scholarly journals Fra-2/AP-1 controls bone formation by regulating osteoblast differentiation and collagen production

2010 ◽  
Vol 190 (6) ◽  
pp. 1093-1106 ◽  
Author(s):  
Aline Bozec ◽  
Latifa Bakiri ◽  
Maria Jimenez ◽  
Thorsten Schinke ◽  
Michael Amling ◽  
...  
Keyword(s):  
Stromal Cells ◽  
Osteoblast Differentiation ◽  
Bone Cells ◽  
Activator Protein 1 ◽  
Bone Homeostasis ◽  
Newborn Mice ◽  
Important Regulator ◽  
Transcription Factor Complex

The activator protein-1 (AP-1) transcription factor complex, in particular the Fos proteins, is an important regulator of bone homeostasis. Fra-2 (Fosl2), a Fos-related protein of the AP-1 family, is expressed in bone cells, and newborn mice lacking Fra-2 exhibit defects in chondrocytes and osteoclasts. Here we show that Fra-2–deficient osteoblasts display a differentiation defect both in vivo and in vitro. Moreover, Fra-2–overexpressing mice are osteosclerotic because of increased differentiation of osteoblasts, which appears to be cell autonomous. Importantly, the osteoblast-specific osteocalcin (Oc) gene and collagen1α2 (col1α2) are transcriptional targets of Fra-2 in both murine and human bone cells. In addition, Fra-2, Oc, and col1 are expressed in stromal cells of human chondroblastic and osteoblastic osteosarcomas (Os’s) as well as during osteoblast differentiation of human Os cell lines. These findings reveal a novel function of Fra-2/AP-1 as a positive regulator of bone and matrix formation in mice and humans.

scholarly journals Protocol of Co-Culture of Human Osteoblasts and Osteoclasts to Test Biomaterials for Bone Tissue Engineering

2022 ◽  
Vol 5 (1) ◽  
pp. 8
Author(s):  
Giorgia Borciani ◽  
Giorgia Montalbano ◽  
Nicola Baldini ◽  
Chiara Vitale-Brovarone ◽  
Gabriela Ciapetti
Keyword(s):  
Tissue Engineering ◽  
Bone Tissue Engineering ◽  
Bone Tissue ◽  
Bone Cells ◽  
Bone Cell ◽  
Seeding Density ◽  
Bone Homeostasis ◽  
Bone Microenvironment

New biomaterials and scaffolds for bone tissue engineering (BTE) applications require to be tested in a bone microenvironment reliable model. On this assumption, the in vitro laboratory protocols with bone cells represent worthy experimental systems improving our knowledge about bone homeostasis, reducing the costs of experimentation. To this day, several models of the bone microenvironment are reported in the literature, but few delineate a protocol for testing new biomaterials using bone cells. Herein we propose a clear protocol to set up an indirect co-culture system of human-derived osteoblasts and osteoclast precursors, providing well-defined criteria such as the cell seeding density, cell:cell ratio, the culture medium, and the proofs of differentiation. The material to be tested may be easily introduced in the system and the cell response analyzed. The physical separation of osteoblasts and osteoclasts allows distinguishing the effects of the material onto the two cell types and to evaluate the correlation between material and cell behavior, cell morphology, and adhesion. The whole protocol requires about 4 to 6 weeks with an intermediate level of expertise. The system is an in vitro model of the bone remodeling system useful in testing innovative materials for bone regeneration, and potentially exploitable in different application fields. The use of human primary cells represents a close replica of the bone cell cooperation in vivo and may be employed as a feasible system to test materials and scaffolds for bone substitution and regeneration.

scholarly journals Myeloma Cells Deplete Bone Marrow Glutamine and Inhibit Osteoblast Differentiation Limiting Asparagine Availability

Cancers ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 3267
Author(s):  
Martina Chiu ◽  
Denise Toscani ◽  
Valentina Marchica ◽  
Giuseppe Taurino ◽  
Federica Costa ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Amino Acid ◽  
Stromal Cells ◽  
Osteoblast Differentiation ◽  
Essential Amino Acids ◽  
Asparagine Synthetase ◽  
Osteolytic Lesions ◽  
Glutamine Transporter

