bluuebunny/crossref_metadata_2025 huggingface dataset:
Catastrophic rock avalanche 3600 years BP from El Capitan, Yosemite Valley, California
Authors: Stock Greg M. , Uhrhammer Robert A.
Published: February 2010

Large rock slope failures from near‐vertical cliffs are an important geomorphic process driving the evolution of mountainous landscapes, particularly glacially steepened cliffs. The morphology and age of a 2·19 × 106 m3 rock avalanche deposit beneath El Capitan in Yosemite Valley indicates a massive prehistoric failure of a large expanse of the southeast face. Geologic mapping of the deposit and the cliff face constrains the rock avalanche source to an area near the summit of ∼8·5 × 104 m2. The rock mass free fell ∼650 m, reaching a maximum velocity of 100 m s−1, impacted the talus slope and spread across the valley floor, extending 670 m from the base of the cliff. Cosmogenic beryllium‐10 exposure ages from boulders in the deposit yield a mean age of 3·6 ± 0·2 ka. The ∼13 kyr time lag between deglaciation and failure suggests that the rock avalanche did not occur as a direct result of glacial debuttressing. The ∼3·6 ka age for the rock avalanche does coincide with estimated late Holocene rupture of the Owens Valley fault and/or White Mountain fault between 3·3 and 3·8 ka. The coincidence of ages, combined with the fact that the most recent (AD 1872) Owens Valley fault rupture triggered numerous large rock falls in Yosemite Valley, suggest that a large magnitude earthquake (≥M7.0) centered in the south‐eastern Sierra Nevada may have triggered the rock avalanche. If correct, the extreme hazard posed by rock avalanches in Yosemite Valley remains present and depends on local earthquake recurrence intervals. Published in 2010 by John Wiley & Sons, Ltd.
Parallel adaptive solution of coupled Rayleigh–Bénard–Marangoni problems with the Navier‐slip
Authors: Peterson J. W. , Carey G. F.
Published: February 2010

This study deals with modeling certain nonlinear interactions that give rise to cellular flow in heated thin fluid layers with thermocapillary surface‐tension at the free surface. Of particular interest in these Rayleigh–Bénard–Marangoni (RBM) studies is the effect of varying roughness (stick and slip) on the base or sides of the fluid container. This stick‐slip behavior at container boundaries and thermocapillary shear stress at the free surface may lead to strongly varying local gradients in the solution that are addressed here using local adaptive mesh refinement. In turn, these local effects influence the global structure of cell patterns resulting from competing buoyancy, surface‐tension and stick‐slip effects. This behavior is illustrated by the results of numerical simulations of cellular flow structure in containers of varying aspect ratio and with spatially varying base boundary treatments. Details of the Navier‐slip approximation and the adaptive mesh refinement strategy are given, together with a brief description of the relevant features of the parallel adaptive software framework, LibMesh, and associated algorithms employed in the present simulations. Copyright © 2010 John Wiley & Sons, Ltd.
Changing the World with Müsli
Authors: Fritzen Florentine
Published: February 2010

The Lebensreform movement campaigned for a life more in tune with nature. Today the movement is only of historical interest, but it has had a lasting impact on health awareness
Going Under the Knife with Mathematics
Authors: Deuflhard Peter
Published: February 2010

Disfigurations that occur in a person's face can be partially corrected by oral and maxillofacial surgery. When planning an operation, highly complex differential equations and three‐dimensional visualisations can be of great assistance
Optics Starts Walking on Two Legs
Authors: Wegener Martin , Linden Stefan
Published: February 2010

Nanoscopically small and artifcially made: Metamaterials open up previously undreamed of possibilities for researchers. Tailored “photonic atoms” help them achieving new optical properties and inspire them to develop innovative applications
Inspired by Nature
Authors: Weigand Bernhard , Neumann Sven Olaf , Steinbrück Helga , Zehner Sebastian
Published: February 2010

An engineer's dream: the shape of a circumflowed object is optimised by the ice formation method, thus facilitating the design of new machine components
Invisible Companions
Authors: Schiffer Hanno
Published: February 2010

Torsten Granzow creates Hightech Ceramics
Glucagon-Like Peptide-1 Receptor Is Present on Human Hepatocytes and Has A Direct Role in Decreasing Hepatic Steatosis in Vitro by Modulating Elements of the Insulin Signaling Pathway
Authors: Gupta Nitika Arora , Mells Jamie , Dunham Richard M. , Grakoui Arash , Handy Jeffrey , Saxena Neeraj Kumar , Anania Frank A.
Published: February 2010

Glucagon-like peptide 1 (GLP-1) is a naturally occurring peptide secreted by the L cells of the small intestine. GLP-1 functions as an incretin and stimulates glucose-mediated insulin production by pancreatic β cells. In this study, we demonstrate that exendin-4/GLP-1 has a cognate receptor on human hepatocytes and that exendin-4 has a direct effect on the reduction of hepatic steatosis in the absence of insulin. Both glucagon-like peptide 1 receptor (GLP/R) messenger RNA and protein were detected on primary human hepatocytes, and receptor was internalized in the presence of GLP-1. Exendin-4 increased the phosphorylation of 3-phosphoinositide-dependent kinase-1 (PDK-1), AKT, and protein kinase C ζ (PKC-ζ) in HepG2 and Huh7 cells. Small interfering RNA against GLP-1R abolished the effects on PDK-1 and PKC-ζ. Treatment with exendin-4 quantitatively reduced triglyceride stores compared with control-treated cells.

