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International audience; Osteogenesis imperfecta (OI), also known as "brittle bone disease", is a rare genetic disorder of the skeleton, whose most benign form I corresponds to autosomal dominant mutations in the genes encoding type I collagen (COLA1, COLA2). Several associated skeletal manifestations are often observed but, surprisingly, while dentin defects often reflect genetic bone disorders, about half of OI patients have no obvious oral manifestations. Here, we investigated the collagen, mineral and mechanical properties of dentin from deciduous teeth collected from patients with mild form of OI and displaying no obvious clinical signs of dentinogenesis imperfecta. For the first time, an increase in the hardness of OI dentin associated with an increase in mineral content compared to healthy patients was reported. In addition, OI altered the tissue characteristics of the dentin-enamel junction but the interfacial gradient was preserved. The impact of changes in molecular structure due to mutations in OI was assessed by Raman microspectroscopy. Our results highlighted a change in the hydroxyproline-proline ratio in direct association with collagen mineralization. Our findings suggest that the evaluation of teeth could be an important aid for mild types of OI that are often difficult to diagnose clinically and provide experimental evidence that hydroxyproline content should be considered in future studies on collagen-based biomaterials.

International audience; A cell-mechanobiological model is used for the prediction of bone density variation in rat tibiae under medium and high mechanical loads. The proposed theoretical-numerical model has only four parameters that need to be identified experimentally. It was used on three groups of male Wistar rats under sedentary, moderate intermittent and continuous running scenarios over an eight week period. The theoretical numerical model was able to predict an increase in bone density under intermittent running (medium intensity mechanical load) and a decrease of bone density under continuous running (higher intensity mechanical load). The numerical predictions were well correlated with the experimental observations of cortical bone thickness variations, and the experimental results of cell activity enabled us to validate the numerical results predictions. The proposed model shows a good capacity to predict bone density variation through medium and high mechanical loads. The mechanobiological balance between osteoblast and osteoclast activity seems to be validated and a foreseen prediction of bone density is made available.

Introduction Les modalites d’imagerie qui aident a mieux comprendre le processus arthrosique sont la radiographie, l’IRM, la tomographie X, les ultrasons, la DXA et le TEP. A ce jour, seuls l’IRM et la tomographie sont des modalites tri-dimensionnelles (3D). L’analyse du cartilage sous forme de cartographie 3D ont ete largement developpe en IRM avec des applications in vivo reservees a la recherche clinique. L’arthroscanner permet de visualiser la surface du cartilage et la presence de calcifications mais est tres peu utilise en pratique clinique. La tomographie spectrale a comptage de photons est une nouvelle technologie qui est l’extension en multi-energie de la tomographie a double energie qui a montre son utilite pour la detection des cristaux d’urate de sodium. L’acces a des images mono-energetiques permet d’ameliorer le contraste des tissus mous habituellement non visibles en scanner classique en particulier le cartilage et le menisque. Nous proposons dans ce travail le developpement de biomarqueurs a type d’analyse morphologique quantitative du cartilage. Materiels et methodes Nous avons utilise un prototype (Philips Healthcare, Haifa) situe au CERMEP, Lyon, il s’agit appareil clinique dote d’un tube a rayons X classique et d’un detecteur a conversion directe de photons resolutif en energie qui permet l’obtention de voxels isotropes de 250 × 250 × 250 microns. L’acquisition dure quelques minutes. Cet appareil permet de recuperer une serie d’images mono-energetiques de 30 keV a 120 keV, nous avons selectionne les images a 60 keV qui offraient le meilleur contraste pour la visualisation du cartilage. Pour ce faire, nous avons etudie 24 specimens de genoux (15 normaux et 9 arthrosiques avec presence d’osteophytes), 5 hommes (âge moyen : 75,6 ± 14,3 ans), 17 femmes (87,7 ± 9,7 ans). Nous avons analyse le tibia et le femur separement des compartiments femoro-tibial medial et lateral. Nous avons utilise le logiciel itk-SNAP 3,8.0 selon un processus semi-automatique avec segmentation manuelle et interpolation. Le parametre mesure est l’epaisseur moyenne du cartilage en mm par la methode 3D des spheres. Resultats Les epaisseurs moyennes (ep_moys) du tibia lateral etaient de 2,82 ± 0,44 pour les normaux (Nx) versus 1,96 ± 0,94 mm pour les arthrosiques (OA), au tibia medial, les ep_moys etaient de 2,14 ± 0,36 Nx versus 1,95 ± 0,5 mm OA. Au femur lateral, les ep_moys etaient de 1,74 ± 0,34 Nx versus 1,32 ± 0,5 mm OA et au femur medial les ep_moys etaient de 1,35 ± 0,3 Nx versus 1,28 ± 0,7 mm OA. La difference a ete evalue a l’aide du test t et les differences etaient significatives au compartiment lateral pour le tibia (p = 0,002), femoral (p = 0,01), la difference n’etait pas significative au tibia medial et limite au niveau du femur medial (p = 0,04). Conclusion Le scanner spectral a comptage de photons est un nouvel outil qui permettra d’analyser sur la meme image des parametres quantitatifs 3D du cartilage et de l’os sous chondral pour ameliorer la comprehension du phenomene arthrosique et mieux suivre l’evolution naturelle ou sous l’effet des traitements.

International audience; While human bone morphogenetic protein-2 (BMP-2) is a promising growth factor for bone regeneration, a major challenge in biomedical applications is finding an optimal carrier for its delivery at the site of injury. Because of their natural affinities for growth factors (including BMP-2) as well as their role in instructing cell function, cultured cell-derived extracellular matrices (ECM) are of special interest. We hereby hypothesized that a “bony matrix” containing mineralized, osteogenic ECM is a potential efficacious carrier of BMP-2 for promoting bone formation and, therefore, compared the efficacy of the decellularized ECM derived from osteogenic-differentiated human mesenchymal stem cells (hMSCs) to the one obtained from ECM from undifferentiated hMSCs. Our results provided evidence that both ECMs can bind BMP-2 and promote bone formation when implanted ectopically in mice. The osteoinductive potential of BMP-2, however, was greater when loaded within an osteogenic MSC-derived ECM; this outcome was correlated with higher sequestration capacity of BMP-2 over time in vivo. Interestingly, although the BMP-2 mainly bound onto the mineral crystals contained within the osteogenic MSC derived-ECM, these mineral components were not involved in the observed higher osteoinductivity, suggesting that the organic components were the critical components for the matrix efficacy as BMP-2 carrier.

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International audience; Most of the last century, bone remodeling models have been proposed based on the observation that bone density is dependent on the intensity of the applied mechanical loads. Most of these cortical or trabecular bone remodeling models are related to the osteocyte mechanosensitivity, and they all have a direct correlation between the bone mineral density and the mechanical strain energy. However, experiments on human athletes show that high-intensity sport activity tends not to increase bone mineral density but rather has a negative impact. Therefore, it appears that the optimum bone mineral density would develop for “medium”-intensity activity (or medium mechanical loads) and not for the highest-intensity one.In this work, we propose a new continuum approach based on bone cell activ-ity being either positive or negative as a function of the intensity of the applied mechanical load. At standard earth gravity without exercise, bone homeostasis is observed with cell activity being at equilibrium. When “medium loads” such as “low-intensity” or “optimized” sport activity are applied, cells are activated and an increase of bone density occurs. On the other hand, “high-intensity loads” such as over-training lead to bone density decrease or bone degradation. Our results are in agreement with the literature and enable us to foresee applications such as optimal sport training for best physical conditions.

International audience; The fixation of hydrogels to biological tissues is a major challenge conditioning the development of implants and surgical techniques. Here, coatings of procoagulant nanoparticles are devised which use the presence of blood to create adhesion between hydrogels and soft internal organs. Those nanostructured coatings are simply adsorbed at the hydrogel surfaces and can rapidly activate the formation of an interfacial blood clot acting as an adhesive joint. This concept is demonstrated on pig liver capsules with model poly(ethylene-glycol) membranes that are intrinsically poorly adhesive. In the absence of blood, ex vivo peeling tests show that coatings with aggregates of bare silica nanoparticles induce a 2- to 4-fold increase in adhesion energy as compared to the uncoated membrane (3 ± 2 J m–2). This effect is found to scale with the specific surface area of the coating. The highest adhesion energies produced by these nanoparticle-coated membranes (10 ± 5 J m–2) approach the value obtained with cyanoacrylate glue (33 ± 11 J m–2) for which tearing of the tissue is observed. Ex vivo pull-off tests show an adhesion strength of coated membranes around 5 ± 1 kPa, which is significantly reduced when operating in vivo (1.0 ± 0.5 kPa). Nevertheless, when blood is introduced at the interface, the in vivo adhesion strength can be improved remarkably with silica coatings, reaching 4 ± 2 kPa after 40 min contact. In addition, these silica-coated membranes can seal and stop the bleeding produced by liver biopsies very rapidly (

Study Design In vitro disk explant culture. Objective Notochordal cells (NCs) have been shown to upregulate matrix production by nucleus pulposus (NP) cells in coculture. To examine the translation of these in vitro results to a nativelike setting, the regenerative potential of NCs injected into NP tissue was assessed in this study. Methods NP explants were cultured after injection with NCs in phosphate-buffered saline (PBS) or with PBS alone (sham). At days 0 and 42, cell viability and morphology, water, DNA, sulfated glycosaminoglycan and hydroxyproline content, and gene expression of anabolic markers were analyzed. Results NCs remained viable during culture, but their morphology changed. The biochemical content remained unchanged, except for the DNA content in the NC group. Overall ACAN expression remained unchanged, whereas COL2A1 decreased during culture. Conclusions No overall anabolic response was observed when NCs were injected into NP explants. NCs were found to survive but did not display the typical NC morphology by the end of the culture period.

