Current understanding and management of allograft vasculopathy

Cytomegalovirus Donor Seropositivity Negatively Affects Survival After Heart Transplantation

OBJECTIVES

Prior studies have shown that cytomegalovirus(CMV) infection is a risk factor for the development of cardiac allograft vasculopathy(CAV) and is associated with reduced long-term survival after heart transplantation. The aim of this ISHLT Transplant Registry study was to compare post-transplant survival in different CMV donor:recipient serologic combinations.

METHODS

We performed a retrospective cohort study, using the ISHLT Thoracic Transplant Registry, on 15,885 adult primary heart transplant recipients with known CMV serologic status between 7/2004 and 6/2014. Post-transplant survival and risk of developing CAV were compared across 4 groups: CMV-seronegative recipients(R-) receiving CMV-positive grafts(D+), intermediate-risk patients(D+R+ and D-R+), and low-risk patients(D-R-).

RESULTS

Baseline characteristics (donor/recipient age, BMI, recipient serum creatinine, blood group, donor cause of death, recipient diagnosis and ischemic time) were mostly balanced between the groups. Kaplan Meier survival analyses over a follow up of 10 years revealed significantly worse survival for both D+ groups as compared to the CMV low risk group (D+R+:56.61% (95%CI 53.94,59.41) vs. D-R-:63.09% (59.74,66.64) p<.01 and D+R-:57.69% (56.03,59.39) vs. D-R-; p<.001), whereas recipient seropositivity alone was not associated with reduced survival (D-R+ vs. D-R- p=.178). The risk of developing CAV after HTx was not significantly increased in D+ as compared to D- groups.

CONCLUSION

In a large contemporary cohort, CMV status at the time of heart transplantation was not associated with CAV development. However, there was a significant association between donor CMV seropositivity and reduced short- and long-term survival after heart transplantation. Approaches to mitigate the impact of CMV on post-transplant survival are needed.Supplemental Visual Abstract; http://links.lww.com/TP/C292.

Cytomegalovirus chemokine receptor M33 knockout reduces chronic allograft rejection in a murine aortic transplant model

BACKGROUND

Numerous studies suggest that cytomegalovirus (CMV) infection may act as isolated risk factor in the development of cardiac allograft vasculopathy (CAV). Viral G protein-coupled receptors (GPCRs) are thought to contribute to the pathogenic changes associated with CMV infection. The aim of this study was to investigate the role of murine cytomegalovirus GPCR M33 in the development of CAV in a murine aortic allograft model.

METHODS

MHC I-mismatched aortas of C.B10 (H2^b) mice were transplanted into BALB/c (H2^d) recipients, which were either mock-infected, infected with wild type (WT) MCMV or MCMV with a deleted M33-receptor gene (delM33). Persistence of cytomegalovirus infection was confirmed by qPCR and by luciferase assay to ensure active viral replication. Grafts were harvested on days 21 and 37 for intragraft mRNA expression and histological analysis.

RESULTS

Active viral replication was demonstrated and MCMV presence was confirmed by PCR within spleen, liver, salivary glands, lung and the aortic transplant. Infection with delM33 resulted in significantly less intimal proliferation compared to WT-MCMV but more pronounced proliferation than in mock-infected allografts (32.19% [delM33] vs. 41.71% [WT-MCMV] vs. 24.33% [MCMV-]). Intragraft expression of most analyzed genes was significantly increased in infected mice. VCAM-1, ICAM-1, PDGFβ, CXCR3 and Granzyme B were distinctly less expressed in grafts of delM33 infected compared to WT infected mice. Cellular infiltration revealed reduced dendritic cells and T cells in grafts infected with delM33 compared to WT MCMV.

CONCLUSIONS

These data suggest that the MCMV encoded receptor M33 plays an important role as a viral effector mechanism contributing to the development of CAV in a murine aortic transplant model.

Glibenclamide ameliorates transplant-induced arteriosclerosis and inhibits macrophage migration and MCP-1 expression

AIMS

Glibenclamide, a diabetes mellitus type 2 medication, has anti-inflammatory and autoimmune properties. This study investigated the effects of glibenclamide on transplant-induced arteriosclerosis as well as the underlying molecular events.

METHODS

Male C57Bl/6 (H-2b) and BALB/c (H-2d) mice were used for aorta transplantation. We used hematoxylin and eosin (HE) and Elastic Van Gieson (EVG) staining for histological assessment, and qRT-PCR and ELISA to measure mRNA and protein levels. Mouse peritoneal macrophages were isolated for lipopolysaccharide (LPS) stimulation and glibenclamide treatment followed by ELISA, Western blot, and Transwell assays.