Multiple myeloma (MM) cells consume huge amounts of glutamine and, as a consequence, the amino acid concentration is lower-than-normal in the bone marrow (BM) of MM patients. Here we show that MM-dependent glutamine depletion induces glutamine synthetase in stromal cells, as demonstrated in BM biopsies of MM patients, and reproduced in vitro by co-culturing human mesenchymal stromal cells (MSCs) with MM cells. Moreover, glutamine depletion hinders osteoblast differentiation of MSCs, which is also severely blunted by the spent, low-glutamine medium of MM cells, and rescued by glutamine restitution. Glutaminase and the concentrative glutamine transporter SNAT2 are induced during osteoblastogenesis in vivo and in vitro, and both needed for MSCs differentiation, pointing to enhanced the requirement for the amino acid. Osteoblastogenesis also triggers the induction of glutamine-dependent asparagine synthetase (ASNS), and, among non-essential amino acids, asparagine rescues differentiation of glutamine-starved MSCs, by restoring the transcriptional profiles of differentiating MSCs altered by glutamine starvation. Thus, reduced asparagine availability provides a mechanistic link between MM-dependent Gln depletion in BM and impairment of osteoblast differentiation. Inhibition of Gln metabolism in MM cells and supplementation of asparagine to stromal cells may, therefore, constitute novel approaches to prevent osteolytic lesions in MM.

scholarly journals The Influence of Radiation on Bone and Bone Cells—Differential Effects on Osteoclasts and Osteoblasts

2020 ◽  
Vol 21 (17) ◽  
pp. 6377
Author(s):  
Anna-Jasmina Donaubauer ◽  
Lisa Deloch ◽  
Ina Becker ◽  
Rainer Fietkau ◽  
Benjamin Frey ◽  
...  
Keyword(s):  
Bone Remodeling ◽  
Bone Cells ◽  
Positive Impact ◽  
Inflammatory Diseases ◽  
Future Research ◽  
Special Focus ◽  
Bone Homeostasis ◽  
Bone Microenvironment

The bone is a complex organ that is dependent on a tight regulation between bone formation by osteoblasts (OBs) and bone resorption by osteoclasts (OCs). These processes can be influenced by environmental factors such as ionizing radiation (IR). In cancer therapy, IR is applied in high doses, leading to detrimental effects on bone, whereas radiation therapy with low doses of IR is applied for chronic degenerative and inflammatory diseases, with a positive impact especially on bone homeostasis. Moreover, the effects of IR are of particular interest in space travel, as astronauts suffer from bone loss due to space radiation and microgravity. This review summarizes the current state of knowledge on the effects of IR on bone with a special focus on the influence on OCs and OBs, as these cells are essential in bone remodeling. In addition, the influence of IR on the bone microenvironment is discussed. In summary, the effects of IR on bone and bone remodeling cells strongly depend on the applied radiation dose, as differential results are provided from in vivo as well as in vitro studies with varying doses of IR. Furthermore, the isolated effects of IR on a single cell type are difficult to determine, as the bone cells and bone microenvironment are building a tightly regulated network, influencing on one another. Therefore, future research is necessary in order to elucidate the influence of different bone cells on the overall radiation-induced effects on bone.

scholarly journals β2-Adrenergic Receptor Signaling in Osteoblasts Contributes to the Catabolic Effect of Glucocorticoids on Bone

Endocrinology ◽  
2011 ◽  
Vol 152 (4) ◽  
pp. 1412-1422 ◽  
Author(s):  
Yun Ma ◽  
Jeffry S. Nyman ◽  
Huan Tao ◽  
Heather H. Moss ◽  
Xiangli Yang ◽  
...  
Keyword(s):  
Bone Loss ◽  
Bone Cells ◽  
Sympathetic Nerves ◽  
Bone Diseases ◽  
Autonomic Nerves ◽  
High Dose ◽  
Bone Homeostasis ◽  
Adrenergic Stimulation

Abstract The sympathetic nervous system is a physiological regulator of bone homeostasis. Autonomic nerves are indeed present in bone, bone cells express the β2-adrenergic receptors (β2AR), and pharmacological or genetic disruption of sympathetic outflow to bone induces bone gain in rodents. These recent findings implied that conditions that affect β2AR signaling in osteoblasts and/or sympathetic drive to bone may contribute to bone diseases. In this study, we show that dexamethasone stimulates the expression of the β2AR in differentiated primary calvarial osteoblasts, as measured by an increase in Adrβ2 mRNA and β2AR protein level after short-term dexamethasone treatment. Isoproterenol-induced cAMP accumulation and the expression of the β2AR target gene Rankl were also significantly increased after dexamethasone pretreatment, indicating that dexamethasone promotes the responsiveness of differentiated osteoblasts to adrenergic stimulation. These in vitro results led to the hypothesis that glucocorticoid-induced bone loss, provoked by increased endogenous or high-dose exogenous glucocorticoids given for the treatment of inflammatory diseases, might, at least in part, be mediated by increased sensitivity of bone-forming cells to the tonic inhibitory effect of sympathetic nerves on bone formation or their stimulatory effect on bone resorption. Supporting this hypothesis, both pharmacological and genetic β2AR blockade in mice significantly reduced the bone catabolic effect of high-dose prednisolone in vivo. This study emphasizes the importance of sympathetic nerves in the regulation of bone homeostasis and indicates that this neuroskeletal signaling axis can be modulated by hormones or drugs and contribute to enhance pathological bone loss.

