T-cell and monocyte subsets, inflammatory molecules, rejection, and hemodynamics early after cardiac transplantation

The evolution of patient-specific precision biomarkers to guide personalized heart-transplant care

Introduction

In parallel to the clinical maturation of heart transplantation over the last 50 years, rejection testing has been revolutionized within the systems biology paradigm triggered by the Human Genome Project.

Areas Covered

We have co-developed the first FDA-cleared diagnostic and prognostic leukocyte gene expression profiling biomarker test in transplantation medicine that gained international evidence-based medicine guideline acceptance to rule out moderate/severe acute cellular cardiac allograft rejection without invasive endomyocardial biopsies. This work prompted molecular re-classification of intragraft biology, culminating in the identification of a pattern of intragraft myocyte injury, in addition to acute cellular rejection and antibody-mediated rejection. This insight stimulated research into non-invasive detection of myocardial allograft injury. The addition of a donor-organ specific myocardial injury marker based on donor-derived cell-free DNA further strengthens the non-invasive monitoring concept, combining the clinical use of two complementary non-invasive blood-based measures, host immune activity-related risk of acute rejection as well as cardiac allograft injury.

Expert Opinion

This novel complementary non-invasive heart transplant monitoring strategy based on leukocyte gene expression profiling and donor-derived cell-free DNA that incorporates longitudinal variability measures provides an exciting novel algorithm of heart transplant allograft monitoring. This algorithm's clinical utility will need to be tested in an appropriately designed randomized clinical trial which is in preparation.

Immunomonitoring of Tacrolimus in Healthy Volunteers: The First Step from PK- to PD-Based Therapeutic Drug Monitoring?

Therapeutic drug monitoring is routinely performed to maintain optimal tacrolimus concentrations in kidney transplant recipients. Nonetheless, toxicity and rejection still occur within an acceptable concentration-range. To have a better understanding of the relationship between tacrolimus dose, tacrolimus concentration, and its effect on the target cell, we developed functional immune tests for the quantification of the tacrolimus effect. Twelve healthy volunteers received a single dose of tacrolimus, after which intracellular and whole blood tacrolimus concentrations were measured and were related to T cell functionality. A significant correlation was found between tacrolimus concentrations in T cells and whole blood concentrations (r = 0.71, p = 0.009), while no correlation was found between tacrolimus concentrations in peripheral blood mononuclear cells (PBMCs) and whole blood (r = 0.35, p = 0.27). Phytohemagglutinin (PHA) induced the production of IL-2 and IFNγ, as well as the inhibition of CD71 and CD154 expression on T cells at 1.5 h post-dose, when maximum tacrolimus levels were observed. Moreover, the in vitro tacrolimus effect of the mentioned markers corresponded with the ex vivo effect after dosing. In conclusion, our results showed that intracellular tacrolimus concentrations mimic whole blood concentrations, and that PHA-induced cytokine production (IL-2 and IFNγ) and activation marker expression (CD71 and CD154) are suitable readout measures to measure the immunosuppressive effect of tacrolimus on the T cell.

The AlloMap™ genomic biomarker story: 10 years after

Over the last >20 years, we have co-developed the rationale for the first diagnostic and prognostic leukocyte gene expression profiling (GEP) biomarker test in transplantation medicine that gained US-FDA-regulatory clearance and international evidence-based medicine guideline acceptance to rule out moderate/severe acute cellular cardiac allograft rejection without invasive endomyocardial biopsies (EMB). Based on this test, a non-invasive clinical algorithm was implemented since 2005. After clinical implementation, this GEP-based monitoring in direct comparison with an EMB-based strategy was non-inferior with respect to detection of clinical rejection, defined as new onset allograft dysfunction with/without histology of ACR, re-transplantation or death, and at the same time improved patient satisfaction. Subsequently, we demonstrated the test's capacity when used as serial monitoring tool to predict these clinical rejection events. In this Personal Viewpoint article, I will discuss the various decision-making branching points that were made in the AlloMap biomarker test development to inform future genomic biomarker test development projects.

