Divergent mitochondrial biogenesis responses in human cardiomyopathy.

BACKGROUND: Mitochondria are key players in the development and progression of heart failure (HF). Mitochondrial (mt) dysfunction leads to diminished energy production and increased cell death contributing to the progression of left ventricular failure. The fundamental mechanisms that underlie mt dysfunction in HF have not been fully elucidated. METHODS AND RESULTS: To characterize mt morphology, biogenesis, and genomic integrity in human HF, we investigated left ventricular tissue from nonfailing hearts and end-stage ischemic (ICM) or dilated (DCM) cardiomyopathic hearts. Although mt dysfunction was present in both types of cardiomyopathy, mt were smaller and increased in number in DCM compared with ICM or nonfailing hearts. mt volume density and mtDNA copy number was increased by ≈2-fold (P<0.001) in DCM hearts in comparison with ICM hearts. These changes were accompanied by an increase in the expression of mtDNA-encoded genes in DCM versus no change in ICM. mtDNA repair and antioxidant genes were reduced in failing hearts, suggestive of a defective repair and protection system, which may account for the 4.1-fold increase in mtDNA deletion mutations in DCM (P<0.05 versus nonfailing hearts, P<0.05 versus ICM). CONCLUSIONS: In DCM, mt dysfunction is associated with mtDNA damage and deletions, which could be a consequence of mutating stress coupled with a peroxisome proliferator-activated receptor γ coactivator 1α-dependent stimulus for mt biogenesis. However, this maladaptive compensatory response contributes to additional oxidative damage. Thus, our findings support further investigations into novel mechanisms and therapeutic strategies for mt dysfunction in DCM.

Unlinked memory helper responses promote long-lasting humoral alloimmunity.

Essential help for long-lived alloantibody responses is theoretically provided only by CD4 T cells that recognize target alloantigen, processed and presented by the allospecific B cell. We demonstrate that in an alloresponse to multiple MHC disparities, cognate help for class-switched alloantibody may also be provided by CD4 T cells specific for a second "helper" alloantigen. This response was much shorter-lived than when help was provided conventionally, by Th cell recognition of target alloantigen. Nevertheless, long-lasting humoral alloimmunity developed when T cell memory against the helper alloantigen was first generated. Costimulatory blockade abrogated alloantibody produced through naive Th cell recognition of target alloantigen but, crucially, blockade was ineffective when help was provided by memory responses to the accessory helper alloantigen. These results suggest that memory Th cell responses against previously encountered graft alloantigen may be the dominant mechanism for providing help to generate new specificities of alloantibody in transplant patients receiving immunosuppression.

New insights on OX40 in the control of T cell immunity and immune tolerance in vivo.

OX40 is a T cell costimulatory molecule that belongs to the TNFR superfamily. In the absence of immune activation, OX40 is selectively expressed by Foxp3(+) regulatory T cells (Tregs), but not by resting conventional T cells. The exact role of OX40 in Treg homeostasis and function remains incompletely defined. In this study, we demonstrate that OX40 engagement in vivo in naive mice induces initial expansion of Foxp3(+) Tregs, but the expanded Tregs have poor suppressive function and exhibit features of exhaustion. We also show that OX40 enables the activation of the Akt and Stat5 pathways in Tregs, resulting in transient proliferation of Tregs and reduced levels of Foxp3 expression. This creates a state of relative IL-2 deficiency in naive mice that further impacts Tregs. This exhausted Treg phenotype can be prevented by exogenous IL-2, as both OX40 and IL-2 agonists drive further expansion of Tregs in vivo. Importantly, Tregs expanded by both OX40 and IL-2 agonists are potent suppressor cells, and in a heart transplant model, they promote long-term allograft survival. Our data reveal a novel role for OX40 in promoting immune tolerance and may have important clinical implications.

Transient low-dose methotrexate induces tolerance to murine anti-thymocyte globulin and together they promote long-term allograft survival.

