A novel ¹⁹F agent for detection and quantification of human dendritic cells using magnetic resonance imaging

Monitoring of cell therapeutics in vivo is of major importance to estimate its efficacy. Here, we present a novel intracellular label for ¹⁹F magnetic resonance imaging (MRI)-based cell tracking, which allows for noninvasive, longitudinal cell tracking without the use of radioisotopes. A key advantage of ¹⁹F MRI is that it allows for absolute quantification of cell numbers directly from the MRI data. The ¹⁹F label was tested in primary human monocyte-derived dendritic cells. These cells took up label effectively, resulting in a labeling of 1.7 ± 0.1 × 10^{13 19}F atoms per cell, with a viability of 80 ± 6%, without the need for electroporation or transfection agents. This results in a minimum detection sensitivity of about 2,000 cells/voxel at 7 T, comparable with gadolinium-labeled cells. Comparison of the detection sensitivity of cells labeled with ¹⁹F, iron oxide and gadolinium over typical tissue background showed that unambiguous detection of the ¹⁹F-labeled cells was simpler than with the contrast agents. The effect of the ¹⁹F agent on cell function was minimal in the context of cell-based vaccines. From these data, we calculate that detection of 30,000 cells in vivo at 3 T with a reasonable signal to noise ratio for ¹⁹F images would require less than 30 min with a conventional fast spin echo sequence, given a coil similar to the one used in this study. This is well within acceptable limits for clinical studies, and thus, we conclude that ¹⁹F MRI for quantitative cell tracking in a clinical setting has great potential.