Les bivalves côtiers Codakia orbicularis et C. orbiculata, de la famille des Lucinidae, abritent des Gammaprotéobactéries endosymbiotiques sulfo-oxydantes dans leurs branchies. Ces deux bivalves vivent dans les herbiers à Thalassia testudinum et hébergent la même bactérie symbiotique selon les analyses effectuées à partir des séquences d’ADNr 16S. Lors de période de stabulation, la population bactérienne symbiotique décroit alors qu’il n’y a pas, dans le même temps, de relargage des symbiotes observé. Des analyses en cytochimie ont montré une forte activité d’enzymes lysosomales lors de ces épisodes de privation de nourriture et de soufre. Il a ainsi été montré que les symbiotes peuvent servir directement de source de nourriture aux bivalves pour survivre lors de ces périodes de crise. Le transfert de carbone des symbiotes vers l’hôte peut être flexible et pourrait consister en un simple transfert de matière organique ou "milking", dans des conditions normales de nutrition et de digestion des symbiotes et devenir du "farming", dans des conditions de stabulation. Jusqu’à ce jour, le symbiote reste non cultivable. De ce fait, l’utilisation de techniques indépendantes de la culture comme les approches –omics ont été mises en place pour étudier la physiologie de cette bactérie symbiotique. Le génome du symbiote a été analysé par Next Generation Sequencing (NGS) permettant ainsi d’obtenir les bases du protéome et ainsi de pouvoir analyser la physiologie du symbiote. Dans ce travail, le protéome des bactéries a été analysé sous différentes conditions. L’oxydation des sulfures est une des voies métaboliques clés du symbiote de Codakia. Cette voie fait très probablement appel au système Sox périplasmique, ainsi qu’à une sulfite réductase cytoplasmique (DsrAB), une APS réductase (AprAB) et une ATP sulfurylase (SopT). De plus, deux autres enzymes additionnelles d’oxydation des sulfures ont pu être mises en évidence dans l’espace périplasmique du symbiote telle que la quinone réductase (Sqr) et la sulfide déhydrogénase (FccAB). Les gènes des enzymes du cycle de Calvin Benson Bassham (CBB) ne semblent pas être tous présents dans le génome du symbiote. Les protéines de la RuBisCO sont abondamment exprimées. Il semblerait que la régénération du ribulose-1,5-bisphosphate soit effectuée de façon non conventionnelle via une phosphofructokinase PPi-dépendante. Une autre caractéristique du CBB est qu’il y a deux formes différentes de RuBisCO codées dans le génome du symbiote. Les deux formes sont exprimées en même temps, mais la forme I de la RuBisCO est 50 fois plus exprimée que la forme II. En plus de la vie autotrophique, plusieurs gènes nécessaires à une vie hétérotrophique sont présents dans le génome. Dans le protéome, les enzymes de la glycolyse et du cycle TCA sont faiblement exprimées. Les protéines du métabolisme du glycogène ont également été identifiées dans le protéome. De plus, plusieurs types de transporteurs comme ABC, TRAP et PTS sont présents dans le génome et certaines formes d’expression de ces transporteurs ont pu être suspectées, y compris lors de la vie intracellulaire du symbiote. De façon inattendue, un groupe de gènes nif est présent dans le génome permettant la fixation de l’azote atmosphérique par le symbiote. Les protéines codées par les gènes clés, comme la nitrogénase NifH/K/D, ont été abondamment trouvées dans le protéome. De plus, l’analyse du protéome montre une régulation forte de ces protéines dans des conditions de stabulation du bivalve hôte. La rubrerythrine est fortement exprimée et servirait à protéger la nitrogénase de l’oxygène au sein des bacteriocytes. L’endosymbiote bactérien code également pour un système de sécrétion de type 6 (T6SS) pour le transport de molécules bactériennes effectrices à travers les membranes du cytoplasme de la cellule hôte et jouerait un rôle possible de communication directe avec l’hôte. / The shallow water bivalves Codakia orbicularis and Codakia orbiculata, both belonging to the family Lucinidae, harbor endosymbiotic sulfur-oxidizing gamma-Proteobacteria in their gills. The bivalves live in seagrass beds of Thalassia testudinum and harbor the same bacterial symbionts according to 16S rDNA sequence analysis. During starvation, the symbiont population decreases while no release of symbionts were observed. We observed lysosomal enzyme activity during sulfide and food starvation with cytochemical staining methods. We suggest that the host uses symbionts as a nutrient source to survive