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Bone Matrix (bone + matrix)
Terms modified by Bone Matrix Selected AbstractsImmunosuppression with FK506 Increases Bone Induction in Demineralized Isogeneic and Xenogeneic Bone Matrix in the RatJOURNAL OF BONE AND MINERAL RESEARCH, Issue 9 2000Dr. Gregor Voggenreiter Abstract The aim of the present study was to investigate a systemic induction of bone formation in rats by immunosuppression with FK506 (1 mg/kg body weight intraperitoneally [ip]) in a model of osteoinduction of isogeneic and xenogeneic demineralized bone matrix (DBM) for a period of 28 days. In particular, alterations of in vitro cytokine synthesis and changes of lymphocyte subsets were studied. DBM was implanted intramuscularly in the abdominal wall of Lewis rats (seven per group). Blood was sampled on days ,7, 0, 7, and 28 for determination of in vitro tumor necrosis factor , (TNF-,) synthesis and lymphocyte subsets by flow cytometry (CD3+, CD4+, CD8+, CD45+, ED9+, and Ia+ antibodies). Ossicles of de novo formed bone and the tibias were removed on day 28 after double tetracycline labeling for histomorphometric analysis. Immunosuppression with FK506 significantly decreased lipopolysaccharide (LPS)-stimulated in vitro cytokine synthesis after 7 days and 28 days (p < 0.05). Compared with control animals FK506 treatment significantly increased the volume of induced bone in isogeneic (2.1 ± 0.3 mm3 vs. 10.8 ± 0.9 mm3) and xenogeneic (0 mm3 vs. 4.7 ± 0.8 mm3) DBM. Bone histomorphometry of the tibias revealed that immunosuppression increased both bone formation and bone resorption, accompanied by a significant reduction in the relative trabecular area (Tb.Ar). FK506 caused a decrease in the counts of CD8+ T cells probably because of destruction or dislocation of these cells. This suggests that the amount of CD8+ cells and the degree of T cell activation in terms of mean fluorescence intensity (MFI) may be associated with bone metabolism. In support of this, statistical analysis revealed a significant positive correlation between parameters of bone formation as well as bone resorption and the CD4+/CD8+ ratio. There was a significant negative correlation between parameters of remodeling of the metaphysis of the tibia and induced bone volume (BV), respectively, and MFI values of CD3+/Ia+ cells. These findings suggest an important role of T lymphocytes in bone formation and bone resorption in vivo. FK506 caused a marked increase of bone formation in DBM. However, the conclusion that immunosuppression increases fracture healing warrants further investigation. [source] Attachment of Osteocyte Cell Processes to the Bone MatrixTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 3 2009L.M. McNamara Abstract In order for osteocytes to perceive mechanical information and regulate bone remodeling accordingly they must be anchored to their extracellular matrix (ECM). To date the nature of this attachment is not understood. Osteocytes are embedded in mineralized bone matrix, but maintain a pericellular space (50,80 nm) to facilitate fluid flow and transport of metabolites. This provides a spatial limit for their attachment to bone matrix. Integrins are cell adhesion proteins that may play a role in osteocyte attachment. However, integrin attachments require proximity between the ECM, cell membrane, and cytoskeleton, which conflicts with the osteocytes requirement for a pericellular fluid space. In this study, we hypothesize that the challenge for osteocytes to attach to surrounding bone matrix, while also maintaining fluid-filled pericellular space, requires different "engineering" solutions than in other tissues that are not similarly constrained. Using novel rapid fixation techniques, to improve cell membrane and matrix protein preservation, and transmission electron microscopy, the attachment of osteocyte processes to their canalicular boundaries are quantified. We report that the canalicular wall is wave-like with periodic conical protrusions extending into the pericellular space. By immunohistochemistry we identify that the integrin ,v,3 may play a role in attachment at these complexes; a punctate pattern of staining of ,3 along the canalicular wall was consistent with observations of periodic protrusions extending into the pericellular space. We propose that during osteocyte attachment the pericellular space is periodically interrupted by underlying collagen fibrils that attach directly to the cell process membrane via integrin-attachments. Anat Rec, 292:355,363, 2009. © 2009 Wiley-Liss, Inc. [source] Nanofiber Generation of Gelatin,Hydroxyapatite Biomimetics for Guided Tissue Regeneration,ADVANCED FUNCTIONAL MATERIALS, Issue 12 2005H.-W. Kim Abstract The development of biomimetic bone matrices is one of the major goals in the bone-regeneration and tissue-engineering fields. Nanocomposites consisting of a natural polymer and hydroxyapatite (HA) nanocrystals, which mimic the human bone matrix, are thus regarded as promising bone regenerative materials. Herein, we developed a biomimetic nanocomposite with a novel nanofibrous structure by employing an electrospinning (ES) method. The HA precipitate/gelatin matrix nanocomposites are lyophilized and dissolved in an organic solvent, and then electrospun under controlled conditions. With this process, we can successfully generate a continuous fiber with a diameter of the order of hundreds of nanometers. The internal structure of the nanofiber features a typical nanocomposite, i.e., HA nanocrystals well distributed within a gelatin matrix. These nanocomposite fibers improve the bone-derived cellular activity significantly when compared to the pure gelatin equivalent. This method of generating a nanofiber of the biomimetic nanocomposite was effective in producing a biomedical membrane with a composition gradient, which is potentially applicable in the field of guided tissue regeneration (GTR). [source] Osteoblastic Tartrate-Resistant Acid Phosphatase: Its Potential Role in the Molecular Mechanism of Osteogenic Action of Fluoride,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 10 2003K-H William Lau Abstract Although type 5 TRACP is recognized as a histochemical and biochemical marker of osteoclasts, there is evidence that bone forming cells, osteoblasts, and osteocytes also express a type 5 TRACP. Accordingly, an osteoblastic type 5 TRACP has been purified from human osteoblasts and from bovine cortical bone matrices. Comparison of biochemical properties of osteoblastic type 5 TRACP with those of osteoclastic type 5 TRACP suggests that osteoblastic type 5 TRACP is a different isoenzyme from osteoclastic type 5 TRACP. Two properties of osteoblastic type 5 TRACP may be relevant to its physiological functions: (1) it acts as a protein-tyrosine phosphatase (protein tyrosine phosphorylation) under physiologically relevant conditions, and (2) it is sensitive to inhibition by clinically relevant concentrations of fluoride. Because fluoride is a stimulator of osteoblastic proliferation and differentiation and a potent osteogenic agent and because protein tyrosine phosphorylation plays an important regulatory role in cell proliferation and differentiation, these unique properties and other evidence summarized in this review led to the proposal that the osteogenic action of fluoride is mediated, at least in part, by the fluoride-mediated inhibition of osteoblastic type 5 TRACP/protein tyrosine phosphorylation, which leads to a stimulation of osteoblast proliferation and differentiation, and subsequently, an increase in bone formation. [source] Growth Hormone Induces Bone Morphogenetic Proteins and Bone-Related Proteins in the Developing Rat PeriodontiumJOURNAL OF BONE AND MINERAL RESEARCH, Issue 6 2001Huika Li Abstract The