Differential regulation of JAK/STAT-signaling in patients with ulcerative colitis and Crohn’s disease

In 2018,the pan-Janus kinase(JAK)inhibitor tofacitinib was launched for the treatment of ulcerative colitis(UC).Although tofacitinib has proven efficacious in patients with active UC,it failed in patients with Crohn’s disease(CD).This finding strongly hints at a different contribution of JAK signaling in both entities.Here,we review the current knowledge on the interplay between the JAK/signal transducer and activator of transcription(STAT)pathway and inflammatory bowel diseases(IBD).In particular,we provide a detailed overview of the differences and similarities of JAK/STAT-signaling in UC and CD,highlight the impact of the JAK/STAT pathway in experimental colitis models and summarize the published evidence on JAK/STAT-signaling in immune cells of IBD as well as the genetic association between the JAK/STAT pathway and IBD.Finally,we describe novel treatment strategies targeting JAK/STAT inhibition in UC and CD and comment on the limitations and challenges of the new drug class.

Assessment of stricturing Crohn's disease:Current clinicalpractice and future avenues

Crohn's disease(CD) is a chronic remittent idiopathic disease. Although the early phase of the disease is commonly characterized by inflammation-driven symptoms, such as diarrhea, the frequency of fibrostenotic complications in patients with CD increases over the long-term course of the disease. This review presents the current diagnostic options for assessing CD-associated strictures. In addition to the endoscopic evaluation of CD strictures, this review summarizes the currently available imaging modalities, including ultrasound and cross-sectional imaging techniques. In addition to stricture detection, differentiating between the primarily inflammatory strictures and the predominantly fibrotic ones is essential for selecting the appropriate treatment strategy(anti-inflammatory medical treatment vs endoscopical or surgical approaches). Therefore, recent imaging advances, such as contrast-enhanced ultrasound and ultrasound elastography, contribute to the development of noninvasive non-radiating imaging of CD-associated strictures. Finally, novel magnetic resonance imaging techniques, such as diffusion-weighted, motility and magnetization transfer imaging, as well as 18F-FDG PET/CT, molecular imaging approaches and biomarkers, are critically reviewed with regard to their potential role in assessing stricturing CD.

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.