A novel experimental porcine model to assess the impact of differential pulmonary blood flow on ischemia-reperfusion injury after unilateral lung transplantation

Abstract

Background: Primary graft dysfunction (PGD) remains a major obstacle after lung transplantation. Ischemia-reperfusion injury is a known contributor to the development of PGD following lung transplantation. We developed a novel approach to assess the impact of increased pulmonary blood flow in a large porcine single-left lung transplantation model.

Materials: Twelve porcine left lung transplants were divided in two groups (n = 6, in low- (LF) and high-flow (HF) group). Donor lungs were stored for 24 h on ice, followed by left lung transplantation. In the HF group, recipient animals were observed for 6 h after reperfusion with partially clamping right pulmonary artery to achieve a higher flow (target flow 40-60% of total cardiac output) to the transplanted lung compared to the LF group, where the right pulmonary artery was not clamped.

Results: Survival at 6 h was 100% in both groups. Histological, functional and biological assessment did not significantly differ between both groups during the first 6 h of reperfusion. injury was also present in the right native lung and showed signs compatible with the pathophysiological hallmarks of ischemia-reperfusion injury.

Conclusions: Partial clamping native pulmonary artery in large animal lung transplantation setting to study the impact of low versus high pulmonary flow on the development of ischemia reperfusion is feasible. In our study, differential blood flow had no effect on IRI. However, our findings might impact future studies with extracorporeal devices and represent a specific intra-operative problem during bilateral sequential single-lung transplantation.

Keywords: Porcine left lung transplantation; Primary graft dysfunction; Pulmonary vascular resistance.

Fig. 1

Schematic picture of experiment set-up. The figure demonstrates the set-up of the experiment of both groups. In both groups, a donor lung was harvested and stored for 24 h on ice. In a second animal (recipient), via left thoracotomy a left pneumonectomy was performed. In the low-flow (LF) group the reperfusion was observed for 6 h without partially clamping the right pulmonary artery. In the high-flow group (HF) the right pulmonary artery was partially clamped after the first 2 h of reperfusion for another 4 h

Fig. 2

Parameters during reperfusion. a–c Assessment of hemodynamic parameters during 6-h reperfusion. CO and flow to the left and right lung were measured, flow through the right PA was calculated. All data are depicted as median ± IQR analyzed with repeated measures two-way ANOVA (a–c) and post hoc multiple comparison test Sidak (x). Time is 6-h reperfusion; CO, cardiac output; PA pulmonary artery; after 2 h of reperfusion, the right pulmonary artery was clamped in the high-flow group (*). d–f Assessment of oxygenation; blood gases samples were taken from carotid artery (P/F ratio), left pulmonary vein (LPV) and right pulmonary vein (RPV). All data are depicted as median ± IQR analyzed with repeated measures two-way ANOVA (d-f) and post hoc multiple comparison test Sidak (x). Time is 6-h reperfusion; pO2, partial pressure of oxygen; after 2 h of reperfusion, the right pulmonary artery was clamped in the high-flow group (*). g Assessment of pulmonary arterial pressure; all data are depicted as median ± IQR analyzed with repeated measures two-way ANOVA (G) and post hoc multiple comparison test Sidak (x). Time is 6-h reperfusion; mPAP, mean pulmonary arterial pressure; after 2 h of reperfusion, the right pulmonary artery was clamped in the high-flow group (*)

Fig. 3

Histology. a The W/D ratios were assessed of lung biopsies at the end after 6 h reperfusion. No significant difference was observed between the low- vs. high-flow group in the right native lug (p = 0.49) and the left transplanted lung (p < 0.99). Data were analyzed with Mann–Whitney test; W/D, wet-to-dry weight ratio; RLL, right lower lobe; LLL, left lower lobe. Left (b) The native right lower lobe (RLL) of the low-flow (LF) group shows mild capillary congestion and mild septal neutrophilic infiltration without presence of intra-alveolar neutrophils. Right (c) The transplanted left lower lobe (LLL) of the low-flow (LF) group shows mild capillary congestion, presence of septal neutrophilic infiltration, intra-alveolar edema and intra-alveolar neutrophils. Left (d) The native right lower lobe (RLL) of the high-flow (HF) group shows prominent capillary congestion and presence of neutrophilic infiltration in the septa. Right (e) The transplanted left lower lobe (LLL) of the (HF) group shows presence of capillary congestion, prominent intra-alveolar edema and presence of septal and intra-alveolar neutrophilic infiltration