Plasma thrombopoietin concentrations in patients with acquired aplastic anemia

Thrombopoietin (TPO) stimulates proliferation and maturation of megakaryocytes in vivo and in vitro. In an attempt to better define the regulation and clinical significance of TPO concentrations, we measured endogenous TPO concentrations in 75 patients with acquired aplastic anemia (AA) and 12 normal controls by a sensitive ELJSA. The mean plasma TPO concentration is 1.3 ±0.5 fmoles/ml in normal controls. The plasma TPO concentrations were significantly higher in patients with AA than in normal controls (p<0.05). (VSAA: 26.5 ±10.5, SAA: 21.3 ±9.9, NSAA: 16.9 ±7.6 fmoles/ml, respectively). TPO levels were serially measured in 23 patients undergoing BMT and in 20 patients receiving immunosuppressive (IS) therapy. Although a decrease in TPO concentrations was observed in patients who achieved self-sustaining hematopoiesis following BMT, we did not find decreases of TPO levels in responders to IS therapy. Whether exogenous TPO will result in increased platelet counts in AA patients with high TPO levels remains to be determined.