International audience; In tissue engineering and regenerative medicine, stem cell-specifically, mesenchymal stromal/stem cells (MSCs)-therapies have fallen short of their initial promise and hype. The observed marginal, to no benefit, success in several applications has been attributed primarily to poor cell survival and engraftment at transplantation sites. MSCs have a metabolism that is flexible enough to enable them to fulfill their various cellular functions and remarkably sensitive to different cellular and environmental cues. At the transplantation sites, MSCs experience hostile environments devoid or, at the very least, severely depleted of oxygen and nutrients. The impact of this particular setting on MSC metabolism ultimately affects their survival and function. In order to develop the next generation of cell-delivery materials and methods, scientists must have a better understanding of the metabolic switches MSCs experience upon transplantation. By designing treatment strategies with cell metabolism in mind, scientists may improve survival and the overall therapeutic potential of MSCs. Here, we provide a comprehensive review of plausible metabolic switches in response to implantation and of the various strategies currently used to leverage MSC metabolism to improve stem cell-based therapeutics. Significance statement: Lack of success of stem cell-based therapies has been largely attributed to the massive cell death observed post-transplantation, which is caused by the metabolic shock these cells experience as they transition from in vitro to a hostile, injured site in vivo. The metabolism in mesenchymal stem cells (MSCs), specifically, is highly sensitive to cellular and environmental cues. In order to improve cell survival rate posttransplantation, it is important that scientists understand, and take into account, the needs and demands of MSC metabolism as they design the next generation of MSC-based therapies.

International audience; Nucleic acid-based therapy has shown great promise in accelerating bone regeneration as well as other diseases. Nucleic acids used in gene therapy mainly are either plasmid DNA (pDNA) or RNAs. Although pDNA therapy has been extensively studied for decades with encouraging preclinical and clinical results, side effects, and low efficiency associated with nuclear trafficking are hard to bypass. Unlike pDNA, RNAs (mRNA, siRNA, miRNA) exert their function in the cytoplasm, thereby being more efficient in hard-to-transfect cells such as primary osteoblasts. RNA interference-based gene silencing represents a negative regulation which knockdown the expression of antagonists that impair osteogenesis process. In contrary, mRNA therapy for osteogenesis represents a positive regulation which delivers mRNA encoding growth factors to accelerate bone regeneration. This review presents a comprehensive summary of the mRNA and siRNA-based therapies and the targets for bone re-generation in case of bone defect and osteoporosis.

Bone marrow-derived multipotent stromal cells (BMMSCs) represent an attractive therapeutic modality for cell therapy in type 2 diabetes mellitus (T2DM)-associated complications. T2DM changes the bone marrow environment, however, its effects on BMMSC properties remain unclear. The present study aimed at investigating select functions and differentiation of BMMSCs harvested from the T2DM microenvironment as potential candidates for regenerative medicine. BMMSCs were obtained from Zucker diabetic fatty (ZDF, an obese-T2DM model) rats and their lean littermates (ZL, controls), and cultured under normoglycemic conditions. The BMMSCs derived from ZDF animals were fewer in number, with limited clonogenicity (by 2-fold), adhesion (by 2.9-fold), proliferation (by 50%), migration capability (by 25%), and increased apoptosis rate (by 2.5-fold) compared to their ZL counterparts. Compared to the cultured ZL-BMMSCs, the ZDF-BMMSCs exhibited (i) enhanced adipogenic differentiation (increased number of lipid droplets by 2-fold, upregulation of the Pparg, AdipoQ, and Fabp genes), possibly due to having been primed to undergo such differentiation in vivo prior to cell isolation, and (ii) different angiogenesis-related gene expression in vitro and decreased proangiogenic potential after transplantation in nude mice. These results provided evidence that the T2DM environment impairs BMMSC expansion and select functions pertinent to their efficacy when used in autologous cell therapies.

The present study aimed at elucidating the effect of local pH in the extracellular microenvironment of tissue engineered (TE) constructs on bone cell functions pertinent to new tissue formation. To this aim, we evaluated the osteogenicity process associated with bone constructs prepared from human, bone marrow-derived stromal cells (hBMSC) combined with 45S5 bioactive glass (BG), a material that induces alkalinization of the external medium. The pH measured in cell-containing BG constructs was around 8.0, i.e., 0.5 unit more alkaline than that in two other cell-containing material (hydroxyapatite/tricalcium phosphate (HA/TCP) and coral) constructs tested. When implanted ectopically in mice, there was no de novo bone tissue in the BG cell-containing constructs, in contrast to results obtained with either HA/TCP or coral ceramics which consistently promoted formation of ectopic bone. In addition, the implanted 50:50 composites of both HA/TCP:BG and coral:BG constructs, that displayed a pH of around 7.8, promoted 20-30 fold less amount of bone tissue. Interestingly, hBMSC viability in BG constructs was not affected compared to the other two types of material constructs tested both in vitro and in vivo. Osteogenic differentiation (specifically, ALP activity and gene expression of RUNX2, ALP and BSP) was not affected when hBMSC were maintained in moderate alkaline pH (≤ 7.90) external milieu in vitro, but was dramatically inhibited at higher pH values. Formation of mineralized nodules in the extracellular matrix of hBMSC was fully inhibited at alkaline (> 7.54) pH values. Most importantly, there is a pH range (specifically, 7.9-8.27) at which hBMSC proliferation was not affected but the osteogenic differentiation of these cells was inhibited. Altogether, these findings provided evidence that excessive alkalinization in the microenvironment of TE constructs (resulting, for example, from material degradation) affects adversely the osteogenic differentiation of osteoprogenitor cells. ispartof: Tissue Engineering Part A vol:20 issue:13 pages:1827-1840 ispartof: location:United States status: published

Study Design Preclinical in vitro culture of human degenerated nucleus pulposus (NP) tissue. Objective Cyclooxygenase 2 inhibitors (e.g., celecoxib) inhibit prostaglandin E2 (PGE2) production, and they have been shown to upregulate regeneration of articular cartilage. In this study, we developed an explant culture system for use with human tissue and tested the potential of celecoxib. Methods NP explants were cultured with or without 1 μM of celecoxib and were analyzed at days 0 and 7 for biochemical content (water, sulfated glycosaminoglycans, hydroxyproline, and DNA), gene expression (for disk matrix anabolic and catabolic markers), and PGE2 content. Results Water and biochemical contents as well as gene expression remained close to native values after 1 week of culture. PGE2 levels were not increased in freshly harvested human NP tissue and thus were not reduced in treated tissues. Although no anabolic effects were observed at the dosage and culture duration used, no detrimental effects were observed and some specimens did respond by lowering PGE2. Conclusions Human degenerated NP explants were successfully cultured in a close to in vivo environment for 1 week. Further research, especially dosage-response studies, is needed to understand the role of PGE2 in low back pain and the potential of celecoxib to treat painful disks.

International audience; Alcohol induced osteoporosis is characterized by a bone mass decrease and microarchitecture alterations. Having observed an excess in osteocyte apoptosis, we aimed to assess the bone tissue biochemistry, particularly in the osteocyte and its environment. For this purpose, we used a model of alcohol induced osteoporosis in rats. Bone sections of cortical bone were investigated using synchrotron UV-microspectrofluorescence at subcellular resolution. We show that bone present three fluorescence peaks at 305, 333 and 385 nm, respectively corresponding to tyrosine, tryptophan and collagen. We have determined that tyrosine/collagen and tryptophan/collagen ratios were higher in the strong alcohol consumption group. Tryptophan is related to the serotonin metabolism involved in bone formation, while tyrosine is involved in the activity of tyrosine kinases and phosphatases in osteocytes. Our experiment represents the first combined synchrotron UV microspectroscopy analysis of bone tissue with a quantitative biochemical characterization in the osteocyte and surrounding matrix performed separately.

International audience; Study design: In vitro analysis.Objective: The aim of this study was to assess the effect of three-dimensional (3D) printing of porous titanium on human mesenchymal stem cell (hMSC) adhesion, proliferation, and osteogenic differentiation.Summary of background data: A proprietary implant using three-dimensional porous titanium (3D-pTi) that mimics trabecu-lar bone structure, roughness, porosity, and modulus of elasticity was created (Ti-LIFE technology™, Spineart SA Switzerland). Such implants may possess osteoinductive properties augmenting fusion in addition to their structural advantages. However, the ability of 3D-pTi to affect in vitro cellular proliferation and osteogenic differentiation remains undefined.Methods: Disks of 3D-pTi with a porosity of 70% to 75% and pore size of 0.9 mm were produced using additive manufacturing technology. 2D Ti6Al4V (2D-Ti) and 2D polyetheretherketone (2D-PEEK) disks were prepared using standard manufacturing process. Tissue culture plastic (TCP) served as the control surface. All discs were characterized using 2D-micros-copy, scanning electron microscopy (SEM), and x-ray micro-computed tomography. Forty thousand hMSCs were seeded on the disks and TCP and cultured for 42 days. hMSC morphology was assessed using environmental SEM and confocal imaging following phalloidin staining. hMSC proliferation was evaluated using DNA fluorescent assay. hMSC differentiation was assessed using RT-qPCR for genes involved in hMSC osteogenic differentiation and biochemical assays were performed for alkaline phosphatase activity (ALP) and calcium content.Results: 3D-pTi lead to a higher cell number as compared to 2D-Ti and 2D-PEEK at D21, D28 and D42. ALP activity of hMSCs seeded into 3D-pTi scaffolds was as high as or higher than that of hMSCs seeded onto TCP controls over all time points and consistently higher than that of hMSCs seeded onto 2D-Ti scaffolds. However, when ALP activity was normalized to protein content, no statistical differences were found between all scaffolds tested and TCP controls.Conclusion: 3D-pTi provides a scaffold for bone formation that structurally mimics cancellous bone and improves hMSC adhesion and proliferation compared to 2D-Ti and PEEK.

