Cytoreductive treatment differentially affects platelet size and cytoskeletal megakaryocyte organization during thrombopoiesis in myeloproliferative neoplasms.
Academic Article
Overview
abstract
Cytoreductive treatment is a main strategy to reduce thrombotic complications and ameliorate symptoms in Phi-negative myeloproliferative neoplasms (MPNs) comprising essential thrombocythemia, polycythemia vera, and primary myelofibrosis. Based on the observation of differences in platelet size during our routine microscopic analysis of blood smears from MPN patients, in this work we studied whether these differences could be dependent on the type of cytoreductive drug used for patients´ treatment and whether changes in platelet size could be induced by the effect of these drugs on thrombopoiesis. Maximum platelet diameter was measured in 120 MPN patients. The effect of drugs on thrombopoiesis was evaluated in normal megakaryocytes (MK) obtained from cord blood-derived CD34+ hematopoietic progenitors. Anagrelide (ANA), α-interferon (IFN) and ruxolitinib (Ruxo) increased, while hydroxyurea (HU) decreased platelet size. MK incubation with these drugs revealed that ANA and IFN induced abnormal proplatelet (PP) architecture and affected microtubular structure, but only ANA altered actin organization, while neither Ruxo nor HU modified MK cytoskeleton. By bioinformatic analysis, RANTES downregulation was identified as a candidate responsible for ANA-induced abnormalities. RANTES downregulation was confirmed in MK incubated with ANA but not with IFN. Addition of recombinant RANTES reverted ANA-induced cytoskeletal abnormalities. Evaluation of RANTES plasmatic levels and platelet RNA expression in MPN patients showed that RANTES decreased in both samples during ANA treatment, suggesting that in vitro findings could reflect ANA action in vivo. In conclusion, this study demonstrates the influence of cytoreductive drugs on platelet size and reveals their differential mechanisms of action during platelet production. TEASER ABSTRACT Platelet size is increased in myeloproliferative patients treated with anagrelide, α-interferon and ruxolitinib and decreased in those under hydroxyurea. Incubation of normal mature megakaryocytes with anagrelide and α-interferon but not with ruxolitinib and hydroxyurea, alter proplatelet architecture. Anagrelide and α-interferon induce microtubular disorganization, but only anagrelide alter actin cytoskeleton and decreases megakaryocyte RANTES expression and release. Anagrelide-induced abnormalities are reverted by RANTES addition. RANTES plasmatic levels and platelet RNA expression are decreased in anagrelide-treated vs untreated patients, suggesting in vitro findings could reflect anagrelide action in vivo.
