The myelin sheath that forms around axons of the brain is essential for proper, high-speed signaling between neurons. Accordingly, degeneration of myelin is believed to be a hallmark pathological feature of normal aging processes, brain injury, and neurodegenerative diseases. However, despite the interest in studying myelinated axons and the loss of myelin integrity that occurs in disease, methods for direct assessment of myelin with microscopic imaging are limited. In postmortem brain tissues, there is a need for new tools to investigate myelin structure and myelin pathology at the level of individual axons.
Due to the unique, multilayered structure of myelin, it is highly anisotropic and therefore also exhibits strong optical birefringence. The birefringence of myelin, which refers to its optical polarization-dependent refractive index, presents the opportunity for sensitive, label-free imaging of myelin structure. This work details the development of a custom birefringence microscopy (BRM) system, which provides the ability to image myelin birefringence with diffraction-limited resolution (up to ~250 nm) and invokes two techniques for either instantaneous qualitative imaging or rapid quantitative imaging. Since imaging is performed rapidly and with a large-area camera, these techniques can be scaled up to investigate significant volumes of brain tissue with a high degree of efficiency. We have determined that proper handling and preparation of brain tissue is critical in preserving myelin structure for imaging, and in turn, we have developed methods of sample preparation that enable myelinated axons to be studied in great detail with BRM. Using postmortem brain sections from both rhesus monkeys and humans, we demonstrate that BRM enables novel studies of myelin structure, both for studying the breakdown of myelin in aging, injury, or disease, as well as for imaging the trajectories of individual myelinated axons at high resolution. As BRM is simple, inexpensive, and provides images of myelin based on label-free contrast, BRM is a platform technology that should find widespread utility across neuroscience. / 2024-08-29T00:00:00Z
| Identifer | oai:union.ndltd.org:bu.edu/oai:open.bu.edu:2144/46635 |
| Date | 30 August 2023 |
| Creators | Blanke, Nathan |
| Contributors | Bigio, Irving J. |
| Source Sets | Boston University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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