O transplante cardíaco é a última opção terapêutica para pacientes portadores de insuficiência cardíaca grave. Apesar dos avanços na terapia imunossupressora, a rejeição continua sendo o principal obstáculo para o sucesso do transplante. No presente estudo, propõe-se avaliar o perfil de expressão gênica no tecido cardíaco. Com isso, espera-se contribuir para o melhor entendimento do processo de rejeição a nível molecular. Foram analisadas as amostras sequenciais (1, 3 e 6 meses, 1 e 2 anos pós-transplante) de biópsias endomiocárdicas em parafina de 63 indivíduos transplantados cardíacos. O diagnóstico de rejeição humoral foi realizado pela detecção de C3d e C4d do complemento na reação de imuno-histoquímica, e as expressões dos genes protetores (ADIPOR1, ADIPOR2, HMOXO-1, BCL2L1 e VEGF) e genes associados à inflamação (IL-6, TNF?, IFN?, TGF-?, AIF-1, NOS2, ICAM, VCAM e MCP-1); foram avaliadas pela reação em cadeia da polimerase quantitativa em tempo real (qPCR). As frequências de indivíduos positivos para C4d (28,6%) e vasculite (20,0%) foram significantemente maiores em relação ao teste de reatividade de anticorpos realizado nos receptores antes do transplante (6,3%). Houve mudança no perfil de expressão gênica no tecido cardíaco após o transplante, com aumento da expressão dos genes inflamatórios (AIF-1, TNF?, IL-6, NOS2 e VCAM) e diminuição da expressão dos genes protetores (ADIPOR1, ADIPOR2, BCL2L1 e VEGF). Além disso, as expressões dos genes ADIPOR1 e ADIPOR2 foram significantemente menores nos indivíduos positivos para C4d (p<0,001) e gene VEGF (p<0,001) no grupo com vasculite. Houve também uma correlação positiva entre a expressão do gene VEGF e ADIPOR1 (r=0,5688) e ADIPOR2 (r=0,5191). Por outro lado, a expressão aumentada do gene VCAM (p<0,001) foi detectada em todos os tipos de rejeição. Conclui-se que, depois do transplante, o sistema imune do receptor passou a reconhecer os antígenos do órgão transplantado. Com isso, ocorreu uma mudança no perfil de expressão gênica no enxerto cardíaco, caracterizada pela expressão aumentada dos genes inflamatórios e diminuição dos genes protetores. A expressão aumentada do gene VCAM associada à baixa expressão dos genes protetores: ADIPOR1, ADIPOR2, BCL2L1 e VEGF resultaram em maior gravidade da rejeição celular, humoral e vasculopatia do aloenxerto cardíaco. / Heart transplantation is the ultimate treatment for patients with severe heart failure. Despite advances in immunosuppressive therapy, rejection still remains the main obstacle to successful transplant. The purpose of this study is to evaluate the gene expression profile in cardiac tissue. With this we hope to contribute to a better understanding of the rejection process at the molecular level. Sequential samples (1, 3, and 6 months, 1 to 2 years post-transplant) endomyocardial biopsies paraffin of 63 heart transplant subjects were analyzed. The diagnosis of humoral rejection was performed by detection of C3d and C4d complement in immunohistochemistry and the expression of protective genes (ADIPOR1, ADIPOR2, HMOXO-1, and VEGF BCL2L1) and genes associated with inflammation (IL-6,TNF?, IFN?, TGF-?, AIF-1, NOS2, ICAM, VCAM and MCP-1); were evaluated by quantitative real-time polymerase chain reaction (qPCR). The frequency of individuals positive for C4d (28.6%) and vasculitis (20.0%) were significantly higher compared to antibodies reactivity test conducted in the recipients before transplantation (6.3%). There was a change in the gene expression profile in cardiac tissue after transplantation, with increased expression of inflammatory genes (AIF-1,TNF?, IL-6, NOS2, and VCAM) and a decreased expression of protective genes (ADIPOR1, ADIPOR2, BCL2L1, and VEGF). Furthermore, the expressions of ADIPOR1 and ADIPOR2 genes were significantly lower in C4d positive individuals (p<0,001), and VEGF (p<0,001) in the group with vasculitis. There was also a positive correlation between VEGF expression and ADIPOR1 (r=0.5688) and DIPOR2 (r=0.5191). Moreover, increased expression of VCAM (p<0,001) was detected in all types of rejection. We conclude that, after transplantation, the recipient\'s immune system began to recognize the antigens of the transplanted organ. Thus, a change in gene expression profile in cardiac graft is characterized by increased inflammatory genes and decreased expression of protective genes. Increased VCAM gene associated with lower expression of protective genes expression: ADIPOR1, ADIPOR2, BCL2L1 and VEGF resulted in increased severity of cellular and humoral rejection and cardiac allograft vasculopathy.