Conclusion:

This is the first report that the G protein–coupled receptor GLP-1R is present on human hepatocytes. Furthermore, it appears that exendin-4 has the same beneficial effects

in vitro

as those seen in our previously published

in vivo

study in

ob/ob

mice, directly reducing hepatocyte steatosis. Future use for human nonalcoholic fatty liver disease, either in combination with dietary manipulation or other pharmacotherapy, may be a significant advance in treatment of this common form of liver disease. (Hepatology 2010)
The role of situational goals and audience on self‐reported emotion experience and expression: Dutch and South Korean children compared
Authors: Novin Sheida , Rieffe Carolien , Mo Theresa J. H.
Published: February 2010

Previous research demonstrates that cultural concerns affect emotional lives. However, the question remains to what extent salient cultural concerns influence emotion experience and expression. In the present study, the role of (i) individualistic versus collectivistic goals and (ii) presence of an authority figure (father) versus an equal status figure (peer), were systematically investigated in 24 Dutch and 23 South Korean children's (a) negative emotion experience and (b) emotion expression and motives using hypothetical conflict situations. The results reveal that for children from both cultures emotion experience did not vary between situational goals and the audience present, however their emotion expression did. More specifically, cultural differences in how negative emotions would be expressed appeared in ‘father’ situations and not in ‘peer’ situations. Cultural differences in children's motives for emotion expression were revealed in situations with a collectivistic goal and not when an individualistic goal was presented. Moreover, within group analyses indicate that Dutch children's emotion expressions were more context‐sensitive than those of South Korean children. These results indicate that some situational features corresponding to cultural concerns partly explained cultural differences, whereas other features did not, helping to improve our understanding about variation in the emotional lives of different cultural groups. Copyright © 2010 John Wiley & Sons, Ltd.
Clinicopathological and protein characterization of BRAF‐ and K‐RAS‐mutated colorectal cancer and implications for prognosis
Authors: Zlobec Inti , Bihl Michel P. , Schwarb Heike , Terracciano Luigi , Lugli Alessandro
Published: February 2010

Recent evidence highlights the potential prognostic and predictive value of BRAF and K‐RAS gene alterations in patients with colorectal cancer. However, a comprehensive evaluation of BRAF and K‐RAS mutations and their specific clinicopathological features, histomorphological presentation and effect on protein expression have not been systematically analyzed. The aim of this study was to characterize the clinicopathological, histomorphological and protein expression profiles of BRAF‐ and K‐RAS‐mutated colorectal cancers and determine their impact on patient survival. Molecular analysis for microsatellite instability (MSI), K‐RAS and BRAF was carried out on paraffin‐embedded samples from 404 patients with primary colorectal cancer. Using tissue microarrays, 36 tumor‐associated and 14 lymphocyte/inflammatory‐associated markers were evaluated by immunohistochemistry. BRAF mutation was associated with right‐sided tumor location (p < 0.001), higher tumor grade (p = 0.029), absence of peritumoral lymphocytic inflammation (p = 0.026) and MSI‐H (p < 0.001). In right‐sided tumors, loss of CDX2 expression was observed in 23 of 24 cases (95.8%). BRAF mutation was a poor prognostic indicator in patients with right‐sided disease (p = 0.01). This result was maintained in multivariable analysis (p < 0.001; HR = 2.82; 95% CI: 1.5–5.5) with pT, pN and vascular invasion and independent of CDX2 expression. K‐RAS mutation, in contrast, was not associated with any of the features analyzed. BRAF gene mutation is an adverse prognostic factor in right‐sided colon cancer patients independent of MSI status and, moreover, in patients with lymph node‐negative disease. These results indicate that molecular analysis for BRAF may be a useful biomarker for identifying patients with right‐sided colon cancer with poor outcome who may benefit from a more individualized course of therapy.
Instrumental variables regressions with uncertain exclusion restrictions: a Bayesian approach
Authors: Kraay Aart
Published: February 2010

The identification of structural parameters in the linear instrumental variables (IV) model is typically achieved by imposing the prior identifying assumption that the error term in the structural equation of interest is orthogonal to the instruments. Since this exclusion restriction is fundamentally untestable, there are often legitimate doubts about the extent to which the exclusion restriction holds. In this paper I illustrate the effects of such prior uncertainty about the validity of the exclusion restriction on inferences based on linear IV models. Using a Bayesian approach, I provide a mapping from prior uncertainty about the exclusion restriction into increased uncertainty about parameters of interest. Moderate prior uncertainty about exclusion restrictions can lead to a substantial loss of precision in estimates of structural parameters. This loss of precision is relatively more important in situations where IV estimates appear to be more precise, for example in larger samples or with stronger instruments. I illustrate these points using several prominent recent empirical papers that use linear IV models. An accompanying electronic table allows users to readily explore the robustness of inferences to uncertainty about the exclusion restriction in their particular applications. Copyright © 2010 John Wiley & Sons, Ltd.
Measuring the impact of nonignorability in panel data with non‐monotone nonresponse
Authors: Xie Hui , Qian Yi
Published: February 2010

The analysis of panel data with non‐monotone nonresponse often relies on the critical and untestable assumption ofignorablemissingness. It is important to assess the consequences of departures from the ignorability assumption. Non‐monotone nonresponse, however, can often make such sensitivity analysis infeasible because the likelihood functions for alternative models involve high‐dimensional and difficult‐to‐evaluate integrals with respect to missing outcomes. We develop an extension of the local sensitivity method that overcomes computational difficulty and completely avoids fitting alternative models and evaluating these high‐dimensional integrals. The proposed method is applicable to a wide range of panel outcomes. We apply the method to a Smoking Trend dataset where we relax the standard ignorability assumption and evaluate how smoking‐trend estimates in different groups of US young adults are affected by alternative assumptions about the missing‐data mechanism. The main finding is that the standard estimate in the black male group is sensitive to nonignorable missingness but those in other groups are reasonably robust. Copyright © 2010 John Wiley & Sons, Ltd.
Profile of toll‐like receptor–positive cells in septic and aseptic loosening of total hip arthroplasty implants
Authors: Pajarinen Jukka , Cenni Elisabetta , Savarino Lucia , Gomez‐Barrena Enrique , Tamaki Yasunobu , Takagi Michiaki , Salo Jari , Konttinen Yrjö T.
Published: February 2010