Rabbit anti-thymocyte globulin (Thymoglobulin) effectively treats transplant rejection but induces anti-rabbit Ab responses, which limits routine readministration. Aiming to tolerize anti-rabbit responses, we coadministered a brief methotrexate regimen with a murine version of Thymoglobulin (mATG) for effects on anti-mATG Abs and cardiac allotransplantation in mice. Although both single and three courses of methotrexate could significantly inhibit anti-drug Ab titers to repeated mATG treatment, surprisingly, the single course given at the first mATG administration was most effective (>99% reduction). The transient methotrexate treatment also significantly improved pharmacokinetics and pharmacodynamics of repeated mATG administration. In the cardiac allograft model, the combination of transient mATG and methotrexate given only at the time of transplant dramatically improved allograft survival (>100 d) over either agent alone (<30 d). Anti-drug Ab titers were reduced and mATG exposure was increased which resulted in prolonged rather than enhanced mATG-mediated effects when combined with methotrexate. Moreover, methotrexate administration significantly reduced alloantibodies, suggesting that methotrexate not only decreases anti-drug Ab responses but also reduces Ab responses to multiple tissue-derived alloantigens simultaneously. These data suggest that mATG and methotrexate together can provide long-term allograft survival potentially through the induction of immune tolerance.

Delayed anti-CD3 therapy results in depletion of alloreactive T cells and the dominance of Foxp3+ CD4+ graft infiltrating cells.

The engineered Fc-nonbinding (crystallizable fragment-nonbinding) CD3 antibody has lower mitogenicity and a precise therapeutic window for disease remission in patients with type 1 diabetes. Before anti-CD3 can be considered for use in transplantation, the most effective timing of treatment relative to transplantation needs to be elucidated. In this study anti-CD3F(ab')2 fragments or saline were administered intravenously for 5 consecutive days (early: d1-3 or delayed: d3-7) to mice transplanted with a cardiac allograft (H2(b)-to-H2(k); d0). Survival of allografts was prolonged in mice treated with the early protocol (MST = 48 days), but most were rejected by d100. In contrast, in mice treated with the delayed protocol allografts continued to survive long term. The delayed protocol significantly inhibited donor alloreactivity at d30 as compared to the early protocol. A marked increase in Foxp3(+) T cells (50.3 ± 1.6%) infiltrating the allografts in mice treated with the delayed protocol was observed (p < 0.0001 vs. early (24.9 ± 2.1%)) at d10; a finding that was maintained in the accepted cardiac allografts at d100. We conclude that the timing of treatment with anti-CD3 therapy is critical for inducing long-term graft survival. Delaying administration effectively inhibits the alloreactivity and promotes the dominance of intragraft Foxp3(+) T cells allowing long-term graft acceptance.

NKG2D blockade attenuated cardiac allograft vasculopathy in a mouse model of cardiac transplantation.

A previous paper has reported that blockade of NKG2D was effective in protecting allograft in murine models of cardiac transplantation, but the mechanism of NKG2D blockade on attenuated cardiac allograft vasculopathy (CAV) was still unknown. In our current study, we found that wild-type recipients treated with anti-NKG2D monoclonal antibody (mAb) plus cytotoxic T lymphocyte antigen (CTLA)-4-immunoglobulin (I)g showed prolonged allograft survivals (>90 days, P < 0·001) significantly and attenuated CAV. These in-vivo results correlated with reduced alloantibody production, low expression of interleukin (IL)-17 and IL-6, while infiltration of regulatory T cells increased. IL-6 administration induced shorter allograft survival and higher CAV grade in CTLA-4-Ig plus anti-NKG2D mAb-treated recipients, whereas IL-17 had no significant effect on allograft survival and CAV grade in CTLA-4-Ig plus anti-NKG2D mAb-treated recipients. Furthermore, the prolonged allograft survival induced by NKG2D blockade was abrogated partially with depletion of regulatory T cells. In conclusion, blockade of NKG2D combined with CTLA-4-Ig attenuated CAV and this effect was associated with lower alloantibody production, inhibited IL-6 expression and enhanced expansion of regulatory T cells.

An animal model of endocardial fibroelastosis.

