Because a major cause of blindness is the destruction of the retinal photoreceptors (while the other portions of the retina generally remain intact), work was initiated in this laboratory to investigate the possibility of restoring some level of visual function through the transplantation of photoreceptors. To this end, a method for separating the intact photoreceptor matrix from the developing retina has been devised, and we have found that with careful surgery, transplantation of these photoreceptors to their appropriate position behind the retina is possible. It is advantageous that the neural connections which the photoreceptors must make to the neural retina are short and that the photoreceptors need to appropriately innervate only the adjacent outer plexiform layer in order for photic activation to be restored. In addition, because transplant tissue rejection is minimal within the eye and since nonvascularized tissue within the eye has shown the least amount of tissue rejection, the chance of the nonvascularized photoreceptor tissue being rejected is limited. This limited vulnerability to transplant rejection in the photoreceptor layer opens up the possibility for the transplantation of tissue that is genetically dissimilar, which would have considerable clinical utility. The animal model used in these experiments is the adult albino rat, blinded by two to four weeks of constant illumination (destroying only photoreceptors and leaving remaining neural retina intact). The intact photoreceptor matirx is removed from the retina of a neonatal or embryonic rat and transplanted to the subretinal space of the host under anesthesia. Following appropriate times for healing and survival, the animal is scarificed and sections are cut and stained. We have found that the photoreceptor matrix remains intact, the cells show continued development and appear healthy, and the host reitna survives insertion of the transplanted photoreceptors. Further experiments are planned to achieve innervation of the outer plexiform layer of the host retina by the photoreceptor matris. Subsequent electrophysiological measures (ERG and visually evoked cortical potentials) are planned to determine the degree of restoration of pholic activation of the blinded retina and visual system.
| Silverman, M S; Hughes, S E (1989) Transplantation of photoreceptors to light-damaged retina. Invest Ophthalmol Vis Sci 30:1684-90 |
