scholarly journals Sirt1 Is a Regulator of Bone Mass and a Repressor of Sost Encoding for Sclerostin, a Bone Formation Inhibitor

Endocrinology ◽  
2011 ◽  
Vol 152 (12) ◽  
pp. 4514-4524 ◽  
Author(s):  
Einav Cohen-Kfir ◽  
Hanna Artsi ◽  
Avi Levin ◽  
Eva Abramowitz ◽  
Alon Bajayo ◽  
...  
Keyword(s):  
Gene Expression ◽  
Bone Formation ◽  
Bone Mass ◽  
Neutralizing Antibody ◽  
Nodule Formation ◽  
Sost Gene ◽  
Skeletal Homeostasis ◽  
Novel Target ◽  
Sirt1 Gene ◽  
Interfering Rna

Sirt1, the mammalian ortholog of the yeast Sir2 (silent information regulator 2), was shown to play an important role in metabolism and in age-associated diseases, but its role in skeletal homeostasis and osteoporosis has yet not been studied. Using 129/Sv mice with a germline mutation in the Sirt1 gene, we demonstrate that Sirt1 haplo-insufficient (Sirt1+/−) female mice exhibit a significant reduction in bone mass characterized by decreased bone formation and increased marrow adipogenesis. Importantly, we identify Sost, encoding for sclerostin, a critical inhibitor of bone formation, as a novel target of Sirt1. Using chromatin immunoprecipitation analysis, we reveal that Sirt1 directly and negatively regulates Sost gene expression by deacetylating histone 3 at lysine 9 at the Sost promoter. Sost down-regulation by small interfering RNA and the administration of a sclerostin-neutralizing antibody restore gene expression of osteocalcin and bone sialoprotein as well as mineralized nodule formation in Sirt1+/− marrow-derived mesenchymal stem cells induced to osteogenesis. These findings reveal a novel role for Sirt1 in bone as a regulator of bone mass and a repressor of sclerostin, and have potential implications suggesting that Sirt1 is a target for promoting bone formation as an anabolic approach for treatment of osteoporosis.

scholarly journals Prolyl Hydroxylase Domain-Containing Protein 3 Gene Expression in Chondrocytes Is Not Essential for Bone Development in Mice

Cells ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 2200
Author(s):  
Weirong Xing ◽  
Sheila Pourteymoor ◽  
Gustavo A. Gomez ◽  
Yian Chen ◽  
Subburaman Mohan
Keyword(s):  
Gene Expression ◽  
Bone Formation ◽  
Bone Mass ◽  
Trabecular Bone ◽  
Bone Volume ◽  
Endochondral Bone Formation ◽  
Chondrocyte Differentiation ◽  
Trabecular Bone Volume ◽  
Endochondral Bone ◽  
Trabecular Bone Mass

We previously showed that conditional disruption of the Phd2 gene in chondrocytes led to a massive increase in long bone trabecular bone mass. Loss of Phd2 gene expression or inhibition of PHD2 activity by a specific inhibitor resulted in a several-fold compensatory increase in Phd3 expression in chondrocytes. To determine if expression of PHD3 plays a role in endochondral bone formation, we conditionally disrupted the Phd3 gene in chondrocytes by crossing Phd3 floxed (Phd3flox/flox) mice with Col2α1-Cre mice. Loss of Phd3 expression in the chondrocytes of Cre+; Phd3flox/flox conditional knockout (cKO) mice was confirmed by real time PCR. At 16 weeks of age, neither body weight nor body length was significantly different in the Phd3 cKO mice compared to Cre−; Phd3flox/flox wild-type (WT) mice. Areal BMD measurements of total body as well as femur, tibia, and lumbar skeletal sites were not significantly different between the cKO and WT mice at 16 weeks of age. Micro-CT measurements revealed significant gender differences in the trabecular bone volume adjusted for tissue volume at the secondary spongiosa of the femur and the tibia for both genotypes, but no genotype difference was found for any of the trabecular bone measurements of either the femur or the tibia. Trabecular bone volume of distal femur epiphysis was not different between cKO and WT mice. Histology analyses revealed Phd3 cKO mice exhibited a comparable chondrocyte differentiation and proliferation, as evidenced by no changes in cartilage thickness and area in the cKO mice as compared to WT littermates. Consistent with the in vivo data, lentiviral shRNA-mediated knockdown of Phd3 expression in chondrocytes did not affect the expression of markers of chondrocyte differentiation (Col2, Col10, Acan, Sox9). Our study found that Phd2 but not Phd3 expressed in chondrocytes regulates endochondral bone formation, and the compensatory increase in Phd3 expression in the chondrocytes of Phd2 cKO mice is not the cause for increased trabecular bone mass in Phd2 cKO mice.

