CONCENTRATIONS OF THROMBOPOIETIN IN BONE-MARROW IN NORMAL SUBJECTS AND IN PATIENTS WITH IDIOPATHIC THROMBOCYTOPENIC PURPURA, APLASTIC-ANEMIA, AND ESSENTIAL THROMBOCYTHEMIA CORRELATE WITH ITS MESSENGER-RNA EXPRESSION OF BONE-MARROW STROMAL CELLS

The function of bone marrow (BM) stromal thrombopoietin (TPO) in megak aryopoiesis remains unknown. In the present study we attempted to clar ify the pathophysiological implications of stromal TPO in normal subje cts (NS) and in patients with idiopathic thrombocytopenic purpura (ITP ), aplastic anemia (AA), and essential thrombocythemia (ET) by measuri ng TPO concentrations in BM and peripheral blood (PB) and by estimatin g the levels of stromal TPO mRNA with TaqMan fluorescence-based post-r everse transcription-polymerase chain reaction product detection syste m. The results showed that TPO concentrations in PB were significantly elevated in patients with ITP (34.9 +/- 11.7 pg/mL) and AA (364.1 +/- 153.5 pg/mL) but within normal range in patients with ET (each 20.0 a nd 22.1; NS, 22.1 +/- 8.2 pg/mL). In all subjects, the TPO concentrati ons in BM correlated well with the PB levels, and the former were cons istently higher than the latter. The concentrations of TPO in BM also correlated with the levels of TPO mRNA in stromal cells. Furthermore, expression levels of TPO mRNA clearly correlated with megakaryocyte co unts in NS and patients with ITP, indicating that stromal TPO actually enhances megakaryopoiesis. Thus, our results in the present study ind icate that TPO from BM stromal cells Is considered to play an essentia l role for megakaryopoiesis under various pathophysiological condition s. (C) 1998 by The American Society of Hematology.