THE NEUROENDOTHELIAL AXIS IN TRAUMATIC BRAIN INJURY: MECHANISMS OF MULTIORGAN DYSFUNCTION, NOVEL THERAPIES, AND FUTURE DIRECTIONS

ABSTRACT

Severe traumatic brain injury (TBI) often initiates a systemic inflammatory response syndrome, which can potentially culminate into multiorgan dysfunction. A central player in this cascade is endotheliopathy, caused by perturbations in homeostatic mechanisms governed by endothelial cells due to injury-induced coagulopathy, heightened sympathoadrenal response, complement activation, and proinflammatory cytokine release. Unique to TBI is the potential disruption of the blood-brain barrier, which may expose neuronal antigens to the peripheral immune system and permit neuroinflammatory mediators to enter systemic circulation, propagating endotheliopathy systemically. This review aims to provide comprehensive insights into the "neuroendothelial axis" underlying endothelial dysfunction after TBI, identify potential diagnostic and prognostic biomarkers, and explore therapeutic strategies targeting these interactions, with the ultimate goal of improving patient outcomes after severe TBI.

Advancing mouse models for transplantation research

Mouse models have been instrumental in understanding mechanisms of transplant rejection and tolerance, but cross-study reproducibility and translation of experimental findings into effective clinical therapies are issues of concern. The Mouse Models in Transplantation symposium gathered scientists and physician-scientists involved in basic and clinical research in transplantation to discuss the strengths and limitations of mouse transplant models and strategies to enhance their utility. Participants recognized that increased procedure standardization, including the use of prespecified, defined endpoints, and statistical power analyses, would benefit the field. They also discussed the generation of new models that incorporate environmental and genetic variables affecting clinical outcomes as potentially important. If implemented, these strategies are expected to improve the reproducibility of mouse studies and increase their translation to clinical trials and, ideally, new Food and Drug Administration-approved drugs.

Role of Extracellular Vesicles in the Propagation of Lung Fibrosis in Systemic Sclerosis

OBJECTIVES

Systemic sclerosis (SSc) has the highest mortality rate among the rheumatic diseases, with lung fibrosis leading as the cause of death. A characteristic of severe SSc-related lung fibrosis is its progressive nature. Although most research has focused on the pathology of the fibrosis, the mechanism mediating the fibrotic spread remains unclear. We hypothesized that extracellular vesicle (EV) communication drives the propagation of SSc lung fibrosis.

METHODS

EVs were isolated from normal (NL) or SSc-derived human lungs and primary lung fibroblasts (pLFs). EVs were also isolated from human fibrotic lungs and pLFs induced experimentally with transforming growth factor-β (TGFβ). Fibrotic potency of EVs was assessed using functional assays in vitro and in vivo. Transmission electron microscopy, nanoparticle tracking analysis, real-time quantitative polymerase chain reaction (RT-qPCR), immunoblotting, and immunofluorescence were used to analyze EVs, their cargo, extracellular matrix (ECM) fractions, and conditioned media.

RESULTS

SSc lungs and pLFs released significantly more EVs than NL lungs, and their EVs showed increased fibrotic content and activity. TGFβ-stimulated NL lung cores and pLFs increased packaging of fibrotic proteins, including fibronectin, collagens, and TGFβ, into released EVs. The EVs induced a fibrotic phenotype in recipient pLFs and in vivo in mouse lungs. Furthermore, EVs interacted with and contributed to the ECM. Finally, suppressing EV release in vivo reduced severity of murine lung fibrosis.

CONCLUSIONS

Our findings highlight EV communication as a novel mechanism for propagation of SSc lung fibrosis. Identifying therapies that reduce EV release, activity, and/or fibrotic cargo in SSc patient lungs may be a viable therapeutic strategy to improve fibrosis.

Reduced Cathepsin L expression and secretion into the extracellular milieu contribute to lung fibrosis in systemic sclerosis

OBJECTIVES

Lung fibrosis is the leading cause of death in SSc, with no cure currently available. Antifibrotic Endostatin (ES) production does not reach therapeutic levels in SSc patients, suggesting a deficit in its release from Collagen XVIII by the main cleavage enzyme, Cathepsin L (CTSL). Thus, elucidating a potential deficit in CTSL expression and activity unravels an underlying molecular cause for SSc-driven lung fibrosis.

METHODS

Fibrosis was induced experimentally using TGF-β in vitro, in primary human lung fibroblasts (pLFs), and ex vivo, in human lung tissues. ES and CTSL expression was quantified using ELISA, RT-qPCR, immunoblotting or immunofluorescence. Recombinant NC1-FLAG peptide was used to assess CTSL cleavage activity. CTSL expression was also compared between SSc vs normal (NL)-derived pLFs and lung tissues.

RESULTS

ES levels were significantly reduced in media conditioned by TGF-β-induced pLFs. TGF-β-stimulated pLFs significantly reduced expression and secretion of CTSL into the extracellular matrix (ECM). CTSL was also sequestered in its inactive form into extracellular vesicles, further reducing its availability in the ECM. Media conditioned by TGF-β-induced pLFs showed reduced cleavage of NC1-Flag and reduced release of the antifibrotic ES fragment. SSc-derived pLFs and lung tissues expressed significantly lower levels of CTSL compared with NL.

CONCLUSIONS

Our findings identify CTSL as a protein protective against lung fibrosis via its activation of antifibrotic ES, and whose expression in SSc pLFs and lung tissues is suppressed. Identifying strategies to boost CTSL endogenous levels in SSc patients could serve as a viable therapeutic strategy.

Connexins in endothelial cells as a therapeutic target for solid organ transplantation

Connexins are a class of membrane proteins widely distributed throughout the body and have various functions based on their location and levels of expression. More specifically, connexin proteins expressed in endothelial cells (ECs) have unique roles in maintaining EC barrier integrity and function-a highly regulated process that is critical for pro-inflammatory and pro-coagulant reactions. In this minireview, we discuss the regulatory influence connexin proteins have in maintaining EC barrier integrity and their role in ischemia-reperfusion injury as it relates to organ transplantation. It is evident that certain isoforms of the connexin protein family are uniquely positioned to have far-reaching effects on preserving organ function; however, there is still much to be learned of their roles in transplant immunology and the application of this knowledge to the development of targeted therapeutics.

