Effect of linoleic acid-albumin on post-thaw survival of in vitro-produced bovine embryos at the 16-cell stage

Impact of reducing lipid content during in vitro embryo production: A systematic review and meta-analysis

There is still no consensus regarding the role of lipid modulators during in vitro embryo production. Thus, we investigated how lipid reducers during the in vitro maturation of oocytes (IVM) or in vitro culture (IVC) of embryos impact their cryotolerance. A literature search was performed using three databases, recovering 43 articles for the systematic review, comprising 75 experiments (13 performed in IVM, 62 in IVC) and testing 13 substances. In 39 % of the experiments, an increase in oocyte and/or embryo survival after cryopreservation was reported, in contrast to 48 % exhibiting no effect, 5 % causing negative effects, and 8 % influencing in a dose-dependent manner. Of the 75 experiments extracted during IVM and IVC, 41 quantified the lipid content. Of those that reduced lipid content (n = 26), 50 % increased cryotolerance, 34 % had no effect, 8 % harmed oocyte/embryo survival, and 8 % had different results depending on the concentration used. Moreover, 28 out of the 43 studies were analyzed under a meta-analytical approach at the IVC stage in cattle. There was an improvement in the cryotolerance of bovine embryos when the lipid content was reduced. Forskolin, l-carnitine, and phenazine ethosulfate positively affected cryotolerance, while conjugated linoleic acid had no effect and impaired embryonic development. Moreover, fetal bovine serum has a positive impact on cryotolerance. SOF and CR1aa IVC media improved cryotolerance, while mSOF showed no effect. In conclusion, lipid modulators did not unanimously improve cryotolerance, especially when used in IVM, but presented positive effects on cryotolerance during IVC when reaching lipid reduction.

Bioactive supplements influencing bovine in vitro embryo development

Ovum pickup and in vitro production (IVP) of bovine embryos are replacing traditional multiple ovulation embryo transfer (MOET) as the primary means for generating transferable embryos from genetically elite sires and dams. However, inefficiencies in the IVP process limit the opportunities to produce large numbers of transferable embryos. Also, the post-transfer competency of IVP embryos is inferior to embryos produced by artificial insemination or MOET. Numerous maternal, paternal, embryonic, and culture-related factors can have adverse effects on IVP success. This review will explore the various efforts made on describing how IVP embryo development and post-transfer competency may be improved by supplementing hormones, growth factors, cytokines, steroids and other bioactive factors found in the oviduct and uterus during early pregnancy. More than 40 of these factors, collectively termed as embryokines, are reviewed here. Several embryokines contain abilities to promote embryo development, including improving embryo survivability, improving blastomere cell numbers, and altering the distribution of blastomere cell types in blastocysts. A select few embryokines also can benefit pregnancy retention after IVP embryo transfer and improve neonatal calf health and performance, although very few embryokine-supplemented embryo transfer studies have been completed. Also, supplementing several embryokines at the same time holds promise for improving IVP embryo development and competency. However, more work is needed to explore the post-transfer consequences of adding these putative embryokines for any adverse outcomes, such as large offspring syndrome and poor postnatal health, and to specify the specific embryokine combinations that will best represent the ideal conditions found in the oviduct and uterus.

Viabilidade de embriões vitrificados oriundos da fertilização in vitro de oócitos de vacas suplementadas com canola

Avaliou-se a produção de oócitos e embriões de vacas Nelore in vitro e a resistência à vitrificação. Foram utilizadas 12 vacas Nelore, distribuídas aleatoriamente em dois tratamentos: T1-tratados com canola em grão (2,0kg/animal/dia) e T2-controle. Cada animal foi aspirado quatro vezes para obtenção de óocitos para fecundação in vitro. Os oócitos foram quantificados e classificados em viáveis ou inviáveis. Os zigotos foram cultivados in vitro e, sete dias após, os embriões foram avaliados quanto à qualidade e grau de desenvolvimento e vitrificados em hastes próprias. Na sequência, foram descongelados e cultivados em 6, 12 e 24 horas, observando-se a taxa de expansão e eclosão. Não houve diferenças (P>0,05) no número total de oócitos viáveis, T1=12,7% e T2=11,0%, na taxa de clivagem, T1=60,6% e T2=61,4%, e taxa de blastocistos, T1=23,7% e T2=27,0%, em função do tratamento. Também não houve influência na taxa de re-expansão, T1=70,5 e T2=59,6%, após a vitrificação e descongelamento. Todavia houve diferença (P<0,06) para a taxa de eclosão, T1=69,2 e T2=35,7. Conclui-se que a adição de canola na dieta de vacas não alterou a produção de embriões; entretanto, os embriões resultantes de oócitos coletados de vacas alimentadas com canola são mais resistentes à vitrificação.

