bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies on the regulation of insulin-like growth factor binding protein 3 secretion in human osteosarcoma cells in vitro
Authors: Nakao Y. , Hilliker S. , Baylink D.J. , Mohan S. 
Published: February 2010

Abstract
Previous studies demonstrated that insulin-like growth factors (IGFs) are important autocrine and paracrine mitogens for human bone cells in vitro and that IGF binding proteins (IGFBPs) are important regulators of the biologic actions of IGFs. Thus, the actions of IGFs may be determined not only by their concentrations but also by the type and amount of IGFBPs produced by human bone cells at a local site in bone. In this study, we sought to determine the effects of dexamethasone, 1,25-(OH)2 D3, and parathyroid hormone (PTH) on the secretion of IGFBP-3 in human osteosarcoma cell lines. Serum-free cultures of low- and high-alkaline phosphatase (ALP) SaOS-2, MG-63, and TE89 human osteosarcoma cells were treated for 24 or 48 h with the effectors and the conditioned media used for determination of IGFBP-3 using a radioimmunoassay. We report that (1) the basal rate of IGFBP-3 secretion (ng/mg cellular protein) was dependent upon cell type, with TE89 &gt; low-ALP Saos-2 &gt; MG-63 &gt; high-ALP SaOS-2 cells, and did not correlate with either basal cell proliferation or basal cellular ALP activity; (2) dexamethasone (10−12-10−7 M) inhibited IGFBP-3 secretion in a dose-dependent manner in low-ALP SaOS-2, MG-63, and TE89 cells but not in high-ALP SaOS-2 cells; (3) 1,25-(OH)2D3 (10−11-10−8 M) stimulated IGFBP-3 secretion in a dose-dependent manner in MG-63, low-ALP SaOS-2, and high-ALP SaOS-2 cells, and the coaddition of TGF-β and 1,25-(OH)2D3 increased synergistically IGFBP-3 secretion and cellular ALP activity in MG-63 cells; and (4) human PTH-(1–34) (0.1–100 ng/ml) had no significant effect on IGFBP-3 secretion in MG-63, low-ALP SaOS-2, or high-ALP SaOS-2 cells. We conclude that such agents as dexamethasone, 1,25-(OH)2D3, and PTH differentially regulate IGFBP-3 secretion in human osteosarcoma cells in vitro.
Analysis of gene expression in human bone biopsies by polymerase chain reaction: Evidence for enhanced cytokine expression in postmenopausal osteoporosis
Authors: Ralston Stuart H. 
Published: February 2010

Abstract
It has been suggested that one of the mechanisms by which estrogen protects against postmenopausal osteoporosis is by modulating the production of cytokines, such as interleukin-1 (IL-1), tumor necrosis factors (TNF), and interleukin-6 (IL-6), in the bone microenvironment. In this study, reverse transcription/polymerase chain reaction (RT/PCR) was used to analyze expression of the mRNAs encoding these cytokines in freshly isolated human bone biopsy samples. Marked differences were found in the prevalence with which certain cytokines were expressed in different patient subgroups. Specifically, IL-1α, IL-1β, and IL-6 mRNAs were expressed significantly more often in bone samples from postmenopausal women with osteoporotic fractures than in postmenopausal women with normal bone density or postmenopausal women on hormone replacement therapy (HRT). The prevalence of IL-1α expression was 54% in bone samples from patients with osteoporotic fractures (n = 22), compared with 30% in nonosteoporotic postmenopausal patients (n = 10) and 10% in postmenopausal patients on HRT (difference between groups by χ test = 7.0; DF = 2,p &lt; 0.05). Corresponding figures for IL-1β were 54 versus 30 versus 0% (χ = 8.6; DF = 2, p &lt; 0.01) and, for IL-6, 94 versus 51 versus 40%; χ = 13.5; DF = 2, p &lt; 0.01). TNF-α was expressed in a similar proportion of osteoporotic (63%) and normal postmenopausal patients (60%), whereas only 10% of HRT-treated patients showed expression of TNF-α (χ = 8.2; DF = 2, p &lt; 0.05). TNF-β was less commonly expressed in osteoporosis (18%) and was not detected at all in normal postmenopausal or HRT-treated patients, but this difference was not significant. Cytokine expression in bone samples from young healthy individuals showed sex-dependent differences in cytokine expression. In males, the pattern was similar to that observed in normal postmenopausal patients, with IL-1α expression in 36%, IL-1β in 36%, TNF-α in 63%, TNF-β in 9%, and IL-6 in 54% of cases. In young females (n = 7), however, the patterns of expression were similar to those in the HRT group, with IL-1α expression in 28%, IL-1β in 14%; TNF-α in 43%, TNF-β in 6%, and IL-6 in 28%. These experiments demonstrate that several cytokine mRNAs are expressed in the bone microenvironment. The high proportion of osteoporotic biopsies that showed expression of IL-1α, IL-1β, TNF-α, and IL-6 mRNAs lends support to the hypothesis that activation of cytokine expression in bone is a feature of postmenopausal osteoporosis and raises the possibility that local release of these cytokines contributes to bone loss in this condition.
Reversal of vertebral deformities in osteoporosis: Measurement error or “rebound”?
Authors: Nelson D.A. , Kleerekoper M. , Peterson E.L. 
Published: February 2010