BACKGROUND: Hypoplastic left heart syndrome (HLHS) is one of the most common severe congenital cardiac anomalies, characterized by a marked hypoplasia of left-sided structures of the heart, which is commonly accompanied by a thick layer of fibroelastic tissue, termed endocardial fibroelastosis (EFE). Because human EFE develops only in fetal or neonatal hearts, and often in association with reduced blood flow, we sought to mimic these conditions by subjecting neonatal and 2-wk-old rat hearts to variations of the heterotopically transplanted heart model with either no intracavitary or normal flow and compare endocardium with human EFE tissue. MATERIALS AND METHODS: Hearts obtained from neonatal and 2-wk-old rats were heterotopically transplanted in young adult Lewis rats in a working (loaded) or nonworking (unloaded) mode. After 2-wk survival, hearts were explanted for histologic analysis by staining for collagen, elastin, and cellular elements. These sections were compared with human EFE tissue from HLHS. RESULTS: EFE, consisting of collagen and elastin with scarce cellular and vascular components, developed only in neonatal unloaded transplanted hearts and displayed the same histopathologic findings as EFE from patients with HLHS. Loaded hearts and 2-wk-old hearts did not show these alterations. CONCLUSIONS: This animal model for EFE will serve as a tool to study the mechanisms of EFE formation, such as fluid forces, in HLHS in a systematic manner. A better understanding of the underlying cause of the EFE formation in HLHS will help to develop novel treatment strategies to better preserve growth of the hypoplastic left ventricle.

Chronic cardiac allograft rejection: critical role of ED-A(+) fibronectin and implications for targeted therapy strategies.

Chronic cardiac allograft rejection is characterized by cardiac allograft vasculopathy (CAV) and cardiac interstitial fibrosis (CIF) causing severe long-term complications after heart transplantation and determining allograft function and patients' prognosis. Until now, there have been no sufficient preventive or therapeutic strategies. CAV and CIF are accompanied by changes in the extracellular matrix, including re-expression of the fetal fibronectin splice variant known as ED-A(+) fibronectin. This molecule has been shown to be crucial for the development of myofibroblasts (MyoFbs) as the main cell type in CIF and for the activation of vascular smooth muscle cells (VSMCs) as the main cell type in CAV. Relevant re-expression and protein deposition of ED-A(+) fibronectin has been demonstrated in animal models of chronic rejection, with spatial association to CAV and CIF, and a quantitative correlation to the rejection grade. The paper by Booth et al published in this issue of The Journal of Pathology could prove for the first time the functional importance of ED-A(+) fibronectin for the development of CIF as a main component of chronic cardiac rejection. Thus, promising conclusions for the development of new diagnostic, preventive, and therapeutic strategies for chronic cardiac rejection focusing on ED-A(+) fibronectin can be suggested.

Recipient-derived EDA fibronectin promotes cardiac allograft fibrosis.

Advances in donor matching and immunosuppressive therapies have decreased the prevalence of acute rejection of cardiac grafts; however, chronic rejection remains a significant obstacle for long-term allograft survival. While initiating elements of anti-allograft immune responses have been identified, the linkage between these factors and the ultimate development of cardiac fibrosis is not well understood. Tissue fibrosis resembles an exaggerated wound healing response, in which extracellular matrix (ECM) molecules are central. One such ECM molecule is an alternatively spliced isoform of the ubiquitous glycoprotein fibronectin (FN), termed extra domain A-containing cellular fibronectin (EDA cFN). EDA cFN is instrumental in fibrogenesis; thus, we hypothesized that it might also regulate fibrotic remodelling associated with chronic rejection. We compared the development of acute and chronic cardiac allograft rejection in EDA cFN-deficient (EDA(-/-)) and wild-type (WT) mice. While EDA(-/-) mice developed acute cardiac rejection in a manner indistinguishable from WT controls, cardiac allografts in EDA(-/-) mice were protected from fibrosis associated with chronic rejection. Decreased fibrosis was not associated with differences in cardiomyocyte hypertrophy or intra-graft expression of pro-fibrotic mediators. Further, we examined expression of EDA cFN and total FN by whole splenocytes under conditions promoting various T-helper lineages. Conditions supporting regulatory T-cell (Treg) development were characterized by greatest production of total FN and EDA cFN, though EDA cFN to total FN ratios were highest in Th1 cultures. These findings indicate that recipient-derived EDA cFN is dispensable for acute allograft rejection responses but that it promotes the development of fibrosis associated with chronic rejection. Further, conditions favouring the development of regulatory T cells, widely considered graft-protective, may drive production of ECM molecules which enhance deleterious remodelling responses. Thus, EDA cFN may be a therapeutic target for ameliorating fibrosis associated with chronic cardiac allograft rejection.

