Die Nicht-alkoholische Steatohepatitis (NASH), gehörig zu der Gruppe der chronischen Lebererkrankungen als eine schwere Form der Nicht-alkoholischen Fettleber-erkrankungen (NAFLD), nimmt in ihrer Prävalenz ständig zu. Gründe dafür sind u.a. eine gesteigerte Nahrungsaufnahme sowie Veränderungen der Nahrungszusammen-setzung. Es kommt zur Ausbildung einer Steatose, die sich unter Mitwirkung verschie-dener Einflussfaktoren zur Steatohepatitis weiterentwickeln kann, wobei die Pathoge-nese noch nicht genau verstanden ist. Die Nicht-alkoholische Steatohepatitis geht oft einher mit Insulinresistenz und starkem Übergewicht. Die Folgen für die Leber sind Funktionseinschränkungen und –verlust, hervorgerufen durch eine massive Akkumula-tion von Triglyzeriden in den Hepatozyten, Entzündungsprozesse sowie einem fibro-tischen Umbau der Leber. Im fortgeschritten Stadium wird eine Lebertransplantation unausweichlich, die jedoch aufgrund des zunehmenden Mangels an Spenderorganen oft nicht möglich ist. Eine Alternative bietet die Transplantation mesenchymaler Stammzellen (MSC). MSC können in vitro in leberzellähnliche Zellen differenziert wer-den und weisen dabei essentielle hepatozytäre Eigenschaften auf, wodurch sie als möglicher Ersatz bzw. als Überbrückungstherapie bis zur Lebertransplantation in Frage kommen. Die vorliegende Arbeit beschäftigte sich mit dieser Fragestellung. Dazu wur-de ein Tiermodell der NASH mittels Methionin-Cholin-defizienter Diät (MCD-Diät) etab-liert und die Transplantation von hepatozytär differenzierten MSC durchgeführt. An-hand spezifischer zellulärer und biochemischer Marker der NASH konnte die Wirkung des Zelltransplantats auf die Empfängerleber analysiert werden. Es hat sich gezeigt, dass die MSC einen anti-inflammatorischen, anti-fibrotischen und pro-proliferativen Einfluss auf das Empfängerparenchym hatten und somit zur Verbesserung der Symptomatik der NASH beitrugen.

Die Nicht-alkoholische Steatohepatitis (NASH), gehörig zu der Gruppe der chronischen Lebererkrankungen als eine schwere Form der Nicht-alkoholischen Fettleber-erkrankungen (NAFLD), nimmt in ihrer Prävalenz ständig zu. Gründe dafür sind u.a. eine gesteigerte Nahrungsaufnahme sowie Veränderungen der Nahrungszusammen-setzung. Es kommt zur Ausbildung einer Steatose, die sich unter Mitwirkung verschie-dener Einflussfaktoren zur Steatohepatitis weiterentwickeln kann, wobei die Pathoge-nese noch nicht genau verstanden ist. Die Nicht-alkoholische Steatohepatitis geht oft einher mit Insulinresistenz und starkem Übergewicht. Die Folgen für die Leber sind Funktionseinschränkungen und –verlust, hervorgerufen durch eine massive Akkumula-tion von Triglyzeriden in den Hepatozyten, Entzündungsprozesse sowie einem fibro-tischen Umbau der Leber. Im fortgeschritten Stadium wird eine Lebertransplantation unausweichlich, die jedoch aufgrund des zunehmenden Mangels an Spenderorganen oft nicht möglich ist. Eine Alternative bietet die Transplantation mesenchymaler Stammzellen (MSC). MSC können in vitro in leberzellähnliche Zellen differenziert wer-den und weisen dabei essentielle hepatozytäre Eigenschaften auf, wodurch sie als möglicher Ersatz bzw. als Überbrückungstherapie bis zur Lebertransplantation in Frage kommen. Die vorliegende Arbeit beschäftigte sich mit dieser Fragestellung. Dazu wur-de ein Tiermodell der NASH mittels Methionin-Cholin-defizienter Diät (MCD-Diät) etab-liert und die Transplantation von hepatozytär differenzierten MSC durchgeführt. An-hand spezifischer zellulärer und biochemischer Marker der NASH konnte die Wirkung des Zelltransplantats auf die Empfängerleber analysiert werden. Es hat sich gezeigt, dass die MSC einen anti-inflammatorischen, anti-fibrotischen und pro-proliferativen Einfluss auf das Empfängerparenchym hatten und somit zur Verbesserung der Symptomatik der NASH beitrugen.

