Induction of Tolerance to Hypothermia by Previous Heat Shock Using Human Fibroblasts in Culture

The technique of organ preservation is limited by the amount of time which organs can be hypothermically stored. A potential method to effectively extend reliable storage times involves the conditioning of cells to better withstand hypothermia by previous exposure to a less severe stress. Using human fibroblasts in culture, we have demonstrated that such an approach may be feasible. Subjecting human diploid IMR-90 fibroblasts to 5 h 42.5°C heat shock was found to improve cell survival more than 10-fold to subsequent 4°C hypothermic exposure. The prior heat shock resulted in the increased synthesis of heat shock proteins (HSPs), the absolute concentrations of which were measured by an assay which utilized sodium dodecyl sulfate–polyacrylamide gel electrophoresis and Western blotting techniques. Both the degree of cold tolerance conferred upon IMR-90 cells and the levels of HSP70 and HSP27 were dependent upon initial heat shock duration. Induced cold tolerance was found to be reversible; longer recovery times at 37°C following heat shock resulted in a loss of this cold-tolerant state as well as a disappearance of HSPs. The fact that the degree of cold tolerance and HSP concentrations showed similar trends with respect to both heat shock time at 42.5°C and subsequent recovery time at 37°C suggests that these proteins may be intimately involved in the induction of cold tolerance.