Cryotolerance Of Embryos Research Articles

Supplementation of culture medium with L-carnitine improves development and cryotolerance of bovine embryos produced in vitro

High lipid content in embryos is associated with low freezing tolerance. This study assessed the effects of exogenous L-carnitine, an enhancer of lipid metabolism, on the in vitro development and freezing survival of bovine embryos. Also, effects on metabolic activity, reactive oxygen species (ROS) and apoptosis were investigated. Supplementation of embryo culture medium with 1.518 mM or 3.030 mM L-carnitine significantly increased the rates of zygote development to the blastocyst stage and blastocyst cell numbers whereas 6.072 mM of this compound did not improve embryo development. Survival rates after slow freezing of blastocysts were significantly higher when embryos were cultured in the presence of 1.518 mM or 3.030 mM L-carnitine compared with the control. A lower density of lipid droplets was detected in L-carnitine-treated blastocysts compared with the control. L-carnitine significantly reduced ROS levels in 2-cell embryos but did not reduce ROS levels at later stages. The apoptotic cell rate was not different between control and L-carnitine-treated blastocysts. L-carnitine significantly increased ATP levels in 2-cell embryos but not at the 8-cell or blastocyst stages. L-carnitine increased the expression of metabolism-related ATP6 and COX1 genes in blastocysts. In conclusion, L-carnitine supplementation enhanced lipid metabolism in embryos resulting in improved development and cryotolerance of bovine blastocysts produced in vitro.

Cryo-tolerance of zygotic embryos from recalcitrant seeds in relation to oxidative stress—A case study on two amaryllid species

Oxidative stress is a major component of cryoinjury in plant tissues. This study investigated the ability of recalcitrant (i.e. desiccation sensitive) Amaryllis belladonna L. and Haemanthus montanus Baker zygotic embryos to survive cryopreservation, in relation to oxidative stress. The study also investigated whether glycerol cryoprotection promoted embryo post-cryo survival by protecting enzymic antioxidant activities. Zygotic embryos excised from hydrated stored seeds were subjected to various combinations of rapid dehydration (to < or >0.4gg−1[dmb]), cryoprotection (with sucrose or glycerol), and cooling (either rapidly or slowly), and were thereafter assessed for viability, extracellular superoxide (O2−) production, lipid peroxidation (TBARS) and antioxidant enzyme activities. Short-term hydrated storage of whole seeds was accompanied by O2− production and lipid peroxidation, but O2− levels were lower than in dehydrated and cooled embryos and viability was 100%, possibly associated with the high activities of certain antioxidant enzymes. Partial dehydration and cryoprotection (in H. montanus only) increased O2− production (especially in cryoprotected-dried embryos) and was associated with some viability loss, but this was not correlated with enhanced lipid peroxidation. Cooling was generally accompanied by the greatest increase in O2− production, and with a decline in viability. In A. belladonna only, post-cryo TBARS levels were generally higher than for fresh and pre-conditioned embryos. Partial dehydration and cooling decreased antioxidant activities, but these were consistently less severe in glycerol cryoprotected-dried, as opposed to non-cryoprotected-dried embryos. Post-cryo viability retention for glycerol cryoprotected-dried embryos was significantly higher than for non-cryoprotected-dried embryos, possibly facilitated by relatively low post-drying TBARS levels and high post-drying and post-rewarming activities of some antioxidant enzymes in the former. Pre-conditioning treatments such as glycerol cryoprotection, when used in combination with partial drying, may enhance post-cryo viability retention in recalcitrant zygotic embryos by protecting the activities of certain antioxidant enzymes during pre-conditioning for, and after retrieval from, cryostorage.

Bovine OPU‐Derived Oocytes can be Matured In Vitro for 16–28 h with Similar Developmental Capacity

The aim of this study was to determine the optimal maturation culture period of ovum pick up (OPU)-derived cumulus oocytes complexes (COCs) in relation to their developmental capacity. Embryo production, embryo cryotolerance, post-transfer embryonic survival and calf characteristics such as gestation length, birthweight and sex ratio were investigated. This retrospective study covers the analyses of ovum pick up -in vitro production and calving results from a commercial programme that took place between March 1994 and September 2004. Donors were both heifers (of which approximately 90% pregnant) and cows (of which approximately 10% pregnant). Embryo production analyses were based on 7800 OPU sessions conducted from January 1995 until January 1999. Analyses of calving rate were based on 13 468 embryo transfers performed during January 1995 until May 2002. Analyses on calf characteristics were based on 2162 calves born between March 1994 and September 2004. The in vitro maturation culture period ranged from 16 to 28 h. The mean production rate of transferable embryos was 16.5% (1.2 embryos per OPU session). Length of maturation culture period did not affect the production of transferable embryos. Mean calving rate was 40.9% and 38.7% for fresh and frozen/thawed embryos, respectively. Calving rate was not affected by the maturation culture period. Mean birthweight, gestation length and proportion of male calves were 46 kg, 281.9 days and 52.8%, respectively. Maturation culture period did not affect these variables. In conclusion, this study shows that the in vitro maturation culture period within the range of 16-28 h does not affect in vitro embryo production, embryo cryotolerance, post-transfer embryonic survival and calf characteristics, suggesting that all COC batches collected by OPU on the same day, can be fertilized in one IVF session without a significant loss in the production from oocyte to calf.

