We recently demonstrated that heat stress induction of heat shock protein 70 (HSP70) in donor animals before harvest decreases posttransplant ischemia-reperfusion injury in preserved rat lung isografts. The purpose of this study was to investigate the feasibility of HSP70 gene transfection into rat lung isografts using an adenoviral vector, and to study the effects of gene expression on subsequent ischemia-reperfusion injury.

In preliminary studies to determine the optimal titer, animals were injected with various titers of adenovirus-HSP70 (saline, 5 × 10⁹, 1 × 10¹⁰, and 2 × 10¹⁰ plaque forming units [pfu]) and sacrificed 5 days after injection. To determine the optimal exposure time, animals were sacrificed at different times (0, 6, 24, and 72 hours) after intravenous injection of adenovirus-HSP70. In a subsequent series of transplant experiments, donors were allocated to three groups according to transfection strategy. Group 1 (n = 8) donors received 5 × 10⁹ pfu adenovirus-HSP70 intravenously, group 2 (n = 7) donors received 5 × 10⁹ pfu adenovirus-β-galactosidase (as a virus control), and group 3 (n = 7) donors received saline and served as a negative control. Twenty-four hours after treatment all grafts were harvested and stored for 18 hours before orthotopic left lung transplantation. Twenty-four hours after implantation animals were sacrificed for assessment. The expression of HSP70 was assessed by Western blot analysis.

In preliminary studies, HSP70 was detectable even at low titers (5 × 10⁹ pfu) of adenovirus-HSP70, and was detectable at low levels as early as 6 hours after intravenous administration. Heat shock protein 70 expression was maximal at 24 hours. In transplant experiments, Western blot analysis showed that overexpression of HSP70 occurred in the HSP70-transfected lungs. The mean arterial oxygenation 24 hours after reperfusion in group 1 was superior in comparison with other groups (p < 0.05). Wet to dry weight ratio (p < 0.05) and myeloperoxidase activity (p < 0.05) were also significantly less in group 1 grafts compared with the other groups.

This study demonstrates that in vivo, donor adenovirus-mediated gene transfer of HSP70 decreases subsequent ischemia-reperfusion injury in rat lung isografts.