• BMB Reports
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• v.55 no.12
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• pp.627-632
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• 2022

Dickkopf-1 (DKK1) is a secreted protein that acts as an antagonist of the canonical WNT/β-catenin pathway, which regulates osteoblast differentiation. However, the role of DKK1 on osteoblast differentiation has not yet been fully clarified. Here, we investigate the functional role of DKK1 on osteoblast differentiation. Primary osteoprogenitor cells were isolated from human spinal bone tissues. To examine the role of DKK1 in osteoblast differentiation, we manipulated the expression of DKK1, and the cells were differentiated into mature osteoblasts. DKK1 overexpression in osteoprogenitor cells promoted matrix mineralization of osteoblast differentiation but did not promote matrix maturation. DKK1 increased Ca⁺ influx and activation of the Ca⁺/calmodulin-dependent protein kinase II Alpha (CAMK2A)-cAMP response element-binding protein 1 (CREB1) and increased translocation of p-CREB1 into the nucleus. In contrast, stable DKK1 knockdown in human osteosarcoma cell line SaOS2 exhibited reduced nuclear translocation of p-CREB1 and matrix mineralization. Overall, we suggest that manipulating DKK1 regulates the matrix mineralization of osteoblasts by Ca⁺-CAMK2A-CREB1, and DKK1 is a crucial gene for bone mineralization of osteoblasts.

• Journal of Life Science
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• v.26 no.3
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• pp.331-337
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• 2016

Although fibroblast growth factor 23 (FGF23) is exclusively produced in osteoblasts and osteocytes, its main target is the kidney, where it decreases phosphate reabsorption by suppressing Na-phosphate cotransporters. Independently of its action on phosphate homeostasis, FGF23 also inhibits bone formation in vivo. In a calvarial osteoblastic cell model, FGF23 was shown to negatively affect extracellular matrix mineralization. This study investigated whether FGF23 had similar effects on osteoblast maturation, including differentiation and mineralization of bone marrow-derived mesenchymal stem cells (MSCs). D1 MSCs were cultured in an osteogenic medium containing β-glycerophosphate, ascorbic acid, and dexamethazone. Osteoblastic differentiation was evaluated by alkaline phosphatase (Alp) staining, and matrix mineralization was evaluated by alizarin red staining and calcium deposition. The expression of differentiation-stimulating genes Runx2, Alp, and osteocalcin and mineralization-inhibiting genes Enpp1 and Ank was analyzed using semiquantitative RT-PCR. Supraphysiological doses of FGF23 did not stimulate proliferation or osteoblastic differentiation of MSCs. Matrix mineralization 1, 2, and 3 weeks after the FGF23 treatment did not vary between control and FGF23 groups, although time-dependent enhancement of mineralization was obvious. Calcium deposition was also unchanged after the FGF23 treatment. mRNA expression levels of differentiation- and mineralization-related genes were also similar between the groups. Despite these negative findings, FGF23 signaling through FGF receptors seemed to function normally, with phosphorylation of the Erk protein more evident in the FGF23 group than in controls. These findings suggest that unlike calvarial osteoblasts, FGF23 is not likely to affect osteoblastic differentiation and mineralization of MSCs.

• Journal of Nutrition and Health
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• v.51 no.5
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• pp.379-385
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• 2018

Purpose: Zinc (Zn) is an essential trace element for bone mineralization and osteoblast function. We examined the effects of Zn deficiency on osteoblast differentiation and mineralization in MC3T3-E1 cells. Methods: Osteoblastic MC3T3-E1 cells were cultured at concentration of 1 to $15{\mu}M$ $ZnCl_2$ (Zn- or Zn+) for 5, 15 and 25 days up to the calcification period. Extracellular matrix mineralization was detected by staining Ca and P deposits using Alizarin Red and von Kossa stain respectively, and alkaline phosphatase (ALP) activity was detected by ALP staining and colorimetric method. Results: Extracellular matrix mineralization was decreased in Zn deficiency over 5, 15, and 25 days. Similarly, staining of ALP activity as the sign of an osteoblast differentiation, was also decreased by Zn deficiency over the same period. Interestingly, the gene expression of bone-related markers (ALP, PTHR; parathyroid hormone receptor, OPN; osteopontin, OC; osteocalcin and COLI; collagen type I), and bone-specific transcription factor Runx2 were downregulated by Zn deficiency for 5 or 15 days, however, this was restored at 25 days. Conclusion: Our data suggests that Zn deficiency inhibits osteoblast differentiation by retarding bone marker gene expression and also inhibits bone mineralization by decreasing Ca/P deposition as well as ALP activity.

