LONG-TERM PHOTORECEPTOR TRANSPLANTS IN DYSTROPHIC AND NORMAL MOUSE RETINA

Purpose. To determine the long-term status of transgenic photoreceptor s transplanted to the subretinal space of both rd mutant (receptorless ) and normal mouse retina. Methods. Microaggregates of neural retina f rom transgenic mice containing lacZ-labeled photoreceptors were transp lanted to the subretinal space of adult rd mutant and normal mice. The transplant site was examined by light and electron microscopy at mont hly intervals up to 9 months after transplantation surgery.Results. Ph otoreceptors develop and survive well if transplanted with the proper orientation to the retinal pigment epithelium (RPE). The status of the photoreceptors, including outer segments and synaptic terminals, appe ar normal for at least 9 months after transplantation; they continue t o express the lacZ reporter gene. Cones survive as well as rods. Trans plants to the normal mouse develop normally, whereas the host photorec eptors displaced from the RPE degenerate. A barrier, formed by Muller cell processes, develops after photoreceptor degeneration in both norm al and rd mouse retina and demarcates host from transplant tissue. Are as can be found in which neural processes have penetrated this barrier . There is no evidence of host-graft rejection. Conclusion. Transplant ed progenitor photoreceptors develop and survive well for long periods of time in either the rd mutant or normal retina if they are properly positioned. In the former, they reconstitute a photoreceptor layer; i n the latter, they replace the host photoreceptor layer, which degener ates after being displaced from the RPE. Areas of potential contact be tween donor and host neurons exist in these transplants.