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

尽管神经发生持续存在于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亚颗粒层，但在脑损伤后，在其他所有不发生神经发生的脑区，神经元的内源性替换并不发生到成年。然而，最近在尝试重建脑损伤后大脑皮质的神经发生方面取得了重大进展，而大脑皮质是一个缺乏成人神经发生的区域。我们以前的工作已经确定转录因子Opol2和Pax6分别是成人室管膜下前体的关键的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的是，我们发现，在急性(刺伤)和慢性(脑淀粉样变性)损伤中，寡核苷酸的强烈诱导是一个共同的特征，而没有神经源性因素被上调(Buffo等人，2005年)。更重要的是，阻断寡核苷酸功能导致刺伤后Pax6表达上调，并导致大脑皮层中增殖的神经胶质细胞产生新的神经元(Buffo等，2005)。我们现在希望将这种神经再生的方法扩展到神经退行性损伤的小鼠模型中。我们以前发现，脑淀粉样变性模型和急性损伤模型之间的神经胶质反应在激活寡核苷酸的胶质细胞类型和它们缺乏细胞增殖方面有很大的不同(Buffo等人，2005年)。为了检验NG2阳性的胶质细胞对淀粉样变性的特异性反应是否也可以在体内引导神经发生，我们将使用伪型病毒载体的细胞类型特异性靶向。我们已经证明，具有Mokola假型的慢病毒载体主要感染NG2阳性的神经胶质细胞，这些细胞在脑淀粉样变性模型中尤为突出。相反，带有LMCV假型的慢病毒载体在体内选择性地感染星形胶质细胞。这些病毒载体将被应用于通过使用显性-阴性结构或诱导Pax6或Ngn2在表现出早期淀粉样变性或概括阿尔茨海默病所有病理特征(包括神经元丧失)的小鼠品系的成年大脑皮质中特定的神经胶质细胞亚群中表达来操纵Opol2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在慢性神经变性模型中指示内源性神经元替换对淀粉样变性模型中的淀粉样变性做出反应的不同胶质亚型。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模式中的潜力和后代。

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.