Transplant Vasculopathy Research Articles

Prognostic value of multislice computed tomography coronary angiography (CTCA) in cardiac transplant vasculopathy

Prognostic value of multislice computed tomography coronary angiography (CTCA) in cardiac transplant vasculopathy

OR56: PROTEIN TYROSINE KINASES SRC AND PI3K REGULATE HLA-II ANTIBODY-INDUCED SURVIVAL PROTEIN EXPRESSION IN ENDOTHELIAL CELLS

Antibody-mediated rejection (AMR) is caused by the development of donor-specific antibodies against polymorphic HLA molecules expressed by the transplanted organ. AMR is a sequential process leading to arterial and parenchymal damage, and ultimately transplant vasculopathy (TV) and graft dysfunction. Endothelial cell (EC) apoptosis followed by vascular repair and remodeling contribute to chronic rejection and development of TV. The pro-survival/anti-apoptotic molecules expressed by EC are members of the Bcl-2 protein family including Bcl-2 and Bcl-xL. The aim of this study was to determine whether HLA-II Ab triggers anti-apoptotic protein expression in EC. HLA-II expression was induced in primary human aortic EC by recombinant adenovirus pAd/PL-DEST encoding CIITA (Ad-CIITA), HLA-II transactivator, or treatment with TNFα and IFNγ. HLA-II expression was determined by flow cytometry, phosphorylation of protein kinase and expression of Bcl-2 and Bcl-xL was measured by Western Blot. Infection of EC with Ad-CIITA or pretreatment of EC with cytokines induced a marked increase in HLA-II expression, including DP, DQ, and DR. Ligation of HLA-II antigens on Ad-CIITA infected or cytokine pretreated EC stimulated a significant increase in phosphorylation of Src, PI3K and activation of mTORC1 pathway including increased phosphorylation of S6K and S6RP. Class II ligation also triggered phosphorylation of the mTORC2-targets Akt and ERK. To determine if class II-mediated mTORC2 activation regulates anti-apoptotic protein function we studied the effect of HLA-II ligation on Bcl-2 and Bcl-xL expression. Stimulation of EC with HLA-II Ab increased Bcl-2 and Bcl-xL expression at 24 h which was completely inhibited by pretreatment with the pharmacological inhibitors rapamycin and KU targeting mTORC2. Pretreatment of EC with the MEK inhibitor UO126 blocked HLA-II Ab-induced BclxL expression, but not Bcl-2 expression indicating ERK is upstream of Bcl-xL but not Bcl-2. Ligation of HLA-II with Ab on EC triggered intracellular signal cascades promoting cell survival via two distinct pathways. These studies support a role for HLA class II-mediated pro-survival signaling in the setting of chronic rejection in which antibodies promote endothelial cell survival contributing to TV.

OR22: LIGATION OF HLA CLASS II MOLECULES BY HLA ANTIBODIES INDUCES ENDOTHELIAL CELL PERMEABILITY AND MONOCYTE TRANSENDOTHELIAL MIGRATION

