Oligonucleotide-based Preconditioning of DCD Cardiac Donors and Its Impact on Cardiac Viability

Heart Transplant and Donors After Circulatory Death: A Clinical-Preclinical Systematic Review

INTRODUCTION

Heart transplantation is the treatment of choice for end-stage heart failure. There is a mismatch between the number of donor hearts available and the number of patients awaiting transplantation. Expanding the donor pool is critically important. The use of hearts donated following circulatory death is one approach to increasing the number of available donor hearts.

MATERIALS AND METHODS

A systematic review was performed according to the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines utilizing Pubmed/MEDLINE and Embase. Articles including adult human studies and preclinical animal studies of heart transplantation following donation after circulatory death were included. Studies of pediatric populations or including organs other than heart were excluded.

RESULTS

Clinical experience and preclinical studies are reviewed. Clinical experience with direct procurement, normothermic regional perfusion, and machine perfusion are included. Preclinical studies addressing organ function assessment and enhancement of performance of marginal organs through preischemic, procurement, preservation, and reperfusion maneuvers are included. Articles addressing the ethical considerations of thoracic transplantation following circulatory death are also reviewed.

CONCLUSIONS

Heart transplantation utilizing organs procured following circulatory death is a promising method to increase the donor pool and offer life-saving transplantation to patients on the waitlist living with end-stage heart failure. There is robust ongoing preclinical and clinical research to optimize this technique and improve organ yield. There are also ongoing ethical considerations that must be addressed by consensus before wide adoption of this approach.

Thoracic organ machine perfusion: A review of concepts with a focus on reconditioning therapies

Thoracic organ transplantation, including lung, heart, and heart-lung transplants are highly regarded as gold standard treatments for patients suffering from heart failure or chronic end stage lung conditions. The relatively high prevalence of conditions necessitating thoracic organ transplants combined with the lack of available organs has resulted in many either dying or becoming too ill to receive a transplant while on the waiting list. There is a dire need to increase both the number of organs available and the utilization of such organs. Improved preservation techniques beyond static storage have shown great potential to lengthen the current period of viability of thoracic organs while outside the body, promising better utilization rates, increased donation distance, and improved matching of donors to recipients. Ex-situ organ perfusion (ESOP) can also make some novel therapeutic strategies viable, and the combination of the ESOP platform with such reconditioning therapies endeavors to better improve functional preservation of organs in addition to making more organs viable for transplantation. Given the abundance of clinical and pre-clinical studies surrounding reconditioning of thoracic organs in combination with ESOP, we summarize in this review important concepts and research regarding thoracic organ machine perfusion in combination with reconditioning therapies.

High Oxygenation During Normothermic Regional Perfusion After Circulatory Death Is Beneficial on Donor Cardiac Function in a Porcine Model

BACKGROUND

Thoracoabdominal normothermic regional perfusion (NRP) is a new method for in situ reperfusion and reanimation of potential donor organs in donation after circulatory death by reperfusion of the thoracic and abdominal organs with oxygenated blood. We investigated effects of high oxygenation (HOX) versus low oxygenation (LOX) during NRP on donor heart function in a porcine model.

METHODS

Pigs (80 kg) underwent a 15-min anoxic cardiac arrest followed by cardiac reanimation on NRP using a heart-lung bypass machine with subsequent assessment 180 minutes post-NRP. The animals were randomized to HOX (FiO2 1.0) or LOX (FiO2 0.21 increased to 0.40 during NRP). Hemodynamic data were obtained by invasive blood pressure and biventricular pressure-volume measurements. Blood gases, biomarkers of inflammation, and oxidative stress were measured.

RESULTS

Eight of 9 animals in the HOX group and 7 of 10 in the LOX group were successfully weaned from NRP. Right ventricular end-systole elastance was significantly improved in the HOX group compared with the LOX group, whereas left ventricular end-systole elastance was preserved at baseline levels. Post-NRP cardiac output, mean arterial, central venous, and pulmonary capillary wedge pressure were all comparable to baseline. Creatinine kinase-MB increased more in the LOX group than the HOX group, whereas proinflammatory cytokines increased more in the HOX group than the LOX group. No difference was found in oxidative stress between groups.

CONCLUSIONS

All hearts weaned from NRP showed acceptable hemodynamic function for transplantation. Hearts exposed to LOX showed more myocardial damage and showed poorer contractile performance than hearts reperfused with high oxygen.

A Novel Rat Model of Cardiac Donation After Circulatory Death Combined With Normothermic ex situ Heart Perfusion

Background: In heart transplantation, the adoption of hearts from donation after circulatory death (DCD) is considered to be a promising approach to expanding the donor pool. Normothermic ex situ heart perfusion (ESHP) is emerging as a novel preservation strategy for DCD hearts. Therefore, pre-clinical animal models of ESHP are essential to address some key issues before efficient clinical translation. We aim to develop a novel, reproducible, and economical rat model of DCD protocol combined with normothermic ESHP.

Methods: Circulatory death of the anesthetized rats in the DCD group was declared when systolic blood pressure below 30 mmHg or asystole was observed after asphyxiation. Additional 15 min of standoff period was allowed to elapse. After perfusion of cold cardioplegia, the DCD hearts were excised and perfused with allogenic blood-based perfusate at constant flow for 90 min in the normothermic ESHP system. Functional assessment and blood gas analysis were performed every 30 min during ESHP. The alteration of DCD hearts submitted to different durations of ESHP (30, 60, and 90 min) in oxidative stress, apoptosis, tissue energy state, inflammatory response, histopathology, cell swelling, and myocardial infarction during ESHP was evaluated. Rats in the non-DCD group were treated similarly but not exposed to warm ischemia and preserved by the normothermic ESHP system for 90 min.

