Influence of the selection of the suture material on the mechanical behavior of a biomaterial to be employed in the construction of implants. Part 2: Porcine pericardium

Decellularized Porcine Pericardium Enhances Autologous Vascularized Matrix as a Prosthesis for Left Ventricular Full-Wall Myocardial Reconstruction

Regenerative grafts for myocardial reconstruction are often mechanically not stable enough to withstand the left ventricle’s high blood pressure. Hence, decellularized pericardium may serve as a stabilizing structure for biological myocardium prostheses. The efficacy of detergent- and enzyme-based protocols to decellularize porcine pericardium was compared. Then, the decellularized pericardium was employed for a primary cover of a transmural left ventricular defect in minipigs (n = 9). This pericardium patch was applied to mitigate the high-pressure load on an autologous stomach tissue, which was utilized as a regenerative tissue prosthesis. Decellularization of the porcine pericardium with deoxycholic acid (DOA)- and enzyme-based protocols (trypsin/EDTA) removed 90% of the original cells (p < 0.001). The trypsin/EDTA protocol significantly altered the matrix architecture compared to the DOA protocol. There were no infections or clinical signs of graft rejection following the transplantation of the decellularized pericardium and the autologous segment of the stomach in the surviving animals (n = 7). A good left ventricular function could be detected via MRI six months following surgery. The biological integration of the graft into the host’s tissue was found histologically. The stabilization of initially fragile grafts with decellularized pericardium facilitates the application of regenerative myocardial prostheses even on the left ventricle.

Transcatheter Aortic Valve Replacement with a Self-Expanding Prosthesis

The self-expanding transcatheter heart valve (Medtronic Cardiovascular Corevalve and Evolut) is a supra-annular, trileafet porcine pericardial valves on a diamond lattice nickel-titanium alloy frame. The TAVR device has undergone significant improvements in design and procedural techniques to further increase safety, efficacy, and durability since they it was first released. Unique design characteristics, as well as patient and procedural factors, favor self-expanding over balloon-expandable prostheses in certain situations. The self-expanding transcatheter heart valve has proven to be an excellent option for severe aortic stenosis patients with any level of surgical risk and preliminary data suggest a comparable durability to surgical tissue valves.

CoreValve® transcatheter self-expandable aortic bioprosthesis

Transcatheter aortic valve implantation has been designed to treat patients affected by severe symptomatic aortic stenosis considered extremely high risk for surgical aortic valve replacement. The CoreValve® (Medtronic Inc., MN, USA) is a multilevel self-expanding and fully radiopaque nitinol frame with a diamond cell configuration that holds a trileaflet porcine pericardial tissue valve and anchors the device in the native anatomy. CoreValve was the first percutaneous valve to be granted the CE mark for transfemoral implantation in May 2007 and the CoreValve US Pivotal Trial is actively underway. The CoreValve is available in four sizes (23, 26, 29 and 31 mm) to serve a broad range of patients' annulus from 18 to 29 mm. All the valves fit into an 18-Fr size catheter. Currently, more than 35,000 patients have been treated in more than 60 countries worldwide from the femoral artery, the axillary artery and, more recently, from a direct aortic approach, with excellent results up to 4-year follow-up.

Impact of processing parameters on the haemocompatibility of Bombyx mori silk films

Silk has traditionally been used for surgical sutures due to its lasting strength and durability; however, the use of purified silk proteins as a scaffold material for vascular tissue engineering goes beyond traditional use and requires application-orientated biocompatibility testing. For this study, a library of Bombyx mori silk films was generated and exposed to various solvents and treatment conditions to reflect current silk processing techniques. The films, along with clinically relevant reference materials, were exposed to human whole blood to determine silk blood compatibility. All substrates showed an initial inflammatory response comparable to polylactide-co-glycolide (PLGA), and a low to moderate haemostasis response similar to polytetrafluoroethylene (PTFE) substrates. In particular, samples that were water annealed at 25 °C for 6 h demonstrated the best blood compatibility based on haemostasis parameters (e.g. platelet decay, thrombin-antithrombin complex, platelet factor 4, granulocytes-platelet conjugates) and inflammatory parameters (e.g. C3b, C5a, CD11b, surface-associated leukocytes). Multiple factors such as treatment temperature and solvent influenced the biological response, though no single physical parameter such as β-sheet content, isoelectric point or contact angle accurately predicted blood compatibility. These findings, when combined with prior in vivo data on silk, support a viable future for silk-based vascular grafts.

Supramolecular structure of human aortic valve and pericardial xenograft material: atomic force microscopy study

Pericardial tissue (bovine or porcine), chemically stabilized with glutaraldehyde (GA), is widely used in cardiovascular surgery in the form of bioprosthetic valves. GA reacts with tissue proteins and creates inter- and intra-molecular cross-links, resulting in improved durability. However, tissue calcification and mechanical damage are still unresolved problems. The purpose of this study was to examine the surface topography of normal human aortic valve and GA-stabilized porcine pericardium tissue in order to gain comparative insight into supramolecular structure of both tissues. The analysis was focused on morphologic evaluation of collagen constituents of the tissues. Atomic force microscopy working in the contact mode in air was employed in the study. Considerable diversity in the spatial orientation of collagen fibrils for the human aortic valve and pericardial tissue were observed. It was found that different forms of collagen fibril packing, i.e. dense and "in phase" or loose, could have an impact on the collagen D-banding pattern. Stabilization with GA introduced significant changes in the surface topography of collagen fibrils and in their spatial organization on the tissue surface. Strong disturbance in the fibril's D-spacing was observed. It was also suggested, that the observed structural changes at the supramolecular level might make an important contribution to the progressive damage and calcification of the tissue. The presented results demonstrate that the AFM method can be useful for non-destructive structural characterization of heart valves and bioprosthetic heart valve material.