Quantitative Dynamic Monitoring of MSCs and MSC-EVs in a Mouse Model of Intracerebral Hemorrhage

Summary Intracerebral hemorrhage (ICH) poses a severe threat as the deadliest form of stroke, and effective treatments to repair the brain damage safely and permanently are yet to be established. Mesenchymal stem cell (MSC)- based therapies show promise by regulating the immune system and facilitating tissue regeneration in ICH affected brain. Recent studies underscore that the primary therapeutic benefits of MSCs come from their paracrine activity, particularly via extracellular vesicles (MSC-EVs). Unlike MSCs, MSC-EVs are much smaller (~40-200 nM) and possess the ability to breach the blood-brain barrier, delivering beneficial factors for nerve growth and immune modulation. Despite recognizing the therapeutic potential of both MSCs and MSC-EVs, understanding their unique behaviors and distribution within affected ICH regions remains incomplete. Moreover, once delivered safe and sensitive methods for precise tracking cells/EVs in vivo, are lacking. So far, the clinical trials for MSC therapy for ICH have been unable to draw clear conclusions about the efficacy of MSCs due to protocol inconsistencies (routes of administration, doses, frequencies, etc.). In addition, the distinct benefits of cell free (EV-based) interventions over whole cells in treating severe conditions such as ICH are not fully explored, which has further hindered advancement of cell/cell-free ICH therapies. To ensure optimal therapy, accurate mapping of the dosage based on actual biodistribution of cells/EVs in the brain and the therapeutic effectiveness of chosen administration routes is crucial. Non-invasive and quantitative monitoring of cells and EVs administered by different routes would help neurologists adjust delivery parameters and monitor immediate cell and EV dispersion to achieve optimal biodistribution profiles. Our proposed study aims to investigate Magnetic Particle Imaging (MPI) which is gaining ground as a promising 'cold' imaging technique to precisely map the distribution of Ultrasmall superparamagnetic iron oxide (USPIO) labeled MSCs and MSC-EVs in an ICH mouse model. Leveraging the high sensitivity of MPI, we seek to quantitatively assess the biodistribution of MSCs and MSC-EVs post-delivery via intravenous, intranasal, and intra-arterial routes while achieving anatomical co-registration through computed tomography (CT). Dynamic in vivo MPI of MSCs and MSC-EVs post-delivery via various routes, can provide insights into their in vivo migration (homing), report on delivery accuracy (on or off target), persistence in tissues, blood and tissue lifespan, as well as elimination pathways, all of which are critical for advancing clinically relevant cell and cell free ICH therapies in clinic.