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Acute myeloid leukemia (AML), a blood malignancy resulting in abnormal hematopoiesis, is associated with alterations in the bone marrow environment (BME). Current treatments for this heterogeneous disease, mainly targeting the leukemic cells, are largely unsuccessful for the majority of AML subtypes. By better understanding the mechanisms by which the BME contributes to leukemogenesis, it may be possible to introduce more effective treatments for AML. Mesenchymal stromal/stem cells (MSCs) are essential cellular components of the BME/hematopoietic niche and have been shown to support normal hematopoiesis. As a critical component, they may have several roles in altering the BME, thus providing an excellent model for studying the BME in-vitro. Several studies have characterized AML-derived MSCs (AML-MSCs). However, their exact role in altering BME remains unclear. Here, we investigated the MSCs' potential role in BME alteration by investigating the genetic profiles of previously characterized AMLMSCs (n=29) and healthy donor MSCs (HD-MSCs) (n=8). We identified that among 7565 common genes, 21 genes were significantly differentially expressed in AMLMSCs. The CD248 gene was identified among these significantly upregulated genes in AML/HD-MSCs (n=29). Focusing on AML-MSCs derived from high-risk patients (HR), CD248 protein was investigated and validated using HR AML-MSCs (n=11) and HD-MSCs (n=4). Interestingly, it was highly abundant in HR samples at the intracellular and cell-surface levels. CD248 is an MSC marker and has a biological significance potentially on their function. To better understand its potential role in MSC, CD248 was knocked down (KD) in HD-MSCs using siRNA (siCD248-MSCs). Functional capacity, the ability of HD-MSCs and siCD248-MSCs to differentiate into cell types that form the BME (adipocytes and osteocytes), and their ability to promote the growth of HL60 human leukemia cell line were assessed. Posttransfection functional assessments showed that siCD248-MSCs had a reduced adipogenic but not osteogenic potential via differentiation assays. Quantitative validation of the adipogenesis pathway by qRT-PCR confirmed the reduction. KD CD248 increased SIRT2 expression and potentially led to adipogenesis inhibition. However, co-culture experiments showed no effect of HD-MSCs or siCD248-MSCs on HL60 proliferation. Together these data showed that CD248 is a potential player in adipogenesis, essential to MSC’s functionality. Thus, it could serve as a prognostic marker and target for AML therapy.

Au début de ma thèse, je me suis intéressé aux processus qui sous-tendent la communication cellulaire et plus spécifiquement les interactions cellule-cellule. Pourquoi une cellule établit-elle un contact spécifique avec une autre cellule ? Comment les cellules répondent-elles à cette interaction et quels en sont les effets ? J'ai utilisé comme modèle d'étude l'interaction entre les cellules souches/stromales mésenchymateuses (CSM) et des lignées de cancer du sein. L'objectif de mon travail a été d'analyser les mécanismes de ces interactions entre CSM et cellules cancéreuses et d'en évaluer les effets sur les fonctions des cellules cancéreuses. En effet, des mécanismes de recrutement des CSM aux sites tumoraux ont été décrits avec des effets sur la progression tumorale, ce qui ouvre par ailleurs des perspectives pour de nouvelles approches thérapeutiques. J'ai tout d'abord développé un système expérimental de microscopie confocale en temps réel pour observer le type d'interaction qui est produit entre les CSM humaines et les cellules de carcinomes mammaires MDA-MB-231 et MCF7. J'ai constaté la formation dynamique de structures tubulaires entre les deux types cellulaires et, de façon surprenante, le passage des mitochondries des CSM vers les cellules cancéreuses. En un deuxième temps, j'ai utilisé un système d'invasion dans une matrice 3D de collagène, que nous avons adapté à la coculture, afin d'observer les effets de l'interaction des MDA-MB-231 avec les CSM. En accord avec la littérature, nous avons constaté une augmentation du pouvoir invasif des cellules cancéreuses, effet qui pouvait être lié au transfert des mitochondries provenant des CSM. Pour répondre à cette question, j'ai mis au point un protocole pour transférer spécifiquement des mitochondries, isolées à partir de cellules, vers d'autres cellules. Ce protocole, exploité dans ce manuscrit pour le transfert de mitochondries de CSM vers les cellules cancéreuses MDA-MB-231, peut être transposé à d'autres types cellulaires et fait l'objet d'une demande de brevet. Nos données indiquent que l'acquisition de mitochondries de CSM par les cellules cancéreuses modifie leurs propriétés fonctionnelles et augmente leur capacité de prolifération et d'invasion. Concernant leur activité métabolique, on observe une augmentation de leur respiration mitochondriale et de leur production d'ATP. Nos données préliminaires suggèrent aussi une augmentation de l'expression transcriptionnelle d'enzymes impliquées dans la synthèse des lipides et l'oxydation