Ex Vivo Heart Perfusion Research Articles

Normothermic Ex Vivo Heart Perfusion With Exosomes From Human Umbilical Cord Mesenchymal Stem Cells Improves Graft Function in Donation After Circulatory Death Hearts.

This study aimed to investigate the cardioprotective effect of exosomes derived from human umbilical cord mesenchymal stem cells on donation after circulatory death (DCD) hearts preserved with normothermic ex vivo heart perfusion (EVHP) in a rat heart transplantation model. Thirty-two male Lewis rats were divided into 2 groups: the control group and the exosome group. The donor-heart rats were subjected to the DCD procedure by suffering a 15-min warm ischemia injury, subsequently preserved with EVHP for 90 min, and then transplanted into recipients via abdominal heterotopic heart transplantation. Vehicle or exosome was added into the perfusate of normothermic EVHP in the control or exosome group. We evaluated left ventricular graft function, myocardial inflammation, and myocardial apoptosis of the donor heart 1.5 h after heart transplantation. Furthermore, we investigate the alternation of myocardial gene expression in the donor hearts between both groups by transcriptome sequencing. The treatment with exosome significantly enhanced cardiac function through increasing left ventricular developed pressure, dp/dt max , and dp/dt min of DCD hearts at 90 min after heart transplantation compared with the control group. The myocardial cells in the exosome group exhibited an orderly arrangement without obvious edema. Furthermore, exosome added into perfusate in the exosome group significantly attenuated the level of inflammatory response and apoptosis. Transcriptome sequencing and RT-qPCR showed the phosphoinositide 3-kinase/protein kinase B pathway was activated after exosome treatment. Normothermic EVHP combined with exosome can be a promising and novel DCD heart preservation strategy, alleviating myocardial ischemia-reperfusion injury in the DCD heart.

Circulating factors, in both donor and ex-vivo heart perfusion, correlate with heart recovery in a pig model of DCD

BackgroundHeart transplantation with donation after circulatory death and ex-situ heart perfusion offers excellent outcomes and increased transplantation rates. However, improved graft evaluation techniques are required to ensure effective utilization of grafts. Therefore, we investigated circulating factors, both in-situ and ex-situ, as potential biomarkers for cardiac graft quality. MethodsCirculatory death was simulated in anesthetized male pigs with warm ischemic durations of 0, 10, 20, or 30 min. Hearts were explanted and underwent ex-situ perfusion for 3h in an unloaded mode, followed by left ventricular loading for 1h, to evaluate cardiac recovery (outcomes). Multiple donor blood and ex-situ perfusate samples were used for biomarker evaluation with either standard biochemical techniques or nuclear magnetic resonance spectroscopy. ResultsCirculating adrenaline, both in the donor and at 10 min ex-situ heart perfusion, negatively correlated with cardiac recovery (p <0.05 for all). We identified several new potential biomarkers for cardiac graft quality that can be measured rapidly and simultaneously with nuclear magnetic resonance spectroscopy. At multiple timepoints during unloaded ex-situ heart perfusion, perfusate levels of acetone, betaine, creatine, creatinine, fumarate, hypoxanthine, lactate, pyruvate and succinate (p <0.05 for all) significantly correlated with outcomes; the optimal timepoint being 60 min. ConclusionsIn heart donation after circulatory death, circulating adrenaline levels are valuable for cardiac graft evaluation. Nuclear magnetic resonance spectroscopy is of particular interest, as it measures multiple metabolites in a short timeframe. Improved biomarkers may allow more precision and therefore better support clinical decisions about transplantation suitability.