89 PHENAZINE ETHOSULFATE AND FETAL CALF SERUM EFFECT IN THE ULTRASTRUCTURE AND DEVELOPMENT OF IN VITRO-PRODUCED BOVINE EMBRYOS

Over the past decades, there have been great advances in in vitro production (IVP) systems, with improved culture methods and new knowledge regarding embryo physiology, ultrastructure and morphology. Currently, the major obstacle associated with the extensive use of this technology is the great sensitivity of IVP embryos to cryopreservation. According to the literature, the reduced cryotolerance of IVP embryos is frequently associated with their high lipid content. Although is not clear until now how the lipid accumulation occurs, it may be influenced by the use of undefined culture media, supplemented with fetal calf serum (FCS); or as a result of embryo energy metabolism abnormalities that affect mitochondrial function, leading to the decrease in both the embryo quality and survival after cryopreservation. In this context, phenazine ethosulfate (PES), a reducer of NADPH electrons, which favours pentose–phosphate pathways and also inhibits the fatty acids synthesis, has been used to increase IVP embryo cryotolerance (Sudano et al. 2011 Theriogenology 75, 1211–1220). The aim of the present study was to evaluate the phenazine ethosulfate and FCS effect in the ultrastructure of IVP bovine embryos. A 2 × 2 factorial experiment design was used to test 2 FCS concentrations (0 or 10%) and the addition of PES (without or with PES) in the culture media. Slaughterhouse ovaries were used to obtain oocytes which were matured and fertilized in vitro (Day 0). Presumptive zygotes (n = 1440) were divided in 4 culture media: SOFaa without FCS; SOFaa without FCS + 0.3 μM PES (started on Day 4); SOFaa + 10% FCS; SOFaa + 10% FCS + 0.3 μM PES (started on Day 4). Embryo development was evaluated after 7 days under standard culture conditions (at 38.5°C in atmosphere of 5% O2, 5% CO2 and 90% N2). Transmission electron microscopy (TEM) was performed on Day-7 blastocysts from each group (n = 5) through standard protocol. For the statistical analysis, the arcsine transformation was applied to blastocyst percentage data and submitted to the ANOVA, followed by Tukeys' test through PROC GLM (SAS Institute Inc., Cary, NC, USA). In the absence of significant interactions, only main effect means are presented. The blastocyst production was not affected (P = 0.47) by the use of PES (42.7 ± 3.2 vs 39.3 ± 3.2, respectively for control and PES Day 4). The addition of 10% of FCS increased (P &lt; 0.0001) the percentage of blastocysts (48.9 ± 3.2 vs 33.0 ± 3.2, respectively, for 10% and 0% of FCS). The ultrastructure analysis showed similar features in embryos from all studied groups. However, embryos cultured in the absence of FCS presented fewer and smaller lipid droplets. Moreover, embryos cultured without FCS presented more cellular debris in the perivitelinic space and in the blastocoele, indicating loss of blastomeres. The use of PES was able to reduce lipid droplets and increase the mitochondrial number in serum-produced embryos. Therefore, the PES decreased lipid content and increased mitochondrial number without affecting the development and ultrastructure of IVP bovine embryos. FAPESP 09/54513-3, 10/09922-0.

88 EFFECT OF VITRIFICATION PROCEDURE ON SURVIVAL RATE OF BOVINE EMBRYOS PRODUCED IN VITRO

Vitrification as a cryopreservation method has many advantages compared with slow freezing. Many variables in the vitrification process exists that influence the survival rates of vitrified oocytes and embryos. These include the cryoprotectants (type, concentration, and duration of exposure), the temperature of the vitrification solution at exposure, the device used for vitrification, and the quality and developmental stage of embryos. It is worthwhile to mention that vitrification protocols successfully used in bovine oocytes and embryos have been used also with human oocytes and embryos. Vitrification is relatively simple, requires no freezing equipment, and relies on the placement of the embryos in a very small volume of vitrification medium that must be cooled at extreme rates not obtainable in regular enclosed straws. The aim of the present study was to evaluate the efficiency of 4 different vitrification protocols on the survival rate of in vitro produced (IVP) bovine embryos. Blastocysts were produced by a standard IVP procedure following in vitro maturation, fertilization, and culture in synthetic oviduct fluid supplemented with 5% fetal calf serum (FCS). On Day 7 (Day of IVF = Day 0), a total of 297 blastocysts were vitrified using (i) the open pulled straw (OPS) in 20% DMSO and 20% ethylene glycol (EG) in a basal medium of TCM-199 with HEPES supplemented with 20% FCS; (ii) the modified OPS, in 20% DMSO, 20% EG, and 0.5 M sucrose in a basal medium of phosphate buffer saline (PBS) supplemented with 20% FCS; (iii) the cryoloop, in 15% DMSO, 15% EG, 10 mg mL–1 Ficoll 70, and 0.65 M sucrose in a basal medium of PBS supplemented with 20% FCS; and (iv) in 0.25 straws in 20% glycerol, 20% EG, 0.3 M sucrose, 3% polyethylene glycol, and 0.3 M xylose in a basal medium of PBS. After warming, embryos were placed in culture for additional 24 h. Re-expansion and hatching rates were measured at 2 and 24 h after warming. Data were analysed by 1-way ANOVA. At 2 h post-warming, the re-expansion of blastocysts vitrified with cryoloop was significantly higher compared with OPS, modified OPS, and the 0.25 straw methods (54.08 ± 15.53 v. 10.40 ± 3.00, 22.67 ± 9.20, and 8.82 ± 2.15, respectively; P ≤ 0.028). At 24 h post-warming, only embryos from cryoloop and modified OPS were still alive with a survival rate of embryos vitrified with cryoloop significantly higher than that of those vitrified with modified OPS (48.45 ± 17.56 v. 3.75 ± 3.75, respectively; P ≤ 0.007). Hatching rates at 24 h post-warming were not different between cryoloop and modified OPS groups (5.63 ± 4.40 and 1.25 ± 1.25, respectively). These results clearly demonstrate that embryo cryotolerance is affected by the method used for cryopreservation. Moreover, cryoloop vitrification was found to be more effective than OPS and 0.25 straw methods for the cryopreservation of bovine embryos.