a hunger crisis. The carbon transfer from the symbionts to the host could be flexible and could consist in transfer of organic matter, "milking", under normal feeding conditions and digestion of the symbionts, "farming", under starved conditions. Until now the symbiont alone is not cultivable. Therefore, cultivation-independent techniques, like -omics approaches were used to analyze the physiology of the symbiont. Next generation sequencing (NGS) was employed to sequence the genomes of symbionts from both hosts, display the backbone for proteomics. The soluble- and membrane-associated symbiont proteomes were analyzed during different conditions. The oxidation of sulfide is one key metabolic pathway of the Codakia symbiont, most probably using the periplasmic Sox-system, a cytoplasmatic sulfite reductase (DsrAB), an APS reductase (AprAB) and an ATP sulfurylase (SopT). Furthermore, indications for two additional putative sulfide oxidation systems in the periplasmic space, the sulfide quinone reductase (Sqr) and the sulfide dehydrogenase (FccAB), could be found. The Calvin Benson Bassham cycle (CBB) of the symbiont is not completely encoded in the genome. The key genes, RuBisCO, are abundantly expressed. It is assumed that the regeneration of the ribulose-1,5-bisphosphate is performed unconventionally via a PPi-dependent phosphofructokinase. Another feature of the CBB is that two different forms of RuBisCO are encoded in the genome. Both are expressed at the same time, but RuBisCO form I is about 50x times more expressed. Additional to the autotrophic lifestyle, all genes for the heterotrophic lifestyle are encoded in the genome. In the proteome, the enzymes related to glycolysis and TCA-cycle were low expressed. Interestingly, proteins for glycogen metabolism were identified in the proteome. Additionally, several types of transporters like ABC, TRAP and PTS are encoded in the genome. In the proteome several indications were found for an expression of these transporters, even in the endosymbiotic lifestyle. Unexpectedly, in the genome a nif gene cluster is encoded for gaseous nitrogen fixation as ammonium source. The key genes, the nitrogenase NifH/K/D, were abundantly identified in proteome. Further, the proteome analyses indicate a strictly down-regulation of these proteins under starvation conditions. Rubrerythrin, a strongly expressed protein and is predicted to protect the nitrogenase against oxygen stress. The bacterial endosymbionts encode a specialized secretion system type 6 (T6SS) for the transport of bacterial effector molecules through the membranes to the host cytoplasm and display one possibility for a direct "communication" with the host. In summary, genomics and proteomics analyses of the Codakia symbiont improved the knowledge about the metabolism of the symbiont in lucinid bivalves.. The genomics and proteomics data generated in this study can be used as a basis for further in-depth analyses of the physiology of the symbionts and interaction with the host.

Syftet med denna studie var att pröva olika teorier om stamning, avseende nivå av muskelspänning vid flytande tal. Tjugofyra försöksdeltagare ingick i studien, tolv stammande och tolv kontrolldeltagare. Försöksdeltagarnas muskelaktivitet i musklerna orbicularis oris (OO) och depressor labii inferior (DLI) uppmättes med hjälp av elektromyografi (EMG) vid flytande tal och vid en icke verbal uppgift, att puta med läpparna. De stammandes grad av stamning bedömdes med The Wright and Ayre Stuttering Self-Rating Profile (WASSP) och Stuttering Severity Instrument, fjärde upplagan, (SSI-4) för att korrelera denna med muskelaktiviteten. Ingen statistisk signifikant skillnad avseende muskelaktivitet mellan grupperna kunde påvisas, varken i flytande tal eller vid den icke verbala uppgiften. Det fanns inte heller något signifikant samband mellan den sammanlagda muskelaktiviteten av OO och DLI vid flytande tal och stamningsgrad uppmätt med SSI-4 respektive WASSP. Inget signifikant samband kunde heller ses mellan OO vid läpputning och stamningsgrad uppmätt med SSI-4 respektive WASSP. Ett negativt signifikant samband påvisades dock mellan muskelaktivering i OO vid flytande tal och självskattad stamningsgrad. Således kan resultatet tyda på att det varken finns någon muskulär hypertoni eller hypotoni i OO och DLI i stammandes flytande tal jämfört med en icke stammande kontrollgrupp. Resultatet indikerar även att det kan finnas tendens till låg muskelaktivering vid svårare stamning.

