Nishiyama Akiko, Watanabe Masahiko, Yang Zhongshu, Bu Jie
Department of Physiology and Neurobiology, University of Connecticut, 3107 Horsebarn Hill Road, Unit 4156, Storrs, CT 06269-4156, USA.
J Neurocytol. 2002 Jul-Aug;31(6-7):437-55. doi: 10.1023/a:1025783412651.
Cells that express the NG2 proteoglycan (NG2+ cells) comprise a unique population of glial cells in the central nervous system. While there is no question that some NG2+ cells differentiate into oligodendrocytes during development, the persistence of numerous NG2+ cells in the mature CNS has raised questions about their identity, relation to other CNS cell types, and functions besides their progenitor role. NG2+ cells also express the alpha receptor for platelet-derived growth factor (PDGF alphaR), a receptor that mediates oligodendrocyte progenitor proliferation during development. Antigenically, NG2+ cells are distinct from fibrous and protoplasmic astrocytes, resting microglia, and mature oligodendrocytes. Therefore, we propose the term polydendrocytes to refer to all NG2-expressing glial cells in the CNS parenchyma. This distinguishes them from the classical glial cell types and identifies them as the fourth major glial population in the CNS. Recent observations suggest that polydendrocytes are complex cells that physically and functionally interact with other cell types in the CNS. Committed oligodendrocyte progenitor cells arise from restricted foci in the ventral ventricular zone in both spinal cord and brain. It remains to be clarified whether there are multiple sources of oligodendrocytes, and if so whether polydendrocytes (NG2+ cells) represent progenitor cells of all oligodendrocyte lineages. Proliferation of NG2+ cells during early development appears to be dependent on PDGF, but the regulatory mechanisms that govern NG2+ cell proliferation in the mature CNS remain unknown. Pulse-chase labeling with bromodeoxyuridine indicates that polydendrocytes that proliferate in the postnatal spinal cord differentiate into oligodendrocytes. Novel experimental approaches are being developed to further elucidate the functional properties and differentiation potential of polydendrocytes.
表达NG2蛋白聚糖的细胞（NG2+细胞）构成了中枢神经系统中一类独特的神经胶质细胞群体。虽然在发育过程中一些NG2+细胞分化为少突胶质细胞这一点毋庸置疑，但成熟中枢神经系统中大量NG2+细胞的持续存在引发了关于它们的身份、与其他中枢神经系统细胞类型的关系以及除了其祖细胞作用之外的功能等问题。NG2+细胞还表达血小板衍生生长因子α受体（PDGFαR），该受体在发育过程中介导少突胶质细胞祖细胞的增殖。在抗原方面，NG2+细胞不同于纤维性和原浆性星形胶质细胞、静息小胶质细胞以及成熟少突胶质细胞。因此，我们提出用“多突胶质细胞”这一术语来指代中枢神经系统实质中所有表达NG2的神经胶质细胞。这将它们与经典的神经胶质细胞类型区分开来，并将它们确定为中枢神经系统中的第四种主要神经胶质细胞群体。最近的观察表明，多突胶质细胞是复杂的细胞，它们在物理和功能上与中枢神经系统中的其他细胞类型相互作用。定向的少突胶质细胞祖细胞起源于脊髓和大脑腹侧脑室区的特定部位。少突胶质细胞是否有多种来源，以及如果有的话多突胶质细胞（NG2+细胞）是否代表所有少突胶质细胞谱系的祖细胞，仍有待阐明。早期发育过程中NG2+细胞的增殖似乎依赖于血小板衍生生长因子，但在成熟中枢神经系统中调控NG2+细胞增殖的机制仍然未知。用溴脱氧尿苷进行脉冲追踪标记表明，出生后脊髓中增殖的多突胶质细胞会分化为少突胶质细胞。正在开发新的实验方法以进一步阐明多突胶质细胞的功能特性和分化潜能。