des acides gras. Ces données, générées grâce au protocole de transfert artificiel de mitochondries mis au point, montrent pour la première fois que les mitochondries des CSM peuvent majorer certaines propriétés cellulaires liées à la progression tumorale, comme la prolifération et l'invasion, et contribuer à une reprogrammation métabolique des cellules cancéreuses. Elles s'intègrent au rôle proposé par la communauté scientifique pour les CSM dans le microenvironnement tumoral. La technique de transfert artificiel de mitochondries nous permettra de répondre à d'autres questions restées ouvertes, comme le rôle possible des mitochondries des CSM dans les résistances développées par les tumeurs vis-à-vis des agents anti-cancéreux. Le protocole de transfert de mitochondries développé au laboratoire constitue une technique de choix et offre de nombreux avantages comparativement à d'autres techniques comme la micro-injection et la génération des hybrides cytoplasmiques. Sa mise en œuvre est en effet simple et reproductible et permet de traiter une grande quantité de cellules. Cette méthode permet d'envisager de nombreuses perspectives et applications dans le domaine de la reprogrammation métabolique, comme par exemple de restaurer les capacités d'une cellule dysfonctionnelle par le transfert de mitochondries issues d'une cellule saine et « métaboliquement active ». / At the beginning of my thesis, I was interested in the process involved in cell communication, more specifically in cell-to-cell interactions. Why does a cell specifically establish contacts with another one, how do cells respond to these interactions and what are the effects? As a model to answer these questions, I studied the interactions between MSCs and two breast cancer cell lines. The study of the communications between MSCs and tumor cells is an alternative to explore and understand tumor progression. MSC recruitment to the tumor is shown to favor the progression of the disease. The mechanisms of this dialogue are multiple and are the object of a great number of studies that aim at finding new therapeutic approaches. The objective of this work was to analyze the interactions between MSCs and cancer cells and evaluate the potential effects of this communication in tumor progression. First, I developed an experimental system of real time confocal microscopy in order to observe the interaction produced between MSCs and the breast carcinoma MDA-MB-231 and MCF-7 cells. I noticed the dynamic formation of tubular structures between the two different cell types and, surprisingly, the passage of mitochondria from MSCs to the cancer cells. Second, we used a 3D system of cell invasion in a collagen matrix, which we adapted for the coculture, in order to observe the effects of the interactions between the MDA-MB-231 and MSCs. In agreement with the literature, we observed an increase in the migratory potential of the cancer cells, an effect that could be linked to the transfer of mitochondria from MSCs to the cancer cells. To answer this question, I set up a protocol to specifically transfer to the cancer cells mitochondria isolated from the MSCs and test directly the functional consequences for the cancer cells. This protocol can be used to transfer mitochondria, not only from MSCs but also from other cells. This method is currently submitted to a patent process. Our results show that the transfer of MSC mitochondria to the cancer cells modifies cancer cells functional properties and increase their invasive and proliferative capacities. Concerning the metabolic activity, we noticed an increase in mitochondrial respiration and ATP production. We also observed an increase in the transcription level of enzymes related to the lipid synthesis and fatty acid oxidation. The results generated with this new protocol of mitochondria transfer show, for the first time, that mitochondria originating from MSCs can improve cellular capacities linked to the tumor progression. The role proposed by the scientific community for the interactions of MSCs with the tumor cells fits with the data generated in our work. Several questions remain open. In particular, could the transfer of mitochondria from MSCs to the cancer cells contribute to the acquisition of resistance to anti-cancer agents observed in patients? The protocol of transfer of mitochondria that we developed in the laboratory is a technique of choice and offers many advantages over other techniques such as microinjection and cytoplasmic hybrids; its implementation is simple and reproducible and can target large numbers of cells. This method opens numerous perspectives and potential applications such as the study of metabolic reprogramming. Thus, we could consider restoring the activity of dysfunctional cells by transferring mitochondria from “metabolically active” or healthy cells. In the long term, one of the applications could be transferring healthy or genetically modified mitochondria to zygotes carrying mitochondrial DNA mutations, in order to treat pathologies like infertility, neuro-degenerative diseases, cancer and premature aging.

