ROLE OF PPAR-GAMMA ACTIVATION IN MEGAKARYOCYTOPOIESIS

PACIENZA N; NEGROTTO S; POZNER RG; MALAVER E; D'ATRI LP; LAZZARI MA; TORRES O; GOMEZ RM; SCHATTNER M

Ginebra, Suiza

Congreso; XXIst Congress of the International Society on Thrombosis and Haemostasis; 2007

ROLE OF PPAR-GAMMA ACTIVATION IN MEGAKARYOCYTOPOIESISN.A. Pacienza, S. Negrotto, R.G. Pozner, E. Malaver, L.P. D'Atri, M.A. Lazzari, O. Torres, R.M. Gomez, M. Schattner. Hemostasis and Thrombosis, National Academy of Medicine, Buenos Aires; Biological Sciences, National University of La Plata, La Plata, ArgentinaIntroduction: Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors that function as regulators of lipid and glucose metabolism and influence cellular proliferation, differentiation and apoptosis. Although PPAR-gamma has been detected in bone marrow stroma, CD34+ cells, erythroid progenitors and megakaryocytes (Mk) its role in hematopoiesis has not been completely established. In this study we evaluated the effect of the natural, 15-deoxydelta12,14-prostaglandin J2 (PGJ), and the synthetic PPAR-gamma agonist, ciglitazone (CGZ), on survival, differentiation and proliferation of CD34+-derived Mk.Methods: CD34+ cells were isolated from human cord blood by immunoselection and cultured with thrombopoietin (TPO) in the presence or absence of PGJ or CGZ. After 10 days, Mk growth was determined by counting total cells and analyzing CD41+ cells. The percentage of CD41+, Annexin V+ cells and cell cycle was evaluated by flow cytometry. MTT proliferation assay was carried out at 3, 7 and 10 days after treatment.Results: PGJ and CGZ significantly decreased Mk growth by inhibition of cell proliferation without modifying CD41+ differentiation in a concentration and time dependent manner (IC50: 5±1ìM, IC50: 20±2ìM, respectively, n=4). The PGJ effect was due to apoptosis and cell cycle arrest of CD34+ cells (Control: G0/1=80±5, S=8±2, G2=12±3%; PGJ (20ìM): G0/1=95±3, S=4±1, G2=1±2*%, n=3). Accordingly, PGJ also inhibited CD34+ expansion mediated by SCF, IL-3, EPO, G-CSF and GM-CSF. At the highest concentration employed, CGZ (40ìM) did not induce apoptosis but triggered cell cycle arrest of TPO-treated CD34+ cells (Control: G0/1=56±4, S=8±2, G2=36±2%; CGZ (40ìM): G0/1=69±3, S=5±1, G2=26±2*%, n=3). (*p<0.05 vs control).Conclusions: Our findings indicate that PPAR-gamma agonists have a general mielosuppressive effect. These results should be taken in consideration in the potential use of PGJ as an antineoplastic drug.