Aim Leukocyte extravasation plays a major rolein the development of allograft rejection and transplant vasculopathy and consists of multiple processes, including leukocyte capture, firm adhesion, transmigration, and loss of endothelial cell integrity causing barrier dysfunction. Ligation of HLA class I molecules by antibodies (Ab) elicits signaling events in endothelial cells (EC) leading to EC cell migration, proliferation and leukocyte recruitment. We hypothesize that ligation of HLA class II molecules on EC by Ab contributes to chronic rejection by transducing intracellular signaling cascades leading to cytoskeletal remodeling, increase in EC permeability and monocyte transmigration. Methods Class II expression on primary EC was achieved by infection with adenoviral recombinant Class II Transactivator (CIITA) subcloned in pAd/PL-DEST. EC were treated with murine mAb against class II (F26C6G1). Stress fiber formation was assessed using Texas Red-phalloidin staining. Protein phosphorylation was assessed by Western blot. Changes in EC permeability were measured by VE-cadherin staining and FITC-dextran permeability. Monocyte MM6 recruitment to EC was measured by immunofluorescence microscopy and monocyte transendothelial migration was determined using a transwell assay. Results Anti-class II Ab significantly increased ERK phosphorylation, stimulated stress fiber formation, reduced VE-cadherin localization in EC junctions and enhanced FITC-dextran permeability. ERK inhibitor UO126 pretreatment abrogated class II-induced stress fiber formation, reversed VE-cadherin expression in EC junctions, and attenuated class II-stimulated FITC-dextran permeability. In addition, treatment of EC with anti-class II antibodies induced a 2-4-fold increase in the recruitment and transmigration of monocytes, which was attenuated by treatment with the ERK inhibitor U0126 or recombinant PSGL1 that blocks monocyte capture. Conclusions Ab ligation of HLA class II molecules on EC stimulates activation of the ERK signaling pathway and actin cytoskeleton remodeling leading to barrier dysfunction and monocyte transendothelial migration. Elucidation of the class II signaling pathways has the potential to identify novel therapeutic targets for treatment of chronic rejection.

Fibroblast growth factor receptor 1 is a key inhibitor of TGFβ signaling in the endothelium.

Abnormal vascular homeostasis can lead to increased proliferation of smooth muscle cells and deposition of extracellular matrix, resulting in neointima formation, which contributes to vascular lumen narrowing, a pathology that underlies diseases including transplant vasculopathy, the recurrence of stenosis, and atherosclerosis. Growth of neointima is in part due to endothelial-to-mesenchymal transition (EndMT), a transforming growth factor-β (TGFβ)-driven process, which leads to increased numbers of smooth muscle cells and fibroblasts and deposition of extracellular matrix. We reported that endothelial cell-specific knockout of fibroblast growth factor receptor 1 (FGFR1) led to activation of TGFβ signaling and development of EndMT in vitro and in vivo. Furthermore, EndMT in human diseased vasculature correlated with decreased abundance of FGFR1. These findings identify FGFR1 as the key regulator of TGFβ signaling and EndMT development.

Abstract 153: IL-10 Accelerates Re-Endothelialization and Inhibits Post-injury Intimal Hyperplasia following Carotid Artery Denudation by Attenuating TNF-alpha-induced Endothelial Cell Dysfunction

The association of inflammation with atherosclerosis and restenosis is now fairly well established. Restenosis, a persistent complication of percutaneous vascular interventions, is thought to be a complex response to injury, which includes early thrombus formation, neointimal growth and acute inflammation. Mononuclear phagocytes are likely participants in the host response to vascular injury, via the secretion of cytokines and chemokines, including TNF-alpha (TNF). Others and we have previously shown that IL-10 inhibits TNF and other inflammatory mediators produced in response to cardiovascular injuries. The specific effect of IL-10 on endothelial cell (EC) biology is not well elucidated. Here we report that in a mouse model of carotid denudation, IL-10 knock-out mice (IL10KO) displayed significantly delayed ReEndothelialization and enhanced neointimal growth compared to their WT counterparts. Exogenous treatment of recombinant IL-10 dramatically blunted the inflammatory cell infiltration and neointimal thickening while significantly accelerating the recovery of the injured endothelium both WT and IL10KO mice. In vitro, IL10 co-treatment reversed TNF-mediated growth arrest, EC cell cycle inhibition, EC-monocyte adhesion and EC apoptosis. At signaling level, IL-10 reduced TNF-induced activation of JNK MAP kinase while simultaneously activating PI3K/Akt pathway. Because IL-10 function and signaling are important components for control of inflammatory responses, these results may provide insights necessary to develop strategies for modulating vascular repair and other accelerated arteriopathies, including transplant vasculopathy and vein graft hyperplasia.

