Heterotopic Cardiac Transplantation Research Articles

Mitochondrion-targeted carboxymethyl chitosan hybrid nanoparticles loaded with Coenzyme Q10 protect cardiac grafts against cold ischaemia‒reperfusion injury in heart transplantation

BackgroundHeart transplantation (HT) has been approved as an optimal therapeutic regimen for patients with terminal-stage cardiac failure. However, cold ischaemia‒reperfusion (I/R) injury remains an unavoidable and outstanding challenge, which is a major factor in early graft dysfunction and an obstacle to long-term survival in HT. Cold I/R injury induces cardiac graft injury by promoting mitochondrial dysfunction and augmenting free radical production and inflammatory responses. We therefore designed a mitochondrion-targeted nanocarrier loaded with Coenzyme Q10 (CoQ10) (CoQ10@TNPs) for treatment of cold I/R injury after cardiac graft in a murine heterotopic cardiac transplantation model.MethodsHybrid nanoparticles composed of CaCO3/CaP/biotinylated-carboxymethylchitosan (CaCO3/CaP/BCMC) were synthesized using the coprecipitation method, and the mitochondria-targeting tetrapeptide SS31 was incorporated onto the surface of the hybrid nanoparticles through biotin-avidin interactions. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) analysis were used for characterisation. In vitro, the hypoxia-reoxygenation model of H9c2 cells was employed to replicate in vivo cold I/R injury and treated with CoQ10@TNPs. The impact of CoQ10@TNPs on H9c2 cell injury was assessed by analysis of oxidative damage and apoptosis. In vivo, donor hearts (DHs) were perfused with preservation solution containing CoQ10@TNPs and stored in vitro at 4 °C for 12 h. The DHs were heterotopically transplanted and analysed for graft function, oxidative damage, apoptosis, and inflammatory markers 1 day post-transplantation.ResultsCoQ10@TNPs were successfully synthesized and delivered CoQ10 to the mitochondria of the cold ischaemic myocardium. In vitro experiments demonstrated that CoQ10@TNPs was taken up by H9c2 cells at 4 °C and localized within the mitochondria, thus ameliorating oxidative stress damage and mitochondrial injury in cold I/R injury. In vivo experiments showed that CoQ10@TNPs accumulated in DH tissue at 4 °C, localized within the mitochondria during cold storage and improved cardiac graft function by attenuating mitochondrial oxidative injury and inflammation.ConclusionsCoQ10@TNPs can precisely deliver CoQ10 to the mitochondria of cold I/R-injured cardiomyocytes to effectively eliminate mitochondrial reactive oxygen species (mtROS), thus reducing oxidative injury and inflammatory reactions in cold I/R-injured graft tissues and finally improving heart graft function. Thus, CoQ10@TNPs offer an effective approach for safeguarding cardiac grafts against extended periods of cold ischaemia, emphasizing the therapeutic potential in mitigating cold I/R injury during HT. These findings present an opportunity to enhance existing results following HT and broaden the range of viable grafts for transplantation.

A murine groin site cardiac transplantation model-applicable tool for studying roles of peripheral lymph nodes in transplantation.

The murine heterotopic cardiac transplantation model has been widely used to study antigen-specific immune responses or new immunosuppressive agents, which have a strong correlation with peripheral lymph nodes. Thus, a new organ transplantation model that is applicable to related studies is needed. Here, we describe a groin-site murine heart transplantation model using a cuff technique, in which the donor aorta and pulmonary artery are anastomosed to the truncated femoral vessels of the recipient. The mean survival time (MST) of the grafts in BALB/c-to-C57BL/6 allo-transplant group was 7.2 ± 0.3 days, and 1.9 ± 0.2 days in BALB/c-to-Sprague-Dawley (SD) rat xeno-transplant group. H&E results show that donor hearts from both groups demonstrate typical pathological features at the endpoint. Evans Blue tracing revealed that the popliteal lymph nodes of the grafted side hindlimb are larger than those of the contralateral side. Moreover, IHC staining for CD3, CD20 shows that the germinal center and cortex region of the grafted side of popliteal lymph nodes is apparently increased than that of the contralateral side. To sum up, this model may serve as an ideal model to study the role of peripheral lymph nodes in organ transplant rejection. In addition, extra-peritoneal grafting makes a step forward in animal welfare under the 3Rs' principle (Replacement, Reduction, Refinement).

