bluuebunny/crossref_metadata_2025_split huggingface dataset:
Frequency-Dependent Effect of Nitric Oxide Donor Nitroglycerin on Bone
Authors: Wimalawansa Sunishka , Chapa Teri , Fang Li , Yallampalli Chandra , Simmons David , Wimalawansa Sunil 
Published: April 2006

Abstract
Recently, we showed that supplementation with nitric oxide (NO) via donor nitroglycerin (NG) alleviated the ovariectomy and corticosteroid-induced bone loss in rats. In humans, high doses or frequent applications of NG (i.e., for angina) lead to rapid loss of its efficacy in relieving angina. To examine whether there is a similar effect on the loss of efficacy of NG on bone, we examined the frequency-dependent effects of NG on bone mineral density (BMD), bone mass, trabecular bone volumes (BV/TV), and blood pressure in rats. Thirty 7-month-old female Brown Norway rats underwent ovariectomy, and an additional six rats were sham-operated. The ovariectomized rats were treated either with vehicle (ovariectomized control), 17β-estradiol (E2; positive control), or 0.2 mg NG (via dermal application) once, twice, or three times a day. Before and at the end of the 10-week treatment period, BMD of the lumbar spine was measured by dual-energy X-ray absorptiometric (DXA) scanning and expressed as a percentage change. BMD in ovariectomized rats was significantly lower (−2.5 ± 2.0%) compared with the sham-operated rats (+6.3 ± 5.3%; p &lt; 0.01). Estrogen therapy completely abolished the ovariectomy-induced potential bone loss (+5.9 ± 3.4%). Application of NG once daily also completely prevented (+6.2 ± 2.8%; p &lt; 0.01) the ovariectomy-induced bone loss (i.e., it was as effective as estrogen). However, the beneficial effects of NG on BMD were significantly reduced with increased frequency of application of NG (+1.9 ± 2.1%, twice a day and −0.2 ± 3.3% three times a day). Estrogen or once daily administration of NG preserved femur weights, BV/TV, and decreased urinary deoxypyridinoline levels as expected. However, a higher level of serum osteocalcin and bone-specific alkaline phosphatase levels were maintained only with once daily administration of NG. There were no adverse effects of these doses of NG on blood pressure, but a tendency to lower blood pressure was noticed with increased frequency of NG. These results confirmed our previous findings that NO donors counteract the bone loss associated with estrogen deficiency. However, these beneficial effects of maintaining BMD are lost with increased frequency of NG application.
Involvement of CCAAT Enhancer Binding Protein Transcription Factors in the Regulation of Prostaglandin G/H Synthase 2 Expression by Interleukin-1 in Osteoblastic MC3T3-E1 Cells
Authors: Harrison John R. , Kelly Penny L. , Pilbeam Carol C. 
Published: April 2006

Abstract
Interleukin-1 (IL-1) stimulates prostaglandin production in bone by a rapid and transient activation of prostaglandin G/H synthase 2 (PGHS-2) gene expression. In osteoblastic MC3T3-E1 cells, IL-1 caused a transient increase in PGHS-2 messenger RNA (mRNA), which peaked at 2 h. IL-1 caused a 2- to 4-fold activation of a 371-base pair (bp) murine PGHS-2 promoter/luciferase construct in stable transfectants. This response mapped to a proximal promoter element(s) located between −150 and −40 bp. This region contains a putative CCAAT enhancer binding protein (C/EBP) site (centered at −135 bp), which shows enhanced binding of C/EBPβ and C/EBPδ by mobility shift analysis after IL-1 treatment. A transient cotransfection approach was used to examine the effects of C/EBPβ and C/EBPδ overexpression. IL-1 caused a maximal 3- to 7-fold stimulation of PGHS-2 promoter activity after 2.5 h. Overexpression of murine C/EBPβ and C/EBPδ caused a dose-dependent increase in basal and IL-1-stimulated luciferase activity. C/EBPδ caused a greater enhancement of basal and IL-1-stimulated promoter activity than C/EBPβ, suggesting that C/EBPδ is a stronger transactivator. Overexpression of p20C/EBPβ, a dominant negative inhibitor of C/EBP function, blocked the stimulation of PGHS-2 promoter activity by IL-1 and blocked the ability of overexpressed C/EBPβ and C/EBPδ to increase basal and IL-1-stimulated promoter activity. Mutagenesis of the C/EBP site reduced, but did not abolish, the stimulation of PGHS-2 promoter activity by IL-1 and blunted the effect of overexpressed C/EBPδ on basal and IL-1-stimulated promoter activity. These results suggest an essential role for C/EBPβ and C/EBPδ in the induction of PGHS-2 gene expression by IL-1 in osteoblastic cells.
Making Rats Rise to Erect Bipedal Stance for Feeding Partially Prevented Orchidectomy-Induced Bone Loss and Added Bone to Intact Rats
Authors: Yao Wei , Jee Webster S. S. , Chen Jianliang , Liu Haoyu , Tam Cherk S. , Cui Liao , Zhou Hua , Setterberg Rebecca B. , Frost Harold M. 
Published: April 2006

