The effect of retinal pigment epithelial cell patch size on growth factor expression

The spatial organization of retinal pigment epithelial (RPE) cells grown in culture was controlled using micropatterning techniques in order to examine the effect of patch size on cell health and differentiation. Understanding this effect is a critical step in the development of multiplexed high throughput fluidic assays and provides a model for replicating disease states associated with the deterioration of retinal tissue during age-related macular degeneration (AMD). Microcontact printing of fibronectin on polystyrene and glass substrates was used to promote cell attachment, forming RPE patches of controlled size and shape. These colonies mimic the effect of atrophy and loss-of-function that occurs in the retina during degenerative diseases such as AMD. After 72 h of cell growth, levels of vascular endothelial growth factor (VEGF), an important biomarker of AMD, were measured. Cells were counted and morphological indicators of cell viability and tight junction formation were assessed via fluorescence microscopy. Up to a twofold increase of VEGF expression per cell was measured as colony size decreased, suggesting that the local microenvironment of, and connections between, RPE cells influences growth factor expression leading to the initiation and progression of diseases such as AMD.