BOVINE PERICARDIUM FOR HEART-VALVE BIOPROSTHESES - IN-VITRO AND IN-VIVO CHARACTERIZATION OF NEW CHEMICAL TREATMENTS

This study is aimed at investigating the bovine pericardium treated wi th different chemical procedures applied to prevent dystrophic calcifi cation; decellularization of the fresh pericardium (samples B and C); fixation of the pericardium with glutaraldehyde (samples A, B, C, D an d E); detoxification with aminoacids (samples A and B) and storage in a solution of benzoic acid esters. Pericardial sacs were harvested and delivered to the laboratories to be submitted to the chemical treatme nts. The samples E have been treated as the samples D but before the i mplantation they were exposed to the surgical lamp in order to promote some drying. The samples were tested for their mechanical properties and shrinkage temperature (at 1 week and after 36 months). The in vivo tests were performed by means of implantation in a paravertebral subc utaneous position in rats. At the explant (2, 4 and 8 weeks) the sampl es were submitted to histological assay and the calcium content determ ined by spectroscopic atomic absorption. All the samples showed loss o f tensile strength and elongation at 36 months (except for the sample A), as well as a moderate diminution of the shrinkage temperature. The histology showed that the decellularized samples (B, C) were thicker than the others and the collagen fibres were extensively homogenated. The cell colonization was macrophagic for the samples A and D while it was also composed of giant cells in the samples B, C and E at 8 weeks . The von Kossa's staining was positive only for the samples D and E a fter 4 weeks of implantation. The calcium content of the samples D was 285.3 mg/g at 8 weeks while in E it was 44.4 mg/g dry tissue at 4 wee ks; for the remaining samples the calcium content did not increase wit h the time (2.1-2.3 mg/g at 8 weeks). In conclusion, the pericardium d ecellularization and detoxification associated with its storage in a g lutaraldehyde-free solution is a promising method in order to realize more durable pericardial bioprostheses. The investigated tissue treatm ents applied to the bovine pericardium permit removal of the calcium n ucleation sites, and hence the avoidance of the severe drawback of the aldehyde crosslink, but at the same time maintain the necessary and w ell known tissue stability.