京都大学 / 新制・課程博士 / 博士(医学) / 甲第25197号 / 医博第5083号 / 新制||医||1072(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 齋藤 潤, 教授 斎藤 通紀, 教授 長船 健二 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

As células estromais mesenquimais (CMMs) se tornaram de grande interesse para a terapia celular devido ao seu potencial de se diferenciar e reconstituir tecidos especializados. Mais recentemente, este interesse tem aumentado significativamente devido à descoberta de que as CMMs são capazes de secretar uma infinidade de mediadores para estimular a regeneração in situ de tecidos lesados. Dessa forma, CMMs podem ser consideradas tanto como um produto terapêutico em si, quanto uma biofábrica de diversas proteínas relevantes do ponto de vista terapêutico. Para atender a estas crescentes demandas, ambas as aplicações requerem o desenvolvimento de processos de expansão celular com alto rendimento, sob condições de cultivo definidas, reprodutíveis, escalonáveis, permitindo a obtenção de produtos com adequada identidade, potência, pureza, segurança e viáveis economicamente. Frente ao exposto, este trabalho teve como objetivos principais o estabelecimento de um processo de expansão de CMMs baseado em biorreatores e a caracterização do secretoma destas células visando aplicações terapêuticas. Para isto, a expansão de CMMs do cordão umbilical (MCUs) foi realizada em frascos multicamadas (MC) e nos biorreatores de leito fixo (LF), tanque agitado com microcarregadores (TA) e fibrasocas (FO). Os resultados mostraram que a taxa de proliferação específica das células foi maior (< tempo de duplicação) no biorreator de FO (36,8 ± 1,7 horas), bem como o fator de expansão (9,8 ± 1,0) e a eficiência na recuperação celular (100%). Um nível similar de produção celular foi observado para o TA, MC e LF com elevado fator de expansão celular (8,8 ± 0,39, 8,7 ± 0,90, 6,9 ± 1,3, respectivamente). No entanto, em termos de eficiência na recuperação celular (%), LF apresentou a menor taxa de recuperação dentre todos os sistemas (18% (± 0,77)), acompanhado pelo TA (61% (± 15,7)). As células mantiveram suas características imunofenotípicas e o potencial de diferenciação em adipócitos, osteócitos e condrócitos em todos os sistemas de cultivo avaliados. Foi também realizada a análise de custos (COG) e avaliação da viabilidade econômica para produção de CMMs visando tratamento da doença do enxerto contra o hospedeiro (DECH) em escala comercial, utilizando os sistemas de cultivo avaliados experimentalmente sob diferentes estratégias de reembolso. Apesar dos resultados experimentais satisfatórios para o biorreator FO, o COG revelou que este sistema tem o maior custo devido aos elevados custos dos consumíveis requeridos e do custo do equipamento. O frasco MC foi considerado como a tecnologia mais rentável e robusta no cenário avaliado e o biorreator TA obteve a segunda posição. O biorreator TA foi escolhido como o mais adequado analisando de maneira conjunta os dados experimentais obtidos, a análise dos custos dos diferentes sistemas de cultivo e a escalonabilidade de cada sistema. Assim, esse biorreator foi eficientemente utilizado para o cultivo de MCUs em condições isentas de SFB e xenoantígenos, sendo possível a produção de uma grande quantidade de células, representando um passo importante no desenvolvimento de um bioprocesso em conformidade com as normas das agências regulatórias. Por fim, com a análise do secretoma das CMMs por espectrometria de massas foi possível a identificação de uma gama enorme de proteínas interessantes (aprox. 2400) envolvidas em importantes processos biológicos. O futuro monitoramento dessas proteínas em biorreatores poderá representar um método inovador e original de produção de produtos livres de células para uso na terapia celular. / Mesenchymal stem/stromal cells (MSC) have become of great interest for cell therapy because of its potential to differentiate and reconstitute specialized tissues. More recently, such interest has significantly increased due to the discovery that MSC are capable of secreting a plethora of mediators to stimulate the in situ regeneration of injured tissues. Thus, MSC can be considered as a therapeutic product itself and as a biofactory of various relevant therapeutic proteins. To meet these increasing demands, both applications require the development of high-yield, reproducible, scalable and cost-effective bioprocesses under defined culture conditions, obtaining products with proper identity, purity and safety. Based on these, the main goal of this work was the establishment of a MSC expansion process based on bioreactors and secretome characterization of