Comparison between direct and indirect labeling methods for monitoring cell trafficking

Objectives Cell trafficking with nuclear medicine modality can be quantitatively monitored biodistribution of radiolabeled cells. In this study, direct labeling method of cell surface proteins with ¹²⁵I sulfo-SHPP and HSV1-tk mediated indirect cell labeling method with ¹³¹I FIAU were comparatively investigated in vitro and in vivo for monitoring of human chronic myeloid leukemia cell.

Methods K562 was retrovirally transduced with HSV1-tk and luciferase. ¹²⁵I SHPP directly reacted with K562-TL cells. For indirect labeling, ¹³¹I FIAU was incubated with K562-TL. Two labeling methods were compared in vitro stability and viability. Biodistribution and bioluminescence imaging of direct and indirect labeled K562-TL performed in nude mice at 2 h and 24 h.

Results The radiolabeling yields of direct and indirect labelings were 7.5±0.4% and 49.5±3.6%. In vitro stability of direct and indirect labeling was 7% and 70% at 24 h. Viabilities of direct and indirect labeled cells were 95.0±3.1% and 98.8±1.4% at 24 h. Bioluminiscence signal was detected mainly in the lung at 2 h and was not detected at 24 h. At 2 h postinjection, direct and indirect labeled cells were predominantly accumulated in lung and liver, respectively. Direct labeled cells were localized in liver, lung and spleen,but indirect labeled cells were accumulated spleen and femur at 24 h.

Conclusions Radiolabeling yield and in vitro stability of indirect labeled cells were higher than those of direct labeled cells. Biodistribution of direct and indirect labeled cells were showed different patterns. These results suggest that proper labeling method should be considered to design the monitoring of cell trafficking.