Rodent Leukocyte Isolation and Radiolabeling for Inflammation Imaging Study.

Purpose: The objective of this study was to describe to develop methods of rodent leukocyte isolation and radiolabeling for in vivo inflammation imaging.

Methods: Thigh muscle inflammation was induced by injection of collagenase. Blood was collected from the jugular vein and separated by Histopaque. The collected cells were incubated in a 37 °C CO incubator for 1~2 h. After incubation, Tc-HMPAO and F-FDG were used to treat leukocytes followed by incubation for 30 min. Tc-HMPAO and F-FDG labeled autologous leukocytes were injected into the tail veins of rats. The images were then acquired at various time points. Image-based lesion to normal muscle ratio was compared.

Results: After Histopaque separation, the proportion of lymphocytes was higher than that of other cell types. After CO incubation, the collected leukocytes were viable, while room temperature exposed leukocytes without CO incubation were non-viable. Granulocytes, especially, were more quickly influenced by various conditions than the mononuclear cells. Labeling efficiencies of Tc-HMPAO and F-FDG were 4.00 ± 2.06 and 1.8%, respectively. Tc-HMPAO- and F-FDG-labeled leukocytes targeted well the inflamed lesion. Tc-HMPAO-labeled leukocytes, but not F-FDG-labeled leukocytes, were found in the abdomen activity.

Conclusion: Inflamed lesions of rats were well visualized using autologous radiolabeled leukocytes. This method might provide good information for understanding inflammatory diseases.