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1. Elucidation of regulatory mechanisms underlying self-renewal and differentiation of hematopoietic stem cells

Keywords: hematopoietic stem cell(s), self-renewal, differentiation, asymmetric division, development/p>

Elucidation of regulatory mechanisms underlying self-renewal and differentiation of hematopoietic stem cells

Our studies focus mainly on investigation of stem cell biology using the hematopoietic stem cell (HSC) as a research model. Recent identification of a variety of stem cell sources including embryonic and somatic (tissue-specific) stem cells has brought about substantial progress in the field of stem cell research. The HSC represents the first stem cell for which identity and existence were determined. Studies on HSCs have provided us with some basic concepts applying to different types of stem cells, yet many of these concepts remain unverified. It therefore is very important to continue basic studies to answer many questions left unsolved and thus to permit contributions to the field of biological research and clinical medicine. HSCs are capable of continuous supply of all lineages of blood cells to each individual for his or her entire life. Both self-renewal and multilineage differentiation potentials enable this task. One major advantage in HSC research lies in that established assay systems allow clonal analysis of each individual stem cell. Using a defined assay system, we can test capabilities of self-renewal and multilineage differentiation at single cell levels using either in vitro or in vivo assays (see Figure 1). We believe that HSC research will eventually make great contributions to the development of safe and efficacious regenerative medicine and gene therapy.

1) Elucidation of molecular mechanisms underlying asymmetrical self-renewal division.

Multicellular organisms depend on asymmetrical cell division, in the process of development, to form every element of their bodies, which are composed of a wide variety of cell types. It is thought that HSCs also utilize asymmetrical division to produce different lineages of hematopoietic cells. HSCs, however, need to self-renew in order to maintain their stem cell compartment. These two tasks can be achieved simultaneously only by asymmetrical self-renewal divisions. We for the first time successfully reproduced in vitro the event of asymmetrical self-renewal division in HSCs. One of our continuous efforts is to elucidate, utilizing established experimental systems, the molecular mechanisms that enable both self-renewal and multilineage differentiation in HSCs.

2 Research on the developmental process of HSCs

Although the HSC pool is known to increase markedly during embryonic development, the precise mechanisms regulating this process remain largely unknown. We think it important to make clear the developmental processes of HSCs, because to do so will culminate in the development of methods to amplify HSCs ex vivo on demand. We have recently identified the step-wise differentiation process from embryonic stem cells to adult-type HSCs. Using this model system, we are now attempting to clarify spatio-temporal patterning of HSC development in a mouse body.

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2. Development of Blood Transfusion System Using iPS Cells Without Donor Blood

Keywords: iPS Cells, integrin

Development of Blood Transfusion System Using iPS Cells Without Donor Blood

Elucidation of the underlying mechanisms by which stemness and quiescence of hematopoietic stem cells are maintained, which may be useful for induction in vitro of differentiation and retention of human iPS cell-derived hematopoietic stem cells.

We are engaging in basic research on the generation of blood cells, including hematopoietic stem cells, platelets, and red blood cells, in vitro from human ES cells / human iPS cells. The research program aims, first, at the development of safe and stable blood supplies for transfusion independently of blood donation and, second, of gene therapy using established hematopoietic stem cells derived from human iPS cells with an appropriate validation. In addition, a recent aim of the program is the elucidation of molecular mechanisms through which quiescence is maintained by mouse and human hematopoietic stem cells, particularly those mediated through adhesion/integrin signaling, which may be useful in vitro for induction and retention of human iPS cell-derived hematopoietic stem cells.

*This division moved to Kyoto Univ. in 2011.

 http://www.cira.kyoto-u.ac.jp/j/research/eto_summary.html

 

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3. Stem cell biology research aiming at development of HSC transplantation medicine with enhanced safety and efficacy

Keywords: hematopoietic stem cell transplantation, gene therapy, graft versus host disease (GVHD), primary immunodeficiency, induced pluripotent stem cells

Stem cell biology research aiming at development of HSC transplantation medicine with enhanced safety and efficacy

Hematopoietic stem cell (HSC) transplantation (HSCT) is the currently available curative treatment for various intractable disorders including genetic diseases, such as primary immunodeficiency, and hematological malignancies, exemplified by leukemias. For genetic disorders, transplantation of autologous HSCs after ex vivo genetic correction has also been carried out in substantial numbers of patients. This form of HSCT is called "stem cell gene therapy". I have personal experience in treating patients with adenosine deaminase deficiency using this type of gene therapy at Hokkaido University. Clinical experience and the knowledge obtained from extensive basic research, however, bear witness that the HSCT medicine must still be much improved to realize ideal treatment measures. This situation has prompted us to continue with research projects, sketched below, to enable the development of transplantation medicine with minimum risk and maximum efficacy. We are curently making significant progress in these studies by utilizing of the abundance of knowledge and experience in HSC biology that has been accumulated in this laboratory.

