Cardiac Rejection Research Articles

Preclinical rationale and current pathways to support the first human clinical trials in cardiac xenotransplantation

Recent initiation of the first FDA-approved cardiac xenotransplantation suggests xenotransplantation could soon become a therapeutic option for patients unable to undergo allotransplantation. Until xenotransplantation is widely applied in clinical practice, consideration of benefit versus risk and approaches to management of clinical xenografts will based at least in part on observations made in experimental xenotransplantation in non-human primates. Indeed, the decision to proceed with clinical trials reflects significant progress in last few years in experimental solid organ and cellular xenotransplantation. Our laboratory at the NIH and now at University of Maryland contributed to this progress, with heterotopic cardiac xenografts surviving more than two years and life-supporting cardiac xenografts survival up to 9 months. Here we describe our contributions to the understanding of the mechanism of cardiac xenograft rejection and development of methods to overcome past hurdles, and finally we share our opinion on the remaining barriers to clinical translation. We also discuss how the first in human xenotransplants might be performed, recipients managed, and graft function monitored.

The Combination of Rhodosin and MMF Prolongs Cardiac Allograft Survival by Inhibiting DC Maturation by Promoting Mitochondrial Fusion.

Despite being the gold-standard treatment for end-stage heart disease, heart transplantation is associated with acute cardiac rejection within 1 year of transplantation. The continuous application of immunosuppressants may cause side effects such as hepatic and renal toxicity, infection, and malignancy. Developing new pharmaceutical strategies to alleviate acute rejection after heart transplantation effectively and safely is of critical importance. In this study, we performed a murine model of MHC-full mismatch cardiac transplantation and showed that the combination of Rhodosin (Rho) and mycophenolate mofetil (MMF) could prevent acute rejection and oxidative stress injury and prolong the survival time of murine heart transplants. The use of Rho plus MMF in allografts improved the balance of Tregs/Teff cells, which had a protective effect on allotransplantation. We also isolated bone marrow-derived dendritic cells (BMDCs) and determined that Rho inhibited DC maturation by promoting mitochondrial fusion mainly through the mitochondrial fusion-related protein MFN1. Herein, we demonstrated that Rho, an active ingredient isolated from the plant Rhodiola rosea with antioxidant and anti-inflammatory activities, could efficiently alleviate acute rejection and significantly prolong murine heart allograft survival when used with a low dose of MMF. More importantly, we found that Rho restrained DC maturation by promoting mitochondrial fusion and decreasing reactive oxygen species (ROS) levels, which then alleviated acute rejection in murine cardiac transplantation. Interestingly, as a novel immunosuppressant, Rho has almost no side effects compared with other traditional immunosuppressants. Taken together, these results suggest that Rho has good clinical auxiliary applications as an effective immunosuppressant and antioxidant, and this study provides an efficient strategy to overcome the side effects of immunosuppressive agents that are currently used in organ transplantation.

Toll-like receptors and damage-associated molecular patterns in the pathogenesis of heart transplant rejection.

Significant strides have been made in our understanding of the immune system and its role in cardiac transplant rejection. Despite the growing knowledge of immune responses, the mortality rate following cardiac transplantation remains grim. Related to procedural and pathological complications, toll-like receptor (TLR) and damage-associated molecular pattern (DAMP) signaling is the most direct and earliest interface between tissue integration and the innate immune response. This in turn can activate an adaptive immune response that further damages myocardial tissue. Furthermore, relevant literature on the status of DAMPs in the context of heart-transplantation remains limited, warranting further attention in clinical and translational research. This review aims to critically appraise the perspectives, advances, and challenges on DAMP-mediated innate immune response in the immune-mediated rejection of cardiac transplantation. Detailed analysis of the influence of TLR and DAMP signaling in mounting the immune response against the transplanted heart holds promise for improving outcomes through early detection and prevention of varied forms of organ rejection.