Oocyte secreted factors improve embryo developmental competence of COCs from small follicles in prepubertal goats

Oocytes secrete soluble paracrine factors called Oocyte Secreted Factors (OSFs) which regulate the cumulus cell phenotype. Follicle populations in ovaries from prepubertal females have smaller diameters than their adult counterparts. Oocytes from small follicles are less competent than those from large follicles. The aim of this study was to investigate, in prepubertal goats, the effect of OSFs secreted by denuded oocytes (DOs) from small (<3 mm) or large (≥3 mm) follicles during IVM on embryo development and the blastocyst quality of cumulus-oocyte complexes (COCs) from small follicles and to determine if GDF9 participates in this process. Treatment groups were: (A) COCs non selected by their follicle size (control group); (B) cumulus oocytes complexes from small follicles (SFCOCs), (C) cumulus oocytes complexes from small follicles co-cultured with denuded oocytes from small follicles (SFCOCs + SFDOs), and (D) cumulus oocytes complexes from small follicles co-cultured with denuded oocytes from large follicles (SFCOCs + LFDOs). The effect of the addition of kinase inhibitor SB-431542, which antagonizes GDF9, was tested in A, C, and D treatment groups. Co-cultured SFCOCs with SFDOs or LFDOs significantly augmented the blastocyst rate in comparison to SFCOCs alone (15.77%, 17.39% vs. 10.31%, respectively). Blastocysts from SFCOCs + LFDOs group showed higher rates of tetraploid nuclei than blastocysts from SFCOCs and the control group (14.43% vs. 5.45% and 5.24%, respectively; P < 0.05). However, we did not observe differences in the hatching rate, mean cell number or embryo cryotolerance (P > 0.05) between the four treatment groups. The addition of SB-431542 during IVM did not have any effect on blastocyst rate (P > 0.05). In conclusion, in prepubertal goats, COCs with a low embryo developmental competence as a consequence of follicle size can be improved by coculturing them with denuded oocytes from both small and large follicles. GDF9 does not seem play a role in this improvement.

Advances in Swine In Vitro Embryo Production Technologies

Recent advances in new technologies to produce cloned and genetically modified pigs involve manipulating oocytes and/or embryos in vitro. Although a great deal of progress has been made, the current IVM-IVF systems still result in major problems: a high rate of polyspermy; and a low development rate and low quality of blastocysts for in vitro compared with the in vivo-produced embryos. This study summarizes recent advancements in IVM-IVF-IVC porcine systems. Recent methods to select monospermic embryos are also discussed. Finally, achievements in vitrification and in somatic cell nuclear transfer are discussed.

118 ARE LIPID CONTENTS AND APOPTOSIS DETERMINANTS OF IN VITRO-PRODUCED BOVINE EMBRYO SUSCEPTIBILITY TO VITRIFICATION?

Supplementation of fetal calf serum (FCS) during culture of bovine in vitro-produced embryos (IVPE) has been correlated with lipid accumulation, representing a limiting factor on embryo cryotolerance. In the present experiment we studied lipid content and apoptosis in Nelore IVPE cultured in different concentrations of FCS. The experimental design was a 4 × 2 × 2 factorial, in which embryos, exposed or not to the metabolic regulator, phenazine ethosulfate (PES), were cultured in 4 concentrations of FCS. In 16 replicates, 560 IVPE were vitrified after cultured in SOFaa supplemented with 0, 2.5, 5 or 10% FCS. On Day 2.5 of culture, one-half of the embryos in each group were treated with 0.3 μM of PES and then returned to standard culture conditions (5% O2, 5% CO2 and 90% N2 atmosphere at 38.5°C). All embryos were vitrified on Day 7 (Campos-Chillòn LF et al. 2006 Theriogenology 65, 1200-1214). After warming, embryos were placed into culture for 12 h under standard conditions. A sample of fresh embryos was stained with Sudan Black B for quantification of small (&lt;2 μm), medium (2-6 μm), and large (&gt;6 μm) cytoplasmic lipid droplets. Apoptosis was analyzed, before and after vitrification, using TUNEL. As a positive control (CV), in vivo-produced embryos were collected from a superovulated Nelore cow. Data were analyzed using ANOVA followed by Tukey’s test; and Pearson’s linear correlation (P &lt; 0.05). The results indicate that FCS concentration and PES treatment had no influence (P &gt; 0.05) on cleavage and blastocyst formation rates (mean of 85.7 ± 2 and 36.6 ± 5, respectively). The total number of cells in fresh embryos was also similar (P &gt; 0.05) among groups (mean of 134.1 ± 28). Additional results are shown in Table 1. Elevated concentrations of FCS increased lipid accumulation (r = 0.9) and the percentage of apoptotic cells in fresh and vitrified embryos, reducing the re-expansion rate after warming. Moreover, the number of apoptotic cells observed in fresh embryos was strongly correlated with the apoptosis observed after vitrification (r = 0.95). Although PES was able to reduce lipid accumulation, it was not efficient at preventing apoptosis in vitrified embryos. In summary, the results of this experiment indicate that the concentration of FCS during culture did not influence cleavage and blastocyst formation in bovine IVPE. We conclude that the apoptosis rate in fresh embryos is a key factor affecting survival after vitrification. Table 1.Lipid droplets, re-expansion, apoptosis of in vivo and IVPE Acknowledgements: FAPESP (07/57766-4).

