Post-thaw development of in vitro produced buffalo embryos cryopreserved by cytoskeletal stabilization and vitrification

The present study was conducted to examine post-thaw in vitro developmental competence of buffalo embryos cryopreserved by cytoskeletal stabilization and vitrification. In vitro produced embryos were incubated with a medium containing cytochalasin-b (cyto-b) in a CO₂ incubator for 40 min for microfilament stabilization and were cryopreserved by a two-step vitrification method at 24℃ in the presence of cyto-b. Initially, the embryos were exposed to 10% ethylene glycol (EG) and 10% dimethylsulfoxide (DMSO) in a base medium for 4 min. After the initial exposure, the embryos were transferred to a 7 µl drop of 25% EG and 25% DMSO in base medium and 0.3 M sucrose for 45 sec. After warming, the embryos were cultured in vitro for 72 h. The post-thaw in vitro developmental competence of the cyto-b-treated embryos did not differ significantly from those vitrified without cyto-b treatment. The hatching rates of morulae vitrified without cyto-b treatment was significantly lower than the non-vitrified control. However, the hatching rate of cyto-b-treated vitrified morulae did not differ significantly from the non-vitrified control. This study demonstrates that freezing of buffalo embryos by cytoskeletal stabilization and vitrification is a reliable method for long-term preservation.     

氨基酸、维生素对水牛体外受精胚胎体外发育的影响

通过在培养液中添加不同浓度的氨基酸或维生素,探讨其对水牛体外受精(IVF)胚胎体外发育的影响.结果表明:(1)非必需氨基酸可显著提高水牛卵母细胞IVF后胚胎的分裂率,但对囊胚发育率无显著影响;(2)低浓度的必需氨基酸对水牛IVF胚胎的发育具有一定促进作用,但高浓度则有抑制作用;(3)维生素对水牛IVF胚胎发育则有促进作用.在培养液中添加维生素,水牛IVF胚胎的分裂率和第7天囊胚发育率显著提高.     

不同冷冻方法对水牛体外生产胚胎冷冻效果的研究

本研究采用不同来源的体外生产胚胎(屠宰场卵巢IVF胚胎,OPU-IVF胚胎,SCNT胚胎),系统研究了不同冷冻方法对水牛体外生产胚胎冷冻效果的影响,以完善水牛体外生产胚胎冷冻方法,进一步提高胚胎冷冻效果。试验选用6～7日龄囊胚分别用不同的冷冻液和不同冷冻方法进行胚胎冷冻。玻璃化冷冻液分别为40%EG、25%EG+25%DMSO和20%EG+20%DMSO+0.5 mol/L蔗糖;程序化冷冻液分别为10%甘油和0.05 mol/L海藻糖+1.8 mol/L EG+0.4%BSA。结果表明:(1)在玻璃化冷冻中,无论何种胚胎不同冷冻液的冷冻效果有明显的差异,但均以20%EG+20%DMSO+0.5 mol/L蔗糖作为冷冻液的冷冻效果最好,并且高于程序化冷冻的存活率;而对于程序化冷冻,用10%甘油作为冷冻液,屠宰场卵巢IVF胚胎的冷冻后存活率略高于用0.05 mol/L海藻糖+1.8 mol/L EG+0.4%BSA的冷冻后存活率,但差异不显著(P>0.05)。(2)VF胚胎利用程序化冷冻胚胎解冻后,在0～24 h内有76.5%胚胎复活,高于玻璃化冷冻的复苏率(48.9%)(P<0.05);而与此相反,在24～48 h内,玻璃化冷冻胚胎的复苏率(42.6%)则高于程序化冷冻(23.5%)(P<0.05)。综上所述,各种来源的水牛体外生产胚胎均可进行冷冻保存,应用玻璃化冷冻的效果好于程序化冷冻,且以20%EG+20%DMSO+0.5 mol/L蔗糖作为冷冻液进行玻璃化冷冻效果最好,但程序化冷冻后的胚胎复苏速度明显快于玻璃化冷冻的速度。     

Effect of cryoprotectant composition on in vitro viability of in vitro fertilized and cloned bovine embryos following vitrification and in-straw dilution

