Les objectifs de ce travail expérimental étaient : 1. Évaluer la place de la lactatémie capillaire comme dispositif de monitorage de l’ischémie et de la reperfusion tissulaire. 2. Comparer le suivi local du taux de lactate, au niveau du compartiment ischémié, par rapport au taux systémique du lactate lors des l’ischémie de membre, l’ischémie intestinale ainsi que durant le choc hémorragique. La mesure capillaire du taux de lactate pourrait permettre: 1. d’affirmer l’existence d’une ischémie tissulaire régionale. Le taux systémique du lactate ne permet ce diagnostic, 2. de confirmer l’efficacité d’une reperfusion au niveau d’un membre préalablement ischémique tandis que la mesure systémique des lactates ne le permet pas. L’affirmation de l’efficacité de la reperfusion et de sa constance, par une mesure aussi simple que la lactatémie capillaire compartimentale représente une avancée majeure en comparaison avec les autres méthodes existantes. La mesure capillaire du taux de lactate systémique dans une situation d’hypoperfusion par choc hémorragique n’est pas associée à augmentation du taux de lactate intra-musculaire. / Our objectives for this experimental work were: 1. Assessment of capillary lactate for tissue ischemia and reperfusion monitoring. 2. Compare the local and systemic capillary lactate time course during compartmental ischemia insults like limb ischemia, intestinal ischemia or during hemorrhagic shock. The capillary measurement of the lactate in IR could be interesting for: 1. Assessing a limb or intestinal tissue ischemia. On the opposite, the systemic measurement could not assess this diagnosis. 2. Assessing the efficiency of a limb reperfusion. On the opposite, the systemic measurement could not assess this diagnosis. The systemic capillary lactate measurement during haemorrhagic shock related hypo perfusion could not be associated with an increase in intra muscular lactate.

A protocol for cauliflower micro-propagule production was developed and optimised for both micropropagation and artificial seed production techniques using meristematic tissues from cauliflower curd. All steps in the protocol were empirically optimised including: blending, sieving, culture methods, liquid culture media composition and plant growth regulator combinations and concentrations. The cost of the micro-propagules could be reduced by as much as 50% on the initial costings reported previously since treatments doubled the number of microshoots produced per culture unit. The research confirmed the suitability of cauliflower microshoots to be encapsulated as artificial seeds and an effective protocol for microshoot encapsulation was designed through the optimization of 1) the production of cauliflower microshoots suitable for encapsulation, 2) encapsulation procedures, 3) artificial seed artificial endosperm structure, 4) conversion materials. The possibility of culturing cauliflower artificial seeds in commercial substrates such as perlite, sand, vermiculite and compost was confirmed. The use of plant preservative mixture (PPM) for the control of contamination in cauliflower culture media and artificial seeds was optimised and the effect of this material on the development of plant material was assessed. It was confirmed that cauliflower artificial seed could be stored in a domestic refrigerator for up to 6 months which could have a great impact in cauliflower breeding programmes. The huge number of cauliflower microshoots that could be produced using this protocol and the homogeneity of the culture system, provided a tool for the molecular analysis of cauliflower microshoots (and artificial seed) abiotic stress tolerance analysis. Various treatments were conducted to improve microshoot cold tolerance and the up-regulation of the CBF/DREB1 transcription factor including low temperature acclimation, mannitol, ABA (abscisic acid) and Mo (molybdenum). Microshoots were confirmed to acclimate successfully using low temperature. Mo was shown to improve the cold tolerance of cauliflower microshoots and to up-regulate CBF/DREB1 in the absence of low temperature acclimation. Acclimation did not increase the accumulation of dehydrin proteins and it is concluded that dehydrins do not play a significant role in the cold tolerance of cauliflower microshoots. Since cauliflower breeding and seed multiplication protocols make extensive use of micropropagation, the studies reported in this research could make a significant impact by decreasing the cost of micropropagation and increasing its reliability. It also opens new perspectives for further research for cauliflower artificial seed production and the possibility of sowing these seeds directly in the field. Furthermore, this research helps to facilitate cauliflower breeding programmes by improving the understanding of abiotic stress tolerance mechanisms and the relationship between different types of abiotic stresses such as cold and drought.