Abstract
The objectives of this study were to investigate the different effects on muscle mass and cancellous (proximal tibial metaphysis [PTM]) and cortical (tibial shaft [TX]) bone mass of sham-operated and orchidectomized (ORX) male rats by making rats rise to erect bipedal stance for feeding. Specially designed raised cages (RC) were used so that the rats had to rise to erect bipedal stance to eat and drink for 12 weeks. Dual-energy X-ray absorptiometry (DEXA) and peripheral quantitative computerized tomography (pQCT) were used to estimate the lean leg mass and bone mineral. Static and dynamic histomorphometry were performed on the triple-labeled undecalcified sections. We found that making the intact rats rise to erect bipedal stance for feeding increased muscle mass, cortical bone volume, and periosteal bone formation. Orchidectomy increased net losses of bone next to the marrow by increasing bone turnover. Making the ORX rats rise to erect bipedal stance increased muscle mass, partially prevented cancellous bone loss in the PTM, and prevented net cortical bone loss in TX induced by ORX by depressing cancellous and endocortical high bone turnover and stimulating periosteal bone formation. The bone-anabolic effects were achieved mainly in the first 4 weeks in the PTM and by 8 weeks in the TX. These findings suggested that making the rats rise to erect bipedal stance for feeding helped to increase muscle mass and cortical bone mass in the tibias of intact rats, increase muscle mass, and partially prevented cancellous and net cortical bone loss in ORX rats.
The Effects of Bone Marrow Transplantation on X-linked Hypophosphatemic Mice
Authors: Miyamura Takako , Tanaka Hiroyuki , Inoue Masaru , Ichinose Youjirou , Seino Yoshiki 
Published: April 2006

Abstract
The genes responsible for X-linked hypophosphatemic (XLH) vitamin D-resistant rickets and the murine homolog, hypophosphatemic mice (Hyp), were identified as PHEX and Phex (phosphate-regulating gene with homology to endopeptidases on the X chromosome), respectively. However, the mechanism by which inactivating mutations of PHEX cause XLH remains unknown. We investigated the mechanisms by syngeneic bone marrow transplantation (BMT) from wild mice to Hyp mice. The expression of the Phex gene was detected in mouse BM cells. BMT introduced a chimerism in recipient Hyp mice and a significant increase in the serum phosphorus level. The renal sodium phosphate cotransporter gene expression was significantly increased. The effect of BMT on the serum phosphorus level depended on engraftment efficiencies, which represent the dosage of normal gene. Similarly, the serum alkaline phosphatase (ALP) activity was decreased and bone mineral density was increased. Furthermore, the renal expression of 25-hydroxyvitamin D3 24-hydroxylase, which is a key enzyme in the catabolic pathway and is increased in XLH/Hyp, was improved. From these results, we conclude that transplantation of normal BM cells improved abnormal bone mineral metabolism and deranged vitamin D metabolism in Hyp by replacing defective gene product(s) with normal gene product(s). This result may provide strong evidence for clinical application of BMT in metabolic bone disorders.
Fibroblastic Stromal Cells Express Receptor Activator of NF-κB Ligand and Support Osteoclast Differentiation
Authors: Dr. Quinn Julian M. W. , Horwood Nicole J. , Elliott Jan , Gillespie Matthew T. , Martin T. John 
Published: April 2006

