April 2011
Volume 52, Issue 14
Free
ARVO Annual Meeting Abstract  |   April 2011
ß1-Integrin Signaling In RGC In Experimental Glaucoma
Author Affiliations & Notes
  • Andrea Rachelle C. Santos
    Ophthalmology,
    Bascom Palmer Eye Institute, Miami, Florida
  • Betty A. Obeso
    Ophthalmology,
    Bascom Palmer Eye Institute, Miami, Florida
  • Jamie Ponmattam
    Ophthalmology,
    Bascom Palmer Eye Institute, Miami, Florida
  • Michaela L. Bajenaru
    Bascom Palmer Eye Institute, Miami, Florida
Investigative Ophthalmology & Visual Science April 2011, Vol.52, 2445. doi:
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      Andrea Rachelle C. Santos, Betty A. Obeso, Jamie Ponmattam, Michaela L. Bajenaru; ß1-Integrin Signaling In RGC In Experimental Glaucoma. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2445.

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

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Abstract

Purpose: : Extracellular matrix integrity in the CNS is essential for neuronal homeostasis and ECM survival signals are transmitted to neurons through the integrin survival pathway. Extensive remodeling of the ECM was identified in glaucoma. We have recently shown integrin survival pathway disruption in RGC in a rat model of retinal ischemia and identified ß1 integrin and FAK as key regulators. This study aims to investigate the role of integrin survival signaling pathway in RGC in glaucoma.

Methods: : Experimental glaucoma was induced in 30 Sprague Dawley rats by laser photocoagulation. Optic nerves and retinas were removed from rats (n=8) at 9 weeks post treatment and processed for histology. Semi-automated counting of the optic nerve axons was performed in optic nerve sections. TUJ1 labeled RGC was counted on corresponding flat mounted retinas. Another group (n=6) was euthanized 6 weeks post treatment and retrogradely labeled with FG. Labeled RGC was counted in flat mounted retinas. Immunohistochemistry and western blotting with laminin, ß1 integrin, FAK, phospho-FAK, Akt, phospho-Akt, and Bcl-xL antibodies were performed in retinal sections and extracts from control and glaucoma eyes.

Results: : After treatment, mean IOP was increased in the treated eye from 8.7 ± 1.05 mm Hg to 18.34 ± 5.86 at 1 week and 18.55 ± 13.04 at 2 weeks. Peak IOP was 37.89 ± 12.83. Axonal loss at 9 weeks post treatment was 34.06 % ± 13.25 in good correlation with the 47% ± 5.6 RGC loss estimated by TUJI staining in corresponding retinas. The number of FG labeled RGC in eyes with glaucoma 6 weeks post treatment was highly reduced and varied from one retinal quadrant to another. FG+RGC were distributed in large wedge shaped areas with smaller diffuse RGC loss of 15-20% to areas where few to no FG+RGC were present. Compared to axonal counts or TUJ1+RGC survival, these results suggest that many surviving RGC are dysfunctional and have impaired retrograde active transport. Immunohistochemistry in retinal sections showed a decrease in laminin expression in the inner limiting membrane and RGC in the glaucomatous eyes. Immunofluorescence with ß1-integrin and P-FAK antibodies showed a decrease in ß1 integrin expression and a remarkable decrease in P-FAK, while FAK was unchanged. The staining pattern was sectorial. Western blotting of retinal extracts showed a 1.2 decrease in ß1 integrin, 2 fold in P-FAK and 2.5 fold decreases in P-Akt and Bcl-xL expression in the glaucomatous eyes.

Conclusions: : Our results suggest that RGC ß1 integrin pro-survival signaling is disrupted in glaucoma and emphasize a role for laminin/integrin signaling pathway in neuronal survival.

Keywords: retina: proximal (bipolar, amacrine, and ganglion cells) • optic nerve • extracellular matrix 
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