bluuebunny/crossref_metadata_2025_split huggingface dataset:
BMP Signaling Is Required for RUNX2-Dependent Induction of the Osteoblast Phenotype
Authors: Phimphilai Mattabhorn , Zhao Zhouran , Boules Heidi , Roca Hernan , Franceschi Renny T 
Published: April 2006

Abstract
RUNX2 expression in mesenchymal cells induces osteoblast differentiation and bone formation. BMP blocking agents were used to show that RUNX2-dependent osteoblast differentiation and transactivation activity both require BMP signaling and, further, that RUNX2 enhances the responsiveness of cells to BMPs.
Introduction: BMPs and the RUNX2 transcription factor are both able to stimulate osteoblast differentiation and bone formation. BMPs function by activating SMAD proteins and other signal transduction pathways to stimulate expression of many target genes including RUNX2. In contrast, RUNX2 induces osteoblast-specific gene expression by directly binding to enhancer regions in target genes. In this study, we examine the interdependence of these two factors in controlling osteoblast differentiation in mesenchymal progenitor cells.
Materials and Methods: C3H10T1/2 mesenchymal cells and primary cultures of marrow stromal cells were transduced with a RUNX2 adenovirus and treated with BMP blocking antibodies or the natural antagonist, NOGGIN. Osteoblast differentiation was determined by assaying alkaline phosphatase and measuring osteoblast-related mRNA using quantitative RT/PCR. Activation of BMP-responsive signal transduction pathways (SMAD, extracellular signal-regulated kinase [ERK], p38, and c-jun-N-terminal kinase [JNK]) was assessed on Western blots.
Results and Conclusions: C3H10T1/2 cells constitutively synthesize BMP2 and 4 mRNA and protein, and this BMP activity is sufficient to activate basal levels of SMAD phosphorylation. Inhibition of BMP signaling was shown to disrupt the ability of RUNX2 to stimulate osteoblast differentiation and transactivate an osteocalcin gene promoter-luciferase reporter in C3H10T1/2 cells. BMP blocking antibodies also inhibited RUNX2-dependent osteoblast differentiation in primary cultures of murine marrow stromal cells. Conversely, RUNX2 expression synergistically stimulated BMP2 signaling in C3H10T1/2 cells. However, RUNX2 did not increase the ability of this BMP to activate SMAD, ERK, p38, and JNK pathways. This study shows that autocrine BMP production is necessary for the RUNX2 transcription factor to be active and that BMPs and RUNX2 cooperatively interact to stimulate osteoblast gene expression.
Effect of Monoterpenes on the Formation and Activation of Osteoclasts In Vitro
Authors: Dolder Silvia , Hofstetter Willy , Wetterwald Antoinette , Mühlbauer Roman C , Felix Rolf 
Published: April 2006

Abstract
Monoterpenes, present in aromatic plants, are known to inhibit bone resorption in vivo. In this in vitro study, they inhibited the activation of osteoclasts only at high concentrations but inhibited the formation at much lower concentrations. Therefore, monoterpenes may act in vivo directly on osteoclastogenesis.
Introduction: Monoterpenes are the major components of essential oils, which are formed in many plants. Typically, they are found in herbs and certain fruits. When fed to rats, they inhibit bone resorption by an unknown mechanism. In this study, their effect on the activity and formation of osteoclasts in vitro was studied.
Materials and Methods: The effect of monoterpenes on the development of osteoclasts was studied in co-cultures of bone marrow cells and osteoblasts and in cultures of spleen cells grown with colony stimulating factor (CSF)-1 and RANKL. In cultures of primary osteoblasts, alkaline phosphatase activity and levels of mRNA encoding RANKL and osteoprotegerin (OPG) mRNA (RT-PCR), and in osteoblast and spleen cell cultures, lactate dehydrogenase activity, a measure of toxicity, were determined. The activity of isolated rat osteoclasts was determined by counting the osteoclasts with actin rings using histofluorometry.
Results: The monoterpenes inhibited the formation of osteoclasts more strongly in co-cultures (≥1 μM) than in cultures of spleen cells (≥10 μM). They had a minor effect on osteoblasts. Toxic effects were not observed. The inhibition of the formation of osteoclasts was not reversed by the addition of farnesol and geranylgeraniol, excluding an effect of the monoterpenes through the mevalonate pathway. A high concentration of 1 mM was required to inhibit the activation of osteoclasts. This effect, shown for menthol and borneol, was reversible.
Conclusions: The results suggest that the monoterpenes inhibit bone resorption in vivo through a direct effect on the formation of osteoclasts acting mainly on the hemopoietic cells.
Long-Term Effects of Calcium Supplementation on Serum Parathyroid Hormone Level, Bone Turnover, and Bone Loss in Elderly Women
Authors: Riggs B. Lawrence , O'Fallon W. Michael , Muhs Joan , O'Connor Michael K. , Kumar Rajiv , Melton L. Joseph 
Published: April 2006

