Biocompatibility and Immunogenicity of Decellularized Allogeneic Aorta in the Orthotopic Rat Model

Peripheral arterial disease causes blood vessel dysfunction that requires surgical intervention. Current surgical interventions employ synthetic or allogeneic vascular grafts, which offer biocompatible material solutions that are not able to regenerate or grow with the patient. Decellularized scaffolds have gained significant momentum in the past few years, since they have the potential to regenerate in the patient. The aim of this study was to investigate the effects of modified decellularization protocol on the biocompatibility and immunogenicity of allogeneic rat abdominal aorta in an orthotopic rat model. Native syngeneic Wistar (W) and allogeneic Dark Agouti (DA) aortas, together with decellularized allogeneic DA aortas, were assessed histologically, immunohistochemically, and biomechanically. The immunogenicity of the untreated and decellularized syngeneic and allogeneic grafts was assessed in W rats, implanted orthotopically. Following implantation for 6 weeks, the grafts were explanted and assessed for the presence of T cells and macrophages by immunohistochemistry, and for their biomechanical integrity and histoarchitecture. No obvious histoarchitectural differences were observed between the native W and DA aortas, with both presenting similar three-layered structures. Histological analysis of decellularized DA aortas did not reveal any remaining cells. Explanted native DA allografts showed media necrosis, partial elastic fiber degradation, and adventitia thickening, as well as infiltration by lymphocytes (CD3(+), CD4(+)) and macrophages (CD68+) in the adventitia. The explanted decellularized DA allografts indicated reduced immune injury compared to the explanted native DA allografts. The explanted native W syngeneic grafts showed a mild immune response, with an intact media and no lymphocyte infiltration. The explanted native DA allografts showed significantly lower collagen phase slope than the decellularized DA allografts before implantation, and significantly higher thickness than the explanted decellularized DA allografts. The results indicated that the modified decellularization protocol did not affect significantly the mechanical and histological properties of the native DA rat aorta. Overall, the immune response was improved by decellularization. Native DA allografts induced an adverse immune response in W rats, whereas syngeneic W grafts showed good tissue integration Impact Statement The generation of a small-caliber arterial graft, utilizing a large vessel of a small animal, such as the aorta of the rat or rabbit, for clinical use in the peripheral arterial tree, can widen the options for arterial prostheses. This in vivo study demonstrated the ability of the decellularization protocol that was used to produce a noncytotoxic acellular small-caliber arterial graft, with sufficient biomechanical and biological integrity to withstand the demanding flow and pressure environment of the rat aorta. This work also demonstrated the superiority of the decellularized homograft over its intact counterpart, in terms of lower immunogenicity.