Embryo transfer in cattle is globally becoming more ubiquitous, but the pregnancy rate is lower than that of artificial insemination. The uterus contains its own bacteria, and concentrations of lipopolysaccharides (LPS) from gram-negative bacteria are higher in uteri affected by endometritis than in healthy uteri and they suppress embryogenesis. The purpose of this study was to investigate the morphological characteristics of bovine embryos with a higher viability and implantability, by analyzing the morphology of bovine blastocysts that successfully hatched under challenge of LPS, using an optical coherence tomography (OCT) system. Developing embryos produced by fertilization that had reached the blastocyst stage on Day 7 were three-dimensionally scanned using an OCT system, then were continued to culture with or without LPS until Day 9, when the presence or absence of hatching was determined. The OCT-captured three-dimensional images were used to quantify 20 different metrics, including inner cell mass (ICM), trophectoderm, blastocoel, and total embryo volume; each of the parameters was compared between the hatched and unhatched embryos. Under the LPS challenge, hatched embryos had higher ICM thickness and volume, and lower trophectoderm thickness than unhatched embryos. Furthermore, hatched embryos under LPS challenge had higher ICM thickness and ICM volume than hatched embryos without LPS challenge. The present results suggest the possibility that ICM thickness and ICM volume calculated by OCT system could be indices for good quality bovine embryos.

中文翻译：

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体外脂多糖暴露下孵化的牛囊胚的三维形态

牛胚胎移植在全球范围内变得越来越普遍，但妊娠率低于人工授精。子宫含有自己的细菌，受子宫内膜炎影响的子宫中来自革兰氏阴性细菌的脂多糖（LPS）浓度高于健康子宫，并且它们会抑制胚胎发生。本研究的目的是通过使用光学相干断层扫描 (OCT) 系统分析在 LPS 攻击下成功孵化的牛囊胚的形态，研究具有更高活力和可植入性的牛胚胎的形态特征。使用 OCT 系统对受精产生的发育中胚胎（在第 7 天达到囊胚阶段）进行三维扫描，然后在有或没有 LPS 的情况下继续培养，直到第 9 天，此时确定是否存在孵化。 OCT 捕获的三维图像用于量化 20 种不同的指标，包括内细胞质量 (ICM)、滋养外胚层、囊胚腔和胚胎总体积；比较孵化和未孵化胚胎的每个参数。在LPS攻击下，孵化的胚胎比未孵化的胚胎具有更高的ICM厚度和体积，以及更低的滋养外胚层厚度。此外，LPS攻击下的孵化胚胎比没有LPS攻击的孵化胚胎具有更高的ICM厚度和ICM体积。目前的结果表明，OCT 系统计算的 ICM 厚度和 ICM 体积可能成为优质牛胚胎的指标。