Novel phosphate–phosphonate hybrid nanomaterials applied to biology

International audienceA new process for preparing oligonucleotide arrays is described that uses surface grafting chemistry which is fundamentally different from the electrostatic adsorption and organic covalent binding methods normally employed. Solid supports are modified with a mixed organic/inorganic zirconium phosphonate monolayer film providing a stable, well-defined interface. Oligonucleotide probes terminated with phosphate are spotted directly to the zirconated surface forming a covalent linkage. Specific binding of terminal phosphate groups with minimal binding of the internal phosphate diesters has been demonstrated. On the other hand, the reaction of a bisphosphonate bone resorption inhibitor (Zoledronate) with calcium deficient apatites (CDAs) was studied as a potential route to local drug delivery systems active against bone resorption disorders. A simple mathematical model of the Zoledronate/CDA interaction was designed that correctly described the adsorption of Zoledronate onto CDAs. The resulting Zoledronate-loaded materials were found to release the drug in different phosphate-containing media, with a satisfactory agreement between experimental data and the values predicted from the model

Innovative nutritional prevention of osteoporosis: the polyphenol fisetin sustains bone health by controlling osteoblasts and osteoclasts differentiation

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L’innovation nutritionnelle au service de la prévention de l’ostéoporose.Cas de la fisétine : un polyphénol capable de protéger notre capital osseux

article présentaté lors du colloque 'Phytomicronutriments' qui s’est tenu à Avignon le 16 décembre 2014.National audienceOsteoporosis is a bone pathology leading to increased fracture risk and challenging quality of life. Since current treatments could exhibit deleterious side effects, the use of food compounds derived from plants represents a promising innovative alternative due to their potential therapeutic and preventive activities against human diseases. We demonstrated the ability of the polyphenol fisetin to counter osteoporosis and deciphered the cellular and molecular mechanisms involved. In vivo, fisetin consumption prevented bone loss in two common mice models for osteroporosis, namely estrogen deficiency and inflammation. Indeed, bone mineral density, micro-architecture parameters and bone markers were positively modulated by fisetin. Consistent with in vivo results, fisetin promoted primary preosteoblasts differentiation and activity by stimulating Runx2 transcriptional activity. Moreover, we showed that fisetin represses RANKL-induced osteoclast differentiation and activity as demonstrated by an inhibition of multinucleated cell formation, TRAP activity and expression of differentiation genes.L'ostéoporose est la principale pathologie osseuse. Elle se traduit par un risque accru de fracture et impacte considérablement la qualité de vie. La prise en charge actuelle est limitée par une prophylaxie non systématique et les effets secondaires des traitements curatifs. Dans ce contexte d'abstention thérapeutique fréquente, l'utilisation de composés alimentaires végétaux représente une alternative innovante et prometteuse en raison de leurs propriétés biologiques spécifiques. Nous avons ainsi démontré le potentiel ostéoprotecteur de la fisétine (un polyphénol) et décrypté les mécanismes cellulaires et moléculaires impliqués. In vivo, la consommation de fisétine limite effectivement le processus d'ostéopénie consécutif à une carence œstrogénique ou une inflammation (deux modèles murins classiques pour l'étude de l'ostéoporose). De fait, la densité minérale osseuse, les paramètres micro-architecturaux et les biomarqueurs du métabolisme osseux sont positivement modulés par la fisétine. Ces données sont corroborées par l'induction in vitro de la différenciation de cellules souches en ostéoblastes et de leur activité, via la stimulation transcriptionnelle de Runx2. De plus, la fisétine réprime la différenciation et l'activité des ostéoclastes induite par RANKL (Receptor Acitvator of NfkB Ligand), comme démontré par une inhibition de la formation de cellules multinucléées, de l'activité de la Tartrate Resistant Acid Phosphatase (TRAP) et de l'expression des gènes de différenciation

An Fgfr3-activating mutation in immature osteoblasts affects the appendicular and craniofacial skeleton

