Racial Differences in Donor-Derived Cell-Free DNA and Mitochondrial DNA After Heart Transplantation, on Behalf of the GRAfT Investigators

BACKGROUND

Black heart transplant patients are at higher risk of acute rejection (AR) and death than White patients. We hypothesized that this risk may be associated with higher levels of donor-derived cell-free DNA (dd-cfDNA) and cell-free mitochondrial DNA.

METHODS

The Genomic Research Alliance for Transplantation is a multicenter, prospective, longitudinal cohort study. Sequencing was used to quantitate dd-cfDNA and polymerase chain reaction to quantitate cell-free mitochondrial DNA in plasma. AR was defined as ≥2R cellular rejection or ≥1 antibody-mediated rejection. The primary composite outcome was AR, graft dysfunction (left ventricular ejection fraction <50% and decrease by ≥10%), or death.

RESULTS

We included 148 patients (65 Black patients and 83 White patients), median age was 56 years and 30% female sex. The incidence of AR was higher in Black patients compared with White patients (43% versus 19%; P=0.002). Antibody-mediated rejection occurred predominantly in Black patients with a prevalence of 20% versus 2% (P<0.001). After transplant, Black patients had higher levels of dd-cfDNA, 0.09% (interquartile range, 0.001-0.30) compared with White patients, 0.05% (interquartile range, 0.001-0.23; P=0.003). Beyond 6 months, Black patients showed a persistent rise in dd-cfDNA with higher levels compared with White patients. Cell-free mitochondrial DNA was higher in Black patients (185 788 copies/mL; interquartile range, 101 252-422 133) compared with White patients (133 841 copies/mL; interquartile range, 75 346-337 990; P<0.001). The primary composite outcome occurred in 43% and 55% of Black patients at 1 and 2 years, compared with 23% and 27% in White patients, P<0.001. In a multivariable model, Black patient race (hazard ratio, 2.61 [95% CI, 1.35-5.04]; P=0.004) and %dd-cfDNA (hazard ratio, 1.15 [95% CI, 1.03-1.28]; P=0.010) were associated with the primary composite outcome.

CONCLUSIONS

Elevated dd-cfDNA and cell-free mitochondrial DNA after heart transplant may mechanistically be implicated in the higher incidence of AR and worse clinical outcomes in Black transplant recipients.

REGISTRATION

URL: https://www.clinicaltrials.gov; Unique identifier: NCT02423070.

Clinical features and allograft failure rates of pulmonary antibody-mediated rejection categories

BACKGROUND

Pulmonary antibody-mediated rejection (AMR) consensus criteria categorize AMR by diagnostic certainty. This study aims to define the clinical features and associated outcomes of these recently defined AMR categories.

METHODS

Adjudication committees reviewed clinical data of 335 lung transplant recipients to define clinical or subclinical AMR based on the presence of allograft dysfunction, and the primary endpoints, time from transplant to allograft failure, a composite endpoint of chronic lung allograft dysfunction and/or death. Clinical AMR was subcategorized based on diagnostic certainty as definite, probable or possible AMR if 4, 3, or 2 characteristic features were present, respectively. Allograft injury was assessed via plasma donor-derived cell-free DNA (ddcfDNA). Risk of allograft failure and allograft injury was compared for AMR categories using regression models.

RESULTS

Over the 38.5 months follow-up, 28.7% of subjects developed clinical AMR (n = 96), 18.5% developed subclinical AMR (n = 62) or 58.3% were no AMR (n = 177). Clinical AMR showed higher risk of allograft failure and ddcfDNA levels compared to subclinical or no AMR. Clinical AMR included definite/probable (n = 21) or possible AMR (n = 75). These subcategories showed similar clinical characteristics, ddcfDNA levels, and risk of allograft failure. However, definite/probable AMR showed greater measures of AMR severity, including degree of allograft dysfunction and risk of death compared to possible AMR.

CONCLUSIONS

Clinical AMR showed greater risk of allograft failure than subclinical AMR or no AMR. Subcategorization of clinical AMR based on diagnostic certainty correlated with AMR severity and risk of death, but not with the risk of allograft failure.

