• Molecules and Cells
• /
• 제39권4호
• /
• pp.316-321
• /
• 2016

The receptor activator of nuclear factor ${\kappa}B$ (RANK) and its ligand RANKL are key regulators of osteoclastogenesis and well-recognized targets in developing treatments for bone disorders associated with excessive bone resorption, such as osteoporosis. Our previous work on the structure of the RANK-RANKL complex revealed that Loop3 of RANK, specifically the non-canonical disulfide bond at the tip, performs a crucial role in specific recognition of RANKL. It also demonstrated that peptide mimics of Loop3 were capable of interfering with the function of RANKL in osteoclastogenesis. Here, we reported the structure-based design of a smaller peptide with enhanced inhibitory efficiency. The kinetic analysis and osteoclast differentiation assay showed that in addition to the sharp turn induced by the disulfide bond, two consecutive arginine residues were also important for binding to RANKL and inhibiting osteoclastogenesis. Docking and molecular dynamics simulations proposed the binding mode of the peptide to the RANKL trimer, showing that the arginine residues provide electrostatic interactions with RANKL and contribute to stabilizing the complex. These findings provided useful information for the rational design of therapeutics for bone diseases associated with RANK/RANKL function.

• International Journal of Oral Biology
• /
• 제30권1호
• /
• pp.23-30
• /
• 2005

Bone remodeling is a process controlled by the action of two major bone cells; the bone forming osteoblast and the bone resorbing osteoclast. In the process of osteoclastogenesis, stromal cells and osteoblast produce RANKL, OPG, and M-CSF, which in turn regulate the osteoclastogenesis. During the bone resorption by activated osteoclasts, extracellular $Ca^{2+}/{PO_4}^{2-}$ concentration and degraded organic materials goes up, providing the hypertonic microenvironment. In this study, we tested the effects of hypertonicity due to the degraded organic materials on osteoclastogenesis in co-culture system. It was examined the cellular response of osteoblastic cell in terms of osteoclastogenesis by applying the sucrose, and mannitol, as a substitute of degraded organic materials to co-culture system. Apart from the sucrose, mannitol, and NaCl was tested to be compared to the effect of organic osmotic particles. The addition of sucrose and mannitol (25, 50, 100, 150, or 200 mM) to co-culture medium inhibited the number of tartrate-resistant acid phosphatase (TRAP) positive multinucleated cells induced by 10 nM $1{\alpha},25(OH)_2vitaminD_3$ ($1{\alpha},25(OH)_2D_3$). However, NaCl did exert harmful effect upon the cells in this co-culture system, which is attributed to DNA damage in high concentration of NaCl. To further investigate the mechanism by which hypertonicity inhibits $1{\alpha},25(OH)_2D_3$-induced osteoclastogenesis, the mRNA expressions of receptor activator of nuclear factor (NF)-kB ligand (RANKL) and osteoprotegerin (OPG) were monitored by RT-PCR. In the presence of sucrose (50 mM), RANKL mRNA expression was decreased in a dose-dependent manner, while the change in OPG and M-CSF mRNA were not occurred in significantly. The RANKL mRNA expression was inhibited for 48 hours in the presence of sucrose (50 mM), but such a decrement recovered after 72 hours. However, there were no considerable changes in the expression of OPG and M-CSF mRNA. Conclusively, these findings strongly suggest that hypertonic stress down-regulates $1{\alpha},25(OH)_2D_3$-induced osteoclastogenesis via RANKL signal pathway in osteoblastic cell, and may playa pivotal role as a regulator that modulates osteoclastogenesis.

• Journal of Periodontal and Implant Science
• /
• 제30권4호
• /
• pp.747-757
• /
• 2000

Cyclosporin A(CsA) is an immunosuppressive agent widely used for preventing graft rejecting response in organ transplantation. The basic properties of CsA to osteoblast has not been well known yet. A better understanding of the mechanisms of CsA function on bone could provide valuable information regarding basic properties of bone remodeling, pharmacotherapeutic intervention in metabolic bone disease, and the consequences of immunosuppression in bone physiology. The purpose of this study was to investigate the effect of CsA on osteoblast by evaluating parameters of proliferation, collagen synthetic activity, alkaline phosphatase activity, and ALP mRNA expression in mouse calvarial cell. 1. CsA ($3{\mu}g/m{\ell}$) treated mouse calvarial cell showed statistically significant increase in cell proliferation.(P<0.05) 2. CsA($1,\; 3{\mu}g/m{\ell}$) treated MC3T3 cell line showed statistically significant increase in cell proliferation. 3. The amount of collagen of CsA($3{\mu}g/m{\ell}$) treated mouse calvarial cell was decreased statistically significantly. 4. Alkaline phosphatase activity was increased statistically significantly in CsA treated group($1{\mu}g/m{\ell}$). 5. mRNA expression of ALP was increased in CsA treated group These results suggest that CsA could affect bone remodeling by modulating proliferation & differentiation of osteoblast.

