Thermal sensitivity of endothelial cells on synthetic vascular graft material

Purpose: The goal is to identify thermal exposures capable of reducing or eliminating cell survival on expanded polytetrafluoroethylene (ePTFE), in an effort to develop a mild hyperthermia treatment of neointimal hyperplasia in ePTFE vascular grafts. Materials and methods: Viable and dead bovine aortic endothelial cells were quantified following different thermal exposure conditions: cells on collagen-coated ePTFE sheets or tissue culture polystyrene dishes were heated at 42 degrees and 45 degrees C to determine their thermal sensitivity on different surfaces, and cells cultured on collagen-coated ePTFE sheets were heated at 43-50 degrees C for various durations, followed by incubation at 37 degrees C for 0 and 20 h, respectively. Significant cell death was set to be 50%. Two types of cell death, apoptosis and necrosis, were distinguished by cell morphology and membrane integrity assessments. Results: The attachment and survival of cells on ePTFE sheets were more sensitive to inhibition by mild heating than those on tissue culture dishes. Exposure to 45 degrees C for 90 min and 50 degrees C for 30 min caused significant necrotic cell death on ePTFE (65% and 75%, respectively). A 37 degrees C/20-h incubation following 30-min exposures at 47 degrees and 50 degrees C increased total cell death (necrosis+apoptosis) from 20% to 50% and 75% to 100%, respectively. Conclusion: Cells grown on ePTFE were more susceptible to mild hyperthermia-induced death, compared to those on tissue culture dishes. Significant cell death on ePTFE mainly via apoptosis can be achieved by optimising temperature and duration of exposure.