Cardiac Graft Research Articles

The Structural and the Functional Aspects of Intercellular Communication in iPSC-Cardiomyocytes.

Recent advances in the technology of producing novel cardiomyocytes from induced pluripotent stem cells (iPSC-cardiomyocytes) fuel new hope for future clinical applications. The use of iPSC-cardiomyocytes is particularly promising for the therapy of cardiac diseases such as myocardial infarction, where these cells could replace scar tissue and restore the functionality of the heart. Despite successful cardiogenic differentiation, medical applications of iPSC-cardiomyocytes are currently limited by their pronounced immature structural and functional phenotype. This review focuses on gap junction function in iPSC-cardiomyocytes and portrays our current understanding around the structural and the functional limitations of intercellular coupling and viable cardiac graft formation involving these novel cardiac muscle cells. We further highlight the role of the gap junction protein connexin 43 as a potential target for improving cell–cell communication and electrical signal propagation across cardiac tissue engineered from iPSC-cardiomyocytes. Better insight into the mechanisms that promote functional intercellular coupling is the foundation that will allow the development of novel strategies to combat the immaturity of iPSC-cardiomyocytes and pave the way toward cardiac tissue regeneration.

Crosslinking and functionalization of acellular patches via the self-assembly of copper@tea polyphenol nanoparticles.

Decellularization is a promising technique to produce natural scaffolds for tissue engineering applications. However, non-crosslinked natural scaffolds disfavor application in cardiovascular surgery due to poor biomechanics and rapid degradation. Herein, we proposed a green strategy to crosslink and functionalize acellular scaffolds via the self-assembly of copper@tea polyphenol nanoparticles (Cu@TP NPs), and the resultant nanocomposite acellular scaffolds were named as Cu@TP-dBPs. The crosslinking degree, biomechanics, denaturation temperature and resistance to enzymatic degradation of Cu@TP-dBPs were comparable to those of glutaraldehyde crosslinked decellularized bovine pericardias (Glut-dBPs). Furthermore, Cu@TP-dBPs were biocompatible and had abilities to inhibit bacterial growth and promote the formation of capillary-like networks. Subcutaneous implantation models demonstrated that Cu@TP-dBPs were free of calcification and allowed for host cell infiltration at Day 21. Cardiac patch graft models confirmed that Cu@TP-dBP patches showed improved ingrowth of functional blood vessels and remodeling of extracellular matrix at Day 60. These results suggested that Cu@TP-dBPs not only had comparable biomechanics and biostability to Glut-dBPs, but also had several advantages over Glut-dBPs in terms of anticalcification, remodeling and integration capabilities. Particularly, they were functional patches possessing antibacterial and proangiogenic activities. These material properties and biological functions made Cu@TP-dBPs a promising functional acellular patch for cardiovascular applications.

Preservation of Nitric Oxide Synthase Activity Required for Beneficial Effects of Hypothermic Oxygenated Perfusion in Cardiac Grafts Obtained with DCD

<h3>Purpose</h3> Cardiac donation after circulatory death (DCD) is a promising option to increase graft availability. We recently reported that cardiac graft preservation with hypothermic oxygenated perfusion (HOPE) between graft procurement and normothermic reperfusion improves graft recovery as compared to preservation with cold static storage (CSS), the current clinical standard. As the precise mechanisms remain incompletely characterized, we investigated the role of preserved nitric oxide synthase (NOS) activity during HOPE on its beneficial effects. <h3>Methods</h3> Using an adult rat model of DCD, hearts underwent in-situ ischemia (21 minutes), were explanted for a cold storage period (30 minutes), and then reperfused under normothermic conditions (60 minutes) with left ventricular loading. Three cold storage conditions were compared: CSS, HOPE, and HOPE with L-NAME (NOS inhibitor). To evaluate potential confounding effects of high coronary flow during early reperfusion in HOPE hearts, bradykinin (BK) was administered to normalize coronary perfusion to HOPE levels in two additional groups (CSS and HOPE with L-NAME). <h3>Results</h3> Cardiac recovery was significantly improved in HOPE vs. CSS hearts, as determined by cardiac output, left ventricular work (heart rate-developed pressure product), contraction and relaxation rates, as well as coronary flow and oxygen efficiency (oxygen consumption per work performed; p<0.05). Strikingly, the addition of L-NAME during HOPE largely abolished its beneficial effects, even when early reperfusion coronary flow was normalized to HOPE levels with BK. Furthermore, preliminary experiments demonstrate a tendency for reduced release of cell death markers in hearts treated with HOPE compared to all other groups. <h3>Conclusion</h3> HOPE provides superior preservation of ventricular and vascular function, as well as improved metabolic recovery, compared to the current clinical standard (CSS). Importantly, preservation of NOS activity during the cold storage period is required for the protective effects of HOPE. The application of HOPE prior to normothermic reperfusion is a promising approach to help optimize cardiac graft recovery following warm ischemia in DCD cardiac grafts.

