Tissue processing techniques for fabrication of covered stents for small-diameter vascular intervention.

Animal-derived pericardial tissue is a widely used biomaterial typically treated with glutaraldehyde (GA) to achieve immunological acceptance and long-term durability. However, GA fixation of biological tissue is associated with long-term failure due to degeneration and calcification. In this study, we evaluated two alternative tissue processing methods for the fabrication of pericardial tissue covered stents: detergent-based decellularization (decell) and limited exposure to GA (gentle-glut). Processed pericardial tissues were extensively characterized both in-vitro and in-vivo. Small-diameter covered stents were fabricated and the ability to seal perforation was evaluated in a flow circuit under physiological blood flow conditions. Results indicate that decell-treated tissue appeared with preserved architecture, tissue strength and stability. Gentle-glut tissue appeared with preserved architecture and increased tissue stability, compared to fresh, unprocessed tissue. Reduction of bioburden was demonstrated for both types of alternative treatments, as for GA fixation. Tensile testing demonstrated that both decell- and gentle-glut treated tissues respond better to low strain, as may occur during balloon inflation and stent deployment. Upon subcutaneous implantation in mice, gentle-glut and to a greater degree decell-treated tissue, elicit better host response, with evidence of active tissue remodeling and no detectable calcification, as compared with GA-treated tissue. Small-diameter stents covered with tissues from all groups successfully sealed perforation under physiological blood flow conditions in-vitro, without compromising flow. In summary, covered stents may perform better with pericardial tissue processed according to the methods described in this study. Adopting this methodology to other types of cardiovascular implants and tissues is also suggested. STATEMENT OF SIGNIFICANCE: Pericardial tissue is a widely used biomaterial for cardiovascular implants, such as covered stents. The use of glutaraldehyde (GA) has become the method of choice for pericardial tissue fixation, making it immunologically acceptable in humans. However, GA-treated tissue is prone to several problems, such as degeneration and calcification that may lead to long-term failure. Here, we studied two alternative tissue processing techniques: fixative-free decellularization and limited exposure to GA. We've shown that both methods achieve better mechanical properties and promote better host acceptance, tissue remodeling and long-term durability. Since the availability of autologous tissue for transplantation is limited, these methods should be adopted for other types of cardiovascular devices, such as bioprosthetic valves, ultimately achieving better long-term results for patients.