Embryonic stem cells, derived either after in vitro fertilization or nuclear transfer, prolong survival of semiallogeneic heart transplants.

Tolerance induction toward allogeneic organ grafts represents one of the major aims of transplantation medicine. Stem cells are promising candidates for promoting donor-specific tolerance. In this study, we investigated the immunomodulatory properties of murine embryonic stem cells (ESCs), obtained either by in vitro fertilization (IVF-ESCs) or by nuclear transfer (NT-ESCs), in heart transplant mouse models. IVF-ESCs did not prolong the survival of fully allogeneic cardiac transplants but significantly prolonged the survival of semiallogeneic hearts from the same ESC donor strain for >100 d in 44% of the animals. However, 28% of transplanted animals infused with IVF-ESCs experienced development of a teratoma. NT-ESCs similarly prolonged semiallogeneic heart graft survival (>100 d in 40% of the animals) but were less teratogenic. By in vitro studies, IVF-ESC and NT-ESC immunoregulation was mediated both by cell contact-dependent mechanisms and by the release of soluble factors. By adding specific inhibitors, we identified PGE(2) as a soluble mediator of ESC immunoregulation. Expansion of regulatory T cells was found in lymphoid organs and in the grafts of IVF-ESC- and NT-ESC-tolerized mice. Our study demonstrates that both IVF-ESCs and NT-ESCs modulate recipient immune response toward tolerance to solid organ transplantation, and that NT-ESCs exhibit a lower tendency for teratoma formation. Because NT-ESCs are obtained by NT of a somatic cell from living individuals into an enucleated oocyte, they could represent a source of donor-derived stem cells to induce tolerance to solid organ allograft.

B lymphocytes differentially influence acute and chronic allograft rejection in mice.

The relative contributions of B lymphocytes and plasma cells during allograft rejection remain unclear. Therefore, the effects of B cell depletion on acute cardiac rejection, chronic renal rejection, and skin graft rejection were compared using CD20 or CD19 mAbs. Both CD20 and CD19 mAbs effectively depleted mature B cells, and CD19 mAb treatment depleted plasmablasts and some plasma cells. B cell depletion did not affect acute cardiac allograft rejection, although CD19 mAb treatment prevented allograft-specific IgG production. Strikingly, CD19 mAb treatment significantly reduced renal allograft rejection and abrogated allograft-specific IgG development, whereas CD20 mAb treatment did not. By contrast, B cell depletion exacerbated skin allograft rejection and augmented the proliferation of adoptively transferred alloantigen-specific CD4(+) T cells, demonstrating that B cells can also negatively regulate allograft rejection. Thereby, B cells can either positively or negatively regulate allograft rejection depending on the nature of the allograft and the intensity of the rejection response. Moreover, CD19 mAb may represent a new approach for depleting both B cells and plasma cells to concomitantly impair T cell activation, inhibit the generation of new allograft-specific Abs, or reduce preexisting allograft-specific Ab levels in transplant patients.

Anticardiac myosin immunity and chronic allograft vasculopathy in heart transplant recipients.

Chronic allograft vasculopathy (CAV) contributes to heart transplant failure, yet its pathogenesis is incompletely understood. Although cellular and humoral alloimmunity are accepted pathogenic mediators, animal models suggest that T cells and Abs reactive to graft-expressed autoantigens, including cardiac myosin (CM), could participate. To test the relationship between CAV and anti-CM autoimmunity in humans, we performed a cross-sectional study of 72 heart transplant recipients: 40 with CAV and 32 without. Sera from 65% of patients with CAV contained anti-CM Abs, whereas <10% contained Abs to other autoantigens (p < 0.05), and only 18% contained anti-HLA Abs (p < 0.05 versus anti-CM). In contrast, 13% of sera from patients without CAV contained anti-CM Abs (p < 0.05; odds ratio [OR], associating CAV with anti-CM Ab = 13, 95% confidence interval [CI] 3.79-44.6). Multivariable analysis confirmed the association to be independent of time posttransplant and the presence of anti-HLA Abs (OR = 28, 95% CI 5.77-133.56). PBMCs from patients with CAV responded more frequently to, and to a broader array of, CM-derived peptides than those without CAV (p = 0.01). Detection of either CM-peptide-reactive T cells or anti-CM Abs was highly and independently indicative of CAV (OR = 45, 95% CI 4.04-500.69). Our data suggest detection of anti-CM immunity could be used as a biomarker for outcome in heart transplantation recipients and support the need for further studies to assess whether anti-CM immunity is a pathogenic mediator of CAV.

