Comparison of MR images and histochemical localization of intra-arterially administered microglia surrounding beta-amyloid deposits in the rat brain.

The therapeutic use of microglial cells has recently received some attention for the treatment of Alzheimer disease (AD), but few non-invasive techniques exist for monitoring the cells after administration. Here we present a magnetic resonance imaging (MRI) technique for tracking microglia injected intra-arterially in vivo. We micro-injected Abeta42 into the left hippocampus and saline into the right hippocampus of rats. We then administered microglia, which were labeled with enhanced green fluorescent protein (EGFP) gene and Resovist, into the carotid artery. After monitoring exogenously administered microglia using MRI, we compared the MR images and the histochemical localization of administered microglia. MRI revealed clear signal changes attributable to Resovist-containing microglia in Abeta-injected areas. Histochemistry demonstrated that EGFP-positive microglia accumulated around Abeta deposits and internalized the peptide. This study demonstrates the usefulness of MRI for non-invasive monitoring of exogenous microglia, and suggests a promising future for microglia/macrophages as therapeutic tools for AD.