Estudos com células tronco mesenquimais (CTm) têm despertado grande interesse devido a seu promissor potencial terapêutico e representam uma alternativa para o tratamento de diversas patologias em diferentes órgãos, inclusive em transplante renal. A rejeição crônica é um dos maiores desafios no transplante tardio e se caracteriza por perda progressiva da função renal causado pela intensa fibrogênese no aloenxerto. Os tratamentos convencionais com imunossupressores, apesar de reduzirem significativamente as crises de rejeição aguda, não interferem na sobrevida do enxerto a longo prazo. A compreensão dos processos fisiopatológicos da doença depende de seu estudo em modelos experimentais, que são de grande importância pois também propiciam uma melhor compreensão dos possíveis tratamentos. O presente estudo teve como objetivo analisar a terapia com células-tronco mesenquimais derivadas de tecido adiposo (CTmTA) no modelo experimental de transplante renal em ratos, para estudar seu efeito na rejeição crônica e avaliar seu potencial efeito imunomodulador. O modelo foi estabelecido com ratos das linhagens isogênicas Fisher (doador) e Lewis (receptor) e os animais transplantados foram divididos em três grupos: ISO (transplante isogênico de Lewis para Lewis, n=6), ALO (transplante alogênico de Fisher para Lewis, n=6) e ALO+CTmTA (transplante alogênico, tratado com CTmTA, n=6). As CTmTA foram caracterizadas por aderência ao plástico, diferenciação nas linhagens adipogênica, condrogênicas e osteogênicas e por citometria de fluxo. Foram inoculadas 1 x 106 células na região subcapsular renal no dia da realização da nefrectomia unilateral direita (10 dias pós-transplante). Após 6 meses foram realizadas análises dos parâmetros clínicos e laboratoriais, além de análise histológica, imunohistoquímica e PCR em tempo real. As CTmTA foram eficientes em prevenir significativamente a elevação da ureia e da creatinina séricas, manter clearence de creatinina em níveis normais, e prevenir a elevação da fração de excreção de Na+ e K+. Além disso, impediram o desenvolvimento de proteinúria e da hipertensão arterial. A análise histológica mostrou uma redução significativa do infiltrado inflamatório de macrófagos e linfócitos T, além de uma diminuição da fibrose intersticial no grupo ALO+CTmTA. O tratamento com CTmTA reduziu significativamente a expressão relativa dos fatores e citocinas pró-inflamatórios tais como INF-y, TNF-alfa, IL1beta e IL-6, além de aumento importante na expressão de IL-4 e IL-10, conhecidas por seu potencial antiinflamatório. Em conclusão, o tratamento com ADMSC em um modelo experimental de transplante renal pode trazer uma nova abordagem terapêutica para controle da rejeição crônica do enxerto. A aparente modulação da resposta imune observada neste trabalho, pode estar associada a uma possível polarização de macrófagos e células T. Outros estudos pré-clínicos e clínicos são necessários para confirmar nossos resultados / Studies involving mesenchymal stem cells (MSCs) have aroused great interest due to their promising therapeutic potential representing an alternative for the treatment of several pathologies in different organs, including renal transplantation. Chronic rejection is one of the major challenges in late transplantation and is characterized by progressive loss of renal function caused by intense fibrogenesis in the allograft. Conventional immunosuppressive treatments, while significantly reducing acute rejection crises, do not interfere with long-term graft survival. Animal model of kidney transplantation can provide a better understanding of the pathophysiological processes and bring a new path to treat chronic rejection. The aim of this project was to analyze the therapy with mesenchymal stem cells derived from adipose tissue (ADMSCs) in the experimental model of kidney transplantation in rats, focus on chronic rejection and evaluate its potential immunomodulatory effect. The model was established with rats of isogenic strains Fisher (donor) and Lewis (recipient), and the transplanted animals were divided into three groups: ISO (isogenic transplantation from Lewis to Lewis, n = 6), ALO (allogenic transplant from Fisher to Lewis, n = 6) and ALO + ADMSCs (allogenic transplantation, treated with ADMSCs, n = 6). ADMSCs were characterized by adhesion to plastic, differentiation in adipogenic, condrogenic and osteogenic lines and by flow cytometry. One million of cells were inoculated under the renal capsule on the day of the right unilateral nephrectomy (10 days after transplantation). After 6 months, clinical and laboratory parameters were analyzed, as well as histological analysis, immunohistochemistry and real-time PCR. ADMSCs were effective in preventing elevation of serum urea and creatinine, elevation of the Na + and K + excretion fraction as well as maintained creatinine clearence at normal levels. Furthermore, the treatment also prevented the development of proteinuria and