T-Cell Surface Antigens and sCD30 as Biomarkers of the Risk of Rejection in Solid Organ Transplantation

T-cell activation is a characteristic of organ rejection. T cells, located in the draining lymph nodes of the transplant recipient, are faced with non-self-molecules presented by antigen presenting cells and become activated. Activated T cells are characterized by up-regulated surface antigens, such as costimulatory molecules, adhesion molecules, chemokine receptors, and major histocompatibility complex class II molecules. Surface antigen expression can be followed by flow cytometry using monoclonal antibodies in either cell function assays using donor-specific or nonspecific stimulation of isolated cells or whole blood and without stimulation on circulating lymphocytes. Molecules such as CD30 can be proteolytically cleaved off the surface of activated cells in vivo, and the determination of the soluble protein (sCD30) in serum or plasma is performed by immunoassays. As promising biomarkers for rejection and long-term transplant outcome, CD28 (costimulatory receptor for CD80 and CD86), CD154 (CD40 ligand), and sCD30 (tumor necrosis factor receptor superfamily, member 8) have been identified. Whereas cell function assays are time-consuming laboratory-developed tests which are difficult to standardize, commercial assays are frequently available for soluble proteins. Therefore, more data from clinical trials have been published for sCD30 compared with the surface antigens on activated T cells. This short review summarizes the association between selected surface antigens and immunosuppression, and rejection in solid organ transplantation.

Lymphocyte surface molecules as immune activation biomarkers

Immunosuppression is mandatory after solid organ transplantation between HLA mismatched individuals. It is a lifelong therapy that needs to be closely monitored to avoid under- and over-immunosuppression. For many drugs, pharmacokinetic monitoring has been proven to be beneficial. However, the therapeutic ranges are statistically derived surrogate markers for the effects that cannot predict the individual response of single patients. Better tailored immunosuppression biomarkers are needed that indicate immune activation. T cells are critically involved in organ rejection, and the means to assess their activation state may be promising to individualize immunosuppressive therapies. Activated T cells can be monitored with flow cytometry based on surface molecules that are typically up regulated or with molecules that are cleaved off the cell surface. Among these molecules are the interleukin-2 receptor (CD25); transferrin receptor (CD71); the T cell co-stimulatory molecules CD28, CD69, and CD154 and sCD30, which is a member of the TNF-alpha family. The effect of immunosuppressive drugs on T cell activation can be recorded with indirect cell function assays or by directly monitoring activated T cells in whole blood. Soluble proteins can be measured with immunoassays. This review provides a summary of the experimental and clinical studies investigating the potential of surface molecules as a tool for immune monitoring. It critically discusses the obstacles and shortcomings from an analytical and diagnostic perspective that are currently preventing their use in multicenter trials and clinical routine monitoring of transplant patients.

Evaluation of an immunological score to assess the risk of severe infection in heart recipients

BACKGROUND

We previously reported how specific humoral and cellular immunological markers that are readily available in clinical practice can be used to identify heart transplant recipients (HTR) at risk of developing severe infections. In this study, we perform an extended analysis to identify immunological profiles that could prove to be superior to individual markers in assessing the risk of infection early after heart transplantation.

METHODS

In a prospective follow-up study, we evaluated 100 HTR at 1 week after transplantation. Laboratory tests included determination of immunoglobulin (Ig) levels (IgG, IgA, IgM), complement factors (C3 and C4), and lymphocyte subsets (CD3+, CD4+, CD8+ T cells, B cells, and natural killer [NK] cells). The prevalence of infection during the first 3 months was registered at scheduled visits after transplantation. Severe infections were defined as all infections requiring hospitalization and intravenous antimicrobial therapy.

RESULTS

During follow-up, 33 patients (33%) developed severe infections. The individual risk factors of severe infection, according to the Cox regression analysis, were as follows: IgG <600 mg/dL (hazard ratio [HR], 2.41; 95% confidence interval [CI], 1.21-4.78; P = 0.012), C3 <80 mg/dL (HR, 4.65; 95% CI, 2.31-9.38; P < 0.0001), C4 <18 mg/dL (HR 2.30, 95% CI, 1.15-4.59; P = 0.018), NK count <30 cells/μL (HR 4.07, 95% CI, 1.76-9.38; P = 0.001), and CD4 count <350 cells/μL (HR, 3.04; 95% CI, 1.47-6.28; P = 0.0027). An immunological score was created. HRs were used to determine the number of points assigned to each of the 5 previously mentioned individual risk factors. The score was obtained from the sum of these factors. In the multivariate Cox regression analysis, the immunological score was useful for identifying patients at risk of infection and was the only variable that maintained a significant association with the development of infection, after adjustment for the 5 individual factors.

CONCLUSION

Patients with an immunological score ≥13 were at the highest risk of severe infections (HR, 9.29; 95% CI, 4.57-18.90; P < 0.0001). This score remained significantly associated with the risk of severe infection after adjustment for clinical risk factors of infection. An immunological score was useful for identifying HTR at risk of developing severe infections. If this score is validated in multicenter studies, it could be easily introduced into clinical practice.

