Stem cell-based therapeutic possibilities have revolutionised medicine. In order to maximise clinical outcome, it is essential to use the optimal cell type and dosage, and cell infusion routes, as well as determine the post-transplantation homing and engraftment efficiency of infused cells. Tracking the fate of transplanted cells is pivotal to monitoring their viability and distribution to the target organ. Several labelling techniques are employed to trace transplanted cells in vivo. In rodents, magnetic-, fluorescence- or luminescence-based imaging methods have been developed and tested for their capacity to evaluate the engraftment of transplanted cells. The majority of these modes of in vivo cell tracking are still in the preclinical phase of investigation. Acquisition of reliable images depends on the specificity of the signal of the labels used at a certain tissue depth. While longitudinal analysis is feasible in preclinical models, and usually relies on histological or molecular analyses for its confirmation, this is still undoable in the clinical setting. Further research in molecular imaging approaches and in ways to follow the in vivo fate of injected cells in humans are required.
Keywords: Biodistribution, Bioluminescence, Biomarkers, Cell delivery route, Cell labelling, Cell tracking, Cornea, Engraftment, Extracellular vesicles, Fluorescence, Homing, Kidney, Liver, Magnetic resonance imaging, Mesenchymal stromal/stem cells, Molecular imaging, Nanoparticles-based tracking, Non-systemic cell delivery, Preclinical research, Systemic cell infusion.