Highly efficient endosomal labeling of progenitor and stem cells with large magnetic particles allows magnetic resonance imaging of single cells.

Kathleen A Hinds, Jonathan M Hill, Erik M Shapiro, Mikko O Laukkanen, Alfonso C Silva, Christian A Combs, Timothy R Varney, Robert S Balaban, Alan P Koretsky, Cynthia E Dunbar

Index: Blood 102(3) , 867-72, (2003)

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Abstract

Tracking transplanted stem cells using magnetic resonance imaging (MRI) could offer biologic insight into homing and engraftment. Ultrasmall dextran-coated iron oxide particles have previously been developed for uptake into cells to allow MRI tracking. We describe a new application of much larger, micron-scale, iron oxide magnetic particles with enhanced MR susceptibility, which enables detection of single cells at resolutions that can be achieved in vivo. In addition, these larger particles possess a fluorophore for histologic confirmation of cell distribution. We demonstrate highly efficient, nontoxic, endosomal uptake of these particles into hematopoietic CD34+ cells and mesenchymal stem cells documented by confocal and electron microscopy. Labeled cells retain biologic activity with preservation of colony-forming ability and differentiation capacity. MRI studies could detect labeled CD34+ cells and mesenchymal stem cells (MSCs) at single cell resolution. This appears to be a promising tool for serial noninvasive monitoring of in vivo cell homing and localization using MRI.