Mast cell neuromuscolar involvement in patients with severe gastrointestinal dysmotility (SGID)

Background: CIIP is a gastrointestinal motility disorder mimicking bowel obstruction in the absence of any lesions occluding the gut lumen. A number of degenerative and inflammatory factors can contribute to enteric neuromuscular abnormalities underlying dysmotility in CIIP. The detection of an inflammatory neuro-myopathies at histopathology may have a special impact in the management of CIIP patients because of obvious therapeutic implications. Aim: From a single center-studied patient cohort, we investigated: 1) CIIP patients with an associated inflammatory neuro-myopathy; 2) clinical, morphological and molecular correlates of those CIIP patients with identified neuro-muscular inflammatory changes. Methods: Thirty consecutive patients (22 F, 8 M; age range: 16-63 yrs) with clinically established and manometrically characterized CIIP underwent laparoscopic surgery to collect ileal full-thickness biopsies for histopathology. Tissue samples from n=4 pts with uncomplicated gut neoplastic disease served as controls. Biopsies were processed for classic H&E and immunohistochemical analysis using a variety of markers for neurons and glia (NSE, NF, Synaptophysin, S100), neurochemical messengers (NOS, VIP, NPY, CGRP, SP/TK), neuronal apoptosis (Bcl-2), interstitial cells of Cajal (ICC, c-Kit) and smooth muscle (actin, myosin, dystophin, caldesmon and COX). Also, antibodies detecting lymphocytes (CD45), macrophages (CD68) and mast cells (c-kit and tryptase) were used. Expression of mRNA coding for COX and NOS isoforms was assessed by reverse transcription (RT) polimerase chain reaction (PCR) on ileal specimens snap-frozen in liquid nitrogen. Results: Among all investigated CIIP patients, ileal biopsies from 11 pts (36%) (10 F, 1 M; age range: 28-63 yrs) had an apparently normal structure as compared to controls. Specifically, enteric plexuses/nerve fibers were normal as demonstrated by the previously mentioned markers. Similarly, c-Kit positive ICC networks and unchanged muscular layers were reported. Both CD45 and CD68 did not reveal immunocytes throughout the neuromuscular layer, while c-Kit and tryptase labeling identified dense mast cell infiltrate not only in the mucosa and submucosa, but also spreading to the neuromuscular component. In association with this finding, a reduced nNOS immunolabeling was detected in about 4/11 (36%) of the positive cases. RT-PCR analysis revealed the expression of COX-1, COX-2, eNOS, iNOS and nNOS… The densitometric analysis… Conclusions: A relevant subset of CIIP pts from a single center cohort showed a neuromuscular mast cell infiltrate as unique histopathologic hallmark. The abnormalities to COX and NOS expression suggest a mast cell dependent mechanisms leading to neuromuscular dysfunction contributing to CIIP in such a context. The present data pave the way targeting mast cell if these infiltrate can be detected in the neuromuscular layer of CIIP pts.