Ghrelin May Inhibit Inflammatory Response and Apoptosis During Ischemia-Reperfusion Injury.

BACKGROUND: Ghrelin, a novel growth hormone-releasing peptide, has both anti-inflammatory and anti-apoptotic effects on human endothelial cells. We evaluated the protective effects of ghrelin against ischemia-reperfusion injury (IRI) in a murine heterotopic cervical heart transplantation model. METHODS: Donor hearts from C57BL/6J wild-type mice, which were kept in cold saline for 60 minutes, were heterotopically transplanted into C57BL/6J wild-type recipients. A day prior to heterotopic cervical heart transplantation, donor animals received either ghrelin (300 nmol/kg) or saline (0.3 mL) intraperitoneally. Upon reperfusion and postoperative day 1, ghrelin or saline was administered to the recipients. Donor hearts were procured on day 2. RESULTS: Ghrelin injection did not result in any adverse effects in donors or recipients. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling-positive cells were significantly decreased in the ghrelin group (0.38% ± 0.21% vs 5.74% ± 3.68%; P < .001). Both cleaved caspase-3 activity and Bcl-2/Bax ratio from the ghrelin group were significantly reduced compared to those in the control. Furthermore, the phosphorylated Akt/Akt ratio was higher in the ghrelin group (0.44 ± 0.21 vs 0.14 ± 0.03; P = .043). Nuclear factor-kappa B p65 nuclear translocation was reduced in the ghrelin hearts compared to the controls (3.17% ± 1.84% vs 19.28% ± 13.14%; P = .009). Vascular cell adhesion molecule-1, intracellular adhesion molecule-1, nuclear factor-kappa B, and tumor necrosis factor alpha levels were also significantly reduced in the ghrelin-treated group. No significant difference was observed in 8-isoprostane production between groups. CONCLUSION: Ghrelin inhibits the inflammatory response and apoptosis during transplant-related IRI. This study demonstrates the protective effects of ghrelin against IRI.

Dynamic Metabolic Changes During Prolonged Ex Situ Heart Perfusion Are Associated With Myocardial Functional Decline.

Ex situ heart perfusion (ESHP) was developed to preserve and evaluate donated hearts in a perfused beating state. However, myocardial function declines during ESHP, which limits the duration of perfusion and the potential to expand the donor pool. In this research, we combine a novel, minimally-invasive sampling approach with comparative global metabolite profiling to evaluate changes in the metabolomic patterns associated with declines in myocardial function during ESHP. Biocompatible solid-phase microextraction (SPME) microprobes serving as chemical biopsy were used to sample heart tissue and perfusate in a translational porcine ESHP model and a small cohort of clinical cases. In addition, six core-needle biopsies of the left ventricular wall were collected to compare the performance of our SPME sampling method against that of traditional tissue-collection. Our state-of-the-art metabolomics platform allowed us to identify a large number of significantly altered metabolites and lipid species that presented comparable profile of alterations to conventional biopsies. However, significant discrepancies in the pool of identified analytes using two sampling methods (SPME vs. biopsy) were also identified concerning mainly compounds susceptible to dynamic biotransformation and most likely being a result of low-invasive nature of SPME. Overall, our results revealed striking metabolic alterations during prolonged 8h-ESHP associated with uncontrolled inflammation not counterbalanced by resolution, endothelial injury, accelerated mitochondrial oxidative stress, the disruption of mitochondrial bioenergetics, and the accumulation of harmful lipid species. In conclusion, the combination of perfusion parameters and metabolomics can uncover various mechanisms of organ injury and recovery, which can help differentiate between donor hearts that are transplantable from those that should be discarded.

Comparing Donor Heart Assessment Strategies During Ex Situ Heart Perfusion to Better Estimate Posttransplant Cardiac Function.

