山羊类ES细胞的分离与克隆

采集山羊交配后6～8d的桑椹胚、囊胚和孵化囊胚,将桑椹胚和囊胚分别放在小鼠原代胎儿成纤维细胞(PMEF)饲养层和同源原代胎儿成纤维细胞(PGEF)饲养层上比较其脱带时间及脱带率。脱带后,将各自一半胚胎切割,把含ICM的半胚分别放在相应饲养层上进行培养,另一半整胚在各自饲养层上继续培养,而孵化囊胚直接于PGEF饲养层上培养。当ICM增殖一定程度时进行传代,以比较其类ES细胞分离与克隆的效果。结果表明,在2种不同饲养层上,囊胚的脱带时间均短于桑椹胚,囊胚的脱带率均高于桑椹胚,而饲养层的种类对胚胎的脱带时间以及脱带率影响不大。脱带切割囊胚不论在PMEF还是在PGEF饲养层上,其贴壁时间均短于脱带整胚及孵化囊胚,而贴壁率高于脱带整胚,与孵化囊胚相似。脱带整胚及脱带切割胚在PMEF饲养层上所获类ES细胞只能维持3代,而在PGEF饲养层上,脱带切割半胚和孵化囊胚所获类ES细胞传至5代。由此认为,对脱带后的胚胎进行切割处理,有利于ICM的贴壁和增殖;应用同源原代胎儿成纤维细胞饲养层培养系统,有利于类ES细胞的分离与克隆。     

Buffalo (Bubalus bubalis) ES Cell–Like Cells are Capable of In Vitro Skeletal Myogenic Differentiation

When buffalo embryonic stem (ES) cell–like cells that expressed surface markers SSEA‐4, TRA‐1‐60, TRA‐1‐81, CD9 and CD90 and intracellular markers OCT4, SOX2 and FOXD3, as shown by immunofluorescence, and that expressed REX‐1 and NUCLEOSTEMIN as confirmed by RT‐PCR, were subjected to suspension culture in hanging drops in absence of LIF and buffalo foetal fibroblast feeder layer support, they differentiated to form three‐dimensional embryoid bodies (EBs). Of 231 EBs examined on Day 3 of suspension culture, 141 (61.3 ± 3.09%) were of compact type, whereas 90 (38.4 ± 3.12%) were of cystic type. The cells obtained from EBs were found to express NF‐68 and NESTIN (ectodermal lineage), BMP‐4 and α‐skeletal actin (mesodermal lineage), and α‐fetoprotein, GATA‐4 and HNF‐4 (endodermal lineage). When these EBs were cultured on gelatin‐coated dishes, they spontaneously differentiated to several cell types such as epithelial‐ and neuron‐like cells. When EBs were cultured in the presence of 1 or 2% DMSO or 10^?8 m or 10^?7 m retinoic acid for 25 days, ES cells could be directed to form muscle cell–like cells, the identity of which was confirmed by expression of α‐actinin by immunofluorescence and of MYF‐5, MYOD and MYOGENIN genes by RT‐PCR. MYOD was first detected on Day 10 in both treatment groups and on Day 15 in controls, whereas MYOGENIN was first detected on Day 10, Day 15 and Day 25 in the presence of retinoic acid, in the presence of DMSO and in controls, respectively. The present study demonstrates the ability of buffalo ES cell–like cells to undergo directed differentiation to cells of skeletal myogenic lineage.     

In vitro culture of bovine embryos in murine ES cell conditioned media negatively affects expression of pluripotency-related markers OCT4, SOX2 and SSEA1

Despite extensive efforts, establishment of bovine embryonic stem (ES) cell lines has not been successful. We hypothesized that culture conditions for in vitro-produced (IVP) embryos, the most used source of inner cell mass (ICM) to obtain ES cells, might affect their undifferentiated state. Therefore, the aim of this work was to improve pluripotency of IVP blastocysts to produce suitable ICM for further culturing. We tested KSR and foetal calf serum (FCS) supplements in SOF medium and ES cell conditioned medium (CM) on IVC (groups: KSR, KSR CM, FCS and FCS CM). Cleavage and blastocyst rates were similar between all groups. Also, embryonic quality, assessed by apoptosis rates (TUNEL assay), total cell number and ICM percentage did not differ between experimental groups. However, expression of pluripotency-related markers was affected. We detected down-regulation of OCT3/4, SOX2 and SSEA1 in ICM of FCS CM blastocysts (p < 0.05). SOX2 gene expression revealed lower levels (p < 0.05) on KSR CM blastocysts and a remarkable variation in SOX2 mRNA levels on FCS-supplemented blastocysts. In conclusion, pluripotency-related markers tend to decrease after supplementation with ES cell CM, suggesting different mechanisms regulating mouse and bovine pluripotency. KSR supplementation did not differ from FCS, but FCS replacement by KSR may produce blastocysts with stable SOX2 gene expression levels.     

