September 2016
Volume 57, Issue 12
Open Access
ARVO Annual Meeting Abstract  |   September 2016
Identification and Quantitation of Anterior and Transition Region Optic Nerve Head (ONH) Cell Proliferation in an Experimental Rat Glaucoma Model
Author Affiliations & Notes
  • Diana C Lozano
    Ophthalmology, Oregon Health & Science University, Portland, Oregon, United States
  • Tiffany Choe
    Ophthalmology, Oregon Health & Science University, Portland, Oregon, United States
  • William O Cepurna
    Ophthalmology, Oregon Health & Science University, Portland, Oregon, United States
  • John C Morrison
    Ophthalmology, Oregon Health & Science University, Portland, Oregon, United States
  • Elaine C Johnson
    Ophthalmology, Oregon Health & Science University, Portland, Oregon, United States
  • Footnotes
    Commercial Relationships   Diana Lozano, None; Tiffany Choe, None; William Cepurna, None; John Morrison, None; Elaine Johnson, None
  • Footnotes
    Support  NIH-RO1EY010145, NIH-2P30EY010572, and Research to Prevent Blindness
Investigative Ophthalmology & Visual Science September 2016, Vol.57, 2537. doi:
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      Diana C Lozano, Tiffany Choe, William O Cepurna, John C Morrison, Elaine C Johnson; Identification and Quantitation of Anterior and Transition Region Optic Nerve Head (ONH) Cell Proliferation in an Experimental Rat Glaucoma Model. Invest. Ophthalmol. Vis. Sci. 2016;57(12):2537.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : Our rat glaucoma model studies show that early glaucomatous injury is characterized by the increased expression of cell proliferation-associated genes in the ONH (Johnson et al IOVS 2011). In similarly injured ONH, there is a 40% increase in ONH volume (Pazos et al, Exp Eye Res 2015). Here we evaluated if this increase is in part due to ONH cell proliferation.

Methods : Chronic IOP elevation was produced by sclerosing the aqueous outflow pathway with hypertonic saline. At 5 weeks post-injection, optic nerve cross-sections were graded for injury on a scale from 1 (normal) to 5 (>50% of axons degenerating). Longitudinal optic nerve sections were immunolabeled and imaged for cell identification and quantification. A Matlab program was developed to semi-automatically quantitate cells in the anterior [the first 150µm posterior to Bruch’s membrane (BM)] and transition ONH (from 250–400µm posterior to BM). Linear and non-linear regression and two-way ANOVA were used to evaluate differences by region and by nerve injury grade in 3 groups: control(n=7), early injury(grade<4;n=17), and advanced injury(grade>=4;n=10).

Results : Greater injury positively correlated with increased nuclear (DAPI+) labeling in both the anterior(P<.0001) and transition(P=.02) regions. Compared to controls, cell proliferation was also indicated by increased numbers of Ki67+ nuclei in both regions of early injury ONH. In general, densities of both differentiated astrocytes (PAX2+ nuclei) and astrocyte precursors (SOX2+ nuclei) in the anterior were twice that in the transition region(P=.006 and P=.0003, respectively). Additionally, SOX2+ nuclear density was 150% higher in the transition region of ONH with advanced injury compared to controls(P=.01). There was a positive, significant linear relationship between injury grade and microglia/macrophage densities (Iba1+ labelling) in both the anterior(P<.0001) and transition(P<.0001) regions. In the anterior ONH, at least 59% of Ki67+ cells labeled with astrocytic markers, while 28% were Iba1+. Similarly, in the transition region, at least 46% were astrocytes, while 16% were Iba1+.

Conclusions : Astrocytic, and to a lesser extent, monocyte/microglial proliferation occurs in the anterior and transition ONH regions of glaucoma model eyes. Proliferation of these cell types is likely to contribute to the dramatic increase in volume of these ONH.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

 

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