of the problems associated with in vitro production of embryos and discusses some of the ways of overcoming these problems.

Hormonal treatments for increasing the oocyte and embryo production in an OPU–IVP system

The objective was to enhance the inherent developmental ability of bovine oocytes retrieved by ultrasound-guided transvaginal aspiration. Various hormonal regimes were utilized to produce partially matured oocytes in vivo, in order to improve embryo development following IVF. In the first experiment, a two-by-two factorial design was used with FSH (multiple versus single dose) and im administration of LH (yes versus no) 6h prior to OPU. In all protocols (which lasted for nine consecutive weeks), ovarian stimulation was performed in the presence of a CIDR. One FSH administration was adequate for ovarian stimulation (9.33+/-0.7 and 10.14+/-0.7 follicles per cow per OPU session); however, multiple injections increased (P<0.05) follicular response (12.97+/-0.7 and 13.97+/-0.7). In the second experiment, a two-by-two factorial design was used to compare the effects, during ovarian stimulation, of the presence or absence of CIDR, and iv treatment with LH 6h prior to OPU (yes versus no), on oocyte competence (judged by blastocyst development rates following IVF). Presence of CIDR during superstimulation had no effect on the follicular response. Administration of LH 6h prior to OPU increased (P<0.05) the oocytes of higher morphological grades, and in the absence of a CIDR, improved (P<0.05) blastocyst development rate. Treatment with LH, 6h prior to OPU without the use of CIDR during ovarian stimulation, resulted in 2.89+/-0.4 blastocysts per cow per OPU session as compared to 1.56+/-0.4, 1.56+/-0.4 and 1.33+/-0.4 for all other groups. In conclusion, compared to single administration, multiple FSH administration increased (P<0.05) available follicles for aspiration. Moreover, when ovarian stimulation in the absence of CIDR was followed by administration of LH 6h prior to OPU, it increased (P<0.05) the number of blastocysts per OPU session.

Comparison of different transvaginal ovum pick-up protocols to optimise oocyte retrieval and embryo production over a 10-week period in cows

The objective was to develop a simple and effective ovum pick-up (OPU) protocol for cows, optimised for oocyte harvest and subsequent in vitro embryo production (IVP). Five protocols differing in collection frequency, dominant follicle removal (DFR) and FSH stimulation were tested on groups of three cows each, over an interval of 10 consecutive weeks. Performance was evaluated on per OPU session, per week and pooled (3 cowsx10weeks) basis. Among the non-stimulated groups, on a per cow per session basis, once- or twice-weekly OPU had no effect on the mean (+/- S.E.M.) number of follicles aspirated, oocytes retrieved and blastocysts produced (0.6+/-0.8 and 0.7 +/- 0.7, respectively). However, DFR 72 h prior to OPU almost doubled blastocyst production (1.2 +/- 1.3). In stimulated groups, FSH treatment (80 mg IM and 120 mg SC) was given once weekly prior to OPU. Treatment with FSH, followed by twice-weekly OPU, failed to show any synergistic effect of FSH and increased aspiration frequency. When FSH was given 36 h after DFR, followed by OPU 48 h later, more (P < 0.05) follicles (16.0 +/- 5.0), oocytes (10.6 +/- 4.5) and embryos (2.1 +/- 1.2) were obtained during each session, but not on a weekly basis. Pooled results over 10 weeks showed an overall improved performance for the treatment groups with twice-weekly OPU sessions, due to double the number of OPU sessions performed. However, the protocol that consisted of DFR, FSH treatment and a subsequent single OPU per week, was the most productive and cost-effective, with potential commercial appeal.