ICR小鼠胚胎干细胞建系初步研究

实验旨在探讨消化方式和胚胎发育阶段对ICR小鼠胚胎干细胞(ES细胞)建系效率的影响。ICR小鼠3.5 d囊胚在饲养层上贴壁后采用单一酶消化或机械化与酶消化法相结合分离隆起的细胞集落,进行传代培养;然后选择二者中较优消化方式对不同发育时期囊胚所形成的细胞集落进行处理。结果表明:采用机械化与胰酶消化相结合的方式,形成的类ES细胞超过7代的比率(85.0%)要显著高于单一的胰酶消化(15.0%)(P<0.05);当用二者相结合的方式对ICR小鼠3.5 d(早期囊胚)、4.0 d(扩张囊胚)和4.5 d(孵化囊胚)所形成的细胞集落进行消化传代培养,三者在贴壁率和形成原代细胞集落率上均无显著差别(P>0.05),但传代超过7代的效率上早期囊胚和扩张囊胚均高于孵化囊胚(P<0.05)。结果提示,采用机械化与酶消化法相结合更适合于3.5～4.0 d ICR小鼠囊胚的ES细胞建系。     

注入嵌合法制作黄牛和水牛种间嵌合胚的初步研究

采用注入嵌合法初步建立了一套黄牛和水牛种间嵌合的程序与方法。采用机械剥离法或免疫外科法分离胚胎内细胞团(ICM),然后注入到已去除ICM的受体囊胚中构建形成水牛和黄牛的嵌合胚。结果发现,在用免疫外科法分离ICM时,抗血清的灭活温度从57℃升至63.5℃,ICM的获得数显著升高(0%vs100%,P<0.01),如若在分离培养液中添加6%的胎牛血清(FCS),ICM的获得数大大降低(97.6%vs0%,P<0.01)。采用免疫外科法分离得到的黄牛ICM进行水牛囊胚的ICM置换重组,重组胚的存活率与机械剥离法得到的ICM无显著差异(91.4%vs87.5%,P>0.05);但囊胚孵化率则显著提高(80%vs43.8%;P<0.05)。以上结果表明,⑴水牛和黄牛胚胎通过ICM置换获得的种间嵌合胚胎能继续发育;⑵用于黄牛ICM分离的兔抗牛抗血清需在63.5℃灭活30min,且分离需在无血清的培养液中进行;⑶通过分离ICM置换进行胚胎嵌合时,免疫外科法优于显微手术法。     

昆明系小鼠胚胎干细胞分离培养的优化

以昆明系小鼠为对象,经过丝裂霉C处理成纤维细胞(Mouse embryonic fibroblast,MEF)制备饲养层,对影响小鼠胚胎干细胞(Embryonic stem cell,ES细胞)分离培养的相关因素进行研究。分别收集小鼠3.5d的囊胚(扩张囊胚)和4.5d囊胚(孵化囊胚)进行培养,比较扩张囊胚和孵化囊胚的贴壁率、原代克隆率及传代率的情况。收集3.5d胚龄的囊胚,通过全胚法和免疫外科法对内细胞团(Inner cell mass,ICM)进行分离培养ICM集落,确定离散ICM的适宜时间。用0.25%胰酶+0.04%EDTA,0.125%胰酶+0.02%EDTA和0.25%胰酶+1%小鸡血清等方法对小鼠ES细胞集落进行传代,观察不同酶浓度对ES细胞分离克隆的影响。结果显示,孵化囊胚的贴壁率高于扩张囊胚(P0.05),但传代率则相反(P0.05),原代克隆率差异不显著(P0.05);一般ICM增殖培养2～3d(免疫外科法)或4～5d(全胚培养法)后,出现典型的克隆集落,再挑取ICM;0.125%胰酶+0.02%EDTA及0.25%胰酶+1%小鸡血清,形成ES原代克隆率较高,2组没有显著性差异(P0.05);结果表明,分离得到的ES细胞经形态学观察,AKP染色,体外分化试验等表明其具有胚胎干细胞的特性。     

