Department of Chemical Engineering, Laval University, Québec, QC, Canada.
Cell Cycle. 2010 Jul 1;9(13):2589-99. doi: 10.4161/cc.9.13.12078.
Megakaryocytes (MK) undergo polyploidization through endomitosis, a mitotic process that ends prematurely due to aborted cytokinesis. To better understand this and other events associated with MK differentiation, we performed long-term and large-field live cell imaging of human MKs derived in cord blood (CB) and bone marrow (BM) CD34(+) cell cultures. Polyploid level of imaged cells was evaluated using three complementary approaches; cell history, cell size and ploidy correlation and nuclei staining. This system and strategy enabled the direct observation of the development of a large number of MKs (n=4865) and to quantify their fates. The most significant finding of this study is that a considerable proportion of polyploid MKs could complete cytokinesis. This unexpected process gave rise to polyploid daughter cell(s) with normal fates and contributed significantly to the expansion of polyploid MKs. Further analyses revealed that the proliferation rate amongst polyploid MKs was inversely correlated to their ploidy level, and that this phenomenon was much more frequent in CB- than BM-derived MKs. Accordingly, endomitosis was identified as the dominant fate of polyploid BM-MKs, while this was less accentuated for polyploid CB-MKs. These findings explain partially why CB-derived MKs remain in lower ploidy class. In conclusion, this study demonstrates that the development of polyploid MK results from the failure and/or success of cytokinesis and brings a new paradigm to the field of megakaryopoiesis.
巨核细胞（MK）通过有丝分裂末期的核内有丝分裂经历多倍体化，由于胞质分裂失败而提前结束。为了更好地理解这一过程和其他与 MK 分化相关的事件，我们对源自脐带血（CB）和骨髓（BM）CD34+细胞培养物的人 MK 进行了长期和大视场活细胞成像。通过三种互补的方法评估成像细胞的多倍体水平；细胞历史、细胞大小和倍性相关性以及核染色。该系统和策略使我们能够直接观察大量 MK 的发育并对其命运进行定量。这项研究的最重要发现是，相当一部分多倍体 MK 可以完成胞质分裂。这个意外的过程产生了具有正常命运的多倍体子细胞，并为多倍体 MK 的扩张做出了重大贡献。进一步的分析表明，多倍体 MK 中的增殖率与其倍性水平呈负相关，并且在 CB 来源的 MK 中比在 BM 来源的 MK 中更为常见。因此，核内有丝分裂被确定为多倍体 BM-MK 的主要命运，而在多倍体 CB-MK 中则不那么明显。这些发现部分解释了为什么 CB 来源的 MK 保持在较低的倍性级别。总之，这项研究表明，多倍体 MK 的发育是由胞质分裂的失败和/或成功导致的，并为巨核细胞生成领域带来了新的范例。