• International Journal of Oral Biology
• /
• 제44권4호
• /
• pp.125-129
• /
• 2019

Osteocalcin is the most abundant non-collagenous protein produced in bone. It has traditionally been regarded as a marker of bone turnover and is thought to act in the bone matrix to regulate mineralization. However, emerging knowledge regarding osteocalcin has expanded to include functions in energy metabolism, fertilization, and regulation of cognition. Fully carboxylated osteocalcin binds to hydroxyapatite, thereby modulating bone turnover, whereas undercarboxylated osteocalcin in the circulation binds to osteocalcin-sensing receptors and acts as a hormone that affects multiple physiological aspects. In this review, we summarize the current knowledge regarding the hormonal actions of osteocalcin in various organs and potential cellular downstream signaling pathway that may be involved.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• 제43권2호
• /
• pp.63-69
• /
• 2017

Nuclear factor I-C (NFI-C) plays a pivotal role in various cellular processes such as odontoblast and osteoblast differentiation. Nfic-deficient mice showed abnormal tooth and bone formation. The transplantation of Nfic-expressing mouse bone marrow stromal cells rescued the impaired bone formation in $Nfic^{-/-}$ mice. Studies suggest that NFI-C regulate osteogenesis and dentinogenesis in concert with several factors including transforming growth factor-${\beta}1$, $Kr{\ddot{u}}ppel$-like factor 4, and ${\beta}$-catenin. This review will focus on the function of NFI-C during tooth and bone formation and on the relevant pathways that involve NFI-C.

• Journal of Periodontal and Implant Science
• /
• 제36권1호
• /
• pp.1-14
• /
• 2006

The purpose of the present study was to evaluate the histologic results of bone cavities that were surgically created in the calvaria of rabbit and filled with $HA/{\beta}-TCP$ composite powders, which had been developed in Korea (Dentium, Korea). Ten young adult rabbits were used. Four defects were surgically produced in calvaria of each rabbit. Each rabbit was anesthetized with Ketamine-HCI (5 mg/kg, Yuhan Cor. Korea) and Xylazine-HCI (1.5 ml/kg, Yuhan Cor. Korea)). An incision was made to the bony cranium and the periosteum was reflected. Using a trephine bur (external diameter: 8 mm, 3i, USA), 4 'through-and-through' bone defects were created with copious irrigation, and classified into 4 groups: control group: no graft materials, experimental group I: normal saline + graft materials: experimental group II: venous blood + graft materials: experimental group III: graft materials only. The defects were randomly filled with graft materials. The defects were closed with resorbable suture material. At the end of the surgical procedure, all animals received a single intramuscular injection of antibiotics Gentamicin (0.1 mg/kg, Dae Sung Microb. Korea). Rabbits were sacrificed with phentobarbital (100 mg/kg) intravenously at 1-, 2-, 4-, 6- and 8-week after. Specimens were treated with hydrochloric acid decalcifying solution (Fisher Scientific, Tustin, CA) and sectioned by bisecting the 8 mm diameter defects. The histologic specimens were prepared in the general method with H & E staining at 6 ${\mu}m$ in thickness. The results were as follows; 1. New bone formation showed from after 2-week of surgery in defect area. As time lapsed, lots of new bone formation and mature bones showed. 2. Histologically, degree of new bone formation could not be discerned among the experimental groups. But, for experimental group II, lots of cells gathered around graft materials after 1-week of surgery, new bone formed slightly faster and than the others at 1-week after. For experimental group I, a few inflammatory finding showed around graft material at after 1-week and after 2-week of surgery. 3. No bone formation did show for control group. Based on histologic results, the new $HA/{\beta}-TCP$ composite powders appeared to act as a scaffolding material for regeneration of osseous defects.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• 제27권1호
• /
• pp.15-24
• /
• 2001