Survival, function, and immune profiling after beating heart transplantation

ObjectiveEx vivo normothermic perfusion of cardiac allografts has expanded the donor pool for heart transplant. Using a beating heart implantation method avoids the second cardioplegic arrest and subsequent ischemia-reperfusion injury typically associated with ex vivo heart perfusion. We sought to describe our institutional experience with beating heart transplantation. MethodsThis was a single-institution retrospective study of adult patients who underwent heart transplantation using ex vivo heart perfusion (EVHP) and a beating heart implantation technique between October 2022 and March 2024. Primary outcomes of interest included survival, initiation of mechanical circulatory support, and rejection. A subanalysis of our institutional series of nonbeating deceased after circulatory death (DCD) heart transplantations was performed as well. ResultsTwenty-four patients underwent isolated heart transplantation with the use of ex vivo heart perfusion and beating heart implantation between October 2022 and March 2024; 21 (87.5%) received hearts from DCD donors, and 3 (12.5%) received hearts from deceased after brain death (DBD) donors. The median duration of follow-up was 192 days (interquartile range [IQR], 124-253.5 days), and 23 out of 24 patients (95.8%) were alive at last follow-up. No patients required initiation of mechanical circulatory support. The majority of patients had pathologic grade 0 rejection at the time of biopsy (n = 16; 66.7%), and the median cell-free DNA percent was 0.04% (IQR, 0.04%-0.09%). The rate of mechanical circulatory support initiation in the 22-patient nonbeating DCD heart transplant cohort was significantly higher, at 36.4% (P < .005). ConclusionsA beating heart implantation technique can be used for transplantation of DCD and DBD hearts on EVHP and is associated with excellent survival and low levels of rejection.

Impact of Hemoglobin Level in Ex Vivo Heart Perfusion on Donation After Circulatory Death Hearts: A Juvenile Porcine Experimental Model.

Ex vivo heart perfusion (EVHP) of donation after circulatory death (DCD) hearts has become an effective strategy in adults; however, the small circulating volume in pediatrics poses the challenge of a low-hemoglobin (Hb) perfusate. We aimed to determine the impact of perfusate Hb levels during EVHP on DCD hearts using a juvenile porcine model. Sixteen DCD piglet hearts (11-14 kg) were reperfused for 4 h in unloaded mode followed by working mode. Metabolism, cardiac function, and cell damage were compared between the low-Hb (Hb, 5.0-5.9 g/dL; n = 8) and control (Hb, 7.5-8.4 g/dL; n = 8) groups. Between-group differences were evaluated using 2-sample t -tests or Fisher's Exact tests. During unloaded mode, the low-Hb group showed lower myocardial oxygen consumption ( P < 0.001), a higher arterial lactate level ( P = 0.001), and worse systolic ventricular function ( P < 0.001). During working mode, the low-Hb group had a lower cardiac output (mean, 71% versus 106% of normal cardiac output, P = 0.010) and a higher arterial lactate level ( P = 0.031). Adjusted cardiac troponin-I ( P = 0.112) did not differ between the groups. Morphological myocyte injury in the left ventricle was more severe in the low-Hb group ( P = 0.028). Low-Hb perfusate with inadequate oxygen delivery induced anaerobic metabolism, resulting in suboptimal DCD heart recovery and declined cardiac function. Arranging an optimal perfusate is crucial to organ protection, and further endeavors to refine the priming volume of EVHP or the transfusion strategy are required.

Jacketed elastomeric tubes for passive self-regulation of pulsatile flow

Regulating pulsatile flow is important to achieve optimal separation and mixing and enhanced heat transfer in microfluidic devices, as well as maintaining homeostasis in biological systems. The human aorta, a composite and layered tube made (among others) of elastin and collagen, is an inspiration for researchers who seek an engineering solution for a self-regulation of pulsatile flow. Here, we present a bio-inspired approach showing that fabric-jacketed elastomeric tubes, manufactured using commercially available silicone rubber and knitted textiles, can be used to regulate pulsatile flow. Our tubes are evaluated via incorporation into a mock-circulatory ‘flow loop’ that replicates the pulsatile fluid flow conditions of an ex-vivo heart perfusion (EVHP) device, a machine used in heart transplants. Pressure waveforms measured near the elastomeric tubing clearly indicated an effective flow regulation. The ‘dynamic stiffening’ behavior of the tubes during deformation is analyzed quantitatively. Broadly, the fabric jackets allow for the tubes to experience greater magnitudes of pressure and distension without risk of asymmetric aneurysm within the expected operating time of an EVHP. Owing to its highly tunable nature, our design may serve as a basis for tubing systems that require passive self-regulation of pulsatile flow.