Results: The DCD hearts showed compromised function at the beginning of ESHP and recovered over time, while non-DCD hearts presented better cardiac function during ESHP. The alteration of DCD hearts in oxidative stress, apoptosis, tissue energy state, histopathological changes, cell swelling, and inflammatory response didn't differ among different durations of ESHP. At the end of 90-min ESHP, DCD, and non-DCD hearts presented similarly in apoptosis, oxidative stress, inflammatory response, myocardial infarction, and histopathological changes. Moreover, the DCD hearts had lower energy storage and more evident cell swelling compared to the non-DCD hearts.

Conclusion: We established a reproducible, clinically relevant, and economical rat model of DCD protocol combined with normothermic ESHP, where the DCD hearts can maintain a stable state during 90-min ESHP.

Heart Donation From Donors After Controlled Circulatory Death

The gold-standard therapy for advanced-stage heart failure is cardiac transplantation. Since the first heart transplant in 1967, the majority of hearts transplanted came from brain death donors. Nevertheless, in recent years, the option of donation after circulatory death (DCD) is gaining importance to increase donor pool. Currently, heart-transplant programs using controlled donation after circulatory death (cDCD) have been implemented in the United Kingdom, Belgium, Australia, United States of America, and, recently, in Spain. In this article, we performed a concise review of the literature in heart cDCD; we summarize the pathophysiology involved in ischemia and reperfusion injury during this process, the different techniques of heart retrieval in cDCD donors, and the strategies that can be used to minimize the damage during retrieval and until transplantation. Heart transplant using DCD hearts is in continuous improvement and must be implemented in experienced cardiac transplant centers.

An Addition of U0126 Protecting Heart Grafts From Prolonged Cold Ischemia-Reperfusion Injury in Heart Transplantation: A New Preservation Strategy

BACKGROUND

Ischemia-reperfusion injury (IRI) is the major cause of primary graft dysfunction in organ transplantation. The mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) signaling pathway plays a crucial role in cell physiological and pathological processes including IRI. This study aims to investigate whether inhibition of ERK signaling with U0126 can prevent prolonged cold IRI in heart transplantation.

METHODS

Rat cardiac cell line H9c2 cells were treated with U0126 before exposure to hypothermic hypoxia/reoxygenation (H/R) conditions. The effect of U0126 on H9c2 cells in response to H/R stress was determined by measuring cell death, reactive oxygen species production, mitochondrial membrane potential, and ERK signaling activation. Mouse syngeneic heterotopic heart transplantation was conducted, where a donor heart was preserved in the University of Wisconsin (UW) solution supplemented with U0126 for 24 hours at 4°C before transplantation. Heart graft function, histopathologic changes, apoptosis, and fibrosis were measured to assess IRI.

RESULTS

Phosphorylated ERK was increased in both in vitro H/R-injured H9c2 cells and in vivo heart grafts with IRI. Pretreatment with U0126 inhibited ERK phosphorylation and prevented H9c2 cells from cell death, reactive oxygen species generation, and mitochondrial membrane potential loss in response to H/R. Preservation of donor hearts with U0126-supplemented solution improved graft function and reduced IRI by reductions in cell apoptosis/death, neutrophil infiltration, and fibrosis of the graft.

CONCLUSIONS

Addition of U0126 to UW solution reduces ERK signal activation and attenuates prolonged cold IRI in a heart transplantation model. ERK inhibition with U0126 may be a useful strategy to minimize IRI in organ transplantation.

Comparison of Experimental Rat Models in Donation After Circulatory Death (DCD): in-situ vs. ex-situ Ischemia

Introduction: Donation after circulatory death (DCD) could substantially improve donor heart availability. However, warm ischemia prior to procurement is of particular concern for cardiac graft quality. We describe a rat model of DCD with in-situ ischemia in order to characterize the physiologic changes during the withdrawal period before graft procurement, to determine effects of cardioplegic graft storage, and to evaluate the post-ischemic cardiac recovery in comparison with an established ex-situ ischemia model.

Methods: Following general anesthesia in male, Wistar rats (404 ± 24 g, n = 25), withdrawal of life-sustaining therapy was simulated by diaphragm transection. Hearts underwent no ischemia or 27 min in-situ ischemia and were explanted. Ex situ, hearts were subjected to a cardioplegic flush and 15 min cold storage or not, and 60 min reperfusion. Cardiac recovery was determined and compared to published results of an entirely ex-situ ischemia model (n = 18).

Results: In donors, hearts were subjected to hypoxia and hemodynamic changes, as well as increased levels of circulating catecholamines and free fatty acids prior to circulatory arrest. Post-ischemic contractile recovery was significantly lower in the in-situ ischemia model compared to the ex-situ model, and the addition of cardioplegic storage improved developed pressure-heart rate product, but not cardiac output.

Conclusion: The in-situ model provides insight into conditions to which the heart is exposed before procurement. Compared to an entirely ex-situ ischemia model, hearts of the in-situ model demonstrated a lower post-ischemic functional recovery, potentially due to systemic changes prior to ischemia, which are partially abrogated by cardioplegic graft storage.