Circulating microRNAs in cellular and antibody-mediated heart transplant rejection

BACKGROUND

Noninvasive monitoring of heart allograft health is important to improve clinical outcomes. MicroRNAs (miRs) are promising biomarkers of cardiovascular disease and limited studies suggest they can be used to noninvasively diagnose acute heart transplant rejection.

METHODS

The Genomic Research Alliance for Transplantation (GRAfT) is a multicenter prospective cohort study that phenotyped heart transplant patients from 5 mid-Atlantic centers. Patients who had no history of rejection after transplant were compared to patients with acute cellular rejection (ACR) or antibody-mediated rejection (AMR). Small RNA sequencing was performed on plasma samples collected at the time of an endomyocardial biopsy. Differential miR expression was performed with adjustment for clinical covariates. Regression was used to develop miR panels with high diagnostic accuracy for ACR and AMR. These panels were then validated in independent samples from GRAfT and Stanford University. Receiver operating characteristic curves were generated and area under the curve (AUC) statistics calculated. Distinct ACR and AMR clinical scores were developed to translate miR expression data for clinical use.

RESULTS

The GRAfT cohort had a median age of 52 years, with 35% females and 45% Black patients. Between GRAfT and Stanford, we included 157 heart transplant patients: 108 controls and 49 with rejection (50 ACR and 38 AMR episodes). After differential miR expression and regression analysis, we identified 12 miRs that accurately discriminate ACR and 17 miRs in AMR. Independent validation of the miR panels within GRAfT led to an ACR AUC 0.92 (95% confidence interval [CI]: 0.86-0.98) and AMR AUC 0.82 (95% CI: 0.74-0.90). The externally validated ACR AUC was 0.72 (95% CI: 0.59-0.82). We developed distinct ACR and AMR miR clinical scores (range 0-100), a score ≥ 65, identified ACR with 86% sensitivity, 76% specificity, and 98% negative predictive value, for AMR score performance was 82%, 84% and 97%, respectively.

CONCLUSIONS

We identified novel miRs that had excellent performance to noninvasively diagnose acute rejection after heart transplantation. Once rigorously validated, the unique clinical ACR and AMR scores usher in an era whereby genomic biomarkers can be used to screen and diagnose the subtype of rejection. These novel biomarkers may potentially alleviate the need for an endomyocardial biopsy while facilitating the initiation of targeted therapy based on the noninvasive diagnosis of ACR or AMR.

Cardiac endocardial left atrial substrate and lesion depth mapping using near-infrared spectroscopy

Atrial fibrillation (AF) is a rapid irregular electrical activity in the upper chamber and the most common sustained cardiac arrhythmia. Many patients require radiofrequency ablation (RFA) therapy to restore sinus rhythm. Pulmonary vein isolation requires distinguishing normal atrial wall from the pulmonary vein tissue, and atrial substrate ablation requires differentiating scar tissue, fibrosis, and adipose tissue. However, current anatomical mapping methods for strategically locating ablation sites by identifying structural substrates in real-time are limited. An intraoperative tool that accurately provides detailed structural information and classifies endocardial substrates could help improve RF guidance during RF ablation therapy. In this work, we propose a 7F NIRS integrated ablation catheter and demonstrate endocardial mapping on ex vivo swine (n = 12) and human (n = 5) left atrium (LA). First, pulmonary vein (PV) sleeve, fibrosis and ablation lesions were identified with NIRS-derived contrast indices. Based on these key spectral features, classification algorithms identified endocardial substrates with high accuracy (<11% error). Then, a predictive model for lesion depth was evaluated on classified lesions. Model predictions correlated well with histological measurements of lesion dimensions (R = 0.984). Classified endocardial substrates and lesion depth were represented in 2D spatial maps. These results suggest NIRS integrated mapping catheters can serve as a complementary tool to the current electroanatomical mapping system to improve treatment efficacy.

