Integrin-α3 is a Functional Marker of Ex Vivo Expanded Long-Term Hematopoietic Stem Cells

Transplantation of expanded hematopoietic stem cells (HSCs) and gene therapy based on HSC engineering have emerged as promising approaches for the treatment of hematological diseases. Nevertheless, the immunophenotype of cultured HSCs remains poorly defined. Here we identify Integrin-α3 (ITGA3) as a marker of cultured HSCs. Exploiting the pyrimidoindole derivative UM171 to expand cord blood cells, we show that ITGA3 expression is sufficient to separate the primitive EPCR+CD90+CD133+CD34+CD45RA- HSC population into two functionally distinct fractions presenting mostly short-term (ITGA3-) and both short-term and long-term (ITGA3+) repopulating potential. ITGA3+ cells exhibit robust multilineage differentiation potential, serial reconstitution ability in immunocompromised mice and a hematopoietic stem cell specific transcriptomic signature. Moreover, ITGA3 expression is functionally required for the long-term engraftment of CB cells. Altogether, our results indicate that ITGA3 is a reliable marker of cultured LT-HSCs and represents an invaluable tool to improve the accuracy of prospective HSC identification in culture.