The Impact of Heat Treatment on Porcine Heart Valve Leaflets

The purpose of this study was to determine the impact of elevated temperature exposure in tissue banking on soft tissues. A secondary objective was to determine the relative ability of various assays to detect changes in soft tissues due to temperature deviations. Porcine pulmonary heart valve leaflets exposed to 37 °C were compared with those incubated at 52 and 67 °C for 10, 30 and 100 min. The analytical methods consisted of (1) viability assessment using the resazurin assay, (2) collagen content using the Sircol assay, and (3) permeability assessment using an electrical conductivity assay. Additionally, histology and two photon microscopy were used to reveal mechanisms of cell and tissue damage. Viability, collagen content, and permeability all decreased following heat treatment. In terms of statistical significance with respect to treatment temperature, cell viability was most affected (p < 0.0001), followed by permeability (p < 0.0001), and then collagen content (p = 0.13). After heat treatment, histology indicated increased apoptosis and two photon microscopy revealed a decrease in collagen fiber organization and an increase in elastin density. These results suggest that measures of cell viability would be best for assessing tissues where the cells are alive and that permeability may be best where cell viability is not intentionally maintained.