Role of Macrophage Subsets in Chronic Allograft Rejection and Novel Strategies to Target Them.

chronic rejection or transplant vasculopathy is a major problem in the clinic hindering long-term transplant survival. Chronic rejection primarily targets the graft vasculature, but the exact mechanism underlying the slow and progressive vasculature damage in transplanted organs remains poorly defined. In the present study, we addressed the role of macrophages in chronic allograft rejection in a mouse heart transplant model. We found that treatment of B6 recipients with a single dose of CTLA-4Ig prolonged the survival of Balb/c heart allografts(MST=35d) as compared to untreated controls (MST=8 days). Histologically, the CTLA-4Ig treated grafts showed signs of extensive chronic rejection characterized by heavy leukocyte infiltration and prominent neointima formation. Phenotypically, macrophages were a key infiltrating cell type in the vascular lesions in the grafts. Further studies revealed a M2 (F4/80+CD206+) phenotype for grafting infiltrating macrophages. An increased number of M2 macrophages were also detected in the spleen of recipient mice that experienced chronic rejection. We polarized macrophages in vitro to M1 and M2 subsets and systemically screened for differences and specific pathways that could be targeted for inhibition of M1 and M2 macrophages. We showed that when macrophages were polarized to a M2 phenotype, they preferentially expressedP2x7 receptor, a member of P2x family receptors that sense metabolites. We also found that oxidized ATP (P2x7R inhibitor)could effectively inhibit M2 induction in vitro. Importantly, in the heart transplant model, CTLA-4Ig plus oxidized ATP induced long-term heart allograft survival(MST>100 days), which was associated with markedly reduced neointima generation in the grafts, and prevention of chronic rejection was associated with significant inhibition of M2 macrophages in situ. Our studies identified a previously unknown mechanism of transplant vasculopathy and pinpointed as a molecular target in the inhibition of infiltrating M2 macrophages and chronic rejection.

DN Treg Cells Specifically Suppress Cognate Alloreactive Memory T Cell By Granzyme B, and Prolong Allograft Survival.

[Background] Since the emphasis of clinical organ transplant survival moved from short term to long term, memory T (Tm) cell, by mediating several key-mechanisms such as transplant vasculopathy and allograft nephropathy, has been recognized as an essential culprit of long term organ rejection. It is inherently resistant to conventional therapies such as apoptosis-induction and co-stimulation-blockade, yet indispensable to the recipient's protective immunity against environmental pathogens. In this study, we show that double-negative (DN) Treg cell might be a delicate solution to this dilemma. [Methods and Results] DN Tregs specifically suppress cognate B6-anti-Balb/c CD8+ Tm both in vitro (suppression rate: 53.9±1.2%), and in vivo, with the CD8+ Tm cell-mediated graft rejection delayed from (21.5±1.7)-day to (63.0±4.7)-day in a BALB/c to B6Rag1-/- skin transplantation, but with no effect on anti-C3H Tm. Both CD8+Tem and Tcm compartments are significantly suppressed by DN Treg. We further identified the suppression as Granzyme B (GzmB)- and perforin (PFN)-dependent. Intriguingly, CD4+ Tm cells resist DN Treg both in vitro and in vivo. For the first time, we found CD4+ Tm highly express Serine Protease Inhibitor-6 (Spi6) ((5.03±1.15)-fold of CD4+ Teff, protein level), an inhibitor of GzmB. The deficiency of Spi6 sensitized CD4+ Tm both in vitro (suppression rate: 10.5±5.8% to 37.5±6.2%) and in vivo (skin-allograft survival from (28.3±5.7)-day to (75.5±7.9)-day) to killing by DN Tregs. Whereas the restored sensitivity can be again abrogated in vitro (suppression rate: 4.5±3.2%) and in vivo (skin-allograft survival (22.5±2.4)-day) by PFN-deficiency in DN Tregs. [Conclusion] In summary, DN Tregs specifically suppress cognate allo-reactive CD8+ Tm cells by GzmB-PFN pathway, and effectively delay CD8+ Tm cell-mediated graft rejection without compromising Tm cell-dependent protective immunity. The fact that CD4+ Tm resists DN Treg by highly expressing Spi6 and can be sensitized by Spi6-deficiency underlines the essential role of Spi6 in CD4+ Tm cell fate, which also shed light to the possibility of combining DN Treg and Spi6-targeting therapy to even further improve long-term allograft survival.

