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‣ Bril: A novel bone-specific modulator of mineralization

MOFFATT, Pierre; GAUMOND, Marie-Helene; SALOIS, Patrick; SELLIN, Karine; BESSETTE, Marie-Claude; GODIN, Eric; OLIVEIRA, Paulo Tambasco de; ATKINS, Gerald J.; NANCI, Antonio; THOMAS, Gethin
Fonte: AMER SOC BONE & MINERAL RES Publicador: AMER SOC BONE & MINERAL RES
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
442.6072%
In the course of attempting to define the bone ""secretome"" using a signal-trap screening approach, we identified a gene encoding a small membrane protein novel to osteoblasts. Although previously identified in silico as ifitm5, no localization or functional studies had been undertaken on this gene. We characterized the expression patterns and localization of this gene in vitro and in vivo and assessed its role in matrix mineralization in vitro. The bone specificity and shown role in mineralization led us to rename the gene bone restricted ifitm-like protein (Bril). Bril encodes a 14.8-kDa 1.34 arnino acid protein with two transmembrane domains. Northern blot analysis showed bone-specific expression with no expression in other embryonic or adult tissues. In situ hybridization and immunohistochemistry in mouse embryos showed expression localized on the developing bone. Screening of cell lines showed Bril expression to be highest in osteoblasts, associated with the onset of matrix maturation/mineralization, suggesting a role in bone formation. Functional evidence of a role in mineralization was shown by adenovirus-mediated Brit overexpression and lentivirus-mediated Bril shRNA knockdown in vitro. Elevated Bril resulted in dose-dependent increases in mineralization in UMR106 and rat primary osteoblasts. Conversely...

‣ Quantificação do potencial osteogênico do osso autógeno + células osteoblásticas implantados em defeito ósseo no rato tratado com cafeína; Quantification of the osteogenic potential of autogenous bone + osteoblastic cells implanted in bone defect in rats treated with caffeine

Macedo, Rander Moreira
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 25/09/2009 Português
Relevância na Pesquisa
345.24438%
Estudos sugerem que a cafeína atua sobre o osso promovendo aumento da excreção de cálcio e inibição da proliferação de osteoblastos, aumentando o risco de fraturas, osteoporose e doença periodontal. Os efeitos da cafeína sobre o tecido ósseo dificultam a aplicação de implantes dentários devido à presença de grandes defeitos ósseos ou volume ósseo insuficiente. Vários métodos são propostos para a regeneração de defeitos ósseos, entre eles, o uso de diferentes tipos de enxertos, os quais demonstram capacidade em promover a formação óssea A despeito das desvantagens, o osso autógeno ainda é considerado a referência padrão como enxerto ósseo, devido ao seu potencial osteogênico, osteoindutor e osteocondutor. A engenharia tecidual óssea tem sido utilizada como uma estratégia para a regeneração óssea. As células tronco mesenquimais são consideradas multipotentes e podem replicar como células indiferenciadas, possuindo potencial para se diferenciarem em linhagens de osso, cartilagem, gordura e cartilagem. O objetivo deste estudo foi quantificar histomorfometricamente a reparação óssea pelo enxerto de uma associação de osso autógeno obtido da calota craniana e células osteoblásticas em defeitos ósseos produzidos pela extração dental de ratos submetidos à administração diária de cafeína. Os animais foram divididos em: Controle (c)...

‣ Avaliação da osteogênese em defeitos ósseos com utilização da engenharia tecidual óssea: uma comparação entre osso autógeno, substituto ósseo e células-tronco mesenquimais; Evaluation of osteogenesis in bone defects using bone tissue engineered: a comparison among autogenous bone, bone substitute and mesenchymal stem cells

