The effects of different thawing methods on cardiac valves cryopreserved in liquid nitrogen with chondroitin sulfate

Objective To estimate the effects of different thawing methods on the histological structure and vitality of cryopreserved homograft cardiac valves in liquid nitrogen with chondroitin sulfate(CS). Methods A total of 48 rabbit aortic valves were randomly divided into control group and experiment groups(Ⅰ ~ Ⅲ,n = 12). All the valves were sterilized,after which the activity of endothelial cells in control group was examined and the valve tissues were observed under light and electron microscopes. In experiment groups,valves were cryopreserved for 1 month in liquid nitrogen contained CS by the same programmed cooling procedure,after which the valves in Group Ⅰ,Ⅱ and Ⅲ were thawed at rates of 100,30,15 ℃ / min,respectively. The cellular activity and pathological observation were also performed. Results Compared with controls,significant morphologic changes and cellular activity impairment were revealed in both Group Ⅰ and Ⅱ(P 0. 05); while there was no significant difference was observed in Group Ⅲ( P 0. 05). Conclusion The thawing rate of 15℃ / min is proven the best procedure in reserving the histological structure and cellular activity of cryopreserved valves.