RÉSUMÉ
Since 2003, the US President's Emergency Plan for AIDS Relief (PEPFAR) has supported implementation and maintenance of health information systems for HIV/AIDS and related diseases, such as tuberculosis, in numerous countries. As the COVID-19 pandemic emerged, several countries conducted rapid assessments and enhanced existing PEPFAR-funded HIV and national health information systems to support COVID-19 surveillance data collection, analysis, visualization, and reporting needs. We describe efforts at the US Centers for Disease Control and Prevention (CDC) headquarters in Atlanta, Georgia, USA, and CDC country offices that enhanced existing health information systems in support COVID-19 pandemic response. We describe CDC activities in Haiti as an illustration of efforts in PEPFAR countries. We also describe how investments used to establish and maintain standards-based health information systems in resource-constrained settings can have positive effects on health systems beyond their original scope.
Sujet(s)
Syndrome d'immunodéficience acquise , COVID-19 , Infections à VIH , Systèmes d'information sur la santé , Humains , Coopération internationale , COVID-19/épidémiologie , COVID-19/prévention et contrôle , Infections à VIH/épidémiologie , Pandémies/prévention et contrôle , Syndrome d'immunodéficience acquise/épidémiologieRÉSUMÉ
In our previous study, we identified differences in the levels of CDH2 and vascular endothelial growth factor (VEGF) between effective and ineffective clones of human umbilical cord blood (hUCB) mesenchymal stem cells (MSCs), with regard to the infarcted rat myocardium. In this study, we compared gene expression profiles between the effective and ineffective clones and identified that endothelin-1 (EDN1) is enriched in the effective clone. In the mechanistic analyses, EDN1 significantly increased expression of CDH2 and VEGF through endothelin receptor A (EDNRA), which was prevented by EDNRA blocker, BQ123. To decipher how EDN1 induced gene expression of CDH2, we performed a promoter activity assay and identified GATA2 and MZF1 as inducers of CDH2. EDN1 significantly enhanced the promoter activity of the CDH2 gene, which was obliterated by the deletion or point mutation at GATA2 or MZF1 binding sequence. Next, therapeutic efficacy of EDN1-priming of hUCB-MSCs was tested in a rat myocardial infarction (MI) model. EDN1-primed MSCs were superior to naive MSCs at 8 weeks after MI in improving myocardial contractility (p < 0.05), reducing fibrosis area (p < 0.05), increasing engraftment efficiency (p < 0.05), and improving capillary density (p < 0.05). In conclusion, EDN1 induces CDH2 and VEGF expression in hUCB-MSCs, leading to the improved therapeutic efficacy in rat MI, suggesting that EDN1 is a potential priming agent for MSCs in regenerative medicine.
RÉSUMÉ
Osteosarcoma is the most common primary tumor of bone occurring in children and adolescents. The histological response to chemotherapy represents a key clinical factor related to survival. We previously showed that statins exhibit antitumor effects in vitro, inducing apoptotic cell death, reducing cell migration and invasion capacities and strengthening cytotoxic effects in combination with standard drugs. Comparative transcriptomic analysis between control and statin-treated cells revealed strong expression of several genes, including metallothionein (MT) 2A. MT2A overexpression by lentiviral transduction reduced bioavailable zinc levels, an effect associated with reduced osteosarcoma cell viability and enhanced cell differentiation. In contrast, MT2A silencing did not modify cell viability but strongly inhibited expression of osteoblastic markers and differentiation process. MT2A overexpression induced chemoresistance to cytotoxic drugs through direct chelation of platinum-containing drugs and indirect action on p53 zinc-dependent activity. In contrast, abrogation of MT2A enhanced cytotoxic action of chemotherapeutic drugs on osteosarcoma cells. Finally, clinical samples derived from chemonaive biopsies revealed that tumor cells expressing low MT2A levels correspond to good prognostic (good responder patients with longer survival rate), whereas high MT2A levels were associated with adverse prognosis (poor responder patients). Taken together, these data show that MT2A contributes to chemotherapy resistance in osteosarcoma, an effect partially mediated by zinc chelation. The data also suggest that MT2A may be a potential new prognostic marker for osteosarcoma sensitivity to chemotherapy.
