激活方法和共培养系统对牛核移植胚胎体外发育的影响

<正>影响体细胞核移植(SCNT)的因素很多,其中重组胚的激活和体外培养是影响核移植的重要因素。卵母细胞的充分激活是提高核移植效率的关键因素之一[1],只有在去核卵母细胞充分激活的基础上,去核卵才可以指导移入的核发生发育程序重编而开始     

核移植前激活受体卵子对牛核移植卵体外发育的影响

本研究探讨了核移植前对受体卵子进行激活、细胞融合开始时间及供体受精卵细胞周期调节对核移植卵体外发育的影响。其结果显示核移植前对受体卵子激活组的细胞融合率与对照组没有差异 ,但重组胚胎的卵裂率、8～ 16细胞期胚胎及囊胚的发育率比对照组明显提高 ;核移植前激活的受体卵子分别在卵子体外成熟开始的第30h和 4 5h与供体细胞进行细胞融合 ,结果 ,30h组的细胞融合率和卵裂率与 4 5h组没有差异 ,但发育到 8～ 16细胞期及囊胚的发育率均比 4 5h的高 ;将供体受精卵用诺考达唑 (Nocodazole)处理后 ,进行核移植的结果 ,处理组的细胞融合率、卵裂率、发育到 8～ 16细胞期和囊胚的发育率与对照组无差异     

亮甲酚蓝染色对牛核移植胚胎体外发育的影响

为研究亮甲酚蓝(brilliant cresyl blue,BCB)染色选择卵母细胞对牛核移植体系的影响,本实验以未进行染色处理的牛卵丘-卵母细胞复合体(COCs)作为对照组,在成熟培养前用26μmol/L亮甲酚蓝染色90 min作为处理组,将处理组依照胞质的颜色分为蓝色组(BCB+)和无色组(BCB-),分别在成熟培养后作为受体,经胞质内注射法构建牛体细胞核移植胚胎,统计体细胞核移植的卵裂数、囊胚数和囊胚细胞数来评价其发育潜能。结果表明:BCB+组的成熟率(80.9%)与对照组(60.2%)和BCB-组(51.9%)差异显著(P<0.05);BCB+组的囊胚率(32.26%)与对照组(21.49%)和BCB-组(5.95%)差异显著(P<0.05),另外BCB+组的囊胚细胞总数(132.5)显著高于其他组(P<0.05)。结果显示,通过亮甲酚蓝染色法筛选出成熟的高质量牛卵母细胞用于体细胞核移植,可以获得更高的克隆囊胚率。     

牛胚胎的核移植

本研究是试验一种牛胚胎核移植的方法,并观察去核的胚胎移植不同龄胚胎的细胞核后的发育情况。先将原核胚胎离心处理,以显示原核,再用非穿透法取出原核,用电击法将其融合到去核的合子中。在Zimmernan细胞融合液中,以100伏电压脉冲20～40微秒,融合膜与电极平行时融合率最高(79％)。用原核胚胎观察了核移植对胚胎发育的影响。将这些胚胎的原核取出再注回,然后保存在绵羊输卵管里5天。结果,从输卵管回收到的完好的核移植胚胎中,5/29(17％)发育到桑葚期或囊胚期,而未作核移植处理的胚胎为11/30(37％)。将2个核移植胚胎移植给母牛,结果都发育成正常犊牛。而移植2-、4-或8-细胞期胚胎细胞核的去原核胚胎中,没有观察到发育现象。     

影响牛早期胚胎体外发育的因素

早期胚胎的体外培养系统比较复杂，包括培养液、温度、气相、湿度、pH值、渗透压、离子浓度、能量来源、血清成分、光、水质和培养皿等等。不同物种的早期胚胎代谢具有差异性，而培养液的组成又极为复杂，这可能是造成各种胚胎培养基差异的根本原因。因为简单培养液不能较大限度地满足胚胎发育的需求成分，所以现在一般培养胚胎都用复合培养液。     

牛胚胎早期体外发育图谱

1988年,我院卢克焕教授在爱尔兰首次报道了体外成熟卵子经体外受精后继续在体外培养成囊胚期胚胎的成就。这种胚胎移植到母牛子宫,可发育成小牛产出。现卢教授在爱尔兰Ovamass公司及英国剑桥大学ABC公司指导及从事此项工作,进行大规模商品胚胎生产,我教研室有8名同志参加,实行国内外相结合的研究。我院畜牧试验站迄今已有11头“试管牛”陆续降生。由     

