Histotypic differentiation of neonatal mouse retina in organ culture

Retinae from neonatal mice were explanted in toto, with or without the retinal pigment epithelium (RPE) and adjoining mesenchymal cells, and maintained in organ culture for up to 3 weeks. The explants remained flat, rosette formation was minimal and histogenetic changes followed in the normal sequence. After 11, 14 and 21 days in vitro the three cellular layers--the outer nuclear layer including well differentiated rod and cone perikarya, the inner nuclear layer and the ganglion cell layer--with the intervening plexiform layers were comparable to those of the in vivo eyes. Electron microscopic analysis revealed that in the explants without RPE the nuclear layers developed as in vivo, but receptor outer segments (ROS) were not formed. When the RPE was present, receptor inner segments appeared normal and ROS including profuse disc structures were developed. Presence of synaptic elements was also recognized. Mesenchymal cells, when present differentiated into choroidal and scleral tissues and appeared to play a supportive role for the RPE cells. The system is described in detail and its suitability for the analysis of various cellular and metabolic factors in the development of the retina is discussed.