La dispersion, caractérisée par les mouvements d’individus dans l’espace conduisant à la production d’un flux de gènes, permet la connectivité des populations. L’étude de la dispersion est devenue d’une importance primordiale pour prédire les conséquences des changements globaux sur la structure et la dynamique des populations. Les espèces à dispersion limitées, comme les chéloniens, sont particulièrement menacées par ces phénomènes. Cette étude se propose d’analyser la dispersion chez la Cistude d’Europe (Emys orbicularis), en régression en Europe, dans un contexte de fragmentation d’habitats et de déterminer les causes de ce comportement via l’analyse de la dynamique et de la génétique des populations. Nos résultats montrent, d’une part, que les temps de générations lents chez les cistudes (environ 12 ans) peuvent ralentir les phénomènes d’érosion génétique par dérive. Cette érosion lente est accentuée en présence de grandes populations même en milieu très fragmenté. D’autre part, la sélection aurait favorisée la philopatrie chez les femelles cistudes dans les milieux peu riches en site de ponte et de faible densité d’individus car elles ont un avantage à la territorialité. A l’inverse, le coût à la dispersion diminuerait pour les mâles car ce comportement éviterait la consanguinité. Les cistudes semblent donc très sensibles à la compétition intra-spécifique. En effet, la relaxation de la densité-dépendance des adultes permet un recrutement important de juvéniles. Cette dynamique favoriserait une récupération rapide des effectifs après une importante perturbation, ce qui est surprenant pour une espèce longévive dont les temps de résilience sont supposés lents. / Dispersal, characterized by the movements of individuals in space leading to gene flows, allows populations to connect. The study of dispersal has become of essential importance to predict the consequences of global changes on the population structures and dynamics. Species with limited dispersal, such as chelonians, are particularly threatened by these phenomena. Our study aimed at analyzing the dispersal of the European pond turtle (Emys orbicularis), in decline in Europe, in a habitats fragmentation context and determining the causes of this behavior through analysis of population dynamics and genetics. Our results show, firstly, that the slow generation time in Emys orbicularis (about 12 years) may slow the genetic erosion by drift. This slow erosion is accentuated with large populations such as Kerkini populations, even with a strong fragmentation. On the other hand, selection would have favored philopatry in females in habitats with few nesting site and deers, because they have the advantage of territoriality. In contrast, the cost of dispersal decreases for males because this behavior allows inbreeding avoidance. The European pond turtles seem very sensitive to intra-specific competition. Indeed, the relaxation of adult density-dependence allows for a significant recruitment of juveniles. This dynamic promotes an unexpected rapid response of the population after a major disturbance, because chelonians are long-lived animals with a late age of first reproduction and very high generation time, therefore, the time of resilience to perturbations is also expected to be high.

The Caspian region and specifically the Apsheron peninsula of Azerbaijan is known to be polluted with a variety of environmental contaminants, making risk assessment difficult. The wetlands of Sumgayit contain particularly complex mixtures of contaminants. Flow cytometry and the micronucleus assay were used to assess chromosomal damage in aquatic turtles and frogs inhabiting contaminated wetlands in Azerbaijan. By evaluating biomarkers that are indicative of somatic effects, elevated chromosomal damage was documented at several sites in Azerbaijan relative to reference sites. Sediment samples were analyzed for polycyclic aromatic hydrocarbons (PAHs), organochlorines (OCs), and mercury to evaluate contaminant associations with genetic damage. Sediment samples revealed heterogeneous patterns of PAH and mercury concentrations throughout Sumgayit. Significant positive correlations were documented between both PAH and mercury sediment concentrations and chromosomal damage. Population genetic methods were employed to study the effects of long-term chronic contaminant exposure in marsh frogs from Sumgayit. The Sumgayit region has reduced levels of genetic diversity, likely due to environmental degradation. One of the most contaminated sites in Sumgayit, WTP, appears to be a source of new mutations as a result of an increased mutation rate. Finally, the Sumgayit region seems to act as an ecological sink, with levels of gene flow into the region exceeding gene flow out of the region. This study provides not only exposure and biomarker data, but also an integrated method for assessing the cumulative population impacts of contaminant exposure by studying both population genetic and evolutionary effects. The results presented here will be used in conjunction with those of ongoing research involving both wildlife and humans to develop comprehensive ecological and human risk assessments.