Macrophage-Derived Extracellular Vesicles (EVs) Have Functional and Metabolic Effects on Cardiac Grafts in a Preclinical Model of Donation After Circulatory Death (DCD)

<h3>Purpose</h3> Donation after circulatory death (DCD) could substantially increase cardiac graft availability. Cardiac ischemia and reperfusion, as occurs during DCD, can trigger the recruitment of macrophages as well as their polarization from the M0 to M1 state, which may occur in parallel with increased glycogen turnover and pentose phosphate flux. Extracellular vesicles (EVs) can transmit the metabolic status of their parent cell to recipient cells. As post-ischemic glucose metabolism is recognized to affect the cardiac recovery, we investigated the effects of M0 and M1 macrophage-derived EV administration during reperfusion on post-ischemic functional recovery and glucose metabolism using an isolated rat heart model of DCD. <h3>Methods</h3> Hearts isolated from adult, male rats were aerobically perfused for 20 minutes, followed by 27 minutes continued perfusion or 27 minutes of warm, global ischemia, and 60 minutes aerobic reperfusion with or without the intravascular administration of EVs. Four experimental groups were examined: 1) continued perfusion, no EVs (No ISCH); 2) ischemia, no EVs (ISCH); 3) ischemia with EVs from M0 macrophages (ISCH M0); 4) ischemia with EVs from M1 macrophages (ISCH M1). Contractile and metabolic post-ischemic recovery were evaluated. Data are reported as mean ± standard deviation. <h3>Results</h3> Left ventricular (LV) work (heart rate-developed pressure product) at 60 minutes reperfusion was significantly decreased in ISCH (17 ± 3) and ISCH M1 (19 ± 3), but not in ISCH M0 (22 ± 3), compared to No ISCH (26 ± 4 mmHg*beats*min^{−1 *}10³; p<0.05 for both). Rates of glycolysis during reperfusion were not different among groups; however, glycogen content was significantly lower after 60 min reperfusion in ISCH M1 (8 ± 2) compared to ISCH M0 (17 ± 3 μmol/g dry; p<0.05). <h3>Conclusion</h3> The ischemia-induced reduction in left ventricular work was improved with M0-, but not M1-, derived EVs. M0 and M1-derived EVs also differentially affected glucose metabolism; M1-macrophage derived EVs limited glycogen content, possibly by increasing glycogen use or turnover and stimulating recipient cells to mimic parent cell metabolic phenotypes. Circulating EVs in the ex-situ perfusion of DCD hearts may be possible targets for modulating metabolic function and optimizing graft recovery following warm ischemia.

BK Virus Nephropathy in HIV-Positive Heart-Kidney Transplant Recipient

<h3>Introduction</h3> BK viral reactivation is common in immunosuppressed states such as advanced HIV and organ transplantation. An important cause of kidney transplant allograft dysfunction and loss is BK reactivation leading to BK virus-associated nephropathy (BKVAN). We describe a problematic case of BKVAN in a combined heart-kidney transplant (HKT) recipient with well controlled HIV. <h3>Case Report</h3> A 46-year-old man with HIV (CD4 726 cells/mm³, HIV viral load <20 copies/mL) on dolutegravir/rilpivirine, non-ischemic cardiomyopathy, and HIV nephropathy underwent HKT with basiliximab induction and maintenance tacrolimus (goal 5-8 ng/mL), mycophenolate mofetil (MMF), and prednisone. Immediate post-transplant course was complicated by delayed renal graft function with acute tubular necrosis and urine leak. HIV has remained well controlled. Post-transplant nadir CD4 count was 639 cells/mm³. The patient developed BK viuria (90,891,555 copies/mL) and BK viremia (4,500 copies/mL) on post-transplant day (PTD) 55 and 62, respectively. Although MMF dose was reduced from 1,000 mg to 500 mg daily, renal allograft biopsy shortly after showed Class B1 BKVAN with no evidence of rejection. Patient began bi-weekly 5 mg/kg cidofovir infusions. Prednisone was decreased from 10 mg to 5 mg daily. Mycophenolate was further reduced to 250 mg daily and steroids were discontinued due to persistently high BK viral load. However, after decline in ejection fraction (EF) to 50% and suspicion for cardiac graft rejection, MMF dose was increased back to 500 mg daily. Endomyocardial biopsies have shown no evidence of rejection with negative donor specific anti-HLA antibodies. Renal function declined with serum creatinine (SCr) peaking at 2.28 mg/dL. Patient has remained on cidofovir infusions and reduced immunosuppression, on which SCr has stabilized to 1.8 mg/dL on PTD 694. Cardiac allograft function remains normal with an EF of 71% on PTD 644. BK viral load peaked at 16,672,298 copies/mL and remains elevated at 4,821 copies/mL on PTD 702. <h3>Summary</h3> We present a case of BKVAN in a HIV+ HKT recipient. This case demonstrates the difficulty of BKVAN management in dual organ transplant since heart allograft management requires higher levels of maintenance immunosuppression. It is unclear if HIV contributed to development of BKVAN in this recipient. Better antiviral therapies are needed for control of BK virus infections after transplant.

