Partial and full-thickness neuroretinal transplants

Adult and embryonic rabbit retinal sheets were transplanted into the subret inal space of adult rabbits. The transplants were either full-thickness wit h intact layering, or gelatin embedded and vibratome sectioned with the inn er retina removed, The full-thickness grafts were positioned subretinally b y means of a glass capillary in which they were partially folded. The vibra tome sectioned ones were placed using a plastic injector in which the gelat in embedded graft was flat. The embryonic full-thickness grafts were follow ed clinically up to 3 months, and the other 3 transplant types up to 1 mont h postoperatively, after which the retina was sectioned and stained for lig ht microscopy. Surgical complications were more common in eyes receiving vibratome section ed grafts with 10 out of 34 eyes displaying blood in the vitreous. Four of these eyes also developed total retinal detachment. Out of 17 eyes receivin g full-thickness grafts, only one displayed these complications. Histologic ally, 11 out of 13 embryonic full-thickness transplants revealed straight, laminated transplants with correct polarity, and with all normal retinal la yers present. In these transplants, fusion with the host increased in time, Of the adult full-thickness transplants, only 1 out of 4 survived, and thi s graft showed signs of degeneration. The vibratome sectioned adult transpl ants in a few cases survived the first two postoperative weeks. In these gr afts, both inner and outer retina were present, indicating an incomplete vi bratome sectioning. With longer postoperative times, the number of survivin g transplants in this group diminished considerably. All vibratome sectione d embryonic transplants developed into rosettes and sometimes also into lam inated sections with reversed polarity. It can be concluded that in rabbits, the surgical technique used for vibrat ome sectioned transplants requires a larger sclerotomy and retinotomy, sinc e they have to be kept flat in the transplanting instrument due to the surr ounding gelatin. This technique is associated with a higher frequency of co mplications than the one used for full-thickness grafts which are more flex ible and can be transplanted with a smaller instrument. Vibratome sectionin g of embryonic grafts results in abnormal morphology and their adult counte rparts only survive if the sectioning is incomplete. Adult full-thickness g rafts show poor survival. Embryonic full-thickness transplants in the major ity of cases develop into laminated retinas with layers parallel to the hos t retinal pigment epithelium. They also survive and integrate well with the host retina. (C) 1999 Academic Press.