hypothesis that growth hormone (GH) up-regulates the expression of enzymes, matrix proteins, and differentiation markers involved in mineralization of tooth and bone matrices was tested by the treatment of Lewis dwarf rats with GH over 5 days. The molar teeth and associated alveolar bone were processed for immunohistochemical demonstration of bone morphogenetic proteins 2 and 4 (BMP-2 and -4), bone morphogenetic protein type IA receptor (BMPR-IA), bone alkaline phosphatase (ALP), osteocalcin (OC), osteopontin (OPN), bone sialoprotein (BSP), and E11 protein (E11). The cementoblasts, osteoblasts, and periodontal ligament (PDL) cells responded to GH by expressing BMP-2 and -4, BMPR-IA, ALP, OC, and OPN and increasing the numbers of these cells. No changes were found in patterns of expression of the late differentiation markers BSP and E11 in response to GH. Thus, GH evokes expression of bone markers of early differentiation in cementoblasts, PDL cells, and osteoblasts of the periodontium. We propose that the induction of BMP-2 and -4 and their receptor by GH compliments the role of GH-induced insulin-like growth factor 1 (IGF-1) in promoting bone and tooth root formation. [source] High-Turnover Periprosthetic Bone Remodeling and Immature Bone Formation Around Loose Cemented Total Hip JointsJOURNAL OF BONE AND MINERAL RESEARCH, Issue 1 2001Michiaki Takagi Abstract Aseptic loosening and periprosthetic osteolysis are the major problems awaiting solution in total hip surgery. The clinical investigation focused on the analysis of periprosthetic bone remodeling to clarify one important key event in the cascade of periprosthetic connective tissue weakening and osteolysis around loose artificial hip joints. Twelve acetabular bone samples adjacent to granulomatous synovial-like membrane of loose hip prosthesis were retrieved at revision surgery and processed for Villanueva bone staining for morphological observation and bone histomorphometric analysis. Eight well-fixed bony samples were used as control. Although osteoclastic surface and eroded surface by osteoclasts were evident in the periprosthetic bone from loose hip joints (p = 0.003 and p = 0.027), increased osteoid/low-mineralized bone matrix (p < 0.001) and osteoid width (p < 0.001) also were significant findings in structural analysis. In addition, not only elevated mineral apposition rate (MAR; p = 0.044) but also increased mineralizing surface (p = 0.044) and bone formation rate (BFR; p = 0.002) in loose periprosthetic bones were shown in dynamic data analysis. These results were confirmed by precise morphological observation by confocal laser scanning microscopy. Active coupling of bone formation and resorption and increased osteocytes with abundant bone canalicular projections were found in combined with the presence of immature bone matrices (osteoid and low-mineralized bone areas) in periprosthetic bones from loose hip joints. These results indicated that active osteoclastic bone resorption and/or defective bone formation are coupled with monocyte/macrophage-mediated foreign body-type granuloma in the synovial-like interface membrane of loose hip joints. Thus, this unique high-turnover periprosthetic bone remodeling with bad bone quality probably is caused by the result of cellular host response combined with inappropriate cyclic mechanical loading. The fragile periprosthetic bone may contribute to hip prosthesis loosening. [source] Buried alive: How osteoblasts become osteocytesDEVELOPMENTAL DYNAMICS, Issue 1 2006Tamara A. Franz-Odendaal Abstract During osteogenesis, osteoblasts lay down osteoid and transform into osteocytes embedded in mineralized bone matrix. Despite the fact that osteocytes are the most abundant cellular component of bone, little is known about the process of osteoblast-to-osteocyte transformation. What is known is that osteoblasts undergo a number of changes during this transformation, yet retain their connections to preosteoblasts and osteocytes. This review explores the osteoblast-to-osteocyte transformation during intramembranous ossification from both morphological and molecular perspectives. We investigate how these data support five schemes that describe how an osteoblast could become entrapped in the bone matrix (in mammals) and suggest one of the five scenarios that best fits as a model. Those osteoblasts on the bone surface that are destined for burial and destined to become osteocytes slow down matrix production compared to neighbouring osteoblasts, which continue to produce bone matrix. That is, cells that continue to produce matrix actively bury cells producing less or no new bone matrix (passive burial). We summarize which morphological and molecular changes could be used as characters (or markers) to follow the transformation process. Developmental Dynamics 235:176,190, 2006. © 2005 Wiley-Liss, Inc. [source] Nanofiber Generation of Gelatin,Hydroxyapatite Biomimetics for Guided Tissue Regeneration,ADVANCED FUNCTIONAL MATERIALS, Issue 12 2005H.-W. Kim Abstract The development of biomimetic bone matrices is one of the major goals in the bone-regeneration and tissue-engineering fields. Nanocomposites consisting of a natural polymer and hydroxyapatite (HA) nanocrystals, which mimic the human bone matrix, are thus regarded as promising bone regenerative materials. Herein, we developed a biomimetic nanocomposite with a novel nanofibrous structure by employing an electrospinning (ES) method. The HA precipitate/gelatin matrix nanocomposites are lyophilized and dissolved in an organic solvent, and then electrospun under controlled conditions. With this process, we can successfully generate a continuous fiber with a diameter of the order of hundreds of nanometers. The internal structure of the nanofiber features a typical nanocomposite, i.e., HA nanocrystals well distributed within a gelatin matrix. These nanocomposite fibers improve the bone-derived cellular activity significantly when compared to the pure gelatin equivalent. This method of generating a nanofiber of the biomimetic nanocomposite was effective in producing a biomedical membrane with a composition gradient, which is potentially applicable in the field of guided tissue regeneration (GTR). [source] Detecting microdamage in boneJOURNAL OF ANATOMY, Issue 2 2003T. C. Lee Abstract Fatigue-induced microdamage in bone contributes to stress and fragility fractures and acts as a stimulus for bone remodelling. Detecting such microdamage is difficult as pre-existing microdamage sustained in vivo must be differentiated from artefactual damage incurred during specimen preparation. This was addressed by bulk staining specimens in alcohol-soluble basic fuchsin dye, but cutting and grinding them in an aqueous medium. Nonetheless, some artefactual cracks are partially stained and careful observation under transmitted light, or epifluorescence microscopy, is required. Fuchsin lodges in cracks, but is not site-specific. Cracks are discontinuities in the calcium-rich bone matrix and chelating agents, which bind calcium, can selectively label them. Oxytetracycline, alizarin complexone, calcein, calcein blue and xylenol orange all selectively bind microcracks and, as they fluoresce at different wavelengths and colours, can be used in sequence to label microcrack growth. New agents that only fluoresce when involved in a chelate are currently being developed , fluorescent photoinduced electron transfer (PET) sensors. Such agents enable microdamage to be quantified and crack growth to be measured and are useful histological tools in providing data for modelling the material behaviour of bone. However, a non-invasive method is needed to measure microdamage in patients. Micro-CT is being studied and initial work with iodine dyes linked to a chelating group