Quantification and localization of hyaluronan in a PTFE polymer implanted in the corneal stroma

The amount and distribution of hyaluronan in a PTFE polymer used to support an artificial cornea implanted in the rabbit cornea were determined. The findings were used to describe the polymer-corneal stroma interface and the reason for the translucence and wettability of this originally opaque and hydrophobic biomaterial. PTFE disks (6 mm in diameter, 0.2 mm thick, 50 microns in pore size) were implanted after a free-hand intralamellar dissection. The corneas were removed 15 days, 1 month, and 3 months after implantation. The hyaluronan content of pepsin-solubilized corneal stromal extracts and its distribution (7 microns cryostat sections) were investigated using an alkaline phosphatase-linked hyaluronectin assay that specifically detects nanogram amounts of hyaluronan. A PTFE polymer implant caused large, transient increases in hyaluronan density in the implanted stroma. The presence of amphiphilic hyaluronan in the polymer 15 days post implantation probably produced translucence and wettability of this opaque, hydrophobic implant despite the absence of cells. The hyaluronan density in the PTFE polymer increased considerably during the first month and then decreased to stabilize at a moderate level by the third month. These changes in hyaluronan density parallel the invasion of the polymer by inflammatory cells during the first month and the subsequent replacement of these cells by fibroblasts. The PTFE polymer is a good interface that is compatible with the native corneal stroma, and our results indicate that hyaluronan, because of its amphiphilic character, plays a major role in the polymer wettability and translucence and in the production of typical corneal extracellular matrix within the pores of the polymer.