Células reticulares fibroblásticas (FRCs, gp38+ e CD31-) e células duplo negativas (DNCs, gp38- e CD31-) são células estromais encontradas em órgãos linfoides secundários, como linfonodos. Enquanto as FRCs têm sido amplamente estudadas, pouco se sabe ainda sobre DNCs. Apesar da função estrutural das FRCs nos linfonodos já estar bem estabelecida, estudos recentes indicam que as FRCs também desempenham um papel fundamental em processos imunológicos, por exemplo, migração celular, ativação e qualidade da resposta imune, além da participação na tolerância periférica. Outra célula estromal em constante estudo são as células-tronco mesenquimais (CTMs), principalmente encontradas na medula óssea. Estas células compartilham similaridades, como por exemplo; são células estromais encontradas em órgãos linfoides, apresentam morfologia e características semelhantes quando cultivadas in vitro e estão envolvidas na resposta imune por mecanismos semelhantes. As CTMs são provenientes de um órgão linfoide primário, cuja função principal não está relacionada à resposta imunológica, entretanto, de acordo com inúmeros trabalhos, estas células possuem capacidade de interferir na ativação de várias células do sistema imunológico. Portanto, nossa hipótese é de que as FRCs e DNCs, que se encontram em um órgão linfoide secundário, cuja função principal remete a resposta imunológica, apresentem também um papel regulador, descrito na literatura como tolerância periférica e contração de uma resposta imunológica já estabelecida. Em nosso estudo mostramos que FRCs e DNCs foram isoladas a partir de linfonodos humanos e devidamente caraterizadas. Evidenciamos que FRCs e DNCs atendem todos os critérios mínimos propostos pela sociedade internacional de terapia celular para serem consideradas células-tronco estromais. Além disso, mostramos que FRCs e DNCs influênciam a proliferação e a expressão de moléculas de homing em linfócitos alogênicos in vitro. Portanto, contribuimos de forma inédita para o entendimento funcional das FRCs e DNCs, visto que estudos em humanos envolvendo estas células são escassos / Fibroblastic reticular cells (FRCs, gp38+ e CD31-) and double-negative cells (DNCs, gp38- e CD31-) are stromal cells found in secondary lymphoid organs, such as lymph nodes. While the FRCs has been widely studied, little is known about DNCs. Despite the structural function of FRCs on lymph nodes is well established, recent studies indicate that FRCs also play a key role in immunological processes, for example, cell migration, immune response activation and quality, beyond their involvement in peripheral tolerance. Another stromal cell type in constant study are mesenchymal stem cells (MSCs), mainly found in bone marrow. These cells share similarities with FRCs and DNCs, for example; they are estromal cells found in lymphoid organs, they present similar morphology and characteristics when cultured in vitro and they are involved in the immune response by similar mechanisms. MSCs are derived from a primary lymphoid organ which the major function is not related to immune response, but according to numerous studies these cells have the capacity of the interfere on activation of various immune cells. Consequently, our hypothesis is that FRCs and DNCs, usually found in secondary lymphoid organ, display immune regulatory roles, which were described in the literature as peripheral tolerance and immune response contraction. In our study we showed that FRCs and DNCs were isolated from human lymph nodes and adequately characterized. We evidenced that FRCs and DNCs meet all minimum criteria proposed by the International Society of Cell Therapy to be considerate a stromal stem cell. Therefore, we contributed in an unpublished manner to the functional understanding of FRCs and DNCs, since human studies involving these cells are scarce

Introduction It is well known that resident adipose stem/stromal cells (ASCs) are a heterogeneous population of multipotent cells characterized by (a) their ability to adhere to plastic; (b) immunophenotypic expression of certain cell surface markers, while lacking others; and (c) the capacity to differentiate into cells of mesodermal origin including osteocytes, chondrocytes and adipocytes. Adipose derived stromal cells offer great therapeutic potential in multiple medical fields, including, orthopedics, cardiology, oncology and degenerative diseases, to name a few. Combining different disciplines of medicine and engineering, organ and tissue repair can be achieved through tissue engineering and regenerative medicine. Adipose derived stromal cells (ASCs) can be utilized as biological vehicles for vector-based gene delivery systems, since they home to sites of inflammation and infection in vivo. In order to reach the long-term aim of clinical translation of cell-based therapy, preclinical safety and efficacy need to be shown in animal models. This has motivated the development of standardized isolation, characterization and differentiation operating procedures as well as an in vivo tracking system for ASCs and lentiviral vector transduction for a vector-based gene