A Modified Murine Heterotopic Heart Transplant Protocol Matching Contemporary Standards of Aseptic Technique, Anesthesia, and Analgesia.

The development of experimental models of cardiac transplantation in animals has contributed to many advances in the fields of immunology and solid organ transplantation. While the heterotopic vascularized murine cardiac transplantation model was initially utilized in studies of graft rejection using combinations of mismatched inbred mouse strains, access to genetically modified strains and therapeutic modalities can provide powerful new preclinical insights. Fundamentally, the surgical methodology for this technique has not changed since its development, especially with respect to important factors such as aseptic technique, anesthesia, and analgesia, which make material impacts on postsurgical morbidity and mortality. Additionally, improvements in perioperative management are expected to provide improvements in both animal welfare and experimental outcomes. This paper reports upon a protocol developed in collaboration with a subject matter expert in veterinary anesthesia and describes the surgical technique with an emphasis on perioperative management. Additionally, we discuss the implications of these refinements and provide details on troubleshooting critical surgical steps for this procedure.

A Modified Murine Heterotopic Heart Transplant Protocol Matching Contemporary Standards of Aseptic Technique, Anesthesia, and Analgesia

The development of experimental models of cardiac transplantation in animals has contributed to many advances in the fields of immunology and solid organ transplantation. While the heterotopic vascularized murine cardiac transplantation model was initially utilized in studies of graft rejection using combinations of mismatched inbred mouse strains, access to genetically modified strains and therapeutic modalities can provide powerful new preclinical insights. Fundamentally, the surgical methodology for this technique has not changed since its development, especially with respect to important factors such as aseptic technique, anesthesia, and analgesia, which make material impacts on postsurgical morbidity and mortality. Additionally, improvements in perioperative management are expected to provide improvements in both animal welfare and experimental outcomes. This paper reports upon a protocol developed in collaboration with a subject matter expert in veterinary anesthesia and describes the surgical technique with an emphasis on perioperative management. Additionally, we discuss the implications of these refinements and provide details on troubleshooting critical surgical steps for this procedure.

Mouse Heterotopic Cervical Cardiac Transplantation Utilizing Vascular Cuffs.

Murine models of cardiac transplantation are frequently utilized to study ischemia-reperfusion injury, innate and adaptive immune responses after transplantation, and the impact of immunomodulatory therapies on graft rejection. Heterotopic cervical heart transplantation in mice was first described in 1991 using sutured anastomoses and subsequently modified to include cuff techniques. This modification allowed for improved success rates, and since then, there have been multiple reports that have proposed further technical improvements. However, translation into more widespread utilization remains limited due to the technical difficulty associated with graft anastomoses, which requires precision to achieve adequate length and caliber of the cuffs to avoid vascular anastomotic twisting or excessive tension, which can result in damage to the graft. The present protocol describes a modified technique for performing heterotopic cervical cardiac transplantation in mice which involves cuff placement on the recipient's common carotid artery and the donor's pulmonary artery in alignment with the direction of the blood flow.