Abstract
Osteoclast formation in bone is supported by osteoblasts expressing receptor activator of NF-κB ligand (RANKL) and macrophage colony-stimulating factor (M-CSF) expression. Numerous osteotropic factors regulate expression levels of RANKL and the RANKL decoy receptor osteoprotegerin (OPG) in osteoblasts, thereby affecting osteoclast differentiation. However, not only is RANKL widely expressed in soft tissues, but osteoclasts have been noted in extraskeletal lesions. We found that cultured skin fibroblastic cells express RANKL, M-CSF, and OPG messenger (mRNA). Stimulation by 1α,25 dihydroxyvitamin D3 [1,25(OH)2D3] plus dexamethasone (Dex) augmented RANKL and diminished OPG mRNA expression in fibroblastic cells and caused the formation of numerous osteoclasts in cocultures of skin fibroblastic cells with hemopoietic cells or monocytes. The osteoclasts thus formed expressed tartrate-resistant acid phosphatase (TRAP) and calcitonin (CT) receptors and formed resorption pits in cortical bone. Osteoclast formation also was stimulated (in the presence of Dex) by prostaglandin E2 (PGE2), interleukin-11 (IL-11), IL-1, tumor necrosis factor-α (TNF-α), and parathyroid hormone-related protein (PTHrP), factors which also stimulate osteoclast formation supported by osteoblasts. In addition, granulocyte-macrophage-CSF (GM-CSF), transforming growth factor-β (TGF-β), and OPG inhibited osteoclast formation in skin fibroblastic cell-hemopoietic cell cocultures; CT reduced only osteoclast nuclearity. Fibroblastic stromal cells from other tissues (lung, respiratory diaphragm, spleen, and tumor) also supported osteoclast formation. Thus, RANKL-positive fibroblastic cells in extraskeletal tissues can support osteoclastogenesis if osteolytic factors and osteoclast precursors are present. Such mesenchymally derived cells may play a role in pathological osteolysis and may be involved in osteoclast formation in extraskeletal tissues.
Integrin and Mechanosensitive Ion Channel-Dependent Tyrosine Phosphorylation of Focal Adhesion Proteins and β-Catenin in Human Articular Chondrocytes After Mechanical Stimulation
Authors: Lee H. S. , Millward-Sadler S. J. , Wright M. O. , Nuki G. , Dr. Salter D. M. 
Published: April 2006

Abstract
Mechanical forces influence chondrocyte metabolism and function. We have previously shown that 0.33 Hz cyclical pressure-induced strain (PIS) results in membrane hyperpolarization of normal human articular chondrocytes (HAC) by activation of Ca2+-dependent K+ small conductance potassium activated calcium (SK) channels. The mechanotransduction pathway involves α5β1-integrin, stretch-activated ion channels (SAC) actin cytoskeleton and tyrosine protein kinases, with subsequent release of the chondroprotective cytokine interleukin-4 (IL-4). The objective of this study was to examine in detail tyrosine phosphorylation events in the mechanotransduction pathway. The results show tyrosine phosphorylation of three major proteins, p125, p90, and p70 within 1 minute of onset of mechanical stimulation. Immunoblotting and immunoprecipitation show these to be focal adhesion kinase (pp125FAK), β-catenin, and paxillin, respectively. Tyrosine phosphorylation of all three proteins is inhibited by RGD containing oligopeptides and gadolinium, which is known to block SAC. β-catenin coimmunoprecipitates with FAK and is colocalized with α5-integrin and pp125FAK. These results indicate a previously unrecognized role for an integrin-β-catenin signaling pathway in human articular chondrocyte (HAC) responses to mechanical stimulation.
Six-Month Daily Administration of Parathyroid Hormone and Parathyroid Hormone—Related Protein Peptides to Adult Ovariectomized Rats Markedly Enhances Bone Mass and Biomechanical Properties: A Comparison of Human Parathyroid Hormone 1–34, Parathyroid Hormone-Related Protein 1–36, and SDZ-Parathyroid Hormone 893
Authors: Stewart A. F. , Cain R. L. , Burr D. B. , Jacob D. , Turner C. H. , Hock J. M. , Drezner Marc K. 
Published: April 2006

