The destructive effect of extracellular ice formation in organized multicellular tissues is known to be a principal reason why conventional techniques of cryopreservation fail to provide effective protection during freezing. Avoidance of ice during cooling can physically be achieved by vitrification, which is the amorphous solidification of a supercooled liquid by adjusting the solute composition and cooling rate such that nucleation and growth of ice crystals is prevented. In principal a biological system can be stabilized in the glassy (vitreous) state without the inherent problems associated with crystallization and so-called solution effects injury that arise from the increased concentration of solutes due to removal of water as ice.
This study was designed to evaluate a vitrification approach to storing a vascular tissue model (rabbit jugular vein) compared with a standard commercial method used clinically and employing slow cooling (l°C/min) with dimethylsulfoxide (DMSO) as the cryoprotective agent (CPA). A baseline vitrification medium (designated VS55) was used to replace at least 50% of the tissue water with a combination of CPAs. and vitrification was achieved using a relatively high cooling rate (> 40°C/min). After rewarming and removal of the CPAs. contractility of the blood vessel segments was evaluated in vitro using standard physiological response tests to a panel of reagents. The maximum contractions achieved in vitrified vessels were all greater than 80% of fresh matched controls with similar drug sensitivities. In contrast, frozen/thawed vessels exhibited maximal contractions below 25% of fresh matched controls with concomitant decreases in drug sensitivity.
This study clearly demonstrates a significant benefit of vitrification compared with conventional freezing and thawing for preserving smooth muscle contractile function of preserved blood vessels. Vitrification may prove to be an effective way to minimize the deleterious effects of freezing and thawing in cryopreserved tissues, or engineered tissue constructs.