Résumé
Induced pluripotent stem cells (iPSC) have revolutionized the study of human diseases. In particular, iPSC-derived retinal pigment epithelium (RPE) is a powerful tool for pathophysiological and therapeutic studies, as it is morphologically and functionally characteristic of the RPE in vivo. iPSC-derived RPE is capable of phagocytosis, fluid transport and polarized growth factor secretion. These functions are regulated by variations in intracellular calcium levels and require the presence of functional ion channels. Here, we demonstrate the polarized expression of L-type calcium channels (CaV1.1 and CaV1.3), T-type calcium channels (CaV3.1 and CaV3.3), potassium channels (MaxiK, Kir 4.1 and Kir7.1) and the chloride channel CLC2 by immunofluorescence studies. We show that the iPSC-RPE is capable of varying intracellular calcium levels by FURA-2 live imaging, and that this is altered following inhibition of specific channels. Furthermore, we demonstrate electrophysiological responses for all three classes of ion channels as recorded by patch-clamp analysis on whole cells. Lastly, we show that inhibition of L-type calcium channels impacts the phagocytosis activity and growth factor secretion of the iPSC-RPE. In conclusion, to our knowledge, we demonstrate for the first time the presence of functional calcium, potassium and chloride channels on iPSC-derived RPE. This further validates this model as a bona fide tissue for physiological and pathophysiological studies. Moreover, these results have important implications in an era where iPSC-derived RPE transplantation is already in the clinic.