Glial cell-mediated spread of retinal degeneration during detachment: A hypothesis based upon studies in rabbits

in human subjects with peripheral retinal detachments, visual deficits are not restricted to the detached retina but are also present in the non-detached tissue. Based upon studies on a rabbit model of rhegmatogenous retinal detachment, we propose a glial cell-mediated mechanism of spread of retinal degeneration into non-detached retinal areas which may also have importance for the understanding of alterations in the human retina. Both detached and attached portions of the rabbit retina display photoreceptor cell degeneration and cystic degeneration of the innermost layers. An inverse mode of photoreceptor cell degeneration in the attached tissue suggests a disturbed support of the photoreceptor cells by Muller cells which show various indications of gliosis (increased expression of intermediate filaments, cell hypertrophy, decreased plasma membrane K+ conductance, increased Ca2+ responsiveness to purinergic stimulation) in both detached and attached tissues. We propose that gliotic alterations of Muller cells contribute to the degeneration of the attached retina, via disturbance of glial homeostasis mechanisms. A down-regulation of the K+ conductance of Muller cells may prevent effective retinal K+ and water clearance, and may favor photoreceptor cell degeneration and edema development. (c) 2005 Elsevier Ltd. All rights reserved.