Prata, Celina Antonio
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 30/08/2010 Português
Relevância na Pesquisa
346.00066%
O tecido ósseo possui potencial regenerativo e capacidade em restaurar completamente sua estrutura e função original. Há situações em que o organismo não consegue por si só, a reparação desejada dos defeitos ósseos. Vários métodos são propostos para a reparação de defeitos ósseos, entre eles, o uso de diferentes tipos de enxertos os quais demonstram capacidade em promover a formação óssea. Por muitos anos o osso autógeno foi considerado a referência padrão como enxerto ósseo, devido as suas vantagens biológicas e potencial osteogênico. Entretanto, por este material apresentar limitações, estimulou-se a pesquisa para um substituto ósseo ideal para o enxerto ósseo autogênico. O advento de um novo biomaterial xenogênico, como o osso bovino, que se comporta como promotor de reparação e é portador de fatores de indução óssea parece representar o futuro da reconstrução de defeitos ósseos. Mas pelo pequeno potencial de regeneração óssea produzida pelos enxertos alógenos e xenógenos, os pesquisadores tem utilizado a bioengenharia tecidual óssea para reconstrução de defeitos ósseos. Diante destas informações, este estudo teve como objetivo quantificar histomorfometricamente a reparação óssea após o enxerto de uma associação de osso autógeno e/ou osso bovino composto (Gen-Mix) associados a células- tronco mesenquimais em defeitos ósseos produzidos pela extração dental de ratos. 108 ratos foram separados em 6 grupos : Controle (c) - o defeito ósseo foi preenchido só por sangue; Osso autógeno (oa) - o defeito ósseo foi preenchido por sangue e osso autógeno; Gen-Mix (G-mix) o defeito ósseo foi preenchido por osso bovino composto (osso medular e cortical)...

‣ Quantificação do potencial osteogênico in vivo do osso autógeno + células osteoblásticas carreadas por uma biocerâmica composta de hidroxiapatita e fosfato tricálcio-β: Estudo qualitativo e quantitativo em microscopia de luz e eletrônica de varredura; Quantification of the osteogenic potential in vivo of autogenous bone + osteoblastic cells carried by a bioceramic consisting of hydroxyapatite and β-tricalcium phosphate: A qualitative and quantitative study by light and scanning electron microscopy

Macedo, Rander Moreira
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 21/06/2013 Português
Relevância na Pesquisa
345.24438%
Durante e após o processo de reparo alveolar pós-extração, ocorre certa remodelação óssea com reduções dimensionais deste tecido podendo comprometer a terapia em implantodontia. A fim de preservar/reconstruir tal tecido, vários métodos são propostos usando diferentes tipos de biomateriais e técnicas, os quais demonstram capacidade em formar osso. O osso autógeno ainda é considerado a referência padrão como enxerto ósseo, devido ao seu potencial osteogênico, osteoindutor e osteocondutor, mas morbidade relativa a este é conhecida. Por isso algumas biocerâmicas têm sido utilizadas, pois são sintéticas, biocompatíveis e com boas propriedades osteopreenchedoras, mas com baixa osteogenicidade. A engenharia tecidual óssea constituída de células tronco mesenquimais diferenciadas em osteoblastos é uma estratégia para o fornecimento adicional celular ao defeito ósseo em reconstrução. O objetivo deste estudo foi qualificar e quantificar a reparação óssea após o enxerto de uma associação de osso autógeno e células osteoblásticas carreadas por uma biocerâmica em defeitos ósseos produzidos pela extração dentária. Os animais foram divididos de acordo com o material implantado no alvéolo dentário pós-extração em: Controle (c)...

‣ Assessment of axial bone rigidity in rats with metabolic diseases using CT-based structural rigidity analysis

