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 /Ch AT 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 μm 2 . Stretch‐corrected ganglionic densities were similar (colon: median 510 ganglia/100 mm 2 [range 386‐1170], rectum: 585 [307‐923]; P  = .99), as were average ganglionic sizes (colon: 57 593 μm 2 [40 301‐126 579], rectum: 54 901 [38 701‐90 211], P  = .36). Ganglionic area density (colon: 11.92 mm 2 per 100 mm 2 [7.53‐18.64], rectum: 9.84 [5.80‐17.19], P  = .10) and stretch‐corrected neuronal densities (colon: 189 neurons/mm 2 [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 Ch AT + 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 .