Ivabradine Use in a Pediatric Heart Transplant Recipient with Refractory Atrial Tachycardia

<h3>Introduction</h3> Ivabradine, an oral I_f channel antagonist, has been used in pediatric and adult heart failure patients for heart rate control, and in adult heart transplant (HT) recipients with sinus tachycardia secondary to cardiac graft denervation. There are little data describing the use of ivabradine in pediatric HT patients. We describe the use of ivabradine in a pediatric HT recipient with refractory ectopic atrial tachycardia (EAT) causing hemodynamic instability. <h3>Case Report</h3> A 3 year old male underwent HT for restrictive cardiomyopathy. Post-transplant course was complicated by pulmonary hypertensive crisis and cardiac arrest, followed by the development of EAT at a rate of >200 bpm and periods of atrial flutter 2 weeks post-transplant. Steroids were started for suspected clinical rejection, but endomyocardial biopsy was reassuring (ACR grade 1R/1A, pAMR0). Hypotension was noted when EAT rate was >170 bpm. Patient was refractory to esmolol, sotalol, and amiodarone. He underwent EP study with ablation of a posterolateral atrial focus, with recurrence of EAT several hours later. Given ongoing hemodynamic instability with EAT, repeat ablation was performed 1 week later with termination of EAT. However, periodic EAT recurred 3 weeks later and he was again symptomatic with recurrent emesis with rates >170 bpm. Ivabradine 0.05 mg/kg twice daily was initiated. After a single dose, the duration and frequency of EAT periods decreased. Rhythm was mostly sinus (SR) with a rate of 90-100 bpm with premature atrial contractions (PACs), few atrial couplets and blocked PACs. No hypotension, bradycardia, or hemodynamic instability was noted. He was discharged home and dose was up-titrated as an outpatient to 0.2 mg/kg twice daily. Six weeks later, a 72 hour Holter monitor showed predominately SR with short bursts of EAT with variable AV conduction, atrial ectopy overall making up <10% of beats, and rare premature ventricular contractions (PVCs). All subsequent clinic ECGs with follow up to 3 months demonstrated SR. Repeat Holter 3 months after initiation of ivabradine showed SR with rare, isolated PACs and PVCs with no EAT. <h3>Summary</h3> Ivabradine can be considered for EAT treatment in pediatric patients post-HT, with no identified side effects.

Longitudinal Echocardiographic Assessment of Donor Hearts in DCD Donors Using Thoracoabdominal Normothermic Regional Perfusion