BACKGROUND: Ex situ heart perfusion (ESHP) limits ischemic periods and enables continuous monitoring of donated hearts; however, a validated assessment method to predict cardiac performance has yet to be established. We compare biventricular contractile and metabolic parameters measured during ESHP to determine the best evaluation strategy to estimate cardiac function following transplantation. METHODS: Donor pigs were assigned to undergo beating-heart donation (n = 9) or donation after circulatory death (n = 8) induced by hypoxia. Hearts were preserved for 4 hours with ESHP while invasive and noninvasive (NI) biventricular contractile, and metabolic assessments were performed. Following transplantation, hearts were evaluated at 3 hours of reperfusion. Spearman correlation was used to determine the relationship between ESHP parameters and posttransplant function. RESULTS: We performed 17 transplants; 14 successfully weaned from bypass (beating-heart donation versus donation after circulatory death; P = 0.580). Left ventricular invasive preload recruitable stroke work (PRSW) (r = 0.770; P = 0.009), NI PRSW (r = 0.730; P = 0.001), and NI maximum elastance (r = 0.706; P = 0.002) strongly correlated with cardiac index (CI) following transplantation. Right ventricular NI PRSW moderately correlated to CI following transplantation (r = 0.688; P = 0.003). Lactate levels were weakly correlated with CI following transplantation (r = -0.495; P = 0.043). None of the echocardiography measurements correlated with cardiac function following transplantation. CONCLUSIONS: Left ventricular functional parameters, especially ventricular work and reserve, provided the best estimation of myocardial performance following transplantation. Furthermore, simple NI estimates of ventricular function proved useful in this setting. Right ventricular and metabolic measurements were limited in their ability to correlate with myocardial recovery. This emphasizes the need for an ESHP platform capable of assessing myocardial contractility and suggests that metabolic parameters alone do not provide a reliable evaluation.

The implementation of physiological afterload during ex situ heart perfusion augments prediction of posttransplant function.

Ex situ heart perfusion (ex situ heart perfusion) is an emerging technique that aims to increase the number of organs available for transplantation by augmenting both donor heart preservation and evaluation. Traditionally, ex situ heart perfusion has been performed in an unloaded Langendorff mode, though more recently groups have begun to use pump-supported working mode (PSWM) and passive afterload working mode (PAWM) to enable contractile evaluation during ex situ heart perfusion. To this point, however, neither the predictive effectiveness of the two working modes nor the predictive power of individual contractile parameters has been analyzed. In this article, we use our previously described system to analyze the predictive relevance of a multitude of contractile parameters measured in each working mode. Ten porcine hearts were excised and perfused ex situ in Langendorff mode for 4 h, evaluated using pressure-volume catheterization in both PSWM and PAWM, and transplanted into size-matched recipient pigs. After 3 h, hearts were weaned from cardiopulmonary bypass and evaluated. When correlating posttransplant measurements to their ex situ counterparts, we report that parameters measured in both modes show sufficient power (Spearman rank coefficient > 0.7) in predicting global posttransplant function, characterized by cardiac index and preload recruitable stroke work. For the prediction of specific posttransplant systolic and diastolic function, however, a large discrepancy between the two working modes was observed. With 9 of 10 measured posttransplant parameters showing stronger correlation with counterparts measured in PAWM, it is concluded that PAWM allows for a more detailed and nuanced prediction of posttransplant function than can be made in PSWM.NEW & NOTEWORTHY Ex situ heart perfusion has been proposed as a means to augment the organ donor pool by improving organ preservation and evaluation between donation and transplantation. Using our multimodal perfusion system, we analyzed the impact of using a "passive afterload working mode" for functional evaluation as compared with the more traditional "pump-supported working mode." Our data suggests that passive afterload working mode allows for a more nuanced prediction of posttransplant function in porcine hearts.

The Implementation of an Adjustable Afterload Module for Ex Situ Heart Perfusion.