Poly (glycerol-sebacate) (PGS) is a synthetic bioelastomer with a covalently crosslinked, three-dimensional network of random coils with hydroxyl groups attached to its backbone. This biodegradable polymer is biocompatible (in vitro and in vivo), tough, elastic, inexpensive, and flexible, and finds potential applications in tissue engineering and regenerative medicine. Due to the slow rate of step-growth polymerisation, the synthesis of PGS prepolymer requires 24-48 h. A batch and a continuous process, if developed, could address the inherent deficiencies (eg. long residence time, venting) associated with the large-scale synthesis of such bioelastomers. However, in order to assess whether this particular system may be adapted to continuous processes, such as reactive extrusion, studies on kinetics of controlled condensation reactions are of vital importance. FT-Raman spectroscopy was used to study the kinetics of the step-growth reactions between glycerol (G) and sebacic acid (SA) at three molar ratios (G:SA= 0.6,0.8,1.0) and three temperatures (120, 130, 140 ˚C). The rate curves followed first-order kinetics with respect to sebacic acid concentration in the kinetics regime. An increase in the molar ratio (G : SA) of the reactants decreased the average functionality of the system and the crosslinking density, resulting in the lowering of the activation energy and pre-exponential factor. The average functionality of the system had a profound effect on the crosslinking density, mechanical properties, and the reaction kinetics of the system. Three different PGS oligomers and films (PGS 0.6, PGS 0.8, PGS 1.0) were thoroughly characterised using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), wide angle X-ray scattering (WAXS), differential scanning calorimetry (DSC), and contact angle measurements. FTIR spectra of PGS oligomers confirmed the formation of ester bonds (1740 cm -1). Quantification of various functional groups in PGS films using XPS was in agreement with the theoretical values of the proposed structure. WAXS results indicated that PGS system with a higher average functionality possesses a higher degree of crystallinity. Crystallisation exotherms and melting endotherms of PGS systems revealed that the average functionality influences the density of crosslinking, degree of crystallinity, and the network structure of bioelastomers. Contact angle studies confirmed that an increase in the average functionality of PGS system increases hydrophilicity, and the surface treatment through aminolysis further increases the hydrophilicity of the films. Batch studies were performed on a Brabender Plasticorder®. The samples collected over a reaction period of 5 h were characterised using Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The number-average molecular weight (Mn) and the weight-average molecular weight (Mw) of the oligoesters were determined using matrix-assisted laser desroption/ionization time-of-flight spectroscopy (MALDI-TOF) and compared with the corresponding values from the benchtop synthesis. It was found that due to higher shear-mixing and better orientation of functional groups, the degree of polymerisation at any stage of the reaction was higher in the Brabender than in the benchtop process. The gel-point of the reaction was determined from the crossover point of storage and loss moduli, and the reaction rate constant was calculated using the torque vs time data of the rheometer. The kinetics rate constant and the extent of the reaction in the Brabender were found to be higher than the corresponding values obtained from the conventional benchtop process by a factor of 2. PGS was found to be thermo-mouldable and adaptable to high-shear mixing, and hence is a better candidate for making thermoplastic elastomers using reactive extrusion. The challenges and possibilities in scaling up a batch process to a continuous process were investigated. The use of a wiped film reactor or a disk reactor along with reactive extrusion and batch-mixing (as a post-extrusion operation) is a commercially viable method to synthesise PGS oligomers. Such a continuous process will boost the production of bioelastomers for tissue engineering application by addressing the constraints in step-growth polymerisation. Finally, the effect of PGS substrate stiffness and surface treatment (aminolysis, hydrolysis, layer-by-layer deposition) on the morphology and lineage of mesenchymal stem cells – which have a capacity to differentiate themselves into cartilage, adipose, tendon, and muscle tissues – was analysed using fluorescence microscopy and DNA and protein assays. Stiffness of the PGS surface and the method of treatment influenced the cell attachment and spreading on different surfaces. However, cells did not differentiate into definite phenotypes at the end of 14 d time-point, indicating that higher time-points are needed to be considered to study the effect of matrix stiffness and surface treatment on cell attachment and phenotype differentiation.