In this study the efficacy of the combination of glycerol (GLY) and ethylene glycol (EG) as cryoprotectants in a vitrification method developed for direct embryo transfer was evaluated by in vitro development of in vitro fertilized (IVF) and somatic cell nuclear transfer (SCNT) embryos after vitrification. The IVF and SCNT blastocysts were vitrified in either 40% GLY, 30% GLY + 10% EG, or 20% GLY + 20% EG using French straws. After warming, the straws were held vertically for 1 min without shaking and were then placed horizontally for 5 min to dilute the cryoprotectants. After washing, the vitrified-warmed embryos were cultured in vitro for 72 h. There were no differences among the vitrification solutions with respect to the rates of vitrified-warmed IVF and SCNT embryos surviving and developing to the hatched blastocyst stage. However, the rates of development to the hatched blastocyst stage of the SCNT embryos vitrified with 40% GLY tended to be higher than those vitrified with 30% GLY + 10% EG or 20% GLY + 20% EG (26% vs. 7-8%, respectively). The development rates to the hatched blastocyst stage of the IVF and SCNT embryos vitrified with solution containing EG were significantly lower (P<0.05) than those of non-vitrified embryos. These results suggest that use of the combination of GLY and EG as cryoprotectants had no beneficial effect on the viability of embryos after in-straw dilution. However, this method is so simple that it can be used for practical direct transfer of vitrified embryos in the field.     

Ghrelin对水牛体外受精和孤雌激活胚胎体外发育的影响

本研究的目的是探讨Ghrelin对水牛体外受精和孤雌激活胚胎体外发育的影响.体外成熟的水牛卵母细胞经体外受精或离子霉素孤雌激活后.分别在舍0,0.5,5,50和500 μg/L Ghrelin的培养液中进行体外培养,观察各组胚胎的卵裂率和囊胚率.结果显示,在培养液中添加不同浓度的Ghrelin对体外受精和孤雌激活胚胎的卵裂率均无显著影响(P>0.05),但添加500 μg/L的Ghrelin显著提高体外受精胚胎的囊胚发育率(33.5% vs 13.7%,P<0.05),50 μg/L或500 μg/L的Ghrelin均显著提高孤雌激活胚胎的囊胚发育率(32.4%和34.6% vs 14.5%,P<0.05).结果表明,培养液中添加Ghrelin对胚胎的早期卵裂没有影响,但可促进水牛体外受精和孤雌激活胚胎囊胚的形成.     

不同血清类型对水牛胚胎体外培养效果的影响

从屠宰场收集水牛卵巢上抽取的卵母细胞,经体外成熟培养后分别进行孤雌激活(PA)和体外受精(IVF),将获得的PA或IVF胚胎分别培养于添加浓度均为5%的牛血清白蛋白(BSA)、胎牛血清(FBS)、炭情水牛血清(OBS)、发情牛血清(OCS)和混合血清(OCS与FBS按1:1混合)的培养液中培养7～9 d,并观察胚胎的体外发育情况.结果,PA胚胎培养在OCS和混合血清组的卵裂率(73.52%,68.07%)和囊胚率(30.59%,27.73%)均显著高于BSA(38.37 %.6.40%)、OBS(44.97%,10.05%)和FBS(52.02%,17.04%)组(P＜0.05);IVF胚胎的卵裂率和囊胚率以OCS组最高(62.50%,22.62%),显著高于BSA(30.50%,6.38%)、OBS(35.48 %,7.10 %)和FBS组(40.11%,11.76%,P＜0.05),但与混合血清组(60.42%,21.35%;P＞0.05)差异不显著.结果表明,在水牛胚胎体外培养体系中添加5%的OCS或混合血清均能有效地促进水牛胚胎的体外发育.     

