Practical measures to improve in vitro blastocyst production in the bovine

From clinics to (cow)mics: a reproductive journey

This manuscript describes the different topics I have been involved in the fields of reproductive physiology and embryo biotechnologies with attempts to address practical issues raised mainly by the breeding industry. The journey started with phenotyping work in the field of reproductive physio-pathology. Other issues were related to the optimization of reproductive biotechnologies to favorize genetic selection. The implementation of genomic selection raised opportunities to develop the use embryo biotechnologies and showed the interest of combining them in the case of embryo genotyping. There is still a need to refine phenotyping for reproductive traits especially for the identification of markers of uterine dysfunction. It is believed that new knowledge generated by combining different molecular approaches will be the source of applications that may benefit AI practice and embryo technologies.

Effect of lanosterol on the in vitro maturation in semi-defined culture system of prepubertal ewe oocytes

The choice of medium and supplements can affect meiotic regulation and may have an impact on the regulation of mammalian oocyte growth and embryonic cell function. The aim of the present study was to assess the effects of oxygen concentration and endogenous lanosterol on the in vitro maturation (IVM) media without serum and based on recombinant human chorionic gonadotrophin in prepubertal ewe oocytes. Firstly, the effect of varying oxygen concentrations (5% and 20%) during IVM in TCM-199 supplemented (4 mg/ml bovine serum albumin (BSA), 100 μM cysteamine, 0.3 mM sodium pyruvate, 0.1 UI/ml recombinant follicle-stimulating hormone (r-FSH; Gonal-F® 75 UI, Serono, Italy), 0.1 UI/ml recombinant leuteinizing hormone (r-LH; Lhadi® 75 UI, Serono, Italy) and 1 μg/ml estradiol-17β) on subsequent nuclear maturation of oocytes examined under ultraviolet light following staining with bisbenzimide (Hoechst 33342) was investigated. Secondly, two concentrations of lanosterol (0, 10 and 50 μM) were added to the IVM medium. Nuclear maturation of oocytes was examined as previously. Lipid content in oocytes, an important indicator of cytoplasmic maturity, was also measured using Nile red fluorescent stain. The results showed that low oxygen concentration affected the nuclear maturation. Similarly, a significantly higher rate of meiosis resumption was observed with 10 μM (72.3%) of lanosterol compared with the control (51.8%) or 50 μM of lanosterol (59.4%). A significantly higher content of lipids was also observed with 10 and 50 μM of lanosterol (7.3 ± 0.2 × 106 and 7.4 ± 0.2 × 106 arbitrary units of fluorescence) compared with the control (6.7 ± 0.2 × 106 arbitrary units of fluorescence). The results indicate that 10 μM lanosterol during IVM in medium without serum and based on recombinant human chorionic gonadotrophin has a positive effect on maturation of prepubertal ewe oocytes.

Culturing in vitro produced blastocysts in sequential media promotes ES cell derivation

Embryonic stem (ES) cell lines are routinely derived from in vivo produced blastocysts. We investigated the efficiency of ES cells derivation from in vitro produced blastocysts either in monoculture or sequential culture. Zygotes from hybrid F1 B6D2 mice were cultured in vitro to the blastocyst stage in Potassium (K(+)) simplex optimised medium (KSOM) throughout or in KSOM and switched to COOK blastocyst medium on day 3 (KSOM-CBM). Blastocysts were explanted on a feeder layer of mitomycin C-inactivated murine embryonic fibroblasts (MEF) in TX-WES medium for ES cell derivation. Sequential KSOM-CBM resulted in improved blastocyst formation compared to KSOM monoculture. ES cells were obtained from 32.1% of explanted blastocsyts cultured in KSOM-CBM versus 18.4% in KSOM alone. ES cell lines were characterized by morphology, expression of SSEA-1, Oct-4 and alkaline phosphatase activity, and normal karyotype. These results indicate that in vitro culture systems to produce blastocysts can influence the efficiency of ES cell line derivation.