preserved blood pressure. Histological analysis showed a significant reduction of macrophages and T cells infiltrate, associated to a decreased of interstitial fibrosis in the ALO + ADMSCs group. In the presence of ADMSCs, there was a significant decrease in the relative expression of INF-y, TNF-alpha, IL1beta and IL-6 factors and pro-inflammatory cytokines, as well as a significant increase in the relative expression of anti-inflammatory cytokines as IL-4 and IL-10. In conclusion, treatment with ADMSC in a transplantation model could open a new approach to control chronic rejection. This apparent modulation of the immune response may be associated with a possible polarization of macrophages and T cells. Further pre-clinical and clinical studies are needed to confirm our findings

Cardiac transplantation is governed by complex immunological mechanisms contributing to different types of allograft rejection. Early non-specific graft failure and chronic rejection (cardiac allograft vasculopathy) represent the main limitations for the recipients’ short- and long-term survival respectively. To date, the pathogenesis of both rejection types remains ill-defined. However, it is believed that they are related to an immunologically mediated potent inflammatory process, occurring whether early after transplantation (acute), or lasting for the lifetime of the graft (chronic).<p> <p>The initiating mechanisms of chronic rejection in solid organ transplantation remain ill-defined. Emerging evidence sustains that graft vasculopathy is primarily driven by alloreactive CD4+ T lymphocytes sensitized by the indirect pathway of allorecognition. To date, whereas the nature of APCs involved in this particular pathway has yet to be identified, it appears challenging to speculate that recipient-derived endothelial cells (ECs) repopulating the graft may represent the main cell targets recognized by indirectly primed alloreactive CD4+ T cells to mediate the rejection of cardiac transplants. In the first part of this thesis, we specifically studied the indirect pathway of allorecognition with a transgenic mice (Marilyn mice) model that expresses a T cell receptor (TCR) transgene which recognizes the male antigen H-Y in an I-Ab-restricted fashion. Our results provide evidence that graft endothelium replacement by recipient-type cells expressing MHC Class II molecules is required for the chronic rejection of vascularized cardiac transplants mediated by indirect pathway alloreactive CD4+ T cells.<p><p>The purpose of the second part of the thesis was to investigate the potential implication of interleukin-22 (IL-22), an early phase secreted proinflammatory cytokine of the IL-10 family, in the acute rejection of cardiac allografts. IL-22 was recently described as an effector key modulator of the inflammatory process produced mainly by differentiated CD4+ T cells of the Th17 lineage. As being closely related to IL-10 and IL-17, both involved in the rejection process of vascularized heart allografts, we attempted to determine the precise role of IL-22 in this process. Experiments were conducted with a recently developed murine model deficient for the IL-22 gene (IL-22KO). The results of the second part of the thesis show that IL-22 is not an effector cytokine in cardiac allograft rejection. In contrast, as being early expressed into the allograft, likely IL-22 plays a protective role in the inflammation leading to acute cardiac rejection, probably depending on a neutrophil-related mechanism. <p><p><p>In conjunction with current understanding of inflammatory and antigen-specific events in allografts, overall, our results provide new insights into the mechanisms of chronic and acute cardiac rejection, thus prompting to further interrogations and appealing novel therapeutic strategies. Pharmacologic manipulation of endothelium is challenging. Given their capacity to sense and rapidly respond to the local environment, ECs are the ideal targets for rapid systemic delivery of therapeutic agents. Combination therapy is required to reduce inflammatory reaction and endothelial activation, to modulate endothelial dysfunction and promote endothelial survival. Also, given that IL-22 may alleviate tissue destruction during inflammatory responses, therapies that enhance its production and protective action in the transplanted organs seem attractive to specifically affect tissue responses, without exerting direct effects on the immune response.<p><p><p> / Doctorat en Sciences médicales / info:eu-repo/semantics/nonPublished