Surface markers of lymphocyte activation and markers of cell proliferation

The individualization of immunosuppression is an approach for preventing rejection in the early phase after transplantation and for avoiding the long-term side effects of over immunosuppression. Pharmacodynamic markers, either specific or nonspecific, have been proposed as complementary tools to drug monitoring of immunosuppressive drugs. A key event in graft rejection is the activation and proliferation of the recipient's lymphocytes, particularly T cells. Activated T cells express surface receptors, such as CD25 (the IL-2 receptor) and CD71 (the transferrin receptor), or co-stimulatory molecules (CD26, CD27, CD28, CD30, CD154 or CD40L, and CD134). Both surface marker expression and cell proliferation are predominately assessed by flow cytometry. Protocols have been established and utilized for both in vitro and ex vivo investigations with either isolated lymphocytes or whole blood. This article reviews the current body of research regarding the use of lymphocyte proliferation and surface activation markers with an emphasis on T cells. Experimental and clinical results related to these markers, as well as methodological issues and open questions, are addressed.

Utility of left ventricular systolic torsion derived from 2-dimensional speckle-tracking echocardiography in monitoring acute cellular rejection in heart transplant recipients

BACKGROUND

Reduced left ventricular torsion (LV-tor) has been reported to be associated with acute rejection in heart transplant (HTx) recipients. We investigated the utility of LV-tor analysis derived from 2-dimensional speckle-tracking echocardiography (2D-STE) for detecting allograft rejection.

METHODS

A total of 301 endomyocardial biopsies (EMBs), right heart catheterizations and echocardiograms were performed in 32 HTx recipients. Echocardiography was done within 3 hours from EMB or simultaneously with the procedures. The LV-tor was defined as the difference between apical and basal end-systolic rotations. The LV-tor values with and without cellular rejection were compared. In addition, we investigated whether the change in LV-tor values predicts the change in rejection grade in each patient. The baseline LV-tor value in each patient was defined as a mean value of the first 3 LV-tor measurements obtained when the patient was free from rejection.

RESULTS

According to the conventional International Society for Heart and Lung Transplantation criteria, 274 biopsies showed a rejection Grade of 0, 1a or 1b (Group AR(-)), whereas 27 biopsies were Grade 2 or higher (Group AR(+)). LV-tor decreased more in Group AR(+) than in Group AR(-) (9.3 ± 0.7 vs 12.2 ± 0.2 degrees, p < 0.0001). In the LV-tor measurement for each patient, the 25% reduction in LV-tor value from baseline predicted Grade 2 or higher rejection with a predictive accuracy of 92.9%.

CONCLUSION

LV-tor derived from 2D-STE could be of clinical value for non-invasive monitoring of acute rejection in HTx recipients.

TNF receptors differentially signal and are differentially expressed and regulated in the human heart

Tumor necrosis factor (TNF) utilizes two receptors, TNFR1 and 2, to initiate target cell responses. We assessed expression of TNF, TNFRs and downstream kinases in cardiac allografts, and compared TNF responses in heart organ cultures from wild-type ((WT)C57BL/6), TNFR1-knockout ((KO)), TNFR2(KO), TNFR1/2(KO) mice. In nonrejecting human heart TNFR1 was strongly expressed coincidentally with inactive apoptosis signal-regulating kinase-1 (ASK1) in cardiomyocytes (CM) and vascular endothelial cells (VEC). TNFR2 was expressed only in VEC. Low levels of TNF localized to microvessels. Rejecting cardiac allografts showed increased TNF in microvessels, diminished TNFR1, activation of ASK1, upregulated TNFR2 co-expressed with activated endothelial/epithelial tyrosine kinase (Etk), increased apoptosis and cell cycle entry in CM. Neither TNFR was expressed significantly by cardiac fibroblasts. In (WT)C57BL/6 myocardium, TNF activated both ASK1 and Etk, and increased both apoptosis and cell cycle entry. TNF-treated TNFR1(KO) myocardium showed little ASK1 activation and apoptosis but increased Etk activation and cell cycle entry, while TNFR2(KO) myocardium showed little Etk activation and cell cycle entry but increased ASK1 activation and apoptosis. These observations demonstrate independent regulation and differential functions of TNFRs in myocardium, consistent with TNFR1-mediated cell death and TNFR2-mediated repair.

Relationship between a validated molecular cardiac transplant rejection classifier and routine organ function parameters

BACKGROUND

As acute cellular cardiac allograft rejection is a systemic process affecting the entire organism, we hypothesized that scores of a peripheral blood mononuclear cell gene expression profiling (GEP) test developed and validated to rule out International Society of Heart and Lung Transplantation (ISHLT) grade > or = 3A/2R acute cellular cardiac allograft rejection also reflects biologically plausible changes of the routinely assessed clinical parameters.

