Microglial and macroglial dynamics in a model of retinitis pigmentosa.

In retinal degenerative diseases, such as retinitis pigmentosa (RP), the characteristic photoreceptor cell death is associated with changes of microglia and macroglia cells. Gene therapy, a promising treatment option for RP, is based on the premise that glial cell remodeling does not impact vision rescue. However, the dynamics of glial cells after treatment at late disease stages are not well understood. Here, we tested the reversibility of specific RP glia phenotypes in a Pde6b-deficient RP gene therapy mouse model. We demonstrated an increased number of activated microglia, retraction of microglial processes, reactive gliosis of Müller cells, astrocyte remodelling and an upregulation of glial fibrillary acidic protein (GFAP) in response to photoreceptor degeneration. Importantly, these changes returned to normal following rod rescue at late disease stages. These results suggest that therapeutic approaches restore the homeostasis between photoreceptors and glial cells.