Parra-Damas Arnaldo, Saura Carlos A
Institut de Neurociències, Departament de Bioquímica i Biologia Molecular, Facultat de Medicina, Universitat Autònoma de Barcelona, Barcelona, Spain.
Centro de Investigación Biomédica en Red Enfermedades Neurodegenerativas, Instituto de Salud Carlos III, Madrid, Spain.
Front Neurosci. 2020 Oct 5;14:914. doi: 10.3389/fnins.2020.00914. eCollection 2020.
Studying the structural alterations occurring during diseases of the nervous system requires imaging heterogeneous cell populations at the circuit, cellular and subcellular levels. Recent advancements in brain tissue clearing and expansion methods allow unprecedented detailed imaging of the nervous system through its entire scale, from circuits to synapses, including neurovascular and brain lymphatics elements. Here, we review the state-of-the-art of brain tissue clearing and expansion methods, mentioning their main advantages and limitations, and suggest their parallel implementation for circuits-to-synapses brain imaging using conventional (diffraction-limited) light microscopy -such as confocal, two-photon and light-sheet microscopy- to interrogate the cellular and molecular basis of neurodegenerative diseases. We discuss recent studies in which clearing and expansion methods have been successfully applied to study neuropathological processes in mouse models and postmortem human brain tissue. Volumetric imaging of cleared intact mouse brains and large human brain samples has allowed unbiased assessment of neuropathological hallmarks. In contrast, nanoscale imaging of expanded cells and brain tissue has been used to study the effect of protein aggregates on specific subcellular structures. Therefore, these approaches can be readily applied to study a wide range of brain processes and pathological mechanisms with cellular and subcellular resolution in a time- and cost-efficient manner. We consider that a broader implementation of these technologies is necessary to reveal the full landscape of cellular and molecular mechanisms underlying neurodegenerative diseases.
研究神经系统疾病过程中发生的结构改变需要在回路、细胞和亚细胞水平对异质细胞群体进行成像。脑组织清除和扩张方法的最新进展使得能够通过从回路到突触的整个尺度，包括神经血管和脑淋巴管元件，对神经系统进行前所未有的详细成像。在这里，我们回顾了脑组织清除和扩张方法的最新技术水平，提及它们的主要优点和局限性，并建议使用传统（衍射极限）光学显微镜（如共聚焦显微镜、双光子显微镜和光片显微镜）对从回路到突触的脑成像并行实施这些方法，以探究神经退行性疾病的细胞和分子基础。我们讨论了最近的一些研究，其中清除和扩张方法已成功应用于研究小鼠模型和死后人类脑组织中的神经病理过程。对清除后的完整小鼠脑和大型人类脑样本进行体积成像，能够对神经病理特征进行无偏评估。相比之下，对扩张后的细胞和脑组织进行纳米级成像已用于研究蛋白质聚集体对特定亚细胞结构的影响。因此，这些方法可以很容易地应用于以时间和成本高效的方式在细胞和亚细胞分辨率下研究广泛的脑过程和病理机制。我们认为，更广泛地应用这些技术对于揭示神经退行性疾病潜在的细胞和分子机制的全貌是必要的。