Bien que les résultats métaboliques de la transplantation d’îlots chez le patient diabétique de type 1 soient désormais bien démontrés, ils sont contrebalancés par les effets indésirables des traitements immunosuppresseurs et la perte de fonctionnalité du greffon à long terme.Au cours de cette thèse, nous avons étudié deux approches complémentaires offrant la perspective de s’affranchir du traitement immunosuppresseur tout en protégeant les îlots de l’apoptose et de la perte de fonctionnalité du greffon induites par les mécanismes d’isolement, de culture et de transplantation : l’immunoisolation des îlots dans des capsules de biomatériaux et la co-transplantation avec des cellules souches mésenchymateuses (CSM).Au sein du projet européen de pancréas artificiel BIOCAPAN, nous avons évalué in vitro, la biocompatibilité de différents biomatériaux et mis en évidence un effet combiné de la présence de CSM et des tripeptides RGD sur le maintien de la viabilité et de la fonctionnalité des îlots encapsulés. L’évaluation ultérieure de la biocompatibilité et de l’effet ajouté de la capsule BIOCAPAN sur des animaux diabétiques permettra la validation de la capsule qui sera proposée à des tests d’essais cliniques.Nous avons également démontré, dans un modèle de co-culture d’îlots avec des CSM dans des conditions de culture classiques et exposées à des cytokines pro-inflammatoires, que les CSM régulaient les capacités sécrétrices des îlots probablement via la régulation de l’hème oxygénase 1 (HO-1). L’identification des facteurs de transcription régulant HO-1 ainsi que des médiateurs permettant la communication entre les deux types cellulaires sont des perspectives de développement.Ce travail a souligné l’intérêt, au sein d’une approche immuno-isolante, de la reconstitution d’un environnement favorable au sein de la capsule permettant la préservation de l’îlot notamment via l’utilisation de CSM. / Although, the metabolic results of islets transplantation for patient with type 1 diabetes are now well documented, they are counteracted by the adverse effects of immunosuppressive therapies and the long-term loss in graft functionality.During this thesis, we worked on two complementary approaches offering the perspective of avoiding immunosuppressive treatment while protecting islets from apoptosis and loss of functionality induced by the mechanisms of isolation, culture and transplantation. These two tools are islet immunoisolation in capsules composed of specific biomaterials and islets co-transplantation with mesenchymal stem cells (MSCs) described for their immunomodulatory, proangiogenic and cytoprotective properties.In the european project of bioartificial pancreas BIOCAPAN, we have evaluated in vitro the biocompatibility of several biomaterials and we have highlight a combined effect of the presence of MSCs and tripeptides RGD on the viability and the functionality maintenance of the encapsulated islets. Subsequent in vivo validation of the biocompatibility and the added effect of the BIOCAPAN capsule on diabetic animals will allow the final validation of the capsule to be proposed for clinical trials.We also demonstrated, in an islet co-culture model with MSCs under conventional culture conditions and exposed to pro-inflammatory cytokines, that MSCs regulate the secretory capacity of islets probably via the regulation of heme oxygenase 1 (HO-1) described for its antioxidant and anti-inflammatory properties. The identification of transcription factors regulating HO-1 as well as mediators, allowing communication between the two cell types, are development perspectives.This work underlined the interest, within an immuno-isolation approach, of the reconstitution of a favorable environment within the capsule allowing the preservation of islet physiology thanks to the use of MSCs.