RESULTS

Glibenclamide inhibited transplant-induced arteriosclerosis in vivo. Morphologically, glibenclamide reduced inflammatory cell accumulation and collagen deposition in the aortas. At the gene level, glibenclamide suppressed aortic cytokine mRNA levels, including interleukin-1β (IL-1β; 10.64 ± 3.19 vs. 23.77 ± 5.72; P < .05), tumor necrosis factor-α (TNF-α; 4.59 ± 0.78 vs. 13.89 ± 5.42; P < .05), and monocyte chemoattractant protein-1 (MCP-1; 202.66 ± 23.44 vs. 1172.73 ± 208.80; P < .01), while IL-1β, TNF-α, and MCP-1 levels were also reduced in the mouse sera two weeks after glibenclamide treatment (IL-1β, 39.40 ± 13.56 ng/ml vs. 78.96 ± 9.39 ng/ml; P < .01; TNF-α, 52.60 ± 13.00 ng/ml vs. 159.73 ± 6.76 ng/ml; P < .01; and MCP-1, 56.60 ± 9.07 ng/ml vs. 223.07 ± 36.28 ng/ml; P < .001). Furthermore, glibenclamide inhibited macrophage expression and secretion of inflammatory factors in vitro through suppressing activation of the nuclear factor-κB (NF-κB) pathway and MCP-1 production.

CONCLUSION

Glibenclamide protected against aorta transplantation-induced arteriosclerosis by reducing inflammatory factors in vivo and inhibited macrophage migration and MCP-1 production in vitro.

Lycopene Ameliorates Transplant Arteriosclerosis in Vascular Allograft Transplantation by Regulating the NO/cGMP Pathways and Rho-Associated Kinases Expression

Objective. Transplant arteriosclerosis is considered one of the major factors affecting the survival time of grafts after organ transplantation. In this study, we proposed a hypothesis of whether lycopene can protect grafted vessels through regulating key proteins expression involved in arteriosclerosis. Methods. Allogeneic aortic transplantation was performed using Brow-Norway rats as donors and Lewis rats as recipients. After transplantation, the recipients were divided into two groups: the allograft group and the lycopene group. Negative control rats (isograft group) were also established. Histopathological staining was performed to observe the pathological changes, and the expression levels of Ki-67, caspase-3, Rho-associated kinases, intercellular adhesion molecules (ICAM-1), and eNOS were assessed. Western blotting analysis and real-time PCR were also performed for quantitative analysis. Results. The histopathological staining showed that vascular stenosis and intimal thickening were not evident after lycopene treatment. The Ki-67, ROCK1, ROCK2, and ICAM-1 expression levels were significantly decreased. However, eNOS expression in grafted arteries and plasma cGMP concentration were increased after lycopene treatment. Conclusions. Lycopene could alleviate vascular arteriosclerosis in allograft transplantation via downregulating Rho-associated kinases and regulating key factor expression through the NO/cGMP pathways, which may provide a potentially effective method for transplant arteriosclerosis in clinical organ transplantation.

Prolyl-hydroxylase inhibitor activating hypoxia-inducible transcription factors reduce levels of transplant arteriosclerosis in a murine aortic allograft model

OBJECTIVES

The development of transplant arteriosclerosis, the hallmark feature of heart transplant rejection, is associated with a chronic immune response and also influenced by an initial injury to the graft through ischaemia and reperfusion. Hypoxia-inducible transcription factor (HIF)-1 pathway signalling has a protective effect against ischaemia-reperfusion injury and has already been demonstrated to ameliorate allograft nephropathy in previous animal studies. Therefore, the aim of this study was to investigate the effect of stabilization of hypoxia-inducible transcription factors with a prolyl-hydroxylase domain (PHD) inhibitor on transplant arteriosclerosis in an experimental aortic allograft model.

METHODS

MHC-class I mismatched C.B10-H2(b)/LilMcdJ donor thoracic aortas were heterotopically transplanted into the abdominal aorta of BALB/c mice. Donor animals received a single dose of the PHD inhibitor 2-(1-chloro-4-hydroxyisoquinoline-3-carboxamido) acetate (ICA) (40 mg/kg) or vehicle i.p. 4 h before transplantation. Intragraft HIF accumulation after ICA treatment was detected by immunohistochemistry before and after cold ischaemia (n = 5). Grafts were harvested 30 days after transplantation and analysed by histology (n = 7) and immunofluorescence (n = 7). In addition, intragraft mRNA expression for cytokines, adhesion molecules and growth factors was determined on Day 14 (n = 7).

RESULTS

Donor preconditioning with ICA resulted in HIF accumulation in the aorta and induction of the HIF target genes vascular endothelial growth factor and transforming growth factor-beta. Vascular lesions were present in both experimental groups. However, there was significantly reduced intimal proliferation in preconditioned grafts when compared with vehicle controls [intimal proliferation 31.3 ± 8% (ICA) vs 55.3 ± 20% (control), P < 0.01]. In addition, experimental groups revealed a down-regulation of E-selectin (-57%) and MCP1 (-33%) expression after ICA pretreatment compared with controls, going along with decreased T-cell [1.4% CD4+ T-cell infiltration vs 8.4% (control) and 4.9% CD8+ T-cell infiltration vs 10.7% (control)], dendritic cell (0.6% dendritic cells infiltration vs 1.9% infiltration(control)] and macrophage infiltration [4.8% macrophages (ICA) vs 10.9% (control)] within vascular grafts.

