• YAKHAK HOEJI
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• v.49 no.1
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• pp.109-113
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• 2005

In the present study treatment of IBMX, a phosphodiesterase (PDE) inhibitor, alone induced osteoclast formation in co-cultures of mouse bone marrow cells and calvarial osteoblasts. However, treatment of IBMX in combination with prostaglandin $E_2\;(PGE_2)$ inhibited osteoclast formation in a dose-dependent manner. Among various isozyme-specific PDE inhibitors, a PDE4 specific inhibitor, rolipram, showed similar effects as IBMX on osteoclast formation. To address the involvement of cyclic adenosine monophosphate (cAMP) in osteoclast formation, cAMP concentration in calvarial osteoblasts was investigated. When calvarial osteoblasts were co-cultured with IBMX alone or in combination with $PGE_2$, the patterns of cAMP concentration in calvarial osteoblasts were differ each other suggesting that cAMP in calvarial osteoblasts subtly regulates osteoclast formation.

• Archives of Pharmacal Research
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• v.27 no.12
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• pp.1258-1262
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• 2004

Phosphodiesterase (PDE) 4 is an enzyme that degrades intracellular cAMP. In the present study, the effect of rolipram, a specific phosphodiesterase (PDE) 4 inhibitor, on osteoclast formation was investigated. Rolipram induced osteoclast formation in cocultures of mouse bone marrow cells and calvarial osteoblasts. This activity was not observed in the absence of calvarial osteoblasts, suggesting that calvarial osteoblasts are likely target cells of rolipram. Osteoclast formation by rolipram was completely blocked by the addition of osteoprotegerin (OPG), a soluble decoy receptor for the osteoclast differentiation factor, TNF-related activation-induced cytokine (TRANCE, identical to RANKL, ODF, and OPGL). Northern blot analysis revealed the effect of rolipram to be associated with the increased expression of TRANCE mRNA in mouse calvarial osteoblasts. Collectively, these data indicate that PDE4 inhibitor up-regulates the TRANCE mRNA expression in osteoblasts, which in turn controls osteoclast formation.

• YAKHAK HOEJI
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• v.48 no.3
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• pp.197-201
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• 2004

Phosphodiesterases (PDEs) are enzymes that degrade intracellular cAMP. In the present study, pentoxifylline, a PDE inhibitor, induced osteoclast formation in co-cultures of mouse bone marrow cells and calvarial osteoblasts. To address the involvement of the osteoclast differentiation factor TNF-related activation-induced cytokine (TRANCE, identical to RANKL, ODF, and OPGL), mouse bone marrow cells and calvarial osteoblasts were co-cultured with pentoxifylline in the presence of OPG, a decoy receptor for TRANCE. The osteoclastogenic effect of pentoxifylline was completely blocked by addition of OPG, suggesting that TRANCE is involved in the osteoclast formation induced by pentoxifylline, Northern blot analysis revealed that pentoxifylline significantly induced TRANCE mRNA expression in calvarial osteoblasts. These results suggests that pentoxifylline regulates TRANCE expression in osteoblasts, which in turn controls osteoclast formation.

• Molecules and Cells
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• v.38 no.1
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• pp.75-80
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• 2015

Osteoclasts are unique cells responsible for the resorption of bone matrix. MicroRNAs (miRNAs) are involved in the regulation of a wide range of physiological processes. Here, we examined the role of miR-26a in RANKL-induced osteoclastogenesis. The expression of miR-26a was upregulated by RANKL at the late stage of osteoclastogenesis. Ectopic expression of an miR-26a mimic in osteoclast precursor cells attenuated osteoclast formation, actin-ring formation, and bone resorption by suppressing the expression of connective tissue growth factor/CCN family 2 (CTGF/CCN2), which can promote osteoclast formation via upregulation of dendritic cell-specific transmembrane protein (DC-STAMP). On the other hand, overexpression of miR-26a inhibitor enhanced RANKL-induced osteoclast formation and function as well as CTGF expression. In addition, the inhibitory effect of miR-26a on osteoclast formation and function was prevented by treatment with recombinant CTGF. Collectively, our results suggest that miR-26a modulates osteoclast formation and function through the regulation of CTGF.

• Journal of Physiology & Pathology in Korean Medicine
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• v.29 no.1
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• pp.51-57
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• 2015

Bone destruction is a pathological symptom of some chronic inflammatory diseases, such as rheumatoid arthritis and periodontitis. Inflammation-induced bone loss of these diseases results from increased number and activity of osteoclasts. Paeoniae Radix Alba has been used in korean traditional medicine to treat disease including inflammation, gynecopathy and various pain. However, these effects have not been tested on osteoclasts, the bone resorbing cells that regulate bone metabolism. Here, we investigated the effects of Paeoniae Radix Alba ethanol extract (PRAE) on receptor activator of nuclear factor-kappa B ligand (RANKL)-mediated osteoclast differentiation and formation. Osteoclast differentiation and formation were measured by tartrate resistant acidic phosphatase (TRAP) staining and TRAP solution assay. The treatment of PRAE on bone marrow derived macrophages (BMMs), which is known as osteoclast precursor cells, inhibited osteoclast differentiation and formation in a dose-dependent manner. In addition, the expression of osteoclast differentiation marker genes was suppressed by PRAE treatment. This inhibitory effect of PRAE resulted from significant repression of c-Fos expression, and subsequent reduction of NFATc1 expression which was previously reported as a master transcription factor for osteoclastogenesis in vitro and in vivo. These results demonstrate that PRAE negatively regulates osteoclast differentiation and formation and suggest that PRAE can be used as a potent preventive or therapeutic candidate for various bone diseases, such as postmenopausal osteoporosis, periodontitis and rheumatoid arthritis.

