Effects of different preservation methods of human iliac veins.

With the progress of vascular anastomosis technology, the radical resection surgery of cancer combining with vascular resection and reconstruction has been focused by surgeon. As a natural substitute material for blood vessel, vascular allografts have good vascular compliance and histocompatibility. Generally, the donated veins could not be used immediately, and need to be well preserved. So, it is greatly significant to do research in the preservation effects of different preservation methods on veins. In this study, the effects of different preservative methods of human iliac veins were compared and analyzed in terms of cell viability, vascular wall structure and tension resistance. The donated human iliac veins were randomly divided into three groups: Cold Storage Group (4 °C) (CSG), Frozen Storage Group (-186 °C) (FSG)and Fresh Control Group (FCG). Six detection time-points of preservation for 1, 3, 5, 7, 14, 28 days were set respectively. There are ten samples in each group and each time-point separately. Survival and apoptosis of vascular cell were evaluated by MTT assay and Tunel fluorescence staining. Tensile test was used to evaluate mechanical properties of vessels. The changes of vascular endothelial cells, smooth muscle cells, collagen fibers and elastic fibers were evaluated by HE staining, Masson staining and EVG staining. Furthermore, the changes of organelles were observed by transmission electron microscope. With the extension of preservation period, the vascular cell viability and tension resistance of two groups decreased, and the apoptotic cells increased gradually. The apoptosis index of CSG was higher than FSG at each time point (P < 0.05). In terms of cell viability, CSG was higher within 3 days (P < 0.05), both groups were same between 3 and 14 days, and then CSG lower than FSG after 14 days (P < 0.05). In terms of tension resistance, CSG was stronger than FSG (P < 0.05) in first 7 days, both groups were same in 2nd week, and then CSG was weaker in 4th week (P < 0.05). In terms of vascular wall structure, in CSG, vascular endothelial cells were damaged and shed, smooth muscle cells were edema after 14 days, but the cell membrane and intercellular connection were still intact. In 4th week, endothelial cells were completely damaged and shed, the boundary of smooth muscle cell membrane was unclear, intercellular connection was damaged. Moreover, organelles were destroyed and disappeared, perinuclear condensation of chromatin was observed, and some cells had incomplete nuclear membrane or nuclear fragmentation; However, there were no obvious changes in the FSG within 28 days. Finally, local exfoliation and destruction of endothelial cells and edema-like changes of organelles were observed; the collagen fibers and elastic fibers of blood vessels in the two groups had no obvious damage and change within 28 days. For excised human iliac vein, cold and frozen storage can effectively preserve the cell viability, wall structure and tension resistance of blood vessels. With the extension of preservation time, the related performance of vessels declined in varying degrees. Within first week, the effect of cold storage is better than frozen storage, but frozen storage is significantly better than cold storage after 2 weeks.