Corneal stromal collagen lysine and hydroxylysine residues

The corneal stromal collagen lysine and hydroxylysine residues are the specific chemical targets for corneal collagen cross-linking (CXL), a therapeutic procedure designed to stabilize the cornea in patients with progressive ectatic diseases such as keratoconus (Wollensak et al., 2003). These residues are found on the collagen fibrils, primarily Type I and Type V, which provide the structural framework and transparency of the corneal stroma (Raiskup & Spoerl, 2013). In keratoconus, the biomechanical integrity of these fibrils is weakened, leading to progressive corneal thinning and irregular astigmatism. During the CXL procedure, riboflavin (Vitamin B2) is applied to the stroma and activated by ultraviolet-A (UVA) light, which generates reactive oxygen species (Subasinghe et al., 2014). These radicals facilitate the formation of new covalent bonds between the amino groups of lysine and hydroxylysine residues on adjacent collagen molecules, effectively "locking" the fibers together. This increase in cross-link density enhances the mechanical stiffness of the cornea, halting the progression of the disease and potentially reducing the need for corneal transplantation (Sinnott et al., 2017). The interaction is not a traditional drug-receptor binding but a photochemical modification of the protein's primary structure. Clinical efficacy is typically monitored through topographic measurements of corneal curvature and thickness.

Other names

Collagen lysine residuesHydroxylysine residuesCorneal collagen fibrilsStromal collagen cross-linking sites

Photo-oxidative cross-linking of collagen residues mediated by riboflavin and UVA light to form covalent bonds between fibrils.