Gasecka Paulina, Jaouen Alexandre, Bioud Fatma-Zohra, B de Aguiar Hilton, Duboisset Julien, Ferrand Patrick, Rigneault Herve, Balla Naveen K, Debarbieux Franck, Brasselet Sophie
Aix Marseille University, CNRS, Centrale Marseille, Institut Fresnel, Marseille, France.
Aix Marseille University, CNRS, Centrale Marseille, Institut Fresnel, Marseille, France.
Biophys J. 2017 Oct 3;113(7):1520-1530. doi: 10.1016/j.bpj.2017.07.033.
Myelin around axons is currently widely studied by structural analyses and large-scale imaging techniques, with the goal to decipher its critical role in neuronal protection. Although there is strong evidence that in myelin, lipid composition, and lipid membrane morphology are affected during the progression of neurodegenerative diseases, there is no quantitative method yet to report its ultrastructure in tissues at both molecular and macroscopic levels, in conditions potentially compatible with in vivo observations. In this work, we study and quantify the molecular order of lipids in myelin at subdiffraction scales, using label-free polarization-resolved coherent anti-Stokes Raman, which exploits coherent anti-Stokes Raman sensitivity to coupling between light polarization and oriented molecular vibrational bonds. Importantly, the method does not use any a priori parameters in the sample such as lipid type, orientational organization, and composition. We show that lipid molecular order of myelin in the mouse spinal cord is significantly reduced throughout the progression of experimental autoimmune encephalomyelitis, a model for multiple sclerosis, even in myelin regions that appear morphologically unaffected. This technique permits us to unravel molecular-scale perturbations of lipid layers at an early stage of the demyelination progression, whereas the membrane architecture at the mesoscopic scale (here ∼100 nm) seems much less affected. Such information cannot be brought by pure morphological observation and, to our knowledge, brings a new perspective to molecular-scale understanding of neurodegenerative diseases.
目前，轴突周围的髓磷脂正通过结构分析和大规模成像技术进行广泛研究，目的是破译其在神经元保护中的关键作用。尽管有强有力的证据表明，在神经退行性疾病进展过程中，髓磷脂中的脂质组成和脂质膜形态会受到影响，但尚未有一种定量方法能够在潜在符合体内观察的条件下，在分子和宏观层面报告其在组织中的超微结构。在这项工作中，我们使用无标记偏振分辨相干反斯托克斯拉曼光谱，研究并量化了亚衍射尺度下髓磷脂中脂质的分子有序性，该技术利用了相干反斯托克斯拉曼对光偏振与定向分子振动键之间耦合的敏感性。重要的是，该方法在样品中不使用任何先验参数，如脂质类型、取向组织和组成。我们表明，在实验性自身免疫性脑脊髓炎（一种多发性硬化症模型）的整个进展过程中，小鼠脊髓中髓磷脂的脂质分子有序性显著降低，即使在形态上未受影响的髓磷脂区域也是如此。这项技术使我们能够在脱髓鞘进展的早期阶段揭示脂质层的分子尺度扰动，而介观尺度（此处约为100纳米）的膜结构似乎受影响较小。据我们所知，这样的信息无法通过单纯的形态学观察获得，它为神经退行性疾病的分子尺度理解带来了新的视角。