Purpose: Intimal smooth muscle cell (SMC) hyperplasia is a main component of the arterial wall response to injury. We have investigated the capacity of a water-soluble nonanticoagulant functionalized dextran (E9) in inhibition of SMC growth in vitro and in vivo. Methods: E9 was obtained with chemical substitutions with anionic and hydrophobic groups on the dextran backbone. SMC proliferation (cell counting, thymidine uptake, cell cycle analysis) was followed in culture in the presence of E9. Western blot analysis against phosphorylated mitogen-activated protein kinase (MAPK), extracellular signal-regulated protein kinase 1/2, and assessment of MAPK activity on serum-stimulated SMCs also were investigated. Binding/displacement experiments, electron microscopy, and cell fractionations were used to follow the binding and internalization of radiolabeled and fluorescentlabeled E9. New Zealand white rabbit iliac arteries were injured with balloon dilatation and stent deployment. Animals were treated for 14 days with saline solution or E9 (5 mg/kg injected subcutaneously, twice daily). Morphometric analyses were carried out in each group (n = 6 arteries, 18 sections). Results: Nonanticoagulant E9 inhibited SMC proliferation in vitro. Tyrosine phosphorylation of MAPK 1/2 and MAPK activity were inhibited with E9 within 5 minutes of incubation. The binding and rapid cytoplasmic internalization of the synthetic compound was evidenced, but, in contrast to heparin, we did not detect any nuclear localization of the antiproliferative E9. In the in vivo model, qualitative modifications of neointimal structure with a thinner fibrocellular neointima were noticed after E9 treatment. Morphometric analyses of stented arteries in E9-treated animals indicated an important reduction (P

Memory and long term potentiation require de novo protein synthesis. A key regulator of this process is mTORC1, a complex comprising the mTOR kinase. Growth factors activate mTORC1 via a pathway involving PI3-kinase, Akt, the TSC complex and the GTPase Rheb. In non-neuronal cells, translocation of mTORC1 to late endocytic compartments (LEs), where Rheb is enriched, is triggered by amino acids. However, the regulation of mTORC1 in neurons remains unclear. In mouse hippocampal neurons, we observed that BDNF and treatments activating NMDA receptors trigger a robust increase in mTORC1 activity. NMDA receptors activation induced a significant recruitment of mTOR onto lysosomes even in the absence of external amino acids, whereas mTORC1 was evenly distributed in neurons under resting conditions. NMDA receptor-induced mTOR translocation to LEs was partly dependent on the BDNF receptor TrkB, suggesting that BDNF contributes to the effect of NMDA receptors on mTORC1 translocation. In addition, the combination of Rheb overexpression and artificial mTORC1 targeting to LEs by means of a modified component of mTORC1 fused with a LE-targeting motif strongly activated mTOR. To gain spatial and temporal control over mTOR localization, we designed an optogenetic module based on light-sensitive dimerizers able to recruit mTOR on LEs. In cells expressing this optogenetic tool, mTOR was translocated to LEs upon photoactivation. In the absence of growth factor, this was not sufficient to activate mTORC1. In contrast, mTORC1 was potently activated by a combination of BDNF and photoactivation. The data demonstrate that two important triggers of synaptic plasticity, BDNF and NMDA receptors, synergistically power the two arms of the mTORC1 activation mechanism, i.e., mTORC1 translocation to LEs and Rheb activation. Moreover, they unmask a functional link between NMDA receptors and mTORC1 that could underlie the changes in the synaptic proteome associated with long-lasting changes in synaptic strength. Supplementary Information The online version contains supplementary material available at 10.1186/s13041-021-00820-8.

The deterioration of the musculoskeletal system is a serious health concern for long-term space missions. The accumulated information over the past decades of space flights showed that microgravity impacts significantly the musculoskeletal system with muscle atrophy and bone loss. Until now, it has been difficult to make reasonable predictions of the bone loss for prolonged space missions due to the lack of in-space experimental data and weak understanding of the mechanobiological bone mechanisms. On earth, the healthy musculoskeletal degradation is mainly age related with osteoporosis and delayed fracture healing. A better understanding of the bone mechanobiological functions could help us improve our model predictions of the musculoskeletal health system during long-term space missions. We develop a numerical model able to predict the bone loss at the mesoscopic scale (bone trabecula) in microgravity. The model is able to correlate the calculated bone degradation mechanism with data available in the literature showing the effective bone density loss measured experimentally. An optimization algorithm is used for an average bone microstructure distribution and long-term prediction. Extrapolation is made to link the local bone loss at the structural scale with the corresponding effective bone strength. The first part of the paper details the extraction of the bone microstructure using micro-CT images and numerical model development. Next, the degradation and optimization schemes are detailed. Finally, some results are presented for long-term degradation.

International audience; The addition of bone morphogenetic protein-2 (BMP-2) with multipotent stromal cells (MSC) is an attractive strategy to enhance the bone-forming potential of MSC-based tissue engineering (TE) constructs. However, the effective dosage of BMP-2 remains to be determined. In this study, we evaluated the effects of human MSCs codelivered with BMP-2 at either low or high dosage on the bone-forming potential of constructs in a mice ectopic model. Our results showed that the addition of only low dose of BMP-2 was beneficial to enhance the bone-forming potential of MSCs, whereas high dose of BMP-2 overcame the advantage of combining this growth factor with MSCs. Expressions of select genes of both murine and human origins in TE constructs demonstrated that the beneficial effect of low dose of BMP-2 with implanted human MSCs did not involve enhanced differentiation of these cells into osteoblasts or induction of paracrine cues but rather involved induction of the osteogenic differentiation of the host progenitors. Therefore, the advantage of combining BMP-2 with MSCs to enhance the bone-forming potential of TE constructs appeared to be an additive effect of both components rather than a synergistic one.

Resume Introduction Malgre l’amelioration des techniques et du materiel de reparation des ruptures de la coiffe des rotateurs, le taux moyen de rupture iterative reste proche de 30 %. L’objectif de cette etude etait d’evaluer l’interet d’une injection de plasma autologue conditionne (ACP™, Arthrex) dans la cicatrisation tendineuse apres une reparation sous arthroscopie. L’hypothese etait que l’utilisation de ACP™ ameliorerait le taux de cicatrisation tendineuse. Materiels et methodes Une etude prospective comparative non randomisee a inclus tous les patients âges de plus de 18 ans, operes en 2010 pour une reparation sous arthroscopie d’une rupture tendineuse transfixiante de la coiffe des rotateurs, une degenerescence graisseuse ≤ 2 selon Goutallier, quel que soit le niveau de retraction tendineuse, sur une epaule vierge et non arthrosique et ne presentant aucune contre-indication a l’arthro-IRM. Le protocole chirurgical etait standardise. La premiere moitie des patients inclus recevait une injection de ACP™ en fin d’intervention dans le tendon repare, la tranche d’avivement des tuberosites et l’espace sous-acromial, et la seconde moitie (controle) n’avait aucun traitement supplementaire. Le critere principal de jugement etait la cicatrisation tendineuse a 6 mois selon Sugaya evaluee sur l’arthro-IRM. Les criteres secondaires etaient la douleur de l’epaule evaluee sur une echelle numerique (de 0 « aucune douleur » a 10 « la pire douleur imaginable ») et le score fonctionnel de Constant. Resultats Sur 58 patients inclus, 2 ont refuse l’arthro-IRM et 7 ont ete perdus de vue. Quarante-neuf (26 ACP™/23 controles) patients ont ete analyses, 20 hommes et 29 femmes âges en moyenne de 61 ± 7,3 ans. Aucune difference significative n’a ete retrouvee sur le taux de cicatrisation a 6 mois (73,1 % ACP™ vs 78,3 % controle, p = 0,75), la douleur de l’epaule (2 ± 1,8 ACP™ vs 2,6 ± 1,7 controle, p = 0,24), et le score de Constant (/100) (77 ± 13,5 groupe ACP™ vs 72,4 ± 12,3 groupe temoin, p = 0,18). Conclusion L’adjonction de ACP™ n’a pas ameliore la cicatrisation de la coiffe des rotateurs reparees sous arthroscopie. Cependant le nombre de patients a ete calcule sur une difference attendue importante et source d’un manque de puissance. Niveau de preuve III ; etude cas-temoins.

International audience; The phenomenon of fluorescence can be used by animals to change effective colouration or patterning, potentially to serve functions including intra- and interspecific signalling. Initially believed to be restricted to marine animals, fluorescent colours are now being described in an increasing number of terrestrial species. Here, we describe unique, highly fluorescent patterns in two species of pumpkin toadlets (Brachycephalus ephippium and B. pitanga). We establish that the origin of the fluorescence lies in the dermal bone of the head and back, visible through a particularly thin skin. By comparing them to those of the closely related species Ischnocnema parva, we demonstrate that pumpkin toadlets’ bones are exceptionally fluorescent. We characterize the luminescence properties of the toadlets’ bones and discuss the potential function of fluorescent patterns in natural lighting conditions.

Background The anterior cruciate ligament rupture is a common injury which mainly affects young and active population. Faced to this problem, the development of synthetic structures for ligament reconstruction is increasing. The most recent researches focused on the development of biodegradable structures that could be functionalized to enhance host integration. This work describes the elaboration of different poly(e-caprolactone) prototypes for the rat anterior cruciate ligament replacement in order to found the best design for further in vivo assays. Methods According to the literature, it was decided to elaborate two different poly(e-caprolactone) prototypes: a braided one and a free-fibers one. A chemical grafting of a bioactive polymer–poly(sodium styrene sulfonate) – was performed on both prototypes and mechanical and biological testing were assessed. Based on these results, one rat was implanted with the best prototype. Results The mechanical and biological results demonstrated that the best prototype to implant was the poly(sodium styrene sulfonate)-grafted braided prototype. After one-month implantation, no inflammation was observable around the scar. The rat demonstrated good flexion and extension of the lower limb without any anterior drawer. The prototype was highly anchored to the bone. ESEM images of the explanted prototype showed the presence of cells and tissue ingrowth along and around the fibers. Conclusion This work demonstrates the feasibility to implant a bioactive and biodegradable synthetic ligament in the rat model without any inflammation and with a good tissue anchoring at a short-term time. This will lead to an extensive in vivo assay.

International audience; Repair and reconstruction of large bone defects remain a significant challenge. Cell construct, containing mesenchymal stem cells (MSCs) and scaffold, is a promising strategy for addressing and treating major orthopedic clinical conditions. However, the design of an ideal cell construct for engineering bone faces two critical challenges (i) matching the scaffold degradation rate to that of new bone formation and (ii) preventing the massive cell death post-implantation (caused by disruption of oxygen and nutrient supply). We will hereby primarily focus on the challenge of survival of MSCs post-implantation. Increasing evidence indicates that metabolic regulation plays a critical role in cell fate and functions. In cell metabolism, glucose is considered the major metabolic substrate to produce ATP via glycolysis when the availability of oxygen is limited. In this paper, we delineate the essential roles of glucose on MSC survival. We aim to provide a different perspective which highlights the importance of considering glucose in the development of tissue engineering strategies in order to improve the efficiency of MSC-based cell constructs in the repair of large bone defects.