绵羊类胚胎干细胞的分离与克隆

从胚胎发育阶段、饲养层和培养体系等方面对影响绵羊类ES细胞分离、克隆效率的因素进行探讨。结果显示：致密桑葚胚和囊胚的ICM增殖率高于囊胚和孵化囊胚。绵羊类ES细胞在同源绵羊胎儿成纤维细胞（SEF）上生长比较缓慢,最终传代次数也低于小鼠胎儿成纤维细胞（MEF）组。培养液中同时添加胎牛血清（FBS）和Knock-out血清替代品（KSR）,绵羊类ES传至7代,添加了碱性成纤维细胞生长因子（bFGF）后,最高可传至8代,而单纯添加KSR或FBS,分别传至4代和5代。对类ES细胞进行AKP染色、核型分析、体外分化试验,证实分离的类ES细胞符合ES细胞的主要特征,而且表达多潜能性细胞因子Nanog。由此认为,致密桑葚胚和囊胚更适合绵羊类ES细胞的体外分离和培养,而且MEF更适合于绵羊类ES细胞的分离传代,培养液中添加5%FBS和15%KSR,比较适合类ES细胞的分离传代,bFGF对绵羊类ES细胞的增殖具有促进作用。     

小鼠皮肤成纤维细胞的体细胞核移植

取成年小鼠唇部皮肤进行培养，分离成纤维细胞并血清饥饿培养1周，用作核供体。对成年小鼠进行超排，取卵母细胞用作核受体，核移植重构胚经SrCl2激活处理6h后，同mM16培养液和小鼠输卵管上皮细胞共培养，把发育到早期囊胚的重构胚转移至小鼠胎儿成纤维细胞饲养层上，添加ES细胞条件培养液，消化分离ICM，然后接种培养，对孵出的ES细胞样集落进行鉴定培养。结果显示，小鼠唇部皮肤成纤维细胞为核供体，核移植重构胚2-细胞率为54．05％，桑椹胚率17．14％，囊胚率6．90％，对照组卵丘细胞的核移植重构胚2-细胞率为60．00％，桑椹胚率21．85％，囊胚率11．69％，但2种供体细胞在支持核移植重构胚发育能力上差异不显著。成纤维细胞重构囊胚中6个囊胚分离出ES细胞样集落，3个ES细胞样集落可稳定传代；对照组卵丘细胞重构囊胚中9个囊胚中分离出ES细胞样集落，5个ES细胞样集落可稳定传代。从核移植重构胚中分离出的ES细胞样集落具有岛状或巢状群体生长形态，生长旺盛的集落可自发分化成单个散在或片状存在的上皮样或梭形细胞，碱性磷酸酶检测为阳性，常规冻存复苏，仍显示ES细胞特征。     

Generation of Buffalo (Bubalus bubalis) Transgenic Chimeric and Nuclear Transfer Embryos Using Embryonic Germ-Like Cells Expressing Enhanced Green Fluorescent Protein

The possibility of producing transgenic buffalo embryos by chimera and nuclear transfer (NT) using buffalo embryonic germ (EG)‐like cells expressing enhanced green fluorescent protein (EGFP) has been explored in this study. Buffalo EG‐like cells and fibroblasts with two to eight passages were transfected with the lined plasmid (pCE‐EGFP‐IRES‐Neo‐dNdB) using Lipofectamine^TM 2000 and selected by culturing in 200 μg/ml G418 for 6–8 days. G418 resistant fibroblasts and EG‐like cells were used for embryo chimera and NT. To produce blastocysts by chimera, 8–16 cells embryos were injected with EG‐like and fibroblast cells. Then, to produce blastocysts by NT, in vitro maturated oocytes were enucleated and afterwards EG‐like/fibroblast cells transferred into the perivitelline space. No statistical differences were observed for the total blastocyst produced by the chimeric method, using EG‐like and fibroblasts as donor cells, resulting on an accomplishment of 35.6% vs 33.3%, respectively. Nevertheless, besides from the 37 blastocysts produced, 23 (62.2%) from EG‐like cells expressed EGFP, none of blastocysts from foetal fibroblasts expressed this protein. When the NT method was used, no statistical difference among different generations was observed in the percentage of oocytes fused, cleaved, and developed to blastocysts after NT for EG‐like cells. On average, the percentage of oocytes fused, cleaved, and developed to blastocysts after NT was respectively 81.8%, 67.7% and 10.7%. For the expression of EGFP, from the 12 blastocysts produced by NT, 7 of them were positive, while none of NT embryos from EGFP positive fibroblasts developed to blastocysts. Results of the present study clearly demonstrated that gene transfected buffalo EG‐like cells have the ability to form chimeric embryos after injecting into buffalo early embryos and reprogramming ability after NT, which can be employed to produce transgenic buffalos through either embryo chimera or NT.     

