Quantification and neurochemical coding of the myenteric plexus in humans : no regional variation between the distal colon and rectum

Background: It remains unclear whether regional variation exists in the human enteric nervous system (ENS) ie, whether intrinsic innervation varies along the gut. Recent classification of gastrointestinal neuropathies has highlighted inadequacies in the quantification of the human ENS. This study used paired wholemounts to accurately quantify and neurochemically code the hindgut myenteric plexus, comparing human distal colon and rectum. Methods: Paired human descending colonic/rectal specimens were procured from 15 patients undergoing anterior resection. Wholemounts of myenteric plexi were triple-immunostained with anti-Hu/NOS/ChAT antibodies. Images were acquired by motorized epifluorescence microscopy, allowing assessment of ganglionic density/size, ganglionic area density, and neuronal density. 'Stretch-corrected' values were calculated using stretched/relaxed tissue dimensions. Key Results: Tile-stitching created a collage with average area 99 300 000 μm2. Stretch-corrected ganglionic densities were similar (colon: median 510 ganglia/100 mm2 [range 386-1170], rectum: 585 [307-923]; P = .99), as were average ganglionic sizes (colon: 57 593 μm2 [40 301-126 579], rectum: 54 901 [38 701-90 211], P = .36). Ganglionic area density (colon: 11.92 mm2 per 100 mm2 [7.53-18.64], rectum: 9.84 [5.80-17.19], P = .10) and stretch-corrected neuronal densities (colon: 189 neurons/mm2 [117-388], rectum: 182 [89-361], P = .31) were also similar, as were the neurochemical profiles of myenteric ganglia, with comparable proportions of NOS+ and ChAT+ neurons (P > .10). Conclusions and Inferences: This study has revealed similar neuronal and ganglionic densities and neurochemical profiles in human distal colon and rectum. Further investigation of other components of the ENS, incorporating additional immunohistochemical markers are required to confirm that there is no regional variation in the human hindgut ENS.