MPI reveals MPI reveals injection route-dependent biodistribution of human mesenchymal stem cells in EAE mice

Magnetic particle imaging (MPI) enables real-time and quantitative tracking of magnetically labeled therapeutic cells with remarkable sensitivity and no tissue background. Human mesenchymal stem cells (hMSCs) possess potent immunomodulatory and regenerative effects in multiple sclerosis (MS), but their efficacy depends on precise delivery and homing to inflamed neural tissues. Using an experimental autoimmune encephalomyelitis (EAE) mouse model for MS, we dynamically tracked ferucarbotran-labeled hMSCs following four sequential intravenous (IV) or intra-arterial (IA) injections. Minute-timescale MPI acquisitions revealed that IV-injected cells were retained predominantly in the pulmonary space with gradual redistribution to the spleen and liver, consistent with remote immunomodulatory activity via splenic engagement. In contrast, IA delivery achieved immediate cerebral accumulation with strong brain signal and concurrent splenic uptake. These findings demonstrate route-dependent biodistribution patterns and confirm the usefulness of MPI for longitudinal assessment of stem cell delivery.