delivery system. Methodology Human ASCs were isolated from lipoaspirate, expanded in culture, immunophenotyped using flow cytometery and induced to differentiate into adipogenic, osteogenic and chondrogenic lineages. Tri-lineage differentiation was confirmed by microscopy. The ASCs were then transduced with green fluorescent protein (GFP)-expressing lentiviral vectors in vitro. The effect of the GFP lentiviral vector on ASCs was investigated by studying ASC immunophenotypic expression of surface markers as well as their capacity to differentiate into osteocytes, chondrocytes and adipocytes. Results The isolated and expanded cell population, from harvested lipoaspirate adhered to recommended ASC identity criteria. The heterogeneity of ASCs was confirmed by the presence of sub-populations. Transduction efficiency in ASC cultures of approximately 80% was observed after introducing a total of 300 μl of concentrated lentiviral vector suspension per 4.8 x 104 cells. No immunophenotypic differences were observed between GFP positive and GFP negative cultures. Flow cytometric analysis revealed a progressive increase in GFP expression following in vitro expansion of transduced ASCs. Both non-transduced and transduced cultures successfully differentiated into osteocytes, chondrocytes and adipocytes. Conclusion The isolated and expanded cell population conformed to the recommended characterization criteria. Heterogeneity was demonstrated with the identification of immunophenotypic sub-populations and semi-quantification of adipogenesis was performed. ASCs were efficiently transduced using the GFP lentiviral vectors produced in our facility. In addition, transduced ASCs maintained adherence to plastic, ASC immunophenotype and were able to differentiate successfully into cells of the three lineages of mesodermal origin. This optimized GFP-ASC transduction technique offers a feasible tracking system as well as a vector-based gene delivery system for future preclinical studies. / Dissertation (MSc)--University of Pretoria, 2015. / tm2015 / Immunology / MSc / Unrestricted

Studies indicate that estrogen enhances Chlamydia trachomatis serovar E infection in genital epithelial cells. Hormones have direct and indirect effects on endometrial epithelial cells. Estrogen and progesterone exposure induces endometrial stromal cells to release effectors that subsequently regulate growth and maturation of uterine epithelial cells. Estrogen enhances C. trachomatis infection by aiding entry and intracellular development in endometrial epithelial cell (Ishikawa, IK)/SHT-290 stromal cell co-culture. Enhanced chlamydial infection was mediated by direct estrogen-stimulated signaling events in epithelial cells and indirectly via estrogen-induced stromal cell effectors. The current study investigates the effects of hormones on chlamydial development using culture conditions representative of the menstrual cycle. Chlamydia trachomatis-infected IK or IK/SHT-290 cultures were exposed to 10(-8) M estrogen (E2), 10(-7) M progesterone (P4) or a combination of both hormones (10(-8) M E2 followed by 10(-9) M E2/10(-7) M P4). Chlamydial infectivity and progeny production were significantly decreased (30-66%) in cultures exposed to progesterone or estrogen/progesterone combination compared to estrogen alone. Thus, progesterone antagonized the positive effects of estrogen on chlamydial infection. These data indicate the susceptibility of endometrial epithelial cells to C. trachomatis infection during the menstrual cycle is altered by phase specific actions of sex hormones in the genital tract.

Master of Science / Department of Anatomy and Physiology / Mark L. Weiss / Wharton's jelly is a non-controversial source of mesenchymal stromal cells. Isolation of the cells is non-invasive and painless. The cells have been shown to have a wide array of therapeutic applications. They have improved symptoms when transplanted in a variety of animal disease models, can be used in tissue engineering applications to grow living tissue ex vivo for transplantation, and can be used as drug delivery vehicles in cancer therapy. The cells have also been shown to be non-immunogenic and immune suppressive. This thesis focuses on optimizing isolation protocols, culture protocols, cryopreservation, and characterization of cells in different growth conditions. Results from the experiments indicate that isolation of cells by enzyme digestion yields cells consistently, a freezing mixture containing 90% FBS and 10% DMSO confers maximum viability, and the expression of mesenchymal stromal cell consensus markers does not change with passage and cryopreservation. The results of the experiments also show that cells grow at a higher rate in 5% oxygen culture conditions compared to 21% oxygen culture conditions, serum does not have an effect on growth of the cells, serum and oxygen do not have effects on the expression of mesenchymal stromal cell consensus markers and the cells are stable without nuclear abnormalities when grown in 5% oxygen and serum free conditions for six passages after first establishing in serum conditions.