Abstract
We report a 4-year randomized, double-blind, placebo-controlled clinical trial in 236 normal postmenopausal women (mean age ± SE, 66.3 ± 0.2 years) who were randomized to a calcium (1600 mg/day as the citrate) or placebo group. The women were seen every 6 months; 177 completed the trial. Net percentage changes in each group are given relative to baseline. The differences in net percentage changes (calcium group minus placebo group) in medians were: for lumbar spine bone density, 2.0% (p &lt; 0.001) at year 1 and 0.3% (not significant) at year 4; for proximal femur bone density, 1.3% (p = 0.003) at year 1 and 1.3% (p = 0.015) at year 4; and for total body bone mineral, 0.4% (p = 0.002) at year 1 and 0.9% (p = 0.017) at year 4. Similar differences at year 4 were: −18.9% (p = 0.002) for parathyroid hormone (PTH), −11.9% (p = 0.026) for serum osteocalcin, and −32.2% (p = 0.003) for urine free pyridinoline. We conclude that long-term administration of calcium supplements to elderly women partially reverses age-related increases in serum PTH level and bone resorption and decreases bone loss. However, the effects on bone loss were weaker than those reported for estrogen, bisphosphonates, or calcitonin therapy, indicating that calcium supplements alone cannot substitute for these in treating established osteoporosis. Nonetheless, because of their safety, high tolerance, and low expense, calcium supplements may be a useful preventive measure for elderly postmenopausal women whose bone mineral density values are normal for their age.
LIF, but Not IL-6, Regulates Osteoprogenitor Differentiation in Rat Calvaria Cell Cultures: Modulation by Dexamethasone
Authors: Dr. Malaval Luc , Gupta Ashwani K. , Liu Fina , Delmas Pierre D. , Aubin Jane E. 
Published: April 2006

Abstract
Cytokines of the interleukin 6 (IL-6) subfamily are a group of factors produced by osteoblasts and acting through the same transducing element, membrane protein gp130. We have previously shown that exogenous (added to the culture medium) leukemia inhibitory factor (LIF) inhibits bone nodule formation and expression of osteoblast-associated genes in fetal rat calvaria (RC) cell cultures and that dexamethasone (Dex) increases the ID50 of LIF. To investigate the respective roles of IL-6–related cytokines and receptors in osteprogenitor differentiation, and their regulatory interplay with Dex, we used reverse transcribed polymerase chain reaction, bioassay, and blocking antibody techniques to assess the time courses of LIF, IL-6, LIF transmembrane receptor, IL-6 receptor, and gp130 expression in RC cell cultures grown with and without Dex. The levels of the mRNAs for IL-6, LIF, and gp130 decreased concomitantly with the formation of bone nodules. Dex treatment, which stimulates bone nodule formation, reduced the expression of LIF and IL-6 mRNAs and IL-6 bioactivity in the culture medium. LIF treatment strongly stimulated the expression of IL-6. Incubation with anti-LIF antibodies increased the number of nodules, while an antibody blocking IL-6 activity had little or no effect on nodule numbers and did not antagonize the action of exogenous LIF, indicating that IL-6 does not mediate the action of LIF in this system. Moreover, although exogenously added IL-6 was active in the cultures as noted by a reduction of nodule mineralization, it had no effect on nodule numbers, i.e., on osteoprogenitor differentiation, in the presence or absence of Dex. In conclusion, IL-6, LIF, and their receptors are expressed throughout the time-course of osteogenesis in RC cell cultures. However, only LIF, but not IL-6, appears to play a significant role in autocrine regulation of osteoblastic differentiation in this system. The antagonist action of Dex on the effects of exogenously added LIF, as well as the bone-promoting action of Dex in RC cell cultures, could be exerted partly through the down-regulation of the expression of endogenous LIF.
IL-1α, IL-1β, IL-6, and TNF-α Steady-State mRNA Levels Analyzed by Reverse Transcription-Competitive PCR in Bone Marrow of Gonadectomized Mice
Authors: Van Bezooijen Rutger L. , Farih-Sips Hetty C. M. , Papapoulos Socrates E. , Löwik Clemens W. G. M. 
Published: April 2006