Smith, M. D.; Baldassarri, S.; Anez-Bustillos, L.; Tseng, A.; Entezari, V.; Zurakowski, David; Snyder, Brian Dale; Nazarian, Ara
Fonte: British Editorial Society of Bone and Joint Surgery Publicador: British Editorial Society of Bone and Joint Surgery
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
441.09152%
Objectives: This study aims to assess the correlation of CT-based structural rigidity analysis with mechanically determined axial rigidity in normal and metabolically diseased rat bone. Methods: A total of 30 rats were divided equally into normal, ovariectomized, and partially nephrectomized groups. Cortical and trabecular bone segments from each animal underwent micro-CT to assess their average and minimum axial rigidities using structural rigidity analysis. Following imaging, all specimens were subjected to uniaxial compression and assessment of mechanically-derived axial rigidity. Results: The average structural rigidity-based axial rigidity was well correlated with the average mechanically-derived axial rigidity results (R(^2) = 0.74). This correlation improved significantly (p < 0.0001) when the CT-based Structural Rigidity Analysis (CTRA) minimum axial rigidity was correlated to the mechanically-derived minimum axial rigidity results (R(^2) = 0.84). Tests of slopes in the mixed model regression analysis indicated a significantly steeper slope for the average axial rigidity compared with the minimum axial rigidity (p = 0.028) and a significant difference in the intercepts (p = 0.022). The CTRA average and minimum axial rigidities were correlated with the mechanically-derived average and minimum axial rigidities using paired t-test analysis (p = 0.37 and p = 0.18...

‣ Genetically modified animal models as tools for studying bone and mineral metabolism

Davey, R.; MacLean, H.; McManus, J.; Findlay, D.; Zajac, J.
Fonte: Amer Soc Bone & Mineral Res Publicador: Amer Soc Bone & Mineral Res
Tipo: Artigo de Revista Científica
Publicado em //2004 Português
Relevância na Pesquisa
442.1922%
Genetic modification of mice is a powerful tool for the study of bone development and metabolism. This review discusses the advantages and disadvantages of various approaches used in bone-related research and the contributions these studies have made to bone biology. Genetic modification of mice is a powerful tool for the study of bone development and metabolism. This review discusses the advantages and disadvantages of various approaches used in bone-related research and the contributions these studies have made to bone biology. The approaches to genetic modification included in this review are (1) overexpression of genes, (2) global gene knockouts, (3) tissue-specific gene deletion, and (4) gene knock-in models. This review also highlights issues that should be considered when using genetically modified animal models, including the rigorous control of genetic background, use of appropriate control lines, and confirmation of tissue specificity of gene expression where appropriate. This technology provides a unique and powerful way to probe the function of genes and is already revolutionizing our approach to understanding the physiology of bone development and metabolism.

‣ TNF-alpha mediates p38 MAP kinase activation and negatively regulates bone formation at the injured growth plate in rats

Zhou, F.; Foster, B.; Zhou, X.F.; Cowin, A.; Xian, C.
Fonte: Amer Soc Bone & Mineral Res Publicador: Amer Soc Bone & Mineral Res
Tipo: Artigo de Revista Científica
Publicado em //2006 Português
Relevância na Pesquisa
442.9593%
UNLABELLED: TNF-alpha is known to inhibit osteoblast differentiation in vitro and yet it is essential for bone fracture repair. Roles of TNF-alpha in the bony repair of injured growth plate were examined in young rats treated with a TNF-alpha antagonist. The results show that TNF-alpha mediates p38 activation, which influences the recruitment, proliferation, and osteoblast differentiation of mesenchymal cells and negatively regulates bone formation at the injured growth plate. INTRODUCTION: TNF-alpha inhibits expression of osteoblast differentiation factor cbfa1 and osteoblast differentiation in vitro and yet TNF-alpha signaling is essential for bone fracture healing. Roles of TNF-alpha in the bony repair of injured growth plate cartilage are unknown. MATERIALS AND METHODS: Roles of TNF-alpha in the activation of p38 mitogen activated protein (MAP) kinase and the subsequent bony repair of the injured growth plate were examined in young rats receiving the TNF-alpha inhibitor ENBREL or saline control. Activation of p38 was determined by Western blot analysis and immunohistochemistry. Inflammatory cell counts on day 1, measurements of repair tissue proportions, and counting of proliferative mesenchymal cells on day 8 at growth plate injury site were carried out (n = 6). Expression of inflammatory cytokines TNF-alpha and IL-1beta...