  • 1) Research attempting improvement in allogeneic HSCT and stem cell gene therapy using murine models of human genetic diseases.
  • 2) Elucidation of the mechanisms underlying graft failure in HSCT and establishment of measures to improve HSC engraftment/repopulation.
  • 3) Establishment of new-generation gene therapy for genetic diseases using induced pluripotent stem cells.

Our ambition is to carry on our own research with high expectancy of results that can be translated into clinical use. Our eventual plan is to proceed through preclinical studies to clinical trials of improved HSCT by making use of the findings obtained from current projects.

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4. Development of Stem Cell Therapy against hematopoietic Disorders

Development of Stem Cell Therapy against hematopoietic Disorders

Our main goal is to establish new strategies such as cell-based immune therapy, gene therapy, and molecular targeting therapy against hematology-oncology related diseases (malignancies, opportunistic infections, autoimmune diseases, and transplantation-related diseases) through genetic manipulation of T-lymphocytes, hematopoietic stem cells, and pluripotent stem cells. Four research projects from bench to bedside are on-going, each shouldering a part of the objective.

  • (1) Regeneration of T-cell immunity by induction of monoclonal T-lymphocytes from iPS cells derived from antigen-specific T-lymphocytes.
  • (2) Development of a myeloproliferative neoplasm murine model by transferring highly purified hematopoietic stem cells genetically modified in respect of cell signaling.
  • (3) Exploitation of the herpes simplex virus thymidine kinase and FDA-approved prodrug ganciclovir-mediated cell-suicide gene therapy system to maximize the safety of clinical pluripotent stem cell therapy.
  • (4) Phase I/II clinical trial "Suicide-gene-modified donor central-memory T-lymphocyte infusion therapy for leukemia patient with relapse after allogeneic hematopoietic stem cell transplantation."

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5. Molecular mechanisms regulating proliferation and differentiation of hepatic stem and progenitor cells during liver development.

Keywords: fetal liver development, liver regeneration, hepatoblasts, cell transplantation

 


 

The liver is central to metabolism, synthesis of serum proteins, detoxification, and homeostasis. The fetal liver, however, displays little such activity; instead it functions as the major hematopoietic organ in the mid- to late-fetal period. Along with embryonic development, the liver loses hematopoietic activity gradually. Another characteristic of liver is its regenerative activity. In regenerative tissues such as hematopoietic cells, skin, and hair, somatic stem cells function in tissue regeneration. In contrast to other regenerative tissues, mature hepatocytes, but not undifferentiated liver stem cells, take part in acute liver regeneration. However, liver stem/progenitor cells are still required in some chronic injury responses, especially when the proliferative ability of differentiated hepatocytes is impaired. Several studies suggest that liver stem/progenitor cells exist in embryonic livers. During liver development, both hepatocytes and cholangiocytes are differentiated from common-precursor cells, called hepatoblasts.
Our groups concentrate on analyses of fetal and adult liver stem/progenitor cells using cell purification via flow cytometry. We recently established an efficient method of culturing clone-sorted postnatal-liver progenitor cells and fetal liver stem/progenitor cells. We found that Y-27632, the Rho-associated kinase (ROCK) inhibitor, increased the efficiency of colony formation derived from postnatal-liver stem cells. Liver stem cells are numerous in the CD45-Ter119-c-Kit-Sca1-CD13+CD49f+CD133+ subpopulation of nonparenchymal cells derived from non-injured postnatal livers. Expansion and reclone-sorting of postnatal-liver stem cells confirmed that these cells have the capacity for bi-potent differentiation and for self-renewal activity.

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6. ERATO Nakauchi Stem Cell and Organ Regeneration Project

Keywords: regeneration of organ, blastocyst complementation, ES or iPS cells

 

 

Currently, organ failure (e.g., kidney, liver, heart) is treated either with an artificial organ or by organ transplantation. However, both approaches have fundamental problems such as medical cost, ethical issues, and the absolute shortage of organ donors. As an alternative, regenerative medicine utilizing stem cells has been a focus of attention. Current stem cell therapy, however, mainly targets diseases that can be treated by cell transplantation. This is because organogenesis requires complex interactions among cells and organs during development, making regeneration of a solid organ effectively impractical to date. The goal of this project is to generate donor ES or iPS cell-derived solid organs in xenogenic animals using blastocyst complementation. The potential of this experimental system will be examined in large animal models. Our study aims at the establishment of basic technology for regenerative medicine.

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About the Center for Stem Cell Biology and Regenerative Medicine, IMSUT
Center for Stem Cell Biology and Regenerative Medicine, IMSUT
Research Organizations

Division of Stem Cell Therapy, Center for Stem Cell Biology and Regenerative Medicine, IMSUT4-6-1 Shirokanedai Minato-ku, Tokyo, 108-8639, Japan -81-3-5449-5450 +81-3-5449-5451 stemcell(at)ims.u-tokyo.ac.jp

  • Center for Stem Cell Biology and Regenerative Medicine, IMSUT
  • Institute of Medical Science, the University of Tokyo
  • The University of Tokyo

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