93 POSTCRYOPRESERVATION VIABILITY OF EMBRYOS FROM NELLORE HEIFERS SUPPLEMENTED WITH RUMEN-PROTECTED FAT

Polyunsaturated fatty acids seem to exert an extra-caloric positive effect on ruminant reproduction, although the reasons for that are still unclear. Although some studies have detected a positive effect of feeding unsaturated fatty acids on embryo development of superovulated Bos taurus cattle (Thangavelu et al. 2007 Theriogenology 68, 949-957), others have not (Petit et al. 2008 J. Dairy Sci. 91, 1786-1790). Our hypothesis was that, although number and quality of embryos from superovulated heifers would not be affected by diet, supplemental fat would improve embryo cryotolerance. Therefore, this study evaluated superovulatory response and embryo production, as well as cryotolerance of embryos cryopreserved through freezing or vitrification in Nellore heifers supplemented with rumen-protected fat. Forty heifers (24 to 36 mo old) were kept in pasture and randomly divided into 2 experimental groups according to supplemental source [F = concentrate with rumen-protected fat (100 g/d of Megalac-E®) and C = control, without fat supplementation]. Supplements were formulated to be isocaloric and isoproteic. Each female underwent both treatments in a cross-over design with approximately 68 d between replicates. After 50 d of feeding, emergence of the wave was synchronized with the aid of hormones to initiate the superovulation protocol. Recovered embryos were frozen or vitrified, and subsequently in vitro embryo development evaluation was accomplished. Data were analyzed using generalized linear models. There was no difference between F and C groups (P &gt; 0.10) regarding superstimulatory response, number of total embryos/ova, viable embryos, degenerate embryos, or unfertilized oocytes recovered. However, group C had a greater superovulatory response than F (18.0 ± 1.3 v. 15.7 ± 1.2 CL; P = 0.06). Group C embryos presented greater hatching rate, independently of the cryopreservation method, at 48 h (33.1 ± 4.0%; n = 148 v. 17.3 ± 3.3%; n = 137; P = 0.009) and at 72 h (44.3 ± 4.2%; n = 148 v. 30.9 ± 4.0%; n = 137; P = 0.04) of in vitro culture. Under the conditions of the present study, supplementation with protected fat did not affect superstimulatory response and quantity or quality of embryos. However embryos from the F group were less tolerant to cryopreservation. Financial support from FAPESP, EMBRAPA, Arm &amp; Hammer, Integral Produbon, and Pfizer of Brazil.

115 ADDITION OF ETHANOL AT SUB-STRESS CONCENTRATIONS DURING IN VITRO MATURATION OF BOVINE OOCYTES IMPROVES BLASTOCYST CRYOTOLERANCE

In in vitro experiments, the percentage of bovine oocytes that develops to the blastocyst stage is much lower compared with the in vivo counterparts. The quality of the oocyte is the main factor affecting blastocyst yield. Moreover, in vitro-produced bovine embryos are more sensitive to cryo-injuries than those produced in vivo. Exposure of oocytes to sub-lethal concentrations of stressors may enhance their quality through upregulation of intracellular shock proteins. We aimed to evaluate whether addition of ethanol at low concentrations (0.27 or 0.53%) during oocyte maturation could have a carry-over effect on embryo quality and could subsequently affect embryo cryotolerance. Cumulus-oocyte complexes (n = 934) were matured in serum-free TCM199 plus 20 ng mL-1 of epidermal growth factor (control), supplemented with ethanol 0.27% (treatment 1) or 0.54% (treatment 2), in 3 replicates. After fertilization, the presumptive zygotes were cultured for 6 days in modified SOF medium supplemented with 5% fetal calf serum (FCS); the number of blastocysts was recorded and classified. Then, expanded blastocysts were cryopreserved by open pulled straw vitrification using the 2-step approach described by Vajta G et al. (1998 Mol. Reprod. Dev. 51, 53-58). After 24 h, vitrified embryos were warmed and cultured in groups of &lt;25 per 50 μL droplet of modified SOF medium with 5% FCS under mineral oil for 48 h and examined for re-expansion and hatching. Differences between the groups in blastocyst yield were analyzed by ANOVA; differences in survival rates between the groups were analyzed using logistic regression analysis. For all statistical models, group was included as fixed effect, and also the effect of replicate was included. Differences were considered to be statistically significant when P &lt; 0.05. Addition of ethanol to in vitro maturation media had no significant effects on blastocyst yield on 7 dpi. Also, addition of ethanol at 0.27% did not affect blastocyst cryotolerance. However, addition of ethanol 0.54% to in vitro maturation media significantly increased the survival of bovine blastocysts after vitrification (P &lt; 0.01; Table 1). The results of the present study indicate that maturation of oocytes under ethanol stress at low concentrations has carry-over effects on embryo quality, leading to improved cryotolerance. Table 1.Survival percentage (mean ± SE) of vitrified expanded bovine blastocysts matured in the presence of sub-stress concentrations of ethanol The authors thank I. Lemahieu and P. Vandamme for their excellent technical support. This research was supported by the special research fund, Ghent University (Grant, BOF/DOS No. 01W05706).

