scholarly journals Gsα enhances commitment of mesenchymal progenitors to the osteoblast lineage but restrains osteoblast differentiation in mice

2011 ◽  
Vol 121 (9) ◽  
pp. 3492-3504 ◽  
Author(s):  
Joy Y. Wu ◽  
Piia Aarnisalo ◽  
Murat Bastepe ◽  
Partha Sinha ◽  
Keertik Fulzele ◽  
...  
Keyword(s):  
Osteoblast Differentiation ◽  
Mesenchymal Progenitors ◽  
Osteoblast Lineage

scholarly journals CHIP promotes Runx2 degradation and negatively regulates osteoblast differentiation

2008 ◽  
Vol 181 (6) ◽  
pp. 959-972 ◽  
Author(s):  
Xueni Li ◽  
Mei Huang ◽  
Huiling Zheng ◽  
Yinyin Wang ◽  
Fangli Ren ◽  
...  
Keyword(s):  
Transcriptional Activation ◽  
Osteoblast Differentiation ◽  
Degradation Mechanism ◽  
Interacting Protein ◽  
E3 Ligases ◽  
Protein Levels ◽  
C Terminus ◽  
Osteoblast Lineage

Runx2, an essential transactivator for osteoblast differentiation, is tightly regulated at both the transcriptional and posttranslational levels. In this paper, we report that CHIP (C terminus of Hsc70-interacting protein)/STUB1 regulates Runx2 protein stability via a ubiquitination-degradation mechanism. CHIP interacts with Runx2 in vitro and in vivo. In the presence of increased Runx2 protein levels, CHIP expression decreases, whereas the expression of other E3 ligases involved in Runx2 degradation, such as Smurf1 or WWP1, remains constant or increases during osteoblast differentiation. Depletion of CHIP results in the stabilization of Runx2, enhances Runx2-mediated transcriptional activation, and promotes osteoblast differentiation in primary calvarial cells. In contrast, CHIP overexpression in preosteoblasts causes Runx2 degradation, inhibits osteoblast differentiation, and instead enhances adipogenesis. Our data suggest that negative regulation of the Runx2 protein by CHIP is critical in the commitment of precursor cells to differentiate into the osteoblast lineage.

scholarly journals Loss of Gsα in the Postnatal Skeleton Leads to Low Bone Mass and a Blunted Response to Anabolic Parathyroid Hormone Therapy

2015 ◽  
Vol 291 (4) ◽  
pp. 1631-1642 ◽  
Author(s):  
Partha Sinha ◽  
Piia Aarnisalo ◽  
Rhiannon Chubb ◽  
Ingrid J. Poulton ◽  
Jun Guo ◽  
...  
Keyword(s):  
Parathyroid Hormone ◽  
Bone Formation ◽  
Bone Mass ◽  
Trabecular Bone ◽  
Phospholipase C ◽  
Osteoblast Differentiation ◽  
Bone Volume ◽  
Trabecular Bone Volume ◽  
Male And Female ◽  
Osteoblast Lineage

Parathyroid hormone (PTH) is an important regulator of osteoblast function and is the only anabolic therapy currently approved for treatment of osteoporosis. The PTH receptor (PTH1R) is a G protein-coupled receptor that signals via multiple G proteins including Gsα. Mice expressing a constitutively active mutant PTH1R exhibited a dramatic increase in trabecular bone that was dependent upon expression of Gsα in the osteoblast lineage. Postnatal removal of Gsα in the osteoblast lineage (P-GsαOsxKO mice) yielded markedly reduced trabecular and cortical bone mass. Treatment with anabolic PTH(1–34) (80 μg/kg/day) for 4 weeks failed to increase trabecular bone volume or cortical thickness in male and female P-GsαOsxKO mice. Surprisingly, in both male and female mice, PTH administration significantly increased osteoblast numbers and bone formation rate in both control and P-GsαOsxKO mice. In mice that express a mutated PTH1R that activates adenylyl cyclase and protein kinase A (PKA) via Gsα but not phospholipase C via Gq/11 (D/D mice), PTH significantly enhanced bone formation, indicating that phospholipase C activation is not required for increased bone turnover in response to PTH. Therefore, although the anabolic effect of intermittent PTH treatment on trabecular bone volume is blunted by deletion of Gsα in osteoblasts, PTH can stimulate osteoblast differentiation and bone formation. Together these findings suggest that alternative signaling pathways beyond Gsα and Gq/11 act downstream of PTH on osteoblast differentiation.

