bluuebunny/crossref_metadata_2025_split huggingface dataset:
Water Content Measured by Proton-Deuteron Exchange NMR Predicts Bone Mineral Density and Mechanical Properties
Authors: Fernández-Seara Maria A , Wehrli Suzanne L , Takahashi Masaya , Wehrli Felix W 
Published: April 2006

Abstract
NMR was used to measure matrix water content in normal and hypomineralized cortical bone. Water content showed an inverse relationship with mineral content, suggesting it could serve as a surrogate measure for the bone's degree of mineralization.
Introduction: So far, true bone mineral density (DMB; degree of mineralization of bone) can not be measured nondestructively.
Materials and Methods: Here, a new technique combining1H nuclear magnetic resonance (NMR) spectroscopy and deuterium isotope exchange was used to measure water content in cortical bone from two groups of rabbits: a control group and a group fed a low-phosphorus (P) diet to induce hypomineralization of the bone matrix.
Results: NMR-derived water content was higher in the P-depleted group and showed an inverse relationship with mineral content (measured gravimetrically and by31P NMR). Hypomineralized bone was found to be weaker than normal bone as demonstrated by mechanical testing. More importantly, the data showed a strong inverse correlation between water content and bone mechanical properties, which indicates that water content could be predictive of the bone's mechanical competence.
Conclusions: Water content could potentially serve as a surrogate measure for the bone's degree of mineralization, and this technique could be used to study other disorders of mineral homeostasis known to alter the mineralization state of the matrix. Although the method presented here is not suitable for in vivo measurements of bone water content, the authors have previously shown that1H NMR images of bone can be acquired; thus, noninvasive quantification of bone water may be feasible.
Relationship Between Changes in Bone Mineral Density and Fracture Risk Reduction With Antiresorptive Drugs: Some Issues With Meta-Analyses
Authors: Delmas PD , Li Zhengqing , Cooper Cyrus 
Published: April 2006

Abstract
Published meta-analyses have investigated the relationship between changes in BMD and fracture risk reduction observed with antiresorptive agents, with inconsistent results. Many factors may affect the outcome of such analyses. Our work explores some of these factors and illustrates the need for caution in interpreting the results of meta-analyses.
Introduction: The role of the increase in bone mineral density (BMD) in fracture risk reduction observed in osteoporotic patients treated with antiresorptive drugs is unclear. We examined the effects of study selection, the use of summary statistics or individual patient data (IPD) as the basis for the analyses, and the choice of BMD values used on the outcome of meta-analyses.
Materials and Methods: To evaluate the effects of study selection, we performed Poisson regression analyses using the results from a number of published studies. To evaluate the effects of using individual patient data instead of summary statistics, we simulated the IPD for vertebral fracture to match the summary statistics for published trials and compared these results with those based on meta-regression using summary statistics. We also evaluated the effect of varying the BMD increase with treatment (3–8%) used in predicting the fracture risk reductions in these simulations.
Results: The Poisson regression, which found a statistically significant relationship between nonvertebral fracture risk and spinal BMD when 18 trials of varying designs, duration, and sample size were included in the analysis (p = 0.02), was no longer significant when the analysis was based on the 7 large studies that were placebo-controlled, at least 3 years in duration (at least 1000 patient-years). Meta-analyses of simulated IPD from 12 trials of six antiresorptive agents gave accurate results regardless of the proportion of vertebral risk reduction assumed to be related to BMD change, whereas meta-regression based on summary statistics always produced an estimate around 50%. When the actual data from two risedronate studies were analyzed, the meta-regression based on summary statistics demonstrated a stronger correlation between BMD change and fracture risk reduction than the results based on the IPD analysis. In predicting the fracture risk reduction, the use of the average BMD gain (3%) observed in all studies in the calculations produced an overall fracture risk reduction very similar to the one observed clinically. In contrast, the use of a large BMD gain (8%) produced a substantially higher estimated fracture risk reduction and resulted in a high proportion of fracture risk reduction being attributed to BMD change.
Conclusions: Many factors may influence the outcome of meta-analyses, and caution should be used in interpreting the results of such analyses when exploring the relationship between BMD changes and fracture risk reduction with antiresorptive therapy of osteoporosis.
Statins Prevent Bisphosphonate-Induced γ,δ-T-Cell Proliferation and Activation In Vitro
Authors: Thompson Keith , Rogers Michael J 
Published: April 2006