Vitrification of in vitro produced ovine embryos at various developmental stages using two methods

This study was conducted to evaluate the effects of developmental stage of in vitro produced (IVP) ovine embryos and the type of vitrification procedure used on embryo cryotolerance. The IVP embryos were vitrified at five different developmental stages: 4-, 8- and 16-cell, morula, and blastocyst. For each stage, half of the embryos were vitrified in either 30 μl 3.4 M glycerol + 4.6 M ethylene glycol in straw (method 1) or in <0.1 μl 2.7 M ethylene glycol + 2.1 M Me 2SO + 0.5 M sucrose placed on the inner surface of a straw (method 2) of vitrification solution, based on two different procedures. After warming embryo viability was determined by assessing the rates of re-expansion, survival, and blastocyst formation. The quality of surviving embryos was evaluated by their hatching rate and blastocyst cell numbers. In both vitrification methods, embryo survival progressively increased as the developmental stage progressed. In method 1 few of the early cleavage stage embryos (4-, 8- and 16-cell) could reach to the blastocyst stage following warming. There was no significant difference in blastocyst cell numbers (total, ICM, and trophectoderm cells) or hatching rate of blastocysts derived from vitrified embryos at different developmental stages. The number of dead cells in vitrified blastocysts in method 1 was higher than for non-vitrified blastocysts ( P < 0.05). The number of apoptotic cells in vitrified blastocysts was higher than for non-vitrified counterparts ( P < 0.05). In conclusion, both the developmental stage of IVP ovine embryos and the method of vitrification have a significant effect on the viability and developmental competence of sheep embryos.

Cryotolerance of Bovine Blastocysts is Affected by Oocyte Maturation in Media Containing Palmitic or Stearic Acid

In this study, non-esterified fatty acids (NEFAs) were added during in vitro maturation at concentrations measured previously in follicular fluid (FF) of high-producing dairy cows in a negative energy status to evaluate their subsequent effect on the embryos cryotolerance. Oocytes were matured for 24 h in serum-free media with or without (negative control) the addition of NEFAs dissolved in ethanol or ethanol alone (positive control). Matured oocytes were fertilized and cultured for 7 days in synthetic oviduct fluid medium supplemented with 5% FCS. Embryos that had at least reached the blastocyst stage were vitrified by open pulled straw (OPS) vitrification. Addition of palmitic (C16 : 0) or stearic acid (C18 : 0) during oocyte maturation had significant negative effects on embryo cryotolerance, whereas ethanol or oleic acid (C18 : 1) had no effect. These in vitro results suggest that high NEFA concentrations in FF during a period of negative energy balance in high-yielding dairy cows can have carry-over effects on embryo quality.

In vitro production and cryotolerance of prepubertal and adult goat blastocysts obtained from oocytes collected by laparoscopic oocyte-pick-up (LOPU) after FSH treatment

This study compares the developmental capacity and cryotolerance of embryos produced from oocytes of stimulated prepubertal and adult Sarda goats. Twelve prepubertal and 13 adult goats were each given 110 and 175 IU FSH, respectively, and cumulus-oocyte complexes (COCs) were collected by laparoscopic oocyte-pick-up (LOPU). After in vitro maturation, fertilisation and culture (IVMFC), blastocysts were vitrified, warmed and blastocoel re-expansion and gene expression were evaluated. Prepubertal goats produced a higher COCs number than adults (mean +/- s.e.m., 89.67 +/- 5.74 and 26.69 +/- 3.66, respectively; P < 0.01). Lower developmental competence was demonstrated in the prepubertal oocytes as shown by a higher number of COCs discarded before IVM (21.1% and 14.7% for prepubertals and adults, respectively; P < 0.01) and IVF (23.4% v. 9.1%; P < 0.01) and by the lower cleavage (55.6% and 70.3%, respectively; P < 0.01) and blastocyst rates (24.2% and 33.9%, respectively; P < 0.05). Compared with the adult, prepubertal vitrified/warmed blastocysts showed significantly (P < 0.05) lower in vitro viability, as determined by the re-expansion rate (62.5% and 40.3%). No differences were observed in the time required for blastocoel re-expansion or in cyclin B1, E-cadherin, Na/K ATPase, HSP90beta and aquaporin 3 messenger RNA quantity. These results show that in vitro-produced embryos produced from prepubertal goat oocytes have a lower developmental rate and cryotolerance compared with their adult counterparts. However, we can assume that the quality of re-expanded embryos does not differ between the two groups.