• The Korean Journal of Physiology and Pharmacology
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• v.3 no.6
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• pp.539-546
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• 1999

Bone is a complex tissue in which resorption and formation continue throughout life. The bone tissue contains various types of cells, of which the bone forming osteoblasts and bone resorbing osteoclasts are mainly responsible for bone remodeling. Periodontal disease represents example of abnormal bone remodeling. Osteoclasts are multinucleated cells present only in bone. It is believed that osteoclast progenitors are hematopoietic origin, and they are recruited from hematopoietic tissues such as bone marrow and circulating blood to bone. Cells present in the osteoclast microenvironment include marrow stromal cells, osteoblasts, macrophages, T-lymphocytes, and marrow cells. These cells produce cytokines that can affect osteoclast formation. In vitro model systems using bone marrow cultures have demonstrated that $IL-l{\beta},\;IL-3,\;TNF-{\alpha},$ bFGF can stimulate the formation of osteoclasts. In contrast, IL-4 inhibits osteoclast formation. Knowledge of cytokines and bFGF that affect osteoclast formation and their capacity to modulate the bone-resorbing process should provide critical insights into normal calcium homeostasis and disorders of bone turnover such as periodontal disease, osteoporosis and Paget's disease.

• YAKHAK HOEJI
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• v.53 no.2
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• pp.78-82
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• 2009

We explored the effects of dexamethasone on osteoclast precursors using BMMs. Dexamethasone inhibited the proliferation of BMMs. Furthermore, it stimulated the osteoclast formation via NFATc1 activation in the presence of RANKL. Since dexamethasone targeted the early stage of osteoclast formation, we investigated its effect on mRNA expression of GR and $IFN-{\beta}$. Whereas dexamethasone had no effects on GR expression in the presence of RANKL, it reduced the expression of $IFN-{\beta}$, suggesting that dexamethasone increased RANKL-induced osteoclast formation by modulating $IFN-{\beta}$.

• YAKHAK HOEJI
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• v.52 no.1
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• pp.43-47
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• 2008

To determine the regulatory roles of PDE4 inhibitor on LPS-induced osteoclastogenesis, we investigated the effect of a PDE4 inhibitor on osteoclast formation in the presence of LPS. A specific PDE4 inhibitor, rolipram, increased LPS-induced osteoclast formation in cocultures. To verify that whether rolipram acts indirectly on osteoblasts, we investigated the TRANCE and COX-2 mRNA expression levels in osteoblasts. Treatment of rolipram increased the expression of TRANCE and COX-2 mRNA in osteoblasts stimulated by LPS. On the contrary, rolipram did not augment the number of osteoclasts differentiated from bone marrow cells by LPS. In conclusion, the stimulation of LPS-induced osteoclast formation by the PDE4 inhibitor are attributable to its indirect effect on osteoblasts, not to their direct effect on bone marrow-derived osteoclast precursors.

• Journal of Oral Medicine and Pain
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• v.25 no.1
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• pp.53-62
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• 2000

Bone marrow culture systems are widely used to differentiate osteoclast-like cells in vitro using several osteotropic hormones. In this study, we isolated and cultured the mouse bone marrow cells with or without some osteotropic hormones such as parathyroid hormone(PTH), prostaglandin $E_2(PGE_2)$ and $l,25(OH)_2-vitamin$ $D_3$(Vit. $D_3$). We confirmed the formation of osteoclast-like cells morphologically and functionally by the expression of tartrate-resistant acid phosphatase(TRAP) and by their capability to resorb dentin slices. We also studied the effects of transforming growth $factor-{\beta}(TGF-{\beta})$ and epidermal growth factor(EGF) on the Vit. $D_3-induced$ osteoclast-like cell formation. In control, a few multinucleated cells were formed whereas PTH and $PGE_2$ increased the number of multinucleated cells. PTH, $PGE_2$ and Vit. $D_3$ induced the formation of TRAP-positive multinucleated cells. After culture of mouse bone marrow cells on the dentin slices with or without osteotropic hormones, giant cells with diverse morphology were found on the dentin slices under the scanning electronmicroscopy. After removing the attached cells, resorption pits were identified on the dentin slices, and the shape of resorption pits was variable. EGF increased the osteoclast-like cell formation induced by Vit. $D_3$, however, $TGF-{\beta}$ showed biphasic effect, which at low concentration, increased and at high concentration, decreased the osteoclast-like cell formation induced by Vit. $D_3$.

• International Journal of Oral Biology
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• v.31 no.2
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• pp.67-72
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• 2006

Nitric oxide(NO) is a labile, uncharged, reactive radical that functions as a sensitive mediator of intercellular communication in diverse tissues. It has been reported that NO is produced by osteoblast and these results may suggest that NO is integrally involved in the regulation of osteoclast formation and osteoclast resorption activity by osteoblastic cells. We examined the effect of cytokines on NO release by mouse bone marrow cell. We also examined the effects of cytokines and sodium nitroprusside(SNP) on the formation of osteoclast-like cell from mouse bone marrow cells in culture. Cytokines stimulated NO production of mouse bone marrow cells, and N-nitro-L-arginine methyl ester, a specific inhibitor of NO synthase, suppressed the cytokine-induced NO production. SNP showed dual action in the generation of osteoclasts. The addition of $30{\mu}M$ SNP inhibited the formation of tartrate resistant acid phosphatase(TRAP)(+) multinucleated cell, whereas lower concentration($3{\mu}M$) of SNP enhanced it. Although the precise action of NO remains to be elucidated in detail, the action of NO in osteoclast generation in our studies seems to be associated, at least in part, with bone metabolism and bone pathophysiology.