A simplified technique for the cryopreservation of vein allografts

Objectives: we assessed the effects of cryopreservation on smooth-muscle cell injury in human vein. Materials and methods: long saphenous vein was collected during surgery and cryopreserved. Smooth-muscle cell damage was assessed after thawing by in situ detection of fragmented DNA. The presence of cryoprotectant (10% dimethyl sulphoxide, DMSO), cooling and warming rates, and the rate of cryoprotectant removal after thawing were examined. Results: control veins exhibited damage in 8.5% (95% confidence interval (CI) 4.7 to 13.4%, n = 13) of smooth-muscle cells compared with 27.7% (95% CI 23.2 to 32.4%, n = 115) in vein frozen in 10% DMSO (p = 0.001). In the presence of DMSO, damage to smooth-muscle cells was independent of the rates of cooling (p = 0.72) and warming (p = 0.45). The rate of dilution to remove the cryoprotectant after thawing also had no effect on cell damage (p = 0.64). In the absence of cryoprotectant, cell damage was doubled to approximately 50% by slow rather than rapid warming (p = 0.01). Conclusion: cooling rate, and the presence of a cryoprotectant, has little effect on smooth-muscle damage, provided that the tissue is warmed rapidly. Slow warming, in the absence of DMSO, causes substantial damage. These results suggest that simplified methods of vein cryopreservation are feasible.