Robust Differentiation of mRNA-Reprogrammed Human Induced Pluripotent Stem Cells Toward a Retinal Lineage

The derivation of human induced pluripotent stem cells (hiPSCs) from patient‐specific sources has allowed for the development of novel approaches to studies of human development and disease. However, traditional methods of generating hiPSCs involve the risks of genomic integration and potential constitutive expression of pluripotency factors and often exhibit low reprogramming efficiencies. The recent description of cellular reprogramming using synthetic mRNA molecules might eliminate these shortcomings; however, the ability of mRNA‐reprogrammed hiPSCs to effectively give rise to retinal cell lineages has yet to be demonstrated. Thus, efforts were undertaken to test the ability and efficiency of mRNA‐reprogrammed hiPSCs to yield retinal cell types in a directed, stepwise manner. hiPSCs were generated from human fibroblasts via mRNA reprogramming, with parallel cultures of isogenic human fibroblasts reprogrammed via retroviral delivery of reprogramming factors. New lines of mRNA‐reprogrammed hiPSCs were established and were subsequently differentiated into a retinal fate using established protocols in a directed, stepwise fashion. The efficiency of retinal differentiation from these lines was compared with retroviral‐derived cell lines at various stages of development. On differentiation, mRNA‐reprogrammed hiPSCs were capable of robust differentiation to a retinal fate, including the derivation of photoreceptors and retinal ganglion cells, at efficiencies often equal to or greater than their retroviral‐derived hiPSC counterparts. Thus, given that hiPSCs derived through mRNA‐based reprogramming strategies offer numerous advantages owing to the lack of genomic integration or constitutive expression of pluripotency genes, such methods likely represent a promising new approach for retinal stem cell research, in particular, those for translational applications.