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TISSUE-SPECIFIC STEM CELLS

Antibodies to Stem Cell Marker Antigens Reduce Engraftment of Hematopoietic Stem Cells

Departments of ^aPathology and Laboratory Medicine and
^bPediatrics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA

Key Words. Hematopoietic stem cells • Hematopoietic stem cell transplantation • Side population cells • Long-term engraftmentSca-1⁺c-Kit⁺Lin^–

Correspondence: Suzanne Kirby, M.D., Ph.D., Lineberger Comprehensive Cancer Center, Campus Box 7295, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, USA. Telephone: 919-966-1947; Fax: 919-966-8212; e-mail: suzanne_kirby{at}med.unc.edu

Received February 6, 2006; accepted for publication September 20, 2006.
First published online in STEM CELLS EXPRESS   September 28, 2006.



Hematopoietic stem cells (HSCs) have enormous potential for use in transplantation and gene therapy. However, the frequency of repopulating HSCs is often very low; thus, highly effective techniques for cell enrichment and maintenance are required to obtain sufficient cell numbers for therapeutic use and for studies of HSC physiology. Common methods of HSC enrichment use antibodies recognizing HSC surface marker antigens. Because antibodies are known to alter the physiology of other cell types, we investigated the effect of such enrichment strategies on the physiology and lineage commitment of HSCs. We sorted HSCs using a method that does not require antibodies: exclusion of Hoechst 33342 to isolate side population (SP) cells. To elucidate the effect of antibody binding on this HSC population, we compared untreated SP cells with SP cells treated with the Sca-1⁺c-Kit⁺Lin^– (SKL) antibody cocktail prior to SP sorting. Our findings revealed that HSCs incubated with the antibody cocktail had decreased expression of the stem cell-associated genes c-Kit, Cd34, Tal-1, and Slamf1 relative to untreated SP cells or to cells treated with polyclonal isotype control antibodies. Moreover, SKL antibodies induced cycling in SP cells and diminished their ability to confer long-term hematopoietic engraftment in lethally irradiated mice. Taken together, these data suggest that antibody-based stem cell isolation procedures can have negative effects on HSC physiology.