Rabbit whole embryo culture.

Although the rabbit is used extensively in developmental toxicity testing, relatively little is known about the fundamental developmental biology of this species let alone mechanisms underlying developmental toxicity. This paucity of information about the rabbit is partly due to the historic lack of whole embryo culture (WEC) methods for the rabbit, which have only been made available fairly recently. In rabbit WEC, early somite stage embryos (gestation day 9) enclosed within an intact amnion and attached to the visceral yolk sac are dissected from maternal tissues and placed in culture for up to 48 h at approximately 37°C and are continuously exposed to an humidified gas atmosphere mixture in a rotating culture system. During this 48 h culture period, major phases of organogenesis can be studied including cardiac looping and segmentation, neural tube closure, and development of anlagen of the otic system, eyes and craniofacial structures, somites and early phases of limb development (up to bud stage), as well as expansion and closure of the visceral yolk sac around the embryo. Following completion of the culture period, embryos are evaluated based on several growth and development parameters and also are assessed for morphological abnormalities. The ability to sustain embryo development independent of the maternal system allows for exposure at precise development stages providing the opportunity study the direct action of a teratogen or one of its metabolites on the developing embryo. Rabbit WEC is perhaps most useful when used in conjunction with rodent WEC methods to investigate species-specific mechanisms of developmental toxicity.