Acute allograft rejection remains a major problem in solid organ transplantation, because rejection may lead to acute or chronic loss of graft function. The failure of certain anti-rejection prophylactic treatments suggests that several unexpected pathways might be involved in the rejection process.<p>The aim of our experiments was to investigate the effector mechanisms responsible for skin graft rejection in mice. To adress this question, we took advantage of the possibility to restrict the alloimmune response to isolated allogeneic MHC class II molecules or to isolated minor transplantation antigens, combined with the possibility to study separately the response of CD4+ or CD8+ T cells in mice deficient for Th1 or Th2 cytokines or cytotoxic molecules. We used the bm12 skin graft combination (C57BL/6 H2Kbm12 grafted on C57BL/6 H2Kb) as a model of single MHC class II disparity and the b2microglobulin skin graft model (C57BL/6 b2m+/+ grafted on C57BL/6 b2m-/-) as a model of minor transplantation antigen disparity. Our goal was to engage a limited number of effectors, trying in a second time to block each rejection pathway selectively. <p>We showed that Fas/FasL-mediated CD4+ T cells cytotoxicity, eosinophil recruitment, activation and degranulation induced by Th2 derived cytokines, and CD4-derived IFN-g production are involved in the rejection of grafts bearing either a single MHC class II disparity or b2m-derived minor histocompatibilty antigens. In addition, rejection of MHC class II disparate skin grafts also includes the participation of neutrophils, in particular conditions where the occurrence of the Th2/eosinophil pathway was prevented. <p>Altogether, our data show a multiplicity and a redundancy of the effector pathways participating in allograft rejection. Among the different effectors pathways identified, including effectors from both innate and adaptive immune systems, some act synergistically, whereas others act as alternative pathways, depending of the degree of donor-recipient mismatch. / Doctorat en Sciences médicales / info:eu-repo/semantics/nonPublished

La greffe d'îlots de Langerhans permet de traiter le diabète de type 1 en restituant une insuline-sécrétion. La moitié des patients reprend l'insuline dans les 5 ans. Cette perte de fonction s'explique par l'absence d'outils de monitoring. Le but de notre travail était de déterminer l'efficacité de l'IRM à diagnostiquer un rejet de greffe, et d'évaluer l'intérêt du monitoring cellulaire chez les patients.Imagerie IRM chez le ratMéthodes : Des îlots syngéniques, allogéniques ou xénogéniques ont été greffés par voie intra-portale à des rats diabétiques après marquage avec une nanoparticule de fer (ferucarbotran). Les IRM étaient réalisées dans une IRM clinique 3T.Résultats : La décroissance du signal était différente suivant les 3 types de greffes. Le signal IRM des greffes allogéniques était significativement plus bas à J4 alors que la glycémie était normale. En prenant un seuil de 84% à J4, l'IRM permet d'obtenir une sensibilité de 91% et une spécificité de 70% Innnuno-monitoring cellulaireMéthodes : Des réactions lymphocytaires mixtes étaient réalisées entre les PBMC des patients greffés, et les splénocytes des donneurs. La réaction immunitaire était évaluée par la sécrétion d'IFNy (ELISpot), par la prolifération cellulaire (cytométrie du flux du Ki67), et par le dosage des cytokines (Bioplex). Le résultat était corrélé à la fonction du greffon évaluée par le (3-score).Résultats : Les patients avec une mauvaise fonction montraient une plus grande réactivité anti-donneur avec l'ELISpot IFNy (p=0,007, r=-0,50) et l'index de prolifération (p=0,006, r=-0,51). Les patients avec une mauvaise fonction avaient des taux d'IFNy, IL-5 et IL-17 plus élevés. / Langerhans islet transplantation allows curingtype 1 diabetes by restoring an endogenous insulin secretion. Halfof patients will resume insulin withinyears. This loss of function may be explained by the lack of monitoring tools able to diagnose an ongoing graft failure. The aims of our work were toevaluate the efficiency of MRI to diagnose islet graft rejection, and to assess the feasibility of immune cellular monitoring in transplanted patients.MRI in the rat mortelMethods: Syngeneic, allogeneic and xenogeneic islets were transplanted intra-portally to diabetic rats after labeling with superparamagnetic ironoxide nanoparticles (ferucarbotran). Images were acquired on a clinical 3T MRI scanner.Results: The signal decreasing was different between the 3 types of transplantations. At day 4, the MRI signal in allogeneic group was significantlylower while glycaemia remained normal. With a cut-off value of 84% at day 4, sensitivity of 91% and specificity of 70% were obtained.Cellular immune monitoringMethods: Mixed lymphocyte cultures were performed with peripheral blood mononuclear cells from recipients and splenocytes from donors. Immunereactivity was assessed by the release of IFNy (ELISpot), cell prolifération (flow cytometry of Ki67), and cytokine quantification (Bioplex). Theresults were correlated to the islet graft function assessed by (5-score.Results: Patients with low islet function showed higher cellular reactivity against donor cells assessed by ELISpot IFNy ((p=0,007, r=-0,50) andproliferation index (p=0,006, r=-0,51). Patients with low graft function had higher levels of IFNy, IL-5 and 1L-17.