A diet enriched in linoleic acid compromises the cryotolerance of embryos from superovulated beef heifers

Dietary rumen-protected fat rich in linoleic acid may affect the superovulatory response and embryo yield; however, its effects on in vivo embryo cryotolerance are unknown in zebu cattle. The present study evaluated the production and cryotolerance after freezing or vitrification of embryos from Nelore heifers supplemented with rumen-protected polyunsaturated fatty acids (PUFA). Forty heifers kept in pasture were randomly distributed into two groups according to the type of feed supplement (F, supplement with rumen-protected PUFA, predominantly linoleic; C, control fat-free supplement with additional corn). Supplements were formulated to be isocaloric and isonitrogenous. Each heifer underwent both treatments in a crossover design with 70 days between replicates. After 50 days feeding, heifers were superovulated. Embryos were evaluated morphologically and vitrified or frozen. After thawing or warming, embryo development was evaluated in vitro. There was no difference between the F and C groups (P > 0.10) in terms of embryo production. Regardless of the cryopreservation method used, Group C embryos had a greater hatching rate after 72 h in vitro culture than Group F embryos (44.3 ± 4.2% (n = 148) vs 30.9 ± 4.0% (n = 137), respectively; P = 0.04). Moreover, vitrified and frozen embryos had similar hatching rates (P > 0.10). In conclusion, dietary rumen-protected PUFA rich in linoleic acid did not improve embryo production and compromised the cryotolerance of conventionally frozen or vitrified embryos from Nelore heifers.

Effect of cis-9,trans-11 and trans-10,cis-12 isomers of conjugated linoleic acid on the integrity and functionality of cryopreserved bovine spermatozoa

Plasma membranes of sperm subjected to low temperatures undergo changes in their structure and permeability. The addition of fatty acids in semen cryopreservation media may influence the sperm motility after thawing, possibly by maintaining the membrane fluidity due to their incorporation in lipid bilayers. In this work, different concentrations of the isomers cis-9,trans-11 and trans-10,cis-12 of conjugated linoleic acid (CLA) were added in the cryopreservation medium of bovine sperm. Four Jersey bulls were used, and the ejaculates were processed as a pool. The Tris-based extender (Dilutris®) was supplemented with 20% egg yolk (MB). The treatments with CLA (Luta-CLA®), which had oily presentation, were prepared from MB with addition of 1% sodium lauryl sulfate, and denominated MBL. The concentrations of CLA tested were 50, 100, and 150 μM. The motility characteristics of the post-thaw semen were analyzed by computerized analysis system (CASA), and plasma membrane integrity and acrosomal and mitochondrial function assessed by the association of the fluorescent probes propidium iodide, fluorescein isothiocyanate-conjugated Pisum sativum agglutinin (FITC-PSA), JC-1 and Hoechst 33342. No significant differences were observed among treatments, excepting for a decreased mitochondrial potential of cells treated with 150 μM CLA. The addition of CLA, at the concentrations used, showed no advantages on the integrity and functionality of bovine sperm submitted to cryopreservation.

