EFEITOS DA REDUÇÃO DO TEMPO DE FIXAÇÃO EM GLUTARALDEÍDO E DA DESCELULARIZAÇÃO SOBRE AS CARACTERÍSTICAS DO PERICÁRDIO BOVINO E SUA CALCIFICAÇÃO IN VIVO

Abstract

Introduction: Bioprosthetic heart valves manufactured with bovine pericardium fixed in glutaraldehyde are the most used to replace defective valves in heart valve disease. However, they require replacement between 10 and 15 years after implantation, due to structural degeneration that is associated with calcification that occurs in bovine pericardium leaflets of bioprosthesis. The main strategies to minimize late post-implantation calcification are focused on the chemical processing of bovine pericardium. The reduction of fixation time with glutaraldehyde, the incubation in amino acids for the inactivation of residual glutaraldehyde aldehydes and the previous decellularization of bovine pericardium have already been suggested by literature, but they need further investigation for an effective clinical application. Furthermore, the combined effect of said anti-calcification techniques has not yet been studied. Objective: To evaluate the effect of decellularization and reduction of fixation time with glutaraldehyde on physical properties of bovine pericardium samples compared to bovine certified pericardium samples, as well as to analyze the effect of these treatments on in vivo calcification of bovine pericardium samples intended for use in heart valves bioprostheses. Material and methods: The bovine pericardium samples were divided into groups: BP10d (fixed with glutaraldehyde for 10 days), BP5d (fixed with glutaraldehyde for 5 days) - both cellularized, and BP5dAC (acellular samples and fixed with glutaraldehyde for 5 days). After fixation, all samples were treated in glutamic acid amino acid solution and characterized by mechanical and thermal stability tests, in addition to histological evaluation by light microscopy, scanning electron microscopy and analysis for the content of calcium by inductively coupled plasma optical emission spectrometry. The tissues were implanted in subcutaneous tissue of rats and serial explants that were obtained after 7, 14, 28, 60 and 120 days were submitted to a new evaluation by ML, SEM and ICP-OES. Results: Microscopic analysis revealed changes in collagen and elastic fibers in the BP10d and BP5dAC groups, but there were no changes on tissue mechanical and thermal properties. For all biological times employed in the study, inflammatory reaction was similar between BP5d and BP5dAC and less intense compared to BP10d. Calcification values were low in all groups, with a lower calcium content in BP5dAC. Conclusion: The combined treatment of decellularization, fixation with glutaraldehyde for 5 days and post-treatment with glutamic acid decreased bovine pericardium calcification and inflammation in a model of subcutaneous implantation in rats, without altering physical and biological properties which are important for the manufacture of bioprosthetic heart valves.