Photoreceptor protection by iris pigment epithelial transplantation transduced with AAV-mediated brain-derived neurotrophic factor gene.

PURPOSE To determine whether subretinal transplantation of iris pigment epithelial (IPE) cells transduced with the adeno-associated virus (AAV2)-mediated brain-derived neurotrophic factor (BDNF) gene can protect photoreceptors against phototoxicity. METHODS The BDNF gene was inserted into AAV2 (AAV2-BDNF), and the recombinant AAV2 was transduced into rat IPE (AAV2-BDNF-IPE) cells at various multiplicities of infection (MOI). The concentrations of AAV capsids and BDNF were determined by enzyme-linked immunosorbent assay (ELISA). The AAV2-BDNF-IPE cells were transplanted into the subretinal space of rats, and the rats were placed under constant light on days 1 and 90 after the transplantation. The thickness of the outer nuclear layer was measured in histologic sections and compared to that of control sections. The expression of beta-galactosidase (LacZ) in the subretinal space was confirmed by LacZ staining after AAV2-LacZ-IPE transplantation. BDNF gene expression after transplantation was confirmed by real-time polymerase chain reaction (PCR). RESULTS Transduction efficiency increased with successive days in culture and increased with higher MOI in vitro. The expression of the BDNF gene in the subretinal space was higher in AAV-BDNF-IPE than with AAV2-LacZ-IPE or with IPE-only transplantation. LacZ expression was observed in the subretinal space 7 and 90 days after transplantation. A statistically significant photoreceptor protection was observed on days 1 and 90 in eyes receiving the AAV2-BDNF-IPE transplant, in both the superior transplant site and the inferior hemispheres which did not receive the transplant. CONCLUSIONS Transplantation of AAV2-BDNF-IPE cells may be an alternative method of delivering neurotrophic factors to the lesion.