Direct contact with mesenchymal stromal cells affects migratory behavior and gene expression profile of CD133+ hematopoietic stem cells during ex vivo expansion

ObjectiveTo investigate the impact of direct contact between mesenchymal stromal cells (MSCs) and CD133+ hematopoietic stem cells in terms of expansion potential, differentiation, migratory capacity, and gene expression profile.Materials and MethodsCD133+-purified hematopoietic progenitor cells were cultured for 7 days on subconfluent MSCs supplemented with growth-factor−containing medium. After ex vivo expansion, nonadherent and adherent cells were collected and analyzed separately.ResultsThe adherent cell population was less differentiated than the nonadherent fraction. CXCR4 was upregulated in the adherent fraction, which was associated with a higher migration capacity toward a stromal cell−derived factor−1 gradient. Colony-forming unit granulocyte-macrophage and long-term culture−initiation cell assays demonstrated a higher clonogenicity and repopulating capacity of the adherent fraction. Genes involved in adhesion, cell-cycle control, motility, and self-renewal were more highly expressed in the adherent fraction.ConclusionAdhesion and direct cell-to-cell contact with an MSC feeder layer supports ex vivo expansion, migratory potential, and stemness of CD133+ hematopoietic progenitor cells.