Distinction between the two major complications of total hip replacement surgery, septic bacterial culture‐positive and aseptic bacterial culture‐negative osteolysis and loosening, is difficult due to the eventual role of bacterial remnants and biofilms, which are recognized by cells provided by toll‐like receptors (TLRs) of the innate immune system. It was hypothesized that cell typing and TLR mapping might provide new information on the pathomechanisms of loosening. To test this hypothesis, septic (n = 10) and aseptic (n = 5) interface tissue as well as mildly inflamed osteoarthritic synovial membrane (n = 5) samples were characterized and compared using antibodies against several cell line‐specific markers, including fibroblast, monocyte/macrophage, T cell, B cell, plasma cell and neutrophil markers, and TLRs. In osteoarthritic synovium, TLR‐positive cells were restricted to surface tissues and only few inflammatory cells were detected, whereas aseptic interface was heavily infiltrated with monocyte/macrophages, which were also the major TLR‐positive cell type rendering the tissue reactive to TLR ligands. Interestingly, septic cases contained also neutrophil and lymphocyte infiltrates of which especially B‐cell infiltrates might be clinically useful in discriminating the two major complications of the joint replacement surgery. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res, 2010
Efficacy of continued alendronate for fractures in women with and without prevalent vertebral fracture: The FLEX Trial
Authors: Schwartz Ann V , Bauer Douglas C , Cummings Steven R , Cauley Jane A , Ensrud Kristine E , Palermo Lisa , Wallace Robert B , Hochberg Marc C , Feldstein Adrianne C , Lombardi Antonio , Black Dennis M ,   for the FLEX Research Group
Published: February 2010

In the Fracture Intervention Trial (FIT) Long Term Extension (FLEX) Trial, 10 years of alendronate (ALN) did not significantly reduce the risk of nonvertebral fractures (NVFs) compared with 5 years of ALN. Continuing ALN reduced the risk of clinical but not morphometric vertebral fractures regardless of baseline vertebral fracture status. In previous studies, ALN efficacy for NVF prevention in women without prevalent vertebral fracture was limited to those with femoral neck (FN) T-scores of −2.5 or less. To determine whether the effect of long-term ALN on fracture differs by vertebral fracture status and femoral neck (FN) T-score, we performed a post hoc analysis using FLEX data, a randomized, double-blind, placebo-controlled trial among 1099 postmenopausal women originally randomized to ALN in the FIT with mean ALN use of 5 years. In the FLEX Trial, women were randomized to placebo (40%) or ALN 5 mg/day (30%) or ALN 10 mg/day (30%) for an additional 5 years. Among women without vertebral fracture at FLEX baseline (n = 720), continuation of ALN reduced NVF in women with FLEX baseline FN T-scores of −2.5 or less [relative risk (RR) = 0.50, 95% confidence interval (CI) 0.26–0.96] but not with T-scores of greater than −2.5 and −2 or less (RR 0.79, 95% CI 0.37–1.66) or with T-scores of greater than −2 (RR 1.41, 95% CI 0.75–2.66; p for interaction = .019). Continuing ALN for 10 years instead of stopping after 5 years reduces NVF risk in women without prevalent vertebral fracture whose FN T-scores, achieved after 5 years of ALN, are −2.5 or less but does not reduce risk of NVF in women whose T-scores are greater than −2. © 2010 American Society for Bone and Mineral Research
A nonsecosteroidal vitamin D receptor ligand with improved therapeutic window of bone efficacy over hypercalcemia
Authors: Sato Masahiko , Lu Jianliang , Iturria Stephen , Stayrook Keith R , Burris Lorri L , Zeng Qing Qiang , Schmidt Allen , Barr Robert J , Montrose-Rafizadeh Chahrzad , Bryant Henry U , Ma Yanfei L
Published: February 2010

Vitamin D3 analogues were shown to be beneficial for osteoporosis and other indications, but their narrow therapeutic window between efficacy and hypercalcemia has limited their clinical utility. A nonsecosteroidal, tissue-selective, orally bioavailable, vitamin D receptor (VDR) ligand was ascertained to be efficacious in bone while having modest calcemic effects in vivo. This compound (VDRM2) potently induced Retinoid X Receptor alpha (RXR)-VDR heterodimerization (EC50 = 7.1 ± 1.6 nM) and induced osteocalcin promoter activity (EC50 = 1.9 ± 1.6 nM). VDRM2 was less potent in inducing Ca2+ channel transient receptor potential cation channel, subfamily V, member 6 (TRPV6) expression (EC50 = 37 ± 12 nM). VDRM2 then was evaluated in osteopenic ovariectomized (OVX) rats and shown to dose-dependently restore vertebral bone mineral density (BMD) from OVX to sham levels at 0.08 µg/kg per day. Hypercalcemia was observed at a dose of 4.6 µg/kg per day of VDRM2, suggesting a safety margin of 57 [90% confidence interval (CI) 35–91]. 1α,25-dihydroxyvitamin D3 [1α,25(OH)2D], ED71, and alfacalcidol restored BMD at 0.030, 0.0055, and 0.046 µg/kg per day, respectively, whereas hypercalcemia was observed at 0.22, 0.027, and 0.23 µg/kg per day, indicating a safety margin of 7.3, 4.9, and 5.0, respectively (90% CIs 4.1–13, 3.2–7.7, and 3.5–6.7, respectively). Histomorphometry showed that VDRM2 increased cortical bone area and stimulated the periosteal bone-formation rate relative to OVX at doses below the hypercalcemic dose. By contrast, ED71 increased the periosteal bone-formation rate only above the hypercalcemic dose. VDRM2 suppressed eroded surface on trabecular bone surfaces at normal serum calcium dosage levels, suggesting dual anabolic and antiresorptive activity. In summary, vitamin D analogues were more potent than VDRM2, but VDRM2 had a greater safety margin, suggesting possible therapeutic potential. © 2010 American Society for Bone and Mineral Research
Tumor-derived syndecan-1 mediates distal cross-talk with bone that enhances osteoclastogenesis
Authors: Kelly Thomas , Suva Larry J , Nicks Kristy M , MacLeod Veronica , Sanderson Ralph D
Published: February 2010

