title: Toward in vivo two-photon analysis of mouse aqueous outflow structure and function.
abstract: The promise of revolutionary insights into intraocular pressure (IOP) and aqueous humor outflow homeostasis, IOP pathogenesis, and novel therapy offered by engineered mouse models has been hindered by a lack of appropriate tools for studying the aqueous drainage tissues in their original 3-dimensional (3D) environment. Advances in 2-photon excitation fluorescence imaging (TPEF) combined with availability of modalities such as transgenic reporter mice and intravital dyes have placed us on the cusp of unlocking the potential of the mouse model for unearthing insights into aqueous drainage structure and function. Multimodality 2-photon imaging permits high-resolution visualization not only of tissue structural organization but also cells and cellular function. It is possible to dig deeper into understanding the cellular basis of aqueous outflow regulation as the technique integrates analysis of tissue structure, cell biology and physiology in a way that could also lead to fresh insights into human glaucoma. We outline recent novel applications of two-photon imaging to analyze the mouse conventional drainage system in vivo or in whole tissues: (1) collagen second harmonic generation (SHG) identifies the locations of episcleral vessels, intrascleral plexuses, collector channels, and Schlemm's canal in the distal aqueous drainage tract; (2) the prospero homeobox protein 1-green fluorescent protein (GFP) reporter helps locate the inner wall of Schlemm's canal; (3) Calcein AM, siGLO™, the fluorescent reporters m-Tomato and GFP, and coherent anti-Stokes scattering (CARS), are adjuncts to TPEF to identify live cells by their membrane or cytosolic locations; (4) autofluorescence and sulforhodamine-B to identify elastic fibers in the living eye. These tools greatly expand our options for analyzing physiological and pathological processes in the aqueous drainage tissues of live mice as a model of the analogous human system.
authors.affiliation: Doheny Eye Institute and Department of Ophthalmology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.
authors.forename: Jose M
authors.initials: JM
authors.lastname: Gonzalez
authors.affiliation: Doheny Eye Institute and Department of Ophthalmology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.
authors.forename: Minhee K
authors.initials: MK
authors.lastname: Ko
authors.affiliation: Intracellular Membrane Trafficking Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Andrius
authors.initials: A
authors.lastname: Masedunskas
authors.affiliation: Department of Surgery, Department of Biochemistry and Molecular Biology, Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA.
authors.forename: Young-Kwon
authors.initials: YK
authors.lastname: Hong
authors.affiliation: Intracellular Membrane Trafficking Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Roberto
authors.initials: R
authors.lastname: Weigert
authors.affiliation: Doheny Eye Institute and Department of Ophthalmology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA. Electronic address: oranghutan@aol.com.
authors.forename: James C H
authors.initials: JCH
authors.lastname: Tan
mesh_terms: D000818:Animals; D001082:Aqueous Humor / Q000000981:diagnostic imaging* / Q000378:metabolism; D005456:Fluorescent Dyes / Q000378:metabolism; D005901:Glaucoma / Q000000981:diagnostic imaging* / Q000378:metabolism; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology; D016850:Limbus Corneae / Q000000981:diagnostic imaging* / Q000378:metabolism; D051379:Mice; D036641:Microscopy, Fluorescence, Multiphoton; D014129:Trabecular Meshwork / Q000000981:diagnostic imaging* / Q000378:metabolism
chemical_list: D005456:Fluorescent Dyes
keywords: Aqueous humor outflow; Collector channel; Conventional outflow; Glaucoma; Multiphoton microscopy; Schlemm’s canal; Second harmonic generation