血小板α-粒子蛋白对巨核细胞生长的作用

Effects of platelet alphagranule proteins on megakaryocytopoiesis

目的研究血小板α粒子蛋白包括血小板反应素１（ｔｈｒｏｍｂｏｓｐｏｎｄｉｎ１，ＴＳＰ１），血小板因子４（ｐｌａｔｅｌｅｔｆａｃｔｏｒ４，ＰＦ４），β血小板球蛋白（βＴｈｒｏｍｂｏｇｌｏｂｕｌｉｎ，βＴＧ）和血小板源性生长因子（ｐｌａｔｅｌｅｔｄｅｒｉｖｅｄｇｒｏｗｔｈｆａｃｔｏｒ，ＰＤＧＦ）对巨核细胞生成的影响和可能的作用机制。方法用血浆凝块巨核细胞集落培养，观察对生长的影响，并进一步使用免疫组化和Ｗｅｓｔｅｒｎｂｌｏｔ证实受体的存在和对ｃｆｏｓ表达的影响。结果（１）ＴＳＰ１和ＰＦ４显著地抑制巨核细胞集落（ＣＦＵＭＫ）的形成，有意义的起始抑制浓度为２５μｇ／ｍｌ（Ｐ＜００５）。比较相同浓度的作用ＴＳＰ１和ＰＦ４有相似的抑制效应，但βＴＧ则无显著的影响。而ＰＤＧＦ显著地刺激巨核细胞的生成，最大的刺激剂量为５０ｎｇ／ｍｌ；（２）血小板生长因子（ＴＰＯ）（２０ｎｇ／ｍｌ）显著地增加ＣＦＵＭＫ的形成，但当加上ＴＳＰ１（５μｇ／ｍｌ）时。ＴＰＯ对巨核细胞的生长作用能被ＴＳＰ１减弱（７１±５５／２×１０５细胞～４１±８０／２×１０５细胞，Ｐ＜００１）；（３）证实骨髓的巨核细胞表达ＴＳＰ受体（Ｃ?

Objective The effects of platelet alphagranule proteins including plateletderived growth factor (PDGF), thrombospondin 1 (TSP1), betathromboglobulin (βTG) and platelet factor 4 (PF4) were investigated as possible feedback mechanisms of megakaryocytopoiesis. Methods A plasma clot clonal assay, immunocytochemical staining and Western blot were used in this study. Results (1) TSP1 and PF4 significantly inhibited megakaryocyte colony (CFUMK) formation whereas PDGF stimulated CFUMK in a dosedependent manner. βTG did not show significant effects on CFUMK. (2) The mitogenic effect of TPO on megakaryocytopoiesis was reduced by TSP1. (3) The TSP receptor (CD36) and PDGF receptor expressions were detected on human bone marrow megakaryocytes. (4) Western blot analysis of human megakaryoblast cell lines demonstrated that PDGF (the BBisoform) induced the expression of the immediateearly gene, cfos, mediated by binding with the PDGF receptor.Conclusion The study has demonstrated that the platelet proteins, TSP1 and PF4, act as negative modulators of megakaryocytopoiesis but PDGF has a stimulatory effect. The inhibitory effect of TSP1 may act by either the direct interaction with its receptors on megakaryocytes/precursors or by modulating the binding of TPO. The signal transduction pathways of these modulators on megakaryocytopoiesis and the physiological significance of the feedback mechanism induced by platelet proteins should be further investigated.