<h3>Purpose</h3> In the U.S., multiple centers are beginning to develop protocols for DCD organ donation. We describe our intraoperative echo thoracoabdominal normothermic regional perfusion (TA-NRP) DCD protocol for initial donor acceptance and mid-term follow up <h3>Methods</h3> After identification of a suitable DCD donor, withdrawal of life support is performed in the OR until circulatory death occurs. After 5 minutes of observation, circulatory death is declared. The sternum is opened, cerebral vessels are ligated, and cardiopulmonary bypass (CPB) is initiated. Transesophageal echocardiogram (TEE) monitors the following parameters to ensure the heart is acceptable: left ventricular ejection fraction (LVEF) ≥50%, mitral valve annulus lateral S wave (MV S wave) ≥10 cm/sec, left ventricular outflow tract time integral (LVOT VTI) ≥15 cm, and right ventricular systolic function (RVEF) normal by visual estimation. The recipient's LVEF and global longitudinal strain rate (GLS) were followed longitudinally for up to 18 months <h3>Results</h3> From January 2020 to October 2021, 10 TA-NRP DCD transplants were performed: 7 isolated hearts, 2 heart-bilateral lung, and 1heart-kidney. Median donor age was 43.5 years (26-51) and there were 9 males (90%). Fifty percent of donors had a history of opioid drug overdose. The mean preoperative donor LVEF was 68%. Mean TEE parameters while weaning off CPB: LVEF 65%, MV lateral S wave 12 cm/sec, and LVOT VTI 19 cm. RVSF was normal for all donors. None of the donors required inotropic support. The recipient median age was 54 years (44-72) and 70% were male. None of the recipients developed cardiac graft failure. At mean follow-up of 392 days, mean LVEF is 64% and mean GLS is -16.7% and all patients are alive. <h3>Conclusion</h3> A standardized intraoperative TEE protocol to assess TA-NRP DCD donor heart function while weaning CPB is of paramount importance to ensure excellent longitudinal recipient graft function.

New Methods to Extend Perfusion Duration of Rat Cardiac Grafts

<h3>Purpose</h3> Cardiac transplant is an established treatment for end-stage heart disease; however, there is a shortage of viable organs. Extending preservation time or reviving marginal grafts would greatly reduce the current shortage. Machine perfusion holds promise to overcome these challenges. Murine models are used due to their low cost, and availability of transgenic lines; however, perfusion are limited to ∼2 hours. Most rat retrograde perfusions apply aortic root pressures of 75-90 mmHg, and flows between 5-25 ml/min. As perfusion time extends, valvular injury, hypertrophy, edema, and graft disfunction can be observed. Methods to avoid these issues include a left ventricular apical drain and increasing oncotic pressure/oxygen delivery using packed red blood cells (pRBCs). Our research tests the effect of lower pressures/flow rates, 30-35 mmHg, 3.5-5 mL/min during a 4-hour normothermic perfusion. <h3>Methods</h3> Hearts from Sprague Dawley rats were retrogradely perfused for 4 hours, under varying flow, pressure, and perfusate parameters (Table 1). <h3>Results</h3> Group 3 (G3) had stable perfusion parameters over 4 hours with high oxygen uptake (average 22.53 mmHg•min•mL⁻¹/gram tissue) and low resistance (average 3.34 mmHg•min•mL⁻¹/gram tissue). Weight was significantly different at 4 hours comparing G3 with no weight gain, to the Controls that had 23% weight gain. Lactate rose in both G3 and Control but was not significant. Finally, G3 sustained full ventricular contraction (>150 bpm), with no arrhythmia, or tachycardia; whereas Control heart rate decreased throughout perfusion, and arrhythmia and tachycardia was noted within 2 hours. <h3>Conclusion</h3> We demonstrate the ability to prolong murine heart perfusion for up to 4 hours. With prolonged function and viability in a murine heart model, this opens a greater potential of low-cost mammalian heart perfusions for research.

The potential of genetically engineered pig heart transplantation in infants with complex congenital heart disease.

Despite advances in surgical and medical techniques, complex congenital heart disease in neonates and infants continues to be associated with significant mortality and morbidity. More than 500 infants in the USA are placed on the cardiac transplantation wait-list annually. However, there remains a critical shortage of deceased human donor organs for transplantation with a median wait-time of 4months. Hence, infant mortality on the heart transplant wait-list in the USA is higher than for any other solid organ transplant group. Orthotopic transplantation of a pig heart as a bridge to allotransplantation might offer the best prospect of long-term survival of these patients. In recent years, there have been several advances in genetic engineering of pigs to mitigate the vigorous antibody-mediated rejection of a pig heart transplanted into a nonhuman primate. In this review, we briefly highlight (i) the history of clinical heart xenotransplantation, (ii) current advances and techniques of genetically engineering pigs, (iii) the current status of pig orthotopic cardiac graft survival in nonhuman primates, and (iv) progress toward pursuing clinical trials of cardiac xenotransplantation. Ultimately, we argue that pig heart xenotransplantation should initially be used as a bridge to cardiac allotransplantation in neonates and infants.