Sujet(s)
Chélateurs/pharmacologie , Résistance aux médicaments antinéoplasiques/effets des médicaments et des substances chimiques , Métallothionéine/métabolisme , Ostéosarcome/traitement médicamenteux , Ostéosarcome/anatomopathologie , Zinc/métabolisme , Adolescent , Atorvastatine , Mort cellulaire/effets des médicaments et des substances chimiques , Différenciation cellulaire/effets des médicaments et des substances chimiques , Différenciation cellulaire/génétique , Lignée cellulaire tumorale , Survie cellulaire/effets des médicaments et des substances chimiques , Survie cellulaire/génétique , Enfant , Résistance aux médicaments antinéoplasiques/génétique , Régulation de l'expression des gènes tumoraux/effets des médicaments et des substances chimiques , Extinction de l'expression des gènes/effets des médicaments et des substances chimiques , Acides heptanoïques/pharmacologie , Humains , Métallothionéine/génétique , Ostéoblastes/effets des médicaments et des substances chimiques , Ostéoblastes/métabolisme , Ostéoblastes/anatomopathologie , Ostéosarcome/génétique , Pronostic , Conformation des protéines , Pyrroles/pharmacologie , ARN messager/génétique , ARN messager/métabolisme , Protéine p53 suppresseur de tumeur/composition chimique , Protéine p53 suppresseur de tumeur/métabolismeRÉSUMÉ
The ubiquitination-proteasome and degradation system is an essential process that regulates protein homeostasis. This system is involved in the regulation of cell proliferation, differentiation and survival, and dysregulations in this system lead to pathologies including cancers. The ubiquitination system is an enzymatic cascade that mediates the marking of target proteins by an ubiquitin label and thereby directs their degradation through the proteasome pathway. The ubiquitination of proteins occurs through a three-step process involving ubiquitin activation by the E1 enzyme, allowing for the transfer to a ubiquitin-conjugated enzyme E2 and to the targeted protein via ubiquitin-protein ligases (E3), the most abundant group of enzymes involved in ubiquitination. Significant advances have been made in our understanding of the role of E3 ubiquitin ligases in the control of bone turnover and tumorigenesis. These ligases are implicated in the regulation of bone cells through the degradation of receptor tyrosine kinases, signaling molecules and transcription factors. Initial studies showed that the E3 ubiquitin ligase c-Cbl, a multi-domain scaffold protein, regulates bone resorption by interacting with several molecules in osteoclasts. Further studies showed that c-Cbl controls the ubiquitination of signaling molecules in osteoblasts and in turn regulates osteoblast proliferation, differentiation and survival. Recent data indicate that c-Cbl expression is decreased in primary bone tumors, resulting in excessive receptor tyrosine kinase signaling. Consistently, c-Cbl ectopic expression reduces bone tumorigenesis by promoting tyrosine kinase receptor degradation. Here, we review the mechanisms of action of E3 ubiquitin ligases in the regulation of normal and pathologic bone formation, and we discuss how targeting the interactions of c-Cbl with some substrates may be a potential therapeutic strategy to promote osteogenesis and to reduce tumorigenesis.
Sujet(s)
Transformation cellulaire néoplasique , Ostéogenèse , Ubiquitin-protein ligases/métabolisme , Animaux , Humains , Tumeurs/métabolisme , Tumeurs/anatomopathologie , Protéines proto-oncogènes c-cbl/génétique , Protéines proto-oncogènes c-cbl/métabolisme , Récepteurs à activité tyrosine kinase/métabolisme , UbiquitinationRÉSUMÉ
Improving bone repair remains an important and challenging issue. Therapeutic approaches to amplify osteogenic cell pool or function include cell and gene therapies. We identified genes that promote human mesenchymal cell differentiation and bone formation. Targeting these or other genes may improve the efficacy of cell therapy for bone repair.
Sujet(s)
Régénération osseuse/physiologie , Thérapie génétique/méthodes , Transplantation de cellules souches mésenchymateuses/méthodes , Régénération osseuse/génétique , Différenciation cellulaire/génétique , Humains , Cellules souches mésenchymateuses/cytologie , Ostéogenèse/génétique , Ostéogenèse/physiologieRÉSUMÉ
Oestrogen deficiency increases the rate of bone remodelling which, in association with a negative remodelling balance (resorption exceeding formation), results in impaired bone architecture, mass and strength. Current anti-osteoporotic drugs act on bone remodelling by inhibiting bone resorption or by promoting its formation. An alternative therapeutic approach is based on the concept of inducing opposite effects on bone resorption and formation. One therapeutic agent, strontium ranelate, was shown to induce opposite effects on bone resorption and formation in pre-clinical studies and to reduce fracture risk in postmenopausal osteoporotic patients. How strontium ranelate acts to improve bone strength in humans remains a matter of debate, however. This review of the most recent pre-clinical and clinical studies is a critical analysis of strontium ranelate's action on bone resorption and formation and how it increases bone mass, microarchitecture and strength in postmenopausal osteoporotic women.