Abstract
Daily administration of parathyroid hormone (PTH) and PTH-related protein (PTHrP) peptides has been shown to increase bone mass and strength in animals and, for PTH, to increase bone mass in humans. Long-term direct comparison of multiple members of the PTH/PTHrP family in vivo has not been reported. We therefore selected three PTH/PTHrP molecules for direct comparison in vivo in an adult rat model of postmenopausal osteoporosis: PTH(1-34), PTHrP(1-36), and the PTH analog, SDZ-PTH 893 {Leu8, Asp10, Lys11, Ala16, Gln18, Thr33, Ala34 human PTH 1–34 [hPTH(1-34)]}. A 6-month study was performed in which adult (6-month-old) vehicle-treated ovariectomized (OVX) and sham OVX rats were compared with OVX rats receiving 40 μg/kg per day of either PTH(1-34), PTHrP(1-36), or PTH-SDZ-893. Bone mass, as assessed by ash weight and densitometry, bone histomorphometry, biomechanical properties at trabecular and cortical sites, and indices of bone formation markedly increased in all three PTH/PTHrP peptide-treated groups as compared with controls. In general, this improvement followed a rank order of SDZ-PTH-893 &gt; PTH &gt; PTHrP. The adverse effect profile also was greatest with SDZ-PTH-893; these rats developed moderate hypercalcemia, marked renal calcium accumulation, and displayed a 13% mortality. These studies show that PTH(1-34), PTHrP(1-36), and PTH-SDZ-893 significantly and progressively increase bone mass and bone strength in this rat model of postmenopausal osteoporosis. The adverse effect profile correlates in general terms with efficacy. All three peptides show promise as skeletal anabolic agents. Further studies in humans will be required to define optimal efficacy-to-adverse effect ratios and relative efficacy for each peptide in human osteoporosis.
Cytokines and Bone Loss in a 5-Year Longitudinal Study—Hormone Replacement Therapy Suppresses Serum Soluble Interleukin-6 Receptor and Increases Interleukin-1-Receptor Antagonist: The Danish Osteoporosis Prevention Study
Authors: Abrahamsen Bo , Bonnevie-Nielsen Vagn , Ebbesen Ebbe Nils , Gram Jeppe , Beck-Nielsen Henning 
Published: April 2006

Abstract
The proinflammatory cytokines interleukin-1β (IL-1β) and IL-6 may play a central role in the acceleration of postmenopausal bone loss, but observational studies have led to contradictory results. Estrogen-dependent changes in the production of IL-1 receptor antagonist (IL-1ra) and the soluble IL-6 receptor (sIL-6R) potentially modify cytokine bioactivity. We therefore assessed the impact of menopause and hormone replacement therapy (HRT) on cytokines and activity modifiers in serum within a 5-year longitudinal study. One hundred sixty perimenopausal women (age 50.1 ± 2.8 years) were randomized to HRT or no treatment. Serum IL-6 increased with age (r = 0.16; p &lt; 0.05), but cytokines did not correlate with baseline bone mineral density (BMD). HRT led to small increases in IL-1ra (p &lt; 0.001) and IL-6 (p &lt; 0.05), with a decrease in sIL-6R (p &lt; 0.01) and no change in IL-1β. No changes were observed in the control group. IL-1ra was inversely correlated with bone loss at the ultradistal forearm (r = 0.29; p &lt; 0.05) and to a lesser degree at the spine (r = 0.20; p = 0.09). In addition, there was a weak positive correlation between sIL-6R and bone loss at the ultradistal forearm (r = 0.26; p &lt; 0.05). High IL-6 levels were associated with slower bone loss (spine r = 0.31, p &lt; 0.01) and controlling for age did not diminish this association. The percent change in sIL-6R during HRT was correlated with the bone loss at the femoral neck (r = −0.29; p &lt; 0.01) and weakly with bone loss in the spine (r = −0.16; p = 0.17). In conclusion, serum IL-1ra and sIL-6R are influenced by HRT and are associated with the rate of bone loss in perimenopausal women.
Partitioning a Daily Mechanical Stimulus into Discrete Loading Bouts Improves the Osteogenic Response to Loading
Authors: Robling Alexander G. , Burr David B. , Turner Charles H. 
Published: April 2006