has shown some promise. In the long term, it is hoped that repeated measurements can be made at critical sites and microdamage accumulation monitored. Quantification of microdamage, together with bone mass measurements, will help in predicting and preventing bone fracture failure in patients with osteoporosis. [source] Hip geometry variation is associated with bone mineralization pathway gene variants: The framingham studyJOURNAL OF BONE AND MINERAL RESEARCH, Issue 7 2010Ching-Lung Cheung Abstract Mineralization of bone matrix is an important process in bone formation; thus defects in mineralization have been implicated in bone mineral density (BMD) and bone structure alterations. Three central regulators of phosphate balance, ALPL, ANKH, and ENPP1, are central in the matrix mineralization process; therefore, the genes encoding them are considered important candidates genes for BMD and bone geometry. To test for an association between these three candidate genes and BMD and bone geometry traits, 124 informative single-nucleotide polymorphisms (SNPs) were selected and genotyped in 1513 unrelated subjects from the Framingham offspring cohort. Initial results showed that SNP rs1974201 in the gene ENPP1 was a susceptibility variant associated with several hip geometric indices, with the strongest p value of 3.8,×,10,7 being observed for femoral neck width. A few modest associations were observed between SNPs in or near ALPL and several bone traits, but no association was observed with ANKH. The association signals observed for SNPs around rs1974201 were attenuated after conditional analysis on rs1974201. Transcription factor binding-site prediction revealed that the HOXA7 binding site was present in the reference sequence with the major allele, whereas this potential binding site is lost in the sequence with the minor allele of rs1974201. In conclusion, we found evidence for association of bone geometry variation with an SNP in ENPP1, a gene in the mineralization pathway. The alteration of a binding site of the deregulator of extracellular matrix HOXA7 warrants further investigation. © 2010 American Society for Bone and Mineral Research [source] Maspin Is Involved in Bone Matrix Maturation by Enhancing the Accumulation of Latent TGF-,,,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 10 2007Reiko Tokuyama Abstract Maspin, a serine protease inhibitor, is expressed by formative osteoblasts. The repression of maspin expression in osteoblastic cells decreased the level of latent TGF-, in the extracellular matrix, whereas the overexpression of maspin increased latent TGF-,. These findings suggest that maspin plays an important role in bone matrix formation, particularly in the accumulation of latent TGF-,. Introduction: Maspin is a serine protease inhibitor that exhibits tumor suppressive and anti-angiogenic activities. This study was performed to elucidate a possible role for maspin in bone formation. Materials and Methods: We performed immunohistochemical analysis of the expression of maspin during endochondral ossification. We evaluated the expression of maspin mRNA and protein in ROS 17/2.8 cells and primary rat osteoblastic cells by RT-PCR, immunocytochemistry, and Western blot analysis. We also examined the accumulation of TGF-, in the extracellular matrix of cultured ROS 17/2.8 cells after transfection with vectors expressing either maspin or maspin antisense. Results: We observed expression of maspin by active osteoblasts in vivo. Rat osteoblastic cells also expressed maspin mRNA and protein in vitro. Moreover, the accumulation of latent TGF-, in the extracellular matrix significantly decreased in cultures exposed to an anti-maspin antibody and when cells were transfected with a maspin antisense-expressing vector. In contrast, accumulation of latent TGF-, in the extracellular matrix increased after transfection of cells with a vector expressing maspin. Conclusions: These findings suggest that maspin expressed in active osteoblasts plays an important physiological role during maturation of the bone matrix, and in particular, during the process of accumulation of latent TGF-, in the extracellular matrix. [source] Remodeling and Vascular Spaces in BoneJOURNAL OF BONE AND MINERAL RESEARCH, Issue 1 2007Erik Fink Eriksen Abstract In recent years, we have come to appreciate that the close association between bone and vasculature plays a pivotal role in the regulation of bone remodeling and fracture repair. In 2001, Hauge et al. characterized a specialized vascular structure, the bone remodeling compartment (BRC), and showed that the outer lining of this compartment was made up of flattened cells, displaying all the characteristics of lining cells in bone. A decrease in bone turnover leads to a decrease in surfaces covered with remodeling compartments, whereas increased turnover causes an increase. Immunoreactivity for all major osteotropic growth factors and cytokines including osteoprotegerin (OPG) and RANKL has been shown in the cells lining the BRC, which makes the BRC the structure of choice for coupling between resorption and formation. The secretion of these factors inside a confined space separated from the bone marrow would facilitate local regulation of the remodeling process without interference from growth factors secreted by blood cells in the marrow space. The BRC creates an environment where cells inside the structure are exposed to denuded bone, which may enable direct cellular interactions with integrins and other matrix factors known to regulate osteoclast/osteoblast activity. However, the denuded bone surface inside the BRC also constitutes an ideal environment for the seeding of bone metastases, known to have high affinity for bone matrix. Reduction in BRC space brought about by antiresorptive therapies such as bisphosphonates reduce the number of skeletal events in advanced cancer, whereas an increase in BRC space induced by remodeling activators like PTH may increase the bone metastatic burden. The BRC has only been characterized in detail in trabecular bone; there is, however, evidence that a similar structure may exist in cortical bone, but further characterization is needed. [source] Bone Material Properties in Trabecular Bone From Human Iliac Crest Biopsies After 3- and 5-Year Treatment With Risedronate,,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 10 2006Erich Durchschlag Abstract Long-term effects of risedronate on bone mineral maturity/crystallinity and collagen cross-link ratio in triple iliac crest biopsies of osteoporotic women were evaluated. In this double-blinded study, 3- and 5-year treatment with risedronate arrested the tissue aging encountered in untreated osteoporosis and in osteoporosis treated with other antiresorptives. This effect may be contributing to risedronate's antifracture efficacy. Introduction: Risedronate is widely used in the treatment of osteoporosis. It reduces bone turnover, increases BMD, and decreases fracture risk. To date, there are no data available on the long-term effects of risedronate on bone material properties in humans. Materials and Methods: Osteoporotic women enrolled in the VERT-NA trial received either risedronate (5 mg/day, orally) or placebo for up to 5 years. All subjects received calcium. They also received vitamin D supplementation if deficient at baseline. Triple iliac crest biopsies were collected from a subset of these subjects at baseline, 3 years, and 5 years. Mineral maturity/crystallinity and collagen cross-link ratio was measured in these biopsies using Fourier transform infrared imaging. Results: Patients that received placebo exhibited increased mineral maturity/crystallinity and collagen cross-link ratio after 3 and 5 years compared with baseline values. On the contrary, patients