牛体细胞核移植技术研究进展

对近年来牛体细胞核移植技术研究的进展作一综述。其中包括:供体细胞种类、传代次数和所处细胞周期的选择;对供体细胞的特殊处理;卵母细胞的采集;传统去核方法的优化、去透明带核移植技术的建立与发展;胚胎重构、激活和体外培养条件的比较与改进等内容。     

体细胞核移植技术在不同物种中的应用及提高其成功率的可能措施

体细胞核移植技术具有极其广阔的应用前景,但极低的成功率限制了这项技术在实践生产中的应用。不同的学者在不同的物种上进行了一系列的尝试,试图提高体细胞核移植的成功率。本文就体细胞核移植技术在不同物种中的成功应用进行阐述,并就如何提高体细胞核移植成功率阐明一些观点。     

哺乳动物体细胞核移植研究进展及应用前景

哺乳动物体细胞核移植克隆技术成功于１９９７ 年,曾引起世界范围内的广泛关注,本文综述了体细胞克隆技术在近两年内的最新研究进展及其在生产、医疗和科学研究方面的应用前景。     

核重编程机制的影响因素

哺乳动物体细胞核移植技术在农业、生物技术、医药生产和濒危动物保护等方面具有很大的潜力和应用价值,已成为目前发育生物学研究的重要方法。但是核重编程仍是核移植技术的关键因素,制约了重构胚胎干细胞的研究。只有供核发生完全重编程,重构胚胎才能正常发育。核重编程与供核者的年龄,供核细胞的组织来源、分化状态、细胞周期、传代次数,供核细胞的表观遗传标记以及供卵者的年龄、卵子的成熟度等因素有关。创造各种适于核重编程的条件有利于从更高的起点开展核移植胚胎干细胞的研究,提高重枸胚胎干细胞建系效率。     

Generation of cloned calves from different types of somatic cells

Six types of bovine somatic cell lines, including a granulosa cell line of Chinese red-breed yellow cattle (YGR), a granulosa cell line of Holstein cow (HGR), two skin fibroblast cell lines of two adult Holstein cows respectively (AFB1 and AFB2), a skin fibroblast cell line (FFB) and an oviduct epithelial cell line (FOV) of a Holstein fetus, were established. Somatic cell nuclear transfer (SCNT) was carried out using these cells as nuclei donor, and a total of 12 healthy calves were cloned. The effects of different types of donor cells on developmental potential of bovine SCNT embryos were investigated, (i) There was no significant difference in development rates to the blastocyst stage for SCNT embryos from YGR and HGR (33.2% and 35.1%, respectively). Pregnancy rates of them were 33.3% and 30.2%, respectively; and birth rates were 16.7% and 11.6%, respectively, (ii) Development rates to the blastocyst stage for SCNT embryos from diffetent individuals (AFB1 and AFB2) differed significantly (27.9% and 39.4%, respectively, P < 0.05). Pregnancy rates of them were 36.2% and 36.4%, respectively; and birth rates were 14.9 % and 27.3%, respectively, (iii) There was significant difference in development rates to the blastocyst stage for SCNT embryos from FFB and FOV of the same fetus (37.9% and 41.5%, respectively,P < 0.05). Pregnancy rates of them were 45.7% and 24.1%, respectively; and birth rates were 22.9 % and 10.3%, respectively. Finally, developmental potential of bovine SCNT embryos from all four types of somatic cells from Holstein cows (HGR, AFB, FFB and FOV) were compared. Forin vitro development stage, development rates to the blastocyst stage for SCNT embryos from HGR, AFB, FFB and FOV were 35.1%^A, 29.4%^B, 37.9%^A and 41.5%^C, respectively (P ^ABC < 0.05); forin vivo development stage, pregnancy rates of them were 30.2%, 36.2%, 45.7% and 24.1%, respectively; and birth rates of them were 11.6%, 17.2%, 22.9% and 10.3% respetively.     

