Recombinant AAV-transduced iris pigment epithelial cell transplantation may transfer vector to native RPE but suppress systemic dissemination.

PURPOSE: To determine whether adenoassociated virus (AAV) vectors transduced into iris pigment epithelial (IPE) cells and transplanted into the subretinal space of rats will transfer the AAV genome to the host cells and whether the vectors are disseminated systemically. METHODS: Recombinant (r)AAV was transduced into rat IPE cells and transplanted into the subretinal space of rats. For the control, rAAVs alone were injected subretinally. The transplanted IPE cells were detected by LacZ staining. Immunohistochemistry, electron microscopy, electroretinography, and fluorescein-dextran angiography were performed. DNA was extracted from various organs and blood and examined for the AAV genome by polymerase chain reaction. RESULTS: No toxicity from rAAV transduction was observed in vitro. LacZ was expressed in the transplanted cells 1 and 2 weeks after transplantation. At 4 and 12 weeks, fewer transplanted cells were detected than at 1 week, and LacZ expression was occasionally detected at the level of host retinal pigment epithelial (RPE) cells. Expression was also detected in ciliary body epithelial cells. The electroretinograms and fluorescein-dextran angiography were only mildly altered. Significantly lower levels of AAV genome were detected in the organs and blood of rats receiving rAAV-IPE cell transplants than with direct intravenous injection of AAV vectors. CONCLUSIONS: AAV-mediated LacZ was expressed in the transplanted cells after subretinal transplantation, and the transplanted IPE cells may transfer the rAAV to host tissues, such as RPE cells, long after the transplantation. This method of gene delivery did not lead to systemic dissemination of the vectors.

Protection of photoreceptor cells from phototoxicity by transplanted retinal pigment epithelial cells expressing different neurotrophic factors.

Transplantation of cells or tissues and the intravitreal injection of neurotrophic factors are two methods that have been used to treat retinal diseases. The purpose of this study was to examine the effects of combining both methods: the transplantation of retinal pigment epithelial (RPE) cells expressing different neurotrophic factors. The neutrophic factors were Axokine, brain derived-neurotrophic factor (BDNF), and basic fibroblast growth factor (bFGF). The enhanced green fluorescence protein (eGFP) gene was used as a reporter gene. These genes were transduced into RPE cells by lipofection, selected by antibiotics, and transplanted into the subretinal space of 108 rats. The rats were examined at 1 week and 3 months after the transplantation to determine whether the transduced cells were present, were expressing the protein, and were able to protect photoreceptors against phototoxicity. The survival of the transplanted cells was monitored by the presence of eGFP. The degree of protection was determined by the thickness of the outer nuclear layer. Our results showed that the degree of photoreceptor protection was different for the different types of neurotrophic factors at 1 week. After 3 months, the number of surviving transplanted cell was markedly reduced, and protection was observed only with the BDNF-transduced RPE cells. A significant degree of rescue was also observed by BDNF-transduced RPE cells in the nontransplanted area of the retina at both the early and late times. Lymphocytic infiltration was not detected in the vitreous, retina, and choroid at any time. We conclude that the transplantation of BDNF-transduced RPE cells can reduce the photoreceptor damage induced by phototoxicity in the transplanted area and weakly in the nontransplanted area.