Cytosporone B (Csn-B), an NR4A1 agonist, attenuates acute cardiac allograft rejection by inducing differential apoptosis of CD4+T cells

CD4+T cell-mediated acute rejection remains a major factor that affects the early survival of transplanted organs post-transplantation. Here, we reveal that nuclear receptor subfamily 4 Group A member 1 (Nr4A1) was upregulated during cardiac allograft rejection and that the increased Nr4A1 was primarily localized in intragraft-infiltrating CD4+T cells. Nr4A1 acts as a transcription factor with an important role in CD4+T cell apoptosis, differentiation and T cell dysfunction, which indicates that Nr4A1 may play a critical role in transplant rejection. Cytosporone B (Csn-B) is a naturally occurring agonist of Nr4A1, and the role of Csn-B in the physiological process of cardiac rejection is poorly defined. This study constructed an acute rejection model of abdominal heterotopic cardiac transplantation in mice and investigated whether Csn-B could attenuate acute transplant rejection by modulating the CD4+T lymphocyte response. The results showed that Csn-B prolonged murine cardiac allograft survival and reduced inflammation in allografts. Subsequently, it was confirmed that Csn-B functions by inducing non-Treg apoptosis and promoting Treg cell differentiation. Finally, we also confirmed that Csn-B attenuates acute rejection by directly targeting Nr4A1 in CD4+T cells. Our data suggest that Csn-B is a promising novel therapeutic approach for acute cardiac allograft rejection.

Low Dose Interleukin-2 Induces Exosomes with Tolerance Markers (PDL1, CD73) and Significantly Delays Development of Chronic Rejection Following Murine Heterotopic Cardiac Transplantation

Purpose Aim of the study is to determine the effect of low dose interleukin-2 (IL-2) therapy on the kinetics of induction of circulating exosomes with tolerance markers (PDL1, CD73) and their role in abrogating chronic rejection following murine heterotopic cardiac transplant (HTx). Methods Allogenic (BALB/c to C57BL/6) HTx was performed heterotopically in abdominal cavity. Costimulatory blockade consisting of MR1 (250 μg/ip day 0) and CTLA4-Ig (200 μg/ip day 2) was performed. Low dose IL-2 (2000IU/day) was administered from day 15 post-transplant for 3 weeks. Sera was collected on days 7-100 for kinetic analysis of exosome induction and characterization of PDL1, CD73, cardiac self-antigens (SAgs) (Myosin, Vimentin), class II MHC trans-activator (CIITA), and 20S proteasome by western blot using specific antibodies (Abs) and Abs to SAgs. Results BALB/c to C57BL/6 HTx rejected transplanted heart with median survival time of 8 (7-9) days. HTx done following costimulatory blockade developed chronic rejection with mean survival time 26 (7-47) days. Exosome and Ab development demonstrated induction of exosomes with Vimentin (2.2± 1.0 vs 0.6±0.1; p Conclusion Circulating exosomes containing cardiac SAgs and development of Abs to SAgs lead to chronic rejection in a murine model occurring after costimulation blockade following allogenic HTx. Low dose IL-2 abrogated chronic rejection and induced circulating exosome with tolerance markers. This result supports an important role for exosomes, inducing tolerance and significantly delaying development of chronic rejection in murine model of chronic cardiac allograft rejection.

Berberine Prolongs Mouse Heart Allograft Survival by Activating T Cell Apoptosis via the Mitochondrial Pathway.

Berberine, which is a traditional Chinese medicine can inhibit tumorigenesis by inducing tumor cell apoptosis. However, the immunoregulatory of effects berberine on T cells remains poorly understood. Here, we first examined whether berberine can prolong allograft survival by regulating the recruitment and function of T cells. Using a major histocompatibility complex complete mismatch mouse heterotopic cardiac transplantation model, we found that the administration of moderate doses (5 mg/kg) of berberine significantly prolonged heart allograft survival to 19 days and elicited no obvious berberine-related toxicity. Compared to that with normal saline treatment, berberine treatment decreased alloreactive T cells in recipient splenocytes and lymph node cells. It also inhibited the activation, proliferation, and function of alloreactive T cells. Most importantly, berberine treatment protected myocardial cells by decreasing CD4+ and CD8+ T cell infiltration and by inhibiting T cell function in allografts. In vivo and in vitro assays revealed that berberine treatment eliminated alloreactive T lymphocytes via the mitochondrial apoptosis pathway, which was validated by transcriptome sequencing. Taken together, we demonstrated that berberine prolongs allograft survival by inducing apoptosis of alloreactive T cells. Thus, our study provides more evidence supporting the potential use of berberine in translational medicine.

