Detection and characterization of murine colitis and carcinogenesis by molecularly targeted contrast-enhanced ultrasound

AIM To study mucosal addressin cellular adhesion molecule-1(MAd CAM-1) and vascular endothelial growth factor(VEGF)-targeted contrast enhanced ultrasound(CEUS) for the assessment of murine colitis and carcinogenesis. METHODS C57BL/6 mice were challenged with 3% dextran sodium-sulfate(DSS) for three, six or nine days to study the development of acute colitis. Ultrasound was performed with and without the addition of unspecific contrast agents. MAd CAM-1-targeted contrast agent was used to detect and quantify MAd CAM-1 expression. Inflammatory driven colorectal azoxymethane(AOM)/DSS-induced carcinogenesis was examined on day 42 and 84 using VEGF-targeted contrast agent. Highly specific tissue echogenicity was quantified using specialized software. Sonographic findings were correlated to tissue staining, western blot analysis and immunohistochemistry to quantify the degree of inflammation and stage of carcinogenesis. RESULTS Native ultrasound detected increased general bowel wall thickening that correlated with more progressed and more severe DSS-colitis(healthy mice: 0.3 mm ± 0.03 vs six days DSS: 0.5 mm ± 0.2 vs nine days DSS: 0.6 mm ± 0.2, P < 0.05). Moreover, these sonographic findings correlated well with clinical parameters such as weight loss(r2 = 0.74) and histological damage(r2 = 0.86)(P < 0.01). In acute DSS-induced murine colitis, CEUS targeted against MAd CAM-1 detected and differentiated stages of mild, moderate and severe colitis via calculation of mean pixel contrast intensity in decibel(9.6 d B ± 1.6 vs 12.9 d B ± 1.4 vs 18 d B ± 3.33, P < 0.05). Employing the AOM/DSSinduced carcinogenesis model, tumor development was monitored by CEUS targeted against VEGF and detected a significantly increased echogenicity in tumors as compared to adjacent healthy mucosa(healthy mucosa, 1.6 d B ± 1.4 vs 42 d, 18.2 d B ± 3.3 vs 84 d, 18.6 d B ± 4.9, P < 0.01). Tissue echogenicity strongly correlated with histological analysis and immunohistochemistry findings(VEGF-positive cells in 10 high power fields of healthy mucosa: 1 ± 1.2 vs 42 d after DSS start: 2.4 ± 1.6 vs 84 d after DSS start: 3.5 ± 1.3, P < 0.01). CONCLUSION Molecularly targeted CEUS is a highly specific and noninvasive imaging modality, which characterizes murine intestinal inflammation and carcinogenesis in vivo.

Diagnostic utility of faecal biomarkers in patients with irritable bowel syndrome

Irritable bowel syndrome(IBS)is a common functional gastrointestinal(GI)disorder characterized by unspecific symptoms.In clinical practice it is crucial to distinguish between non-inflammatory functional problems and inflammatory,malignant or infectious diseases of the GI tract.Differentiation between these involves the use of clinical,radiological,endoscopic,histological and serological techniques,which are invasive,expensive,time-consuming and/or hindered by inaccuracies arising from subjective components.A range of faecal markers now appears to have the potential to greatly assist in the differentiation of inflammatory bowel disease(IBD)and IBS.Faecal markers of neutrophil influx into the mucosa are reliable indicators of intestinal inflammation and their role has been mainly studied in discriminating IBD from non-IBD conditions(including IBS)rather than organic from non-organic diseases.Phagocytespecific proteins of the S100 family(S100A12,calprotectin)are amongst the most promising faecal biomarkers of inflammation.Faecal leukocyte degranulation markers(lactoferrin,polymorphonuclear elastase and myeloperoxidase)have also been suggested as diagnostic tools for the differentiation of IBD and IBS.More recently,additional proteins,including granins,defensins and matrix-metalloproteases,have been discussed as differential diagnostic markers in IBD and IBS.In this review,some of the most promising faecal markers,which have the potential to differentiate IBD and IBS and to advance diagnostic practices,will be discussed.

Diagnostic imaging advances in murine models of colitis

Inflammatory bowel diseases(IBD) such as Crohn's disease and ulcerative colitis are chronic-remittent inflammatory disorders of the gastrointestinal tract still evoking challenging clinical diagnostic and therapeutic situations. Murine models of experimental colitis are a vital component of research into human IBD concerning questions of its complex pathogenesis or the evaluation of potential new drugs. To monitor the course of colitis, to the present day, classical parameters like histological tissue alterations or analysis of mucosal cytokine/chemokine expression often require euthanasia of animals. Recent advances mean revolutionary noninvasive imaging techniques for in vivo murine colitis diagnostics are increasingly available. These novel and emerging imaging techniques not only allow direct visualization of intestinal inflammation, but also enable molecular imaging and targeting of specific alterations of the inflamed murine mucosa. For the first time, in vivo imaging techniques allow for longitudinal examinations and evaluation of intra-individual therapeutic response. This review discusses the latest developments in the different fields of ultrasound, molecularly targeted contrast agent ultrasound, fluorescence endoscopy, confocal laser endomicroscopy as well as tomographic imaging with magnetic resonance imaging, computed tomography and fluorescence-mediated tomography,discussing their individual limitations and potential future diagnostic applications in the management of human patients with IBD.