Abstract
A single 3-minute bout of mechanical loading increases bone formation in the rat tibia. We hypothesized that more frequent, shorter loading bouts would elicit a greater osteogenic response than a single 3-minute bout. The right tibias of 36 adult female Sprague-Dawley rats were subjected to 360 bending cycles per day of a 54N force delivered in 1, 2, 4, or 6 bouts on each of the 3 loading days. Rats in the 6-bouts/day group received 60 bending cycles per bout (60 × 6); rats in the 4-bouts/day group received 90 bending cycles per bout (90 × 4); the 2- and 1-bouts/day groups received 180 and 360 bending cycles per bout, respectively (180 × 2 and 360 × 1). A nonloaded, age-matched control group (0 × 0) and two sham-bending groups (60 × 6 and 360 × 1) also were included. Fluorochrome labeling revealed a 10-fold increase in endocortical lamellar bone formation rate (BFR/bone surface [BS]) in the right tibia versus the left (nonloaded) side in the 60 × 6 bending group. Endocortical BFR/BS in the right tibia of the 4-, 2-, and 1-bout bending groups exhibited 8-, 4-, and 4-fold increases, respectively, over the control side. Relative (right minus left) values for endocortical BFR/BS, mineralizing surface (MS/BS), and mineral apposition rate (MAR) were 65–94% greater in the 90 × 4 and 60 × 6 bending groups compared to the 360 × 1 bending group. Sham-bending tibias exhibited relative endocortical bone formation values similar to those collected from the control (0 × 0) group. The data show that 360 daily loading cycles applied at intervals of 60 × 6 or 90 × 4 represent a more osteogenic stimulus than 360 cycles applied all at once, and that mechanical loading is more osteogenic when divided into discrete loading bouts. Presumably, bone cells become increasingly “deaf” to the mechanical stimulus as loading cycles persist uninterrupted, and by allowing a rest period between loading bouts, the osteogenic effectiveness of subsequent cycles can be increased.
In Vitro Apatite Induction by Phosphophoryn Immobilized on Modified Collagen Fibrils
Authors: Saito Takashi , Yamauchi Mitsuo , Abiko Yoshihiro , Matsuda Koichi , Crenshaw Miles A. 
Published: April 2006

Abstract
Noncollagenous phosphoproteins that interact with type I collagen are thought to nucleate the mineral phase to collagen network of mineralized tissues. Previously, we found that phosphophoryn cross-linked to type I collagen was an effective nucleator of apatite. Here, we investigated the potential role of collagen telopeptide structure on this nucleation. We used pepsin and sodium borohydride (NaBH4) to modify the telopeptide region and reducible cross-links in the collagen fibrils and determined the effect on mineral induction by phosphophoryn cross-linked to it. The amount of phosphophoryn cross-linked to NaBH4-reduced collagen fibrils was higher than that to intact (unmodified) collagen fibrils. However, the amount of phosphophoryn cross-linked to collagen that lacked the telopeptides (atelocollagen) was 25% of that cross-linked to intact collagen fibrils. Each preparation was incubated at 37°C in metastable calcium phosphate solutions that did not spontaneously precipitate. Apatite was induced by phosphophoryn cross-linked to intact collagen fibrils at 15.0 h whereas phosphophoryn cross-linked to reduced collagen fibrils induced apatite formation after 10.9 h. Enough phosphophoryn was cross-linked to atelocollagen to induce mineral formation, but it did not. The failure of the phosphophoryn-atelocollagen complex to nucleate mineral might have been caused by a cross-linking pattern in the helical portion of the collagen molecule that did not promote the growth of the calcium-phosphate clusters into nuclei. The present study indicates that the telopeptide domains of type I collagen play a role in the interaction with phosphophoryn, which is critical for the nucleation process.
Hedgehog Proteins Stimulate Chondrogenic Cell Differentiation and Cartilage Formation
Authors: Enomoto-Iwamoto Motomi , Nakamura Takashi , Aikawa Tomonao , Higuchi Yoshinobu , Yuasa Takahito , Yamaguchi Akira , Nohno Tsutomu , Noji Sumihare , Matsuya Tokuzo , Kurisu Kojiro , Koyama Eiki , Pacifici Maurizio , Dr. Iwamoto Masahiro 
Published: April 2006