Background: Adipose-derived stem/stromal cells (ASCs) isolated from the stromal vascular fraction are a source of mesenchymal stem cells that have been shown to be beneficial in many regenerative medicine applications. ASCs are an attractive source of stem cells in particular, due to their lack of immunogenicity. This study examines differences between mitochondrial bioenergetic profiles of ASCs isolated from adipose tissue of five peri-organ regions: pericardial, thymic, knee, shoulder, and abdomen. Results: Flow cytometry showed that the majority of each ASC population isolated from the adipose tissue of 12 donors, with an n = 3 for each tissue type, were positive for MSC markers CD90, CD73, and CD105, and negative for hematopoietic markers CD34, CD11B, CD19, and CD45. Bioenergetic profiles were obtained for ASCs with an n = 4 for each tissue type and graphed together for comparison. Mitochondrial stress tests provided the following measurements: basal respiration rate (measured as oxygen consumption rate [pmol O-2/min], ATP production, proton leak, maximal respiration, respiratory control ratio, coupling efficiency, and non-mitochondrial respiration. Glycolytic stress tests provided the following measurements: basal glycolysis rate (measured as extracellular acidification rate [mpH/min]), glycolytic capacity, glycolytic reserve, and non-glycolytic acidification. Conclusions: The main goal of this manuscript was to provide baseline reference values for future experiments and to compare bioenergetic potentials of ASCs isolated from adipose tissue harvested from different anatomical locations. Through an investigation of mitochondrial respiration and glycolysis, it was demonstrated that bioenergetic profiles do not significantly differ by region due to depot-dependent and donor-dependent variability. Thus, although the physiological function, microenvironment and anatomical harvest site may directly affect the characteristics of ASCs isolated from different organ regions, the ultimate utility of ASCs remains independent of the anatomical harvest site.

Malgré le rôle des variants constitutivement actifs du récepteur des androgènes (RA) et du stroma tumoral dans le cancer de la prostate résistant à la castration (CRPC), leurs relations restent inconnues. Nous rapportons l’impact de l’interleukine-6 (IL-6) sécrétée par les cellules stromales prostatiques (PrSC) sur les cellules épithéliales tumorales prostatiques exprimant les variants autonomes du RA. Le milieu de culture conditionné par les PrSC (CMPrSC) contenait des taux élevés d’IL-6 et induisait une augmentation de l’activité transcriptionnelle de STAT3 dans les LNCaP et C4-2b exprimant le variant RAQ640X, via une activation de pY705-STAT3. Cette activité de STAT3 était inhibée par la neutralisation de l’IL-6. L’analyse par mRNA array et RT-qPCR a mis en évidence un profil transcriptomique spécifique lié à l’expression du RAQ640X et à l’exposition au CMPrSC, impliquant les fonctions de motilité, d’invasion et de migration cellulaires, et l’expression de gènes favorisant la dissémination métastatique. Ainsi, nos résultats illustrent une coopération épithélio-stromale «privilégiée» en présence de variants autonomes du RA, impliquée dans la progression tumorale. / Constitutively active androgen receptor (AR) variants and stromal microenvironment are involved in castration resistant prostate cancer (CRPC), but their relationship remains unknown. We describe the effects of interleukin-6 (IL6) secreted from prostate stromal fibroblast cells (PrSC) towards prostate epithelial cancer cells expressing constitutively active AR variants. Conditioned culture medium from PrSC (CMPrSC) contained high levels of IL-6 and led to an increased STAT3 transcriptional activity in LNCaP and C4-2b cells expressing the ARQ640X variant, through pY705-STAT3 activation. This STAT3 activity was significantly diminished with neutralizing antibody anti-IL6. Gene expression analysis using mRNA array and RT-qPCR highlighted a specific transcriptional profile related to ARQ640X expression and PrSC exposure, resulting in cellular motility, invasion and cellular migration, and IL-6 genes expression promoting metastatic dissemination. Overall, our data emphasize a “preferred” epithelio-stromal cooperation when expressing constitutive active RA variants, which contributes to tumor progression.

