Heat shock protein 70 induced by heat stress protects heterotopically transplanted hearts in rats.

Heat shock protein 70 (HSP70) protects cardiac function against ischemia-reperfusion injury through gene transfection, although it is not a clinically practical and economical method. This study investigated whether heat stress-induced HSP70 protects heterotopically transplanted donor hearts. A total of 60 donor rats were randomly divided into 6 groups. Five of those received heat stress and one was a control group. Donor hearts were heterotopically transplanted into recipient rats at five time points, following the heat stress (0, 24, 48, 96 and 192 h). The levels of HSP70 expression in donor hearts and the variation of myocardial enzymes in receptor blood or donor hearts were measured 24 h after transplantation. The donated hearts were also examined under a microscope for pathological changes. HSP70 expression was the highest in the 24-h group (p≤0.01) and decreased gradually in the 48- and 96-h groups. No statistically significant difference was found in the HSP70 expression in the control, the 0- and 192-h groups (p≥0.05). Of all the groups, the 24-h group had the lowest lactate dehydrogenase and creatine kinase muscle band concentrations in receptor blood. Moreover, this group showed the lowest malondialdehyde concentration and the highest atriphosphate concentration (p≤0.01), demonstrated by the mildest inflammatory injury in the transplanted hearts. We found a time-dose-effect relationship among heat stress, HSP70 and the protection of donor hearts. Heat stress is a practical method that can be clinically applied to protect donor hearts against ischemia-reperfusion injury by inducing endogenous HSP70, which indicates the future direction of clinical practice.