that received risedronate retained baseline values in both bone material indices throughout. A more spatially detailed analysis revealed that this was achieved mainly through beneficial effects on active bone-forming areas. Surprisingly, patients that received risedronate achieved premenopausal values at bone-forming areas in both indices after 5 years of treatment. Conclusion: Long-term treatment with risedronate affects bone material properties (mineral maturity/crystallinity and collagen cross-link ratio) and arrests the tissue aging apparent in untreated osteoporosis. These changes at the material level of the bone matrix may contribute to risedronate's rapid and sustained antifracture efficacy in osteoporotic patients. [source] In Silico Modeling and Simulation of Bone Biology: A ProposalJOURNAL OF BONE AND MINERAL RESEARCH, Issue 7 2005Nadine A Defranoux Abstract Contemporary, computer-based mathematical modeling techniques make it possible to represent complex biological mechanisms in a manner that permits hypothesis testing in silico. This perspective shows how such approaches might be applied to bone remodeling and therapeutic research. Currently, the dominant conceptual model applied in bone research involves the dynamic balance between the continual build-up and breakdown of bone matrix by two cell types, the osteoblasts and osteoclasts, acting together as a coordinated, remodeling unit. This conceptualization has served extraordinarily well as a focal point for understanding how mutations, chemical mediators, and mechanical force, as well as external influences (e.g., drugs, diet) affect bone structure and function. However, the need remains to better understand and predict the consequences of manipulating any single factor, or combination of factors, within the context of this complex system's multiple interacting pathways. Mathematical models are a natural extension of conceptual models, providing dynamic, quantitative descriptions of the relationships among interacting components. This formalization creates the ability to simulate the natural behavior of a system, as well as its modulation by therapeutic or dietetic interventions. A number of mathematical models have been developed to study complex bone functions, but most include only a limited set of biological components needed to address a few specific questions. However, it is possible to develop larger, multiscale models that capture the dynamic interactions of many biological components and relate them to important physiological or pathological outcomes that allow broader study. Examples of such models include Entelos' PhysioLab platforms. These models simulate the dynamic, quantitative interactions among a biological system's biochemicals, cells, tissues, and organs and how they give rise to key physiologic and pathophysiologic outcomes. We propose that a similar predictive, dynamical, multiscale mathematical model of bone remodeling and metabolism would provide a better understanding of the mechanisms governing these phenomena as well as serve as an in silico platform for testing pharmaceutical and clinical interventions on metabolic bone disease. [source] Increased Bone Formation in Mice Lacking Plasminogen Activators,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 7 2003E Daci Abstract Plasminogen activators tPA and uPA are involved in tissue remodeling, but their role in bone growth is undefined. Mice lacking tPA and uPA show increased bone formation and bone mass. The noncollagenous components of bone matrix are also increased, probably from defective degradation. This study underlines the importance of controlled bone matrix remodeling for normal endochondral ossification. Introduction: Proteolytic pathways are suggested to play a role in endochondral ossification. To elucidate the involvement of the plasminogen activators tPA and uPA in this process, we characterized the long bone phenotype in mice deficient in both tPA and uPA (tPA,/,:uPA,/,). Materials and Methods: Bones of 2- to 7-day-old tPA,/,:uPA,/, and wild-type (WT) mice were studied using bone histomorphometry, electron microscopy analysis, and biochemical assessment of bone matrix components. Cell-mediated degradation of metabolically labeled bone matrix, osteoblast proliferation, and osteoblast differentiation, both at the gene and protein level, were studied in vitro using cells derived from both genotypes. Results: Deficiency of the plasminogen activators led to elongation of the bones and to increased bone mass (25% more trabecular bone in the proximal tibial metaphysis), without altering the morphology of the growth plate. In addition, the composition of bone matrix was modified in plasminogen activator deficient mice, because an increased amount of proteoglycans (2×), osteocalcin (+45%), and fibronectin (+36%) was detected. Matrix degradation assays showed that plasminogen activators, by generating plasmin, participate in osteoblast-mediated degradation of the noncollagenous components of bone matrix. In addition, proliferation of primary osteoblasts derived from plasminogen activator-deficient mice was increased by 35%. Finally, osteoblast differentiation and formation of a mineralized bone matrix were enhanced in osteoblast cultures derived from tPA,/,:uPA,/, mice. Conclusions: The data presented indicate the importance of the plasminogen system in degradation of the noncollagenous components of bone matrix and suggest that the accumulation of these proteins in bone matrix,as occurs during plasminogen activator deficiency,may in turn stimulate osteoblast function, resulting in increased bone formation. [source] Positive Linear Growth and Bone Responses to Growth Hormone Treatment in Children With Types III and IV Osteogenesis Imperfecta: High Predictive Value of the Carboxyterminal Propeptide of Type I Procollagen,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 2 2003Joan C Marini MD Abstract Extreme short stature is a cardinal feature of severe osteogenesis imperfecta (OI), types III and IV. We conducted a treatment trial of growth hormone in children with OI and followed linear growth velocity, bone metabolism markers, histomorphometrics, and vertebral bone density. Twenty-six children with types III and IV OI, ages 4.5,12 years, were treated with recombinant growth hormone (rGH), 0.1,0.2 IU/kg per day for 6 days/week, for at least 1 year. Length, insulin-like growth factor (IGF-I), insulin-like growth factor binding protein (IGFBP-3), bone metabolic markers, and vertebral bone density by DXA were evaluated at 6-month intervals. An iliac crest biopsy was obtained at baseline and 12 months. Approximately one-half of the treated OI children sustained a 50% or more increase in linear growth over their baseline growth rate. Most responders (10 of 14) had moderate type IV OI. All participants had positive IGF-I, IGFBP-3, osteocalcin, and bone-specific alkaline phosphatase responses. Only the linear growth responders had a significant increase in vertebral DXA z-score and a significant decrease in long bone fractures. After 1 year of treatment, responders' iliac crest biopsy showed significant increases in cancellous bone volume, trabecular number, and bone formation rate. Responders were distinguished from nonresponders by higher baseline carboxyterminal propeptide (PICP) values (p < 0.05), suggesting they have an intrinsically higher capacity for collagen production. The results show that growth hormone can cause a sustained increase in the linear growth rate of children with OI, despite the abnormal collagen in their bone matrix. In the first year of treatment, growth responders achieve increased bone formation rate and density, and decreased fracture rates. The baseline plasma concentration of PICP