Narrow-Band Imaging Endoscopy As a Novel Tool to Assess In Vivo Mucosal Angiogenesis in Inflammatory Bowel Disease: A Preliminary Report

Abstract

Background: Angiogenesis is a novel component of inflammatory bowel disease (IBD) pathogenesis. We have recently reported that in both Crohn's disease (CD) and ulcerative colitis (UC) actively inflamed mucosa, there is an increase of microvascular density, as assessed by CD31 staining. Narrow-band imaging (NBI) is a novel endoscopic technique that preferentially enhances the mucosal surface and the network of superficial capillaries. We aimed to investigate if NBI could be a useful tool to detect in vivo angiogenesis in IBD patients. Methods: Conventional and NBI colonoscopy was performed on 9 patients (6 UC and 3 CD) with colonic inflammation. Based on the vascular pattern intensity with NBI, we distinguished areas with a stronger (blacker) capillary vascular pattern (NBI+) compared with normal mucosa showing regular vascular pattern (NBI−). For each patient, biopsy samples were taken in 5 endoscopically normal areas and NBI−, in 5 normal areas at conventional endoscopy but NBI+, and in 5 endoscopically inflamed areas and positive at NBI. CD31 staining was performed by immunohistochemistry, and microvascular density assessed by vessel count. Results: NBI allowed to clearly detect mucosal microvasculature in IBD intestine. NBI was able to visualize areas of abnormal microvascular changes, not detected at conventional colonoscopy. Compared to endoscopically normal areas at conventional colonoscopy and NBI-, areas with a normal mucosa at conventional colonoscopy but with a stronger capillary vascular pattern (NBI+) displayed a significant (p < 0.05) increase in angiogenesis (12 ± 1 versus 18 ± 2 vessels/field). Areas inflamed at conventional endoscopy and NBI+ displayed a significant (p < 0.01) increase in vessel density (24 ± 7 vessel/field) compared to endoscopically normal areas at conventional colonoscopy and NBI. Finally, a stronger vascular pattern of the colonic mucosa (NBI+) was significantly associated with an increase in leukocyte infiltrate as assessed at histological analysis compared to the areas in which both conventional and NBI endoscopy did not show significant mucosal changes. Conclusions: NBI may be a useful tool that may allow in vivo imaging of intestinal angiogenesis observed in IBD, and could be used in clinical trials aimed to monitor the clinical effect of anti-angiogenic compounds in IBD. Larger studies are warranted to validate this endoscopical technique.