scholarly journals CCAAT/Enhancer-Binding Protein Homologous Protein (CHOP) Regulates Osteoblast Differentiation

2006 ◽  
Vol 26 (16) ◽  
pp. 6105-6116 ◽  
Author(s):  
Ken Shirakawa ◽  
Shingo Maeda ◽  
Tomomi Gotoh ◽  
Makoto Hayashi ◽  
Kenichi Shinomiya ◽  
...  
Keyword(s):  
Osteoblast Differentiation ◽  
Binding Activity ◽  
Bmp Signaling ◽  
Dominant Negative ◽  
Dependent Manner ◽  
Mesenchymal Progenitors ◽  
Homologous Protein ◽  
Dna Binding Activity ◽  
Dominant Negative Inhibitor ◽  
Primary Osteoblasts

ABSTRACT Differentiation of committed osteoblasts is controlled by complex activities involving signal transduction and gene expression, and Runx2 and Osterix function as master regulators for this process. Recently, CCAAT/enhancer-binding proteins (C/EBPs) have been reported to regulate osteogenesis in addition to adipogenesis. However, the roles of C/EBP transcription factors in the control of osteoblast differentiation have yet to be fully elucidated. Here we show that C/EBP homologous protein (CHOP; also known as C/EBPζ) is expressed in bone as well as in mesenchymal progenitors and primary osteoblasts. Overexpression of CHOP reduces alkaline phosphatase activity in primary osteoblasts and suppresses the formation of calcified bone nodules. CHOP-deficient osteoblasts differentiate more strongly than their wild-type counterparts, suggesting that endogenous CHOP plays an important role in the inhibition of osteoblast differentiation. Furthermore, endogenous CHOP induces differentiation of calvarial osteoblasts upon bone morphogenetic protein (BMP) treatment. CHOP forms heterodimers with C/EBPβ and inhibits the DNA-binding activity as well as Runx2-binding activity of C/EBPβ, leading to inhibition of osteocalcin gene transcription. These findings indicate that CHOP acts as a dominant-negative inhibitor of C/EBPβ and prevents osteoblast differentiation but promotes BMP signaling in a cell-type-dependent manner. Thus, endogenous CHOP may have dual roles in regulating osteoblast differentiation and bone formation.

scholarly journals Osterix Marks a Distinct Population of Circulatory Bone Marrow Mesenchymal Stem Cells That Is Increased upon Oncogenic Stress

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 1-1
Author(s):  
Rafael Heinz Montoya ◽  
Rasoul Pourebrahim ◽  
Zoe Alaniz ◽  
Lauren B Ostermann ◽  
Jared K. Burks ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Fluorescence Microscopy ◽  
Stromal Cells ◽  
Research Funding ◽  
Osteoblast Differentiation ◽  
Mesenchymal Progenitor Cells ◽  
Flow Cytometric ◽  
Reporter Mice ◽  
Marrow Mesenchymal Stem Cells ◽  
Osteoblast Lineage