The Caspian region and specifically the Apsheron peninsula of Azerbaijan is known to be polluted with a variety of environmental contaminants, making risk assessment difficult. The wetlands of Sumgayit contain particularly complex mixtures of contaminants. Flow cytometry and the micronucleus assay were used to assess chromosomal damage in aquatic turtles and frogs inhabiting contaminated wetlands in Azerbaijan. By evaluating biomarkers that are indicative of somatic effects, elevated chromosomal damage was documented at several sites in Azerbaijan relative to reference sites. Sediment samples were analyzed for polycyclic aromatic hydrocarbons (PAHs), organochlorines (OCs), and mercury to evaluate contaminant associations with genetic damage. Sediment samples revealed heterogeneous patterns of PAH and mercury concentrations throughout Sumgayit. Significant positive correlations were documented between both PAH and mercury sediment concentrations and chromosomal damage. Population genetic methods were employed to study the effects of long-term chronic contaminant exposure in marsh frogs from Sumgayit. The Sumgayit region has reduced levels of genetic diversity, likely due to environmental degradation. One of the most contaminated sites in Sumgayit, WTP, appears to be a source of new mutations as a result of an increased mutation rate. Finally, the Sumgayit region seems to act as an ecological sink, with levels of gene flow into the region exceeding gene flow out of the region. This study provides not only exposure and biomarker data, but also an integrated method for assessing the cumulative population impacts of contaminant exposure by studying both population genetic and evolutionary effects. The results presented here will be used in conjunction with those of ongoing research involving both wildlife and humans to develop comprehensive ecological and human risk assessments.

L’empreinte humaine sur Terre est si profonde qu’elle entraine des changements environnementaux qui affectent et modifient le fonctionnement des écosystèmes. Parmi tous les biotopes, les écosystèmes aquatiques continentaux sont des habitats remarquables qui abritent une grande biodiversité, mais qui sont aussi les plus menacés par les activitéshumaines. Les principales causes de la perte de qualité de l'eau et de la perturbation des ces écosystèmes comprennent la pollution des eaux et l'introduction d'espèces exotiques. La partie première partie de ce travail de thèse a montré des invasions parasitaires sur les populations de tortues d'eau douce indigènes, transmis par des espèces de tortues introduites. De plus, la nécessité d'étudier et de décrire les nouvelles espèces de parasites invasives avec des techniques plus performantes a été soulignée. La deuxième partie de cette thèse a consisté en l'élaboration d'un outil pour évaluer l'état de la santé des populations de tortues d'eau douce sauvages, ce qui reflète également le niveau de contamination des cours d'eau. / Human imprint on Earth is actually so profound leading global environmental changes that affects and modifies the functioning of ecosystems. Among the natural biomes, freshwater ecosystems are remarkable habitats that comprise great species biodiversity but are also the most threatened by human activities. The main causes of the loss of water quality anddisruption of freshwater ecosystems includes water pollution and the introduction of alien species. The fisrt part of this thesis showed invasion of parasites on native freshwater turtle populations, carried by introduced turtle species. Furthermore, it highlighted the necessary to study and describe the new invasive parasite species with more performant technics. The second part of this thesis consisted in the development of a tool to evaluate the status of thehealth of wild freshwater turtle populations, allowed also the level of contamination of the watercourses.

