Dedicated Pinhole SPECT of Intestinal Neutrophil Recruitment in a Mouse Model of

Evaluating the efficacy of therapy in experimental inflammatory bowel disease (IBD) requires information about inflammatory ac-tivity in bowel segments or leukocyte recruitment and about kinet-ics in the follow-up of treatment. This study evaluated a noninva-sive scintigraphic technique able to assess neutrophil trafficking in a mouse model of dextran sulfate sodium (DSS)–induced colitis. Methods: Groups of 4 BALB/c mice were assessed at baseline and after 1, 3, 5, and 8 d of treatment with DSS. Donor neutrophils were harvested by rinsing of the peritoneal cavity with phosphate-buffered saline 5 h after intraperitoneal injection of proteose peptone contained in phosphate-buffered saline and labeled with freshly prepared 99mTc-hexamethylpropylene amine oxime (HMPAO). Pinhole SPECT of the abdomenwas performed 1 h after reinjection of 50 MBq of labeled neutrophils. In addition, the se-verity of inflammation was determined by histologic examination. The possibilities of the technique were illustrated by scintigraphic assessment of neutrophil trafficking with and without blocking of neutrophil migration by a CD97 monoclonal antibody in mice with DSS-induced colitis. Results: Colonic uptake of 99mTc-HMPAO neutrophils was determined with dedicated animal pinhole SPECT inmice with DSS-induced colitis and correlated well with histologic findings (R 0.81) and wet colon weight (R 0.87) and moder-ately with clinical weight loss (R 0.62). The neutrophil uptake ratio was reduced significantly (P 0.01) by blocking of neutrophil migration capacity with the CD97 antibody. Conclusion: Animal pinhole SPECT can be used to study inflammatory activity and neutrophil recruitment in vivo in experimental colitis