(985) Circulating Factors, Measured Both in the Donor and During Ex-Vivo Heart Perfusion, Correlate with Subsequent Heart Recovery in a Pig Model of Dcd

(985) Circulating Factors, Measured Both in the Donor and During Ex-Vivo Heart Perfusion, Correlate with Subsequent Heart Recovery in a Pig Model of Dcd

(501) Ex-Vivo Heart Perfusion for Cardiac Transplantation: An Initial Experience in the United States

(501) Ex-Vivo Heart Perfusion for Cardiac Transplantation: An Initial Experience in the United States

Normothermic ex vivo heart perfusion with NLRP3 inflammasome inhibitor Mcc950 treatment improves cardiac function of circulatory death hearts after transplantation.

The utilization of donation after circulatory death (DCD) hearts can enlarge the donor pool. However, DCD hearts suffer from serious ischemia/reperfusion injury (IRI). Recent studies found that the activation of NLRP3 inflammasome could play a significant role in organ IRI. Mcc950, which is a novel inhibitor of the NLRP3 inflammasome, can be applied to treat various kinds of cardiovascular diseases. Therefore, we hypothesized that the treatment of mcc950 could protect DCD hearts preserved with normothermic ex vivo heart perfusion (EVHP) against myocardial IRI via inhibiting NLRP3 inflammasome in a rat heart transplantation model of DCD. Donor-heart rats were randomly divided into four groups: Control group; Vehicle group; MP-mcc950 group; and MP + PO-mcc950 group. Mcc950 was added into the perfusate of normothermic EVHP in the MP-mcc950 and MP + PO-mcc950 groups, and was injected into the left external jugular vein after heart transplantation in the MP + PO-mcc950 group. Cardiac functional assessment was performed. The level of oxidative stress, inflammatory response, apoptosis, and NLRP3 inflammasome-associated protein of donor hearts were evaluated. The treatment with mcc950 significantly increased the developed pressure (DP), dP/dtmax, and dP/dtmin of the left ventricular of DCD hearts at 90 min after heart transplantation in both MP-mcc950 and MP + PO-mcc950 groups. Furthermore, mcc950 added into perfusate and injected after transplantation in both MP-mcc950 and MP + PO-mcc950 groups significantly attenuated the level of oxidative stress, inflammatory response, apoptosis, and NLRP3 inflammasome compared with the vehicle group. Normothermic EVHP combined with mcc950 treatment can be a promising and novel DCD heart preservation strategy, which can alleviate myocardial IRI via inhibiting NLRP3 inflammasome.

Left ventricular assist device mode: Co-pulse left ventricular unloading in a working mode of ex vivo heart perfusion

For normothermic ex vivo heart perfusion (EVHP), a resting mode and working mode have been proposed. We newly developed a left ventricular assist device (LVAD) mode that supports heart contraction by co-pulse synchronized LVAD. Following resting mode during time 0 to 1 hour, pig hearts (n=18) were perfused in either resting, working, or LVAD mode during time 1 to 5 hour, and then myocardial function was evaluated in working mode at 6 hour. The preservation ratio was defined as the myocardial mechanical function at 330 minute divided by the function at 75 minute. In LVAD mode, LVAD unloaded the pressure and the volume in the left ventricle in the systolic phase. The LVAD group was significantly associated with higher preservation ratios in cardiac output (resting, 33 ± 3; working, 35 ± 5; LVAD, 76% ± 5%; p < 0.001), stroke work, dP/dt maximum, and dP/dt minimum compared with the other groups. Glucose consumption was significantly reduced in the resting group. The LVAD group was significantly associated with higher myocardial oxygen consumption (resting, 2.2 ± 0.3; working; 4.6 ± 0.5; LVAD, 6.1 ± 0.5 mL O2/min/100 g, p < 0.001) and higher adenosine triphosphate (ATP) levels (resting, 1.1 ± 0.1; working, 0.7 ± 0.1; LVAD, 1.6 ± 0.2 μmol/g, p=0.001) compared with the others. These data suggest that myocardial mechanical function was better preserved in LVAD mode than in resting and working modes. Although our data suggested similar glycolysis activity in the LVAD and working groups, the higher final ATP in the LVAD group might be explained by reduced external work in LVAD.

