A GRADIENT OF BASIC FIBROBLAST GROWTH-FACTOR IN ROD PHOTORECEPTORS INTHE NORMAL HUMAN RETINA

Retinitis pigmentosa (RP) is an inherited disease that causes primary degeneration of rod photoreceptors in the retina. Although the causal gene (e.g. rhodopsin) is thought to be expressed in all rods across th e retina, the degeneration is typically nonuniform, with rods in the f ar periphery surviving significantly longer than those in the midperip hery and macula. Basic fibroblast growth factor (bFGF) is a putative s urvival factor for photoreceptors, and the characteristic regional pat tern of rod cell survival in RP suggested that bFGF might be distribut ed nonuniformly in the human retina. We performed double-label immunoc ytochemistry on 15 normal human retinas, using anti-bFGF and other ant ibody markers for retinal neurons and glia. Immunoreactivity for bFGF was consistently absent from cones but was present in rods, population s of cone bipolar and amacrine cells, Muller glial cells, and astrocyt es. In the macula, the percentage of bFGF-reactive rods was very low ( similar to 0.5%) but it increased in a central to peripheral gradient, accounting for up to similar to 88% of the rods in the far periphery. These findings suggest that a central to peripheral gradient of rod b FGF is present in normal human retina and may influence the pattern of photoreceptor degeneration in RP. The absence of bFGF in cones and th e low number of bFGF-positive rods in the macula may correlate with th e vulnerability of these cells in RP, age-related macular degeneration , and other retinal diseases.