A artrose, também chamada de osteoartrose ou osteoartrite (OA), é a terceira doença de maior incidência no Mundo. Nesse trabalho, buscou-se criar uma lesão osteocartilaginosa em joelhos de ratos Wistar machos com seis meses de vida, objetivando constituir um modelo animal para estudo da OA humana e, a partir desse modelo, avaliar biomateriais de forma isolada ou associados entre si e avaliados quanto à sua segurança biológica e potencial de reparação tecidual. Além disto, foi analisado o efeito reparador de células-tronco mesenquimais da polpa do dente de leite humano (MSC) isoladamente e em associação com o biomaterial formado por: Titânio + Poli Vinil Álcool + Ac. Hialurônico, nesse estudo denominado de TRIGEL (TRG). O Ac. Hialurônico (HA), por suas propriedades visco elásticas, o pó de Titânio (Ti), devido às suas propriedades biológicas únicas de ostoeintegração e o polímero Poli Vinil Álcool (PVA), com suas propriedades hidrofílicas, promovendo a formação do Hidrogel, os quais associados entre si formam um compósito, o TRG, que foi aplicado sobre uma lesão padrão no joelho da pata pélvica direita de ratos Wistar machos de seis meses de idade. Para a obtenção da lesão padrão, os animais foram divididos em três grupos de cincoanimais e cada grupo foi submetido a uma intervenção cirúrgica em seus joelhos direitos, utilizando três técnicas cirúrgicas diferentes, a saber: Grupo (I): Remoção cirúrgica dos meniscos medial e lateral mais perfuração do platô tibial seguido da aspiração da medula óssea através dessa perfuração por meio de seringa e agulha. Grupo (II): Remoção dos meniscos mais perfuração, sem aspiração, Grupo (III): Apenas a perfuração. Todos os animais foram autopsiados após 30 dias. Os joelhos dos quinze animais que constituíam os três grupos foram devidamente catalogados e enviados para a empresa Histotech, para a confecção das lâminas, tendo sido eleito, por análise histológica, o Grupo (I), por demonstrar menor reparo tecidual espontâneo. Em tese, o TRG teria as seguintes propriedades: Uma fonte de reparação tecidual (visco terapia) dada pelo HA e a capacidade amortecedora e carreadora de células-tronco do polímero PVA, que se hidrata, formando o hidrogel. O Ti, pela sua propriedade de osteointegração formaria um tampão sobre as áreas de matriz óssea exposta o que possibilitaria o afluxo de novos condrócitos, que também pode ocorrer pela ação das células-tronco. Livrar a superfície articular das áreas com exposição da matriz óssea é fundamental para o bloqueio das proteases que perpetuam a fisiopatologia da OA. Após tratamento estatístico dos diversos ensaios, utilizando-se os diversos biomateriais no tratamento da lesão, o TRG foi o biomaterial que apresentou o melhor resultado de força entre os grupos. No estudo histológico, foi evidenciada a presença de tecido cartilaginoso supra- lesional, o que só ocorreu nos animais dos grupos que receberam: apenas TRG, TRG associado com células-tronco e aquele que recebeu apenas MSCs. No entanto, mais estudos, com animais de maior porte e mais velhos, devem ser realizados para melhor analisar a segurança e o potencial terapêutico do compósito Trigel. / Osteoarthritis, or osteoarthritis (OA) is the third most debilitating disease in the world. In this study, we attempted to create an osteocartilaginous lesion in the knees of six months old male Wistar rats, aiming to constitute an animal model for the study of human OA and to use this model to evaluate the therapeutic potential of biomaterials, which are already well known for their biocompatibility properties in the clinical practice. The biomaterials were used in isolation or associated with each other and then evaluated for their biological safety and tissue repair capacity. Mesenchymal stem cells, obtained from human dental pulp from deciduous teeth (MSC) were evaluated alone and in association with the biomaterial formed by: Titanium + Poly Vinyl Alcohol + Ac. Hyaluronic, here called TRIGEL (TRG). Due to its visco-elastic properties, the Ti powder, due to its unique biological properties of ostointegration and the polymer PVA, with its hydrophylic properties, forming a hydrogel, were associated to form the composite named TRIGEL, (TRG), which was applied to a standard knee injury of the right