OBJECTIVETo explore certain principle of how osteoprotegerin (OPG) and osteoprotegerin ligand (OPGL) take part in the periodontal tissues remodeling under the combined influence of inflammation and orthodontic force.

METHODSThe positive signals of OPG and OPGL mRNA were measured with in situ hybridzation after orthodontic tooth movement in the experimental periodontitis groups and control ones.

RESULTSThe OPG and OPGL mRNA expression intensity in the experimental group showed difference from control. All their optical density index reached a peak in day 2, respectively.

CONCLUSIONOPG and OPGL play important roles in the periodontal reconstruction induced by inflammation irritation and orthodontic force, and complex interaction could exist between the two factors.

Humans ; Osteoprotegerin ; Periodontitis ; RANK Ligand ; RNA, Messenger ; Tooth Movement Techniques

The hyperosmotic stimulus is regarded as a mechanical factor for bone remodeling. However, whether the hyperosmotic stimulus affects 1alpha, 25-dihydroxyvitamin D3 (1alpha,25(OH)2D3)-induced osteoclastogenesis is not clear. In the present study, the effect of the hyperosmotic stimulus on 1alpha,25(OH)2D3-induced osteoclastogenesis was investigated in an osteoblast-preosteoclast co-culture system. Serial doses of sucrose were applied as a mechanical force. These hyperosmotic stimuli significantly evoked a reduced number of 1alpha,25(OH)2D3-induced tartrate-resistant acid phosphatase-positive multinucleated cells and 1alpha,25(OH)2D3-induced bone-resorbing pit area in a co-culture system. In osteoblastic cells, receptor activator of nuclear factor kappaB ligand (RANKL) and Runx2 expressions were down-regulated in response to 1alpha,25(OH)2D3. Knockdown of Runx2 inhibited 1alpha,25(OH)2D3-induced RANKL expression in osteoblastic cells. Finally, the hyperosmotic stimulus induced the overexpression of TonEBP in osteoblastic cells. These results suggest that hyperosmolarity leads to the down-regulation of 1alpha,25(OH)2D3-induced osteoclastogenesis, suppressing Runx2 and RANKL expression due to the TonEBP overexpression in osteoblastic cells.
Bone Remodeling ; Coculture Techniques ; Down-Regulation ; Osteoblasts ; RANK Ligand ; Sucrose

Denosumab, a specific inhibitor of RANK ligand, is a novel therapy for postmenopausal osteoporosis and related disorders. An extensive clinical development program has evaluated the clinical efficacy and safety of denosumab with several thousand patients being followed for up to 10 years. Combined with more than six years of postmarketing experience, these studies provide substantial confidence that denosumab is a convenient and appropriate treatment for patients, including Asians, at high risk for fracture. This review will summarize the clinical development of denosumab and lessons learned since its approval for clinical use in 2010.
Asian Continental Ancestry Group ; Denosumab* ; Female ; Humans ; Osteoporosis* ; Osteoporosis, Postmenopausal ; RANK Ligand ; Treatment Outcome

Receptor activator of nuclear factor-κB ligand (RANKL) is an osteoblast/stromal cell-derived essential factor for osteoclastogenesis. During endochondral bone formation, hypertrophic chondrocytes calcify cartilage matrix that is subsequently resorbed by osteoclasts in order to be replaced by new bone. Hypoxia-induced upregulation of RANKL expression has been previously demonstrated in an in vitro system using osteoblasts; however, the involved mechanism remains unclear in chondrocytes. In the present study, we investigated whether hypoxia regulates RANKL expression in ATDC5 cells, a murine chondrogenic cell line, and hypoxia-inducible factor-1α (HIF-1α) mediates hypoxia-induced RANKL expression by transactivating the RANKL promoter. The expression levels of RANKL mRNA and protein, as well as HIF-1α protein, were significantly increased in ATDC5 cells under hypoxic condition. Constitutively active HIF-1α alone significantly increased the levels of RANKL expression under normoxic conditions, whereas dominant negative HIF-1α reduced hypoxia-induced RANKL expression. HIF-1α increased RANKL promoter reporter activity in a HIF-1α binding element-dependent manner in ATDC5 cells. Hypoxia-induced RANKL levels were much higher in differentiated ATDC5 cells, as compared to proliferating ATDC5 cells. These results suggested that under hypoxic conditions, HIF-1α mediates induction of RANKL expression in chondrocytes; in addition, hypoxia plays a role in osteoclastogenesis during endochondral bone formation, at least in part, through the induction of RANKL expression in hypertrophic chondrocytes.
Anoxia* ; Cartilage ; Cell Line ; Chondrocytes* ; Osteoblasts ; Osteoclasts ; Osteogenesis ; RANK Ligand ; RNA, Messenger ; Up-Regulation

