Towards maturation of human otic hair cell–like cells in pluripotent stem cell–derived organoid transplants

Human otic organoids generated from pluripotent stem cells (PSCs) provide a promising platform for modeling, drug testing, and cell-based therapies of inner ear diseases. However, providing the appropriate niche that resembles inner ear development and its vasculature to generate otic organoids is less conspicuous. Here, we devised a strategy to enhance maturation of otic progenitor cells toward human hair cell–like cells (HCLCs) by assembling three-dimensional (3D) otic organoids that contain human PSC-derived otic cells, endothelial cells, and mesenchymal stem cells (MSCs). Heterotopic implantation of otic organoids, designated as grafted otic organoids (GOs), in ex ovo chick embryo chorioallantoic membrane (CAM) stimulated maturation of the HCLCs. Functional analysis revealed the presence of voltage-gated potassium currents without detectable sodium currents in these cells in the GOs. Our results demonstrated that implantation of 3D heterotypic cell mixtures of otic organoids improved maturation of human HCLCs. This GO-derived HCLCs could be an attractive source for drug discovery and other biomedical applications.