74 EFFECT OF BETA-MERCAPTOETHANOL ON THE VITRIFICATION CRYOTOLERANCE OF BOVINE IN VITRO-PRODUCED EMBRYOS

The control of oxidative processes in in vitro production (IVP) systems by the use of additives may be an alternative approach to improve embryo cryotolerance. The aim of this study was to verify the effect of β-mercaptoethanol (βME) on the cryotolerance of bovine IVP embryos. In 7 replications, and following IVM-IVF, presumptive zygotes (n = 3735) were in vitro-cultured in SOF medium supplemented or not with 100 μm βME (IVC treatment), at 38.5°C and high humidity. The initial 24 h of IVC was performed in 5% CO2 in air, with the remaining 6 days of IVC carried out in 5% CO2, 5% O2, and 90% N2. On Day 7, resulting blastocysts and expanded blastocysts were vitrified in glass micropipettes in a solution with 20% ethylene glycol + 20% propylene glycol. After warming, embryos were randomly allocated to 1 of 2 sub-groups for an additional 72 h of IVC to the hatching blastocyst (HBL) stage, in fresh SOF medium supplemented or not with 100 μm βME (PVC treatment), at 38.5°C, high humidity and 5% CO2. Experimental groups were as follows: G1 (βME-free medium during IVC and PVC); G2 (βME only during PVC); G3 (βME only during IVC); and G4 (βME during IVC and PVC). Cleavage (Day 2) and blastocyst (Day 7) rates in the IVC treatment and hatching rates (Days 7 to 9) for the PVC treatment were analyzed by the chi-square test, for P &lt; 0.05. Total cell number (TCN) estimated by fluorescence staining in HBL derived from vitrified and nonvitrified embryos was analyzed by ANOVA. The use of βME during IVC did not affect cleavage rates (βME-free, 1491/1858, 80.2% v. βME, 1522/1877, 81.1%), but negatively affected development to the blastocyst stage (βME-free, 813/1858, 43.8% v. βME, 525/1877, 28.0%). Following vitrification, however, βME supplementation during PVC improved hatching rates (G2, 58.1% and G4, 63.8%) compared with groups without the additive (G1, 36.6% and G3, 42.0%). In addition, the presence of βME either during IVC or PVC, or during both culture periods, increased TCN in HBL from vitrified embryos (Table 1). The use of βME during IVC, irrespective of the presence of βME during the PCV period, caused an increase in TCN in HBL in G3 + G4, with no effects on hatching rates (Table 1b), whereas the addition of βME during PVC, irrespective of the presence of βME during the IVC period, resulted in greater hatching rates and TCN in HBL in G2 + G4 than in G1 + G3 (Table 1). In conclusion, the addition of βME during the IVC period did not affect cleavage, but reduced blastocyst yield. Despite that, βME supplementation during the IVC period appeared to have increased the cryotolerance of the resulting blastocysts, expressed by greater TCN in HBL, whereas βME supplementation during the PVC period also improved embryo survival to the vitrification process, manifested by greater hatching rates and TCN in HBL. Table 1.Effect of βME on the cryotolerance of bovine IVP embryos This study was supported by a grant from CNPq/Brazil.

High Hydrostatic Pressure Treatment of Porcine Oocytes before Handmade Cloning Improves Developmental Competence and Cryosurvival

An innovative technique, called the high hydrostatic pressure (HHP) treatment, has been recently reported to improve the cryosurvival of gametes or embryos in certain mammalian species. The aim of the present study was to investigate the in vitro and in vivo developmental competence and cryotolerance of embryos produced by handmade cloning (HMC) after pressure treatment of recipient oocytes. In vitro-matured porcine oocytes were treated with a sublethal hydrostatic pressure of 20 MPa (200 times greater than atmospheric pressure) and recovered for either 1 or 2 h (HHP1 and HHP2 groups, respectively) before they were used for HMC. After 7 days of in vitro culture, blastocyst rates and mean cell numbers were determined. Randomly selected blastocysts were vitrified with the Cryotop method based on minimum volume cooling procedure. The blastocyst rate was higher in the HHP2 group than in the control group (68.2 +/- 4.1% vs. 46.4 +/- 4.2%; p < 0.01), while there was no difference between HHP1 and control group (52.1 +/- 1.2% vs. 49.0 +/- 2.7%; p > 0.05). Similar mean cell numbers of produced blastocysts were obtained in HHP2 and control groups (56 +/- 4 vs. 49 +/- 5; p > 0.05). Subsequent blastocyst vitrification with the Cryotop method resulted in significantly higher survival rate after thawing in the HHP2 group than in the control group (61.6 +/- 4.0% vs. 30.2 +/- 30.9%; p < 0.01). Fifty-six and 57 day 5 to day 7 fresh blastocysts in HHP1 group were transferred into two recipient sows on day 5 of the estrous cycle. One recipient was diagnosed pregnant and gave birth to two healthy piglets by naturally delivery on day 122 of gestation. This pilot study proved that the sublethal HHP treatment of porcine oocytes before HMC results in improved in vitro developmental competence and cryotolerance, and supports embryonic and fetal development as well as pregnancy establishment and maintenance up to the birth of healthy piglets.

