Children with aganglionic colon present with a constellation of symptoms (e.g., severe constipation, diarrhea, intestinal inflammation) that predispose to sepsis, and can be life-threatening. Surgical correction eradicates these symptoms in most cases. But in up to 30% of cases, surgery fails to cure the disorder, and thereafter, children suffer from chronic enterocolitis that can lead to bacteremia, outright sepsis, and even death. Almost nothing is known about the underlying mechanisms of this postoperative enterocolitis. As a means to pursue mechanistic studies, we created an animal model of postoperative enterocolitis associated with aganglionosis using the Endothelin Receptor B-null mouse with colonic aganglionosis. We developed a novel microsurgical procedure that is essentially identical to the operation performed clinically, and essentially cures aganglionic megacolon in Ednrb-/- mice, just as it does in human patients. We found that a significant proportion of Ednrb- /- mice develop postoperative enterocolitis despite satisfactory surgical outcome, similar to what occurs clinically in human patients. In the course of our studies, we serendipitously discovered a spectrum of striking immune abnormalities in Ednrb-/- mice. These abnormalities occur at or shortly after birth, appear to worsen with age, and include reduced spleen size, reduced absolute numbers of lymphocytes in the spleen, marked reduction in marginal zone B cells and B cell/T cell ratio in the spleen, thymic involution, and bone marrow abnormalities. Upon examination of mice with a genetic lack of entdothelin-3 (ET3;the preferred ligand for the Ednrb receptor), we found very similar immune abnormalities. Our preliminary studies thus far are consistent with the interpretation that ET3 signaling through Ednrb is required for normal development of the immune system, and/or for normal function of the immune system in the adult animal. We therefore propose that 1) ET3/Ednrb signaling is essential for normal development of the immune system;2) when disrupted, two distinct phenotypic features emerge: colonic aganglionosis, with a marked propensity to develop enterocolities even after successful surgical correction, and an immune system that displays marked structural and functional abnormalities. We suspect that these two phenotypic features are indeed related to one another, and our ultimate goal is to understand and describe in molecular and cellular terms the precise basis of the interrelationships. This K08 application proposes an a detailed, comprehensive training plan that will allow the applicant to pursue immunologic studies related to disrupted ET3/Ednrb signaling. An outstanding team of Mentors will directly oversee the research training and the all aspects of the investigation. The ultimate goal is for the applicant to leverage the data obtained during this proposed investigation into a successful R01 application. This will then allow the applicant to become an independently-funded surgeon-scientist investigating the role of specific signaling pathways and genes in immune development and function, and how these are linked to colonic ganglionosis and the associated enterocolitis that occurs in these diseases.
We developed an animal model of enterocolitis associated with aganglionosis using the Endothelin Receptor B-null mouse with colonic aganglionosis that closely mimics the features of the human condition. During our studies, we made a critical new observation that the Ednrb-null mice also had lymphopenia-albeit as yet undescribed-role in development of enterocolitis. Our novel findings suggest that ET3-Ednrb signaling plays a critical role for normal immune system development in mice, which forms the basis of this proposal.
|Demehri, Farokh R; Frykman, Philip K; Cheng, Zhi et al. (2016) Altered fecal short chain fatty acid composition in children with a history of Hirschsprung-associated enterocolitis. J Pediatr Surg 51:81-6|
|Wieck, Minna M; El-Nachef, Wael N; Hou, Xiaogang et al. (2016) Human and Murine Tissue-Engineered Colon Exhibit Diverse Neuronal Subtypes and Can Be Populated by Enteric Nervous System Progenitor Cells When Donor Colon Is Aganglionic. Tissue Eng Part A 22:53-64|
|Frykman, Philip K; Nordenskjöld, Agneta; Kawaguchi, Akemi et al. (2015) Characterization of Bacterial and Fungal Microbiome in Children with Hirschsprung Disease with and without a History of Enterocolitis: A Multicenter Study. PLoS One 10:e0124172|
|Frykman, Philip K; Cheng, Zhi; Wang, Xiao et al. (2015) Enterocolitis causes profound lymphoid depletion in endothelin receptor B- and endothelin 3-null mouse models of Hirschsprung-associated enterocolitis. Eur J Immunol 45:807-17|
|Short, Scott S; Pierce, James R; Burke, Rita V et al. (2014) Is routine preoperative screening echocardiogram indicated in all children with congenital duodenal obstruction? Pediatr Surg Int 30:609-14|
|Short, Scott S; Papillon, Stephanie; Berel, Dror et al. (2014) Late onset of necrotizing enterocolitis in the full-term infant is associated with increased mortality: results from a two-center analysis. J Pediatr Surg 49:950-3|
|Burkardt, Deepika D'Cunha; Graham Jr, John M; Short, Scott S et al. (2014) Advances in Hirschsprung disease genetics and treatment strategies: an update for the primary care pediatrician. Clin Pediatr (Phila) 53:71-81|
|Short, Scott S; Dubinsky, Marla C; Rabizadeh, Shervin et al. (2013) Distinct phenotypes of children with perianal perforating Crohn's disease. J Pediatr Surg 48:1301-5|
|Jensen, Aaron R; Short, Scott S; Anselmo, Dean M et al. (2013) Laparoscopic versus open treatment of congenital duodenal obstruction: multicenter short-term outcomes analysis. J Laparoendosc Adv Surg Tech A 23:876-80|
|Aggarwal, Amit; Jain, Manu; Frykman, Philip K et al. (2013) Multiphoton microscopy to identify and characterize the transition zone in a mouse model of Hirschsprung disease. J Pediatr Surg 48:1288-93|
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