Department for Biomedical Sciences, University of Veterinary Medicine, Veterinaerplatz 1, A-1210 Vienna, Austria.
Department of Agrobiotechnology, IFA-Tulln, University of Natural Resources and Life Science, Konrad Lorenz Strasse 20, 3430 Tulln, Austria.
Animal. 2020 Mar;14(S1):s103-s112. doi: 10.1017/S175173111900315X.
Assisted reproduction techniques (ARTs) provide access to early stage embryos whose analysis and assessment deliver valuable information. The handling of embryos, including the in vitro production of bovine embryos, is a rapidly evolving area which nonetheless exposes the embryos to unnatural conditions for a period of time. The Fallopian tube provides innumerable quantitative and qualitative factors, all of which guarantee the successful development of the embryo. It is well known that the Fallopian tube can be bypassed, using embryo transfer, resulting in successful implantation in the target recipient animal and the birth of calves. However, the question arises as to whether such circumvention has a negative impact on the embryo during this sensitive development period. First crosstalk between the embryo and its environment confirms mutual recognition activities and indicate bilateral effects. Nowadays, in vitro production of bovine embryos is a well-established technology. However, it is still evident that in vitro generated embryos are not qualitatively comparable to embryos obtained ex vivo. To counteract these differences, comparative studies between in vitro and ex vivo embryos are advantageous, as embryos grown in their physiological environment can provide a blueprint or gold standard against which to compare embryos produced in vitro. Attempts to harness the bovine oviduct were sometimes very invasive and did not result in wide acceptance and routine use. Long-term development and refinement of transvaginal endoscopy for accessing the bovine oviduct has meanwhile been routinely applied for research as well as in practice. Comparative studies combining in vitro development with development in the cattle oviduct revealed that the environmental conditions to which the embryo is exposed before activation of the embryonic genome can have detrimental and lasting effects on its further development. These effects are manifested as deviations in gene expression profiles and methylation signatures as well as frequency of whole chromosomal or segmental aberrations. Furthermore, it was shown that hormonal superstimulation (multiple ovulation and embryo transfer), varying progesterone concentrations as well as metabolic disorders caused by high milk production, markedly affected embryo development in the postpartum period. Assisted reproductive techniques that allow the production and handling of extra numbers of generated embryos promise to have a very high impact on scientific and practical application. Any influence on the early embryonic life, both in animals and in vitro, is accompanied by a sensitive change in embryonic activity and should be assessed in vivo on the basis of physiological conditions before being used for ART.
辅助生殖技术（ART）为获取早期胚胎提供了途径，这些胚胎的分析和评估提供了有价值的信息。胚胎的处理，包括牛胚胎的体外生产，是一个迅速发展的领域，但胚胎在这段时间内会暴露在非自然的条件下。输卵管提供了无数的数量和质量因素，所有这些因素都保证了胚胎的成功发育。众所周知，可以通过胚胎移植绕过输卵管，从而使目标受体动物成功植入并产下小牛。然而，问题是，在这个敏感的发育时期，这种规避是否会对胚胎产生负面影响。首先，胚胎与其环境之间的首次交流确认了相互识别活动，并表明了双边效应。如今，牛胚胎的体外生产已经是一项成熟的技术。然而，体外生成的胚胎在质量上仍然明显不如从体内获得的胚胎。为了克服这些差异，体外和体内胚胎之间的比较研究是有利的，因为在生理环境中生长的胚胎可以提供蓝图或金标准，与体外生产的胚胎进行比较。利用牛输卵管的尝试有时非常具有侵入性，并没有得到广泛的接受和常规应用。与此同时，为了获取牛输卵管，经阴道内镜技术的长期发展和改进已被常规应用于研究和实践。将体外发育与牛输卵管内的发育相结合的比较研究表明，胚胎在激活胚胎基因组之前暴露的环境条件可能对其进一步发育产生有害和持久的影响。这些影响表现为基因表达谱和甲基化特征的偏差，以及整个染色体或片段的畸变频率增加。此外，还表明激素超刺激（多排卵和胚胎移植）、孕酮浓度的变化以及高产奶引起的代谢紊乱，显著影响了产后胚胎的发育。允许产生和处理额外数量的胚胎的辅助生殖技术有望对科学和实际应用产生非常大的影响。在动物和体外条件下，对早期胚胎生命的任何影响都伴随着胚胎活动的敏感变化，应该在用于 ART 之前，根据生理条件在体内进行评估。
