The architecture of a collagen coating on a synthetic polymer influences epithelial adhesion

The current study sought to identify a collagen coating methodology for application to polymer surfaces that would provide for the development of adhesive structures responsible for the sustained adhesion of corneal epithelial tissue. We compared an uncoated microporous polycarbonate surface and equivalent surfaces coated with either covalently immobilized collagen I or chemically crosslinked collagen I gel in a corneal explant outgrowth assay over 21 days. Electron microscopy was used to examine the formation of hemidesmosomes, basal lamina, and anchoring fibrils at the tissue-polymer interface. The crosslinked collagen gel preparation supported the overlying epithelial tissue across the pore openings and allowed for the formation of identifiable basal lamina, hemidesmosomes, and anchoring fibrils between the epithelial tissue and the polymer surface. Hemidesmosomal plaque, but no basal lamina or anchoring fibril formation, occurred on the uncoated surface or on that coated with covalently immobilized collagen I. We propose that the collagen matrix provided by the crosslinked collagen gel was reorganized by the epithelial tissue and that this, combined with the secretion of ECM molecules, served to limit the diffusion of basement membrane components, which permitted an increase in the local concentration of these molecules, which favored the assembly of epithelial adhesive structures.