Flaumenhaft Robert, Dilks James R, Richardson Jennifer, Alden Eva, Patel-Hett Sunita R, Battinelli Elisabeth, Klement Giannoula L, Sola-Visner Martha, Italiano Joseph E
Division of Hemostasis and Thrombosis, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA.
Blood. 2009 Jan 29;113(5):1112-21. doi: 10.1182/blood-2008-06-163832. Epub 2008 Sep 18.
Platelet microparticles are a normal constituent of circulating blood. Several studies have demonstrated positive correlations between thrombotic states and platelet microparticle levels. Yet little is known about the processes by which platelet microparticles are generated in vivo. We now characterize microparticles derived directly from megakaryocytes. Video microscopy of live mouse megakaryocytes demonstrated that microparticles form as submicron beads along the lengths of slender, unbranched micropodia. These microparticles are CD41(+), CD42b(+), and express surface phosphatidylserine. Megakaryocyte microparticle generation is resistant to inhibition of microtubule assembly, which is critical to platelet formation, and augmented by inhibition of actin polymerization. To determine whether circulating microparticles are derived primarily from activated platelets or megakaryocytes, we identified markers that distinguish between these 2 populations. CD62P and LAMP-1 were found only on mouse microparticles from activated platelets. In contrast, full-length filamin A was found in megakaryocyte-derived microparticles, but not microparticles from activated platelets. Circulating microparticles isolated from mice were CD62P(-), LAMP-1(-) and expressed full-length filamin A, indicating a megakaryocytic origin. Similarly, circulating microparticles isolated from healthy volunteers were CD62P(-) and expressed full-length filamin A. Cultured human megakaryocytes elaborated microparticles that were CD41(+), CD42b(+), and express surface phosphatidylserine. These results indicate that direct production by megakaryocytes represents a physiologic means to generate circulating platelet microparticles.
血小板微粒是循环血液的正常组成部分。多项研究表明血栓形成状态与血小板微粒水平之间存在正相关。然而，关于血小板微粒在体内产生的过程却知之甚少。我们现在对直接源自巨核细胞的微粒进行了表征。对活小鼠巨核细胞进行视频显微镜观察显示，微粒沿着细长、无分支的微丝足的长度形成亚微米级的小珠。这些微粒是CD41(+)、CD42b(+)，并表达表面磷脂酰丝氨酸。巨核细胞微粒的产生对微管组装的抑制具有抗性，而微管组装对血小板形成至关重要，并且通过抑制肌动蛋白聚合而增强。为了确定循环微粒主要源自活化血小板还是巨核细胞，我们鉴定了区分这两种细胞群体的标志物。发现CD62P和LAMP-1仅存在于活化血小板产生的小鼠微粒上。相反，全长细丝蛋白A存在于巨核细胞衍生的微粒中，但不存在于活化血小板产生的微粒中。从小鼠分离的循环微粒是CD62P(-)、LAMP-1(-)，并表达全长细丝蛋白A，表明其起源于巨核细胞。同样，从健康志愿者分离的循环微粒是CD62P(-)，并表达全长细丝蛋白A。培养的人巨核细胞产生的微粒是CD41(+)、CD42b(+)，并表达表面磷脂酰丝氨酸。这些结果表明，巨核细胞直接产生是生成循环血小板微粒的一种生理方式。
