bluuebunny/crossref_metadata_2025_split huggingface dataset:
Skeletal Unloading Alleviates the Anabolic Action of Intermittent PTH(1–34) in Mouse Tibia in Association With Inhibition of PTH-Induced Increase in c-fos mRNA in Bone Marrow Cells
Authors: Tanaka Shinya , Sakai Akinori , Tanaka Masahiro , Otomo Hajime , Okimoto Nobukazu , Sakata Takeshi , Nakamura Toshitaka 
Published: April 2006

Abstract
We analyzed the effect of unloading by tail suspension on the anabolic action of intermittent PTH in the tibia of growing mice. Unloading alleviated the PTH-induced increase of bone formation and accelerated bone resorption, consequently reducing bone mass. Reduction of the PTH-induced anabolic actions on bone was associated with unloading, which was apparently related to suppression of c-fos mRNA expression in bone marrow.
Introduction: The effects of intermittent parathyroid hormone (PTH) administration on unloading bone have not been well elucidated at the cellular and molecular levels. We tested the effects of PTH on unloaded tibias of tail-suspended mice.
Materials and Methods: Eighty male C57BL/6J mice, 8 weeks of age, were divided into four groups with loading or unloading and administration of PTH (40 μg/kg body weight) or vehicle five times per week. Mice were killed at 8 or 15 days, and both tibias were obtained. Bone histomorphometry of the trabecular bone in the proximal tibia, development of osteogenic cells, and mRNA expression of osteogenic molecules in bone marrow cells were assessed.
Results and Conclusions: At 15 days of unloading, bone volume decreased in PTH-treated mice. The increase in the bone formation rate by PTH was depressed, and the osteoclast surface was thoroughly increased. The increase in alkaline phosphatase-positive colony-forming units-fibroblastic (CFU-f) colonies induced by PTH was maintained and that of TRACP+ multinucleated cells enhanced. The PTH-induced increase in c-fos mRNA was depressed, but the increases in Osterix and RANKL mRNA were maintained. Unloading promoted the PTH-associated osteoclastogenesis and seemed to delay the progression of osteogenic differentiation in association with reduction of the PTH-dependent increase of c-fos mRNA in bone marrow cells.
Long-Term Sensitivity of Uterus and Hypothalamus/Pituitary Axis to 17β-Estradiol Is Higher Than That of Bone in Rats
Authors: Erben Reinhold G , Brunner Katrin S , Breig Bianca 
Published: April 2006

Abstract
We examined the long-term sensitivity of uterus and bone to low-dose 17β-estradiol in a 4-month experiment in OVX rats and found that a dose of estradiol that fully protected against uterine atrophy did not protect against bone loss. Our results suggest higher estrogen sensitivity of the uterus compared with bone.
Introduction: Estrogen is essential for the function of reproductive tissues and for the normal acquisition and maintenance of bone mass in females. This study was designed to examine the long-term sensitivity of the uterus and bone to low-dose estrogen.
Materials and Methods: In preliminary experiments, we determined the lowest subcutaneous dose of 17β-estradiol able to fully protect against uterine atrophy in ovariectomized (OVX) rats. This dose was found to be 1.5 μg/kg, given five times per week. Subsequently, groups of sham-operated (SHAM) or OVX 6-month-old rats (n = 8 each) were subcutaneously injected with vehicle or 1.5 μg/kg 17β-estradiol five times per week. All animals were killed 4 months after surgery. Serum osteocalcin and urinary deoxypyridinoline were measured as biochemical markers of bone turnover. Bones were analyzed by bone histomorphometry and pQCT.
Results and Conclusions: Our study clearly showed that a dose of estradiol that restores physiological estradiol serum levels, fully maintains uterine weight in OVX rats at the SHAM control level, and suppresses serum follicle-stimulating hormone (FSH) by 67% relative to OVX vehicle controls does not provide significant protection against OVX-induced bone loss at different cancellous and cortical bone sites. We conclude that the long-term sensitivity of the uterus and the hypothalamus/pituitary axis to 17β-estradiol is higher than that of bone in rats.
Dissociation Between Global Markers of Bone Formation and Direct Measurement of Spinal Bone Formation in Osteoporosis
Authors: Frost Michelle L , Fogelman Ignac , Blake Glen M , Marsden Paul K , Cook Gary JR 
Published: April 2006

