Platelets, December 2010; 21(8): 648–657 ORIGINAL ARTICLE Valproic acid and all trans retinoic acid differentially induce megakaryopoiesis and platelet-like particle formation from the megakaryoblastic cell line MEG-01 N. SCHWEINFURTH 1 *, S. HOHMANN 2 *, M. DEUSCHLE 1 , F. LEDERBOGEN 1 , & P. SCHLOSS 1 1 Department of Psychiatry and Psychotherapy, and 2 Department of Child and Adolescent Psychiatry, Central Institute of Mental Health, University of Heidelberg/Medical Faculty Mannheim, Mannheim, Germany (Received 6 May 2010; revised 3 August 2010; accepted 3 August 2010) Abstract Both, the activity of transcription factors as well as epigenetic alterations in defined DNA regions regulate cellular differentiation processes. Hence, neuronal differentiation from neural progenitor cells is promoted by the transcription factor all trans retinoic acid (ATRA) and the histone deacetylase inhibitor valproic acid (VPA). VPA has also been shown to be involved in differentiation of tumor cells and to greatly improve the reprogramming of human somatic cells to induced pluripotent stem cells. Here we have investigated the impact of ATRA and VPA on the differentiation of megakaryoctes and platelets from the megakaryocyte progenitor cell line MEG-01. Our results show that treatment with ATRA (10 11 M) and VPA (2  10 3 M) induces megakaryopoiesis of MEG-01 cells as estimated by polyploidy, formation of characteristic proplatelets and elevated expression of the megakaryocytic markers CD41 and CD61. The resulting megakaryocytes stayed viable for more than 3 weeks and shed platelet-like particles positive for CD41, CD61 and CD42b into the supernatant. Platelet-like particles responded to thrombin receptor activating peptide (TRAP-6) with increased externalization of P-selectin. Thus, ATRA and VPA proved to be efficient agents for the gentle induction of megakaryopoiesis and thrombopoiesis of MEG-01 cells providing the possibility to study molecular events underlying megakaryopoiesis and human platelet production over longer time periods. Keywords: Megakaryopoiesis, valproic acid, all-trans retinoic acid, MEG-01 cells Introduction Blood platelets are small anucleate subcellular frag- ments and important players in haemostatic pro- cesses by adhering to sites of injury and recruiting other platelets by intercellular signaling. Platelet activation then induces platelet aggregation followed by the formation of the haemostatic blood clot. On the other side, inappropriate platelet activation and subsequent thrombus formation plays a crucial role in many diseases and disorders such as myocardial infarction, thrombosis and stroke [1, 2]. Platelets are derived from bone marrow megakaryocytes, which are highly specialized multinucleate cells with mul- tiple long cytoplasmic extensions. These tubular protrusions are called proplatelets and platelets mature and bud only from the ends of the megakar- yocytic protoplasts [3, 4]. Megakaryocytes them- selves originate from megakaryocyte progenitor cells which in turn are derived from pluripotent haema- topoietic stem cells [5–7]. Megakaryocytes represent only a small fraction of 0.4% of total bone marrow cells [8] and it was the successful isolation of immortalized cell lines with megakaryocytic lineage that allowed detailed studies on megakaryopoiesis (for review see [9]). Among others, the clonal human megakaryoblastic leukae- mia cell line MEG-01 displays phenotypic properties that resemble closely those of megakaryoblasts but not other blood cell lineages [10]. Differentiation of MEG-01 cells to megarkaryocytes can be induced by the protein kinase C (PKC) activating phorbol ester Correspondence: Dr. P. Schloss, Biochemical Laboratory, Department of Psychiatry and Psychotherapy, Central Institute of Mental Health, J5, 68159 Mannheim, Germany. Tel: 0049-621-1703-2901. Fax: 0049-621-1703-6255. E-mail: patrick.schloss@zi-mannheim.de * The two authors have contributed equally to this work. ISSN 0953–7104 print/ISSN 1369–1635 online ß 2010 Informa Healthcare Ltd. DOI: 10.3109/09537104.2010.513748 Platelets Downloaded from informahealthcare.com by University of Groningen on 08/26/11 For personal use only.