Costimulation blockade protocols are promising alternatives to the use of chronic immunosuppression for promoting long-term allograft survival. However, the efficacy of costimulation blockade-based protocols is decreased by environmental insults such as viral infections. For example, lymphocytic choriomeningitis virus (LCMV) infection at the time of costimulation blockade treatment abrogates skin allograft survival in mice. In this dissertation, we test the hypothesis that viruses shorten allograft survival by activating the innate immune system through pattern-recognition receptors (PRRs), such as toll-like receptors (TLRs). To investigate the role of innate immunity in shortening allograft survival, costimulation blockade-treated mice were co-injected with TLR2 (Pam3Cys), TLR3 (polyinosinic:polycytidylic acid, poly(I:C)), TLR4 (lipopolysaccharide, LPS), or TLR9 (CpG DNA) agonists, followed by transplantation with skin allografts 7 days later. Costimulation blockade prolonged skin allograft survival that was shortened in mice coinjected with TLR agonists. To investigate the underlying mechanisms of this observation, we used synchimeric mice, which circulate trace populations of anti-H2b transgenic alloreactive CD8+ T cells. In synchimeric mice treated with costimulation blockade, co-administration of all four TLR agonists prevented deletion of alloreactive CD8+ T cells. These alloreactive CD8+ T cells 1) expressed the proliferation marker Ki-67, 2) upregulated CD44, and 3) failed to undergo apoptosis. We also demonstrate that costimulation blockade-treated CD8α-deficient mice exhibit prolonged allograft survival when co-injected with LPS. These data suggest that TLR agonists shorten allograft survival by impairing the apoptosis of alloreactive CD8+T cells. We further delineate the mechanism by which TLR agonists shorten allograft survival by demonstrating that LPS and poly(I:C) fail to shorten allograft survival in IFNRI- deficient mice. Interestingly, the ability of poly(I:C) to more potently induce IFN-α/β than LPS correlates with its superior abilities to shorten islet allograft survival and induce allo-specific CTL activity as measured by an in vivo cytotoxicity assay. The ability to shorten allograft survival and induce IFN-α/β is a TLR-dependent process for LPS, but is a TLR-independent process for poly(I:C). Strikingly, the injection of IFN-β impairs alloreactive CD8+T cell deletion and shortens allograft survival, similar to LPS and poly(I:C). These data suggest that LPS and poly(I:C) shorten allograft survival by inducing IFN-α/β through two different mechanisms. Finally, we present data showing that viruses (LCMV, Pichinde virus, murine cytomegalovirus and vaccinia virus) impair alloreactive CD8+T cell deletion and shorten allograft survival, in a manner comparable to LPS and poly(I:C). Similar to LPS, LCMV and MCMV exhibit an impaired ability to shorten allograft survival in MyD88-deficient mice. These data suggest that the MyD88 pathway is required for certain viruses and TLR-agonists to shorten allograft survival. In this dissertation, we present data supporting an important role for TLRs and IFN- α/β in shortening allograft induced by costimulation blockade. Our findings suggest that targeting these pathways during the peri-transplant period may enhance the efficacy of costimulation blockade protocols in the clinic.

No description available.