Effect of energy source during culture on in vitro embryo development, resistance to cryopreservation and sex ratio

The aim of this work was to evaluate whether minimizing the glucose concentration during culture or replacing the hexose with other energy substrates and/or embryotrophic compounds would affect the in vitro development, the resistance to cryopreservation and the sex ratio of bovine embryos. In vitro matured and fertilized oocytes were randomly assigned to 4 groups for in vitro culture, that differed in the energy substrates included: group A) 1.5 mM glucose, as in standard SOF; group B) 0.15 mM glucose; group C) 0.125 mM G3P, in the presence of 0.15 mM glucose and group D) 0.34 mM citrate, in combination with 2.77 mM myo-inositol. Blastocysts were evaluated on day 7, then vitrified by cryotop in 16.5% DMSO, 16.5% EG and 0.5 M sucrose and warmed in decreasing concentration of sucrose (0.25 to 0.15 M sucrose). The survival rates were assessed after 24 h in vitro culture. Finally, the blastocysts produced were sexed by PCR. An increased blastocyst rate was recorded in groups B, C and D, i.e., when glucose concentration was reduced, compared to group A (28.2, 41.0, 35.7 and 35.8, respectively in groups A, B, C and D; P < 0.01). However, the embryos cultured in group D showed the slowest developmental speed, indicated by the lowest percentage of advanced stage-embryos (expanded and hatched blastocysts) out of the total blastocysts (56.1, 45.8, 56.9 and 31.8 %, respectively in groups A, B, C and D; P < 0.01). Furthermore, survival rates after 24 h culture of vitrified-warmed blastocysts also decreased in group D (73.3, 73.1, 71.4 and 58.4%, respectively in groups A, B, C and D; P < 0.01). Interestingly, in group D a higher percentage of female embryos was obtained compared to group A, with intermediate values in groups B and C (45.6, 53.4, 50.0 and 61.5%, respectively in groups A, B, C and D; P < 0.05). In conclusion, it was demonstrated that the energy substrate during in vitro culture affects both the production and the viability of blastocysts. Furthermore, manipulating the metabolic profile of embryos during in vitro culture may have an impact on sex ratio.

Consequences of in vitro culture conditions on embryo development and quality

Despite major efforts directed at improving the yield of blastocysts from immature oocytes in vitro, the quality of such blastocysts continually lags behind that of blastocysts produced in vivo. These differences are manifested at the level of morphology, metabolism, gene expression and cryotolerance, and may have a knock-on effect further along the developmental axis. Evidence suggesting that in vitro culture conditions, while capable of producing blastocysts in relatively high numbers, are far from optimal with deficiencies being manifested in terms of abnormally large offspring. It is clear nowadays that modification of the post-fertilization culture environment in vitro can improve blastocyst quality to some extent.

Factors affecting cryosurvival of nuclear-transferred bovine and swamp buffalo blastocysts: effects of hatching stage, linoleic acid–albumin in IVC medium and Ficoll supplementation to vitrification solution

The objective was to determine whether the hatching stage of cattle and swamp buffalo somatic cell nuclear-transferred (SCNT) blastocysts affected cryosurvival after vitrification, and whether addition of linoleic acid-albumin (LAA) to the IVC medium and Ficoll to the vitrification solution improves cryosurvival. Fused couplets were activated with ethanol and cycloheximide-cytochalasin D (day 0), and were allowed to develop in the presence of 0.3% BSA or 0.1% LAA+0.2% BSA. Hatching blastocysts were harvested at day 7.0 (cattle) or day 6.5 (buffalo), and classified into one of three categories, according to the ratio of extruding embryonic diameter from zona to embryonic diameter inside the zona. The blastocysts were vitrified in 20% DMSO+20% ethylene glycol+0.5M sucrose, with or without 10% Ficoll in TCM199+20% FBS, using Cryotop as a cryodevice. The post-thaw survival of the blastocysts was assessed by in vitro culture for 24h. In cattle, when the LAA-supplemented IVC medium and the Ficoll-free vitrification solution were used, cryosurvival of the early-hatching blastocysts (77%) was not different from those of middle- and late-hatching blastocysts (74 and 80%, respectively). Inclusion of Ficoll in the vitrification solution did not improve the cryosurvival of SCNT blastocysts (54 to 68%). Early-hatching SCNT blastocysts produced in the absence of LAA were sensitive to the vitrification procedure (cryosurvival 56%; P<0.05 versus 80% in the late-hatching blastocysts). The full-term developmental potential of SCNT blastocysts was proven only in the non-vitrified control group. In buffalo, the mean cryosurvival of hatching SCNT blastocysts produced with LAA (89%) was not different from that of those produced without LAA (87%). In conclusion, bovine SCNT blastocysts, regardless of their hatching stage, were relatively resistant to vitrification by the ultra-rapid cooling procedure when the blastocysts were produced in the presence of LAA. Furthermore, swamp buffalo SCNT blastocysts were more tolerant of vitrification than bovine SCNT blastocysts.