Abstract
Regional bone metabolism measured using18F-fluoride PET was assessed in 72 postmenopausal women classified as normal, osteopenic, or osteoporotic. Lower values of regional bone formation activity at the lumbar spine were seen in osteoporotic women, whereas global markers of bone formation were significantly increased.
Introduction: Evaluations of global bone remodeling have revealed that increased bone turnover is a feature of patients with osteoporosis. The noninvasive functional imaging technique of18F-fluoride positron emission tomography (PET) allows the direct quantitative assessment of bone metabolism at specific sites in the skeleton, including the clinically important site of the lumbar spine.
Materials and Methods: The aim of this study was to compare regional skeletal kinetics in 72 postmenopausal women (mean age, 61 years) classified as normal, osteopenic, or osteoporotic according to their BMD T score at the lumbar spine. Each woman had a dynamic PET scan of the lumbar spine after injection of 90 MBq18F-fluoride ion and measurements of biochemical markers of bone formation and resorption. The arterial plasma input function was derived using aorta arterial activity from the PET image. Time-activity curves were obtained by placing regions of interest over the lumbar vertebrae. A three-compartmental model was used to calculate bone blood flow (K1) and the net plasma clearance of tracer to bone mineral (Ki), reflecting regional osteoblastic activity (ml/minutes/ml). Rate constants k2, k3, and k4, which describe transport between plasma, the extracellular fluid (ECF) compartment, and the bone mineral compartment, were also measured.
Results: The net uptake of fluoride to the bone mineral compartment (Ki) was significantly lower in the osteoporotic group compared with both the osteopenic and normal groups, with a mean difference of 0.005 ml/minutes/ml (16.7%). The fraction of the tracer in the extravascular tissue space that underwent specific binding to bone mineral (k3/k2 + k3) was also significantly reduced in the women classified as osteoporotic. In contrast, levels of bone-specific alkaline phosphatase (BSALP) were significantly higher in the osteoporotic group compared with the normal and osteopenic groups by 35% and 27%, respectively. A significant negative correlation (r = −0.41) was observed between levels of BSALP and the fraction of the tracer that underwent specific binding to bone mineral.
Conclusion: Lower values of Ki, a measurement of regional bone formation activity, were seen in women classified as osteoporotic, whereas levels of BSALP, a measure of global bone formation, were significantly increased. These findings are suggestive of increased global skeletal bone turnover in women with postmenopausal osteoporosis but with relatively reduced regional bone formation at the predominantly trabecular site of the lumbar spine.
Degradation of the Organic Phase of Bone by Osteoclasts: A Secondary Role for Lysosomal Acidification
Authors: Henriksen Kim , Sørensen Mette G , Nielsen Rasmus H , Gram Jeppe , Schaller Sophie , Dziegiel Morten H , Everts Vincent , Bollerslev Jens , Karsdal Morten A 
Published: April 2006

