In vivo platelet production from mature megakaryocytes: Does platelet release occur via proplatelets?
In vivo platelet production from mature megakaryocytes: Does platelet release occur via proplatelets?
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DOI：
10.1532/ijh97.04177
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发表时间：
2005-04-01
影响因子：
2.1
通讯作者：
Kosaki, G
中科院分区：
文献类型：
--
作者：
Kosaki, G
虽然血小板被普遍认为是由巨核细胞（MK）产生的，但血小板在体内形成和从MK释放的机制仍然存在争议。一种理论，称为前血小板理论，假定血小板从前血小板过程中释放，前血小板过程从MK突出到位于骨髓造血区室中的血窦中。在涉及相关分子事件的详细分析的体外实验中观察到前血小板形成（PPF）。PPF也被用作MK成熟的标志物。然而，PPF被认为是一种非生理现象。另一方面，透射电子显微镜（TEM）分析显示，通过浸没固定制备的骨髓和肺毛细血管中MK细胞质的爆炸性碎片形成血小板。此外，TEM和扫描电子显微镜研究的液体培养的MK保持在悬浮液中显示，血小板形成发生没有PPF。相反，已报道血小板形成的机制是由血小板区域组成的MK细胞质的爆炸性和全球性碎片。此外，在体内和离体观察血小板释放的MK与相差显微镜强烈支持爆炸破碎理论。考虑到所有观察结果，PPF可能不是真实条件下MK释放血小板的先决条件。本文提出了一个新的“原片晶”概念来支持爆炸碎裂理论。此外，肺在血小板生成中的作用进行了审查和讨论。(c)2005日本血液学会。
Although platelets are universally accepted to be born from megakaryocytes (MKs), the mechanism by which platelets are formed and released from MKs in vivo remains controversial. One theory, known as the proplatelet theory, postulates that platelets are released from proplatelet processes protruding from MKs into sinusoids located in the bone marrow hematopoietic compartment. Proplatelet formation (PPF) has been observed in in vitro experiments involving detailed analyses of related molecular events. PPF has also been used as a marker of MK maturation. However, PPF is suggested to be a non-physiological phenomenon. On the other band, transmission electron microscopy (TEM) analyses have revealed platelet formation via explosive fragmentation of MK cytoplasm in bone marrow and lung capillaries prepared by immersion fixation. Moreover, TEM and scanning electron microscopy studies of liquid-cultured MKs kept in suspension show that platelet formation occurs without PPF. Rather, an explosive and global fragmentation of the MK cytoplasm composed of platelet territories has been reported as the mechanism of platelet formation. In addition, in vivo and ex vivo observations of platelet release from MKs with phase-contrast microscopy strongly support the explosive-fragmentation theory. With all observations taken into account, PPF may not be a prerequisite for platelet release from MKs under real-life conditions. In this review, a new "protoplatelet" concept is proposed to support the explosive-fragmentation theory. Additionally, the role of the lungs in platelet production is reviewed and discussed. (c) 2005 The Japanese Society of Hematology.