N-Octanoyl-Dopamine Attenuates Transplant Vasculopathy in Rat Aortic Allografts by Smooth Muscle Cell Preservation.

N-Octanoyl-Dopamine Attenuates Transplant Vasculopathy in Rat Aortic Allografts by Smooth Muscle Cell Preservation.

Identification of Novel Mechanisms of Tolerance Resistance Induced By OX40.

Induction of donor specific tolerance remains an important goal in transplantation and to identify and overcome barriers to tolerance will significantly improve transplant outcomes in the clinic. In the present study, we examined the effector programs that evade tolerance induction by costimulatory blockade in a mouse heart transplant model. Blocking CD40-CD40L costimulation using an anti-CD40L monoclonal antibody (MR1) induced prolonged survival of C57BL/6 heart allografts in BALB/c recipients (MST>60 days). However, we found that MR1 completely failed to prolong survival of heart allografts that express the OX40L transgene (OX40Ltg grafts) (MST=9 days), indicating that OX40 signaling evades tolerance induction by costimulatory blockade. Histologically, rejection of OX40Ltg heart allografts was associated with extensive lymphocyte infiltration, and a significant proportion of graft infiltrating T cells produced IL-9 (40%), while few of them produced IL-4 or IFN-γ, suggesting that OX40 may drive a new mechanism of tolerance resistance. In an in vitro T cell polarization assay, we showed that OX40 engagement inhibited the induction of TH17 cells by TGF-β/IL-6 and that of inducible Treg cells by TGF- β/IL-2. Instead, OX40 diverted CD4+ T cells to IL-9 producing TH9 cells. Mechanistically, OX40 signaling mediated the induction of TH9 cells by triggering noncanonical NF-κB activation in activated T cells. In an in vivo CFSE model in which CD4+ T cells were stimulated by alloantigens, blocking CD40-CD40L costimulation induced TH9 cells only in the presence of OX40 signaling. These data suggest that induction of TH9 cells may constitute a novel mechanism of tolerance resistance. Interestingly, blocking OX40 costimulation induced long-term heart allograft survival (MST>100 days) and markedly reduced transplant vasculopathy (chronic allograft rejection) in CD40L-/- recipient mice. In conclusion, we identified that OX40 dramatically induces the generation of TH9 cells both in vitro and in vivo, and TH9 cells are closely involved in tolerance resistance. These findings may lead to the development of new therapeutics to promote graft tolerance in transplantation.

Chronic rejection in vascularized composite allografts.

To convey key issues surrounding chronic rejection in vascularized composite tissue allotransplantation (VCA), and to highlight pathologic features consistent with VCA chronic rejection. Features consistent with chronic rejection have been reported in three VCA animal models, and have been observed in a paucity of human knee and hand transplants. These features include transplant vasculopathy with intimal hyperplasia, tertiary lymphoid follicles, graft fibrosis, and graft edema. Transplant vasculopathy has been the most consistent finding across cases, and has resulted in graft dysfunction and loss. Antibody-mediated rejection has not been conclusively reported in animal models or human subjects, although some cases have demonstrated donor-specific antibody in conjunction with C4d deposition. Multiple immunologic and non-immunologic mechanisms of VCA chronic rejection have been proposed. As in solid organ transplantation, chronic rejection in VCA remains ill-defined. Transplant vasculopathy appears to be a key feature of chronic VCA rejection, whereas tertiary lymphoid follicles, graft fibrosis, and graft edema appear to be less-specific findings. Intimal hyperplasia can be detected with advanced imaging modalities.

206 Prospects for Utilisation of Late Outgrowth Endothelial Progenitor Cells as Therapy to Prevent Transplant Vasculopathy

Renal transplantation is a successful treatment for patients with renal failure but its long-term efficacy is limited by untreatable transplant vasculopathy (TA). Endothelial damage contributes to TA and is potentially...

How much do we really know about statins and transplant vasculopathy?

