Cell tracking using magnetic resonance imaging

Abstract

Cell tracking by in vivo magnetic resonance imaging (MRI) requires strategies of labelling the cells with MRI contrast agents. The principal routes to achieve efficient cell labelling for neurological applications are discussed with methodological advantages and caveats. Beyond temporo-spatial localization of labelled cells, the investigation of functional cell status is of great interest to allow studies of functional cell dynamics. The two major approaches to reach this goal, use of responsive contrast agents and generation of transgenic cell lines, are discussed.

Figure 1. Macrophage activity at 6 days post-stroke induction in the rat brain

Comparison of in vivo T₂*-weighted MRI with Prussian blue tissue staining for iron content and ED1 immunohistochemistry for macrophage presence. A, coronal section through the edge of the ischaemic territory, depicting the cortical lesion as a dark area due to iron-rich macrophages covering the ischaemic lesion. B, Prussian blue tissue staining of the corresponding section and C, ED1 immunohistochemical staining. D and E show in vivo MRI and ED1 staining through the centre of the ischaemic lesion, resulting in a clearly demarcated macrophage lining at the surface of the lesion.

Figure 2. Migration of implanted stem cells towards the infarct

Above, in vivo MRI of USPIO-labelled stem cells after implantation into the hemisphere opposite to the stroke. Red arrows indicate stem cells migrating from the primary implantation sites (yellow arrows) along the corpus callosum (left image, at 6 days) towards the ischaemic borderzone (right image, at 8 days). Below, immunohistochemistry of the GFP-positive stem cells in the target zone at the lesion border. GFP staining shows morphological correlate of differentiated stem cells; double staining of GFP with NeuN for neurons or with GFAP for glia shows differentiation potential of implanted stem cells in the target area.