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A mouse ocular explant model that enables the study of living optic nerve head events after acute and chronic intraocular pressure elevation: Focusing on retinal ganglion cell axons and mitochondria.
Exp Eye Res. 2017 07; 160:106-115.EE

Abstract

We developed an explant model of the mouse eye and optic nerve that facilitates the study of retinal ganglion cell axons and mitochondria in the living optic nerve head (ONH) in an ex vivo environment. Two transgenic mouse strains were used, one expressing yellow fluorescent protein in selected axons and a second strain expressing cyan fluorescent protein in all mitochondria. We viewed an explanted mouse eye and optic nerve by laser scanning microscopy at and behind the ONH, the site of glaucoma injury. Explants from previously untreated mice were studied with the intraocular pressure (IOP) set artificially at normal or elevated levels for several hours. Explants were also studied from eyes that had undergone chronic IOP elevation from 14 h to 6 weeks prior to ex vivo study. Image analysis in static images and video of individual mitochondria or axonal structure determined effects of acute and chronic IOP elevation. At normal IOP, fluorescent axonal structure was stable for up to 3 h under ex vivo conditions. After chronic IOP elevation, axonal integrity index values indicated fragmentation of axon structure in the ONH. In mice with fluorescent mitochondria, the normal density decreased with distance behind the ONH by 45% (p = 0.002, t-test). Density increased with prior chronic IOP elevation to 21,300 ± 4176 mitochondria/mm2 compared to control 16,110 ± 3159 mitochondria/mm2 (p = 0.025, t-test), but did not increase significantly after 4 h, acute IOP elevation (1.5% decrease in density, p = 0.83, t-test). Mean normal mitochondrial length of 2.3 ± 1.4 μm became 13% smaller after 4 h of IOP elevation ex vivo compared to baseline (p = 0.015, t-test, N-10). Normal mitochondrial speed of movement was significantly slower in the anterograde direction (towards the brain) than retrograde, but there were more mitochondria in motion and traveling longer lengths in anterograde direction. The percent of mitochondria in motion decreased by >50% with acute IOP increase to 30 mm Hg after 60 min. A new ocular explant model implemented with eyes from transgenic mice with fluorescent cellular components provided real time measurement of the early events in experimental glaucoma and quantitative outcomes for neuroprotection therapy experiments.

Authors+Show Affiliations

From the Glaucoma Center of Excellence, Wilmer Ophthalmological Institute, Johns Hopkins University, Baltimore, MD, USA. Electronic address: fcone1@jhmi.edu.From the Glaucoma Center of Excellence, Wilmer Ophthalmological Institute, Johns Hopkins University, Baltimore, MD, USA.From the Glaucoma Center of Excellence, Wilmer Ophthalmological Institute, Johns Hopkins University, Baltimore, MD, USA.From the Glaucoma Center of Excellence, Wilmer Ophthalmological Institute, Johns Hopkins University, Baltimore, MD, USA.From the Glaucoma Center of Excellence, Wilmer Ophthalmological Institute, Johns Hopkins University, Baltimore, MD, USA.From the Glaucoma Center of Excellence, Wilmer Ophthalmological Institute, Johns Hopkins University, Baltimore, MD, USA.From the Glaucoma Center of Excellence, Wilmer Ophthalmological Institute, Johns Hopkins University, Baltimore, MD, USA.

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Research Support, N.I.H., Extramural

