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OBJECTIVES It was previously shown that the combination of clopidogrel and everolimus reduced the development of transplant arteriosclerosis. The aim of this study was to investigate whether delayed onset of treatment, similar to the clinical situation after heart transplantation, inhibits progression of transplant arteriosclerosis. METHODS Fully allogeneic C57BL/6 (H2-b) donor aortas were transplanted into CBA.J (H2-k) recipients treated with clopidogrel and everolimus alone or in combination starting on Days 1, 7 or 14. Grafts were analysed by histology and alloantibodies were detected by fluorescence activated cell sorting after transplantation. RESULTS Delayed platelet inhibition with clopidogrel reduced the development of transplant arteriosclerosis [neointima formation (Day 14): 50 ± 4 vs 84 ± 9% (control)]. The combination of clopidogrel and everolimus almost abolished formation of transplant arteriosclerosis when therapy was started on Day 1 [neointima formation (Day 1): 14 ± 5 vs 84 ± 9% (control)] and also showed a remarkable reduction in both delayed treatment groups [neointima formation (Day 7): 24 ± 7 vs 84 ± 9% (control); neointima formation (Day 14): 28 ± 11 vs 84 ± 9% (control)]. Platelet inhibition alone and in combination with everolimus resulted in reduced alloantibody production. CONCLUSIONS These results demonstrate that delayed treatment with clopidogrel and everolimus—representative of a clinical setting—prevents the progression of transplant arteriosclerosis and impairs humoral immunity in this experimental model. [ABSTRACT FROM PUBLISHER]

Plerixafor, a hematopoietic stem cell mobilization agent, increases the peripheral blood content of effector and regulatory T cells and may have beneficial effects on cardiac allograft vasculopathy. The aim of the current study was to evaluate its effects in a murine aortic allograft model using different application procedures. Allogeneic donor aorta grafts (n = 8/group) from C57BL/6 mice(H2b) were abdominally transplanted into CBA mice (H2k). Plerixafor application was performed either continuously for 14 d using abdominally implanted osmotic pumps (1 mg/kg/d) or i.p. with a single dose (1 and 5 mg/kg) on day 0 or pulsed injections of 1 mg/kg on days 0, 7, 14, and 21. Cell distribution was monitored by FACS. Aortic grafts were evaluated for neointima development by Elastica-van-Gieson on day 30. Immunofluorescence and intragraft gene expression analysis were performed. On day 14, significantly fewer hematopoietic stem cells were found in the bone marrow of all plerixafor-treated mice. In the pulsed application group, significantly more hematopoietic stem cells were found in the peripheral blood on day 14 (0.045 ± 0.002%; p < 0.01 [pulsed]; versus 0.0068 ± 0.002% [control]) and also more regulatory T cells. PCR revealed lower inflammatory cytokines. The luminal occlusion was significantly reduced in the pulsed treated group (33.65 ± 8.84 versus 53.13 ± 12.41) going along with decreased neointimal CD4+ T cell and plasmacytoid dendritic cell infiltration, as well as less smooth muscle cell proliferation. The application of plerixafor attenuates chronic rejection in aortic allografts via immunomodulatory effects. Injection of repeated low-dose plerixafor is the most effective application form in the aortic transplant model., (Copyright © 2024 by The American Association of Immunologists, Inc.)

Objectives: Endomyocardial biopsies are the criterion standard in diagnosing acute cardiac transplant rejection. This study sought to analyze mRNA expression profiles of various immuneresponse-related genes in endomyocardial biopsies of heart transplant patients and to correlate the results with histologic findings., Materials and Methods: Forty-three biopsies obtained from 6 heart transplant recipients experiencing acute rejection were analyzed for granzyme B, CTLA4, IL-6, TGF-beta, and TNFa expression using real-time polymerase chain reaction. The results were compared with the histologic findings. Biopsies obtained before, during, and after acute rejection episodes were grouped according to the International Society of Heart and Lung Transplantation standard biopsy grading from 1990. Group 1 consisted of biopsies with International Society of Heart and Lung Transplantation grade 0 (n=12), group 2 of International Society of Heart and Lung Transplantation grade 1A (n=14), and group 3 of International Society of Heart and Lung Transplantation grades 1B, 2, 3A, and 4 (n=17)., Results: A strong correlation was seen between histologic groups and gene expression of granzyme B, which showed the highest overall transcript levels. CTLA4 was elevated in group 2, but no further increase in the rejecting group 3 was seen. For IL-6, TGF-beta, and TNFa gene expression was strongly elevated in group 3 compared with groups 1 and 2. On analysis of biopsies with International Society of Heart and Lung Transplantation, grade 0 and 1A, relative to the time point of rejection, we found a substantial increase in mRNA expression of all analyzed immune response-related genes before a rejection episode. The strongest up-regulation was seen for granzyme B, TNFa, and TGF-beta., Conclusions: Our data suggest that analyses of gene expression provides valuable information in diagnosing heart transplant rejection. Furthermore, analyses of granzyme B, TGF-beta, and TNFa might not only confirm an ongoing rejection episode, but also may have a positive predictive value.