A regeneração óssea é um processo fisiológico que promove a neoformação de tecido ósseo saudável e funcional com características idênticas antes da lesão. Entretanto, frente a defeitos críticos, o osso é incapaz de se regenerar espontaneamente. Diante destas deficiências, a bioengenharia de tecidos ósseos (BTO) é uma opção promissora para a regeneração deste tipo de defeito. A maioria das abordagens de BTO utiliza as células-tronco mesenquimais da medula óssea (BMSC), porém, a coleta de BMSC dos pacientes é um processo bastante invasivo e doloroso. Por estas desvantagens, a busca por abordagens acessíveis e menos invasivas de novas fontes de células-tronco (CT) se tornou necessária. Neste contexto, as células-tronco de polpa de dentes decíduos (SHED) foram identificadas e sua aplicação na BTO, desde então, vem sendo amplamente estudada devido ao seu potencial osteogênico e por se tratar de uma fonte não invasiva. A obtenção de células-tronco do músculo orbicular do lábio (OOMDSC) também não causa dor adicional aos indivíduos, pois os fragmentos deste tecido são rotineiramente descartados durante as cirurgias de reconstrução do lábio. No presente trabalho investigamos o potencial de diferenciação osteoblástico in vitro e in vivo das OOMDSC e comparamos com as SHED, além disto, associamos estas células a biomateriais de HA/&beta;-TCP e investigamos a sua contribuição na neoformação óssea in vivo. O imunofenótipo de cada amostra de SHED e OOMDSC foi verificado para certificar a identidade de CT mesenquimais. Em seguida, as células em cultura foram submetidas à diferenciação osteoblástica in vitro. Em 9 e 14 dias de diferenciação as OOMDSC apresentaram menor atividade de fosfatase alcalina (p<0,0001) e menor marcação de matriz extracelular mineralizada, comparado às SHED (p<0,001), enquanto que em 21 dias estas diferenças não foram mais observadas. Quando associadas a biomateriais e implantadas em defeitos críticos calvariais bilaterais em ratos Wistar, tanto OOMDSC e SHED foram capazes de induzir neoformação óssea após 50 dias de cirurgia, conforme evidenciado pela análise morfológica e por micro-CT. Todavia, as células ósseas encontradas nos sítios da neoformação óssea não eram de origem humana. A avaliação da neoformação óssea in vivo induzida por SHED assim como a sua distribuição no enxerto foi verificada também em 07, 15 e 30 dias pós-cirúrgicos. Nestes períodos não há evidência de neoformação óssea, entretanto, as SHED estão localizadas no tecido conjuntivo que se forma e preenche o enxerto. Além disto, os dados sugerem que estas células estão relacionadas à modificações na microarquitetura do biomaterial e ainda à modulação dos números dos osteoclastos, também verificada nestas amostras. Portanto, podemos concluir que as OOMDSC são tão capazes de se diferenciar em osteoblastos quanto às SHED in vitro, porém esta diferenciação é mais lenta. Os experimentos in vivo indicam que as SHED possuem maior capacidade de indução à neoformação óssea quando comparadas às OOMDSC e que, em nosso modelo, as CT humanas não se diferenciam em osteoblastos in vivo. De qualquer forma a adição das CT ao biomaterial favorece a neoformação óssea, variações de microarquitetura e modulação dos osteoclastos. O fato de as ilhas ósseas não serem de origem humana indica que as células-tronco possam estar secretando fatores de indução à osteogênese, estimulando a neoformação óssea a partir das células do hospedeiro. / Bone regeneration is a physiological process, which promotes the growth of tissue at the site of injury, with the same characteristics of the original bone. However, when faced with critical defects the bone is unable to regenerate spontaneously. Bone tissue engineering (BTE) is a promising option for regenerating this type of defect. The majority of the approaches in BTE use Bone Marrow derived Mesenchymal Stem Cells (BMSC); however, the aspiration of bone marrow is a very invasive and painful procedure. Due to these disadvantages, the search for new, affordable and less invasive sources of stem cells (SC) has become necessary. In this context, stem cells from exfoliated deciduous teeth (SHED) have been identified and their application in BTE, since then, has been widely studied because they can be obtained non-invasively and due to their osteogenic potential. Stem cells from the orbicularis oris muscle (OOMDSC) are also obtained non-invasively and do not cause additional pain to individuals, because the fragments of this tissue are routinely