Un cadre théorique classique pour expliquer comment les mouvements volontaires sont générés et optimisés implique l'existence d'un modèle interne basé sur les conséquences sensorielles de ses propres actions. Le cervelet est souvent considéré comme une structure où ces modèles pourraient être efficacement stockés et mis-à-jour. Parmi tous les systèmes sensoriels, le système vestibulaire est probablement celui où la plus grande proportion de stimuli est auto-générés et pourtant peu étudié en conditions actifs. Pour appréhender le rôle du vestibulo-cervelet, nous avons enregistré des cellules de Purkinje du nodulus en condition active chez le rongeur, associé à l'enregistrement quantitatif des signaux inertiels produits par les mouvements de la tête. Cela a nécessité le développent d'outils de mesure adaptés au petit animal. Ces outils, absents du commerce, sont capable d'enregistrer, et cela sans aucun câble, les mouvements inertiels (accélération linéaire et vitesse angulaire) de celui ci offrant une représentation des informations vestibulaires. Les résultats présentés dans cette thèse montrent que, au moins dans des conditions actives, les cellules de Purkinje présentent une sensibilité sélective à certaines composantes du mouvement de la tête. La diversité des réponses observées démontre de plus que chaque cellule possède son propre " champ récepteur vestibulaire ". Il a ainsi été montré que certaines cellules avaient un champ récepteur en coordonnées égocentriques et d'autres allocentriques. Cette distinction s'inscrit dans le problème général de la transformation par le cervelet des coordonnées vestibulaires et de la représentation de l'environnement. / A classical and theoretical explaining framework how voluntary movements are generated and optimized implies the existence of an internal model based on the sensory consequences of own actions. The cerebellum is often considered as a structure where the models could be effectively stored and made-to-day. Of all the sensory systems, the vestibular system is probably one where the largest proportion of stimuli are self-generated but yet little studied in active conditions. To understand the role of the vestibular-cerebellum, we recorded Purkinje cells from nodulus in active condition in rodents associated with quantitative recording of inertial signals produced by head motion. This required developing the measurement tools adapted to small animals. These tools, absent of trade, are capable of recording, without any cables, the inertial movement (linear acceleration and angular velocity) of this one as a representation of vestibular information. The results presented in this thesis show that, at least in active condition, Purkinje cells exhibit selective sensitivity to certain components of the head movement. The diversity of responses observed further demonstrates that each cell has its own "vestibular receptive field". It has thus been shown that some cells have a receptive field in egocentric coordinates while others allocentric. This results is part of the general problem of the coordinate transformation and of the environment representation by the vestibular cerebellum.