Direct NP- A cost-effective extraction-free RT-qPCR based test for SARS-CoV-2

Over 2.4 million daily total tests are currently being performed for SARS-CoV-2, in the United States. The most common SARS-CoV-2 tests require RNA extraction and purification. Extraction of RNA is a time-consuming and costly step that requires a constant supply of reagents and accessories. With the current testing demand, the supply chain remains the bottleneck for RNA extraction. Here, we report Direct NP- a cost-effective extraction-free RT-qPCR based dualplex test for SARS-CoV-2 from Nasopharyngeal (NP) swab specimens. Direct NP detects SARS-CoV-2 viral RNA from heat-denatured patient specimens using a dualplex RT-qPCR assay. Direct NP showed 92.5% positive percentage agreement (PPA) (95% Confidence Interval (CI) = 79.61%-98.43%) and 97% negative percent agreement (NPA) (95% CI = 89.11-100%) with the CDC assay. Direct NP reduces the cost per test to $2, making it suitable for broad-scale testing while lowering the cost burden on the healthcare system.

Carbon Monoxide Activates PERK-Regulated Autophagy to Induce Immunometabolic Reprogramming and Boost Antitumor T-cell Function

Mitochondria and endoplasmic reticulum (ER) share structural and functional networks and activate well-orchestrated signaling processes to shape cells' fate and function. While persistent ER stress (ERS) response leads to mitochondrial collapse, moderate ERS promotes mitochondrial function. Strategies to boost antitumor T-cell function by targeting ER-mitochondria cross-talk have not yet been exploited. Here, we used carbon monoxide (CO), a short-lived gaseous molecule, to test whether engaging moderate ERS conditions can improve mitochondrial and antitumor functions in T cells. In melanoma antigen-specific T cells, CO-induced transient activation of ERS sensor protein kinase R-like endoplasmic reticulum kinase (PERK) significantly increased antitumor T-cell function. Furthermore, CO-induced PERK activation temporarily halted protein translation and induced protective autophagy, including mitophagy. The use of LC3-GFP enabled differentiation between the cells that prepare themselves to undergo active autophagy (LC3-GFPpos) and those that fail to enter the process (LC3-GFPneg). LC3-GFPpos T cells showed strong antitumor potential, whereas LC3-GFPneg cells exhibited a T regulatory-like phenotype, harbored dysfunctional mitochondria, and accumulated abnormal metabolite content. These anomalous ratios of metabolites rendered the cells with a hypermethylated state and distinct epigenetic profile, limiting their antitumor activity. Overall, this study shows that ERS-activated autophagy pathways modify the mitochondrial function and epigenetically reprogram T cells toward a superior antitumor phenotype to achieve robust tumor control.

SIGNIFICANCE

Transient activation of ER stress with carbon monoxide drives mitochondrial biogenesis and protective autophagy that elicits superior antitumor T-cell function, revealing an approach to improving adoptive cell efficacy therapy.

Nanotherapeutics in transplantation: How do we get to clinical implementation?

Patients undergoing organ transplantation transition from one life-altering issue (organ dysfunction) to a lifelong commitment-immunosuppression. Regimens of immunosuppressive agents (ISAs) come with significant side effects and comorbidities. Recently, the use of nanoparticles (NPs) as a solution to the problems associated with the long-term and systemic use of ISAs in transplantation has emerged. This minireview describes the role of NPs in organ transplantation and discusses obstacles to clinical implementation and pathways to clinical translation.

Modulating donor mitochondrial fusion/fission delivers immunoprotective effects in cardiac transplantation

Early insults associated with cardiac transplantation increase the immunogenicity of donor microvascular endothelial cells (ECs), which interact with recipient alloreactive memory T cells and promote responses leading to allograft rejection. Thus, modulating EC immunogenicity could potentially alter T cell responses. Recent studies have shown modulating mitochondrial fusion/fission alters immune cell phenotype. Here, we assess whether modulating mitochondrial fusion/fission reduces EC immunogenicity and alters EC-T cell interactions. By knocking down DRP1, a mitochondrial fission protein, or by using the small molecules M1, a fusion promoter, and Mdivi1, a fission inhibitor, we demonstrate that promoting mitochondrial fusion reduced EC immunogenicity to allogeneic CD8⁺ T cells, shown by decreased T cell cytotoxic proteins, decreased EC VCAM-1, MHC-I expression, and increased PD-L1 expression. Co-cultured T cells also displayed decreased memory frequencies and Ki-67 proliferative index. For in vivo significance, we used a novel murine brain-dead donor transplant model. Balb/c hearts pretreated with M1/Mdivi1 after brain-death induction were heterotopically transplanted into C57BL/6 recipients. We demonstrate that, in line with our in vitro studies, M1/Mdivi1 pretreatment protected cardiac allografts from injury, decreased infiltrating T cell production of cytotoxic proteins, and prolonged allograft survival. Collectively, our data show promoting mitochondrial fusion in donor ECs mitigates recipient T cell responses and leads to significantly improved cardiac transplant survival.

T-cell Immunometabolism: Therapeutic Implications in Organ Transplantation

Although solid-organ transplantation has evolved steadily with many breakthroughs in the past 110 y, many problems remain to be addressed, and advanced therapeutic strategies need to be considered. T-cell immunometabolism is a rapidly advancing field that has gathered much attention recently, providing ample mechanistic insight from which many novel therapeutic approaches have been developed. Applications from the field include antitumor and antimicrobial therapies, as well as for reversing graft-versus-host disease and autoimmune diseases. However, the immunometabolism of T cells remains underexplored in solid-organ transplantation. In this review, we will highlight key findings from hallmark studies centered around various metabolic modes preferred by different T-cell subtypes (categorized into naive, effector, regulatory, and memory T cells), including glycolysis, glutaminolysis, oxidative phosphorylation, fatty acid synthesis, and oxidation. This review will discuss the underlying cellular signaling components that affect these processes, including the transcription factors myelocytomatosis oncogene, hypoxia-inducible factor 1-alpha, estrogen-related receptor alpha, and sterol regulatory element-binding proteins, along with the mechanistic target of rapamycin and adenosine monophosphate-activated protein kinase signaling. We will also explore potential therapeutic strategies targeting these pathways, as applied to the potential for tolerance induction in solid-organ transplantation.