Normothermic Ex Vivo Heart Perfusion with Mesenchymal Stem Cell-Derived Conditioned Medium Improves Myocardial Tissue Protection in Rat Donation after Circulatory Death Hearts.

Adopting hearts from donation after circulatory death (DCD) is a promising approach to enlarge the donor pool. Nevertheless, DCD hearts experience severe warm ischemia/reperfusion (I/R) injury. Recent studies have demonstrated that conditioned medium (CM) derived from bone marrow mesenchymal stem cells (BMSCs) has the potential of reducing organ I/R injury. Therefore, we investigated whether DCD heart preservation with normothermic ex vivo heart perfusion (EVHP) and BMSCs-CM treatment could alleviate myocardial warm I/R injury in the DCD hearts. We randomly divided donor rats into two groups: (1) DCD-Control group and (2) DCD-CM group. Before DCD heart preservation with the normothermic EVHP system for 105 minutes, rats suffered from a 25-minute warm ischemia injury in the DCD procedure. Vehicle or CM (300 μl) was added to the perfusate at the beginning of the perfusion process. The cardiac function of DCD hearts in the DCD-Control and DCD-CM groups was measured every 30 minutes. Besides, non-DCD hearts were harvested from the beating-heart rats. The antibody array demonstrated that the CM contained 14 bioactive factors involved in apoptosis, inflammation, and oxidative stress. Warm ischemia injury resulted in a significant increase in the level of oxidative stress, inflammation, and apoptosis in the DCD hearts of DCD-Control group. Furthermore, compared with the DCD-Control group, CM treatment increased the developed pressure, dP/dtmax and dP/dtmin of the left ventricular in the DCD hearts during a 90-minute EVHP. Moreover, the administration of CM attenuated the level of oxidative stress, inflammation, and apoptosis in the DCD hearts of the DCD-CM group. Normothermic EVHP combined with CM treatment can alleviate warm I/R injury in the DCD hearts by decreasing the level of oxidative stress, inflammatory response, and apoptosis, which might alleviate the shortage of donor hearts by adopting DCD hearts.

Strategies for Expanding Donors Pool in Heart Transplantation.

Heart transplant remains the criterion standard treatment for patients in end-stage heart failure. Improvement in the post-heart transplant outcomes in the last decade has contributed to increased demand for organs. Worldwide each year, more than 5000 heart transplants are performed and 50,000 people become candidates for heart transplant. In the last 50 years, there have been several attempts to expand donor criteria to increase the donor pool. Despite making hepatitis C virus, opioid overdose death, old age allowable and changing the allocation system, the gap between supply and demand is widening and unfortunately, thousands die every year waiting due to the critical shortage of organs. New technologies for heart donation after circulatory death have emerged, particularly normothermic regional organ perfusion and ex-vivo heart perfusion using organ care systems. However, these technologies still do not fill the gap. Continuous advancements in areas such as regenerative medicine and xenotransplantation, among others, are needed to overcome the shortage of heart donors for heart transplantation.

