Inflamed pouch mucosa possesses altered tight junctions indicating recurrence of inflammatory bowel disease.
OBJECTIVE
The etiology of pouchitis after coloproctomucosectomy with ileal pouch-anal anastomosis in patients with ulcerative colitis is still unknown. Beside changes in luminal antigens, the immunological predisposition is assumed to be responsible. In previous electrophysiological studies, we showed that mucosal barrier and transport function in pouchitis is markedly reduced. Thus, the aim of the present study was to analyze barrier function on the molecular level.


METHODS
Pouch biopsies of 36 ulcerative colitis patients were analyzed. Time points were (1) intraoperative immediately prior to ileal pouch-anal anastomosis (n = 13), (2) >1 year after ileostomy closure (pouch, n = 12), and (3) during pouchitis (n = 11). Control terminal ileum biopsies were obtained from eight patients undergoing hemicolectomy due to carcinoma. Expression of tight junction proteins was analyzed by Western blotting and confocal laser-scanning microscopy. To elucidate effects on epithelial barrier properties, impedance spectroscopy was performed in miniaturized Ussing chambers.


RESULTS
In pouchitis, epithelial resistance was markedly reduced compared to non-inflamed pouch and control ileum. Expression of tight junction proteins claudin-1, 3, 4, 5, and 7 and occludin revealed differential expression regulation with the tightening tight junction protein claudin-1 being decreased and an increase of the pore-forming claudin-2, whereas other claudins remained constant. Morphometry indicated the mucosal surface to be unchanged.


CONCLUSIONS
Pouchitis is characterized by a selective change of tight junction proteins in favor of opening the epithelial tight junction and, thus, the paracellular pathway, which contributes to the inflammatory process. This resembles changes in inflammatory bowel disease (IBD) and indicates IBD recurrence in pouchitis.
Amasheh
Salah
S
Institute of Clinical Physiology, CBF, Charité, Freie Universität und Humboldt Universität, 12200, Berlin, Germany. salah.amasheh@charite.de
Dullat
Sonja
S
Fromm
Michael
M
Schulzke
Jörg D
JD
Buhr
Heinz J
HJ
Kroesen
Anton J
AJ
D015153:Blotting, Western; D062445:Claudin-1; D057167:Claudins; D003720:Densitometry; D055724:Electrophysiological Phenomena; D005260:Female; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000150:complications* / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D018613:Microscopy, Confocal; D019449:Pouchitis / Q000150:complications* / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D012008:Recurrence; D019108:Tight Junctions / Q000378:metabolism* / Q000473:pathology*
C568108:CLDN1 protein, human; C491875:CLDN2 protein, human; D062445:Claudin-1; D057167:Claudins; D008565:Membrane Proteins