A simplified technique for the cryopreservation of vein allografts

Objectives: we assessed the effects of cryopreservation on smooth-muscle ce ll 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% dimet hyl sulphoxide, DMSO), cooling and warming rates, and the rate of cryoprote ctant removal after thawing were examined. Results: control veins exhibited damage in 8.5% (95% confidence interval (C I) 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 pre sence of DMSO, damage to smooth-muscle cells was independent of the rates o f 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 approxima tely 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 res ults suggest that simplified methods of vein cryopreservation are feasible.