Analysis of Heart Development in Cultured Rat Embryos

The long-range goal of this research is to establish anin vitrosystem that will permit pertubation of mammalian heart development andin situexamination of the cellular and molecular events underlying cardiac morphogenesis. Rat embryos at 9.5–11.5 days of gestation were placed in culture bottles containing rat serum and Tyrodeʹs solution. Embryos cultured for 24 and 48 h were compared to age-matchedin vivocontrols for morphological score, morphometric analysis of heart development, and confocal and electron microscopic analysis of myofiber pattern formation. Morphological scores indicated that embryos cultured for 24 h from day 9.5 to 10.5 had essentially normal development when compared to age-matched embryos allowed to developin vivo. Development of embryos maintained for 48 h in culture was slightly delayed at 66–68% of age matchedin vivoembryos. Analysis of hearts from embryos allowed to develop 9.5–11.5 daysin vivoplus 24 and 48 h in culture showed that the ventricular thickness and height, as well as the truncal, atrial and ventricular diameters were equivalent to those of hearts from age-matchedin vivocontrols. Hearts from embryos allowed to develop from 11.5–12.5 daysin vitroand cultured for 24 and 48 h had smaller left ventricular and atrial dimensions than controls. Cardiac myofibrillogenesis and myofibrillar pattern formation in embryos cultured from 9.5 days ofin vivodevelopment for 48 h were also normal. These studies indicate that the rat whole embryo culture system is a useful model to study several critical periods in mammalian heart development.