The variability of ovum pick-up response and in vitro embryo production from monozygotic twin cows

Oocytes were recovered by ovum pick up (OPU) from nine pairs of monozygotic twin German Simmental cows. The hypothesis was that there is less variability between identical twins versus among non-related individuals in the variation in the recovery of oocytes by OPU and in the efficiency of in vitro embryo production. Estrous cycles were synchronized with two doses of cloprostenol, 11 days apart. Beginning 3-4 days after synchronized estrus, OPU was done twice weekly (every 3 or 4 days; total of 11 sessions). The influence of repeated OPU on estrous cyclicity was established by estrus detection, plasma progesterone concentrations, and ovarian ultrasonography. There were no differences among days of collection for the number and quality of cumulus oocyte-complexes (COCs), and rates of cleavage and blastocyst formation. A total of 1,661 COCs, including 657 (39.6%) good-quality COCs, were recovered. From 1,457 (87.7%) cultured COCs, 827 zygotes cleaved and 314 blastocysts were produced on Day 7. The total number of COCs and the blastocyst rates varied among pairs of monozygotic twins; within pairs, only slight differences were observed. In conclusion, recovery of COCs and production of embryos had substantially less variation within pairs of monozygotic twins than among non-related cattle.

Desenvolvimento pós-fecundação de oócitos bovinos pré-maturados em fluido folicular

Estudou-se o efeito da pré-maturação em fluido folicular bovino (FFb) sobre o potencial de desenvolvimento de ovócitos bovinos imaturos. Complexo cumulus- ovócitos (CCO) e FFb foram obtidos de ovários coletados em matadouro. O FFb foi inativado e os CCOs imaturos distribuídos em quatro tratamentos: (T1) 70% de FFb em Talp Hepes, (T2) 100% de FFb, (T3) 100% de Talp Hepes, e (T4) controle. Em T1, T2 e T3 os CCOs foram pré - maturados por cinco horas a 37ºC em ar e posteriormente maturados in vitro. Em T4 a maturação ocorreu logo após a aspiração. Depois de fecundados in vitro, os ovócitos foram co-cultivados com células do cumulus por 10 dias. Avaliaram-se as taxas de clivagem, de produção de blastocistos no sétimo e oitavo dias pós- fecundação (PF), de produção total e de blastocistos eclodidos no oitavo e nono dias PF. Calcularam-se as taxas de blastocistos no sétimo e oitavo dia e de blastocistos eclodidos em função do total de blastocistos produzidos. As taxas de clivagem, de produção total e de blastocistos eclodidos não diferiram entre os tratamentos (P>0,05), entretanto a produção de blastocistos no sétimo dia foi menor nos tratamentos com FFb e Talp Hepes (P<0,05). Concluiu-se que FFb e Talp Hepes na pré-maturação por cinco horas atrasam o desenvolvimento embrionário sem comprometer a taxa de produção total de embriões ou sua viabilidade.

Large offspring syndrome and other consequences of ruminant embryo culture in vitro: relevance to blastocyst culture in human ART

In vitro production of embryos from domestic animals is used to augment conventional genetic improvement programmes in agriculture and to facilitate advances in gene transfer and cloning. However, production of embryos in vitro exposes them to hazards not normally encountered in vivo and, as a result, there have been unforeseen consequences including the large offspring syndrome. This syndrome is manifest as abnormal growth and development at fetal, neonatal and later stages after transfer of embryos cultured in vitro for up to 1 week after fertilization. Our embryo culture and fetal development studies have begun to characterize many of the genetic, metabolic and developmental features associated with the syndrome. This review considers the findings of these studies in the context of blastocyst production in vitro, emphasizing the impact of culture strategies on ruminant (cattle and sheep) embryo composition and developmental competence. The need to alter in vitro production strategies to safeguard oocytes and embryos during culture is discussed. Finally, the implications of experiences gained in domestic animal studies are considered in the context of current options for human embryo culture. The need for an appreciation of the sensitivity of the embryo to its environment and the possible short- and long-term consequences of inappropriate in vitro production strategies are considered.

