CxGELSIX: A novel preparation of type VI collagen with possible use as a biomaterial

Purpose. This study was initiated to evaluate tissue acceptance and stabili ty of a novel type VI collagen preparation (CxGelsix) as a biomaterial in t he rabbit corneal stroma. We hypothesized that CxGelsix, embedded intrastro mally, does nor have any adverse affect on surrounding corneal tissues, and remains intact in the presence of an acute inflammatory reaction during co rneal wound healing. Methods. Type VI collagen was extracted and purified f rom rabbit corneal stroma under nondenaturing conditions. This preparation, Gelsix, was concentrated and cross-linked with polyethylene glycol to prod uce a transparent film (CxGelsix). Discs of CxGelsix, 4.0-mm diameter, 9- t o 35-mu m thick were implanted intrastromally and clinically examined perio dically for 4 months. In another experiment. implantation of CxGelsix. 2.0- mm-diameter. was followed by corneal wounding adjacent to the implant and e xamined clinically for 30 weeks. At the end of these periods, the tissues f rom these experiments were processed for light and transmission electron mi croscopy. Results. An intralamellar 4.0-mm-diameter disc of CxGelsix does n ot alter the structure of corneal epithelium above the implant, suggesting normal transport of nutrients through CxGelsix. Moreover, no structural abn ormalities were seen in the rest of the cornea, and the cornea remains tran sparent. Although the cornea accepts the presence of CxGelsix disc as judge d by clinical criteria, gradual degradation of the implant is seen ultrastr ucturally. CxGelsix is remarkably stable despite its exposure to endogenous enzymes during inflammation and wound healing. Partial degradation of the implant occurs only after many months, and it is gradually replaced with bu ndles of fine collagen fibrils reminiscent of normal cornea. Conclusion. Th e results of this study suggest that CxGelsix is potentially useful as a bi omaterial.