Thrombopoietin and flt-3 ligand expand cord blood progenitors

Cord blood progenitor cells were cultured ex vivo for up to 25 weeks in the presence of flt-3 ligand (FL), thrombopoietin (TPO), or both. Left panel: The total number of nucleated cells increased only with the combination of hematopoietic growth factors. Middle panel: Both CD34+38- and CD34+38+ cells were markedly expanded by the cytokine combination but the CD34+ cells did not survive in the presence of FL or TPO alone. Right panel: Hematopoietic progenitor cells - granulocyte-macrophage (CFU-GM), megakaryocyte (CFU-Meg), multilineage (CFU- GEMM), and erythroid (BFU-E) - increased exponentially during the period of culture with FL plus TPO.