Accumulation and distribution of neutral lipid droplets is non-uniform in ovine blastocysts produced in vitro in either the presence or absence of serum

Sheep zygotes were cultured in serum-free or serum-supplemented media to determine effects on blastocyst yields and within-blastocyst abundance and distribution of neutral lipid droplets. Embryos cultured in synthetic oviduct fluid supplemented with bovine serum albumin (0.4% w/v) (SBSA) generated similar blastocyst yields (mean ± s.e.m. = 20% ± 5) to those in synthetic oviduct fluid supplemented with serum (10% v/v) from ewes fed a diet containing 0% (SZFO; 26% ± 2) or 3% fish oil (S3FO; 23% ± 3). SBSA zygotes generated more good-quality blastocysts than their SZFO or S3FO counterparts (P < 0.05). Within-blastocyst abundance of neutral lipid droplets was non-uniform; data were collected from discrete embryo sectors (each = 2700 µm2) representing highest (H), intermediate (I) and lowest (L) densities of accumulation. For all sectors, area (µm2) occupied by lipid droplets in SBSA blastocysts (mean H = 470; I = 370; L = 245) was smaller (P < 0.01) than occupied in others (SBSA : SZFO = 1 : 1.41, 1 : 1.48 and 1 : 1.42; SBSA : S3FO = 1 : 1.36, 1 : 1.30 and 1 : 1.31; data for H, I and L, respectively). Among S3FO blastocysts only, inferior quality was associated with greater lipid abundance. Overall, embryo culture in the presence of serum increased neutral lipid droplet abundance but accumulation was non-uniform.

Efficient production of sex-identified and cryosurvived bovine in-vitro produced blastocysts

To establish a protocol for production of bovine in-vitro produced (IVP) blastocysts that were sex-identified and cryopreserved, we examined the sexing efficiency and accuracy of Day-3 and Day-4 embryos by polymerase chain reaction (PCR), the development of the biopsied embryos into Day-7 blastocysts and the freezability of these blastocysts by vitrification in gel-loading tips. One or two blastomeres were isolated from IVP embryos at either the 8-cell or 16-cell stage (Days 3 and 4, respectively) by a pressing-out method, and were then subjected to primer extension preamplification (PEP)-PCR. The successful sex-identification rate of biopsied samples amplified, purified and analyzed for sex by a second PCR (88.9%) was higher than that of those amplified and analyzed without purification (32.0%). Developmental rates into Day-7 blastocysts of biopsied embryos (Day-3, 65.5%; Day-4, 70.8%) were similar to those of non-biopsied control embryos (Day-3, 74.5%; Day-4, 65.1%). Total cell numbers and the inner cell mass (ICM) ratio of blastocysts derived from biopsied embryos were also comparable with those of control embryos. Blastocysts were vitrified-warmed in the presence of 20% DMSO, 20% ethylene glycol and 0.6M sucrose using gel-loading tips as containers. The proportions of biopsied blastocysts that were hatched or hatching rates after warming were high, regardless of the biopsy time (Day-3, 94.1%; Day-4, 91.9%), similar to the rates for control blastocysts (Day-3, 97.5%; Day-4, 96.9%). In conclusion, a protocol that allows sexing of Day-3 and Day-4 bovine embryos without compromising either the developmental ability to the blastocyst stage or freezability of Day-7 blastocysts was developed.