252 VITRIFICATION OF BOVINE BLASTOCYSTS PRODUCED AFTER OOCYTE MATURATION IN MEDIA CONTAINING FATTY ACIDS

High concentrations of non-esterified fatty acids (NEFA) during negative energy balance (NEB) in high yielding dairy cows have been proven to be partially responsible for reduced fertility. This hypothesis has been tested by the addition of NEFAs to in vitro maturation medium at concentrations present in follicular fluid during NEB. We aimed to evaluate whether high concentrations of palmitic acid (C16:0) (PA), stearic acid (C18:0) (SA), or oleic acid (C18:1) (OA) during oocyte maturation could have a carry-over effect on embryo quality and could subsequently affect embryo cryotolerance. Cumulus–oocyte complexes (n = 4600) were matured in serum-free TCM199 plus epidermal growth factor (EGF, 20 ng mL–1; negative control), supplemented with ethanol alone (positive control) or with 0.133 mmol L–1 PA, 0.067 mmol L–1 SA, or 0.200 mmol L–1 OA (NEFAs dissolved in ethanol). The three NEFAs were tested separately in 4 replicates for PA and 5 replicates for OA or SA. Each fatty acid tested per replicate including a negative and a positive control group. After the embryos were cultured for 7 days in SOF medium, the number of blastocysts was recorded and classified as expanded, hatching, or hatched. Then, blastocysts were cryopreserved by open pulled straw vitrification using the two-step approach described by Vajta et al. (1998 Mol. Reprod. Dev. 51, 53–58). Vitrified warmed embryos were cultured in groups of &lt;25 per 50-μL droplet of modified SOF medium with 5% fetal calf serum (FCS) under mineral oil for 48 h and examined for re-expansion and hatching. The percentages of survival in the different treatment groups were analyzed using logistic regression analyses, including the effect of replicates. Survival or not was included as the dependent variable and group was the independent variable. For every fatty acid a separate model was used. For all analyses, differences were considered to be statistically significant at the P &lt; 0.05 level. Addition of OA to in vitro maturation media had no significant effects on cryotolerance of embryos. However, addition of PA or SA to in vitro maturation media (Table 1) significantly (P &lt; 0.05) decreased the survival of bovine blastocysts from 79% in the positive control to 57% in PA and from 61% to 53% in SA. The results of the present study indicate that maturation of oocytes in the presence of NEB-associated concentrations of PA and SA can have carry-over effects on embryo quality, leading to reduced cryotolerance. We suggest that elevated NEFA concentrations in the follicular fluid may be one of the factors through which NEB exerts its negative effects on fertility in high yielding dairy cows. Table 1. Survival percentage (mean ± SD) of vitrified expanded bovine blastocysts matured in palmitic acid (C16:0) or stearic acid (C18:0) The authors thank J. Mestach and G. Spaepen for their excellent technical support. This research was supported by the Ministry of the Flemish Community, Belgium, in cooperation with the Ministry of Higher Education, Egypt.

Effects of fetal calf serum, phenazine ethosulfate and either glucose or fructose during in vitro culture of bovine embryos on embryonic development after cryopreservation

This study investigated effects of hexoses, fetal calf serum (FCS), and phenazine ethosulfate (PES) during the culture of bovine embryos on blastocyst development and survival after cryopreservation by slow freezing or vitrification. The basal, control medium was chemically defined (CDM) plus 0.5% fatty acid-free BSA. In vitro-produced bovine zygotes were cultured in CDM-1 with 0.5 mM glucose; after 60 hr, 8-cell embryos were cultured 4.5 days in CDM-2. The 8-cell embryos were randomly allocated to a 2 x 3 x 2 x 3 factorial experimental design with two energy substrates (2 mM glucose or fructose); three additives (0.3 microM PES, 10% FCS, and control); two cryopreservation methods using no animal products (conventional slow freezing or vitrification); and semen from three bulls with two replicates for each bull. A total of 1,107 blastocysts were produced. Fructose resulted in 13% more blastocysts per oocyte than glucose (37.2% vs. 32.9%), and per 8-cell embryo (51.3% vs. 45.3%; P < 0.01). No differences were found for additives (P > 0.1) control, FCS, or PES for blastocysts per oocyte or per 8-cell embryo. There was a significant interaction (P < 0.05) between additives and hexoses for blastocyst production; although trends were similar, the benefit of fructose compared to glucose was greater for controls than for FCS or PES. Culture of embryos with PES, which reduces cytoplasmic lipid content, improved cryotolerance of bovine embryos; post-cryopreservation survival of blastocysts averaged over vitrification and slow freezing (between which there was no difference) was 91.9%, 84.9%, and 60.2% of unfrozen controls (P < 0.01) for PES, control, and FCS groups, respectively.

Modifying oocytes and embryos to improve their cryopreservation

Numerous studies indicate that in vitro-produced bovine embryos do not survive cryopreservation as well as those produced in vivo. Furthermore, embryos cultured in vitro in the absence of blood serum are more cryotolerant than embryos cultured in media containing serum. Although in vivo-produced embryos are more cryotolerant, there appear to be breed differences. Most if not all of these observations are correlated with cytoplasmic lipid content of embryos; more and larger lipid droplets are associated with reduced cryotolerance. This review concerns strategies for modifying oocytes and embryos to increase cryosurvival. Reduction of cytoplasmic lipid content of embryos with phenazine ethosulfate (PES), a compound that oxidizes NADPH, even improved cryotolerance of bovine embryos cultured in the absence of serum. Whether cytoplasmic lipid content per se or associated changes in lipid composition of cell membranes are responsible for differences in cryotolerance is unknown. Increasing cholesterol content of membranes of sperm and oocytes via cholesterol-loaded cyclodextrin also appears to improve cryotolerance. While lipids have been emphasized and appear to be important, non-lipid aspects of cell composition also likely affect cryotolerance, and might be modified to improve cryotolerance. Additional research on mechanisms of variation in cryotolerance will be applicable to circumvent cryo-intolerance attributable to variation associated with the individual animal, breed, species, cell type, and factors such as nutrition and season of the year.

