The Role of Astrocytes in Myelin Maintenance and Regeneration Myelin is a fundamental component of mature neural networks that is affected in a large number of pathological conditions of the central nervous system (CNS). Several of these debilitating diseases are thought to be related to astrocyte malfunction so a better in vivo understanding of how astrocytes contribute to the maintenance of mature myelin sheaths and oligodendrocytes is crucial. We have developed a new technique that allows high resolution label-free in vivo imaging of myelinated axons. This technique takes advantage of the high refractive index of lipid rich multilayered myelin and is based on spectral confocal reflectance (SCoRe) microscopy. Using SCoRe we have obtained for the first time long-term images of the dynamics of cortical myelin on the cellular scale in a living animal. Our preliminary data shows this technique as well as fluorescence imaging of astrocytes, oligodendrocytes and axons are a powerful set of tools that in combination provide a wealth of information about fine structural dynamics of these structures in vivo. We demonstrate the feasibility to track the development of myelin pathology in a dysmyelinating mutant mouse and determine the temporal dynamics of demyelination after single oligodendrocyte and astrocyte ablation. We propose to use these powerful techniques to address three fundamental questions concerning the role astrocytes play in myelin maintenance and regeneration. First, we will determine whether astrocyte presence is necessary for myelin and oligodendrocyte structural maintenance in vivo. Next we will use single cell ablation techniques to determine if astrocytes are required for or alter the temporal dynamics of oligodendrocyte remyelination in vivo. Finally we will determine how manipulation of candidate molecules in single astrocytes influences local myelin structural maintenance and regeneration in vivo. Together these experiments will provide novel insight into the fundamental in vivo roles played by astrocytes on the maintenance and regeneration capabilities of myelin and oligodendrocytes.
Myelination is a critical functional component of the central nervous system circuitry. Our limited knowledge of the in vivo interaction between astrocytes and myelin impedes our ability to understand the role astrocytes play in debilitating demyelinating and neurodegenerative diseases. We have developed a new technique (SCoRe) that allows high resolution label-free in vivo imaging of myelinated axons. This grant proposes to use this technique in combination with other cellular in vivo imaging methods to determine for the first time how single astrocytes contribute to myelin maintenance and regeneration in the adult.