Effect of vitrification procedures on the subsequent development of in vitro matured swamp buffalo oocytes following in vitro fertilization

Nowadays, the efficiency of buffalo oocytes cryopreservation is still low. The purpose of this study was to evaluate effects of two combinations of cryoprotectant agents (CPAs) and two vitrification devices for vitrification of swamp buffalo oocytes on their survival after vitrification warming, and subsequent developmental ability after in vitro fertilization. In vitro matured (IVM) oocytes were vitrified by either Cryotop (CT) or solid surface vitrification (SSV) interacting with vitrification solution A (VA) or B (VB). In the VA or VB solution exposed test, the oocytes showed similar survival rates, but decreased blastocyst rates after in vitro fertilization compared with that of untreated oocytes. After vitrification, the CT method combined with VA solution yielded a higher survival rate (91.3 ± 5.84%) of vitrified oocytes than that combined with VB solution (69.8 ± 4.19%–75.8 ± 4.55%); however, all the vitrification treatments showed lower blastocyst rates (1.1 ± 0.07%–5.2 ± 0.24%) compared with that of untreated oocytes (18.0 ± 1.09%). Our results indicated that combined vitrification treatments in this study did not improve the decreased ability of vitrified oocytes developing to the blastocyst stage.     

Seasonality and photoperiod influence in vitro production of buffalo embryos

Buffalo is considered short-day breeder in tropical and subtropical part of the world and seasonality and photoperiodism impart major influence on its fertility. However, its impact on in vitro embryo production (IVEP) remains elusive. Therefore, this study investigated the effect of seasonal variations and photoperiodism on morphological and molecular parameters of IVEP in buffalo. For this purpose, we conducted two different experiments on the oocytes obtained by aspirating follicles from abattoir derived ovaries. In Exp. I, retrospective analysis was performed for oocyte recovery, blastocyst and hatching rate, during four consecutive seasonal periods (i.e. January–March, April–June, July–September and October–December). In Exp. II, oocytes from peak breeding and non-breeding seasons were subjected to 24 hr in vitro maturation and evaluated for polar body extrusion to assess maturation rate. Results showed that embryo development was markedly low during second quarter (April–June) and maximum during fourth quarter (October–December) of the year; referred as non-breeding and breeding seasons, respectively. Comparative data analysis demonstrated that poor oocyte quality is major reason for lesser efficiency of embryo production during non-breeding season than peak breeding season as suggested by poor oocyte recovery (2.31 ± 0.10 vs. 3.65 ± 0.27) and maturation rate (33.32 ± 2.1 vs. 63.15 ± 7.31). Subsequently, comparative gene expression analysis of blastocysts during peak breeding season significantly upregulated pluripotency gene (OCT-4) and downregulated heat shock protein 90, as compared to non-breeding season. Therefore, it could be divulged from the present study that seasonal variations and photoperiodism have profound effect on oocyte quality and subsequent embryo development. It is recommended to find suitable additives for in vitro maturation that could mitigate seasonal effects.     

BOEC＋CCs、TAURIN对水牛卵母细胞体外受精及早期胚胎发育的影响

利用屠宰场废弃的水牛卵巢、观察在受精液和早期胚胎培养液中添加BOEC＋CCs(输卵管上皮细胞＋颗粒细胞）、Taurin(牛磺酸）对体外受精率及早期胚胎发育的影响。分别在受精液和早期胚胎培养液中添加BOEC＋CCs或70μM Taurin，获得的受精率分别为39．5％、40．9％，囊胚率分别为28．1％、20％，均极显著地高于对照组（P＜0．01）；同时比较发现，两实验组的受精率无明显差异，但囊胚率差异显著（P＜0．05）。     

表皮生长因子对水牛胚胎体外发育及凋亡的影响

为了探讨表皮生长因子(EGF)对水牛早期胚胎体外发育及凋亡的影响,通过收集屠宰场卵巢卵母细胞进行体外成熟和体外受精,将假定的受精卵置于含不同浓度EGF(0,25,50和100 ng/mL)的培养液中培养,检查分裂率和囊胚发育率,用细胞凋亡试剂盒(Annexin-V-FluosStaining kit)试剂染色,统计囊胚细胞凋亡率和坏死率。结果表明:50 ng/mL EGF组的孵化囊胚率显著高于对照组(P<0.05),该组细胞凋亡率和坏死率显著低于对照组(P<0.05)。100 ng/mL EGF的卵裂率、囊胚率、D7囊胚率和孵化囊胚率显著低于对照组和其他试验组(P<0.05)。细胞凋亡率和坏死率显著高于其他各组(P<0.05)。提示:一定浓度的EGF可提高囊胚孵化率,并可抑制胚胎细胞的凋亡。     

