Time-Series Single Cell RNA Sequencing of Inner Ear Organoid Development

We report the application of single cell RNA sequencing for determining cell type and quantity in developing inner ear organoids derived from human pluripotent stem cells. By obtaining samples from multiple time points throughout differentiation, we developed a roadmap at single cell resolution of the multiple cell lineages which give rise to in vitro inner ear tissue as well as 'off-target' tissue types. We find that the cells in the day 0 sample contained primarily a homogenous population of pluripotent stem cells. On day 3, after treatment with BMP4, we find that the cells have differentiated into a split between surface ectoderm, the progenitor of the inner ear tissue, and neuroectoderm. On day 6 and 8, we observed the emergence of cranial placode tissue, both anterior and posterior. Then, after treatment starting on day 8 with a WNT agonist, CHIR, we observed the maturation of inner ear tissue into hair cells and neurons, starting on day 18 and increasing through the last time point collected, day 36. This study provides an atlas of inner ear organoid differentiation from human pluripotent stem cells. We examined 10 time points during the differentiation of inner ear organoids by single cell RNA-sequencing. We also collected samples for comparison at days 10 and 13 which did not receive CHIR treatment.