Abstract
Sonic hedgehog (Shh) and Indian hedgehog (Ihh) are important regulators of skeletogenesis, but their roles in this complex multistep process are not fully understood. Recent studies have suggested that the proteins participate in the differentiation of chondrogenic precursor cells into chondrocytes. In the present study, we have tested this possibility more directly. We found that implantation of dermal fibroblasts expressing hedgehog proteins into nude mice induces ectopic cartilage and bone formation. Immunohistological and reverse-transcription polymerase chain reaction (RT-PCR) analyses revealed that the ectopic tissues derived largely if not exclusively from host cells. We found also that treatment of clonal prechondrogenic RMD-1 and ATDC5 cells in culture with Ihh or recombinant amino half of Shh (recombinant N-terminal portion of Shh [rShh-N]) induced their differentiation into chondrocytes, as revealed by cytoarchitectural changes, Alcian blue staining and proteoglycan synthesis. Induction of RMD-1 cell differentiation by Ihh or rShh-N was synergistically enhanced by cotreatment with bone morphogenetic protein 2 (BMP-2) but was blocked by cotreatment with fibroblast growth factor 2 (FGF-2). Our findings indicate that hedgehog proteins have the ability to promote differentiation of chondrogenic precursor cells and that their action in this process can be influenced and modified by synergistic or antagonist cofactors.
Coordinate Expression of Novel Genes During Osteoblast Differentiation
Authors: Seth Arun , Lee Barbara K. , Qi Shirley , Vary Calvin P. H. 
Published: April 2006

Abstract
To achieve new insights into the coordinate regulation of gene expression during osteoblast differentiation we utilized an approach involving global analysis of gene expression to obtain the identities of messenger RNAs (mRNAs) expressed using an established in vitro model of bone development. MC3T3-E1 osteoblast-like cells were induced to differentiate by the addition of β-glycerophosphate (β-GP) and ascorbic acid. RNA samples derived from induced and uninduced control MC3T3-E1 cells were used to prepare complementary DNA (cDNA) for serial analysis of gene expression (SAGE). A preliminary SAGE database was produced and used to prepare a hybridization array to further facilitate the characterization of changes in the expression levels of 92 of the SAGE-mRNA assignments after induction of osteoblast differentiation, specifically after 6 days and 14 days of ascorbate treatment. SAGE-array hybridization analysis revealed coordinate induction of a number of mRNAs including Rab24, calponin, and calcyclin. Levels of MSY-1, SH3P2, fibronectin, α-collagen, procollagen, and LAMP1 mRNAs, present at day 6 postinduction, were markedly reduced by day 14 postinduction. A number of unanticipated and potentially important developmental genes were identified including the transforming growth factor β (TGF-β) superfamily member Lefty-1. Lefty-1 transcript and translation product were found to be induced during the course of MC3T3-E1 cell differentiation. We present evidence, using transient transfection and antibody neutralization approaches, that Lefty-1 modulates the induction of alkaline phosphatase (ALP) after treatment of MC3T3-E1 cells with ascorbate and β-GP. These data should provide useful new information for future analysis of transcriptional events in osteoblast differentiation and mineralization.