scholarly journals Functions of vasopressin and oxytocin in bone mass regulation

2015 ◽  
Vol 113 (1) ◽  
pp. 164-169 ◽  
Author(s):  
Li Sun ◽  
Roberto Tamma ◽  
Tony Yuen ◽  
Graziana Colaianni ◽  
Yaoting Ji ◽  
...  
Keyword(s):  
Gene Expression ◽  
Bone Formation ◽  
Bone Mass ◽  
High Bone Mass ◽  
Nuclear Extracts ◽  
High Bone ◽  
High Bone Mass Phenotype ◽  
Opposing Effects ◽  
G Protein Coupled

Prior studies show that oxytocin (Oxt) and vasopressin (Avp) have opposing actions on the skeleton exerted through high-affinity G protein-coupled receptors. We explored whether Avp and Oxtr can share their receptors in the regulation of bone formation by osteoblasts. We show that the Avp receptor 1α (Avpr1α) and the Oxt receptor (Oxtr) have opposing effects on bone mass: Oxtr−/− mice have osteopenia, and Avpr1α−/− mice display a high bone mass phenotype. More notably, this high bone mass phenotype is reversed by the deletion of Oxtr in Oxtr−/−:Avpr1α−/− double-mutant mice. However, although Oxtr is not indispensable for Avp action in inhibiting osteoblastogenesis and gene expression, Avp-stimulated gene expression is inhibited when the Oxtr is deleted in Avpr1α−/− cells. In contrast, Oxt does not interact with Avprs in vivo in a model of lactation-induced bone loss in which Oxt levels are high. Immunofluorescence microscopy of isolated nucleoplasts and Western blotting and MALDI-TOF of nuclear extracts show that Avp triggers Avpr1α localization to the nucleus. Finally, a specific Avpr2 inhibitor, tolvaptan, does not affect bone formation or bone mass, suggesting that Avpr2, which primarily functions in the kidney, does not have a significant role in bone remodeling.

scholarly journals The Type 2 Cannabinoid Receptor Regulates Bone Mass and Ovariectomy-Induced Bone Loss by Affecting Osteoblast Differentiation and Bone Formation

Endocrinology ◽  
2011 ◽  
Vol 152 (6) ◽  
pp. 2141-2149 ◽  
Author(s):  
Antonia Sophocleous ◽  
Euphemie Landao-Bassonga ◽  
Robert J. van‘t Hof ◽  
Aymen I. Idris ◽  
Stuart H. Ralston
Keyword(s):  
Bone Loss ◽  
Bone Formation ◽  
Bone Mass ◽  
Osteoblast Differentiation ◽  
Cannabinoid Receptor ◽  
Nodule Formation ◽  
Wild Type

The type 2 cannabinoid receptor (CB2) has been reported to regulate bone mass and bone turnover but the mechanisms responsible are incompletely understood. In this study we investigated the role that the CB2 pathway plays in bone metabolism using a combination of genetic and pharmacological approaches. Bone mass and turnover were normal in young mice with targeted inactivation of CB2 receptor (CB2−/−), but by 12 months of age, they had developed high-turnover osteoporosis with relative uncoupling of bone resorption from bone formation. Primary osteoblasts from CB2−/− mice had a reduced capacity to form bone nodules in vitro when compared with cells from wild-type littermates and also had impaired PTH-induced alkaline phosphatase (ALP) activity. The CB2-selective agonist HU308 stimulated bone nodule formation in wild-type osteoblasts but had no effect in CB2−/− osteoblasts. Further studies in MC3T3-E1 osteoblast like cells showed that HU308 promoted cell migration and activated ERK phosphorylation, and these effects were blocked by the CB2 selective inverse agonist AM630. Finally, HU308 partially protected against ovariectomy induced bone loss in wild-type mice in vivo, primarily by stimulating bone formation, whereas no protective effects were observed in ovariectomized CB2−/− mice. These studies indicate that the CB2 regulates osteoblast differentiation in vitro and bone formation in vivo.

