title: Thrombospondin-1 inhibits in vitro megakaryocytopoiesis via CD36.
abstract: Thrombospondin-1 (TSP-1) is an inhibitor of angiogenesis, inducing apoptosis of the endothelial cells via CD36 signaling mechanism. We investigated CD36 expression and the effect of TSP-1 on megakaryocytopoiesis, with and without pegylated recombinant human megakaryocyte growth and development factor (PEG-rHuMGDF), and with and without blocking TSP-1 binding with receptor CD36 on megakaryocytic cells. Our data showed that TSP-1 induced a dose-dependent growth inhibition in both murine and human colony forming unit-megakaryocyte (CFU-MK) assays and significantly counteracted the mitogenic effect from PEG-rHuMGDF. Moreover, the growth suppression induced by TSP-1 was correlated with CD36 expression in megakaryocytic cell lines, where growth inhibition was demonstrated in CD36 positive (Meg-01, Dami and CHRF-288-11) but not in CD36 negative (M-07e) cell lines. More importantly, the inhibitory effect of TSP-1 on both human CFU-MK and Meg-01 cells was partially but significantly reversed by the addition of FA6-152 (anti-CD36), a blocking antibody which blocks the access of TSP-1 to CD36 receptor, suggesting that the TSP-1-induced inhibition of megakaryocytopoiesis is probably mediated in part by the binding of TSP-1 to CD36 expressed on the megakaryocytic progenitors. Thus, our findings represent the first demonstration that TSP-1 inhibits in vitro megakaryocytopoiesis via interaction with CD36.
authors.affiliation: Department of Paediatrics, The Prince of Wales Hospital, The Chinese University of Hong Kong, Shatin, Hong Kong, China. yang1091@cuhk.edu.hk
authors.forename: Mo
authors.initials: M
authors.lastname: Yang
authors.forename: Karen
authors.initials: K
authors.lastname: Li
authors.forename: Margaret Heung Ling
authors.initials: MH
authors.lastname: Ng
authors.forename: Patrick Man Pan
authors.initials: PM
authors.lastname: Yuen
authors.forename: Tai Fai
authors.initials: TF
authors.lastname: Fok
authors.forename: Chi Kong
authors.initials: CK
authors.lastname: Li
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Hogg
authors.forename: Beng H
authors.initials: BH
authors.lastname: Chong
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D018955:CD36 Antigens / Q000276:immunology / Q000378:metabolism / Q000502:physiology*; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D006412:Hematopoietic Stem Cells / Q000187:drug effects; D006801:Humans; D051379:Mice; D010978:Platelet Factor 4 / Q000494:pharmacology; D011092:Polyethylene Glycols / Q000494:pharmacology; D011485:Protein Binding; D011994:Recombinant Proteins / Q000494:pharmacology; D034061:Thrombopoiesis / Q000187:drug effects*; D013926:Thrombopoietin / Q000494:pharmacology; D019700:Thrombospondin 1 / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D000911:Antibodies, Monoclonal; D018955:CD36 Antigens; D011994:Recombinant Proteins; D019700:Thrombospondin 1; C103117:polyethylene glycol-recombinant human megakaryocyte growth and development factor; D010978:Platelet Factor 4; D011092:Polyethylene Glycols; D013926:Thrombopoietin