Experimental study on the effect of different thawing rate on viability of cryopreserved human aortic valvehomograft in liquid nitrogen

Objective To find a good thawing method which can maximally maintain the viability ofhuman aortic valve homograft (AVH). Method Thirty-six AVH were randomly divided into 6 groups:Fresh AVH was in group 1, and the other 5 AVHs were cryopreserved in liquid nitrogen for 3 months, thenthawed to 4℃ at the following rate: 42℃ water-bath thawing (group 2), 1. 0±0. 54℃ /min (group 3), 4. 0±0. 54℃ /min (group 4), 10.0±2. 0℃/min (group 5), 30.0±4.5℃/min (group 6). The effects were evaluated by the following criteria: trypan blue staining fro living cell counting, 24 h glucose metabolic rate,3H-TdR incorporation, and leaflet tissue culture. Result Living cell counting, glucose metabolic rate and 3 HTdR incorporation in group 1 were significantly higher than in the other groups (P0.05), and in group 4significantly. higher than in groups 2, 3, 5 and 6 (P0.05). Cell growth in tissue culture of group 1 was 3 to4 days earlier than the other groups. Conclusion Liquid nitrogen caused certain degrees of damage to cryopreserved AVH. 4℃/min thawing caused less damage to cryopreserved AVH.