Multiple cell types make up the human upper airway epithelium, a tissue that both turns over in homeostasis and can regenerate following injury in a manner dependent on resident stem cells. Mouse models have illuminated many of the cell state changes and molecular regulators of airway homeostasis and regeneration, and new technologies are allowing researchers to ask whether the same processes apply in humans. In their Techniques and Resources article, Pascal Barbry, Laure-Emmanuelle Zaragosi and colleagues utilise the power of single-cell sequencing technology to investigate human airway lineage trajectories, targeting a 3D in vitro model of airway regeneration as well as fresh airway tissue. The inferred lineage trajectories derived from single-cell sequencing demonstrate that club cells are precursors of multiciliated cells (MCCs) and goblet cells (GCs), and GCs can be precursors of MCCs. Refined clustering reveals additional populations of cells, including a novel pre-MCC cell type designated ‘deuterosomal’ (as they express many genes involved in multiciliogenesis). Finally, the authors assay expression of keratins and key signalling pathway members during the process of differentiation, providing a detailed repertoire of factors potentially regulating the process. This comprehensive single-cell atlas provides both insights into the cellular basis of human lung homeostasis and regeneration and a rich resource for future studies.