‣ Fractal analysis of cancellous bone in disease

Parkinson, Ian Henry
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado Formato: 904393 bytes; 832922 bytes; 1290063 bytes; 3555072 bytes; 212300 bytes; application/pdf; application/pdf; application/pdf; application/pdf; application/pdf
Publicado em //2002 Português
Relevância na Pesquisa
345.9115%
The principal aim of this thesis was to develop and implement a standardised protocol for the fractal analysis of cancellous bone architecture. Cancellous bone structure from different skeletal sites in groups of osteoporotic, osteoarthritic and normal individuals was analysed. The results of fractal analysis were explained in the context of conventional bone histomorphometry and a priori knowledge to advance the understanding of cancellous bone architecture. There has been much effort devoted to the pursuit of descriptors of cancellous bone complexity. The aim of these endeavours has been to develop morphological descriptors of bone quality that explain the functional properties of the cancellous bone structure for age-related changes, the effect of disease processes or the effect of therapeutic agents on the diseased skeleton. The fractal analysis of the complexity of cancellous bone architecture promises to be an exciting addition to existing analytical techniques. The establishment of a standardised methodology for the fractal analysis of cancellous bone encompassed many components. Knowledge of the stereological and histomorphometric principles that are employed in currently available techniques enabled a comprehensive examination of the factors that effect the measurement of the fractal dimensions. The methodology presented in this thesis has been optimised specifically for measuring sectional fractal dimensions in histological sections of cancellous bone. The sectional fractal dimensions show that...

‣ Mineralization and Bone Resorption Are Regulated by the Androgen Receptor in Male Mice

Chiang, C.; Chiu, M.; Moore, A.; Anderson, P.; Ghasem-Zadeh, A.; McManus, J.; Ma, C.; Seeman, E.; Clemens, T.; Morris, H.; Zajac, J.; Davey, R.
Fonte: Amer Soc Bone & Mineral Res Publicador: Amer Soc Bone & Mineral Res
Tipo: Artigo de Revista Científica
Publicado em //2009 Português
Relevância na Pesquisa
443.95836%
Androgens play a key role in skeletal growth and bone maintenance; however, their mechanism of action remains unclear. To address this, we selectively deleted the androgen receptor (AR) in terminally differentiated, mineralizing osteoblasts using the Cre/loxP system in mice (osteocalcin-Cre AR knockouts [mOBL-ARKOs]). Male mOBL-ARKOs had decreased femoral trabecular bone volume compared with littermate controls because of a reduction in trabecular number at 6, 12, and 24 wk of age, indicative of increased bone resorption. The effects of AR inactivation in mineralizing osteoblasts was most marked in the young mutant mice at 6 wk of age when rates of bone turnover are high, with a 35% reduction in trabecular bone volume, decreased cortical thickness, and abnormalities in the mineralization of bone matrix, characterized by increased unmineralized bone matrix and a decrease in the amount of mineralizing surface. This impairment in bone architecture in the mOBL-ARKOs persisted throughout adulthood despite an unexpected compensatory increase in osteoblast activity. Our findings show that androgens act through the AR in mineralizing osteoblasts to maintain bone by regulating bone resorption and the coordination of bone matrix synthesis and mineralization...

‣ Bril: A novel bone-specific modulator of mineralization

Moffatt, P.; Gaumond, M.H.; Salois, P.; Sellin, K.; Bessette, M.C.; Godin, E.; De Oliveira, P.; Atkins, G.; Nanci, A.; Thomas, G.
Fonte: Amer Soc Bone & Mineral Res Publicador: Amer Soc Bone & Mineral Res
Tipo: Artigo de Revista Científica
Publicado em //2008 Português
Relevância na Pesquisa
442.6072%
In the course of attempting to define the bone "secretome" using a signal-trap screening approach, we identified a gene encoding a small membrane protein novel to osteoblasts. Although previously identified in silico as ifitm5, no localization or functional studies had been undertaken on this gene. We characterized the expression patterns and localization of this gene in vitro and in vivo and assessed its role in matrix mineralization in vitro. The bone specificity and shown role in mineralization led us to rename the gene bone restricted ifitm-like protein (Bril). Bril encodes a 14.8-kDa 134 amino acid protein with two transmembrane domains. Northern blot analysis showed bone-specific expression with no expression in other embryonic or adult tissues. In situ hybridization and immunohistochemistry in mouse embryos showed expression localized on the developing bone. Screening of cell lines showed Bril expression to be highest in osteoblasts, associated with the onset of matrix maturation/mineralization, suggesting a role in bone formation. Functional evidence of a role in mineralization was shown by adenovirus-mediated Bril overexpression and lentivirus-mediated Bril shRNA knockdown in vitro. Elevated Bril resulted in dose-dependent increases in mineralization in UMR106 and rat primary osteoblasts. Conversely...

