A new in vitro system for studying secondary palate development

An in vitro system was devised which supports palate development in partially dissected embryonic mouse heads. The heads were suspended in the culture chamber so that they were not held in a fixed orientation and were constantly surrounded with a fluid medium. Under these circumstances the developing palate must effect closure without the aid of gravitational forces. The culture medium was constantly circulated, gassed with 95% O₂, 5% CO₂ using hollow fiber gas permeation devices, and kept at 34°C. Swiss Webster mouse embryos of 12 days 12-18 hr (ca. 48 hr prior to expected in vivo closure) or 13 days 8-14 hr (ca. 24 hr prior to closure) were used to test the ability of the system to support palatal development. Embryonic heads were dissected in one of 2 ways before culture: brain and tongue removed, or brain, tongue and mandible removed. After 24 hr in culture, preparations of either age with only the brain and tongue removed had made substantially greater progress than their counterparts with the brain, tongue and mandible removed. With only the brain and tongue removed, the palatal shelves were contacting, adhered or fused in 67% of the older embryos, whereas most of the embryos of the same age cultured with the brain, tongue and mandible removed had shelves that were not fully elevated and still separated by a moderate gap. Thus for maximal progress in the present system, the oral cavity must be intact except for the tongue.