Regenerative Medicine in the Cornea

The biomaterials and stem cell-based methods and combinations of both are used extensively to replace part or the full thickness of damaged or diseased corneas. In addition, in situ methods for stabilizing and restoring the cornea as alternatives to surgery are rapidly gaining acceptance. This chapter presents these new developments along with the artificial corneas or keratoprostheses (KPros) that are tested or are in clinical use. Surface modification with combinations of peptides, including the cell adhesion peptides RGDS and YIGSR as well as synergistic counterparts PHSRN and PDSGR, demonstrates that corneal epithelial cell adhesion is greatly improved on surfaces with the cell adhesion peptides and at least one of the counterparts. A strategy employed to improve epithelialization is through the use of growth factors. In particular, epidermal growth factor (EGF) is a potent stimulator of corneal epithelial cell proliferation and migration and is active in the wound healing process. The covalent binding of EGF to poly(dimethyl siloxane) (PDMS) substrates via a polyethylene glycol (PEG) tether significantly improves cell coverage of the polymer in vitro. Keratoprostheses (KPro) (commonly referred to as artificial corneas) are usually completely synthetic constructs designed to replace the central portion of an opaque cornea. Most KPro designs are based upon the "core and skirt" concept, with a transparent central optic surrounded by a porous, flexible skirt that enables cellular integration of the host tissue through fibroblast in-growth for anchorage.