Elucidating the role of interleukin-22 in Hirschsprung Associated enterocolitis pathogenesis - PROJECT SUMMARY/ABSTRACT Hirschsprung disease associated enterocolitis (HAEC) is the leading cause of death in children who lack enteric neurons in distal bowel, a birth defect called Hirschsprung disease. The etiology of HAEC is not well understood, but hypothesized disease mechanisms include altered gut microbes (“dysbiosis”), abnormal mucosal immune system and epithelial barrier defects. To date, there are no immune-targeted therapies to treat or prevent HAEC, but new treatments are needed. This proposal builds on the candidate’s preliminary data suggesting interleukin 22 (IL22) critically modulates HAEC risk and HAEC severity. The central hypothesis is that enteric nervous system (ENS) signaling induces IL22 release and facilitates IL22 epithelial responses to enhance mucosal immunity and strengthen epithelial barrier functions that prevent enterocolitis. The Piebald lethal (sl/sl) Hirschsprung disease mouse model of HAEC will be used, as survival of sl/sl mice is dramatically (> 3-fold) altered by diet (Tjaden et al, in BioRxiv and submitted) and IL22 mRNA is much higher in sl/sl fed a Protective diet that extends median survival (“late onset HAEC”). Aim 1 will define the cellular source(s) of IL22 from bowel regions of sl/sl model mice that develop early or late onset HAEC. In parallel, this aim tests the hypothesis that IL22 prevents HAEC, by using genetic and pharmacologic strategies to alter IL22 levels. Aim 2 will precisely define the role of IL22 on epithelial integrity, stem cell renewal and differentiation in organoids derived from sl/sl mice with early or late onset HAEC and from children with Hirschsprung disease with or without HAEC. Organoids facilitate studies of epithelial stem cell biology and IL22-epithelium interactions in the absence of microbes, neurons, or diffusible small molecules such as neurotransmitters. Collectively, these studies will determine cellular sources of IL22, the effect of ENS cells on IL22 secretion, the role of IL22 in enterocolitis, and the impact of Hirschsprung disease associated aganglionosis on epithelial cell biology. These studies build on the candidate’s training as a pediatric gastroenterologist, who has clinical exposure to the diagnosis and treatment of children with Hirschsprung disease and HAEC, as well as her basic science training in enteric nervous system biology. As the work proceeds, she will become an expert in mucosal immunology and epithelial biology with a focus on neuro-immune and neuro-epithelial interactions. The mentors, Dr. Robert Heuckeroth, and Dr. Kathryn Hamilton are experts in ENS biology and epithelial biology respectively. Both mentors have a strong commitment to mentorship and NIH funding track records. Experiments will be conducted at the Children’s Hospital of Philadelphia and Perelman School of Medicine at the University of Pennsylvania, a collegial, collaborative and state-of-the art institution. The professional development and training plan will position the candidate as a successful pediatrician-scientist, who is focused on the prevention and treatment of Hirschsprung associated enterocolitis. These studies should determine if IL22-based therapies would likely be successful in HAEC, and if a human clinical trial is appropriate.
