(53i) Lubrication Properties of Glycoproteins on Dry-Eye Mimic Ocular Surfaces

Dry eye disease affects hundreds of millions of people around the world, but a definitive pathology still remains elusive. In a subset of dry eye patients, alterations in mucin expression and abnormal glycosylation patterns were found in patients’ tear samples. A lack or a reduced amount of mucin molecules on the ocular surface can lead to an increased frictional damage. However, it is technologically challenging to quantify the relation between mucin deficiency and the altered properties of ocular surfaces. Here we investigated the interfacial and adhesive properties of mucin-deficient corneal and conjunctival epithelial cells. To study the surface properties of corneal epithelium, we utilized the captive bubble method to quantify its contact angle hysteresis. Results showed that the contact angle hysteresis of corneal epithelium was dominated by its surface morphology rather than its mucin expression. To determine the adhesive and frictional properties of live cell surfaces, we customized a live cell rheometer and performed stress relaxation experiments on a novel in vitro dry eye model that mimics the mucin-deficient dry eye ocular environment. Results showed that mucin-deficient corneal epithelial surfaces exhibited increased adhesive strengths against conjunctival epithelial surfaces. Furthermore, an addition of a mucin-like recombinant lubricin molecules rescued the lubrication functions of the ocular surface in a dose-dependent fashion. The results suggested that membrane-bound glycoproteins are sufficient to modify the adhesive properties of ocular surfaces. A simple model was proposed to explain the observed trend in the frictional and adhesive response of live cell surfaces in the presence of additional protein molecules.