White adipose tissue is not just a storage organ. It is now recognised as an endocrine organ. It secretes many substances known as adipokines, which are thought to link obesity with type 2 diabetes (T2D). One of the most important adipokines is adiponectin. It is a peptide hormone consisting of 244 amino acids with molecular weight of 30 KD. It circulates in plasma in high concentrations (3-30 4g/ml). Adiponectin polymerises to form many bigger forms. Those are low molecular weight (LMW); middle molecular weight (MMW) and high molecular weight (HMW). The HMW adiponectin is the active form of the hormone. The concentrations of most adipokines are increased in obese people. Adiponectin is unusual in that its concentration is lower in obese people. Consequently its concentration is decreased in some related metabolic disorders. Its concentrations decrease in cardiovascular diseases, diabetes, dyslipidemia and insulin resistances. It is well known that exercise increases insulin sensitivity, also adiponectin was reported to regulate insulin. The effect of exercise on the adiponectin concentrations in plasma is controversial, but the extent to which the exercise regulates the interstitial adiponectin concentrations is not fully examined. The main site of adipokines secretion is adipose tissue. Therefore the study of these substances at the site of their production has a special interest. Recently, microdialysis techniques have been extended to become important in the measurement of substances in the extracellular fluid of many tissues such as subcutaneous adipose tissue. In particular, it has been used for measurement of adipokines. This thesis includes three studies. The first study was aimed at examining the effect of one hour of moderate exercise at 50% of maximum oxygen consumption v on adiponectin concentration in dialysate samples taken from subcutaneous abdominal adipose tissues (SCAAT). 15 healthy young female volunteers, age 22.8 ± 3.0 years (mean ± SD) participated in this experiment divided into two groups depending on their body mass index (BMI), a lean group BMI 22.2 ± 1.6 kg/m2 (mean ± SD) and an overweight group BMI 27.7 ± 1.9 kg/m2 (mean ± SD). The samples were collected using CMA 66 M. Alzwayi iii microdialysis catheters with membrane cut off 100 KD. Fitness assessment was done for all volunteers about one week before the main trials. The main trials were done on two consecutive days, a rest day and an exercise day. Each day lasted for 4 to 6 hours. On the first day the microdialysis catheter were inserted in abdominal subcutaneous tissue 4 cm lateral to the umbilicus on the left side. Dialysate samples were collected every 30 - 45 minutes. On the exercise day volunteers exercised for one hour at 50% 2 . V O max. All samples were analysed for adiponectin concentrations using Mercodia ELISA technique. The principle findings of this study were that CMA 66 microdialysis catheters worked effectively for two consecutive days for fluid recovery. Adiponectin concentrations were very low and varied, in same volunteer from time to time, and between volunteers. However, the statistical analysis showed no significant difference in adiponectin concentrations between lean and overweight groups. Adiponectin concentrations in the first two samples on the first day of the insertion were significantly higher than the first two samples on the second day of the insertion. Finally, adiponectin concentrations in dialysate samples recovered by 100 KD microdialysis catheters were very low. Therefore, the effect of the exercise was not clear. The second study aimed to compare the adiponectin concentrations in plasma and dialysate samples. Six healthy male volunteers age 32.8 ± 13.1 years and BMI 25.9 ± 3.3 kg/m2 (mean ± SD), were recruited for this study. The experiment was run for two consecutive days using the same microdialysis catheters CMA 66. Dialysate samples were collected as before. 2 ml of blood samples were collected using a cannula inserted into the anticubital vein. Samples were taken every hour for a period of five hours each day. The plasma and dialysate samples were analysed for adiponectin using the Mercodia kits. Adiponectin concentrations in plasma samples were 256 and 1791 times higher than the adiponectin concentrations in dialysate samples. The conclusion of the two studies was that the CMA 66 microdialysis catheter with cut off 100 KD membranes only recovers a small part of the total adiponectin present. M. Alzwayi iv Therefore a third study was designed to use plasma samples. The aim of the study was to investigate the effect of acute exercise at 50% 2 . V O max on HMW adiponectin, total adiponectin, interleukin (IL)-6, tumour necrosis factor alpha (TNF-α), insulin and glucose concentrations directly after the exercise, one hour after and 48 hours. 13 young healthy female volunteers age 24.3 ± 2.7 years and BMI 21.9 ± 2.2 kg/m2 (mean ± SD) contributed in this study. The volunteers were invited for five visits. Their fitness was measured on the first visit. Then they came for two main trials rest day and exercise day, which they were randomly assigned. The main trails lasted for two hours. Three blood samples were collected each day using same cannulated system in the second study. The volunteers followed 48 hours after each trial, one blood sample were collected each day. The 8 plasma samples were analysed for: total adiponectin and insulin concentrations via Mercodia ELISA kits, HMW adiponectin, IL-6 and TNF-α concentration via R&D systems and glucose concentration using the glucose oxidase colorimetric method. The results showed no statistical difference in total or HMW adiponectin, TNF-α and glucose concentrations under the effect of moderate exercise at 50% 2 . V O max either directly or 48 (p value > 0.05). IL-6 concentrations increased about two fold one hour after the exercise above the resting level (P value < 0.05). IL-6 concentrations return to the basal level 48 hour latter. Insulin concentrations show a decrease one hour after the exercise finished. The number of volunteers was small and the change was close to significance. A one way ANOVA returned a P value of < 0.05, but a two way ANOVA with repeated measures returned a P value of > 0.05. In conclusion, the acute exercise at 50% 2 . V O max changes IL-6 concentrations but it has no effect on adiponectin concentrations in dialysate or plasma samples. Low adiponectin concentration is related to obesity, insulin resistance and T2D. Therefore, increase in adiponectin concentration probably lies in weight loss and the exercise may play role, even if it has little direct action on adiponectin concentration.