Effect of centrifugation treatment before vitrification on the viability of porcine mature oocytes and zygotes produced in vitro

The aim of the present study was to investigate the effects of centrifugation pretreatment on the viability and nuclear status of porcine in vitro matured (IVM) oocytes and on the developmental competence of in vitro fertilized (IVF) oocytes (zygotes) after cryopreservation by vitrification (Solid Surface Vitrification; SSV). Mature oocytes having the first polar body after IVM and zygotes having the second polar body at 10 h after IVF were centrifuged at 10,000 x g at 37 C for 20 min and then subjected to SSV. Their viability was evaluated by morphological appearance and fluorescein diacetate staining. The nuclear status of oocytes was evaluated 6 h after vitrification. The developmental ability to the blastocyst stage of vitrified zygotes was evaluated after 6 days of in vitro culture. Although centrifugation did not damage the oocytes directly, it drastically reduced the rate of live oocytes after SSV. The rates of vitrification-induced parthenogenetic activation were similar in both centrifuged and non-centrifuged oocytes (42.4 and 47.4%, respectively). Centrifugation had no significant effects on the viability of pronuclear oocytes. The development of vitrified zygotes to the blastocyst stage was significantly lower than that of the control irrespective of centrifugation pretreatment. There was no difference in the cleavage and blastocyst rates between the control and centrifuged zygotes after vitrification. There was also no difference in the total cell numbers of blastocysts between the control and centrifuged zygotes irrespective of vitrification. These results reveal that, in IVM porcine oocytes, centrifugation pretreatment is highly detrimental to cryotolerance; however, in zygotes, it has only a slight effect on viability and does not alter the developmental competence of surviving zygotes.     

Effect of replacement of pyruvate/lactate in culture medium with glucose on preimplantation development of porcine embryos in vitro

The effect of glucose supplementation at different times in in vitro culture on the developmental competence of in vitro produced (IVP) porcine embryos was examined. In Experiment 1, when IVP embryos were cultured in modified NCSU-37 supplemented with pyruvate and lactate (IVC-pyr/lac) for 0 h, 24 h, 48 h, 72 h, 96 h, or 118 h and subsequently in modified NCSU-37 supplemented with glucose (IVC-glu) until Day 6 (Day 0=day of in vitro fertilization), the rates of blastocyst formation were significantly higher in embryos cultured in IVC-pyr/lac for 24 or 48 h (24.4% and 23.0%, respectively) than in embryos cultured in IVC-pyr/lac for the whole culture period (14.5%). However, there were no significant differences between embryos obtained after the energy source replacement and embryos cultured in IVC-glu for the whole culture period on the rates (15.2%-24.4%, and 16.8% respectively). Replacement of pyruvate/lactate with glucose at 58 h of culture in Experiment 2 significantly enhanced the rate (31.3%) compared to those after replacement at 48 h, 53 h and 63 h of culture (20.6%, 20.8%, and 21.1%, respectively). In conclusion, replacement of pyruvate/lactate with glucose as the energy substrate was optimal at 58 h of culture for the development of porcine embryos to the blastocyst stage.     

Effect of group culture and embryo-culture conditioned medium on development of bovine embryos

We investigated the effect of group culture on bovine embryo development, and also investigated the effect of embryo-culture conditioned medium on developmental competence of individually cultured bovine embryos. Slaughterhouse-derived bovine oocytes were matured and fertilized in vitro. The presumptive zygotes were cultured individually or cultured in groups of 2 to 5 embryos with a constant culture density (5 mul/embryo). After 7 days of culture, the rates of embryos developed to the blastocyst stage were significantly higher (P < 0.05) in group cultures of more than 3 embryos/drop than for embryo culture of 1 or 2 embryos/drop. These results suggest a beneficial effect of group culture may be exerted by possible growth promoting factors secreted by embryos. In the next experiment, we investigated the effect of timing of fresh medium replacement on the development of embryos cultured in groups. The blastocyst formation rate was lower when culture medium was replaced freshly on days 2-4 after fertilization than on days 5-6. The blastocyst formation rates of single-cultured embryos were significantly (p < 0.05) increased by the addition of conditioned medium derived from multiple-embryo culture. These results indicate that group culture promotes embryo development and that embryo culture-derived conditioned medium is effective for supporting development of single cultured embryos.     

