Morphology of Tissue Reaction in Rats after Subcutaneous Implantation of Porcine Pericardium and Aortic Valve Leaflets Devitalized by Cryoradiation

The decrease of immunogenicity is a priority requirement to pre-implantation treatment of the xenogeneic graft tissue. To create tissue implants of the pericardium and aortic valve leaflets, we have developed a method of devitalizing treatment, based on the combined effect of low temperatures (-196 °C) and ionizing β-radiation. This approach provides deletion to the main targets of biomaterial immunogenicity due to the effects of successive cryoand radiation damage, as well as the activation of radiation-induced apoptosis. The purpose of research was to assess the impact of low-temperature and radiation and their synergistic effect on the biocompatibility of devitalized xenogeneic tissues. METHODS. Histological tests were used to study tissue reaction in experimental animals after implantation of native porcine pericardium and aortic valve leaflets (control), grafts after freezing-thawing and grafts after freezing-thawing with irradiation at a dose of 25 kGy. After 7, 14 days and 1, 3, 6 and 12 months we evaluated the morphological changes of implant structure, inflammatory response of the recipient’s tissue, formation of the capsule and its degree of maturity, the xenogeneic cells survival and recovery of recipient’s surrounding tissue. RESULTS. Comparative analysis has revealed fundamental differences of engraftment indicators and tissue reaction of cryopreserved and irradiated samples from implants after freezing and β-radiation. Cryoradiation processing greatly reduced the immune response to the implantation. Devitalized tissues promoted early stimulation of recipient’s tissues repair, maintained compactness and structural integrity. After a year the border between the implant and connective tissue erased, biomaterial was fully sprouted with recipient’s tissue. The observed changes testify to the integration of implant’s connective tissue, followed by its replacement. CONCLUSION. Our study has confirmed the possibility of using xenogeneic pericardium and aortic valve leaflets, being modified by cryoradiation method to restore soft tissue structures.