Le rejet d’allogreffe dépend de la reconnaissance d’antigènes d’histocompatibilité étrangers par le système immunitaire du receveur. En l'absence de thérapies immunosuppressives, la réaction inflammatoire éventuelle conduit à la destruction rapide du tissu transplanté. Le rôle critique joué par les lymphocytes T CD4+ dans le rejet aigu d'allogreffe est bien établi. Cependant, les contributions respectives des lymphocytes CD4+ Th1 et Th2 dans la réaction de rejet sont controversées. Alors que le rôle des cellules Th1 dans la pathogénèse du rejet est bien établi, l'hypothèse que les cellules Th2 favorisent l'acceptation de la greffe est invalide puisque ces cellules sont capables de déclencher des voies alternatives de rejet. En effet, la fonction effectrice des lymphocytes Th2 a été démontrée dans beaucoup de modèles de rejet de greffe ou de tumeur, et dans la maladie du greffon contre l'hôte. Les caractéristiques principales du rejet de type Th2 sont sa dépendance envers la production d'IL-4 et d'IL-5, le recrutement d'éosinophiles au site du rejet, et son inhibition par les lymphocytes T CD8+ alloréactifs. Les éosinophiles activés exercent leur activité cytotoxique par la libération de plusieurs molécules cytotoxiques comme l’EDN, l’ECP, la MBP et l’EPO. Ces molécules sont probablement responsables de la capacité des éosinophies à affecter la perméabilité vasculaire et à induire des dégâts tissulaires dans les organes rejetés.<p><p>L'interleukine 9 (IL-9) est une cytokine produite par les lymphocytes T qui joue un rôle important dans les voies effectrices Th2. Dans la littérature, l’IL-9 est fortement associée au développement de l’éosinophilie tissulaire. Dans notre première étude, nous avons analysé le rôle joué par l'IL-9 dans le rejet d'allogreffe bm12 par des souris B6 (pour C57BL/6), un modèle dans le lequel une simple disparité au niveau de la molécule du CMH de classe II favorise une réaction inflammatoire de type Th2. Dans ce modèle, de faible alloantigénicité, les greffes cardiaques bm12 survivent presque indéfiniment dans les receveurs B6 (>60 jours). Nos expériences ont été conçues afin de savoir si l’expression de l’IL-9 au niveau de la greffe pouvait modifier la survie de greffes cardiaques exprimant les alloantigènes bm12. Nous avons ainsi montré que la production locale d’IL-9 induit le rejet des allogreffes cardiaques exprimant l’alloantigène I-Abm12 (survie <30jours). Aucun des organes transgéniques pour l’IL-9 n’a survécu plus de 30 jours alors que des greffes non transgéniques ne furent pas rejetées (>50 jours). L’analyse histologique des allogreffes cardiaques transgéniques pour l’IL-9 montre une infiltration cellulaire dense du myocarde. La composante principale de cet infiltrat est la présence de nombreux éosinophiles. <p><p>Pour étudier la contribution des cytokines de type Th2, comme l’IL-4 et l’IL-5, dans le rejet des cœurs transgéniques pour l’IL-9, nous avons sélectivement bloqué ces cytokines lors du processus de rejet. Le traitement avec des anticorps neutralisant l’IL-4 bloque complètement le rejet induit par l’IL-9 et permet la survie à long terme des allogreffes cardiaques. Au point de vue de l’histologie ces greffes ne montrent ni infiltration leucocytaire ni artériopathie. Afin de déterminer si l’infiltration éosinophilique induite par l’IL-9 provient de l’activité directe de l’IL-9 ou est le résultat de la sécrétion d’IL-5, un traitement avec un anticorps anti-IL-5 a été appliqué aux receveurs d'allogreffe cardiaque. Ce traitement augmente la survie de la majorité des allogreffes et modifie de manière marquée la composition de l’infiltrat cellulaire en prévenant le recrutement des éosinophiles. De manière intéressante, les cœurs transgéniques pour l’IL-9 qui survivent indéfiniment après le traitement anti-IL-5 arborent une importante fibrose. <p><p>A la différence du cœur bm12, la peau bm12 greffée sur un receveur B6 subit un rejet rapide et l'histologie des greffes rejetées révèle la présence d'infiltrats denses à éosinophiles. Notre laboratoire a montré que ce processus de rejet est dirigé par les lymphocytes T CD4+ alloréactifs et que les souris B6 déficientes pour l'IL-5 et la voie de cytotoxicité Fas/Fas-L sont incapables de rejeter des peaux bm12. Nos premiers résultats laissaient supposer un rôle pour l'IL-9 dans notre modèle de rejet de greffes en disparité des molécules du CMH de classe II: premièrement, nous avions observé la production d'IL-9 par les lymphocytes T de type Th2 alloréactifs et deuxièmement, l'ARNm d'IL-9 était fortement exprimé au niveau des allogreffes de peaux rejetées. C’est pourquoi, la survie de peaux bm12, déficientes pour la molécule Fas, greffées sur des receveurs B6 déficients pour l'IL-9 (B6.IL-9-/-) a été comparée avec celle de peaux transplantées sur des receveurs B6. Nous avons montré que, comme les souris B6 normales, les animaux B6.IL-9-/- rejettent leur greffe dans les 15 jours. Donc, contrairement à l'IL-5, l'IL-9 n'est pas essentielle pour le rejet de peau dirigé par les cellules T CD4+ de type Th2 dans notre modèle de disparité des molécules du CMH de classe II.