1. Einleitung Multipotente mesenchymale Stromazellen (MSC) stellen eine interessante Therapieoption in der regenerativen Medizin verschiedener Erkrankungen dar. Aufgrund ihrer Herkunft aus mesodermalem Gewebe ist ihr Einsatz in der Therapie von Sehnenerkrankungen als günstig anzusehen, wo sie bei Pferden bereits erfolgreich verwendet werden. Da dieser Erkrankungskomplex mit degenerativen Veränderungen der Achillessehne des Menschen vergleichbar ist, wäre eine Translation der gewonnenen Ergebnisse in die Humanmedizin wünschenswert. Die zugrunde liegenden Wirkmechanismen bei der Sehnenregeneration sind allerdings bis zum heutigen Tage noch nicht vollständig geklärt. Unter anderem wird eine tenogene Differenzierung der MSC mit nachfolgender Produktion von extrazellulärer Matrix (EZM) diskutiert. Als Nachweis hierfür wird die Genexpression von Matrixproteinen sowie Transkriptionsfaktoren angesehen. Die Isolation von MSC ist aus verschiedenen Geweben möglich; allerdings haben Untersuchungen deutliche Unterschiede in den in-vitro-Charakteristika zwischen den Zellquellen aufgezeigt. Trotz dieser unterschiedlichen Eigenschaften fasst die International Society for Cellular Therapy (ISCT) seit 2006 humane MSC als plastikadhärente Zellen mit tripotentem Differenzierungspotential sowie einem definierten Antigenprofil zusammen. Um eine Vergleichbarkeit equiner und humaner MSC und somit eine bessere Übertragbarkeit gewonnener Erkenntnisse aus der Pferdemedizin zu erreichen, steht aktuell die Untersuchung der geforderten Antigenexpression noch aus. 2. Ziele der Untersuchung In der vorliegenden Arbeit sollte daher erstmalig eine vollständige Charakterisierung des geforderten Antigenprofils equiner MSC aus fünf verschiedenen Quellen durchgeführt werden, um einen Vergleich mit humanen Zellen zu ermöglichen. Zudem sollte eine vergleichende Darstellung der Sehnenmarkerexpression durchgeführt werden, welche das Wissen um die in-vitro-Eigenschaften von MSC erweitern und in Folge zur Auswahl einer optimal für die Therapie von Sehnenerkrankungen geeigneten Zellquelle beitragen soll. 3. Materialien und Methoden In der ersten Studie wurden equine MSC aus Knochenmark, Fettgewebe, Nabelschnurblut, Nabelschnurgewebe und Sehnengewebe bis zur Passage 3 kultiviert und anschließend mittels Durchflusszytometrie auf das Vorkommen der Antigene CD 29, CD 44, CD 73, CD 90 und CD 105 sowie das Fehlen der Antigene CD 14, CD 34, CD 45, CD 79α und MHC II untersucht. In der zweiten Studie wurde eine Genexpressionsanalyse der Sehnenmarker Kollagen 1A2, Kollagen 3A1, Decorin, Tenascin-C und Skleraxis vergleichend mittels Echtzeitpolymerasekettenreaktion an den isolierten Zellen durchgeführt. In beiden Studien wurde eine Probenzahl von n= 6 für jede Zellquelle untersucht. 4. Ergebnisse Keine der untersuchten Zellquellen erfüllte die MSC-Definition der ISCT bezüglich des Antigenprofils. Insbesondere durch den fehlenden Nachweis CD 73 (< 3,07 %) in allen untersuchten Proben unterscheiden sich equine und humane MSC. Die einzigen stabil exprimierten Antigene sind die zusätzlich untersuchten Proteine CD 29 (37,5 % - 65,42 %) und CD 44 (32,2 % - 97,18 %). Das Vorkommen CD 105 konnte in MSC aus Fett- und Sehnengewebe belegt werden. Zusätzlich war ein Nachweis von CD 90 in MSC aus Fettgewebe möglich, welche somit die größte Ähnlichkeit mit der humanen Zellpopulation aufweisen. Die Studie zur Genexpressionsanalyse weist auf eine Basisexpression von Kollagen 1A2, 3A1 und Decorin in MSC aus verschiedenen Quellen hin, welche über der von nativem Sehnengewebe liegt. Auch hier weisen wiederum MSC aus Fettgewebe die höchste Expression auf. 5. Schlussfolgerungen Die vorliegende Arbeit leistet einen Beitrag zu einer vertiefenden in-vitroCharakterisierung equiner MSC. Das Antigenprofil equiner MSC ist nicht vollständig mit dem humaner identisch. Eine abschließende Beurteilung sollte durch Untersuchungen mit spezies-spezifischen Antikörpern erfolgen. Die Ergebnisse der Genexpressionsanalyse unterstützen die Theorie, dass MSC die Sehnenheilung durch Produktion von extrazellulärer Matrix beeinflussen. Der Einsatz von MSC aus Fettgewebe in der Therapie von Sehnenerkrankungen sollte forciert werden, da ihre hohe Sehnenmarkerexpression einen Hinweis auf eine Verbesserung der Sehnenregeneration darstellt.