• BMB Reports
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• v.44 no.10
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• pp.659-664
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• 2011

As part of the search for biologically active anti-osteoporotic agents that enhance differentiation and mineralization of osteoblastic MC3T3-E1 cells, we identified the ginsenoside Rh2(S), which is an active component in ginseng. Rh2(S) stimulates osteoblastic differentiation and mineralization, as manifested by the up-regulation of differentiation markers (alkaline phosphatase and osteogenic genes) and Alizarin Red staining, respectively. Rh2(S) activates p38 mitogen-activated protein kinase (MAPK) in time- and concentration-dependent manners, and Rh2(S)-induced differentiation and mineralization of osteoblastic cells were totally inhibited in the presence of the p38 MAPK inhibitor, SB203580. In addition, pretreatment with Go6976, a protein kinase D (PKD) inhibitor, significantly reversed the Rh2(S)-induced p38 MAPK activation, indicating that PKD might be an upstream kinase for p38 MAPK in MC3T3-E1 cells. Taken together, these results suggest that Rh2(S) induces the differentiation and mineralization of MC3T3-E1 cells through activation of PKD/p38 MAPK signaling pathways, and these findings provide a molecular basis for the osteogenic effect of Rh2(S).

• BMB Reports
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• v.45 no.10
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• pp.571-576
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• 2012

Radiotherapy is considered to cause detrimental effects on bone tissue eventually increasing bone loss and fracture risk. However, there is a great controversy on the real effects of irradiation itself on osteoblasts, and the mechanisms by which irradiation affects osteoblast differentiation and mineralization are not completely understood. We explored how X-ray radiation influences differentiation and bone-specific gene expression in mouse calvarial osteoblasts. Irradiation at 2 Gy not only increased differentiation and mineralization of the cells, but also upregulated the expression of alkaline phosphatase, type I collagen, osteopontin, and osteocalcin at early stages of differentiation. However, irradiation at higher doses (>2 Gy) did not stimulate osteoblast differentiation, rather it suppressed DNA synthesis by the cells without a toxic effect. Additional experiments suggested that transforming growth factor-beta 1 and runt-transcription factor 2 play important roles in irradiation- stimulated bone differentiation by acting as upstream regulators of bone-specific markers.

• Journal of Periodontal and Implant Science
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• v.43 no.4
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• pp.168-176
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• 2013

Purpose: The purpose of the current study was to examine the effect of dexamethasone (Dex) at various concentrations on the apoptosis and mineralization of human periodontal ligament (hPDL) cells. Methods: hPDL cells were obtained from the mid-third of premolars extracted for orthodontic reasons, and a primary culture of hPDL cells was prepared using an explant technique. Groups of cells were divided according to the concentration of Dex (0, 1, 10, 100, and 1,000 nM). A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was performed for evaluation of cellular viability, and alkaline phosphatase activity was examined for osteogenic differentiation of hPDL cells. Alizarin Red S staining was performed for observation of mineralization, and real-time polymerase chain reaction was performed for the evaluation of related genes. Results: Increasing the Dex concentration was found to reduce cellular viability, with an increase in alkaline phosphatase activity and mineralization. Within the range of Dex concentrations tested in this study, 100 nM of Dex was found to promote the most vigorous differentiation and mineralization of hPDL cells. Dex-induced osteogenic differentiation and mineralization was accompanied by an increase in the level of osteogenic and apoptosis-related genes and a reduction in the level of antiapoptotic genes. The decrease in hPDL cellular viability by glucocorticoid may be explained in part by the increased prevalence of cell apoptosis, as demonstrated by BAX expression and decreased expression of the antiapoptotic gene, Bcl-2. Conclusions: An increase in hPDL cell differentiation rather than cellular viability at an early stage is likely to be a key factor in glucocorticoid induced mineralization. In addition, apoptosis might play an important role in Dex-induced tissue regeneration; however, further study is needed for investigation of the precise mechanism.

• Journal of Periodontal and Implant Science
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• v.41 no.4
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• pp.167-175
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• 2011

Purpose: Periodontal ligament (PDL) cell differentiation into osteoblasts is important in bone formation. Bone formation is a complex biological process and involves several tightly regulated gene expression patterns of bone-related proteins. The expression patterns of bone related proteins are regulated in a temporal manner both in vivo and in vitro. The aim of this study was to observe the gene expression profile in PDL cell proliferation, differentiation, and mineralization in vitro. Methods: PDL cells were grown until confluence, which were then designated as day 0, and nodule formation was induced by the addition of 50 ${\mu}g$/mL ascorbic acid, 10 mM ${\beta}$-glycerophosphate, and 100 nM dexamethasone to the medium. The dishes were stained with Alizarin Red S on days 1, 7, 14, and 21. Real-time polymerase chain reaction was performed for the detection of various genes on days 0, 1, 7, 14, and 21. Results: On day 0 with a confluent monolayer, in the active proliferative stage, c-myc gene expression was observed at its maximal level. On day 7 with a multilayer, alkaline phosphatase, bone morphogenetic protein (BMP)-2, and BMP-4 gene expression had increased and this was followed by maximal expression of osteocalcin on day 14 with the initiation of nodule mineralization. In relationship to apoptosis, c-fos gene expression peaked on day 21 and was characterized by the post-mineralization stage. Here, various genes were regulated in a temporal manner during PDL fibroblast proliferation, extracellular matrix maturation, and mineralization. The gene expression pattern was similar. Conclusions: We can speculate that the gene expression pattern occurs during PDL cell proliferation, differentiation, and mineralization. On the basis of these results, it might be possible to understand the various factors that influence PDL cell proliferation, extracellular matrix maturation, and mineralization with regard to gene expression patterns.