Monotherapy With Anti-CD70 Antibody Causes Long-Term Mouse Cardiac Allograft Acceptance With Induction of Tolerogenic Dendritic Cells.

Allograft rejection has been an obstacle for the long-term survival of patients. CD70, a tumor necrosis factor (TNF) family member critically expressed on antigen-presenting cells and strongly but transiently up-regulated during lymphocyte activation, represents an important co-stimulatory molecule that induces effective T cell responses. We used a mouse heterotopic cardiac transplantation model to evaluate the effects of monotherapy with the antibody targeting mouse CD70 (FR70) on transplantation tolerance and its immunoregulatory activity. FR70-treated C3H recipient mice permanently accepted B6 fully mismatched cardiac allografts. Consistent with the graft survival, the infiltration of CD8+ T cells in the graft was reduced, dendritic cells were differentiated into a tolerogenic status, and the number of regulatory T cells was elevated both in the graft and the recipient’s spleen. In addition, naïve C3H given an adoptive transfer of spleen cells from the primary recipients with FR70 treatment accepted a heart graft from a matching B6 donor but not third-party BALB/c mice. Our findings show that treatment with FR70 induced regulatory cells and inhibited cytotoxic T cell proliferation, which led to long-term acceptance of mouse cardiac allografts. These findings highlight the potential role of anti-CD70 antibodies as a clinically effective treatment for allograft rejection.

Skills to Perform Vessel Eversion in Mouse Cervical Cardiac Transplantation with Cuff Technique.

Introduction:The mouse heterotopic cardiac transplant model has been extensively used to explore transplant immunity. Although the cuff technique facilitates the operation, the procedure remains difficult, and vessel eversion is the most difficult step. Cuff movement and everted vessel wall slippage are the main adverse factors in vessel eversion. Traditional strategies to prevent these factors focus on cuff fixation, while more steps or surgical instruments would be required.Methods:According to the reported protocols and our experience, the vessel eversion skills were modified and used for transplantation. Cardiac grafts from C57BL/6(H-2b) or BALB/c(H-2d) mice were transplanted into C57BL/6(H-2b) mice. The operating times of recent 90 operations, which were divided into 9 groups according to their sequence, were summarized and analyzed.Results:The mouse cervical cardiac transplantation was successfully performed by using the modified vessel eversion skills. The cuff movement, which is the most important adverse factor to prevent vessel eversion, was effectively prevented. In the recent 90 operations, the total operating time was 47.3±7.9 min and the success rate was 98%.Conclusions:The modified surgical skills simplify the vessel eversion in mouse cervical cardiac transplantation with cuff technique, characterized by less cuff movement, fewer steps, and surgical instruments. Using these surgical skills, the transplant can be performed in a short time.

Heterotopic Porcine Cardiac Xenotransplantation in the Intra-Abdominal Position in a Non-Human Primate Model

Heterotopic cardiac transplantation in the intra-abdominal position in a large animal model has been essential in the progression of the field of cardiac transplantation. Our group has over 10 years of experience in cardiac xenotransplantation with pig to baboon models, the longest xenograft of which survived over 900 days, with rejection only after reducing immunosuppression. This article aims to clarify our approach to this model in order to allow others to share success in long-term survival. Here, we demonstrate the approach to implantation of a cardiac graft into the intra-abdominal position in a baboon recipient for the study of transplantation and briefly highlight our model’s ability to provide insight into not only xenotransplantation but across disciplines. We include details that have provided us with consistent success in this model; performance of the anastomoses, de-airing of the graft, implantation of a long-term telemetry device for invasive graft monitoring, and ideal geometric positioning of the heart and telemetry device in the limited space of the recipient abdomen. We additionally detail surveillance techniques to assess long-term graft function.

Optimization of the Cuff Technique for Murine Heart Transplantation.

