Changes of the Structural and Biomechanical Properties of the Bovine Pericardium after the Removal of alpha-Gal Epitopes by Decellularization and alpha-Galactosidase Treatment

ABSTRACT

BACKGROUND: Bovine pericardium is one of the most widely used materials in bioprosthetic heart valves. Immunologic responses have been implicated as potential causes of limited durability of xenogenic valves. This study aimed to determine the effectiveness of decellularization and alpha-galactosidase (alpha-gal) to remove major xenoreactive antigens from xenogenic tissues. MATERIALS AND METHODS: Recombinant Bacteroides thetaiotaomicron (B. thetaiotaomicron) alpha-gal or decellularization, or both were used to remove alpha-gal from bovine pericardium. It was confirmed by alpha-gal-bovine serum albumin-based enzyme-linked immunosorbent assay (ELISA), high-performance anion exchange chromatography, flow cytometry, 3,3'-diaminobenzidine-staining, and lectin-based ELISA. The mechanical properties of bovine pericardium after decellularization or alpha-gal treatment were investigated by tests of tensile-strength, permeability, and compliance. Collagen fiber rearrangement was also evaluated by a 20,000x transmission electron microscope (TEM). RESULTS: Recombinant B. thetaiotaomicron alpha-gal could effectively remove alpha-gal from bovine pericardium B. thetaiotaomicron (0.1 U/mL, pH 7.2) while recombinant human alpha-gal removed it recombinant human alpha-gal (10 U/mL, pH 5.0). There was no difference in the mechanical properties of fresh and recombinant alpha-gal-treated bovine pericardium. Furthermore, the TEM findings demonstrated that recombinant alpha-gal made no difference in the arrangement of collagen fiber bundles with decellularization. CONCLUSION: Recombinant B. thetaiotaomicron alpha-gal effectively removed alpha-gal from bovine pericardium with a small amount under physiological conditions compared to human recombinant alpha-gal, which may alleviate the harmful xenoreactive immunologic responses of alpha-gal. Recombinant alpha-gal treatment had no adverse effects on the mechanical properties of bovine pericardium.