Superovulation and embryo transfer in Bos indicus cattle

Compared to Bos taurus breeds, Bos indicus breeds of cattle present several differences in reproductive physiology. Follicular diameter at deviation and at the time of ovulatory capability are smaller in B. indicus breeds. Furthermore, B. indicus breeds have a greater sensitivity to gonadotropins, a shorter duration of estrus, and more often express estrus during the night. These differences must be considered when setting up embryo transfer programs for B. indicus cattle. In recent studies, we evaluated follicular dynamics and superovulatory responses in B. indicus donors with the objective of implementing fixed-time AI protocols in superstimulated donors. Protocols using estradiol and progesterone/progestrogen releasing devices to control follicular wave emergence were as efficacious as in B. taurus cattle, allowing the initiation of superstimulatory treatments (with lower dosages of FSH than in B. taurus donors) at a self-appointed time. Furthermore, results presented herein indicate that delaying the removal of progesterone/progestogen-releasing devices, combined with the administration of GnRH or pLH 12 h after the last FSH injection, results in synchronous ovulations, permitting the application of fixed-time AI of donors without the necessity of estrus detection and without compromising the results.

Isolation of Genes Associated with Developmentally Competent Bovine Oocytes and Quantitation of Their Levels During Development1

We have performed suppressive subtraction hybridization (SSH) of populations of developmentally competent and incompetent bovine oocytes from large (> or =5-mm) and small (< or =2-mm) follicles to isolate messenger RNA associated with the attainment of developmental competency. RNA was amplified in a linear fashion and then subjected to the SSH procedure to produce a library enriched for genes associated with competency. One thousand clones of this library were subjected to a differential screening approach to identify 31 potentially upregulated isolates. Sequencing revealed these to represent 21 genes. To rigorously identify the degree of upregulation and reproducibility thereof, we examined the expression of these genes in three separate pools of developmentally competent and incompetent oocytes by quantitative real-time PCR. Results indicated that upregulation varied from zero to threefold, showing that accurate quantification is essential for the interpretation of such differential screening experiments. Furthermore, it appears that the molecular causes for poor developmental capacity may be highly complex and be reliant on many small changes. We further characterized a selection of these novel and known maternally expressed genes for their absolute expression levels during maturation in the presence or absence of an inhibitor of transcription and during preattachment development. Last, the effect of nuclear transfer on the levels of these genes was assayed. Nuclear transfer was found to differentially affect transcript levels of genes expressed after embryonic genome activation but did not prevent the degradation of maternal transcripts or result in activation of maternal genes that are silent at blastocyst stages.

Origin of bovine follicular fluid and its effect during in vitro maturation on the developmental competence of bovine oocytes

Protein supplementation during in vitro maturation can profoundly affect both the rate and overall efficiency of the maturation procedure. The present study was conducted to assess the ability of different concentrations (1, 5, and 10%) of bovine follicular fluid (bFF) to support in vitro maturation of oocytes and subsequent developmental capacity. The bFF was derived either from competent follicles ( > 8 mm) obtained by transvaginal recovery following superovulation or from a pool of small follicles (2-5 mm) from abbatoir-derived ovaries. Bovine oocytes were cultured for 24 h in synthetic oviduct fluid medium (m-SOF) supplemented with polyvinylpyrrolidone. Following fertilization and embryo culture, more oocytes (P < 0.05) reached the blastocyst stage when oocytes were cultured with 5% bFF from competent follicles (41 +/- 3.7%) compared with bFF derived from small follicles (16 +/- 2.9%). Estradiol and recombinant human follicle stimulating hormone added to the competent bFF during maturation acted in synergy to increase blastocyst production rate (P < 0.05); this blastocyst production rate (57 +/- 1.2%) was higher than those obtained with the addition of these two hormones to bFF derived from small follicles (26 +/- 2.9%). The quality of blastocysts obtained was reflected by inner cell mass (51.30 +/- 3.5 and 25.50 +/- 3.7) and trophectoderm cell numbers (99.72 +/- 2.5 and 94.80 +/- 4.7) for bFF from competent and small follicles, respectively. In conclusion, follicular fluid originating from competent follicles increased the developmental competence of abbatoir-derived oocytes.

Effect of culture environment on embryo quality and gene expression - experience from animal studies

Recent studies comparing bovine oocyte maturation, fertilization and embryo culture in vivo and in vitro have demonstrated that the origin of the oocyte is the main factor affecting blastocyst yield, while the post-fertilization culture environment is critical in determining blastocyst quality, measured in terms of cryotolerance and relative transcript abundance, irrespective of the origin of the oocyte. Production of embryos in vitro, particularly when using an extended period of in-vitro culture, may predispose the embryo to phenomena such as the large offspring syndrome, which is likely to alter gene expression, particularly of imprinted genes. It is clear now that the post-fertilization culture environment has a profound effect on the relative abundance of gene transcripts within the embryo, and culture under suboptimal conditions for as little as 1 day can lead to perturbations in the pattern of expression.