Renal allograft surveillance with allospecific T-cytotoxic memory cells

Background

Allo-antigen-specific T-cytotoxic memory cells (TcM) which express CD40 ligand (CD154) in overnight lymphocyte co-culture are strongly associated with acute cellular rejection (ACR) seen in “for cause” biopsies for renal allograft dysfunction. Specifically, when the likelihood of rejection is increased, donor-specific allospecific TcM exceed those induced by HLA-non-identical third-party cell by 1.15-fold or greater.

Methods

The performance of allospecific TcM was evaluated retrospectively in primary renal transplant recipients (RTR) at routine clinical visits, cross-sectionally at presentation for biopsies, and serially. Performance metrics were sensitivity, specificity, positive and negative predictive values (PPV and NPV).

Results

Twenty-two primary RTR, median age 45 years (range 19–72) were tested with allospecific CD154 + TcM. Samples were obtained at the mean ± SD time interval of 806 ± 239 days after kidney transplantation. Six of 22 patients experienced biopsy proven T- Cell Mediated Rejection (TCMR). A seventh showed antibody mediated rejection (ABMR). Of these seven patients six demonstrated increased likelihood of rejection with allospecific TcM (sensitivity 83%). Ten of these 15 patients with no rejection had a negative test (specificity 67%). False positive tests were seen in five patients. Six out of 11 patients with positive tests had ACR/ABMR with a PPV of 54%, while 10 out of 11 patients with negative tests were non-rejecters with a NPV of 91%.

Conclusion

Allospecific T-cytotoxic memory cells distinguished primary RTR with quiescent allografts from those with dysfunction. With serial surveillance measures, this test system may facilitate decisions to manage immunosuppression in RTR.

A Simplified Model for Heterotopic Heart Valve Transplantation in Rodents

There is an urgent clinical need for heart valve replacements that can grow in children. Heart valve transplantation is proposed as a new type of transplant with the potential to deliver durable heart valves capable of somatic growth with no requirement for anticoagulation. However, the immunobiology of heart valve transplants remains unexplored, highlighting the need for animal models to study this new type of transplant. Previous rat models for heterotopic aortic valve transplantation into the abdominal aorta have been described, though they are technically challenging and costly. For addressing this challenge, a renal subcapsular transplant model was developed in rodents as a practical and more straightforward method for studying heart valve transplant immunobiology. In this model, a single aortic valve leaflet is harvested and inserted into the renal subcapsular space. The kidney is easily accessible, and the transplanted tissue is securely contained in a subcapsular space that is well vascularized and can accommodate a variety of tissue sizes. Furthermore, because a single rat can provide three donor aortic leaflets and a single kidney can provide multiple sites for transplanted tissue, fewer rats are required for a given study. Here, the transplantation technique is described, providing a significant step forward in studying the transplant immunology of heart valve transplantation.

Immune Privilege of Heart Valves

Immune privilege is an evolutionary adaptation that protects vital tissues with limited regenerative capacity from collateral damage by the immune response. Classical examples include the anterior chamber of the eye and the brain. More recently, the placenta, testes and articular cartilage were found to have similar immune privilege. What all of these tissues have in common is their vital function for evolutionary fitness and a limited regenerative capacity. Immune privilege is clinically relevant, because corneal transplantation and meniscal transplantation do not require immunosuppression. The heart valves also serve a vital function and have limited regenerative capacity after damage. Moreover, experimental and clinical evidence from heart valve transplantation suggests that the heart valves are spared from alloimmune injury. Here we review this evidence and propose the concept of heart valves as immune privileged sites. This concept has important clinical implications for heart valve transplantation.

Cellular Viability of Partial Heart Transplant Grafts in Cold Storage

Congenital heart defects are the most common types of birth defects in humans. Children with congenital heart defects frequently require heart valve replacement with an implant. Unfortunately, conventional heart valve implants do not grow. Therefore, these children are committed to serial re-operations for successively larger implant exchanges. Partial heart transplantation is a new and innovative approach to deliver growing heart valve implants. However, the transplant biology of partial heart transplant grafts remains unexplored. This is a critical barrier for clinical translation. Therefore, we investigated the cellular viability of partial heart transplants in cold storage. Histology and immunohistochemistry revealed no morphological differences in heart valves after 6, 24, or 48 h of cold storage. Moreover, immunohistochemistry showed that the marker for apoptosis activated caspase 3 and the marker for cell division Ki67 remained unchanged after 48 h of cold storage. Finally, quantification of fluorescing resorufin showed no statistically significant decrease in cellular metabolic activity in heart valves after 48 h of cold storage. We conclude that partial heart transplants remain viable after 48 h of cold storage. These findings represent the first step toward translating partial heart transplantation from the bench to the bedside because they have direct clinical implications for the procurement logistics of this new type of transplant.

Alterations of lipid metabolism provide serologic biomarkers for the detection of asymptomatic versus symptomatic COVID-19 patients

COVID-19 pandemic exerts a health care emergency around the world. The illness severity is heterogeneous. It is mostly unknown why some individuals who are positive for SARS-CoV-2 antibodies stay asymptomatic while others show moderate to severe disease symptoms. Reliable biomarkers for early detection of the disease are urgently needed to attenuate the virus's spread and help make early treatment decisions. Bioactive sphingolipids play a crucial role in the regulation of viral infections and pro-inflammatory responses involved in the severity of COVID-19. However, any roles of sphingolipids in COVID-19 development or detection remain unknown. In this study, lipidomics measurement of serum sphingolipids demonstrated that reduced sphingosine levels are highly associated with the development of symptomatic COVID-19 in the majority (99.24%) SARS-CoV-2-infected patients compared to asymptomatic counterparts. The majority of asymptomatic individuals (73%) exhibited increased acid ceramidase (AC) in their serum, measured by Western blotting, consistent with elevated sphingosine levels compared to SARS-CoV-2 antibody negative controls. AC protein was also reduced in almost all of the symptomatic patients' serum, linked to reduced sphingosine levels, measured in longitudinal acute or convalescent COVID-19 samples. Thus, reduced sphingosine levels provide a sensitive and selective serologic biomarker for the early identification of asymptomatic versus symptomatic COVID-19 patients.

