Characterization of thrombopoietin kinetics within 60 days after allogeneic hematopoietic stem cell transplantation and its correlation with megakaryocyte ploidy distribution

Thrombopoietin (TPO) has been identified as a key cytokine for both megakaryogenesis and thrombopoiesis. We attempt to characterize the kinetics of TPO and its correlation with megakaryocytes (MKs) ploidy distribution pattern within 60 d after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Forty-six consecutive patients undergoing allo-HSCT from October 2008 to December 2008 were included. TPO levels and ploidy distribution patterns of MKs were measured using ELISA and flow cytometric analysis, respectively. The results indicated that TPO levels and the platelet count followed opposite trends after allo-HSCT. The preconditioning TPO levels and the number of transplanted CD34(+) cells were significant predisposing factors for rapid platelet engraftment (p = 0.010 and 0.007, respectively) by multivariate analysis. There was a reduction of ploidy and an increase in immature MKs in patients with higher endogenous TPO levels (>250 pg/mL) on day 60 after allo-HSCT. Moreover, lower TPO levels (250 pg/mL) on day 60 after allo-HSCT were associated with significantly improved five-yr overall survival (p = 0.021) and reduced transplant-related mortality (p = 0.033). In conclusion, endogenous TPO levels may be associated with platelet recovery and have prognostic significance during allo-HSCT.