Sujet(s)
Agents de maintien de la densité osseuse/usage thérapeutique , Remodelage osseux/effets des médicaments et des substances chimiques , Résorption osseuse/prévention et contrôle , Composés organométalliques/usage thérapeutique , Ostéoporose post-ménopausique/prévention et contrôle , Thiophènes/usage thérapeutique , Sujet âgé , Animaux , Densité osseuse/effets des médicaments et des substances chimiques , Agents de maintien de la densité osseuse/pharmacologie , Femelle , Humains , Composés organométalliques/pharmacologie , Ostéoporose post-ménopausique/physiopathologie , Fractures ostéoporotiques/prévention et contrôle , Thiophènes/pharmacologieRÉSUMÉ
OBJECTIVES: Endoscopy and imaging are necessary to diagnose glottis carcinoma. Today, CT scan is the gold standard but MR imaging should be more sensitive for neoplastic invasion detection. The purpose of this study was to determine which exam to perform (CT scan or MRI) for neoplastic invasion. MATERIAL AND METHODS: This prospective study span a 18 months period. Seven patients with glottis carcinoma (TI-T2) underwent CT and MR imaging before surgery. Findings at imaging and pathologic examination were compared. RESULTS: Both CT and MR imaging were interesting, more specific (90%) than sensitive (74%). The anterior commissure, ventricles, subglottis, thyroid and arytenoid cartilages are the more difficult area analyzing. CONCLUSION: CT imaging stays the gold standard. MR imaging is more effective on second intention to refine the data. Indications are being improved, with complete cure and more preserved laryngealfunctions.
Sujet(s)
Carcinomes/diagnostic , Glotte , Tumeurs du larynx/diagnostic , Imagerie par résonance magnétique , Tomodensitométrie , Adulte , Sujet âgé , Carcinomes/imagerie diagnostique , Carcinomes/anatomopathologie , Protocoles cliniques , Produits de contraste , Femelle , Études de suivi , Glotte/anatomopathologie , Humains , Tumeurs du larynx/imagerie diagnostique , Tumeurs du larynx/anatomopathologie , Mâle , Adulte d'âge moyen , Stadification tumorale , Études prospectives , Sensibilité et spécificité , Facteurs tempsRÉSUMÉ
The mechanisms underlying the altered osteoblastogenesis and bone loss in response to disuse are incompletely understood. Using the rat tail suspension model, we studied the effect of skeletal unloading on osteoblast and osteocyte apoptosis. Tail suspension for 2 to 7 days decreased tibial bone mass and induced early apoptotic loss of osteoblasts and delayed apoptotic loss of osteocytes. Surrenal gland weight and plasma corticosterone levels did not differ in loaded and unloaded rats at any time point, indicating that osteoblast/osteocyte apoptosis occurred independently of endogenous glucocorticoids. The mechanistic basis for the disuse-induced osteoblast/osteocyte apoptosis was examined. We found that alpha5beta1 integrin and phosphorylated phosphatidyl-inositol-3 kinase (p-PI3K) protein levels were transiently decreased in unloaded metaphyseal long bone compared to loaded bones. In contrast, p-FAK and p-ERK p42/44 levels were not significantly altered. Interestingly, the reduced p-PI3K levels in unloaded long bone was associated with decreased levels of the survival protein Bcl-2 with unaltered Bax levels, causing increased Bax/Bcl-2 levels. The results indicate that skeletal unloading in rats induces a glucocorticoid-independent, immediate increase in osteoblast apoptosis associated with decreased alpha5beta1-PI3K-Bcl-2 survival pathway in rat bone, which may contribute to the altered osteoblastogenesis and osteopenia induced by unloading.
