The relationship between thrombopoietin (TPO) and its receptor cMpl in thrombocytopenic conditions has not been entirely clarified. To elucidate this interplay may expand the spectrum of indications of TPO mimetics. In this study we have explored the relationship between TPO and cMpl in platelets and megakaryocytes of 43 patients with thrombocytopenia due to idiopathic thrombocytopenic purpura (ITP), bone marrow hypoplasia, myelodysplastic syndromes (MDS), and familial thrombocytopenia. Data were compared to cMpl and TPO in patients with a normal platelet count and in patients with thrombocytosis due to essential thrombocythemia (ET). All but familial patients showed higher TPO compared to controls. All thrombocytopenic states were invariably associated with increased expression of platelet cMPL compared to healthy controls. ET patients showed normal TPO and a trend toward a reduced cMpl expression. Immunofluorescence of bone marrow sections from patients with ITP and MDS failed to show a peculiar pattern compared to controls. Multiple mechanisms regulate TPO and cMpl in thrombocytopenic conditions.
Keywords: thrombocytopenia; thrombopoiesis; thrombopoietin; thrombopoietin receptor.