ABCG2 expression is correlated neither to side population nor to hematopoietic progenitor function in human umbilical cord blood.
OBJECTIVE
The ABCG2 transporter has been identified as a determinant of the side population (SP) in murine bone marrow and a potential marker for primitive stem cells. To assess the potential of the SP phenotype and ABCG2 expression to identify stem cells in human umbilical cord blood (hUCB), we have examined directly the relationship between SP; expression of ABCG2, CD133, and CD34; and hematopoietic potential in UCB samples.


METHODS
Multicolor fluorescence activated cell sorting analysis was combined with the Hoechst SP procedure to allow the simultaneous detection of the SP phenotype together with surface markers in cells from fresh and cryopreserved UCB. Sorted populations were analyzed for cobblestone area-forming cell (CAFC) activity and by quantitative reverse transcriptase polymerase chain reaction for expression of mRNA from the ABC transporters ABCG2, MDR1, and MRP1. ABCG2(+) cells were enriched by magnetic-activated cell sorting for stringent analysis.


RESULTS
hUCB-derived SP cells were negative for ABCG2, but comprise approximately 20% CD133(+)/CD34(+) cells. Sorted SP cells from UCB were enriched 20-fold for week 13 CAFC activity, while magnetic-activated cell sorting-enriched ABCG2(+) cells retained no hematopoietic activity either in CAFC or liquid cultures. There was no significant difference in the SP frequency, immunophenotype, or CAFC potential of fresh and cryopreserved UCB. ABCG2 mRNA was not enriched in the SP and was specifically diminished ninefold in CD133 cells, which were eightfold enriched for MDR1 mRNA.


CONCLUSIONS
We find no evidence for an association of ABCG2 with SP activity or hematopoietic progenitor function in hUCB.
Alt
Rüdiger
R
Division of Hematology and Oncology, University of Leipzig, Leipzig, Germany.
Wilhelm
Franziska
F
Pelz-Ackermann
Oliver
O
Egger
Dietmar
D
Niederwieser
Dietger
D
Cross
Michael
M
D000071916:AC133 Antigen; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000096:biosynthesis*; D000818:Animals; D015703:Antigens, CD / Q000096:biosynthesis; D018952:Antigens, CD34 / Q000096:biosynthesis; D000943:Antigens, Differentiation / Q000096:biosynthesis*; D005312:Fetal Blood / Q000166:cytology / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000502:physiology*; D006023:Glycoproteins / Q000096:biosynthesis; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D051379:Mice; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000096:biosynthesis; D009363:Neoplasm Proteins / Q000096:biosynthesis*; D010455:Peptides
D000071916:AC133 Antigen; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D015703:Antigens, CD; D018952:Antigens, CD34; D000943:Antigens, Differentiation; D006023:Glycoproteins; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009363:Neoplasm Proteins; D010455:Peptides; C513055:ABCB1 protein, human; C116614:ABCG2 protein, human; C000606023:PROM1 protein, human; C000606024:Prom1 protein, mouse; C421109:multidrug resistance-associated protein 1