these cells targeting therapeutic applications. The MSC expansion was performed using multi-layered flasks (ML) and fixed bed (PB), stirred tank (STR) and hollow fiber (HF) bioreactors. The results showed that the proliferation rate of the cells was higher (< doubling time) in the HF bioreactor (36.8 ± 1.7 hours), as well as the expansion fold-increase (9.8±1.0) and harvesting efficiency (100%). A similar level of cell production was observed for STR, ML and PB with high fold-increase (8.8±0.39, 8.7±0.90, 6.9±1.3, respectively). However, in terms of harvesting efficiency (%), PB bioreactor presented the lowest retrieval rate across all the technologies (18% (±0.77)), followed by STR (61% (±15.7)). The cells retained their functional properties after culture in all the culture systems evaluated. This study was then extended through the use of a bioprocess economics tool for the evaluation of the economic feasibility of producing MSC-based treatment for acute graft vs. host disease (aGvHD) at commercial scale, using the culture systems experimentally evaluated under different reimbursement strategies. Despite the advantageous experimental results of HF bioreactors, the COG analysis has revealed that this is the least cost effective cell culture system to be used, due to its high consumable and equipment costs. ML flasks ranked first as the most cost effective and robust technology in this scenario and microcarrier-based technologies (STR) ranked in second position. The STR bioreactor was chosen as the most suitable for MSC expansion analyzing the experimental data, COG analysis and scalability of each culture system. Thus, STR bioreactor was efficiently tested for MSC expansion under serum and xeno-free conditions and it was possible to produce a large amount of cells. The development of a scalable microcarrier-based stirred culture system using xeno-free culture medium that suits the intrinsic features of UCM-derived MSC represents an important step towards a GMP compliant large-scale production platform for these promising cell therapy candidates. Finally, with the MSC secretome analysis by mass spectrometry it was possible to identify a wide range of interesting proteins (approx. 2400) involved in important biological processes. The future monitoring of these proteins in bioreactors may represent a novel and unique method of producing cell-free products for use in cellular therapy.

As células estromais mesenquimais (CMMs) se tornaram de grande interesse para a terapia celular devido ao seu potencial de se diferenciar e reconstituir tecidos especializados. Mais recentemente, este interesse tem aumentado significativamente devido à descoberta de que as CMMs são capazes de secretar uma infinidade de mediadores para estimular a regeneração in situ de tecidos lesados. Dessa forma, CMMs podem ser consideradas tanto como um produto terapêutico em si, quanto uma biofábrica de diversas proteínas relevantes do ponto de vista terapêutico. Para atender a estas crescentes demandas, ambas as aplicações requerem o desenvolvimento de processos de expansão celular com alto rendimento, sob condições de cultivo definidas, reprodutíveis, escalonáveis, permitindo a obtenção de produtos com adequada identidade, potência, pureza, segurança e viáveis economicamente. Frente ao exposto, este trabalho teve como objetivos principais o estabelecimento de um processo de expansão de CMMs baseado em biorreatores e a caracterização do secretoma destas células visando aplicações terapêuticas. Para isto, a expansão de CMMs do cordão umbilical (MCUs) foi realizada em frascos multicamadas (MC) e nos biorreatores de leito fixo (LF), tanque agitado com microcarregadores (TA) e fibrasocas (FO). Os resultados mostraram que a taxa de proliferação específica das células foi maior (< tempo de duplicação) no biorreator de FO (36,8 ± 1,7 horas), bem como o fator de expansão (9,8 ± 1,0) e a eficiência na recuperação celular (100%). Um nível similar de produção celular foi observado para o TA, MC e LF com elevado fator de expansão celular (8,8 ± 0,39, 8,7 ± 0,90, 6,9 ± 1,3, respectivamente). No entanto, em termos de eficiência na recuperação celular (%), LF apresentou a menor taxa de recuperação dentre todos os sistemas (18% (± 0,77)), acompanhado pelo TA (61% (± 15,7)). As células mantiveram suas características imunofenotípicas e o potencial de diferenciação em adipócitos, osteócitos e condrócitos em todos os sistemas de cultivo avaliados. Foi também realizada a análise de custos (COG) e avaliação da viabilidade econômica para produção de CMMs visando tratamento da doença do enxerto contra o hospedeiro (DECH) em