It is the responsibility of a major medical journal to publish information that will constructively influence patient care. Optimally, each manuscript should transmit a ‘take-home message’. And this one does. So, let us track the evolution of the message presented in the review by Som et al. [1] in this issue of the World Journal of Surgery. When the Framingham Heart Study began in 1948, hypertension and a rising plasma cholesterol were considered to be routine and inevitable consequences of aging. However, physicians rapidly recognized that blood pressure control was good. But, manipulation of plasma cholesterol is conceptually trickier.

MHC class I signaling: new functional perspectives for an old molecule.

Donor-specific antibodies are associated with refractory rejection episodes and poor allograft outcomes in solid organ transplantation. Our understanding of antibody-mediated allograft injury is expanding beyond complement deposition. In fact, unique mechanisms of alloantibodies are advancing our knowledge about transplant vasculopathy and antibody-mediated rejection. These include direct effects on the endothelium, resulting in the recruitment of leukocytes, chemokine and cytokine production, and stimulation of innate and adaptive alloresponses. These effects will be the focus of the following review.

Everolimus Inhibits Anti-HLA I Antibody-Mediated Endothelial Cell Signaling, Migration and Proliferation More Potently Than Sirolimus

Antibody (Ab) crosslinking of HLA I molecules on the surface of endothelial cells triggers proliferative and pro-survival intracellular signaling, which is implicated in the process of chronic allograft rejection, also known as transplant vasculopathy (TV). The purpose of this study was to investigate the role of mammalian target of rapamycin (mTOR) in HLA I Ab-induced signaling cascades. Everolimus provides a tool to establish how the mTOR signal network regulates HLA I-mediated migration, proliferation and survival. We found that everolimus inhibits mTOR complex 1 (mTORC1) by disassociating Raptor from mTOR, thereby preventing class I-induced phosphorylation of mTOR, p70S6K, S6RP and 4E-BP1, and resultant class I-stimulated cell migration and proliferation. Furthermore, we found that everolimus inhibits class I-mediated mTORC2 activation (1) by disassociating Rictor and Sin1 from mTOR; (2) by preventing class I-stimulated Akt phosphorylation and (3) by preventing class I-mediated ERK phosphorylation. These results suggest that everolimus is more effective than sirolimus at antagonizing both mTORC1 and mTORC2, the latter of which is critical in endothelial cell functional changes leading to TV in solid organ transplantation after HLA I crosslinking. Our findings point to a potential therapeutic effect of everolimus in prevention of chronic Ab-mediated rejection.

Lower dosing of enteric-coated mycophenolate sodium (Myfortic) can achieve target mycophenolic acid exposure rapidly in most Chinese renal transplant patients: a pilot study

There are few pharmacokinetic data for enteric-coated mycophenolate sodium (EC-MPS) in Chinese kidney transplant recipients. Previously, we demonstrated that patients with 540mg EC-MPS reached target exposure on day 4 after transplantation. The aim of this study was further to confirm that mycophenolic acid (MPA) delivery with a daily total dose 1080mg EC-MPS is adequate during the early-phase posttransplantation and preliminarily assess the pharmacokinetics after a single dose and multiple doses of EC-MPS in Chinese live-donor kidney transplant recipients. Twelve patients (eight men and four women, mean age 41.3±6.78years) treated with EC-MPS, cyclosporine and corticosteroids were included in this study. Patients received a single oral dose of EC-MPS 540mg, then 540mg twice daily. MPA concentrations were measured by high-performance liquid chromatography. Twelve-hour pharmacokinetic profiles were obtained after the single oral dose and multiple doses on day 4 postoperation. The pharmacokinetic parameters were compared between a single dose and multiple doses. By using multiple stepwise regression analysis, we obtained two predictive equations of MPA systemic exposure. Bland-Altman analysis was developed to test agreement between the observed MPA area under the concentration-time curve (AUC) and the predicted MPA AUC. The mean (range) MPA AUC was 42±14.67 (29.29-75.95) mg/lh after the first dose, and 44.72±14.57 (32.06-80.79) mg/lh on day 4 after operation. MPA exposure provided by a single dose and multiple doses were similar (p>0.05). The best equations obtained were the following: 20.003+1.181C6h +7.22C8h (r=0.936) and 17.023+3.11C1h +1.245+4.988C8h (r=0.964). These equation models showed an optimal agreement between the observed MPA AUC and the predicted MPA AUC. Lower dosing of EC-MPS, compared with the standard dose (720mg twice daily), may provide enough MPA exposure for Chinese live-donor kidney transplant patients on day 4. Given that the MPA exposure by AUC correlates with the incidence of acute rejection episodes and transplant vasculopathy, the present findings may have clinical implications, and the optimum dose range of EC-MPS for patients in all ranges of body weight should also be determined.

