Intestinal failure is caused by a variety of enteropathies ranging from short bowel syndrome due to conditions such as necrotizing enterocolitis to congenital intestinal disorders. The mainstay therapy for patients with intestinal failure is parenteral nutrition (PN) but there are significant clinical complications associated with PN including infections, hepatic dysfunction and sepsis. Thus, a major challenge for intestinal research is to successfully develop new concepts and therapeutic approaches for the treatment of patients with intestinal failure that are dependent on PN. Advances in intestinal stem cell (ISC) biology, obtained through analysis of genetically-modified mice and cell lineage tracing studies, have garnered much interest in ISCs as a therapeutic target. Our long-term goal is to understand the extracellular signaling pathways that regulate human ISC niche, and how these pathways can be utilized for regenerative medicine or modulated in disease states such as intestinal failure. The recent development of directed differentiation of human pluripotent stem cells into intestinal tissue has afforded new opportunities to study human gastrointestinal development, tissue homeostasis and disease processes in vitro. Human intestinal organoids (HIOs) provide an in vitro model to study the direct interactions of epithelial and mesenchymal signals involved in maintenance of the ISC niche. Significantly, for patients with severe enteropathies where access to intestinal tissue is restricted, iPSC-derived HIOs provide a novel approach to study the intestinal biology of these patients. ADAM17 (TNF? converting enzyme) is a ubiquitously expressed sheddase responsible for shedding and activation of several growth factor/cytokine receptor families. In the mouse intestine, ADAM17 is implicated in complex intercellular communication involving EGFR/ErbB and TNFR signaling within multiple cell types of the ISC niche to maintain intestinal homeostasis, especially when faced with intestinal injury and inflammation. Recently, several patients from two different families were identified with distinct homozygous autosomal recessive ADAM17 null mutations defining a new rare congenital intestinal disorder termed neonatal inflammation skin and bowel syndrome. Our central hypothesis is that ADAM17 regulates signaling cross-talk between epithelium and mesenchyme of the human ISC niche. We will address this hypothesis in 3 aims: 1. generation of ADAM17 mutant and ADAM17 mutation corrected iPSC lines from dermal fibrobalsts obtained from an ADAM17 null patient. 2. Analysis of intestinal programming from ADAM17 mutant and ADAM17 mutation corrected iPSCs using HIOs and HIO xenograft transplantation and 3. Study the contribution of ADAM17 signaling from epithelial and mesenchymal layers from these HIOs. At the conclusion of this project, we should have gained detailed understanding of the role for ADAM17 signaling in maintaining the human ISC niche and defined ADAM17 or its substrates as potential new molecular targets, that may result in new approaches for stem cell therapies in regenerative medicine and for the treatment of intestinal failure.
ADAM17 is a sheddase responsible for ectodomain processing of a variety of membrane-anchored growth factors/cytokines and their receptors. In mice, ADAM17 deficiency leads to developmental defects in multiple organ systems including the gastrointestinal tract. The recent identification of rare pediatric patients harboring different ADAM17 null mutations has afforded the opportunity to study ADAM17 signaling in humans. In this grant application, we propose to use intestinal programming of iPSC lines derived from a patient harboring an autosomal recessive ADAM17 mutation to study the role of ADAM17 signaling in human intestinal homeostasis.