OCT4 Expression in Outgrowth Colonies Derived from Porcine Inner Cell Masses and Epiblasts

The present study was conducted to test different methods for porcine inner cell mass (ICM) and epiblast isolation and to evaluate the morphology and expression of pluripotency genes in ICM‐ and epiblast‐derived outgrowth colonies (OCs) and passages thereof with particular attention on the relationship between OCT4 expression and embryonic stem cell (ESC)‐like morphology. A total of 104 zona pellucida‐enclosed and 101 hatched blastocysts were subjected to four different methods of ICM and epiblast isolation, respectively: Manual isolation, immunosurgery, immunosurgery with manual cleaning, or whole blastocyst culture. OCs were established on mouse embryonic fibroblast (MEF) cells and categorized according to morphology and OCT4 staining. Although all isolation methods resulted in ESC‐like OCs, immunosurgery with manual cleaning yielded significantly higher rates of ICM/epiblast attachment and subsequent ESC‐like morphology, whereas no significant difference was found between ICM and epiblasts with respect to these characteristics. All ESC‐like OCs showed nuclear OCT4 staining and expression of OCT4, NANOG and SOX2 as evaluated by RT‐PCR. Upon initial passages, the expression of pluripotency markers was, however, gradually lost in spite of maintained ESC‐like morphology. In conclusion, we have established a robust system for derivation of ESC‐like OCs from porcine ICM and epiblasts and we have shown that localization of OCT4 is associated with an ESC‐like morphology although this relationship is lost during early passages.     

小鼠胚胎干细胞培养、克隆、分离、传代研究

对影响小鼠胚胎干细胞（Embryonic stem cells,ES细胞）培养、克隆、分离、传代效果的因素进行了探索研究。应用223枚昆明白小鼠胚胎和20枚129品系小鼠胚胎的研究结果表明，129品系小鼠胚胎比昆明白小鼠胚胎更适合作为ES细胞建系的材料，两者FS出现率差异显著（P＜0．05）；以DMEM＋10％NBS＋10％FCS为基础培养液，分别加入LIF、胰岛素、LIF＋SCF，极显著提高昆明白小鼠胚胎贴壁率，ICM生长率及F1、F2出现率（P＜0．01），而在DMEM＋10％NBS＋10％FCS＋LIF＋SCF为培养液，得到昆明白小鼠胚胎最高贴壁率、ICM生长率及传代率；4dpc胚胎传代情况显著好于3．5dpc胚胎（P＜0．05）。     

Cell Counts and Survival to Vitrification of Bovine In Vitro Produced Blastocysts Subjected to Sublethal High Hydrostatic Pressure

This work analyses the effects of a high hydrostatic pressure (HHP) treatment on in vitro survival of in vitro produced (IVP) bovine embryos vitrified with the Cryologic Vitrification Method (CVM). Consequences on embryo quality in terms of cell proliferation and differentiation, and levels of embryonic Heat Shock Protein 70 (Hsp‐70) were also examined. Day 7 and 8 bovine in vitro‐produced blastocysts were submitted to an HHP treatment (60 MPa, at 32°C for 1 h) and allowed to recover for 1 or 2 h in culture medium. The HHP treatment did not improve blastocyst survival rates after vitrification/warming. Survival (24 h post‐warming) and hatching (48 h post‐warming) rates were 79.3 ± 4.9 and 51.8 ± 4.2 vs 73.9 ± 4.2 and 44.7 ± 4.1 for untreated controls and HHP‐treated embryos, respectively. Total cell numbers measured in fresh embryos were reduced after 1 h at 32°C, with or without HHP treatment, indicating that cell proliferation was stopped as a result of stress. Vitrified HHP‐treated embryos that hatched at 48 h after warming showed increased cell numbers in their ICM compared with untreated controls (50.2 ± 3.1 vs 38.8 ± 2.7), indicating higher embryo quality. Treatment of blastocysts with HHP did not alter the level of the Hsp‐70 protein. In our conditions, HHP treatment did not affect the cryoresistance of these embryos. However, combination of HHP treatment and vitrification in fibreplugs resulted in an increase in the ICM cell number of hatched embryos 48 h post‐warming.     

