Abstracts S225( 554)Characterization of Endothelial Function Following Various Ischemic Durations in an Isolated Rat Heart Model of Donation After Circulatory DeathN. Mendez Carmona , R.K. Wyss, M. Arnold, T.P. Carrel, H.T. Tevaearai Stahel, S.L. Longnus. Department of Cardiovascular Surgery, Bern University Hospital, Bern, Switzerland.Purpose: Donation after circulatory death (DCD) could significantly improve cardiac graft availability, thereby allowing a greater number of transplantations for patients in need of this life saving therapy. However, DCD hearts undergo potentially deleterious warm ischemia and reperfusion (I/R). As endothelial damage is a key factor in cardiac I/R injury, we aimed to characterize hemody-namic and endothelial function following various durations of warm ischemia to improve the timing and choice of cardioprotective therapies.Methods: Isolated, working, rat hearts were perfused for 20’ aerobically, then underwent various periods of warm global ischemia (I), followed by reperfusion (R) of 30’ or 60’. Hemodynamic parameters were monitored and endothelial function was assessed by comparing vasodilatory responses between endothelium-dependent (bradykinin; 10 -9 and 10 -8 M) and endothe-lium-independent (sodium nitroprusside; 3x10 -5 M) vasodilators.Results: At 60’ R, recovery of left ventricular work (heart rate-developed pres-sure product) was significantly lower with 27’ I (76% ± 12), 30’ I (67% ± 15) and 33’ I (31% ± 20) compared with non-ischemic hearts (0’ I; 100% ± 11; p < 0.05 for all), but was unchanged with 21’ I (91% ± 5) and 24’ I (88% ± 13; n= 7-8/ group). After 30’ R, endothelial function was impaired ≥ 24’ I compared with 0’ I hearts, while smooth muscle function was impaired only with ischemic durations ≥ 27’ I (p < 0.05 for all; n= 6/group). After 60’ R, the proportion of phospho-rylated endothelial nitric oxide synthase (p-eNOS) significantly increased with ischemic durations ≥ 21’ I compared with 0’ I hearts (p < 0.05), but not changed with 33’ I. Furthermore, compared with 0’ I hearts, edema was significantly greater ≥ 27’ I compared with non-ischemic hearts (p < 0.05 for all).Conclusion: Endothelial dysfunction occurs with shorter periods of ischemia than those required to induce hemodynamic and smooth muscle dysfunc-tion. With ischemic periods of 24’ I endothelial function is significantly decreased, despite high levels of p-eNOS, suggesting eNOS uncoupling. A window of opportunity therefore exists for application of endothelial-based therapies aimed at optimizing both endothelial and myocardial recovery. These therapies may ultimately be used to improve DCD graft quality and facilitate heart transplantation.( 555)Bronchial-arterial-circulation-sparing (BACS) Lung Preservation: A Novel Strategy in Lung TransplantationS. Tane , 1 K. Noda, 1 J. D'Cunha, 1 J.D. Luketich, 1 N. Shigemura. 2 1 Department of Cardiothoracic Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA; 2 Division of Cardiovascular Surgery, Temple University Health System and Lewis Katz School of Medicine, Philadelphia, PA.Purpose: Microvasculature damage in transplanted lungs, resulting from dis-rupted bronchial arterial circulation at the time of transplantation appears to trigger chronic lung allograft dysfunction (CLAD) development, and maintain-ing a functional microvasculature throughout the transplant process could be one of the most promising determinants for the long-term health of transplanted lungs. Based on this rationale, we have recently developed bronchial-arterial-circulation-sparing (BACS) lung preservation approach to overcome CLAD.Methods: Using Lewis rats, lungs were procured and preserved using the fol-lowing two methods: 1. BACS approach where both bronchial and pulmonary artery were synchronously perfused (Figure A); 2. Standard approach where pulmonary artery alone was perfused. After 4h of cold ischemia, these lungs were evaluated on ex vivo lung perfusion (EVLP) for their vascular tone and microvasculature damage by using two photon microscope method. And finally, these lungs were transplanted to the recipient and 1h after reperfusion, their lung function was compared between the two approaches.Results: After 4h cold ischemia, BACS group exhibited significantly lower expression of phosphorylated myosin light chain (p-MLC) in their pulmonary artery, a key component of vascular smooth muscle contraction measured by western blotting (Figure B). On EVLP, BACS group showed lower pul-monary vascular resistance (Figure C). Two photon microscopy analysis damaged severely. 3). The mixture of cold and warm ischemia presented both cold and warm I/R injury.Conclusion: Cold I/R injury is featured by epithelium-centered damage and infiltration, whereas warm I/R injury mainly causes diffused alveolar dam-age and infiltration.( 553)Facilitating Donation After Circulatory Death in Heart Transplantation: Effects of Cardioprotective Reperfusion Strategies on MitochondriaM.N. Sanz , E. Farine, P. Niederberger, N. Méndez-Carmona, R.K. Wyss, M. Arnold, P. Gulak, T.P. Carrel, H.T. Tevaearai Stahel, S.L. Longnus. Department of Cardiovascular Surgery, Inselspital, Bern University Hospital, Department for BioMedical Research, University of Bern, Bern, Switzerland.Purpose: Donation after circulatory death (DCD) is a promising solution for increasing cardiac graft availability, but concerns persist due to ischemia/reperfusion injury (IRI). Using an isolated rat heart model of DCD, we iden-tified three reperfusion strategies that significantly improve post-ischemic contractile recovery 1 : mild hypothermia (MH), mechanical post-conditioning (MPC) and hypoxia (HY). Given the key role of mitochondria in IRI, we hypothesized that mitochondrial changes contribute to these cardioprotec-tive strategies.Methods: Hearts of 41 adult, male Wistar rats underwent 20 min aerobic perfusion, 27 min global ischemia and 60 min reperfusion. Five experimental conditions were compared (n= 8-9/group): no ischemia, ischemia without strategy, and ischemia plus reperfusion strategy (MH, MPC or HY). A panel of mitochondrial-related parameters, measured either during early reperfu-sion (10 min) or at end reperfusion (60 min), were correlated with post-ischemic hemodynamic recovery (Spearman correlations; p-values corrected for multiple comparisons).Results: Correlations between mitochondrial-related parameters and recov-ery outcomes at 60 min reperfusion are shown in Figure. Additionally, each strategy showed a different pattern of correlations between early reperfusion mitochondrial parameters (cytochrome c release, oxygen consumption and coupling) and outcomes of cardiac function (p < 0.05 for all).Conclusion: The cardioprotective reperfusion strategies, MH, MPC or HY, appear to modify mitochondrial function, but through different mechanisms. In addition, several early mitochondrial-related parameters correlate with contractile recovery. Thus, further investigation into reperfusion-induced effects on mitochondria may aid in the identification of new therapeutic targets to optimize graft recovery and facilitate DCD heart transplantation. References:1. Farine E, et al. Frontiers in Physiology (2016).