A molecular single-cell lung atlas of lethal COVID-19

Respiratory failure is the leading cause of death in patients with severe SARS-CoV-2 infection^1,2, but the host response at the lung tissue level is poorly understood. Here we performed single-nucleus RNA sequencing of about 116,000 nuclei from the lungs of nineteen individuals who died of COVID-19 and underwent rapid autopsy and seven control individuals. Integrated analyses identified substantial alterations in cellular composition, transcriptional cell states, and cell-to-cell interactions, thereby providing insight into the biology of lethal COVID-19. The lungs from individuals with COVID-19 were highly inflamed, with dense infiltration of aberrantly activated monocyte-derived macrophages and alveolar macrophages, but had impaired T cell responses. Monocyte/macrophage-derived interleukin-1β and epithelial cell-derived interleukin-6 were unique features of SARS-CoV-2 infection compared to other viral and bacterial causes of pneumonia. Alveolar type 2 cells adopted an inflammation-associated transient progenitor cell state and failed to undergo full transition into alveolar type 1 cells, resulting in impaired lung regeneration. Furthermore, we identified expansion of recently described CTHRC1⁺ pathological fibroblasts³ contributing to rapidly ensuing pulmonary fibrosis in COVID-19. Inference of protein activity and ligand-receptor interactions identified putative drug targets to disrupt deleterious circuits. This atlas enables the dissection of lethal COVID-19, may inform our understanding of long-term complications of COVID-19 survivors, and provides an important resource for therapeutic development.

Tale of a Black Heart!

Alkaptonuria is a rare condition of inborn error of metabolism. Association with aortic stenosis has been described; however, diagnosis at the time of valve replacement is infrequent. Recognition of this condition has potential management implications as the durability of prosthetic valves in such cases is unknown. We describe a case report which depicts these unique aspects.

Donor-derived cell-free DNA accurately detects acute rejection in lung transplant patients, a multicenter cohort study

BACKGROUND

Acute rejection, which includes antibody-mediated rejection and acute cellular rejection, is a risk factor for lung allograft loss. Lung transplant patients often undergo surveillance transbronchial biopsies to detect and treat acute rejection before irreversible chronic rejection develops. Limitations of this approach include its invasiveness and high interobserver variability. We tested the performance of percent donor-derived cell-free DNA (%ddcfDNA), a non-invasive blood test, to detect acute rejection.

METHODS

This multicenter cohort study monitored 148 lung transplant subjects over a median of 19.6 months. We collected serial plasma samples contemporaneously with TBBx to measure %ddcfDNA. Clinical data was collected to adjudicate for acute rejection. The primary analysis consisted of computing the area-under-the-receiver-operating-characteristic-curve of %ddcfDNA to detect acute rejection. Secondary analysis determined %ddcfDNA rule-out thresholds for acute rejection.

RESULTS

ddcfDNA levels were high after transplant surgery and decayed logarithmically. With acute rejection, ddcfDNA levels rose six-fold higher than controls. ddcfDNA levels also correlated with severity of lung function decline and histological grading of rejection. %ddcfDNA area-under-the-receiver-operating-characteristic-curve for acute rejection, AMR, and ACR were 0.89, 0.93, and 0.83, respectively. ddcfDNA levels of <0.5% and <1.0% showed a negative predictive value of 96% and 90% for acute rejection, respectively. Histopathology detected one-third of episodes with ddcfDNA levels ≥1.0%, even though >90% of these events were coincident to clinical complications missed by histopathology.

CONCLUSIONS

This study demonstrates that %ddcfDNA reliably detects acute rejection and other clinical complications potentially missed by histopathology, lending support to its use as a non-invasive marker of allograft injury.

T cell repertoire analysis suggests a prominent bystander response in human cardiac allograft vasculopathy