L'angiogenèse est un processus physiologique qui correspond à la formation de nouveaux vaisseaux sanguins à partir d'un réseau vasculaire préexistant et est régulée par l'équilibre entre les facteurs endogènes pro- et anti-angiogéniques. La rupture de cet équilibre est associée à de nombreuses pathologies dont l'ischémie, la rétinopathie ou encore la progression tumorale. Etant donné que les cellules endothéliales, principal type cellulaire composant les vaisseaux sanguins expriment les récepteurs à activité tyrosine kinase du facteur anticoagulant, la protéine S, Tyro3, Axl et Mer et produisent de la protéine S, l'objectif de ce travail est d'étudier le rôle, de la protéine S dans l'angiogenèse. Dans la première partie de ce travail, nous avons montré in vivo que la protéine S inhibe l'angiogenèse induite par les facteurs pro-angiogéniques (VEGFA et FGF2). Parallèlement, nous avons observé in vitro une inhibition par la protéine S de la prolifération et de la migration des cellules endothéliales induites par le VEGFA. Cet effet est corrélé à l'inhibition par la protéine S des voies de signalisation des MAP-Kinases et de la phosphatidylinositol 3-kinase (PIK3) induites par le VEGFA. Nous avons ensuite mis en évidence, par l'utilisation d'inhibiteurs pharmacologiques et de petits ARNs interférents, que la protéine S inhibe, via l'activation du récepteur Mer et le recrutement de la protéine phosphatase SHP2, l'activation du VEGFR2, le principal récepteur du VEGFA. Dans la deuxième partie, nous avons montré de manière intéressante que le rôle joué par la protéine S lors de l'angiogenèse est plus complexe, puisqu'elle est capable d'activer directement la voie de signalisatio / Angiogenesis is a physiological process that leads to new blood vessel formation and is regulated by a balance between pro-and anti-angiogenic endogenous factors. Disruption of this balance leads to many pathologies such as ischemia, retinopathies or tumor growth. Because endothelial cells, the main cellular type composing blood vessels, produce the anticoagulant factor, protein S and express its tyrosine kinase receptors Tyro3, Axl and Mer, we investigated the implication of protein S in angiogenesis. In the first part of this work, we demonstrated that protein S inhibits pro-angiogenic factors (VEGFA and FGF2)-induced angiogenesis in vivo. We also observed an inhibition of VEGFA-dependent endothelial cell proliferation and migration induced by protein S. These effects were correlated with protein S induced inhibition of VEGFA-dependent MAP-Kinases (Erk1, Erk2) and phosphatidylinositol 3-kinase (PIK3) activation. Furthermore, we demonstrated, using pharmacological inhibitors and small interfering RNAs, that protein S inhibits VEGFA-induced VEGFR-2 activation through Mer receptor activation and SHP2 protein phosphatase recruitment. In the second part, we demonstrated that, protein S on its own, is able to induce MAP-kinases pathway activation and endothelial cells proliferation. These cellular and molecular effects involved Mer receptor and SHP2 protein activation and required protein kinase SRC recruitment. Our results describe for the first time that protein S is an endogenous regulator for angiogenesis both in vitro and in vivo and may form the framework for the use of protein S as part of an anti-angiogenic treatment.

