• International Journal of Oral Biology
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• 제33권4호
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• pp.179-186
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• 2008

Several lines of evidence suggest that osteocytes play a critical role in bone remodeling. Both healthy and apoptotic osteocytes can send signals to other bone surface cells such as osteoblasts, osteoclasts, osteoclast precursors, and bone lining cells through canalicular networks. Osteocytes responding to mechanical strain may also send signals to other cells. To determine the role for osteocytes an mechanical strain in bone remodeling, we examined the effects of fluid flow shear stress on osteoclast precursor cell and osteoblast proliferation and recruitment induced by osteocytes. In addition, the effects of fluid flow shear stress on osteocyte M-CSF, RANKL, and OPG mRNA expression were also examined. MLO-Y4 cells were used as an in vitro model for osteocytes, RAW 264.7 cells and MOCP-5 cells as osteoclast precursors, and 2T3 cells as osteoblasts. MLO-Y4 cells conditioned medium (Y4-CM) was collected after 24h culture. For fluid flow experiments, MLO-Y4 cells were exposed to 2h of pulsatile fluid flow (PFF) at 2, 4, 8, $16{\pm}0.6\;dynes/cm^2$ using the Flexcell $Streamer^{TM}$ system. For proliferation assays, MOCP-5, RAW 264.7, and 2T3 cells were cultured with control media or 10-100% Y4 CM. Cells were cultured for 3d, and then cells were counted. RAW 264.7 and 2T3 cell migration was assayed using transwells with control media or 10-100% Y4-CM. M-CSF, RANKL and OPG in MLO-Y4 mRNA expression was determined by semiquantitative RT-PCR. Y4-CM increased osteoclast precursor proliferation and migration, but decreased 2T3 cell proliferation and migration. CM from MLO-Y4 cells exposed to PFF caused decreased RAW 267.4 cell proliferation and migration and 2T3 migration compared to control Y4-CM. However, Y4-CM from cells exposed to PFF had no effect on 2T3 osteoblastic cell proliferation. PFF decreased RNAKL mRNA and increased OPG mRNA in MLO-Y4 cells compared to control(without PFF). PFF had no effect on M-CSF mRNA expression in MLO-Y4 cells. These results suggest that osteocytes can regulate bone remodeling by communication with osteoclast precursors and osteoblasts and that osteocytes can communicate mechanical signals to other cells.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제20권3호
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• pp.217-227
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• 1998

Calcium sulfate(plaster of Paris) has been used in dental and orthopedic surgery for about 100 years. It is well known that the plaster is bioresorbable, biocompatible, defect conformable and moldable. The purpose of this study is to evaluate two effects of calcium sulfate on bone regeneration, that is, the effects of graft materials and barrier for bone regeneration. Cortical bone defects were formed for recipient site on the femurs of 19 Sprague-Dawley rats. The autogenous particulated bone and calcium sulfate were grafted to the defects. Calcium sulfate paste, $Gore-Tex^R$ membrane(W.L. GORE & ASSOCIATES LTD., U.S.A.) and rubber sheet were used for the shielding materials. The results were as follows : 1. Calcium sulfate that had been grafted in the cortical bone defect was almost resorbed before bone remodeling, resultantly had little effect on bone regeneration. 2. Resoption process of calcium sulfate grafted on the bone grafting area tends to be accelerated, as being divided into numerous small particles progressively. Under the situation where the calcium sulfate was protected, with the coverage of fascia, $Gore-Tex^R$ membrane or rubber sheet, new bone formation was confirmed with presence of calcium sulfate particles over 6 weeks after grafting. 3. In the case of calcium sulfate covered with membrane, distinct bone formation was observed on the marrow space of femur adjacent to the plaster mass. 4. Rubber shielded plaster group revealed new bone trabeculae under the rubber sheet, but it showed ischemic degeneration of superficial cortical bone.

• Journal of Periodontal and Implant Science
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• 제45권2호
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• pp.62-68
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• 2015

Purpose: The goal of this study was to investigate the histomorphometric characteristics of the healing process of microcracks in the cortical bone after the installation of mini-implants (MIs). Methods: Self-drilling MIs were inserted into the tibial diaphysis of twelve adult male New Zealand rabbits. Four MIs per rabbit were placed randomly. The animals were divided into four groups according to the length of the healing period: group A was sacrificed immediately, group B was sacrificed after one week, group C was sacrificed after two weeks, and group D was sacrificed after four weeks. Cortical bone thickness was measured using micro-computed tomography, and histomorphometric analyses of the cumulative length of the microcracks (CLCr) and the total number of microcracks (NCr) were performed using hematoxylin and eosin staining. Results: The microcracks were radially and concentrically aligned in the peri-MI bone. The CLCr decreased significantly one week after the surgery, mainly due to healing of the concentrically aligned microcracks. The CLCr showed another significant decrease from two weeks after the surgery to four weeks after the surgery, mainly reflecting healing of the radially aligned microcracks. A statistically significant decrease in the NCr occurred as the microcracks healed from zero weeks to two weeks. However, no significant difference in the NCr was found between groups C and D. Conclusions: In order to improve the primary stability of MIs, delayed loading and a healing period of a certain length are recommended to ensure the optimal healing of microcracks and bone remodeling.