Comparative analysis of antibodies to SARS-CoV-2 between asymptomatic and convalescent patients

The SARS-CoV-2 viral pandemic has induced a global health crisis, which requires more in-depth investigation into immunological responses to develop effective treatments and vaccines. To understand protective immunity against COVID-19, we screened over 60,000 asymptomatic individuals in the Southeastern United States for IgG antibody positivity against the viral Spike protein, and approximately 3% were positive. Of these 3%, individuals with the highest anti-S or anti-RBD IgG level showed a strong correlation with inhibition of ACE2 binding and cross-reactivity against non-SARS-CoV-2 coronavirus S-proteins. We also analyzed samples from 94 SARS-CoV-2 patients and compared them with those of asymptomatic individuals. SARS-CoV-2 symptomatic patients had decreased antibody responses, ACE2 binding inhibition, and antibody cross-reactivity. Our study shows that healthy individuals can mount robust immune responses against SARS-CoV-2 without symptoms. Furthermore, IgG antibody responses against S and RBD may correlate with high inhibition of ACE2 binding in individuals tested for SARS-CoV-2 infection or post vaccination.

Adoptive Transfer of Regulatory Immune Cells in Organ Transplantation

Chronic graft rejection remains a significant barrier to solid organ transplantation as a treatment for end-organ failure. Patients receiving organ transplants typically require systemic immunosuppression in the form of pharmacological immunosuppressants for the duration of their lives, leaving these patients vulnerable to opportunistic infections, malignancies, and other use-restricting side-effects. In recent years, a substantial amount of research has focused on the use of cell-based therapies for the induction of graft tolerance. Inducing or adoptively transferring regulatory cell types, including regulatory T cells, myeloid-derived suppressor cells, and IL-10 secreting B cells, has the potential to produce graft-specific tolerance in transplant recipients. Significant progress has been made in the optimization of these cell-based therapeutic strategies as our understanding of their underlying mechanisms increases and new immunoengineering technologies become more widely available. Still, many questions remain to be answered regarding optimal cell types to use, appropriate dosage and timing, and adjuvant therapies. In this review, we summarize what is known about the cellular mechanisms that underly the current cell-based therapies being developed for the prevention of allograft rejection, the different strategies being explored to optimize these therapies, and all of the completed and ongoing clinical trials involving these therapies.

Maintaining Equity and Access: Successful Implementation of a Virtual Kidney Transplantation Evaluation

BACKGROUND

Maintaining access to kidney transplantation during a pandemic is a challenge, particularly for centers that serve a large rural and minority patient population with an additional burden of travel. The aim of this article was to describe our experience with the rollout and use of a virtual pretransplantation evaluation platform to facilitate ongoing transplant waitlisting during the early peak of the COVID-19 pandemic.

STUDY DESIGN

This is a retrospective analysis of the process improvement project implemented to continue the evaluation of potential kidney transplantation candidates and ensure waitlist placement during the COVID-19 pandemic. Operational metrics include transplantation volume per month, referral volume per month, pretransplantation patients halted before completing an evaluation per month, evaluations completed per month, and patients waitlisted per month.

RESULTS

Between April and September 2020, a total of 1,258 patients completed an evaluation. Two hundred and forty-seven patients were halted during this time period before completing a full evaluation. One hundred and fifty-two patients were presented at selection and 113 were placed on the waitlist. In addition, the number of patients in the active referral phase was able to be reduced by 46%. More evaluations were completed within the virtual platform (n = 930 vs n = 880), yielding similar additions to the waitlist in 2020 (n = 282) vs 2019 (n = 308) despite the COVID-19 pandemic.

CONCLUSIONS

The virtual platform allowed continued maintenance of a large kidney transplantation program despite the inability to have in-person visits. The value of this platform will likely transform our approach to the pretransplantation process and provides an additional valuable method to improve patient equity and access to transplantation.

Small Bowel Perforation as the Initial Manifestation of Post-Transplant Lymphoproliferative Disorder in a Kidney and Pancreas Transplant Recipient: A Case Report

Post-transplant lymphoproliferative disorder (PTLD) comprises a broad spectrum of diseases and is a rare but serious complication of solid organ transplantation. We report the case of a 45-year-old simultaneous pancreas and kidney (SPK) transplant recipient with diffuse, early-onset PTLD, manifesting as jejunal perforation at 6 months after transplantation. The patient underwent urgent small bowel resection of the affected portion of jejunum. The surgical pathology report was significant for diffuse large B-cell lymphoma. Subsequently, the patient underwent a full workup, including upper and lower endoscopy and whole-body positron emission tomography that revealed involvement of the axial skeleton and multiple abdominal organs with sparing of the grafts. He was treated with rituximab and intrathecal methotrexate for central nervous system prophylaxis. The patient experienced complete resolution of disease by positron emission tomography 8 months after initial presentation. We found no previous report in the literature of intestinal perforation as the initial presentation of PTLD in SPK transplant recipients.

A comprehensive review of the impact of tacrolimus intrapatient variability on clinical outcomes in kidney transplantation

Tacrolimus (Tac) is widely used to prevent rejection and graft loss in solid organ transplantation. A limiting characteristic of Tac is the high intra and interpatient variability associated with its use. Routine therapeutic drug monitoring (TDM) is necessary to facilitate Tac management and to avoid undesirable clinical outcomes. However, whole blood trough concentrations commonly utilized in TDM are not strong predictors of the detrimental clinical outcomes of interest. Recently, researchers have focused on Tac intrapatient variability (Tac IPV) as a novel marker to better assess patient risk. Higher Tac IPV has been associated with a number of mechanisms leading to shortened graft survival. Medication nonadherence (MNA) is considered to be the primary determinant of high Tac IPV and perhaps the most modifiable risk factor. An understanding of the methodology behind Tac IPV is imperative to its recognition as an important prognostic measure and integration into clinical practice. Therapeutic interventions targeting MNA and reducing Tac IPV are crucial to improving long-term graft survival.

Autophagy Induced due to Moderate Endoplasmic Reticulum Stress in T Cells Enhances Immunotherapeutic Tumor Control

A number of external or internal stimuli cause endoplasmic reticulum (ER) stress conditions. In response to ER stress, stressed cells activate well-orchestrated cellular signaling processes to resolve the stress or remove itself by triggering apoptosis. In the tumor microenvironment, induction of sustained ER stress is known to dampen the antitumor activity of T cells. However, how T cells respond to suboptimal ER stimuli is unknown. Using melanoma antigen gp100 reactive T cells, we found that T cells transiently activate protein kinase R-like endoplasmic reticulum kinase (PERK) dependent signaling network to ameliorate low level of ER stress. While transient PERK activation in T cell enhances stemness, promotes mitochondrial biogenesis, increases T cells anti-tumor immunity in B16 melanoma bearing mouse, overexpression of PERK triggers T cell dysfunctionality and death. Mechanistically, we discovered that transient activation of PERK decreases overall protein translation and induces protective autophagy to prevent cell damage. Conversely, knockdown of PERK abrogates autophagy activation, hampers mitochondrial biogenesis in response to suboptimal ER stress, which in turn compromises antitumor function. Furthermore, blocking autophagy in T cells hampers T cell anti-tumor activity. Lastly, using gp100 reactive LC3-GFP expressing T cells we demonstrated that, T cells that initiate autophagy due to suboptimal ER stress show better anti-tumor potential compared to those, that fail to enter into the process. Overall, these preclinical data highlight that, both transient ER stress and autophagy pathways are important for healthy T cell function and therapeutically, can be manipulated to regulate their antitumor potential.

