BIOCOMPATIBILITY AND IMMUNOLOGICAL PROPERTIES OF PERICARDIAL TISSUE STABILIZED BY DYE-MEDIATED PHOTOOXIDATION

Background and aims of the study: Bovine and porcine pericardial tissu es stabilized by dye-mediated photooxidation have found application as bioprosthetic heart valve material. Methods: To help predict clinical performance, a series of tests were performed to assess the biocompat ibility and immunologic properties of these materials. Results and Con clusions: Photooxidized bovine or porcine pericardium sterilized with an iodine-based solution were found to be non-cytotoxic, nonhemolytic, and non-mutagenic. Oil or saline extracts of these tissues passed tes ts for intracutaneous toxicity (irritation), acute systemic toxicity, and subchronic toxicity. Histopathology of 90-day implants of these ti ssues in the rabbit model demonstrated no significant macroscopic reac tion and only slight microscopic response. Using a rabbit model to ass ess immune response, both bovine and porcine pericardial tissues elici ted low levels of antibody. Furthermore, tissue photooxidation or iodi ne sterilization did not increase the overall level of antibodies. Glu taraldehyde-treated tissue also elicited low antibody levels which wer e higher than photooxidized tissue-induced levels. Absorption studies indicated that the photooxidation process may generate new epitopes, p ossibly collagen cross-links. Using the juvenile sheep model to assess in vivo performance, bioprosthetic valves made with photooxidized tis sue were implanted and allowed to serve as functional implants for up to two years. Upon explant, the photooxidized pericardial leaflets wer e found to be non-calcific and partially covered with a layer of host cells. Histological cross-sections stained with von Willebrand's facto r confirmed this layer as endothelial cells.