Shear and Modulus Measurements of Individual Corneal Epithelial Cells

Abstract

Purpose: : Living human corneal epithelial cells have been probed in vitro via atomic force microscopy, revealing the frictional characteristics and stiffness of the outer surfaces of mature corneal cells in media.

Methods: : Human corneal epithelial (HCE) cells from an immortalized cell line (HCE-T) were cultured under Dulbecco’s Modified Eagle Medium containing 10 ng/ml human epithelial growth factor (EGF). The cells were maintained under sterile cell media during experimentation.

Results: : Shear stresses of 0.40 kPa measured at the surface of individual corneal epithelial cells are among the lowest reported values for aqueous lubrication. The mechanical properties of individual epithelial cells have been further probed through nanometer scale indentation measurements. An elastic foundation model, based on experimentally verifiable parameters including cell diameter and thickness, is used to fit the indentation data, producing an effective elastic modulus of 16.5 kPa and highlighting the highly compliant nature of the cell surface. The elastic foundation model is found to more accurately fit the experimental data, to avoid unverifiable assumptions, and to produce a modulus significantly higher than that of the widely used Hertz-Sneddon model.

Conclusions: : The results provide a baseline understanding of the mechanical properties of individual corneal cells and again highlight the opportunities for probing the details of mechanobiology related to the function of the eye surface and for conducting interfacial/solution studies at the cellular level.

Keywords: cornea: epithelium • cell membrane/membrane specializations • cornea: basic science