Sensory innervation of the anal canal and anorectal line in Hirschsprung's disease: histological evidence from mouse models.

Abstract

We used non-Hirschsprung's disease (HD) Sox10-Venus Transgenic mice (non-HDSV-mice), an endothelin receptor-B knockout mouse model of HD (HD-mice), and C57B6C3 wild controls (C-mice) to identify the correlation between the anorectal line (ARL) and successful transanal pull-through (TAPT). In non-HDSV-mice, intestinal neural crest-derived cells can be visualized with Venus,-a green fluorescent protein-without histochemical staining. We exposed the anal canal in each non-HDSV-mouse and marked the ARL directly with red ink. Specimens of anus and rectum from HD- and C-mice were immunostained with sensory nerve markers substance P and calcitonin gene related peptide (CGRP) and Hematoxylin and Eosin. Stereoscopic microscopy confirmed a squamous-columnar epithelial junction corresponding to the red ink in non-HDSV-mice. Fluorescence microscopy showed intense Venus expression proximal to the ARL and little enteric nerve expression distally. Substance P and CGRP expression were strong in the basal layer of the anal transitional zone (ATZ) in both HD- and C-mice; i.e., distal sensory innervation was normal in HD-mice. The ARL delineated a distinct demarcation in sensory innervation that is normal even in HD-mice. Thus, the initial incision during TAPT should be based on the ARL because it is readily identifiable and intimately involved with bowel function.