Abstract
The acute phase response is the major adverse effect of intravenously administered N-BPs. In this study we show that N-BPs cause γ,δ-T-cell activation and proliferation in vitro by an indirect mechanism through inhibition of FPP synthase, an effect that can be overcome by inhibiting HMG-CoA reductase with a statin. These studies clarify the probable initial cause of the acute phase response to N-BP drugs and suggest a possible way of preventing this phenomenon.
Introduction: The acute phase response is the major adverse effect of intravenously administered nitrogen-containing bisphosphonate drugs (N-BPs), used in the treatment of metabolic bone diseases. This effect has recently been attributed to their action as non-peptide antigens and direct stimulation of γ,δ-T-cells. However, because N-BPs are potent inhibitors of farnesyl diphosphate (FPP) synthase, they could cause indirect activation of γ,δ-T-cells owing to the accumulation of intermediates upstream of FPP synthase in the mevalonate pathway, such as isopentenyl diphosphate/dimethylallyl diphosphate, which are known γ,δ-T-cell agonists.
Materials and Methods: Peripheral blood mononuclear cells (PBMCs) were isolated from healthy volunteers and treated with N-BP, statin, or intermediates/inhibitors of the mevalonate pathway for 7 days in the presence of interleukin (IL)-2. Flow cytometric analysis of the T-cell-gated population was used to quantify the proportion of γ,δ-T-cells in the CD3+ population.
Results and Conclusions: The ability of N-BPs to stimulate proliferation of CD3+ γ,δ-T-cells in human PBMC cultures matched the ability to inhibit FPP synthase. γ,δ-T-cell proliferation and activation (interferon γ [IFNγ] and TNFα release) was prevented by mevastatin or lovastatin, which inhibit HMG-CoA reductase upstream of FPP synthase and prevent the synthesis of isopentenyl diphosphate/dimethylallyl diphosphate. Desoxolovastatin, an analog of lovastatin incapable of inhibiting HMG-CoA reductase, did not overcome the stimulatory effect of N-BP. Furthermore, statins did not prevent the activation of γ,δ-T-cells by a synthetic γ,δ-T-cell agonist or by anti-CD3 antibody. Together, these observations show that N-BPs indirectly stimulate the proliferation and activation of γ,δ-T-cells caused by inhibition of FPP synthase and intracellular accumulation of isopentenyl diphosphate/dimethylallyl diphosphate in PBMCs. Because activation of γ,δ-T-cells could be the initiating event in the acute phase response to bisphosphonate therapy, co-administration of a statin could be an effective approach to prevent this adverse effect.
Actin-Related Protein 2/3 Complex Is Required for Actin Ring Formation
Authors: Hurst I Rita , Zuo Jian , Jiang Jin , Holliday L Shannon 
Published: April 2006

Abstract
Actin rings are vital for osteoclastic bone resorption, and actin-related protein 2/3 complex is a pivotal regulator of actin polymerization. Actin-related protein 2/3 complex was found in the podosomes of actin rings. A short interfering RNA knocked down expression of actin-related protein 2 in osteoclasts and disrupted actin rings, suggesting that the complex is crucial to actin ring formation.
Introduction: To resorb bone, osteoclasts form an extracellular acidic compartment segregated by a sealing zone. This is dependent on an actin ring that is composed of filamentous actin organized into dynamic structures called podosomes. The actin-related protein 2/3 (Arp2/3) complex is a vital regulator of actin polymerization. We tested whether the Arp2/3 complex is a component of actin rings and is important for actin ring formation.
Materials and Methods: Western blot analysis was used to determine levels of Arp2 and Arp3, two components of the Arp2/3 complex in osteoclast-like cells. Confocal microscopy studies using antibodies for immunocytochemistry demonstrated localization of Arp2/3 complex in osteoclasts. Short interfering RNA oligonucleotides (siRNAs) were made against Arp2 and used to knock down its expression.
Results: A 3-fold increase in Arp2 and Arp3 was detected during RANKL-induced differentiation of RAW 264.7 cells into osteoclast-like cells. Arp2/3 complex was concentrated in actin rings and enriched near the sealing zone. Arp2/3 complex co-localized with cortactin, a component of podosomes, but not vinculin, which surrounds podosomes. siRNA against Arp2, transfected into RAW 264.7 cells 5 days after stimulation with RANKL, reduced Arp2 protein levels 70% compared with cells transfected with ineffective siRNAs. Cytochemical characterization of RAW 264.7 osteoclast-like cells and marrow osteoclasts in which Arp2 was knocked down revealed fewer podosomes and no actin rings, although many cells remained well spread.
Conclusions: These data show that Arp2/3 complex is a component of actin rings and that the presence of Arp2/3 complex is vital to the formation of actin rings. In addition, the results show the use of siRNAs for the study of RAW 264.7 osteoclast-like cells.
Cooperation Between TGF-β and Wnt Pathways During Chondrocyte and Adipocyte Differentiation of Human Marrow Stromal Cells
Authors: Zhou Shuanhu , Eid Karim , Glowacki Julie 
Published: April 2006

