In vivo protection of photoreceptors from light damage by pigment epithelium-derived factor

PURPOSE. To determine whether pigment epithelium-derived factor (PEDF) exhi bits neurotrophic and neuroprotective activities in vivo for photoreceptor cells. METHODS. Sprague-Dawley albino rats were injected intravitreally with 2 mug PEDF or a mixture of 1 mug basic fibroblast growth factor (bFGF)/1 mug PED F in a volume of 1 mul phosphate-buffered saline (PBS). Animals were expose d to constant lilt for different periods at an illuminance level of 1200 to 1500 lux. The electroretinogram (ERG) waveforms of both eyes in the same a nimal were simultaneously recorded to evaluate functional protection. The m orphologic protection was evaluated by quantitative histology. RESULTS. Intravitreal injection of PEDF before exposure to constant light r esulted in significant morphologic and functional protection of photorecept or cells in the retina of light-damaged rats. This protection depended on t he duration and severity of light damage. The protection was eliminated by extending the light exposure to 10 days. Injection of PEDF at 0, 1, and 2 d ays after constant light exposure did not provide significant protection ab ove that seen in PBS-injected eyes. Combination of PEDF with bFGF improved functional protection of photoreceptor cells. CONCLUSIONS. The data demonstrate that PEDF protected photoreceptor cells a gainst light damage. This is significant, because it may open new avenues f or the study of molecular mechanisms underlying degenerative processes. Thi s, in turn, may lead to the development of therapeutic strategies for the p revention and treatment of degenerative diseases of the retina.