Topical doxycycline can induce expression of BDNF in transduced retinal pigment epithelial cells transplanted into the subretinal space

PURPOSE. To determine whether topical doxycycline (DOX) induces the expression of brain-derived neurotrophic factor (BDNF) by BDNF-transduced retinal pigment epithelial (RPE) cells transplanted into the subretinal space of rats. METHODS. A rat RPE cell line that can express BDNF by exposure to DOX was created (Tet-BDNF-RPE). The expression of BDNF was examined by ELISA, Western blot analysis, and real-time PCR. The expression of BDNF was controlled by exposure to DOX in vitro. Tet-BDNF-RPE cells were transplanted into the subretinal space of rats, and the rats were exposed to constant light 1 day or 1 month after the transplantation. The rats were followed with or without topical DOX and examined electrophysiologically and histologically. RESULTS. The expression of BDNF was upregulated by exposure of Tet-BDNF-RPE cells to DOX in vitro. The optimal concentration for inducing BDNF expression was 0.5 to 1.0 mu g/mL DOX. BDNF expression was also increased in vivo by topical DOX after subretinal transplantation of Tet-BDNF-RPE cells. Statistically significant protection of the electroretinogram amplitudes were found 3 days or 1 month after transplantation, and the outer nuclear layer was better preserved 7 days or 1 month after transplantation in the rats treated by 5 or 10 mg/mL/d topical DOX than rats treated by other conditions or shamoperation rats. CONCLUSIONS. The expression of BDNF can be significantly increased by topical DOX after Tet-BDNF-RPE subretinal transplantation. Better photoreceptor protection against phototoxicity was achieved by DOX eye drops after the cell transplantation.