9 research outputs found
Exploring the Extracellular Matrix to Create Biomaterials
The extracellular matrix (ECM) represents the framework of tissues and organs and is involved in cell differentiation and function. The study of ECM is challenging and required a combination of identification and imaging techniques to give a valuable scheme of its composition, organization, and finally function. The study of ECM enables to culture cells ex vivo, but cultures are restricted to two-dimensional surfaces, whereas in the meantime, material sciences were developing devices able to bring cell culture in a three-dimensional (3D) environment. This chapter presents basic techniques to investigate extracellular matrices composition and organization. Basic knowledge on ECM composition and organization should inspire material scientists to propose more biologically relevant materials. In a second time, we present strategies available to create ex vivo models of ECM and a series of examples of 3D materials that were engineered to investigate cell adhesion, phenotype, and differentiation in a biologically relevant microenvironment. The production of a gold-standard material is possible for a specific biological question, and it might be developed from an intelligible dialogue between material scientists, that bring engineering strategies, and cell biologists who implement the material design to meet the biological process that has to be investigated ex vivo
Liquid crystalline properties of type I collagen: Perspectives in tissue morphogenesis
Collagen molecules form the major part of tissues like bone, cornea or tendon where they organize into ordered fibrillar networks. The acid-soluble protein spontaneously assembles in liquid crystalline phases, characterized in polarized light microscopy and X-ray diffraction. Collagen fibrillogenesis obtained in condensed media establishes a link between the fibrillar networks described in vivo and the mesomorphic states obtained in vitro. Cellematrix interactions on these biomimetic materials are currently analysed with perspectives in tissue engineering. In a morphogenetic context, we propose the hypothesis of a liquid crystalline order, between soluble precursor molecules, preceding fibrillogenesis
MATRICES FIBRILLAIRES DENSES DE COLLAGĂNE : MATĂRIAUX POUR LA RĂPARATION OSSEUSE ET L'ĂTUDE D'OSTĂOBLASTES EN TROIS DIMENSIONS
rĂ©digĂ© du 15.06.08 au 15.09.08 ces travaux ont donnĂ© lieu Ă 2 publication: Vigier et al, J Biomed Mater Res 2010 et Vigier et al, Tissue Eng 2011Bone tissue ensures the continuity and strength of the skeleton, so as an essential role in mineral homeostasis. Many pathologies, associated with bone resection, require materials to fill the defect. This thesis evaluates the bone healing properties of materials made with collagen solutions at medium (5mg/mL) and high (40mg/mL) concentrations. These two scaffolds are structurally described by light and electron microscopy and compared with classicalyl used freeze-dried collagen sponges. In long term in vitro culture, transformed and primary osteoblasts proliferate, present a cuboidal shape and are arranged in monolayer at the surface of the 5mg/mL matrix, instead of a more resting morphology on the 40mg/mL scaffolds and sponges. In presence of inorganic phosphate, both fibrillar matrices are mineralised by the activity of osteoblasts, despite sponges exhibited spontaneous mineralization. When added inside a rat skull defect, collagen matrices enhanced the healing up to 80% of the surface fill by new bone, compared with 40% without treatment. Collagen density modulates the degradation of the scaffolds, but both are colonized by vascular cells and osteprogenitors that synthesise new bone. With combined microscopy techniques, we observed that primary osteoblasts, inside the three dimensional collagen fibrils network during in vitro cultures, follow a morphological transition. Osteoblasts inside the matrix exhibit long cytoplasmic processes and are connected together, and with the surface, by gap junctions