Comparison between in vitro embryo production using Y-sorted sperm and timed artificial insemination with non-sorted sperm to produce crossbred calves.

Due to the increasing use of in vitro embryo production (IVEP) and the importance of crossbreeding for beef production, pregnancy rates of Nelore recipients were evaluated following Fixed Time Embryo Transfer with fresh or vitrified IVEP embryos produced with Y-sorted sperm of Angus bulls (B. taurus) or Fixed Time Artificial Insemination using non-sorted sperm. For IVEP in Experiment 1, oocytes were obtained using Ovum Pick Up (OPU) (n = 84 embryos) or from ovaries from a slaughterhouse (SLAUGHTER, n = 66 embryos). In Experiment 2, with oocytes obtained by OPU, IVEP embryos were fresh (FRESH, n = 271) or after vitrification/warming (VITRIFIED, n = 79) and PR was compared with FTAI (n = 239). In Experiment 1, cleavage rates were 63.8% and 39.1% for OPU and SLAUGHTER groups, respectively (P = 0.02), and blastocyst rates were 30.5% and 14.7%, respectively (P = 0.09). The PR was similar when considering the source of oocytes (OPU = 35.7%; SLAUGHTER = 25.8%; P = 0.17). In Experiment 2, there was no difference in PR for FRESH or VITRIFIED embryos (34.3% and 30.4%, respectively, P = 0.72), but lesser than FTAI (47.7, P = 0.002). It is concluded that the IVEP with Y-sorted sperm associated with vitrification or embryos produced with oocytes from different sources did not affect PR when there was transfer of crossbred embryos into recipients, and can optimize large-scale application of IVEP technology; however, FTAI pregnancy rates with non-sex sorted sperm were greater.

Comparison of different methods for exogenous DNA uptake by bovine spermatozoa / Comparação de diferentes métodos de incorporação de DNA exógeno pelo espermatozoide bovino

Although genetic manipulation of farm animals is of great interest for animal production and the pharmaceutical industry, its efficiency remains far from satisfactory. Pronuclear injection, which is the most widely used technique for such modification, mainly in mice, remains limited for this species. Some alternatives have been developed such as sperm mediated gene transfer, in which the spermatozoa are used as vectors for DNA delivery during in vitro fertilization. Mature sperm cells are able to spontaneously bind exogenous DNA molecules which may be internalized into sperm nuclei. Given the potential of sperm mediated gene transfer for livestock animals transgenesis, the aim of this study was to evaluate four methods of DNA uptake for sperm mediated gene transfer in bovine: incubation with DNA, plasma membrane alteration induced by calcium ionophore followed by incubation with DNA, electroporation and lipofection. Spermatozoa not exposed to exogenous DNA were used as control group. Cleavage, blastocyst and hatching rates were recorded at 72 hours post insemination (hpi), days 9 and 12 of embryo culture, respectively. Exogenous DNA-positive embryos were evaluated by PCR. No effect of treatment was observed on cleavage, blastocyst and hatching rates. In addition, percentage of DNA positive blastocysts did not differ among experimental groups. In spite of the low number of positive embryos, our results show that all treatments presented similar efficiencies for DNA delivery during in vitro fertilization. In conclusion, although the development rates were similar and constant in all groups, other factors such as exogenous DNA sequence, size and concentration should be considered to improve sperm mediated gene transfer.

Apesar da manipulação genética de animais domésticos ser de grande interesse para a produção animal e para a indústria farmacêutica, a sua eficiência ainda é insatisfatória. A injeção pronuclear, a técnica mais utilizada para tal propósito, principalmente em camundongos, ainda apresenta limitações para esta espécie. Algumas alternativas têm sido desenvolvidas como o uso de espermatozoides como vetores para transferência gênica, na qual a célula espermática tem habilidade espontânea de se ligar à molécula de DNA e internalizá-la. Dado o potencial da transferência gênica mediada por espermatozoide para animais domésticos transgênicos, o objetivo do presente trabalho foi a avaliação de quatro métodos de incorporação de DNA para a transferência gênica mediada por espermatozoides na espécie bovina: incubação com DNA, alteração da membrana plasmática induzida por cálcio ionóforo seguida por incubação com o DNA exógeno, eletroporação e lipofecção. Espermatozoides não expostos ao DNA exógeno foram usados como grupo controle. Os índices de clivagem, blastocisto e eclosão foram avaliados, respectivamente, as 72 horas após a inseminação dos oócitos, bem como, aos 9 e 12 dias de cultivo embrionário. Os embriões positivos para o DNA exógeno foram avaliados por PCR. Nenhum efeito de tratamento foi observado nos índices de clivagem, blastocisto e eclosão. Além disso, a porcentagem de blastocistos positivos para o DNA exógeno não diferiu entre os grupos experimentais. Apesar do baixo número de embriões positivos para DNA exógeno, os resultados obtidos mostram que todos os tratamentos apresentaram eficiências similares. A conclusão obtida foi que, apesar de os índices de desenvolvimento embrionário terem sido similares e constante em todos os grupos experimentais, outros fatores como a sequência, o tamanho e a concentração do DNA exógeno devem ser avaliados para melhorar a transferência gênica mediada por espermatozoides.