Sujet(s)
Apoptose , Os et tissu osseux/métabolisme , Intégrine alpha5bêta1/métabolisme , Ostéoblastes/physiologie , Phosphatidylinositol 3-kinases/métabolisme , Protéines proto-oncogènes c-bcl-2/métabolisme , Mise en charge/physiologie , Glandes surrénales/anatomie et histologie , Animaux , Os et tissu osseux/composition chimique , Os et tissu osseux/cytologie , Corticostérone/sang , Extracellular Signal-Regulated MAP Kinases/métabolisme , Focal adhesion kinase 1/métabolisme , Suspension des membres postérieurs , Intégrine alpha5bêta1/analyse , Mâle , Taille d'organe , Ostéoblastes/cytologie , Ostéoblastes/métabolisme , Phosphatidylinositol 3-kinases/analyse , Protéines proto-oncogènes c-bcl-2/analyse , Rats , Rat Wistar , Transduction du signalRÉSUMÉ
Osteosarcoma is the most common primary bone tumour in young adults. Despite improved prognosis, resistance to chemotherapy remains responsible for failure of osteosarcoma treatment. The identification of signals that promote apoptosis may provide clues to develop new therapeutic strategies for chemoresistant osteosarcoma. Here, we show that lipophilic statins (atorvastatin, simvastatin, cerivastatin) markedly induce caspases-dependent apoptosis in various human osteosarcoma cells, independently of bone morphogenetic protein (BMP)-2 signaling and cell differentiation. Although statins increased BMP-2 expression, the proapoptotic effect of statins was not prevented by the BMP antagonist noggin, and was abolished by mevalonate and geranylgeranylpyrophosphate, suggesting the involvement of defective protein geranylgeranylation. Consistently, lipophilic statins induced membrane RhoA relocalization to the cytosol and inhibited RhoA activity, which resulted in decreased phospho-p42/p44- mitogen-activated protein kinases (MAPKs) and Bcl-2 levels. Constitutively active RhoA rescued phospho-p42/p44-MAPKs and Bcl-2 and abolished statin-induced apoptosis. Thus, lipophilic statins induce caspase-dependent osteosarcoma cell apoptosis by a RhoA-p42/p44 MAPKs-Bcl-2-mediated mechanism, independently of BMP-2 signaling and cell differentiation.
Sujet(s)
Anticholestérolémiants/pharmacologie , Apoptose/effets des médicaments et des substances chimiques , Protéines morphogénétiques osseuses/métabolisme , Extracellular Signal-Regulated MAP Kinases/antagonistes et inhibiteurs , Ostéosarcome/anatomopathologie , Protéines proto-oncogènes c-bcl-2/antagonistes et inhibiteurs , Facteur de croissance transformant bêta/métabolisme , Protéine G RhoA/métabolisme , Atorvastatine , Protéine morphogénétique osseuse de type 2 , Protéines morphogénétiques osseuses/génétique , Caspases/métabolisme , Différenciation cellulaire/effets des médicaments et des substances chimiques , Survie cellulaire/effets des médicaments et des substances chimiques , Activation enzymatique/effets des médicaments et des substances chimiques , Régulation de l'expression des gènes tumoraux/effets des médicaments et des substances chimiques , Acides heptanoïques/pharmacologie , Humains , Ostéosarcome/génétique , Phénotype , Phosphorylation/effets des médicaments et des substances chimiques , Polyisoprényl-phosphates/métabolisme , Transport des protéines/effets des médicaments et des substances chimiques , Protéines proto-oncogènes c-bcl-2/métabolisme , Pyridines/pharmacologie , Pyrroles/pharmacologie , ARN messager/génétique , ARN messager/métabolisme , Transduction du signal/effets des médicaments et des substances chimiques , Simvastatine/pharmacologie , Facteur de croissance transformant bêta/génétique , Protéine G RhoA/antagonistes et inhibiteursRÉSUMÉ
Osteoporosis associated with estrogen deficiency results from an imbalance between bone resorption and formation, causing deterioration of bone architecture and decreased bone mass. Anti-osteoporotic therapies that have been developed so far include either anticatabolic or anabolic drugs. Strontium ranelate is a newly developed drug that induces opposite effects on bone resorption and formation. This dual original mode of action was demonstrated in experimental studies on bone cells and pharmacological studies in animals. In vitro, strontium ranelate was shown to decrease bone resorption. This effect resulted from a decreased differentiation and resorbing activity of osteoclasts and increased osteoclast apoptosis. In contrast, strontium ranelate was shown to enhance preosteoblastic cell replication and collagen synthesis in culture without affecting bone mineralization. In vivo, strontium ranelate promoted bone formation and reduced bone resorption in intact mice, an effect which resulted in increased vertebral bone mass. Additionally, strontium ranelate was found to reduce resorption and long bone loss induced by hind limb immobilization in rats. Finally, strontium ranelate administration decreased bone resorption and maintained bone formation in adult ovariectomized rats, which resulted in prevention of bone loss. In clinical trials (Spinal Osteoporosis Therapeutic Intervention [SOTI]), bone alkaline phosphatase levels increased, whereas C cross-linking telopeptide of type I collagen (CTX) levels decreased in patients treated with strontium ranelate compared with placebo at all time points. These pharmacological and clinical studies suggest that strontium ranelate acts by increasing bone formation and decreasing bone resorption and that these effects result in improved bone mass in vivo.