细胞松弛素B对水牛体细胞核移植效果的影响

以水牛耳皮成纤维细胞为供体细胞,采用电融合方法,探讨细胞松弛素B(CB)对水牛体细胞核移植效果的影响.体外成熟培养22～24 h的水牛卵母细胞去核后.将经0.1 mg/L Aphidicolin(APD)+0.5%FBS培养2～9 d的水牛耳皮成纤维细胞注射到卵周隙中再经电融合(100 V/mm,15μs,电脉冲3次)构建核移植重构胚.重构胚经化学激活后(5 μmol/L)离子霉素5 min,2 mmol/L 6-DMAP 3 h)培养,7～9 d评定其胚胎发育能力.结果显示,在含CB(3 mg/L)的融合液中进行电融合后,核移植的融合率、重组胚的存活率、卵裂率和囊胚率与对照组(不含CB)相比均无显著差异(P>0.05);核移植重组胚激活前用含CB(6 mg/L)的培养液培养1 h,其激活后的存活率(97.52%)和体外囊胚发育率(22.09%)均显著地高于未经CB处理的重组胚的存活率(93.87%)和囊胚率(13.25%,P<0.05);重组胚经离子霉素激活5 min后,在6-DMAP+CB中培养3 h的分裂率明显低于放在6-DMAP中培养3 h的分裂率(65.37% vs 78.92%,P<0.05),但囊胚发育率无显著差异(11.19% vs 10.96%,P>0.05).这表明水牛体细胞核移植电融合时,融合液中不添加CB,而核移植重组胚激活前经CB培养处理后,有利于胚胎的进一步发育,但激活后用CB培养处理会降低胚胎的发育率.     

A comparison of different vitrification devices and the effect of blastocoele collapse on the cryosurvival of in vitro produced porcine embryos

The aim of this study was to determine the optimum conditions for vitrifying in vitro produced day 7 porcine embryos using different vitrification devices and blastocoele collapse methods. Firstly embryos were collapsed by micro-pipetting, needle puncture and sucrose with and without conducting vitrification. In the next experiment, non-collapsed embryos were vitrified in an open device using either superfine open-pulled straws (SOPS) or the CryoLoop^TM system, or vitrified in a closed device using either the CryoTip^TM or Cryo Bio^TM’s high security vitrification system (HSV). The post-thaw survival of embryos vitrified in the open devices did not differ significantly (SOPS: 37.3%; CryoLoop^TM: 37.3%) nor did the post-thaw survival of embryos vitrified in the closed devices (CryoTip™: 38.5%; HSV: 42.5%). The re-expansion rate of embryos that were collapsed via micro-pipetting (76.0%) did not differ from those that were punctured (75.0%) or collapsed via sucrose (79.6%) when vitrification was not performed. However, embryos collapsed via sucrose solutions (24.5%) and needle puncture (16.0%) prior to vitrification were significantly less likely to survive vitrification than the control (non-collapsed) embryos (53.6%, P < 0.05). The findings show that both open and closed vitrification devices were equally effective for the vitrification of porcine blastocysts. Collapsing blastocysts prior to vitrification did not improve survival, which is inconsistent with the findings of studies in other species. This may be due to the extremely sensitive nature of porcine embryos, and/or the invasiveness of the collapsing procedures.     