不同培养体系对牛胚胎体外发育的影响

采用离子霉素和6-二甲氨基嘌呤(6-DMAP)对牛体外成熟卵母细胞进行联合激活,激活后采用不同的培养体系进行体外培养,观察不同的培养液对牛孤雌激活胚体外发育能力的影响。3种培养体系分别为:A(0~48 h:CR1aa+3 mg/mL BSA;48 h~7 d:CR1aa+10%FBS),B(连续7 d均为SOFaa+3 mg/mL BSA),C(0~5 d:SOFaa+3 mg/mL BSA;6~7 d:SOFaa+10%FBS)。结果表明:3种培养液对卵裂率没有显著性影响,分别为87.22%,94.33%和91.30%,但囊胚发育率存在显著性差异,以A效果最好,其囊胚发育率为25.56%;C次之,囊胚发育率为11.80%;B最低,囊胚发育率为3.55%。之后选择最佳的培养液进行体外受精实验,结果表明CR1aa可用做牛胚胎体外生产的培养液。     

NGF和BDNF对猪孤雌激活胚胎体外发育的影响

在NCSU-23改良培养液中分别添加不同质量浓度的脑源性神经生长因子(不rain-derived neurotrophic factor,BDNF)和神经生长因子(nerve growth factor,NGF),观察其对猪孤雌激活胚胎体外生长的影响。结果显示:在培养液中添加40μg/L的BDNF,可促进猪孤雌激活胚胎的囊胚形成;在猪PA胚胎培养液中添加不同质量浓度的NGF,对猪孤雌激活胚胎的在卵裂率、囊胚率和囊胚孵化率影响不明显。结果表明,在NCSU-23改良培养液中添加一定质量浓度的BDNF可促进猪孤雌激活胚胎体外培养过程中囊胚的形成。     

Development In Vitro and Mitochondrial Fate of Interspecies Cloned Embryos

Although the technique of interspecies somatic cell nuclear transfer can be used to increase the population size of endangered mammals, the mitochondrial heteroplasmy in cloned embryos and animals makes this idea doubtful. In present study, goat–sheep cloned embryos were constructed by fusing goat foetal fibroblasts (GFFs) into sheep oocytes and then cultured in vitro to investigate the capability of sheep oocyte dedifferentiating GFF nucleus. Moreover, at each stage of 1‐ (immediately after fused), 2‐, 4‐, 8‐, 16‐cell, morula and blastocyst, the copy number of mtDNA from GFF and sheep oocyte was examined using real‐time PCR. The results showed that: 7.4% of the fused cloned embryos can develop to the blastocyst stage; in the process of one cell to the morula stage, the copy number of two kinds of mtDNA was stable relatively; however, in the process of morula to the blastocyst stage, the decreasing in the copy number of GFF‐derived mtDNA, while the increasing in sheep oocyte‐derived, resulted in their ratio of decreasing sharply from 2.0 ± 1.0% to 0.012 ± 0.004%. This study demonstrates that: (i) the goat–sheep cloned embryos have the ability to develop to blastocyst in vitro; (ii) from the morula stage to the blastocyst stage of goat–sheep cloned embryos, goat derived mitochondria can be gradually replaced with those from sheep oocyte.     

紫外线照射时间对孤雌激活和体外受精胚胎发育的影响

用核荧光染料 Hoechst3 3 3 42对 5组牛成熟卵母细胞染色后 ,以紫外线 ( UV)分别照射0 ,10 ,2 0 ,3 0 s和 40 s。观察和分析对孤雌激活胚胎和体外受精胚胎卵裂及体外发育的影响。结果表明 ,经 UV照射 0 ,10 ,2 0 ,3 0 s和 40 s的卵母细胞孤雌激活后的卵裂率分别为 80 .8% ,77.9% ,72 % ,61.4%和 45 % ,囊胚发育率分别为 3 9.2 % ,3 6.4% ,19.4% ,14 .5 %和 11.1% ;UV照射 2 0 s以上的囊胚发育率都极显著低于UV未照射和照射 10 s的卵母细胞 ( P <0 .0 1) ,UV照射卵母细胞超过 2 0 s降低了孤雌激活胚胎的体外发育潜力 ;体外受精胚胎中 ,UV照射2 0 s以上与未照射和照射 10 s组相比 ,卵裂率和囊胚发育率显著差异 ( P >0 .0 5 ) ,U V照射卵母细胞超过 2 0 s时 ,显著降低了体外受精胚胎的发育潜力。由此可知 ,卵母细胞经染色后 ,UV照射时间应控制在 2 0 s以内 ,并以照射 10 s时 ,对孤雌激活胚和体外受精胚的体外发育影响最小     

