Engele J, Bohn M C
Department of Neurobiology and Anatomy, University of Rochester Medical Center, New York 14642.
Dev Biol. 1992 Aug;152(2):363-72. doi: 10.1016/0012-1606(92)90143-5.
Acidic fibroblast growth factor (aFGF) and basic fibroblast growth factor (bFGF) are present in high levels in most areas of the embryonic rodent brain. To begin to understand the role of these growth factors in brain development, the effects of aFGF and bFGF on dissociated cell cultures prepared from embryonic and neonatal rat brain were studied. Addition of aFGF and heparin or bFGF alone to serum-free cultures of the dissociated Embryonic Day (E) 14.5 mesencephalon stimulates cell proliferation, as judged by [3H]thymidine autoradiography, leading to a maximal 75-fold increase in the total number of cells. This effect is dose-dependent with half-maximal increases at concentrations of about 5-6 ng/ml of aFGF or bFGF and is inhibited by the FGF antagonist HBGF-1U. The effect of aFGF on cell proliferation in cultures prepared from E14.5 mesencephalon is similar to that in cultures prepared from E14.5 cortex. However, in cultures prepared from E14.5 rhombencephalon or diencephalon, the proliferative effect of aFGF is much reduced. In all brain areas studied, the proliferative effect of aFGF declines with increasing age. Immunocytochemical analysis of E14.5 mesencephalic cultures demonstrated that the aFGF-induced increase in cell number is due to the proliferation of A2B5-immunoreactive (IR) glial precursor cells, but not of neuronal precursors, fibroblasts, or microglial cells. Moreover, differentiated glial fibrillary acidic protein-IR astrocytes and 2',3'-cyclic nucleotide 3'-phosphohydrolase-IR oligodendrocytes were not observed in cultures continuously treated with aFGF or bFGF, but were observed in high numbers after removal of the growth factors. These results suggest (1) that aFGF and bFGF are potent mitogens for glial precursor cells in all embryonic brain regions, (2) that the magnitude of the effects of aFGF depends on embryonic age and brain region, and (3) that both growth factors inhibit the differentiation of astrocyte or oligodendrocyte precursors. These observations made in vitro strongly support the hypothesis that FGF plays a critical role in gliogenesis and the timing of glial differentiation in the brain.
酸性成纤维细胞生长因子（aFGF）和碱性成纤维细胞生长因子（bFGF）在胚胎期啮齿动物脑的大多数区域中含量很高。为了开始了解这些生长因子在脑发育中的作用，研究了aFGF和bFGF对从胚胎和新生大鼠脑制备的解离细胞培养物的影响。通过[³H]胸苷放射自显影判断，向解离的胚胎第14.5天（E14.5）中脑的无血清培养物中添加aFGF和肝素或单独添加bFGF可刺激细胞增殖，导致细胞总数最多增加75倍。这种效应具有剂量依赖性，在aFGF或bFGF浓度约为5 - 6 ng/ml时达到半数最大增加，并且被FGF拮抗剂HBGF - 1U抑制。aFGF对从E14.5中脑制备的培养物中细胞增殖的作用与从E14.5皮质制备的培养物中的作用相似。然而，在从E14.5菱脑或间脑制备的培养物中，aFGF的增殖作用大大降低。在所有研究的脑区中，aFGF的增殖作用随着年龄增长而下降。对E14.5中脑培养物的免疫细胞化学分析表明，aFGF诱导的细胞数量增加是由于A2B5免疫反应性（IR）神经胶质前体细胞的增殖，而不是神经元前体细胞、成纤维细胞或小胶质细胞的增殖。此外，在持续用aFGF或bFGF处理的培养物中未观察到分化的胶质纤维酸性蛋白 - IR星形胶质细胞和2'，3'-环核苷酸3'-磷酸水解酶 - IR少突胶质细胞，但在去除生长因子后大量观察到。这些结果表明：（1）aFGF和bFGF是所有胚胎脑区神经胶质前体细胞的有效促有丝分裂剂；（2）aFGF作用的大小取决于胚胎年龄和脑区；（3）两种生长因子均抑制星形胶质细胞或少突胶质细胞前体的分化。这些体外观察结果有力地支持了FGF在脑胶质发生和神经胶质分化时间方面起关键作用的假说。