体细胞核移植胚胎核重编程的研究进展

尽管在多种哺乳动物种系中成功制备了体细胞克隆后代,但当前的克隆技术仍有许多亟待解决的问题。体细胞核移植胚胎大多存在许多发育异常,造成了妊娠早期高流产率和出生后高死亡率。有研究认为,克隆胚胎发育障碍的一个重要的原因是供体细胞的遗传重编程不完全。哺乳动物种系中,DNA甲基化是胚胎发育期转录调节的必需步骤,除了单拷贝基因序列外,在基因组很多的区域都可以观测到克隆胚胎的异常甲基化。此外,克隆胚胎的基因印迹也存在异常。     

细胞核重编程对克隆的影响

细胞核重编程是哺乳动物正常受精胚胎和克隆胚胎发育过程中的一个重要特性,主要是对表观遗传学特征进行重新编写,包括染色质重塑、组蛋白修饰、DNA甲基化、印记基因表达、X染色体失活等表观遗传修饰的改变。通过细胞核重编程,首先,受精卵和克隆胚胎的供体核停止其特有的基因表达程序,恢复为全能状态的基因表达程序;然后,受精胚胎和克隆胚胎的细胞再从全能状态重新进入分化状态,最终形成各种组织和器官。近年来,不少研究表明,克隆胚胎的细胞核重编程存在不同程度的表观遗传修饰异常,可能对克隆及其农业和医学应用有着重要影响。本文就正常和克隆胚胎细胞核重编程的研究进展以及克隆胚胎的细胞核重编程异常对克隆的影响作一综述,并对目前有关治疗性克隆前景的不同看法进行了讨论。     

Experimental cloning of embryos through human-rabbit inter-species nuclear transfer

Therapeutic cloning, which is based on human somatic cell nuclear transfer, is one of our major research objectives. Though inter-species nuclear transfer has been introduced to construct human somatic cell cloned embryos, the effects of type, passage, and preparation method of donor cells on embryo development remain unclear. In our experiment, cloned embryos were reconstructed with different passage and preparation methods of ossocartilaginous cell, skin fibroblast, and cumulus cells. The cumulus cell embryos showed significantly higher development rates than the other two (P < 0.05). The development rate of embryos reconstructed with skin fibroblasts of different passage number and somatic cells of different chilling durations showed no significant difference. Also, fluorescence in situ hybridization (FISH) was conducted to detect nuclear derivation of the embryos. The result showed that the nuclei of the inter-species cloned embryo cells came from human. We conclude that (1) cloned embryos can be constructed through human-rabbit interspecies nuclear transfer; (2) different kinds of somatic cells result in different efficiency of nuclear transfer, while in vitro passage of the donor does not influence embryo development; (3) refrigeration is a convenient and efficient donor cell preparation method. Finally, it is feasible to detect DNA genotype through FISH. Translated from Zoological Research, 2005, 26(4): 416–421 [译自: 动物学研究]     

Stem cell research in China

In the past 5 years, China has increased its efforts in the field of stem cell research and practice. Basic research mainly focuses on bone marrow and embryonic stem cells. Clinical applications of stem cells in the treatment of acute heart failure, acute liver failure and lower limb ischaemia have been reported by many hospitals. China enacted its 'Ethical Guidelines for Human Embryonic Stem Cell Research' in 2003. At present, China has the most liberal and favourable environments for human embryonic stem cell research.     

体细胞核移植诱导的表观遗传学变化

体细胞核移植技术是指将一个分化的体细胞核置入去核的卵母细胞中,并发育产生与供体细胞遗传背景一致的克隆后代的技术。目前,世界上通过体细胞核移植技术已经产生了许多的克隆动物。但克隆过程中还存在着很多问题,比如,克隆效率太低、克隆个体常伴有表型异常和早亡等,从而使该技术应有的应用潜力不能得到充分的发挥。体细胞表观遗传学重编程的不完全或紊乱是造成核移植诸多问题的主要原因。近十多年来,人们对体细胞核移植后的重编程进行了广泛的研究,其核心内容包括核及核外结构的重塑、DNA甲基化模式的重建、基因印迹和x染色体失活、组蛋白乙酰化模式的重建、端粒长度恢复等,以期能够对其重编程加以人为干预,从而提高动物克隆效率。本文拟对体细胞核移植诱导的重编程研究进展加以综述,希望对体细胞重编程机制的阐明有所启发。     