Abstract
Human marrow stromal cells have the potential to differentiate to chondrocytes or adipocytes. We show interactions between TGF-β and Wnt signaling pathways during stimulation of chondrogenesis and inhibition of adipogenesis. Combining these signals may be useful in marrow stromal cell therapies.
Introduction: Human bone marrow stromal cells (hMSCs) have the potential to differentiate to lineages of mesenchymal tissues, including cartilage, fat, bone, tendon, and muscle. Agents like transforming growth factor (TGF)-β promote chondrocyte differentiation at the expense of adipocyte differentiation. In other processes, TGF-β and Wnt/wingless signaling pathways play major roles in controling certain developmental events and activation of specific target genes. We tested whether these pathways interact during differentiation of chondrocytes and adipocytes in human marrow stromal cells.
Materials and Methods: Both a line of human marrow stromal cells (KM101) and freshly isolated hMSCs were studied. Reverse transcriptase-polymerase chain reaction (RT-PCR), Western blot, and macroarrays were used for analysis of the modulation of TGF-β1 on Wnt signaling-associated genes, chondrocyte differentiation genes, and TGFβ/bone morphogenetic protein (BMP) signaling-associated genes in KM101 cells. Early passage hMSCs obtained from 42- and 58-year-old women were used for the effects of TGF-β and/or Wnt (mimicked by LiCl) signals on chondrocyte and adipocyte differentiation in two-dimensional (2-D) cultures, 3-D pellet cultures, and collagen sponges.
Results: As indicated by macroarray, RT-PCR, and Western blot, TGF-β activated genes in the TGF-β/Smad pathway, upregulated Wnt2, Wnt4, Wnt5a, Wnt7a, Wnt10a, and Wnt co-receptor LRP5, and increased nuclear accumulation and stability of β-catenin in KM101 cells. TGF-β upregulated chondrocyte gene expression in KM101 cells and also stimulated chondrocyte differentiation and inhibited adipocyte differentiation in hMSCs, synergistically with Wnt signal. Finally, hMSCs cultured in 3-D collagen sponges were stimulated by TGF-β1 to express aggrecan and collagen type II mRNA, whereas expression of lipoprotein lipase was inhibited.
Conclusions: In summary, TGF-β stimulated chondrocyte differentiation and inhibited adipocyte differentiation of hMSCs in vitro. The activation of both TGF-β and Wnt signal pathways by TGF-β, and synergy between TGF-β and Wnt signals, supports the view that Wnt-mediated signaling is one of the mechanisms of TGF-β's effects on chondrocyte and adipocyte differentiation of hMSCs.
Skeletal Unloading Induces Resistance to Insulin-Like Growth Factor-I (IGF-I) by Inhibiting Activation of the IGF-I Signaling Pathways
Authors: Sakata Takeshi , Wang Yongmei , Halloran Bernard P , Elalieh Hashem Z , Cao Jay , Bikle Daniel D 
Published: April 2006

