While the iPSCs technology holds the promise to becoming an efficient therapy for many neurodegenerative diseases that currently have no cure, there remains the risk of encountering multiple unanticipated outcomes when applying them on humans. The risks range from unwanted biological effects and immune response, toxicity, neoplasm formation, disease transmission, reactivation of latent viruses, to rejection of the cells by the body. It is difficult to determine and pinpoint the risks as they depend on several factors, including the cells that are used to achieve pluripotency, the status of the differentiated cells, their proliferation capacity, the technique of administration of the pluripotency genes, the level of manipulation, the growth factors used, the dilemma of retaining epigenetic memory, the intended site of injection, the reversibility or even irreversibility of the applied treatment, the susceptibility of the administered cells for disease, the incomplete suppression of the four transgenes after differentiation, the persistence of undifferentiated cells, and the survival of the transplanted cells in vivo (Okita et al., 2007). The known risks so far that were obtained mostly from animal models include tumor
