Research and Development Group, Zen-noh Embryo Transfer Center, Kamishihoro, Hokkaido, Japan; Department of Veterinary Medical Science, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
Research and Development Group, Zen-noh Embryo Transfer Center, Kamishihoro, Hokkaido, Japan.
Theriogenology. 2021 Feb;161:243-251. doi: 10.1016/j.theriogenology.2020.12.001. Epub 2020 Dec 9.
The present study aimed to elucidate the developmental kinetics, growth potential, and viability of bovine embryos produced in vitro with sexed semen. Bovine oocytes were fertilized in vitro using unsorted and X-sorted semen from the same Holstein bulls, and the kinetics of in vitro development were continuously monitored for 10 d through time-lapse cinematography. The blastocyst formation rate was lower in the X-sorted group than in the unsorted group (P < 0.01), whereas the normal fertilization rate did not differ between groups. Morphokinetic evaluation revealed that the incidence of blastomere fusion during the first cleavage division, termed reverse cleavage, was higher in the X-sorted group (P < 0.01). Furthermore, embryos produced with X-sorted semen showed slower growth throughout the developmental period than embryos produced with unsorted semen (P < 0.01). The cell number of the trophectoderm and inner cell mass of blastocysts was reduced in the X-sorted group (P < 0.01). In embryos that developed to the blastocyst stage, the hatchability (P < 0.05), chromosomal normality (P < 0.01), and survivability after the conventional frozen-thawing process (P < 0.05) were reduced in the X-sorted group compared to that in the unsorted group, indicating a compromised viability of embryos derived from X-sorted semen. Taken together, the first cleavage dysmorphism, delayed embryo growth, and impaired viability of embryos developed to the blastocyst stage may explain the mechanism of reduced fertility in embryos derived from sexed semen. The kinetic evaluation of early embryo development and de-selection of embryos presenting the aberrant first cleavage would be valid for clinical application to produce sexed embryos with high implantation potential.
本研究旨在阐明使用性控精液体外生产的牛胚胎的发育动力学、生长潜力和活力。使用来自同一荷斯坦公牛的未经分选和 X 分选精液体外受精牛卵母细胞，并通过延时摄影连续监测体外发育的动力学 10 天。囊胚形成率在 X 分选组中低于未分选组（P < 0.01），而正常受精率在两组之间没有差异。形态动力学评估显示，在第一次卵裂分裂期间发生的胚胎裂球融合，称为反向分裂的发生率在 X 分选组中更高（P < 0.01）。此外，与使用未分选精液生产的胚胎相比，使用 X 分选精液生产的胚胎在整个发育期间的生长速度较慢（P < 0.01）。X 分选组的囊胚滋养层和内细胞团的细胞数减少（P < 0.01）。在发育到囊胚阶段的胚胎中，X 分选组的孵化率（P < 0.05）、染色体正常率（P < 0.01）和常规冷冻解冻后存活率（P < 0.05）均降低，表明 X 分选精液生产的胚胎活力受损。综上所述，第一次卵裂畸形、胚胎生长延迟和囊胚阶段发育的胚胎活力受损可能解释了性控精液生产的胚胎生育力降低的机制。对早期胚胎发育的动力学评估和对表现出异常第一次卵裂的胚胎的选择淘汰，将为生产具有高植入潜力的性控胚胎的临床应用提供有效方法。
