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Original Article |
1 Department of Immunohematology and Bloodtransfusion Leiden University Medical Center, Leiden
2 Department of Experimental Immunology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
Correspondence: Melisssa van Pel, PhD, Section of Stem Cell Biology Department of Immunohematology and Bloodtransfusion, Leiden University Medical Center, PO Box 9600, 2300 RC Leiden, The Netherlands E-mail:m.van_pel{at}LUMC.nl
ABSTRACT
Background: CD97 is a member of the EGF-TM7 family of adhesion receptors and is broadly expressed on hematopoietic cells. The aim of this study is to investigate the expression of CD97 on hematopoietic stem- and progenitor cells (HSC/HPC).
Design and Methods: CD97 expression on HSC/HPC was studied in BALB/c, C57BL/6 and DBA/1 mice using flow-cytometry. Functional HSC/HPC characteristics were investigated in vitro and in vivo by progenitor cell assays, cobblestone area forming cell (CAFC) assays and bone marrow cell (BMC) transplantation.
Results: Analysis of CD97 expression on murine bone marrow cells showed three major populations i.e. CD97HI, CD97INT and CD97NEG cells. Functional studies revealed that radioprotective capacity and cobblestone area forming cell -day 28–35 activity reside in the CD97INT bone marrow cell fraction while CFU-GM colony-forming capacity mainly resides in the CD97NEG population in all strains. In C57BL/6 and DBA/1 mice CD97NEG and CD97HI bone marrow cells show hematopoietic stem cell characteristics as well. Further functional analysis of BALB/c CD97INT bone marrow cells revealed that c-KitHICD97INT BMC exhibit HSC activity and are 1.5-fold enriched for CAFC-day 35 activity compared to c-KitHI BMC. Moreover, phenotypical analysis showed that BALB/c and C57BL/6 HSC are CD97INT, while DBA/1 HSC are CD97HI.
Conclusions: CD97 is differentially expressed on HSC and HPC. Committed progenitor cell activity is largely comprised in the CD97NEG fraction, while the CD97INT population contains HSC activity. In BALB/c mice, CD97 expression can be applied to almost completely separate colony-forming cells and cells exhibiting radioprotective capacity. In addition we propose that the CD97INTc-KitHI phenotype allows a simple and rapid purification of murine hematopoietic stem cells.
Key words: hematopoietic stem cells, CD97, mouse model, hematopoietic progenitor cells.
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