Abstract
We showed that unloading markedly diminished the effects of IGF-I to activate its signaling pathways, and the disintegrin echistatin showed a similar block in osteoprogenitor cells. Furthermore, unloading decreased αVβ3 integrin expression. These results show that skeletal unloading induces resistance to IGF-I by inhibiting activation of the IGF-I signaling pathways at least in part through downregulation of integrin signaling.
Introduction: We have previously reported that skeletal unloading induces resistance to insulin-like growth factor-I (IGF-I) with respect to bone formation. However, the underlying mechanism remains unclear. The aim of this study was to clarify how skeletal unloading induces resistance to the effects of IGF-I administration in vivo and in vitro with respect to bone formation.
Materials and Methods: We first determined the response of bone to IGF-I administration in vivo during skeletal unloading. We then evaluated the response of osteoprogenitor cells isolated from unloaded bones to IGF-I treatment in vitro with respect to activation of the IGF-I signaling pathways. Finally we examined the potential role of integrins in mediating the responsiveness of osteoprogenitor cells to IGF-I.
Results: IGF-I administration in vivo significantly increased proliferation of osteoblasts. Unloading markedly decreased proliferation and blocked the ability of IGF-I to increase proliferation. On a cellular level, IGF-I treatment in vitro stimulated the activation of its receptor, Ras, ERK1/2 (p44/42 MAPK), and Akt in cultured osteoprogenitor cells from normally loaded bones, but these effects were markedly diminished in cells from unloaded bones. These results were not caused by altered phosphatase activity or changes in receptor binding to IGF-I. Inhibition of the Ras/MAPK pathway was more impacted by unloading than that of Akt. The disintegrin echistatin (an antagonist of the αVβ3 integrin) blocked the ability of IGF-I to stimulate its receptor phosphorylation and osteoblast proliferation, similar to that seen in cells from unloaded bone. Furthermore, unloading significantly decreased the mRNA levels both of αV and β3 integrin subunits in osteoprogenitor cells.
Conclusion: These results indicate that skeletal unloading induces resistance to IGF-I by inhibiting the activation of IGF-I signaling pathways, at least in part, through downregulation of integrin signaling, resulting in decreased proliferation of osteoblasts and their precursors.
Prevention of Glucocorticoid-Induced Apoptosis in Osteocytes and Osteoblasts by Calbindin-D28k
Authors: Liu Yan , Porta Angela , Peng Xiaorong , Gengaro Kristen , Cunningham Earlene B , Li Hong , Dominguez Luis A , Bellido Teresita , Christakos Sylvia 
Published: April 2006

Abstract
This study show for the first time that calbindin-D28k can prevent glucocorticoid-induced bone cell death. The anti-apoptotic effect of calbindin-D28k involves inhibition of glucocorticoid induced caspase 3 activation as well as ERK activation.
Introduction: Recent studies have indicated that deleterious effects of glucocorticoids on bone involve increased apoptosis of osteocytes and osteoblasts. Because the calcium-binding protein calbindin-D28k has been reported to be anti-apoptotic in different cell types and in response to a variety of insults, we investigated whether calbindin-D28k could protect against glucocorticoid-induced cell death in bone cells.
Materials and Methods: Apoptosis was induced by addition of dexamethasone (dex; 10−6 M) for 6 h to MLO-Y4 osteocytic cells as well as to osteoblastic cells. Apoptosis percentage was determined by examining the nuclear morphology of transfected cells. Caspase 3 activity was evaluated in bone cells and in vitro. SELDI mass spectrometry (MS) was used to examine calbindin-D28k-caspase 3 interaction. Phosphorylation of calbindin-D28k was examined by32P incorporation as well as by MALDI-TOF MS. ERK activation was determined by Western blot.
Results: The pro-apoptotic effect of dex in MLO-Y4 cells was completely inhibited in cells transfected with calbindin-D28k cDNA (5.6% apoptosis in calbindin-D28k transfected cells compared with 16.2% apoptosis in vector-transfected cells, p &lt; 0.05). Similar results were observed in osteoblastic cells. We found that dex-induced apoptosis in bone cells was accompanied by an increase in caspase 3 activity. This increase in caspase 3 activity was inhibited in the presence of calbindin-D28k. In vitro assays indicated a concentration-dependent inhibition of caspase 3 by calbindin-D28k (Ki = 0.22 μM). Calbindin-D28k was found to inhibit caspase 3 specifically because the activity of other caspases was unaffected by calbindin-D28k. The anti-apoptotic effect of calbindin-D28k in response to dex was also reproducibly associated with an increase in the phosphorylation of ERK 1 and 2, suggesting that calbindin-D28k affects more than one signal in the glucocorticoid-induced apoptotic pathway.
Conclusion: Calbindin-D28k, a natural non-oncogenic protein, could be an important target in the therapeutic intervention of glucocorticoid-induced osteoporosis.
BMD Is Reduced in HIV-Infected Men Irrespective of Treatment
Authors: Amiel C , Ostertag A , Slama L , Baudoin C , N'Guyen T , Lajeunie E , Neit-Ngeilh L , Rozenbaum W , De Vernejoul MC 
Published: April 2006

