In Vitro and In Vivo Development of the Human Airway at Single-Cell Resolution.

Bud tip progenitor cells give rise to all murine lung epithelial lineages and have been described in the developing human lung; however, the mechanisms controlling human bud tip differentiation into specific lineages are unclear. Here, we used homogeneous human bud tip organoid cultures and identified SMAD signaling as a key regulator of the bud tip-to-airway transition. SMAD induction led to the differentiation of airway-like organoids possessing functional basal cells capable of clonal expansion and multilineage differentiation. To benchmark in vitro-derived organoids, we developed a single-cell mRNA sequencing atlas of the human lung from 11.5 to 21 weeks of development, which revealed high degrees of similarity between the in vitro-derived and in vivo airway. Together, this work sheds light on human airway differentiation in vitro and provides a single-cell atlas of the developing human lung.
Competing Interests: Declaration of Interests J.R.S. and A.J.M. are co-inventors on patents filed by the Regents of the University of Michigan relating to the isolation and maintenance of lung bud tip progenitor cells and the differentiation of lung epithelial progenitor cells into basal cells.
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