scholarly journals Transcriptional Modulator Ifrd1 Regulates Osteoclast Differentiation through Enhancing the NF-κB/NFATc1 Pathway

2016 ◽  
Vol 36 (19) ◽  
pp. 2451-2463 ◽  
Author(s):  
Takashi Iezaki ◽  
Kazuya Fukasawa ◽  
Gyujin Park ◽  
Tetsuhiro Horie ◽  
Takashi Kanayama ◽  
...  
Keyword(s):  
Bone Loss ◽  
Osteoclast Differentiation ◽  
Nuclear Factor Κb ◽  
Bone Diseases ◽  
Nuclear Factor ◽  
Activator Protein 1 ◽  
Bone Homeostasis ◽  
Activated T Cells

Bone homeostasis is maintained by the synergistic actions of bone-resorbing osteoclasts and bone-forming osteoblasts. Here, we show that the transcriptional coactivator/repressor interferon-related developmental regulator 1 (Ifrd1) is expressed in osteoclast lineages and represents a component of the machinery that regulates bone homeostasis. Ifrd1 expression was transcriptionally regulated in preosteoclasts by receptor activator of nuclear factor κB (NF-κB) ligand (RANKL) through activator protein 1. Global deletion of murineIfrd1increased bone formation and decreased bone resorption, leading to a higher bone mass. Deletion ofIfrd1in osteoclast precursors prevented RANKL-induced bone loss, although no bone loss was observed under normal physiological conditions. RANKL-dependent osteoclastogenesis was impairedin vitroinIfrd1-deleted bone marrow macrophages (BMMs).Ifrd1deficiency increased the acetylation of p65 at residues K122 and K123 via the inhibition of histone deacetylase-dependent deacetylation in BMMs. This repressed the NF-κB-dependent transcription of nuclear factor of activated T cells, cytoplasmic 1 (NFATc1), an essential regulator of osteoclastogenesis. These findings suggest that an Ifrd1/NF-κB/NFATc1 axis plays a pivotal role in bone remodelingin vivoand represents a therapeutic target for bone diseases.

scholarly journals Recombinant Irisin Prevents the Reduction of Osteoblast Differentiation Induced by Stimulated Microgravity through Increasing β-Catenin Expression

2020 ◽  
Vol 21 (4) ◽  
pp. 1259 ◽  
Author(s):  
Zhihao Chen ◽  
Yan Zhang ◽  
Fan Zhao ◽  
Chong Yin ◽  
Chaofei Yang ◽  
...  
Keyword(s):  
Bone Formation ◽  
Osteoblast Differentiation ◽  
Simulated Microgravity ◽  
Marker Gene ◽  
Calcium Deposition ◽  
Bone Homeostasis ◽  
Mice Model ◽  
Beneficial Effects

Background: Irisin, a novel exercise-induced myokine, was shown to mediate beneficial effects of exercise in osteoporosis. Microgravity is a major threat to bone homeostasis of astronauts during long-term spaceflight, which results in decreased bone formation. Methods: The hind-limb unloading mice model and a random position machine are respectively used to simulate microgravity in vivo and in vitro. Results: We demonstrate that not only are bone formation and osteoblast differentiation decreased, but the expression of fibronectin type III domain-containing 5 (Fdnc5; irisin precursor) is also downregulated under simulated microgravity. Moreover, a lower dose of recombinant irisin (r-irisin) (1 nM) promotes osteogenic marker gene (alkaline phosphatase (Alp), collagen type 1 alpha-1(ColIα1)) expressions, ALP activity, and calcium deposition in primary osteoblasts, with no significant effect on osteoblast proliferation. Furthermore, r-irisin could recover the decrease in osteoblast differentiation induced by simulated microgravity. We also find that r-irisin increases β-catenin expression and partly neutralizes the decrease in β-catenin expression induced by simulated microgravity. In addition, β-catenin overexpression could also in part attenuate osteoblast differentiation reduction induced by simulated microgravity. Conclusions: The present study is the first to show that r-irisin positively regulates osteoblast differentiation under simulated microgravity through increasing β-catenin expression, which may reveal a novel mechanism, and it provides a prevention strategy for bone loss and muscle atrophy induced by microgravity.