Glucose transporter expression is developmentally regulated in in vitro derived bovine preimplantation embryos

Glucose is readily been taken up and utilized by preimplantation embryos from different species. However, a comprehensive analysis of the glucose transporter expression throughout preimplantation development is still missing. Here, we have investigated the expression of facilitative glucose transporters (Glut1-5 and 8) and sodium-dependent-glucose transporter (SGLT-I) in bovine oocytes and preimplantation embryos up to d16 of development, using RT-PCR and immunohistochemistry. The embryos were produced in vitro by IVM-IVF. Glut1, Glut3, Glut8, and SGLT-I were expressed in all stages studied. Glut4 transcripts were first detected at the blastocyst stage. Glut2 expression was restricted to the period of blastocyst elongation at d14 and d16. Transcription of the fructose transporter Glut5 started at the 8-/16-cell stage. Our results show a distinct expression pattern for glucose transporters during bovine embryo development in vitro indicating specialized functions for these isoforms at different developmental stages in bovine embryos. Mol. Reprod. Dev. 60:370-376,

From co-culture to defined medium: state of the art and practical considerations

Embryo culture in domestic and laboratory animals, and also in humans has developed significantly during recent decades. It is the aim of this review to consider the historical development of different culture systems, with a special emphasis on the recent tendency to remove somatic cells and undefined proteins from the culture systems for sanitary reasons. In addition to the sanitary aspect, developing more standardized culture conditions is useful for diminishing variation between laboratories and for studying the needs of the embryo.

Efeito de sistema de cultivo, célula somática e soro em co-cultura sobre o desenvolvimento de embriões bovinos fecundados in vitro

O objetivo deste experimento foi o de avaliar o efeito de sistemas de cultivo e de diferentes células somáticas e soro bovino na co-cultura sobre a produção de embriões bovinos fecundados in vitro. No experimento um avaliou-se o efeito do sistema de co-cultura com células da tuba uterina e do sistema "definido". No experimento dois utilizaram-se células da granulosa ou da tuba uterina para a co-cultura em meio CR1aa (Charles Rosenkrans). No experimento três utilizou-se soro de vaca em cio (SVC) ou soro fetal bovino (SFB), ambos em co-cultura com células da granulosa em CR1aa. Os ovócitos utilizados foram obtidos de ovários colhidos em matadouro e maturados in vitro em meio 199 com soro de vaca em cio e FSH por 24h. Após a maturação, os ovócitos foram fecundados in vitro por 22h e posteriormente divididos aleatoriamente nos tratamentos. Avaliaram-se a taxa de clivagem no dia três do cultivo, a produção de blastocistos nos dias sete e oito, e de blastocistos eclodidos nos dias nove e dez. Não houve diferença entre os sistemas em co-cultura e "definido" quanto à taxa de clivagem (80,7% e 75,4%) e de produção de blastocisto (19,4% e 17,7%). Entretanto, a taxa de blastocistos eclodidos foi superior para o sistema em co-cultura (37,5%) quando comparado com o sistema "definido" (8,7%). O cultivo embrionário em células da tuba uterina ou da granulosa resultaram em taxas de clivagem, produção de blastocisto e blastocistos eclodidos semelhantes entre si (65,5% e 66,7% de clivagem, 11,6% e 13,7% de blastocistos e 23,1% e 50,0% de blastocistos eclodidos; P>0,05), bem como o cultivo com SFB ou SVC (63,9% e 70,2% de clivagem, 14,3% e 8,7% de blastocisto e 41,2% e 33,3% de blastocistos eclodidos; P>0,05). Conclui-se que o sistema de cultivo "definido" pode ser utilizado para estudos com cultivo de embriões in vitro, no entanto, os resultados quanto à taxa de eclosão ainda são inferiores ao sistema em co-cultura. As células da granulosa e da tuba uterina possuem efeito semelhante sobre o desenvolvimento embrionário, assim como o soro de vaca em cio e o soro fetal bovino, quando em co-cultura.

