Transient Heat Stress During Ex-Vivo Lung Perfusion Induces the Heat Shock Response and Preserves Lung Function in Pig Model

Abstract

<h3>Purpose</h3> The heat shock response (HSR) is a highly conserved adaptative response to thermic stress, related to the induced expression of heat shock proteins (HSPs) which promote significant cytoprotection. We hypothesized that thermal preconditioning (TP) with a well-calibrated heat stress (HS) applied during EVLP elicits a HSR and improves lung graft function by interfering with immune inflammation and oxidative stress pathways. <h3>Methods</h3> Donor lungs (n=12) underwent extended hypothermic preservation of 16h. Lungs were assigned into two groups: 1) Control (n=6): 4h EVLP at 37°C; and 2) TP, (n=6): normothermic EVLP (37°C, 2h), followed by hyperthermic EVLP (42°, 30min), and normothermic EVLP (37°C, 1.5h). Ex-vivo lung function was assessed by measuring airway pressure, lung compliance and pulmonary vascular resistance. We determined expression of HSPs in tissue, and lung damage and oxidative stress biomarkers in tissue, BAL and perfusate at multiple time points. <h3>Results</h3> Lungs undergoing thermal preconditioning (TP group) showed significantly lower pulmonary arterial pressure and vascular resistance, increased dynamic and static pulmonary compliance and reduced airway pressure with no changes in oxygenation capacity as compared to lungs in the control group. At the end of EVLP, lungs in TP group had significant increase of lung mRNA of Hspa1a, Hsc70 and Hmox-1, reduction of nitrotyrosine (3-NT) in lung tissue, and reduction of LDH, CK18-M30 and proteins in BAL fluid. TP during ELVP decreased the expression of TNFα, IL6/IL10, MPO and IL-8 in BAL consistent with inflammasome inhibition. <h3>Conclusion</h3> Transient heat stress during EVLP induces HSR and reduces nitroxidative stress, cellular injury and edema, and prevents functional deterioration of pig lungs after extended cold ischemia. These data indicate the therapeutic potential of thermal preconditioning as a way to recondition damaged lungs and to improve current preservation strategies.