‣ Perivascular niche of postnatal mesenchymal stem cells in human bone marrow and dental pulp

Shi, S.; Gronthos, S.
Fonte: Amer Soc Bone & Mineral Res Publicador: Amer Soc Bone & Mineral Res
Tipo: Artigo de Revista Científica
Publicado em //2003 Português
Relevância na Pesquisa
440.33984%
Mesenchymal stem cell populations have previously been identified in adult bone marrow and dental pulp that are capable of regenerating the bone marrow and dental pulp microenvironments, respectively. Here we show that these stem cell populations reside in the microvasculature of their tissue of origin. Human bone marrow stromal stem cells (BMSSCs) and dental pulp stem cells (DPSCs) were isolated by immunoselection using the antibody, STRO-1, which recognizes an antigen on perivascular cells in bone marrow and dental pulp tissue. Freshly isolated STRO-1 positive BMSSCs and DPSCs were tested for expression of vascular antigens known to be expressed by endothelial cells (von Willebrand factor, CD146), smooth muscle cells, and pericytes (-smooth muscle actin, CD146), and a pericyte-associated antigen (3G5), by immunohistochemistry, fluorescence-activated cell sorting (FACS), and/or immunomagnetic bead selection. Both BMSSCs and DPSCs lacked expression of von Willebrand factor but were found to be positive for -smooth muscle actin and CD146. Furthermore, the majority of DPSCs expressed the pericyte marker, 3G5, while only a minor population of BMSSCs were found to be positive for 3G5. The finding that BMSSCs and DPSCs both display phenotypes consistent with different perivascular cell populations...

‣ Influence of orthogonal overload on human vertebral trabecular bone mechanical properties

Badiei, A.; Bottema, M.; Fazzalari, N.
Fonte: Amer Soc Bone & Mineral Res Publicador: Amer Soc Bone & Mineral Res
Tipo: Artigo de Revista Científica
Publicado em //2007 Português
Relevância na Pesquisa
441.09152%
Arash Badiei, Murk J. Bottema and Nicola L. Fazzalari; Copyright © 2007 American Society for Bone and Mineral Research

‣ The tyrosine kinase inhibitor dasatinib dysregulates bone remodeling through inhibition of osteoclasts in vivo

Vandyke, K.; Dewar, A.; Diamond, P.; Fitter, S.; Schultz, C.; Sims, N.; Zannettino, A.
Fonte: Amer Soc Bone & Mineral Res Publicador: Amer Soc Bone & Mineral Res
Tipo: Artigo de Revista Científica
Publicado em //2010 Português
Relevância na Pesquisa
442.6072%
Dasatinib is a potent tyrosine kinase inhibitor that is used to treat chronic myeloid leukemia in patients resistant or intolerant to imatinib mesylate. While designed to inhibit Abl and Src kinases, dasatinib shows multitarget effects, including inhibition of the macrophage colony-stimulating factor (M-CSF) receptor c-fms. We have shown previously that dasatinib abrogates osteoclast formation and activity in vitro owing, in part, to its specificity for c-fms. In this study we examined whether dasatinib could significantly alter bone volume in a model of physiologic bone turnover. Sprague-Dawley rats were administered dasatinib (5 mg/kg/day) or vehicle by gavage or zoledronic acid (ZOL; 100 microg/kg/6 weeks) subcutaneously. Following 4, 8, and 12 weeks of treatment, serum biochemical, bone morphometric, and histologic analyses were performed. Whole-body bone mineral density and tibial cortical thickness where unchanged in the dasatinib- or ZOL-treated animals relative to controls. However, micro-computed tomographic (microCT) analysis of cancellous bone at the proximal tibias showed that trabecular volume (BV/TV) and thickness (Tb.Th) were increased in dasatinib-treated animals at levels comparable with those of the ZOL-treated group. These changes were associated with a decrease in osteoclast numbers (N.Oc/B.Pm) and surface (Oc.S/BS) and decreased serum levels of the osteoclast marker c-terminal collagen crosslinks (CTX-1). Mineral apposition rate (MAR)...

