[A challenge towards the clinical application of induced pluripotent stem cell technology for the treatment of Parkinson's disease].

Parkinson's disease has been so far commonly treated with medication therapy. Although the medication works effectively in the initial phase, it turns out to be less effective at the later stage of the disease. Recently, induced pluripotent stem (iPS) cells have attracted much attention because of their potential to cure diseases such as Parkinson's disease. Due to the accumulating clinical experiences of cell transplantation procedures with aborted fetal tissues, Parkinson's disease has become one of the most promising targets for the clinical application of this iPS cell technology. In this review, we will summarize the ongoing research in the field of iPS cells and Parkinson's disease. The method for establishing iPS cells has advanced rapidly that can be applied in the clinical stage in terms of avoiding the use of viral vectors, xenogenic materials, etc. The differentiation protocol to derive the dopamine neurons from iPS cells has also been improved. However, several issues, such as the risk of tumor formation and the poor survival of the grafted dopamine neurons in vivo remain to be solved before these cells can be used in the clinical settings. Other than cell transplantations, iPS cell technology can also provide a valuable platform for disease analysis and drug development with in vitro systems of human cells. Several lines of iPS cells have already been established from Parkinson's disease patients with either sporadic or genetic background. For patients to achieve maximum benefits of this technology, further research must be conducted in both fields, that is, cell transplantation and the disease modeling with patient-derived iPS cells.