Gene Expression Differences between DCD and DBD Lungs are Mitigated by Ex Vivo Lung Perfusion (EVLP)

Abstract

Donation after cardiac death (DCD) donor lungs have been shown to be less pro-inflammatory than donation after brain death (DBD) lungs, likely due to the absence of brain-death related inflammatory physiology. However, it is unclear whether this difference is clinically significant following reperfusion either by EVLP or transplantation. We sought to examine the effect of EVLP on gene expression in DCD and DBD lungs. DCD (n=97) and DBD (n=122) lung tissue samples were collected pre- and post- 4h of EVLP and snap frozen for future analysis. RNA was extracted and hybridized to Affymetrix Clariom D microarrays and resulting transcriptomes analyzed for differential gene expression. Banked EVLP perfusates from DCD (n=24) and DBD (n=24) cases were assayed for IL-6, IL-8, IL-10, IL-1B, sTNFR1, and sTREM1, over 15 min intervals for three hours (n=48). We confirmed as expected, that DCD lungs demonstrated lower levels of inflammatory transcripts and cytokine protein levels than DBD lungs prior to EVLP. However, following EVLP, there were no significant gene expression differences across the entire transcriptome (Fig. 1A) and protein levels in the perfusate of IL-6, IL-8, and IL-10 similarly equalized (Fig. 1B). As DCD and DBD lungs are different in the potential injuries they are exposed to, the initial inflammatory milieu differs. However, the additional inflammation observed in DBD lungs does not further progress during EVLP and gene expression differences between DCD and DBD lungs instead become equalized. EVLP may therefore play a pre-conditioning role for subsequent reperfusion after transplantation.