Can Growth Factors be Used to Avoid Corneal Blindness?

The cornea is the clear, convex window covering the eye that provides 2/3 of the eye's focusing power. Transparency of the cornea comes from the orderly nanostructure of its stromal layer, which is maintained by specialized keratocyte cells. When the cornea is injured, keratocytes respond by differentiating into myofibroblasts, which act to quickly close the wound—with scar tissue. Myofibroblasts contain stress fibers that pull an injury closed; however, the stress fibers scatter light and distort the refracting surface of the cornea. Here we study the effects of three growth factors (GFs) that are known to modulate the myofibroblast phenotype: epidermal growth factor, platelet-derived growth factor and fibroblast growth factor. In culture, corneal cells were induced to differentiate into myofibroblasts. Then they were exposed to each GF at 5 concentrations (0.1, 1, 10, 50, 100 ng/mL) to find the optimal concentration that reduces the expression of alpha-smooth muscle actin (α-SMA), the cellular marker for myofibroblasts. Three methods were used to determine levels of α-SMA gene and protein expression after exposure to the GFs: quantitative DNA amplification (qPCR), Western blotting, and immunostaining. Preliminary results reveal that the effect of GF concentration is non-monotonic: low concentrations (0.1-10 ng/mL) simulate α-SMA expression, while higher concentrations (such as100 ng/mL) successfully reduce α-SMA expression in more than 90% of cells. These results indicate that GFs can be used to influence the corneal wound-healing process, but that they must be introduced carefully to provide the appropriate concentration at the wound site.