EFFECTS OF RETINAL LASER PHOTOCOAGULATION ON PHOTORECEPTOR BASIC FIBROBLAST GROWTH-FACTOR AND SURVIVAL

Purpose. In an unpublished study, the authors found that immunoreactiv ity for basic fibroblast growth factor (bFGF) is increased in rod phot oreceptors adjacent to long-standing laser burns in human diabetic ret inas. The goal of this study was to determine whether laser photocoagu lation produces a similar increase in photoreceptor bFGF and promotes survival of these cells in dystrophic rodent retinas. Methods. Thresho ld (whitening) and subthreshold (nonwhitening) laser burns were made i n retinas of normal and Royal College of Surgeons (RCS) mts and normal and rds mice, The retinas were processed for immunocytochemical and m orphometric analyses. Results. In nonlasered normal rat and mouse reti nas, bFGF immunoreactivity was prominent in the nuclei of Muller cells and astrocytes. Photoreceptors were bFGF negative except for a zone o f bFGF-ummunoreactive rods near the era serrata. Some photoreceptors i n nonlasered retinas of RCS rats and rds mice became bFGF immunoreacti ve. After laser treatment, bFGF immunoreactivity was markedly increase d in all photoreceptors flanking the threshold burns and within the su bthreshold burns in normal and mutant rats and mice. In RCS mt retinas , photoreceptor bFGF immunoreactivity remained elevated within subthre shold burns and flanking the threshold burns, and photoreceptor surviv al was prolonged, In rds mouse retinas, increased bFGF immunoreactivit y in photoreceptors was not sustained and their degeneration was not r etarded. Conclusions. Laser treatment of RCS rat retinas produced a su stained increase in bFGF immunoreactivity in photoreceptors and prolon ged their survival, but laser treatment of rds mouse retinas did not h ave a long-term effect on photoreceptor bFGF immunoreactivity or survi val. Although species differences in laser effects on photoreceptor bF GF and survival are apparent, the finding that rods flanking laser bur ns in human retinas have sustained increases in bFGF immunoreactivity suggests that laser treatment may be useful for prolonging survival of mutant photoreceptors in retinas of patients with retinitis pigmentos a.