T cells are implicated in the pathogenesis of cardiac allograft vasculopathy (CAV), yet their clonality, specificity, and function are incompletely defined. Here we used T cell receptor β chain (TCRB) sequencing to study the T cell repertoire in the coronary artery, endomyocardium, and peripheral blood at the time of retransplant in four cases of CAV and compared it to the immunoglobulin heavy chain variable region (IGHV) repertoire from the same samples. High-dimensional flow cytometry coupled with single-cell PCR was also used to define the T cell phenotype. Extensive overlap was observed between intragraft and blood TCRBs in all cases, a finding supported by robust quantitative diversity metrics. In contrast, blood and graft IGHV repertoires from the same samples showed minimal overlap. Coronary infiltrates included CD4⁺ and CD8⁺ memory T cells expressing inflammatory (IFNγ, TNFα) and profibrotic (TGFβ) cytokines. These were distinguishable from the peripheral blood based on memory, activation, and tissue residency markers (CD45RO, CTLA-4, and CD69). Importantly, high-frequency rearrangements were traced back to endomyocardial biopsies (2-6 years prior). Comparison with four HLA-mismatched blood donors revealed a repertoire of shared TCRBs, including a subset of recently described cross-reactive sequences. These findings provide supportive evidence for an active local intragraft bystander T cell response in late-stage CAV.

Cell-Free DNA to Detect Heart Allograft Acute Rejection

BACKGROUND

After heart transplantation, endomyocardial biopsy (EMBx) is used to monitor for acute rejection (AR). Unfortunately, EMBx is invasive, and its conventional histological interpretation has limitations. This is a validation study to assess the performance of a sensitive blood biomarker-percent donor-derived cell-free DNA (%ddcfDNA)-for detection of AR in cardiac transplant recipients.

METHODS

This multicenter, prospective cohort study recruited heart transplant subjects and collected plasma samples contemporaneously with EMBx for %ddcfDNA measurement by shotgun sequencing. Histopathology data were collected to define AR, its 2 phenotypes (acute cellular rejection [ACR] and antibody-mediated rejection [AMR]), and controls without rejection. The primary analysis was to compare %ddcfDNA levels (median and interquartile range [IQR]) for AR, AMR, and ACR with controls and to determine %ddcfDNA test characteristics using receiver-operator characteristics analysis.

RESULTS

The study included 171 subjects with median posttransplant follow-up of 17.7 months (IQR, 12.1-23.6), with 1392 EMBx, and 1834 %ddcfDNA measures available for analysis. Median %ddcfDNA levels decayed after surgery to 0.13% (IQR, 0.03%-0.21%) by 28 days. Also, %ddcfDNA increased again with AR compared with control values (0.38% [IQR, 0.31-0.83%], versus 0.03% [IQR, 0.01-0.14%]; P<0.001). The rise was detected 0.5 and 3.2 months before histopathologic diagnosis of ACR and AMR. The area under the receiver operator characteristic curve for AR was 0.92. A 0.25%ddcfDNA threshold had a negative predictive value for AR of 99% and would have safely eliminated 81% of EMBx. In addition, %ddcfDNA showed distinctive characteristics comparing AMR with ACR, including 5-fold higher levels (AMR ≥2, 1.68% [IQR, 0.49-2.79%] versus ACR grade ≥2R, 0.34% [IQR, 0.28-0.72%]), higher area under the receiver operator characteristic curve (0.95 versus 0.85), higher guanosine-cytosine content, and higher percentage of short ddcfDNA fragments.

CONCLUSIONS

We found that %ddcfDNA detected AR with a high area under the receiver operator characteristic curve and negative predictive value. Monitoring with ddcfDNA demonstrated excellent performance characteristics for both ACR and AMR and led to earlier detection than the EMBx-based monitoring. This study supports the use of %ddcfDNA to monitor for AR in patients with heart transplant and paves the way for a clinical utility study. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT02423070.

A Rare Case of Cardiac Mesenchymal Hamartoma and Comprehensive Review of the Literature With Emphasis on Histopathology

Hamartomas are primary, benign neoplastic lesions that most commonly derive from a single variably differentiated cell lineage. Here, we report an unusual case of a cardiac hamartoma. A 62-year-old woman presented with chest pain and palpitations. Serial imaging revealed a large slowly growing and highly vascularized left ventricular mass, which required surgical resection. Microscopically, the lesion was composed of nodular fibrovascular proliferation with haphazardly embedded muscle bundles and peripheral calcifications. Immunohistochemical studies revealed prominent muscle-specific actin positive and smooth muscle actin positive muscle fiber bundles within a disorganized fibrovascular stroma. This characterization is most consistent with cardiac mesenchymal hamartoma. Relevant differential diagnoses for this lesion include hamartoma of mature cardiac myocytes (HMCMs) and intramuscular hemangioma. The prominent smooth muscle differentiation of muscle bundles was incompatible with defining features of HMCM. Absence of S100-positive nerve and mature adipose cells distinguished this lesion from the recently defined, heterogeneous cardiac mesenchymal hamartoma. Forty-seven cases of cardiac hamartoma reported from 1970 to 2020 were reviewed to provide histopathologic context.