CONCLUSIONS

These data of an animal transplant model show that the pharmaceutical activation of HIF with endogenous up-regulation of protective target genes leads to adaptation of the graft to low oxygen-saturation and hereby attenuates the development of transplant arteriosclerosis and allograft injury. Pharmaceutical inhibition of PHDs appears to be a very attractive strategy for organ preservation that deserves further clinical evaluation.

SOCS1 prevents graft arteriosclerosis by preserving endothelial cell function

OBJECTIVES

The aim of this study was to determine the role of suppressor of cytokine signaling 1 (SOCS1) in graft arteriosclerosis (GA).

BACKGROUND

GA, the major cause of late cardiac allograft failure, is initiated by immune-mediated endothelial activation resulting in vascular inflammation and consequent neointima formation. SOCS1, a negative regulator of cytokine signaling, is highly expressed in endothelial cells (ECs) and may prevent endothelial inflammatory responses and phenotypic activation.

METHODS

Clinical specimens of coronary arteries with GA, with atherosclerosis, or without disease were collected for histological analysis. SOCS1 knockout or vascular endothelial SOCS1 (VESOCS1) transgenic mice were used in an aorta transplant model of GA. Mouse aortic ECs were isolated for in vitro assays.

RESULTS

Dramatic but specific reduction of endothelial SOCS1 was observed in human GA and atherosclerosis specimens, which suggested the importance of SOCS1 in maintaining normal endothelial function. SOCS1 deletion in mice resulted in basal EC dysfunction. After transplantation, SOCS1-deficient aortic grafts augmented leukocyte recruitment and neointima formation, whereas endothelial overexpression of SOCS1 diminished arterial rejection. Induction of endothelial adhesion molecules in early stages of GA was suppressed by the VESOCS1 transgene, and this effect was confirmed in cultured aortic ECs. Moreover, VESOCS1 maintained better vascular function during GA progression. Mechanistically, endothelial SOCS1, by modulating both basal and cytokine-induced expression of the adhesion molecules platelet/endothelial cell adhesion molecule-1, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1, restrained leukocyte adhesion and transendothelial migration during inflammatory cell infiltration.

CONCLUSIONS

SOCS1 prevents GA progression by preserving endothelial function and attenuating cytokine-induced adhesion molecule expression in vascular endothelium.

Procurement regimens to reduce ischemia reperfusion injury of vascular grafts

BACKGROUND

Ischemia reperfusion injury is an important nonimmunological factor contributing to the development of chronic rejection. The aim of this study was to compare different cell culture media in terms of vascular lesion formation after ischemia reperfusion injury.

METHODS

BALB/c aortic grafts were incubated in different cell media (endothelial cell growth, ECG, RPMI-1640 and Waymouth/Ham's F12) for various time spans (5, 6.5 and 8.5 h) at 37°C and implanted into syngeneic BALB/c recipients. On day 30 after implantation, histology, immunofluorescence and morphometric measurements were performed.

RESULTS

A total of 36 transplants were performed for this study with an overall survival rate of 72.2%. The most frequent complication was thrombosis of the aortic graft (n = 9) and there was one late death due to other courses. All the recipients with vascular grafts incubated in the ECG medium survived and showed no signs of intimal proliferation independent of the time of ischemia. Aortic grafts incubated in the RPMI medium resulted in a reduced recipient survival rate of 66.7% and grafts incubated in the Waymouth medium showed only a 50% survival by day 30. Analysis of the vascular morphology revealed moderate amounts of intimal proliferation within two aortic grafts in this group. CD31 staining revealed superior endothelial cell integrity after incubation with the ECG medium.

CONCLUSIONS

Data from the current study suggest that under optimized conditions vascular grafts can be safely kept in tissue culture up to 8.5 h without significant ischemic damage. Differences in vascular integrity and animal survival depended mostly on the respective tissue culture medium used for the storage of the vessel.