Near-Wall Fluid Mechanics Of A Pulsatile Flow Through A Compliant Tube

The demand for heart transplantation far exceeds the supply. This shortage is mainly due to the high percentage of discarded hearts and the narrow time window of only six hours that the current standard preservation method, static cold storage (SCS), allows for completing the entire procedure from donor to recipient patient. An alternative method called ex-vivo heart perfusion (EVHP) maintains a human donor heart beating outside the body for the time preceding transplantation surgery. By keeping the donor heart beating in a quasi-physiological mode of operation and assessing its functions, the organ's health can be monitored so that, ultimately, the transplant time window can be extended to increase the geographic availability of donors. In order to improve and optimize the EVHP system, fundamental understanding of the system physics is needed. To achieve this, the present work aims to investigate the relationship between pulsatile flow and compliance, evaluating the near wall region of a compliant tube with a particular focus on the formation of the viscous boundary layer. Thus, an experimental setup was designed to replicate the flow loop of the EVHP system and an optical transparent compliant tube that mimics the functioning of the body's largest and most compliant artery, the aorta, was custom-made to allow optical access to the flow field matching the refractive index of the working fluid. A pulsatile waveform is generated using a computer-controlled mechanical diaphragm pump, also equipped with a tri-leaf exit valve to simulate the physiological working condition of the heart. In the present work, the flow field is assessed by first performing stereo particle image velocimetry (PIV) on the bulk flow to investigate the large-scale phenomena within a compliant tube and the results of these experiments will be further used as a guide to interrogate smaller near-wall regions of interest in the flow. The preliminary results show, in addition to the general characteristics of a pulsatile flow through a compliant tube, a potential complex fluid-structure relationship between the pulsatile flow and the moving wall of the tube has been observed. The presentation of this work will discuss the experimental setup and review the preliminary results presented here in addition to others findings that are still being analyzed, data processing is underway to do so.

Production of living myocardial slices from circulatory death hearts after exvivo heart perfusion.

Living myocardial slices (LMS) are ultrathin sections of beating cardiac tissue that maintain 3-dimensional microarchitecture and multicellularity and are cultured under conditions of near-physiological preload and continuous electrical excitation.1 LMS are mostly produced from human surgical biopsies obtained from heart transplantations or mechanical support implantations, limiting the type and availability of provided tissue. Here, we present a recently validated novel technique for LMS1 that we implemented for donation after circulatory death (DCD) porcine slaughterhouse hearts on ex vivo heart perfusion (EVHP).

Left Ventricular Assist Device Mode: Co-Pulse Left Ventricular Unloading in Working Mode of Ex Vivo Heart Perfusion

<h3>Purpose</h3> As normothermic ex vivo heart perfusion (EVHP), resting mode and working mode have been proposed. Herein we newly developed left ventricular assist device (LVAD) mode in EVHP: a novel EVHP mode that supported heart contraction by co-pulse synchronized LVAD. <h3>Methods</h3> Following resting mode at 0-1 hour, pig hearts (n = 18) were perfused using cellular perfusate in either of resting, working, and LVAD mode at 1-5 hour, and then myocardial function was evaluated in working mode in all cases at 6 hour. Preservation ratio in the evaluation was defined as myocardial function at 6 hour/myocardial function at 1 hour. Metabolic markers were measured every hour. In LVAD mode, LVAD unloaded the perfusate in left ventricle in systolic phase (Figure). <h3>Results</h3> LVAD mode group was significantly associated with higher preservation ratio in cardiac output (LVAD, 76 ± 5; Resting, 33 ± 3; Working, 35 ± 5%, P < 0.001), stroke work, dP/dt max, and dP/dt min, compared with other groups (Table). Glucose consumption were significantly reduced in resting mode group. LVAD mode group was associated with higher myocardial oxygen consumption (MVO₂) (LVAD, 6.1 ± 0.5; Resting, 2.2 ± 0.3; Working, 4.6 ± 0.5 mL O₂/mion/100g, P < 0.001) and higher ATP level (LVAD, 1.6 ± 0.2; Resting, 1.1 ± 0.1; Working, 0.7 ± 0.1 μmol/g, P = 0.003), compared with other groups. <h3>Conclusion</h3> These data suggest that myocardial function was better preserved in LVAD mode than in resting and working mode. Although similar glycolysis activity was suspected in LVAD and working groups, higher final ATP in LVAD group might be explained by reduced external work in LVAD.

