The increasing clinical use of donor vascular grafts for reconstructive procedures requires optimization of preservation solutions and standardized vessel protection protocols to improve vessel graft quality. We have previously reported about a new N-acetylhistidine-buffered, potassium-chloride and amino acid-enriched preservation solution containing the iron chelators desferal (100 mM) and LK 614 (20 mM) which provided excellent protection on pig aorta and rat superior mesenteric artery. We now extended our studies to human vessel grafts using as a model the human internal mammary artery (HIMA). Specifically, we studied the maintenance of vessel tone development and endothelium dependent and independent vasodilatory function after prolonged cold storage (4°C). In addition to the new solution we studied 3 traditional solutions: physiological saline solution (PSS), sodium chloride (NaCl), and histidine-tryptophan-ketoglutarate (HTK) solution.

HIMA vessels (1.5–3 mm outer diameter) were studied in a Mulvany apparatus at 37°C (PSS) and a vessel wall tension equivalent to an intraluminal pressure of 100 mm Hg. After constriction with norepinephrine dose-response curves of acetylcholine (Ach, 10^-9–10^-4.5 M) and sodium nitroprusside (SNP, 10^-9–10^-4 M) were determined immediately after vessel isolation (2–4 h) and after prolonged storage periods up to 2 weeks.

When HIMA were stored in NaCl or PSS for more than 10 h, tone development after application of norepinephrine failed. Thus, vessel relaxation could not be assessed. In contrast, HIMA stored in the new solution or HTK did develop tone even after 4 days cold storage. However, after 4 days storage in HTK vessel wall tension during norepinephrine exposure was significantly reduced in comparison to 4 h storage. Furthermore, endothelium-dependent relaxation was significantly decreased (40%) after 4 days cold storage in HTK. At the same time endothelium-independent relaxation was still completely preserved.

Most importantly, after 4 days cold storage in the new solution vessel tone development during norepinephrine was preserved as well as endothelium-dependent and –independent relaxations (80–100%). The new solution specifically protected relaxation properties toward Ach up to 2 weeks (40%) and SNP-induced relaxation up to 3 weeks (>90%). Fractional NO-, prostaglandin- and EDHF-dependent relaxations in response to acetylcholine were unchanged after 4 days of storage in the new solution.

These results provide compelling evidence that the new storage solution is superior to traditional storage solutions including HTK, PSS, and NaCl. The new solution is able to provide excellent protection of endothelial function after more than 4 days cold storage. This will enable to develop improved cold storage protocols and to extend the periods of safe storage of vessels for tissue transplantation.