Human cytomegalovirus infection leads to elevated levels of transplant arteriosclerosis in a humanized mouse aortic xenograft model

Recent findings emphasized an important role of human cytomegalovirus (HCMV) infection in the development of transplant arteriosclerosis. Therefore, the aim of this study was to develop a human peripheral blood lymphocyte (hu-PBL)/Rag-2(-/-) γc(-/-) mouse-xenograft-model to investigate both immunological as well as viral effector mechanisms in the progression of transplant arteriosclerosis. For this, sidebranches from the internal mammary artery were recovered during coronary artery bypass graft surgery, tissue-typed and infected with HCMV. Then, size-matched sidebranches were implanted into the infrarenal aorta of Rag-2(-/-) γc(-/-) mice. The animals were reconstituted with human peripheral blood mononuclear cells (PBMCs) 7 days after transplantation. HCMV-infection was confirmed by Taqman-PCR and immunofluorescence analyses. Arterial grafts were analyzed by histology on day 40 after transplantation. PBMC-reconstituted Rag-2(-/-) γc(-/-) animals showed splenic chimerism levels ranging from 1-16% human cells. After reconstitution, Rag-2(-/-) γc(-/-) mice developed human leukocyte infiltrates in their grafts and vascular lesions that were significantly elevated after infection. Cellular infiltration revealed significantly increased ICAM-1 and PDGF-R-β expression after HCMV-infection of the graft. Arterial grafts from unreconstituted Rag-2(-/-) γc(-/-) recipients showed no vascular lesions. These data demonstrate a causative relationship between HCMV-infection as an isolated risk factor and the development of transplant-arteriosclerosis in a humanized mouse arterial-transplant-model possibly by elevated ICAM-1 and PDGF-R-β expression.

Reperfusion injury intensifies the adaptive human T cell alloresponse in a human-mouse chimeric artery model

OBJECTIVE

Perioperative nonimmune injuries to an allograft can decrease graft survival. We have developed a model for studying this process using human materials.

METHODS AND RESULTS

Human artery segments were transplanted as infrarenal aortic interposition grafts into an immunodeficient mouse host, allowed to "heal in" for 30 days, and then retransplanted into a second mouse host. To induce a reperfusion injury, the healed-in artery segments were incubated for 3 hours under hypoxic conditions ex vivo before retransplantation. To induce immunologic rejection, the animals receiving the retransplanted artery segment were adoptively transferred with human peripheral blood mononuclear cells or purified T cells from a donor allogeneic to the artery 1 week before surgery. To compare rejection of injured versus healthy tissues, these manipulations were combined. Results were analyzed ex vivo by histology, morphometry, immunohistochemistry, and mRNA quantitation or in vivo by ultrasound. Our results showed that reperfusion injury, which otherwise heals with minimal sequelae, intensifies the degree of allogeneic T cell-mediated injury to human artery segments.

CONCLUSIONS

We developed a new human-mouse chimeric model demonstrating interactions of reperfusion injury and alloimmunity using human cells and tissues that may be adapted to study other forms of nonimmune injury and other types of adaptive immune responses.

Thalidomide attenuates graft arteriosclerosis of aortic transplant in a rat model

OBJECTIVE

The purpose of the current study was to evaluate the effects of thalidomide on graft arteriosclerosis.

MATERIALS AND METHODS

Male Lewis rats received abdominal aorta grafts from male Brown-Norway rats. The animals were divided into 4 groups: no treatment controls, a low-dose group that received thalidomide (50 mg/kg per day), a middle dose group that received thalidomide (100 mg/kg per day), and a high-dose group that received thalidomide (200 mg/kg per day) by daily intragastric administration. Rats were humanely killed at 60 days after surgery. The grafted aortas were analyzed by histology, immunohistochemistry, and Western blot analysis. The serum was analyzed by an enzyme-linked immunosorbent assay (ELISA).

RESULTS

The neointimal thickness of the thalidomide treated aortas was significantly thinner compared with that of no treatment aortas (P < .05). Vascular endothelial growth factor (VEGF), platelet-derived growth factor, and intracellular adhesian molecule (ICAM-1) protein expression in the treatment group were significantly lower than those in the control group (P < .05). Moreover, thalidomide significantly inhibited the production of VEGF and ICAM-1 in serum (P < .05).

CONCLUSION

Our data suggested that thalidomide can attenuate graft arteriosclerosis so as to protect aortic grafts.

Cordyceps sinensis extracts attenuate aortic transplant arteriosclerosis in rats

BACKGROUND

Transplant arteriosclerosis is a hallmark of chronic rejection and is still the major limiting factor affecting the success of long-term organ transplants. Development of transplant arteriosclerosis is refractory to conventional immunosuppressive drugs, and adequate therapy is not yet available. The aim of this study was to determine the role of Cordyceps sinensis extracts in reducing the formation of transplant arteriosclerosis in a rat aortic transplant model.

METHODS

Lewis rat aortic allografts were transplanted into Brown-Norway recipient rats. Recipients received 0.5, 1, 2, and 5 mg/kg of Cordyceps sinensis extracts (or control saline) daily via intragastric injection for 60 d. Grafts were harvested 60 d post-transplantation and intimal thickness determined microscopically following hematoxylin and eosin (H and E) staining and abdominal aorta protein profiles determined by Western blot analysis. Cellular localization was assessed by histology and immunohistochemistry and the serum analyzed for tumor necrosis factor alpha (TNF-α) and intercellular adhesion molecule-1 (ICAM-1) by enzyme-linked immunosorbent assay (ELISA).

