title: Ex vivo and in vivo imaging of myelin fibers in mouse brain by coherent anti-Stokes Raman scattering microscopy.
abstract: Coherent anti-Stokes Raman scattering (CARS) microscopy was applied to image myelinated fibers in different regions of a mouse brain. The CARS signal from the CH2 symmetric stretching vibration allows label-free imaging of myelin sheath with 3D sub-micron resolution. Compared with two-photon excited fluorescence imaging with lipophilic dye labeling, CARS microscopy provides sharper contrast and avoids photobleaching. The CARS signal exhibits excitation polarization dependence which can be eliminated by reconstruction of two complementary images with perpendicular excitation polarizations. The capability of imaging myelinated fibers without exogenous labeling was used to map the whole brain white matter in brain slices and to analyze the microstructural anatomy of brain axons. Quantitative information about fiber volume%, myelin density, and fiber orientations was derived. Combining CARS with two-photon excited fluorescence allowed multimodal imaging of myelinated axons and other cells. Furthermore, in vivo CARS imaging on an upright microscope clearly identified fiber bundles in brain subcortex white matter. These advances open up new opportunities for the study of brain connectivity and neurological disorders.
authors.affiliation: Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: Yan
authors.initials: Y
authors.lastname: Fu
authors.forename: T Brandon
authors.initials: TB
authors.lastname: Huff
authors.forename: Han-Wei
authors.initials: HW
authors.lastname: Wang
authors.forename: Haifeng
authors.initials: H
authors.lastname: Wang
authors.forename: Ji-Xin
authors.initials: JX
authors.lastname: Cheng
mesh_terms: D000818:Animals; D001369:Axons / Q000378:metabolism; D001921:Brain / Q000166:cytology*; D002467:Cell Nucleus / Q000378:metabolism; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional / Q000379:methods*; D051379:Mice; D008807:Mice, Inbred BALB C; D008853:Microscopy / Q000379:methods*; D009413:Nerve Fibers, Myelinated / Q000378:metabolism*; D009929:Organ Size; D015203:Reproducibility of Results; D013059:Spectrum Analysis, Raman / Q000379:methods*