‣ EphB4 enhances the process of endochondral ossification and inhibits remodeling during bone fracture repair

Arthur, A.; Panagopoulos, R.; Cooper, L.; Menicanin, D.; Parkinson, I.; Codrington, J.; Vandyke, K.; Zannettino, A.; Koblar, S.; Sims, N.; Matsuo, K.; Gronthos, S.
Fonte: Amer Soc Bone & Mineral Res Publicador: Amer Soc Bone & Mineral Res
Tipo: Artigo de Revista Científica
Publicado em //2013 Português
Relevância na Pesquisa
441.09152%
Previous reports have identified a role for the tyrosine kinase receptor EphB4 and its ligand, ephrinB2, as potential mediators of both bone formation by osteoblasts and bone resorption by osteoclasts. In the present study, we examined the role of EphB4 during bone repair after traumatic injury. We performed femoral fractures with internal fixation in transgenic mice that overexpress EphB4 under the collagen type 1 promoter (Col1-EphB4) and investigated the bone repair process up to 12 weeks postfracture. The data indicated that Col1-EphB4 mice exhibited stiffer and stronger bones after fracture compared with wild-type mice. The fractured bones of Col1-EphB4 transgenic mice displayed significantly greater tissue and bone volume 2 weeks postfracture compared with that of wild-type mice. These findings correlated with increased chondrogenesis and mineral formation within the callus site at 2 weeks postfracture, as demonstrated by increased safranin O and von Kossa staining, respectively. Interestingly, Col1-EphB4 mice were found to possess significantly greater numbers of clonogenic mesenchymal stromal progenitor cells (CFU-F), with an increased capacity to form mineralized nodules in vitro under osteogenic conditions, when compared with those of the wild-type control mice. Furthermore...

‣ Morphological changes of autoclaved autogenic bone implantation and autoclaved autogenic bone supplernented with allogenic demineralized bone matrix in rat parietal bone

Young, T.Q.; Matsuda, Mikio; Takekawa, M.; Ohtsubo, S.; Tsuyama, K.; Kita, S.
Fonte: Murcia : F. Hernández Publicador: Murcia : F. Hernández
Tipo: Artigo de Revista Científica Formato: application/pdf
Português
Relevância na Pesquisa
345.17047%
The healing process of resected, autoclaved (121 7,20 minutes) and re-implanted bone in the rat parietal bone was compared with that of autoclaved bone that was supplemented with allogenic bone matrix (AAA-bone), using a scanning electron microscope and a light microscope. In the implant without AAA-bone, bone union and replacement of the autoclaved bone was seen at 2 weeks after implantation. There was no evidence of any inflammatory reaction around the autoclaved bone. The implant was gradually replaced by the new bone. In the implant with AAA-bone, the new bone formation around the implanted bone was more abundant than that of the implant without AAA-bone. An inflammatory reaction was also observed after 1 week. The replacement of the implant with AAA-bone was inferior to the nonsupplemented group. The reason for the poor replacement was the disturbance of the blood supply in the implant by abundant new bone formation. In these results, the autoclaved bone re-implantation was an excellent bone substitute with osteoconductive ability and biocompatibility. The implantation with AAA-bone was good for the new bone formation, but the position and the technique of supplement with AAAbone have to be more deeply investigated.

