ANALYSIS OF HEART DEVELOPMENT IN CULTURED RAT EMBRYOS

The long-range goal of this research is to establish an in vitro syste m that will permit pertubation of mammalian heart development and in s itu examination of the cellular and molecular events underlying cardia c morphogenesis. Rat embryos at 9.5-11.5 days of gestation were placed in culture bottles containing rat serum and Tyrode's solution. Embryo s cultured for 24 and 48 h were compared to age-matched in vivo contro ls for morphological score, morphometric analysis of heart development , and confocal and electron microscopic analysis of myofiber pattern f ormation. Morphological scores indicated that embryos cultured for 24 h from day 9.5 to 10.5 had essentially normal development when compare d to age-matched embryos allowed to develop in vivo. Development of em bryos maintained for 48 h in culture was slightly delayed at 66-68% of age matched in vivo embryos. Analysis of hearts from embryos allowed to develop 9.5-11.5 days in vivo plus 24 and 48 h in culture showed th at the ventricular thickness and height, as well as the truncal, atria l and ventricular diameters were equivalent to those of hearts from ag e-matched in vivo controls. Hearts from embryos allowed to develop fro m 11.5-12.5 days in vitro and cultured for 24 and 48 h had smaller lef t ventricular and atrial dimensions than controls. Cardiac myofibrillo genesis and myofibrillar pattern formation in embryos cultured from 9. 5 days of in vivo development for 48 h were also normal. These studies indicate that the rat whole embryo culture system is a useful model t o study several critical periods in mammalian heart development. (C) 1 997 Academic Press Limited