Abstract
Abstract: :
Purpose: To compare the extent and timing of microglial and macrophage responsiveness to RD in the retina of different species. Methods: Experimental RDs were created in the eyes of cats, rabbits, and ground squirrels and the retinas harvested at 1, 3, 7 or 28 days later. Human tissue was obtained as retinectomy specimens taken as part of reattachment surgery. Microglia and macrophages were labeled with biotinylated Griffonia simplicifolia isolectin B4 (cat, rabbit, squirrel) or biotinylated Ricinus communis agglutinin I (human) overnight at 4oC. Streptavidin, conjugated to Cy2, was subsequently added overnight. The sections were viewed using a BioRad 1024 confocal microscope. Results: Labeled macrophages and microglia were distinguished based on their morphology and/or location. In control retina, lightly labeled microglia were observed in the inner and/or outer plexiform layers in all species. In the cat and rabbit (rod–dominated species), a progressive increase in the number of labeled cells, particularly in the outer retina, occurred beginning at 1 day of RD. The labeling pattern in long term human RDs was similar to that observed in the longer duration cat RDs, that is many labeled cells were present distributed throughout the inner and outer retina. Activated cells could be found in the ground squirrel retina but the overall response was dramatically less. In cat retinas reattached for 28 days after 3 days of RD, labeled cells were dispersed in all retinal layers, but were predominantly associated with patches of poor outer segment morphology. Conclusions: Microglial and macrophage activation appear to be a general and long–lasting response to detachment, although not all species are equally reactive. In the cat and rabbit retina, the response begins quickly, within a day. This apparently represents a long–term response since labeled cells were still observed among photoreceptors in cat retinas reattached for a month and in long–term human RDs. In contrast, the cone dominated ground squirrel retina, which shows a rapid and profound photoreceptor degeneration after detachment, had a greatly attenuated response. Modulating the microglial response following experimental RD may help determine how the activation of these cells influence the cellular responses of the retina to injury caused by RD.
Keywords: retinal detachment • microglia • retinal degenerations: cell biology