Notre approche biomimétique permet de régénérer une dent entière. Un protocole en deux étapes à partir de réassociations de cellules dentaires embryonnaires permet le développement de la couronne in vitro et, après implantation, la différenciation fonctionnelle des cellules, l’initiation du développement radiculaire et la vascularisation dentaire. Cependant, l’absence d’innervation a nécessité des expériences complémentaires :- La co-implantation de réassociations cellulaires avec un ganglion trigéminal permet la croissance d’axones autour de la dent formée, mais pas dans le mésenchyme dentaire.- Pour tenter de résoudre ce problème, la régénération axonale a été testée dans un contexte immunodéprimé en utilisant la cyclosporine A (CsA). Dans ces conditions, des fibres nerveuses entrent dans la pulpe dentaire, jusqu’aux odontoblastes. Cependant, la CsA a aussi un effet direct sur la croissance axonale.- Des co-implantations chez des souris immunodéprimées (Nude) montrent que l’immunomodulation seule suffit pour l’innervation de la dent.- Dans la dent, les axones assurent différentes fonctions en interagissant avec les cellules voisines. Les relations entre axones et autres cellules (odontoblastes, cellules endothéliales, péricytes et cellules gliales) ont été analysées dans les mésenchymes dentaire et péri-dentaire de réassociations implantées et comparées à ce que l’on observe pour une molaire physiologique à un stade similaire.Ce travail décrit les conditions permettant l’innervation des dents régénérées. Des expériences préliminaires encourageantes ont été réalisées avec des cellules souches pour remplacer la CsA. / Our biomimetic approach allowed the regeneration of a whole tooth. Using embryonic dental cells, a two-steps protocol allowed crown formation in vitro and, after implantation, functional cells differentiation, initiation of root formation and tooth vascularization. However, the teeth were not innervated, which led to complementary experiments:- The co-implantation of cell re-associations with a trigeminal ganglion allowed axonal growth around the forming teeth, but not in the dental mesenchyme. - To try to solve this point, axonal regeneration was tested in immunodepressed conditions, using cyclosporin A (CsA). In these conditions, nerve fibers entered the dental pulp and reached odontoblasts. However, CsA shows multiple effects, including direct ones on nerve growth. - Co-implantations were performed in immunocompromised Nude mice allowed axons to reach the odontoblast layer, thus showing that immunomodulation is sufficient.- Axons in the dental mesenchyme interfere with several functions by interacting with neighbor cells. Relationships between axons and other cells (odontoblasts, endothelial cells, pericytes and glial cells) were analyzed in the peridental and dental mesenchymes of implanted reassociations and compared to the physiological situation in developing molars at similar stage. This work describes conditions allowing the innervation of engineered teeth. Preliminary encouraging attempts have been made to replace CsA by using stem cells.

Les traitements actuels des lésions osseuses maxillo-faciales ont été éprouvés. La greffe autogène présente les propriétés idéales, mais montre des inconvénients : douleurs chroniques, infection… Certains comblements proposés ne permettent pas une néoformation vasculaire, garante de la viabilité des tissus régénérés pour des lésions importantes. Il faut alors développer des implants avec les caractéristiques recherchées et trouver les moyens de lutter contre le risque infectieux. Ce travail présente les résultats de recherches menées sur la fabrication d’implants nanofibreux mimant la MEC du tissu osseux, dotés d’une porosité favorable à une formation vasculaire et pouvant être fonctionnalisés par des facteurs de croissance / des cellules. Une réflexion éthique est menée sur le développement de ces avancées et sur leurs applications afin de garantir qu’elles constituent un réel progrès pour les patients. Il est aussi montré que l’on peut améliorer la sécurité des soins dans le traitement des lésions osseuses maxillo-faciales en développant des équipements dans le champ de l’hygiène et par la mise en place de procédures visant à évaluer leur efficacité. / Current treatments of maxillofacial bone defects have now been proven. Only the autogenous graft presents the ideal properties but shows complications: chronic pain, infection... Some bone filling techniques that are currently available do not allow the formation of blood vessels, guaranteeing the sustainability of the regenerated tissue for large lesions. It is then necessary to develop implants in that way, and to find ways to fight effectively the risk of infection. This work presents the results of research conducted on the fabrication of nanofibrous implants mimicking the ECM of bone tissue, with a porosity that is favorable to a vascular formation. These implants can be functionalized with growth factors / cells. Ethical considerations are provided on the development of these advances, but also on their applications to ensure that these developments constitute a real progress in the interest of patients. Moreover, this work shows that it is possible to improve the safety of care in the treatment of maxillofacial bone defects, with the development of equipment in the field of hygiene and the establishment of procedures to assess their effectiveness.