Abstract
Loss of gonadal function in both females and males is associated with increased rates of bone loss by a yet unidentified mechanism. There is ample evidence that cytokines that are produced in the bone microenvironment and stimulate the activity and/or formation of osteoclasts are involved. In the present study, we examined whether gonadectomy increases cytokine production via increased transcription in the bone marrow of mice. For this, the in vivo steady-state mRNA levels of multiple cytokines were determined in the central bone marrow compartment of mice at different time points following ovariectomy or orchidectomy by reverse transcription-competitive polymerase chain reaction. The limit of detectable differences in mRNA expression was approximately 2-fold. Bone marrow mRNA levels of the cytokines interleukin-1α (IL-1α), interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) were elevated up to 30-fold after treatment of mice with lipopolysaccharide. Following gonadectomy, there were no differences in the mRNA expression of these cytokines in bone marrow of female and male mice 4, 7, and 14 days after surgery. Gender steroid deficiency does not, therefore, increase steady-state mRNA levels of IL-1α, IL-1β, IL-6, and TNF-α in cells of the central bone marrow compartment in mice. If changes have occurred these should have been less than 2-fold or in a small cell population. These results do not preclude an important role of these cytokines in the induction of bone loss after gonadectomy. For example, bone marrow cells situated close to the bone surface or bone cells may be responsible for increased cytokine synthesis. Alternatively, the loss of gender steroids may alter post-transcriptional events in cytokine synthesis and activity or may modify the responsiveness of target cells.
The Derivation and Characterization of Stromal Cell Lines from the Bone Marrow of p53−/− Mice: New Insights into Osteoblast and Adipocyte Differentiation
Authors: Thompson Deborah L. , Lum Karen D. , Nygaard Sean C. , Kuestner Rolf E. , Kelly Katherine A. , Gimble Jeffrey M. , Moore Emma E. 
Published: April 2006

Abstract
We have derived a series of clonal cell lines from the bone marrow of p53−/− mice that represent different stages of osteoblast and adipocyte differentiation. All cell lines show indefinite growth potential (&gt;300 population doublings) and have generation times of 12–20 h. These cell lines have been grouped into three categories. The least mature clones are heterogeneous and appear to contain a subpopulation of stem cells, which can spontaneously generate foci that contain either adipocytes or mineralizing osteoblasts. The second category of clones are homogenous and clearly correspond to mature osteoblasts because they express high levels of the anticipated osteoblastic markers in a stable fashion and cannot differentiate into adipocytes even in the presence of inducers. The clones in the third category are the most unique. Initially they appeared to correspond to mature osteoblasts because they express alkaline phosphatase in a homogenous manner, secrete type I collagen, show a significant cyclic adenosine monophosphate response to parathyroid hormone, secrete osteocalcin, and mineralize extensively after only 4–7 days. However, in contrast to the mature osteoblasts, these clones can be induced to undergo massive adipocyte differentiation, and this differentiation is accompanied by the complete loss of expression of all osteoblastic markers except alkaline phosphatase. These observations indicate that some cells that have acquired all of the characteristics of mature osteoblasts can be diverted to the adipocyte pathway. Further characterization of these clones may be particularly relevant to osteoporotic conditions where increased adipocyte formation appears to occur at the expense of osteoblast formation.
Acute Changes in Trabecular Bone Connectivity and Osteoclast Activity in the Ovariectomized Rat In Vivo
Authors: Lane Nancy E. , Thompson Jennifer M. , Haupt David , Kimmel Donald B. , Modin Gunnar , Kinney John H. 
Published: April 2006