Emphysema-associated Autoreactive Antibodies Exacerbate Post-Lung Transplant Ischemia-Reperfusion Injury

Chronic obstructive pulmonary disease-associated chronic inflammation has been shown to lead to an autoimmune phenotype characterized in part by the presence of lung autoreactive antibodies. We hypothesized that ischemia-reperfusion injury (IRI) liberates epitopes that would facilitate preexisting autoantibody binding, thereby exacerbating lung injury after transplant. We induced emphysema in C57BL/6 mice through 6 months of cigarette smoke (CS) exposure. Mice with CS exposure had significantly elevated serum autoantibodies compared with non-smoke-exposed age-matched (NS) mice. To determine the impact of a full preexisting autoantibody repertoire on IRI, we transplanted BALB/c donor lungs into NS or CS recipients and analyzed grafts 48 hours after transplant. CS recipients had significantly increased lung injury and immune cell infiltration after transplant. Immunofluorescence staining revealed increased IgM, IgG, and C3d deposition in CS recipients. To exclude confounding alloreactivity and confirm the role of preexisting autoantibodies in IRI, syngeneic Rag1^-/- (recombination-activating protein 1-knockout) transplants were performed in which recipients were reconstituted with pooled serum from CS or NS mice. Serum from CS-exposed mice significantly increased IRI compared with control mice, with trends in antibody and C3d deposition similar to those seen in allografts. These data demonstrate that pretransplant CS exposure is associated with increased IgM/IgG autoantibodies, which, upon transplant, bind to the donor lung, activate complement, and exacerbate post-transplant IRI.

Donor pretreatment with nebulized complement C3a receptor antagonist mitigates brain-death induced immunological injury post-lung transplant

Donor brain death (BD) is an inherent part of lung transplantation (LTx) and a key contributor to ischemia-reperfusion injury (IRI). Complement activation occurs as a consequence of BD in other solid organ Tx and exacerbates IRI, but the role of complement in LTx has not been investigated. Here, we investigate the utility of delivering nebulized C3a receptor antagonist (C3aRA) pretransplant to BD donor lungs in order to reduce post-LTx IRI. BD was induced in Balb/c donors, and lungs nebulized with C3aRA or vehicle 30 minutes prior to lung procurement. Lungs were then cold stored for 18 hours before transplantation into C57Bl/6 recipients. Donor lungs from living donors (LD) were removed and similarly stored. At 6 hours and 5 days post-LTx, recipients of BD donor lungs had exacerbated IRI and acute rejection (AR), respectively, compared to recipients receiving LD lungs, as determined by increased histopathological injury, immune cells, and cytokine levels. A single pretransplant nebulized dose of C3aRA to the donor significantly reduced IRI as compared to vehicle-treated BD donors, and returned IRI and AR grades to that seen following LD LTx. These data demonstrate a role for complement inhibition in the amelioration of IRI post-LTx in the context of donor BD.

"Mirror, Mirror on the Wall"… Pediatric liver transplantation in the case of situs inversus totalis with a disrupted inferior vena cava

We present the unique case of a 15-month-old male born with biliary atresia and situs inversus totalis and disrupted inferior vena cava who underwent a successful liver transplantation. The patient had previously undergone a failed Kasai procedure and presented with persistent hyperbilirubinemia. The patient was transplanted with a left lateral segment donor having standard arterial anatomy. Technical considerations included identifying completely replaced arterial anatomy in the recipient from the superior mesenteric artery and creating a branch patch between the gastroduodenal artery and HA, anastomosing the donor left hepatic vein to confluences of the donor left, middle, and right hepatic veins, using a "lazy-S" configuration of portal vein anastomosis, and suspending the allograft to the abdominal wall. Post-operatively, his liver function tests and total bilirubin normalized and he progressed to tolerating an oral diet with tube-feed supplementation.

HDAC inhibition helps post-MI healing by modulating macrophage polarization

AIMS

Following an acute myocardial infarction (MI) the extracellular matrix (ECM) undergoes remodeling in order to prevent dilation of the infarct area and maintain cardiac output. Excessive and prolonged inflammation following an MI exacerbates adverse ventricular remodeling. Macrophages are an integral part of the inflammatory response that contribute to this remodeling. Treatment with histone deacetylase (HDAC) inhibitors preserves LV function and myocardial remodeling in the post-MI heart. This study tested whether inhibition of HDAC activity resulted in preserving post-MI LV function through the regulation of macrophage phenotype and early resolution of inflammation.

METHODS AND RESULTS

HDAC inhibition does not affect the recruitment of CD45⁺ leukocytes, CD45⁺/CD11b⁺ inflammatory monocytes or CD45⁺/CD11b⁺CD86⁺ inflammatory macrophages for the first 3 days following infarct. Further, HDAC inhibition does not change the high expression level of the inflammatory cytokines in the first days following MI. However, by day 7, there was a significant reduction in the levels of CD45⁺/Cd11b⁺ and CD45⁺/CD11b⁺/CD86⁺ cells with HDAC inhibition. Remarkably, HDAC inhibition resulted in the dramatic increase in the recruitment of CD45⁺/CD11b⁺/CD206⁺ alternatively activated macrophages as early as 1 day which remained significantly elevated until 5 days post-MI. qRT-PCR revealed that HDAC inhibitor treatment shifts the cytokine and chemokine environment towards an M2 phenotype with upregulation of M2 markers at 1 and 5 days post-MI. Importantly, HDAC inhibition correlates with significant preservation of both LV ejection fraction and end-diastolic volume and is associated with a significant increase in micro-vessel density in the border zone at 14 days post-MI.