细胞抽提物诱导的体细胞重编程

体细胞重编程是指在特定条件下将已分化的体细胞去分化逆转回原始多能状态或转分化为其他类型细胞。目前诱导体细胞重编程的方法主要有：体细胞核移植、细胞融合、特定转录因子转染、细胞抽提物诱导等。近年来抽提物诱导体细胞重编程越来越受到研究者的关注。利用此法, 通过重编程不仅可以获得需要类型的细胞, 而且方便识别与重编程有关的细胞因子, 探求重编程的机制。文章简略概述诱导体细胞重编程的方法, 并重点阐述细胞抽提物诱导体细胞重编程的研究进展。     

microRNAs和体细胞重编程

体细胞重编程与microRNAs(miRNAs)均为近年来研究的热点问题。到目前为止,能成功诱导体细胞形成多能性干细胞的体细胞重编程方法有核移植(nuclear transfer,NT)和外源因子诱导形成多能干细胞(induced pluripotent stem cells,iPSc)两种,这两种方法让人们看到了体细胞重编程在细胞治疗方面具有诱人的应用前景。miRNAs是真核生物中存在的一类长度为22nt左右起调控作用的内源性非编码RNA,它在转录后水平调节靶基因的表达,是细胞内基因表达的基本调控机制之一。近年的研究结果表明,miRNAs在干细胞干性维持和分化过程中具有重要的调节作用,从miRNAs角度研究体细胞重编程机理将对体细胞重编程的应用具有重要意义。     

供体细胞与哺乳动物体细胞核移植

哺乳动物体细胞核移植(克隆)技术在转基因动物生产、珍稀动物资源复原与保护、生物学基础研究等方面业已显示出重要的应用价值,而目前该技术还与诱导多能干细胞技术一同被认为是创制患者特异性多能干细胞,为再生医学临床"细胞治疗"提供素材的最佳手段。但是,体细胞克隆的效率仍不理想,关键机制还不清楚,严重制约了该技术的推广。因此,如何提高克隆效率已成为人们普遍关心的首要问题。在体细胞克隆技术所涉及的各环节中,供体细胞是影响克隆效率的最关键因素之一。该文从供体细胞的生物学因素和技术因素两方面进行了回顾,旨在为进一步探寻建立物种或供体细胞个性化准备方案,为提高动物克隆效率提供参考。     

Effects of donor cells on in vitro development of cloned bovine embryos

The donor cells from different individuals and with different foreign genes introduced were investigated to determine their effects on the efficiency of somatic cell nuclear transfer (SCNT). The bovine ear fibroblast from different individuals was isolated, cultured, and then transfected with foreign genes to establish the stable cell lines, which were used as donor cells for nuclear transfer. The ooeytes were obtained through ovum pick up operation. After in vitro maturation, the M II phase oocytes were selected as receptors for nuclear transfer.The reconstructed embryos were cultured in vitro and observed at 2 h, 48 h, and 7 days after transfer to assess the rate of fusion using cleaved and blastoeyst as the parameters of SCNT efficiency. The donor cells from different individuals (04036, 06081, 06088, and 06129)had no obvious effect on the fusion and cleaved rate, whereas there was significant difference in the blastocyst rate (P<0.05), and the rate was 62.3%, 37.0%, 35.1%, and 15.6%, respectively. There was no significant difference among the rate of fusion, cleaved and blastocyst in donor cells with different foreign genes (P>0.05). It was concluded that the genetic background of the donor cells could affect the effi-ciency of SCNT, while the introduction of foreign genes into the donor cells had no obvious effect on the efficiency. This study provides useful information for the SCNT and would benefit in promoting the efficiency.