Low-glucose enhances keratocyte-characteristic phenotype from corneal stromal cells in serum-free conditions

The avascular cornea is a uniquely-isolated organ, with its stroma constituting a nutrient-poor environment. Consequently, the availability of metabolites such as glucose to corneal stromal cells is considerably reduced compared with other tissues, or indeed with media commonly used to culture these cells in vitro. However, the role of glucose in the behaviour of human corneal keratocytes has been overlooked. As such, we sought to investigate the effects of low-glucose formulations on the phenotype of human corneal stromal cells. Cells cultured in low-glucose were able to survive for extended periods when compared to high-glucose, serum-free conditions. Furthermore, low-glucose enhanced their reversal to a keratocyte-characteristic phenotype. Specifically, cells within low-glucose medium assumed dendritic morphologies, with bean-shaped condensed nuclei, absence of alpha-smooth muscle actin or stress fibres, and a corresponding reduction in migratory and contractile activities when compared with high-glucose, serum-free conditions. Moreover, cells within low-glucose uniquely recovered the ability to express a robust keratocyte-characteristic marker, CD34, while still expressing elevated levels of other representative phenotypic markers such as keratocan, lumican, ALDH1A1, and ALDH3A1. These results indicate that low-glucose enhances keratocyte-characteristic phenotype above and beyond established media formulations and thus has important implications for corneal biology in health and disease.