Visualizing cell-specific metabolite localization in fresh retinal tissue explants
Retinitis pigmentosa (RP) refers to a group of neurodegenerative eye diseases which are characterized by the sequential death of rod and cone photoreceptors, the cells responsible for night and daylight vision, respectively. In RP, mutations are rod-specific, however, cones are also affected. Recent studies have implicated glucose deprivation in degenerating cones, regardless of the type of rod mutation. The retinal pigment epithelium (RPE) transports glucose from the blood to photoreceptors and, in turn, removes lactate, which it can use as its own fuel source. It has been hypothesized that, following the death of rods, lactate levels are diminished causing the RPE to withhold glucose and resulting in nutrient deprivation in cones. However, direct measurement of the relative concentration and localization of lactate and glucose in retinal cell types has not been carried out. We have developed fluorescent lifetime imaging microscopy (FLIM)-based metabolite sensors that can be delivered into the mouse eye and expressed using cell type specific promoters. Using this technology, we can detect lactate and glucose at single cell resolution within fresh RPE explants, enabling investigation into the metabolic dysregulation associated with RP.