Cardiac graft loss in transplant recipient with Chagas disease

American Journal of TransplantationVolume 22, Issue 3 p. 991-993 CONTINUING MEDICAL EDUCATION Cardiac graft loss in transplant recipient with Chagas disease Monica Samuel Avila, Corresponding Author Monica Samuel Avila mo_avila@hotmail.com orcid.org/0000-0003-3712-1175 Hospital Sirio Libanes, Sao Paulo, Brazil Correspondence Monica Samuel Avila, Hospital Sirio Libanes, Sao Paulo, Brazil. Email: mo_avila@hotmail.comSearch for more papers by this authorDeborah de Sá Pereira Belfort, Deborah de Sá Pereira Belfort orcid.org/0000-0003-0207-3986 Hospital Sirio Libanes, Sao Paulo, BrazilSearch for more papers by this authorVictor de Vicente Leite, Victor de Vicente Leite Pontificia Universidade Católica, Campinas, Sao Paulo, BrazilSearch for more papers by this authorLéa Maria Macruz Ferreira Demarche, Léa Maria Macruz Ferreira Demarche Pathology Department, Heart Institute (InCor), do Jospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, Sao Paulo, BrazilSearch for more papers by this authorSilvia Moreira Ayub-Ferreira, Silvia Moreira Ayub-Ferreira Hospital Sirio Libanes, Sao Paulo, BrazilSearch for more papers by this author Monica Samuel Avila, Corresponding Author Monica Samuel Avila mo_avila@hotmail.com orcid.org/0000-0003-3712-1175 Hospital Sirio Libanes, Sao Paulo, Brazil Correspondence Monica Samuel Avila, Hospital Sirio Libanes, Sao Paulo, Brazil. Email: mo_avila@hotmail.comSearch for more papers by this authorDeborah de Sá Pereira Belfort, Deborah de Sá Pereira Belfort orcid.org/0000-0003-0207-3986 Hospital Sirio Libanes, Sao Paulo, BrazilSearch for more papers by this authorVictor de Vicente Leite, Victor de Vicente Leite Pontificia Universidade Católica, Campinas, Sao Paulo, BrazilSearch for more papers by this authorLéa Maria Macruz Ferreira Demarche, Léa Maria Macruz Ferreira Demarche Pathology Department, Heart Institute (InCor), do Jospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, Sao Paulo, BrazilSearch for more papers by this authorSilvia Moreira Ayub-Ferreira, Silvia Moreira Ayub-Ferreira Hospital Sirio Libanes, Sao Paulo, BrazilSearch for more papers by this author First published: 03 March 2022 https://doi.org/10.1111/ajt.16919Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume22, Issue3March 2022Pages 991-993 AST and ASTS members - please log in via your Society website for full journal access.AST Members >> ASTS Members >> RelatedInformation

Temperature-Related Effects of Myocardial Protection Strategies in Swine Hearts after Prolonged Warm Ischemia.

Insufficient supply of cardiac grafts represents a severe obstacle in heart transplantation. Donation after circulatory death (DCD), in addition to conventional donation after brain death, is one promising option to overcome the organ shortage. However, DCD organs undergo an inevitably longer period of unprotected warm ischemia between circulatory arrest and graft procurement. In this scenario, we aim to improve heart preservation after a warm ischemic period of 20 min by testing different settings of myocardial protective strategies. Pig hearts were collected from a slaughterhouse and assigned to one of the five experimental groups: baseline (BL), cold cardioplegia (CC), cold cardioplegia + adenosine (CC-ADN), normothermic cardioplegia (NtC + CC) or normothermic cardioplegia + cold cardioplegia + adenosine (NtC-ADN + CC). After treatment, tissue biopsies were taken to assess mitochondrial morphology, antioxidant enzyme activity, lipid peroxidation and cytokine and chemokine expressions. NtC + CC treatment significantly prevented mitochondria swelling and mitochondrial cristae loss. Moreover, the antioxidant enzyme activity was lower in this group, as was lipid peroxidation, and the pro-inflammatory chemokine GM-CSF was diminished. Finally, we demonstrated that normothermic cardioplegia preserved mitochondria morphology, thus preventing oxidative stress and the subsequent inflammatory response. Therefore, normothermic cardioplegia is a better approach to preserve the heart after a warm ischemia period, with respect to cold cardioplegia, before transplantation.