RESULTS

C. sinensis administration resulted in a significant reduction in neointimal formation (neointimal thickness 8.27 ± 1.95 μm [0.5 mg/kg], 3.69 ± 1.43 μm [1 mg/kg], 3.69 ± 1.43 μm [1 mg/kg], 3.69 ± 1.43 μm [1 mg/kg] versus 11.42 ± 2.67 μm [control]) and in the proliferative activity of vascular smooth muscle cells. In addition, localized expression of TNF-α and ICAM-1 in transplant aortas was characterized by immunohistochemistry and immunoblot analyses demonstrating that C. sinensis treatment significantly reduced TNF-α and ICAM-1 levels compared with levels observed in controls (P < 0.05). Serum TNF-α and ICAM-1 levels were significantly reduced in C. sinensis-treated animals compared with controls (P < 0.05).

CONCLUSION

C. sinensis treatment effectively reduced the formation of transplant arteriosclerosis in a rat aortic transplant model.

Murine cytomegalovirus infection leads to increased levels of transplant arteriosclerosis in a murine aortic allograft model

INTRODUCTION

Cytomegalovirus infection after heart transplantation is considered as risk factor for the development of transplant arteriosclerosis. Therefore, the aim of this study was to investigate the effect of murine cytomegalovirus (MCMV) as a single risk factor on transplant arteriosclerosis in an experimental aortic allograft model.

METHODS

Major histocompatibility complex class I-mismatched aortas of C.B10-H2(b)/LilMcdJ donor were transplanted into BALB/c recipients, which were either mock-infected or infected with MCMV (strain Smith) on day 7 and harvested 37 days after transplantation. In one experimental group animals received a daily dose of everolimus to increase the viral load of recipients. Grafts were analyzed by histology, morphometry, and immunofluorescence. Intragraft cytokine mRNA production was analyzed by real-time polymerase chain reaction (PCR), and persistence of cytomegalovirus infection was confirmed by TaqMan PCR.

RESULTS

After infection with MCMV, there was significantly more intimal proliferation when compared with uninfected controls (intimal proliferation 83.5%+/-9.6% [MCMV] vs. 43.9%+/-5.1% [MCMV]), indicating that MCMV plays a role in the development of transplant arteriosclerosis. Even after treatment with everolimus, MCMV infection pronounced significantly more intimal proliferation (intimal proliferation 52.5%+/-7.3% [MCMV] vs. 20.2%+/-1.7% [MCMV]). Intragraft mRNA expression showed significantly higher production of CD62E, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1 after infection with MCMV. Cellular infiltration revealed significantly more CD4, CD8, and dendritic cells. We could also confirm the presence of MCMV for the duration of the experimental protocol by PCR within the spleen, liver, salivary glands, lung, and the aortic transplant.

CONCLUSION

These data suggest that MCMV infection plays an important role in the development of transplant arteriosclerosis.

Combination of clopidogrel and everolimus dramatically reduced the development of transplant arteriosclerosis in murine aortic allografts

Our group has shown that platelet inhibition with clopidogrel, an antagonist of the P2Y12 adenosine diphosphate receptor on platelets, reduced the formation of transplant arteriosclerosis. The aim of this study was to investigate whether a combination of cyclosporin or everolimus with clopidogrel has a beneficial effect on the development of transplant arteriosclerosis. Fully MHC mismatched C57Bl/6 (H2(b)) donor aortas were transplanted into CBA.J (H2(k)) recipients and mice received either clopidogrel alone (1 mg/kg/day) or in combination with cyclosporin (2 mg/kg/day) or everolimus (0.05 mg/kg/day). Grafts were analysed by histology and morphometry on day 30 after transplantation. In mice treated with clopidogrel alone, transplant arteriosclerosis was significantly reduced [intima proliferation 56 +/- 11% vs. 81 +/- 7% (control)/n = 7]. Daily application of everolimus reduced the development of transplant arteriosclerosis compared with untreated controls [intima proliferation of 29 +/- 9% vs. 81 +/- 7% (control)/n = 7]. Strikingly, combination of clopidogrel and everolimus almost abolished the formation of transplant arteriosclerosis [intima proliferation: 11 +/- 8% vs. 81 +/- 7% (control)/n = 7]. By contrast, combination of cyclosporin and clopidogrel compared with clopidogrel alone showed no additive effect. These results demonstrate that combination of platelet- and mammalian target of Rapamycin-inhibition can dramatically reduce the development of transplant arteriosclerosis.

Attenuation of transplant arteriosclerosis with clopidogrel is associated with a reduction of infiltrating dendritic cells and macrophages in murine aortic allografts

BACKGROUND

Monotherapy with clopidogrel reduced the formation of transplant arteriosclerosis in a murine aortic allograft model. However, the underlying immunologic mechanisms are still unknown.