Sperm-mediated gene transfer: effect on bovine in vitro embryo production.

The technique of sperm-mediated gene transfer (SMGT) can be used to delivery exogenous DNA into the oocyte. However, it has low repeatability and produces inconsistent results. In order to optimize this technique, it is necessary to study the mechanism by which DNA enters the sperm cell and integrates in the sperm genome. Furthermore, studies must focus in the maintenance of sperm cell viability and function. The aim of this study was to evaluate different SMGT protocols of sperm electroporation or capacitation (CaI) aiming to maintain sperm viability in the production of bovine embryos in vitro. Frozen-thawed semen was divided in two experimental groups (electroporation or CaI) and one control group (non-treated cells). For the electroporation method, five different voltages (100, 500, 750, 1000 or 1500 V) with 25 µF capacitance were used. For CaI treatment, combinations of two CaI concentrations (250 nM or 500 nM), two incubation periods of sperm cells with CaI (1 or 5 min) and two incubation periods that mimicked time of sperm cell interaction with exogenous DNA molecules (1 or 2 h) were evaluated. According to our data, electroporation and CaI treatments do not prevent sperm penetration and oocyte fertilization and can be an alternative method to achieve satisfactory DNA delivery in SMGT protocols.

Effects of different cryopreservation methods on post-thaw culture conditions of in vitro produced bovine embryos.

The aim of this work was to evaluate the effect of cryopreservation protocols on subsequent development of in vitro produced bovine embryos under different culture conditions. Expanded in vitro produced blastocysts (n = 600) harvested on days 7-9 were submitted to controlled freezing [slow freezing group: 10% ethylene glycol (EG) for 10 min and 1.2°C/min cryopreservation]; quick-freezing [rapid freezing group: 10% EG for 10 min, 20% EG + 20% glycerol (Gly) for 30 s]; or vitrification [vitrification group: 10% EG for 10 min, 25% EG + 25% Gly for 30 s] protocols. Control group embryos were not exposed to cryoprotectant or cryopreservation protocols and the hatching rate was evaluated on day 12 post-insemination. In order to evaluate development, frozen-thawed embryos were subjected to granulosa cell co-culture in TCM199 or SOFaa for 4 days. Data were analyzed by PROC MIXED model using SAS Systems for Windows®. Values were significant at p < 0.05. The hatching rate of the control group was 46.09%. In embryos cultured in TCM199, slow freezing and vitrification group hatching rates were 44.65 ± 5.94% and 9.43 ± 6.77%, respectively. In embryos cultured in SOFaa, slow freezing and vitrification groups showed hatching rates of 11.65 ± 3.37 and 8.67 ± 4.47%, respectively. In contrast, the rapid freezing group embryos did not hatch, regardless of culture medium. The slow freezing group showed higher hatching rates than other cryopreservation groups. Under such conditions, controlled freezing (1.2°C/min) can be an alternative to cryopreservation of in vitro produced bovine embryos.

