Expression of Integrin β3 Is Correlated to the Properties of Quiescent Hemopoietic Stem Cells Possessing the Side Population Phenotype

With significant attention paid to the field of tissue-specific stem cells, the identification of stem cell-specific markers is of considerable importance. Previously, the side population (SP) phenotype, with the capacity to efflux the DNA-binding dye Hoechst 33342, has been recognized as a common feature of adult tissue-specific stem cells. In this study, we show that high expression of integrin β3 (CD61) is an attribute of SP cells isolated from mouse bone marrow. Additionally, we confirmed that the expression of integrin β3 is correlated with properties of quiescent hemopoietic stem cells (HSCs) including the strength of the SP phenotype, cell cycle arrest, expression of HSC markers, and long-term hemopoiesis. Importantly, Lineage− (Lin−)/integrin β3high (β3high) SP cells have as strong a capacity for long-term hemopoiesis as c-Kit+/Sca-1+/Lin− SP cells, which are regarded as one of the most highly enriched HSC populations. Finally, the integrin β3 subunit that is present in SP cells having the properties of HSCs, is associated with integrin αv (CD51). Therefore, our results demonstrate that high expression of integrin β3 is correlated to the properties of quiescent HSCs and suggest that the integrin β3 subunit is available as a common surface marker of tissue-specific stem cells.