discarded during lip reconstruction surgeries. In the present work we investigated, in vitro and in vivo, the osteoblastic differentiation potential of OOMDSC and compared with SHED; furthermore, we associated these cells with HA/&beta;-TCP scaffolds and investigate its contribution in the bone formation in vivo. The immunophenotype of each OOMDSC and SHED sample was verified to attest their mesenchymal stem cell identity. Then, cell cultures were submitted to osteoblastic differentiation in vitro. In 9 and 14 days of differentiation, OOMDSC exhibited lower alkaline phosphatase activity (p <0.0001) and lower mineralized extracellular matrix staining compared to SHED (p <0.001), whereas at 21 days, these differences were no longer observed. When associated with scaffolds and implanted into bilateral critical-sized calvarial defects in Wistar rats, both OOMDSC and SHED were able to induce bone formation after 50 days of surgery, as evidenced by morphological analysis and micro-CT. However, bone cells found at sites of bone formation were not of human origin. The evaluation of new bone formation in vivo induced by SHED as well as its distribution in the graft was performed at 07, 15 and 30 days after surgery. During these periods there was no evidence of new bone formation, however, SHED were located in the connective tissue that formed and filled the graft. Furthermore, our results suggest that these cells are related to changes in the microarchitecture of the scaffold and also to the modulation of the number of osteoclasts observed in these samples. In summary, our results suggest that OOMDSC are as capable to differentiate into osteoblasts as SHED in vitro, but this differentiation is slower. In vivo experiments indicate that SHED has a greater ability to induce bone formation when compared with OOMDSC, and that in our model, the human stem cells do not differentiate into osteoblasts in vivo. Nonetheless, the addition of SC to the scaffolds promotes bone formation, as well as variations in microarchitecture and modulation of osteoclasts. The fact that the bone islands are not of human origin indicates that the stem cells may be secreting osteogenesis-inducing factors, stimulating the host\'s cells to regenerate the defects.

A regeneração óssea é um processo fisiológico que promove a neoformação de tecido ósseo saudável e funcional com características idênticas antes da lesão. Entretanto, frente a defeitos críticos, o osso é incapaz de se regenerar espontaneamente. Diante destas deficiências, a bioengenharia de tecidos ósseos (BTO) é uma opção promissora para a regeneração deste tipo de defeito. A maioria das abordagens de BTO utiliza as células-tronco mesenquimais da medula óssea (BMSC), porém, a coleta de BMSC dos pacientes é um processo bastante invasivo e doloroso. Por estas desvantagens, a busca por abordagens acessíveis e menos invasivas de novas fontes de células-tronco (CT) se tornou necessária. Neste contexto, as células-tronco de polpa de dentes decíduos (SHED) foram identificadas e sua aplicação na BTO, desde então, vem sendo amplamente estudada devido ao seu potencial osteogênico e por se tratar de uma fonte não invasiva. A obtenção de células-tronco do músculo orbicular do lábio (OOMDSC) também não causa dor adicional aos indivíduos, pois os fragmentos deste tecido são rotineiramente descartados durante as cirurgias de reconstrução do lábio. No presente trabalho investigamos o potencial de diferenciação osteoblástico in vitro e in vivo das OOMDSC e comparamos com as SHED, além disto, associamos estas células a biomateriais de HA/&beta;-TCP e investigamos a sua contribuição na neoformação óssea in vivo. O imunofenótipo de cada amostra de SHED e OOMDSC foi verificado para certificar a identidade de CT mesenquimais. Em seguida, as células em cultura foram submetidas à diferenciação osteoblástica in vitro. Em 9 e 14 dias de diferenciação as OOMDSC apresentaram menor atividade de fosfatase alcalina (p<0,0001) e menor marcação de matriz extracelular mineralizada, comparado às SHED (p<0,001), enquanto que em 21 dias estas diferenças não foram mais observadas. Quando associadas a biomateriais e implantadas em defeitos críticos calvariais bilaterais em ratos Wistar, tanto OOMDSC e SHED foram capazes de induzir neoformação óssea após 50 dias de cirurgia, conforme evidenciado pela análise morfológica e por micro-CT. Todavia, as células ósseas encontradas nos sítios da neoformação óssea não eram de origem humana. A avaliação da neoformação