Follicular oocyte growth and acquisition of developmental competence

At birth the ovaries of mammalian females contain a finite store of primordial follicle oocytes. Each oocyte and its surrounding follicle cells share a communication system, the gap junction network, which facilitates the transfer of signals as well as nutrients in to and out off the oocyte and between follicle cells. The connexin family of proteins form the building blocks of this communication network, their expression is specific to the differentiated state of the granulose cell and the stage of folliculogenesis. Factors such as the c-kit receptor and its ligand, IGF-I, IGF-I receptors and the IGF binding proteins, members of the transforming growth factor beta (TGFbeta) family, in particular, some of the bone morphogenetic proteins, play prominent roles in oogenesis, primordial follicle activation and subsequent follicle/oocyte development culminating in oocyte ovulation. The oocyte undergoes a progressive series of morphological modifications as it grows and proceeds through the different stages of development. These structural rearrangements facilitate the increasing energy and nucleic acid synthesis requirements of the developing oocyte and are a prerequisite to the oocytes achievement of meiotic and embryo developmental competence. Several factors determine the ultimate competence of the oocyte, these have been investigated and attempts made to mimic these conditions in vitro. The complexity of the orchestration of the events that control oocyte growth and ultimate acquisition of developmental competence is under continuous investigation. The present review describes some of the findings to date.

Oocyte and embryo quality: effect of origin, culture conditions and gene expression patterns

In general, the majority of immature bovine oocytes fail to develop to the blastocyst stage following maturation, fertilization and culture in vitro. The evidence suggests that while culture conditions during in vitro embryo production can impact on the developmental potential of the early embryo, the intrinsic quality of the oocyte is the key factor determining the proportion of oocytes developing to the blastocyst stage. In addition, evidence suggests that the period of post-fertilization embryo culture is the most critical in determining blastocyst quality. This paper reviews the current literature, with emphasis on the bovine model, demonstrating evidence for an effect of oocyte origin and/or in vitro maturation conditions on the developmental capacity and gene expression patterns in the oocyte. Furthermore, the well-documented effects of post-fertilization culture environment on embryo gene expression and quality are highlighted.

Comparison of coasting and intravenous albumin in the prevention of ovarian hyperstimulation syndrome

OBJECTIVE

To compare the efficacy of coasting to prevent ovarian hyperstimulation syndrome (OHSS) with i.v. albumin and to determine if different timing of gonadotropin coasting would affect the IVF outcomes.

DESIGN

Retrospective study.

SETTING

University hospital-based IVF program.

PATIENT(S)

One hundred sixty-two women undergoing IVF treatment cycles who were considered to be at high risk for developing OHSS.

INTERVENTION(S)

Gonadotropin administration was withheld in 60 patients: either coasting occurred before follicular maturation (early coasting subset, n = 28) or follicular maturity was attained before coasting (late coasting subset, n = 32). Outcomes were compared in 102 patients at risk for OHSS who received i.v. albumin on the day of oocyte retrieval.

MAIN OUTCOME MEASURE(S)

Incidence of OHSS and outcome parameters.

RESULT(S)

Although the fertilization rates and the incidence of OHSS did not differ significantly between the coasting and i.v. albumin groups, the mean number of oocytes retrieved, the pregnancy rates, and implantation rates were significantly lower in the coasting group. There is no statistical difference in the entire outcome examined and the incidence of OHSS between the early and late coasting subsets.

CONCLUSION(S)

Coasting is as effective as i.v. albumin in preventing OHSS in high-risk patients but yields inferior pregnancy rates. Early coasting is as successful as late coasting in preventing OHSS with similar IVF outcome.

