Quantification and Monitoring of Inflammation in Murine Inflammatory Bowel Disease with Targeted Contrast-enhanced US

Purpose: To evaluate ultrasonography (US) by using contrast agent microbubbles (MBs) targeted to P-selectin (MB P-selectin ) to quantify P-selectin expression levels in infl amed tissue and to monitor response to therapy in a murine model of chemically induced infl ammatory bowel disease (IBD). Materials and Methods: All procedures in which laboratory animals were used were approved by the institutional administrative panel on laboratory animal care. Binding affi nity and specifi city of MB P-selectin were tested in cell culture experiments under fl ow shear stress conditions and compared with control MBs (MB Control ). In vivo binding specifi city of MB P-selectin to P-selectin was tested in mice with trinitrobenzenesulfonic acid–induced colitis ( n = 22) and control mice ( n = 10). Monitoring of anti–tumor necrosis factor a antibody ther- apy was performed over 5 days in an additional 30 mice with colitis by using P-selectin-targeted US imaging, by measuring bowel wall thickness and perfusion, and by us- ing a clinical disease activity index score. In vivo targeted contrast material–enhanced US signal was quantitatively correlated with ex vivo expression levels of P-selectin as assessed by quantitative immunofl uorescence. Results: Attachment of MB P-selectin to endothelial cells was signifi - cantly ( P = .0001) higher than attachment of MB Control and signifi cantly ( r = 0.83, P = .04) correlated with expression levels of P-selectin on endothelial cells. In vivo US signal in mice with colitis was signifi cantly higher ( P = .0001) with MB P-selectin than with MB Control . In treated mice, in vivo US signal decreased signifi cantly ( P = .0001) compared with that in nontreated mice and correlated well with ex vivo P-selectin expression levels ( r = 0.69; P = .04). Co- lonic wall thickness ( P > .06), bowel wall perfusion ( P > .85), and clinical disease activity scoring ( P > .06) were not signifi cantly different between treated and nontreated mice at any time. Conclusion: Targeted contrast-enhanced US imaging enables noninvasive in vivo quantifi cation and monitoring of P-selectin expres- sion in infl ammation in murine IBD.