Blockade of Notch ligand δ1 promotes allograft survival by inhibiting alloreactive Th1 cells and cytotoxic T cell generation.

The Notch signaling pathway has been recently shown to contribute to T cell differentiation in vitro. However, the in vivo function of Notch signaling in transplantation remains unknown. In this study, we investigated the importance of Delta1 in regulating the alloimmune response in vivo. Delta1 expression was upregulated on dendritic cells and monocytes/macrophages upon transplantation in a BALB/c into B6 vascularized cardiac transplant model. Whereas administration of anti-Delta1 mAb only slightly delayed survival of cardiac allografts in this fully MHC-mismatched model, it significantly prolonged graft survival in combination with single-dose CTLA4-Ig or in CD28 knockout recipients. The prolongation of allograft survival was associated with Th2 polarization and a decrease in Th1 and granzyme B-producing cytotoxic T cells. The survival benefit of Delta1 blockade was abrogated after IL-4 neutralization and in STAT6KO recipients, but was maintained in STAT4KO recipients, reinforcing the key role of Th2 cell development in its graft-prolonging effects. To our knowledge, these data demonstrate for the first time an important role of Delta1 in alloimmunity, identifying Delta1 ligand as a potential novel target for immunomodulation in transplantation.

IL-33 expands suppressive CD11b+ Gr-1(int) and regulatory T cells, including ST2L+ Foxp3+ cells, and mediates regulatory T cell-dependent promotion of cardiac allograft survival.

IL-33 administration is associated with facilitation of Th2 responses and cardioprotective properties in rodent models. However, in heart transplantation, the mechanism by which IL-33, signaling through ST2L (the membrane-bound form of ST2), promotes transplant survival is unclear. We report that IL-33 administration, while facilitating Th2 responses, also increases immunoregulatory myeloid cells and CD4(+) Foxp3(+) regulatory T cells (Tregs) in mice. IL-33 expands functional myeloid-derived suppressor cells, CD11b(+) cells that exhibit intermediate (int) levels of Gr-1 and potent T cell suppressive function. Furthermore, IL-33 administration causes an St2-dependent expansion of suppressive CD4(+) Foxp3(+) Tregs, including an ST2L(+) population. IL-33 monotherapy after fully allogeneic mouse heart transplantation resulted in significant graft prolongation associated with increased Th2-type responses and decreased systemic CD8(+) IFN-γ(+) cells. Also, despite reducing overall CD3(+) cell infiltration of the graft, IL-33 administration markedly increased intragraft Foxp3(+) cells. Whereas control graft recipients displayed increases in systemic CD11b(+) Gr-1(hi) cells, IL-33-treated recipients exhibited increased CD11b(+) Gr-1(int) cells. Enhanced ST2 expression was observed in the myocardium and endothelium of rejecting allografts, however the therapeutic effect of IL-33 required recipient St2 expression and was dependent on Tregs. These findings reveal a new immunoregulatory property of IL-33. Specifically, in addition to supporting Th2 responses, IL-33 facilitates regulatory cells, particularly functional CD4(+) Foxp3(+) Tregs that underlie IL-33-mediated cardiac allograft survival.

[The donor's heart 22 years after the orthotopic transplantation].

The orthotopic heart transplantation is an acknowledge method for the treatment of cardiomyopathies of various etiology. Specific vasculopathy of the transplanted heart is considered to be a significant problem of the long-term postoperative period and serves the reason of low 10-years survival rates (not more then 50%). The issue unites the experience of follow-up and intravital electronic microscopy of transplantated heart's biopsies from 20 patients. Previously unknown data can help the clarification of posttransplantational cardiomyopathy.

Interleukin-17 accelerates allograft rejection by suppressing regulatory T cell expansion.

