Reconstitution of Complete Organs from Single-cell Suspensions of Chick Embryos in Advanced Stages of Differentiation.

Embryonic development proceeds in long sequences of interactions among cells and cell groups. Some of these interactions determine essential characteristics of tissues and organs, whereas others are merely of a permissive nature. For a given portion of an egg or embryo, the relevant interactions may (a) occur almost entirely within its own confines, or (b) be initiated, expedited or specifically supplemented by interactions with other portions. Principle (a), referred to under various names ("autonomization,"l "emancipation,"2 "segregation,"3 "selforganization,"4' 5) has been stressed by Weiss as the most basic, yet also most obscure, property of a developing organism.2 Principle (b), commonly referred to as "induction" 5, 6 and implying all sorts of adjuvant and permissive steps along the course of (a), however, has commanded an ever greater share of attention, work, and emphasis in recent years, to the point of creating the illusion, especially among those not fully familiar with the intricacies of embryology, that the principle of "induct on" holds the major, if not the exclusive, key to the understanding of development. It is with a view of restoring a more balanced perspective that we present the results reported in this paper, even though they are still incomplete. They are so unexpectedly demonstrative in proving the scope and power of principle (a), i.e., of self-organization without instructive outside intervention, that it seems warranted to communicate them at this time. They demonstrate the fact that cells which have already constituted a functional organ can, after complete isolation, dispersal, and random recombination, reconstitute that same type of organ once again, and can do so in an indifferent environment from which they could have received no cues as to how to do it. The study of the behavior of metazoan cells liberated from their organized tissue associations in the body, begun in sponges and hydroids,7' 8 has recently been extended with signal success to higher forms. The new trend had two points of origin. In 1950 and '52, Weiss and Andres9' 10 used single cell suspensions, obtained by dissociating embryonic tissues, to study the fate of such cells when disseminated in olderz.embryos by the. vascular route. Also in 1952, Moscona and Mosconat'1 used cell~from disociateV embryonic tissues to test their ability to reaggregate and to proceed with typical histogenesis in tissue culture.