Nucl Med Mol Imaging.  2020 Jun;54(3):147-155. 10.1007/s13139-020-00645-8.

Rodent Leukocyte Isolation and Radiolabeling for Inflammation Imaging Study

• Kim EM
• Oh PS
• Boud F
• Jeong HJ
• Lim ST
• Sohn MH

• KMID: 2507687
• DOI: http://doi.org/10.1007/s13139-020-00645-8

Abstract

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 CO₂ incubator for 1~2 h. After incubation, ^99mTc-HMPAO and ¹⁸F-FDG were used to treat leukocytes followed by incubation for 30 min. ^99mTc-HMPAO and ¹⁸F-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 CO₂ incubation, the collected leukocytes were viable, while room temperature exposed leukocytes without CO₂ incubation were non-viable. Granulocytes, especially, were more quickly influenced by various conditions than the mononuclear cells. Labeling efficiencies of ^99mTc-HMPAO and ¹⁸F-FDG were 4.00 ± 2.06 and 1.8%, respectively. ^99mTc-HMPAO- and ¹⁸F-FDG-labeled leukocytes targeted well the inflamed lesion. ^99mTc-HMPAO-labeled leukocytes, but not ¹⁸F-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.

Keyword

Cell isolation; Radiolabeled leukocytes; Inflammation; ^99mTc-HMPAO; ¹⁸F-FDG