Commemorative Lectures

Research on generating tissues and organs lost as a result of illness or injury has been conducted for several decades. Human embryonic stem (ES) cells, as first reported 12 years ago, have a pluripotent differentiation ability and a high capacity for proliferation, and they are capable of generating cells for any tissues and organs. There have been high expectations that this regenerative medicine will play a significant role in curing numerous intractable diseases. However, there have been underlying issues, such as ethical issues, concerning the sacrifice of fertilized eggs to generate ES cells as well as challenges relating to adverse rejections when the cells are transplanted into a human body. In order to avoid these issues, we embarked on research to generate embryonic-like stem cells from differentiated cells. After several years of research, with the introduction of merely four genes – Oct3/4, Sox2, Klf4, and c-Myc, we successfully derived induced pluripotent stem (iPS) cells from the skin fibroblasts of a mouse, which was reported in the journal Cell in 2006 for the first time in the world. We also reported the generation of iPS cells from human skin fibroblasts in 2007. Because the established iPS cells from patients have similar characteristics to those of ES cells, iPS cell technology has an enormous potential. It is expected that iPS cells will assist in unraveling the mechanisms for numerous diseases that have challenged researchers, in searching for new drugs, as well as in evaluating both drug effectiveness and adverse effects. Moreover, iPS cells may become a promising source of cell transplant treatments for such diseases as myocardial infarction, diabetes, spinal cord injury, and Parkinson's disease once the clinical safety of the cells are confirmed and other problems are solved. Studies confirm that iPS cells have been successfully established from Japanese people of varying ages, and no significant differences have been found among them in terms of pluripotency. However, from the viewpoint of cell transplantation treatment, challenges still remain concerning time saving for cell generation and cost reduction, not to mention establishing protocols to generate clinical-grade iPS cells. We plan to produce iPS cells from donors having various transplantation matching adaptabilities, and to set up an “iPS cell bank for regeneration medicine.” Today, researchers at many universities and corporations around the world are participating in iPS cell research, and cell generation methods are rapidly improving. It has been reported that iPS cells have been used to differentiate cells for tissues and organs such as nerves, cardiac muscle, and blood. In the new research building recently completed at Kyoto University, thanks to the extended support of many people, we would like to dedicate our full strength and effort for the next 10 years to develop a new medical science based on iPS cells.