Gliosis und Neurogenese - neue Ansätze zur regenerativen Therapie im Alzheimer Maus Modell

虽然神经发生持续在成年哺乳动物大脑的有限区域，如侧脑室侧壁的室管膜下区或海马颗粒下层，但在所有其他大脑区域中，神经发生在成年期不发生的脑损伤后，神经元的内源性替代不会发生。然而，最近在试图在大脑皮层（一个缺乏成人神经发生的区域）重建脑损伤后的神经发生方面取得了重大进展。我们先前的工作已经鉴定了转录因子Olig2和Pax6分别作为成年室管膜下前体的关键抗神经源性和促神经源性信号（Hack等人，2005年）。与其抗神经源性功能一致，我们发现Olig2的强诱导是急性（刺伤）和慢性（脑淀粉样变性）损伤的共同标志，而没有神经源性因子被上调（Buffo et al.，2005年）。更重要的是，阻断Olig2功能导致刺伤损伤后Pax6上调，并导致大脑皮层中由增殖的神经胶质细胞产生新的神经元（Buffo et al.，我们现在希望将这种神经元再生的方法扩展到神经退行性病变的小鼠模型。我们先前发现，在脑淀粉样变性模型和急性损伤之间，神经胶质反应在激活Olig2的神经胶质细胞的类型和它们缺乏细胞增殖方面有很大的不同（Buffo et al.，2005年）。为了检查是否NG2阳性神经胶质细胞特异性反应淀粉样变性也可以在体内指示神经发生，我们将采用细胞类型特异性靶向假型病毒载体。我们已经表明，慢病毒载体与Mokola假型感染主要是NG2阳性神经胶质细胞，这是特别突出的模型中的脑淀粉样变性。相反，具有LMCV假型的慢病毒载体在体内选择性地感染星形胶质细胞。这些病毒载体将通过使用显性阴性构建体或诱导Pax6或Ngn 2在显示早期淀粉样变性或重现阿尔茨海默病的所有病理学标志（包括神经元损失）的小鼠品系的成年皮质中的特定胶质细胞亚群中表达来应用于操纵Olig2功能。这些实验将阐明在急性损伤中触发神经发生的分子机制是否也可以指导慢性神经变性模型中对淀粉样变性反应的不同胶质细胞亚型中的内源性神经元替代。此外，病毒谱系追踪将进一步使我们能够确定不同类型的神经胶质细胞在不同损伤范例中的潜力和后代。

Although neurogenesis persists in restricted regions of the adult mammalian brain such as the subpendymal zone in the lateral wall of the lateral ventricle or the hippocampal subgranular layer, endogenous replacement of neurons does not take place after brain injury in all other brain regions where neurogenesis does not occur into adulthood. However, recently major progress has been made in the attempt to reinstruct neurogenesis after brain injury in the cerebral cortex, an area devoid of adult neurogenesis. Our previous work has identified the transcription factors Olig2 and Pax6 as respectively key anti-neurogenic and pro-neurogenic signals of adult subependymal precursors (Hack et al., 2005). Consistent with its anti-neurogenic function, we found that a strong induction of Olig2 was a common hallmark of both acute (stab-wound) and chronic (cerebral amyloidosis) injuries, while no neurogenic factors were upregulated (Buffo et al., 2005). More importantly, blockade of Olig2 function led to Pax6-upregulation after stabwound injury and resulted in the generation of new neurons from proliferating glial cells in the cerebral cortex (Buffo et al., 2005).We now would like to expand this approach towards neuronal regeneration to mouse models of neurodegenerative lesions. We discovered previously that the gliotic reaction differs profoundly between a model of cerebral amyloidosis and acute injury in regard to the type of glial cells activating Olig2 and their lack of cell proliferation (Buffo et al., 2005). To examine whether the NG2-positive glial cells specifically reacting to amyloidosis can also be instructed towards neurogenesis in vivo we will employ cell type-specific targeting of pseudotyped viral vectors. We have shown that lentiviral vectors with the Mokola pseudotype infect predominantly NG2-positive glial cells that are particularly prominent in the model of cerebral amyloidosis. Conversely, lentiviral vectors with the LMCV pseudotype infect selectively astrocytes in vivo. These viral vectors will be applied to manipulate Olig2 function by the use of dominant-negative constructs or inducing Pax6 or Ngn2 expression in the specific subset of glial cells in the adult cortex of mouse strains showing early amyloidosis or recapitulating all the pathological hallmarks of the Alzheimer disease, including neuronal loss. These experiments will clarify whether the very same molecular machinery that triggers neurogenesis in acute injuries can also instruct endogenous neuronal replacement in the distinct glial subtypes reacting to amyloidosis in chronic neurodegeneration models. Moreover, the viral lineage tracing will further allow us to determine the potential and progeny of distinct types of glial cells in different injuryparadigms.