Transplantation as a therapy for retinitis pigmentosa?

Considerable excitement and surprise has attended reports given at several recent international meetings by Professor Manuel del Cerro from the University of Rochester on a series of patients who received transplants of fetal retina as a treatment for retinitis pigmentosa (Soc Neurosci Abstracts1996;22:319). Some of these patients appeared to show improved vision. Given the gloomy prognosis at present for patients with retinal degenerative diseases, this is good news. This work developed from a series of laboratory studies conducted over the past 25 years in which cells have been transplanted to the central nervous system, as a potential treatment for certain neurodegenerative diseases. About 12 years ago, several groups began transplantation studies in animal models of retinal degeneration. Two separate situations were suggested, either transplanted photoreceptors could take the place of photoreceptors that had already degenerated, forming new connections with the rest of the retina to restore vision, or they could protect remaining photoreceptors, especially cones, from further damage. Experimental studies have yet to show whether if new connections do occur they can restore normal visual function. The possibility of cone protection has yet to be validated.

It is with this background that the first clinical experiments have been conducted in retinitis pigmentosa patients. So far, evidence of improvement is anecdotal; no careful objective tests using third party observers have yet been reported. No control studies have yet been undertaken and while these are a controversial aspect to any clinical experiment, they are nevertheless essential for proper evaluation. It is hoped that these issues will be addressed once the work is presented …