Department of Molecular and Cellular Neurobiology, Gunma University Graduate School of Medicine, 3-39-22 Showa-machi, Maebashi, Gunma 371-8511, Japan.
Cerebellum. 2012 Mar;11(1):181-93. doi: 10.1007/s12311-011-0294-x.
Neural stem cells are generally considered to be committed to becoming precursor cells before terminally differentiating into either neurons or glial cells during neural development. Neuronal and oligodendrocyte precursor cells have been identified in several areas in the murine central nervous system. The presence of astrocyte precursor cells (APCs) is not so well understood. The present study provides several lines of evidence that CD44-positive cells are APCs in the early postnatal mouse cerebellum. In developing mouse cerebellum, CD44-positive cells, mostly located in the white matter, were positive for the markers of the astrocyte lineage, but negative for the markers of mature astrocytes. CD44-positive cells were purified from postnatal cerebellum by fluorescence-activated cell sorting and characterized in vitro. In the absence of any signaling molecule, many cells died by apoptosis. The surviving cells gradually expressed glial fibrillary acidic protein, a marker for mature astrocytes, indicating that differentiation into mature astrocytes is the default program for these cells. The cells produced no neurospheres nor neurons nor oligodendrocytes under any condition examined, indicating these cells are not neural stem cells. Leukemia inhibitory factor greatly promoted astrocytic differentiation of CD44-positive cells, whereas bone morphogenetic protein 4 (BMP4) did not. Fibroblast growth factor-2 was a potent mitogen for these cells, but was insufficient for survival. BMP4 inhibited activation of caspase-3 and greatly promoted survival, suggesting a novel role for BMP4 in the control of development of astrocytes in cerebellum. We isolated and characterized only CD44 strongly positive large cells and discarded small and/or CD44 weakly positive cells in this study. Further studies are necessary to characterize these cells to help determine whether CD44 is a selective and specific marker for APCs in the developing mouse cerebellum. In conclusion, we succeeded in preparing APC candidates from developing mouse cerebellum, characterized them in vitro, and found that BMPs are survival factors for these cells.
神经干细胞通常被认为在神经发育过程中，先成为前体细胞，然后终末分化为神经元或神经胶质细胞。在啮齿动物中枢神经系统的几个区域已经鉴定出神经元和少突胶质前体细胞。星形胶质细胞前体细胞（APCs）的存在则不太清楚。本研究提供了几条证据，表明 CD44 阳性细胞是早期出生后小鼠小脑的 APCs。在发育中的小鼠小脑，CD44 阳性细胞，主要位于白质中，为星形胶质细胞谱系的标志物阳性，但为成熟星形胶质细胞的标志物阴性。CD44 阳性细胞通过荧光激活细胞分选从小鼠出生后的小脑纯化，并在体外进行了特征描述。在没有任何信号分子的情况下，许多细胞通过细胞凋亡死亡。存活的细胞逐渐表达神经胶质原纤维酸性蛋白，这是成熟星形胶质细胞的标志物，表明这些细胞向成熟星形胶质细胞分化是其默认程序。在任何检查的条件下，这些细胞都不会产生神经球、神经元或少突胶质细胞，表明这些细胞不是神经干细胞。白血病抑制因子极大地促进了 CD44 阳性细胞的星形胶质细胞分化，而骨形态发生蛋白 4（BMP4）则没有。成纤维细胞生长因子-2 是这些细胞的有效有丝分裂原，但不足以维持其存活。BMP4 抑制半胱天冬酶-3 的激活，并极大地促进了细胞的存活，这表明 BMP4 在控制小脑星形胶质细胞发育中具有新的作用。在这项研究中，我们仅分离和鉴定了 CD44 强阳性的大细胞，并丢弃了小细胞和/或 CD44 弱阳性的细胞。进一步的研究是必要的，以对这些细胞进行特征描述，以帮助确定 CD44 是否是发育中小鼠小脑 APCs 的选择性和特异性标志物。总之，我们成功地从小鼠发育中的小脑制备了 APC 候选物，在体外对其进行了特征描述，并发现 BMPs 是这些细胞的存活因子。