Bone marrow mesenchymal stem cells (BM-MSCs) are multipotent stromal cells that can differentiate into a variety of lineages and play a critical role in tissue homeostasis upon injury and repair. Previous studies using Osx-Cre transgenic mice have demonstrated that the expression of Sp7 (Osterix) marks a population of mesenchymal progenitor cells that can differentiate to osteoblasts as well as bone marrow stromal cells (Mizoguchi et al., 2014). Using a lineage-tracing system, we show that in addition to marking mesenchymal progenitor cells in the bone marrow, Osx-Cre also marks a population of BM-MSCs that circulate throughout the body and home in different tissues such as lung, spleen, intestine and muscle. Osx-Cre mice crossed with R26-mTmG reporter mice were analyzed at E14.5 and adulthood by fluorescence microscopy and flow cytometry. At E14.5, GFP+ cells were exclusively located in bone tissues. At two months of age, GFP+ cells were detectable in blood and many other tissues such as lung, liver, spleen and intestine. Flow cytometric profiling indicated that the GFP+ cells were positive for BM-MSC markers CD105, CD73 and CD140a. In order to exclude the possibility of non-specific recombination of the reporter in the non-osteoblast-lineage, as previously reported, we performed a pulse chase experiment utilizing Osx-CreER;mTmG mice. Fluorescence microscopy of the bone marrow upon Tamoxifen injection revealed that Cre activity was primarily limited to the osteoblast-lineage and bone tissue, whereas GFP+ cells were undetectable in lung and spleen, indicating that the GFP+ cells in the lung migrated from the bone marrow. Given that previous reports identified p53 as a negative regulator of osteoblast differentiation (Lengner et al., 2006), we further sought to determine the effect of p53 on circulatory BM-MSCs. Flow cytometric analysis of Osx-Cre;p53Fx/Fx;mTmG peripheral blood cells revealed a significant reduction of circulatory GFP+ cells as compared to p53 wild type mice (p<0.0001) suggesting a role for p53 in expansion of circulatory BM-MSCs. To further characterize the population of circulatory BM-MSCs in a cancer model, we analyzed the population of GFP+ cells in a syngeneic leukemia using fluorescence microscopy and flow cytometry. We transplanted p53 wildtype (Osx-Cre;mTmG) and p53 mutant (Osx-Cre;p53Fx/R172H;mTmG) reporter mice with AML-ETO-Turquoise leukemia cells and the population of GFP+ cells were analyzed three weeks after transplant. The population of GFP+MSCs were significantly increased in bone marrow and spleen, indicating the recruitment of circulatory BM-MSCs. Conclusion: We present the Osx-Cre;mTmG mouse as a faithful model to study circulatory BM-MSCs in vivo and identified a role for p53 in the regulation of circulatory BM-MSCs. We previously reported that BM-derived MSCs home to solid tumors and their metastases and can be successfully used as gene-delivery vehicles, both in murine models and in patients (Studeny et al. JCI 2001, Andreeff et al. AACR 2018). This model is the first to conduct studies of circulating MSCs and to further analyze their role in tumor biology and therapy. Lengner, C.J., Steinman, H.A., Gagnon, J., Smith, T.W., Henderson, J.E., Kream, B.E., Stein, G.S., Lian, J.B., and Jones, S.N. (2006). Osteoblast differentiation and skeletal development are regulated by Mdm2-p53 signaling. J Cell Biol 172, 909-921. Mizoguchi, T., Pinho, S., Ahmed, J., Kunisaki, Y., Hanoun, M., Mendelson, A., Ono, N., Kronenberg, H.M., and Frenette, P.S. (2014). Osterix marks distinct waves of primitive and definitive stromal progenitors during bone marrow development. Dev Cell 29, 340-349. Figure Disclosures Andreeff: Daiichi-Sankyo; Breast Cancer Research Foundation; CPRIT; NIH/NCI; Amgen; AstraZeneca: Research Funding; Centre for Drug Research & Development; Cancer UK; NCI-CTEP; German Research Council; Leukemia Lymphoma Foundation (LLS); NCI-RDCRN (Rare Disease Clin Network); CLL Founcdation; BioLineRx; SentiBio; Aptose Biosciences, Inc: Membership on an entity's Board of Directors or advisory committees; Daiichi-Sankyo; Jazz Pharmaceuticals; Celgene; Amgen; AstraZeneca; 6 Dimensions Capital: Consultancy; Amgen: Research Funding.