Abstract
Osteoclasts degrade bone matrix by secretion of hydrochloric acid and proteases. We studied the processes involved in the degradation of the organic matrix of bone in detail and found that lysosomal acidification is involved in this process and that MMPs are capable of degrading the organic matrix in the absence of cathepsin K.
Introduction: Osteoclasts resorb bone by secretion of acid by the vacuolar H+-adenosine triphosphatase (V-ATPase) and the chloride channel ClC-7, followed by degradation of the matrix, mainly collagen type I, by cathepsin K and possibly by matrix metalloproteinases (MMPs). However, the switch from acidification to proteolysis and the exact roles of both the ion transporters and the proteinases still remain to be studied.
Materials and Methods: We isolated CD14+ monocytes from human peripheral blood from either controls or patients with autosomal dominant osteopetrosis type II (ADOII) caused by defective ClC-7 function and cultured them in the presence of RANKL and macrophage-colony stimulating factor (M-CSF) to generate osteoclasts. We decalcified cortical bovine bone slices and studied the osteoclasts with respect to morphology, markers, and degradation of the decalcified matrix in the presence of various inhibitors of osteoclast acidification and proteolysis, using normal calcified bone as a reference.
Results: We found that ADOII osteoclasts not only have reduced resorption of the calcified matrix, but also 40% reduced degradation of the organic phase of bone. We found that both acidification inhibitors and cathepsin K inhibitors reduced degradation of the organic matrix by 40% in normal osteoclasts, but had no effect in the ADOII osteoclasts. Furthermore, we showed that inhibition of MMPs leads to a 70% reduction in the degradation of the organic bone matrix and that MMPs and cathepsin K have additive effects. Finally, we show that osteoclastic MMPs mediate release of the carboxyterminal telopeptide of type I collagen (ICTP) fragment in the absence of cathepsin K activity, and therefore, to some extent, are able to compensate for the loss of cathepsin K activity.
Conclusions: These data clearly show that osteoclastic acidification of the lysosomes plays a hitherto nonrecognized role in degradation of the organic matrix. Furthermore, these data shed light on the complicated interplay between acidification dependent and independent proteolytic processes, mediated by cathepsin K and the MMPs, respectively.
Smad3-Deficient Chondrocytes Have Enhanced BMP Signaling and Accelerated Differentiation
Authors: Li Tian-Fang , Darowish Michael , Zuscik Michael J , Chen Di , Schwarz Edward M , Rosier Randy N , Drissi Hicham , O'Keefe Regis J 
Published: April 2006

Abstract
Smad3 deficiency accelerates chondrocyte maturation and leads to osteoarthritis. Primary chondrocytes without Smad3 lack compensatory increases of TGF-β signaling factors, but BMP-related gene expression is increased. Smad2 or Smad3 overexpression and BMP blockade abrogate accelerated maturation in Smad3−/− chondrocytes. BMP signaling is increased in TGF-β deficiency and is required for accelerated chondrocyte maturation.
Introduction: Disruption of TGF-β signaling results in accelerated chondrocyte maturation and leads to postnatal dwarfism and premature osteoarthritis. The mechanisms involved in this process were studied using in vitro murine chondrocyte cultures.
Materials and Methods: Primary chondrocytes were isolated from the sterna of neonatal wildtype and Smad3−/− mice. Expressions of maturational markers, as well as genes involved in TGF-β and BMP signaling were examined. Chondrocytes were treated with TGF-β and BMP-2, and effects on maturation-related genes and BMP/TGF-β responsive reporters were examined. Recombinant noggin or retroviral vectors expressing Smad2 or Smad3 were added to the cultures.
Results: Expression of colX and other maturational markers was markedly increased in Smad3−/− chondrocytes. Smad3−/− chondrocytes lacked compensatory increases in Smad2, Smad4, TGFRII, Sno, or Smurf2 and had reduced expression of TGF-β1 and TGFRI. In contrast, Smad1, Smad5, BMP2, and BMP6 expression was increased, suggesting a shift from TGF-β toward BMP signaling. In Smad3−/− chondrocytes, alternative TGF-β signaling pathways remained responsive, as shown by luciferase assays. These non-Smad3-dependent TGF-β pathways reduced colX expression and alkaline phosphatase activity in TGF-β-treated Smad3−/− cultures, but only partially. In contrast, Smad3−/− chondrocytes were more responsive to BMP-2 treatment and had increased colX expression, phosphoSmads 1, 5, and 8 levels, and luciferase reporter activity. Overexpression of both Smad2 and Smad3 blocked spontaneous maturation in Smad3-deficient chondrocytes. Maturation was also abrogated by the addition of noggin, an extracellular BMP inhibitor.
Conclusions: These findings show a key role for BMP signaling during the chondrocyte maturation, occurring with loss of TGF-β signaling with important implications for osteoarthritis and cartilage diseases.
Loop Diuretics Increase Bone Turnover and Decrease BMD in Osteopenic Postmenopausal Women: Results From a Randomized Controlled Study With Bumetanide
Authors: Rejnmark Lars , Vestergaard Peter , Heickendorff Lene , Andreasen Frederik , Mosekilde Leif 
Published: April 2006