Murine cardiac transplantation has been performed for more than 40 years. With advancements in microsurgery, certain new techniques have been used to improve surgical efficiency. In our lab, we have optimized the cuff technique with two major steps. First, we used the inner tube technique to insert a temporary inner tube into the external jugular vein and carotid artery blood vessel to facilitate eversion of the vessel over the cuff. Second, we performed complete heterotopic cardiac transplantation through the collaboration of two experienced surgeons. These modifications effectively reduced the operation time to 25 minutes, with a success rate of 95%. In this report, we describe these procedures in detail and provide a supplemental video. We believe that this report on the improved cuff technique will offer practical guidance for murine heterotopic heart transplantation and will enhance the utility of this mouse model for basic research.

Mesenchymal stem cells transfected with sFgl2 inhibit the acute rejection of heart transplantation in mice by regulating macrophage activation

BackgroundMesenchymal stem cells (MSCs) have become a promising candidate for cell-based immune therapy for acute rejection (AR) after heart transplantation due to possessing immunomodulatory properties. In this study, we evaluated the efficacy of soluble fibronectin-like protein 2 (sFgl2) overexpressing mesenchymal stem cells (sFgl2-MSCs) in inhibiting AR of heart transplantation in mice by regulating immune tolerance through inducing M2 phenotype macrophage polarization.Methods and resultsThe sFgl2, a novel immunomodulatory factor secreted by regulatory T cells, was transfected into MSCs to enhance their immunosuppressive functions. After being co-cultured for 72 h, the sFgl2-MSCs inhibited M1 polarization whereas promoted M2 of polarization macrophages through STAT1 and NF-κB pathways in vitro. Besides, the sFgl2-MSCs significantly enhanced the migration and phagocytosis ability of macrophages stimulated with interferon-γ (IFN-γ) and lipopolysaccharide (LPS). Further, the application potential of sFgl2-MSCs in AR treatment was demonstrated by heterotopic cardiac transplantation in mice. The tissue damage and macrophage infiltration were evaluated by H&E and immunohistochemistry staining, and the secretion of inflammatory cytokines was analyzed by ELISA. The results showed that sFgl2-MSCs injected intravenously were able to locate in the graft, promote the M2 polarization of macrophages in vivo, regulate the local and systemic immune response, significantly protect tissues from damaging, and finally prolonged the survival time of mice heart grafts.ConclusionsFgl2-MSCs ameliorate AR of heart transplantation by regulating macrophages, which provides a new idea for the development of anti-AR treatment methods after heart transplantation.

An Immunological Model for Heterotopic Heart and Cardiac Muscle Cell Transplantation in Rats

An Immunological Model for Heterotopic Heart and Cardiac Muscle Cell Transplantation in Rats

An Immunological Model for Heterotopic Heart and Cardiac Muscle Cell Transplantation in Rats

Heterotopic heart transplantation in rats has been a commonly used model for diverse immunological studies for more than 50 years. Several modifications have been reported since the first description in 1964. After 30 years of performing heterotopic heart transplantation in rats, we have developed a simplified surgical approach, which can be easily taught and performed without further surgical training or background. After dissection of the ascending aorta and the pulmonary artery and ligation of superior and inferior caval and pulmonary veins, the donor heart is harvested and subsequently perfused with ice-cold saline solution supplemented with heparin. After clamping and incising the recipient abdominal vessels, the donor ascending aorta and pulmonary artery are anastomosed to the recipient abdominal aorta and inferior vena cava, respectively, using continuous running sutures. Depending on different donor-recipient combinations, this model allows analyses of either acute or chronic rejection of allografts. The immunological significance of this model is further enhanced by a novel approach of in-ear injection of vital cardiac muscle cells and subsequent analysis of draining cervical lymphatic tissue.

