title: Label-free imaging of Schwann cell myelination by third harmonic generation microscopy.
abstract: Understanding the dynamic axon-glial cell interaction underlying myelination is hampered by the lack of suitable imaging techniques. Here we demonstrate third harmonic generation microscopy (THGM) for label-free imaging of myelinating Schwann cells in live culture and ex vivo and in vivo tissue. A 3D structure was acquired for a variety of compact and noncompact myelin domains, including juxtaparanodes, Schmidt-Lanterman incisures, and Cajal bands. Other subcellular features of Schwann cells that escape traditional optical microscopies were also visualized. We tested THGM for morphometry of compact myelin. Unlike current methods based on electron microscopy, g-ratio could be determined along an extended length of myelinated fiber in the physiological condition. The precision of THGM-based g-ratio estimation was corroborated in mouse models of hypomyelination. Finally, we demonstrated the feasibility of THGM to monitor morphological changes of myelin during postnatal development and degeneration. The outstanding capabilities of THGM may be useful for elucidation of the mechanism of myelin formation and pathogenesis.
authors.affiliation: Departments of Physics and hyungsik.lim@hunter.cuny.edu.
authors.forename: Hyungsik
authors.initials: H
authors.lastname: Lim
authors.affiliation: Departments of Physics and.
authors.forename: Denis
authors.initials: D
authors.lastname: Sharoukhov
authors.affiliation: Biology, Hunter College of the City University of New York, New York, NY 10065; and.
authors.forename: Imran
authors.initials: I
authors.lastname: Kassim
authors.affiliation: Department of Cell Biology and Neurology, New York University School of Medicine, NY 11203.
authors.forename: Yanqing
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Cell Biology and Neurology, New York University School of Medicine, NY 11203.
authors.forename: James L
authors.initials: JL
authors.lastname: Salzer
authors.affiliation: Biology, Hunter College of the City University of New York, New York, NY 10065; and.
authors.forename: Carmen V
authors.initials: CV
authors.lastname: Melendez-Vasquez
mesh_terms: D000818:Animals; D003711:Demyelinating Diseases / Q000473:pathology; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007834:Lasers; D051379:Mice; D008853:Microscopy / Q000379:methods*; D036641:Microscopy, Fluorescence, Multiphoton / Q000379:methods; D009186:Myelin Sheath / Q000737:chemistry*; D051381:Rats; D012583:Schwann Cells / Q000166:cytology*
keywords: Schwann cell; label-free imaging; morphometry; multiphoton microscopy; myelin