Biostability, durability and calcification of cryopreserved human pericardium after rapid glutaraldehyde-stabilization versus multistep ADAPT(R) treatment in a subcutaneous rat model

Abstract

Autologous pericardium rapidly fixed with glutaraldehyde (GA) in theatre is considered in many cardiac surgery centres the best material currently available for intracardiac, valvular or vascular repair. Implanted non-fixed autologous tissues suffer rapid degeneration, shrinkage and absorption whereas standard xenotypic fixed tissues cause local cytotoxicity and calcification. In the present study, using a subcutaneous rat model, we tested the biostability, durability and calcification potential of four different pericardium patches treated with GA and relevant to current clinical practice. Pericardium samples were divided into four groups according to the method of treatment. Group I consisted of bovine pericardium (BP) fixed with 0.6% GA (control), Group II cryopreserved human pericardium (CHP) rapidly fixed with 0.6% GA for 4 min and detoxified with MgCl₂, Group III CHP treated with the multistep ADAPT^® process (delipidized, decellularized with Tx-100, deoxycholate, IgePal CA-630 and denucleased, fixed in 0.05% monomeric GA and detoxified) and Group IV BP treated with the multistep ADAPT^® process (CardioCel^®). Biostability was determined by shrinkage temperature which measures the degree of cross-linking, and durability assessed by resistance to a mixture of proteinases (pronase digestion). Treated pericardium samples (n = 10 in each of Groups I–IV) were implanted in the subcutaneous rat model for 8 and 16 weeks, followed by histology and calcium analysis (atomic absorption spectrophotometry). The biostability and the durability of both CHP and BP after the multistep ADAPT^® treatment remained stable without any microscopic calcification. Extractable calcium levels of CHP were significantly (P < 0.01) reduced in Group II (1.89 ± 0.77 μg Ca/mg tissue) compared with Group I (64.37 ± 6.25 μg/mg) after 8 weeks. Calcification of CHP (Group III) and BP (Group IV) after the multistep ADAPT^® treatment was significantly reduced (1.43 ± 0.48 µg/mg and 0.75 ± 0.10 μg/mg, respectively) compared with Group I (282.52 ± 18.26 μg/mg) and the rapidly treated CHP in Group II (11.32 ± 3.21 μg/mg) after 16 weeks. Improved biostability and durability with reduced calcification of tissues after the multistep ADAPT^® tissue treatment suggest improved alternative substitutes to autologous pericardium.