Abstract：
Somatic cell nuclear transfer (SCNT) is one of the primary methods for production of genetically engineered sheep, which allows for gene editing or transgene introduction in somatic cells. The use of SCNT eliminates the risk of genetic mosaicism in embryos and animals that is commonly observed after zygote micromanipulations. This retrospective analysis of SCNT in sheep performed at Utah State University, spanning from 2016 to 2021, examined parameters that may impact pregnancy and full-term development, including donor oocytes (donor age), donor cell lines, SCNT parameters (time of oocyte activation following SCNT, number of transferred embryos, in vitro maturation and culture conditions), and recipients (surgical number and ovulatory status), as well as factors that may correlate with large offspring syndrome or abnormal offspring syndrome (LOS/AOS) in the fetuses and lambs. Our findings indicated that compared to prepubertal oocytes, the SCNT embryos produced from adult sheep oocytes had comparable in vitro maturation rates, pregnancy and full-term development rates, as well as SCNT efficiency. In addition, earlier activation time of SCNT embryos (e.g. 24-26 h post maturation) was correlated to the early pregnancy loss rate, full-term rate, and SCNT efficiency. Compared to our standard serum-containing medium, commercial serum-free culture medium showed a positive correlation with the full-term development of sheep SCNT embryos. Transferring 15-30 embryos per recipient resulted in consistently good pregnancy rates. Surgical numbers and ovulatory status (having at least one follicle between 6 and 12 mm in size or a corpus hemorrhagicum (CH)) of recipients did not affect pregnancy and full-term development rates. In summary, this retrospective analysis identified parameters for improving pregnancy and full-term development of SCNT embryos in sheep.
摘要：
体细胞核移植（SCNT）是生产基因工程绵羊的主要方法之一，允许在体细胞中进行基因编辑或转基因导入。SCNT的使用消除了在合子微操作后通常观察到的胚胎和动物中遗传镶嵌的风险。这项在犹他州立大学进行的绵羊SCNT的回顾性分析，从2016年到2021年，检查了可能影响怀孕和足月发育的参数，包括供体卵母细胞（供体年龄），供细胞系,SCNT参数(SCNT后卵母细胞激活的时间，移植的胚胎数量，体外成熟和培养条件)，和接受者（手术次数和排卵状态），以及可能与胎儿和羔羊的大后代综合征或异常后代综合征（LOS/AOS）相关的因素。我们的研究结果表明，与青春期前卵母细胞相比，从成年绵羊卵母细胞产生的SCNT胚胎具有相当的体外成熟率，怀孕和足月发育率，以及SCNT效率。此外,SCNT胚胎的早期激活时间（例如成熟后24-26小时）与早期妊娠损失率相关，全额利率，SCNT效率。与我们的标准含血清培养基相比，商品化无血清培养基与绵羊SCNT胚胎的足月发育呈正相关。每个受体移植15-30个胚胎会导致持续良好的怀孕率。受者的手术数量和排卵状态（至少有一个大小在6至12毫米之间的卵泡或出血体（CH））不影响妊娠和足月发育率。总之,这项回顾性分析确定了改善绵羊SCNT胚胎妊娠和足月发育的参数.