Sujet(s)
Agents de maintien de la densité osseuse , Résorption osseuse , Composés organométalliques , Ostéogenèse/effets des médicaments et des substances chimiques , Ostéoporose post-ménopausique/traitement médicamenteux , Thiophènes , Animaux , Marqueurs biologiques/métabolisme , Agents de maintien de la densité osseuse/pharmacologie , Agents de maintien de la densité osseuse/usage thérapeutique , Fractures osseuses/étiologie , Humains , Composés organométalliques/pharmacologie , Composés organométalliques/usage thérapeutique , Ostéoporose post-ménopausique/complications , Ovariectomie , Contention physique , Thiophènes/pharmacologie , Thiophènes/usage thérapeutiqueRÉSUMÉ
Bone loss occuring with unloading is associated with decreased osteoblastogenesis and increased bone marrow adipogenesis, resulting in bone loss and decreased bone formation. Here, we review the present knowledge on the role of PPARgamma in the control of osteoblastogenesis and bone mass in skeletal unloading. We showed that PPARgamma positively promotes adipogenesis and negatively regulates osteoblast differentiation of bone marrow stromal cells in unloading, resulting in bone loss. Manipulation of PPARgamma2 expression by exogenous TGF-beta2 inhibits the exaggerated adipogenesis and corrects the balance between osteoblastogenesis and adipogenesis induced by unloading, leading to prevention of bone loss. This shows that PPARgamma plays an important role in the control of bone mass in unloaded bone. Moreover, this opens the possibility that manipulation of PPARgamma may correct the balance between osteoblastogenesis and adipogenesis and prevent bone loss, which may have potential implications in the treatment of bone loss in clinical conditions.
RÉSUMÉ
The first experimental mouse model for FGF2 in bone dysplasia was made serendipitously by overexpression of FGF from a constitutive promoter. The results were not widely accepted, rightfully drew skepticism, and were difficult to publish; because of over 2,000 studies published on FGF-2 at the time (1993), only a few reported a role of FGF-2 in bone growth and differentiation. However, mapping of human dwarfisms to mutations of the FGFRs shortly, thereafter, made the case that bone growth and remodeling was a major physiological function for FGF. Subsequent production of numerous transgenic and targeted null mice for several genes in the bone growth and remodeling pathways have marvelously elucidated the role of FGFs and their interactions with other genes. Indeed, studies of the FGF pathway present one of the best success stories for use of experimental genetics in functionally parsing morphogenetic regulatory pathways. What remains largely unresolved is the pleiotropic nature of FGF-2. How does it accelerate growth in one cell then stimulate apoptosis or retard growth for another cell in the same type of tissue? Some of the answers may come through distinguishing the FGF-2 protein isoforms, made from alternative translation start sites, these appear to have substantially different functions. Although we have made substantial progress, there is still much to be learned regarding FGF-2 as a most complex, enigmatic protein. Studies of genetic models in mice and human FGFR mutations have provided strong evidence that FGFRs are important modulators of osteoblast function during membranous bone formation. However, there is some controversy regarding the effects of FGFR signaling in human and murine genetic models. Although significant progress has been made in our understanding of FGFR signaling, several questions remain concerning the signaling pathways involved in osteoblast regulation by activated FGFR. Additionally, little is known about the specific role of FGFR target genes involved in cranial bone formation. These issues need to be addressed in future in in vitro and in vivo approaches to better understand the molecular mechanisms of action of FGFR signaling in osteoblasts that result in anabolic effects in bone formation.
Sujet(s)
Craniosynostoses/métabolisme , Facteurs de croissance fibroblastique/métabolisme , Ostéochondrodysplasies/métabolisme , Transduction du signal , Animaux , Apoptose , Développement osseux , Différenciation cellulaire , Modèles animaux de maladie humaine , Humains , Ligands , Souris , Souris knockout , Souris transgéniques , Modèles biologiques , Modèles génétiques , Mutation , Ostéoblastes/métabolisme , Isoformes de protéinesRÉSUMÉ
Strontium ranelate has been shown to decrease the risk of fractures in postmenopausal women. Its efficacy in clinical studies results from its unique mode of action, on both bone resorption and bone formation. Pharmacological studies in animals have shown that strontium ranelate decreases bone resorption and increases bone formation, resulting in increased bone mass. In ovariectomized rats, strontium ranelate prevented the reduction in bone mineral content and the decrease in trabecular bone volume induced by estrogen deficiency. In this model, strontium ranelate decreased bone resorption, whereas bone formation was maintained at a high level as documented by plasma biochemical markers and histomorphometric indices of bone formation. In the model of osteopenia induced by hind-limb immobilization in rats, strontium ranelate reduced histomorphometric parameters of bone resorption and partially prevented long-bone loss, as assessed by bone mineral content, bone volume, and biochemical indices of bone resorption. In intact mice, strontium ranelate increased bone formation and vertebral bone mass. In intact growing rats, strontium ranelate increased the bone trabecular volume without alteration of mineralization. The unique mode of action of strontium ranelate on bone formation and resorption was supported by in vitro studies. In rat calvaria culture systems and rat osteoblastic cell cultures, strontium ranelate enhanced preosteoblastic cell replication and increased collagen synthesis by osteoblasts. Moreover, strontium ranelate decreased bone resorption in organ cultures and decreased the resorbing activity of isolated mouse osteoclasts. The assessment of bone markers in a clinical trial [Spinal Osteoporosis Therapeutic Intervention (SOTI)] supports the mode of action of strontium ranelate: bone alkaline phosphatase levels increased and C-telopeptide of type I collagen levels decreased in treated patients compared with the placebo group at all time points. Thus, pharmacological and clinical studies suggest that strontium ranelate optimizes bone resorption and bone formation, resulting in increased bone mass, which may be of great value in the treatment of osteoporosis.