CONCLUSION

Inhibition of HDAC activity result in the early recruitment of reparative CD45⁺/CD11b⁺/CD206⁺ macrophages in the post-MI heart and correlates with improved ventricular function and remodeling. This work identifies a very promising therapeutic opportunity to manage macrophage phenotype and enhance resolution of inflammation in the post-MI heart.

Microdissection of Primary Renal Tissue Segments and Incorporation with Novel Scaffold-free Construct Technology

Kidney transplantation is now a mainstream therapy for end-stage renal disease. However, with approximately 96,000 people on the waiting list and only one-fourth of these patients achieving transplantation, there is a dire need for alternatives for those with failing organs. In order to decrease the harmful consequences of dialysis along with the overall healthcare costs it incurs, active investigation is ongoing in search of alternative solutions to organ transplantation. Implantable tissue-engineered renal cellular constructs are one such feasible approach to replacing lost renal functionality. Here, described for the first time, is the microdissection of murine kidneys for isolation of living corticomedullary renal segments. These segments are capable of rapid incorporation within scaffold-free endothelial-fibroblast constructs which may enable rapid connection with host vasculature once implanted. Adult mouse kidneys were procured from living donors, followed by stereoscope microdissection to obtain renal segments 200 - 300 µm in diameter. Multiple renal constructs were fabricated using primary renal segments harvested from only one kidney. This method demonstrates a procedure which could salvage functional renal tissue from organs that would otherwise be discarded.

Organ preservation with targeted rapamycin nanoparticles: a pre-treatment strategy preventing chronic rejection in vivo

Hypothermic preservation is the standard of care for storing organs prior to transplantation. Endothelial and epithelial injury associated with hypothermic storage causes downstream graft injury and, as such, the choice of an ideal donor organ preservation solution remains controversial. Cold storage solutions, by design, minimize cellular necrosis and optimize cellular osmotic potential, but do little to assuage immunological cell activation or immune cell priming post transplantation. Thus, here we explore the efficacy of our previously described novel Targeted Rapamycin Micelles (TRaM) as an additive to standard-of-care University of Wisconsin preservation solution as a means to alter the immunological microenvironment post transplantation using in vivo models of tracheal and aortic allograft transplantation. In all models of transplantation, grafts pre-treated with 100 ng mL^-1 of TRaM augmented preservation solution ex vivo showed a significant inhibition of chronic rejection post-transplantation, as compared to UW augmented with free rapamycin at a ten-fold higher dose. Here, for the first time, we present a novel method of organ pretreatment using a nanotherapeutic-based cellular targeted delivery system that enables donor administration of rapamycin, at a ten-fold decreased dose during cold storage. Clinically, these pretreatment strategies may positively impact post-transplant outcomes and can be readily translated to clinical scenarios.

Incidence and impact of adverse drug events contributing to hospital readmissions in kidney transplant recipients

BACKGROUND

The incidence and impact of adverse drug events (ADEs) leading to hospitalization and as a predominant risk factor for late graft loss has not been studied in transplantation.

METHODS

This was a longitudinal cohort study of adult kidney recipients transplanted between 2005 and 2010 and followed through 2013. There were 3 cohorts: no readmissions, readmissions not due to an adverse drug event, and adverse drug events contributing to readmissions. The rationale of the adverse drug events contribution to the readmission was categorized in terms of probability, preventability, and severity.

RESULTS

A total of 837 patients with 963 hospital readmissions were included; 47.9% had at least one hospital readmission and 65.0% of readmissions were deemed as having an ADE contribute. The predominant causes of readmissions related to ADEs included non-opportunistic infections (39.6%), opportunistic infections (10.5%), rejection (18.1%), and acute kidney injury (11.8%). Over time, readmissions due to under-immunosuppression (rejection) significantly decreased (-1.6% per year), while those due to over-immunosuppression (infection, cancer, or cytopenias) significantly increased (2.1% increase per year [difference 3.7%, P = .026]). Delayed graft function, rejection, creatinine, graft loss, and death were all significantly greater in those with an ADE that contributed to a readmission compared the other two cohorts (P < .05).

CONCLUSION

These results demonstrate that ADEs may be associated with a significant increase in the risk of hospital readmission after kidney transplant and subsequent graft loss.

Utilization of the Iliac Artery as Inflow in the Morbidly Obese During Orthotopic Liver Transplantation: A Case Report

Arterial conduits are a well-recognized technique used in liver transplantation to achieve allograft arterial inflow when conventional hepatic arterial inflow is compromised. Indications for ectopic inflow include native arterial disease at the time of initial transplantation, as well as reconstruction in the setting of thrombotic complications. Although supraceliac or infrarenal aortic reconstructions are preferred approaches, the right common iliac artery represents a viable alternative. We present the case of a morbidly obese patient with occlusive atheromatous plaque at the celiac origin not amenable to preoperative angioplasty who underwent reconstruction with a donor iliac artery conduit to the recipient right common iliac artery. His hepatic arterial inflow remained patent postoperatively with no thrombotic or hemorrhagic complications.

Nanotechnological Approaches to Immunosuppression and Tolerance Induction

PURPOSE OF REVIEW

Several preclinical studies have engineered nanoparticles for immune regulation, and have shown promising results in the fields of autoimmunity and cancer. In solid organ transplantation, the use of nanoparticle-based immune regulation has only just begun to emerge but holds significant promise for the improvement of our current standard of care immunosuppressive regimens. In this review, we will shed light on the current status of nanoparticle-engineered immunotherapeutics, and the potential application of these technologies to the field of organ transplantation. Further we discuss different strategies for delivery and potential cellular targeting moieties that could be utilized to obviate the need for high dose systemic immunosuppressive regimens.

RECENT FINDINGS

Recent studies have shown the potential of immunosuppressive laden nanoparticles to increase bioavailability, drug release, and specifically target immune cell compartments as methods to provide recipient immunosuppressive sparing strategies.

SUMMARY

Nanoparticle centered immunosuppressive strategies hold the potential to usher in a new era in transplant recipient management and could hold the key to minimizing off-target effects of immunosuppressants, along with prolonging transplant survival.