AbstractTo study effects of loop diuretics on bone, 87 women were randomized to 1 year of treatment with bumetanide or placebo. Compared with placebo, bumetanide decreased BMD by 2% at the total hip and by 1.4% at the whole body. Levels of biochemical bone markers were lower in the placebo than in the bumetanide group. Thus, treatment with loop diuretics affects bone metabolism.Introduction: Loop diuretics may affect bone because they increase the renal calcium excretion and alters the diurnal rhythm of plasma PTH levels. We studied the effects of 1 year of treatment with the loop diuretic bumetanide on bone metabolism.Materials and Methods: In a double-blinded design, 87 healthy postmenopausal women with osteopenia were randomized to 1-year bumetanide treatment 2 mg/day or placebo. BMD, plasma levels of calcitropic hormones, and biochemical bone markers were measured at baseline, after 1 year of treatment (week 52), and 6 months after withdrawal of treatment (week 78). Calcium (800 mg/day) and vitamin D (10 μg/day) were administered to all participants during the entire 1.5-year study period.Results: Compared with placebo, urinary calcium (+17%) and plasma PTH levels (+9%) increased significantly in response to bumetanide. After 1 year of treatment, BMD in the bumetanide compared with the placebo group was significantly decreased by 2% at the total hip and ultradistal forearm and by 1.4% at the whole body. In addition, levels of biochemical markers of bone turnover differed significantly (∼20%) between groups, with lower levels in the placebo than in the bumetanide group. Six months after the end of treatment, the effects of bumetanide were weakening.Conclusions: Treatment with loop diuretics affects bone turnover and decreases BMD. Further studies may reveal whether loop diuretics should be considered as a risk factor for fracture.
Two-Year Clinical Trial of Oral Alendronate Versus Intravenous Pamidronate in Children With Osteogenesis Imperfecta
Authors: DiMeglio Linda A , Peacock Munro 
Published: April 2006

Abstract
A 2-year prospective, partially randomized open-label trial comparing oral alendronate with intravenous pamidronate therapy in children with OI showed equivalence in increasing total body BMD, spine BMD, and linear growth, and decreasing bone turnover and fracture incidence. Children with mild OI had greater responses than severe OI in BMD and growth.
Introduction: Bisphosphonate therapies increase BMD and may reduce fractures in children with osteogenesis imperfecta (OI). A study directly comparing oral with intravenous bisphosphonate has not been published. This clinical trial compares oral alendronate with intravenous pamidronate in children with OI using an open-label, prospective, 2-year, randomized design.
Materials and Methods: Children over the age of 3 years were stratified by bone age, pubertal stage, and type of OI and then randomized to receive oral alendronate 1 mg/kg/day in tablet form or intravenous pamidronate, 3 mg/kg/4 months. One child was assigned to pamidronate. One child randomized to intravenous pamidronate changed to oral alendronate. Eighteen children completed 12 months of therapy: nine on oral alendronate and nine on intravenous pamidronate. Primary outcome efficacy was increase in BMD. Secondary outcomes included changes in bone turnover biomarkers, fracture incidence, and growth.
Results: Total body and lumbar spine BMD increased, turnover markers decreased, and linear growth increased equivalently with oral and intravenous therapy. Fracture incidence showed a trend to decrease in both groups, with a significant decrease in fracture rates when the oral and intravenous groups were pooled. There were greater responses in BMD and growth in children with milder OI (type I) than those with more severe disease (types III and IV), but there were no significant effects of age or pubertal stage.
Conclusions: Oral and intravenous bisphosphonate therapies are equally effective in children with OI and are particularly effective in milder forms. The oral route is highly acceptable in children and has practical advantages over the intravenous route.
Association of Functionally Different RUNX2 P2 Promoter Alleles With BMD
Authors: Doecke James D , Day Christopher J , Stephens Alexandre SJ , Carter Shea L , van Daal Angela , Kotowicz Mark A , Nicholson Geoff C , Morrison Nigel A 
Published: April 2006

