Cardiac allograft rejection

Splenectomy increases the survival time of heart allograft via developing immune tolerance

Background

The spleen is an active lymphoid organ. The effect of splenectomy on the immune response remains unclear. This study investigated whether splenectomy can induce immune tolerance and has a beneficial role in cardiac allograft.

Methods

Wistar rats were used for heart donors. The Sprague–Dawley (SD) rats designated as the recipients of heart transplantation (HT) were randomly assigned into four groups: sham, splenectomy, HT, splenectomy + HT. The survival of transplanted hearts was assessed by daily checking of abdominal palpation. At various time points after transplantation, the transplanted hearts were collected and histologically examined; the level of CD₄⁺CD₂₅⁺ T regulatory lymphocytes (Tregs) and rate of lymphocyte apoptosis (annexin-v⁺ PI⁺ cells) in the blood were analyzed by using flow cytometric method.

Results

1) Splenectomy significantly prolonged the mean survival time of heart allografts (7 ± 1.1 days and 27 ± 1.5 days for HT and splenectomy + HT, respectively; n = 12-14/group, HT vs. splenectomy + HT, p < 0.001); 2) Splenectomy delayed pathological changes (inflammatory cell infiltration, myocardial damage) of the transplanted hearts in splenectomy + HT rats; 3) The level of CD₄⁺CD₂₅⁺ Tregs in the blood of splenectomized rats was significantly increased within 7 days (2.4 ± 0.5%, 4.9 ± 1.3% and 5.3 ± 1.0% for sham, splenectomy and splenectomy + HT, respectively; n = 15/group, sham vs. splenectomy or splenectomy + HT, p < 0.05) after splenectomy surgery and gradually decreased to baseline level; 4) Splenectomy increased the rate of lymphocyte apoptosis (day 7: 0.3 ± 0.05%, 3.9 ± 0.9% and 4.1 ± 0.9% for sham, splenectomy and splenectomy + HT, respectively; n = 15/group, sham vs. splenectomy or splenectomy + HT, p < 0.05) in a pattern similar to the change of the CD₄⁺CD₂₅⁺ Tregs in the blood.

Conclusions

Splenectomy inhibits the development of pathology and prolongs the survival time of cardiac allograft. The responsible mechanism is associated with induction of immune tolerance via elevating CD₄⁺CD₂₅⁺ Tregs and increasing lymphocyte apoptosis.

Alemtuzumab for cytolytic induction of immunosuppression in heart transplant recipients

OBJECTIVE

To review available evidence about the safety and efficacy of alemtuzumab for induction of immunosuppression in heart transplant recipients.

DATA SOURCES

Searches of MEDLINE, EMBASE, and Cochrane databases were conducted. Key search terms included alemtuzumab, Campath-1H, CD52, lymphocyte, cytolytic, induction, immunosuppression, rejection, and cardiac transplantation. Additional pertinent data were identified through a search of abstracts from major transplant meetings.

STUDY SELECTION AND DATA EXTRACTION

All English-language articles and abstracts identified from the data sources were evaluated. All primary data were eligible for inclusion if they evaluated the safety or efficacy of alemtuzumab for induction of immunosuppression in heart transplant patients. One retrospective cohort, 1 case series, 1 case-control series, and 1 open-label trial were identified and included for review.

DATA SYNTHESIS

Acute cellular rejection occurs in 40% to 70% of heart transplant recipients within the first 6 months after transplant and is associated with significant morbidity and mortality. Depleting and nondepleting antibodies have displayed positive outcomes in inducing immunosuppression; however, the ideal induction strategy that balances efficacy and toxicity remains elusive. Alemtuzumab, a cytolytic anti-CD52 antibody, has been used to induce immunosuppression in kidney, pancreas, liver, intestine, and lung transplant recipients, and its use in heart transplant has been investigated. Studies of use of alemtuzumab to induce immunosuppression in heart transplant patients have shown low rates of rejection; however, it has not been directly compared with other immunosuppression-inducing agents and safety data are limited.

CONCLUSIONS

Although alemtuzumab may be a practical option for inducing immunosuppression, data are insufficient to recommend its routine use in deference to more established agents. Large, randomized clinical trials with extended durations of follow-up must be conducted to characterize its efficacy and safety further.

Allogeneic cardiospheres safely boost cardiac function and attenuate adverse remodeling after myocardial infarction in immunologically mismatched rat strains

OBJECTIVES

We sought to characterize the immunologic profile of allogeneic cardiospheres, which are 3-dimensional, self-assembling, cardiac-derived microtissues, and to evaluate their safety and efficacy in repairing ischemic heart tissue.

BACKGROUND

Intramyocardial injection of autologous cardiospheres ameliorates remodeling and improves global function in infarcted myocardium. It is as yet unknown whether allogeneic cardiospheres are similarly effective without eliciting deleterious immune reactions.