Contemporary review of heart transplant immunology and immunosuppressive therapy

Background Survival after heart transplantation (HT) has improved considerably since the first HT was performed in 1967 in Cape Town, South Africa. Understanding immunology behind organ rejection has paved way for advances in the assessment of pre-transplant compatibility, development of newer and more specific immunosuppressive drugs, and management of rejection. Objectives Unlike medical therapy for heart failure, transplant protocols vary considerably between different centers. These variations in protocols generally reflect unique population characteristics and the availability of resources. This review article aims to provide a consolidated update on contemporary cardiac transplant medicine. We also aim to highlight local practice and its difference from our international counterparts. Methods A literature search was performed on Pubmed and Cochrane Central Register of Controlled Trials to identify trials and review articles that discussed heart transplant immunology and protocols. The International Society for Heart and Lung Transplant (ISHLT) guidelines were also reviewed. We focused on risk factors, prevention strategies, and treatment of cardiac rejection. Results A total of 48 articles were selected to provide a comprehensive overview of the contemporary practice of cardiac transplant immunosuppressive therapy. Comparisons were made with local data and practice protocols to highlight key differences. Conclusion Heart transplant covers a small subset of cardiac patients and much of the evidence is derived from empirical observations and retrospective analysis. This accounts for the heterogeneity in care and treatment protocols. More studies are needed to select best practices from around the world to further improve outcomes.

Exosomes: Potential executors of IL‐35 gene‐modified adipose‐derived mesenchymal stem cells in inhibiting acute rejection after heart transplantation

Heart transplantation has become the only 'cure' for end-stage heart diseases, but acute allograft rejection is the major obstacle to the survival of patients. Our previous studies showed that IL-35 gene-modified adipose-derived mesenchymal stem cells (IL-35-ASCs) can effectively inhibit graft rejection and prolong the survival of transplanted hearts in mice. This study further explored the mechanism of IL-35-ASCs, especially focusing on the important role of IL-35-ASC-derived exosomes (IL-35-ASCexos) in inhibiting acute rejection. IL-35-ASCs were constructed in vitro and pretreated with IL-35 neutralizing antibody and GW4869 (an inhibitor of neutral sphingomyelinase that impairs exosome biogenesis/release). Then, pretreated IL-35-ASCs and CD4+ T cells were cocultured in Transwell plates, and changes in regulatory T cells (Tregs) and cytokines were detected. Then, IL-35-ASCexos were extracted, identified and analysed, and their immunoregulatory effects on CD4+ T cells were studied through coculture experiments. Finally, IL-35-ASCexos were applied to a mouse heart transplantation model to investigate the therapeutic effects on acute rejection of the allograft. The coculture experiment showed that the IL-35-neutralizing antibody could not completely block the immunosuppressive function of IL-35-ASCs, while GW4869 could effectively reduce their immunoregulatory characteristics. Similar to IL-35-ASCs, IL-35-ASCexos also have powerful immunosuppressive properties, effectively upregulating the Treg ratio in vivo and in vitro and prolonging graft survival. As the main effectors of IL-35-ASCs, these findings highlight the therapeutic potential of IL-35-ASCexos in inhibiting acute cardiac rejection of the allograft. Although the specific mechanism remains unclear and needs to be further explored, IL-35-ASCexos therapy is expected to become a new method to inhibit acute graft rejection.

The usefulness of electrocardiogram in the recognition of cardiac transplant rejection

The usefulness of electrocardiogram in the recognition of cardiac transplant rejection

Cardiac microstructural alterations in immune-inflammatory myocardial disease: a retrospective case-control study

BackgroundImmune-inflammatory myocardial disease contributes to multiple chronic cardiac processes, but access to non-invasive screening is limited. We have previously developed a method of echocardiographic texture analysis, called the high-spectrum signal intensity coefficient (HS-SIC) which assesses myocardial microstructure and previously associated with myocardial fibrosis. We aimed to determine whether this echocardiographic texture analysis of cardiac microstructure can identify inflammatory cardiac disease in the clinical setting.MethodsWe conducted a retrospective case-control study of 318 patients with distinct clinical myocardial pathologies and 20 healthy controls. Populations included myocarditis, atypical chest pain/palpitations, STEMI, severe aortic stenosis, acute COVID infection, amyloidosis, and cardiac transplantation with acute rejection, without current rejection but with prior rejection, and with no history of rejection. We assessed the HS-SIC’s ability to differentiate between a broader diversity of clinical groups and healthy controls. We used Kruskal-Wallis tests to compare HS-SIC values measured in each of the clinical populations with those in the healthy control group and compared HS-SIC values between the subgroups of cardiac transplantation rejection status.ResultsFor the total sample of N = 338, the mean age was 49.6 ± 20.9 years and 50% were women. The mean ± standard error of the mean of HS-SIC were: 0.668 ± 0.074 for controls, 0.552 ± 0.049 for atypical chest pain/palpitations, 0.425 ± 0.058 for myocarditis, 0.881 ± 0.129 for STEMI, 1.116 ± 0.196 for severe aortic stenosis, 0.904 ± 0.116 for acute COVID, and 0.698 ± 0.103 for amyloidosis. Among cardiac transplant recipients, HS-SIC values were 0.478 ± 0.999 for active rejection, 0.594 ± 0.091 for prior rejection, and 1.191 ± 0.442 for never rejection. We observed significant differences in HS-SIC between controls and myocarditis (P = 0.0014), active rejection (P = 0.0076), and atypical chest pain or palpitations (P = 0.0014); as well as between transplant patients with active rejection and those without current or prior rejection (P = 0.031).ConclusionsAn echocardiographic method can be used to characterize tissue signatures of microstructural changes across a spectrum of cardiac disease including immune-inflammatory conditions.