BACKGROUND: Interleukin-17 (IL-17), which is predominantly produced by T helper 17 cells distinct from T helper 1 or T helper 2 cells, participates in the pathogenesis of infectious, autoimmune, and allergic disorders. However, the precise role in allograft rejection remains uncertain. In the present study, we investigated the role of IL-17 in acute allograft rejection using IL-17-deficient mice. METHODS AND RESULTS: Donor hearts from FVB mice were heterotopically transplanted into either C57BL/6J-IL-17-deficient (IL-17(-/-)) or -wild-type mice. Allograft survival was significantly prolonged in IL-17(-/-) recipient mice due to reduced local inflammation accompanied by decreased inflammatory cell recruitment and cytokine/chemokine expression. IL-17(-/-) recipient mice exhibited decreased IL-6 production and reciprocally enhanced regulatory T cell expansion, suggesting a contribution of regulatory T cells to prolonged allograft survival. Indeed, allografts transplanted into anti-CD25 mAb-treated IL-17(-/-) recipient mice (regulatory T cell-depleted) developed acute rejection similar to wild-type recipient mice. Surprisingly, we found that gamma delta T cells rather than CD4(+) and CD8(+) T cells were key IL-17 producers in the allografts. In support, equivalent allograft rejection was observed in Rag-2(-/-) recipient mice engrafted with either wild-type or IL-17(-/-) CD4(+) and CD8(+) T cells. Finally, hearts transplanted into gamma delta T cell-deficient mice resulted in decreased allograft rejection compared with wild-type controls. CONCLUSIONS: During heart transplantation, (1) IL-17 is crucial for acceleration of acute rejection; (2) IL-17-deficiency enhances regulatory T cell expansion; and (3) gamma delta T cells rather than CD4(+) and CD8(+) T cells are a potential source of IL-17. IL-17 neutralization may provide a potential target for novel therapeutic treatment for cardiac allograft rejection.

Tolerance induction towards cardiac allografts under costimulation blockade is impaired in CCR7-deficient animals but can be restored by adoptive transfer of syngeneic plasmacytoid dendritic cells.

Deficiency of transplant recipients for the chemokine receptor CCR7 was originally described to slightly increase the survival time of vascularized solid organ grafts, probably due to a reduced priming of alloreactive T cells. Using a model of allotolerance induction by donor-specific splenocyte transfusion (DST) in combination with anti-CD40L mAb-mediated costimulation blockade (CSB), we show here a striking failure of CCR7-deficient (CCR7(-/-) ) recipients to tolerate cardiac allografts. Furthermore, in addition to the recently described lack of Treg, CCR7(-/-) mice were found to harbor significantly reduced numbers of plasmacytoid dendritic cells (pDCs) within peripheral as well as mesenteric lymph nodes (LNs), but not the bone marrow or spleen. pDCs had previously been suggested to function as tolerogenic APC during allograft transplantation, and a single transfer of syngeneic WT pDCs, but not conventional DCs, was indeed sufficient to rescue graft survival in DST+CSB-treated CCR7(-/-) recipients in a dose-dependent manner. We therefore conclude that the nearly complete absence of pDCs within LNs of CCR7(-/-) mice prevents the successful induction of DST+CSB-mediated allotolerance, leading to the observed acute rejection of cardiac allografts under tolerizing conditions.

Targeted complement inhibitors protect against posttransplant cardiac ischemia and reperfusion injury and reveal an important role for the alternative pathway of complement activation.

Ischemia reperfusion injury (IRI) is an unavoidable event during solid organ transplantation and is a major contributor to early graft dysfunction and subsequent graft immunogenicity. In a therapeutic paradigm using targeted complement inhibitors, we investigated the role of complement, and specifically the alternative pathway of complement, in IRI to heart isografts. Mouse heterotopic isograft heart transplants were performed in C57BL/6 mice treated with a single injection of either CR2-Crry (inhibits all complement pathways) or CR2-fH (inhibits alternative complement pathway) immediately posttransplantation. Transplanted hearts were harvested at 12 and 48 h for analysis. Both inhibitors resulted in a significant reduction in myocardial IRI, as measured by histology and serum cardiac troponin I levels. Furthermore, compared with untreated controls, both inhibitors reduced graft complement deposition, neutrophil and macrophage infiltration, adhesion molecule expression (P-selectin, E-selectin, and I-CAM-1), and proinflammatory cytokine expression (TNF-α, IL-1ß, KC, and MCP-1). The reduction in myocardial damage and cellular infiltration was not significantly different between CR2-Crry- and CR2-fH-treated mice, although adhesion molecule and cytokine levels were significantly lower in CR2-Crry-treated mice compared with CR2-fH-treated mice. In conclusion, the alternative complement pathway plays a major contributing role in myocardial IRI after heart transplantation, and local (targeted) complement inhibition has the potential to provide an effective and safe therapeutic strategy to reduce graft injury. Although total complement blockade may be somewhat more efficacious in terms of reducing inflammation, specific blockade of the alternative pathway is likely to be less immunosuppressive in an already immunocompromised recipient.