牛胚胎原代和继代细胞核移植结果比较

比较了原代和继代核移植的操作各环节以及核移植胚胎在体外发育能力上的差异。通过显微操作将体外受精发育而来的８～３２细胞期胚胎的单个卵裂球注入激活的去核卵母细胞的卵周隙内,并用８０Ｖ/mm、４０us２次电脉冲诱导卵裂球与去核卵母细胞融合,借此进行牛胚胎的原代核移 体外发育来的８～３２细胞期的原代核移植胚胎作为供体,用原代核移植相同的方法进行牛胚胎的继代移植。原代核移植的存活率和融合率（８７．３％和６８．５     

供体细胞对猪体细胞克隆胚胎早期发育的影响

以中国农业大学实验用小型猪香猪胎儿成纤维细胞、成年耳成纤维细胞和颗粒细胞3种细胞系为供体细胞进行核移植。比较了血清饥饿法和接触抑制法处理胎儿成纤维细胞诱导进入G0／G1期的效率，发现二者差异不显著（P〉0．05），血清饥饿2d和4d差异不明显，同样接触抑制2d和4d差异也不显著（P〉0．05）。系统研究了影响克隆胚胎发育的供体因素：血清饥饿与否、细胞形态、细胞类型及个体差异等，结果表明：血清饥饿处理对克隆胚的早期发育没有明显的促进作用；圆形光滑细胞有利于细胞融合，对早期发育无显著影响（P〉0．05）；不同个体、不同类型的供体细胞对克隆胚囊胚发育率有一定的影响。     

Chemical Activation with a Combination of Ionomycin and Dehydroleucodine for Production of Parthenogenetic,ICSI and Cloned Bovine Embryos

The aim of this study was to evaluate the potential of dehydroleucodine (DhL), a new drug isolated from a medicinal herb used in Argentina, for activation of bovine oocyte. Several DhL concentrations and exposure times after ionomycin (Io) treatment were tested. The optimal DhL treatment, found for parthenogenetic development, was employed to produce bovine embryos by intracytoplasmic sperm injection (ICSI) and somatic cell nuclear transfer (SCNT). The best parthenogenic embryo developments were observed with 5 μm Io for 4 min followed by 5 μm DhL concentration and after 3‐h exposure time (52.3% cleavage; 17.4% morulae; 7.3% blastocyst; n = 109). This treatment generated no significant differences with standard Io plus 6‐dimethylaminopurine (DMAP) treatment in preimplantation embryo development. In our conditions, the embryo development reached after ICSI and SCNT assisted by the DhL treatment did not differ in terms of cleavage and blastocyst development from activation with standard Io plus DMAP treatment (p > 0.05). In conclusion, DhL utilization to activate oocytes and induce development of parthenogenotes, ICSI‐embryos or SCNT‐embryos is reported here for first time.     

不同化学激活剂对牛卵丘细胞重构胚发育的影响

本研究主要研究了Ⅰ:Ionomycin+6 甲氨基嘌呤（6DMAP）、Ⅱ:Ionomycin+放线菌酮（CHX）、Ⅲ:体积分数7%乙醇+6 DMAP、Ⅳ:体积分数7%乙醇+CHX 4种不同化学激活方法对牛胞质内卵丘细胞全细胞注射法所获得重构胚的激活及前期发育的影响。Ionomycin和7%乙醇的处理时间为5 min, 6DMAP的处理时间为4 h,CHX的处理时间为5 h。结果表明,重构胚与颗粒细胞单层细胞共培养2 d后,各组卵裂率分别为52.6%、52.8%、53.8%和54.2%,差异不显著（P＞0.05）;培养8 d后,Ⅰ组激活的囊胚发育率（20.0%）极显著高于其他组（P＜0.01）,其他各组之间差异不显著,分别为8.5%、10.2%和6.1%;培养10 d后,Ⅰ组激活的囊胚孵化率（10.7%）极显著高于其他组（P＜0.01）,其他各组之间差异不显著,分别为2.3%、3.0%和1.8%。结果提示,4种激活方法均可以有效的激活重构胚,但Ionomycin+6 DMAP法激活重构胚的囊胚率和囊胚孵化率均极显著高于其它3组,说明Ionomycin+6 DMAP激活法有利于牛重构胚的发育,可以获得较理想的囊胚率,是胞质内全细胞注射法克隆的理想激活方法。     