Neutralisation of Dkk-1 protects from systemic bone loss during inflammation and reduces sclerostin expression

2010 ◽  
Vol 69 (12) ◽  
pp. 2152-2159 ◽  
Author(s):  
Gisela Ruiz Heiland ◽  
Karin Zwerina ◽  
Wolfgang Baum ◽  
Trayana Kireva ◽  
Jörg H Distler ◽  
...  
Keyword(s):  
Bone Loss ◽  
Bone Formation ◽  
Osteoblast Differentiation ◽  
Bone Architecture ◽  
Bone Homeostasis ◽  
Osteocyte Death ◽  
Primary Osteoblasts ◽  
Systemic Bone Loss

IntroductionInflammation is a major risk factor for systemic bone loss. Proinflammatory cytokines like tumour necrosis factor (TNF) affect bone homeostasis and induce bone loss. It was hypothesised that impaired bone formation is a key component in inflammatory bone loss and that Dkk-1, a Wnt antagonist, is a strong inhibitor of osteoblast-mediated bone formation.MethodsTNF transgenic (hTNFtg) mice were treated with neutralising antibodies against TNF, Dkk-1 or a combination of both agents. Systemic bone architecture was analysed by bone histomorphometry. The expression of β-catenin, osteoprotegerin and osteocalcin was analysed. In vitro, primary osteoblasts were stimulated with TNF and analysed for their metabolic activity and expression of Dkk-1 and sclerostin. Sclerostin expression and osteocyte death upon Dkk-1 blockade were analysed in vivo.ResultsNeutralisation of Dkk-1 completely protected hTNFtg mice from inflammatory bone loss by preventing TNF-mediated impaired osteoblast function and enhanced osteoclast activity. These findings were accompanied by enhanced skeletal expression of β-catenin, osteocalcin and osteoprotegerin. In vitro, TNF rapidly increased Dkk-1 expression in primary osteoblasts and effectively blocked osteoblast differentiation. Moreover, blockade of Dkk-1 not only rescued impaired osteoblastogenesis but also neutralised TNF-mediated sclerostin expression in fully differentiated osteoblasts in vitro and in vivo.ConclusionsThese findings indicate that low bone formation and expression of Dkk-1 trigger inflammatory bone loss. Dkk-1 blocks osteoblast differentiation, induces sclerostin expression and leads to osteocyte death. Inhibition of Dkk-1 may thus be considered as a potent strategy to protect bone from inflammatory damage.

scholarly journals PKC-δ deficiency in B cells displays osteopenia accompanied with upregulation of RANKL expression and osteoclast–osteoblast uncoupling

2020 ◽  
Vol 11 (9) ◽  
Author(s):  
Shangfu Li ◽  
Qiuli Liu ◽  
Depeng Wu ◽  
Tianwei He ◽  
Jinbo Yuan ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Bone Structure ◽  
Bone Cells ◽  
Osteoclast Differentiation ◽  
Bone Homeostasis ◽  
Osteoblast Proliferation ◽  
And Function

Abstract PKC-δ is an important molecule for B-cell proliferation and tolerance. B cells have long been recognized to play a part in osteoimmunology and pathological bone loss. However, the role of B cells with PKC-δ deficiency in bone homeostasis and the underlying mechanisms are unknown. We generated mice with PKC-δ deletion selectively in B cells by crossing PKC-δ-loxP mice with CD19-Cre mice. We studied their bone phenotype using micro-CT and histology. Next, immune organs were obtained and analyzed. Western blotting was used to determine the RANKL/OPG ratio in vitro in B-cell cultures, ELISA assay and immunohistochemistry were used to analyze in vivo RANKL/OPG balance in serum and bone sections respectively. Finally, we utilized osteoclastogenesis to study osteoclast function via hydroxyapatite resorption assay, and isolated primary calvaria osteoblasts to investigate osteoblast proliferation and differentiation. We also investigated osteoclast and osteoblast biology in co-culture with B-cell supernatants. We found that mice with PKC-δ deficiency in B cells displayed an osteopenia phenotype in the trabecular and cortical compartment of long bones. In addition, PKC-δ deletion resulted in changes of trabecular bone structure in association with activation of osteoclast bone resorption and decrease in osteoblast parameters. As expected, inactivation of PKC-δ in B cells resulted in changes in spleen B-cell number, function, and distribution. Consistently, the RANKL/OPG ratio was elevated remarkably in B-cell culture, in the serum and in bone specimens after loss of PKC-δ in B cells. Finally, in vitro analysis revealed that PKC-δ ablation suppressed osteoclast differentiation and function but co-culture with B-cell supernatant reversed the suppression effect, as well as impaired osteoblast proliferation and function, indicative of osteoclast–osteoblast uncoupling. In conclusion, PKC-δ plays an important role in the interplay between B cells in the immune system and bone cells in the pathogenesis of bone lytic diseases.

