Newborn rat retinal cells transplanted into a retinal lesion site in adult host eyes

We report the successful grafting of embryonic (newborn) rat retina into a lesion site (die-back zone) of an adult retina with a corresponding 90-100% survival rate. A penetrating lesion was made through the sclera, choroid and retina on the superior surface of the host eye and closed with microsutures. The lesion site was either allowed to stabilize for 5 weeks or immediately received a retinal graft. Retinas were removed from 1-day-old neonate donors, drawn through a small gauge needle and injected into the fresh or stabilized lesion site. Host animals were sacrificed and the eyes processed for light, scanning- and transmission-electron microscopic analysis at 1, 2, and 4 weeks after grafting. Analysis of sections through grafted tissue within the lesion site revealed that the neonatal cells not only survived at all times examined but also continued their development reminiscent of normal littermate controls. Examination of 4-week grafts revealed a laminar pattern similar to adult ganglion cell, inner plexiform, inner nuclear, and outer plexiform layers as well as developing photoreceptor neurons. The grafted tissue could easily be delivered into the retinal lesion site where it established a pattern of retinal layers within the die-back zone. In addition, the plexiform areas of the graft appeared to integrate with those of the host. The age of the adult retina lesion transplantation site had little effect on the graft/host integrative phenomenon. These studies show for the first time a method utilizing immature retinal grafts to fill and/or bridge the wound area of the lesioned adult mammalian retina. These observations also demonstrate the utility of using this model for the study of numerous retinal developmental phenomena.