Summary of Research Project Results under JSPS FY2004
"Research for the Future Program"

1. Research Institution   Keio University
2. Research Area Life Sciences
3. Research Field Development, Differentiation, and Regeneration
4. Term of Project FY 2000 - FY 2004
5. Project Number 00L01504
6. Title of Project Characterization of Somatic Stem Cells and Tissue Reconstruction

7. Project Leader

Name Institution, Department Title of Position
Toshio, Suda Keio University, School of Medicine Professor

8. Core Members

Names Institution, Department Title of Position
Tetsuya, Taga Kumamoto University, Institute of Molecular Embryology and Genetics Professor
Atsushi, Hirao Keio University, School of Medicine Assistant Professor
Hideyuki, Saya Kumamoto University, Faculty of Medical and Pharmaceutical Sciences Professor

9. Summary of Research Results

<Keio University research group>
Interaction of hematopoietic stem cells (HSCs) with their microenvironments, known as the stem cell niches, is critical for cell cycle regulation of HSCs. We have revealed a molecular mechanism by which the cell cycle of HSCs is regulated by the niche. HSCs expressing the receptor tyrosine kinase Tie2 are adhere to osteoblasts in the BM niche. The interaction of Tie2 and its ligand Angiopoietin-1 (Ang-1) leads to tight adhesion of HSCs to osteoblasts through N-cadherin, resulting in maintainance of long-term repopulating activity of HSCs.
To analyze the self-renewal capacity of HSCs in the niche, we investigated the role of"Ataxia telangiectasia mutated" (ATM) protein, a key molecule of cell cycle checkpoint. ATM regulates the reconstitutive capacity of the HSC, which was associated with elevated reactive oxygen species (ROS). Treatment of anti-oxidative reagents restored the reconstitutive capacity of ATM-/- HSCs. From these findings, the involvement of oxidative stress is shown in interaction between HSCs and the niche.
<Kumamoto University research group>
We identified new molecular mechanisms regulating stem cell maintenance, differentiation, mitosis, cell motility and adhesion, which are essential events for tissue construction. (1) We found that implantation of neural stem cells expressing BMP antagonist to spinal cord-injured mice contributes to aster recovery. (2) We have identified a subpopulation of C6 glioma cells, based on the Hoechst33342 dye-staining profile, which has cancer stem characteristics. This subpopulation shows malignant phenotype as well as multipotency. (3) During embryogenesis, definitive hematopoiesis arises in the AGM region. We found that a Ras/MAP kinse pathway inhibitor Spred-2, an adaptor molecule Lnk, and STAT3 serine727 kinase HIPK2 inhibits AGM hematopoiesis. (4) We clarified that Aurora-A kinase plays an important role in various mitotic events such as mitotic entry, centrosome separation and chromosome alignment and demonstrated its significance in tissue construction and tumorigenesis. (5) We also investigated how adhesion molecule CD44 regulates cell motility and found that interalization of CD44 with hyarulonic acids and cleavage of CD44 by metalloproteases are critical steps for cells to move in the matrix.

10. Key Words

( 1 ) self-renewality ( 2 ) microenvironment ( 3 ) cell cycle
( 4 ) neural stem cell ( 5 ) hematopoietic stem cell ( 6 ) cell differentiation
( 7 ) mitosis ( 8 ) cell adhesion ( 9 ) extracelluar matrix