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Establishment of more efficient and safer methods for clinical-grade iPS cells

To realize the above aim, we will study on the following items.

  1. Development of the methods for iPS cell generation without retroviral vector
  2. Comparative analysis of human iPS cells and ES cells
  3. Verification of the safety of human iPS cells
  4. Analysis of the pathophysiological mechanism of incurable diseases and development of new drugs and therapy by disease models derived from patient iPS cells


We generated induced pluripotent stem cells (iPSCs) by introducing 4 genes (Oct3/4, Sox2, Klf4 and c-Myc) into mouse fibroblasts in 2006, and subsequently generated human iPSCs by the same method in 2007. iPSCs have similar characteristics to ES cells, such as morphology, proliferation, gene expression and epigenetic states. iPSCs can differentiate into 3 germ layers in vitro and produce teratoma in vivo. Mouse iPSCs give rise to adult chimeric mice that were competed germline transmission. These results indicated that mouse iPSCs had the same level of pluripotency as mouse ES cells. For human iPSCs, there are no “gold standards” confirming the contribution to chimerism or germline-competence. It should be elucidated whether human iPSCs possess the similar pluripotency to human ES cells.

Before clinical application, safety of human iPSCs should be confirmed. In fact, both chimera mice and progenies derived mouse iPSCs have increased incidence of tumor formation, due primarily to reactivation of c-Myc retroviruses. We created mouse iPSCs without the c-Myc retroviruses and chimera mice derived from these c-Myc minus iPSCs did not demonstrate the increased incidence of tumor formation, however, efficiency of iPSCs generation were significantly lower without c-Myc retrovirus. Chimera mice derived from c-Myc minus iPSCs exhibited slightly higher mortality, but not tumorgenicity, and the cause of death remained to be determined.

Not a few patients suffer from incurable diseases. Since iPSC technique is established, we can generate disease-tissues, which were unable to obtain before, from the patient derived iPSCs. By using the disease models from patient specific iPSCs, we may elucidate the pathophysiological mechanism of the disease, leading to the drug discovery and development of the therapy.

Possible Achievement:

  1. We may develop more effective and safer methods for clinical grade iPSCs by selecting non-integrating vectors, best combination of reprogramming factors, and suitable culture conditions.
  2. Noble comparison studies between iPSCs and ES cells enable us to select the best iPSCs, resulting in standardization of the safe iPSCs selection procedures.
  3. The safety and quality of human iPSCs must be assessed by large animals such as monkey and pigs in long terms, while short term studies in mice were somewhat confusing. As advancing researches, we will develop MHC homozygotes and/or SCID animals in these species for transplantation studies. By using these animals, safety assessment of human iPSCs may become more reliable, accelerating the clinical application.
  4. We may get disease-tissues from patient derived iPSCs, thereafter, we will be able to elucidate the pathophysiological mechanisms and/or adverse molecular pathway of the disease, leading to drug discovery and new therapy. We may also develop effective differentiation methods of iPSCs to the nominating specific tissues for regenerative medicine.