Photoreceptor-horizontal cell reaggregation in monolayer cultures of neonatal rabbit retina.

It has been widely reported that trypsin-dissociated embryonic or neonatal retinal neurons have the ability to reaggregate into histotypic structures when grown in suspension. We now demonstrate that suspension culture is not required and that cell-specific aggregates can also be generated in papain-dissociated cell cultures of neonatal rabbit retina grown on laminin-coated glass coverslips. This culture preparation permitted the direct observation of a rapid and specific reaggregation of retinal cell types into two discrete types of clusters characterized by different morphologies as well as distinct labeling patterns of cell-specific antibodies and lectins. The first cluster type was composed of cells of the outer retina (photoreceptors in specific arrangements with horizontal cells); the second was composed of cells of the inner retina (amacrines and perhaps ganglion cells). The two cluster types were not intermingled, but rather they were segregated from each other, creating a spatial separation of inner from outer retinal cells across the coverslip. Video microscopy revealed that the separation was achieved rapidly (<1 hour) and that neither cell migration nor cell division was required for construction and segregation of cell-specific reaggregates. This novel observation suggests that repulsive as well as attractive factors exist that result in an initial sorting of cells from the outer and inner retina during early development.