Tumor-stimulated bone resorption fuels tumor growth and marks a dramatic decline in the health and prognosis of breast cancer patients. Identifying mechanisms that mediate cross-talk between tumor and bone remains a key challenge. We previously demonstrated that breast cancer cells expressing high levels of heparanase exhibit enhanced shedding of the syndecan-1 proteoglycan. Moreover, when these heparanase-high cells are implanted in the mammary fat pad, they elevate bone resorption. In this study, conditioned medium from breast cancer cells expressing high levels of heparanase was shown to significantly stimulate human osteoclastogenesis in vitro (p < .05). The osteoclastogenic activity in the medium of heparanase-high cells was traced to the presence of syndecan-1, intact heparan sulfate chains, and heat-labile factor(s), including the chemokine interleukin 8 (IL-8). The enhanced osteoclastogenesis promoted by the heparanase-high cells results in a dramatic increase in bone resorption in vitro. In addition, the long bones of animals bearing heparanase-high tumors in the mammary fat pad had significantly higher numbers of osteoclasts compared with animals bearing tumors expressing low levels of heparanase (p < .05). Together these data suggest that syndecan-1 shed by tumor cells exerts biologic effects distal to the primary tumor and that it participates in driving osteoclastogenesis and the resulting bone destruction. © 2010 American Society for Bone and Mineral Research
Prevalent fractures are related to cortical bone geometry in young healthy men at age of peak bone mass
Authors: Taes Youri , Lapauw Bruno , Griet Vanbillemont , De Bacquer Dirk , Goemaere Stefan , Zmierczak Hans , Kaufman Jean-Marc
Published: February 2010

Low areal bone mass is a risk factor for fractures in men. Limited data are available on fractures and bone geometry in men, and the relation with sex steroids is incompletely understood. We investigated prevalent fractures in relation to peak bone mass, bone geometry, and sex steroids in healthy young men. Healthy male siblings (n = 677) at the age of peak bone mass (25 to 45 years) were recruited in a cross-sectional population-based study. Trabecular and cortical bone parameters of the radius and cortical bone parameters of the tibia were assessed using peripheral quantitative computed tomography (pQCT). Areal bone mineral density (aBMD) was determined using dual-energy X-ray absorptiometry (DXA). Sex steroids were determined using immunoassays, and fracture prevalence was assessed using questionnaires. Fractures in young men were associated with a longer limb length, shorter trunk, lower trabecular BMD, smaller cortical bone area, and smaller cortical thickness (p < .005) but not with bone-size-adjusted volumetic BMD (vBMD). With decreasing cortical thickness [odds ratio (OR) 1.4/SD, p ≤ .001] and decreasing cortical area (OR 1.5/SD, p ≤ .001), fracture odds ratios increased. No association between sex steroid concentrations and prevalent fractures was observed. Childhood fractures (≤15 years) were associated with a thinner bone cortex (−5%, p ≤ .005) and smaller periosteal size (−3%, p ≤ .005). Fractures occurring later than 15 years of age were associated with a thinner bone cortex (−3%, p ≤ .05) and larger endosteal circumference (+3%, p ≤ .05) without differences in periosteal bone size. In conclusion, prevalent fractures in healthy young men are associated with unfavorable bone geometry and not with cortical vBMD when adjusting for bone size. Moreover, the data suggest different mechanisms of childhood fractures and fractures during adult life. © 2010 American Society for Bone and Mineral Research
Uncoupled angiogenesis and osteogenesis in nicotine-compromised bone healing
Authors: Ma Li , Zheng Li Wu , Sham Mai Har , Cheung Lim Kwong
Published: February 2010

Nicotine is the main chemical component responsible for tobacco addiction. This study aimed to evaluate the influence of nicotine on angiogenesis and osteogenesis and the associated expression of angiogenic and osteogenic mediators during bone healing. Forty-eight adult New Zealand White rabbits were randomly assigned to a nicotine group and a control group. Nicotine pellets (1.5 g, 60-day time release) or placebo pellets were implanted in the neck subcutaneous tissue. The nicotine or placebo exposure time for all the animals was 7 weeks. Unilateral mandibular distraction osteogenesis was performed. Eight animals in each group were euthanized on day 5, day 11 of active distraction, and week 1 of consolidation, respectively. The mandibular samples were subjected to radiographic, histologic, immunohistochemical, and real-time reverse-transcriptase polymerase chain reaction examinations. Nicotine exposure upregulated the expression of hypoxia inducible factor 1α and vascular endothelial growth factor and enhanced angiogenesis but inhibited the expression of bone morphogenetic protein 2 and impaired bone healing. The results indicate that nicotine decouples angiogenesis and osteogenesis in this rabbit model of distraction osteogenesis, and the enhanced angiogenesis cannot compensate for the adverse effects of nicotine on bone healing. © 2010 American Society for Bone and Mineral Research
Elevated serum levels of IGF-1 are sufficient to establish normal body size and skeletal properties even in the absence of tissue IGF-1
Authors: Elis Sebastien , Courtland Hayden-William , Wu Yingjie , Rosen Clifford J , Sun Hui , Jepsen Karl J , Majeska Robert J , Yakar Shoshana
Published: February 2010