Advances in the osteoblast lineage

1998 ◽  
Vol 76 (6) ◽  
pp. 899-910 ◽  
Author(s):  
Jane E Aubin
Keyword(s):  
Gene Expression ◽  
Cell Culture ◽  
Osteoblast Differentiation ◽  
Skeletal Development ◽  
Proliferation And Differentiation ◽  
Gene Expression Heterogeneity ◽  
Adult Organism ◽  
Differential Gene ◽  
Osteoblast Markers ◽  
Osteoblast Lineage

Osteoblasts are the skeletal cells responsible for synthesis, deposition and mineralization of the extracellular matrix of bone. By mechanisms that are only beginning to be understood, stem and primitive osteoprogenitors and related mesenchymal precursors arise in the embryo and at least some appear to persist in the adult organism, where they contribute to replacement of osteoblasts in bone turnover and in fracture healing. In this review, we describe the morphological, molecular, and biochemical criteria by which osteoblasts are defined and cell culture approaches that have helped to clarify transitional stages in osteoblast differentiation. Current understanding of differential expression of osteoblast-associated genes during osteoprogenitor proliferation and differentiation to mature matrix synthesizing osteoblasts is summarized. Evidence is provided to support the hypothesis that the mature osteoblast phenotype is heterogeneous with subpopulations of osteoblasts expressing only subsets of the known osteoblast markers. Throughout this paper, outstanding uncertainties and areas for future investigation are also identified.Key words: skeletal development, differential gene expression, heterogeneity.

scholarly journals Role of RUNX2 in Melanoma: A New Player in Tumor Progression and Resistance to Therapy

2021 ◽  
Author(s):  
Rachael Pulica ◽  
Cohen Solal Karine ◽  
Ahmed Lasfar
Keyword(s):  
Osteoblast Differentiation ◽  
Skeletal Development ◽  
Critical Role ◽  
Invasion And Metastasis ◽  
Braf Mutations ◽  
Mesenchymal Progenitors ◽  
Oncogenic Pathways ◽  
Cancer Types ◽  
Braf Mutant

RUNX2, a transcription factor, initially known for its indispensable role in skeletal development. RUNX2 is essential for osteoblast differentiation and the maintain of the osteocyte balance. RUNX2 acts directly on osteoblasts via Fgf pathway or on mesenchymal progenitors through Hedgehog, Wnt, Pthlh and DLX5. Currently, many reports point its critical role in the progression and metastasis of several cancer types. RUNX2 is involved in EMT process, invasion and metastasis through the modulation of important oncogenic pathways, including Wnt, FAK/PTK and AKT. In melanoma, RUNX2 is a key player in mediating intrinsic RTK-associated pro-oncogenic properties. We have showed a dramatic up regulation of RUNX2 expression with concomitant up-regulation of EGFR, IGF-1R and AXL, in melanoma cells rendered resistant to BRAF mutant inhibitors. Approximately half of melanomas carry BRAF mutations which enhance tumor invasion and metastasis. In this chapter, we describe the potential mechanisms, leading to the upregulation of RUNX2 in melanoma with BRAF mutations. We also highlight the critical role of PI3K/AKT in the expression and activation of RUNX2, and its consequences on the regulation of many critical factors, controlling cancer invasion and metastasis.