• International Journal of Oral Biology
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• v.43 no.3
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• pp.133-140
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• 2018

Resveratrol (3,4',5,-trihydroxystilbene), a phytoalexin present in grapes, exerts a variety of actions to reduce superoxides, prevents diabetes mellitus, and inhibits inflammation. Resveratrol acts as a chemo-preventive agent and induces apoptotic cell death in various cancer cells. However, the role of resveratrol in odontoblastic cell differentiation is unclear. In this study, the effect of resveratrol on regulating odontoblast differentiation was examined in MDPC-23 mouse odontoblastic cells derived from mouse dental papilla cells. Resveratrol significantly accelerated mineralization as compared with the control culture in differentiation of MDPC-23 cells. Resveratrol significantly increased expression of ALP mRNA as compared with the control in differentiation of MDPC-23 cells. Resveratrol significantly accelerated expression of Col I mRNA as compared with the control in differentiation of MDPC-23 cells. Resveratrol significantly increased expressions of DSPP and DMP-1 mRNAs as compared with the control in differentiation of MDPC-23 cells. Treatment of resveratrol did not significantly affect cell proliferation in MDPC-23 cells. Results suggest resveratrol facilitates odontoblast differentiation and mineralization in differentiation of MDPC-23 cells, and may have potential properties for development and clinical application of dentin regeneration materials.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.28 no.2
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• pp.114-125
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• 2002

This study was designed to evaluate the influence of fibroblasts or connective tissue from mouse oral mucosa on differentiation of neonatal mouse calvaria-derived osteoblasts and mineralization of bone nodules. Primary cell cultures from mouse calvarial osteoblasts and 2-4 passaged fibroblasts from oral mucosa were co-cultured in monolayer cultures, devided into 6 experimental group according to cell density or cell confluency. Osteoblasts were also co-cultured with fibroblasts in $Transwell^{(R)}$ culture plate with different co-cultured period according to osteoblast differentiation. The alkaline phosphatase activity were measured in monolayer cultures and cultures using $Transwell^{(R)}$. The mineralized bone nodules were presented by Von Kossa staining and density of mineralized nodules was measured by image analysis. The connective tissues with or without osteoblast seeding were cultured and examined histologically by Von Kossa and Trichrome Goldner staining. The results were as follows; 1. Prolonged maturation of matrix and delayed mineralization of bone nodules were resulted in monolayer cultures. 2. Co-culture of fibroblast with osteoblast using $Transwell^{(R)}$ during osteoblast proliferation stage stimulated proliferation of osteoblasts and increased alkaline phosphatase activity and mineralization of bone nodules. 3. Co-culture of fibroblast with osteoblast using $Transwell^{(R)}$ during matrix mineralization stage decreased and delayed mineralization of bone nodules. 4. In vitro cultured connective tissue with osteoblast seeding resulted in proliferation of osteoblasts and matrix formation with mineralization.

• Korean Journal of Oriental Medicine
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• v.13 no.1 s.19
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• pp.139-145
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• 2007

Emodin is one of the main active components of a traditional Korean medicine isolated from the root and rhizomes of Rheum palmatum L. In this study, of 222 natural compounds to evaluate the anabolic activities, emodin activated bone morphogenetic protein (BMP)-2 promoter in the differentiation process of mouse osteoblastic MC3T3-E1 cells. Emodin was shown to significantly stimulate the activity and expression of alkaline phosphatase, an earlyphase marker of osteoblastic differentiation, on the differentiation day 7, and induce the osteopontin mRNA expression from the differentiation day 14. In addition, low concentration (up to 5 M) of emodin dramatically promoted the induction of mineralization in MC3T3-E1 subclone 4 cells. The stimulatory effect of emodin on the osteoblast differentiation/mineralization could be associated with its potential to stimulate the BMP-2 gene expression. Although further studies are needed to determine the precise mechanism, this study suggests that the use of herbal medicine containing natural compounds with anabolic activity such as emodin could have a beneficial effect on bone health.