Use of recombinant insulin-like growth factor 1 (IGF-1) as a treatment for primary IGF-1 deficiency in children has become increasingly common. When untreated, primary IGF-1 deficiency may lead to a range of metabolic disorders, including lipid abnormalities, insulin resistance, and decreased bone density. To date, results of this therapy are considered encouraging; however, our understanding of the role played by IGF-1 during development remains limited. Studies on long-term treatment with recombinant IGF-1 in both children and animals are few. Here, we used two novel transgenic mouse strains to test the long-term effects of elevated circulating IGF-1 on body size and skeletal development. Overexpression of the rat igf1 transgene in livers of mice with otherwise normal IGF-1 expression (HIT mice) resulted in approximately threefold increases in serum IGF-1 levels throughout growth, as well as greater body mass and enhanced skeletal size, architecture, and mechanical properties. When the igf1 transgene was overexpressed in livers of igf1 null mice (KO-HIT), the comparably elevated serum IGF-1 failed to overcome growth and skeletal deficiencies during neonatal and early postnatal growth. However, between 4 and 16 weeks of age, increased serum IGF-1 fully compensated for the absence of locally produced IGF-1 because body weights and lengths of KO-HIT mice became comparable with controls. Furthermore, micro-computed tomography (µCT) analysis revealed that early deficits in skeletal structure of KO-HIT mice were restored to control levels by adulthood. Our data indicate that in the absence of tissue igf1 gene expression, maintaining long-term elevations in serum IGF-1 is sufficient to establish normal body size, body composition, and both skeletal architecture and mechanical function. © 2010 American Society for Bone and Mineral Research
Osthole stimulates osteoblast differentiation and bone formation by activation of β-catenin–BMP signaling
Authors: Tang De-Zhi , Hou Wei , Zhou Quan , Zhang Minjie , Holz Jonathan , Sheu Tzong-Jen , Li Tian-Fang , Cheng Shao-Dan , Shi Qi , Harris Stephen E , Chen Di , Wang Yong-Jun
Published: February 2010

Osteoporosis is defined as reduced bone mineral density with a high risk of fragile fracture. Current available treatment regimens include antiresorptive drugs such as estrogen receptor analogues and bisphosphates and anabolic agents such as parathyroid hormone (PTH). However, neither option is completely satisfactory because of adverse effects. It is thus highly desirable to identify novel anabolic agents to improve future osteoporosis treatment. Osthole, a coumarin-like derivative extracted from Chinese herbs, has been shown to stimulate osteoblast proliferation and differentiation, but its effect on bone formation in vivo and underlying mechanism remain unknown. In this study, we found that local injection of Osthole significantly increased new bone formation on the surface of mouse calvaria. Ovariectomy caused evident bone loss in rats, whereas Osthole largely prevented such loss, as shown by improved bone microarchitecture, histomorphometric parameters, and biomechanical properties. In vitro studies demonstrated that Osthole activated Wnt/β-catenin signaling, increased Bmp2 expression, and stimulated osteoblast differentiation. Targeted deletion of the β-catenin and Bmp2 genes abolished the stimulatory effect of Osthole on osteoblast differentiation. Since deletion of the Bmp2 gene did not affect Osthole-induced β-catenin expression and the deletion of the β-catenin gene inhibited Osthole-regulated Bmp2 expression in osteoblasts, we propose that Osthole acts through β-catenin–BMP signaling to promote osteoblast differentiation. Our findings demonstrate that Osthole could be a potential anabolic agent to stimulate bone formation and prevent estrogen deficiency–induced bone loss. © 2010 American Society for Bone and Mineral Research
Increased prevalence of bisphosphonate-related osteonecrosis of the jaw with vitamin D deficiency in rats
Authors: Hokugo Akishige , Christensen Russell , Chung Evelyn M , Sung Eric C , Felsenfeld Alan L , Sayre James W , Garrett Neal , Adams John S , Nishimura Ichiro
Published: February 2010

Necrotic bone exposure in the oral cavity has recently been reported in patients treated with nitrogen-containing bisphosphonates as part of their therapeutic regimen for multiple myeloma or metastatic cancers to bone. It has been postulated that systemic conditions associated with cancer patients combined with tooth extraction may increase the risk of osteonecrosis of the jaw (ONJ). The objective of this study was to establish an animal model of bisphosphonate-related ONJ by testing the combination of these risk factors. The generation of ONJ lesions in rats resembling human disease was achieved under the confluence of intravenous injection of zoledronate (ZOL; 35 µg/kg every 2 weeks), maxillary molar extraction, and vitamin D deficiency [VitD(−)]. The prevalence of ONJ in the VitD(−)/ZOL group was 66.7%, which was significantly higher (p < .05, Fisher exact test) than the control (0%), VitD(−) (0%), and ZOL alone (14.3%) groups. Similar to human patients, rat ONJ lesions prolonged the oral exposure of necrotic bone sequestra and were uniquely associated with pseudoepitheliomatous hyperplasia. The number of terminal deoxynucleotidyl transferase–mediated deoxyuridine triphosphate–biotin nick-end label–positive (TUNEL+) osteoclasts significantly increased on the surface of post–tooth extraction alveolar bone of the VitD(−)/ZOL group, where sustained inflammation was depicted by [18F]fluorodeoxyglucose micro-positron emission tomography (µPET). ONJ lesions were found to be associated with dense accumulation of mixed inflammatory/immune cells. These cells, composed of neutrophils and lymphocytes, appeared to juxtapose apoptotic osteoclasts. It is suggested that the pathophysiologic mechanism(s) underpinning ONJ may involve the interaction between bisphosphonates and compromised vitamin D functions in the realm of skeletal homeostasis and innate immunity. © 2010 American Society for Bone and Mineral Research
Timing of ibuprofen use and bone mineral density adaptations to exercise training
Authors: Kohrt Wendy M , Barry Daniel W , Pelt Rachael E Van , Jankowski Catherine M , Wolfe Pamela , Schwartz Robert S
Published: February 2010

