The inner-most surface of the intestine is lined by single-layered, well-polarized epithelial cells. In the last several years, significant advances have been made in establishing in vitro culture systems that support the long-term growth of intestinal epithelial stem cells. By combining these cell culture technologies with the stem cell transplantation methods that my research group has developed, I will investigate the mechanisms regulating the structural and functional maintenance of intestinal epithelial tissues.

First I will address how intestinal stem cells build up a cystic structure in vitro, which invariably allocates the apical membrane to its inner surface and the basal membrane to the outer side. In particular, I will look into the initial process by which such cellular polarity is introduced, analyzing the spatiotemporal behavior of membrane proteins during the early phase of cyst formation from single cells. Secondly, I will assess the role of extracellular milieu in regulating intestinal epithelial polarity. The intestinal organoids grown in culture have a luminal space inside where the cells create a unique environment by secreting or transporting many substances. By analyzing the composition of the luminal fluid, we will assess how the composition gradient across the cultured cells would influence the form, function or the polarity of colonic cells in vitro. Thirdly, I will investigate how small intestinal (SI) stem cells would behave in vivo when cultured in vitro and then transplanted. We have previously demonstrated that the cultured colonic stem cells are able to regenerate normal epithelia when transplanted onto the damaged colon in mice. By extending such approach, I will test whether the SI stem cells in culture retain their tissue regeneration capabilities.

To characterize intestinal stem cell behavior during the formation of tubular structures with functional polarity would be central to the development of regenerative medicine approaches. The achievement of this project would build a basis for a novel and effective therapy for various intestinal diseases in which the stem cell populations are damaged.