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

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 α-galactosidase (α-gal) to remove major xenoreactive antigens from xenogenic tissues. MATERIALS AND METHODS: Recombinant Bacteroides thetaiotaomicron (B. thetaiotaomicron) α-gal or decellularization, or both were used to remove α-gal from bovine pericardium. It was confirmed by α-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 α-gal treatment were investigated by tests of tensile-strength, permeability, and compliance. Collagen fiber rearrangement was also evaluated by a 20,000× transmission electron microscope (TEM). RESULTS: Recombinant B. thetaiotaomicron α-gal could effectively remove α-gal from bovine pericardium B. thetaiotaomicron (0.1 U/mL, pH 7.2) while recombinant human α-gal removed it recombinant human α-gal (10 U/mL, pH 5.0). There was no difference in the mechanical properties of fresh and recombinant α-gal-treated bovine pericardium. Furthermore, the TEM findings demonstrated that recombinant α-gal made no difference in the arrangement of collagen fiber bundles with decellularization. CONCLUSION: Recombinant B. thetaiotaomicron α-gal effectively removed α-gal from bovine pericardium with a small amount under physiological conditions compared to human recombinant α-gal, which may alleviate the harmful xenoreactive immunologic responses of α-gal. Recombinant α-gal treatment had no adverse effects on the mechanical properties of bovine pericardium.