The contribution of the bone marrow microenvironment in myelodysplastic syndrome is controversial. We therefore analyzed the functional properties of primary mesenchymal stromal cells from patients with myelodysplastic syndrome in the presence or absence of lenalidomide. Compared to healthy controls, clonality and growth were reduced across all disease stages. Furthermore, differentiation defects and particular expression of adhesion and cell surface molecules (e.g. CD166, CD29, CD146) were detected. Interestingly, the levels of stromal derived factor 1-alpha in patients’ cells culture supernatants were almost 2-fold lower (P<0.01) than those in controls and this was paralleled by a reduced induction of migration of CD34+ hematopoietic cells. Co-cultures of mesenchymal stromal cells from patients with CD34+ cells from healthy donors resulted in reduced numbers of cobblestone area-forming cells and fewer colony-forming units. Exposure of stromal cells from patients and controls to lenalidomide led to a further reduction of stromal derived factor 1-alpha secretion and cobblestone area formation, respectively. Moreover, lenalidomide pretreatment of mesenchymal stromal cells from patients with low but not high-risk myelodysplastic syndrome was able to rescue impaired erythroid and myeloid colony formation of early hematopoietic progenitors. In conclusion, our analyses support the notion that the stromal microenvironment is involved in the pathophysiology of myelodysplastic syndrome thus representing a potential target for therapeutic interventions.

Le cancer du sein est le cancer le plus fréquent chez la femme et représente un problème de santé publique majeur. L'agressivité des tumeurs mammaires varie notamment en fonction de leurstatut pour le récepteur α des oestrogènes (ERα). Les cancers du sein n'exprimant pas ERα ont unmauvais pronostic, de part leur capacité métastatique plus importante. Cependant, les facteurs sous jacents à cette plus grande agressivité des cancers ERα-négatifs restent mal compris. Il est aujourd'hui admis que la progression tumorale et la dissémination métastatique dépendent, non seulement des propriétés intrinsèques des cellules cancéreuses, mais également des régulations exercées sur ces cellules par le micro environnement tumoral. Les interactions entre les cellules cancéreuses et les cellules présentes au niveau du site tumoral, telles que les cellules leucocytaires,les cellules endothéliales, ainsi que les cellules stromales, sont nécessaires au développement et à l'évolution de la tumeur. Ces interactions sont médiées via la production d'hormones, de cytokines ainsi que de chimiokines. Les cellules stromales mésenchymateuses (MSC) sont de composants essentiels du stroma tumoral. Leur rôle dans la progression des tumeurs reste, pour le moment, très controversé. L'objectif de notre projet a été de comprendre les raisons pour lesquelles les MSC peuvent favoriser ou inhiber le développement tumoral. Nous nous sommes, dans un premier temps,intéressés aux interactions entre les cellules cancéreuses mammaires et les MSC. Nous avons déterminé si le fait que les cellules cancéreuses soit métastatiques ou non modifiait le phénotype des MSC et leur réponse dans les régulations de la croissance tumorale. Nous avons ainsi constaté quel es facteurs sécrétés spécifiquement par les cellules cancéreuses métastatiques ERα-négativesinduisaient la production de certaines chimiokines, dont CXCL5. Ces chimiokines peuvent êtressécrétées par les cellules du microenvironnement mais également par les cellules cancéreuses ellesmêmes.Nous avons donc étudié le rôle de CXCL5 dans l'agressivité des tumeurs mammaires. Nousavons ainsi montré que ces chimiokines induisent, in vitro, une augmentation des propriétésprolifératives, invasives et migratoires des cellules cancéreuses. Cette étude nous à permis demontrer que les chimiokines et les interactions entre les cellules cancéreuses et les MSC pouvaientêtre impliquées dans la progression tumorale ainsi que dans l'agressivité des tumeurs mammaires. / Breast cancer remains in Europe and USA the first cause of death by cancer for women.Breast cancer aggressiveness relies in particular on estrogen receptor α (ERa) status. Breast cancers which do not express ERα are more metastatic and have a poorer prognosis, than ERα-positivetumors. However underlying factors involved in these invasive properties are poorly understood.Today, it is established that tumor progression is regulated by intrinsic cancer cells properties, and byinteractions between cancer cells and surrounding microenvironment. Several evidences suggest thatleukocytes, endothelial cells, fibroblasts and infiltrating cells present in stromal compartment caninteract with tumor cells through the production of hormones, cytokines and chemokines.Mesenchymal stromal cells (MSC) belong also to the stromal compartment. Recent studies havehighlighted their potential role in cancer growth and metastasis. However, the ability of MSC to favor orprevent cancer progression remains controversial. The aim of this work was to understand the roles ofMSC in tumor progression and to explain the differential effects of MSC on cancer cells, depending onthe type of cancer cells involved. First, we were analyzed MSC and cancer cells interactions, anddetermined if metastatic cancer cells could affect MSC phenotypes and its response in terms of tumorgrowth. We observed that metastatic breast cancer cells secreted factors, which could highly enhancethe release by MSC of several chemokines, including CXCL5. CXCL5 can be secreted by stromal cellsbut also by cancer cells themselves. We next showed in vitro that CXCL5 increased proliferative,invasive and migratory properties of breast cancer cells. This study allowed us to demonstrate thatchemokines play a role in the cross-talk between MSC and breast cancer cells, and that they play akey role in tumor proliferation and aggressiveness.