The XVth Banff Conference on Allograft Pathology the Banff Workshop Heart Report: Improving the diagnostic yield from endomyocardial biopsies and Quilty effect revisited

The XVth Banff Conference on Allograft Pathology meeting was held on September 23-27, 2019, in Pittsburgh, Pennsylvania, USA. During this meeting, two main topics in cardiac transplant pathology were addressed: (a) Improvement of endomyocardial biopsy (EMB) accuracy for the diagnosis of rejection and other significant injury patterns, and (b) the orphaned lesion known as Quilty effect or nodular endocardial infiltrates. Molecular technologies have evolved in recent years, deciphering pathophysiology of cardiac rejection. Diagnostically, it is time to integrate the histopathology of EMBs and molecular data. The goal is to incorporate molecular pathology, performed on the same paraffin block as a companion test for histopathology, to yield more accurate and objective EMB interpretation. Application of digital image analysis from hematoxylin and eosin (H&E) stain to multiplex labeling is another means of extracting additional information from EMBs. New concepts have emerged exploring the multifaceted significance of myocardial injury, minimal rejection patterns supported by molecular profiles, and lesions of arteriolitis/vasculitis in the setting of T cell-mediated rejection (TCMR) and antibody-mediated rejection (AMR). The orphaned lesion known as Quilty effect or nodular endocardial infiltrates. A state-of-the-art session with historical aspects and current dilemmas was reviewed, and possible pathogenesis proposed, based on advances in immunology to explain conflicting data. The Quilty effect will be the subject of a multicenter project to explore whether it functions as a tertiary lymphoid organ.

Generation and persistence of human tissue-resident memory T cells in lung transplantation

Tissue-resident memory T cells (T_RM) maintain immunity in diverse sites as determined in mouse models, whereas their establishment and role in human tissues have been difficult to assess. Here, we investigated human lung T_RM generation, maintenance, and function in airway samples obtained longitudinally from human leukocyte antigen (HLA)-disparate lung transplant recipients, where donor and recipient T cells could be localized and tracked over time. Donor T cells persist specifically in the lungs (and not blood) of transplant recipients and express high levels of T_RM signature markers including CD69, CD103, and CD49a, whereas lung-infiltrating recipient T cells gradually acquire T_RM phenotypes over months in vivo. Single-cell transcriptome profiling of airway T cells reveals that donor T cells comprise two T_RM-like subsets with varying levels of expression of T_RM-associated genes, whereas recipient T cells comprised non-T_RM and similar T_RM-like subpopulations, suggesting de novo T_RM generation. Transplant recipients exhibiting higher frequencies of persisting donor T_RM experienced fewer adverse clinical events such as primary graft dysfunction and acute cellular rejection compared with recipients with low donor T_RM persistence, suggesting that monitoring T_RM dynamics could be clinically informative. Together, our results provide spatial and temporal insights into how human T_RM develop, function, persist, and affect tissue integrity within the complexities of lung transplantation.

88. Public Health Service (PHS) Increased-Risk Factors in Organ Donors: A Review of the OPTN Ad hoc Disease Transmission Advisory Committee (DTAC)

Background

In the United States, all deceased donors (DD) are evaluated for behavioral risk factors for human immunodeficiency virus (HIV), hepatitis B (HBV), and hepatitis C (HCV) infection during the past 12 months. DD with behavioral risk factors or hemodilution are designated as PHS increased risk donors (IRD). Since 2013, the number of IRD has increased from 13.4% of DD to 27% in 2018. Despite a low residual risk of disease transmission after a negative nucleic acid test for HIV/HBV/HCV, the considerable underutilization of IRD has driven an interest in revising the PHS IRD 2013 guidelines. The objective of this study was to describe the epidemiology of IRD with the goal of guiding policy change and maximize organ use.