hind leg of male Wistar rats. In order to elect the standard lesion, the animals were divided into three groups with five animals each and each group underwent a surgical intervention in their right knees, with three different surgical techniques being applied, namely: Group (1): Surgical removal ofmedial and lateral meniscus plus perforation of the tibial plateau, followed by aspiration of the bone marrow through this perforation using syringe and needle. Group (2): Removal of the meniscus plus perforation, without aspiration, Group (3): Drilling only. All groups were autopsied 30 days after the procedure and all groups were autopsied at 30 days post-procedure. The knees of the 15 animals that constituted the three groups were analyzed histologically and Group (1) (meniscus removed, perforated and aspirated), was elected as the standard lesion since it demonstrated less spontaneous tissue repair. TRG has the following properties: HA is used as a source of tissue repair (visco therapy) and hydration of the polymer; PVA, forms a hydrogel\", with damping action and as a stem cells carrier, whereas Ti was used due to its ósseo-integration, which would allow coating of the exposed bone matrix and this intra-osseous osteo-integration response would form an intercalating buffer. The healthy cartilage surfaces around this structural buffer would allow the reception of new chondrocytes or the action of the cells on TRG properties. Freeing the articular surface of the areas with bone matrix exposure is critical for blocking the proteases that perpetuate the pathophysiology of OA. In the various biomaterial tests in the treatment of the standard lesions, TRG was statistically shown to be the one that better mimicked the non-injured group. The histological study demonstrated the presence of a supra-lesional cartilagenous tissue, which only occurred in the groups which received: only TRG, mesenchymal stem cells associated with TRG and that which received only MSCs. However, further studies with larger and older animals should be pursued to better assess the safety and therapeutic potential of the Trigel composite.

A artrose, também chamada de osteoartrose ou osteoartrite (OA), é a terceira doença de maior incidência no Mundo. Nesse trabalho, buscou-se criar uma lesão osteocartilaginosa em joelhos de ratos Wistar machos com seis meses de vida, objetivando constituir um modelo animal para estudo da OA humana e, a partir desse modelo, avaliar biomateriais de forma isolada ou associados entre si e avaliados quanto à sua segurança biológica e potencial de reparação tecidual. Além disto, foi analisado o efeito reparador de células-tronco mesenquimais da polpa do dente de leite humano (MSC) isoladamente e em associação com o biomaterial formado por: Titânio + Poli Vinil Álcool + Ac. Hialurônico, nesse estudo denominado de TRIGEL (TRG). O Ac. Hialurônico (HA), por suas propriedades visco elásticas, o pó de Titânio (Ti), devido às suas propriedades biológicas únicas de ostoeintegração e o polímero Poli Vinil Álcool (PVA), com suas propriedades hidrofílicas, promovendo a formação do Hidrogel, os quais associados entre si formam um compósito, o TRG, que foi aplicado sobre uma lesão padrão no joelho da pata pélvica direita de ratos Wistar machos de seis meses de idade. Para a obtenção da lesão padrão, os animais foram divididos em três grupos de cincoanimais e cada grupo foi submetido a uma intervenção cirúrgica em seus joelhos direitos, utilizando três técnicas cirúrgicas diferentes, a saber: Grupo (I): Remoção cirúrgica dos meniscos medial e lateral mais perfuração do platô tibial seguido da aspiração da medula óssea através dessa perfuração por meio de seringa e agulha. Grupo (II): Remoção dos meniscos mais perfuração, sem aspiração, Grupo (III): Apenas a perfuração. Todos os animais foram autopsiados após 30 dias. Os joelhos dos quinze animais que constituíam os três grupos foram devidamente catalogados e enviados para a empresa Histotech, para a confecção das lâminas, tendo sido eleito, por análise histológica, o Grupo (I), por demonstrar menor reparo tecidual espontâneo. Em tese, o TRG teria as seguintes propriedades: Uma fonte de reparação tecidual (visco terapia) dada pelo HA e a capacidade amortecedora e carreadora