Background  Cold storage scheme is a commonly used short-term preservation method of isolated vascular tissue in clinical practice at present, but its effective preservation time and its impact on the structure and function of isolated vascular tissue are still lack of systematic research.

  Objective  To explore the advantages and disadvantages of cold storage and frozen storage for the preservation of human iliac vein.

  Methods  Human iliac veins were randomly divided into Cold Storage (CS) group and Frozen Storage (FS) group, and they were stored for 1 d, 3 d, 5 d, 1 week, 2 weeks and 4 weeks. The mechanical properties of blood vessels were evaluated by ultimate stress test, and the survival and apoptosis of vascular cells were evaluated by MTT colorimetry and TUNEL fluorescence staining. The changes of vascular endothelial cells, smooth muscle cells, collagen fibers and elastic fibers were evaluated by HE staining, Masson staining and EVG staining.

  Results  With the prolongation of storage time, the apoptotic cells of blood vessels in both groups gradually increased, the cell viability gradually decreased, and the tensile properties gradually weakened. No significant apoptotic cells appeared in the CS group and FS group within 5 days of storage, but with the prolongation of storage time, the apoptotic cells in both groups gradually increased, and the apoptotic indices in the CS group were higher than those in the FS group at 1 week (6.09% ± 0.90% vs 3.96% ± 0.69%, P = 0.001), 2 weeks (34.58% ± 3.40% vs 7.45% ± 1.74%, P < 0.001), and 4 weeks (74.90% ± 5.68% vs 31.23% ± 1.52%, P < 0.001). In terms of cell viability, the apoptotic indices in the CS group were higher than those in the FS group at 1 day (2.27 ± 0.22 OD/m vs 1.64 ± 0.30 OD/m, P = 0.002) and 3 days (2.11 ± 0.14 OD/m vs 1.59 ± 0.31 OD/m, P = 0.001). Cell viability was comparable between the two groups from 5 days to 2 weeks, and it was lower in the CS group than that of FS group after 2 weeks (0.83 ± 0.24 OD/m vs 1.29 ± 0.15 OD/m, P = 0.001) and 4 weeks (0.48 ± 0.27 OD/m vs 1.15 ± 0.27 OD/m, P < 0.001). At day 1 (11.98 ± 0.55 N vs 10.96 ± 0.56 N, P = 0.004), day 3 (11.88 ± 0.40 N vs 10.89 ± 0.60 N, P = 0.002) and day 5 (11.72 ± 0.71 N vs 10.97 ± 0.55 N, P = 0.004) after preservation, the tensile performance of the CS group was stronger than that of the FS group; the tensile effect of the two groups was comparable between 1 week and 2 weeks, and the tensile performance of the CS group was weaker than that of the FS group after 4 weeks (10.11 ± 0.48 N vs 10.73 ± 0.62 N, P = 0.042). In the CS group, vascular endothelial cells were destroyed and detached after 2 weeks of storage, and endothelial cells were completely destroyed and detached after 4 weeks of storage; in the FS group, focal detachment and destruction of endothelial cells were observed only after 4 weeks of storage; within 4 weeks, there were no significant destruction changes in vascular collagen fibers and elastic fibers in both groups.

  Conclusion  Within 2 weeks, the preservation effect of cold storage scheme is equivalent to that of frozen storage scheme, which can be used as a safe and reliable preservation scheme for isolated veins. After 4 weeks, the preservation effect of deep low temperature freezing scheme is better than that of low temperature refrigeration.