June 2013
Volume 54, Issue 15
Free
ARVO Annual Meeting Abstract  |   June 2013
The role of glycosaminoglycans in the mechanical behavior of the posterior sclera
Author Affiliations & Notes
  • Barbara Murienne
    Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD
  • Harry Quigley
    Glaucoma Center of Excellence, Johns Hopkins Wilmer Eye Institute, Baltimore, MD
  • Thao Nguyen
    Department of Mechanical Engineering, Johns Hopkins University, Baltimore, MD
  • Footnotes
    Commercial Relationships Barbara Murienne, None; Harry Quigley, Sensimed (C), Genetech (C), Merck (C), Sucampo (C); Thao Nguyen, None
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science June 2013, Vol.54, 52. doi:https://doi.org/
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      Barbara Murienne, Harry Quigley, Thao Nguyen; The role of glycosaminoglycans in the mechanical behavior of the posterior sclera. Invest. Ophthalmol. Vis. Sci. 2013;54(15):52. doi: https://doi.org/.

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

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Abstract
 
Purpose
 

To investigate the role of glycosaminoglycans (GAGs) in the mechanical behavior of the posterior sclera.

 
Methods
 

The posterior sclera from 6-9 months old pig eyes was dissected within 72 hours of enucleation. Mechanical testing was performed through a series of pressure-controlled load-unload and ramp-hold tests (Myers et al., Acta Biomater., 2010). 3D digital image correlation was used to calculate the full-field surface displacements and analytical methods were developed to calculate circumferential and longitudinal strains. Each scleral cup was tested before and after overnight treatment at 37°C with Chondroitinase ABC at 2 units/ml in a modified Tris buffer at pH 8.0 (Sigma). Sulphated GAG (sGAG) removal was assessed quantitatively using the Blyscan assay (Biocolor) after sample digestion with Papain (Boubriak et al., Exp Eye Res., 2003). Student’s t-test was used for statistical analysis.

 
Results
 

Preliminary results suggest that removing GAGs accelerates the creep and recovery rates (Fig. 1), increases tissue extensibility but has no noticeable effect on the stiffness of the loading curve. Assessment of sGAG removal showed a 57.7 ± 9.2% mean decrease in sGAG content after treatment with Chondroitinase ABC (n=4, p<0.01, Fig. 2). Experiments using DPBS instead of Tris buffer to rinse the samples showed a much higher decrease in sGAG content (94.6 ± 0.83%, n=4, p<0.01), suggesting that even if in average 57.7% sGAGs are extracted out of the tissue using Tris buffer, at least 94% are disconnected from their environment.

 
Conclusions
 

Changes in GAG levels may contribute to the observed myopia-related (Phillips et al., Invest Ophthalmol Vis Sci., 2000) or glaucoma-related (Coudrillier et al., Biomech Model Mechanobiol., 2012) changes in the viscoelastic behavior of the sclera.

 
 
Figure 1. Creep response at 45mmHg in the circumferential and longitudinal directions, before and after enzymatic treatment with Chondroitinase ABC.
 
Figure 1. Creep response at 45mmHg in the circumferential and longitudinal directions, before and after enzymatic treatment with Chondroitinase ABC.
 
 
Figure 2. Blyscan assay results for the control and treated groups rinsed with Tris buffer.
 
Figure 2. Blyscan assay results for the control and treated groups rinsed with Tris buffer.
 
Keywords: 708 sclera • 661 proteoglycans/glycosaminoglycans  
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