Incidence, risk factors, and outcomes of opportunistic infections in pediatric renal transplant recipients

OIs present significant risks to patients following solid organ transplantation. The purpose of this study was to identify risk factors for the development of OIs after kidney transplantation in pediatric patients and to evaluate the impact of OIs on outcomes in this patient population. A single-center retrospective longitudinal cohort analysis including pediatric patients 21 yr of age or younger transplanted from July 1999 to June 2013 at an academic medical center was conducted. Patients were excluded if they received multi-organ transplant. A total of 175 patients were included in the study. Patients who developed OIs were more likely to be female and younger at the time of transplant. A six-factor risk model for OI development was developed. Death, disease recurrence, and PTLD development were similar between groups but trended toward increased incidence in the OI group. Incidence of rejection was significantly higher in the OI group (p = 0.04). Patients who developed OIs had several important risk factors, including younger age, EBV-negative serostatus, CMV donor (+)/recipient (-), biopsy-proven acute rejection, ANC <1000, MMF dose >500 mg/m(2), and any infection. Incidence of rejection was higher in the OI group, but rate of graft loss was not statistically different.

A simplified cuff technique for abdominal aortic transplantation in mice

BACKGROUND

Allograft arteriopathy is still a leading cause of late organ failure. The aortic allograft model in mice has been used to study chronic rejection and has given useful information in the development of graft arteriosclerosis. However, the technical difficulties of small vessel anastomoses still continue to limit its widespread use. We introduce a new simple method for aortic transplantation in mice.

METHODS

The descending aorta or infrarenal aorta from the donor mouse was anastomosed to the infrarenal aorta using a cuff technique. Aortic transplantation was performed in 30 mice, 10 isografts and 20 allografts. No immunosuppression was administered, and the recipients were sacrificed at day 28. The grafts were histologically analyzed.

RESULTS

Implantation of grafts could be completed in an average of 23 min. There was no technical failure in all 60 anastomoses. The overall survival rate was 93.3%. Histology of aortas revealed typical aspects of chronic rejection in the allografts at day 28. No significant lesion was observed in isografts.

CONCLUSIONS

We have developed an innovative, stable, and simple aortic transplantation model in mice, which is useful for vascular research in transplantation and beyond.

Immunosuppressive nano-therapeutic micelles downregulate endothelial cell inflammation and immunogenicity

In this study, we developed a stable, nontoxic novel micelle nanoparticle to attenuate responses of endothelial cell (EC) inflammation when subjected to oxidative stress, such as observed in organ transplantation. Targeted Rapamycin Micelles (TRaM) were synthesized using PEG-PE-amine and N-palmitoyl homocysteine (PHC) with further tailoring of the micelle using targeting peptides (cRGD) and labeling with far-red fluorescent dye for tracking during cellular uptake studies. Our results revealed that the TRaM was approximately 10 nm in diameter and underwent successful internalization in Human Umbilical Vein EC (HUVEC) lines. Uptake efficiency of TRaM nanoparticles was improved with the addition of a targeting moiety. In addition, our TRaM therapy was able to downregulate both mouse cardiac endothelial cell (MCEC) and HUVEC production and release of the pro-inflammatory cytokines, IL-6 and IL-8 in normal oxygen tension and hypoxic conditions. We were also able to demonstrate a dose-dependent uptake of TRaM therapy into biologic tissues ex vivo. Taken together, these data demonstrate the feasibility of targeted drug delivery in transplantation, which has the potential for conferring local immunosuppressive effects without systemic consequences while also dampening endothelial cell injury responses.

Internal biliary stenting during orthotopic liver transplantation: anastomotic complications, post-transplant biliary interventions, and survival

BACKGROUND

Biliary complications are a leading source of surgical morbidity following orthotopic liver transplantation (OLT).

METHODS

We examined how prophylactic internal biliary stent placement during OLT affected post-transplant morbidity and mortality in a single-center retrospective cohort study of 513 recipients (2006-2012). Recipient and donor covariates were collected. Biliary complications included major and minor anastomotic leaks, strictures, or stenoses. Multivariate regression models were created to estimate how operative biliary stents affected outcomes.

RESULTS

About 87.3% (n = 448) of recipients had a duct-to-duct biliary anastomosis, and 43.1% (n = 221) had biliary stents placed. The biliary complication rate was <15% at five yr, and 44.8% (n = 230) overall. Stenting was not protective from anastomotic biliary complications (p = 0.06). Stenting was associated with a 74% higher adjusted risk of needing multiple endoscopic retrograde cholangiographies (ERCs; odds ratio [OR] 1.74, p = 0.011), and trended toward a lower adjusted risk for repetitive percutaneous transhepatic cholangiography (PTCs; OR 0.56, p = 0.063). Stenting had no effect on the cumulative freedom from biliary complications (p = 0.94). Biliary complications were associated with mortality (HR 1.86, p = 0.014) and was unaffected by stenting (aHR = 0.72, p = 0.246).

CONCLUSIONS

Biliary stenting during OLT does not deter biliary complications and is associated with higher risk of multiple invasive biliary interventions, particularly ERCs. Surgeons should evaluate the utility of biliary stents at OLT within this context.

Cardiovascular risk factors contribute to disparities in graft outcomes in African American renal transplant recipients: a retrospective analysis

Data examining cardiovascular (CV) risk factors in renal transplant recipients (RTRs) and their contribution to the disparity in graft survival between African American (AA) patients and non-AAs is limited. A single-center, retrospective analysis of 1003 adult RTRs from January 1, 2000 to May 1, 2008 to inspect the impact of race on post-transplant CV events, treatment of CV risk factors and their independent influence on graft outcomes was performed. AAs experienced a higher incidence of late graft loss, with 1- and 5-year graft survival rates of 93% and 76% vs 95% and 84% in the non-AA group, respectively. AA patients had a higher prevalence of hypertension (HTN) and diabetes mellitus (DM) and demonstrated reduced control of DM post-transplant (AA 74% vs non-AA 82%, p = 0.053). Multivariate analysis for graft survival indicated acute rejection, delayed graft function (DGF) and incidence of CV events were significant risk factors for graft failure, while the use of beta-blockers, angiotensin-converting enzyme (ACE) inhibitors or angiotensin II receptor blockers (ARBs) and 3-hydroxy-3-methyl-glutaryl-coenzyme A (HMG-CoA) reductase inhibitors were protective. In conclusion, after controlling for CV risk factors and events, race did not have an independent effect on outcomes, suggesting CV risk factors and events contribute to this disparity. Clinical summary. AAs experienced a higher rate of graft failure and CV events; after adjusting for multiple immunological and CV risk factors, race no longer remained an independent risk factor for post-transplant CV events or graft failure; although disparities in post-transplant outcomes remain, race alone does not account for the disparity; the racial disparity is due to the higher incidence of DGF and acute rejection, as well as traditional CV risk factors, including HTN and DM.

