APOPTOSIS OF RETINAL PHOTORECEPTORS DURING DEVELOPMENT IN-VITRO - PROTECTIVE EFFECT OF DOCOSAHEXAENOIC ACID

When rat retinal cells are cultured in a serum-free medium, the photor eceptor cells start dying after 7 days. The addition of docosahexaenoi c acid (DHA) to the cultures prevents the selective death of photorece ptors. Here it is shown that, unlike other retinal neurons, photorecep tors die through an apoptotic pathway. Hallmarks of apoptosis, such as nuclear fragmentation and condensation and DNA cleavage forming a lad der pattern on an agarose gel, were observed. The timing and high sele ctivity of the triggering of photoreceptor cell apoptosis suggest the existence of a programmed cell death. Compared with other fatty acids, DHA not only was the most effective in promoting photoreceptor surviv al, but also the only one to decrease the number of apoptotic nuclei. The results suggest that DHA is important among the factors preventing apoptosis of photoreceptors in the developing retina. A limitation in the availability of this fatty acid might trigger apoptosis as a resu lt of the failure to develop functional photoreceptor outer segments.