Retinal Pigment Epithelium Phagocytosis and Retinal Degenerative Diseases

In the mammalian retina, photoreceptors rely on the continuous renewal of their outer segments to preserve their function as light-sensing cells, thereby ensuring lifelong vision. This process entails the routine phagocytosis of shed photoreceptor outer segments (POS) by the retinal pigment epithelium (RPE). Phagocytosis of POS by RPE is a highly circadian-regulated process that is dependent on intricate and tightly controlled cellular signaling pathways. This article provides a systematic review of the research on the regulation and functional implications of the RPE phagocytic signaling system. Therefore, a deeper understanding of the role of retinal pigment epithelial phagocytosis in the pathogenesis of retinal degeneration can inform the development of potential therapeutic targets to prevent the irreversible loss of retinal pigment epithelium and photoreceptor cells, thereby preventing retinal degenerative diseases. This article summarizes the soluble and membrane-bound molecules produced by the RPE that are associated with phagocytosis and discusses their specific roles in POS phagocytosis and retinal degenerative disorders, potentially aiding in the prevention or treatment of retinal degenerative diseases.