The effect of TAVI-simulation and perfusion on the cell layer of decellularized and re-seeded homografts

Objective Tissue engineering aspires to create organs and tissue from autologous cells, which mimic the function of native tissue as closely as possible. However, before a tissue engineered valve can be implanted, various experiments on the performance of the valve are necessary. Information regarding the reaction of a cell layer to different stimuli enables the prediction of the reaction in vivo. A minimal invasive implantation procedure might have effects on the cell layer. The transcatheter valve implantation (TAVI) is a minimal invasive procedure to implant an aortic valve. Escpecially for older and morbid patients the minimal invasive approach decreases postoperative morbidity and mortality. Currently available valves for TAVI are biologic valves with a limited durability. Younger patients in particular would benefit from a tissue engineered valve with a potentially longer durability and growth potential. Methods and Material Aortic homografts (n=4) were first decellularized and then recellularized with fibroblasts (FB) and endothelial cells (EC). The cells were harvested from saphenous veins, which were collected during aortocoronary bypass operations. After valve recellularization, a TAVI simulation was performed. The homografts were crimped for 10 min and then expanded using a catheter balloon. A dynamic bioreactor enabled the simulation of pulsatile flow conditions. The valves were exposed to increasing flow rates over the period of three days (d1 = 1 l/min, d2 = 1.5 l/min, d3 = 2 l/min). After all processing steps, the final testing samples were taken and analyzed. Cell layer topography was evaluated with scanning electron microscopy (SEM). An immunohistochemial (IHC) analysis enabled the assessment of the cell layer, structure of the extracellular matrix (ECM) and inflammation reaction. Results SEM evaluation of the samples after perfusion displayed an inhomogeneous cell layer. EC staining demonstrated a damaged cell layer. The IHC analysis of FB presented a similar result, with the exception of the ventricular side of the aortic valve leaflet. This part of the leaflet retained more of the earlier seeded FB. Conclusion The cell layers on the homografts, especially the EC layer, took considerable damage during the crimping and perfusion procedure. Interestingly, the ventricular side of the aortic valve leaflet seemed to have sustained less damage compared to the arterial side. A tissue engineered construct for TAVI has to withstand the strains of the implantation and perfusion process. Further studies are necessary to evaluate the damage and to develop a procedure which enables a safe transportation of the tissueengineered valve