Background In transcatheter aortic valve implantation (TAVI), optimal selection of fluoroscopic projections that permit orthogonal visualization of the aortic valve plane is important but may be ...difficult to achieve. Objective We developed and validated a simple method to predict suitable fluoroscopic projections on the basis of cardiac CT datasets. Methods In 75 consecutive patients that underwent TAVI, angulations in which a 35-mm thick maximum intensity projection would render all aortic valve calcium into 1 plane were determined by manual interaction with contrast-enhanced dual-source CT datasets. TAVI operators used the predicted angulation for the first aortic angiogram and performed additional aortic angiograms if no satisfactory view of the aortic valve plane was obtained. Predicted angulations were compared with the angulation used for valve implantation. Radiation exposure and contrast use was compared between patients with accurate prediction of fluoroscopic angulations by CT and patients in whom CT failed to predict a suitable view. Results The mean difference between the predicted angulation according to CT and the angulation used for implantation was 3 ± 6 degrees. CT predicted a suitable angulation (<5-degree deviation) in 63 of 75 cases (84%). The mean number of aortic angiograms acquired in patients with correct prediction (1.02 ± 0.1) was significantly lower than in patients with incorrect prediction of the implantation angle by CT (3.0 ± 1.7; P < 0.001). Contrast agent required for the entire TAVI procedure was lower in patients with correct prediction (72 ± 36 mL vs 106 ± 39 mL; P = 0.001). Conclusion CT permits prediction of suitable angulations for TAVI in most cases.
In ischemic hearts, venous retroperfusion is a potential myocardial revascularization strategy. This study aimed to refine the technical and functional aspects of a pig model of acute myocardial ...infarction and retroperfusion with respect to the azygos connection. Global retroperfusion after ligation of the ramus interventricularis paraconalis (equivalent to the left anterior descending artery in humans) was performed in 16 Landrace pigs (Sus scrofa domestica). Coronary sinus perfusion was performed in 8 pigs (P+) but not in the other 8 (P-), and the azygos vein was ligated (L+) 4 of the 8 pigs in each of these groups but left open (L-) in the remaining animals. Hemodynamic performance (for example, cardiac output, stroke volume) was significantly better in P+L+ pigs that underwent coronary sinus perfusion with ligation of the azygos vein compared with all other animals. In addition, troponin I release was significant lower in P+L+ pigs (1.7 ± 1.3 ng/mL) than in P-L- (5.47 ± 2.1 ng/mL), P-L+ (6.63 ± 2.4 ng/mL), and P+L- (4.81 ± 2.3 ng/mL) pigs. Effective retrograde flow and thus hemodynamic stability was achieved by ligation of the azygos vein. Therefore, experiments focusing on global retroperfusion will benefit from effective inhibition of the blood flow through the azygos vein.
Summary
Experimental and clinical data provide evidence that TNF‐α contributes to acute and chronic allograft rejection. In this study, we explored the effect of TNF‐α 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 (H2k) recipients with 250 μg infliximab (cumulative dose 1.25 mg) reduced luminal occlusion of C57Bl/6 (H2b) aortic grafts on day 30 from 77 ± 5% in untreated controls to 52 ± 6%. Increasing the dose of anti‐TNF‐α antibody had no further beneficial effect. Treatment with human control immunoglobulin had no effect on intima proliferation. Under TNF‐α blockade, ICAM‐1 and PDGF mRNA expression within the grafts was strongly reduced, whereas iNOS expression was enhanced. The data show that TNF‐α blockade using infliximab can reduce the development of transplant arteriosclerosis in fully mismatched murine aortic grafts.
OBJECTIVESCytomegalovirus (CMV) infection after heart transplantation is considered as risk factor for the development of cardiac allograft vasculopathy (CAV), a serious long-term complication after ...heart transplantation. In previous work we could show that murine CMV infection (MCMV) leads to increased levels of CAV. MCMV genome encodes the G protein-coupled receptor (GPCR) M33 which is associated with virus latency and replication in the host. Therefore we analyzed if M33 knockout could prevent CMV induced CAV development.
METHODSA M33 deleted murine CMV (delM33) was created via homologous recombination. Following abdominal aortic transplantation in MHC-I mismatched mice, animals were infected with 1x106 pfu delM33 or wildtype (wt). 30 days after infection grafts were recovered and histologically analyzed for neointima formation. A second group of grafts was recovered after 14 days for qPCR analysis of cytokine expression.