óssea in vivo induzida por SHED assim como a sua distribuição no enxerto foi verificada também em 07, 15 e 30 dias pós-cirúrgicos. Nestes períodos não há evidência de neoformação óssea, entretanto, as SHED estão localizadas no tecido conjuntivo que se forma e preenche o enxerto. Além disto, os dados sugerem que estas células estão relacionadas à modificações na microarquitetura do biomaterial e ainda à modulação dos números dos osteoclastos, também verificada nestas amostras. Portanto, podemos concluir que as OOMDSC são tão capazes de se diferenciar em osteoblastos quanto às SHED in vitro, porém esta diferenciação é mais lenta. Os experimentos in vivo indicam que as SHED possuem maior capacidade de indução à neoformação óssea quando comparadas às OOMDSC e que, em nosso modelo, as CT humanas não se diferenciam em osteoblastos in vivo. De qualquer forma a adição das CT ao biomaterial favorece a neoformação óssea, variações de microarquitetura e modulação dos osteoclastos. O fato de as ilhas ósseas não serem de origem humana indica que as células-tronco possam estar secretando fatores de indução à osteogênese, estimulando a neoformação óssea a partir das células do hospedeiro. / Bone regeneration is a physiological process, which promotes the growth of tissue at the site of injury, with the same characteristics of the original bone. However, when faced with critical defects the bone is unable to regenerate spontaneously. Bone tissue engineering (BTE) is a promising option for regenerating this type of defect. The majority of the approaches in BTE use Bone Marrow derived Mesenchymal Stem Cells (BMSC); however, the aspiration of bone marrow is a very invasive and painful procedure. Due to these disadvantages, the search for new, affordable and less invasive sources of stem cells (SC) has become necessary. In this context, stem cells from exfoliated deciduous teeth (SHED) have been identified and their application in BTE, since then, has been widely studied because they can be obtained non-invasively and due to their osteogenic potential. Stem cells from the orbicularis oris muscle (OOMDSC) are also obtained non-invasively and do not cause additional pain to individuals, because the fragments of this tissue are routinely discarded during lip reconstruction surgeries. In the present work we investigated, in vitro and in vivo, the osteoblastic differentiation potential of OOMDSC and compared with SHED; furthermore, we associated these cells with HA/&beta;-TCP scaffolds and investigate its contribution in the bone formation in vivo. The immunophenotype of each OOMDSC and SHED sample was verified to attest their mesenchymal stem cell identity. Then, cell cultures were submitted to osteoblastic differentiation in vitro. In 9 and 14 days of differentiation, OOMDSC exhibited lower alkaline phosphatase activity (p <0.0001) and lower mineralized extracellular matrix staining compared to SHED (p <0.001), whereas at 21 days, these differences were no longer observed. When associated with scaffolds and implanted into bilateral critical-sized calvarial defects in Wistar rats, both OOMDSC and SHED were able to induce bone formation after 50 days of surgery, as evidenced by morphological analysis and micro-CT. However, bone cells found at sites of bone formation were not of human origin. The evaluation of new bone formation in vivo induced by SHED as well as its distribution in the graft was performed at 07, 15 and 30 days after surgery. During these periods there was no evidence of new bone formation, however, SHED were located in the connective tissue that formed and filled the graft. Furthermore, our results suggest that these cells are related to changes in the microarchitecture of the scaffold and also to the modulation of the number of osteoclasts observed in these samples. In summary, our results suggest that OOMDSC are as capable to differentiate into osteoblasts as SHED in vitro, but this differentiation is slower. In vivo experiments indicate that SHED has a greater ability to induce bone formation when compared with OOMDSC, and that in our model, the human stem cells do not differentiate into osteoblasts in vivo. Nonetheless, the addition of SC to the scaffolds promotes bone formation, as well as variations in microarchitecture and modulation of osteoclasts. The fact that the bone islands are not of human origin indicates that the stem cells may be secreting osteogenesis-inducing factors, stimulating the host\'s cells to regenerate the defects.