Time interval between FSH priming and aspiration of immature human oocytes for in-vitro maturation: a prospective randomized study

This prospective randomized controlled study was performed to examine the influence of coasting for 2 days versus 3 days following a fixed daily dose of FSH for 3 days. The outcome was 2-fold. In the first experiment (n = 50 cycles), the incidence of apoptosis in granulosa cells was compared. In the second experiment (n = 28 cycles), the rates of maturation, fertilization, cleavage, pregnancy and implantation were compared. In addition, clinical pregnancy rate per aspiration was registered. Granulosa cells were collected from follicular aspirates and pooled for each patient. The APOPTAG Detection Kit was used for staining of the granulosa cells and detection of apoptosis. Oocytes were matured in vitro for 28-30 h before intracytoplasmic sperm injection. The incidence of apoptosis in granulosa cells did not differ between granulosa cells obtained after 2 days coasting (n = 25 cycles) compared with granulosa cells obtained after 3 days coasting (n = 25 cycles) (26.2 versus 26.2%). When oocytes obtained after coasting for 2 days (n = 12 cycles) were compared with oocytes obtained after coasting for 3 days (n = 16 cycles), no significant difference was found between rates of maturation (63 versus 65%), fertilization (60 versus 68%), cleavage (86 versus 92%) or implantation [5/12; 42 versus 1/12 (8%)]. A higher clinical pregnancy rate per aspiration [5/16 (31%) versus 1/12 (8%)] was obtained after coasting for 3 days compared with coasting for 2 days. The difference was not significant. This randomized study showed no difference in apoptosis of granulosa cells and no difference in developmental competence of oocytes obtained after coasting for 3 days compared with 2 days coasting.

Factors affecting oocyte quality and quantity in commercial application of embryo technologies in the cattle breeding industry

With the introduction of multiple ovulation, embryo recovery and transfer techniques (MOET) plus embryo freeze-thaw methods in the early 1980s, the breeding industry has the tools in hand to increase the number of calves from donors of high genetic merit. In the early 1990s, the introduction of ovum pick-up followed by in vitro embryo production (OPU-IVP) opened up even greater possibilities. Using these technologies, we challenge biological mechanisms in reproduction. Where normally one oocyte per estrous cycle will develop to ovulation, now numerous other oocytes that otherwise would have degenerated are expected to develop into an embryo. Completion of oocyte growth and pre-maturation in vivo before final maturation both appear to be essential phases in order to obtain competence to develop into an embryo and finally a healthy offspring. In order to increase oocyte quality and quantity in embryo production technologies, current procedures focus primarily on improving the homogeneity of the population of oocytes with regard to growth and state of pre-maturation at the start of a treatment. In the case of MOET, dominant follicle removal (DFR) before superovulation treatment improves the number of viable embryos per session from 3.9 to 5.4 in cows but not in heifers and a prolonged period of follicle development obtained by preventing release of the endogenous LH surge increases the number of ova but not the number of viable embryos per session. In the case of OPU-IVP, the frequency of OPU clearly affects quantity and quality of the collected oocytes and FSH stimulation prior to OPU every 2 weeks resulted in 3.3 embryos per session. Analysis of 7,800 OPU sessions demonstrated that the oocyte yield is dependent on the team, in particular, the technician manipulating the ovaries. It is concluded that an increased understanding of the processes of oocyte growth, pre- and final maturation will help to improve the efficiency of embryo technologies. However, somewhere we will meet the limits dictated by nature.

Manipulation of follicular development to produce developmentally competent bovine oocytes