Remote noninvasive allograft rejection monitoring for heart transplant recipients: study protocol for the novel evaluation with home electrocardiogram and remote transmission (NEW HEART) study.

BACKGROUND: Acute allograft rejection is a major cause of early mortality in the first year after heart transplantation in adults. Although endomyocardial biopsy (EMB) is not a perfect "gold standard" for a correct diagnosis of acute allograft rejection, it is considered the best available test and thus, is the current standard practice. Unfortunately, EMB is an invasive and costly procedure that is not without risk. Recent evidence suggests that acute allograft rejection causes delays in ventricular repolarization and thereby increases the cellular action potential duration resulting in a longer QT interval on the electrocardiogram (ECG). No prospective study to date has investigated whether such increases in the QT interval could provide early detection of acute allograft rejection. Therefore, in the Novel Evaluation With Home Electrocardiogram And Remote Transmission (NEW HEART) study, we plan to investigate the potential benefit of daily home QT interval monitoring to predict acute allograft rejection. METHODS/DESIGN: The NEW HEART study is a prospective, double-blind, multi-center descriptive research study. A sample of 325 adult heart transplant recipients will be recruited within six weeks of transplant from three sites in the United States. Subjects will receive the HeartView™ ECG recorder and its companion Internet Transmitter, which will transmit the subject's ECG to a Core Laboratory. Subjects will be instructed to record and transmit an ECG recording daily for 6 months. An increase in the QTC interval from the previous day of at least 25 ms that persists for 3 consecutive days will be considered abnormal. The number and grade of acute allograft rejection episodes, as well as all-cause mortality, will be collected for one year following transplant surgery. DISCUSSION: This study will provide "real world" prospective data to determine the sensitivity and specificity of QTC as an early non invasive marker of cellular rejection in transplant recipients during the first post-transplant year. A non-invasive indicator of early allograft rejection in heart transplant recipients has the potential to limit the number and severity of rejection episodes by reducing the time and cost of rejection surveillance and by shortening the time to recognition of rejection. TRIAL REGISTRATION: ClinicalTrials.gov: NCT01365806.

CD34+CD140b+ cells and circulating CXCL12 correlate with the angiographically assessed severity of cardiac allograft vasculopathy.

AIMS: We sought to determine whether circulating vascular progenitor cells, such as endothelial progenitor cells (EPCs) or smooth muscle progenitor cells (SPCs), were associated with the severity of cardiac allograft vasculopathy (CAV). METHODS AND RESULTS: CD34(+)CD140b(+) SPCs and CD34(+)KDR(+) EPCs were measured in the peripheral circulation of 187 adult heart transplant recipients by flow cytometry. Cardiac allograft vasculopathy was quantified by angiography using a CAV-specific scoring system. Cardiac allograft vasculopathy was present in 84 patients (44.7%) and was classified as mild in 59 and severe in 25 cases. Circulating SPCs were more frequently detectable in CAV patients than in patients without CAV. The number of CD34(+)CD140b(+) cells showed a stepwise increase in patients with moderate and severe CAV. Smooth muscle progenitor cell counts were higher in patients with coronary stent implant compared with unstented patients with CAV. In contrast, peripheral CD34(+)KDR(+) EPC counts were not changed in CAV patients. Plasma CXCL12 levels correlated with the degree of CAV and SPC counts. None of the different immunosuppressive drug regimes was related to the SPC count or the CXCL12 levels. A multivariate regression analysis revealed that the SPC count was independently associated with the presence of CAV. CONCLUSION: Circulating SPCs, but not EPCs, and plasma CXCL12 concentrations are elevated in CAV patients, indicating that they play prominent roles in transplant arteriosclerosis.