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Cancer Cell death Cell cycle Cytoskeleton Exo/endocytosis Differentiation Division Organelles Signalling Stem cells Trafficking
Cell Biology International (2009) 33, 1222–1229 (Printed in Great Britain)
Stimulation of the side population fraction of ATDC5 chondroprogenitors by hypoxia
Koshi N. Kishimotoa*, Carol L. Oxfordb and A. Hari Reddia*
aCenter for Tissue Regeneration and Repair, Department of Orthopaedic Surgery, School of Medicine, University of California at Davis, Sacramento, CA 95817, USA
bOptical Biology Core Facility, Department of Pathology, School of Medicine, University of California at Davis, Davis, CA 95616, USA


The influence of oxygen tension on the side population (SP) fraction sorted from ATDC5 chondroprogenitor cells was investigated. ATDC5 cells cultured in normoxia (20%) or hypoxia (1% oxygen) were compared. The SP fraction was significantly higher in the cells cultured in hypoxia. The gene expression of 3 ABC transporters, abcb1a/b (mdr1a/b) and abcg2 (bcrp1) was quantified by RT-PCR. SP cells were characterized by the higher expression of abcb1a. The expression levels of abcb1b and abcg2 were higher than abcb1a. However, there was no significant difference between SP and non-SP fractions in the expression of abcb1b and abcg2. The telomeric repeat amplification protocol assay showed that SP cells tended to show lower telomerase activity than non-SP cells. Chondrogenic properties of ATDC5 cells derived from SP or non-SP were assessed by micromass culture. There were not significant differences between SP and non-SP derived cells in Alcian blue staining and sox9, Aggrecan, Col2a1 and SZP mRNA expression. The results demonstrate that the SP fraction was stimulated by hypoxia and chondrogenic properties of SP and non-SP fraction of ATDC5 cells were similar.

Key words: Side population, Stem/progenitor cells, ABC transporter, Telomerase activity.

*Corresponding authors. UC Davis Medical Center, Res Bldg I Rm, 2000 4635 Second Avenue, Sacramento, CA 95817, USA.

Received 13 September 2008/18 March 2009; accepted 3 June 2009


ISSN Print: 1065-6995
ISSN Electronic: 1095-8355
Published by Portland Press Limited on behalf of the International Federation for Cell Biology (IFCB)