International audience; Reports on the association of periodontal disease (PD) with systemic lupus erythematosus (SLE) have regularly been published. PD is a set of chronic inflammatory conditions linked to a dysbiotic microbial biofilm, which affects the periodontal tissues, resulting eventually in their destruction and contributing to systemic inflammation. SLE is a multi-system chronic inflammatory autoimmune disease that has a wide range of clinical presentations, touching multiple organ systems. Many epidemiological studies have investigated the two-way relationship between PD and SLE, though their results are heterogeneous. SLE and PD are multifactorial conditions and many biological-based hypotheses suggest common physiopathological pathways between the two diseases, including genetics, microbiology, immunity, and environmental common risk factors. By focusing on recent clinical and translational research, this review aimed to discuss and give an overview of the relationship of SLE with PD, as well as looking at the similarities in the immune-pathological aspects and the possible mechanisms connecting the development and progression of both diseases.

Currently, medical imaging modalities involving X-rays play an essential role in diagnosing this pathology thanks to the good visualization of bone structure. The fluoroscopy on the other hand is used in the operating room to assist and guide the surgical gesture, now available with mobile systems which can adapt to restricted areas of operating rooms. These systems can generate two-dimensional (2D) images such as of radiography or three-dimensional (3D) images such as the scanner, based on the principle of tomography which is used in the diagnosis of pathologies. The generation of these images in 2D/3D dimensions is possible thanks to the mobile C-arm or O-arm already used for surgery. However, these devices have one major disadvantage: the amount of radiation dose they create. When exposed to high radiation doses, they become dangerous threat to both patients and operators. In this thesis, for we will try to respond to two problematics: For which tomographic configurations, for a strategy dose reduction for applications in orthopaedical surgery? what reconstruction methods are best suited to the use of morphometric criteria? How to improve the diagnosis of osteo-articular pathologies based on the analysis of 3D scanner images? I will address these objectives, on the one hand, in the field of orthopaedical surgery. To respond to the first two objectives, our approach has been experimental. The knee specimen was firstly imaged by a prototype C-arm coupling a cone-beam X-ray source to a plane sensor. This prototype was developed by our partners in the FUI-3D4Carm project with the aim of being integrated on a C-arm to get an intraoperative 3D image. We tested several dose reduction scenarios with 2 types of reconstruction algorithms, 1) classical Felkamp (FDK) and 2) Iterative (SART). We tested the reduction of the intensity (mAs), the number of projections and the angular range on the quality of the images. Various evaluation approaches were performed by expert qualitative assessment, digital image quality indicators based on grey levels, structure and finally segmentation methods. On the other hand, in the context of rheumatology, the objective is to quantify the variations in joint width as a biomarker using 3D images for the diagnosis of osteoarthritis in order to answer our third objective. We studied variations in joint spacing at the initial time and at 36 months in a longitudinal study of patients suffering from osteoarthritis. To carry out this quantification, a hybrid segmentation method was developed. It is based on two segmentation methods: a classification segmentation to select the bone part, followed by an active contour method, called "Snake", to extract the joint space. We have been able to demonstrate which criteria for which images are potentially usable for orthopaedic surgery: i) an intensity greater than 5mAs, ii) a minimum threshold angular range of 170°, iii) a minimum number of projections of 200. Then we were also able to demonstrate that the choice of the reconstruction algorithm depends on its use. Indeed, the FDK algorithm gives a better visualization of the bone structure and observers tend to favor it. Whereas images reconstructed with the SART algorithm offer a better similarity on geometric criteria and allow a more stable segmentation. Finally, we were able to obtain preliminary results on the quantification of joint spacing using a semi-automated segmentation method on patients suffering from osteoarthritis. We have identified good segmentation results in 60% of the cases, which suggests that this method is potentially interesting but still needs to be improved., De nos jours, les modalités utilisant des rayons X joue un rôle essentiel dans le diagnostic des pathologies rhumatismales en particulier l’arthrose. Cette modalité permet une bonne visualisation de la structure osseuse essentielle dans ce domaine. En chirurgie orthopédique, la radiographie garde un rôle essentiel avant, pendant et après la chirurgie, la fluoroscopie X basée sur des systèmes mobiles étant adaptée à cet environnement pour aider le geste opératoire. Ces modalités peuvent générer soit des images bidimensionnelles (2D) comme en radiographie soit des images tridimensionnelles (3D) avec le scanner basé sur le principe de la tomographie. L’approche 3D est néanmoins indispensable pour rendre compte de la complexité des structures osseuses. Des méthodes dérivées de la radiographie et plus rarement du scanner permettent de suivre quantitativement l’évolution de l’interligne articulaire. Des arceaux mobiles en forme de C (C-arm) ou de O (O-arm) sont utilisés pour la chirurgie et génèrent des images 2D rarement 3D. Néanmoins, ces appareils présentent comme inconvénient majeur le caractère irradiant qui doit être réduit pour les patients et les manipulateurs. Dans cette thèse, nous tenterons de répondre à trois problématiques : 1) quelles sont les conditions limites pour l’obtention d’images exploitables pour la chirurgie orthopédique dans l’optique de réductions de dose, 2) quelles méthodes de reconstruction sont les plus adaptées pour l’utilisation de critères morphométriques, 3) Comment améliorer le diagnostic de pathologie ostéo-articulaire tel que la gonarthrose à partir de l’analyse d’images 3D de scanners. Pour répondre aux deux premiers objectifs, notre démarche a été expérimentale. Une pièce anatomique de genou a été imagée tout abord par un prototype de C-arm couplant une source X à faisceau conique à un capteur plan. Ce prototype a été développé par nos partenaires du projet FUI-3D4Carm avec comme but d’être intégré sur un arceau C-Arm pour obtenir d’une image 3D en peropératoire. Nous avons testé plusieurs scénarios de diminution de dose avec 2 types d’algorithmes de reconstruction, 1) classique de type Felkamp (FDK) et 2) Itératif (SART). Nous avons testé la diminution de l’ampérage (mAs), du nombre de projections et de la plage angulaire sur la qualité des images. Différentes approches d’évaluation ont été abordées par une appréciation qualitative d’experts, des indicateurs numériques de qualité des images basés sur les niveaux de gris, la structure et pour finir des méthodes de segmentation. Pour répondre à notre troisième objectif, nous avons étudié les variations de l’interligne articulaire au temps initial et à 36 mois dans d’une étude longitudinale de patientes souffrant de gonarthrose. Pour procéder à cette quantification, une méthode de segmentation hybride a été développée. Elle repose sur deux méthodes de segmentation : une segmentation par classification pour sélectionner la partie osseuse, suivie d’une méthode du contour actif, nommé « Snake », pour extraire l’interligne articulaire. Nous avons pu démontrer qu’il existe des critères pour lesquels des images sont potentiellement exploitables pour la chirurgie orthopédique : i) avoir une intensité supérieure à 5mAs, ii) un seuil minimum de plage angulaire de 170°, iii) un nombre de projections minimum de 200. Puis nous avons pu également démontrer que le choix de l’algorithme de reconstruction dépend de son utilisation. En effet, l’algorithme FDK donne une meilleure visualisation de la structure osseuse et les observateurs ont tendance à le privilégier. Tandis que les images reconstruites avec l’algorithme SART offrent une meilleure similarité sur des critères géométriques et permettent une segmentation plus stable. Enfin, nous avons pu obtenir des résultats préliminaires sur la quantification de l’interligne articulaire à l’aide d’une méthode de segmentation semi-automatisée sur des patientes souffrant d’arthrose.

Spectral computed tomography acquires energy-resolved data that allows recovery of densities of constituents of an object. This can be achieved by decomposing the measured spectral projection into material projections, and passing these decomposed projections through a tomographic reconstruction algorithm, to get the volumetric mass density of each material. Material decomposition is a nonlinear inverse problem that has been traditionally solved using model-based material decomposition algorithms. However, the forward model is difficult to estimate in real prototypes. Moreover, the traditional regularizers used to stabilized inversions are not fully relevant in the projection domain.In this study, we propose a deep-learning method for material decomposition in the projection domain. We validate our methodology with numerical phantoms of human knees that are created from synchrotron CT scans. We consider four different scans for training, and one for validation. The measurements are corrupted by Poisson noise, assuming that at most 105 photons hit the detector. Compared to a regularized Gauss-Newton algorithm, the proposed deep-learning approach provides a compromise between noise and resolution, which reduces the computation time by a factor of 100.

International audience; Denoising algorithms via sparse representation are among the state-of-the art for image restoration. On previous work, we proposed SPADE-a sparse-and prior-based method for 3D-image denoising. In this work, we extend this idea to learning approaches and propose a novel residual-U-Net prior-based (ResPrU-Net) method that exploits a prior image. The proposed ResPrU-Net architecture has two inputs, the noisy image and the prior image, and a residual connection that connects the prior image to the output of the network. We compare ResPrU-Net to U-Net and SPADE on human knee data acquired on a spectral computerized tomography scanner. The prior image is built from the noisy image by combining information from neighbor slices and it is the same for both SPADE and ResPrU-Net. For deep learning approaches, we use four knee samples and data augmentation for training, one knee for validation and two for test. Results show that for high noise, U-Net leads to worst results, with images that are excessively blurred. Prior-based methods, SPADE and ResPrU-Net, outperformed U-Net, leading to restored images that present similar image quality than the target. ResPrU-Net provides slightly better results than SPADE. For low noise, methods present similar results.

