An ultrastructural study on retinal neural and pigment epithelial cells in ovine neuronal ceroid-lipofuscinosis.

Ovine neuronal ceroid-lipofuscinosis represents another well studied model for human neuronal ceroid-lipofuscinosis (NCL). Accumulation of abnormal lipopigments in various retinal neurons, and loss of photoreceptors are similar to the lesions in human juvenile NCL and indicate that the sheep is a suitable model in which to study the pathogenesis of both NCL lipopigment formation and retinopathia pigmentosa. However, this latter process is not as advanced in NCL-diseased sheep as in human patients but far more obvious than in canine NCL in which retinopathy cannot be unequivocally documented. Ovine NCL shares with canine NCL peculiar lamellar inclusions in retinal pigment epithelial cells which may indicate an impaired catabolism of phagocytosed photoreceptor outer segments. As the peculiar lamellar inclusions seen in RPE cells of both NCL-diseased sheep and dogs do not very much resemble the phagocytosed photoreceptor outer segments, it may be assumed that in NCL the final steps in complete removal of these phagocytosed photoreceptor outer segments are also defective.