April 2011
Volume 52, Issue 14
ARVO Annual Meeting Abstract  |   April 2011
Modulus of Elasticity of Healthy and Glaucomatous Schlemm’s Canal Cells
Author Affiliations & Notes
  • Rocio Vargas-Pinto
    Biomedical Engineering, Northwestern University, Evanston, Illinois
  • Kristin M. Perkumas
    University of Arizona, Tucson, Arizona
  • W Daniel Stamer
    Ophthalmology & Vision Science,
    University of Arizona, Tucson, Arizona
  • Mark Johnson
    Biomedical Engineering, Northwestern University, Evanston, Illinois
  • Footnotes
    Commercial Relationships  Rocio Vargas-Pinto, None; Kristin M. Perkumas, None; W Daniel Stamer, None; Mark Johnson, None
  • Footnotes
    Support  National Glaucoma Research, a program of AHAF, NIH Grant EY09699, EY17007, and T32 EY007128.
Investigative Ophthalmology & Visual Science April 2011, Vol.52, 4814. doi:
  • Views
  • Share
  • Tools
    • Alerts
      This feature is available to authenticated users only.
      Sign In or Create an Account ×
    • Get Citation

      Rocio Vargas-Pinto, Kristin M. Perkumas, W Daniel Stamer, Mark Johnson; Modulus of Elasticity of Healthy and Glaucomatous Schlemm’s Canal Cells. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4814.

      Download citation file:

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

  • Supplements

Purpose: : Changes in stiffness of the inner wall endothelium of Schlemm’s Canal (SC) may contribute to the increased outflow resistance characteristic of glaucoma. We used Atomic Force Microscopy (AFM) with various tip sizes to assess the differences in elasticity between cultured SC cells from normal and glaucomatous donors.

Methods: : SC cells were isolated from healthy donors (4 normal cell strains) and donors previously diagnosed with glaucoma (4 glaucoma cell strains). Cultured cells were stained with Calcein AM and Hoechst fluorescent dyes to determine cell viability and the location of the nucleus respectively. AFM force measurements were made using silicon nitride sharp pyramidal tips (nominal angle of 35°) and tips with polystyrene spherical attachments (diameters of 4.5 and 10 µm). Young’s Modulus (E) was calculated using the modified Hertz model. The AFM indentation was modeled using finite element software to determine the effect cortex stiffness would have on the measured modulus based on the tip geometry.

Results: : Young’s Modulus for SC cells measured with pyramidal tips was similar for normal cells (9.4± 12.4 kPa, n=76) and glaucoma cells (9.1± 10.6 kPa, n=98). When using spherical tips, lower values were obtained for normal cells (4.5 µm tip: 2.0± 2.4 kPa, n=69; 10 µm tip: 2.2± 3.5 kPa, n=108) compared to glaucoma cells (4.5 µm tip: 3.1± 3.9 kPa, n=75; 10 µm tip: 3.9± 9.9 kPa, n=82. Also, the mean variance in E measured with spherical tips was seven times greater for glaucomatous cells. No significant differences in stiffness were found between the cytoplasm and nuclear regions for either normal or glaucoma cells. The finite element model showed that measurements using the pyramidal tip are strongly affected by the stiffness of the cell cortex, while values measured with the spherical tip are only weakly influenced by the cortex stiffness.

Conclusions: : The significantly higher modulus and greatly increased variance measured using spherical tips suggest that there are differences in stiffness between normal and glaucomatous SC cells. The lack of such a finding using pyramidal tips indicates that the altered stiffness is likely in the cell body and not in the cell cortex.

Keywords: cytoskeleton • cell membrane/membrane specializations • outflow: trabecular meshwork 

This PDF is available to Subscribers Only

Sign in or purchase a subscription to access this content. ×

You must be signed into an individual account to use this feature.