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.

An Intervention Trial for Strengthening Medical Adherence after Heart Transplantation.

In heart transplant recipients, nonadherence is associated with higher risk of morbidity and mortality. Can a psychoeducational intervention enhance adherence to medical recommendations? We randomized 200 patients awaiting heart transplantation on the high urgency wait list to a manualized psychoeducational intervention or standard care. Follow-up continued to three years after transplantation. Primary endpoint was adherence to immunosuppressive medication, assessed at 3, 6, 12, 24, and 36 months posttransplant. Secondary endpoints were barriers to adherence during follow-up and clinical outcomes, including cardiac rejection within the first postoperative year and postoperative 3-year mortality. Fifty patients died before or within the first 3 months of transplantation. The primary endpoint was analyzed in 66 patients in the intervention group and 66 in the control group. Both study groups showed almost maximal adherence to immunosuppressive medication throughout follow-up, with no significant time x treatment interaction (P>0.99). Likewise, there was no significant time x treatment interaction (P=0.41) on barriers to adherence. The percentage of patients with International Society for Heart and Lung Transplantation standard grade 1 and 2 rejection was in the intervention and control groups 82.5% and 78.7%, respectively, and 8.8% and 13.1%, respectively, without significant differences between study groups (P=0.75). Considering all randomized and transplanted patients in the intervention group (N=85) and control group (N=87), postoperative 3-year mortality was 29.4% and 27.6%, respectively (P=0.82). Adherence to immunosuppressive medication was high, even without a complex, manualized psychoeducational intervention. The intervention had no significant positive impact on cardiac rejection and mortality.

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.

Electron Microscopy Reveals Evidence of Perinuclear Clustering of Mitochondria in Cardiac Biopsy-Proven Allograft Rejection.

Acute cellular rejection is a major complication in heart transplantation. We focus on the analysis of new ultrastructural findings in cardiac biopsy rejection based on mitochondrial intracellular organization. This study includes heart transplanted patients from a single center who were referred for endomyocardial biopsies as a scheduled routine screening. Participants were divided into two groups: patients transplanted without allograft rejection (Grade 0R), and patients with biopsy-proven allograft rejection (Grade ≥ 2R). Using electronic microscopy, we detected a significant increase in the volume density of mitochondria (p < 0.0001) and dense bodies (p < 0.01) in the rejection group. The most relevant finding was the presence of local accumulations of mitochondria close to the nuclear envelope, pressing and molding the morphology of this membrane in all rejection samples (100%). We identified this perinuclear clustering of mitochondria phenomenon in a 68 ± 27% of the total cardiac nucleus observed from rejection samples. We did not observe this phenomenon in any non-rejection samples, reflecting excellent sensitivity and specificity. We have identified a specific phenomenon affecting the architecture of the nuclear membrane—perinuclear clustering of mitochondria—in endomyocardial biopsies from patients with cardiac rejection. This ultrastructural approach might complement and improve the diagnosis of rejection.

The role of the electrocardiogram in the recognition of cardiac transplant rejection: A systematic review and meta-analysis.

