Influence of Glutaraldehyde Fixation on the Detection of SLA-I and II Antigens and Calcification Tendency in Porcine Cardiac Tissue

Abstract

Immunological effects have been addressed as key factors for the long-term results of biological porcine aortic prostheses. In this study we investigated the influence of glutaraldehyde fixation on the expression of SLA (swine leucocyte antigens) and the calcification of porcine cardiac tissue. Deparaffinized sections obtained from porcine aortic tissue were fixed in a buffered glutaraldehyde solution for 1, 2, 3, 24 and 72 hours, respectively, and finally immunostained with monoclonal anti-SLA class I antibody 2.27-3a and anti-SLA-II antibody MSA3. Sixteen samples from fixed porcine cardiac tissue and, for comparison, 8 samples from leaflets of Toronto-SPV and Freestyle valves were implanted subcutaneously in 10 Wistar rats for 12 weeks and their calcium content was measured by atomic absorption spectrophotometry. SLA-I epitopes were no longer detectable using anti-SLA-I antibodies after fixation for 3 h. The SLA-II antigens remained detectable after longer fixation period. Short-time fixation resulted in marked calcification of the porcine cardiac tissue and to destruction of the SLA-I epitopes, whereas, even after longer fixation time, the epitopes of the SLA-II antigen remain unaffected. Chelate formation due to glutaraldehyde treatment provides protection against calcification. Short-time fixed porcine cardiac tissue has a tendency towards a greater degree of calcification than longer fixation periods. Based on the present results, it is pointless to set the length of fixation to switch off the immunogenicity.