‣ Scanning electron microscopic and light microscopic observations on morphological changes of freeze-dried bone implantation in rats

Matsuda, Mikio; Satoh, Y.; Ono, K.
Fonte: Murcia : F. Hernández Publicador: Murcia : F. Hernández
Tipo: Artigo de Revista Científica Formato: application/pdf
Português
Relevância na Pesquisa
345.59715%
Bone remodelling after the implantation of freeze-dried autogenous bone in rat parietal bone was compared with fresh autogenous bone transplantation, using a scanning electron and light microscope revealed the time intervals after transplantationfimplantation. The light microscope revealed the time delay of the bone remodelling in the implantation, compared with the transplantations. The scanning electron microscope showed that the differences between the two groups were in the states of bone union and bone resorption. In the fresh bone group, the newly-formed bone filled the spaces between host and the transplanted bones at 2 to 3 weeks after the transplantation: the newly-formed bone fused and melted into the transplanted bone. New bone formation was more dominant on the bone surface in the dura mater side than in the skin side. The union was almost completed at 5 weeks. In freeze-dried bone implantation, the bone union in the contact space was very poor and the implanted bone was mainly covered by the new bone, which developed from the host bone surface in the dura mater side at 2 to 3 weeks after the implantation. What is noteworthy is that bone resorbed areas showing numerous Howship's lacunae were mainly observed on the host bone surface in the vicinity of newly-formed bone. However in freeze-dried bone implantation...

‣ The role of vitamin D receptor in osteoblasts and bone mineralisation.

Lam, Nga Ngoc
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2013 Português
Relevância na Pesquisa
345.9115%
Age-related bone loss is associated with a change in bone remodelling characterised by decreased bone formation relative to bone resorption. It is well described that age-related bone loss is accelerated as a consequence of vitamin D deficiency, a process which can be replicated in rodent studies. While vitamin D has been shown to play important roles for adequate bone mineralisation and the prevention of osteoporosis, the exact mechanisms remain controversial. It is clear that vitamin D is necessary for the stimulation of intestinal calcium and phosphate absorption, maintenance of calcium homeostasis and supply of calcium and phosphate for bone mineralisation. However, vitamin D has also been shown to directly act on bone cells to promote mineralisation as well as regulate bone resorption. The question of the essential nature of the in vivo role for the direct actions of vitamin D on bone has proven to be difficult to resolve. The only published mouse model which addresses the direct actions of vitamin D in osteoblasts is the osteoblast-specific vitamin D receptor transgenic mouse, or OSVDR mouse. Using this transgenic mouse model, it has been reported that the enhanced vitamin D activity in osteoblasts promotes bone formation and mediates reduction in bone resorption most likely through reduced RANKL signalling of osteoclastogenesis. The reported overall bone phenotype of the OSVDR was increased vertebral trabecular bone as well as increased cortical bone volume leading to increased bone strength. In contrast to the findings in OSVDR mice...

‣ Vitamin D Depletion Induces RANKL-Mediated Osteoclastogenesis and Bone Loss in a Rodent Model

Anderson, P.; Sawyer, R.; Moore, A.; May, B.; O'Loughlin, P.; Morris, H.
Fonte: Amer Soc Bone & Mineral Res Publicador: Amer Soc Bone & Mineral Res
Tipo: Artigo de Revista Científica
Publicado em //2008 Português
Relevância na Pesquisa
441.09152%
The association between increased risk of hip fracture and low vitamin D status has long been recognized. However, the level of vitamin D required to maintain bone strength is controversial. We used a rodent model of vitamin D depletion to quantify the 25-hydroxyvitamin D (25D) levels required for normal mineralization. Six groups of 10-wk-old male Sprague-Dawley rats (n = 42) were fed a diet containing 0.4% calcium and various levels of dietary vitamin D3 for 4 mo to achieve stable mean serum 25D levels ranging between 10 and 115 nM. At 7 mo of age, animals were killed, and the histomorphometry of distal and proximal femora and L2 vertebra was analyzed. Total RNA was extracted from whole femora for real-time RT-PCR analyses. In the distal femoral metaphysis, trabecular bone mineral volume (BV/TV) showed a significant positive association with circulating 25D levels (r2 = 0.42, p < 0.01) in the animals with serum 25D levels between 20 and 115 nM. Osteoclast surface (Oc.S) levels were positively associated with RANKL:OPG mRNA ratio, higher in groups with lower serum 25D levels, and were independent of serum 1,25D levels. Serum 25D levels <80 nM gave rise to osteopenia as a result of increased osteoclastogenesis, suggesting that levels of 25D >80 nM are needed for optimal bone volume. These data indicate that serum 25D levels are a major determinant of osteoclastogenesis and bone mineral volume and are consistent with the levels of 25D recommended to reduce the risk of fracture in humans.; Paul H Anderson...

