P165	An evaluative comparison of mechanical and electrical properties of fresh and cryopreserved arteries.
1K.Wachal, 1M.Gabriel, 3Z.Tylczynski, 3P.Biskupski, 4A.Korcz, 2K.Pawlaczyk
1Department of General and Vascular Surgery, Poznan University of Medical Sciences, Poznań, PL; 2Department of Hypertension and Vascular and Internal Diseases, Poznan University of Medical Sciences, Poznań, PL; 3Adam Mickiewicz University, Faculty of Physics, Poznań, PL; 4Institute of Human Genetics, Polish Academy of Sciences, Poznań, PL.

Implantation of cryopreserved allogenic arteries to patients with graft infections is the method used in our Department. Good knowledge of mechanical properties of the arterial wall (kept in different cryopreservation conditions) is very important for their clinical estimation. The aim of our study was to compare elasticity, compliance and electrical properties of fresh vs cryopreserved arterial grafts. We also tested different methods of cryopreservation. We analyzed abdominal aortas from 16 weeks-old LEW rats stored in different media and conditions of cryopreservation (4 groups). After 30 days samples were unfrozen in 37°C and their mechanical properties were evaluated by DMA 242 analyzer; electrical properties were analyzed by electrical impedance spectrometer HP 4284A. Results of our study showed that cryopreservation of arterial grafts increased their compliance. We confirmed that storing samples at -80°C reduced degeneration of arterial walls. Storage of the samples at -40°C increases the compliance and makes them useless as allogenic grafts. Temporary changes and absolute value of storage modulus after drying of the samples kept in liquid nitrogen indicate greater tissue distraction in comparison to those kept at higher temperature. Electrical conductance depends on and increases with applying frequencies within the range of 100Hz-1Mz. During the measurement we observed the biggest changes of electrical conductance at the highest frequencies. Primary electrical conductance is smaller in cryopreserved samples than in fresh samples. We observed reduction of electrical conductance in fresh tissues after about 4 hours and in cryopreserved samples after a few minutes. Conclusions: To maintain the mechanical properties of arterial wall it is very important to store them in 0,9% NaCl. Drying of the arteries wall causes an increase of rigidity and a decrease of elasticity. This process finishes after removing tissues from natural environment after 40-50 minutes. We observed faster drying of cryopreserved tissues in comparison to fresh tissues in mechanical study. This process was confirmed in histological study. Electrical conductance changes depend to a small degree on the cryopreservation condition. Mechanical and electrical examination proved that storage of blood vessels at –80°C causes the smallest destruction of blood vessels.

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