Superstimulation in donor cows increases the number of cumulus-oocyte complexes (COC), but when compared to in vivo maturation, in vitro maturation results in only half as many blastocysts after prolonged in vitro culture. The objective of this study was to establish a superstimulation protocol that would produce a maximal number of competent COC for standard in vitro embryo production. During experiment 1, eight cyclic Holstein heifers were superstimulated with four doses of FSH. Half the heifers received an injection of LH 6 h before ovum pick-up (OPU). The COC were collected following OPU either 33 or 48 h following the last FSH injection (coasting period). During experiment 2, six cyclic Holstein heifers were superstimulated with six doses of FSH, and in half the heifers, LH was administered 6 h before OPU. The COC were collected following ultrasound-guided transvaginal aspiration of both ovaries 48 h after the last FSH injection (coasting period). The COC originating from follicles with a diameter of 5 mm or more (n = 180 for experiment 1 and 57 for experiment 2) were subjected to standard in vitro maturation, fertilization, and development. When animals were administered four doses of FSH, 48 h of coasting resulted in significantly more 5- to 10-mm follicles (P < 0.01) than 33 h of coasting. If a 33-h coasting period was used, administration of LH 6 h before OPU resulted in a significant increase in both percentage of blastocysts and embryo production rate at Days 7 and 8 (P < or = 0.05) of in vitro culture. If a 48-h coasting period was used, LH injection did not affect the rates of blastocyst production. When donors were administered six doses of FSH with a 48-h coasting period, the highest results, although not significant (P < 0.08), were obtained when animals received LH 6 h before OPU, with 80% +/- 9% (mean +/- SEM) blastocysts and 0.8 +/- 0.09 embryo produced per COC retrieved per heifer at Day 8 of culture. Never has in vitro technology been so close to producing 100% developmentally competent COC.

Differential Display and Suppressive Subtractive Hybridization Used to Identify Granulosa Cell Messenger RNA Associated with Bovine Oocyte Developmental Competence1

The main objective of this study was to identify mRNA expressed in the granulosa cells characterizing differentiated follicles bearing developmentally competent bovine oocytes. Analytical comparisons were made on mRNA pools of granulosa cells using differential display reverse transcription polymerase chain reaction (DDRT) analysis and suppressive subtractive hybridization (SSH). With DDRT, mRNA patterns of granulosa cells from small (< 4 mm) and large (> 8 mm) follicles cultured in the presence or absence of LH were compared to identify mRNA associated with follicular size or with the LH response. Nine clones were sequenced, and two were identified. One of the clones, DRAK 1, was associated with the presence of LH in the medium. Other comparisons directed toward the identification of mRNA associated with the presence of a competent oocyte were done on granulosa cells collected in vivo from superstimulated heifers. With the DDRT analysis, four clones associated with the oocyte developmental competence status were identified. With the SSH analysis, four clones specific to the presence of an incompetent oocyte were sequenced and none were identified, whereas 49 clones specific to the presence of a competent oocyte were sequenced and 18 were identified. Among these clones, early growth response 1, sprouty 2, cytochrome C oxidase, matrix metalloproteinase inducer, matrix metalloproteinase, epiregulin, prostaglandin receptor, and progesterone receptor were the most relevant to the ovarian physiology being examined.

Resumption of meiosis: mechanism involved in meiotic progression and its relation with developmental competence

It has been more than 10 years since the first calf was born following in vitro maturation of a bovine oocyte. During that period, a number of modifications have been made to the culture conditions during the maturation period but still most oocytes failed to produce viable embryos. Recently, the pretreatment of donors leading to clear improvements in oocyte developmental competence has been achieved. These treatments can be either 1) ovarian stimulation with FSH followed by the slaughter of the animal and the incubation of ovaries before oocyte aspiration or 2) the transvaginal aspiration of oocytes from FSH-stimulated animals following a "coasting period" of 48 hours. These 2 treatments indicate the necessity of preparing the immature oocyte before using it. An alternative to the animal pretreatment would be to recreate in vitro the conditions present in more mature follicles. It is believed that the ability of the oocyte to become an embryo depends on the accumulation of specific information in the form of mRNA or proteins. Because the consequences of that change become visible 4 days later at the early 8-cell stage, the favorite hypothesis is that the oocyte accumulates stable mRNA and that accumulation requires an active transcription machinery. Therefore, to improve oocyte's potential, follicular instructions must be given before the germinal vesicle breakdown induced by oocyte aspiration and culture. The culture of bovine oocytes in a state of meiotic arrest could potentially allow the correct follicular signal(s) to change the development potential of an oocyte. The unraveling of the mechanism for cell control of meiotic arrest opens the way to a functional and reversible culture system for immature oocytes. The remaining challenge is to discover follicular signals or factors to apply during the in vitro culture period to enhance the competence of oocytes.

Development of human oocytes matured in vitro for 28 or 36 hours

OBJECTIVE

To compare the effects on human oocytes of in vitro maturation periods of 28 hours and 36 hours.