METHODS

We retrospectively analyzed 76 patients who underwent GEP testing, at the time of their routine clinical follow-up in our Institution between February 1, 2006 and January 31, 2007. Data were analyzed with t-test, nonparametric tests, bivariate Spearman's correlation, and multivariate linear regression modeling.

RESULTS

More activated GEP-score correlated with longer corrected QT (QTc)-interval (r = 0.377, p = 0.001, n = 63), longer QRS duration (r = 0.231, p = 0.03, n = 66), higher heart rate (r = 0.221, p = 0.037, n = 66), higher serum creatinine (r = 0.26, p = 0.01, n = 75), higher gamma-glutamyl transferase (GGT) GGT (r = 0.266, p = 0.037, n = 46), lower pulmonary artery oxygen saturation (r = -0.313, p = 0.003, n = 76), lower platelet count (r = -0.372, p = 0.001, n = 74), lower monocyte count (r = -0.208, p = 0.040, n = 72), and lower high-density lipoprotein (HDL) HDL level (r = -0.242, p = 0.041, n = 53). Multivariate analysis showed a significant amount of variance in the GEP score independently explained by the variability of QTc-interval (beta = 1.998, p = 0.001) and platelet count (beta = -1.540, p = 0.017). Post hoc analysis of the 11 individual GEP-classifier genes showed WDRA40 (p = 0.02) and ras homolog gene family, member U (RHOU) RHOU (p = 0.01) independently related to mixed venous O(2)Sat%.

CONCLUSION

A GEP test developed and validated to detect the absence of cardiac rejection correlates with electrocardiographic and hemodynamic cardiac parameters as well as renal, hepatic, bone marrow, and lipid metabolism parameters suggesting a complex relationship between rejection, leukocytes, and organ function within the continuum between alloimmunological quiescence and rejection.

Elevated levels of serum interleukin-6 are associated with low grade cellular rejection in patients with heart transplantation

Endomyocardial biopsy is the gold-standard procedure to diagnose acute cellular rejection after heart transplantation. This study assessed whether the blood levels of cytokines involved in inflammation and immune activation are useful to detect the presence of acute cellular rejection.

METHODS

Blood specimens collected before 275 endomyocardial biopsies in 66 patients were assayed for levels of TNFalpha, IL6, IL1beta, and IL2 receptor. The biopsies were grouped according to the presence (n = 41) or absence (n = 234) of acute cellular rejection grade > or = 3A of the International Society for Heart and Lung Transplantation. We compared the levels of cytokines in the two groups.

RESULTS

Circulating IL6 levels were significantly higher when there was a low grade (0-2) cellular rejection in the biopsy versus the group of biopsies grade > or = 3A (19.8 +/- 27 versus 12.9 +/- 10 pg/mL; P = .001). An IL6 level higher than 30 pg/mL showed a negative predictive value of 95% for the presence of acute rejection grade > or = 3A.

CONCLUSION

In heart transplant patients, high levels of serum IL6 were associated with low grade cellular rejection. Determination of IL6 levels may be useful to reduce the number of endomyocardial biopsies during follow-up in these patients.

Noninvasive discrimination of rejection in cardiac allograft recipients using gene expression profiling

Rejection diagnosis by endomyocardial biopsy (EMB) is invasive, expensive and variable. We investigated gene expression profiling of peripheral blood mononuclear cells (PBMC) to discriminate ISHLT grade 0 rejection (quiescence) from moderate/severe rejection (ISHLT > or = 3A). Patients were followed prospectively with blood sampling at post-transplant visits. Biopsies were graded by ISHLT criteria locally and by three independent pathologists blinded to clinical data. Known alloimmune pathways and leukocyte microarrays identified 252 candidate genes for which real-time PCR assays were developed. An 11 gene real-time PCR test was derived from a training set (n = 145 samples, 107 patients) using linear discriminant analysis (LDA), converted into a score (0-40), and validated prospectively in an independent set (n = 63 samples, 63 patients). The test distinguished biopsy-defined moderate/severe rejection from quiescence (p = 0.0018) in the validation set, and had agreement of 84% (95% CI 66% C94%) with grade ISHLT > or = 3A rejection. Patients >1 year post-transplant with scores below 30 (approximately 68% of the study population) are very unlikely to have grade > or = 3A rejection (NPV = 99.6%). Gene expression testing can detect absence of moderate/severe rejection, thus avoiding biopsy in certain clinical settings. Additional clinical experience is needed to establish the role of molecular testing for clinical event prediction and immunosuppression management.