The purpose of this study is to evaluate the tissue response in applying of various bone substitutes included toothash-plaster mixture, resorbable hydroxylapatite (HA) and demineralized freeze-dried bone and to show the clinical usefulness of toothash-plaster mixture for the repair of craniomaxillofacial bone defect. For this experiment, 100 Sprague-Dawley rats weighing 200gm or more were used. There were four experimental groups: group I, toothash-plaster mixture; group II, demineralized freeze-dried bone; group III, resorbable HA; and group IV, control group. A full thickness, round bone defect measuring 10mm in diameter was created in the midcranium, and the substitutes cited above were embedded in the experimental rats based on their group assignment. Blood clot was filled in the rats assigned to the control group. Experimental rats were sacrificed on the 1st, 3rd, 5th, 8th, 12th and 24th week after implantation and stained with the hematoxylineosin, Masson's Trichrome, using Van Gieson's stain method, and were examined under light microscope. The results were as follows: 1. In all the groups, prominent inflammatory reaction and the infiltration of multinucleated giant cells were noted during the early stage. Gradual healing decreased this reaction. 2. Among the rats in the experimental group II, which were given demineralized freeze-dried bone implants, active formation of new bone traveculae manifested. Chondroid tissues appeared, and it was suggested that the defect was filled with newly formed bone by virtue of osteoinductive activity. On the 12th week after the experiments, most of the defect was filled with newly formed bone trabeculae. 3. In experimental groups I and III, it was noted that HA manifested a healing process similar to that characterized by the toothash-plaster mixture, but inflammatory reaction was more prominent in experimental group I. Active osteoblasts were observed along the periphery of osteoid tissues, while newly formed bone trabeculae appeared adjacent to the implanted materials three weeks later. Formation increased to the extent that newly formed bone trabeculae fused directly with the host bone. Increase in new bone ingrowth into the filling materials was revealed by both experimental groups. 4. In the control group, new bone formation adjacent to the host bone was observed, but most of the defect was filled with mature connective tissue 24 weeks after the experiments.

• BMB Reports
• /
• 제57권7호
• /
• pp.330-335
• /
• 2024

Arginine methylation, which is catalyzed by protein arginine methyltransferases (Prmts), is known to play a key role in various biological processes. However, the function of Prmts in osteogenic differentiation of mesenchymal stem cells (MSCs) has not been clearly understood. In the current study, we attempted to elucidate a positive role of Prmt7 in osteogenic differentiation. Prmt7-depleted C3H/10T1/2 cells or bone marrow mesenchymal stem cells (BMSCs) showed the attenuated expression of osteogenic specific genes and Alizarin red staining compared to the wild-type cells. Furthermore, we found that Prmt7 deficiency reduced the activation of bone morphogenetic protein (BMP) signaling cascade, which is essential for the regulation of cell fate commitment and osteogenesis. Taken together, our data indicate that Prmt7 plays important regulatory roles in osteogenic differentiation.

• International Journal of Oral Biology
• /
• 제45권3호
• /
• pp.92-98
• /
• 2020

Periodontitis is a bacteria-induced inflammatory disease associated with alveolar bone loss. Osteoclast is a macrophage-lineage cell that exhibits phagocytic activity; however, osteoclast phagocytic activity has not been demonstrated under pathological conditions. Diabetes is a pathological condition that exacerbates alveolar bone loss via periodontitis; therefore, we examined phagocytic osteoclasts in diabetic rats that had periodontitis. The rats were divided into the control (C), periodontitis (P), and diabetes with periodontitis (DP) groups. Diabetes and periodontitis were induced by streptozotocin injection and ligature of the mandibular first molars, respectively. On days 3 and 20 after the ligature, the rats were sacrificed, and osteoclasts containing inclusions were quantified by tartrate-resistant acid phosphatase staining. On day 3, there were more osteoclasts containing inclusions in the DP group than in the C group. Among inclusions, osteocyte-like cells and dense bodies were more frequently observed in the DP group than in the C group. Cytoplasm-like structures were elevated more in the DP group than in the C and P groups. However, no differences were observed on day 20. Interestingly, some osteoclasts were in contact with the osteocytes within the exposed lacunae and contained several inclusions within a large vacuole. Thus, the elevation of phagocytic osteoclasts in rats with diabetes and periodontitis provides insight into the role of osteoclast phagocytic activity under pathological conditions.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• 제26권5호
• /
• pp.527-532
• /
• 2000

A review of the literature, provided by a MEDLINE search from 1980 through June 1999, was performed. This study was screened that 649 patients received 679 sinus lift grafts in which 2056 implants were placed. The types of grafts in sinus augmentation were autogenous bone, corticocancellous block bone, allogenic bone, and a variety of alloplastic materials. Results of these grafts are presented. The most frequent complications was the infection of maxillary sinus. Long-term follow-up is necessary to advance the sinus elevation and to support posterior maxillary restorations.