de células-tronco do polímero PVA, que se hidrata, formando o hidrogel. O Ti, pela sua propriedade de osteointegração formaria um tampão sobre as áreas de matriz óssea exposta o que possibilitaria o afluxo de novos condrócitos, que também pode ocorrer pela ação das células-tronco. Livrar a superfície articular das áreas com exposição da matriz óssea é fundamental para o bloqueio das proteases que perpetuam a fisiopatologia da OA. Após tratamento estatístico dos diversos ensaios, utilizando-se os diversos biomateriais no tratamento da lesão, o TRG foi o biomaterial que apresentou o melhor resultado de força entre os grupos. No estudo histológico, foi evidenciada a presença de tecido cartilaginoso supra- lesional, o que só ocorreu nos animais dos grupos que receberam: apenas TRG, TRG associado com células-tronco e aquele que recebeu apenas MSCs. No entanto, mais estudos, com animais de maior porte e mais velhos, devem ser realizados para melhor analisar a segurança e o potencial terapêutico do compósito Trigel. / Osteoarthritis, or osteoarthritis (OA) is the third most debilitating disease in the world. In this study, we attempted to create an osteocartilaginous lesion in the knees of six months old male Wistar rats, aiming to constitute an animal model for the study of human OA and to use this model to evaluate the therapeutic potential of biomaterials, which are already well known for their biocompatibility properties in the clinical practice. The biomaterials were used in isolation or associated with each other and then evaluated for their biological safety and tissue repair capacity. Mesenchymal stem cells, obtained from human dental pulp from deciduous teeth (MSC) were evaluated alone and in association with the biomaterial formed by: Titanium + Poly Vinyl Alcohol + Ac. Hyaluronic, here called TRIGEL (TRG). Due to its visco-elastic properties, the Ti powder, due to its unique biological properties of ostointegration and the polymer PVA, with its hydrophylic properties, forming a hydrogel, were associated to form the composite named TRIGEL, (TRG), which was applied to a standard knee injury of the right hind leg of male Wistar rats. In order to elect the standard lesion, the animals were divided into three groups with five animals each and each group underwent a surgical intervention in their right knees, with three different surgical techniques being applied, namely: Group (1): Surgical removal ofmedial and lateral meniscus plus perforation of the tibial plateau, followed by aspiration of the bone marrow through this perforation using syringe and needle. Group (2): Removal of the meniscus plus perforation, without aspiration, Group (3): Drilling only. All groups were autopsied 30 days after the procedure and all groups were autopsied at 30 days post-procedure. The knees of the 15 animals that constituted the three groups were analyzed histologically and Group (1) (meniscus removed, perforated and aspirated), was elected as the standard lesion since it demonstrated less spontaneous tissue repair. TRG has the following properties: HA is used as a source of tissue repair (visco therapy) and hydration of the polymer; PVA, forms a hydrogel\", with damping action and as a stem cells carrier, whereas Ti was used due to its ósseo-integration, which would allow coating of the exposed bone matrix and this intra-osseous osteo-integration response would form an intercalating buffer. The healthy cartilage surfaces around this structural buffer would allow the reception of new chondrocytes or the action of the cells on TRG properties. Freeing the articular surface of the areas with bone matrix exposure is critical for blocking the proteases that perpetuate the pathophysiology of OA. In the various biomaterial tests in the treatment of the standard lesions, TRG was statistically shown to be the one that better mimicked the non-injured group. The histological study demonstrated the presence of a supra-lesional cartilagenous tissue, which only occurred in the groups which received: only TRG, mesenchymal stem cells associated with TRG and that which received only MSCs. However, further studies with larger and older animals should be pursued to better assess the safety and therapeutic potential of the Trigel composite.