Predictive value of left ventricular ejection fraction for the occurrence of postoperative myocardial infarction after coronary endarterectomy in patients with diffuse coronary artery disease

Objective: To investigate the predictive value of ejection fraction for the postoperative myocardial infarction after coronary endarterectomy (CE) in patients with diffuse coronary artery disease (DCAD). Methods: Patients who underwent cardiac artery bypass graft (CABG) surgery and CE in Beijing Anzhen Hospital affiliated to Capital Medical University from May 2018 to December 2020 were enrolled in this prospective observational study. Baseline features including age, sex and echocardiography parameters were obtained. Left ventricular ejection fraction(EF) was measured by echocardiography. The patients were divided into postoperative myocardial infarction (PMI) group and non-PMI group according to PMI occurrence. Linear regression analysis, logistic regression model, and receiver operating characteristic(ROC) curve were used to analyze the correlation between left ventricular ejection fraction and PMI and the influencing factors. Results: A total of 120 patients were enrolled in the study. There were 32 patients (27%) in the PMI group (male 27(84%), age (62±8)), inferior myocardial infarction occurred in 24 (75%) patients. There were 88 patients (73%) in the non-PMI group (male 70(80%), age (62±8)). EF (55% (49%, 64%) vs. 62% (55%, 67%), P=0.01) was significantly lower in the PMI group than in the non-PMI group. Perioperative TNI, IABP use and length of hospitalization were significantly higher in the PMI group than in the non-PMI group. Multivariate logistic regression showed that lower EF was an independent risk factor of PMI (OR=0.93, 95%CI: 0.89-0.98, P=0.01) after adjusting age, sex and body mass index. ROC curve analysis showed that EF<60% could sufficiently predict the occurrence of PMI (AUC= 0.67, sensitivity 64%, specificity 69%, P=0.01). Linear regression analysis showed that left ventricular end-diastolic diameter (OR=-0.52, 95%CI:-1.13-0.60, P<0.001), graft flow in left anterior descending (OR=-0.20, 95%CI:-0.15-0.01, P=0.02) and history of diabetes (OR=-0.28, 95%CI:-8.25-1.85, P=0.002) were negatively correlated with preoperative EF value. Conclusion: Lower preoperative EF is an independent risk factor for PMI after CABG and CE in DCAD patients, closely related to the left ventricular end-diastolic diameter, graft flow in left anterior descending artery and diabetes mellitus.

Bioinformatics Identification of Candidate Biomarkers in Endomyocardial Biopsy and Peripheral Blood for Cardiac Allograft Rejection.

BackgroundCardiac allograft rejection is still a crucial barrier to achieving satisfactory outcomes after surgery. In this study, we propose to find candidate biomarkers from endomyocardial biopsy (EMB) and peripheral blood (PB) samples for efficient diagnosis and treatment of cardiac allograft rejection.Material/MethodsMicroarray datasets were obtained from the Gene Expression Omnibus (GEO). Differentially expressed genes (DEGs) of cardiac allograft rejection patients and control subjects from EMB and PB samples were screened using the online tool GEO2R. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis of all samples’ DEGs were performed with the DAVID online tool. Protein–protein interaction (PPI) networks were constructed and visualized using Cytoscape and the top 10 hub genes were selected. Finally, the most highly enriched GO and KEGG pathways of the top 10 hub genes were determined.ResultsA total of 57 502 genes from EMB samples and 131 624 genes from PB samples were identified. Gene characteristics and enrichment analysis indicated that both EMB and PB samples contained DEGs involved in antigen presentation, immune cells activation, inflammatory process, and cellular injuries. In EMB samples, there were some DEGs related to heart tissue injury and cardiac malfunction. Moreover, DEGs that regulates hypoxia-induced factors and erythrocyte function in response of ischemia and hypoxia stress were present in PB samples but were absent in EMB samples.ConclusionsThe screened differentially expressed genes (DEGs) from EMB and PB samples of patients with cardiac graft rejection are potential candidate biomarkers of diagnosis and treatment.

Obesity and dyslipidemia predict cardiac allograft vasculopathy and graft loss in children and adolescents post-heart transplant: A PHTS multi-institutional analysis.

