The effect of cryopreservation on the immunogenicity of allogeneic cardiac valves.

A proportion of implanted cryopreserved allogeneic cardiac valves (ACV) fail due to tissue degeneration initiated by immunological reactions. This study was carried out in a rat model system [Brown Norway (BN; RT1(n)) to Lewis (RT1(l))] to determine the possibility of cryoimmunomodulation of ACV. The immunogenicity of fresh and cryopreserved (1 degrees, 5 degrees, 10 degrees, 30 degrees, and >100 degrees C/min) BN aortic valve conduits (AVC) was assessed using a mixed AVC cell/responder lymphocyte reaction. No significant differences (p > 0.05) in immunogenicity between fresh and cryopreserved (1 degrees C/min and 5 degrees C/min) AVC were observed between 120 and 168 h of co-culture. A significant reduction in immunogenicity was observed with AVC cryopreserved using cooling rates of 10 degrees, 30 degrees, and >100 degrees C/min. The viability of fresh and cryopreserved AVC was determined by a [3H]proline uptake assay. A decrease in viability was observed at cooling rates of more than 1 degrees C/min. The feasibility of cryoimmunomodulation of ACV with the maintenance of viability of a proportion of cells was demonstrated.