Hoelker M, Kassens A, Salilew-Wondim D, Sieme H, Wrenzycki C, Tesfaye D, Neuhoff C, Schellander K, Held-Hoelker E
Research Facility Frankenforst, Faculty of Agriculture, University of Bonn, Königswinter, Germany; Institute of Animal Science, Animal Breeding and Husbandry Group, University of Bonn, Endenicher Allee 15, Bonn, Germany; Center of Integrated Dairy Research (CIDRe), University of Bonn, Meckenheimer Allee 172, 53115 Bonn, Germany.
Unit for Reproductive Medicine, Clinic for Horses, University of Veterinary Medicine Hannover, Bünteweg 15, Hannover, Germany.
Theriogenology. 2017 Jul 15;97:41-49. doi: 10.1016/j.theriogenology.2017.04.009. Epub 2017 Apr 5.
To circumvent the negative impacts of in vitro culture on bovine embryos, we have recently established a new method, the so called intra-follicular oocyte transfer (IFOT), enabling in vivo fertilization and in vivo development of in vitro matured oocytes up to the blastocyst stage as well as to term. In this study, we raised the question whether immature bovine oocytes could also be transferred into a pre-ovulatory follicle to support in vivo maturation prior to subsequent in vivo fertilization, in vivo development as well as to term. To unravel that question, a total of 791 immature oocytes were transferred in groups of ∼50 into pre-ovulatory follicles of 16 recipient heifers. Consequently, we were able to recollect a total of 306 structures 8 days thereafter (38.5%). All in all, 12 heifers (75%) gave embryos developed to the morula or blastocyst stage in addition to the expected native embryos. Among all recollected structures, 40.1% had developed to the morula and/or blastocyst stage, meaning a total efficiency of 17.3% based on all transferred oocytes. Of impact, IFOT-embryos reached significantly higher developmental rates to the Morula and/or blastocyst stage until day 7 compared to in vitro cultured control embryos, despite being derived from the same charge of slaughterhouse ovaries (40.1 vs. 29.3%). This implicates a beneficial effect of the follicular environment for the intrinsic quality of the fertilized embryos during maturation and for subsequent developmental rates up to the blastocyst stage. Finally, the birth of two healthy calves after transfer of frozen-thawed IFOT-derived blastocysts to final recipients established the first proof of principle that IFOT of immature bovine oocytes generates bovine blastocysts bearing developmental capacity to term. Likewise, to the best of our knowledge, these calves are the first calves derived from full in vivo development of immature slaughterhouse derived oocytes. Thus, the results of the present study clearly demonstrate that IFOT of immature slaughterhouse-derived oocytes is now a feasible technique. Since efficiencies following IFOT achieved within the present study were improved compared to previous studies, IFOT now offers an attractive option for designing new scientific experiments.
为规避体外培养对牛胚胎的负面影响，我们最近建立了一种新方法，即所谓的卵泡内卵母细胞移植（IFOT），该方法可使体外成熟的卵母细胞在体内受精并发育至囊胚阶段乃至足月。在本研究中，我们提出一个问题：未成熟的牛卵母细胞是否也能被移植到排卵前卵泡中，以支持其在随后的体内受精、体内发育直至足月前的体内成熟。为解答这个问题，我们将总共791个未成熟卵母细胞分成每组约50个，移植到16头受体小母牛的排卵前卵泡中。结果，8天后我们总共回收了306个结构（38.5%）。总体而言，除了预期的自然胚胎外，12头小母牛（75%）产出了发育至桑椹胚或囊胚阶段的胚胎。在所有回收的结构中，40.1%发育至桑椹胚和/或囊胚阶段，这意味着基于所有移植卵母细胞的总效率为17.3%。重要的是，尽管IFOT胚胎和体外培养的对照胚胎来自同一批屠宰场卵巢，但与体外培养的对照胚胎相比，IFOT胚胎在第7天前发育至桑椹胚和/或囊胚阶段的比率显著更高（40.1%对29.3%）。这表明卵泡环境对受精胚胎在成熟过程中的内在质量以及随后直至囊胚阶段的发育速率具有有益影响。最后，将冷冻解冻的IFOT来源的囊胚移植到最终受体后，两头健康小牛的出生确立了首个原理证明，即未成熟牛卵母细胞的IFOT可产生具有发育至足月能力的牛囊胚。同样，据我们所知，这些小牛是首批完全通过未成熟屠宰场来源卵母细胞的体内发育而获得的小牛。因此，本研究结果清楚地表明，未成熟屠宰场来源卵母细胞的IFOT现在是一种可行的技术。由于本研究中IFOT后的效率比之前的研究有所提高，IFOT现在为设计新的科学实验提供了一个有吸引力的选择。