METHODS

Fully major histocompatibility complex-mismatched C57BL/6 (H2b) donor aortas were transplanted into CBA.J (H2k) recipients and mice received different doses (1, 10, and 20 mg/kg) of clopidogrel, an antagonist of the P2Y12 ADP receptor on platelets, or control saline for 30 days. Blood was analyzed for changes in adhesion molecule and sCD40L concentrations by ELISA. Grafts were analyzed by histology, morphometry, and immunofluorescence on day 30 after transplantation. Intragraft cytokine mRNA production was analyzed by reverse-transcriptase polymerase chain reaction on day 14 after transplantation.

RESULTS

Treatment with clopidogrel resulted in significantly decreased blood concentrations of sCD40L and P-selectin after transplantation. Cellular analysis of the aortic transplant revealed fewer numbers of infiltrating dendritic cells (CD205+) and macrophages (F4/80+) after application of clopidogrel, whereas T-cells within the graft were unaltered. In addition cellular P-/E-selectin, ICAM-1, and platelet-derived-growth-factor (PDGF)-beta surface expression were significantly reduced as compared with untreated controls. Intragraft mRNA expression confirmed these results and showed significant lower production of P-/E-selectin, ICAM-1, and PDGF-beta after treatment with clopidogrel. Antiglycoprotein-Ib and antiglycoprotein VI had no beneficial effect on the development of transplant arteriosclerosis.

CONCLUSION

This report shows that application of clopidogrel after transplantation results in a reduction in adhesion molecule expression within the blood and transplant tissue and is associated with reduced transendothelial migration of dendritic cells and macrophages within the vascular wall.

Host-derived smooth muscle cells accumulate in cardiac allografts: role of inflammation and monocyte chemoattractant protein 1

Transplant arteriosclerosis is characterized by inflammation and intimal thickening caused by accumulation of smooth muscle cells (SMCs) both from donor and recipient. We assessed the relationship between clinical factors and the presence of host-derived SMCs in 124 myocardial biopsies from 26 consecutive patients who received hearts from opposite-sex donors. Clinical and demographic information was obtained from the patients' medical records. Host-derived SMCs accounted for 3.35±2.3% of cells in arterioles (range, 0.08–12.51%). As shown by linear regression analysis, an increased number of SMCs was associated with rejection grade (mean, 1.41±1.03, p = 0.034) and the number of leukocytes (19.1±12.7 per 20 high-power fields, p = 0.01). The accumulation of host-derived SMCs was associated with an increased number of leukocytes in the allografts. In vitro, monocyte chemoattractant protein 1 (MCP-1) released from leukocytes was crucial for SMC migration. After heart allotransplantion, mice treated with MCP-1-specific antibodies had significantly fewer host-derived SMCs in the grafts than mice treated with isotypic antibody controls. We conclude that the number of host-derived SMCs in human cardiac allografts is associated with the rejection grade and that MCP-1 may play pivotal role in recruiting host-derived SMCs into cardiac allografts.

The first year post-heart transplantation: use of immunosuppressive drugs and early complications

A large number of heart transplants are performed annually in different transplant centers in the United States. This is partly because of the improved survival of patients who undergo cardiac transplantation, thus making it a more viable option in the management of end-stage heart failure. The survival benefit after heart transplantation is a result of newer immunosuppressive drug regimens and a better understanding of their effects and interactions. Several studies, mostly involving a small number of patients, describe use and comparison of the many distinct immunosuppressive drugs available to date. Interestingly, many transplant centers perform in-house typical induction treatment regimens because of their own experience and intra-institutional preference. This review summarizes current practices of immunosuppressive drug therapy in the first year post-heart transplant based on the available clinical evidence and discusses future options of heart transplant immunosuppressive drug therapies.

Interferon-γ Axis in Graft Arteriosclerosis

Cardiac transplantation is the most effective treatment for advanced heart failure. Despite improvements in immunosuppression therapy that prevent acute rejection, cardiac allografts fail at rates of 3% to 5% per posttransplant year. The hallmark morphological lesion of chronically failing cardiac allografts, also seen in chronic renal and liver graft failure, is luminal stenosis of blood vessels, especially of conduit arteries. Late graft failure results from widespread secondary ischemic injury to the graft parenchyma rather than direct immune-mediated damage. Although this process affects the entire graft vasculature, graft arteriosclerosis is a suitable term to describe the problem because it applies to different types of failing organs and because it emphasizes the central feature, namely an accelerated form of arterial injury and remodeling. The precise pathogenesis of graft arteriosclerosis is unknown. In this review, we make the case that the signature T-helper type 1 cytokine, interferon (IFN)-γ, is a key effector in graft arteriosclerosis, which, together with the IFN-γ–inducing cytokine interleukin-12 and IFN-γ–inducible chemokines such as CXCR3 ligands, constitute a positive feedback loop for T-cell activation, differentiation, and recruitment that we refer to as the IFN-γ axis. We evaluate the evidence to support this hypothesis in clinical observational and experimental animal studies. Additionally, we examine the regulation of IFN-γ production within the artery wall, the effects of IFN-γ on vessel wall cells, and the outcome of therapeutic agents on IFN-γ production and signaling. These observations lead us to suggest that new therapies for graft arteriosclerosis should be optimized which focus on reducing IFN-γ synthesis or actions.