scholarly journals cGMP-dependent protein kinase-2 regulates bone mass and prevents diabetic bone loss

2018 ◽  
Vol 238 (3) ◽  
pp. 203-219 ◽  
Author(s):  
Ghania Ramdani ◽  
Nadine Schall ◽  
Hema Kalyanaraman ◽  
Nisreen Wahwah ◽  
Sahar Moheize ◽  
...  
Keyword(s):  
Gene Expression ◽  
Protein Kinase ◽  
Bone Loss ◽  
Bone Formation ◽  
Transgenic Mice ◽  
Bone Mass ◽  
Related Gene ◽  
Dependent Protein Kinase ◽  
Cgmp Dependent Protein Kinase ◽  
Dependent Protein

NO/cGMP signaling is important for bone remodeling in response to mechanical and hormonal stimuli, but the downstream mediator(s) regulating skeletal homeostasis are incompletely defined. We generated transgenic mice expressing a partly-activated, mutant cGMP-dependent protein kinase type 2 (PKG2R242Q) under control of the osteoblast-specific Col1a1 promoter to characterize the role of PKG2 in post-natal bone formation. Primary osteoblasts from these mice showed a two- to three-fold increase in basal and total PKG2 activity; they proliferated faster and were resistant to apoptosis compared to cells from WT mice. Male Col1a1-Prkg2 R242Q transgenic mice had increased osteoblast numbers, bone formation rates and Wnt/β-catenin-related gene expression in bone and a higher trabecular bone mass compared to their WT littermates. Streptozotocin-induced type 1 diabetes suppressed bone formation and caused rapid bone loss in WT mice, but male transgenic mice were protected from these effects. Surprisingly, we found no significant difference in bone micro-architecture or Wnt/β-catenin-related gene expression between female WT and transgenic mice; female mice of both genotypes showed higher systemic and osteoblastic NO/cGMP generation compared to their male counterparts, and a higher level of endogenous PKG2 activity may be responsible for masking effects of the PKG2R242Q transgene in females. Our data support sexual dimorphism in Wnt/β-catenin signaling and PKG2 regulation of this crucial pathway in bone homeostasis. This work establishes PKG2 as a key regulator of osteoblast proliferation and post-natal bone formation.

scholarly journals N-Cadherin Interacts with Axin and LRP5 To Negatively Regulate Wnt/β-Catenin Signaling, Osteoblast Function, and Bone Formation

2008 ◽  
Vol 29 (4) ◽  
pp. 953-964 ◽  
Author(s):  
Eric Haÿ ◽  
Emmanuel Laplantine ◽  
Valérie Geoffroy ◽  
Monique Frain ◽  
Thomas Kohler ◽  
...  
Keyword(s):  
Gene Expression ◽  
Bone Formation ◽  
Transgenic Mice ◽  
Bone Mass ◽  
Wnt Signaling ◽  
Adhesion Molecule ◽  
Molecular Complex ◽  
Tail Domain ◽  
Osteoblast Function ◽  
Canonical Wnt

