Ameliorative effect of PN-277 on laser-induced retinal damage.

Background: The retinal damage induced by laser photocoagulation increases considerably by the secondary degeneration process whereby tissues adjacent to the primary lesion are destroyed. As the neuroprotective effect of immunization by PN-277 was previously demonstrated in models of retina, optic nerve, brain, and spinal cord lesions, it may be used also for reducing retinal damage induced by laser. The aim of this study was to evaluate the neuroprotective effect of immunization with PN-277 in reducing the spread of laser-induced retinal damage.

Methods: Standard argon laser lesions were created in 36 DA pigmented rats. Seven days before exposure to laser, the rats were divided into a test group (n = 18) that was pre-immunized with intraperitoneal injection of PN-277 and control group (n = 18) treated with saline. Histological and morphometrical evaluations of the retinal lesions were preformed 3, 20, and 60 days after the injury.

Results: Significant ameliorative effect was demonstrated in the retinas of the pre-immunized animals 60 days after exposure to laser. The diameter of the lesion was 356 microm as compared with 406 microm (P < 0.01), the cell density of the photoreceptor cell bodies measured in the whole lesion was 72.4% of normal as compared with 64.5% (P = 0.01), and at the center of the lesion it was 57.3% of normal as compared with 38.2% (P < 0.01) (treated and control groups, respectively).

Conclusions: Immunization with PN-277 has an ameliorative effect in neural tissue such as the retina. This type of immunization may be of clinical significance in reducing laser-induced retinal injuries in humans.