Development and de novo protein synthetic activity of bovine embryos produced in vitro in different culture systems

In vitro matured (IVM) and fertilized (IVF) putative Day 1 zygotes (Day 0 = IVF) were allocated randomly to culture in formulations based on Synthetic Oviduct Fluid (SOF) medium and identified on the basis of their contrasting principal supplements, which were 10% v/v steer serum (SS; n = 558) or 4 mg/mL crystalline BSA (SBSA; n = 531) or 3 mg/mL polyvinyl alcohol (SPVA; n = 607) in 9 replicates. SBSA and SPVA also contained 10 microg/mL non-essential amino acids, while the former was further supplemented with 20 microL/mL essential amino acids and the latter with 0.5 mmol/L sodium citrate and 5 ng/mL epidermal growth factor. Zygotes were cultured in 20 microL drops (4 zygotes per drop) until Day 8 in an atmosphere of 5% CO2, 5% O2 and 90% N2 at 39 degrees C and droplets were renewed every 48 hours. The incidence of zygote cleavage was lower (P < 0.05) in SS (mean +/- SEM = 61 +/- 3%) than in SBSA (76 +/- 3%) but not in SPVA (72 +/- 4%) up to Day 3. The SPVA generated a lower yield of blastocysts on Day 7 (12 +/- 2%; P < 0.001) and by Day 8 (21 +/- 4%; P < 0.01) than did SS (33 +/- 3%; 40 +/- 3%) and SBSA (30 +/- 3%; 37 +/- 4%). Cell numbers (n) and diameters (d) of blastocysts on Day 8 were greater (P < 0.001; Replicates 1 to 5) in embryos from SBSA (n, 156 +/- 9; d, 203 +/- 4 microm) than in those from SS (n, 81 +/- 4; d, 177 +/- 3 microm) and SPVA (n, 76 +/- 5; d, 167 +/- 3 microm). Embryos produced in SS incorporated less 3H-phenylalanine into PCA-precipitable protein (replicates 6 to 9; log10 dpm = 3.03 +/- 0.04) than did embryos cultured in SBSA (3.21 +/- 0.03; P < 0.001) or in SPVA (3.14 +/- 0.03; NS). In conclusion, blastocyst yield was poor in SPVA, but the embryos had metabolic activities similar to those of embryos produced in SBSA. Blastocyst yields from SS were not compromised but their capacity for de novo protein synthesis was reduced significantly.

New method for culture of zona-included or zona-free embryos: the Well of the Well (WOW) system

Culture of mammalian zygotes individually and in small groups results in lower developmental rates than culture of large groups. Zona-free zygotes also have impaired developmental potential in current culture systems. This paper describes a new approach to resolve the problems, the Well of the Well (WOW) system. Small wells (WOWs) were formed in four-well dishes by melting the bottom with heated steel rods. The WOWs were then rinsed, the wells were filled with medium, and the embryos were placed into the WOWs. To test the value of the WOW system a 3 x 3 factorial experiment was performed. Bovine presumptive zygotes were cultured from day 1 to day 7 (day 0: day of insemination) using three modules (single embryos, embryo groups of five, or single zona-digested embryos) and three different culture systems (400 microl medium, 200 microl drops, or WOWs). An additional control group consisted of 40 to 50 embryos cultured in 400 microl medium. The WOW system resulted in higher blastocyst/oocyte rates for all three modules (single: 59%; group of five: 61%; single zona-digested: 53%) than the culture in drops or in wells (P < 0.05 for all). The developmental rate was independent of the number of WOWs per well. The cell number of blastocysts cultured in the WOW system did not differ from that of the controls. Apart from its theoretical value in revealing the role of different factors influencing embryo development in vitro, the WOW system may have immediate practical consequences in certain areas of mammalian embryo production.

Effect of bovine herpesvirus-1 or bovine viral diarrhea virus on development of in vitro-produced bovine embryos