BackgroundIn cardiac transplant recipients, the electrocardiogram (ECG) is a noninvasive measure of early allograft rejection. The ECG can predict an acute cellular rejection, thus shortening the time to recognition of rejection. Earlier diagnosis has the potential to reduce the number and severity of rejection episodes.MethodologyA systematic literature review was conducted to identify and select the original research reports on using electrocardiography in diagnosing cardiac transplant rejection in accordance with the PRISMA guidelines. Studies included reported sensitivity and specificity of ECG readings in heart transplant recipients during the first post‐transplant year. Data were analyzed with Review manager version 5.4. p‐value was used in testing the significant difference.ResultsAfter the removal of duplicates, 98 articles were eligible for screening. After the full‐text screening, a total of 17 papers were included in the review based on the above criteria. A meta‐analysis of five studies was done.ConclusionIn heart transplant recipients, a noninvasive measure of early allograft rejection has the potential to reduce the number and severity of rejection episodes by reducing the time and cost of surveillance of rejection and shortening the time to recognition of rejection.

Cytosporone B (Csn-B), an NR4A1 agonist, attenuates acute cardiac allograft rejection by inducing differential apoptosis of CD4+T cells

CD4+T cell-mediated acute rejection remains a major factor that affects the early survival of transplanted organs post-transplantation. Here, we reveal that nuclear receptor subfamily 4 Group A member 1 (Nr4A1) was upregulated during cardiac allograft rejection and that the increased Nr4A1 was primarily localized in intragraft-infiltrating CD4+T cells. Nr4A1 acts as a transcription factor with an important role in CD4+T cell apoptosis, differentiation and T cell dysfunction, which indicates that Nr4A1 may play a critical role in transplant rejection. Cytosporone B (Csn-B) is a naturally occurring agonist of Nr4A1, and the role of Csn-B in the physiological process of cardiac rejection is poorly defined. This study constructed an acute rejection model of abdominal heterotopic cardiac transplantation in mice and investigated whether Csn-B could attenuate acute transplant rejection by modulating the CD4+T lymphocyte response. The results showed that Csn-B prolonged murine cardiac allograft survival and reduced inflammation in allografts. Subsequently, it was confirmed that Csn-B functions by inducing non-Treg apoptosis and promoting Treg cell differentiation. Finally, we also confirmed that Csn-B attenuates acute rejection by directly targeting Nr4A1 in CD4+T cells. Our data suggest that Csn-B is a promising novel therapeutic approach for acute cardiac allograft rejection.

Late Cardiac Antibody-Mediated Rejection: A Only Heart Duel.

Late Cardiac Antibody-Mediated Rejection: A Only Heart Duel.

Correlation Between Microvascular Inflammation in Endomyocardial Biopsies and Rejection Transcripts, Donor-specific Antibodies, and Graft Dysfunction in Antibody-mediated Rejection.

The pathology-based diagnosis of cardiac antibody-mediated rejection (AMR) relies on the 2013 International Society for Heart and Lung Transplantation Working Formulation, in which microvascular inflammation (MVI) is considered as present or absent regardless of its extent. This work assessed the biological and clinical value of a semiquantitative evaluation of the extent of MVI in endomyocardial biopsies (EMBs). We retrospectively graded the extent of MVI in 291 EMB from 291 patients according to a 4-point scale in which MVI scores of 0, 1, 2, and 3 represented 0%, 1%-10%, 11%-50%, and >50% of the myocardial area, respectively. We analyzed the association between the MVI score and tissue rejection molecular activity assessed by microarrays or reverse transcriptase multiplex ligation-dependent probe amplification, current pathology classification (pathologic AMR [pAMR]), anti-HLA donor-specific antibodies, and graft dysfunction. Overall, 172 (59.1%), 33 (11.4%), 42 (14.4%), and 44 (15.1%) EMB were given MVI scores of 0, 1, 2, and 3, respectively. pAMR1(H+) and pAMR2/3 categories were found to be heterogeneous in terms of MVI score. Acute cellular rejection grades did not influence the MVI score. In both molecular approaches, we observed a stepwise increase in the expression of AMR-related transcripts with increasing MVI scores, independent of the C4d or CD68 status (P < 0.001). Both the frequency and mean fluorescence intensity of donor-specific antibodies gradually increased with the MVI score (P < 0.001). Acute graft dysfunction was more frequent in MVI score 3 (P < 0.001). The intensity of MVI in EMB, based on a semiquantitative evaluation of its extent, has biological and clinical importance.