Sujet(s)
Développement osseux/effets des médicaments et des substances chimiques , Résorption osseuse/traitement médicamenteux , Composés organométalliques/usage thérapeutique , Ostéoporose/traitement médicamenteux , Thiophènes/usage thérapeutique , Agents découplants/usage thérapeutique , Phosphatase alcaline/sang , Animaux , Marqueurs biologiques/sang , Essais cliniques de phase III comme sujet , Collagène/sang , Collagène de type I , Femelle , Haplorhini , Humains , Souris , Modèles animaux , Techniques de culture d'organes , Ostéoporose/sang , Ostéoporose/physiopathologie , Ovariectomie , Peptides/sang , RatsRÉSUMÉ
To determine the molecular mechanisms by which N-cadherin transcription is regulated, we cloned and sequenced a 3681-bp of the 5'-flanking region of the human N-cadherin gene. Deletion analysis of the proximal region identified a minimal 318-bp region with strong promoter activity in human osteoblasts. The cryptic promoter is characterized by high GC content and a GA-rich binding core that may bind zing finger transcription factors. Electrophoretic mobility shift assays (EMSA), competition and supershift EMSA revealed that an Sp1/Sp3 binding site acts as a basal regulatory element of the promoter in osteoblasts. Incubation of osteoblast nuclear extracts with -163/-131 wild-type probe containing the GA-rich binding core revealed another specific complex, which was not formed with a -163/-131 probe mutated in the GA repeat. EMSA identified the nuclear factor involved as myeloid zinc finger-1 (MZF1). Mutation analysis showed that Sp1/Sp3 and MZF1 binding sites contribute to basal promoter activity. Cotransfection analyses showed that Sp1 and MZF1 overexpression increases whereas Sp3 antagonizes Sp1-induced N-cadherin promoter activity in osteoblasts. RT-PCR analysis showed that human osteoblastic cells express MZF1 and that Sp1/MZF1 overexpression increased N-cadherin expression. These results indicate that Sp1/Sp3 and MZF1 are important transcription factors regulating N-cadherin promoter activity and expression in osteoblasts.
Sujet(s)
Cadhérines/génétique , Protéines de liaison à l'ADN/métabolisme , Ostéoblastes/métabolisme , Régions promotrices (génétique)/génétique , Facteur de transcription Sp1/métabolisme , Facteurs de transcription/métabolisme , Région 5' flanquante/génétique , Séquence d'acides aminés/génétique , Séquence nucléotidique/génétique , Sites de fixation/génétique , Différenciation cellulaire/génétique , Lignée de cellules transformées , Lignée cellulaire tumorale , Protéines de liaison à l'ADN/génétique , Exons/génétique , Régulation de l'expression des gènes/génétique , Gènes régulateurs/génétique , Humains , Facteurs de transcription Krüppel-like , Sondes moléculaires , Données de séquences moléculaires , Structure tertiaire des protéines/génétique , Facteur de transcription Sp1/génétique , Facteur de transcription Sp3 , Facteurs de transcription/génétique , Régulation positive/génétiqueRÉSUMÉ
The molecular mechanisms regulating the adipogenic differentiation of bone marrow stromal cells in vivo remain largely unknown. In this study, we investigated the regulatory effects of transforming growth factor beta-2 (TGF-beta2) on transcription factors involved in adipogenic differentiation induced by hind limb suspension in rat bone marrow stromal cells in vivo. Time course real-time quantitative reverse-transcription polymerase chain reaction (RT-PCR) analysis of gene expression showed that skeletal unloading progressively increases the expression of CCAAT/enhancer-binding protein (C/EBP)alpha and C/EBPbeta alpha at 5 days in bone marrow stromal cells resulting in increased peroxisome proliferator-activated receptor gamma (PPARgamma2) transcripts at 7 days. TGF-beta2 administration in unloaded rats corrected the rise in C/EBPalpha and C/EBPbeta transcripts induced by unloading in bone marrow stromal cells. This resulted in inhibition of PPARgamma2 expression that was associated with increased Runx2 expression. Additionally, the inhibition of C/EBPalpha and C/EBPbeta expression by TGF-beta2 was associated with increased PPARgamma serine phosphorylation in bone marrow stromal cells, a mechanism that inhibits PPARgamma transactivating activity. The sequential inhibitory effect of TGF-beta2 on C/EBPalpha, C/EBPbeta, and PPARgamma2 resulted in reduced LPL expression and abolition of bone marrow stromal cell adipogenic differentiation, which contributed to prevent bone loss induced by skeletal unloading. We conclude that TGF-beta2 inhibits the excessive adipogenic differentiation of bone marrow stromal cells induced by skeletal unloading by inhibiting C/EBPalpha, C/EBPbeta, and PPARgamma expression and activity, which provides a sequential mechanism by which TGF-beta2 regulates adipogenic differentiation of bone marrow stromal cells in vivo.
