Prominin-1-immunoreactive cells in light-induced retinal degeneration.

AM SUBURO, M CASTAÑEDA, V TORBIDONI, M IRIBARNE.

Florida, United States.

Congreso; Association for Research in Vision and Ophthalmology, Annual meeting, 2007; 2007

Association for Research in Vision and Ophthalmology,

Purpose:Prominin-1 (PROM1) is a membrane glycoprotein expressed in a large population of somatic stem and progenitor cells including neuroepithelial cells and endothelial and hematopoietic progenitors. In the retina, PROM1 is found in photoreceptor outer segments and we have recently described it in a subpopulation of glial cells. Since gliosis is an important component of retinal diseases, we have evaluated changes in PROM1 immunoreactivity associated to light-induced retinal degeneration. Methods:Male BALB/c mice were bred under a light/darkness cycle of 12 hours each with maximum illumination levels of 60 lux. Experimental animals were submitted to 1,500 lux during 4 days. Mice were perfused with paraformaldehyde and cryosections were immunostained with antibodies against PROM1 and glial fibrillary acidic protein (GFAP). Antibody binding was detected with immunoenzymatic or immunofluorescent procedures. Results:In control BALB-c mice, PROM1 was associated to photoreceptors, RPE microvilli, and glial processes. PROM1 appeared in outer and inner segments of rods and cones, being most strongly expressed at the boundary between outer and inner segments. Double immunofluorescence demonstrated that PROM1 was present in retinal and optic nerve astrocytes. In light-injured retinas, PROM1 immunostaining of photoreceptors was decreased, but strong staining was still found in the region of the connecting cilium. PROM1 positive astrocytes increased in number and complexity of their processes. Remarkably, PROM1 immunoreactivity appeared in vascular endothelia of the retina, particularly in the capillary loops of the outer retinal plexus Conclusions:Reduction of photoreceptor associated PROM1 is consistent with light-induced deterioration of the outer segments. By contrast, increase of astrocyte-associated PROM1 reflects the gliosis accompanying retinal degeneration. Since PROM1 prefers membrane curvatures and is selectively associated with plasma membrane protrusions, the increase of this marker during gliosis probably reflects the dynamic behaviour of astrocytic processes. In addition, astrocyte-associated PROM1 could also be related to their presumptive role as neurogenic precursors. The presence of PROM1 in adult endothelia is usually considered a sign of vasculogenesis, since it would reflect the engraftment of circulating endothelial cell progenitors. Thus, PROM1 labeling of endothelia in light-injured retina probably reflects some degree of endothelial dysfunction, perhaps including an augmented turnover of endothelial cell progenitors.