ABSTRACT Wnt signaling plays an important role in the regulation of bone formation and bone mass. The mechanisms that regulate canonical Wnt signaling in osteoblasts are not fully understood. We show here a novel mechanism by which the adhesion molecule N-cadherin interacts with the Wnt coreceptor LRP5 and regulates canonical Wnt/β-catenin signaling in osteoblasts. We demonstrate that N-cadherin, besides associating with β-catenin at the membrane, forms a molecular complex with axin and LRP5 involving the LRP5 cytoplasmic tail domain. N-cadherin overexpression in osteoblasts increases N-cadherin-LRP5 interaction, causing increased β-catenin degradation and altered TCF/LEF transcription in response to Wnt3a. This mechanism results in decreased osteoblast gene expression and osteogenesis in basal conditions and in response to Wnt3a. Consistent with a functional mechanism, silencing N-cadherin expression in control cells increases TCF/LEF transcription and enhances the response to Wnt3a. Using N-cadherin transgenic mice, we show that increased N-cadherin-LRP5 interaction resulting from targeted overexpression of N-cadherin in osteoblasts causes increased β-catenin ubiquitination and results in cell-autonomous defective osteoblast function, reduced bone formation, and delayed bone mass acquisition. These data indicate that a previously unrecognized N-cadherin-axin-LRP5 interaction negatively regulates Wnt/β-catenin signaling and is critical in the regulation of osteoblast function, bone formation, and bone mass.

scholarly journals The Sirtuin1 Activator SRT3025 Down-Regulates Sclerostin and Rescues Ovariectomy-Induced Bone Loss and Biomechanical Deterioration in Female Mice

Endocrinology ◽  
2014 ◽  
Vol 155 (9) ◽  
pp. 3508-3515 ◽  
Author(s):  
Hanna Artsi ◽  
Einav Cohen-Kfir ◽  
Irina Gurt ◽  
Ron Shahar ◽  
Alon Bajayo ◽  
...  
Keyword(s):  
Bone Loss ◽  
Bone Formation ◽  
Bone Mass ◽  
Biomechanical Properties ◽  
Negative Regulator ◽  
Long Bone ◽  
Type I ◽  
Reciprocal Effect ◽  
Sost Gene

Abstract Estrogen deficiency leads to rapid bone loss and skeletal fragility. Sclerostin, encoded by the sost gene, and a product of the osteocyte, is a negative regulator of bone formation. Blocking sclerostin increases bone mass and strength in animals and humans. Sirtuin1 (Sirt1), a player in aging and metabolism, regulates bone mass and inhibits sost expression by deacetylating histone 3 at its promoter. We asked whether a Sirt1-activating compound could rescue ovariectomy (OVX)-induced bone loss and biomechanical deterioration in 9-week-old C57BL/6 mice. OVX resulted in a substantial decrease in skeletal Sirt1 expression accompanied by an increase in sclerostin. Oral administration of SRT3025, a Sirt1 activator, at 50 and 100 mg/kg·d for 6 weeks starting 6 weeks after OVX fully reversed the deleterious effects of OVX on vertebral bone mass, microarchitecture, and femoral biomechanical properties. Treatment with SRT3025 decreased bone sclerostin expression and increased cortical periosteal mineralizing surface and serum propeptide of type I procollagen, a bone formation marker. In vitro, in the murine long bone osteocyte-Y4 osteocyte-like cell line SRT3025 down-regulated sclerostin and inactive β-catenin, whereas a reciprocal effect was observed with EX-527, a Sirt1 inhibitor. Sirt1 activation by Sirt1-activating compounds is a potential novel pathway to down-regulate sclerostin and design anabolic therapies for osteoporosis concurrently ameliorating other metabolic and age-associated conditions.

scholarly journals Sclerostin Antibody Treatment Increases Bone Formation, Bone Mass, and Bone Strength in a Rat Model of Postmenopausal Osteoporosis*

2009 ◽  
Vol 24 (4) ◽  
pp. 578-588 ◽  
Author(s):  
Xiaodong Li ◽  
Michael S Ominsky ◽  
Kelly S Warmington ◽  
Sean Morony ◽  
Jianhua Gong ◽  
...  
Keyword(s):  
Bone Formation ◽  
Bone Mass ◽  
Postmenopausal Osteoporosis ◽  
Bone Strength ◽  
Rat Model ◽  
Antibody Treatment ◽  
Sclerostin Antibody

scholarly journals CircFAM13B promotes the proliferation of hepatocellular carcinoma by sponging miR-212, upregulating E2F5 expression and activating the P53 pathway

