Highly efficient paramagnetic labelling of embryonic and neuronal stem cells.

Recent developments in stem cell and gene therapy will require methods to monitor stem cell survival and integration repeatedly and non-invasively with a high temporal and spatial resolution in vivo. The aim of this study was to visualise embryonic and neuronal stem cells with standard contrast agents using a conventional clinical 1.5-Tesla scanner. We therefore modified standard transfection protocols including lipofection (Lipofectin and Lipofectamine) and calcium phosphate transfection for the efficient uptake of paramagnetic particles [gadolinium-diethylene triamine penta-acetic acid (Gd-DTPA)] in stem cells. Using this approach we obtained intracellular labelling efficiencies of up to 83%. Neither the proliferation capacity nor the differentiation efficiency was affected. Identical differentiation of labelled and unlabelled embryonic and neuronal cells was observed. The established labelling techniques used in this study displayed high labelling efficiencies in embryonic and neuronal stem cells without any alterations of cellular biology; therefore this approach might be a suitable method for targeting stem cells.