Heat shock improves recovery and provides protection against global ischemia after hypothermic storage

Background. Improved methods of donor heart preparation before preservation could allow for prolonged storage and permit remote procurement of these organs. Previous studies have shown that overexpression of heat- shock protein 72 provides protection against ischemic cardiac damage. We sought to determine whether rats subjected to heat stress with only 6-hour recovery could acquire protection to a subsequent heart storage for 12 hours at 4°C. Methods. Three groups of animals (n = 10 each) were studied: control, sham-treated, and heat-shocked rats (whole-body hyperthermia 42°C for 15 minutes). After 12-hour cold ischemia hearts were reperfused on a Langendorff column. To confirm any differences in functional recovery, hearts were then subjected to an additional 15-minute period of warm global ischemia after which function and lactate dehydrogenase enzyme leakage were measured. Results. Heat-shocked animals showed marked improvements compared with controls in left ventricular developed pressure (63 ± 4 mm Hg versus 44 ± 4 mm Hg, p < 0.05) heart rate x developed pressure (13,883 ± 1,174 beats per minute x mm Hg versus 8,492 ± 1,564 beats per minute x mm Hg, p < 0.05), rate of ventricular pressure increase (1,912 ± 112 mm Hg/second versus 1,215 ± 162 mm Hg/second, p < 0.005), rate of ventricular pressure decrease (1,258 ± 89 mm Hg/second versus 774 ± 106 mm Hg/second, p < 0.005). Diastolic compliance and lactate dehydrogenase release were improved in heat-shocked animals compared with controls and shamtreated animals. Differences between heat-shocked animals and control or sham-treated animals were further increased after the additional 15-minute period of warm ischemia. Western blot experiments confirmed increased heat-shock protein 72 levels in heat- shocked animals (> threefold) compared with sham-treated animals and controls. Conclusions. Heat shock 6 hours before heart removal resulted in marked expression of heat-shock protein 72 and protected isolated rat hearts by increased functional recovery and decreased cellular necrosis after 12- hour cold ischemia in a protocol mimicking that of heart preservation for transplantation. Protection was further confirmed after an additional 15- minute period of warm ischemia.