Department of Animal Science, Tottori Livestock Research Center, Tottori 680-8553, Japan.
SCREEN Holdings Co., Ltd., Kyoto 612-8486, Japan.
J Reprod Dev. 2023 Oct 20;69(5):239-245. doi: 10.1262/jrd.2023-009. Epub 2023 Aug 11.
Although embryo transfer is widely applied in cattle, many of the transferred embryos do not result in pregnancy. To determine a new parameter for bovine embryo evaluation, we investigated the relationships between in vitro hatchability and embryo morphological parameters using optical coherence tomography (OCT) that we established recently. Bovine embryos were obtained from Japanese Black cattle by in vitro fertilization (IVF). The quality of the blastocysts was examined under an inverted microscope and confirmed as Codes 1-3 according to the IETS standards for embryo evaluation. The OCT images of the embryos were captured on Day 7 after IVF, and the embryos were cultured until Day 9 to determine their hatchability. During OCT, the embryos were irradiated with near-infrared light for a few minutes to obtain three-dimensional images. In total, 22 parameters were assessed for each of the 42 embryos, of which 25 hatched (H embryos) and 17 did not (NH embryos). The thickness of the trophectoderm (TE) and TE+zona pellucida (ZP) was lesser, and the volumes of the TE, ZP, blastocoel, and whole embryo and blastocoel diameter were greater in the H embryos than in the NH embryos. PCA identified that the increase in the blastocoel-related value along with the decrease in the thickness-related value of the TE and/or ZP could be indicators for evaluating the hatchability of bovine IVF embryos. These results support the idea that OCT-captured structural data of blastocyst-stage embryos can be used as a potential model to predict the quality of bovine embryos.
虽然胚胎移植在牛中被广泛应用，但许多移植的胚胎并没有导致妊娠。为了确定牛胚胎评估的新参数，我们使用最近建立的光学相干断层扫描（OCT）技术研究了体外孵化率与胚胎形态学参数之间的关系。牛胚胎通过体外受精（IVF）从日本黑牛中获得。使用倒置显微镜检查囊胚的质量，并根据胚胎评估的 IETS 标准确认为代码 1-3。在 IVF 后第 7 天采集胚胎的 OCT 图像，并将胚胎培养至第 9 天以确定其孵化率。在 OCT 期间，胚胎被近红外光照射几分钟以获得三维图像。总共对 42 个胚胎中的每个胚胎评估了 22 个参数，其中 25 个孵化（H 胚胎），17 个未孵化（NH 胚胎）。H 胚胎的滋养层（TE）和 TE+透明带（ZP）的厚度较小，TE、ZP、囊胚腔、整个胚胎和囊胚腔直径的体积较大。PCA 确定，随着 TE 和/或 ZP 的厚度相关值的降低，囊胚腔相关值的增加可以作为评估牛 IVF 胚胎孵化率的指标。这些结果支持这样一种观点，即 OCT 捕获的囊胚期胚胎的结构数据可以用作预测牛胚胎质量的潜在模型。