A Novel Intraventricular Balloon Technique for Functional Assessment of Hearts from Donation After Circulatory Death

<h3>Purpose</h3> Functional assessment of hearts from donation after circulatory death (DCD) on ex-vivo heart perfusion (EVHP) is not well-established. Conventional intraventricular balloon (IVB) techniques, used for isolated heart perfusion in large animal models sacrifice the mitral valve to stabilize the balloon inside the left ventricle (LV), making it inapplicable for the clinical setting. This study demonstrates the effectiveness of a novel IVB technique to assess cardiac function during reperfusion and compares it to pressure-volume catheter measurements in a pediatric porcine DCD heart model. <h3>Methods</h3> Twelve pigs (9.5 ± 1.4 kg) were used. DCD hearts were harvested after 15 min of global warm ischemia due to asphyxic circulatory arrest and reperfused on EVHP for 2 hours. Isovolumetric LV pressure was measured during reperfusion with a saline-filled balloon inserted into the LV via a pulmonary vein orifice. The balloon was made from polyethylene wrap and connected to an 8 Fr sheath and pressure catheter, which was fixed with the left atrium via a purse-string suture around the origin of the pulmonary vein. DCD hearts were then switched to the working model (WM), pumping 120% of cardiac output, to measure cardiac function by using a pressure-volume catheter. Between-parameter correlations were assessed by Spearman's Rank Correlation Coefficient. <h3>Results</h3> Maximum first derivative of the LV pressure (dp/dt) measured by the IVB at 90 min of reperfusion showed moderate positive correlation (r_s = 0.61, p = 0.04) and coronary venous lactate levels showed moderate negative correlation (r_s = -0.55, p = 0.06) to respective measurements in the WM. Minimum dp/dt measured by the IVB at 60 min of reperfusion showed moderate positive correlation to measurements in the WM (r_s = 0.60, p = 0.04) and to tau in the WM (r_s = 0.52, p = 0.08). There was no significant difference between LV end-diastolic pressure during reperfusion and left atrial pressure in the WM. Myocardial oxygen consumption during reperfusion was less than 60% of that in the WM. <h3>Conclusion</h3> Functional parameters of contractility and relaxation measured by the IVB showed significant correlations to respective parameters in the WM. Therefore, this mitral valve sparing IVB technique can be used to confirm adequacy of cardiac function of DCD hearts in the early phase of reperfusion without the need to fully preload the heart.

Ex vivo perfusion of the donor heart: Preliminary experience in high-risk transplantations

The number of heart transplantations (HTs) has decreased in France since 2017 (-5%/year) despite a stable rate of patients referred on the waiting list. Ex vivo heart perfusion (EVHP) is an innovative approach for organ preservation, reducing graft ischaemic time and facilitating continuous organ monitoring before transplantation. To report our preliminary experience of seven donor hearts preserved with EVHP, including the first heart resuscitated after circulatory-determined death in France. Seven hearts were procured from donation after brain death (DBD) for HT or donation after circulatory-determined death (DCD) for research purposes (Protocol PFS20-004, Agence de la Biomédecine, La Plaine Saint-Denis, France). All grafts were preserved using the Organ Care System® (TransMedics Inc., Andover, MA, USA) for normothermic EVHP. Perfusion parameters were adjusted to achieve stable or decreasing arterial lactate trend consistent with suitability for organ transplantation. Indications for EVHP were assessment of a marginal graft in four cases, prolonged preservation in two cases (anticipated duration for retrieval of recipient's heart>3hours) and resuscitation after circulatory-determined death in one case. Median duration of EVHP was 270 (interquartile range 216-343) minutes. five were transplanted, with a median ex situ preservation time (ischaemic time+EVHP time) of 334 (interquartile range 326-444) minutes. The two other grafts were discarded for HT. Three recipients had extracorporeal life support after HT, and presented complete cardiac recovery within a week after HT. One patient died at day 11 because of septic shock. The 3-month survival rate was 75% among recipients. Three months after HT, the left ventricular ejection fraction was>60% in all cases. EVHP enabled safe prolonged preservation and assessment of marginal grafts. This approach provides an opportunity to expand the donor pool by resuscitating grafts from donors with extended criteria, including controlled DCD.

Normothermic ex vivo Heart Perfusion Combined With Melatonin Enhances Myocardial Protection in Rat Donation After Circulatory Death Hearts via Inhibiting NLRP3 Inflammasome-Mediated Pyroptosis.