Megakaryocyte-driven changes in bone health: lessons from mouse models of myelofibrosis and related disorders

2021 ◽  
Author(s):  
Mariya Stavnichuk ◽  
Svetlana V. Komarova
Keyword(s):  
Bone Marrow ◽  
Mouse Models ◽  
Cell Function ◽  
Bone Cells ◽  
Bone Marrow Cells ◽  
Bone Cell ◽  
Bone Architecture ◽  
Bone Homeostasis

Over the years, numerous studies demonstrated reciprocal communications between processes of bone marrow hematopoiesis and bone remodeling. Megakaryocytes, rare bone marrow cells responsible for platelet production, were demonstrated to be involved in bone homeostasis. Myelofibrosis, characterized by an increase in pleomorphic megakaryocytes in the bone marrow, commonly leads to the development of osteosclerosis. In vivo, an increase in megakaryocyte number was shown to result in osteosclerosis in GATA-1low, NF-E2-/-, TPOhigh, Mpllf/f;PF4cre, Lnk-/-, Mpig6b-/-, Mpig6bfl/fl;Gp1ba-Cr+/KI, Pt-vWD mouse models. In vitro, megakaryocytes stimulate osteoblast proliferation and have variable effects on osteoclast proliferation and activity through soluble factors and direct cell-cell communications. Intriguingly, new studies revealed that the ability of megakaryocytes to communicate with bone cells is affected by the age and sex of animals. This mini-review summarises changes seen in bone architecture and bone cell function in mouse models with an elevated number of megakaryocytes and the effects megakaryocytes have on osteoblasts and osteoclasts in vitro, and discusses potential molecular players that can mediate these effects.

scholarly journals Adaptor protein CrkII negatively regulates osteoblast differentiation and function through JNK phosphorylation

2019 ◽  
Vol 51 (9) ◽  
pp. 1-10 ◽  
Author(s):  
Jung Ha Kim ◽  
Kabsun Kim ◽  
Inyoung Kim ◽  
Semun Seong ◽  
Kwang-Il Nam ◽  
...  
Keyword(s):  
Osteoblast Differentiation ◽  
Type I Collagen ◽  
Bone Cells ◽  
Biological Activities ◽  
Osteoclast Differentiation ◽  
Adaptor Protein ◽  
Type I ◽  
And Function

Abstract The adaptor protein CrkII is involved in several biological activities, including mitogenesis, phagocytosis, and cytoskeleton reorganization. Previously, we demonstrated that CrkII plays an important role in osteoclast differentiation and function through Rac1 activation both in vitro and in vivo. In this study, we investigated whether CrkII also regulates the differentiation and function of another type of bone cells, osteoblasts. Overexpression of CrkII in primary osteoblasts inhibited bone morphogenetic protein (BMP) 2-induced osteoblast differentiation and function, whereas knockdown of CrkII expression exerted the opposite effect. Importantly, CrkII strongly enhanced c-Jun-N-terminal kinase (JNK) phosphorylation, and the CrkII overexpression-mediated attenuation of osteoblast differentiation and function was recovered by JNK inhibitor treatment. Furthermore, transgenic mice overexpressing CrkII under control of the alpha-1 type I collagen promoter exhibited a reduced bone mass phenotype. Together, these results indicate that CrkII negatively regulates osteoblast differentiation and function through JNK phosphorylation. Given that CrkII acts as a negative and positive regulator of osteoblast and osteoclast differentiation, respectively, the regulation of CrkII expression in bone cells may help to develop new strategies to enhance bone formation and inhibit bone resorption.

Sign in / Sign up

Export Citation Format

Share Document