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Zusammenfassung:
Dissociated E5-E6 chick retinal cells in the presence of PE-cells have the capacity to reaggregate and reconstruct all main layers of an intact E10-E14 retina after 14-21 days in rotary culture(l). Now we have tried to correlate patterns of proliferation with differentiation phenomena occurring during the formation of these 'retinoids'. Determination of cell numbers in aggregates after 9 days in culture reveals a 4-fold increase in R-aggregates (composed of retinal cells alone) and a 5-fold increase in RPE-aggregates (retinal cells and PE-cells). Compared with retinae in vivo, the time course and the amount of 3 H-thymidine uptake in aggregates shows a decrease to 20 % during the first day and then is similar (R-Aggregates) or even accelerated (RPE- aggregates) for the next three days. A double-label procedure showed striking differences in the spatial order of thymidine- and AChE-positive cells within RPE- and R-aggregates. In R-aggregates thymidine- incorporating cells are distributed over the whole aggregate. They express high amounts of AChE at the periphery, but no layered arrangement in the center of the aggregates. In RPE-aggregates proliferating cells are arranged in a concentric band in the outer part and differentiated cells are localized in the inner part of the aggregate. Concomitantly an AChE-positive layer arises in the middle of the RPE-aggregate, which possibly is composed of INL cells. It marks a clear border between differentiated and proliferating cells after 2-4 days in culture. We conclude that the high degree of organization in these aggregates is accompanied by pronounced rates of proliferation. In RPE-aggregates proliferation and differentiation (AChE) occur in separate lamina showing similarities to the sequence observed in an in vivo retina.
