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Purpose Ischemia reperfusion injury (I/R) is the major cause of primary graft dysfunction (PGD) after lung transplantation. I/R and PGD feature alveolar epithelial and endothelial damage, lung edema and inflammation. Edema resorption then depends on the restoration of alveolar epithelial integrity and the ability of alveolar cells to reabsorb Na+ (through ENaC channels) and fluid. We hypothesized that alveolar epithelial damage, and repair, are critical in PGD pathophysiology and resolution. Therefore, our aim was to identify novel biomarkers and therapeutic targets associated with I/R using cellular and animal models as well as human samples from lung transplants. Methods The impact of a protocol mimicking hypothermic ischemia and warm reperfusion was first tested on primary rat alveolar epithelial cell cultures. Then, the impact of I/R was studied in vivo using models of inflammatory stress induced by LPS infusion or after unilateral lung transplantation in pigs. Finally, lung biopsies from donor grafts were collected during lung transplantations. After defining PGD grades within the recipients, alveolar alterations were finally analyzed within donor graft tissues. Results In primary rat cell cultures, the I/R mimicking protocol impaired tight junction proteins (ZO-1), transepithelial resistance, wound repair capacity as well as expression in ENaC and CFTR channels. Treatment with a KvLQT1 K+ channel activator (R-L3) accelerated the repair rates and enhanced barrier integrity (ZO-1 staining) as well as ENaC and CFTR protein expressions. In the porcine models, an exacerbated inflammatory response was observed along with alveolar damage, lung edema and decreased ZO-1, ENaC and CFTR expressions. Our preliminary analyses also indicated that among lung transplants subsequently developing PGD, an inflammatory response and reduced ENaC, CFTR and ZO-1 expressions were already observed within biopsies from donor grafts, collected before transplantation. Conclusion Altogether our data support the hypothesis of alveolar epithelial dysfunction, after I/R injury. Based on these observations, our goal is to investigate a potential relationship between donor phenotypic factors, markers of epithelial damage/dysfunction within the grafts, inflammatory levels and the subsequent development of PGD in lung recipients.

Purpose Ischemia reperfusion (I/R) is a major cause of primary graft dysfunction (PGD) after lung transplantation. I/R and PGD feature endothelial/alveolar epithelial damage, lung edema and inflammation. Edema resorption depends on the restoration of alveolar integrity and its ability to reabsorb Na+ (ENaC) and fluid. We hypothesized that alveolar epithelial damage and repair are critical in PGD pathophysiology and resolution. Our aim is to identify novel markers and therapeutic targets associated with I/R using cellular and animal models as well as human samples from lung transplants. Methods Mimicking I/R protocol was used to evaluate alveolar epithelial barrier integrity and capacity of wound healing in primary cultures of rat's alveolar epithelial cells. These cell cultures were then treated with an activator of K+ channel (KvLQT1). In a porcine model of ischemia/ex-vivo reperfusion, an inflammatory stress was induced by i.v. infusion with LPS. Finally, samples were collected from 38 lung transplant patients. Results In primary cell cultures, we showed altered ENaC and tight junction protein (ZO-1) expression after injury. A decline in transepithelial resistance (TER) and altered alveolar wound repair rates were also observed following the mimicking I/R protocol. Treatment with K+ channel activator (R-L3) showed enhanced repair rates, barrier integrity (higher TER, ZO-1 staining) and ENaC expression. In our porcine model, lung damage and edema was observed as well as exacerbated inflammatory response and decreased ENaC expression. Preliminary data from lung transplant samples indicated an inflammatory response and decreased ENaC and ZO-1 expression in patients with PGD. Conclusion Our data support the hypothesis of alveolar epithelial dysfunction after I/R injury. We will now investigate a potential correlation between levels of inflammatory molecules and epithelial damage markers in bronchoalveolar lavages and blood samples (at different time-points) from lung transplants with various PGD scores.