Abstract 13830: Prediction of Cardiac Rejection Trajectories via Machine Learning Derived Features From Digital Endomyocardial Biopsy Images

Introduction: Cellular rejection occurs in 20-40% of transplant recipients with an increased risk of graft failure. Previously, we developed a model for predicting ISHLT rejection grades via the automated extraction of morphologic features in Endomyocardial biopsy (EMB) images. Considering the frequent discordance between conventional rejection grade and clinical rejection severity, in this work, we sought to identify morphologic features that predict the clinical trajectory of rejection events. Methods: Our study comprised 299 EMBs with grade and trajectory labels. Trajectory labels are based on the development of overt clinical signs of allograft injury as “clinically evident” or “clinically silent”. Morphologic features describing number, spatial arrangement of lymphocytes, and shape, orientation of interstitial fibers were computationally extracted. To identify the top features associated with clinically evident disease, the T-test method was applied across 500 iterations of 3-fold cross validation. In each iteration, a quadratic discriminant analysis model was trained with top 10 features on 2 folds of dataset using trajectory labels (M trj ) and was validated on one hold out test set. This model was trained using grade labels (M grd ) to predict “high” (2R + 3R) or “low” (0R + 1R). To assess feature importance, in each model, the frequency of every feature appearing in the classifier was measured through iterations. Results: The mean area under the receiver operating curve of M trj and M grd was 0.80±0.04 and 0.84±0.02 correspondingly. The top features for predicting grades differ substantially from those for predicting clinical trajectory (Figure 1). Conclusions: The additional features required to predict clinical trajectory vs. rejection grade may explain the discordance between conventional histology and rejection syndrome observed in clinical practice, and highlights the translational potential of computer-assisted histologic analysis of EMBs.

Cyclophilin D Regulates the Nuclear Translocation of AIF, Cardiac Endothelial Cell Necroptosis and Murine Cardiac Transplant Injury.

Ischemia-reperfusion injury (IRI) is an inevitable consequence of organ transplant procedure and associated with acute and chronic organ rejection in transplantation. IRI leads to various forms of programmed cell death, which worsens tissue damage and accelerates transplant rejection. We recently demonstrated that necroptosis participates in murine cardiac microvascular endothelial cell (MVEC) death and murine cardiac transplant rejection. However, MVEC death under a more complex IRI model has not been studied. In this study, we found that simulating IRI conditions in vitro by hypoxia, reoxygenation and treatment with inflammatory cytokines induced necroptosis in MVECs. Interestingly, the apoptosis-inducing factor (AIF) translocated to the nucleus during MVEC necroptosis, which is regulated by the mitochondrial permeability molecule cyclophilin D (CypD). Furthermore, CypD deficiency in donor cardiac grafts inhibited AIF translocation and mitigated graft IRI and rejection (n = 7; p = 0.002). Our studies indicate that CypD and AIF play significant roles in MVEC necroptosis and cardiac transplant rejection following IRI. Targeting CypD and its downstream AIF may be a plausible approach to inhibit IRI-caused cardiac damage and improve transplant survival.

Cardiac allograft vasculopathy and acute rejection surveillance in the same procedure through a single vascular access. High volume center experience

Abstract Introduction Cardiac Allograft Vasculopathy (CAV) and Acute Rejection (AR) surveillance after a Heart Transplant (HT) is based on the performance of Coronary Angiography (CAG) that requires arterial access and Endomyocardial Biopsy, normally Ventricular Right (RV-EMB), which requires venous access. Depending on the clinical indication, HT patients are referred to the cath lab to perform both procedures in the same day. We evaluated the effectiveness and safety of performing a Left Ventricular Endomyocardial Biopsy (LV-EMB) and a CAG with a single artery access. Methods We retrospectively analyzed HT patients referred to cath lab for surveillance of AR and CAV on the same day between January 2018 and March 2021. We compared the procedures performed with two accesses (Group 1; CAG + RV-EMB) versus procedures made with a single artery access (Group 2; CAG + LV-EMB). Results 121 Procedures were performed within the indicated period, 96 (79.3%) belong to the double access group and 25 (20.7%) to the single access group. All procedures were successful and without major complications. There were only 2 cases of insufficient sample, one for each group. Baseline characteristics in both groups and AR or CAV presence were similar (table). Total procedure time (52.00±15.30 vs 33.36±18.69min) and fluoroscopic time (10.70±4.89 vs 6.84±1.82 min) were significantly shorter in the single access group (p&amp;lt;0.001 in both). The most used arterial access in group 2 was the right radial artery (15; 60%) followed by the right femoral artery (5; 20%). Conclusions Performing an endomyocardial biopsy and coronary angiography through a single arterial access is as effective and safe as with double access, arterial and additional venous. Procedure time and fluoroscopic time is significantly less when it is performed through the same access. Funding Acknowledgement Type of funding sources: None.