escala comercial, utilizando os sistemas de cultivo avaliados experimentalmente sob diferentes estratégias de reembolso. Apesar dos resultados experimentais satisfatórios para o biorreator FO, o COG revelou que este sistema tem o maior custo devido aos elevados custos dos consumíveis requeridos e do custo do equipamento. O frasco MC foi considerado como a tecnologia mais rentável e robusta no cenário avaliado e o biorreator TA obteve a segunda posição. O biorreator TA foi escolhido como o mais adequado analisando de maneira conjunta os dados experimentais obtidos, a análise dos custos dos diferentes sistemas de cultivo e a escalonabilidade de cada sistema. Assim, esse biorreator foi eficientemente utilizado para o cultivo de MCUs em condições isentas de SFB e xenoantígenos, sendo possível a produção de uma grande quantidade de células, representando um passo importante no desenvolvimento de um bioprocesso em conformidade com as normas das agências regulatórias. Por fim, com a análise do secretoma das CMMs por espectrometria de massas foi possível a identificação de uma gama enorme de proteínas interessantes (aprox. 2400) envolvidas em importantes processos biológicos. O futuro monitoramento dessas proteínas em biorreatores poderá representar um método inovador e original de produção de produtos livres de células para uso na terapia celular. / Mesenchymal stem/stromal cells (MSC) have become of great interest for cell therapy because of its potential to differentiate and reconstitute specialized tissues. More recently, such interest has significantly increased due to the discovery that MSC are capable of secreting a plethora of mediators to stimulate the in situ regeneration of injured tissues. Thus, MSC can be considered as a therapeutic product itself and as a biofactory of various relevant therapeutic proteins. To meet these increasing demands, both applications require the development of high-yield, reproducible, scalable and cost-effective bioprocesses under defined culture conditions, obtaining products with proper identity, purity and safety. Based on these, the main goal of this work was the establishment of a MSC expansion process based on bioreactors and secretome characterization of these cells targeting therapeutic applications. The MSC expansion was performed using multi-layered flasks (ML) and fixed bed (PB), stirred tank (STR) and hollow fiber (HF) bioreactors. The results showed that the proliferation rate of the cells was higher (< doubling time) in the HF bioreactor (36.8 ± 1.7 hours), as well as the expansion fold-increase (9.8±1.0) and harvesting efficiency (100%). A similar level of cell production was observed for STR, ML and PB with high fold-increase (8.8±0.39, 8.7±0.90, 6.9±1.3, respectively). However, in terms of harvesting efficiency (%), PB bioreactor presented the lowest retrieval rate across all the technologies (18% (±0.77)), followed by STR (61% (±15.7)). The cells retained their functional properties after culture in all the culture systems evaluated. This study was then extended through the use of a bioprocess economics tool for the evaluation of the economic feasibility of producing MSC-based treatment for acute graft vs. host disease (aGvHD) at commercial scale, using the culture systems experimentally evaluated under different reimbursement strategies. Despite the advantageous experimental results of HF bioreactors, the COG analysis has revealed that this is the least cost effective cell culture system to be used, due to its high consumable and equipment costs. ML flasks ranked first as the most cost effective and robust technology in this scenario and microcarrier-based technologies (STR) ranked in second position. The STR bioreactor was chosen as the most suitable for MSC expansion analyzing the experimental data, COG analysis and scalability of each culture system. Thus, STR bioreactor was efficiently tested for MSC expansion under serum and xeno-free conditions and it was possible to produce a large amount of cells. The development of a scalable microcarrier-based stirred culture system using xeno-free culture medium that suits the intrinsic features of UCM-derived MSC represents an important step towards a GMP compliant large-scale production platform for these promising cell therapy candidates. Finally, with the MSC secretome analysis by mass spectrometry it was possible to identify a wide range of interesting proteins (approx. 2400) involved in important biological processes. The future monitoring of these proteins in bioreactors may represent a novel and unique method of producing cell-free products for use in cellular therapy.