was an excellent predictor of positive response. [source] Smad3 Promotes Alkaline Phosphatase Activity and Mineralization of Osteoblastic MC3T3-E1 Cells,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 7 2002Hideaki Sowa Abstract Transforming growth factor (TGF) , is abundantly stored in bone matrix and appears to regulate bone metabolism. Although the Smad family proteins are critical components of the TGF-, signaling pathways, the roles of Smad3 in the expression of osteoblastic phenotypes remain poorly understood. Therefore, this study was performed to clarify the roles of Smad3 in the regulation of proliferation, expression of bone matrix proteins, and mineralization in osteoblasts by using mouse osteoblastic cell line MC3T3-E1 cells stably transfected with Smad3. Smad3 significantly inhibited [3H]thymidine incorporation and fluorescent intensity of the MTT-dye assay, compared with empty vector. Moreover, Smad3 increased the levels of type I procollagen, osteopontin (OPN), and matrix Gla protein (MGP) mRNA in Northern blotting. These effects of Smad3 mimicked the effects of TGF-, on the same cells. On the other hand, Smad3 greatly enhanced ALP activity and mineralization of MC3T3-E1 cells compared with empty vector, although TGF-, inhibited ALP activity and mineralization of wild-type MC3T3-E1 cells. A type I collagen synthesis inhibitor L -azetidine-2-carboxylic acid, as well as osteocalcin (OCN), significantly antagonized Smad3-stimulated ALP activity and mineralization of MC3T3-E1 cells. In conclusion, this study showed that in mouse osteoblastic cells, Smad3 inhibited proliferation, but it also enhanced ALP activity, mineralization, and the levels of bone matrix proteins such as type I collagen (COLI), OPN, and MGP. We propose that Smad3 plays an important role in osteoblastic bone formation and might help to elucidate the transcriptional mechanism of bone formation and possibly lead to the development of bone-forming drugs. [source] High-Turnover Periprosthetic Bone Remodeling and Immature Bone Formation Around Loose Cemented Total Hip JointsJOURNAL OF BONE AND MINERAL RESEARCH, Issue 1 2001Michiaki Takagi Abstract Aseptic loosening and periprosthetic osteolysis are the major problems awaiting solution in total hip surgery. The clinical investigation focused on the analysis of periprosthetic bone remodeling to clarify one important key event in the cascade of periprosthetic connective tissue weakening and osteolysis around loose artificial hip joints. Twelve acetabular bone samples adjacent to granulomatous synovial-like membrane of loose hip prosthesis were retrieved at revision surgery and processed for Villanueva bone staining for morphological observation and bone histomorphometric analysis. Eight well-fixed bony samples were used as control. Although osteoclastic surface and eroded surface by osteoclasts were evident in the periprosthetic bone from loose hip joints (p = 0.003 and p = 0.027), increased osteoid/low-mineralized bone matrix (p < 0.001) and osteoid width (p < 0.001) also were significant findings in structural analysis. In addition, not only elevated mineral apposition rate (MAR; p = 0.044) but also increased mineralizing surface (p = 0.044) and bone formation rate (BFR; p = 0.002) in loose periprosthetic bones were shown in dynamic data analysis. These results were confirmed by precise morphological observation by confocal laser scanning microscopy. Active coupling of bone formation and resorption and increased osteocytes with abundant bone canalicular projections were found in combined with the presence of immature bone matrices (osteoid and low-mineralized bone areas) in periprosthetic bones from loose hip joints. These results indicated that active osteoclastic bone resorption and/or defective bone formation are coupled with monocyte/macrophage-mediated foreign body-type granuloma in the synovial-like interface membrane of loose hip joints. Thus, this unique high-turnover periprosthetic bone remodeling with bad bone quality probably is caused by the result of cellular host response combined with inappropriate cyclic mechanical loading. The fragile periprosthetic bone may contribute to hip prosthesis loosening. [source] Immunosuppression with FK506 Increases Bone Induction in Demineralized Isogeneic and Xenogeneic Bone Matrix in the RatJOURNAL OF BONE AND MINERAL RESEARCH, Issue 9 2000Dr. Gregor Voggenreiter Abstract The aim of the present study was to investigate a systemic induction of bone formation in rats by immunosuppression with FK506 (1 mg/kg body weight intraperitoneally [ip]) in a model of osteoinduction of isogeneic and xenogeneic demineralized bone matrix (DBM) for a period of 28 days. In particular, alterations of in vitro cytokine synthesis and changes of lymphocyte subsets were studied. DBM was implanted intramuscularly in the abdominal wall of Lewis rats (seven per group). Blood was sampled on days ,7, 0, 7, and 28 for determination of in vitro tumor necrosis factor , (TNF-,) synthesis and lymphocyte subsets by flow cytometry (CD3+, CD4+, CD8+, CD45+, ED9+, and Ia+ antibodies). Ossicles of de novo formed bone and the tibias were removed on day 28 after double tetracycline labeling for histomorphometric analysis. Immunosuppression with FK506 significantly decreased lipopolysaccharide (LPS)-stimulated in vitro cytokine synthesis after 7 days and 28 days (p < 0.05). Compared with control animals FK506 treatment significantly increased the volume of induced bone in isogeneic (2.1 ± 0.3 mm3 vs. 10.8 ± 0.9 mm3) and xenogeneic (0 mm3 vs. 4.7 ± 0.8 mm3) DBM. Bone histomorphometry of the tibias revealed that immunosuppression increased both bone formation and bone resorption, accompanied by a significant reduction in the relative trabecular area (Tb.Ar). FK506 caused a decrease in the counts of CD8+ T cells probably because of destruction or dislocation of these cells. This suggests that the amount of CD8+ cells and the degree of T cell activation in terms of mean fluorescence intensity (MFI) may be associated with bone metabolism. In support of this, statistical analysis revealed a significant positive correlation between parameters of bone formation as well as bone resorption and the CD4+/CD8+ ratio. There was a significant negative correlation between parameters of remodeling of the metaphysis of the tibia and induced bone volume (BV), respectively, and MFI values of CD3+/Ia+ cells. These findings suggest an important role of T lymphocytes in bone formation and bone resorption in vivo. FK506 caused a marked increase of bone formation in DBM. However, the conclusion that immunosuppression increases fracture healing warrants further investigation. [source] Mice Lacking the Plasminogen Activator Inhibitor 1 Are Protected from Trabecular Bone Loss Induced by Estrogen DeficiencyJOURNAL OF BONE AND MINERAL RESEARCH, Issue 8 2000E. Daci Abstract Bone turnover requires the interaction of several proteases during the resorption phase. Indirect evidence suggests that the plasminogen activator/plasmin pathway is involved in bone resorption and turnover, and recently we have shown that this cascade plays a role in the degradation of nonmineralized bone matrix in vitro. To elucidate the role of the plasminogen activator inhibitor 1 (PAI-1) in bone turnover in vivo, bone metabolism was analyzed in mice deficient in the expression of PAI-1 gene (PAI-1,/,) at baseline (8-week-old mice) and 4 weeks after ovariectomy (OVX) or sham operation (Sham) and compared with wild-type (WT) mice. PAI-1 inactivation was without any effect on bone metabolism at baseline or in Sham mice. However, significant differences were observed in the response of WT and PAI-1,/, mice to ovariectomy. The OVX WT mice showed, as expected, decreased trabecular bone volume (BV/TV) and increased osteoid surface (OS/BS) and bone formation rate (BFR), as assessed by histomorphometric analysis of the proximal tibial metaphysis. In contrast, no significant change in any of the histomorphometric variables studied was detected in PAI-1,/, mice after ovariectomy. As a result, the OVX PAI-1,/, had a significantly higher BV/TV, lower OS/BS, lower mineral apposition rate (MAR) and BFR when compared with the OVX WT mice. However, a comparable decrease in the cortical thickness was observed in OVX PAI-1,/, and WT mice. In addition, the cortical mineral content and density assessed in the distal femoral metaphysis by peripheral quantitative computed tomography (pQCT), decreased significantly after ovariectomy, without difference between PAI-1,/, mice and WT mice. In conclusion, basal bone turnover and bone mass are only minimally affected by PAI-1 inactivation. In conditions of estrogen deficiency, PAI-1 inactivation protects against trabecular bone loss but does not affect cortical bone loss, suggesting a site-specific role for PAI-1 in bone turnover. [source] Loss of Osteocyte Integrity in Association with Microdamage and Bone Remodeling After Fatigue In Vivo,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 1 2000Olivier Verborgt Abstract As a result of fatigue, bone sustains microdamage, which is then repaired by bone-remodeling processes. How osteoclastic activity is targeted at the removal of microdamaged regions of bone matrix is unknown. In the current studies, we tested the hypothesis that changes in osteocyte integrity, through the initiation of regulated cell death (apoptosis), are associated with fatigue-related microdamage and bone resorption. Ulnae of adult rats were fatigue-loaded to produce a known degree of matrix damage. Osteocyte integrity was then assessed histomorphometrically from terminal deoxynucleotidyl transferase,mediated deoxyuridine triphosphate,nick end labeling (TUNEL),stained sections to detect cells undergoing DNA fragmentation associated with apoptosis; toluidine blue,stained sections were used for secondary morphological confirmation. Ten days after loading, large numbers of TUNEL-positive osteocytes were found in bone surrounding microcracks and in bone surrounding intracortical resorption spaces (,300% increases over controls, p < 0.005). TUNEL labeling in loaded ulnae at sites distant from microcracks or resorption foci did not differ from that in control bone. Osteocytes in toluidine blue,stained sections showed equivalent trends to TUNEL-stained sections, with significant increases in pyknotic nuclei and empty lacunae associated with microcracks and intracortical resorption spaces. TUNEL-positive osteocytes were observed around bone microdamage by 1 day after loading (p < 0.01 relative to baseline), and their number remained elevated throughout the entire experimental period. Increases in empty lacunae and decreases in normal osteocyte numbers were observed over time as well. These studies show that (1) osteocyte apoptosis is induced by bone fatigue, (2) this apoptosis is localized to regions of bone that contain microcracks, and (3) osteoclastic resorption after fatigue also coincides with regions of osteocyte apoptosis. The strong associations between microdamage, osteocyte apoptosis, and subsequent bone remodeling support the hypothesis that osteocyte apoptosis provides a key part of the activation or signaling mechanisms by which osteoclasts target bone for removal after fatigue-induced matrix injury. [source] Evaluation of processed bovine cancellous bone matrix seeded with syngenic osteoblasts in a critical size calvarial defect rat modelJOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 3 2006U. Kneser Abstract Introduction: Biologic bone substitutes may offer alternatives to bone grafting procedures. The aim of this study was to evaluate a preformed bone substitute based on processed bovine cancellous bone (PBCB) with or without osteogenic cells in a critical size calvarial defect rat model. Methods: Discs of PBCB (Tutobone®) were seeded with second passage fibrin gel-immobilized syngenic osteoblasts (group A, n = 40). Cell-free matrices (group B, n = 28) and untreated defects (group C; n=28) served as controls. Specimens were explanted between day 0 and 4 months after implantation and were subjected to histological and morphometric evaluation. Results: At 1 month, bone formation was limited to small peripheral areas. At 2 and 4 months, significant bone formation, matrix resorption as well as integration of the implants was evident in groups A and B. In group C no significant regeneration of the defects was observed. Morphometric analysis did not disclose differences in bone formation in matrices from groups A and B. Carboxyfluorescine-Diacetate-Succinimidylester (CFDA) labeling demonstrated low survival rates of transplanted cells. Discussion: Osteoblasts seeded into PBCB matrix display a differentiated phenotype following a 14 days cell culture period. Lack of initial vascularization may explain the absence of added osteogenicity in constructs from group A in comparison to group B. PBCB is well integrated and represents even without osteogenic cells a promising biomaterial for reconstruction of critical size calvarial bone defects. [source] Optimized transfection of diced siRNA into mature primary human osteoclasts: Inhibition of cathepsin K mediated bone resorption by siRNAJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 5 2005Christina I. Selinger Abstract Osteoclasts are large multinucleated cells responsible for bone resorption. Bone resorption is dependent on the liberation of calcium by acid and protease destruction of the bone matrix by proteinases. The key proteinase produced by the osteoclast is cathepsin K. Targeted knock-down of cathepsin K was performed using small inhibitory RNA (siRNA). siRNA is a method that introduces short double-stranded RNA molecules that instruct the RNA-induced silencing complex (RISC) to degrade mRNA species complementary to the siRNA. Transfection of siRNA by lipid cations allows for short-term inhibition of expression of the targeted gene. We show that transfection of primary human osteoclasts with siRNA to cathepsin K reduces expression by ,60% and significantly inhibits bone resorption with a reduction of both resorption pit numbers (P,=,0.018) and resorbed area (P,=,0.013). We also show that FuGENE 6 is an effective lipid transfection reagent with which to transfect primary human osteoclasts, that does not produce off-target effects. © 2005 Wiley-Liss, Inc. [source] Transforming growth factor- , stimulates Interleukin-11 production by human periodontal ligament and gingival fibroblastsJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 3 2006R. Yashiro Abstract Background: Transforming growth factor (TGF)- , is a potent multifunctional polypeptide, abundant in the bone matrix. Interleukin (IL)-11 is a pleiotropic cytokine with effects on multiple cell types. The present study was performed to evaluate the regulatory effects of TGF- , on IL-11 production by human periodontal ligament cells (PDL) and human gingival fibroblasts (HGF). Material and Methods: The expression of TGF- , receptor in PDL and HGF were observed using flow cytometry. PDL and HGF were stimulated with TGF- , with or without protein kinase C (PKC) inhibitors and activator. IL-11, bone morphogenetic protein-2 (BMP-2) and TGF- , mRNA expression was quantified by real-time polymerase chain reaction (PCR). IL-11 production was measured using enzyme-linked immunosorbent assay. Results: PDL and HGF expressed both TGF- , receptor I and TGF- , receptor II on the cell surfaces. IL-11 mRNA expression and IL-11 production were augmented by TGF- , in both PDL and HGF, with higher values