Burrows, Tessa; Paterson, Chase; Harris, Tom; Jones, Justin; Elizabeth, Vargis (Utah State University)
Faculty Advisor: Vragis, Elizabeth (College of Engineering, Biological Engineering Department)
Age-related macular degeneration (AMD) is the leading cause of vision loss and blindness in developed nations. To better treat this disease, an accurate model of the retina is needed to study how its healthy and diseased functions. Modeling Bruch's membrane (BM) — a semipermeable layer separates the specialized cells in the retina from blood vessels and becomes more thick and brittle with age — can aid in identifying how the cells associated with AMD, retinal pigmented epithelial (RPE) cells, grow and respond to stress. This project identifies how the brittleness and thickness of a synthetic BM affects cell function and stress factor production in RPE cells. Previous research compared the growth of RPE cells on Transwell membranes and recombinant spider silk proteins (rSSPs) to model BM, and found rSSPs membranes to support RPE growth. Using rSSPs, nonporous membranes with thicknesses of approximately 36 and 50 µm were fabricated to simulate a thicker and more brittle, aged BM. Control assessments were performed with Transwell support membranes, and with 15 µm rSSPs membranes which have been found to support the growth of RPE cells. RPE cells (ARPE-19) were grown on the membranes to confluency and the permeability of the membrane-cell complex was assessed with a size dependent permeability assay with fluorescent dyes of varying molecular weight. Preliminary results found that 36 and 50 µm membranes have a lower permeability coefficient with 7 days of cell growth and a 10 kDa dye. This project is ongoing, and future work includes protein staining to determine the formation of tight junctions and the expression of vascular growth factors associated with AMD. Differences in permeability across the thicker cell-membrane complexes suggest RPE cells have a reduced ability to transport waste across BM. Using rSSPs provides a tunable substrate to quantify the importance of BM in AMD.