Ex vivo cell labeling with ⁶⁴ Cu–pyruvaldehyde-bis( N ⁴ -methylthiosemicarbazone) for imaging cell trafficking in mice with positron-emission tomography

Abstract

We have used copper-64-pyruvaldehyde-bis( N 4 -methylthiosemicarbazone) ( 64 Cu–PTSM) to radiolabel cells ex vivo for in vivo positron-emission tomography (PET) imaging studies of cell trafficking in mice and for eventual application in patients. 2-[ 18 F]-Fluoro-2-deoxy- d -glucose (FDG) cell labeling also was evaluated for comparison. 64 Cu–PTSM uptake by C6 rat glioma (C6) cells increased for 180 min and then stabilized. The labeling efficiency was directly proportional to 64 Cu–PTSM concentration and influenced negatively by serum. Label uptake per cell was greater with 64 Cu–PTSM than with FDG. However, both 64 Cu–PTSM- and FDG-labeled cells showed efflux of cell activity into supernatant. The 64 Cu–PTSM labeling procedure did not interfere significantly with C6 cell viability and proliferation rate. MicroPET images of living mice indicate that tail-vein-injected labeled C6 cells traffic to the lungs and liver. In addition, transient splenic accumulation of radioactivity was clearly detectable in a mouse scanned at 3.33 h postinfusion of 64 Cu–PTSM-labeled lymphocytes. In contrast, the liver was the principal organ of tracer localization after tail-vein administration of 64 Cu–PTSM alone. These results indicate that in vivo imaging of cell trafficking is possible with 64 Cu–PTSM-labeled cells. Given the longer t 1/2 of 64 Cu (12.7 h) relative to 18 F (110 min), longer cell-tracking periods (up to 24–36 h) should be possible now with PET.

In vivo tracking of genetically engineered, anti-HER2/neu directed natural killer cells to HER2/neu positive mammary tumors with magnetic resonance imaging

“…Cell tracking with MR imaging has a well known limited sensitivity compared to cell labeling techniques with radioactive tracers (14)(15)(16)(17). Further studies have to show, if our labeling method is sensitive enough for potential clinical applications.…”

“…In addition to be tailored to specific properties of already transfected NK cells, our technique provides potential advantages compared to previously described techniques for labeling of other cell types with radioactive, fluorescent or (super-) paramagnetic markers (14)(15)(16)(17)(18)(19)(20). Our MR labeling technique is noninvasive, easy to apply, less toxic (no radiotoxic cell damage) and provides 3D imaging data with high anatomical resolution.…”

“…Currently available cell labeling techniques are based on radioactive, fluorescent or (super-)paramagnetic markers (14)(15)(16)(17)(18)(19)(20)(21). Labeling techniques with radioactive markers provide a high sensitivity but limited spatial resolution and the risk of radiotoxic cell damage (14)(15)(16)(17).…”

“…Labeling techniques with radioactive markers provide a high sensitivity but limited spatial resolution and the risk of radiotoxic cell damage (14)(15)(16)(17). Labeling techniques with fluorescent markers provide a high sensitivity, but limited anatomical resolution and are currently restricted to experimental applications (18,19).…”

Migration, fate and in vivo imaging of adult stem cells in the CNS

“…Several techniques for in vivo cellular imaging are now available that allow the characterization of transplanted cells in the living organism, including magnetic resonance imaging (MRI), 23 bioluminescence, 24 positron emission tomography 25 and multiple photon microscopy. 26 All of these imaging methods, based on different principles, provide distinctive, usually complementary information.…”