Role for Circulating Exosomes with Cardiac Self-Antigens (Myosin and Vimentin) in the Pathogenesis of Chronic Rejection in a Murine Heterotopic Model of Cardiac Transplantation

The aim of the study is to determine the of kinetics of circulating exosomes induced with cardiac self-antigens (SAgs) (Myosin, Vimentin) and their role in de novo development of antibodies (Abs) to SAgs leading to chronic rejection following heterotopic cardiac transplantation (HTx). Allogenic (BALB/c to C57BL/6) HTx was performed heterotopically in the abdominal cavity. Costimulatory blockade consisting of MR1 (250 μg i.p.) and CTLA4-Ig (200 μg i.p.) treatment (days 0 and 2, respectively) resulted in prolongation of HTx for 45-60 days. However, histopathological analysis demonstrated chronic rejection as evidenced by myocyte damage, cellular infiltration with mononuclear cells and fibrosis. Sera were collected on days 7, 15, 30, and 45 for kinetic analysis of exosome induction, Ab development, and characterization of exosomes for cardiac SAgs, transcription factors, class II MHC trans-activator (CIITA), nuclear factor κB (NF-κB) and 20S proteasome by western blot using specific Abs. BALB/c to C57BL/6 HTx rejected heart on day 7 to 8. Sera, at the time of rejection, demonstrated exosomes with SAgs, CIITA, NF-κB and 20S proteasome. HTx done following costimulatory blockade developed chronic rejection between 45 to 60 days. Kinetic studies demonstrated induction of circulating exosomes containing SAgs; Myosin (3.3 vs 1.09; p<0.05) and Vimentin (4 vs 1.35; p<0.01), CIITA (29.4 vs 1.55; p<0.01), NF-κB (2.3 vs 1.2; p<0.05) respectively on day 15 following transplantation. 20S proteasome levels were elevated on day 30 and 45 (5.4 & 9.0 vs 1.49; p<0.01). Development of Abs to Myosin also occurred on day 15 (772±557 vs 187±50; p<0.01) and persisted till day 45 (1289±409 vs 187±50) when chronic rejection of HTx noticed. Circulating exosomes containing SAgs, transcription factors, and development of Abs to SAgs preceded development of chronic rejection in a murine model of chronic rejection occurring after co-stimulation blockade in allogenic HTx, thus, supporting an important role for circulating exosomes induced following HTx in breaking the tolerance induced by co-stimulation blockade resulting in immune responses leading to chronic rejection.

Heterotopic Cardiac Transplantation: Long-term Results and Fate of the Native Heart

The long-term results of heterotopic cardiac transplantation have not been well defined. Patient survival rates and the fate of the native heart remain unclear. This study is a retrospective review of all 46 heterotopic cardiac transplantations performed at a single institution, the Texas Heart Institute in Houston, Texas, between 1982 and 2017. Four patients who underwent heterotopic transplantation as an emergency procedure for cardiogenic shock were excluded. Three of the procedures were repeat transplantations in patients who had previously undergone heterotopic transplantation; the 3 repeat transplantations were excluded, but the original procedures were not. Follow-up was 100% complete for mortality and 77% complete (30 of 39 patients) for assessment of preoperative indication for surgery and postoperative cardiac function. For the 39 patients, the 1-year, 5-year, and 10-year survival rates were 69%, 36%, and 21%, respectively. One patient remains alive 25 years after the transplantation procedure. The most frequent indication for heterotopic transplantation was pulmonary vascular resistance greater than 4 Wood units (n= 11), followed by weight greater than 112.5 kg (n= 7). In most patients, native heart left ventricular ejection fraction stabilized over time to between 10% and 30%. Sinus rhythm was preserved in 87% (26 of 30) of native hearts at long-term follow-up. Heterotopic cardiac transplantation is an acceptable procedure that should be considered for obese patients (especially those heavier than 112.5 kg) and patients with elevated pulmonary vascular resistance (especially those with pulmonary vascular resistance >4.0 Wood units). After heterotopic transplantation, native cardiac function appears to stabilize, and there is potential for native heart recovery.