Sujet(s)
Cellules de la moelle osseuse/cytologie , Protéines liant les séquences stimulatrices de type CCAAT/métabolisme , Récepteur PPAR gamma/métabolisme , Cellules stromales/cytologie , Facteur de croissance transformant bêta/pharmacologie , Animaux , Cellules de la moelle osseuse/métabolisme , Différenciation cellulaire/effets des médicaments et des substances chimiques , Différenciation cellulaire/physiologie , Régulation de l'expression des gènes/effets des médicaments et des substances chimiques , Régulation de l'expression des gènes/physiologie , Mâle , Rats , Rat Wistar , Cellules stromales/métabolisme , Facteur de croissance transformant bêta-2RÉSUMÉ
Fibroblast growth factor-2 (FGF-2) is an important molecule that controls bone formation through activation of osteoblastic cell replication and differentiation. The role of FGF-2 on human osteoblast survival and the signaling pathway that mediates its effect are not known. We studied the effect of FGF-2 on apoptosis induced by low serum concentration and the signal transduction pathway involved in this effect in human primary calvaria osteoblasts and immortalized osteoblastic cells. Treatment with FGF-2 for 24-48 h protected against osteoblast apoptosis induced by low serum concentration, through specific inhibition of caspase-2 and caspase-3 activity. Pharmacological inhibition of MEK-1 and p38 MAPK had no effect on the inhibition of caspases-2 and -3 induced by FGF-2. In contrast, inhibition of PI3K with LY294002 abolished the FGF-2-induced inhibition of caspases-2 and -3. FGF-2 increased PI3K activity but did not induce phosphorylation of Akt or the downstream effector p70 S6 kinase. FGF-2 also induced GSK-3alpha and beta phosphorylation in osteoblastic cells, which however did not result in beta-catenin accumulation or Lef/Tcf transcriptional activity. In contrast, lithium induced beta-catenin accumulation, Lef/Tcf transcriptional activation and increased caspase-2 and -3 activity. The results indicate that the immediate protective effect of FGF-2 on human osteoblastic cell apoptosis involves PI3K and inhibition of downstream caspases, independently of GSK-3 and beta-catenin-Lef/Tcf-mediated transcription.
