Changes in membrane conductance play a pathogenic role in osmotic glial cell swelling in detached retinas

Detachment of the neural retina from the pigment epithelium may be associated with tissue edema; however, the mechanisms of fluid accumulation are not understood. Because retinal detachment is usually not accompanied by vascular leakage, we investigated whether the osmotic swelling characteristics of retinal glial (Muller) cells are changed after experimental detachment of the porcine retina. Osmotic stress, induced by application of a hypotonic bath solution to retinal slices, caused swelling of Muller cell bodies in 7-day-detached retinas, but no swelling was inducible in slices of control retinas. Muller cell somata in slices of retinal areas that surround local detachment in situ also showed osmotic swelling, albeit at a smaller amplitude. The amplitude of osmotic Muller cell swelling correlated with the decrease in the K+ conductance, suggesting a causal relationship between both gliotic alterations. Further factors implicated in Muller cell swelling were inflammatory mediators and oxidative stress. We propose that a dysregulation of the ion and water transport through Muller cells may impair the fluid absorption from the retinal tissue, resulting in chronic fluid accumulation after detachment. This knowledge may lead to a better understanding of the mechanisms involved in retinal degeneration after detachment.