Methods

This is a retrospective cohort study of DD during 2018. Characteristics of IRD were compared with non-IRD. A random 10% sample of IRD was selected for manual review of text narratives and donor questionnaires submitted by organ procurement organizations to determine specific PHS IRD factors. Categorical variables were compared using the χ ² test and continuous variables were compared using a 2-sample t-test for independent samples.

Results

Among 10,721 DD in 2018, 2,904 were designated IRD (27.1%) with regional variability noted (Figure). Compared with non-IRD, IRD were younger (median age 35 vs. 45 years, P < 0.001) and more often died from drug intoxication (33.2 vs. 5.6%, P < 0.001). Hemodilution was found in 6.8% of all IRD and was the only factor for IRD designation in 60% of pediatric donors <12 years old. The random sample of IRD (N = 288) was similar to IRD population for age, gender, ethnicity, cause of death, and region of recovery (table). Descriptive analysis of the random sample showed that intravenous drug use was the most common behavioral risk factor (N = 124, 43.1%), followed by incarceration (N = 108, 37.5%). Most DD met only 1 criterion (N = 179, 62%); 21% met 2 criteria; and 17% had >3 criteria.

Conclusion

This study represents the most detailed description of PHS IRD factors since the adoption of the new guidelines in 2013. Understanding the prevalence of factors that lead to IRD designation will help inform future policy development, optimize safe DD use, and increase the number of transplants.

Disclosures

All Authors: No reported Disclosures.

Real-time optical spectroscopic monitoring of nonirrigated lesion progression within atrial and ventricular tissues

Despite considerable advances in guidance of radiofrequency ablation (RFA) therapy for the treatment of cardiac arrhythmias, success rates have been hampered by a lack of tools for precise intraoperative evaluation of lesion extent. Near-infrared spectroscopic (NIRS) techniques are sensitive to tissue structural and biomolecular properties, characteristics that are directly altered by radiofrequency (RF) treatment. In this work, a combined NIRS-RFA catheter is developed for real-time monitoring of tissue reflectance during RF energy delivery. An algorithm is proposed for processing NIR spectra to approximate nonirrigated lesion depth in both atrial and ventricular tissues. The probe optical geometry was designed to bias measurement influence toward absorption enabling enhanced sensitivity to changes in tissue composition. A set of parameters termed "lesion optical indices" are defined encapsulating spectral differences between ablated and unablated tissue. Utilizing these features, a model for real-time tissue spectra classification and lesion size estimation is presented. Experimental validation conducted within freshly excised porcine cardiac specimens showed strong concordance between algorithm estimates and post-hoc tissue assessment.

Donor-derived cell-free DNA predicts allograft failure and mortality after lung transplantation

Background

Allograft failure is common in lung-transplant recipients and leads to poor outcomes including early death. No reliable clinical tools exist to identify patients at high risk for allograft failure. This study tested the use of donor-derived cell-free DNA (%ddcfDNA) as a sensitive marker of early graft injury to predict impending allograft failure.

Methods

This multicenter, prospective cohort study enrolled 106 subjects who underwent lung transplantation and monitored them after transplantation for the development of allograft failure (defined as severe chronic lung allograft dysfunction [CLAD], retransplantation, and/or death from respiratory failure). Plasma samples were collected serially in the first three months following transplantation and assayed for %ddcfDNA by shotgun sequencing. We computed the average levels of ddcfDNA over three months for each patient (avddDNA) and determined its relationship to allograft failure using Cox-regression analysis.

Findings

avddDNA was highly variable among subjects: median values were 3·6%, 1·6% and 0·7% for the upper, middle, and low tertiles, respectively (range 0·1%–9·9%). Compared to subjects in the low and middle tertiles, those with avddDNA in the upper tertile had a 6·6-fold higher risk of developing allograft failure (95% confidence interval 1·6–19·9, p = 0·007), lower peak FEV1 values, and more frequent %ddcfDNA elevations that were not clinically detectable.