Obesity and dyslipidemia afflict children of all ages. We explored the prevalence of obesity and dyslipidemia in pediatric heart transplant (HT) recipients and its effects on cardiac allograft vasculopathy (CAV) and survival. This study included primary HT recipients (≤18years) transplanted between 01/1996 and 12/2018 included in the Pediatric Heart Transplant Society database. Obesity was categorized according to WHO/CDC guidelines and dyslipidemia according to the National Cholesterol Education Program. Kaplan-Meier analyses for CAV and graft loss stratified for BMI and lipid panels were generated and risk factors identified using multivariate analyses. Among 6291 HT patients (median age [range] at HT=4.3 [0.6-12.8]years; 45% Female; 68% White), 56% had a normal BMI at HT. Obese patients at HT had an increased risk for graft loss (HR 1.19, 95% CI 1.01-1.4, p=.04). Poor total cholesterol (TC), LDL-C, and TG were associated with the risk of both CAV (HR 1.79, p<.0001; HR 1.65, p=.0015; HR 1.53, p<.0001, respectively) and graft loss (HR 1.58, p=.0008; HR 1.22, p=.04; HR 1.43, p=.0007, respectively). Pediatric patients who are obese at the time of HT and dyslipidemic at 1year post-HT are at an increased risk for CAV and graft loss. Preventative interventions may reduce morbidity and mortality among this cohort.

Evaluation of Cardiac Graft Function by Echocardiography in Mice

Generally, graft function in the murine cardiac allograft transplant model is assessed daily by palpating the heart for evidence of contraction. To our knowledge, few reports have investigated the correlation of cardiac graft function using echocardiography and immunohistochemical studies. In this study, we investigated the efficacy of echocardiographic and histologic evaluation of alloimmune responses in the acute phase of murine cardiac allografts. Fully vascularized heterotopic hearts from CBA (allogeneic group) or C57BL/6 (syngeneic group) donors were transplanted into C57BL/6 recipients using microsurgical techniques. Fluctuations in heart rate, left ventricular ejection fraction (LVEF), left ventricular functional shortening (LVFS), right ventricular outflow tract maximal systolic velocity (RVOT Vmax), and RVOT velocity time integral (RVOT VTI) were evaluated on postoperative days (PODs) 1, 3, 5, 7, and 9 after transplantation using an ultrasonic device. Histologic studies were also performed. The syngeneic group did not show a complete cessation of heartbeat or deterioration of cardiac function. CBA recipients in the allogeneic group rejected cardiac allografts on POD 9 after grafting. LVEF and LVFS in the allogeneic group gradually decreased on POD 9. Consistent with the time-course echocardiographic evaluation, histologic studies showed gradual atrophy of the left ventricle. In contrast, RVOT Vmax and RVOT VTI in the allogeneic group were not significantly different during the observation period. Additionally, the thickness of the right ventricular wall did not change until POD 7. The present findings suggested that echocardiography may help to evaluate time-course murine cardiac graft function through left ventricular parameters such as LVEF and LVFS.

Mimicking Native Heart Tissue Physiology and Pathology in Silk Fibroin Constructs through a Perfusion-Based Dynamic Mechanical Stimulation Microdevice.

In vitro cardiomyocyte (CM) maturation is an imperative step to replicate native heart tissue-like structures as cardiac tissue grafts or as drug screening platforms. CMs are known to interpret biophysical cues such as stiffness, topography, external mechanical stimulation or dynamic perfusion load through mechanotransduction and change their behavior, organization, and maturation. In this regard, a silk-based cardiac tissue (CT) coupled with a dynamic perfusion-based mechanical stimulation platform (DMM) for achieving maturation and functionality in vitro is tried to be delivered. Silk fibroin (SF) is used to fabricate lamellar scaffolds to provide native tissue-like anisotropic architecture and is found to be nonimmunogenic and biocompatible allowing cardiomyocyte attachment and growth in vitro. Further, the scaffolds display excellent mechanical properties by their ability to undergo cyclic compressions without any deformation when places in the DMM. Gradient compression strains (5% to 20%), mimicking the native physiological and pathological conditions, are applied to the cardiomyocyte culture seeded on lamellar silk scaffolds in the DMM. A strain-dependent difference in cardiomyocyte maturation, gene expression, sarcomere elongation, and extracellular matrix formation is observed. These silk-based CTs matured in the DMM can open up several avenues toward the development of host-specific grafts and in vitro models for drug screening.