A novel 2,4-diaminopyrimidine derivative as selective inhibitor of protein kinase C theta prevents allograft rejection in a rat heart transplant model

Protein kinase C theta (PKCθ) plays a critical role in T cell signaling and is an attractive target for the treatment of T cell-mediated diseases such as transplant rejection and autoimmune disease. To identify PKCθ inhibitors, we focused on the 2,6-diamino-3-carbamoyl-5-cyanopyrazine derivative 2, which exhibited moderate PKCθ inhibitory activity. Optimization of 2 identified the 2,4-diamino-5-cyanopyrimidine derivative 16c, which exhibited potent PKCθ inhibitory activity and showed good selectivity against other PKC isozymes. Compound 16c prolonged graft survival in an in vivo rat heterotopic cardiac transplant model.

P163 Accommodation in transplantation – A new model

Aim First defined as the survival and function of an organ graft in the face of otherwise lethal immunity and inflammation, accommodation might be the most common outcome of ABO-incompatible and a frequent outcome of ABO-compatible but HLA-disparate organ grafts. Accommodation was postulated to reflect an acquired resistance to injury; however, more recent work reveals a far more complex condition reflecting predisposing factors of donor and recipient origin and dynamic processes, extending over time and beyond survival and death of cells assaulted by the immune system. The overall goal of the research was to identify and test genetic determinants of accommodation. Methods We investigated donor and recipient genes and processes potentially contributing to accommodation, as it develops over periods of days, by analysis of clinical kidney transplants, murine heterotopic cardiac transplants and cell cultures. Results Human kidney transplant recipients were found commonly to exhibit B cell responses specific for the donor. The nature of these responses anticipated rejection or absence of rejection, suggesting that qualitative aspects of immunity such clonal persistence and affinity maturation, as much as presence or absence of immunity determines graft fate. Genetic loci impacting on the character of adaptive immune responses were sought and two highly polymorphic (non-MHC) loci, TNFRSF13B and TNFRSF17, were identified. Sequencing revealed distinct regions in which variants correlated with rejection versus graft well being. Mice with gene variants introduced in the locus corresponding to the human ”rejection-associated” locus predicted the quality of immune responses to model antigens and the severity of rejection of heterotopic allografts. Conclusions These findings contribute to a larger and more complex picture of biological interactions between graft and recipients that determine whether immunity eventuates in accommodation or rejection of transplants. The interactions have implications that extend beyond organ transplantation.

Depletion of macrophages from Cytomegalovirus (CMV) latently infected donor allografts decreases CMV mediated immunopathology and prevents CMV-accelerated chronic rejection

Abstract Cytomegalovirus (CMV), a ubiquitous β-herpesvirus, is linked to acceleration of solid organ transplant vascular sclerosis (TVS) and chronic rejection (CR). Latent CMV infection increases cardiac-resident macrophages and T cells that may increase inflammation and promote allograft rejection. To investigate the role of cardiac macrophages in CMV mediated TVS/CR, macrophages were depleted from CMV+ donor allografts prior to transplantation using clodronate liposomes (clod) in our rat heart transplant model. Latently rat CMV infected donor F344 rats were treated with clod or PBS or control liposomes 3 days prior to heterotopic cardiac transplant into CMV-naïve Lewis rats and macrophage depletion was validated. Donor hearts were transplanted and monitored daily for rejection. Clod treatment significantly increased graft survival from 61 days post-transplant to 84 days. The severity of graft vessel disease was decreased compared to controls. Clod treatment significant decreased macrophage and T cell infiltration into allograft tissue versus controls. Clod treatment also altered allograft tissue protein and gene expression cytokine/chemokine profiles toward a phenotype that promotes graft survival by reducing the allograft inflammation. Clod treatment did not prevent CMV reactivation since all recipients seroconverted and CMV DNA was detectable in recipient salivary glands. Depletion of donor macrophages prior to transplant represents a novel method to modulate allograft rejection immunity and prevent the negative impact of CMV on allograft recipient survival.