Gonzales D S, Bavister B D
Department of Animal Health & Biomedical Sciences, University of Wisconsin, Madison 53706, USA.
Biol Reprod. 1995 Feb;52(2):470-80. doi: 10.1095/biolreprod52.2.470.
The timing and mode of hamster blastocyst escape from the zona pellucida in vitro ("hatching") and in vivo were compared on the basis of dynamic and static images captured on videotape and computer, respectively. In vivo, most embryos (> or = 80%) escaped between 0030 h and 0600 h on Day 4 of pregnancy. The zona gradually thinned globally and greatly increased in diameter, eventually disappearing. Attachment of blastocysts to the uterine epithelium followed within 4 h. Retarded embryos also showed global zona lysis. In contrast, zona escape in vitro was delayed > or = 29 h both in blastocysts cultured from 1-cell embryos and in blastocysts flushed from uteri of mated, naturally cycling hamsters at 2330 h on Day 3. Zonae were focally lysed; then blastocysts egressed through the hole, leaving most of the zona intact. Global zona lysis never occurred, and retarded embryos did not escape. In conclusion, the striking morphological and temporal differences in zona escape indicate that the hatching behavior routinely observed in cultured hamster blastocysts is not representative of normal events, and implicate a uterine contribution to normal zona escape that is lacking in culture.
分别基于录像带和计算机捕捉的动态和静态图像，对仓鼠囊胚在体外（“孵化”）和体内从透明带中逸出的时间和方式进行了比较。在体内，大多数胚胎（≥80%）在妊娠第4天的00:30至06:00之间逸出。透明带逐渐整体变薄，直径大幅增加，最终消失。囊胚在4小时内随后附着于子宫上皮。发育迟缓的胚胎也表现出整体透明带溶解。相比之下，无论是从1细胞胚胎培养的囊胚，还是在第3天23:30从交配的自然周期仓鼠子宫中冲洗出的囊胚，其在体外的透明带逸出都延迟了≥29小时。透明带局部溶解；然后囊胚通过孔洞逸出，大部分透明带保持完整。从未发生过整体透明带溶解，发育迟缓的胚胎也未逸出。总之，透明带逸出在形态和时间上的显著差异表明，在培养的仓鼠囊胚中常规观察到的孵化行为并不代表正常情况，这意味着子宫对正常透明带逸出有贡献，而在培养中缺乏这种贡献。