in PDL. PKC inhibitors partially suppressed TGF- , -induced IL-11 production in PDL and HGF, whereas activator enhanced it. TGF- , mRNA and BMP-2 mRNA expression were up-regulated by TGF- , in PDL. Conclusion: These results suggest that PDL produce IL-11 in response to TGF- ,. [source] Osteogenesis by guided tissue regeneration and demineralized bone matrixJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 3 2003N. Mardas Abstract Aim:, To evaluate in a discriminating capsule model whether bone formation by guided tissue regeneration (GTR) may be influenced by concomitant implantation of demineralized bone matrix (DBM). Materials and Methods:, Thirty 4-month-old male albino rats of the Wistar strain were used in the study. Following surgical exposure of the mandibular ramus, a hemispherical, Teflon capsule (5.0 mm in diameter), loosely packed with a standardized amount of DBM, was placed with its open part facing the lateral bone surface of the ramus. At the contralateral side, an empty capsule was placed, serving as control. After healing periods of 15, 30, and 120 days, groups of 10 animals were sacrificed and 40,70 ,m thick undecalcified sections of the capsules were produced. In the sections, the cross-sectional areas of (1) the space created by the capsule, (2) newly formed bone, (3) DBM particles, (4) loose connective tissue as well as the (5) height of the capsules, and (6) that of the newly formed bone were measured. Results:, Increasing bone fill was observed in both test and control sites from 30 to 120 days. After 30 days of healing, the mean amount of bone was approx. 3% of the cross-sectional area of the capsules at the test sites while it was 8% in the control sites (p<0.05). However, no statistically significant differences were observed between the test (46%) and control (64%) sites after 120 days regarding any of the measured parameters (p>0.05). The newly formed bone in the DBM group at 120 days, on the other hand, appeared more dense than that in the control capsules. Conclusion:, DBM used as an adjunct to GTR did not provide any added effect on bone formation but increased the density of the newly formed bone. Zusammenfassung Ziel: Die Untersuchung in einem Kapselmodell, welches differenzieren kann, ob die Knochenbildung durch GTR durch die gleichzeitige Implantation von demineralisierter Knochenmatrix (DBM) beeinflusst werden könnte Material und Methoden: Dreißig männliche 4-Monate-alte Albinoratten des Wistar Stammes wurden in der Studie verwendet. Nach der chirurgischen Freilegung des Unterkieferastes wurde eine halbkugelförmige Teflonkapsel (5,0 mm Durchmesser), welche locker mit einer standardisierten Menge von DBM versehen war, wurde mit ihrer offenen Fläche auf die seitlichen Knochenfläche des Ramus gelegt. Auf der kontralateralen Seite diente eine leere Kapsel als Kontrolle. Nach Heilungsintervallen von 15, 30 und 120 Tagen wurden Gruppen von 10 Tieren geopfert und 40-70 ,m dicke nicht-entkalkte Schnitte der Kapseln wurden hergestellt. An den Schnitten wurde die Querschnittsfläche von: 1) der Fläche, die von der Kapsel geschaffen wurde, 2) dem neu gebildeten Knochen, 3) den DBM-Partikeln, 4) dem lockeren Bindegewebe gemessen, als auch 5) die Höhe der Kapseln und 6) des neu gebildeten Knochens bestimmt. Ergebnisse: Von Tag 30 zu Tag 120 wurde sowohl bei den Test- als auch bei den Kontrollstellen eine erhöhte Knochenauffüllung beobachtet. Nach 30 Tagen der Heilung betrug an den Teststellen die mittlere Knochenmenge ungefähr 3% der Querschnittsfläche der Kapseln, während sie an den Kontrollstellen 8% (p<0,05) betrug. Jedoch wurde nach 120 Tagen bei keinem der gemessenen Parameter eine statistisch signifikante Differenz zwischen den Test- (46%) und den Kontrollstellen (64%) beobachtet. Auf der anderen Seite erschien nach 120 Tagen in der DBM-Gruppe der neu gebildete Knochen dichter als in den Kontrollkapseln Schlussfolgerung: DBM welches als Zusatz bei der GTR verwendet wurde, lieferte keinen zusätzlichen Effekt bei der Knochenbildung, aber erhöhte die Dichte des neu gebildeten Knochens. Résumé Le but de cette étude a été d'évaluer dans un modèle de capsule discriminatoire si la formation osseuse par regénération tissulaire guidée (GTR) pouvait être influencée par l'implantation concomitante de matrice osseuse déminéralisée (DBM). Trente rats albinos mâles âgés de quatre mois de la souche Wistar ont été utilisés pour cette étude. A la suite de l'exposition chirurgicale de la branche montante mandibulaire, une capsule en téflon hémisphérique de 0,5 mm de diamètre remplie sans tassement avec une quantité standardisée de DBM a été placée avec sa partie ouverte contre la surface osseuse latérale de la branche. Du côté contralatéral, une capsule vide était placée servant de contrôle. Après des périodes de guérison de 15, 30 et 120 jours, des groupes de dix animaux ont été tués et des coupes non-décalcifiées de 40 à 70 ,m d'épaisseur des capsules ont été effectuées. Dans ces coupes, une aire sur coupe transversale contenant 1) l'espace créé par la capsule, 2) l'os néoformé, 3) des particules DBM, 4) du tissu conjonctif lâche; 5) la hauteur des capsules et 6) et celle de l'os néoformé ont été mesurés. Un comblement osseux de plus en plus important tant dans les sites contrôles que les sites tests a été constaté entre les jours 30 et 120. Après 30 jours de guérison, la quantité moyenne d'os formait approximativement 3% de l'aire de la coupe des capsules dans les sites tests tandis qu'elle était de 8% dans les sites contrôles (p<0,05). Cependant, aucune différence statistique n'a été observée entre les sites tests (46%) et les sites contrôles (64%) après 120 jours pour les paramètres mesurés (p>0,05). L'os néoformé dans le groupe DBM à 120 jours semblait plus dense que dans les capsules contrôles. Le DBM utilisé durant la GTR n'apportait aucun effet additionnel sur la formation osseuse mais augmentait cependant la densité du nouvel os formé. [source] Augmentation of osseous phenotypes in vivo with a synthetic peptideJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 4 2007Xinhua Lin Abstract The synthetic peptide B2A2-K-NS augmented the in vitro expression of osseous phenotypes when cells were stimulated with BMP-2, an osteoinductive growth factor. B2A2-K-NS significantly enhanced the effects of BMP-2-induced alkaline phosphatase activity and mineralization. In the absence of BMP-2, B2A2-K-NS did not have an effect on these endpoints. Based on these observations, in vivo studies were conducted to evaluate if B2A2-K-NS could augment osseous phenotypes in an osteoinductive environment in which BMP-2 should be present. In one study, human demineralized bone matrix (DBM) was used to generate an osteoinductive environment and the effects of B2A2-K-NS on ectopic mineralization of subcutaneous implants evaluated. In the second study, a noncritical sized defect in rabbit ulnas with inherent reparative capacity was used as the osteoinductive environment and was treated with or without B2A2-K-NS. In the DBM studies, B2A2-K-NS augmented mineralization as determined using a combination of radiographic analysis and von Kossa staining at 4 weeks postimplant. In the rabbit ulna model, B2A2-K-NS significantly increased the radiographic bone density in the defects compared to carrier-only or no-treatment controls after 6 weeks. Histological staining confirmed that B2A2-K-NS generated a pronounced bone repair response. The results are consistent with the hypothesis that B2A2-K-NS augments osseous phenotypes in an osteoinductive environment, and suggests that B2A2-K-NS may have clinical utility. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 25:531,539, 2007 [source] The efficacy of cylindrical titanium mesh cage for the reconstruction of a critical-size canine segmental femoral diaphyseal defectJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 7 2006Ronald W. Lindsey Abstract The authors developed a novel technique for the reconstruction of large segmental long bone defects using a cylindrical titanium mesh cage (CTMC). Although the initial clinical reports have been favorable, the CTMC technique has yet to be validated in a clinically relevant large animal model, which is the purpose of this study. Under general anesthesia, a unilateral, 3-cm mid-diaphyseal segmental defect was created in the femur of an adult canine. The defect reconstruction technique consisted of a CTMC that was packed and surrounded with a standard volume of morselized canine cancellous allograft and canine demineralized bone matrix. The limb was stabilized with a reamed titanium intramedullary nail. Animals were distributed into four experimental groups: in Groups A, B, and C (six dogs each), defects were CTMC reconstructed, and the animals euthanized at 6, 12, and 18 weeks, respectively; in Group D (three dogs), the same defect reconstruction was performed but without a CTMC, and the animals were euthanized at 18 weeks. The femurs were harvested and analyzed by gross inspection, plain radiography, computed tomography (CT), and single photon emission computed tomography (SPECT). The femurs were mechanically tested in axial torsion to failure; two randomly selected defect femurs from each group were analyzed histologically. Groups A, B, and C specimens gross inspection, plain radiography, and CT, demonstrated bony restoration of the defect, and SPECT confirmed sustained biological activity throughout the CTMC. Compared to the contralateral femur, the 6-, 12-, and 18-week mean defect torsional stiffness was 44.4, 45.7, and 72.5%, respectively; the mean torsional strength was 51.0, 73.6, and 83.4%, respectively. Histology documented new bone formation spanning the defect. Conversely, Group D specimens (without CTMC) demonstrated no meaningful bone formation, biologic activity, or mechanical integrity at 18 weeks. The CTMC technique facilitated healing of a canine femur segmental defect model, while the same technique without a cage did not. The CTMC technique may be a viable alternative for the treatment of segmental long bone defects. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 24:1438,1453, 2006 [source] Accelerated repair of cortical bone defects using a synthetic extracellular matrix to deliver human demineralized bone matrixJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 7 2006Yanchun Liu Abstract Injectable hydrogel and porous sponge formulations of CarbylanÔ-GSX, a crosslinked synthetic extracellular matrix (ECM), were used to deliver human demineralized bone matrix (DBM) in a rat femoral defect model. A cortical, full-thickness 5-mm defect was created in two femurs of each rat. Six rats were assigned to each of five experimental groups (thus, 12 defects per group). The defects were either untreated or filled with CarbylanÔ-GSX hydrogel or sponges with or without 20% (w/v) DBM. Radiographs were obtained on day 1 and at weeks 2, 4, 6, and 8 postsurgery of each femur. Animals were sacrificed at week 8 postsurgery and each femur was fixed, embedded, sectioned, and processed for Masson's Trichrome staining. The bone defects were measured from radiographs and the fraction of bone healing was calculated. The average fractions of bone healing for each group were statistically different among all groups, and all treatment groups were significantly better than the control group. The CarbylanÔ-GSX sponge with DBM was superior to the sponge without DBM and to the hydrogel with DBM. Histology showed that defects treated with the CarbylanÔ-GSX sponge plus DBM were completely filled with newly generated bone tissue with a thickness comparable to native bone. CarbylanÔ-GSX sponge was an optimal delivery vehicle for human DBM to accelerate bone healing. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 24:1454,1462, 2006 [source] Early bone in-growth ability of alumina ceramic implants loaded with tissue-engineered boneJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 4 2006Yasuaki Tohma Abstract To enhance early bonding of an alumina ceramic implant to bone, we evaluated a method of seeding the implant surface with bone marrow mesenchymal cells that differentiated to osteoblasts and bone matrix prior to implantation. The usefulness of the method was evaluated in Japanese white rabbits. In our study, an alumina ceramic test piece loaded with differentiated osteoblasts and bone matrix by a tissue engineering technique was implanted into rabbit bones. Three weeks after the procedure, evaluation of mechanical bonding and histological examination were performed. Histological examination of the noncell-loaded implant surfaces showed no bone infiltration into the implant gap. However, the cell-loaded implant surfaces exhibited new bone infiltration into the implant gap with mechanical bonding. In the mechanical test, the average failure load was 0.60 kgf for the noncell-loaded side and 1.49 kgf for the cell-loaded side. Preculturing mesenchymal cells on the surface of the alumina ceramic prior to implantation increased the debonding strength by two and half times. The present findings indicate early bonding between the implant and bone three weeks after the procedure. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res [source] Rapid quantitative bioassay of osteoinductionJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 3 2000Huston Davis Adkisson We developed a reproducible, relatively rapid bioassay that quantitatively correlates with the osteoinductive capacity of demineralized bone matrix obtained from human long bones. We have found that Saos human osteosarcoma cells proliferate in response to incubation with demineralized bone matrix and that an index of this proliferative activity correlates with demineralized bone matrix-induced osteogenesis in vivo. The bioassay (Saos cell proliferation) had an interassay coefficient of variation of 23 ± 2% and an intra-assay cocfficient of 11 ± 1%. Cell proliferation was normalized to a standard sample of demineralized bone matrix with a clinically high osteoinductive capacity, which was assigned a value of one. The Saos cell proliferation for each sample was related to the standard and assigned a value placing it into thc low (0.00-0.39), intermediate (0.40-0.69). or high (0.70-1.49) osteoinductivc index group. Osteoinduction of human demineralized bone matrix was quantitated by expressing new bone formation as a function of the total bone volume (new bone plus the demineralized bone powder). The demineralized bone matrix was placed in pouches formed in the rectus abdominis muscles of athymic rats, and endochondral bone formation was assessed at 35 days following implantation, when marrow spaces in the ossicles were formed by new bone bridging the spaces between demineralized bone matrix particles. The proliferative index correlated with the area of new bone formation in histological sections ol the newly formed ossicles. When the proliferative index (the osteoinductive index) was divided into low, intermediate. and high groups, the correlation between it and new bone formation (osteoinduction) was 0.850 (p < 0.0005) in 25 samples of demineralized bone matrix. There was no overlap in the osteoinduction stimulated between the samples with low and high osteoinductive indices. We conclude that the proliferation assay is useful for the routine screening of bone allograft donors for osteoinductivc potential. Furthermore, the two-dimensional area of new bone formation. as it relates to total new bone area, is a quantitative measure of osteoinduction. [source] | |||||||||||||||||||||||||