Yingwei Wu MD, Presenter: Nothing to Disclose

Karen Briley-Saebo PhD, Abstract Co-Author: Nothing to Disclose

Xiaofeng Tao MD, PhD, Abstract Co-Author: Nothing to Disclose

Nanxin Hao, Abstract Co-Author: Nothing to Disclose

To evaluate the feasibility of MR imaging to depict the in vivo recruitment of superparamagnetic iron oxide (SPIO)-labeled macrophages in inflammatory bowel disease(IBD) and identify disease activity.

This study was approved by the institution's committee on animal research. Fifteen C57/B6 Dextran Sulfate Sodium-induced (DSS-induced) IBD mice and fifteen control C57/B6 mice were included in this study. Clinical disease activity score and pathology disease score was identified with each mouse in two groups under standrad creteria. Peritoneal macrophages were harvested from thioglycollate-treated C57/B6 mice, cultured, and labeled with SPIO. The labeling efficacy of the macrophages was determined by measuring the total iron content using inductively coupled plasma mass spectrometry The sensitivity of the MR method was tested using ex-vivo macropahge phantoms. 5 x 106 of SPIO-labeled macrophages was administered through the tail vein in each group. Each subgroup with 5 mice was imaged on a 9.4-T MR imager 0,4,24 hours after macrophage administration. Regions-of-interest were drawn on the intestinal area.The signal intensity of each pixel was normalized to the standard deviation of adjacent noise prior to linear fitting of the signal-to-noise ratio versus echo time.R2* fitting was performed on a pixel-by-pixel basis.Difference of signal intensity of between two groups and timepoints was compared and ROC analysis was performed based on clinical and pathology disease score. 

Ex-vivolly,ICP-MS revealed strong Feridex uptake (7.4 pg Fe/cell) by the macrophage. Good correlation between the R2* values and cell number was observed ex-vivo (R2=0.9938).Invivoly,a low-Signal intensity(SI) zone was predominantly seen in bowel wall of DSS group mice both 4and 24 hours after SPIO-labeled macrophage administration. Prussian blue staining also showed SPIO labeled macrophage recruitment inintestinal epithelium 4 hours after its administration.  Lower SI was revealed in DSS mice than in control mice(p<0.01). SI had good correlation both with IBD clinical and pathology activity scores with the coefficient of 0.31 and 0.39respectively.

This study demonstrates that intravenously administered SPIO-labeled macrophages can be used in evaluating IBD disease activity.

MR tracking SPIO labeled macrophages can detect inflammation and is recommended in the initial evaluation of inflammatory disease.

Wu, Y, Briley-Saebo, K, Tao, X, Hao, N, MR Tracking SPIO-labeled Macrophages in Monitoring Inflammatory Bowel Disease (IBD) and Evaluating Disease Activity.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11009668.html