Long-term cold storage effect of Univesity of Wisconsin (UW) solution on vascular endothelial function of rat aorta.

There are few and oppositing data in the literature concerning the cold storage effect of University of Wisconsin (UW) solution on vascular smooth muscle viability and endothelial function. Some reports demonstrated that UW solution is more suitable than Eurocollins solution for short-term storage of blood vessels, as well as for long-term preservation of arteries. Other Authors observed that solutions containing an higher potassium concentration, such as UW, can affect the homeostasis of the vascular tissue, alterating the equilibrium among the several vasoactive endothelium-derived substances. Endothelial cells release vasoactive substances exerting major effects on local vasoregulation. Among them, the powerful relaxation of vascular smooth cells and the inhibition of platelet adhesion and aggregation. In a previous study, we observed the positive effect on morphology of in-situ flushing and preservation of cold UW solution on human iliac arteries harvested during multiple cadaveric organ procurement. On the other hand, an alteration of the endothelium-dependent vascular regulation have been reported even in presence of an endothelial cell integrity. We investigated the effect of long-term cold storage in UW solution, on functional as well as morphologic changes of the rat aortae. The data were analysed with the unpaired, doubled-sided Studentʹs t-test and a P-value less than 0.05 was considered significant. Male Wistar rats, weighing 220-240 g, maintained under standard condition were used in this study. All the animals were anaesthetized by ether inhalation. The in-itu flushing of the thoracic aorta was performed through the abdominal aorta, with 10 ml of cold University of Wisconsin solution. The vascular segments were then stored in UW solution and kept at 4°C up to 48 hours. Circumferential biopsy samples of aorta segments were routinelly processed for scanning (SEM) and trasmission electron microscopy (TEM). The endothelium-dependent relaxation was evaluated during an organ bath assay, as the acetylcholine-mediated vasodilatation of aortic strips. The segments of aorta used as controls produced a contractile response to NE 10-7 M of 429 +/− 54 mg (mean +/− SE), and 307 +/− 16, after 48 h. The percentages of relaxation to ACH 10 −5 M of the aorta controls and of the aortic segments after 48 hours of cold storage in UW solution, were 82,2+/−2,3% and 65,2+/−6,2%, respectively. Moreover, a complete relaxation-response to nitric oxide (NO) 10 −6 M was observed in all aorta segments stored for 48 hours. At the same time, TEM and SEM reveals focal disendothelialization and little initial damage of the smooth muscle cells. These results suggest that UW solution is suitable for cold long-term vascular allografts storage intended for transplantation.