(601h) Cryopreservation of Pluripotent Stem Cell-Derived Neural Progenitor Aggregates Labeled with Iron Oxide Particles for MRI Analysis

Clinical applications of neural progenitor cells (NPCs) require large quantities of cells which can be obtained through pluripotent stem cell (PSC) expansion, differentiation, and cryopreservation.  Magnetic resonance imaging (MRI) provides an effective approach to track the labeled NPCs for neural transplantation and neurological disorder treatments.  However, labeling the cryopreserved NPCs after thaw can be limited by the inefficient intracellular labeling and variations in labeling efficiency.  Therefore, cryopreservation of the pre-labeled NPCs can offer the uniform cell population and operational convenience for the following in vivo transplantation.  In this study, the feasibility of cryopreserving PSC-derived NPC aggregates labeled with micron-sized particles of iron oxide (MPIO) was investigated.  The NPC aggregates were derived from embryoid body formation and were labeled with different concentration of MPIO in the range of 0 to 100 μg Fe per mL.  The MPIO-labeled cell survival, proliferation, cytoskeleton distribution, cytotoxicity, the level of oxidative stress, and neural differentiation were evaluated before and after cryopreservation.  The results indicated that intracellular MPIO incorporation was retained after cryopreservation (70-80% labeling efficiency), which did not significantly affect the cell recovery, proliferation, cytotoxicity and neural lineage commitment.  The labeled cells maintained similar pattern of cytoskeleton distribution and the expression level of oxidative stress compared to non-labeled cells.  MRI analysis was performed in the phantom tissue environment containing cell layers with different MPIO exposures separated by agarose gels.  The results showed comparable detectability for the MPIO-labeled cells before and after cryopreservation indicated by T2 and T2* relaxation rates.  These findings indicate the feasibility of cryopreserving MPIO-labeled PSC-derived NPC aggregates for potential large scale banking toward various in vitro and in vivo studies.