Maturação e desenvolvimento embrionário in vitro de oócitos bovinos após bloqueio da meiose com inibidores de MPF / In vitro maturation and embryo development of bovine oocytes after meiosis blockage with MPF inhibitors

O objetivo deste estudo foi avaliar a maturação e o desenvolvimento embrionário após a fecundação in vitro de oócitos bovinos que tiveram a maturação bloqueada com Butirolactona I e Roscovitina em meio de pré-maturação suplementado com soro fetal bovino (SFB). Oócitos foram divididos em 4 grupos: Controle 0 hora, Controle (maturação por 24 horas), Butirolactona I (bloqueio da maturação com 150μM de Butirolactona I por 24 horas, seguido de 24 horas de maturação) e Roscovitina (bloqueio da maturação com 50μM de Roscovitina por 24 horas, seguido de 24 horas de maturação). Para avaliar a maturação nuclear, os oócitos foram fixados e corados em aceto orceína. Parte dos oócitos dos grupos Controle 24 horas, Roscovitina e Butirolactona I após o período de maturação, foi fecundado in vitro. O desenvolvimento embrionário foi avaliado pelos índices de clivagem (D3) e formação de blastocistos (D7). Oócitos do grupo Butirolactona I apresentaram índices de Vesícula Germinativa após o bloqueio e de Metáfase 2 após a maturação semelhantes ao dos grupos Controle 0 hora e Controle, respectivamente. Por outro lado, a Roscovitina apresentou menores índices de Vesícula Germinativa e Metáfase 2. Os grupos Controle e Butirolactona I apresentaram maiores índices de clivagens. O grupo Controle apresentou maior produção de blastocistos que o Roscovitina e não diferiu do grupo Butirolactona I. Conclui-se que a Butiroloactona I pode ser utilizada no sistema de pré-maturação em meio contendo SFB, pois apresentou resultados semelhantes ao do grupo Controle o mesmo não ocorrendo com a Roscovitina, que apresentou menores índices de maturação oocitária e de desenvolvimento embrionário.

This study evaluated the bovine oocyte maturation and embryo development after in vitro fertilization. The maturation of the oocytes was blocked using Butyrolactone I and Roscovitine using pre-maturation medium supplemented with fetal calf serum (FCS). The ocytes were divided in four groups: Control 0 hour, Control (24 hours of maturation), Roscovitine (maturation blockage with 50mM Roscovitine during 24 hours followed by 24 hours of maturation), and Butyrolactone I (maturation blockage with 150mM Butyrolactone I during 24 hours followed by 24 hours of maturation). The oocytes were fixed and stained with aceto orcein to evaluate the nuclear maturation. After the maturation period, the remaining oocytes of the Control group, Roscovitine, and Butyrolactone I were fertilized in vitro. Embryo development was assessed by the cleavage rate (D3) and blastocysts formation (D7). The Butyrolactone I group had similar rates of germinal vesical stage oocytes during blockage, and Metaphase 2 after maturation, comparing to Control group at 0 hour and Control group, respectively. On the other hand, the Roscovitine group had lower rates of vesical stage oocytes during blockage, and Metaphase 2 after maturation comparing to Control groups. After in vitro fertilization, higher rates of cleavage were observed in Control and Butyrolactone I groups. For the blastocyst formation rate, the Control group showed better results than Roscovitine group. In summary, Butyrolactone I group had similar results to the Control group, and for this reason, is suitable for pre-maturation of bovine oocytes using FCS. In contrast, Roscovitine group had lower oocyte maturation and embryo development.

In vitro maturation of pig oocytes with different media, hormone and meiosis inhibitors.

This study evaluated in vitro maturation of pig oocytes in two maturation media (TCM199 and NCSU23) supplemented with 10% porcine follicular fluid (pFF) or 0.1% polyvinyl alcohol (PVA) and four hormonal treatments. The best media was then used to evaluate the effect of reversible meiosis inhibitors cycloheximide (5 microgram/ml) [DOSAGE ERROR CORRECTED]and butyrolactone I (12.5M) on the maturation of pig oocytes was evaluated. After maturation for 44 h, the oocytes were fixed, stained, and examined under epifluorescence microscopy. The comparison of the proportion of oocytes in metaphase II revealed that hormonal treatment 2(incubation for 22 h - 10 ng EGF/ml, 10 IU hCG/ml and 10 IU eCG/ml, followed by incubation for 22 h - 10 ng EGF/ml) presented higher repeatability percentages: TCM+ PVA (54.5% - 61/112); TCM+ pFF (65.0% - 63/97);NCSU23 + PVA (54.6% - 65/119), and NCSU23 + pFF (58.1% - 61/105). The comparison of maturation media showed that TCM199 presented more constant results than NCSU23. Regarding supplementation with pFF or PVA, TCM199 with pFF presented better results. The comparison between butyrolactone I and cycloheximide demonstrated that both drugs effectively inhibited meiosis; however, only cycloheximide presented metaphase II percentages similar to the control (70.29% and 75.49%, respectively). In conclusion, it is recommended the use of TCM199 medium supplemented with pFF and hormonal treatment with 10 ng EGF/ml, 10 UI hCG/mland 10 UI eCG/ml during the first 22 h and more 22 h with 10 ng EGF/ml for the pig oocytes maturation. Butyrolactone I and cycloheximide effectively arrested/resumpted maturation; however, the oocytes percentages in metaphase II was the same for both cycloheximide and the control groups.

