Quantitative Assessment of Inflammation in a Porcine Acute Terminal Ileitis Model: US with a Molecularly Targeted Contrast Agent

Abstract

Purpose:To evaluate the feasibility and reproducibility of ultrasonography (US) performed with dual-selectin-targeted contrast agent microbubbles (MBs) for assessment of inflammation in a porcine acute terminal ileitis model, with histologic findings as a reference standard. Materials and Methods:The study had institutional Animal Care and Use Committee approval. Acute terminal ileitis was established in 19 pigs; four pigs served as control pigs. The ileum was imaged with clinical-grade dual P-and E-selectin-targeted MBs (MB Selectin ) at increasing doses (0.5, 1.0, 2.5, 5.0, 10, and 20 3 10 8 MB per kilogram of body weight) and with control nontargeted MBs (MB Control ). For reproducibility testing, examinations were repeated twice after the MB Selectin and MB Control injections. After imaging, scanned ileal segments were analyzed ex vivo both for inflammation grade (by using hematoxylin-eosin staining) and for expression of selectins (by using quantitative immunofluorescence analysis). Statistical analysis was performed by using the t test, intraclass correlation coefficients (ICCs), and Spearman correlation analysis. Results:Imaging signal increased linearly (P , .001) between a dose of 0.5 and a dose of 5.0 3 10 8 MB/kg and plateaued between a dose of 10 and a dose of 20 3 10 8 MB/ kg. Imaging signals were reproducible (ICC = 0.70), and administration of MB Selectin in acute ileitis resulted in a significantly higher (P , .001) imaging signal compared with that in control ileum and MB Control . Ex vivo histologic grades of inflammation correlated well with in vivo US signal (r = 0.79), and expression levels of both P-selectin (37.4% 6 14.7 [standard deviation] of vessels positive; P , .001) and E-selectin (31.2% 6 25.7) in vessels in the bowel wall of segments with ileitis were higher than in control ileum (5.1% 6 3.7 for P-selectin and 4.8% 6 2.3 for E-selectin). Conclusion:Quantitative measurements of inflammation obtained by using dual-selectin-targeted US are reproducible and correlate well with the extent of inflammation at histologic examination in a porcine acute ileitis model as a next step toward clinical translation.q RSNA, 2015

US Molecular Imaging of Acute Ileitis: Anti-Inflammatory Treatment Response Monitored with Targeted Microbubbles in a Preclinical Model

“…US molecular imaging combines the advantages of US with those of molecular imaging by using molecularly targeted contrast agent microbubbles and has been recently translated to first-in-human clinical trials in cancer imaging (20,21). By targeting binding ligands to the microbubble shell that recognize inflammation markers that are overexpressed in patients with IBD such as P-selectin and Eselectin (22)(23)(24)(25), US molecular imaging allows quantitative assessment of inflammation in IBD at the molecular level at various anatomic sites after a single injection of molecularly targeted contrast agent (23)(24)(25)(26). Proof-of-principle studies have shown the feasibility of dual P-and E-selectin-targeted US molecular imaging for assessment of inflammation and excellent correlation with other molecular imaging techniques such as PET and histologic examination and immunofluorescence as reference standards in various rodent models of acute and acute-on-chronic IBD (24,25).…”

“…Proof-of-principle studies have shown the feasibility of dual P-and E-selectin-targeted US molecular imaging for assessment of inflammation and excellent correlation with other molecular imaging techniques such as PET and histologic examination and immunofluorescence as reference standards in various rodent models of acute and acute-on-chronic IBD (24,25). Recently, dual-selectin-targeted US molecular imaging has moved from rodent models to a large-animal model of acute ileitis in swine (23). However, to the best of our knowledge, no study has evaluated whether US molecular imaging using clinically translatable dual-selectin-targeted contrast agent microbubbles allows longitudinal monitoring of inflammation in a large-animal model of acute IBD in response to treatment as a next step toward clinical translation of this emerging technology.…”

“…IBD comprises ulcerative colitis and CD. A swine model of terminal ileitis has been developed for quantification of inflammation by using US molecular imaging in IBD (23). Therefore, the purpose of this study was to evaluate whether dual-selectin-targeted US molecular imaging allows longitudinal monitoring of anti-inflammatory treatment effects in an acute terminal ileitis model in swine.…”

Contrast-enhanced harmonic endoscopic ultrasound: Future perspectives

“…Leveraging the natural pathway of leukocyte rolling on inflamed vascular endothelial cells, a clinically translatable, dual-targeted contrast agent specific for the leukocyte adhesion molecules P- and E-select in has been shown to enable accurate quantification of inflammation in animal models of chemically induced colitis and ileitis. [1011]…”

Quantitative Ultrasound Molecular Imaging in Large Blood Vessel Environments

“…Myocardial ischemia was detected using P-selectin and/or E-selectin targeted microbubbles in a murine model [37], [38], [89], a rat model [90], [91], and a primate model [92]. Additionally, inflammatory bowel disease was imaged using Pselectin and E-selectin targeted microbubbles in a murine model [93], [94] and a swine model [95]. Dual-targeted microbubbles were utilized to further enhance targeting [40], [87]- [89], [91], [92], [94].…”