International audienceAchondroplasia (ACH), the most common form of dwarfism is caused by a missense mutation in the gene coding for fibroblast growth factor receptor 3 (FGFR3). The resulting increase in FGFR3 signaling perturbs the proliferation and differentiation of chondrocytes (CCs), alters the process of endochondral ossification and thus reduces bone elongation. Increased FGFR3 signaling in osteoblasts (OBs) might also contribute to bone anomalies in ACH. In the present study of a mouse model of ACH, we sought to determine whether or not FGFR3 overactivation in OBs leads to bone modifications. The model carries an Fgfr3 activating mutation (Fgfr3 Y367C/+) that accurately mimics ACH; we targeted the mutation to either immature OBs and hypertrophic CCs or to mature OBs by using the Osx-cre and collagen 1α1 (2.3kb-Col1α1)-cre mouse strains, respectively. We observed that Fgfr3 activation in immature OBs and hypertrophic CCs (Osx-Fgfr3) not only perturbed the hypertrophic cells of the growth plate (thus affecting long bone growth) but also led to osteopenia and low cortical thickness in long bones in adult (3-month-old) mice but not in growing (3-week-old) mice. Importantly, craniofacial membranous bone defects were present in the adult mice. In contrast, activation of Fgfr3 in mature OBs (Col1-Fgfr3) had very limited effects on skeletal shape, size and micro-architecture. In vitro, we observed that Fgfr3 activation in immature OBs was associated with low mineralization activity. In conclusion, immature OBs appears to be affected by Fgfr3 overactivation, which might contribute to the bone modifications observed in ACH independently of CCs

The polyphenol fisetin protects bone by repressing NF-kB and MKP-1-dependent signaling pathways in osteoclasts

National audienceOsteoporosis is a bone pathology leading to increase fractures risk and challenging quality of life. Since current treatments could exhibit deleterious side effects, the use of food compounds derived from plants represents a promising innovative alternative due to their potential therapeutic and preventive activities against human diseases. In this study, we investigated the ability of the polyphenol fisetin to counter osteoporosis and analyzed the cellular and molecular mechanisms involved. In vivo, fisetin consumption significantly prevented bone loss in estrogen deficiency and inflammation mice osteoporosis models. Indeed, bone mineral density, micro-architecture parameters and bone markers were positively modulated by fisetin. Consistent with in vivo results, we showed that fisetin represses RANKL-induced osteoclast differentiation and activity as demonstrated by an inhibition of multinucleated cells formation, TRAP activity and differentiation genes expression. The signaling pathways NF-kB, p38 MAPK, JNK and the key transcription factors c-Fos and NFATc1 expressions induced by RANKL, were negatively regulated by fisetin. We further showed that fisetin inhibits the constitutive proteasomal degradation of MKP-1, the phosphatase that deactivates p38 and JNK. Consistently, using shRNA stable cell lines, we demonstrated that impairment of MKP-1 decreases fisetin potency. Taken together, these results strongly support that fisetin should be further considered as a bone protective agent

Involvement of caspase-3 during mesenchymal stem cells differentiation?

International audienc

Involvement of caspase-3 during mesenchymal stem cells differentiation?

International audienc

Culture medium modulates the behaviour of human dental pulp-derived cells: technical note.

International audienc

Dexamethasone stimulates differentiation of odontoblast-like cells in human dental pulp cultures

International audienceRegenerative dental pulp strategies require the identification of precursors able to differentiate into odontoblast-like cells that secrete reparative dentin after injury. Pericytes have the ability to give rise to osteoblasts, chondrocytes, and adipocytes, a feature that has led to the suggestion that odontoblast-like cells could derive from these perivascular cells. In order to gain new insights into this hypothesis, we investigated the effects of dexamethasone (Dex), a synthetic glucocorticoid employed to induce osteogenic differentiation in vitro, in a previously reported model of human dental pulp cultures containing pericytes as identified by their expression of smooth muscle actin (SMA) and their specific ultrastructural morphology. Our data indicated that Dex (10(-8) M) significantly inhibited cell proliferation and markedly reduced the proportion of SMA-positive cells. Conversely, Dex strongly stimulated alkaline phosphatase (ALP) activity and induced the expression of the transcript encoding the major odontoblastic marker, dentin sialophosphoprotein. Nevertheless, parathyroid hormone/parathyroid hormone-related peptide receptor, core-binding factor a1/osf 2, osteonectin, and lipoprotein lipase mRNA levels were not modified by Dex treatment. Dex also increased the proportion of cells expressing STRO-1, a marker of multipotential mesenchymal progenitor cells. These observations indicate that glucocorticoids regulate the commitment of progenitors derived from dental pulp cells to form odontoblast-like cells, while reducing the proportion of SMA-positive cells. These results provide new perspectives in deciphering the cellular and molecular mechanisms leading to reparative dentinogenesis