Immature bovine oocyte cryopreservation: comparison of different associations with ethylene glycol, glycerol and dimethylsulfoxide.

Research on different cryoprotectants and their associations is important for successful vitrification, since greater cryoprotectant concentration of vitrification solution may be toxic to oocytes. The aim of the present research was to compare the efficiency of immature bovine oocyte vitrification in different associations of ethylene glycol (EG), glycerol and dimethylsulfoxide (Me(2)SO). In the first experiment, oocytes were exposed to the cryoprotectant for either 30 or 60s in final solutions of EG+DMSO1 (20% EG+20% Me(2)SO) or EG+DMSO2 (25% EG+25% Me(2)SO) or EG+GLY (25% EG+25% glycerol). In the second experiment, the oocytes were vitrified in open pulled straws (OPS) using 30s exposure of final solutions of EG+DMSO1 or EG+DMSO2 or EG+GLY. Maturation rates of 30s exposure groups were not different from the control, but 60s cryoprotectant exposure was toxic, decreasing maturation rates. The vitrification with EG+DMSO2 resulted in enhanced maturation rate (29.2%) as compared with EG+DMSO1 (11.7%) and EG+GLY (4.3%) treatments. These data demonstrate that concentration and type of cryoprotectant have important effects on the developmental competence of vitrified oocytes.

Criopreservação e desenvolvimento in vitro de embriões bovinos / Cryopreservation and in vitro survival of bovine embryos

O objetivo deste trabalho foi estudar a remoção do crioprotetor, em duas ou três etapas, em embriões bovinos produzidos in vitro após a congelação em vapor de Nirtogênio. Blastocistos expandidos (1329) foram mantidos em co-cultivo (controle) ou criopreservados em 3 protocolos de congelação em vapor de nitrogênio. Os embriões foram equilibrados na solução de 10% de EG por 10 minutos e em 17%, 22% ou 28% de EG por 30 segundos. Após o envase, as palhetas foram mantidas em vapor de nitrogênio por 2 minutos e armazenadas em nitrogênio líquido. Após a descongelação, os crioprotetores foram diluídos em duas etapas, usando 0,3M de sacarose e solução isotônica ou em três etapas usando 0,3M de sacarose + 10% de EG; 0,3M de sacarose e solução isotônica. Os embriões foram co-cultivados com células da granulosa, avaliando as taxas de re-expansão após 24 horas e de eclosão após 24, 48, 72 e 96 horas. Para os grupos congelados no vapor e diluição do crioprotetor em duas etapas, as taxas de eclosão foram de 1,94; 11,88 e 6,06% para EG17, EG 22 e EG 28 respectivamente. Já para os grupos com diluição do crioprotetor em três etapas, as taxas de eclosão foram de 4,67; 9,90 e 10,78% para EG17, EG22 e EG28 respectivamente.

The aim of this study was to evaluate the dilution of cryoprotectant in 2 or steps of bovine in vitro-produced embryos after quick-freezing. A total of 1329 expanded blastocyst were kept in co-culture as control group or cryopreserved by 3 quick-freezing protocols. The embryos were exposed to 10% EG for 10 minutes then to 17%, 22% or 28% for 30 seconds. After loading, the straws were held in nitrogen vapor for 2 minutes and then plunged and stored in liquid nitrogen. After warming, cryoprotectants were diluted in two steps using 0.3 M sucrose and isotonic solution, or three steps using 0.3 M sucrose + 10% EG then 0.3 M sucrose and isotonic solution. Embryos were co-cultured on a granulosa cell monolayer and evaluated after 24 hours for re-expansion and at 24, 48, 72 and 96 hours of co-culture for hatching rates. The in vitro survival rates of embryos cryopreserved by the quick-freezing method and two-step cryoprotectant dilution were 1.94; 11.88 and 6.06%, for EG17, EG22 and EG28 groups, respectively. At the three step dilution, the in vitro survival rates were 4.67; 9.90 and 10.78% for EG17, EG22 and EG28 groups, respectively.