Ciber of Mental Health (CIBERSAM), Instituto de Salud Carlos III, Madrid, Spain.
Stem Cells. 2011 Oct;29(10):1628-39. doi: 10.1002/stem.710.
Neural precursor cells (NPCs) are activated in central nervous system injury. However, despite being multipotential, their progeny differentiates into astrocytes rather than neurons in situ. We have investigated the role of epidermal growth factor receptor (EGFR) in the generation of non-neurogenic conditions. Cultured mouse subventricular zone NPCs exposed to differentiating conditions for 4 days generated approximately 50% astrocytes and 30% neuroblasts. Inhibition of EGFR with 4-(3-chloroanilino)-6,7-dimethoxyquinazoline significantly increased the number of neuroblasts and decreased that of astrocytes. The same effects were observed upon treatment with the metalloprotease inhibitor galardin, N-[(2R)-2-(hydroxamidocarbonylmethyl)-4-methylpentanoyl]-L-tryptophan methylamide (GM 6001), which prevented endogenous transforming growth factor-α (TGF-α) release. These results suggested that metalloprotease-dependent EGFR-ligand shedding maintained EGFR activation and favored gliogenesis over neurogenesis. Using a disintegrin and metalloprotease 17 (ADAM-17) small interference RNAs transfection of NPCs, ADAM-17 was identified as the metalloprotease involved in cell differentiation in these cultures. In vivo experiments revealed a significant upregulation of ADAM-17 mRNA and de novo expression of ADAM-17 protein in areas of cortical injury in adult mice. Local NPCs, identified by nestin staining, expressed high levels of ADAM-17, as well as TGF-α and EGFR, the three molecules necessary to prevent neurogenesis and promote glial differentiation in vitro. Chronic local infusions of GM6001 resulted in a notable increase in the number of neuroblasts around the lesion. These results indicate that, in vivo, the activation of a metalloprotease, most probably ADAM-17, initiates EGFR-ligand shedding and EGFR activation in an autocrine manner, preventing the generation of new neurons from NPCs. Inhibition of ADAM-17, the limiting step in this sequence, may contribute to the generation of neurogenic niches in areas of brain damage.
神经前体细胞（NPC）在中枢神经系统损伤中被激活。然而，尽管具有多能性，但它们的后代在原位分化为星形胶质细胞而不是神经元。我们研究了表皮生长因子受体（EGFR）在非神经生成条件产生中的作用。将培养的小鼠侧脑室下区 NPC 暴露于分化条件下 4 天，产生约 50%的星形胶质细胞和 30%的神经母细胞。用 4-（3-氯苯胺基）-6,7-二甲氧基喹唑啉抑制 EGFR，可显著增加神经母细胞的数量，减少星形胶质细胞的数量。用金属蛋白酶抑制剂加兰他敏、N-[(2R)-2-（羟氨羰基甲基）-4-甲基戊酰基]-L-色氨酸甲酰胺（GM6001）处理也观察到相同的效果，该药物可防止内源性转化生长因子-α（TGF-α）释放。这些结果表明，金属蛋白酶依赖性 EGFR 配体脱落维持 EGFR 激活，并有利于神经发生而不是神经发生。用金属蛋白酶 17（ADAM-17）小干扰 RNA 转染 NPC，发现 ADAM-17 是这些培养物中细胞分化所涉及的金属蛋白酶。体内实验显示，成年小鼠皮质损伤区 ADAM-17 mRNA 显著上调，ADAM-17 蛋白重新表达。在体外，这三种分子可防止神经发生并促进神经胶质分化，局部 NPC 经巢蛋白染色鉴定，表达高水平的 ADAM-17、TGF-α和 EGFR。局部 NPC 长期输注 GM6001 可导致损伤周围神经母细胞数量显著增加。这些结果表明，在体内，一种金属蛋白酶（很可能是 ADAM-17）的激活以自分泌方式启动 EGFR 配体脱落和 EGFR 激活，阻止 NPC 产生新的神经元。抑制 ADAM-17，即该序列的限制步骤，可能有助于在脑损伤区域产生神经发生龛。