Inhibition of Restenosis Development after Mechanical Injury: A New Field of Application for Malononitrilamides?

OBJECTIVE

To investigate the efficacy of the malononitrilamide FK778 to prevent vascular smooth muscle cell (SMC) migration/proliferation, and vascular fibrosis, the key events in restenosis development using in vivo and in vitro studies.

BACKGROUND

Since the high rate of restenosis after percutaneous transluminal coronary angioplasty limited its long-term success, the implementation of locally delivered antiproliferative/immunosuppressive agents became advantageous.

METHODS

Rats underwent balloon denudation of the abdominal aorta and received sirolimus, tacrolimus, or FK778 for 28 days in varying doses. Aortas were harvested for histologic evaluation, profibrotic gene expression, and organ chamber studies. Antifibrotic, antiproliferative and antimigratory effects of the immunosuppressants were further evaluated in vitro.

RESULTS

Histology of untreated animals revealed marked intimal hyperplasia with moderate luminal obliteration. Neointima formation was dose-dependently attenuated by all three agents with FK778 and sirolimus being most efficacious. Organ chamber relaxation studies showed a leftward shift of the nitroglycerin and the acetylcholine dose-responses in all treatment groups, indicating diminished endothelial dysfunction. In vivo, only FK778 treatment revealed a significant downregulation of the TGF-beta/vasorin system which could be explained by upregulation of the TGF-beta-inhibitory mediator SMAD7. In vitro, FK778 showed most potent antiproliferative and antimigratory effects on SMC compared with sirolimus and tacrolimus. Only the antiproliferative effect of FK778 was due to pyrimidine synthesis blockade and could be reversed by uridine supplementation.

CONCLUSIONS

The malononitrilamide FK778 proved highly efficacious against restenosis development by targeting two major components of intimal hyperplasia: SMC proliferation/migration and vascular fibrosis. Thus, the introduction of malononitrilamide-loaded stents may be a promising effort for future strategies.

Clopidogrel reduces the development of transplant arteriosclerosis

BACKGROUND

Transplant arteriosclerosis, the hallmark feature of chronic rejection, is still the major limiting factor for the long-term success of heart transplantation. Platelets have been implicated to play a role in the pathogenesis of this disease. Therefore the aim of this study was to investigate whether platelet inhibition alone has a positive effect on the development of transplant arteriosclerosis.

METHODS

Fully major histocompatibility complex-mismatched C57BL/6 (H2(b)) donor aortas were transplanted into CBA (H2(k)) recipients, and mice received different doses (1, 10, and 20 mg/kg) of clopidogrel or control saline as a daily intraperitoneal injection for 30 days. Blood was analyzed on days 2, 7, 14, and 30 by using a platelet aggregation test (adenosine diphosphate) for effectiveness of the treatment. Grafts were analyzed by means of histology and morphometry on day 30 after transplantation.

RESULTS

When mice were treated daily with 1 mg/kg clopidogrel in the absence of any other immunosuppression, transplant arteriosclerosis was significantly reduced compared with that seen in saline-treated control animals (intimal proliferation of 66% +/- 9% [1 mg/kg clopidogrel] vs 77% +/- 5% [control], n = 7, P < or = .03). Daily application of 10 mg/kg and 20 mg/kg clopidogrel also significantly reduced the development of transplant arteriosclerosis compared with that seen in control animals (intimal proliferation of 61% +/- 11% [10 mg/kg clopidogrel] vs 54% +/- 10% [20 mg/kg clopidogrel] vs 77% +/- 5% [control], n = 8, P < or = .003). There was, however, no additional beneficial effect when compared with mice treated with 1 mg/kg clopidogrel (P = .06). Isografts did not show any signs of vascular lesions on day 30 after transplantation.

CONCLUSION

These results demonstrate that monotherapy with clopidogrel can effectively reduce the formation of transplant arteriosclerosis in a murine aortic allograft model.

Normalization of Right Ventricular Performance and Remodeling Evaluated by Magnetic Resonance Imaging at Late Follow-up of Heart Transplantation: Relationship Between Function, Exercise Capacity and Pulmonary Vascular Resistance

BACKGROUND

Right ventricular (RV) dysfunction remains one of the most prominent complications during the period immediately after heart transplantation (HT); however, late adaptation of the RV has not been well described. The aim of our study was to evaluate RV function and remodeling using magnetic resonance imaging (MRI) and to correlate it with exercise capacity and also with hemodynamic data obtained before HT.