Abstract
Osteoporosis has be reported to be a complication of active antiretroviral therapy of HIV infection. We studied 148 HIV-infected men stratified according to their treatment. Our data show that these patients have an average 9% decreased BMD, irrespective of their treatment. Low body mass index and high resorption markers were associated with low bone density.
Introduction: Osteoporosis has been reported in HIV-infected (HIV+) patients, and it has been suggested that it may be linked to protease-inhibitor treatments (PI).
Materials and Methods: To assess this risk and to investigate its putative link with treatments, we compared the bone density of HIV+ men, who were either receiving treatment (including PI [PI+], n = 49; without PI [PI−], n = 51) or untreated (UT, n = 48). We included 81 age-matched control HIV-negative (HIV−) males (age, 40 ± 8 years).
Results: BMD adjusted for age (Z-score) was lower in the HIV+ patients at the lumbar spine (HIV+: −1.08 ± 1.21, HIV−: −0.06 ± 1.26, p &lt; 0.001) and the femoral neck (HIV+: −0.39 ± 1.05, HIV−: 0.25 ± 0.87, p &lt; 0.001). The prevalence of osteoporosis was 16% in HIV+ and 4% in HIV− subjects (p &lt; 0.01). In the HIV+ subjects, the Z-score was correlated only to body mass index (r = 0.27 at lumbar spine and 0.35 at femoral neck). Untreated HIV+ patients had a negative Z-score (−0.82 ± 1.15 for the lumbar spine), which was not different from the one of treated HIV+ patients. In the PI+ and PI− groups, the Z-score did not depend on the presence of lipodystrophy or the proportion of fat in the abdomen and legs measured by DXA. Markers of bone remodeling were measured in the 132 HIV+ and 35 HIV− subjects. Compared with controls, HIV+ patients had lower bone alkaline phosphatase and higher urinary cross-laps/Cr, which was negatively correlated with the Z-score at both the femoral neck (r = −0.22) and lumbar spine (r = −0.21). TNFα was increased in untreated compared with treated HIV+ subjects and was not correlated to the Z-score.
Conclusion: Our cross-sectional study does not show any deleterious effect of the treatment but does indicate a decrease in bone density in HIV+ patients irrespective of the treatment. This low bone density is in part related to the low body weight and is associated with increased bone resorption.
Reproducibility and Side Differences of Mechanical Tests for Determining the Structural Strength of the Proximal Femur
Authors: Eckstein Felix , Wunderer Caecilia , Boehm Holger , Kuhn Volker , Priemel Mathias , Link Thomas M , Lochmüller Eva-Maria 
Published: April 2006

Abstract
In this experimental study, we evaluated the reproducibility error of mechanical strength tests of the proximal femur when simulating a fall on the trochanter. Based on side differences in femoral failure loads in 55 pairs of femora, we estimated the upper limit of the precision error to be 15% for the side impact test, whereas the intersubject variability was &gt;40%.
Introduction: Mechanical tests are commonly used as the gold standard for determining one of the main functions of bones, that is, to provide mechanical strength. However, it is unknown what magnitude of error is associated with these tests. Here we investigate the precision error and side difference of a side impact test of the proximal femur.
Materials and Methods: BMC was measured using DXA in 54 pairs of femora from donors 79.0 ± 10.6 years of age. Bones were tested to failure, simulating a fall on the greater trochanter.
Results: Failure loads were 3951 ± 1659N (CV% = 42%) on the right and 3900 ± 1652N (CV% = 42%) on the left (no significant side difference). The average random difference of femoral BMC was 7 ± 7% and that of femoral failure loads was 17 ± 12%. The correlation between BMC and failure load was 79% (r2), but the association between side differences in failure load with those in BMC was only 4%. When confining the analysis to pairs with less than 5% differences in BMC (n = 31), side differences in failure loads were 15 ± 13%. When correcting failure loads for side differences of BMC, the difference was 16 ± 15%
Conclusions: These results suggest that the upper limit of the precision error for femoral strength tests is ∼15% in a side impact configuration. Given the large intersubject variability of failure loads, this test provides an efficient tool for determining the structural strength of the proximal femur in a fall.