The authors sought to determine whether recombinant human thrombopoietin (TPO) acts synergistically with other cytokines on burst-forming unit-erythroid (BFU-E)-derived and colony-forming unit-granulocyte/macrophage (CFU-GM)-derived colony formations from cord blood. Cord blood nonadherent mononuclear cells (MNC) from normal full-term neonates were cultured in a methylcellulose system. When cultured with 5 × 104 MNC/mL, erythropoietin (EPO) 2 U/mL, interleukin-3 (IL-3) 50 ng/mL, and/or TPO 400 ng/mL (experiment 1), the addition of TPO to EPO gave rise to more BFU-E-derived colonies (p = .002). The addition of TPO to EPO + IL-3 gave rise to more BFU-E-derived colonies (p = .006) also. TPO synergizes erythropoiesis from cord blood. When cultured with IL-3 50 ng/mL, granulocyte colony-stimulating factor (G-CSF) 25 ng/mL, and/or TPO 400 ng/mL, the addition of TPO to IL-3 gave rise to more CFU-GM-derived colonies (p = .002). The addition of TPO to G-CSF gave rise to more CFU-GM-derived colonies (p = .002) also. TPO synergizes myelopoiesis from cord blood. Thus, TPO has synergistic effects on both erythropoiesis and myelopoiesis from cord blood. In the identical conditions of culture, cord blood had significantly greater BFU-E-derived or CFU-GM-derived colony formation than bone marrow (in a previous report by the authors) did. When cultured under conditions similar to those of experiment 1, but with 1 × 104 cord blood MNC/mL and TPO 100 ng/mL (experiment 2), results similar to those in the experiment 1 also revealed that TPO has synergistic effects on erythropoiesis and myelopoiesis from cord blood. In every individual assay, the numbers of BFU-E-derived or CFU-GM-derived colonies in experiment 1 were significantly higher than those in experiment 2.
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