Substance P--an underlying factor for pouchitis? Prospective study of substance P- and vasoactive intestinal polypeptide-immunoreactive innervation and mast cells.

Recent studies suggest that substance P (SP), vasoactive intestinal polypeptide (VIP), and mast cells play a role in inflammatory processes of the bowel. The aim of this study was to evaluate the distribution of SP and VIP immunoreactivities and to count mast cells in the ileal pouch of patients, who had pouchitis after restorative proctocolectomy performed for treatment of ulcerative colitis (UC), and to compare the findings in the same patients after a follow-up period. Nine patients with pouchitis underwent clinical evaluation, endoscopy of the pouch, and histological examination, which were repeated after the follow-up period of 14 months on average. The number and intensity of SP- and VIP-immunoreactive nerve fibers were visualized by immunofluorescence microscopy and subjected to quantitative scoring, and the number of mast cells per unit area was counted. The results were compared to the histological findings and the clinical status. Lamina propria contained fibers showing bright immunofluorescence for SP and VIP. The mean fluorescence intensity score of SP-immunoreactive nerve fibers in the lamina propria remained similar after the follow-up period (2.99 +/- 0.79 and 2.06 +/- 0.82, NS). SP-immunoreactive innervation correlated with the grade of acute (R2 = 0.5396, P = 0.0242) and chronic inflammation (R2 = 0.4561, P = 0.0459), while SP and VIP immunoreactivity, mast cell count, and histological changes did not correlate with the clinical status. The present study demonstrates an increase in the density of SP-immunoreactive nerve fibers in inflamed ileal pouch mucosa of clinically asymptomatic pouchitis patients. These results raise the possibility of therapeutic interference of SP-related processes in treatment of pouchitis.