Les affections articulaires touchant le cartilage, telles que les lésions focales et l’arthrose, correspondent aux principales causes de baisse de performance et d’arrêt prématuré de la carrière sportive du cheval. Ainsi, le traitement des affections du cartilage représente un enjeu vétérinaire majeur dans le monde équin, du fait des importantes pertes financières qu’elles occasionnent à la filière. Les faibles capacités de réparation intrinsèque du cartilage, ainsi que l’absence de thérapie à long terme des dommages cartilagineux, nécessitent le recours à des thérapies de nouvelles générations telle que l’ingénierie tissulaire du cartilage. Dans ce cadre, notre étude s’est attachée à comparer différents types cellulaires pour la génération de cartilage in vitro, afin d’envisager une implantation pour traiter les atteintes cartilagineuses chez le cheval. Une technique initialement développée chez l’Homme, la transplantation de chondrocytes autologues, représente toujours un « gold standard » en ingénierie tissulaire du cartilage. Dans ce travail de thèse, après avoir développé une nouvelle génération de substitut cartilagineux de haute qualité biologique, à partir de chondrocytes articulaires équins, des limites techniques et biologiques inhérentes au type cellulaire persistent. Ainsi, nos travaux se sont tournés vers la recherche de types cellulaires alternatifs. Les cellules souches/stromales mésenchymateuses (CSM) néonatales issues de cordon ombilical telles que les CSM de sang placentaire (CSM-SPL) et les CSM de gelée de Wharton (CSM-GW) pourraient représenter un avantage thérapeutique du fait de leur isolement non-invasif, de leur forte prolifération cellulaire et de leur capacité de différenciation en chondrocyte. Il est néanmoins indispensable de définir le meilleur candidat thérapeutique, parmi ces deux sources cellulaires, pour l’obtention d’un substitut cartilagineux de qualité biologique optimale. Ces résultats de thèse ont montré d’importantes différences dans le processus de chondrogenèse de ces deux sources de CSM néonatales et plaident en faveur de l’utilisation des CSM-SPL dans le cadre d’une stratégie thérapeutique d’ingénierie tissulaire du cartilage équin. Ces travaux ont permis une meilleure compréhension de la biologie du chondrocyte et des CSM. De surcroît, ces travaux permettent d’envisager de futurs essais cliniques chez le cheval, afin de traiter les affections articulaires de ce modèle gros animal. / Articular cartilage disorders, such as focal defects and osteoarthritis, are the main causes of decreased performance or early retirement of sport- and racehorses. Thus, cartilage disorders represent a major veterinary issue in the equine industry, due to significant financial losses. Poor intrinsic cartilage repair properties and the absence of long- term therapy for cartilage defects lead to the development and use of new generation therapies such as autologous chondrocytes implantation. In this context, our study aimed to compare different cell types for the in vitro cartilage generation, in order to implant the biological substitute to treat cartilage defects in the horse. A therapeutic strategy initially developed in human medicine, the autologous chondrocytes transplantation, always represents a "gold standard" in cartilage tissue engineering. In the present study, after developing a new generation of cartilaginous substitute of high biological quality, composed of equine articular chondrocytes, technical and biological limits inherent to the cell type persist. Thus, we have used alternative cell types such as neonatal mesenchymal stem/stromal cells (MSCs) from umbilical cord, such as umbilical cord blood MSC (UCB-MSCs) and umbilical cord matrix or Wharton jelly MSCs (UCM- MSCs). These MSCs sources could represent a therapeutic advantage due to their non-invasive isolation, their high cell proliferation and their ability to differentiate into chondrocytes. Nevertheless, it is essential to define the best therapeutic candidate between these two MSCs sources, to obtain an optimal quality for the neocartilaginous substitute. Our data highlighted important differences in the chondrogenesis process of these two neonatal MSCs sources, allowing us to consider UCB-MSCs as the best therapeutic candidate for equine cartilage tissue engineering. This work allows a better understanding of the chondrocyte and MSCs biology. Moreover, this work leads the way to setting-up future clinical trials in the horse, in order to treat articular defects of this large animal model.