不同化学激活剂对牛卵丘细胞重构胚发育的影响

本文主要研究了①离子霉素（Ion）＋6-二甲基氨基嘌呤（6-DMAP）、②Ion＋放线菌酮（CHX）、③体积分数7％乙醇＋6-DMAP、④体积分数7％乙醇＋CHX四种不同化学激活方法对牛胞质内卵丘细胞全细胞注射法所获得重构胚的激活及前期发育的影响。Ion和7％乙醇的处理时间为5min,6-DMAP的处理时间为4h．CHX的处理时间为5h。结果表明,重构胚与颗粒细胞单层细胞共培养2d后,各组卵裂率分别为52．7％、51．5％、53．2％和54．0％．差异不显著（P〉0．05）;培养8d后,①组激活的囊胚发育率（20．0％）极显著高于其他组（P〈0．01）,其他各组之间差异不显著．分别为8．5％、10．2％和6．1％;培养10d后,①组激活的囊胚孵化率（10．7％）极显著高于其他组（P〈0．01）．其他各组之间差异不显著,分别为2．3％、3．0％和1．8％。表明,4种激活方法均可以有效地激活重构胚,但Ion＋6-DMAP法激活重构胚的囊胚率和囊胚孵化率均极显著高于其他3组,说明Ion＋6-DMAP激活法有利于牛重构胚的发育．可以获得较理想的囊胚率．是胞质内全细胞注射法克隆的理想激活方法。     

Cellular Composition and Viability of Cloned Bovine Embryos Using Exogene-Transfected Somatic Cells

The present study compared the efficiency of transgenic (TG) cloned embryo production by somatic cell nuclear transfer (SCNT) with fetal-derived fibroblast cells (FFCs) which were transfected with pEGFP-N1 to in vitro-fertilized (IVF), parthenogenetic and SCNT counterparts by evaluating the rates of cleavage and blastocyst formation, apoptosis rate at different developmental stages, cell number, ploidy and gene expression in blastocysts. In SCNT and TG embryos, the rates of cleavage and blastocyst formation were significantly lower (p < 0.05) than those of IVF controls, but it did not differ between SCNT and TG embryos. In IVF control, 86.7% embryos displayed diploid chromosomal complements and the rates were significantly (p < 0.05) higher than those of SCNT and TG embryos. Most TG embryos (79%) with FFCs expressed the gene by both PCR and under fluorescence microscopy. The expression of apoptosis by TUNEL was first detected at six to eight cell stages in all embryos of IVF, SCNT and TG groups, but the expression rate at each developmental stages was significantly higher (p < 0.05) in SCNT and TG embryos than in IVF counterparts. The expression rate in inner cell mass (ICM) of TG embryos was significantly higher (p < 0.05) than in SCNT and IVF embryos. These results indicate that the high occurrence of apoptosis observed in SCNT and TG embryos compared with IVF counterparts might influence the developmental competence. Moreover, the SCNT embryos derived using non-transfected donor cells exhibited a lower apoptosis expression in ICM cells than in TG embryos derived using pEGP-N1-transfected donor cells suggesting a possible role of negative gene effect in TG embryos.     

Efficient Production of Cloned Bovine Embryos Using cdc2 kinase Inhibitor

This study was carried out to compare the effects of the combination of ionomycin with a H1‐histone kinase inhibitor (dimethylaminopurine, DMAP) or cdc2 kinase inhibitor (sodium pyrophosphate, SPP) on the development of reconstituted bovine eggs. For this study, the enucleated bovine oocytes were injected with a presumptive primordial germ cell pre‐treated with 1% sodium citrate, and randomly allocated into three activation groups: Group 1 (ionomycin 5 μm , 5 min), Group 2 (ionomycin + DMAP 1.9 mm , 3 h), and Group 3 (ionomycin + SPP 2 mm , 3 h). The reconstituted eggs were compared on the rates of cleavage and development with the blastocyst stage and the ploidy of embryos at 96 h post‐activation. Cleavage rates and blastocyst development in Groups 1, 2 and 3 were 7 and 0%, 63 and 17%, and 53 and 14%, respectively. The chromosomal composition differed significantly (p < 0.05) among treatments. Although the embryos in Group 1 had significantly lower developments, 60% of embryos evaluated had diploid chromosomal sets. In contrast, ～60% of embryos in Group 2 had abnormal ploidy (21% polyploid and 38% mixoploid). In Group 3, the appearance of abnormal chromosome sets was reduced with the proportion of diploid embryos being increased to 86% (19 of 22), significantly higher (p < 0.05) than in Group 2. It can be concluded that the use of SPP with ionomycin reduces greatly the incidence of chromosomal abnormalities, and may be applicable for the activation of nuclear transplant bovine embryos.