(589g) Interfacial and Cohesive Properties of Ocular Epithelia

The ocular surface is composed of the corneal epithelium and the tear film. Under constant environmental interrogations at the air-liquid interface, the ocular surface needs to overcome evaporation and maintain hydrated for vision clarity. A loss in ocular surface homeostasis can lead to dry eye disease, which remains the most common reason for ophthalmology practitioner visits. The interfacial properties of corneal epithelium, the top cellular surface in the human eye, are paramount to maintaining the ocular environment's homeostasis. However, few studies have investigated the interfacial properties of ocular epithelia due to a lack of suitable measurement methods. In this project, we measured the contact angle hysteresis of stratified corneal epithelium cultured from an immortalized corneal cell line. The results indicate that surface morphology, instead of surface chemistry, is the main contributor to the high contact angle hysteresis in mature corneal epithelium. We modified the Schultz method that measures high-energy solid surface tension to measure the surface tension of stratified corneal epithelial layers. The interfacial tension of stratified corneal epithelial layers at the cell/medium interface was on the order of 0.1 mN/m, consistent with the values of the interfacial tension of other epithelial sheets measured with surface tensiometers. Surprisingly, the surface tension at the cell/air interface was sufficient to delaminate corneal epithelium from the substrate under low calcium conditions. We obtained the epithelial tension as a function of strain from the delamination experiments. The results showed that the cortical tension of the cytoskeletal components, instead of the adhesive forces at the cell adherens junctions, was the predominant contributor to the mechanical integrity of the epithelial sheet, consistent with previous reports. Overall, we illustrated a suite of simple methods to measure the interfacial properties of ocular epithelia that is adaptive to a wide range of epithelial tissues.