and thus could be related to osteocytes. This work enlightens the potential of the collagen dense fibrillar matrices for bone repair as well as ECM models for in vitro studies.L'os, tissu conjonctif minĂ©ralisĂ©, assure les fonctions de protection, de support et de motilitĂ©. De nombreuses pathologies osseuses requiĂšrent l'utilisation d'implants naturels ou synthĂ©tiques et le vieillissement de la population accroĂźt cette demande. La thĂšse a eu pour objet d'Ă©valuer les potentiels de reconstruction osseuse de matĂ©riaux prĂ©parĂ©s Ă partir de solutions de collagĂšne de concentration moyenne (5mg/mL) et haute (40mg/mL). Ces matĂ©riaux fibrillaires, simple Ă façonner, ont Ă©tĂ© caractĂ©risĂ©s par microscopie photonique et Ă©lectronique et comparĂ©s aux Ă©ponges de collagĂšne dĂ©jĂ utilisĂ©es en thĂ©rapeutique. En culture in vitro Ă long terme, des ostĂ©oblastes humains, primaires ou transformĂ©s, se multiplient et s'organisent en une monocouche Ă©pithĂ©lioĂŻde sur les matrices Ă 5mg/mL, ou en cellules plates et allongĂ©es sur les matrices Ă 40mg/mL. La minĂ©ralisation des matrices, en conditions standard, n'a lieu qu'en prĂ©sence d'ostĂ©oblastes tandis que les Ă©ponges minĂ©ralisent de façon spontanĂ©e. Dans un dĂ©faut crĂąnien engendrĂ© chez le rat, les matrices ont permit son comblement Ă plus de 80%. Elles sont colonisĂ©es par les ostĂ©oprogĂ©niteurs qui se diffĂ©rencient et synthĂ©tisent de l'os minĂ©ralisĂ© ; leur concentration module leur dĂ©gradation. En contact en 3D avec le rĂ©seau fibrillaire les otĂ©oblastes primaires apparaissent dendritiques et s'organisent en syncytium, reliĂ©s par des jonctions communicantes. Cette transition morphologique est dĂ©crite in vitro par une approche combinĂ©e de microscopies. Ces travaux valident l'utilitĂ© des matrices fibrillaires de collagĂšne pour l'ingĂ©nierie de l'os. Ils confirment Ă©galement l'intĂ©rĂȘt que peut tirer la recherche fondamentale de disposer de matrices extracellulaires modĂšles
Comparison of Cryptographic Verification Tools Dealing with Algebraic Properties
International audienceRecently Kuesters et al proposed two new methods using ProVerif for analyzing cryptographic protocols with Exclusive-Or and Diffie-Hellman properties. Some tools, for instance CL-Atse and OFMC, are able to deal with Exclusive-Or and Diffie-Hellman. In this article we compare time efficiency of these tools verifying some protocols of the litterature that are designed with such algebraic properties
Aspects molĂ©culaires de lâadhĂ©rence cellulaire cadhĂ©rine-dĂ©pendante : les premiers moments de lâinteraction
Les cadhĂ©rines reprĂ©sentent une des principales familles de molĂ©cules dâadhĂ©rence cellulaire et jouent un rĂŽle crucial dans la mise en place des tissus au stade embryonnaire et dans leur cohĂ©sion Ă lâĂąge adulte. Ces glycoprotĂ©ines rĂ©alisent des interactions de type homophile dĂ©pendantes du calcium. Ces derniĂšres annĂ©es, diffĂ©rentes approches expĂ©rimentales ont Ă©tĂ© utilisĂ©es pour rĂ©soudre les bases molĂ©culaires de ces interactions. Les donnĂ©es de la littĂ©rature sont relativement confuses en ce qui concerne le mode dâinteraction de ces molĂ©cules. DiffĂ©rents modĂšles ont Ă©tĂ© proposĂ©s, et le mĂ©canisme dâadhĂ©rence est encore soumis Ă controverses. De rĂ©centes approches biophysiques conjuguĂ©es aux techniques classiques de biologie nous permettront de progresser vers une meilleure comprĂ©hension du mĂ©canisme par lequel les cadhĂ©rines rĂ©gulent lâadhĂ©rence cellulaire. La prise en compte des propriĂ©tĂ©s cinĂ©tiques de ces interactions au niveau unimolĂ©culaire apporte ainsi un Ă©clairage nouveau sur ces rĂ©gulations molĂ©culaires
The ecology of modern and fossil vertebrates revisited by lithium isotopes