In previous experiments, zona pellucida (ZP)-intact in vitro-produced (IVP) embryos incubated for 1 hr with 10(6.3) TCID(50)/ml bovine herpes virus-1 (BHV-1), 10(5.3) TCID(50)/ml cytopathic (CP) bovine viral diarrhea virus (BVDV) or 10(5.3) TCID(50)/ml noncytopathic (NCP) BVDV showed no signs of virus replication or embryonic degeneration. The aims of the present study were to investigate whether a prolonged presence (24 hr or 8 days) of 10(6.3) TCID(50)/ml BHV-1 or 10(5.3) TCID(50)/ml BVDV in an in vitro embryo production system affected the rate of cleavage and embryonic development of ZP-intact embryos, and to point out eventual causes of adverse effects. When virus was present in each step of an IVP system, significantly lower rates of cleavage and blastocyst formation of virus-exposed embryos were observed, in comparison with control embryos (P < 0.01). When embryos were only exposed to virus during the in vitro fertilization (IVF), the rates of cleavage and blastocyst formation were significantly affected. The introduction of BHV-1 or BVDV during in vitro maturation (IVM) or in vitro culture (IVC) resulted only in significantly lower rates of blastocyst (P < 0.01). In all experiments, virus replication was not detected in the embryonic cells. On the other hand, virus replication was clearly demonstrated in oviductal cells in the co-culture system, resulting in a degeneration of these cells. In an additional experiment, synthetic oviduct fluid (SOF) without somatic cells was used as an alternative culture system. Even when SOF-embryos were exposed to 10(6.3) TCID(50)/ml BHV-1 or 10(5.3) TCID(50)/ml CP, and NCP BVDV, the rates of blastocyst formation of the BHV-1-, CP-, and NCP BVDV-exposed embryos were not different from the unexposed control embryos, 23%, 24%, and 24%, respectively, vs. 27%. Taken together, it can be concluded that the virus-induced adverse effects on embryonic development in conventional co-cultures were due to changes in the embryonic environment caused by infection of oviductal cells.

Factors that influence follicle recruitment, growth and ovulation during ovarian superstimulation in heifers: opportunities to increase ovulation rate and embryo recovery by delaying the exposure of follicles to LH

The outcome of ovarian follicular superstimulation protocols in heifers is influenced by the number of follicles that are stimulated to grow and the number induced to ovulate. At present, only a proportion of the follicles that are stimulated to grow progress to ovulation. The argument is developed in this review that failure of some of these follicles to ovulate may be due not to an intrinsic deficiency but rather to their relatively small size when the FSH treatment is initiated. Consequently, these follicles do not have the opportunity to undergo full maturation within the time frame of a conventional superstimulation protocol Based on this argument, we propose that delaying the LH surge would allow for completion of maturation by a greater number of follicles, resulting in an increased ovulation rate and in recovery of a greater number of viable embryos.

Effect of cryoprotectants and their concentration on post-thaw survival and development of expanded mouse blastocysts frozen by a simple rapid-freezing procedure

Experiments were conducted to develop a simple rapid-freezing protocol for expanded mouse blastocyst-stage embryos. The effect of type of cryoprotectant (ethylene glycol and propylene glycol) and its concentrations (4.5, 6.0 and 7.0 mol/L each with 0.5 mol/L sucrose) on morphological survival and development in vitro were studied. The survival and development of embryos frozen with best concentration of each cryoprotectant pre-exposed to either a low concentration (1.5 mol/L with 0.25 mol/L sucrose) of the respective cryoprotectant or ascending concentrations of sucrose were also compared. The in vivo development of embryos frozen with best protocol (pre-exposure to 1.5 mol followed by 7.0 mol ethylene glycol) was compared with nonfrozen embryos. The rate of re-expansion and hatching was influenced by the type and concentration of the cryoprotectant. A significantly higher re-expansion and hatching rate was achieved at 7.0 mol of both cryoprotectants compared with 4.5 and 6.0 mol of the respective cryoprotectants. When comparing 2 cryoprotectants, a higher (P < 0.05) rate of hatching was obtained with ethylene glycol at 7.0 mol compared with a similar concentration of propylene glycol. The highest re-expansion (91%) and hatching (86%) of expanded blastocysts was achieved with pre-exposure of embryos to a low concentration of ethylene glycol followed by freezing in the same cryoprotectant at 7.0 mol. The transfer of embryos frozen using this protocol resulted in the development of live fetuses. The proportion of live fetuses in the pregnant recipients with frozen-thawed embryos were not different from those transferred nonfrozen embryos (49 vs 57%). It may be concluded that simple rapid-freezing with dehydration in ascending sucrose concentrations or pre-equilibration in a low concentration of ethylene glycol or propylene glycol followed by exposure to the respective cryoprotectant at 7.0 mol resulted in high survival and development of expanded blastocysts. Ethylene glycol at 7.0 mol with pre-equilibration is, however, most effective for cryopreservation of this stage in the mouse.