Prostaglandins (PGs) are essential signaling factors in bone mechanotransduction. In animals, inhibition of the enzyme responsible for PG synthesis (cyclooxygenase) by nonsteroidal anti-inflammatory drugs (NSAIDs) blocks the bone-formation response to loading when administered before, but not immediately after, loading. The aim of this proof-of-concept study was to determine whether the timing of NSAID use influences bone mineral density (BMD) adaptations to exercise in humans. Healthy premenopausal women (n = 73) aged 21 to 40 years completed a supervised 9-month weight-bearing exercise training program. They were randomized to take (1) ibuprofen (400 mg) before exercise, placebo after (IBUP/PLAC), (2) placebo before, ibuprofen after (PLAC/IBUP), or (3) placebo before and after (PLAC/PLAC) exercise. Relative changes in hip and lumbar spine BMD from before to after exercise training were assessed using a Hologic Delphi-W dual-energy X-ray absorptiometry (DXA) instrument. Because this was the first study to evaluate whether ibuprofen use affects skeletal adaptations to exercise, only women who were compliant with exercise were included in the primary analyses (IBUP/PLAC, n = 17; PLAC/PLAC, n = 23; and PLAC/IBUP, n = 14). There was a significant effect of drug treatment, adjusted for baseline BMD, on the BMD response to exercise for regions of the hip (total, p < .001; neck, p = .026; trochanter, p = .040; shaft, p = .019) but not the spine (p = .242). The largest increases in BMD occurred in the group that took ibuprofen after exercise. Total-hip BMD changes averaged –0.2% ± 1.3%, 0.4% ± 1.8%, and 2.1% ± 1.7% in the IBUP/PLAC, PLAC/PLAC, and PLAC/IBUP groups, respectively. This preliminary study suggests that taking NSAIDs after exercise enhances the adaptive response of BMD to exercise, whereas taking NSAIDs before may impair the adaptive response. © 2010 American Society for Bone and Mineral Research
Smurf1 inhibits mesenchymal stem cell proliferation and differentiation into osteoblasts through JunB degradation
Authors: Zhao Lan , Huang Jian , Guo Ruolin , Wang Yi , Chen Di , Xing Lianping
Published: February 2010

Ubiquitin ligase Smurf1-deficient mice develop an increased-bone-mass phenotype in an age-dependent manner. It was reported that such a bone-mass increase is related to enhanced activities of differentiated osteoblasts. Although osteoblasts are of mesenchymal stem cell (MSC) origin and MSC proliferation and differentiation can have significant impacts on bone formation, it remains largely unknown whether regulation of MSCs plays a role in the bone-mass increase of Smurf1-deficient mice. In this study we found that bone marrow mesenchymal progenitor cells from Smurf1−/− mice form significantly increased alkaline phosphatase–positive colonies, indicating roles of MSC proliferation and differentiation in bone-mass accrual of Smurf1−/− mice. Interestingly, Smurf1−/− cells have an elevated protein level of AP-1 transcription factor JunB. Biochemical experiments demonstrate that Smurf1 interacts with JunB through the PY motif and targets JunB protein for ubiquitination and proteasomal degradation. Indeed, Smurf1-deficient MSCs have higher proliferation rates, consistent with the facts that cyclin D1 mRNA and protein both are increased in Smurf1−/− cells and JunB can induce cyclinD1 promoter. Moreover, JunB overexpression induces osteoblast differentiation, shown by higher expression of osteoblast markers, and JunB knock-down not only decreases osteoblast differentiation but also restores the osteogenic potential to wild-type level in Smurf1−/− cells. In conclusion, our results suggest that Smurf1 negatively regulates MSC proliferation and differentiation by controlling JunB turnover through an ubiquitin-proteasome pathway. © 2010 American Society for Bone and Mineral Research
rBMP represses Wnt signaling and influences skeletal progenitor cell fate specification during bone repair
Authors: Minear Steve , Leucht Philipp , Miller Samara , Helms Jill A
Published: February 2010

Bone morphogenetic proteins (BMPs) participate in multiple stages of the fetal skeletogenic program from promoting cell condensation to regulating chondrogenesis and bone formation through endochondral ossification. Here, we show that these pleiotropic functions are recapitulated when recombinant BMPs are used to augment skeletal tissue repair. In addition to their well-documented ability to stimulate chondrogenesis in a skeletal injury, we show that recombinant BMPs (rBMPs) simultaneously suppress the differentiation of skeletal progenitor cells in the endosteum and bone marrow cavity to an osteoblast lineage. Both the prochondrogenic and antiosteogenic effects are achieved because rBMP inhibits endogenous β-catenin-dependent Wnt signaling. In the injured periosteum, this repression of Wnt activity results in sox9 upregulation; consequently, cells in the injured periosteum adopt a chondrogenic fate. In the injured endosteum, rBMP also inhibits Wnt signaling, which results in the runx2 and collagen type I downregulation; consequently, cells in this region fail to differentiate into osteoblasts. In muscle surrounding the skeletal injury site, rBMP treatment induces Smad phosphorylation followed by exuberant cell proliferation, an increase in alkaline phosphatase activity, and chondrogenic differentiation. Thus different populations of adult skeletal progenitor cells interpret the same rBMP stimulus in unique ways, and these responses mirror the pleiotropic effects of BMPs during fetal skeletogenesis. These mechanistic insights may be particularly useful for optimizing the reparative potential of rBMPs while simultaneously minimizing their adverse outcomes. © 2010 American Society for Bone and Mineral Research
Gs G protein–coupled receptor signaling in osteoblasts elicits age-dependent effects on bone formation
Authors: Hsiao Edward C , Boudignon Benjamin M , Halloran Bernard P , Nissenson Robert A , Conklin Bruce R
Published: February 2010