Les douleurs viscérales chroniques font partie des effets secondaires des patients traités pour des cancers de la zone pelvienne. Ces douleurs peuvent affecter grandement la qualité de vie de ces patients. Dans les cas les plus graves, il n'existe pas de traitement analgésique efficace. Ainsi le développement de nouvelles stratégies thérapeutiques efficaces constitue un enjeu majeur. Au sein de notre laboratoire, le potentiel réparateur et immuno-modulateur des cellules stromales mésenchymateuses (CSM) a déjà été démontré dans un modèle d'ulcération colorectale radio-induite chez le rat. Dans ce contexte, l'objectif de ma thèse était d'évaluer d'abord la pertinence de l'utilisation de ce modèle pour l'étude de l'hypersensibilité viscérale persistante radio-induite, puis, le bénéfice thérapeutique de l'utilisation des CSM comme agent antinociceptif. Nous avons dans un premier temps démontré, dans ce modèle, le maintien au cours du temps d'une hypersensibilité viscérale associée à une sensibilisation centrale persistante après irradiation, validant ainsi le modèle. Nous avons ensuite montré l'implication des mastocytes (MC) et suggéré l'implication du neuromédiateur NO dans les mécanismes de la sensibilisation périphérique sous-tendant une telle hypersensibilité. Nous avons enfin mis en évidence que le traitement par des CSM permettait la réduction de l'hypersensibilité viscérale radio-induite persistante. La capacité des CSM à moduler l'activation des MC et/ou leurs interactions avec les fibres nerveuses pourrait être impliquée dans leur action antinociceptive. En conclusion, ce travail a permis d'élargir le spectre d'action thérapeutique des CSM dans notre modèle d'étude. / Patients who undergo pelvic radiotherapy may develop significant incidence of undesirable chronic gastrointestinal complications resulting from radiation-induced damages around the tumour. Chronic visceral pain is one of the radiation-induced side effects that greatly affects the quality of life of “cancer survivors”. The lack of effective analgesic treatment highlights the importance of novel and effective therapeutic strategies. In our laboratory, mesenchymal stromal cell (MSC) based approach showed beneficial immunomodulatory and regenerative effects in a rat model of irreversible radiation-induced colonic ulcers. The goal of my work was to assess the relevance of this model to study radiation-induced visceral persistent hypersensitivity and its modulation by MSC treatment. We first demonstrated that this model is associated with long-lasting visceral hypersensitivity and central neuronal sensitization. In this context we showed then that mast cells (MC) are involved in the mechanism of peripheral sensitization. Moreover, we suggested the implication of the neuromediator NO• in the pathophysiology of persistent radiation-induced visceral hypersensitivity. We also suggested that MSC treatment reversed radiation-induced hypersensitivity by a mechanism that in part may involve the modulation of MC activation and/or the decrease in the number of MC and nerve fiber interactions. In addition, MSC treatment reduced the percentage of nitrinergic neurons, increased after irradiation, and restored colonic muscular contractibility. Such processes may promote the therapeutic benefit of MSC observed in our study. In conclusion, this work provided new insights on the therapeutic benefit of MSC in our study model and a new argument in favour of their use in a future clinical trial to cure abdominopelvic radiotherapy side effects.