Functional status and quality of life in patients surviving 10 years after lung transplantation

Although many lung allograft recipients achieve long-term survival, there is a lack of published data regarding these patients' functional status and quality of life (QoL). We evaluated all 10-year survivors at our institution and, utilizing the SF-36 questionnaire, compared their QoL to population normative and chronic illness data. Twenty-eight (29%) of 96 patients survived > or =10 years following 11 single, 6 bilateral and 11 heart-lung procedures. At the most recent evaluation, median FEV(1) in single and double lung recipients was predicted to be 54% and 74%, respectively. Five (18%) patients had BOS score 0, 13 (46%) BOS 1, 5 (18%) BOS 2 and 5 (18%) BOS 3 and median time to BOS was 7 years. Four (14%) patients required renal replacement therapy. Three patients (11%) developed symptomatic osteoporosis, 2 (7%) post-transplant lymphoma and 1 (4%) an ischaemic stroke. Scores for physical function, role-physical/emotional and general health, but not mental health and bodily pain, were significantly lower compared to normative and chronic illness data. Energy and social-function scores were significantly lower than normative data alone. Long-term survival after lung transplantation is characterized by an absence or delayed development of BOS, low iatrogenic morbidity and preserved mental, but reduced physical health status.

HLA-specific antibodies are risk factors for lymphocytic bronchiolitis and chronic lung allograft dysfunction

Bronchiolitis obliterans syndrome (BOS) represents a major limitation in lung transplantation. While acute rejection is widely considered the most important risk factor for BOS, the impact of HLA-specific antibodies is less understood. Of 51 lung recipients who were prospectively tested during a 4.2 +/- 1.6-year period, 14 patients developed HLA-specific antibodies. A multi-factorial analysis was performed to correlate the prevalence of BOS with HLA antibodies, persistent-recurrent acute rejection (ACR-PR), lymphocytic bronchiolitis, and HLA-A, -B, and -DR mismatches. HLA-specific antibodies were associated with ACR-PR (10/14 vs. 11/37 with no antibodies, p < 0.05), lymphocytic bronchiolitis (8/14 vs. 10/37, p < 0.05), and BOS (10/14, vs. 9/37, p < 0.005). Other risk factors for BOS were: lymphocytic bronchiolitis (13/18 vs. 6/33 with no lymphocytic bronchiolitis, p < 0.0001), ACR-PR (12/21 vs. 7/30 with no ACR-PR, p < 0.05), and the number of HLA-DR mismatches (1.7 +/- 0.48 in BOS vs. 1.2 +/- 0.63 without BOS, p < 0.05). The presence of antibodies exhibited a cumulative effect on BOS when it was associated with either lymphocytic bronchiolitis or ACR-PR. The complex relationship between the development of HLA antibodies and acute and chronic lung allograft rejection determines the importance of post-transplant screening for HLA-specific antibodies as a prognostic element for lung allograft outcome.

Viral chemokine-binding proteins inhibit inflammatory responses and aortic allograft transplant vasculopathy in rat models

BACKGROUND

Both CC and CXC chemokines direct monocyte and T-cell migration and activation at sites of vascular injury, but the relative contributions of each chemokine class to transplant vasculopathy development have not been defined. The nonselective C, CC, and CXC chemokine binding protein, M-T7, inhibits vasculopathy development after angioplasty and after renal transplant. We have assessed the effects of three viral chemokine-binding proteins with differing ranges of chemokine inhibition on plaque growth in rats after aortic allograft transplant.

METHODS

One of two myxomaviral chemokine binding proteins, (1). M-T1, a selective CC chemokine inhibitor, or (2). M-T7, a nonselective chemokine-binding protein, was given immediately after transplant. A separate group was treated with the gamma68-herpesvirus protein, M3, a C, CC, CXC, and CX3C binding protein, with preferential CC binding.

RESULTS

Intimal hyperplasia was significantly reduced at late times posttransplant after infusion of each chemokine-binding protein (P <0.05). Early inhibition of macrophage and T-cell invasion was associated with a late decrease in vasculopathy development. Infusion of an inactive myxomavirus protein did not inhibit plaque growth. Combined high-dose M-T1 and M-T7 did not reduce plaque growth or early cell invasion to a greater extent than either protein alone. Coinfusion of the CC chemokines macrophage chemoattractant protein-1 and macrophage inflammatory protein-1alpha neutralized M-T1 and M-T7 inhibition of monocyte invasion, respectively, suggesting a key role for CC chemokine-mediated cellular influx.