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Ying Xie ◽  
Xiaofeng Hang ◽  
Wensheng Xu ◽  
Jing Gu ◽  
Yuanjing Zhang ◽  
...  
Keyword(s):  
Gene Expression ◽  
Hepatocellular Carcinoma ◽  
Gene Expression Omnibus ◽  
Differentially Expressed ◽  
In Vivo Studies ◽  
Circular Rnas ◽  
Novel Target ◽  
Underlying Mechanisms

Abstract Background Most of the biological functions of circular RNAs (circRNAs) and the potential underlying mechanisms in hepatocellular carcinoma (HCC) have not yet been discovered. Methods In this study, using circRNA expression data from HCC tumor tissues and adjacent tissues from the Gene Expression Omnibus database, we identified out differentially expressed circRNAs and verified them by qRT-PCT. Functional experiments were performed to evaluate the effects of circFAM13B in HCC in vitro and in vivo. Results We found that circFAM13B was the most significantly differentially expressed circRNA in HCC tissue. Subsequently, in vitro and in vivo studies also demonstrated that circFAM13B promoted the proliferation of HCC. Further studies revealed that circFAM13B, a sponge of miR-212, is involved in the regulation of E2F5 gene expression by competitively binding to miR-212, inhibits the activation of the P53 signalling pathway, and promotes the proliferation of HCC cells. Conclusions Our findings revealed the mechanism underlying the regulatory role played by circFAM13B, miR-212 and E2F5 in HCC. This study provides a new theoretical basis and novel target for the clinical prevention and treatment of HCC.

scholarly journals The Development of Molecular Biology of Osteoporosis

2021 ◽  
Vol 22 (15) ◽  
pp. 8182
Author(s):  
Yongguang Gao ◽  
Suryaji Patil ◽  
Jingxian Jia
Keyword(s):  
Bone Resorption ◽  
Molecular Biology ◽  
Bone Formation ◽  
Bone Mass ◽  
Bone Remodeling ◽  
Bone Cells ◽  
Cell Activity ◽  
Bone Cell ◽  
Bone Disorders ◽  
Molecular Aspects

Osteoporosis is one of the major bone disorders that affects both women and men, and causes bone deterioration and bone strength. Bone remodeling maintains bone mass and mineral homeostasis through the balanced action of osteoblasts and osteoclasts, which are responsible for bone formation and bone resorption, respectively. The imbalance in bone remodeling is known to be the main cause of osteoporosis. The imbalance can be the result of the action of various molecules produced by one bone cell that acts on other bone cells and influence cell activity. The understanding of the effect of these molecules on bone can help identify new targets and therapeutics to prevent and treat bone disorders. In this article, we have focused on molecules that are produced by osteoblasts, osteocytes, and osteoclasts and their mechanism of action on these cells. We have also summarized the different pharmacological osteoporosis treatments that target different molecular aspects of these bone cells to minimize osteoporosis.

scholarly journals Ostm1 from Mouse to Human: Insights into Osteoclast Maturation

2020 ◽  
Vol 21 (16) ◽  
pp. 5600 ◽  
Author(s):  
Jean Vacher ◽  
Michael Bruccoleri ◽  
Monica Pata
Keyword(s):  
Bone Formation ◽  
Bone Mass ◽  
Bone Fractures ◽  
Bone Development ◽  
Bone Matrix ◽  
Adult Life ◽  
Cell Types ◽  
Severe Form ◽  
Isolation And Characterization

The maintenance of bone mass is a dynamic process that requires a strict balance between bone formation and resorption. Bone formation is controlled by osteoblasts, while osteoclasts are responsible for resorption of the bone matrix. The opposite functions of these cell types have to be tightly regulated not only during normal bone development, but also during adult life, to maintain serum calcium homeostasis and sustain bone integrity to prevent bone fractures. Disruption of the control of bone synthesis or resorption can lead to an over accumulation of bone tissue in osteopetrosis or conversely to a net depletion of the bone mass in osteoporosis. Moreover, high levels of bone resorption with focal bone formation can cause Paget’s disease. Here, we summarize the steps toward isolation and characterization of the osteopetrosis associated trans-membrane protein 1 (Ostm1) gene and protein, essential for proper osteoclast maturation, and responsible when mutated for the most severe form of osteopetrosis in mice and humans.

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