In vitro cell on cell dry eye model incorporating normal stress control

We expect marked differences in normal stress response between healthy and dry eyes. The change in distances between the cell layers (represented by a fluorescent coating on the cell culture dish) is interpreted as the strain acting on the cell layer. Compression and tensile moduli of healthy and dry eyes can hence be extracted from these images by elaborating XZ-views.

The intensity profiles of the green fluorescence channel (fluorescent coating on the cell culture surface) are fitted with Gaussians. The peak-to-peak distance corresponds to the separation distance between the cell layers. We assess the collective behavior of an entire cell layer in-situ.

Methodologically it is different from single-cell techniques (like AFM). We observe compression moduli on the order of 5 kPa. We find a non-significant change in the compression modulus of the dry eye cell layers.

However, there is embrittlement in dry eye cell layers upon decompression. Healthy cell layers with intact mucins show strong ductility and viscoelasticity, and their original states are not recovered upon decompression.