Intestinal fibrosis drives tonic contraction of the aganglionic bowel in Hirschsprung disease

About This Grant

PROJECT SUMMARY Hirschsprung disease (HSCR) is a serious congenital enteric neuropathy characterized by a narrowed segment of distal bowel where enteric ganglia are absent and intestinal motility is lacking. This leads to a functional bowel obstruction that causes severe obstipation, proximal megacolon, life threatening enterocolitis, and need for major surgery to remove the aganglionic segment. Both the pre-operative and post-operative periods present significant challenges for patients. Before surgery, infants require rectal irrigations 1-2 times daily to evacuate stool. After surgery, at least 50% of patients experience late complications, including persistent obstructive symptoms, fecal soiling, post-operative enterocolitis, pelvic nerve injury, damage to anal sphincters, residual aganglionosis, transition zone pull-through, and unexplained dysmotility. The morbidity of HSCR, both pre- and post-operatively, highlights the limitations of our current management and emphasizes a critical unmet need to develop a novel treatment approach to this life-threatening disease. This research proposal addresses that need by introducing an innovative hypothesis on the pathophysiology of HSCR, specifically the central role of fibrosis in the aganglionic segment. The narrow aganglionic segment in HSCR is commonly described as “tonically contracted” or “spastic,” a phenomenon attributed to uninhibited innervation by extrinsic cholinergic nerves, or to altered expression of ion channels, cytoskeletal components, and gap junction proteins. We hypothesize that the aganglionic narrowing is instead due to fibrotic remodeling of the gut wall, shifting the focus away from neuronal and protein imbalance and opening new avenues to target fibrosis in HSCR. We aim to characterize the cellular and molecular features of the aganglionic segment and to test the therapeutic potential of anti-fibrotic therapy, both as a stand-alone therapy and in combination with enteric neuronal stem cell transplantation. Aim 1 leverages multiple novel methodologies to characterize matrisome composition, immune cell populations, and bowel stiffness in the aganglionic colon of HSCR mice. Aim 2 tests the effects of anti-fibrotic therapy on the success of enteric neuronal stem cell transplantation to remodel fibrosis in the gut wall, which has not been previously studied. This new pharmacologic strategy aims to improve the early, pre-operative course of the disease by relaxing the narrowed segment to facilitate the passage of stool and reduce the risk of life-threatening obstruction and fecal stasis, offering significant clinical value by reducing the morbidity associated with pre-operative complications. Understanding and treating fibrosis in the aganglionic segment could enhance the success of regenerative cell therapy by creating a more permissive microenvironment into which transplanted cells are delivered. Overall, successful completion of the proposed aims will have a significant impact on our understanding of the pathophysiology of Hirschsprung disease and on its treatment.