Dimethyl sulfoxide concentration in fresh and cryopreserved porcine valved conduit tissues

The time-dependent penetration of the cryoprotectant dimethylsulfoxide (DMSO) into porcine aortic conduit and the effectiveness of dilutional removal of cryoprotectant from these tissues were evaluated using high performance liquid chromatography. Incubation of intact conduit tissues in 1.4 mol/liter (10%) DMSO at 4 degrees C revealed that the cryoprotectant penetrated the tissues in a nonlinear time-dependent manner requiring 80 to 120 min to achieve a tissue concentration of approximately 0.7 mol/liter tissue water volume. This concentration approximated 54% of the theoretical media concentration (1.3 mol/liter) occurring through dilution effects of addition of the tissue to the medium. The osmolality of the medium decreased linearly in a time-dependent manner from 2975 to 2860 mOsmol/kg water over 80 min for a negative slope of 1.28 mOsmol/kg water/min. Analysis of the concentrations of DMSO in tissues undergoing dilutional removal at 4 degrees C revealed that dilutional removal at low temperatures may not be an effective means of removing DMSO from cryopreserved cardiovascular tissues. It requires approximately 40 to 50 min at 4 degrees C for tissue concentrations of DMSO to be reduced to 0.24 mol/liter tissue water volume, which is far in excess of the concentration expected to be present in the tissue and suspending solution (< 0.03 mol/liter media) at equilibrium. It is suggested that protocols for removal of DMSO from thawed allograft heart valves which do not allow the temperature to increase above 4 degrees C during the removal process may not provide sufficient incubation time to permit the cryoprotectant (DMSO) to diffuse from the tissues during a clinical post-thawing preparation for clinical transplantation.