It is now well established that physical exercise has unquestionable beneficial effects on bone tissue and metabolism. However, no consensus regarding the osteogenic effects of exercise on healthy or healing bone has been reached yet. The objective of this work is (i) to evaluate the effects of two running protocols (continuous vs. intermittent) on the parameters of bone quality and bone metabolism, and (ii) to evaluate the preventive effects of these running protocols on bone repair in Wistar rats. We demonstrated here that high-intensity interval-running has positive effects on cortical bone quality, while moderate continuous running has beneficial effects on trabecular bone but is detrimental to cortical bone. These effects also depend on the bone (tibia vs. femur). In addition, our data suggest that both running protocols accelerate the repair of a non-critical bone defect in the tibia but not in the femur, possibly by modulating bone resorption. Associating different types of running is more beneficial to bone health than just one. As part of the refinement of animal models, the use of the tibia would be more suitable to study bone healing than the femur, Il est désormais bien établi que la pratique d’un exercice physique a des effets bénéfiques sur le tissu osseux et son métabolisme. Cependant, aucun consensus n’a encore été établi en ce qui concerne les effets ostéogéniques de l’exercice sur l’os sain ou en cours de réparation. L’objectif de ce travail est d’une part d’évaluer les effets de deux protocoles de course (continue vs. Intermittente) sur les paramètres de la qualité osseuse et le métabolisme osseux, d’autre part d’évaluer les effets de la pratique préventive de ces protocoles de course sur la réparation osseuse chez le rat Wistar. Ces travaux mettent en évidence un effet bénéfique de la course intermittente avec intervalles de haute intensité sur la qualité de l’os cortical tandis que la course continue modérée a des effets bénéfiques sur la qualité de l’os trabéculaire mais néfastes sur l’os cortical. Ces effets dépendent également de l’os étudié (tibia vs. fémur). De plus, nos données suggèrent que les deux protocoles de course accélèrent la réparation d’un défaut osseux de taille non critique dans le tibia mais pas dans le fémur, probablement par modulation de la résorption osseuse. La pratique de différents types de course serait plus bénéfique à la santé osseuse qu’un seul. Dans le cadre du raffinement des modèles animaux, l’utilisation du tibia serait plus adaptée à l’étude de la guérison osseuse que le fémur

Oro-facial bone loss is a major problem in oral and maxillofacial rehabilitation. They have various and varied causes: cancer, cysts, cleft palates, infections or trauma. The management of such bone defects requires the use of bone grafts. Autogenous bone or autograft is the standard gold but has disadvantages: i) the need for a second surgical site, ii) morbidity, iii) increased operating time, iv) limited amount of bone to be removed. To overcome these pitfalls, alternative therapeutics to bone autograft are used, in particular bone substitutes derived from human (allografts), animal (xenografts) or synthetic (alloplastic) bone tissue. Allografts are a credible alternative to autografts and are nowaday widely used in reconstructive and regenerative surgery. These allografts are either mineralized (FDBA: Freeze-Dried Bone Allograft) or demineralized (DFDBA: Demineralized Freeze-Dried Bone Allograft) and come in powder or gel form depending on the support used in the case of DBM (Demineralized Bone Matrix). This PhD project aims to show the osteoformative potential of a new bone allograft formulation, partially demineralized as an injectable paste, in two different models for rat calvaria; it is a PDBM (Partially Demineralized Bone Matrix). The first model is the rat calvarial defect model. Critical size defects (8 mm diameter) and sub-critical size defects (6 mm and 4 mm diameter) are performed on rat calvaria and then left empty or filled with the PDBM. Micro sacnner (µCT) and histological results showed the positive effect of PDBM in the bone repair of 6 and 8 mm diameter defects. Similarly, molecular biology (RT-PCR) showed the positive effect of PDBM in the early expression of genes involved in osteoformation. The 2nd model is a vertical bone augmentation model. A bone chamber (custom-made cylinder of Polyetheretherketone) of 6 mm high and 5 mm in diameter is attached to the rat calvarias after perforating it with 3 small holes 1 mm in diameter. The bone chambers are filled with either PDBM or Bio-Oss®. The µCT and histological results revealed an osteoformative potential for PDBM in the bone chambers. These results support the idea that allografts are a viable option for the treatment of periodontal and maxillofacial defects.; Les pertes osseuses de la sphère oro-faciale constituent un problème majeur dans la réhabilitation orale et maxillo-faciale. Elles ont des causes diverses et variées : cancers, kystes, fentes palatines, infections ou traumatismes. La prise en charge de tels défauts osseux nécessite l’utilisation de greffes osseuses. L’os autogène ou autogreffe constitue le gold standard mais présente des inconvénients: i) la nécessité de recourir à un second site opératoire, ii) morbidité subséquente, iii) une augmentation du temps opératoire, iv) une quantité limitée d’os à prélever. Pour pallier à ces écueils, des alternatives thérapeutiques à l’autogreffe osseuse sont utilisés notamment des substituts osseux dérivés des tissus osseux humains (allogreffes), animaux (xénogreffes) ou synthétiques (alloplastiques). Les allogreffes constituent une bonne alternative aux autogreffes et sont, aujourd’hui, largement utilisées en chirurgie reconstructive et régénérative. Ces allogreffes sont soit minéralisées (FDBA : Freeze-Dried Bone Allograft) ou déminéralisées (DFDBA : Demineralized Freeze-Dried Bone Allograft) et se présentent sous forme de poudre ou de gel selon le support utilisé dans le cas des DBM (Demineralized Bone Matrix). Ce projet de Doctorat avait pour but de montrer le potentiel ostéoformateur d’une nouvelle formulation d’allogreffe osseuse, partiellement déminéralisée sous forme de pâte injectable, dans deux modèles différents au niveau de la calvaria de rat : il s’agit d’une Matrice Osseuse Partiellement Déminéralisée (MOPD). Le 1er modèle est celui de défauts de calvaria de rat. Des défauts de taille critique (8 mm de diamètre) et sub-critique (6 mm et 4 mm de diamètre) sont réalisés sur la calvaria des rats puis laissés vides ou comblés avec la MOPD. Les résultats du micro scanner (µCT) et ceux histologiques ont montré l’effet positif de la MOPD dans la réparation osseuse des défauts de 6 et 8 mm de diamètre. De même, la biologie moléculaire (RT-PCR) a montré l’effet positif de la MOPD dans l’expression précoce des gènes impliqués dans l’ostéoformation. Le 2e modèle est celui d’augmentation osseuse verticale. Une chambre à os en Polyétherétherkétone (PEEK) de 6 mm de haut et 5 mm de diamètre est fixée sur la calvaria des rats après avoir perforé cette dernière de 3 petits trous de 1 mm de diamètre. Les chambres à os sont remplies soit de MOPD soit d’os bovin déprotéinisé (Bio-Oss®). Les résultats du µCT et ceux histologiques ont révélé un potentiel ostéoformateur de la MOPD dans les chambres à os. Ces résultats confortent l’idée que les allogreffes sont une option viable pour le traitement des défauts parodontaux et maxillo-faciaux.

Summary Most organs and tissues in the body, including bone, can repair after an injury due to the activation of endogenous adult stem/progenitor cells to replace the damaged tissue. Inherent dysfunctions of the endogenous stem/progenitor cells in skeletal repair disorders are still poorly understood. Here, we report that Fgfr3Y637C/+ over-activating mutation in Prx1-derived skeletal stem/progenitor cells leads to failure of fracture consolidation. We show that periosteal cells (PCs) carrying the Fgfr3Y637C/+ mutation can engage in osteogenic and chondrogenic lineages, but following transplantation do not undergo terminal chondrocyte hypertrophy and transformation into bone causing pseudarthrosis. Instead, Prx1Cre;Fgfr3Y637C/+ PCs give rise to fibrocartilage and fibrosis. Conversely, wild-type PCs transplanted at the fracture site of Prx1Cre;Fgfr3Y637C/+ mice allow hypertrophic cartilage transition to bone and permit fracture consolidation. The results thus highlight cartilage-to-bone transformation as a necessary step for bone repair and FGFR3 signaling within PCs as a key regulator of this transformation., Graphical Abstract, Highlights • Fgfr3Y367C activating mutation in skeletal stem/progenitor cells prevents bone healing • Intrinsic deficiencies in transplanted Prx1Cre;Fgfr3Y637C/+ PCs cause pseudarthrosis • Prx1Cre;Fgfr3Y637C/+ PCs cannot support cartilage-to-bone transformation • Wild-type PCs can rescue the Prx1Cre;Fgfr3Y637C/+ pseudarthrosis phenotype, Julien et al. report a severe bone repair phenotype associated with pseudarthrosis and functional impairment of periosteal cells (PCs) in Prx1Cre;Fgfr3Y637C/+ mice. PCs carrying the Fgfr3Y367C activating mutation cannot undergo cartilage-to-bone transformation thus uncovering an essential role of this transformation step in bone healing.

International audience; Allogenic demineralized bone matrix has been developed as a reliable alternative to the autologous bone graft. In the present study, we assessed the osteoformation potential of a partially demineralized bone matrix (PDBM) in a paste form obtained without an added carrier. This formulation included the preparation of cancelous bone from femoral heads after decellularision, delipidation, demineralization in HCl and autoclaving at 121 • C. Structural and biochemical characteristics of PDBM were determined using FTIR (Fourier transform infrared spectroscopy), hydroxyproline, DNA content assays, and optical ellipsometry. The osteoformation potential was evaluated in 8-, 6-, and 4-mm-diameter rat-calvarial bone defects by in vivo micro-CT analysis, performed immediately after surgery on days 0, 15, 30, 45, and 60. Moreover, histological and histomorphometric analyses were done on day 60. PDBM was compared to cancelous bone powder (BP) before its partial demineralization. The expression levels of selected inflammation-, angiogenesis-, and bone-related genes were also investigated by RT-PCR, 3, 7, and 14 days after surgery. Compared to the control group, the PDBM group exhibited a significant increase (p < 0.05) in radiopacity in 8-mm-and 6-mm-diameter defects at all time points tested. On day 60, the amount of newly-formed bone was greater (16 and 1.6 folds; p < 0.001; respectively) compared to that in control defects. No bone formation was observed in defects filled with BP regardeless of the size. In 8-mm-diameter defect, PDBM was effective enough to induce the upregulation of genes pertinent to inflammation (i.e., TNFα, IL-6, and IL-8), angiogenesis (i.e., VEGF, VWF), and osteogenesis (ALP, RUNX2, BGLAP, SP7) by day 3 after surgery. This study showed that the tested PDBM deeply influences the early critical events involved in bone regeneration and exhibits efficient osteoformation capacity, making it an attractive graft option for treating defects in periodontal and maxillofacial areas.