PURPOSE: Windkessel impedance analysis has proven to be an effective technique for instituting artificial afterload on ex situ hearts. Traditional fixed parameter afterload modules, however, are unable to handle the changing contractile conditions associated with prolonged ex situ heart perfusion. In this paper, an adjustable afterload module is described comprising of three fully adjustable sub-components: a systemic resistor, a proximal resistor and a compliance chamber. METHODS: Using a centrifugal pump, the systemic resistor and compliance chamber were subjected to testing across their operating ranges, whereby the predictability of resistance and compliance values was evaluated. The components were then assembled, and the full module tested on three separate porcine hearts perfused for 6 h with success defined by the ability to maintain physiological systolic and diastolic aortic pressures across flow rate variability. RESULTS: For both the systemic resistor and compliance chamber, experimental measurements agreed with their theoretical equivalents, with coefficients of determination of 0.99 and 0.97 for the systemic resistor and compliance chamber, respectively. During ex situ perfusion, overall 95% confidence intervals demonstrate that physiological systolic (95-96.21 mmHg) and diastolic (26.8-28.8 mmHg) pressures were successfully maintained, despite large variability in aortic flow. Left ventricular contractile parameters, were found to be in line with those in previous studies, suggesting the afterload module has no detrimental impact on functional preservation. CONCLUSIONS: We conclude that due to the demonstrable control of our afterload module, we can maintain physiological aortic pressures in a passive afterload working mode across prolonged perfusion periods, enabling effective perfusion regardless of contractile performance.

A Pre-Clinical Porcine Model of Orthotopic Heart Transplantation.

Fifty-years following the first successful report, cardiac transplantation remains the gold-standard treatment for eligible patients with advanced heart failure. Multiple small-animal models of heart transplantation have been used to study the acute and long-term effects of novel therapies. However, few are tested and demonstrated success in clinical trials. It is of critical importance to evaluate new therapies in a clinically relevant large-animal model for efficient and reliable translation of basic studies' findings. Here, we describe a pre-clinical large-animal (porcine) model of orthotopic heart transplantation that has been firmly established and previously used to investigate novel cardioprotective strategies. This procedure focuses on acute ischemia-reperfusion injury and is a reliable method to investigate novel interventions which have been tested and validated in smaller experimental models, such as the murine model. We demonstrate its usefulness in assessing cardiac performance during the early post-transplantation period and other potential possibilities enabled by the model.

Hearts Donated After Circulatory Death and Reconditioned Using Normothermic Regional Perfusion Can Be Successfully Transplanted Following an Extended Period of Static Storage.

BACKGROUND: There has been an increased interest in donation after circulatory death (DCD) to expand donor pool for cardiac transplantation. Normothermic regional perfusion (NRP) allows in situ assessment of DCD hearts, allowing only acceptable organs to be procured. We sought to determine if extended cold storage was possible for DCD hearts following NRP and to compare hearts stored using standard cold storage with a novel cardioprotective solution designed for room temperature storage. METHODS AND RESULTS: Donor pigs underwent hypoxic cardiac arrest (DCD) followed by 15 minutes of warm ischemia and resuscitation on NRP. They were then randomly assigned to static storage with histidine-tryptophan-ketoglutarate (HTK) at 4°C (HTK group, n=5) or SOM-TRN-001 at 21°C (SOM group, n=5). Conventional beating-heart donations were used as controls (n=4). Fourteen transplants were successfully performed. HTK hearts showed initial dysfunction following reperfusion; however, they demonstrated significant recovery up to 3 hours post-transplant. No significant differences were seen between HTK and control hearts post-transplantation (cardiac index: control 49.5±6% and HTK 48.5±5% of baseline). SOM improved myocardial preservation; hearts showed stable contractility after transplantation (cardiac index: 113.0±43% of NRP function) and improved diastolic function compared with HTK. Preservation in SOM also significantly reduced proinflammatory cytokine production and release following transplantation and partially prevented endothelial dysfunction. CONCLUSIONS: DCD hearts stored using a standard preservation solution demonstrated comparable post-transplantation myocardial function to standard controls. Thus, short periods of cold storage following successful NRP and documented adequate function is an acceptable strategy for DCD hearts. Preservation in SOM at room temperature is feasible and can improve cardiac recovery by minimizing endothelial dysfunction and tissue injury.