Alterations in the immunohistochemical expression of Das-1 and CG-3 in colonic mucosal biopsy specimens helps distinguish ulcerative colitis from Crohn disease and from other forms of colitis

Evolution and New Horizons of Endoscopy in Inflammatory Bowel Diseases

Endoscopy is the mainstay of inflammatory bowel disease (IBD) evaluation and the pillar of colorectal cancer surveillance. Endoscopic equipment, both hardware and software, are advancing at an incredible pace. Virtual chromoendoscopy is now widely available, allowing the detection of subtle inflammatory changes, thus reducing the gap between endoscopic and histologic assessment. The progress in the field of artificial intelligence (AI) has been remarkable, and numerous applications are now in an advanced stage of development. Computer-aided diagnosis (CAD) systems are likely to reshape most of the evaluations that are now prerogative of human endoscopists. Furthermore, sophisticated tools such as endocytoscopy and probe-based confocal laser endomicroscopy (pCLE) are enhancing our assessment of inflammation and dysplasia. Finally, pCLE combined with molecular labeling could pave the way to a new paradigm of personalized medicine. This review aims to summarize the main changes that occurred in the field of IBD endoscopy and to explore the most promising novelties.

Endoscopic biopsy features and diagnostic challenges of adult Crohn's disease at initial presentation

AIMS

Endoscopic biopsy diagnosis of Crohn's disease (CD) is problematic due to lack of specific microscopic features and patchy involvement. There is no documentation of the pattern and severity of microscopic features of CD at initial presentation in adults or children. We aimed to assess the initial mucosal biopsy features of CD in adults and to identify any specific features to confirm the diagnosis.

METHODS

Thirty sets of initial, adult endoscopic biopsies suspected to be CD with subsequent resections, repeat biopsies with long-term follow-up, and/or other confirmatory laboratory results were analysed by three gastrointestinal pathologists, blinded for the final diagnosis for mucosal architectural changes, epithelial abnormalities, chronic and active inflammation and changes of muscularis mucosae and submucosa. There were 25 cases of CD and five cases of non-CD for comparison (3 tuberculosis and 2 right-sided diverticular disease and associated colitis). Cases confirmed as ulcerative colitis were excluded, as diagnostic challenges are already well established.

RESULTS

The majority of initial biopsies (96%) of CD were abnormal with active chronic ileocolitis with a very high proportion (80%) showing the classic combination of abnormal mucosal architecture, epithelial abnormalities and active chronic inflammation. The most sensitive feature was lamina proprial chronic inflammation (sensitivity 92.7%). Sensitivity for other features was as follows: active inflammation 87.8%, basal plasmacytosis 82.1%, architectural changes 80.5% and epithelial abnormalities 70.7%. Abnormalities were found in 94% of ileal and 76% of colonic biopsies. No feature was specific as all tuberculosis and diverticular disease cases showed the classic combination. Granulomata were seen in 10 of 41 CD, in all five tuberculosis and in no diverticular disease biopsies. Small, tight, well defined granulomata characterised CD over large coalesced ganulomata of tuberculosis. Paneth cell and pseudopyloric metaplasia was seen only in CD (2/25).

CONCLUSIONS

Initial endoscopic biopsies of adult CD are significantly abnormal and a majority shows active chronic ileocolitis. The features are sufficiently important to suspect CD at initial presentation in the appropriate clinical setting. Tuberculosis and diverticular disease associated colitis are two important mimics to consider in addition to ulcerative colitis.

Antibody to tropomyosin isoform 5 and complement induce the lysis of colonocytes in ulcerative colitis

OBJECTIVES

Tropomyosins (TMs) are cytoskeletal microfilament proteins present in all eukaryotic cells. Human TM isoform 5 (hTM5) is the predominant isoform in colonic epithelial cells. Antibodies against hTM5 are found both in the sera and in the mucosa of patients with ulcerative colitis (UC) but not Crohn's disease (CD). We investigated whether anti-hTM5 autoantibodies are pathogenic.

METHODS

Normal-appearing colonic mucosal biopsy specimens were incubated with autologous serum. After 45 min, deposition of the complement component C3b was identified by indirect immunofluorescence assay (IFA). Additional specimens were incubated with autologous serum fixed in formalin, and their architecture was examined by hematoxylin and eosin (H&E) staining.

RESULTS

For 79% of UC patients, autologous serum caused C3b staining along the colonic epithelium. Recombinant hTM5 or anti-hTM5 monoclonal antibody blocked serum-induced C3b deposition. Immunoglobulin G (IgG) antibody and affinity-purified anti-hTM5 IgG antibody from UC sera with complement caused C3b deposition, indicating specificity of hTM5 as an autoantigen. When analyzed by H&E staining, sera obtained from 71% of UC patients caused a significant loss of epithelium. This process was inhibited by Fc fragments, indicating that it is complement mediated. With medium, normal, or CD serum, there was no C3b deposition or morphological changes of the colonic epithelium, indicating disease specificity. The ileal mucosa was not affected by UC sera, suggesting specificity for the colon. In UC mucosa, expression of hTM5 increased.

CONCLUSIONS

hTM5 acts as an autoantigen in UC. hTM5-specific IgG autoantibody in sera from UC patients induces C3b deposition and destruction of colonic epithelial cells, suggesting a direct pathogenic effect. If used as a diagnostic test to distinguish UC from CD, IFA would have 79% sensitivity and 100% specificity. Development of blocking antibodies may lead to novel therapies.