RPE Synthesis

In aged eyes, RPE undergoes several pronounced morphological changes, including accumulation of lipofuscin, loss of melanin granules, and decrease in cell density. Despite the morphological changes are profound, aged healthy RPE monolayer remains intact and functional. However, in age-related macular degeneration (AMD), loss or degeneration of RPE cells on the macular region can lead to degeneration of photoreceptor and lose of the central vision. Numerous factors have been proposed as potential AMD pathogens including accumulation of drusen, genetic mutation in complement factors, inflammatory response, photooxidative stress, accumulation of N-retinylidene-N-retinylethanol-amine (A2E), and ischemia. Despite none of these pathogens has been recognized as the direct cause of AMD, prolong exposure to a combination of these factors can lead to RPE degeneration or death. Based on the formation of neovascular tissues, AMD has two forms: wet AMD (with neovascularization) and dry AMD (without neovascularization). 85% of the AMD cases is the dry from, yet wet AMD accounts for 90% of the total …show more content…
Dry AMD progress relatively slower, it usually takes years to develop into a more advanced form called geographic atrophy (GA). GA is characterized by one or multiple RPE atrophy areas emerge and develop on and near the macular. This death of RPE will lead to degeneration of photoreceptor and loss of the central vision. Different from the wet AMD, RPE-to-mesenchymal transition and formation of fibrotic scars were not observed in GA. Conversely, recent histological and transcriptomic studies indicate that progression of GA is likely due to apoptosis of RPE around the lesions without evidence of an effective wound healing response. Currently, there is no approved treatment for GA. However, transplanation of stem cell-derived RPE to compensate the loss of the host RPE cells is a promising