Lung Function and Inflammatory Profiling of Damaged Rat Donor Lungs Following EVLP Heat Stress with Different Temperatures

Abstract

<h3>Purpose</h3> Ex-vivo lung perfusion (EVLP) is a validated technique allowing evaluation and reconditioning of damaged donor lungs to make them suitable for lung transplantation. Moderate hyperthermia is known to exert cytoprotective effect, via induction and accumulation of specific proteins, known as heat shock proteins (HSPs). We hypothesized that thermal preconditioning (TP) with a well-calibrated heat stress applied during EVLP could improve lung graft by reduction of oxidative stress, cell death and inflammation. <h3>Methods</h3> Male rats were randomly assigned into 5 groups: controls (Ctrl, n=5) and four heat stress groups (HS of 41.5°C; 42.0°C; 42.5°C or 43.5°C, n=5). In all groups, lungs were kept <i>in situ</i> for 1h at room temperature, then flushed with cold Perfadex. Heart-lung block was harvested and kept at 4°C for 1h, then mounted on the EVLP system for 3h. In Ctrl group, the temperature perfusion solution was kept at 37°C the all-time. In the HS groups, a heat shock was done for 30 minutes after 1h of EVLP by heating the perfusion solution at different temperature. At the end of EVLP, lungs were snap-frozen and kept at -80°C for further tissue analysis. <h3>Results</h3> Static pulmonary compliance SPC ratio (180 min to 60 min of EVLP) was significantly increased in the 41.5°C group compared to Ctrl group, while it was significantly reduced in 43.5°C group. The weight gain was significantly reduced in 41.5°C, whereas increased in 43.5°C group. In all HS groups, except in 43.5°C, protein levels of inducible HSP72 and Heme oxygenase-1 (HO-1) were significantly increased compared to Ctrl. Reduction of caspase 3 activation (apoptosis marker) was seen in all groups but reached significant level only in 41.5°C and 43.5°C groups. In all HS groups, we could see a reduction of inflammatory mediators such as, IL-1α, IL-1β, and TNF-α, a reduction of the release of CC16 (a marker of lung epithelial injury), as well as a reduction of IL-1β in Steen solution. <h3>Conclusion</h3> Thermal preconditioning during EVLP can decrease apoptotic cell death and inflammation of damaged lungs. These findings demonstrate that EVLP in association with well calibrated thermal preconditioning (41.5°C) could be a promising therapeutic platform improving lung quality of damaged donor lungs.