Cryopreservation and Sexing of In Vivo- and In Vitro-Produced Bovine Embryos for Their Practical Use

My research awarded includes contributions to cryopreservation and sexing of bovine embryos produced in vitro and in vivo, as follows; (1) In vivo-derived morulae and blastocysts were cryopreserved in the presence of 10% glycerol, and the embryos were transferred into recipients after two-step dilution of glycerol in straw, with a practically acceptable pregnancy rate. (2) The survival rate of 16-cell stage embryos frozen in the medium with ethylene glycol was higher than that with DMSO or 1,2-propanediol. Addition of linoleic acid-albumin to culture medium enhanced the survival rate of post-thaw bovine 16-cell stage in vitro-produced (IVP) embryos. (3) Polarization of cytoplasmic lipid droplets by centrifugation of 2-cell stage embryos was found effective to increase freezing tolerance in 16-cell stage embryos developed from the centrifuged embryos, because blastomeres of 16-cell stage embryos were mostly lipid-free. (4) The usefulness of gel-loading tip (GL-Tip) as a container for ultra-rapid vitrification was demonstrated in IVP embryos from 2-cell to blastocyst stages, with a higher in vitro survival than the conventional two-step freezing. (5) PCR analysis for sexing of in vivo-derived Day-7 embryos indicated that male embryos developed faster and graded higher than female embryos. But such correlation between genetic sex and embryonic development was not found in IVP embryos obtained from individual cows. (6) Addition of 0.1-1.0% deproteinized hemodialysate product from calf blood to culture medium increased the producing efficiency of demi-embryos with good quality. Female embryos rather than male embryos required a longer time to repair after bisection. (7) In vivo-derived bovine embryos after biopsy for sexing by PCR analysis and subsequent vitrification using GL-Tips are available to practical use in the field. (8) Introduction of primer extension preamplification-PCR and purification of DNA product before standard sexing PCR of biopsy samples from Day 3-4 in vitro-derived embryos allowed accurate sex determination, and Day-7 blastocysts developed from Day 3-4 embryos were cryopreserved by GL-Tip vitrification without a loss of their viability. Thus the field application of bovine embryo transfer is in part supported by improvements of technologies in embryo cryopreservation and sex pre-determination.

Cryopreservation of human hematopoietic cells with membrane stabilizers and bioantioxidants as additives in the conventional freezing medium

Cord blood (CB) and fetal liver (FL) cells are two alternative sources of human hematopoietic stem cells. Optimization of cryopreservation protocols is an important aspect in the banking of these tissues. Out of the multiple factors responsible for cryodamage of cells, membrane leakage and oxygen free-radical generation have been shown to contribute substantially toward the process. We have studied the effect of certain additives, like membrane stabilizers and bioantioxidants, to the conventional freezing medium on viability, nucleated cell recovery, and clonogenic potential of frozen cells. Our results show that trehalose, a membrane stabilizer, when used in combination with 10% dimethyl sulfoxide (DMSO) affords better cryoprotection as evidenced by significantly increased colony formation as compared to 10% DMSO alone. The cryoprotection afforded by trehalose persists at least for 1.5 years and there is no bias toward protection of a particular lineage. We also found that this increased cryoprotective effect of trehalose is seen both at -196 degrees C and -80 degrees C storage temperatures. Addition of taurine, an amino acid, another membrane stabilizer, and a natural cryoprotectant to the traditional freezing medium also results in beneficial effect. Of the three bioantioxidants tested, i.e., ascorbic acid, alpha-tocopherol acetate, and catalase, catalase shows maximum cryoprotective effect both at -196 degrees C and at -80 degrees C. Because the mode of cryoprotective action of catalase and trehalose are totally different, we tried a combination of these two compounds along with 10% DMSO. At -196 degrees C the protection afforded by the combination was significantly better than that afforded by individual components. At -80 degrees C, however, the combination did not give any added protection as compared to the individual single additives, although it was significantly better than 10% DMSO alone. These results indicate that the addition of membrane stabilizers and antioxidants to the conventional freezing medium may help to improve post thaw recovery of hematopoietic cells.