METHODS

We prospectively evaluated RV function of 25 heart-transplanted patients, without cardiac allograft vasculopathy, who were documented by negative dobutamine stress echocardiography during late follow-up (Group 1, 6 +/- 4.3 years) using MRI. We then compared Group 1 with a control group consisting of 10 patients, who were < or =1 year post-HT (Group 2), hemodynamically stable, and with the same pre-operative hemodynamic features as Group 1. Their pulmonary arterial systolic blood pressure (PSBP) varied from 17 to 67 mm Hg (43.2 +/- 15.3) and pulmonary vascular resistance (PVR) from 1.0 to 5.4 Wood units (2.5 +/- 1.12). The following parameters were studied: RV end-diastolic volume (EDV) and systolic volume (ESV); stroke volume (SV); ejection fraction (EF); and mass (M). We also evaluated the VO2 peak and slope VE/VCO2 values during a treadmill test. Data were analyzed and correlated with the hemodynamic values of PVR and PSBP obtained pre-HT.

RESULTS

In Group 1, treadmill evaluation data showed exercise VO2 peak (19.9 +/- 3.19 ml/kg/min) and slope VE/VCO2 (36.9 +/- 4.5) values comparable to those of sedentary individuals; RV variables according to MRI were within normal ranges, with the following mean values for Groups 1 and 2, respectively: RVEDV, 99.6 +/- 4.0 ml vs 127 +/- 16 ml (p = 0.03); RVESV, 42 +/- 2 ml vs 58.5 +/- 9 ml (p = 0.01); RVSV, 57 +/- 3 ml vs 71 +/- 10 ml (p = 0.1); RVEF, 58 +/- 1.4% vs 54 +/- 3.8% (p = 0.29); and RVM, 43.4 +/- 1.9 g vs 74 +/- 8.8 g (p = 0.001). There was no correlation between hemodynamic pulmonary values before HT or any other index of late RV performance, including RV remodeling and hypertrophy, in our study population (p = not significant).

CONCLUSIONS

In contrast to what we would expect for heart transplant patients at late follow-up, the RV may adapt to pulmonary pressure and resistance, with reverse remodeling characterized by volume and mass reduction, leading to normalization of RV function despite abnormal hemodynamic pulmonary values being measured before HT. There was no influence on the low exercise capacity observed in these patients, in the absence of cardiac allograft vasculopathy.

Dobutamine myocardial scintigraphy for the prediction of cardiac events after heart transplantation

BACKGROUND

The long-term outcome after heart transplantation (HTx) is essentially influenced by the occurrence and extent of cardiac allograft vasculopathy (CAV). Single photon emission computed tomography-myocardial perfusion imaging (SPECT-MPI) has been shown to be a useful and cost-effective non-invasive method in patients with known or suspected coronary artery disease, but its role in detecting CAV remains unclear.

AIM

To evaluate the accuracy and predictive value of dobutamine MPI in patients after HTx during a 12-month follow-up.

METHODS

Seventy-seven patients (60 males, 17 females) underwent a total of 216 dobutamine MPI examinations over a period of 5 years. Examinations were obtained an average of 89+/-42 months after orthotopic HTx according to a 1-day protocol using 99mTc-methoxyisobutylisonitrile (99mTc-MIBI) with and without attenuation correction. For the present study, findings from 77 MPI examinations (one MPI examination per patient) were analysed visually and semiquantitatively using a 20-segment model. Summed stress scores (SSS) and summed rest scores (SRS) were calculated and receiver operating characteristic (ROC) analysis was performed to detect optimum threshold values. Patients were followed up for 12 months and cardiac events were registered.

RESULTS

Cardiac events were observed in 10 of the 77 patients. Good interobserver agreement was found for global visual and SRS-/SSS-based analysis (kappa=0.74 and 0.66, respectively). SSS was superior to SRS in the detection of cardiac events. ROC analysis showed an optimized SSS threshold value of three. For predicting a cardiac event during the 12-month follow-up, global visual and semiquantitative analysis reached sensitivities of 90% and 90%, specificities of 72% and 88%, accuracies of 74% and 87%, positive predictive values of 32% and 53% and negative predictive values of 98% and 98%, respectively. The sensitivity, specificity, accuracy and positive and negative predictive values for MPI to detect clinically relevant coronary artery stenoses (> or =50%) at conventional coronary angiography were 83%, 87%, 86%, 56% and 96%, respectively.

CONCLUSIONS

Non-invasive dobutamine MPI reliably identifies patients at risk for subsequent cardiac events in cases of CAV, with a high negative predictive value of 98% and an accuracy of 87%.