ObjectiveThe adoption of hearts from donation after circulatory death (DCD) is a promising approach for the shortage of suitable organs in heart transplantation. However, DCD hearts suffer from serious ischemia/reperfusion injury (IRI). Recent studies demonstrate that nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome-mediated pyroptosis is a novel target to ameliorate myocardial IRI. Melatonin is shown to inhibit NLRP3 inflammasome-mediated pyroptosis. Therefore, this study is designed to verify the hypothesis that melatonin can protect the heart graft preserved with ex vivo heart perfusion (EVHP) against myocardial IRI via inhibiting NLRP3 inflammasome-mediated pyroptosis in a rat model of DCD.MethodsDonor-heart rats were randomly divided into three groups: (1) Control group: non-DCD hearts were harvested from heart-beating rats and immediately preserved with allogenic blood-based perfusate at constant flow for 105 min in the normothermic EVHP system; (2) DCD-vehicle group; and (3) DCD-melatonin group: rats were subjected to the DCD procedure with 25 min of warm ischemia injury and preserved by the normothermic EVHP system for 105 min. Melatonin (200 μmol/L) or vehicle was perfused in the cardioplegia and throughout the whole EVHP period. Cardiac functional assessment was performed every 30 min during EVHP. The level of oxidative stress, inflammatory response, apoptosis, and NLRP3 inflammasome-mediated pyroptosis of heart grafts submitted to EVHP were evaluated.ResultsTwenty five-minute warm ischemia injury resulted in a significant decrease in the developed pressure (DP), dP/dtmax, and dP/dtmin of left ventricular of the DCD hearts, while the treatment with melatonin significantly increased the DP, dP/dtmax of the left ventricular of DCD hearts compared with DCD-vehicle group. Furthermore, warm ischemia injury led to a significant increase in the level of oxidative stress, inflammatory response, apoptosis, and NLRP3 inflammasome-mediated pyroptosis in the hearts preserved with EVHP. However, melatonin added in the cardioplegia and throughout the EVHP period significantly attenuated the level of oxidative stress, inflammatory response, apoptosis, and NLRP3 inflammasome-mediated pyroptosis compared with DCD-vehicle group.ConclusionEVHP combined with melatonin post-conditioning attenuates myocardial IRI in DCD hearts by inhibiting NLRP3 inflammasome-mediated pyroptosis, which might expand the donor pool by the adoption of transplantable DCD hearts.

Hyperkalemia: Major but still understudied complication among heart transplant recipients.

Hyperkalemia is a recognized and potentially life-threatening complication of heart transplantation. In the complex biosystem created by transplantation, recipients are susceptible to multiple mechanisms for hyperkalemia which are discussed in detail in this manuscript. Hyperkalemia in heart transplantation could occur pre-transplant, during the transplant period, or post-transplant. Pre-transplant causes of hyperkalemia include hypothermia, donor heart preservation solutions, conventional cardioplegia, normokalemic cardioplegia, continuous warm reperfusion technique, and ex-vivo heart perfusion. Intra-transplant causes of hyperkalemia include anesthetic medications used during the procedure, heparinization, blood transfusions, and a low output state. Finally, post-transplant causes of hyperkalemia include hemostasis and drug-induced hyperkalemia. Hyperkalemia has been studied in kidney and liver transplant recipients, but there is limited data on the incidence, causes, management, and prevention in heart transplant recipients. Hyperkalemia is associated with an increased risk of hospital mortality and readmission in these patients. This review describes the current literature pertaining to the causes, pathophysiology, and treatment of hyperkalemia in patients undergoing heart transplantation and focuses primarily on post-heart transplantation.

Twenty-four-hour normothermic perfusion of isolated exvivo hearts using plasma exchange.

