Harris Craig
Toxicology Program, Department of Environmental Health Sciences, University of Michigan, Ann Arbor, MI, USA.
Methods Mol Biol. 2012;889:215-37. doi: 10.1007/978-1-61779-867-2_13.
The direct effects of chemical exposures, environmental extremes, and nutrient quality/quantity have been very difficult to study in mammalian embryos due to their anatomical inaccessibility, paucity of tissues, and other factors such as real ethical concerns in human studies. Many acute and chronic developmental anomalies can trace their origins to postimplantation phases of gestation where the organs are first being established and growth and differentiation are in highly active states of flux. Most agents and conditions that produce birth defects are believed to act during this period of organogenesis. The evolution of rodent whole embryo culture (WEC) techniques has provided a valuable experimental model where physiological conditions and exposures can be carefully controlled and manipulated to test hypotheses and explore biochemical and molecular mechanisms of action. Exposure to chemical agents can be controlled through their direct addition to the culture medium. Optimal in vitro culture conditions support the growth of intact, viable conceptuses (embryo and associated extraembryonic membranes) from early egg cylinder stages through establishment of the neural plate, gastrulation, neural tube closure, onset of active heartbeat and circulation, and the initial formation of all major organ systems that occur prior to the establishment of a functional placenta. Detailed comparisons of in vivo and in vitro growth show that conceptuses grown in WEC are nearly identical, structurally and functionally, to conceptuses of the same developmental stage that are allowed to develop normally in vivo. Culture conditions and mechanical apparatus can be modified to suit a large number of different experimental approaches and paradigms.
由于哺乳动物胚胎解剖位置难以接近、组织稀少以及人类研究中存在的实际伦理问题等因素，化学物质暴露、极端环境和营养质量/数量的直接影响在哺乳动物胚胎中一直很难研究。许多急性和慢性发育异常可追溯到妊娠植入后阶段，此时器官开始形成，生长和分化处于高度活跃的变化状态。大多数导致出生缺陷的因素和条件被认为在器官发生期起作用。啮齿动物全胚胎培养（WEC）技术的发展提供了一个有价值的实验模型，在这个模型中，可以仔细控制和操纵生理条件及暴露情况，以检验假设并探索作用的生化和分子机制。通过将化学物质直接添加到培养基中，可以控制对化学物质的暴露。最佳的体外培养条件支持完整、有活力的概念体（胚胎及相关的胚外膜）从早期卵柱阶段生长到神经板形成、原肠胚形成、神经管闭合、心跳和循环开始以及在功能性胎盘建立之前所有主要器官系统的初步形成。体内和体外生长的详细比较表明，在WEC中生长的概念体在结构和功能上与在体内正常发育的相同发育阶段的概念体几乎相同。培养条件和机械设备可以进行修改，以适应大量不同的实验方法和范式。
