Induced Pluripotent Stem Cells as a Tool to Decipher the Normal and Abnormal Development of the Esophagus and Trachea from Normal Morphogenesis to Esophageal Atresia, Tracheomalacia, and Laryngo–Tracheal Clefts

The development of the esophagus and trachea following the septation of the anterior foregut is a highly regulated process involving bidirectional communication between the endoderm and mesoderm. Signaling pathways such as the Bone Morphogenetic Protein family, Wnt/β-catenin, Sonic Hedgehog, and Fibroblast Growth Factor family mediate this complex crosstalk to induce the dorsal-ventral patterning of the anterior foregut as well as lineage specification. Even though the mechanisms are not fully understood, dysregulation of signaling pathways may lead to congenital malformations such as tracheomalacia, laryngeal-tracheal clefts and multiple types of esophageal atresia with/without tracheoesophageal fistula (EA/TEF). Human induced pluripotent stem cells (iPSCs) provide a robust <i>in vitro</i> platform to monitor the normal and abnormal development of esophagus and trachea and to understand the roles of the endoderm and mesoderm during anterior foregut development. Recent studies have demonstrated that direct differentiation of iPSCs into epithelial and mesenchymal lineages can recapitulate the key stages of foregut development. In this regard, in the current paper, we review the signaling pathways involved in the development of organs deriving from the anterior foregut as well as the roles of the endoderm and mesoderm revealed by previous studies. Furthermore, we discuss the use of iPSCs as a valuable model for investigating the bidirectional communications between the endoderm and mesoderm, which can broaden our knowledge and understanding of the critical mechanisms leading to normal and abnormal development of the esophagus and trachea.