DESIGN

Retrospective analysis.

SETTING

University teaching hospital.

PATIENT(S)

A total of 48 infertile patients undergoing 55 cycles who volunteered for the experimental treatments.

INTERVENTION(S)

Immature oocytes were aspirated with use of transvaginal ultrasonography. Oocytes were matured, fertilized by intracytoplasmic sperm injection, and cultured for 2.5 or 3 days before being replaced into the uterus.

MAIN OUTCOME MEASURE(S)

Oocyte maturation, fertilization and cleavage rates, and clinical pregnancy rate.

RESULT(S)

Maturation of oocytes for either 28 hours or 36 hours before insemination resulted in similar rates of maturation, fertilization, and cleavage. The clinical pregnancy rate was similar in both groups (14%-15%).

CONCLUSION(S)

Shortening the in vitro maturation period does not compromise subsequent embryonic development.

Bovine follicular development and its effect on the in vitro competence of oocytes

The current knowledge is reviewed concerning correlations between follicular development in the cow and the competence of matured oocytes to develop into an embryo following IVF and IVC. At the follicular size of 3 mm, some oocytes become competent and the proportion of competent oocytes does not increase during development up to 7 mm. The proportion of competent oocytes increases greatly in follicles > 8 mm in both untreated and gonadotropin-stimulated cows. The competence of in vitro-matured oocytes from these large follicles is lower than the competence of in vivo-matured oocytes. These observations lead to the following concept. Oocytes have acquired an intrinsic capacity to develop into an embryo after IVM-IVF-IVC at the follicular stage of 3 mm, but require an additional "prematuration" to express this competence. In vivo, this prematuration occurs during preovulatory development before the occurrence of the LH surge. In follicles of 3-7 mm, a low level of atresia appears to improve the in vitro competence of oocytes which may act via a prematuration-like effect. A thorough understanding, however, of the effect of atresia and other factors on the competence of this highly heterogeneous oocyte population is still missing. Two routes to improve the embryo yield in ovum pick-up (OPU) practice are discussed.

The time interval between FSH administration and ovarian aspiration influences the development of cattle oocytes

Depriving the ovary of exogenous FSH for 1, 2 or 3 d following a bolus injection of FSH was shown to influence the quality of the recovered oocytes. Thus, we compared the developmental competence of oocytes from heifers which had been stimulated for 3 d with FSH (Folltropin-V) and, after an interval of 36, 48 or 60 h, underwent blind transvaginal aspiration. The ovaries of heifers with a palpable or functional corpus luteum were aspirated to remove all large follicles 2 d prior to being injected with either 6 doses of saline (S), 6 doses (20 mg/mL) of FSH (F), or in 6 decreasing doses of FSH (3, 3, 2, 2, 1, 1 mL; Fd). Follicles were counted and classified (medium: 5 to 10 mm, large: >10 mm) with ultrasonography before each aspiration. The oocytes recovered were classified, matured, fertilized, and developed in vitro. On a per animal basis, 1.5, 5.2 and 4.7 large and 1.5, 10.7 and 10.7 medium follicles were counted for S, F and Fd, respectively. A mean of 3.3, 9.1 and 7.7 oocytes was recovered for treatments S, F and Fd, respectively and 58, 94 and 82% were enclosed in a nonexpanded cumulus or a corona layer. Oocyte development rates were based on counts of embryos with 32 or more nuclei at Day 6.5. When oocytes were recovered 36 h after the last injection, an average of 1, 2.7 and 2 embryos per animal was obtained with S, F and Fd, respectively; at 48 h, 0.75, 4.25 and 1 embryo; and at 60 h, 0, 2.5 and 2.7 embryos. Variance analysis was performed, and the protected LSD test indicated that treatment F at 48 h resulted in a significantly higher embryo rate than Fd at 48 h (P<0.05) or S (all times; P<0.05). The reduced effect of the Fd regimen could be due to the decreasing FSH support during follicular growth or to the lower total amount of FSH given. In conclusion, these results indicate an advantage of using moderate (3 d) follicle stimulation followed by a period of FSH starvation to obtain optimal embryo production.