Interpretation

Lung transplant patients with early unresolving allograft injury measured via %ddcfDNA are at risk of subsequent allograft injury, which is often clinically silent, and progresses to allograft failure.

Fund

National Institutes of Health.

Histological Changes in the Rat Femoral Artery Following the Use of the Empty-and-Refill Test

BACKGROUND

 This study examines the effects of the empty-and-refill patency test on rat femoral arteries in the longer postoperative time period.

METHODS

 A simple arterial anastomosis was performed bilaterally on 20 rats. The empty-and-refill test was performed unilaterally in all rats, leaving the contralateral artery as an internal control. Rats were divided into two cohorts of 10 rats and survived for 48 hours and 2 weeks. Vessel patency was assessed prior to closing and immediately prior to sacrifice. The femoral arteries were harvested bilaterally and hematoxylin and eosin stains were performed. The femoral artery distal to the anastomosis in the region of the empty-and-refill test was histologically evaluated.

RESULTS

 All vessels were patent at the time of sacrifice. There was no statistical difference in the numeric scoring between the experimental and control vessels in the 48-hour cohort. Almost all vessels harvested at 48 hours showed endothelial cell loss distal to the anastomosis regardless of whether they underwent the empty-and-refill test. The only statistically significant difference in the 2-week cohort was an increase in adventitial smooth muscle proliferation in the experimental group. There were no other statistically significant results between the experimental and control groups at 2 weeks. An overall comparison of both cohorts revealed a statistically significant increase in endothelial cell number and intimal proliferation by 2 weeks postsurgery.

CONCLUSION

 The empty-and-refill test does not compromise rat femoral artery anastomotic patency, nor does it produce histological damage either 48 hours or 2 weeks postsurgery.

Applying rigor and reproducibility standards to assay donor-derived cell-free DNA as a non-invasive method for detection of acute rejection and graft injury after heart transplantation

BACKGROUND

Use of new genomic techniques in clinical settings requires that such methods are rigorous and reproducible. Previous studies have shown that quantitation of donor-derived cell-free DNA (%ddcfDNA) by unbiased shotgun sequencing is a sensitive, non-invasive marker of acute rejection after heart transplantation. The primary goal of this study was to assess the reproducibility of %ddcfDNA measurements across technical replicates, manual vs automated platforms, and rejection phenotypes in distinct patient cohorts.

METHODS

After developing and validating the %ddcfDNA assay, we subjected the method to a rigorous test of its reproducibility. We measured %ddcfDNA in technical replicates performed by 2 independent laboratories and verified the reproducibility of %ddcfDNA patterns of 2 rejection phenotypes: acute cellular rejection and antibody-mediated rejection in distinct patient cohorts.

RESULTS

We observed strong concordance of technical-replicate %ddcfDNA measurements across 2 independent laboratories (slope = 1.02, R² > 0.99, p < 10^-6), as well as across manual and automated platforms (slope = 0.80, R² = 0.92, p < 0.001). The %ddcfDNA measurements in distinct heart transplant cohorts had similar baselines and error rates. The %ddcfDNA temporal patterns associated with rejection phenotypes were similar in both patient cohorts; however, the quantity of ddcfDNA was significantly higher in samples with severe vs mild histologic rejection grade (2.73% vs 0.14%, respectively; p < 0.001).

CONCLUSIONS

The %ddcfDNA assay is precise and reproducible across laboratories and in samples from 2 distinct types of heart transplant rejection. These findings pave the way for larger studies to assess the clinical utility of %ddcfDNA as a marker of acute rejection after heart transplantation.

