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

OBJECTIVES: 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. METHODS: 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(R) 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(R) process (CardioCel(R)). 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). RESULTS: The biostability and the durability of both CHP and BP after the multistep ADAPT(R) 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 mu g Ca/mg tissue) compared with Group I (64.37 +/- 6.25 mu g/mg) after 8 weeks. Calcification of CHP (Group III) and BP (Group IV) after the multistep ADAPT(R) treatment was significantly reduced (1.43 +/- 0.48 mu g/mg and 0.75 +/- 0.10 mu g/mg, respectively) compared with Group I (282.52 +/- 18.26 mu g/mg) and the rapidly treated CHP in Group II (11.32 +/- 3.21 mu g/mg) after 16 weeks. CONCLUSIONS: Improved biostability and durability with reduced calcification of tissues after the multistep ADAPT(R) tissue treatment suggest improved alternative substitutes to autologous pericardium.