Magnetic Resonance Imaging of Monocytes Labeled with Ultrasmall Superparamagnetic Particles of Iron Oxide Using Magnetoelectroporation in an Animal Model of Multiple Sclerosis

Infiltrated monocytes play a crucial role in the demyelination process during multiple sclerosis (MS), an inflammatory disease of the central nervous system (CNS). Still, methods to monitor their infiltration pattern over time are lacking. In this study, magnetoelectroporation (MEP) was used to label rat monocytes with the superparamagnetic iron oxide particles Sinerem, Endorem, and Supravist. Supravist-labeled monocytes were injected in rats that we induced with experimental autoimmune encephalomyelitis, a model for MS. Imaging at 4.7 and 9.4 T revealed multiple foci of decreased signal intensity predominantly located in the cerebellum. Immunohistochemical evaluation confirmed the presence of intracellular iron in infiltrated cells, indicating the suitability of MEP to specifically follow labeled monocytes in vivo in this disease model. This technique may be further optimized and potentially used in MS patients to assess monocyte migration into the brain and to monitor the efficacy of therapeutic agents aimed at blocking cellular migration into the CNS.