Development of large and small blastomeres from 2‐cell embryos produced in vitro in pigs

In the present study, we examined the development to blastocysts of large and small blastomeres from unevenly cleaved 2‐cell embryos (uneven 2‐cell embryos) in pigs. Proportion of blastocysts derived from large blastomeres (52.8 ± 6.4%) was significantly higher (P < 0.05) compared with small ones (32.1 ± 4.6%). However, there were no differences in total cell number, inner cell mass (ICM) cell number and ICM/total cells ratio between them. Of 53 sister blastomere pairs in the same embryos examined there were 12 pairs (22.6%) in which both blastomeres developed to blastocysts, 16 pairs (30.2%) in which only large blastomeres developed to blastocysts, and five pairs (9.4%) in which only small blastomeres developed to blastocysts. Relative total amount of active mitochondria in small blastomeres were lower (P < 0.05) than that of large blastomeres and blastomeres from evenly cleaved 2‐cell embryos. However, there was no difference in relative density of active mitochondria in these three types of blastomeres. In conclusion, blastocysts derived from small and large blastomeres in uneven 2‐cell embryos had comparable quality in terms of cell number, ICM number, ICM/total cell ratio and distribution of active mitochondria. The results suggest that these blastomeres may contribute multiple offspring production in pigs.     

猪孤雌胚胎干细胞建系的研究

以猪孤雌激活囊胚为材料,囊胚透明带消化后采用全胚培养,培养液中添加不同培养成分或因子（如FGF2,LIF,2i等）,以及选择不同的初始培养液体积来筛选猪胚胎干细胞（embryonic stem cell,ES细胞）建系的优化培养体系。囊胚内细胞团形成的细胞集落采用胰酶消化传代。结果显示：透明带消化后,囊胚贴壁率显著升高（19．4％VS．8．8％）（P〈0．05）;初始培养液体积比平常培养液体积（0．30mL／孔,24孔培养板）减半条件下,能显著提高其贴壁率（91．7％VS 20．0％）（P〈0．01）,而且获得了可传至7代的类ES细胞系2株,碱性磷酸酶染色成阳性;当用2i因子（CHIR99021和PD03025901）去替代培养液中的FGF2,囊胚贴壁率（29．400VS53．3％）和原代集落形成率（20．0％VS 87．5％）反而显著下降（P〈0．01）。这表明培养液添加了FGF2和LIF（不舍2i因子）,用24孔板培养,最初培养体积为0．15mL,透明带消化的培养体系比较适合猪孤雌激活胚的ES细胞建系。     

Improved isolation and culture of embryonic stem cells from Chinese miniature pig

Pigs serve as a better research model for human beings than other species. The Chinese laboratory miniature pig is a new laboratory animal and is expected to be applicable in many medical research fields. This study was to establish effective technologies to isolate and culture ES cells in Chinese miniature pigs. For isolation of the inner cell mass from blastocysts, an enzyme-digestive method was compared with the traditional immunosurgery. Isolated ICM were cultured in three feeder cell layers: mouse embryonic fibroblasts (MEF), porcine embryonic fibroblasts (PEF) and a continuous cell line of mouse embryonic fibroblasts (STO). Microtubule activity of the three feeder cells was further examined by immunofluorescence. ICM were successfully isolated from 85% of blastocysts by the enzyme-digestive method, compared to only 40% by immunosurgery. When ICM were cultured in three feeder layers for two to three days, 75%, 65% and 20% of ICMs formed primary cell colonies in MEF, PEF and STO, respectively. Colonies were also formed during subcultures after 9, 5 and 1 passage in MEF, PEF and STO, respectively. Microtubules in STO cells were significantly fewer than those in MEF and PEF. When the ES-like cells were cultured in a differentiation medium, they differentiated to neuron-like cells and other types of cells. These results indicate that healthier ICM can be obtained with the enzyme-digestive method. Successful culture of ICM to ES-like cells has been achieved not only in MEF, but also in homologous (pig) feeder layer. The ES cells obtained in the present study were pluripotent.     

An Inter‐Subspecies Cloned Buffalo (Bubalus bubalis) Obtained by Transferring of Cryopreserved Embryos via Somatic Cell Nuclear Transfer

The aim of this study was to explore the feasibility of cryopreservation of inter‐subspecies cloned embryos in buffalo. In our experiment, river buffalo ear fibroblast nucleus was fused into swamp buffalo oocyte cytoplasm. The blastocyst formation rate for nuclear transfer of freshly thawed cells was not different from those of growing cells, confluent or serum‐starved cells. A total of 122 cloned blastocysts derived from cryopreserved fibroblasts were cryopreserved and thawed, 37 were survived, the cryosurvival rate was 30.3%. The survived blastocysts were transferred into 15 recipient buffalos. Five of the recipients established pregnancy, but four of them aborted on day 53, 59, 145 and 179 of gestation respectively. One cross‐bred buffalo (Murrah × Swamp buffalo (2n = 49) received three embryos delivered a 40.5 kg female calf by natural delivery on day 320 of gestation. Up to now (13‐month old), the cloned calf has been growing well with no abnormity observed. These results demonstrated that cryopreservation of inter‐subspecies cloned embryos is feasible to produce buffalo offspring.