Thyroid Hormone-Activated Signaling Pathways are Essential for Development of Intestinal Stem Cells

Intestinal homeostasis is maintained by strict regulation of stem cell function. In mammals, several sig-naling pathways, including the formation of stem cell niches, are involved in stem cell regulation. How-ever, little is known of the molecular mechanisms involved in postembryonic maturation of the verte-brate intestine, that is, the acquisition of cell renewal systems, including stem cell development and niche formation. Using thyroid hormone (TH)-dependent intestinal remodeling during amphibian meta-morphosis as a model to study these mechanisms, we found that several signaling pathways, including the SHH/BMP4, WNT, Notch, and Hippo pathways, are regulated by TH and involved in stem cell regulation. In this review, we highlight findings regarding the role of these signaling pathways and dis-cuss potential future avenues of study. (J Nippon Med Sch 2023; 90: 246?252)