Intracellular Labeling of Pluripotent Stem Cell-Derived Neural Progenitor Aggregates with Micron-Sized Particles of Iron Oxide for Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) can be used to assess the fate of the transplanted stem cells, including the neural progenitor cells (NPC) derived from pluripotent stem cell (PSC), in the injured nervous system.  NPCs are usually derived from PSCs through the formation of embryoid body (EB), and 3D multicellular structures have been maintained to enhance the function of PSC-derived neural cells.  This study investigated the effect of labeling multicellular EB-NPC aggregates with micron-sized particles of iron oxides (MPIO) for MRI.  While labeling and tracking single stem cells have been demonstrated for MPIO, the ability to label multicellular aggregates and consequences on cellular effects have yet to be characterized fully.  In this study, intact and dissociated EB-NPC aggregates were labeled with various concentrations of MPIOs and analyzed by fluorescent imaging, flow cytometry and in vitro MRI for labeling efficiency and detectability.  Moreover, the effects of MPIO on cell viability, cytotoxicity, proliferation and neural differentiation were evaluated.  MPIO incorporation did not affect the proliferation and neural differentiation of EB-NPCs.  However, intact EB-NPC aggregates showed higher cell proliferation and viability compared to the dissociated cells.  Despite diffusion limitation at low MPIO concentration, higher concentrations of MPIO (i.e. 10 μg Fe/mL) were able to label EB-NPC aggregates at similar efficiency to the dissociated cells.  In vitro MRI showed efficient MPIO detection over 2-3 population doublings.  This study demonstrated the feasibility of using MPIO to label EB-NPC aggregates for future animal study.