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Methods: Six porcine pulmonary allografts were har-vested from mini-pigs, and cryopreserved for four weeks. In two pigs, the grafts were decellularized with Triton X solution, after which static reseeding of the valve surface was performed for 48 h with autologous endothelial cells harvested from a leg artery. Decellularization, but not reseeding, was carried out in two mini-pigs, and cryopreservation alone in two mini-pigs. Whilst under right heart bypass, the right ventricular outflow tract was replaced in six minipigs. The grafts were explanted after four weeks; analysis included direct pressure measurement, echocardiography, macroscopy, light microscopy with hematoxylin and eosin staining, and immunohistochemical studies to identify macrophages, T lymphocytes, and endothelial cells.

Results: Hemodynamically and macroscopically, there were no major differences between the three groups. In the cryopreservation-only group, immunohistochemistry showed an influx of macrophages, and T lymphocytes at the cusps. Endothelial cell coverage was found in the decellularized and decellularized+ cell-seeded groups, but no macrophages and T lymphocytes were found at the cusps.

Conclusion: Decellularization of the cryopreserved allograft may reduce the inflammatory response and improve its long-term durability.