METHODS

We expanded cardiospheres from male Wistar Kyoto rat hearts and injected them surgically in the peri-infarct zone of Wistar Kyoto (syngeneic group, n = 28) and Brown Norway female rats (allogeneic group, n = 29). Female rats from both strains (n = 37) injected with normal saline served as controls.

RESULTS

In vitro, cardiospheres expressed a low immunogenic profile and inhibited proliferation of alloreactive T cells. In vivo, cell engraftment was similar in the syngeneic and allogeneic groups 1 week and 3 weeks after transplantation. Reductions in scar size and scar collagen content and increases in viable mass in the risk region were accompanied by improvements in left ventricular function and attenuation of left ventricle remodeling that were sustained during 6 months of follow up. Transplantation of allogeneic cardiospheres increased tissue expression of the regenerative growth factors vascular endothelial growth factor, hepatocyte growth factor, and insulin-like growth factor-1, stimulating angiogenesis. Syngeneic and allogeneic cardiospheres attenuated the inflammatory response observed histologically in the peri-infarct region.

CONCLUSIONS

Allogeneic cardiospheres increase viable myocardium, decrease scar, improve function, and attenuate adverse remodeling in the infarcted rat heart, without deleterious immunological sequelae. These observations lay the groundwork for developing cardiospheres as a novel off-the-shelf microtissue product for myocardial regeneration.

New issues in heart transplantation for heart failure

OPINION STATEMENT

Heart transplantation is the preferred therapy for patients with end-stage heart failure with refractory symptoms despite optimal medical and device therapy. The major impediment to survival is rejection and infection in the short term and cardiac allograft vasculopathy and malignancy in the long term. Current therapies are focused on the prevention and treatment of rejection and limiting the long-term problems of cardiac allograft vasculopathy and malignancy. Advances in monitoring assays now allow better assessment of rejection and the level of immune response. This will allow clinicians, in the future, to tailor current therapies to the needs of individual heart transplant recipients to maximize benefit and minimize toxicity.

Biomarkers of heart transplant rejection: the good, the bad, and the ugly!

Acute cellular rejection (ACR), antibody-mediated rejection (AMR), and cardiac allograft vasculopathy (CAV) are important limitations for the long-term survival of heart transplant recipients. Although much progress has been made in reducing ACR with modern immunosuppressive treatments and continuous biopsy surveillance, there is still a long way to go to better understand and treat AMR, to enable early detection of patients at risk of CAV, and to reduce the development and sustained progression of this irreversible disease that permanently compromises graft function. This review considers the advances made in ACR detection and treatment allowing a more prolonged survival and the risk factors leading to endothelial injury, dysfunction, inflammation, and subsequent CAV, as well as new treatment modalities for CAV. The review also evaluates the controversies around the definition, pathogenesis, and treatment of AMR. To date, much progress is still needed to significantly reduce post-transplant complications and increase graft and patient survival.

Inflammation in myocardial diseases

Inflammatory processes underlie a broad spectrum of conditions that injure the heart muscle and cause both structural and functional deficits. In this article, we address current knowledge regarding 4 common forms of myocardial inflammation: myocardial ischemia and reperfusion, sepsis, viral myocarditis, and immune rejection. Each of these pathological states has its own unique features in pathogenesis and disease evolution, but all reflect inflammatory mechanisms that are partially shared. From the point of injury to the mobilization of innate and adaptive immune responses and inflammatory amplification, the cellular and soluble mediators and mechanisms examined in this review will be discussed with a view that both beneficial and adverse consequences arise in these human conditions.

Suppression of cardiac allograft vasculopathy in mice by inhibition of CC-motif chemokine receptor 5

Cardiac allograft vasculopathy (CAV) is the leading cause of late morbidity and mortality in heart-transplant patients. Increasing evidences support the important role of chemokines and their receptors in transplant immunology. Chemokine-chemokine receptor interaction and subsequent recruitment of T-lymphocytes to the graft are early events in the development of chronic rejection of transplanted hearts. In this study, we first inhibited CC-motif chemokine receptor 5 (CCR5) expression by using lentiviral-mediated gene transfer of an anti-CCR5 siRNA, which introduced through CD34(+) hematopoietic stem/progenitor cell transplantation. Stably marked lymphocytes expressing siRNA and consistent downregulation of CCR5 expression were detected. Our results showed that survival was significantly prolonged in CCR5 knock-down mice and donor hearts from siRNA-treated mice developed markedly less CAV. Infiltration of CD4(+) and CD8(+) T-lymphocytes into transplanted hearts was also markedly decreased. These findings suggest that CCR5 plays an important role in CAV development and inhibition of this chemokine could improve long-term survival after cardiac transplantation.