Lung pre-conditioning during ex-vivo lung perfusion: results of an experimental study

Background: Clinical data suggest a benefit of transplanting lungs after Ex-Vivo Lung Perfusion (EVLP). Objective: To explore the bio-molecular and cellular mechanisms that might explain a role of EVLP on lung pre-conditioning. Material and methods: EVLP was run for 180 min on Sprague-Dawley rat lungs (Hugo Sachs System). Cytokine and chemokine release in the perfusate was assayed by Luminex xMAP\uae Technology. Cells recovered in the perfusate were counted, characterized (May-Gr\ufcnwald Giemsa staining), and cultured to assess viability (Trypan blue exclusion). Gene expression was investigated using custom low-density arrays. Hierarchical cluster analysis was performed with DNA-chip program. Differentially expressed genes were identified using Significance Analysis of Microarrays (SAM), considering lungs from naive (Native) or from sham-operated rats (Sham) as controls. Western blot analysis (SDS-PAGE) was performed to explore activation of signaling pathways. Results: A total of 15 animals were investigated: Native, Sham, EVLP (n=5 each). The EVLP system was stable over time, with no signs of lung edema (W/D: 5.3\ub10.5). At 180 min, mediators in the perfusate with highest median value were: TIMP-1, MIP-2, MCP-1, and IL-6. A total of 11.03\ub11.43x10^6 cells were recovered after EVLP: 91\ub11% lymphocytes with 82% viability after 24 h of culture. Unsupervised analysis revealed that EVLP induced a specific transcriptional signature (P=0.003). Pattern of genes up-regulated included inflammation, resolution of inflammation, antiapoptosis/survival, heat-shock/redox while neutrophil related genes were down-regulated (q=0). STAT3, MAP kinase (ERK1/2, p38), and NFKB signaling pathways were activated after EVLP. Conclusion: EVLP is associated with a number of bio-molecular and cellular mechanisms compatible with pre-conditioning of the lung