CONCLUSION

Viral chemokine-modulating proteins effectively reduce aortic allograft vasculopathy, acting predominantly through inhibition of a CC chemokine-mediated response.

Surrogate markers for late cardiac allograft survival

While no definite well-validated surrogate marker for late cardiac allograft outcome is available, the early detection of cardiac allograft vasculopathy represents the 'key' candidate as an effective surrogate. Intravascular ultrasound detected intimal thickening has been noted to possess prognostic capability despite the presence of a normal coronary angiogram. Several prospective investigations have pointed to accurate thresholds of intimal thickening that are prognostically relevant and predict not only future angiographic disease but also hard allograft related endpoints including ischemic cardiac events, allograft failure, and death. Because of the resolution of intravascular ultrasound, this technique accords reproducibility and the ability to standardize the degree of intimal thickening over time. Other candidates that may serve as surrogates once appropriately evaluated include measures of allograft pump function, intragraft histology, and peripheral markers including but not limited to structural proteins (cardiac specific troponins), inflammatory markers (CRP), fibrogenic markers (TGF-beta, fibroblast growth factor), and immune markers (anti-HLA Ab and indirect alloantibodies).

Orthotopic heart transplantation: highlights and limitations

A little more than three decades after the successful introduction of cardiac transplantation, this revolutionary concept of advanced heart failure treatment has gained tremendous momentum and is considered the gold standard therapy in selected patients. More specific modalities of immunosuppression continue to decrease the impact of acute and chronic rejection and immunosuppression-related side effects. The success of cardiac transplantation has led to a widespread initiation of transplant programs and a run on cardiac transplantation waiting lists. The increasing gap between waiting lists and donor organ supply has stimulated research to identify those patients who benefit most from cardiac transplantation, as well as research to develop alternative therapies for advanced heart failure. Furthermore, it serves as a stimulus to address paradigmatic issues that are fundamental to modern medicine and society.

Brief hypoxia conditions monocytes to protect reperfused cardiocytes against cell death via the CD11b receptor

BACKGROUND

Traditionally leukocytes have been viewed as the mediators and effectors of cell injury after tissue ischemia and reperfusion through the indiscriminate release of toxic cytokines and oxygen free radicals. This can be detrimental to functioning of the transplanted heart when reperfused after implantation. Paradoxically, evidence now suggests that certain cytotoxic cytokines and even oxygen free radicals can be cytoprotective in smaller concentrations. This study sought to determine whether cultured human monocytes can be pre-conditioned by brief hypoxia to protect cardiomyocytes from cell death after hypoxia and re-oxygenation.

METHODS

Cultured human monocytes were exposed to transient hypoxia (10 minutes), after which we determined CD11b expression using flow cytometry. The 3 control groups comprised immunoglobulin G-negative controls, fMLP-positive controls, and virgin monocyte (VM) controls. We studied chick embryonic ventricular myocytes in a flow-through chamber while controlling flow rate, pH, O(2), and CO2 tension. We quantified cardiomyocyte viability using propidium iodide (5 micromol/liter). Cell systems of cardiomyocytes alone, cardiomyocytes and VM, human monocytes exposed to transient hypoxia before coculture with cardiomyocytes (PCHM-cardiomyocyte), and PCHM cocultured with anti-CD11b antibodies for 30 minutes before coculture with cardiomyocytes (CDHM-cardiomyocyte) were subjected to 1 hour of hypoxia and 3 hours of re-oxygenation, and cell death was determined. The experiment was repeated and the cell systems fixed, stained, and examined for monocytes adhering to cardiomyocytes.

RESULTS

CD11b expression increased significantly with both transient hypoxia and fMLP (18.39% +/- 4.116%, n = 5, and 37.04% +/- 7.783%, n = 5, respectively, p < 0.05 vs VM 100%, n = 5). Coculture of cardiomyocytes with VM had no effects on cardiocyte death (40.6% +/- 6.1%, n = 6) compared with controls (46.5% +/- 4.0%, n = 10). The PCHM cocultured with cardiomyocytes significantly decreased cardiomyocyte death (25.2% +/- 4.7%, n = 6, p < 0.05). This protection was abrogated by the addition of CD11b-blocking antibodies to PCHM before coculture with cardiomyocytes (51.0% +/- 6.1%, n = 6, p < 0.05). The PCHM showed increased adhesion to cardiomyocytes (5.4 +/- 0.38/high-power [HP] field vs 0.67 +/- 0.24/HP field in VM, p < 0.05). The increased adhesion was abolished by CD11b-blocking antibody (0.78 +/- 0.28 vs 0.67 +/- 0.24 cells/HP field, p < 0.05).