Abstract
Estrogen deficiency results in a loss of trabecular bone mass and structure that leads to an increased incidence of osteoporotic fractures. The purpose of this study was to determine the time course for trabecular structure deterioration and changes in bone turnover just after ovariectomy in the rat. Six-month-old female virgin Sprague-Dawley rats had their right proximal tibia scanned by X-ray tomographic microscopy (XTM) at baseline (day 0). Animals were then randomized into two groups, and in each group 9 were sham-operated and 11 were ovariectomized and had repeat XTM scans on days 5, 13, 29, and 42 postovariectomy in group 1 and on days 8, 13, 33, and 50 postovariectomy in group 2. Urine was collected for deoxypyridinoline (DPD) cross-link measurements 24 h before each XTM scan and analyzed by ELISA. Trabecular bone structural variables and bone turnover endpoints were calculated from XTM data and standard histomorphometry. Trabecular connectivity decreased 27% by days 5 and 8 postovariectomy (p &lt; 0.01) and continued to decrease up to day 50 postovariectomy (p &lt; 0.01). The trabecular bone volume decreased 25% by 8 days postovariectomy (p &lt; 0.01), and it continued to decrease through day 50. DPD cross-link excretion had increased 37% on day 13 (p &lt; 0.01) and by over 100% of baseline by day 50 postovariectomy. Trabecular bone connectivity and volume deteriorate rapidly while DPD cross-link excretion increased more slowly in acute estrogen deficiency. These data suggest that if an agent is to preserve fully trabecular bone structure, it must be instituted very early in the estrogen-deficient state. They also suggest that a lag time exists before DPD excretion properly mirrors newly induced conditions of high bone turnover in this rat model.
Differential Effects of Aminosubstituted Analogs of Hydroxy Bisphosphonates on the Growth of Dictyostelium discoideum
Authors: Brown R. J. , Van Beek E. , Watts D. J. , Löwik C. W. G. M. , Papapoulos S. E. 
Published: April 2006

Abstract
Replacing the hydroxyl group in the bone-binding site of three clinically useful bisphosphonates (etidronate, pamidronate, and olpadronate) by an amino group resulted in great differences in their antiresorptive potencies in vitro. In the present study, this is also shown in vivo in mice treated with the six bisphosphonates at doses of up to 16 μM/kg/day for 12 days. Because binding to bone mineral is nearly the same for all tested bisphosphonates, these findings suggest that the aminosubstitution affects the cellular action of the bisphosphonates. This was tested in the cellular slime mould Dictyostelium discoideum in which cellular effects of bisphosphonates can be examined independently of binding to bone mineral. Etidronate and its aminosubstituted analog were equipotent in inhibiting amebal growth, while pamidronate was somewhat more potent than its analog. Whereas olpadronate was a potent inhibitor of axenic growth of Dictyostelium amebae, the aminosubstitution reduced its potency drastically (IC50 12 μM and 700 μM, respectively). The similarities between the inhibitory effects of the bisphosphonates tested on bone resorption in vitro and in vivo and on the growth of Dictyostelium amebae confirm that the differences in antiresorptive potencies found reflect differences in cellular effects and suggest that bisphosphonates may bind to more than one intracellular target.
Hereditary 1,25-Dihydroxyvitamin D–Resistant Rickets Due to an Opal Mutation Causing Premature Termination of the Vitamin D Receptor
Authors: Zhu Wenjing , Malloy Peter J. , Delvin Edgard , Chabot Gilles , Feldman David 
Published: April 2006

