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.

Inhibition of TNF-alpha reduces transplant arteriosclerosis in a murine aortic transplant model.

Experimental and clinical data provide evidence that TNF-alpha contributes to acute and chronic allograft rejection. In this study, we explored the effect of TNF-alpha blockade using the chimeric monoclonal antibody infliximab on the development of transplant arterisoclerosis in a fully mismatched aortic allograft model. Post-transplant treatment of CBA (H2(k)) recipients with 250 mug infliximab (cumulative dose 1.25 mg) reduced luminal occlusion of C57Bl/6 (H2(b)) aortic grafts on day 30 from 77 +/- 5% in untreated controls to 52 +/- 6%. Increasing the dose of anti-TNF-alpha antibody had no further beneficial effect. Treatment with human control immunoglobulin had no effect on intima proliferation. Under TNF-alpha blockade, ICAM-1 and PDGF mRNA expression within the grafts was strongly reduced, whereas iNOS expression was enhanced. The data show that TNF-alpha blockade using infliximab can reduce the development of transplant arteriosclerosis in fully mismatched murine aortic grafts.

Increased transplant arteriosclerosis in the absence of CCR7 is associated with reduced expression of Foxp3.

BACKGROUND: The chemokine receptor CCR7 plays a pivotal role in the homing of naïve T cells and regulatory T cells to secondary lymphoid organs and the migration of dendritic cells into afferent lymphatic vessels. Antigen presentation, T cell recruitment, and expansion of regulatory cells are crucial events in establishing and controlling chronic allograft dysfunction. In this study, we report an important role for chemokine receptor CCR7 in the development of transplant arteriosclerosis. METHODS: Fully major histocompatibility complex-mismatched CBA (H2) donor aortas were transplanted into BALB/c-CCR7 (H2), BALB/c-CCR7 (H2), or BALB/c-CCR7 (H2) recipients. Grafts were analyzed by histology, morphometry, and immunofluorescence on day 30 after transplantation. Intragraft cytokine mRNA production was analyzed by realtime polymerase chain reaction on day 14 after transplantation. RESULTS: After implanting fully major histocompatibility complex-mismatched donor aortas into CCR7-deficient recipients, transplant arteriosclerosis was significantly elevated. CD4 depletion resulted in a reduction of intima proliferation in CCR7 recipients whereas CD8 depletion had no effect. Analysis of aortic grafts from CCR7 recipients revealed high numbers of infiltrating CD4, F4/80, and CD205 cells. Furthermore, intragraft cytokine production showed higher levels of interleukin-4, interleukin-12, and eotaxin mRNA expression, whereas significantly lower Foxp3 mRNA expression was observed in CCR7 recipients. CONCLUSION: These data suggest that although alloantigen presentation in secondary lymphoid organs is hampered in CCR7-deficient recipients, this process may take place within the allograft itself, leading to increased formation of transplant arteriosclerosis. The decrease in Foxp3 expression despite increased in CD4 T cell infiltration indicates a reduction in T regulatory cells possibly influencing the intensity of the graft rejection.

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.