International audience; Oxidative stress (OS) plays a pivotal role in diabetes mellitus (DM) onset, progression, and chronic complications. Hyperglycemia-induced reactive oxygen species (ROS) have been shown to reduce insulin secretion from pancreatic β-cells, to impair insulin sensitivity and signaling in insulin-responsive tissues, and to alter endothelial cells function in both type 1 and type 2 DM. As a powerful antioxidant without side effects, astaxanthin (ASX), a xanthophyll carotenoid, has been suggested to contribute to the prevention and treatment of DM-associated pathologies. ASX reduces inflammation, OS, and apoptosis by regulating different OS pathways though the exact mechanism remains elusive. Based on several studies conducted on type 1 and type 2 DM animal models, orally or parenterally administrated ASX improves insulin resistance and insulin secretion; reduces hyperglycemia; and exerts protective effects against retinopathy, nephropathy, and neuropathy. However, more experimental support is needed to define conditions for its use. Moreover, its efficacy in diabetic patients is poorly explored. In the present review, we aimed to identify the up-to-date biological effects and underlying mechanisms of ASX on the ROS-induced DM-associated metabolic disorders and subsequent complications. The development of an in-depth research to better understand the biological mechanisms involved and to identify the most effective ASX dosage and route of administration is deemed necessary.

Application of messenger RNA (mRNA) for bone regeneration is a promising alternative to DNA, recombinant proteins and peptides. However, exogenous in vitro transcribed mRNA (IVT mRNA) triggers innate immune response resulting in mRNA degradation and translation inhibition. Inspired by the ability of viral immune evasion proteins to inhibit host cell responses against viral RNA, we applied non-structural protein-1 (NS1) from Influenza A virus (A/Texas/36/1991) as an IVT mRNA enhancer. We evidenced a dose-dependent blocking of RNA sensors by NS1 expression. The co-delivery of NS1 mRNA with mRNA of reporter genes significantly increased the translation efficiency. Interestingly, unlike the use of nucleosides modification, NS1-mediated mRNA translation enhancement does not dependent to cell type. Dual delivery of NS1 mRNA and BMP-2 mRNA to murine pluripotent stem cells (C3H10T1/2), promoted osteogenic differentiation evidenced by enhanced expression of osteoblastic markers (e.g. alkaline phosphatase, type I collagen, osteopontin, and osteocalcin), and extracellular mineralization. Overall, these results support the adjuvant potentiality of NS1 for mRNA-based regenerative therapies. STATEMENT OF SIGNIFICANCE: mRNA therapy has the potential to improve the efficiency of nucleic acid based regenerative medicine. Up to now, the incorporation of expensive modified nucleotides is a common way to avoid IVT mRNA-induced detrimental immunogenicity. We here introduce co-delivery of Influenza virus immune evasion protein-NS1 coding mRNA as a strategy to suppress RNA sensors for maximizing IVT mRNA expression. An increased osteogenic commitment of pluripotent stem cells was observed after BMP2 mRNA and NS1 mRNA delivery. This study revealed how applying non-modified mRNA with NS1 could be a promising alternative as a therapeutic in bone regeneration.

International audience

Mesenchymal stem cells (MSCs) hold considerable promise in tissue engineering (TE). However, their poor survival when exogenously administered limits their therapeutic potential. Previous studies from our group demonstrated that lack of glucose (glc) (but not of oxygen) is fatal to human MSCs because it serves as a pro-survival and pro-angiogenic molecule for human MSCs (hMSCs) upon transplantation. However, which energy-providing pathways MSCs use to metabolize glc upon transplantation? Are there alternative energetic nutrients to replace glc? And most importantly, do hMSCs possess significant intracellular glc reserves for ensuring their survival upon transplantation? These remain open questions at the forefront of TE based-therapies. In this study, we established for the first time that the in vivo environment experienced by hMSCs is best reflected by near-anoxia (0.1% O2) rather than hypoxia (1%–5% O2) in vitro. Under these near-anoxia conditions, hMSCs rely almost exclusively on glc through anerobic glycolysis for ATP production and are unable to use either exogenous glutamine, serine, or pyruvate as energy substrates. Most importantly, hMSCs are unable to adapt their metabolism to the lack of exogenous glc, possess a very limited internal stock of glc and virtually no ATP reserves. This lack of downregulation of energy turnover as a function of exogenous glc level results in a rapid depletion of hMSC energy reserves that explains their poor survival rate. These new insights prompt for the development of glc-releasing scaffolds to overcome this roadblock plaguing the field of TE based-therapies.

The architectural features of synthetic bone grafts are key parameters for regulating cell functions and tissue formation for the successful repair of bone defects. In this regard, macroporous structures based on triply-periodic minimal surfaces (TPMS) are considered to have untapped potential. In the present study, custom-made implants based on a gyroid structure, with (GPRC) and without (GP) a cortical-like reinforcement, were specifically designed to fit an intended bone defect in rat femurs. Sintered hydroxyapatite implants were produced using a dedicated additive manufacturing technology and their morphological, physico-chemical and mechanical features were characterized. The implants' integrity and ability to support bone ingrowth were assessed after 4, 6 and 8 weeks of implantation in a 3-mm-long, femoral defect in Lewis rats. GP and GPRC implants were manufactured with comparable macro- to nano-architectures. Cortical-like reinforcement significantly improved implant effective stiffness and resistance to fracture after implantation. This cortical-like reinforcement also concentrated new bone formation in the core of the GPRC implants, without affecting newly formed bone quantity or maturity. This study showed, for the first time, that custom-made TPMS-based bioceramic implants could be produced and successfully implanted in load-bearing sites. Adding a cortical-like reinforcement (GPRC implants) was a relevant solution to improve implant mechanical resistance, and changed osteogenic mechanism compared to the GP implants. STATEMENT OF SIGNIFICANCE: Architectural features are known to be key parameters for successful bone repair using synthetic bioceramic bone graft. So far, conventional manufacturing techniques, lacking reproducibility and complete control of the implant macro-architecture, impeded the exploration of complex architectures, such as triply periodic minimal surfaces (TPMS), which are foreseen to have an unrivaled potential for bone repair. Using a new additive manufacturing process, macroporous TPMS-based bioceramics implants were produced in calcium phosphate, characterized and implanted in a femoral defect in rats. The results showed, for the first time, that such macroporous implants can be successfully implanted in anatomical load-bearing sites when a cortical-like outer shell is added. This outer shell also concentrated new bone formation in the implant center, without affecting new bone quantity or maturity.

Mesenchymal stem cells (MSCs) are appealing candidates for regenerative medicine applications. Today, MSCs are more and more using to clinical trials for repairing injured tissues or organs. Upon implantation, however, cells encounter an avascular microenvironment depleted of oxygen and nutrients that is responsible for their massive death post-transplantation, a major roadblock to successful clinical therapies. This issue can be overcome by in situ supplying glucose that acts as the main metabolic fuel for MSCs in hypoxia and enhances their survival and functionality. However, energy-providing pathways used by MSCs upon transplantation and their plausible metabolic switches in response to this ischemic environment are not well understood. Moreover, any strategy, based on continuous glucose delivery to fuel cells, have not been designed for improving MSC survival and functionality post-implantation. The first aim of this PhD project is to better understand the energetic metabolism used by MSCs upon transplantation. We establish for the first time that the in vivo environment experienced by hMSCs is best reflected by near-anoxia (0.1% pO2) in vitro associated with glucose and serum depletion. Under this « ischemic » in vitro model, hMSCs rely almost exclusively on glucose through anaerobic glycolysis to produce ATP. Moreover, hMSCs are unable to adapt their energetic metabolism to the lack of exogenous glucose, possess a very limited stock of glucose and no ATP reserves. This lack of downregulation of energy turnover results in a rapid depletion of hMSCs energy reserves, explaining their poor survival rate. The next (and main) aim of this PhD project is to develop and test an enzyme-controlled, nutritive hydrogel with an inbuilt system of glucose delivery to improve MSC survival and functionality. This novel hydrogel, previously based on a patent (EP14306700), is made of both fibrin, starch (a polymer of glucose), and amyloglucosidase (AMG, an enzyme that releases glucose from starch), and provides physiological levels of glucose to fuel MSCs via glycolysis. hMSCS loaded in the novel starch/AMG hydrogel exhibit improved cell viability and paracrine functions for up to 14 days under the “ischemic” in vitro model. Most importantly, in addition to enhanced MSC viability, this nutritive hydrogel promoted paracrine functions when implanted in an ectopic model.Looking forward, and given the current wide interest in the use of stem cells for regenerative medicine applications, the novel inbuilt system of glucose delivery has the potential of improved tissue engineering and regenerative methodologies, which enhance cell survival and functionality after implantation.; Les cellules souches mésenchymateuses (CSMs) apparaissent comme des candidates idéales en ingénierie tissulaire. De plus en plus d’essais cliniques utilisent aujourd’hui cette source cellulaire dans l’objectif de réparer des tissus ou organes lésés afin de restaurer leur fonction. Cependant, une fois implantées, les CSMs meurent rapidement et massivement, réduisant considérablement le succès de cette approche thérapeutique. Bien que cette mort massive soit multifactorielle, l’environnement ischémique (caractérisé entre autre, par la déplétion en oxygène et en nutriments) dans lequel les cellules sont confrontées une fois implantées, semble être la cause principale. De plus, le facteur limitant la survie cellulaire au sein de cet environnement avasculaire est de façon surprenante, non pas l’absence d’oxygène, mais l’absence de glucose. Toutefois, les voies métaboliques utilisées par les CSMs après implantation afin de convertir le glucose en énergie ne sont, à ce jour, que peu comprises. De plus, aucune stratégie basée sur l’apport continu de glucose aux cellules n’a été jusqu’à présent établie afin d’améliorer la survie, et par conséquent, la fonctionnalité des CSMs après implantation. La première étude de ce projet de doctorat vise à comprendre davantage le métabolisme énergétique emprunté par le glucose au sein des CSMs après implantation. Nous avons démontré que les conditions quasi-anoxiques (0.1% pO2) associées à l’absence de glucose et de sérum reflètent au mieux in vitro le microenvironnement d’implantation in vivo. Au sein de cet environnement, les CSMs produisent leur énergie sous forme d’ATP exclusivement via la glycolyse anaérobie à partir d’un unique substrat, le glucose. Or, le glucose manque dans cet environnement ischémique et les CSMs possèdent des réserves glycolytiques très limitées qu’elles vident en 24 heures, puis consomment la totalité de leurs réserves d’ATP en 3 jours, entrainant une mort cellulaire massive et rapide.La seconde (et principale) étude consiste à développer et à évaluer une stratégie basée sur l’apport continu de glucose pour améliorer la survie et la fonctionnalité des CSMs après implantation. Nous avons, pour la première fois, apporté la preuve de concept qu’un hydrogel nutritif, composé d’un système de polymère de glucose (amidon) et d’une enzyme (amyloglucosidase), ayant préalablement fait l’objet d’un brevet (EP 14306700), permet d’améliorer la survie de CSMs pendant 14 jours, à la fois au sein d’un modèle ischémique in vitro ainsi que dans un modèle ectopique post-implantation. De plus, ce dispositif innovant permet d’améliorer les fonctions paracrines des CSMs, augmentant notamment la néovascularisation jusqu’à 21 jours après implantation. En augmentant la survie et la fonctionnalité des CSMs après implantation grâce à un apport continu en glucose, l’hydrogel nutritif composé d’amidon et d’AMG apparait comme une stratégie d’intérêt pour améliorer les résultats thérapeutiques des produits à base de cellules souches en ingénierie tissulaire.