‣ Osteoblast deletion of exon 3 of the androgen receptor gene results in trabecular bone loss in adult male mice

Notini, A.; McManus, J.; Moore, A.; Bouxsein, M.; Jimenez, M.; Chiu, W.; Glatt, V.; Kream, B.; Handelsman, D.; Morris, H.; Zajac, J.; Davey, R.
Fonte: Amer Soc Bone & Mineral Res Publicador: Amer Soc Bone & Mineral Res
Tipo: Artigo de Revista Científica
Publicado em //2007 Português
Relevância na Pesquisa
443.95836%
The mechanism of androgen action on bone was studied in male mice with the AR deleted in mature osteoblasts. These mice had decreased trabecular bone volume associated with a decrease in trabecular number, suggesting that androgens may act directly on osteoblasts to maintain trabecular bone. Introduction: Androgens modulate bone cell activity and are important for the maintenance of bone mass. However, the mechanisms by which they exert these actions on bone remain poorly defined. The aim of this study was to investigate the role of androgens acting through the classical androgen receptor (AR) signaling pathways (i.e., DNA-binding dependent pathways) in osteoblasts using male mice in which exon 3 of the AR gene was deleted specifically in mature osteoblasts. Materials and Methods: Mice with a floxed exon 3 of the AR gene were bred with Col 2.3-cre transgenic mice, in which Cre recombinase is expressed in mineralizing osteoblasts. The skeletal phenotype of mutant mice was assessed by histomorphometry and quantitative μCT at 6, 12, and 32 weeks of age (n = 8 per group). Wildtype, hemizygous exon 3 floxed and hemizygous Col 2.3-cre male littermates were used as controls. Data were analyzed by one-way ANOVA and Tukey's posthoc test. Results: μCT analysis of the fifth lumbar vertebral body showed that these mice had reduced trabecular bone volume (p < 0.05) at 32 weeks of age compared with controls. This was associated with a decrease in trabecular number (p < 0.01) at 12 and 32 weeks of age...

‣ Validity of synthetic bone as a substitute for osteoporotic cadaveric femoral heads in mechanical testing: a biomechanical study

O'Neill, F; Condon, F; McGloughlin, Timothy M.; Lenehan, B; Coffey, Calvin J; Walsh, Michael T.
Fonte: British Editorial Society of Bone and Joint Surgery Publicador: British Editorial Society of Bone and Joint Surgery
Tipo: info:eu-repo/semantics/article; all_ul_research; ul_published_reviewed
Português
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peer-reviewed; IntroductionThe objective of this study was to determine if a synthetic bone substitute would provide results similar to bone from osteoporotic femoral heads during in vitro testing with orthopaedic implants. If the synthetic material could produce results similar to those of the osteoporotic bone, it could reduce or eliminate the need for testing of implants on bone.MethodsPushout studies were performed with the dynamic hip screw (DHS) and the DHS Blade in both cadaveric femoral heads and artificial bone substitutes in the form of polyurethane foam blocks of different density. The pushout studies were performed as a means of comparing the force displacement curves produced by each implant within each material.ResultsThe results demonstrated that test material with a density of 0.16 g/cm(3) (block A) produced qualitatively similar force displacement curves for the DHS and qualitatively and quantitatively similar force displacement curves for the DHS Blade, whereas the test material with a density of 0.08 g/cm(3) (block B) did not produce results that were predictive of those recorded within the osteoporotic cadaveric femoral heads.ConclusionThis study demonstrates that synthetic material with a density of 0.16 g/cm(3) can provide a good substitute for cadaveric osteoporotic femoral heads in the testing of implants. However we do recognise that no synthetic material can be considered as a definitive substitute for bone...