CONCLUSIONS

These results suggest that monocytes activated by transient hypoxia protect cardiomyocytes during hypoxia and re-oxygenation through expression of CD11b receptors. These cells seem to adhere to myocytes through this receptor to achieve this effect. The exact mechanism is unclear and requires further study. Autologous recipient monocytes may be pre-conditioned to protect the donor heart during reperfusion.

Sequential monitoring of intragraft cytokine mRNA expression in relation to diastolic left ventricular wall thickness and function early after heart transplantation

Because production of immune regulatory proteins may play a role in early graft dysfunction after heart transplantation, we analyzed whether intragraft cytokine messenger RNA (mRNA) expression levels are associated with diastolic left ventricular function in cardiac allografts. We intensively monitored 16 cardiac allograft recipients during the first 3 months after transplantation. The mRNA expression levels of tumor necrosis factor (TNF-alpha), monocyte chemoattractant protein-1 (MCP-1), transforming growth factor (TGF-beta), platelet derived growth factor (PDGF-A), and basic fibroblast growth factor (bFGF) were measured in endomyocardial biopsies (n = 123) by quantitative RT-PCR. To determine diastolic allograft function, concurrent M-mode and two-dimensional Doppler echocardiograms were analyzed for the following parameters: left ventricular total wall thickness, maximal early and atrial mitral flow velocity, deceleration time of maximal early mitral flow velocity, and isovolumetric relaxation period. During the first 3 months post-transplant an overall decrease in mRNA expression levels of almost all measured cytokines was observed, which paralleled an improvement in diastolic left ventricular wall thickness and function. However, no straightforward relationship could be found between a specific cytokine mRNA expression pattern and the studied echocardiographic parameters. Our data suggest that the improvement in diastolic left ventricular function is associated with a general reduction of inflammation within the allograft, rather than related to a specific cytokine expression pattern.

Overexpression of soluble fas attenuates transplant arteriosclerosis in rat aortic allografts

BACKGROUND

The killing of vascular cells by activated macrophages is an important step in the process of destabilization of the arterial wall. The death receptor Fas is implicated in vascular cell death. Hence, we extended our studies in a rat aortic allograft model, using adenovirus-mediated overexpression of soluble Fas (sFas) to block Fas binding to Fas ligand (Fas-L). The contribution of Fas to vascular cell injury and consequent transplant arteriosclerosis was investigated.

METHODS AND RESULTS

Activated monocytes in the presence of macrophage colony-stimulating factor induce endothelial cell apoptosis in vitro, which was significantly inhibited by adenovirus-mediated sFas overexpression. Next, donor rat abdominal aortas were either untreated or transduced with adenoviruses encoding (1) rat soluble Fas (Ad3rsFas), (2) no insert (Ad3Null), and (3) beta-galactosidase (Ad3nBg). A total of 175 aortic grafts were harvested 2 to 90 days after transplantation. Vascular cell apoptosis and CD45+ cell infiltration were significantly reduced in Ad3rsFas-transduced aortas, as compared with control allografts. Moreover, the control allografts developed marked intimal thickening, whereas Ad3rsFas-transduced allografts had significantly less neointima until the 90-day time point.

CONCLUSIONS

sFas overexpression protects the integrity of the vessel wall from immune injury and attenuates transplant arteriosclerosis.

The interleukin-6/interleukin-6-receptor system is activated in donor hearts

OBJECTIVES

To assess the potential of the donor heart to respond to interleukin-6 (IL6), the present study investigated the expression of IL6 receptor components in the myocardium of donor hearts before transplantation.

BACKGROUND

Donor heart dysfunction early after transplantation has been associated with the cytokine storm after donor brain death. Proinflammatory cytokines are thought to play a central role in this process. Interleukin-6 is of specific interest because it has been associated with cardiac allograft dysfunction and is related to an impaired prognosis. Its action requires expression of the specific IL6 receptor (IL6R), and the common signal transducer of the IL6 family glycoprotein 130 (gp130) in the donor heart.

METHODS

The activation of IL6, IL6R and gp130 messenger ribonucleic acid (mRNA) and protein was studied via reverse transcription-polymerase chain reaction (RT-PCR) and immunohistology in donor hearts (n = 6) and compared with patients undergoing evaluation of ventricular arrhythmias (control, n = 9) or with advanced heart failure (n = 20).

RESULTS

Messenger RNA of IL6, IL6R and gp130 was strongly expressed in all chambers of donor hearts, whereas right ventricles of control patients did not show any expression (donor vs. control: p < 0.005). Right ventricles of failing hearts showed IL6, IL6R and gp130 mRNA levels comparable with those found in donor hearts. Immunohistochemistry paralleled the RT-PCR data on the protein level. While IL6 was mainly expressed by myocytes, both receptor components were preferentially found mainly on interstitial cells.