Age-dependent changes in skeletal growth are important for regulating skeletal expansion and determining peak bone mass. However, how G protein–coupled receptors (GPCRs) regulate these changes is poorly understood. Previously, we described a mouse model expressing Rs1, an engineered receptor with high basal Gs activity. Rs1 expression in osteoblasts induced a dramatic age-dependent increase in trabecular bone with features resembling fibrous dysplasia. To further investigate how activation of the Gs-GPCR pathway affects bone formation at different ages, we used the tetracycline-inducible system in the ColI(2.3)+/Rs1+ mouse model to control the timing of Rs1 expression. We found that the Rs1 phenotype developed rapidly between postnatal days 4 and 6, that delayed Rs1 expression resulted in attenuation of the Rs1 phenotype, and that the Rs1-induced bone growth and deformities were markedly reversed when Rs1 expression was suppressed in adult mice. These findings suggest a distinct window of increased osteoblast responsiveness to Gs signaling during the early postnatal period. In addition, adult bones encode information about their normal shape and structure independently from mechanisms regulating bone expansion. Finally, our model provides a powerful tool for investigating the effects of continuous Gs-GPCR signaling on dynamic bone growth and remodeling. © 2010 American Society for Bone and Mineral Research.
Sorting of growth plate chondrocytes allows the isolation and characterization of cells of a defined differentiation status
Authors: Belluoccio Daniele , Etich Julia , Rosenbaum Sabrina , Frie Christian , Grskovic Ivan , Stermann Jacek , Ehlen Harald , Vogel Simon , Zaucke Frank , Mark Klaus von der , Bateman John F , Brachvogel Bent
Published: February 2010

Axial growth of long bones occurs through a coordinated process of growth plate chondrocyte proliferation and differentiation. This maturation of chondrocytes is reflected in a zonal change in gene expression and cell morphology from resting to proliferative, prehypertrophic, and hypertrophic chondrocytes of the growth plate followed by ossification. A major experimental limitation in understanding growth plate biology and pathophysiology is the lack of a robust technique to isolate cells from the different zones, particularly from small animals. Here, we report on a new strategy for separating distinct chondrocyte populations from mouse growth plates. By transcriptome profiling of microdissected zones of growth plates, we identified novel, zone-specific cell surface markers and used these for flow cytometry and immunomagnetic cell separation to quantify, enrich, and characterize chondrocytes populations with respect to their differentiation status. This approach provides a novel platform to study cartilage development and characterize mouse growth plate chondrocytes to reveal unique cellular phenotypes of the distinct subpopulations within the growth plate. © 2010 American Society for Bone and Mineral Research
SQSTM1 gene analysis and gene-environment interaction in Paget's disease of bone
Authors: Gennari Luigi , Gianfrancesco Fernando , Di Stefano Marco , Rendina Domenico , Merlotti Daniela , Esposito Teresa , Gallone Salvatore , Fusco Pina , Rainero Innocenzo , Fenoglio Pierpaola , Mancini Maria , Martini Giuseppe , Bergui Simona , De Filippo Gianpaolo , Isaia Giancarlo , Strazzullo Pasquale , Nuti Ranuccio , Mossetti Giuseppe
Published: February 2010

Even though SQSTM1 gene mutations have been identified in a consistent number of patients, the etiology of Paget's disease of bone (PDB) remains in part unknown. In this study we analyzed SQSTM1 mutations in 533 of 608 consecutive PDB patients from several regions, including the high-prevalence area of Campania (also characterized by increased severity of PDB, higher number of familial cases, and peculiar phenotypic characteristics as giant cell tumor). Eleven different mutations (Y383X, P387L, P392L, E396X, M401V, M404V, G411S, D423X, G425E, G425R, and A427D) were observed in 34 of 92 (37%) and 43 of 441 (10%) of familial and sporadic PDB patients, respectively. All five patients with giant cell tumor complicating familial PDB were negative for SQSTM1 mutations. An increased heterogeneity and a different distribution of mutations were observed in southern Italy (showing 9 of the 11 mutations) than in central and northern Italy. Genotype-phenotype analysis showed only a modest reduction in age at diagnosis in patients with truncating versus missense mutations, whereas the number of affected skeletal sites did not differ significantly. Patients from Campania had the highest prevalence of animal contacts (i.e., working or living on a farm or pet ownership) without any difference between patients with or without mutation. However, when familial cases from Campania were considered, animal contacts were observed in 90% of families without mutations. Interestingly, a progressive age-related decrease in the prevalence of animal contacts, as well as a parallel increase in the prevalence of SQSTM1 mutations, was observed in most regions except in the subgroup of patients from Campania. Moreover, patients reporting animal contacts showed an increased number of affected sites (2.54 ± 2.0 versus 2.19 ± 1.9, p < .05) over patients without animal contacts. This difference also was evidenced in the subgroup of patients with SQSTM1 mutations (3.84 ± 2.5 versus 2.76 ± 2.2, p < .05). Overall, these data suggest that animal-related factors may be important in the etiology of PDB and may interact with SQSTM1 mutations in influencing disease severity. © 2010 American Society for Bone and Mineral Research
IKKβ activation is sufficient for RANK-independent osteoclast differentiation and osteolysis
Authors: Otero Jesse E , Dai Simon , Alhawagri Muhammad A , Darwech Isra , Abu-Amer Yousef
Published: February 2010

