In Vivo Cellular Magnetic Imaging: Labeled versus Unlabeled Cells

摘要

Superparamagnetic iron oxide (SPIO)-labeling of cells has been applied formagnetic resonance imaging (MRI) cell tracking for over 30 years, havingresulted in a dozen or so clinical trials. SPIO nanoparticles are biodegradableand can be broken down into elemental iron, and hence the toleranceof cells to magnetic labeling has been overall high. Over the years, however,single reports have accumulated demonstrating that the proliferation,migration, adhesion, and differentiation of magnetically labeled cells maydiffer from unlabeled cells, with inhibition of chondrocytic differentiationof labeled human mesenchymal stem cells (hMSCs) as a notable example.This historical perspective provides an overview of some of the drawbacksthat can be encountered with magnetic labeling. Now that magneticparticle imaging (MPI) cell tracking is emerging as a new in vivo cellularimaging modality, there has been a renaissance in the formulation of SPIOnanoparticles this time optimized for MPI. Lessons learned from the occasionalpast pitfalls encountered with SPIO-labeling of cells for MRI mayexpedite the possible future clinical translation of (combined) MRI/MPI celltracking.