Sujet(s)
Protéines du cytosquelette/métabolisme , Facteur de croissance fibroblastique de type 2/métabolisme , Ostéoblastes/métabolisme , Ostéogenèse/physiologie , Phosphatidylinositol 3-kinases/métabolisme , Transduction du signal/physiologie , Transactivateurs/métabolisme , Apoptose/effets des médicaments et des substances chimiques , Apoptose/physiologie , Protéines du sang/déficit , Caspase-2 , Caspase-3 , Inhibiteurs des caspases , Caspases/métabolisme , Lignée de cellules transformées , Survie cellulaire/effets des médicaments et des substances chimiques , Survie cellulaire/physiologie , Cellules cultivées , Protéines de liaison à l'ADN/agonistes , Protéines de liaison à l'ADN/métabolisme , Antienzymes/pharmacologie , Rétrocontrôle physiologique/effets des médicaments et des substances chimiques , Rétrocontrôle physiologique/physiologie , Facteur de croissance fibroblastique de type 2/pharmacologie , Glycogen Synthase Kinase 3/effets des médicaments et des substances chimiques , Glycogen Synthase Kinase 3/métabolisme , Humains , Lithium/pharmacologie , Facteur de transcription LEF-1 , Ostéoblastes/cytologie , Ostéoblastes/effets des médicaments et des substances chimiques , Ostéogenèse/effets des médicaments et des substances chimiques , Inhibiteurs des phosphoinositide-3 kinases , Phosphorylation/effets des médicaments et des substances chimiques , Transduction du signal/effets des médicaments et des substances chimiques , Facteurs de transcription/agonistes , Facteurs de transcription/métabolisme , Régulation positive/effets des médicaments et des substances chimiques , Régulation positive/physiologie , bêta-CaténineRÉSUMÉ
There is growing evidence that strontium ranelate (SR; S12911-2, PROTELOS; Institut de Recherches Internationales Servier, Courbevoie, France), a compound containing 2 atoms of stable strontium (Sr), influences bone cells and bone metabolism in vitro and in vivo. We previously reported that SR increases bone mass in rats and mice by stimulating bone formation and inhibiting bone resorption. We also showed that short-term treatment with SR enhances osteoblastic cell recruitment and function in short-term rat calvaria cultures. Because Sr incorporates into the bone matrix, it was of interest to determine whether SR may affect matrix mineralization in long-term culture. To this goal, osteogenic mouse calvaria-derived MC3T3-E1 osteoblastic cells were cultured for up to 14 days in the presence of ascorbic acid and phosphate to induce matrix formation and mineralization. Matrix formation was determined by incorporation of tritiated proline during collagen synthesis. Matrix mineralization was quantified by measuring the number and surface of mineralized nodules using a digital image analyzer. In this model, 1,25(OH)2 vitamin D (1 nmol/L) used as internal control, increased alkaline phosphatase (ALP) activity, an early osteoblast marker, on days 4, 10, and 14 of culture. Treatment with SR (1 mmol/L Sr(2+)) increased ALP activity at days 4 and 14 of culture. SR also increased collagen synthesis at days 4 and 10 of culture. In contrast, 1,25(OH)2 vitamin D (1 nmol/L) inhibited collagen synthesis at 4 to 14 days of culture. Long-term treatment with SR (0.1 to 1 mmol/L Sr(2+)) dose dependently increased Sr concentration into the calcified nodules, but did not alter matrix mineralization in long-term culture, as shown by the ratio of the surface of mineralized nodules to the number of mineralized nodules on day 14 of culture. These results show that long-term treatment with SR increases collagenous matrix formation by MC3T3-E1 osteoblasts without inducing deleterious effect on matrix mineralization.
Sujet(s)
Composés organométalliques/pharmacologie , Ostéoblastes/effets des médicaments et des substances chimiques , Ostéoblastes/métabolisme , Thiophènes/pharmacologie , Phosphatase alcaline/métabolisme , Animaux , Calcification physiologique/effets des médicaments et des substances chimiques , Calcification physiologique/physiologie , Calcitriol/analogues et dérivés , Calcitriol/pharmacologie , Calcium/métabolisme , Lignée cellulaire , Collagène/biosynthèse , Matrice extracellulaire/effets des médicaments et des substances chimiques , Matrice extracellulaire/métabolisme , Matrice extracellulaire/physiologie , Magnésium/métabolisme , Souris , Composés organométalliques/métabolisme , Ostéoblastes/cytologie , Ostéogenèse/effets des médicaments et des substances chimiques , Ostéogenèse/physiologie , Strontium/métabolisme , Thiophènes/métabolismeRÉSUMÉ
Human bone marrow stroma contains pluripotent mesenchymal progenitor cells that can give rise to many mesenchymal lineages, including chondroblasts, adipocytes or osteoblasts. The differentiation of these cells towards a specific lineage is dependent on hormonal and local factors activating specific transcription factors. Attempts have been recently made to identify osteoprogenitor cells in the human bone marrow and to identify the molecular mechanisms responsible for lineage-specific differentiation of human bone marrow stromal cells. Using a clonal pluripotent human bone marrow stromal cell line with tri-potential characteristics, we have provided evidence for a controlled reciprocal regulation of osteoblast/chondroblast and osteoblast/adipocyte differentiation of human bone marrow stromal cells. We have also shown that administration of TGFss that regulates the expression of specific osteoblast and adipocyte transcription factors can promote osteoblast differentiation and inhibit adipocyte conversion of rat marrow stromal cells in vivo. This indicates that the reciprocal relationship between osteoblastogenesis and adipogenesis can be manipulated in vivo in order to improve bone formation. Future studies will have to identify key signals for lineage-specific differentiation of human marrow stromal cells. This may result in the development of therapeutic strategies to promote the differentiation of these cells towards the osteoblast lineage and to inhibit excessive bone marrow adipogenesis associated with aging.