Basic Study
Copyright ©The Author(s) 2016. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. May 21, 2016; 22(19): 4662-4672
Published online May 21, 2016. doi: 10.3748/wjg.v22.i19.4662
Altered tryptophan hydroxylase 2 expression in enteric serotonergic nerves in Hirschsprung’s-associated enterocolitis
David Coyle, Justin M Murphy, Brian Doyle, Anne Marie O’Donnell, John Gillick, Prem Puri
David Coyle, John Gillick, Temple Street Children’s University Hospital, Dublin 1, Ireland
David Coyle, Justin M Murphy, Brian Doyle, Anne Marie O’Donnell, Prem Puri, National Children’s Research Centre, Our Lady’s Children’s Hospital, Dublin 12, Ireland
Author contributions: Coyle D performed the experimental procedures and is the primary author of the final manuscript; Murphy JM and Doyle B carried out experimental procedures; O’Donnell AM, Gillick J and Puri P designed the study and co-authored and revised the final manuscript.
Institutional review board statement: Ethical approval was granted by the Institutional Review Boards of Our Lady’s Children’s Hospital, Crumlin (GEN 292.12) and Temple Street Children’s University Hospital (13.003) prior to commencement of patient enrolment and specimen collection.
Informed consent statement: Informed written consent was obtained from the parents/legal guardians of all children enrolled in this study.
Conflict-of-interest statement: The authors declare no conflicts of interest.
Data sharing statement: Data pertaining to experimental work and population characteristics is available from prem.puri@ncrc.ie.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Prem Puri, Professor, MS, FRCS, FRCS (Ed), FACS, FAAP (Hon.), DSc (Hon.), National Children’s Research Centre, Our Lady’s Children’s Hospital, Crumlin Rd., Dublin 12, Ireland. prem.puri@ucd.ie
Telephone: +353-1-4096420 Fax: +353-1-4550201
Received: November 25, 2015
Peer-review started: December 1, 2015
First decision: December 31, 2015
Revised: January 11, 2016
Accepted: January 17, 2016
Article in press: January 18, 2016
Published online: May 21, 2016
Abstract

AIM: To determine if expression of colonic tryptophan hydroxylase-2 (TPH2), a surrogate marker of neuronal 5-hydroxytryptamine, is altered in Hirschsprung’s-associated enterocolitis.

METHODS: Entire resected colonic specimens were collected at the time of pull-through operation in children with Hirschsprung’s disease (HSCR, n = 12). Five of these patients had a history of pre-operative Hirschsprung’s-associated enterocolitis (HAEC). Controls were collected at colostomy closure in children with anorectal malformation (n = 10). The distribution of expression of TPH2 was evaluated using immunofluorescence and confocal microscopy. Protein expression of TPH2 was quantified using western blot analysis in the deep smooth muscle layers.

RESULTS: TPH2 was co-expressed in nitrergic and cholinergic ganglia in the myenteric and submucosal plexuses in ganglionic colon in HSCR and healthy controls. Co-expression was also seen in submucosal interstitial cells of Cajal and PDGFRα+ cells. The density of TPH2 immuno-positive fibers decreased incrementally from ganglionic bowel to transition zone bowel to aganglionic bowel in the myenteric plexus. Expression of TPH2 was reduced in ganglionic bowel in those affected by pre-operative HAEC compared to those without HAEC and healthy controls. However, expression of TPH2 was similar or high compared to controls in the colons of children who had undergone diverting colostomy for medically refractory HAEC.

CONCLUSION: Altered TPH2 expression in colonic serotonergic nerves of patients with HSCR complicated by HAEC may contribute to intestinal secretory and motor disturbances, including recurrent HAEC.

Keywords: Serotonin, Tryptophan hydroxylase 2, Hirschsprung, Enterocolitis, Ganglionic

Core tip: Despite optimal surgery, children with a history of Hirschsprung’s disease (HSCR) complicated by Hirschsprung’s-associated enterocolitis (HAEC) are at higher risk of long-term colonic dysfunction. Tryptophan hydroxylase-2 (TPH2) is a surrogate marker for neuronal 5-hydroxytryptamine (5-HT). We hypothesized that expression of TPH2 is altered in the colon of children with HAEC. We found the density of serotonergic nerves to be differentially reduced in the ganglionic colon of children with HSCR and HAEC compared to those without HAEC compared to controls, although expression is normalized in those with diverting colostomy. Abnormal neuronal 5-HT expression may contribute to post-operative colonic dysfunction in HSCR.