Denoising algorithms via sparse representation are among the state-of-the art for 2D image restoration. In this work, we propose a novel sparse and prior-based algorithm for 3D image denoising (SPADE). SPADE is a modification of total variation (TV) problem with an additional functional that promotes sparsity with respect to a prior image. The prior is obtained from the noisy image by combining information from neighbor slices. The functional is minimized using the split Bregman method, which leads to an efficient method for large scale 3D denoising, with computational cost given by three FFT per iteration. SPADE is compared to TV and dictionary learning on the Shepp-Logan phantom and on human knee data acquired on a spectral computerized tomography scanner. SPADE converges in approximately ten iterations and provides comparable or better results than the other methods. In addition, the exploitation of the prior image avoids the patchy, cartoon-like images provided by TV and provides a more natural texture.

Atmospheric pollution is a striking regional issue for public health and ecosystems and has major global impacts on climate. Particulate matter (PM) can be of primary or secondary origin and its sources, both natural and anthropogenic, are very heterogeneous in space and time. Hence, many efforts have been made worldwide to get a better knowledge of PM sources, in order to set effective reduction strategies. To this end, several distinct approaches may be used among which: (i) the localization of potential source areas with trajectory-based statistical receptor models (TRMs) which combine PM concentrations observed at receptor sites with computed back trajectories (BTs) of air masses, and (ii) the estimation of PM source contribution and chemical speciation with deterministic chemistry transport models (CTMs) based on emission inventories and detailed chemistry-transport processes. This study aims at testing the coherence between two independant approaches, CTMs and TRMs, for the geographical localization of the sources impacting a region of study. The case study refers to PM10 pollution in the Hauts-de-France region (HdF) in the North of France for the year 2010. The considered TRMs are multi-site Concentration Field (CF) and Potential Source Contribution Function (PSCF) applied to 12 receptor sites using the Zefir package. The considered CTM is CHIMERE using detailed EDGAR European emission data. First, TRMs showed that some given far-located European countries (named “Far-East” countries) could have a strong but infrequent impact on PM10 levels in the study region, while some given nearer European countries (named “Near-East” countries) had a frequent and predominant impact. Then, the contributions of each of these TRM-highlighted regions to PM10 concentrations over the study area were analyzed by CHIMERE simulations. The potential influence of another non TRM-highlighted region (i.e. the “British Isles”) was also studied for comparison. The CTM results confirmed the prevalence of the Near-East source area in terms of mass contribution throughout the year and particularly during high-concentration periods. Therefore results obtained from CHIMERE CTM and multi-site CF and PSCF TRMs showed consistency, highlighting the interest for further comparison of both CTMs and TRMs independent approaches in other regions as well as for other pollutants.

Osteoarthritis (OA) is a disease of the whole joint characterized by cartilage loss and subchondral bone remodeling. The role of microcracks in cartilage integrity and subchondral bone homeostasis is not fully understood. The main goal of this work was to evaluate microcrack density in both calcified cartilage and subchondral bone plate in relation to cartilage damage in humans and to better define the association of microcracks and osteocyte density in subchondral bone.We investigated 18 bone cores from cadaveric human knees that were stained with En-Bloc Basic Fuchsin. We quantified microcrack density, osteocyte density, cartilage surfaces and cartilage damage. The presence of microcracks was confirmed for each bone core by scanning electron microscopy. Finally, trabecular subchondral bone parameters were measured by micro-CT.Microcracks were detected in both calcified cartilage and subchondral bone plate. The density of microcracks in both calcified cartilage (CC) and subchondral bone plate (SBP) was negatively correlated with cartilage damage (r = -0.45, p 0.05). The presence of microcracks in SBP was associated with a lower histological OA score. Osteocytes formed a dendrite network that abruptly stopped at the border of calcified cartilage. Osteocyte density in subchondral bone plate was increased in the presence of microcracks in calcified cartilage.Subchondral bone plate microcracks might be required for maintaining cartilage homeostasis. Microcracks in calcified cartilage may trigger osteocyte density in subchondral bone plate with subsequent regulation of subchondral bone remodeling to prevent cartilage damage.

Background Calcium pyrophosphate dihydrate deposition disease (CPPD) has been reported to involve the spine, but few systematic studies have been published. Objective To further characterize the spinal involvement with CPPD by a review of CPPD patients hospitalized in a rheumatology department. Methods We retrospectively reviewed data for patients consecutively admitted with a diagnosis of CPPD in the rheumatology department of Lariboisiere hospital in Paris, France over 5 years by using a standardized protocol and electronic case report forms. Imaging studies were also reviewed. Results Spinal CPPD was diagnosed in 37/152 (24.3%) CPPD patients. Patient with spinal involvement had more widespread peripheral CC. The cervical (n = 21) and lumbar (n = 19) segments were most involved. CT-scan was more sensitive than plain radiographs for detecting spinal calcifications. Crown dens syndrome was a prominent feature of cervical involvement. Inflammatory sterile spondylo-discitis was observed in 6 patients. Lesions were frequently multiple and were classified into 4 types. Ruling out septic discitis required image-guided biopsies in 3 patients. Sacroiliac involvement included calcification in 5 patients and severe sterile destructive arthropathy and joint fusion in one patient each. Degenerative changes were common, and CPPD could not be implicated because of the patients ‘age and lack of a control population. In 12 patients, severe clinical features requiring hospitalization were related to such degenerative changes. Conclusion Symptomatic involvement of the spine was observed in 24% of this series of hospitalized CPPD patients. Specific entities were the cause of hospitalisation in 25 of the 37 patients with spinal calcification and included inflammatory pain related to crystal deposits and destructive arthropathy of the spine and sacroiliac joints. Discitis exhibited a wide range of MRI features and biopsies were needed to rule out infection in 3 of the 6 discitis.

Introduction Despite improvements in technique and materials for rotator cuff repair, mean re-tear rates remain close to 30%. The aim of the present study was to assess injection of Autologous Conditioned Plasma (ACP™, Arthrex) for tendon healing after arthroscopic repair. The study hypothesis was that ACP™ improves the tendon-healing rate. Material and method A non-randomized comparative prospective study included all patients aged over 18 years operated on in 2010 for arthroscopic repair of full-thickness rotator cuff tear with ≤ 2 fatty degeneration on the Goutallier classification, whatever the severity of retraction, on virgin non-osteoarthritic shoulder without contraindications for magnetic resonance (MR) arthrography. The surgical protocol was standardized. The first half of the patient sample received end-of-procedure ACP™ injection to the repaired tendon, tuberosity freshening surface and subacromial space, and the second (control) half received no supplementary treatment. The main endpoint was tendon healing on MR arthrography at 6 months according to Sugaya. Secondary endpoints comprised shoulder pain at rest on a numerical scale (0 = no pain to 10 = worst imaginable pain) and Constant functional score. Results Two of the 58 patients refused MR arthrography and 7 were lost to follow-up. Forty-nine patients (26 ACP™, 23 controls) were analyzed: 20 male, 29 female; mean age, 61 ± 7.3 years. There were no significant intergroup differences in healing rate at 6 months (ACP™ 73.1% vs. 78.3% controls; p = 0.75), shoulder pain (2 ± 1.8 vs. 2.6 ± 1.7, respectively; p = 0.24), or Constant score (77 ± 13.5/100 vs. 72.4 ± 12.3, respectively; p = 0.18). Conclusion Associating ACP™ did not improve healing after arthroscopic rotator cuff repair. Sample size, however, had been calculated for a large expected difference, leading to lack of power. Level of evidence III; case-control study.

International audience; Osteoarthritis is the most common degenerative joint disease. Spectral computed tomography generates energy-resolved data which enable identification of materials within the sample and offer improved soft tissue contrast compared to conventional X-ray CT. In this work, we propose a realistic numerical phantom of a knee to assess the feasibility of spectral CT for osteoarthritis. The phantom is created from experimental synchrotron CT mono-energetic images. After simulating spectral CT data, we perform material decomposition using Gauss-Newton method, for different noise levels. Then, we reconstruct virtual mono-energetic images. We compare decompositions and mono-energetic images with the phantom using mean-squared error. When performing material decomposition and tomographic reconstruction, we obtain less than 1 % error for both, using noisy data. Moreover , it is possible to see cartilage with naked eye on virtual mono-energetic images. This phantom has great potential to assess the feasibility and current limitations of spectral CT to characterize knee osteoarthritis.