Dans le cadre du développement d’un larynx artificiel, les expérimentations sur l’animal et les essais cliniques ont mis en évidence un défaut de ré-épithélialisation de la face endoluminale de la prothèse. Cet épithélium respiratoire est absolument nécessaire pour obtenir un dispositif implantable totalement intégré dans le corps mais également pour la fonctionnalité d’un tel implant. Dans ce travail nous avons développé de nouveaux films d’hydrogels de collagène et d’acide hyaluronique interpénétrés et réticulés pour assurer une repousse épithéliale rapide. Ces films d’hydrogels optimisés ont une résistance suffisante à l’hydrolyse pour limiter leur dégradation précoce une fois implantés. Ils ont été fonctionnalisés par des facteurs de croissance et de différenciation cellulaire libérés de façon progressive avec un résultat objectivé sur la prolifération cellulaire. L’encapsulation de cellules immunitaire et l’utilisation de cytokines dans ces gels permettent également de moduler la réponse inflammatoire vers un processus de cicatrisation plutôt que de rejet. / As part of the development of an artificial larynx, in vivo experiments and clinical trials have revealed a defect in re-epithelialization of the endoluminal side of the prosthesis. This respiratory epithelium is absolutely necessary to obtain an implantable device fully integrated into the body but also for the functionality of such an implant. In this work we have developed patches of interpenetrated and reticulated hydrogels based on collagen and hyaluronic acid to ensure rapid epithelial regrowth. These optimized hydrogel patches have sufficient resistance to hydrolysis to limit their early degradation once implanted. They have been functionalized by growth and cell differentiation factors that are released gradually with an objectified result on cell proliferation. Encapsulation of immune cells and the use of cytokines in these gels also modulate the inflammatory response towards a healing process rather than rejection.

Le ranelate de strontium (RS) est un traitement anti-ostéoporotique agissant sur la formation osseuse via les ostéoblastes et la résorption osseuse via les ostéoclastes grâce au Calcium Sensing Receptor (CaSR). L’activité physique (EXE) est bien connue pour améliorer les propriétés osseuses. Dans ce travail, nous avons étudié ① l’effet de différentes activités physiques (tapis roulant et impact). Nous avons observé que 10 impacts par jour pendant 8 semaines à 45cm de hauteur ont eu des effets bénéfiques sur l’os (paramètres de microarchitecture et biomécanique, marqueurs du remodelage). ② L’étude du RS et de l’EXE sur l’os de rate ovariectomisée a montré que le RS a des effets comparables à l’EXE et que le RS+EXE ont des effets cumulatifs sur l’os (paramètres de microarchitecture et biomécanique, marqueurs du remodelage). ③ Enfin, une étude in vivo sur des MLO-Y4 a montré la présence des CaSR sur la membrane des ostéocytes et leur nombre est modulé en fonction de la concentration en RS. De plus, le RS a un effet sur la différenciation des CSM lors d’une différenciation ostéogénique en favorisant la différenciation ostéocytaire et elle est modulée par la concentration en RS. En conclusion, ce travail a démontré l’importance d’une pratique d’un exercice physique et du traitement du RS contre l’ostéoporose : maintien de la balance du remodelage osseux du côté de la formation. L’effet cumulatif du RS+EXE s’explique par le fait que le RS agit sur les ostéoblastes, ostéocytes et ostéoclastes via les CaSR et l’EXE sur les mécanorécepteurs des ostéocytes. / Strontium ranelate (SR) is an anti-osteoroporotic treatment acting on bone formation via osteoblasts and bone resorption via osteoclasts thanks to Calcium Sensing Receptor (CaSR). Physical activity is well known to improve bone properties. In this work, we studied ① different physical acticities (treadmill and impact). We observed that 10 impacts per day during 8 weeks from 45cm of height had beneficial effects on bone (microarchitecture and biomechanical