The additive effects of combined murine nuclear migration protein with murine thrombopoietin in vitro and in vivo on normal and myelosuppressed mice

The human homolog of a fungal nuclear migration protein (hNUDC) has recently been shown in in vitro studies to overlap in function with the cytokine factor thrombopoietin (TPO) in its ability to induce human megakaryocyte development. In the present study, we sought to confirm the hypothesis that combination of TPO and NUDC may result in additive or synergistic effects on megakaryocyte maturation in bone marrow. For this purpose, murine bone marrow cells were stimulated with murine NUDC (mNUDC), either alone or in conjunction with murine thrombopoietin (mTPO), in serum-free medium. Studies showed that mNUDC + mTPO treatments resulted in the greatest number of colony-forming unit of megakaryocytes. Concomitantly, mNUDC + mTPO enhanced expression of CD61 and elicited the largest number of megakaryocytes, with higher ploidy and larger size. In addition, in vivo experiments revealed an elevation of platelet levels in normal and thrombocytopenic mice that had been administered mTPO + mNUDC. Moreover, mRNA levels of mNUDC and murine thrombopoietin receptor were much higher than the levels of mTPO mRNA at two different phases of normal murine megakaryocyte maturation. Furthermore, levels of ERK1/2 and Akt phosphorylation are higher with mNUDC in combination with mTPO. This study demonstrates that the combination of mTPO and mNUDC provides additive induction of megakaryocyte maturation in vitro and platelet production in vivo.