Monocytes differentiate into osteoclasts through stimulation of receptor activator of NF-κB (RANK). Many downstream effectors of RANK play a positive role in osteoclastogenesis, but their relative importance in osteoclast differentiation is unclear. We report the discovery that activation of a single pathway downstream of RANK is sufficient for osteoclast differentiation. In this regard, introduction of constitutively activated IKKβ (IKKβSSEE) but not wild-type IKKβ into monocytes stimulates differentiation of bona fide osteoclasts in the absence of RANK ligand (RANKL). This phenomenon is independent of upstream signals because IKKβSSEE induced the development of bone-resorbing osteoclasts from RANK and IKKα knockout monocytes and in conditions in which NEMO-IKKβ association was inhibited. NF-κB p100 and p105, but not RelB, were critical mediators of this effect. Inflammatory autocrine signaling by tumor necrosis factor α (TNF-α) and interleukin 1 (IL-1) were dispensable for the spontaneous osteoclastogenesis driven by IKKβSSEE. More important, adenoviral gene transfer of IKKβSSEE induced osteoclasts and osteolysis in calvariae and knees of mice. Our data establish the sufficiency of IKKβ activation for osteolysis and suggest that IKKβ hyperactivation may play a role in conditions of pathologic bone destruction refractory to RANK/RANKL proximal therapeutic interventions. © 2010 American Society for Bone and Mineral Research
Thyroid hormone-mediated growth and differentiation of growth plate chondrocytes involves IGF-1 modulation of β-catenin signaling
Authors: Wang Lai , Shao Yvonne Y , Ballock R Tracy
Published: February 2010

Thyroid hormone regulates terminal differentiation of growth plate chondrocytes in part through modulation of the Wnt/β-catenin signaling pathway. Insulin-like growth factor 1 (IGF-1) has been described as a stabilizer of β-catenin, and thyroid hormone is a known stimulator of IGF-1 receptor expression. The purpose of this study was to test the hypothesis that IGF-1 signaling is involved in the interaction between the thyroid hormone and the Wnt/β-catenin signaling pathways in regulating growth plate chondrocyte proliferation and differentiation. The results show that IGF-1 and the IGF- receptor (IGF1R) stimulate Wnt-4 expression and β-catenin activation in growth plate chondrocytes. The positive effects of IGF-1/IGF1R on chondrocyte proliferation and terminal differentiation are partially inhibited by the Wnt antagonists sFRP3 and Dkk1. T3 activates IGF-1/IGF1R signaling and IGF-1-dependent PI3K/Akt/GSK-3β signaling in growth plate chondrocytes undergoing proliferation and differentiation to prehypertrophy. T3-mediated Wnt-4 expression, β-catenin activation, cell proliferation, and terminal differentiation of growth plate chondrocytes are partially prevented by the IGF1R inhibitor picropodophyllin as well as by the PI3K/Akt signaling inhibitors LY294002 and Akti1/2. These data indicate that the interactions between thyroid hormone and β-catenin signaling in regulating growth plate chondrocyte proliferation and terminal differentiation are modulated by IGF-1/IGF1R signaling through both the Wnt and PI3K/Akt signaling pathways. While chondrocyte proliferation may be triggered by the IGF-1/IGF1R-mediated PI3K/Akt/GSK3β pathway, cell hypertrophy is likely due to activation of Wnt/β-catenin signaling, which is at least in part initiated by IGF-1 signaling or the IGF-1-activated PI3K/Akt signaling pathway. © 2010 American Society for Bone and Mineral Research
A role for ethanol-induced oxidative stress in controlling lineage commitment of mesenchymal stromal cells through inhibition of Wnt/β-catenin signaling
Authors: Chen Jin-Ran , Lazarenko Oxana P , Shankar Kartik , Blackburn Michael L , Badger Thomas M , Ronis Martin J
Published: February 2010

The mechanisms by which chronic ethanol intake induces bone loss remain unclear. In females, the skeletal response to ethanol varies depending on physiologic status (e.g., cycling, pregnancy, or lactation). Ethanol-induced oxidative stress appears to be a key event leading to skeletal toxicity. In this study, ethanol-containing liquid diets were fed to postlactational female Sprague-Dawley rats intragastrically for 4 weeks beginning at weaning. Ethanol consumption decreased bone mineral density (BMD) compared with control animals during this period of bone rebuilding following the end of lactation. Coadministration of the antioxidant N-acetylcysteine (NAC) was able to block bone loss and downregulation of the bone-formation markers alkaline phosphatase and osteocalcin in serum and gene expression in bone. Real-time array analysis of total RNA isolated from bone tissue revealed that the majority of Wnt signaling components were downregulated by chronic ethanol infusion. Real-time PCR confirmed downregulated gene expression in a subset of the Wnt signaling components by ethanol. However, the Wnt antagonist DKK1 was upregulated by ethanol. The key canonical Wnt signaling molecule β-catenin protein expression was inhibited, while glycogen synthase kinase-3-β was dephosphorylated by ethanol in bone and preosteoblastic cells. These actions of ethanol were blocked by NAC. Ethanol treatment inactivated TCF/LEF gene transcription, eliminated β-catenin nuclear translocation in osteoblasts, and reciprocally suppressed osteoblastogenesis and enhanced adipogenesis. These effects of ethanol on lineage commitment of mesenchymal stem cells were eliminated by NAC pretreatment. These observations are consistent with the hypothesis that ethanol inhibits bone formation through stimulation of oxidative stress to suppress Wnt signaling. © 2010 American Society for Bone and Mineral Research