<p><p>Néanmoins, les allogreffes de peaux, dans notre modèle de disparité des molécules du CMH de classe II, contiennent moins d’éosinophiles lorsqu’elles sont rejetées par des receveurs déficients pour la synthèse d’IL-9 (IL-9-/-). En plus du modèle bm12, nous avons également observé un rôle de l’IL-9 dans un autre modèle de rejet Th2. Il a été montré par notre laboratoire que le rejet d’allogreffes cardiaques Balb/c complètement incompatibles par des souris receveuses B6.CD8-/- est caractérisé par le recrutement d’éosinophiles dans l’organe rejeté (106). Dans celui-ci, l’ARNm de l’IL-9 est présent pendant le rejet, de même que l’IL-4 et l’IL-5 et les greffes rejetées par des receveurs IL-9-/- contiennent moins d’éosinophiles par rapport à des receveurs contrôles. Les mécanismes par lesquels l’IL-9 induit le recrutement des éosinophiles ne sont pas complètement connus.<p><p>L’IL-5 est considérée comme la cytokine clé pour le développement de l’éosinophilie. De plus, le rejet aigu des cœurs transgéniques pour l’IL-9 est caractérisé par une infiltration massive d'éosinophiles et est inhibé lors de la neutralisation de l'IL-5. Nous avons entrepris la seconde étude pour investiguer le lien fonctionnel entre l’IL-9 et l’IL-5 dans le rejet d’allogreffe, ce qui permettra de mieux comprendre le recrutement des éosinophiles par l’IL-9.<p><p>Bien que le rejet ne soit pas inhibé par le manque d’IL-9, les allogreffes rejetées par les souris déficientes en IL-9 contiennent moins d’éosinophiles par rapport à des souris contrôles et présentent une production plus faible d’IL-5 par les cellules T alloréactives. De manière intéressante, la production optimale d’IL-5 après une stimulation allogénique requiert un récepteur à l’IL-9 (IL-9R) fonctionnel sur les cellules répondeuses. De plus, l’infiltration d’éosinophiles induite par l’IL-9 est absente dans des peaux transplantées sur des receveurs déficients pour le récepteur de l’IL-9. Finalement, la production d’IL-5 par des cellules T CD4+ stimulées par l’anti-CD3 est abolie par la neutralisation de l’IL-9. <p><p>En conclusion, nous pouvons dire que l'IL-9 est capable d'induire un rejet de type Th2, caractérisé par une forte infiltration d’éosinophiles et une dépendance à l'IL-5 et à l'IL-4. Notre étude montre également que l’IL-9 peut agir directement sur les cellules T CD4+ pour induire leur capacité à sécréter de l’IL-5. Cependant, l’IL-9 n’est pas indispensable au processus de rejet Th2 et il est probable que lorsque l’IL-9 est bloquée d'autres cytokines soient capables de compenser son absence. Notre étude permet une meilleure compréhension des voies complexes du recrutement des éosinophiles.<p> / Doctorat en sciences biomédicales / info:eu-repo/semantics/nonPublished

Indiana University-Purdue University Indianapolis (IUPUI) / In the US, more than 1 million burn injuries are reported annually. About 45,000 injuries due to fires and burns result in hospitalization and ten percent of these result in death every year. Advances in burn treatment have led to a reduction in mortality rate over the last decades. Since more patients are surviving the initial resuscitation phase even with very large areas of skin being burned away, wound care has become increasingly important to ensure continued patient survival and improvement. While currently a common treatment for third degree burn wounds, skin grafts have several drawbacks. The availability of donor sites for autografts may be limited, especially in incidences of extensive skin loss. The rejection associated with the use of allografts and xenografts may render them inadequate or undesirable. Even if a suitable graft is found, poor retention due to infection, hematoma, and low vascularity at the recipient site are other drawbacks associated with the use of skin grafts as a primary treatment for severe burn wounds. As such, research has been done into alternative treatments, which