RESULTSIn vivo imaging using luciferase ensured successful infection of wt and delM33 virus within treated mice. Measurement of aortic lumen obliteration caused by neointima development revealed that infection with wildtype MCMV significantly increased vessel occlusion compared to uninfected controls 41,71% ± 9,06% vs. 24,33% ± 11,70%; p<.05, n=6. Infection with M33 deleted MCMV also resulted in elevated neointima proliferation compared to controls, but this was significantly reduced as compared to wildtype infected grafts 32,19% ± 7,26% vs. 41,71% ± 9,06%; p<.05, n=6.
CONCLUSIONDeletion of the M33 receptor gene reduces MCMV promoted development of CAV after abdominal aortic transplantation in mice. Further investigations are under progress regarding the human (HCMV) US28 homologue of M33 in a genetically modified mouse model.
OBJECTIVESPrevious reports suggest a role of platelet derived growth factor (PDGF) in the development of cardiac allograft vasculopathy (CAV). The pharmaceutical blockade of tyrosine kinases may ...alter the expression of different growth factor receptorsplatelet derived growth factor (PDGF), vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF) and hereby play a role in the context of cardiac allograft vasculopathy. Therefore the aim of this study was to determine the impact of tyrosine kinase inhibition on the development of cardiac allograft vasculopathy in a mouse model.
METHODSFully allogeneic mouse aortas from C57BL/6 mice (H2b) were abdominally transplanted into CBA mice (H2k). Recipients were treated with tyrosine kinase inhibitor nintedanib (60mg/kg/d) and sacrificed on day 14 for cytokine PCR analysis of the graft or on day 30 for (immuno-) histological measurements.
RESULTSAortic grafts treated with tyrosine kinase inhibitor nintedanib showed significantly reduced neointima proliferation (33% ± 12% vs. 54% ± 13%) after 30 days. These findings go along with significantly reduced amounts of smooth muscle cells (SMC) (20% ± 9% vs. 42% ± 10%) within the neointima. Further immunofluorescence analysis revealed no relevant difference in the percentages of dendritic cells, macrophages and CD4+ T-cells within the neointima. Meanwhile, the expression of both PDGF receptor subtypes α and β was reduced within the neointima of the aortic grafts. Additionally, we found a reduced gene expression of the ligand PDGF-B, a mitogen for SMC, and of the pro-inflammatory CD40L.
CONCLUSIONPDGF receptor blockade via inhibition of receptor tyrosine kinases seems to be a promising way to prevent the development of cardiac allograft vasculopathy in a mouse model. We would speculate a direct inhibition of the migration and proliferation of smooth muscle cells with a resulting decrease of neointima formation as the mechanism of action.
Abstract Background Rodent models are a very helpful tool to investigate immunological mechanisms in allograft rejection. The aim of this study was to compare two different immunodeficient recipients ...in a humanized mouse model of arterial xenotransplantation in terms of reconstitution of the human immune system and rejection of the arterial graft. Methods Side branches of human mammary artery were transplanted as infrarenal aortic interposition grafts into C.B-17–SCID beige and C57BL/6–Rag2−/− γc−/− recipients. 7 days after surgery mice were reconstituted with 5 × 107 human peripheral blood mononuclear cells (hu PBMCs) and 30 days after reconstitution mice were sacrificed and histologic analysis was performed. Peripheral blood and splenocytes were investigated by FACS and ELISA analysis to ensure engraftment of human CD45+ cells. Results Transplant arteriosclerosis developed in non-PBMC-reconstituted C.B-17–SCID beige mice (intimal proliferation: 36.31 ± 4.37%), but significantly less in C57BL/6–Rag2−/− γc−/− recipients (intimal proliferation: 12.26 ± 5.21%). After reconstitution with 5 × 107 unfractionated human PBMCs both mouse strains showed intima proliferation 30 days after reconstitution (C.B-17–SCID beige: 28.49 ± 7.95% and C57BL/6–Rag2−/− γc−/− : 44.58 ± 11.08%). Whereas only very few human CD45+ cells were found in mouse blood and spleen of C.B-17–SCID beige mice, C57BL/6–Rag2−/− γc−/− mice revealed a reliable reconstitution. In addition, levels of human IgG and IgM within the peripheral blood were markedly higher in C57BL/6–Rag2−/− γc−/− recipients. Conclusion In this study we can show, that the use of C57BL/6–Rag2−/− γc−/− mice may be advantageous compared to C.B-17–SCID beige recipients in a humanized mouse model of vessel transplantation.
