ON THE MECHANISM OF TISSUE RECONSTRUCTION BY DISSOCIATED CELLS, I. POPULATION KINETICS, DIFFERENTIAL ADHESIVENESS, AND THE ABSENCE OF DIRECTED MIGRATION

Abstract

Experiments are described in which dissociated chick embryonic heart and neural retinal cells have been used to construct common aggregates containing decreasing proportions of heart cells. When heart cells comprise an appreciable fraction of the volume of the aggregates they assemble into one or more islands of heart tissue within the interior of each aggregate. Such inlands are internal but not necessarily central. When heart cells comprise only about 1% of the volume of the aggregates they remain distributed in all locations other than the surfaces themselves. The results demonstrate that sorting-out of cells and the selective positioning of reconstructed tissues within aggregates occur in the absence of directed migration of these cells along radial concentration gradients which may be established within the aggregates. These events are in all likelihood brought about by the preferential cohesion of heart cells when they collide as a consequence of their random movements. A formal similarity is noted between the essential properties of sorting-out cell systems and those of 2-phase systems of mutually immiscible liquids. Certain properties of the former are shown to be entirely comparable with corresponding properties of the latter, and certain other properties of cellular systems are indicated as being predictable from and formally analogous with the well-understood behavior of oil-and-water systems.