兔和小鼠早期胚胎ICM在ES培养系统中行为的比较

COMPARISON OF THE BEHAVIOR OF RABBIT AND MOUSE EMBRYOS ICM INCUBATED IN ES CULTURE SYSTEM

比较了兔和小鼠早期胚胎在小鼠ES培养系统中生长和发育的特征。结果发现 ,“两者在体外的早期发育程序和时间表”基本一致。但两者的生长方式不同 :( 1 )小鼠胚胎的滋胚层 (TB)能推开饲养层 (feeder)直接铺展在培养皿上 ;兔胚的TB推开饲养层的力量较小 ,大多数胚胎铺展在饲养层之上 ;( 2 )小鼠胚外内胚层 (ExEn)分化后紧紧包裹在ICM (innercellmass)之外。而兔胚ExEnⅠ和Ⅱ依次从ICM分化出来 ,迁离ICM呈单层生长。故小鼠的ICM生长在自己营造的一封闭的、保护良好的微环境中。而兔胚ICM直接与饲养层接触没有任何保护措施。在现有的ES培养系统中 ,小鼠ICM呈聚集生长并正确表达AKP和SSEA 1 ,而兔胚ICM生长呈多态性。根据AKP和SSEA 1的表达以及细胞分化的程序说明 ,只有聚集生长者为兔胚ICM的正常态 ,迁移型和单层生长的ICM为异常态。说明现有的ES培养系统对兔胚可能有不利因子存在 ,应进一步改善。本文已为筛选最佳培养条件提供了正负选择的指标。

The growth and developmental behaviors between rabbit and mice embryos was compared in ES culture system. It was found that the developmental program and chronologies of the rabbit embryos were consistent with those of mouse embryos. However the fashions of in vitro growth between mouse and rabbit embryos were different: 1. The trophablast cells of mouse embryo pushed the feeder cells away, and spread into a layer around the ICM at the bottom of the dish. Most of the trophablast cells of rabbit embryo could not push the feeder cells away, but spread onto the feeder layer forming a disc of embryo; 2. The ICMs of mice embryos grew on the top of its trophablast cells, while the rabbit ICMs grew under the trophablast layer; 3. The extraembryonic endoderm of mouse embryo after differentiation wrapped around the ICM closely. Whereas the extraembryonic endoderms Ⅰ and Ⅱ of the rabbit embryo differentiated from ICM respectively, moved away from the ICM and spread as a monolayer between the ICM and the trophablast. So the mouse ICM grew within a sealed off and well protected microenvironment which was constructed by itself. Although the ICM of rabbit embryo was covered with its trophablast and extraenbryonic endoderms, the ICM can reach the feeder cells without any protection. When these embryos with different growth fashions were incubated in ES culture system, the mice ICMs grew as clumps, and the clumps expressed the AKP and SSEA 1 correctly; while the rabbit embryo grew in different fashions, some grew as clumps or bands, some grew as monolayer, most of the rabbit ICMs grew as migration clumps. Depending on the expression of AKP and SSEA 1 as well as the cell differentiation programs of ICM, it shows that only the ICM grown as clump and band types are the normal developmental ICM of rabbit embryo. The migration type ICM or monolayer types ICM are the abnormal development. Thus we have provided the positive and negative selection markers for setting up the best culture system. These results show that the ES culture system used in our experiment is more satisfactory for the growth of mouse embryos, but cannot support normal development for rabbit embryos.