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The original article [1] contains an error in the legend of Fig 5 whereby the descriptions for panels 5d and 5e are incorrect; as such, the corrected legend can be viewed below with its respective figure images.

The original article [1] contains an error in the legend of Fig 5 whereby the descriptions for panels 5d and 5e are incorrect; as such, the corrected legend can be viewed below with its respective figure images.

BackgroundDysfunction of the retinal pigment epithelium (RPE) is implicated in numerous forms of retinal degeneration. The readily accessible environment of the eye makes it particularly suitable for the transplantation of RPE cells, which can now be derived from autologous induced pluripotent stem cells (iPSCs), to treat retinal degeneration. For RPE transplantation to become feasible in the clinic, patient-specific somatic cells should be reprogrammed to iPSCs without the introduction of reprogramming genes into the genome of the host cell, and then subsequently differentiated into RPE cells that are well characterized for safety and functionality prior to transplantation.MethodsWe have reprogrammed human dermal fibroblasts to iPSCs using nonintegrating RNA, and differentiated the iPSCs toward an RPE fate (iPSC-RPE), under Good Manufacturing Practice (GMP)-compatible conditions.ResultsUsing highly sensitive assays for cell polarity, structure, organelle trafficking, and function, we found that iPSC-RPE cells in culture exhibited key characteristics of native RPE. Importantly, we demonstrate for the first time with any stem cell-derived RPE cell that live cells are able to support dynamic organelle transport. This highly sensitive test is critical for RPE cells intended for transplantation, since defects in intracellular motility have been shown to promote RPE pathogenesis akin to that found in macular degeneration. To test their capabilities for in-vivo transplantation, we injected the iPSC-RPE cells into the subretinal space of a mouse model of retinal degeneration, and demonstrated that the transplanted cells are capable of rescuing lost RPE function.ConclusionsThis report documents the successful generation, under GMP-compatible conditions, of human iPSC-RPE cells that possess specific characteristics of healthy RPE. The report adds to a growing literature on the utility of human iPSC-RPE cells for cell culture investigations on pathogenicity and for therapeutic transplantation, by corroborating findings of others, and providing important new information on essential RPE cell biological properties.

BackgroundDysfunction of the retinal pigment epithelium (RPE) is implicated in numerous forms of retinal degeneration. The readily accessible environment of the eye makes it particularly suitable for the transplantation of RPE cells, which can now be derived from autologous induced pluripotent stem cells (iPSCs), to treat retinal degeneration. For RPE transplantation to become feasible in the clinic, patient-specific somatic cells should be reprogrammed to iPSCs without the introduction of reprogramming genes into the genome of the host cell, and then subsequently differentiated into RPE cells that are well characterized for safety and functionality prior to transplantation.MethodsWe have reprogrammed human dermal fibroblasts to iPSCs using nonintegrating RNA, and differentiated the iPSCs toward an RPE fate (iPSC-RPE), under Good Manufacturing Practice (GMP)-compatible conditions.ResultsUsing highly sensitive assays for cell polarity, structure, organelle trafficking, and function, we found that iPSC-RPE cells in culture exhibited key characteristics of native RPE. Importantly, we demonstrate for the first time with any stem cell-derived RPE cell that live cells are able to support dynamic organelle transport. This highly sensitive test is critical for RPE cells intended for transplantation, since defects in intracellular motility have been shown to promote RPE pathogenesis akin to that found in macular degeneration. To test their capabilities for in-vivo transplantation, we injected the iPSC-RPE cells into the subretinal space of a mouse model of retinal degeneration, and demonstrated that the transplanted cells are capable of rescuing lost RPE function.ConclusionsThis report documents the successful generation, under GMP-compatible conditions, of human iPSC-RPE cells that possess specific characteristics of healthy RPE. The report adds to a growing literature on the utility of human iPSC-RPE cells for cell culture investigations on pathogenicity and for therapeutic transplantation, by corroborating findings of others, and providing important new information on essential RPE cell biological properties.

Airways are exposed to myriad environmental and damaging agents such as reactive oxygen species (ROS), which also have physiological roles as signaling molecules that regulate stem cell function. However, the functional significance of both steady and dynamically changing ROS levels in different stem cell populations, as well as downstream mechanisms that integrate ROS sensing into decisions regarding stem cell homeostasis, are unclear. Here, we show in mouse and human airway basal stem cells (ABSCs) that intracellular flux from low to moderate ROS levels is required for stem cell self-renewal and proliferation. Changing ROS levels activate Nrf2, which activates the Notch pathway to stimulate ABSC self-renewal and an antioxidant program that scavenges intracellular ROS, returning overall ROS levels to a low state to maintain homeostatic balance. This redox-mediated regulation of lung stem cell function has significant implications for stem cell biology, repair of lung injuries, and diseases such as cancer.

Both basal and submucosal gland (SMG) duct stem cells of the airway epithelium are capable of sphere formation in the in vitro sphere assay, although the efficiency at which this occurs is very low. We sought to improve this efficiency of sphere formation by identifying subpopulations of airway basal stem cells (ABSC) and SMG duct cells based on their aldehyde dehydrogenase (ALDH) activity. ALDH(hi) ABSCs and SMG duct cells were highly enriched for the population of cells that could make spheres, while the co-culture of ALDH(hi) differentiated cells with the ALDH(hi) ABSCs increased their sphere-forming efficiency. Specific ALDH agonists and antagonists were used to show that airway specific ALDH isozymes are important for ABSC proliferation. Pathway analysis of gene expression profiling of ALDH(hi) and ALDH(lo) ABSCs revealed a significant upregulation of the arachidonic acid (AA) metabolism pathway in ALDH(hi) ABSCs. We confirmed the importance of this pathway in the metabolism of proliferating ALDH(hi) ABSCs using bioenergetics studies as well as agonists and antagonists of the AA pathway. These studies could lead to the development of novel strategies for altering ABSC proliferation in the airway epithelium.