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

• Advances in biomechanics and applications
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• 제1권3호
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• pp.211-225
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• 2014

The usual assumption that the increase of fractures in aging bone is due entirely to lower bone density is taken back with respect to the possibility that aging bone fractures result from a loss of stability, or buckling, in the structure of the bone lattice. Buckling is an instability mode that becomes likely in end-loaded structures when they become too slender and lose lateral support. The relative importance of bone density and architecture in etiology bone fractures are poorly understood and the need for improved mechanistic understanding of bone failure is at the core of important clinical problems such as osteoporosis, as well as basic biological issues such as bone formation and adaptation. These observations motivated the present work in which simplified adaptive-beam buckling model is formulated within the context of the adaptive elasticity (Cowin and Hegedus 1976, Hegedus and Cowin 1976). Our results indicate that bone loss activation process leads systematically to the apparition of new elastic instabilities that can conduct to bone-buckling mechanism of fracture.

• BMB Reports
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• 제43권8호
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• pp.524-529
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• 2010

Glucocorticoids (GCs) are useful drugs for the treatment of various diseases, but their use for prolonged periods can cause severe side effects such as osteoporosis. GCs have a direct effect on bone cells, where they can arrest bone formation, in part through the inhibition of osteoblast. On the other hand, GCs potently suppress osteoclast resorptive activity by disrupting its cytoskeleton based on the inhibition of RhoA, Rac and Vav3 in response to macrophage colony-stimulating factor. GCs also interfere with microtubule distribution and stability, which are critical for cytoskeletal organization in osteoclasts. Thus, GCs inhibit microtubule-dependent cytoskeletal organization in osteoclasts, which, in the context of bone remodeling, further dampens bone formation.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.1038-1041
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• 2004

In this study, developed a micro-level experimental setup to measure pore pressure and poroelastic modulus in various strain and strain rate about a stress in micro-structure of bone tissue. It is essential device in the development of the model to analysis the interstitial bone fluid flow of the lacuno-canalicular system to be known that would effect on the bone remodeling. The constitution of the experimental setup is as follows, microscopic image processing system; actuator control unit; load measurement system. A pilot study was used an artificial chemical wood to have similar poroelastic property of bone matrix and conducted to validate the suitability of the measurement system.

• Childhood Kidney Diseases
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• 제10권1호
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• pp.1-7
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• 2006

Osteopontin (OPN) is a glycosylated phosphoprotein which mediates cell adhesion and migration, and is produced by bone, macrophages, endothelial cells, and epithelial cells. The many regulatory functions of OPN include bone remodeling, tumor invasion, wound repair, and promotion of cell survival. It is produced by renal tubular epithelial cells, and expression is upregulated in glomerulonephritis, hypertension, ischemic acute renal failure, renal ablation, and UUO. In this review, we discuss about osteopontin in general aspect, expression, role on the development and pathologic condition of neonatal kidney.

• 대한치과교정학회지
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• 제41권1호
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• pp.6-15
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• 2011

마이크로 임플란트 시술의 중요한 위험요인 중 하나로 치근접촉 문제가 있으나, 관련 연구는 결과 분석에 치중되어 있고, 치근접촉이 마이크로 임플란트 안정성 상실로 이어지는 기전에 대한 연구는 아직 미흡한 것으로 보인다. 이에, 본 연구에서는 생역학적 측면에서 그 영향을 분석하였다. Absoanchor 마이크로 임플란트(SH1312-7, Dentos Inc., Daegu, Korea) 첨부가 치근에 접촉되어 있을 때, 저작압 전달에 의한 마이크로 임플란트 변위가 인접골에 가하는 압축응력을 축대칭 유한요소모델을 사용하여 계산하였다. 요소별 응력이 해면골의 최대압축강도나, 치밀골의 비정상 골개조 임계능력을 넘을 경우 해당 요소를 순차적으로 해석모델에서 제거하며 실행한 6단계해석의 결과, 마이크로 임플란트에 인접한 해면골의 전체적인 파절과 과부하에 따른 치밀골의 비정상 골개조가 임플란트 지지력 상실에 주 요인이 될 것으로 평가되었다. 치밀골의 과부하 영역은 초기에는 치밀골판의 하부에 존재하였으나 상부로 확장되었고, 응력 재분포로 인한 감소효과 없이 양성 되먹임(positive feedback)으로 결국 치밀골 전 두께로 확대됨을 관찰하였다. 본 연구를 통해 치근접촉된 마이크로 임플란트가 인접골을 훼손시켜 안정성 상실로 이어지는 과정을 모사할 수 있었으며, 이로부터 치근접촉에 따른 마이크로 임플란트의 불량한 예후에 대한 생역학적 측면의 원인을 파악할 수 있었다.

• BMB Reports
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• 제43권8호
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• pp.513-523
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• 2010

Cytokines that bind to and signal through the gp130 co-receptor subunit include interleukin (IL)-6, IL-11, oncostatin M (OSM), leukemia inhibitory factor (LIF), cardiotrophin-1 (CT-1), and ciliary neutrophic factor (CNTF). Apart from contributing to inflammation, gp130 signalling cytokines also function in the maintenance of bone homeostasis. Expression of each of these cytokines and their ligand-specific receptors is observed in bone and joint cells, and bone-active hormones and inflammatory cytokines regulate their expression. gp130 signalling cytokines have been shown to regulate the differentiation and activity of osteoblasts, osteoclasts and chondrocytes. Furthermore, cytokine and receptor specific gene-knockout mouse models have identified distinct roles for each of these cytokines in regulating bone resorption, bone formation and bone growth. This review will discuss the current models of paracrine and endocrine actions of gp130-signalling cytokines in bone remodelling and growth, as well as their impact in pathologic bone remodelling evident in periodontal disease, rheumatoid arthritis, spondylarthropathies and osteoarthritis.