Visualization of the Superparamagnetic Iron Oxide (SPIO)-Labeled Bone Marrow Stromal Cells Using a 3.0-T MRI—a Pilot Study for Clinical Testing of Neurotransplantation

Recent studies have elucidated that transplantation of the bone marrow stromal cells (BMSC) has therapeutic potential for the central nervous system (CNS) disorders. However, no imaging modalities have been established to track the engrafted cells in the CNS in clinical situation. This study aimed to investigate the ability of magnetic resonance imaging (MRI) to visualize the BMSC labeled with superparamagnetic iron oxide (SPIO). The BMSC of mice were labeled with SPIO. Various numbers of the cells were injected into the agar phantom and were visualized using a 3.0-T MR apparatus. The SPIO-labeled cells were injected into the temperature-sensitive gelation polymer (TGP) hydrogel and were cultured for 7 days. They were also visualized just after the injection and at 7 days postinjection. After a 7-day culture, they were stained with Turnbull blue technique. T2-, T2*-, and susceptibility-weighted imaging could identify minimally 1,000 cells in the agar or TGP hydrogel, although it was difficult to quantify their number on MRI. All of these sequences could track the SPIO-labeled BMSC for at least 7 days when injected into the TGP. Turnbull blue staining revealed the survival and proliferation of the SPIO-labeled BMSC in the TGP for 7 days. The findings strongly suggest that the SPIO labeling may enable to track minimally 1,000 cells engrafted in the CNS on clinical MR apparatus. These data would be valuable to consider the application of imaging technique into cell transplantation therapy for CNS disorders.