Abstract
RUNX2 gene SNPs were genotyped in subjects from the upper and lower deciles of age- and weight-adjusted femoral neck BMD. Of 16 SNPs in RUNX2 and its two promoters (P1 and P2), only SNPs in the P2 promoter were significantly associated with BMD. These P2 promoter SNPs were functionally different in gel-shift and promoter activity assays.
Introduction: Specific osteoblast genes are induced by Runx2, a cell-specific transcription factor that is a candidate gene for controlling BMD. We tested the hypothesis that RUNX2 genetic variation is associated with BMD.
Materials and Methods: From a population repository of normal subjects, the age- and weight-adjusted femoral neck BMD was ranked, and the upper and lower deciles (n = 132 each) were taken to represent the adjusted extremes of the population distribution. In these 264 subjects, we identified 16 allelic variations within the RUNX2 gene and promoters (P1 and P2) through DNA sequencing and denaturing high-performance liquid chromatography. Characterization of these alleles was performed through allele-specific cloning, transfection into ROS 17/2.8 cells, luciferase reporter analysis, and electrophoretic mobility shift assays.
Results: Within the P2 promoter were three polymorphic nucleotides for which the minor alleles were over-represented in the upper decile of BMD (0.117 and 0.064 in the upper and lower deciles, respectively). These alleles are in near complete linkage disequilibrium with each other and represent a haplotype block that is significantly associated with increased BMD. The common and rare P2 promoter alleles were cloned upstream of luciferase, and when transfected into osteoblast-like cells, the construct representing the rare haplotype showed significantly greater P2 promoter activity than the common haplotype.
Conclusions: Because the high BMD allele had higher P2 promoter activity, the data suggest that greater RUNX2 P2 promoter activity is associated with higher BMD.
Effects of Oral Alendronate on BMD in Adult Patients With Osteogenesis Imperfecta: A 3-Year Randomized Placebo-Controlled Trial
Authors: Chevrel Guillaume , Schott Anne-Marie , Fontanges Elisabeth , Charrin Jeanne E , Lina-Granade Geneviève , Duboeuf François , Garnero Patrick , Arlot Monique , Raynal Claude , Meunier Pierre J 
Published: April 2006

Abstract
A 3-year, randomized, double-blind, placebo-controlled trial evaluated the effect of oral alendronate on the BMD of 64 adult patients with osteogenesis imperfecta. The mean increases in the lumbar spine BMD were 10.1 ± 9.8% (p &lt; 0.001) and 0.7 ± 5.7% in the alendronate and placebo groups, respectively. Oral alendronate increases BMD in adult patients with osteogenesis imperfecta.
Introduction: This study evaluated the effect of oral alendronate on the BMD of adult patients with osteogenesis imperfecta.
Materials and Methods: We carried out a 3-year, randomized, double-blind, placebo-controlled trial of oral alendronate in 64 adult patients with osteogenesis imperfecta. The primary endpoint was the difference between the groups in the mean percent change in lumbar spine BMD at 3 years. Secondary outcomes included changes in BMD of total hip, vertebral and peripheral fracture incidence, pain, hearing loss, and bone turnover biochemical markers. Patients were treated daily with either placebo or 10 mg alendronate. All received 1 g of calcium and 800 IU of vitamin D daily.
Results: The mean ± SD increases in the lumbar spine BMD were 10.1 ± 9.8% (p &lt; 0.001) and 0.7 ± 5.7% in the alendronate and placebo groups, respectively. Hip BMD increased in the alendronate group by 3.3 ± 0.5% (p = 0.001) and decreased in the placebo group by 0.3 ± 0.6%. The sample size was not sufficient to determine an effect of alendronate on fracture rate. A significant increase of the pain score was noted in the alendronate group (p = 0.04) in the intent-to-treat analysis but not in the per protocol analysis. There was no change in hearing in either group. Bone resorption and formation biochemical markers were significantly decreased in the alendronate group (p &lt; 0.001). There were no differences in severe adverse effects between the groups, but there was an increase in nonsevere upper gastrointestinal effects in the alendronate group (p = 0.003).
Conclusions: Oral alendronate increases BMD and increase nonsevere gastrointestinal adverse effects but does not modify the hearing loss in adult patients with osteogenesis imperfecta. More studies are needed to evaluate an effect on the fracture rate.