parameters, bone remodeling markers). ② The study of SR and EXE effects on bone ovariectomized rats showed that RS had similar effects to EXE and SR+EXE had cumulative effects on bone (microarchitecture and biomechanical parameters, bone remodeling markers). ③ Finally, an in vivo study on MLO-Y4 showed CaSR presence on osteocyte with their number depending on SR concentration. Moreover, RS had positive effects on CSM differentiation in favor of osteocyte differentiation and it is modulated by SR concentration. In conclusion, this work has demonstrated the importance of taking physical exercise as well as SR treatment for osteoporosis: maintaining the bone remodeling in favor of bone formation. The cumulative effect of SR+EXE is explained by the fact the SR acts on osteoblasts, osteocytes and osteoclasts via CaSR and the EXE on osteocyte mechanoreceptors.

Notre équipe a développé un protocole d’ingénierie de l’organe dentaire basé sur la biomimétique et l’utilisation de cellules dentaires embryonnaires dissociées. La recherche de ressources cellulaires permettant d’éviter le recours aux cellules embryonnaire reste un défi majeur, et nécessite une meilleure connaissance des paramètres limitants. Nous avons testé les potentialités odontogènes de lignées cellulaires, dentaires ou non, embryonnaires ou adultes. Le développement dentaire étant contrôlé par des interactions réciproques entre ectomésenchyme dérivé des crêtes neurales et épithélium, ces cellules ont été réassociés à un épithélium dentaire compétent. Nous avons recherché la formation de dents in vitro et/ou après implantation chez la souris adulte et étudié un certain nombre de paramètres biologiques et techniques. Ainsi, nous avons étudié l’impact de l’âge, de la mise en culture, et de l’hétérogénéité cellulaire sur les potentialités odontogènes des cellules mésenchymateuses. Nos résultats montrent que le potentiel odontogène des différentes lignées mésenchymateuses testées pouvait être lié à l’âge des cellules et qu’il est perdu lorsque les cellules mésenchymateuses sont cultivées avant d’être ré-associées. Ceci pouvant s’expliquer par un changement phénotypique, nous avons testé un certain nombre de gènes essentiels au développement dentaire, et suivi l’expression de marqueurs de surface. Les changements observés peuvent être liés à une sélection cellulaire in vitro pouvant conduire à des modifications de l’hétérogénéité des cellules en monocouche. / Our laboratory has developed a protocol for tooth organ engineering, based on biomimetic and the use of dissociated embryonic dental cells. Searching for mesenchymal cell sources avoiding the use of embryonic cells still remains a major challenge. We tested the odontogenic potential of several cell lines, dental or not, embryonic or adult. These cells were re-associated with a competent intact dental epithelium. We searched for tooth formation in vitro and/or after implantation in adult mice and studied different biological and technical parameters. For this purpose we analyzed the effects of the age, of a pre-culture step, and of the cellular heterogeneity on the odontogenetic potential of mesenchymal cells. To test the heterogeneity, we compared the patterns of expression of cell surface markers in cultured and implanted re-association with those observed during tooth development..Our results show that the absence of odontogenetic potential in the different cell lines that were tested, in part depends on the age of cells and that it is lost when mesenchymal cells are cultured in monolayer before their re-association. This could be explained by phenotypical changes as shown by testing several genes involved in tooth development, and tracing cell surface markers expression. Changes were observed, wich could be related to a cell selection in vitro, leading to variations in cellular heterogeneity. Indeed, pulpal cellular heterogeneity shows specific patterns of expression, that are space-time defined during tooth development, and is controlled by epithelial-mesenchymal interactions.