Toll-like receptor 3 is an endogenous sensor of cell death and a potential target for induction of long-term cardiac transplant survival

Inflammation posttransplant is directly linked to cell death programs including apoptosis and necrosis. Cell death leads to the release of cellular contents which can promote inflammation. Targeting of these pathways should be an effective strategy to prevent transplant rejection. Toll-like receptor 3 (TLR3) is emerging as a major endogenous sensor of inflammation. In this study, we assessed the role of TLR3 on cell death and transplant rejection. We showed that TLR3 is highly expressed on mouse microvascular endothelial cell (ECs) and the endothelium of cardiac grafts. We demonstrated that TLR3 interacting with dsRNA or self-RNA triggered apoptosis and necroptosis in ECs. Interestingly, TLR3-induced necroptosis led mitochondrial damage. Inhibition of the mitochondrial membrane permeability molecule Cyclophilin D prevented necroptosis in ECs. In vivo, endothelium damage and activities of caspase-3 and mixed lineage kinase domain-like protein were inhibited in TLR3-/- cardiac grafts compared with C57BL/6 grafts posttransplant (n=5, p<.001). Importantly, TLR3-/- cardiac grafts had prolonged survival in allogeneic BALB/c mice (mean survival=121±67 vs. 31±6days of C57BL/6 grafts, n=7, p=.002). In summary, our study suggests that TLR3 is an important cell death inducer in ECs and cardiac grafts and thus a potential therapeutic target in preventing cardiac transplant rejection.

Diagnostic Accuracy of Cardiovascular Magnetic Resonance for Cardiac Transplant Rejection: A Meta-Analysis

ObjectivesThe aim of this meta-analysis was to assess the diagnostic performance of various CMR imaging parameters for evaluating acute cardiac transplant rejection. BackgroundEndomyocardial biopsy is the current gold standard for detection of acute cardiac transplant rejection. Cardiac magnetic resonance (CMR) is uniquely capable of myocardial tissue characterization and may be useful as a noninvasive alternative for the diagnosis of graft rejection. MethodsPubMed and Web of Science were searched for relevant publications reporting on the use of CMR myocardial tissue characterization for detection of acute cardiac transplant rejection with endomyocardial biopsy as the reference standard. Pooled sensitivity, specificity, and hierarchical modeling–based summary receiver-operating characteristic curves were calculated. ResultsOf 478 papers, 10 studies comprising 564 patients were included. The sensitivity and specificity for the detection of acute cardiac transplant rejection were 84.6 (95% CI: 65.6-94.0) and 70.1 (95% CI: 54.2-82.2) for T1, 86.5 (95% CI: 72.1-94.1) and 85.9 (95% CI: 65.2-94.6) for T2, 91.3 (95% CI: 63.9-98.4) and 67.6 (95% CI: 56.1-77.4) for extracellular volume fraction (ECV), and 50.1 (95% CI: 31.2-68.9) and 60.2 (95% CI: 36.7-79.7) for late gadolinium enhancement (LGE). The areas under the hierarchical modeling–based summary receiver-operating characteristic curve were 0.84 (95% CI: 0.81-0.87) for T1, 0.92 (95% CI: 0.89-94) for T2, 0.78 (95% CI: 0.74-0.81) for ECV, and 0.56 (95% CI: 0.51-0.60) for LGE. T2 values demonstrated the highest diagnostic accuracy, followed by native T1, ECV, and LGE (all P values <0.001 for T1, ECV, and LGE vs T2). ConclusionsT2 mapping demonstrated higher diagnostic accuracy than other CMR techniques. Native T1 and ECV provide high diagnostic use but lower diagnostic accuracy compared with T2, which was related primarily to lower specificity. LGE showed poor diagnostic performance for detection of rejection.