Cell therapy for central nervous system (CNS) diseases including stroke, traumatic brain injury, spinal cord injury, and Parkinson's disease are now shifting from "basic research" to "clinical trials and approved therapies". The results obtained from the clinical research promise to alleviate CNS damage which have long been considered as unrecoverable. Autologous bone marrow derived mesenchymal stem cell product "Stemirac" was approved for insurance-covered therapy against acute spinal cord injury under the new Japanese regulation, and many more clinical trials focused especially on ischemic stroke are currently executed in Japan. However, there persist several unsolved issues including ideal cell types, transplantation routes, transplantation timing, and types of disease, which need to be clarified to maximize the effect of cell therapy. Hence, it is important for neurosurgeons to understand the current status of stem cell therapy as a treatment for patients suffering from CNS diseases.
Stem cell therapy for central nervous system disorders have launched from basic research to the clinical trial phase. Many clinical trials are currently executed in Japan including ischemic stroke, traumatic brain injury, Parkingson's disease, and spinal cord injury. The preliminary data from these trials are promising and there is a strong expectation both from the medical and patient point of view. However, there are still so many unsolved questions which require further experimental procedures. The questions include cell types, transplantation route, transplantation timing and cell dosages. This article will highlight the basic knowledge of stem cell and the preliminary result of clinical trials launched in Japan.
In recent years, the clinical application of regenerative medicine using stem cells has been heralded as a new approach to the treatment of cerebral infarction. Our translational researches about bone marrow stromal cells (BMSC) transplantation for stroke was supported by Initiative for Accelerating Regulatory Science in Innovative Drug, Medical Device, and Regenerative Medicine, which is the fund from Ministry of Health, Labour and Welfare in Japan, from 2012. Our on-going clinical trial, Research on Advanced Intervention using Novel Bone marrOW stem cell (RAINBOW) study, is a phase Ⅰ study for acute ischemic stroke and the first subject was enrolled in June 2017. Autologous BMSCs were cultured with human platelet lysate (PL), instead of fetal calf serum (FCS), in the cell processing center. The cells were transplanted around the infarct stereotactically. In advance, the donor cells were labeled with superparamagnetic iron oxide (SPIO) for cell tracking using MRI. After the transplantation, 18F-fluorodeoxyglucose (FDG) PET and 123I-Iomazenil SPECT were performed for the analysis of cellular function and brain metabolism. We expect that our study will evolve the autologous BMSC transplantation for stroke into the next generation. In the present article, we report our experience from the point of view of mechanisms of actions and therapeutic strategy, nonclinical studies, and subject screening in the clinical trials.