Synthetic recovery of impulse propagation in myocardial infarction via silicon carbide semiconductive nanowires

Myocardial infarction causes 7.3 million deaths worldwide, mostly for fibrillation that electrically originates from the damaged areas of the left ventricle. Conventional cardiac bypass graft and percutaneous coronary interventions allow reperfusion of the downstream tissue but do not counteract the bioelectrical alteration originated from the infarct area. Genetic, cellular, and tissue engineering therapies are promising avenues but require days/months for permitting proper functional tissue regeneration. Here we engineered biocompatible silicon carbide semiconductive nanowires that synthetically couple, via membrane nanobridge formations, isolated beating cardiomyocytes over distance, restoring physiological cell-cell conductance, thereby permitting the synchronization of bioelectrical activity in otherwise uncoupled cells. Local in-situ multiple injections of nanowires in the left ventricular infarcted regions allow rapid reinstatement of impulse propagation across damaged areas and recover electrogram parameters and conduction velocity. Here we propose this nanomedical intervention as a strategy for reducing ventricular arrhythmia after acute myocardial infarction.

Single-Cell RNA sequencing reveals immune cell dynamics and local intercellular communication in acute murine cardiac allograft rejection.

Rationale: Transplant rejection is a major impediment to long-term allograft survival, in which the actions of immune cells are of fundamental importance. However, the immune cell dynamics and local intercellular communication of acute cardiac allograft rejection are not completely clear.Methods: Here we performed single-cell RNA sequencing on CD45+ immune cells isolated from cardiac grafts and spleens in a model of murine heterotopic heart transplantation. Moreover, we applied unsupervised clustering, functional enrichment analysis, cell trajectory construction and intercellular communication analysis to explore the immune cell dynamics and local intercellular communication of acute cardiac allograft rejection at single-cell level. The effect of CXCR3 antagonist and neutralizing antibody against its ligand on allograft rejection and T cell function was evaluated in murine heart transplantation model.Results: We presented the immune cell landscape of acute murine cardiac allograft rejection at single-cell resolution, and uncovered the functional characteristics and differentiation trajectory of several alloreactive cell subpopulations, including Mki67hi CTLs, Ccl5hi CTLs, activated Tregs and alloreactive B cells. We demonstrated local intercellular communication and revealed the upregulation of CXCR3 and its ligands in cardiac allografts. Finally, CXCR3 blockade significantly suppressed acute cardiac allograft rejection and inhibited the alloreactive T cell function.Conclusions: These results provide a new insight into the immune cell dynamics and local intercellular communication of acute cardiac allograft rejection, and suggest CXCR3 pathway may serve as a potential therapeutic target for transplant rejection.

The Effect of Donor-Recipient Race and Ethnicity Match on Liver Transplantation Outcome in The United States

Introduction: Recipient race/ethnicity (R/E) affect liver transplantation (LT) outcomes. However, the effect of donor R/E or donor-recipient R/E match is not well studied. We aimed to describe the impact of different donor and recipient R/E match on post-LT survival in the United States. Methods: We performed a retrospective study using the Scientific Registry of Transplant Recipient (SRTR) database. Donors and recipients are categorized into five R/E groups: Asian, Black, Latino, non-Latino White, and Others. We used Kaplan-Meier and Cox Proportional Hazards models for statistical analyses, adjusted for donor and recipient covariates. Results: 85,427 LT recipients between 2002 and 2019 were included in this study. Compared to non-Latino white donors or recipients, Asian and Black recipients had the lowest and highest risk of post LT mortality, respectively. Additionally, multivariate-adjusted models demonstrated that receiving Asian donor liver is associated with worse survival in all recipients besides Asians. Furthermore, the mortality risk for Black recipients normalized only when receiving livers from Black donors. However, this advantage of exact R/E matching is not distinctly evident in other R/E groups. Lastly, the effect size of donor and recipient R/E on post-LT survival is comparable to, if not higher than, many other known risk factors such as BMI, receiving cardiac death donor grafts, etc., suggesting unknown sources of variance. Conclusion: Donor and recipient R/E has significant associations with post-LT overall survival. Further studies must identify the uncharacterized social determinants of health and biologic factors with particular attention to addressing systemic racism within practice of LT.

Ex Vivo Delivery of Viral Vectors by Organ Perfusion for Cardiac Transplantation Gene Therapy.

Recent advances in ex vivo perfusion have enabled an extended preservation time for solid organs prior to transplantation allowing for possible resuscitation of the donor organ during the preservation period. Opportunities to provide viral vector-mediated gene therapy to the entire cardiac graft during this extended preservation period may lead to improvements in cardiac transplantation outcomes. Here we describe how to achieve successful gene delivery using viral vectors to an entire cardiac graft by normothermic, ex vivo perfusion. This protocol has been confirmed with the most highly utilized viral vector types in gene therapy clinical studies (adenoviral [Ad] and adeno-associated viral vector [AAV]).