include but are not limited to artificial skin, cell therapy, and growth factor application. We propose the delivery of adipose derived stem cells (ASC) in combination with endothelial progenitor cells (EC) via Integra Dermal Regenerative Template (DRT) to promote faster graft vascularization and thus faster healing of wounds. Integra DRT is an acellular skin substitute that consists of a dermal layer composed of bovine collagen and chondroitin-6-sulfate glycosaminoglycan, and an "epidermal" layer, which consists of silicone polymer. This silicone layer is removed after the collagen matrix is adequately vascularized (usually takes 2-3 weeks), and then a thin layer autograft is applied to the top of the neo-dermis. ASC are derived from the stromal-vascular fraction (SVF) of adipose tissue and are a readily available, pluripotent, mesenchymal cell known to promote angiogenesis. They are being explored as a treatment for a myriad of diseases and conditions, including wound healing. In combination with ECs, they form stable microvessel networks in vitro and in vivo. In our work, we found that ASC+EC form stable microvessel networks when cultured on Integra DRT. Also, ASC and ASC+EC conditioned media promoted both survival and migration of human epidermal keratinocytes compared to control medium. In a full thickness wound healing model, using healthy NSG mice, the ASC+EC case showed a significantly higher rate of wound closure compared to control. Based on best linear unbiased estimates (BLUE), the difference between the healing rates of ASC alone treatment and the Control treatment group is -0.45 +/- 0.22 mm²/day (p=0.041), which is not less than 0.025 and thus not statistically significant (Bonferroni Adjusted). However, the BLUE for the difference between the ASC+EC group and the Control group healing rates is -0.55 +/- 0.28 mm²/day (p = 0.017<0.025, Bonferroni Adjusted), which is statistically significant. Histology revealed a significantly higher number of vessels compared to control in both ASC alone and ASC+EC case. CD31 staining revealed the presence of human vessels in ASC+EC treatment scaffolds. We conclude that the combination of ASC and EC can be used to accelerate healing of full-thickness wounds when delivered to site of the wound via Integra. This result is especially compelling due to the fact that the mice used were all healthy. Thus our treatment shows an improvement in healing rate even compared to normal wound healing.

Indiana University-Purdue University Indianapolis (IUPUI) / Solid organ transplantation is limited by available donor allografts. Pig to human transplantation, xenotransplantation, could potentially solve this problem if physiologic and immunologic incompatibilities are overcome. Genetic modifications of pigs have proven valuable in the study of xenotransplantation by improving pig to human compatibility. More genetic targets must be identified for clinical success. First, this study examines platelet homeostasis incompatibilities leading to acute thrombocytopenia in liver xenotransplantation. Mechanisms for xenogeneic thrombocytopenia were evaluated using liver macrophages, Kupffer cells, leading to identification of CD18, beta-2 integrin, as a potential target for modification. When disruption of CD18 was accomplished, human platelet binding and clearance by pig Kupffer cells was inhibited. Further, human and pig platelet surface carbohydrates were examined demonstrating significant differences in carbohydrates known to be involved with platelet homeostasis. Carbohydrate recognition domains of receptors responsible for platelet clearance Macrophage antigen complex-1 (CD11b/CD18) and Asialoglycoprotein receptor 1 in pigs were found to be different from those in humans, further supporting the involvement of platelet surface carbohydrate differences in xenogeneic thrombocytopenia. Second, immunologic incompatibilities due to antibody recognition of antigens resulting in antibody-mediated rejection were studied. Identification of relevant targets was systematically approached through evaluation of a known xenoantigenic protein fibronectin from genetically modified pigs. N-Glycolylneuraminic acid, a sialic acid not found in humans, was expressed on pig fibronectin and was identified as an antigenic epitope recognized by human IgG. These studies have provided further insight into xenogeneic thrombocytopenia and antibody-mediated rejection, and have identified potential targets to improve pig to human transplant compatibility.