Immunocytochemical localization of lysozyme and alpha-1-antichymotrypsin in the term human placenta: an attempt to characterize the Hofbauer cell

The intracellular localization of lysozyme (LSZ) and alpha-1-antichymotrypsin (A1Ac), glycoproteins associated with macrophages, was used to confirm the monocytic lineage of the Hofbauer cell and to assess the maturity of its macrophage function. The peroxidase-labeled antigen method was used to localize these proteins, as well as immunoglobulins, light chains, and albumin, in Bouin-fixed, paraffin-embedded sections of 24 normal term placentas. The demonstration of the latter substances was used as an indication of passive diffusion or phagocytosis of serum proteins resulting in intracellular localization unrelated to synthesis. In all the placentas examined a strong cytoplasmic reaction for A1Ac was seen in the Hofbauer cells. The same cells on adjacent sections did not stain for LSZ, while the occasional maternal macrophage and numerous polymorphonuclear leukocytes in the intervillous spaces gave a positive reaction. The detection of A1Ac supports the contention that these cells are macrophages, previously suggested by their phagocytic capability and the demonstration of Fc receptors and nonspecific esterases. Since they do not appear to contain LSZ, a bactericidal enzyme, we propose that these cells are not fully differentiated macrophages, and the lack of this enzyme may have some relevance to the pathogenesis of certain placental infections.

Clozapine-associated cardiac dysfunction during a gastroenteritis outbreak

We report that two young adult patients who were initiated with clozapine for severe psychosis during a hospital-wide gastroenteritis outbreak went into severe shock. Neither patient had troponin elevation. Each required left ventricular assist device support for myocarditis. Endomyocardial biopsy revealed lymphocytic myocarditis in one patient and eosinophilic myocarditis in the other. The former patient expired. Polymerase chain reaction testing was negative for Coxsackie virus. These two patients illustrate that myocarditis can occur at usual incipient doses and that there may be an epidemiologic risk associated with gastroenteritis. Although the white blood cell (WBC) count is expected to decrease with clozapine, these patients had persistently elevated WBC counts. In conclusion, physicians should exercise caution when prescribing clozapine, especially for those with diarrhea.

The 2013 International Society for Heart and Lung Transplantation Working Formulation for the standardization of nomenclature in the pathologic diagnosis of antibody-mediated rejection in heart transplantation

During the last 25 years, antibody-mediated rejection of the cardiac allograft has evolved from a relatively obscure concept to a recognized clinical complication in the management of heart transplant patients. Herein we report the consensus findings from a series of meetings held between 2010-2012 to develop a Working Formulation for the pathologic diagnosis, grading, and reporting of cardiac antibody-mediated rejection. The diagnostic criteria for its morphologic and immunopathologic components are enumerated, illustrated, and described in detail. Numerous challenges and unresolved clinical, immunologic, and pathologic questions remain to which a Working Formulation may facilitate answers.

Cardiac transplantation in patients with hypertrophic cardiomyopathy

Cardiac transplantation is a treatment option for patients with hypertrophic cardiomyopathy (HC) who developed refractory heart failure and/or intractable arrhythmia. However, the pretransplant characteristics and post-transplant prognosis for patients with nondilated idiopathic HC has not yet fully elucidated. Therefore, we retrospectively reviewed 813 consecutive transplant recipients undergoing cardiac transplantation at Columbia University Medical Center from 1999 to 2010 and compared the clinical course of 41 patients with idiopathic HC with that of 373 patients with ischemic heart disease and 398 patients with other heart disease. The patients with HC were younger than those with ischemic heart disease (47.8 ± 14.0 vs 57.1 ± 9.4 years; p <0.0001). The proportion of patients undergoing ventricular assist devise surgery for bridge-to-transplant was lower in patients with HC than in those with ischemic heart disease or other heart disease (14.6% vs 31.1% vs 35.7%, all p <0.01). The post-transplant survival of those with HC was better than that for those with ischemic heart disease (90.1% vs 85.8% and 83.9% vs 67.1% at 1 and 5 years, respectively; p = 0.0359), although it was not significantly different from those with other heart disease. Proportional hazards analysis revealed that the subjects with HC had reduced post-transplant mortality (hazard ratio 0.4760, 95% confidential interval 0.1889 to 0.9762; p = 0.042) on univariate, but not multivariate, analysis. Most patients with HC had nondilated left ventricles (left ventricular end-diastolic dimension ≤ 55 mm; n = 27), and post-transplant survival did not differ from that for those with dilated left ventricles (left ventricular end-diastolic dimension >55 mm; n = 14). In conclusion, the post-transplant survival of those with HC did not differ from those of the subjects who underwent transplant for other non-HC indications.