The process of reconstruction of histological architecture from dissociated retinal cells

1. Dissociated neural retinal cells of 7-day-old chick embryos were reaggregated under rotation culture and the relation between the several kinetic changes in reaggregation and further histogenesis occurring in the reaggregates was analysed. 2. Aggregates formed by 72 hours' culturing consisted of many rosettes, each of which contained a receptor lumen in its center, and the ganglion lumen with many ganglionic cells. 3. Cell sorting occurred within a rosette, but not within an aggregate. 4. Retinal cells labeled with³H-thymidine and unlabeled cells were allowed to reaggregate separately. By mixing such labeled and unlabeled aggregates formed in the early phase of reaggregation, further fusion of aggregates was achieved. Through these experiments, the following facts were revealed. 4a. In 2 to 3 hours of culturing, primary aggregates of 35 to 70 μ diameter were formed. 4b. All cells within these primary aggregates were well oriented, and the orientation of cells persisted through the further process of fusion of aggregates. 4c. By the fusion of more than 10 primary aggregates, the H unit which contained a full set of structures of the reconstructed neural retina was formed. 4d. The final aggregate was formed by the fusion of aggregates of H units. The ganglion lumen was formed between the two cell groups of H units. 5. When a primary aggregate consisting of about 20 cells was transferred into stationary culture, a single rosette was formed in it. 6. On the basis of these results, the mechanism of the reconstruction of the histological architecture from dissociated retinal cells is discussed.