La leucémie myélomonocytaire chronique (LMMC) est une hémopathie myéloïde rare du sujet âgé. Les caractéristiques cliniques, génétiques et moléculaires de la maladie sont bien connues. L’expression très hétérogène de la maladie ne peut être expliquée par la seule hétérogénéité génétique du clone leucémique. Les altérations épigénétiques jouent manifestement un rôle important. Le rôle de facteurs extrinsèques issus du microenvironnement est plus obscur. La niche hématopoïétique est le siège d’interactions entre cellules. Deux schémas non-exclusifs d’altération primaire ou secondaire de la niche sont proposés. Le premier implique que l’émergence d’un clone hématopoïétique modifie son environnement. Le second postule que le premier évènement dans l’émergence d’une hémopathie clonale est une altération de l’environnement. Mon travail de thèse a étudié les altérations du microenvironnement médullaire chez les patients et leur impact sur la physiopathologie de la maladie selon 2 axes: 1) la mise au point d’un modèle murin de reconstitution de la niche hématopoïetique humaine et 2) la caractérisation des cellules souches mésenchymateuses des patients. Dans une première partie, j’ai transposé un modèle rapporté en 2016 à l’étude de la LMMC. Ce modèle de greffe de cellules médullaires humaines chez la souris immunodéprimée s’est avéré difficilement reproductible. Dans la seconde partie, j’ai analysé les cellules souches mésenchymateuses de patients atteints de LMMC. J’ai identifié la production excessive d’IGFBP2 (Insuline-like Growth Factor Binding Protein 2), conséquence probable d’une dérégulation épigénétique. Le séquençage des CSM à l’échelle unicellulaire a révélé une restriction de l’hétérogénéité de ces cellules dont une fraction seulement produit IGFBP2. Finalement, j’ai montré qu’IGFBP2 favorise la différenciation des progéni-teurs myéloïdes vers la lignée monocytaire. IGFBP2 pourrait donc contribuer à amplifier la monocytose caractéristique de cette maladie.En conclusion, la LMMC s’accompagne de modifications des cellules de la niche hématopoÏétique dont certaines produisent des quantités excessive d’IGFBP2. La recherche de l’origine de ce dérèglement et de son importance dans la progression de la maladie permettra d’évaluer l’intérêt potentiel d’une neutralisation de cette cytokine à des fins thérapeutiques. / Chronic myelomonocytic leukemia (CMML, is a rare myeloid hemopathy of the elderly. Clinical, genetic and molecular characteristics of the disease are well-known. The highly heterogeneous expression of the disease can’t be solely explained by genetic heterogeneity of the leukemic clone. Epigenetic alterations obviously play an important role. However, the role of extrinsic factors from the medullar microenvironment in CMML physiopathology is still poorly understood. The hematopoietic niche hosts a lot of bi-directionnal interactions between cells. Two non-exclusive schemes of primary and secondary alterations of the niche can be proposed. First postulate implies that the emergence of a hematopoietic clone alters its environment. The second one supposes that the first event causing the emergence of a clonal hemopathy is an alteration of the environment. My PhD work consisted of studying medullar alterations in patients and their impact on CMML physiopathology upon 2 axes: 1) to set up a murine model of human hematopoietic niche reconstitution 2) to caracterise mesenchymal stem cells from CMML patient ex vivo. During the first part of my PhD, I adapted a model published in 2016 to CMML. This model of human MSC graft in immunodeficient mice proved to be hardly reproducible. During the second part, I analysed of CMML patients MSC. I identified an excessive production of IGFBP2 (Insuline-like Growth Factor Binding Protein 2) probably secondary to an epigenetic disregulation. Single cell RNA sequencing revealed a restriction of MSC heterogeneity of which only a fraction produces IGFBP2. Finally, I showed that IGFBP2 favors myeloid progenitors differenciation towards monocytic lineage. IGFBP2 could therefore contribute to the amplification of CMML characteristic monocytosis.To conclude, CMML goes along with modifications of hematopoietic niche cells, some of which produce excessive amounts of IGFBP2. Investigation on the origin of this alteration and its significance in disease progression should allow to evaluate the potential interest of its neutralization for therapeutic strategies.