Abstract
Mutations in the vitamin D receptor (VDR) gene have been shown to cause hereditary vitamin D–resistant rickets (HVDRR). The patient in this study is a young French-Canadian boy with no known consanguinity in his family. The child exhibited the clinical characteristics of HVDRR with early onset rickets, hypocalcemia, secondary hyperparathyroidism, and elevated 1,25-dihydroxyvitamin D (1,25(OH)2D) levels as well as total alopecia. Fibroblasts were cultured from a skin biopsy of the patient and used to assess the VDR. Northern blot analysis showed that a normal size VDR transcript was expressed; however, [3H]1,25(OH)2D3-binding levels were very low and Western blot analysis failed to detect any VDR protein. Total resistance to 1,25(OH)2D3 was demonstrated by the failure of the cultured fibroblasts to induce the transcription of the 25-hydroxyvitamin D-24-hydroxylase gene when treated with high concentrations of 1,25(OH)2D3. Analysis of the DNA sequence revealed a unique C to T base change corresponding to nucleotide 218 of the VDR cDNA. This single base substitution changes the codon for arginine (CGA) to an opal stop codon (TGA), resulting in the truncation of the VDR at amino acid 30. The Arg30stop mutation prematurely terminates translation and deletes 398 amino acids including most of the zinc fingers as well as the entire ligand-binding domain. Restriction fragment length polymorphism analysis of a DdeI restriction site created by the mutation showed that the parents were heterozygous for the mutant allele. In conclusion, the Arg30stop mutation truncates the VDR and leads to a hormone-resistant condition which is the molecular basis of HVDRR in this patient.
Distraction Bone Healing Versus Osteotomy Healing: A Comparative Biochemical Analysis
Authors: Lammens Johan , Liu Zhendong , Aerssens Jeroen , Dequeker Jan , Fabry Guy 
Published: April 2006

Abstract
This study investigates the biochemical changes in a canine tibia lengthening model in comparison with a nonlengthened osteotomy model. The lengthened and the osteotomized callus and a contralateral corresponding segment were analyzed for their mineralization profile, collagen content, osteocalcin, insulin-like growth factor I (IGF-I), and transforming growth factor β1 (TGF-β1). Examinations of bone samples were performed using specimens excised at different time intervals (respectively at 3, 5, 7, 9, and 13 weeks postoperatively). Several serum parameters (alkaline phosphatase [ALP], osteocalcin, IGF-I, and TGF-β1) were also measured during the experimental period. A progressive increase in mineral parameters was noticed in both the lengthened and the osteotomized areas. A higher level of hydroxyproline and TGF-β1 was observed in the lengthened area compared with the osteotomized area. IGF-I showed a significant increase in both the lengthened and contralateral control area at the later stage of the experimental period in the lengthened group. In serum, a high level of TGF-β1 and a progressively increasing osteocalcin concentration were observed in the lengthened dogs in comparison with the osteotomized dogs. Serum ALP was significantly increased in both models during the experimental period. Serum IGF-I was increased in the lengthened models during the distraction period and decreased in the osteotomized models at the early stage of the experimental period. These results suggest that the mechanical strain induced by the Ilizarov distraction procedure stimulates osteoblast proliferation and promotes biosynthesis of bone extracellular matrix in distracted callus. Our data furthermore show that this process is different compared with normal fracture healing.
Rapid Bone Loss Is Associated with Increased Levels of Biochemical Markers
Authors: Dr. Ross Philip D. , Knowlton William 
Published: April 2006

Abstract
We examined associations of biochemical markers of bone turnover with rapid bone loss, as measured by changes in bone mineral density (BMD). To improve the precision of bone loss estimates, calcaneal BMD was measured up to eight times over a long interval (13 years) among postmenopausal women (mean age = 62 years at baseline). Women with fractures during the previous year, and users of corticosteroids, active vitamin D, bisphosphonates or calcitonin were excluded to avoid potential transient effects on marker levels. Among the remaining 354 women, markers were measured for 100 women with the fastest BMD loss (rapid loss group; mean = 2.2%/year) and 100 with the slowest loss (mean = 0.4%/year). Two markers of bone formation, serum bone alkaline phosphatase (Alkphase-B; BAP) and osteocalcin (NovoCalcin; OC), and two markers of bone resorption, urinary creatinine-corrected free deoxypyridinoline (Pyrilinks-D; DPD) and free pyridinolines (Pyrilinks; PYD), were measured. In separate logistic regression models, each of the markers was strongly associated with rapid loss: the odds of rapid loss increased by 1.8 to 2.0 times for each 1.0 standard deviation (SD) increase of the marker. For BAP levels 2 SD above the mean, the probability of rapid bone loss was 80%; in contrast, the probability was only 20% at 2 SD below the mean. The other markers yielded similar results. We conclude that these markers are associated with rapid bone loss; this relationship appears to be continuous, with progressively greater risk of rapid bone loss with increasing levels of biomarkers. Prospective studies that include the entire distribution of bone loss rates are warranted to confirm these findings.