Osteocytes may function as mechanotransducers by regulating local osteoclastogenesis. Reduced availability of oxygen, i.e. hypoxia, could occur during disuse, bone development, and fracture. Receptor activator of nuclear factor-kappaB ligand (RANKL) is an osteoblast/stromal cell derived essential factor for osteoclastogenesis. The hypoxia induced osteoclastogenesis via increased RANKL expression in osteoblasts was demonstrated. Hypoxic regulation of gene expression generally involves activation of the hypoxia-inducible factor (HIF) transcription pathway. In the present study, we investigated whether hypoxia regulates RANKL expression in murine osteocytes and HIF-1alpha mediates hypoxia-induced RANKL expression by transactivating RANKL promoter, to elucidate the role of osteocyte in osteoclastogenesis in the context of hypoxic condition. The expression levels of RANKL mRNA and protein, as well as hypoxia inducible factor-1alpha (HIF-1alpha) protein, were significantly increased in hypoxic condition in MLO-Y4s. Constitutively active HIF-1alpha alone significantly increased the levels of RANKL expression in MLO-Y4s under normoxic conditions, whereas dominant negative HIF-1alpha blocked hypoxia-induced RANKL expression. To further explore to find if HIF-1alpha directly regulates RANKL transcription, a luciferase reporter assay was conducted. Hypoxia significantly increased RANKL promoter activity, whereas mutations of putative HIF-1alpha binding elements in RANKL promoter prevented this hypoxia-induced RANKL promoter activity in MLO-Y4s. These results suggest that HIF-1alpha mediates hypoxia-induced up-regulation of RANKL expression, and that in osteocytes of mechanically unloaded bone, hypoxia enhances osteoclastogenesis, at least in part, via an increased RANKL expression in osteocytes.
Anoxia* ; Bone Development ; Gene Expression Regulation ; Luciferases ; Osteoblasts ; Osteocytes* ; Oxygen ; RANK Ligand* ; RNA, Messenger ; Up-Regulation

INTRODUCTION: Diabetes mellitus, as a major health problem for the elderly has been shown to alter the properties of the bone and impair bone healing around a titanium implant in both humans and animals. The aim of this study was to examine the effect of adipose-derived stem cells on the healing process around a titanium implant in streptozotocin-induced diabetic rats. MATERIALS AND METHODS: Thirteen rats were divided into two groups: adipose-derived stem cells injected group and a control group. A titanium screw implant (diameter: 2.0 mm, length: 3.5 mm) was placed into both tibia of 13 rats: 13 right tibia as the control group and 13 left tibia as the experimental group. The rats were sacrificed at different intervals (1, 2, and 4 weeks) after implantation for histopathology observations and immunohistochemistric analysis. RESULTS: The histopathological findings revealed earlier new formed bone in the experimental group than the control group. In particular, at 1 week after implantation, the experimental group showed more newly formed bone and collagen around the implant than the control group. In immunohistochemistric analysis, osteoprotegerin (OPG) expression in the experimental group increased early compared to that of the control group until 2 weeks after implantation. However, after 2 weeks, OPG expression in the experimental group was similar to OPG expression in the control group. The receptor activator of nuclear factor kappaB ligand (RANKL) expression in the experimental group increased early compared to that of the control group, and then decreased at 2 weeks. After 2 weeks, the level of RANKL expression was similar in both groups. CONCLUSION: These results suggest that adipose-derived stem cells in implantation can promote bone healing around titanium, particularly in diabetes mellitus induced animals.
Aged ; Animals ; Collagen ; Dental Implants ; Diabetes Mellitus ; Humans ; Osteoprotegerin ; RANK Ligand ; Rats ; Stem Cells ; Tibia ; Titanium

OBJECTIVETo study the effect of high glucose and mannitol (osmotic control) on receptor activator of nuclear factor kappa B ligand (RANKL)-induced osteoclastogenesis and Notch2 expression using bone marrow macrophages (BMMs) from mice. Furthermore, the effect of Notch2 activation on RANKL-induced osteoclastogenesis with high glucose concentration was explored.

METHODSPreosteoclasts were cultured and exposed to sustained high glucose (0, 5, 10, 20, 40 mmol x L(-1)) levels to mimic diabetic conditions. Osteoclast formation was analyzed using tartrate resistant acid phosphatase (TRAP) assay. Expression of Notch2 gene was analyzed using real-time polymerase chain reaction. Constitutively over-expressed active Notch2, via stable transfection of exogenous ICN2 (intracellular fragment of Notch2) in preosteoclasts and the effect of Notch2 over expression on osteoclastogenesis was analyzed using Western blotting and TRAP staining.