Blockade of the CD40-CD154 costimulatory pathway can prolong allograft survival, but does not prevent the development of transplant arteriosclerosis in several models. In this study, we investigated ...the mechanisms of CD40-CD154-independent transplant arteriosclerosis in major histocompatibility complex (MHC)-class I-mismatched aortic allografts.
MHC class I-mismatched CBK (H2k+Kb) donor aortas were transplanted into CBA (H2k) recipients who can only recognize the graft through CD8+ T cells and CD4+ T cells responding to the class I MHC mismatch through the indirect pathway of allorecognition. Recipients were treated with anti-CD154 antibody (MR1) alone or in combination with anti-CD8 (YTS169) or anti-interleukin (IL)-4 (11B11) antibodies. Grafts were analyzed by histology on days 30 and 60 and for intragraft mRNA expression on day 14 after transplantation.
Repeated treatment with anti-CD154 alone or in combination with anti-CD8 antibody did not prevent intimal proliferation compared with untreated controls (65%+/-6%, 62%+/-9%, and 71%+/-7% luminal occlusion, respectively, 60 days after transplantation). In both treatment groups, the expression of IL-4, IL-5, and eotaxin was increased compared with control grafts, and an eosinophilic infiltration was observed. Neutralizing IL-4 in combination with CD40-CD154 blockade and CD8+ T-cell depletion abrogated transplant arteriosclerosis (9%+/-4% luminal occlusion 60 days after transplantation).
Prolonged treatment with anti-CD154 was not able to prevent the development of transplant arteriosclerosis in MHC class I-mismatched aortic allografts, in the presence or absence of CD8+ T cells. This CD40-CD154 pathway resistant transplant arteriosclerosis was mediated by IL-4, because neutralizing IL-4 in addition to CD40-CD154 costimulation blockade and CD8+ T-cell depletion prevented its development.
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.
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.
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.
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.
Summary
Angiograms of cardiac transplant (HTx) recipients were to be evaluated in a ring experiment and a joint consensus on criteria of angiographic evaluation of coronary arteries of HTx patients ...was to be reached. Twenty‐four coronary angiograms from 11 hospitals were circulated. One hundred eighty‐eight blinded evaluations were returned. A joint evaluation by six experienced cardiologists was used as reference standard and a consensus evaluation form was developed. Significant lesions (stenosis 75%, 50% in the left main coronary artery) were diagnosed in 10/23 abnormal coronary angiograms (41.7%). Interventional revascularization was recommended in 8/10 (80%). In 21 coronary angiograms distal pruning was found and in 11/21 (52.4%) cases with distal pruning occlusion of at least one peripheral vessel was detected. The best kappa value (0.7) was found for the presence of at least one clinically significant stenosis. Agreement on the site and grade of local stenosis was much less. Some agreement on remodeling was found in assessing diffuse narrowing in the LCA (kappa = 0.371, P < 0.001). The kappa value for peripheral obliteration was 0.331 (P = 0.001). Angiographic evaluation of cardiac allograft vasculopathy, particularly of diffuse and peripheral disease and remodeling, needs standardization. This should be performed in a downward compatible improvement process.
The lack of suitable target vessels remains a challenge for aortocoronary bypass grafting in end-stage coronary heart disease. This study aimed to investigate the arterialization of cardiac veins as ...an alternative myocardial revascularization strategy in an experimental long-term model in pigs. Selective retrograde perfusion of a coronary vein (aorta to coronary vein bypass, retrobypass) before ligation of the ramus interventricularis paraconalis (equivalent to the left anterior descending artery in humans) was performed in 20 German Landrace pigs (Sus scrofa domestica). Retroperfusion of the left anterior descending vein was performed in 10 pigs (RP+) but not in the other 10 (RP-), and the vena cordis magna was ligated (L+) in 5 pigs in each of these groups but left open (L-) in the remaining animals. Hemodynamic performance (for example, cardiac output) was significantly better in the group that underwent selective retroperfusion with proximal ligation of vena cordis magna (RP+L+; 4.1 L/min) compared with the other groups (RP+L-, 2.5 L/min; RP-L+, 2.2 L/min; RP-L-, 1.9 L/min). Long-term survival was significantly better in RP+L+ pigs (112±16 d) than in all other groups. Histologic follow-up studies showed significantly less necrosis in the RP+L+ group compared with all other groups. Venous retroperfusion is an effective technique to achieve long-term survival after acute occlusion of the left anterior descending artery in a pig model. In this model, proximal ligation of vena cordis magna is essential.
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