CONCLUSIONS

The expression of the IL6 receptor components in the donor heart before transplantation establishes the condition sine qua non for the response of the donor heart to circulating IL6. This mechanism may explain the close association of elevated IL6 serum levels to acute cardiac allograft dysfunction in the early perioperative period.

Microvascular prothrombogenicity and transplant coronary artery disease

A major impediment for the long-term success of heart transplantation is the development of transplant coronary artery disease (CAD). Several risk factors for the development of transplant CAD are associated with the transformation of a normal thromboresistant microvasculature into a prothrombogenic microvasculature. Prothrombogenicity is characterized by loss of anticoagulation (i.e. loss of antithrombin), loss of fibrinolytic activity (i.e., loss of tissue plasminogen activator) and presence of endothelial activation (i.e. upregulation of endothelial intercellular adhesion molecule-1 and major histocompatibility class II antigen human leukocyte antigen-DR) in the arterial allograft microvasculature. Microvascular prothrombogenicity during the first trimester after transplantation is directly associated with subsequent development of transplant CAD. Although the mechanisms responsible for the loss of thromboresistant endothelium are unclear, the fact that changes in the anticoagulant, fibrinolytic, and activational status of endothelial cells may occur early after transplantation suggests a peritransplant phenomenon as an initiating event. Reducing prothrombogenicity of the cardiac microvasculature early after transplantation could slow the development of transplant CAD and significantly improve allograft survival.

Gene expression of inflammatory mediators in different chambers of the human heart

BACKGROUND

Inflammatory genes may be unevenly expressed in different heart chambers.

METHODS

Biopsies were taken simultaneously from the right atrium (RA), left atrium (LA), and left ventricle (LV) of 19 patients before cardioplegic arrest during open heart surgery. The mRNA expression of tumor necrosis factor alpha (TNFalpha), interleukin 1beta (IL-1beta), inducible and endothelial nitric oxide synthase (iNOS and eNOS), endothelin-1 (ET-1), E-selectin (CD62E), intercellular adhesion molecule-1 (ICAM-1) and its ligand CD18, and CD25 was evaluated with semiquantitative reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

Expression of TNFalpha mRNA was higher in RA than LA and LV (p<0.05), whereas IL-1beta was more expressed in LA than RA (p<0.05), which was higher than LV (p<0.0001). There were no significant regional differences in the expression of ICAM-1, CD62E, CD25, iNOS, and eNOS. CD18 was higher in RA than LA (p<0.05); ET-1 was more expressed in RA than LV (p<0.04). Patients with stable angina had no expression of eNOS.

CONCLUSIONS

Gene expression of inflammatory mediators was detected in the hearts of patients with different cardiovascular disorders, and was unevenly distributed in different heart chambers. Cardiac biopsies should be taken from the same site.

Metallothionein: localization in human transplant endomyocardium, relation to cytokines and allograft function

BACKGROUND

The aim of this study was to investigate the role of metallothionein in cardiac transplants in relation to cytokines and allograft function. Recent studies have revealed an association of allograft dysfunction with elevated proinflammatory cytokines independent of cellular rejection. In animal experiments, cytokines induced overexpression of metallothionein, a low-molecular-weight protein implicated in cellular stress response.

METHODS

In 105 consecutive biopsies from 15 patients during the first 3 months after heart transplantation, metallothionein expression was investigated immunohistochemically. Its relation to serum interleukin-6, tumor necrosis factor-alpha, interleukin-2 (IL-2), soluble interleukin-2 receptor rejection, and echocardiographic parameters was determined. Forty-three biopsies of 12 patients with idiopathic ventricular tachycardia served as controls.

RESULTS

Metallothionein expression was demonstrated in small vessels, cardiomyocytes, fibrocytes, and interstitial round cells. A positive relation between interleukin-6 levels and the number of metallothionein-positive small vessels (p < 0.028) was observed. Patients with lower serum IL-2 levels showed significantly higher numbers of metallothionein-positive small vessels (p < 0.043). Grafts with prolonged ischemic time (>150 minutes) showed a significantly higher myocardial metallothionein score (p < 0.021). Metallothionein expression was associated with lower fractional shortening, larger left ventricular end-systolic diameter, and lower mean arterial pressure but not with acute cellular rejection.

CONCLUSIONS

Metallothionein expression is associated with elevated interleukin-6 and decreased interleukin-2 serum levels and left ventricular allograft dysfunction in the absence of rejection.