RESULTSThe osteoclast number with 20 mmol x L(-1) glucose (110.3 +/- 6.8) and 40 mmol x L(1) glucose (72.0 +/- 8.0) was significantly less than the group with 20mmol x L(-1) mannitol (152.7 +/- 7.0) and 40 mmol x L(-1) mannitol (157.0 +/- 12.5). The relative gene expression of Notch2 with 20 mmol x L(-1) glucose (1.65 +/- 0.23) and 40 mmol x L(-1) glucose (1.10 +/- 0.11) was significantly less than the group with 20 mmol x L(-1) mannitol (2.82 +/- 0.28) and 40 mmol x L(-1) mannitol (2.42 +/- 0.27) (P < 0.05). The osteoclast number after Notch2 activation (ICN2-OE) with 20 mmol x L(-1) glucose (206.7+/- 7.8) and 40 mmol x L(-1) glucose (178.3 +/- 11.5) was significantly more than the control group (EMPTY) (102.3 +/- 8.7 and 76.0 +/- 10.1 respectively) ( P < 0.05).

CONCLUSIONNotch2 signaling activation may promote osteoclastogenesis under high glucose concentration.

Animals ; Blotting, Western ; Cell Differentiation ; Cells, Cultured ; Glucose ; In Vitro Techniques ; Macrophages ; Mice ; Osteoclasts ; RANK Ligand ; Transfection

OBJECTIVETo investigate the expression of receptor activator of nuclear factor kappaB ligand (RANKL) and osteoprotegerin (OPG) in periapical cyst and periapical granuloma by comparison with the expression in the normal periodontal tissue as control, and to identify their functional mechanism in the bone destruction of periapical cyst and granuloma.

METHODS20 periapical cyst tissues (cyst group), 20 periapical granuloma tissues (granuloma group), and 20 normal periodontal tissues (control group) were collected respectively. Immunohistochemical technology was performed to detect the expression of RANKL and OPG in above three groups.

RESULTSIn cyst group, granuloma group and control group, the expression of RANKL were 75.00 +/- 7.54, 68.40 +/- 6.74 and 29.40 +/- 2.46, respectively. The expression of OPG were 38.10 +/- 7.09, 47.65 +/- 13.85 and 58.60 +/- 5.88, respectively. The differences among the three groups were statistically significant (P<0.05). RANKL and OPG in cysts group were negatively correlated (r=-0.56, P=0.01) and were not correlated with granuloma and control group (P>0.05).

CONCLUSIONRANKL and OPG play roles in the bone absorption of periapical disease. In periapical disease, abnormal expression of RANKL and OPG are detected, RANKL significantly increase, OPG decrease, bone absorption accelerate and osteolytic lesion are observed. In periapical cyst, the bone absorption is more active compared with periapical granuloma.

Humans ; Male ; Osteoprotegerin ; Periapical Granuloma ; RANK Ligand ; Radicular Cyst ; Receptor Activator of Nuclear Factor-kappa B

Aseptic loosening is one of the most frequent long-term complications after joint replacement,which limits the service life of prostheses. A lot of studies have been focused on interface membranes around prostheses recently. In interface membranes, there are plenty of macrophagocytes and desmocytes,which play vital roles in osteolysis. This study gave a review of interface membrane including its formation, cellulosity, osteolysis factor, immunity reaction and turnover. The advances of interface membranes will help us to comprehend the pathogenesy and treatment of the aseptic loosening.
Humans ; Joint Prosthesis ; adverse effects ; Membranes ; Osteolysis ; RANK Ligand ; physiology ; T-Lymphocytes ; immunology

The physiological reconstruction of bone is strictly dependent on bone resorption. Bone resorption is believed to be a complicated molecular reaction process that occurs in the microcircumstance of bone tissue. A lot of enzymes and factors take part in this process, yet there are not enough data with reference to the activation of osteoclast, resorption of bone matrix, regulation of bone resorption. In this paper we review the importance of matrix metalloproteinases (MMPs) in transfer of osteoclast and degradation of bone matrix, and the function of receptor activator of NF-kappaB-ligand (RANKL) and osteoprotegerin (OPG) in regulation of bone resorption.
Bone Resorption ; Humans ; Matrix Metalloproteinases ; metabolism ; Osteoclasts ; physiology ; Osteoprotegerin ; physiology ; RANK Ligand ; physiology