95 EFFECT OF ESTROUS COW SERUM ON SURVIVAL OF IN VITRO-PRODUCED BOVINE EMBRYOS AFTER SLOW FREEZING OR VITRIFICATION

Until now, the major obstacle associated with the extensive use of in vitro-produced bovine embryos is the lack of suitable methods to cryopreserve them. At least two approaches exist for overcoming this problem. One is to adjust cryopreservation methods to the requirements of these embryos, and the other is to improve embryo quality by using an appropriate in vitro environment for embryo production. The objective of this study was to determine the effect of estrous cow serum (ECS) during in vitro culture on embryo survival after cryopreservation by slow freezing or vitrification. Cumulus-oocytes complexes were in vitro-matured and fertilized as previously described (Ferre et al. 2003 Theriogenology 59, 301 abst). Presumptive zygotes were denuded from cumulus cells and cultured in groups of 50 in 400 μL drops of CR1aa medium. Seventy-two hour post-insemination (PI) embryos were randomly separated into three groups. Each group was then cultured in CR1aa + 5% ECS (without BSA; CR1-ECS), CR1aa + 3 mg/mL BSA (CR1-BSA), or CR1aa + 5% ECS + 3 mg/mL BSA (CR1-ECS-BSA). Embryos were cultured under 38.5°C, 5% CO2, 5% O2, and 90% N2. At 7.5 days PI, blastocysts from each group were double stained using propidium iodide and bisbenzimide (Hoechst 33342) to determine damaged cells and total cell number. The remaining embryos were randomly cryopreserved by freezing (1.5 M ethylene glycol; cooled at 0.5°C/min to −35°C) or vitrification (open pulled straw, Vajta et al. 1998 Mol. Reprod. Dev. 51, 53–58). After thawing or warming, embryos were cultured in CR1-ECS-BSA to evaluate embryo survival (hatching rate). Data were analyzed by χ2, ANOVA and Student's t-test (SAS Institute, Inc., Cary, NC, USA). Total cell number was higher in embryos cultured in CR1-ECS than in CR1-BSA or CR1-ECS-BSA (CR1-ECS: 142.1 ± 4.7, n = 23 vs. CR1-BSA 124.7 ± 4.9, n = 21, and CR1-ECS-BSA 125.8 ± 4.5, n = 25; t-test, P &lt; 0.05). No differences were found in percent of damaged cells (CR1-ECS: 0.7%; CR1-BSA: 1.8%; CR1-ECS-BSA: 0.7%). Blastocyst survival after thawing was affected by cryopreservation methods and culture media (P &lt; 0.01, Table 1). No interaction was found between both factors. In conclusion, under our experimental conditions elimination of ECS from CR1aa medium improves embryo cryotolerance. Vitrification allows for higher survival rates, regardless of the presence of serum during embryo culture. Table 1. Effect of cryopreservation method and serum supplementation during embryo culture on survival rate of in vitro-produced bovine embryos

FSH different regimes affect the developmental capacity and cryotolerance of embryos derived from oocytes collected by ovum pick-up in donor sheep

The objective of the present study was to compare the developmental capacity of sheep oocytes obtained by OPU after two different ovarian stimulations, and cryotolerance to vitrification procedures of in vitro derived embryos after in vitro maturation, fertilisation and culture of these oocytes. Sheep were divided into three groups: (A) no treatment (control); (B) constant doses of FSH (FSH-c); (C) decreasing doses of FSH (FSH-d). Ovine groups FSH-c and FSH-d were synchronised by the insertion of intravaginal sponges left in situ for 7 days; FSH (total dose: 96 IU) was administered in four doses given every 12 h starting on Day 5. Twelve hours after the last FSH administration oocytes were collected by OPU technique. The control group showed a significantly lower number ( P<0.05) of follicles (166) than FSH-c (294) and FSH-d (317) groups, while the number of follicles >5 mm was significantly higher ( P<0.01) in FSH-d group, showing that this protocol stimulates the growth of a different follicle population compared to FSH-c group. The control group showed a higher number of <2 mm follicles ( P<0.01). We did not find any difference in oocyte quality between the three groups and therefore the percentage of discarded oocytes was similar. No significant differences were found between control, FSH-c and FSH-d groups in terms of maturation (90.9, 85.7 and 87.7%, respectively) and fertilisation rates (75.2, 80.9 and 83.7%, respectively) while a significantly higher ( P<0.01) blastocyst rate was observed in the FSH-c group than in the FSH-d and control groups (20.4% versus 11.8 and 13.7%, respectively). After vitrification, warming and 72 h in vitro culture, the hatching rate was significantly higher ( P<0.01) in the control (87.5%) and FSH-c (90.5%) groups than in the FSH-d group (66.7%). Control and FSH-c groups showed a significantly higher ( P<0.001) number of total cells than FSH-d group (217.6±26.5 and 203.0±33.2 versus 147.5±20.2), while no differences were observed in ICM cell rates in the control (35.6±3.8), FSH-c (37.1±4.6) and FSH-d (36.6±6.7) groups. These results indicate that donor sheep stimulated with FSH-c produced better quality oocytes and blastocysts showing better cryotolerance than ewes given the decreasing doses treatment.