International audienceThe vertebrate fossil record documents a plethora of transitions between aquatic and terrestrial environments but their causes are still debated. Quantifying the salinity of living environments is therefore crucial for precising the sequence of ecological transitions. Here, we measured lithium stable isotope composition of mineralized tissues (ÎŽ 7 Limt) of extant and extinct vertebrates from various aquatic environments: seawater, freshwater/terrestrial, and "transitional environments" (i.e. brackish waters, or seasonal access to freshwater and seawater). We report statistically higher ÎŽ 7 Limt values for seawater vertebrates than freshwater ones, taxonomic groups considered separately. Moreover, vertebrates living in transitional environments have intermediate ÎŽ 7 Limt values. Therefore, we show that ÎŽ 7 Limt values of both extant and extinct vertebrates can discriminate their aquatic habitat
Justice et sociétés rurales
Si les violences et les conflits ruraux ont fait lâobjet dâimportants travaux, il nâen est pas de mĂȘme pour la justice. En effet, « la justice Ă la campagne » a Ă©tĂ© en grande partie dĂ©laissĂ©e par la recherche. Or la notion de justice, placĂ©e aujourdâhui au centre de nombreux travaux et rĂ©flexions, tant Ă lâĂ©chelle europĂ©enne quâĂ lâĂ©chelle internationale, sâavĂšre ambivalente et complexe puisquâelle peut aller de la demande dâune meilleure justice sociale Ă la volontĂ© de saisir les inĂ©galitĂ©s socio-spatiales afin dâassurer des amĂ©nagements du territoire qui correspondent aux aspirations des acteurs. Dans les perceptions communes, la justice se confond avec lâinstitution judiciaire, câest-Ă -dire avec le « systĂšme des tribunaux », mais elle dĂ©borde le seul examen de lâappareil judicaire. Prise dans lâunivers des sociĂ©tĂ©s rurales, la justice est un outil de rĂ©gulation sociale et dâarbitrage, mais elle est aussi prise dans une multiplicitĂ© dâusages, depuis les stratĂ©gies dâĂ©vitement jusquâĂ des processus dâinstrumentalisation en passant par des formes dâignorance rĂ©ciproques. Pour aborder ce vaste champ de recherche, trois entrĂ©es ont Ă©tĂ© privilĂ©giĂ©es. La premiĂšre traite plus particuliĂšrement de la justice spatiale et de lâĂ©quitĂ© des territoires. La deuxiĂšme aborde la question de la proximitĂ© et du pluralisme, la troisiĂšme et derniĂšre est consacrĂ©e aux processus dâinstrumentalisation et dâaccommodation. Le prĂ©sent ouvrage, issu des travaux de chercheurs venant de plusieurs disciplines (histoire, droit, sociologie, gĂ©ographie, histoire de lâart) a pour ambition de confronter les approches, de rendre compte de la vitalitĂ© de la recherche et des enjeux quâelle rĂ©vĂšle en les inscrivant dans la longue durĂ©e, de la fin de lâAncien RĂ©gime Ă nos jours
Prognostic value of high-sensitivity measurable residual disease assessment after front-line chemoimmunotherapy in chronic lymphocytic leukemia
International audienceMeasurable residual disease (MRD) status is widely adopted in clinical trials in patients with chronic lymphocytic leukemia (CLL). Findings from FILO group trials (CLL2007FMP, CLL2007SA, CLL2010FMP) enabled investigation of the prognostic value of high-sensitivity (0.7âĂâ10-5) MRD assessment using flow cytometry, in blood (Nâ=â401) and bone marrow (Nâ=â339), after fludarabine, cyclophosphamide, and rituximab (FCR)-based chemoimmunotherapy in a homogeneous population with long follow-up (median 49.5 months). Addition of low-level positive MRDâ<â0.01% to MRDââ„â0.01% increased the proportion of cases with positive MRD in blood by 39% and in bone marrow by 27%. Compared to low-level positive MRDâ<â0.01%, undetectable MRD was associated with significantly longer progression-free survival (PFS) when using blood (72.2 versus 42.7 months; hazard ratio 0.40, pâ=â0.0003), but not when using bone marrow. Upon further stratification, positive blood MRD at any level, compared to undetectable blood MRD, was associated with shorter PFS irrespective of clinical complete or partial remission, and a lower 5-year PFS rate irrespective of IGHV-mutated or -unmutated status (all pâ<â0.05). In conclusion, high-sensitivity (0.0007%) MRD assessment in blood yielded additional prognostic information beyond the current standard sensitivity (0.01%). Our approach provides a model for future determination of the optimal MRD investigative strategy for any regimen