Cross-circulation of plasma from a paracorporeal animal allows successful exvivo heart perfusion (EVHP) for 3days. Little is known about the feasibility of prolonged EVHP without a paracorporeal animal. These experiments evaluated plasma exchange (PX) that infuses fresh plasma, whereas an equal amount is removed to replace paracorporeal cross-circulation. Ten hearts were procured from 8 to 10kg piglets and maintained with EVHP. The EVHP circuit was primed with platelet- and leukocyte-reduced blood. Plasma obtained from stored porcine blood (4°C for ≤7days) was infused and removed with a plasma separator at 1mL/h/g cardiac tissue (n=5) in the PX group. Controls (n=5) used the same EVHP without PX. Antegrade aortic perfusion was adjusted to reach physiologic coronary flow of 0.7 to 1.2mL/min/g, normothermia (37°C), and hemoglobin ≥8g/dL. Viability was assessed by hemodynamic metrics, metabolic assays, and histopathology. All PX hearts remained viable for 24hours compared with only 1 control (P=.015). Coronary resistance was higher in the PX versus controls (1.06± 0.06mm Hg/mL/min; 0.58±0.02mm Hg/mL/min [P<.05]). Lactatelevels were lower in PX (2.8-4.2mmol/L) versus controls (3.6-7.6mmol/L) (P<.05). PX demonstrated a trend toward preservation of left ventricle systolic pressure (63.0±10.9mm Hg) versus controls (37±22.0mm Hg) (P>.05). In mixed effect models, oxygen consumption was higher with PX (P<.05). Histopathologic evaluation confirmed extensive myocardial degeneration and worse interstitial edema in controls. These results demonstrate that EVHP can be successfully maintained for at least 24hours using continuous PX. This eliminates the need for a paracorporeal animal and provides an important step toward clinical application.

The role of beta-hydroxybutyrate as inducer for adult cardiomyocyte proliferation during reprogramming in vivo

Abstract Background Regional loss of myocardium is the dominant cause of heart failure due to coronary artery disease. In mammals, the response to injury shows some similarities with border zone myocytes remodeling, but little proliferation and repair occur in adult mammalian hearts. Several studies have identified some cell cycle-related genes essential for dramatically inducing neonatal CM proliferation, but the same effects cannot be replicated in adult CMs. This implies that there is an underlying mechanism (an inducer) that is yet to be discovered, that should first be activated in order to subsequently increase adult CM proliferation efficiently in vivo. Purpose To determine the inducer for the purpose of efficiently increasing adult CM proliferation, and to examine its therapeutic potential for heart regeneration after injury. Methods Transgenic mice (αMHC-rtTA-OSKM), whose adult CMs can be specifically induced by Yamanaka's OSKM factors, were generated to systemically examine the early stage of iPSC reprogramming after tetracycline treatment. These induced reprogramming CMs were further isolated for gene ontology analysis by microarray to determine the specific inducer for the purpose of efficiently increasing CM proliferation. Finally, the inducer was applied to a mouse model of myocardial infarction (MI) to confirm its therapeutic potential for heart regeneration after injury. Results OSKM expressions of αMHC-rtTA-OSKM were confirmed to only increase in CMs after tetracycline treatment in vivo, and BrdU+ CM% was more than 2-times higher in isolated adult CMs from αMHC-rtTA-OSKM mice treated with tetracycline for 2 days compared to PBS-treated mice. More H3P+/cTnT+ population% was also confirmed in this CM-disorganized reprogramming hearts compared to normal hearts. Microarray data revealed that the morphological changes of the reprogrammed CMs were due to a metabolic switch shown in gene ontology analysis. Thus, we profiled the metabolic switch in normal and CM reprogramming hearts by perfusing them with 13C-labeled metabolic substrates through the Langendorff ex-vivo working heart perfusion system. Through 13C NMR spectroscopy we determined that TCA cycle metabolites were 2-times lower while β-hydroxybutyrate were 2-times higher in the reprogrammed hearts compared to that in control hearts. Next, we surprisingly found that β-hydroxybutyrate supplement in MI mice at post-MI day 3 improved the heart function but showed the opposite effects when supplement was administered at post-MI day 7. Thus, the timing of β-hydroxybutyrate supplement is important for increasing adult CM proliferation for effectiveness of heart regeneration after MI. Conclusion This is the first study to identify the metabolism shift to increase β-hydroxybutyrate as the inducer for the purpose of efficiently increasing adult CM proliferation, which supports heart function improvement when treating at short period immediately after MI. Funding Acknowledgement Type of funding source: Private grant(s) and/or Sponsorship. Main funding source(s): 2020 Academia Sinica Young Scholarship Travel Award