431 - Connexins: A New Target for the Prevention of Transplant Vasculopathy?

The humoral immune response, particularly anti-HLA antibodies, is involved in transplant vasculopathy (TV), representing the main cause of transplant organ failure, and characterized by an intimal hyperplasia due to smooth muscle cells (SMC) proliferation. This disease is still poorly amenable to treatment. We recently reported a role for the sphingolipid pathway as a trigger for SMC proliferation elicited by anti HLA antibodies, but the precise mechanisms involved are still unclear. We hypothesized that gap-junctions (GJ) could play a role by regulating the sphingolipid pathway, and that their inhibition could prevent the development of TV.

ELEVATE: an innovative study design to assess the efficacy, safety, and evolution of cardiovascular parameters in de novo kidney transplant recipients after early conversion from a calcineurin inhibitor to everolimus

ELEVATE: an innovative study design to assess the efficacy, safety, and evolution of cardiovascular parameters in de novo kidney transplant recipients after early conversion from a calcineurin inhibitor to everolimus Markus van der Giet,1 Josep M Cruzado,2 Johan W de Fijter,3 Hallvard Holdaas,4 Zailong Wang,5 Antonio Speziale,6 Guido Junge61Department of Nephrology, Campus Benjamin Franklin, Charite'-Universitätsmedizin, Berlin, Germany; 2Department of Nephrology, University Hospital of Bellvitge, L'Hospitalet de Llobregat, Barcelona, Spain; 3Department of Nephrology, Leiden University Medical Center, Leiden, The Netherlands; 4Section of Nephrology, Department of Transplant Medicine, Oslo University Hospital, Rikshospitalet, Oslo, Norway; 5Biometrics and Statistical Science, Novartis Pharmaceuticals, East Hanover, NJ, USA; 6Research and Development, Novartis Pharma AG, Basel, SwitzerlandAbstract: Progressive decline in allograft function and cardiovascular mortality after kidney transplantation remain major clinical challenges that can potentially be addressed by the mammalian target of rapamycin (mTOR) inhibitors, everolimus and sirolimus. mTOR inhibitors maintain immunosuppressive efficacy after minimization of calcineurin inhibitor (CNI) therapy and can achieve significant long-term improvements in renal function. Recently, data have accumulated that suggest mTOR inhibitors may offer cardioprotective effects. In animal models, inhibition of mTOR leads to regression of cardiac hypertrophy, and the limited data consistently point to a remodeling benefit following heart transplantation. Experimentally, mTOR inhibitors restrict atherogenesis, confirmed clinically by intravascular ultrasound data demonstrating lower rates of transplant vasculopathy in heart transplant recipients on everolimus. Lastly, mTOR inhibitors appear to ameliorate arterial stiffness, a known risk factor for post-transplant cardiovascular events, but data remain sparse. The ELEVATE study will examine the renal effect of early conversion from CNI therapy to everolimus after kidney transplantation. Key secondary endpoints include the change in left ventricular mass index, the first time this endpoint has been included in a prospective study of an mTOR inhibitor. The occurrence of cardiovascular events will be rigorously documented and pulse wave velocity is being measured in a subpopulation of patients. Results from this innovative trial are awaited with interest.Keywords: cardiovascular, calcineurin inhibitors, ELEVATE, everolimus, kidney transplantation, mammalian target of rapamycin

Chronic allograft rejection: A significant hurdle to transplant success.

