Course of retinal ganglion cell loss and microglial activation in two models of neuronal degeneration

AbstractPurposeOrganotypic retinal cultures (COR) are inherently a model of retinal axotomy and detachment. In vivo, optic nerve axotomy causes degeneration of retinal ganglion cells (RGCs). Our objective is to evaluate and compare the time course of RGC death and the activation of microglial cells (MCs) in vivo and in vitro.MethodsC57/Bl6 mice were used. For the in vitro model, retinas were dissected and cultured in supplemented medium, and axotomy in vivo was done to the left optic nerve. In both models, retinas were analyzed from 24 hours to 9 days. RGCs were immunodetected with Brn3a, MCs with Iba1 and the density in the medial retinal area was quantified for both populations.ResultsThe loss of RGCs was similar in vivo and in vitro during the first days, but from 5 days onwards RGC loss is quicker and more abrupt in vitro than in vivo. MC morphology differs between both models and their density is smaller in vitro than in vivo at all time points.ConclusionsRGCs loss in vitro and in vivo follows the same kinetics at early time points. Morphologically, MCs seem to be differently activated in both models, and because their density is lower in vitro than in vivo, it is possible that in vivo either MCs or circulating macrophages invade the retina to cope with RGC degeneration.