Epstein-Barr virus (EBV) related acute liver failure: a case series from the US Acute Liver Failure Study Group

PURPOSE

Acute liver failure (ALF) is a rare clinical syndrome associated with a high case fatality rate. Asymptomatic primary infection with Epstein-Barr virus (EBV) is common in the general population while acute hepatitis and jaundice are much less common and ALF has been rarely reported. We reviewed the presenting features as well as clinical outcomes amongst consecutive adults with EBV-related ALF.

METHODS

Amongst the 1,887 adult ALF patients enrolled into the US ALF Study Group from January 1998 to February 2012, there were four patients (0.21 %) with EBV-related ALF. Diagnostic criteria for acute EBV infection included compatible serologies and/or the detection of EBV-encoded RNA (EBER) in liver tissue.

RESULTS

Median patient age was 30 years (range 18-44); 75 % were male, and only 25 % were immunosuppressed. The median presenting ALT was 504 IU/mL (range 156-4,920), median Alk P was 431 (range 136-1,009), and median bilirubin was 17 mg/dL (range 13-22.1). Liver biopsy findings ranged from cholestasis to submassive necrosis with EBER + staining in two of the three samples tested. Although all of the patients were treated with an antiviral agent, two died of ALF, one underwent liver transplantation (LT) and one survived with supportive care and is well at 5 years. A review of the literature identified four additional LT recipients with favorable long-term outcomes.

CONCLUSION

Primary EBV infection accounts for <1 % of consecutive adult ALF cases but is associated with a high case fatality rate. LT is associated with favorable short- and long-term outcomes.

A prospective, randomized trial of complete avoidance of steroids in liver transplantation with follow-up of over 7 years

OBJECTIVES

Steroids are a mainstay of treatment in orthotopic liver transplantation (OLT) and are associated with significant morbidity. This trial was conducted to assess the efficacy of steroids avoidance.

METHODS

Patients undergoing OLT between June 2002 and April 2005 were entered into a prospective, randomized trial of complete steroids avoidance and followed until November 2011. Recipients received either standard therapy (n = 50) or complete steroids avoidance (n = 50). Analyses were performed on an intention-to-treat basis. The mean follow-up of all recipients was 2095 ± 117 days. Sixteen (32%) recipients randomized to the steroids avoidance group ultimately received steroids for clinical indications.

RESULTS

Incidences of diabetes and hypertension prior to or after OLT were similar in both groups, as was the incidence of rejection. Patient and graft survival rates at 1, 3 and 5 years were lower in the steroids avoidance group than in the standard therapy group (patient survival: 1-year, 80% versus 86%; 3-year, 68% versus 76%; 5-year, 60% versus 72%; graft survival: 1-year, 76% versus 76%; 3-year, 64% versus 74%; 5-year, 56% versus 72%), but the differences were not statistically different.

CONCLUSIONS

Complete steroids avoidance provides liver transplant recipients with minimal benefit and appears to result in a concerning trend towards decreased graft and recipient survival. The present data support the use of at least a short course of steroids after liver transplantation.

Low-dose rapamycin treatment increases the ability of human regulatory T cells to inhibit transplant arteriosclerosis in vivo

Regulatory T cells (T(reg)) are currently being tested in clinical trials as a potential therapy in cell and solid organ transplantation. The immunosuppressive drug rapamycin has been shown to preferentially promote T(reg) expansion. Here, we hypothesized that adjunctive rapamycin therapy might potentiate the ability of ex vivo expanded human T(reg) to inhibit vascular allograft rejection in a humanized mouse model of arterial transplantation. We studied the influence of combined treatment with low-dose rapamycin and subtherapeutic T(reg) numbers on the development of transplant arteriosclerosis (TA) in human arterial grafts transplanted into immunodeficient BALB/cRag2(-/-) Il2rg(-/-) mice reconstituted with allogeneic human peripheral blood mononuclear cell. In addition, we assessed the effects of the treatment on the proliferation and apoptosis of naïve/effector T cells. The combined therapy efficiently suppressed T-cell proliferation in vivo and in vitro. Neointima formation in the human arterial allografts was potently inhibited compared with each treatment alone. Interestingly, CD4(+) but not CD8(+) T lymphocytes were sensitive to T(reg) and rapamycin-induced apoptosis in vitro. Our data support the concept that rapamycin can be used as an adjunctive therapy to improve efficacy of T(reg)-based immunosuppressive protocols in clinical practice. By inhibiting TA, T(reg) and rapamycin may prevent chronic transplant dysfunction and improve long-term allograft survival.

Inflammatory Ly-6C(hi) monocytes play an important role in the development of severe transplant arteriosclerosis in hyperlipidemic recipients

Objective

Transplant arteriosclerosis (TA) restricts long-term survival of heart transplant recipients. Although the role of monocyte/macrophages is well established in native atherosclerosis, it has been studied to a much lesser extent in TA. Plasma cholesterol is the most important non-immunologic risk factor for development of TA but the underlying mechanisms are largely unknown. We hypothesized that monocyte/macrophages might play an important role in the pathogenesis of TA under hyperlipidemic conditions.

Methods

We studied TA in fully mismatched arterial allografts transplanted into hyperlipidemic ApoE^−/− recipients compared to wild-type controls. The recruitment of distinct monocyte populations into the grafts was tracked by in vivo labelling with fluorescent microspheres. We used antibody-mediated depletion protocols to dissect the relative contribution of T lymphocytes and monocytes to disease development.

Results

In the hyperlipidemic environment the progression of TA was highly exacerbated and the inflammatory CD11b⁺CD115⁺Ly-6C^hi monocytes were preferentially recruited into the neointima. The number of macrophage-derived foam cells present in the grafts strongly correlated with plasma cholesterol and disease severity. Depletion of Ly-6C^hi monocytes and neutrophils significantly inhibited macrophage accumulation and disease progression. The accelerated monocyte recruitment occurs through a T cell-independent mechanism, as T cell depletion did not influence macrophage accumulation into the grafts.

Conclusions

Our study identifies for the first time the involvement of inflammatory Ly-6C^hi monocytes into the pathogenesis of TA, particularly in conditions of hyperlipidemia. Targeted therapies modulating the recruitment and activation of these cells could potentially delay coronary allograft vasculopathy and improve long-term survival of heart transplant recipients.