Growth factor staining patterns in the pig retina following retinal laser photocoagulation

Aim-To identify changes in growth factor expression in miniature pig retinas following retinal laser photocoagulation. Methods-Pigs were sacrificed at different times (15 minutes to 42 days) post-laser and the retinas were immunolabelled for basic fibroblast growth factor, insulin-like growth factor I, transforming growth factor beta, epidermal growth factor, transforming growth factor alpha, platelet derived growth factor, vascular endothelial growth factor, and epidermal growth factor receptor. Total mRNA levels were also determined. Results-With the exception of vascular endothelial growth factor, immunoreactivity for all other growth factors studied and epidermal growth factor receptor was observed throughout normal non-lasered control retina, generally being high in the retinal pigment epithelium and low in the neural retina. Changes in growth factor expression following laser photocoagulation were observed only in burn areas and changes were mainly confined to the retinal pigment epithelium and outer nuclear layer. The immunoreactivity within retinal pigment epithelial cells in burn areas was either absent or decreased following laser treatment but returned to normal by 21 days. The immunoreactivity was increased within the outer nuclear layer of burn areas during the healing process but returned to normal by 42 days. Vascular endothelial growth factor immunoreactivity was weak/absent in the normal retina and remained unchanged following laser photocoagulation. Change of total mRNA levels in burn areas during time post-laser was confined to retinal pigment epithelial cells, being low immediately following photocoagulation and returning to normal by 42 days. Conclusions-These results demonstrate a temporal alteration in growth factor expression and transcriptional activity in the retina following laser photocoagulation.