[Histopathological studies on the rds mouse retina--relationship between photoreceptor and pigment epithelial cells]

We used light and electron microscopy to examine detailed ultrastructural changes in the course of the development and degeneration of the rds mouse (rds/rds) retina with particular reference to the relationship between the photoreceptor and retinal pigment epithelial cells. During the first 6 postpartum days, the mutant retina showed the same developmental pattern as in normal mice. After that, however, rds mouse retinas failed to develop the photoreceptor outer segments. After 14 days, the photoreceptor inner segments and the cilia were all arranged parallel in the same direction in which the pigment epithelial cells extend their long microvilli. The inner segments and the cilia were very long and surrounded by the microvilli of the retinal pigment epithelial cells in the mutant retinas 21 days postpartum or latter. Some inner segments and cilia showed cytoplasmic degeneration in the part surrounded by the microvilli, while the other part appeared normal. There were pigment epithelial cells that contained fragments of the inner segments. The photoreceptor nucleus and inner segment were reduced in number after 21 days. These findings indicate that the pigment epithelial cells play a role in photoreceptor degeneration in rds mice.