Phenotypic variation of retinal pigment epithelium in age-related macular degeneration.

PURPOSE

To determine whether retinal pigment epithelium (RPE) in eyes with age-related macular degeneration (ARMD) express vimentin and alpha smooth muscle actin (alphaSMA), two cytoskeletal proteins associated with phenotypic variation in culture.

METHODS

Six eyes with late ARMD and three age-matched control eyes were preserved in buffered 4% paraformaldehyde and cryosectioned at 10 microm. Stages of RPE morphology and pigmentation were assessed by the Alabama Age-Related Macular Degeneration Grading System. Vimentin, alphaSMA, and glial fibrillary acidic protein (GFAP) expression was detected by indirect immunofluorescence. These results were compared with regional variations in disease severity.

RESULTS

RPE changes in ARMD included acquired expression of vimentin, but alphaSMA-positive cells were rare. GFAP expression increased in Müller cells in the neural retina in association with RPE changes and photoreceptor degeneration.

CONCLUSIONS

The initial stages of RPE changes in eyes with ARMD mimic those reported for cultured RPE cells. The absence of alphaSMA-positive cells in regions of RPE atrophy suggests that RPE are lost rather than persist in a dedifferentiated state.