Language

eng

PubMed ID

28414059

Citation

Kimball, Elizabeth C., et al. "A Mouse Ocular Explant Model That Enables the Study of Living Optic Nerve Head Events After Acute and Chronic Intraocular Pressure Elevation: Focusing On Retinal Ganglion Cell Axons and Mitochondria." Experimental Eye Research, vol. 160, 2017, pp. 106-115.
Kimball EC, Pease ME, Steinhart MR, et al. A mouse ocular explant model that enables the study of living optic nerve head events after acute and chronic intraocular pressure elevation: Focusing on retinal ganglion cell axons and mitochondria. Exp Eye Res. 2017;160:106-115.
Kimball, E. C., Pease, M. E., Steinhart, M. R., Oglesby, E. N., Pitha, I., Nguyen, C., & Quigley, H. A. (2017). A mouse ocular explant model that enables the study of living optic nerve head events after acute and chronic intraocular pressure elevation: Focusing on retinal ganglion cell axons and mitochondria. Experimental Eye Research, 160, 106-115. https://doi.org/10.1016/j.exer.2017.04.003
Kimball EC, et al. A Mouse Ocular Explant Model That Enables the Study of Living Optic Nerve Head Events After Acute and Chronic Intraocular Pressure Elevation: Focusing On Retinal Ganglion Cell Axons and Mitochondria. Exp Eye Res. 2017;160:106-115. PubMed PMID: 28414059.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - A mouse ocular explant model that enables the study of living optic nerve head events after acute and chronic intraocular pressure elevation: Focusing on retinal ganglion cell axons and mitochondria. AU - Kimball,Elizabeth C, AU - Pease,Mary E, AU - Steinhart,Matthew R, AU - Oglesby,Ericka N, AU - Pitha,Ian, AU - Nguyen,Cathy, AU - Quigley,Harry A, Y1 - 2017/04/14/ PY - 2016/09/26/received PY - 2017/01/03/revised PY - 2017/04/09/accepted PY - 2017/4/18/pubmed PY - 2017/8/10/medline PY - 2017/4/18/entrez KW - Axons KW - Glaucoma KW - Mitochondria KW - Mouse KW - Retinal ganglion cell KW - Sclera KW - Transport block SP - 106 EP - 115 JF - Experimental eye research JO - Exp Eye Res VL - 160 N2 - We developed an explant model of the mouse eye and optic nerve that facilitates the study of retinal ganglion cell axons and mitochondria in the living optic nerve head (ONH) in an ex vivo environment. Two transgenic mouse strains were used, one expressing yellow fluorescent protein in selected axons and a second strain expressing cyan fluorescent protein in all mitochondria. We viewed an explanted mouse eye and optic nerve by laser scanning microscopy at and behind the ONH, the site of glaucoma injury. Explants from previously untreated mice were studied with the intraocular pressure (IOP) set artificially at normal or elevated levels for several hours. Explants were also studied from eyes that had undergone chronic IOP elevation from 14 h to 6 weeks prior to ex vivo study. Image analysis in static images and video of individual mitochondria or axonal structure determined effects of acute and chronic IOP elevation. At normal IOP, fluorescent axonal structure was stable for up to 3 h under ex vivo conditions. After chronic IOP elevation, axonal integrity index values indicated fragmentation of axon structure in the ONH. In mice with fluorescent mitochondria, the normal density decreased with distance behind the ONH by 45% (p = 0.002, t-test). Density increased with prior chronic IOP elevation to 21,300 ± 4176 mitochondria/mm2 compared to control 16,110 ± 3159 mitochondria/mm2 (p = 0.025, t-test), but did not increase significantly after 4 h, acute IOP elevation (1.5% decrease in density, p = 0.83, t-test). Mean normal mitochondrial length of 2.3 ± 1.4 μm became 13% smaller after 4 h of IOP elevation ex vivo compared to baseline (p = 0.015, t-test, N-10). Normal mitochondrial speed of movement was significantly slower in the anterograde direction (towards the brain) than retrograde, but there were more mitochondria in motion and traveling longer lengths in anterograde direction. The percent of mitochondria in motion decreased by >50% with acute IOP increase to 30 mm Hg after 60 min. A new ocular explant model implemented with eyes from transgenic mice with fluorescent cellular components provided real time measurement of the early events in experimental glaucoma and quantitative outcomes for neuroprotection therapy experiments. SN - 1096-0007 UR - https://www.unboundmedicine.com/medline/citation/28414059/A_mouse_ocular_explant_model_that_enables_the_study_of_living_optic_nerve_head_events_after_acute_and_chronic_intraocular_pressure_elevation:_Focusing_on_retinal_ganglion_cell_axons_and_mitochondria_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0014-4835(16)30290-1 DB - PRIME DP - Unbound Medicine ER -