The state-of-the-art immunosuppression drugs do not ensure indefinite transplant survival, and most transplants are continuously lost to chronic rejection even years posttransplantation. This form of rejection is responsible for long-term failure of transplanted organs. The mechanisms involved in development of chronic rejection are not well-understood. One of the main features of chronic rejection is progressive luminal narrowing of graft vessels, which results in compromised blood flow, ischemia, cell death, and finally graft failure. All the existing immunosuppressive regimens are targeting acute rejection, and at present there is no available therapy for prevention of chronic rejection. Chronic rejection involves two major, but interrelated responses: The first is the host immune response against the transplant mediated primarily by alloreactive T and B cells, and the second is injury and repair of the graft (vasculopathy of graft vessels). Here we focus on recent advances in understanding the cellular and molecular aspects of chronic transplant vasculopathy and function of macrophages, topics pivotal for development of novel antichronic rejection therapies.

Abstract 19088: Synstatin: A Peptide-Based Switch to Alter the Phenotype of Vascular Smooth Muscle Cells

Introduction: Vascular proliferative diseases such as primary atherosclerosis, postangioplasty restenosis, and transplant vasculopathy reduce the likelihood of success in vascular interventions. The ability of activated vascular smooth muscle cells (vSMCs) to contribute to the vascular lesion mass and to the inflammatory state of the vessel wall after injury is well known. An understanding of the mechanistic basis of vSMC activation can result in more effective therapies for improving vascular outcomes. Hypothesis: Prior work has suggested that loss of the transmembrane receptor, syndecan-1, can de-differentiate vSMCs. Given the extended reach of the glycosaminoglycan chains of syndecan-1, we hypothesized that the interaction of syndecan-1 with other receptors and matrix molecules can affect vSMC phenotype. It has been identified that the ectodomain of syndecan-1 can regulate the activation of α v β 3 and α v β 5 integrins on mammary carcinoma cells, fibroblasts, and endothelial cells. Further, the peptide synstatin (SSTN) has been found to inhibit this interaction of syndecan-1 with the α v β 3 and α v β 5 integrins. Thus, we further hypothesized that SSTN could modulate vSMC phenotype, affording mechanistic insights into syndecan-1’s role in vSMC differentiation. Findings: We performed gene expression studies for studying the effect of SSTN addition on the differentiation of primary human aortic SMCs. Real time PCR (n=4) indicated lower levels of smooth muscle-specific differentiation markers [[Unable to Display Character: –]] smooth muscle α-actin, calponin, and smoothelin in SSTN-treated vSMCs. Further, higher levels of the inflammatory markers [[Unable to Display Character: –]] IL-6, ICAM-1, and VCAM-1, and of heparanase, an endoglycosidase which cleaves heparan sulfate (GAG) chains, were observed. This indicates that an SSTN-based tumor stopper, as proposed in literature, could potentially result in vSMC activation and increase the inflammatory state of the blood vessel wall. Conclusion: Taken together, our results support a positive role for syndecan-1 in promoting vSMC differentiation, reducing the chances of intimal hyperplasia after vascular injury. It also indicates that the interaction of syndecan-1 with the integrins α v β 3 and α v β 5 may be a necessary condition for the differentiation of vSMCs.

Small cells, big effects: the role of platelets in transplant vasculopathy

Platelets are the cellular mediator of thrombosis, but also represent an important part of the immune system. Platelets store numerous pre-formed inflammatory molecules in their granules and produce immune mediators de novo upon stimulation. Activated platelets express adhesion molecules that can interact with endothelial cells and leukocytes both at the site of inflammatory insult and in the circulation. Platelets therefore drive and potentiate vascular inflammation by direct and indirect interactions with both endothelial cells and leukocytes. Platelet activation has been associated with the pathogenesis of inflammatory diseases such as atherosclerosis, arthritis, and cerebral malaria, in addition to transplant vasculopathy. In this review we will discuss immune roles for platelets in the context of transplant vascular inflammation.