Bidirectional Wnt signaling between endoderm and mesoderm confer tracheal identity in mouse and human.

The periodic cartilage and smooth muscle structures in mammalian trachea are derived from tracheal mesoderm, and tracheal malformations result in serious respiratory defects in neonates. Here we show that canonical Wnt signaling in mesoderm is critical to confer trachea mesenchymal identity in human and mouse. Loss of β-catenin in fetal mouse mesoderm caused loss of Tbx4+ tracheal mesoderm and tracheal cartilage agenesis. The Tbx4 expression relied on endodermal Wnt activity and its downstream Wnt ligand but independent of known Nkx2.1-mediated respiratory development, suggesting that bidirectional Wnt signaling between endoderm and mesoderm promotes trachea development. Repopulating in vivo model, activating Wnt, Bmp signaling in mouse embryonic stem cell (ESC)-derived lateral plate mesoderm (LPM) generated tracheal mesoderm containing chondrocytes and smooth muscle cells. For human ESC-derived LPM, SHH activation was required along with Wnt to generate proper tracheal mesoderm. Together, these findings may contribute to developing applications for human tracheal tissue repair.