Effect of time of the addition of glucose to a medium on the development of 1-cell stage mouse embryos

In the present study, 1‐cell stage mouse embryos were cultured with or without glucose, and their development to the blastocyst stage was compared. Embryos cultured in a glucose‐free medium had a higher percentage of development to the 8‐cell stage, and they had higher developmental speeds compared with those cultured in a glucose‐containing medium. The percentages of embryos that developed to the early blastocyst stage, blastocyst stage and expanded blastocyst stage were much lower than those developed in a glucose‐containing medium. This suggests that the culture of 1‐cell stage embryos in a glucose‐containing medium inhibits development at the 8‐cell stage, and that glucose is necessary for blastocyst formation. Previous reports indicate that, from the 1‐cell stage to the 4‐cell stage, glucose inhibits embryo development. In the present study, exposure of early embryos to a glucose‐free medium improved subsequent embryo development, and there was no difference in the percentage of development to the stages ranging from the 8‐cell stage to the expanded blastocyst stage between embryos cultured in a glucose‐free medium from the 1‐cell stage to the 2‐cell, 4‐cell and 8‐cell stage. This indicates that embryo development is improved when a 1‐cell stage embryo is exposed to a glucose‐free medium before and during the 2‐cell stage, and glucose only has an inhibitory effect on embryo development during conversion from the 1‐cell stage to the 2‐cell stage.     

表皮生长因子对无透明带小鼠胚胎体外发育的影响

为了观察不同浓度的表皮生长因子对无透明带小鼠胚胎体外发育的影响,试验将小鼠原核期胚胎用链霉蛋白酶去除透明带后,分别置于含有不同浓度的表皮生长因子无血清胚胎体外培养液中培养,观察各期胚胎的发育情况.结果表明:除0.01 ng/mL表皮生长因子添加组胚胎的2细胞发育率和囊胚回收率与添加0.1 ng/mL表皮生长因子处理组差异不显著外(P>0.05),其体外胚胎各期的发育率、囊胚回收率和囊胚细胞数与其他处理组比较均差异显著(P<0.05).说明一定浓度的表皮生长因子可以提高无透明带小鼠胚胎体外培养各期的发育率,但是高浓度的表皮生长因子对无透明带小鼠胚胎的体外发育有一定的抑制作用.     

L-肉碱对水牛卵母细胞体外成熟的影响

以水牛为模型,通过探讨L-肉碱(L-carnitine)对水牛卵母细胞体外成熟的影响,同时深入研究添加L-肉碱后卵母细胞抗氧化能力的变化情况,以进一步阐明L-肉碱影响卵母细胞成熟的作用机制。水牛卵丘-卵母细胞复合体(COCs)在添加有不同质量浓度的L-肉碱(0,1,10,100 mg/L即对照组、Ⅰ组、Ⅱ组和Ⅲ组)的成熟液中体外成熟培养24h后,统计卵母细胞第一极体排出率。结果显示:Ⅰ组、Ⅱ组和Ⅲ组卵母细胞第一极体排出率分别为(64.44±1.93)%、(66.17±2.76)%和(63.27±1.19)%,与对照组(56.60±1.56)%相比差异显著(P<0.05)。免疫荧光染色观察显示:添加L-肉碱的各处理组的卵母细胞中活性氧的含量显著低于对照组(P<0.05)。同时,利用酶联免疫法测定卵母细胞中脂质过氧化物丙二醛的含量,结果显示Ⅰ组、Ⅱ组和Ⅲ组的卵母细胞中脂质过氧化物丙二醛的含量分别为0.125 797,0.125 217,0.124 155μmol/L,极显著低于对照组(0.142 609μmol/L)(P<0.01)。此外,采用实时荧光定量PCR方法检测卵母细胞周围的卵丘细胞中卵丘扩展相关基因ptx3、has2以及卵母细胞抗氧化相关基因gpx4的表达情况,分析结果显示:Ⅰ组、Ⅱ组和Ⅲ组卵丘细胞中has2的表达量均显著高于对照组的表达量(P<0.05),其中以Ⅱ组的最高;而Ⅱ组和Ⅲ组的卵丘细胞中ptx3基因和卵母细胞中gpx4基因的表达量显著高于对照组(P<0.05)。综上可知,水牛卵母细胞体外成熟液中添加适合质量浓度的L-肉碱能显著提高卵母细胞体外成熟率,推测L-肉碱可以通过提高卵母细胞抗氧化能力来促进卵母细胞的体外成熟。