Advances in induced Pluripotent Stem cell therapy for neurological diseases

Induced Pluripotent Stem (iPS) cells are regarded to be potential supply source of cells for application to cell replacement therapies. Recent scientific papers indicated that human iPS cells are capable of differentiating into glutamatergic neurons, dopaminergic neurons, and motor neurons. However, tumorigenesis in iPS cells is a serious problem which should be overcome for clinical application. Recently, we evaluated the influence of ischemic condition on undifferentiated iPS cells within a transient Middle Cerebral Artery Occlusion (MCAO) using a mouse model. Undifferentiated iPS cells (5 × 10⁵) were injected into the ipsilateral striatum and cortex, which were considered as the ischemic boundary zone at 24 hours after MCAO. Ischemic brains treated with iPS cells tended to form teratoma with larger volume compared with those in intact brains. c~Myc, Oct3/4 and Sox2 were strongly expressed in iPS-derived tumors of the ischemic brain. Above results indicated that the transcriptional factors integrated into the genome by retrovirus vectors might promote teratoma formation in the ischemic brain. Potential interaction between integrated transcriptional factors and iPS cell characteristics needs to be kept in mind, for the development of transplantation therapy.