This work is devoted to the processing of bone morphogenetic protein (BMP-2) functionalized silicate substituted hydroxyapatite (SiHA) ceramic spheres. The motivation behind it is to develop injectable hydrogel/bioceramic composites for bone reconstruction applications. SiHA microspheres were shaped by spray drying and thoroughly characterized. The silicate substitution was used to provide preferred chemical sites at the ceramic surface for the covalent immobilization of BMP-2. In order to control the density and the release of the immobilized BMP-2, its grafting was performed via ethoxysilanes and polyethylene glycols. A method based on Kaiser's test was used to quantify the free amino groups of grafted organosilanes available at the ceramic surface for BMP-2 immobilization. The SiHA surface modification was investigated by means of X-ray photoelectron spectroscopy, Fourier transformed infrared spectroscopy and thermogravimetry coupled with mass spectrometry. The BMP-2 bioactivity was assessed, in vitro, by measuring the luciferase expression of a stably transfected C3H10 cell line (C3H10-BRE/Luc cells). The results provided evidence that the BMP-2 grafted onto SiHA spheres remained bioactive.

International audience; CR_Chimie_22_HAL_Chappard_8Juin2015 1 1 Analysis of hydroxyapatite crystallites in subchondral bone by Fourier transform infrared spectroscopy and powder neutron diffraction methods Analyse des cristaux d'hydroxyapatite dans l'os sous chondral par spectroscopie infra-rouge à transformée de Fourier et diffraction neutronique sur poudres ABSTRACT English Fourier Transform Infrared (FTIR) spectroscopy and powder neutron diffraction (PND) were performed in human subchondral bone covered (C+) or not covered by cartilage (C-) to study hydroxyapatite. With FTIR, the carbonation rate was 30% with identical spectra in C+ and C-. With PND, the width of the diffraction peak (hkl=002) highlighted the anisotropy of nanocrystals (with needle and/or platelet-like shape) along the c-axis with average length of 50 nm and thickness of 10 nm and with no difference between C+ and C- .; Des expérimentations par spectroscopie infrarouge à transformée de Fourier (FTIR) et par diffraction neutronique sur poudres (PND) ont été réalisées sur de l’os sous-chondral humain recouvert (C+) ou non recouvert par le cartilage (C) pour étudier l’hydroxyapatite (HAP).En FTIR, le taux de carbonatation est de 30% avec des spectres identiques pour C+ et C−. Avec la PND, la largeur du pic de diffraction (hkl = 002) a mis en évidence l'anisotropie des nanocristaux (en forme aiguille et/ou de plaquettes) le long de l'axe c, avec une longueur moyenne de 50 nm et une épaisseur de 10 nm, sans différence entre C+ et C−.

International audience; This study aimed at characterizing the impact of type 2 diabetes mellitus (T2DM) on the bone marrow mesenchymal stem cell (BMMSC) secre-tome and angiogenic properties. BMMSCs from Zucker diabetic fatty rats (ZDF) (a T2DM model) and Zucker LEAN littermates (control) were cultured. The supernatant conditioned media (CM) from BMMSCs of diabetic and control rats were collected and analysed. Compared to results obtained using CM from LEAN-BMMSCs, the bioactive content of ZDF-BMMSC CM (i) differently affects endothelial cell (HUVEC) functions in vitro by inducing increased (3.5-fold; P < 0.01) formation of tubule-like structures and migration of these cells (3-fold; P < 0.001), as well as promotes improved vascular formation in vivo, and (ii) contains different levels of angiogenic factors (e.g. IGF1) and mediators, such as OSTP, CATD, FMOD LTBP1 and LTBP2, which are involved in angiogenesis and/or extracellular matrix composition. Addition of neutralizing antibodies against IGF-1, LTBP1 or LTBP2 in the CM of BMMSCs from diabetic rats decreased its stimulatory effect on HUVEC migration by approximately 60%, 40% or 40%, respectively. These results demonstrate that BMMSCs from T2DM rats have a unique secretome with distinct angiogenic properties and provide new insights into the role of BMMSCs in aberrant angiogenesis in the diabetic milieu.

Tissue constructs containing mesenchymal stem cells (MSCs) are appealing strategies for repairing large segmental bone defects, but they do not allow consistent bone healing and early cell death was identified as a cause of failure. However, little is known about cell survival in the clinical microenvironment encountered during bone healing process. Osteoconductive coral scaffold with or without luciferase-labeled human MSCs were implanted either in a critical segmental femoral bone defect stabilized by plate or subcutaneously in 44 mice. Cell survival was evaluated by serial bioluminescence imaging (BLI) and osteogenic capabilities by histology and microcomputed tomography. Comparisons between groups were performed with two-way analysis of variance test. Twenty mice were sacrificed 2 weeks after surgery for short-term evaluation and 24 mice at 10 weeks for long-term evaluation. BLI provided evidence of fast and continuous cell death: 85% decrease of the BLI signal over the first 2 weeks in both locations; in fact, less than 2% of the initial cell number was present in all constructs analyzed 4 weeks postimplantation and less than 1% of the initial cell number by 8 weeks postimplantation. By 2 weeks postimplantation, the amount of newly formed bone was self-limited and was similar to ectopic and orthotopic groups. By 10 weeks postimplantation, bone formation was significantly enhanced in the presence of MSCs in orthotopic site and the amount of newly formed bone in cell-containing constructs implanted in orthotopic locations was significantly higher than that observed in the ectopic group. Our results indicated that hMSCs promote bone formation despite early and massive cell death when loaded on coral scaffolds. Interestingly, bone formation was higher in orthotopic than ectopic site despite the same survival pattern. Ectopic implantation of cell-containing constructs is suitable to evaluate cell survival, but assessment of bone formation ability requires orthotopic implantation.

Now that diabetes reaches pandemic proportions, this thesis focuses on the effect of T2DM on bone. Very few studies document the effect of T2DM on maxillo-facial bone and their endomembraneous repair.After a short review on bone, diabetes and animal study models, we will showcase our results of the impact of T2DM on, (i) vascular and bone repair of calvarial defects in ZDF rats; (ii) the vascular and bone microarchitechture of ZDF rat’s femur; (iii) the secretome and angiogenic properties of zdf rat’s bone marrow stromal cells (BMSC). These studies showed an alteration of bone repair in critical size defects, and an impaired vascular repair in critical and subcritical T2DM defects. We also found evidences of bone and vascular microarchitechture impairement in ZDF femur. At a cellular level, T2DM BMSCs have an unique angiogenic profile. These findings may contribute to the better understanding of the adverse vascular healing in T2DM and provide successful bone healing therapies for patients with T2DM.; A l’heure où le diabète prend des proportions pandémiques, nous nous sommes intéressés dans le cadre de cette thèse à l’étude de l’impact du diabète de type 2 (TD2M) sur l’os. Il y a peu d’études documentant l’impact de T2DM sur les os maxillo-faciaux d’origine endomembranaire et leurs réparations. Après une introduction bibliographique sur l’os, le diabète et les modèles d’études animaux, nous exposerons nos résultats sur (i) l’étude de la réparation vasculaire et osseuse des défauts de calvaria de rats diabètiques ZDF; (ii) l’impact du T2DM sur la structure osseuse et vasculaire des fémurs de rats ZDF; et (iii) l’altération des propriétés angiogéniques et du sécrétome des cellules souches mésenchymateuses de la moelle osseuse (BMSC) par le T2DM. Ces études ont permis de mettre en évidence l’altération de la réparation osseuse dans les défauts de taille-critique et l’altération de la réparation vasculaire dans les défauts de tailles critique et sous-critique de la calvaria de rats T2DM. De même, la microarchitecture osseuse (corticale et trabéculaire) et la vascularisation se trouvent significativement altérées par le T2DM dans les fémurs de rats ZDF. Au niveau cellulaire, le sécrétome des BMSCs de rat ZDF présente un profil angiogénique différent de celui des rats ZL contrôles, ce qui peut apporter des éléments de réponses permettant la compréhension de la vascularisation paradoxale dans un contexte T2DM. Ces résultats devraient permettre d’améliorer la compréhension de l’effet du T2DM sur la cicatrisation osseuse, afin d’améliorer les stratégies thérapeutiques.

Now that diabetes reaches pandemic proportions, this thesis focuses on the effect of T2DM on bone. Very few studies document the effect of T2DM on maxillo-facial bone and their endomembraneous repair.After a short review on bone, diabetes and animal study models, we will showcase our results of the impact of T2DM on, (i) vascular and bone repair of calvarial defects in ZDF rats; (ii) the vascular and bone microarchitechture of ZDF rat’s femur; (iii) the secretome and angiogenic properties of zdf rat’s bone marrow stromal cells (BMSC). These studies showed an alteration of bone repair in critical size defects, and an impaired vascular repair in critical and subcritical T2DM defects. We also found evidences of bone and vascular microarchitechture impairement in ZDF femur. At a cellular level, T2DM BMSCs have an unique angiogenic profile. These findings may contribute to the better understanding of the adverse vascular healing in T2DM and provide successful bone healing therapies for patients with T2DM.; A l’heure où le diabète prend des proportions pandémiques, nous nous sommes intéressés dans le cadre de cette thèse à l’étude de l’impact du diabète de type 2 (TD2M) sur l’os. Il y a peu d’études documentant l’impact de T2DM sur les os maxillo-faciaux d’origine endomembranaire et leurs réparations. Après une introduction bibliographique sur l’os, le diabète et les modèles d’études animaux, nous exposerons nos résultats sur (i) l’étude de la réparation vasculaire et osseuse des défauts de calvaria de rats diabètiques ZDF; (ii) l’impact du T2DM sur la structure osseuse et vasculaire des fémurs de rats ZDF; et (iii) l’altération des propriétés angiogéniques et du sécrétome des cellules souches mésenchymateuses de la moelle osseuse (BMSC) par le T2DM. Ces études ont permis de mettre en évidence l’altération de la réparation osseuse dans les défauts de taille-critique et l’altération de la réparation vasculaire dans les défauts de tailles critique et sous-critique de la calvaria de rats T2DM. De même, la microarchitecture osseuse (corticale et trabéculaire) et la vascularisation se trouvent significativement altérées par le T2DM dans les fémurs de rats ZDF. Au niveau cellulaire, le sécrétome des BMSCs de rat ZDF présente un profil angiogénique différent de celui des rats ZL contrôles, ce qui peut apporter des éléments de réponses permettant la compréhension de la vascularisation paradoxale dans un contexte T2DM. Ces résultats devraient permettre d’améliorer la compréhension de l’effet du T2DM sur la cicatrisation osseuse, afin d’améliorer les stratégies thérapeutiques.

International audience