Suppression of Mesenchymal Stromal Cell (MSC) Differentiation in Multiple Myeloma (MM) Is Restricted to the Osteoblast Lineage

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 2752-2752
Author(s):  
Flavi a Esteve ◽  
Chang Sook Hong ◽  
Alissa Huston ◽  
Veronica Garcia Palacios ◽  
Judy Anderson ◽  
...  
Keyword(s):  
Bone Disease ◽  
Osteoblast Differentiation ◽  
Bone Lesions ◽  
Osteoblast Activity ◽  
Lytic Bone Lesions ◽  
Oil Red O Staining ◽  
Osteoblast Lineage ◽  
Oil Red O ◽  
Msc Differentiation ◽  
Group 1

Abstract Lytic bone lesions in patients with MM rarely heal even when patients are in complete remission for long periods of time. The mechanism behind this prolonged suppression of osteoblast activity is yet to be elucidated, and when or whether the osteoblast suppression can be reversed is unknown. Several possibilities could explain osteoblast suppression in MM: quantitative MSCs depletion induced by MM cells; a permanent block in MSC differentiation to the osteoblast lineage; and/or an inability of MSCs to differentiate in a hostile microenvironment. To distinguish among these possibilities, we developed a murine model of MM bone disease that permits us to assess the time course for development of osteoblast inhibition of MSC differentiation of osteoblasts, if this inhibition is reversible anytime during the process, and if the differentiation is restricted to permanent blockade of osteoblast differentiation. We generated a murine MM cell line genetically modified to contain the TK gene, which allows ablation of the cells by ganciclovir while sparing hematopoietic and stromal cell progenitors. MM cells also contained GFP for tumor estimation and a blasticidin resistance cassette for selection of transfected cells. Hematopoietic precursors and MSCs were cocultured with the MM cells in media containing ganciclovir to assess for toxic effects of this drug on cell differentiation (bystander effect). Murine MM cells or saline was also injected into the right tibia of SCID mice on day 0 and tumor lesions were documented by weekly imaging of right tibias by micro-QCT and by measurement of IgG2b in serum. Mice were treated with intraperitoneal ganciclovir or saline for 14 days starting at different time points (group 1 = 1d; group 2 = 8d; or group 3 = 14d) after tumor injection, and were sacrificed at week 5. MSCs were recovered from right tibias, cultured in osteogenic media, and alkaline phosphatase levels determined after 10 days of culture to assess osteoblast activity. MSCs were also cultured in adipogenic media, and the presence of mature adipocytes was visualized by Oil Red O staining. There was no toxic effect of ganciclovir on hematopoietic colony formation or osteoblast differentiation. Lytic bone lesions were documented in mice injected with MM cells by micro-QCT at 4 weeks in groups 2 and 3 and progressed thereafter, but not in group 1 after intratibial injection of MM cells. MSCs from group 1 mice showed greater osteoblast activity when sacrificed at 5 weeks compared to other groups. Mice in group 1 surviving 5 weeks eventually developed MM bone disease and succumbed to it at a much later time than the other groups (p<.01). Significant elevations of serum IgG2b levels were detectable at week 4 in mice from groups 2 and 3 and correlated with the development of bone lytic lesions. Harvesting cells from tumor bearing tibias yielded similar numbers of MSCs in all groups. Comparable levels of adipocytic differentiation by Oil Red O staining were observed among MSC from all groups of mice. These results demonstrate that MSC depletion cannot explain the absent osteoblast activity in this model of MM. MSC differentiation appears to be selectively blocked from the osteoblast lineage. Suppression of osteoblast activity required >24hr exposure to MM cells in vivo and correlated with relative tumor burden. Studies are underway to determine if osteoblast suppression is permanent or can be reversed in this model. This model of MM bone disease should permit the further elucidation of the mechanisms responsible for osteoblast suppression in MM, and testing of anabolic agents in a model that does not require treatment of mice with agents to eradicate MM cells and that are toxic to the marrow microenvironment.

scholarly journals Notch signaling maintains bone marrow mesenchymal progenitors by suppressing osteoblast differentiation

2008 ◽  
Vol 14 (3) ◽  
pp. 306-314 ◽  
Author(s):  
Matthew J Hilton ◽  
Xiaolin Tu ◽  
Ximei Wu ◽  
Shuting Bai ◽  
Haibo Zhao ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Notch Signaling ◽  
Osteoblast Differentiation ◽  
Mesenchymal Progenitors
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