Abstract
Digitized morphometry of vertebral bodies on lateral spine films is used to identify and quantify vertebral deformities or fractures. One problem associated with this method is the phenomenon of “disappearing fractures,” which results from the apparent increase in vertebral body heights of previously deformed vertebrae on subsequent radiographs. These have been considered biologically implausible and therefore a result of measurement error. Measurement error is unlikely to be unidirectional, so that a proportion of fractures identified by morphometry is also the result of measurement error. Since some vertebral deformities are real events, some disappearances of deformities detected by morphometry may be real events. In this report, we examine the data from our clinical trial of sodium fluoride in spinal osteoporosis to assess critically the plausibility of two hypotheses: (1) The “rebound” phenomenon results from measurement error. If this is the case, then some fractures of the same magnitude as the rebound must also represent measurement error. (2) Some deformed vertebrae in fact rebound toward their original shape and size, displaying an elastic response to deformation. If this occurs, then some vertebral deformities are transient events, not true fractures. We conclude that the variability inherent in morphometric data obtained from serial spine x-rays results in both disappearing fractures and a high false positive fracture rate. The use of more stringent criteria for defining significant deformities, or true fractures, will minimize these problems. We cannot exclude the second hypothesis, that some vertebral deformities may be transient events, but this needs further study.
Bone resorption assessed by immunoassay of urinary cross-linked collagen peptides in patients with osteogenesis imperfecta
Authors: Dr. Brenner Rolf E. , Vetter Ulrich , Bollen Anne-Marie , Mörike Martin , Eyre David R. 
Published: February 2010

Abstract
Urinary excretion of type I collagen cross-linked N-telopeptides was studied in 52 children and adolescents with osteogenesis imperfecta (OI) and found to be above the 75th percentile of controls in 44 of the patients. OI patients suffering from fractures during the preceding 6 months had significantly higher values (p &lt; 0.05). In contrast, patients with better motor performance tended to have lower values (p = 0.059). The concentration of urinary type I collagen cross-linked N-telopeptides was positively correlated with urinary calcium excretion (p &lt; 0.05), which was found to be elevated in 20 of the patients. Our results show that during childhood and adolescence in OI not only the synthesis but also the turnover of mature cross-linked type I collagen is disturbed and provide evidence that bone resorption rates are elevated.
Geometric structure of the femoral neck measured using dual-energy X-ray absorptiometry
Authors: Yoshikawa T. , Turner C.H. , Peacock M. , Slemenda C.W. , Weaver C.M. , Teegarden D. , Markwardt P. , Burr D.B. 
Published: February 2010

Abstract
An algorithm was developed to estimate the strength of the femoral neck from data generated by the dual-energy x-ray absorptiometry (DXA). This algorithm considers shape of the proximal femur as well as cross-sectional moment of inertia (CSMI) in the estimate. Proximal femora (10) from cadavers of white adults and an aluminum step wedge were scanned with the Lunar DPX to validate the calculation of CSMI. After scanning, each femoral neck was sectioned at its narrowest portion for direct measurement of CSMI. Three healthy young women were scanned five times each to evaluate the reproducibility of geometric measurements using DXA. There was a strong linear association between the CSMI measured directly and using DXA in both cadaver bones (r2 = 0.96) and the aluminum step wedge (r2 = 0.99). The coefficient of variation for CSMI from repeated measurements using DXA was less than 3%. This indicates that it is possible to estimate reproducibly the bending rigidity of bone from DXA measurements. The data from 306 normal subjects were analyzed to investigate geometric changes in the femoral neck with age. Although there was no strong correlation between CSMI and age in normal subjects of either sex, safety factor (SF, an index of strength of the femoral neck during walking) and fall index (FI, an index of the strength of the femoral neck during a fall) decrease with age in both sexes. We observed an alteration of the geometric structure of the femoral neck with age that may increase the stress on the femoral neck and decrease SF and FI.
Cellular and matrix changes before and at the time of calcification in the growth plate studied in vitro: Arrest of type X collagen synthesis and net loss of collagen when calcification is initiated
Authors: DR. Alini Mauro , Carey Dennis , Hirata Soichiro , Grynpas Marc D. , Pidoux Isabelle , Poole A. Robin 
Published: February 2010

Abstract
To understand the growth, maturation, and regulation of growth plate chondrocytes, it is necessary to isolate the different chondrocytes into distinct subpopulations of maturational development. Five subpopulations (A—E) of bovine fetal growth plate chondrocytes were separated by discontinuous gradient centrifugation. Four subpopulations (B, C, D, and E, from low to high density) with good viability were cultured at high density in microwells for up to 30 days. They all established an extensive extracellular matrix composed of proteoglycan and collagen. The largest and least dense cells in subpopulation B were the first to synthesize (at days 5–6) type X collagen and to calcify this matrix. Matrix calcification (formation of hydroxyapatite in the presence of sodium β-glycerophosphate) always followed the initiation of type X synthesis. All the other subpopulations synthesized type X collagen and calcified their extracellular matrix. Although these events occurred in the same order, they were delayed according to the order of increasing cell size. These observations indicate that these subpopulations represent different stages in cellular maturation that lead to expression of the hypertrophic phenotype. Once mineral formation was well established, there was an increase in the matrix content of the C-propeptide of type II collagen (which is known to bind to hydroxyapatite and accumulate in calcifying extracellular matrix). This was accompanied by a reduction in the total collagen content, which accompanied an abrupt reduction in type X collagen synthesis, whereas type II collagen synthesis was largely maintained. These reductions in collagen content and type II collagen synthesis were not observed in the absence of calcification (β-glycerophosphate omitted from culture). This new culture system recreates many of the sequential cellular and extracellular changes exhibited in situ during the development of the physis and provides new information about cellular and extracellular matrix changes that occur before and at the time of calcification.
High-dose glucocorticoids in multiple sclerosis patients exert direct effects on the kidney and skeleton
Authors: Dr. Cosman F. , Nieves J. , Herbert J. , Shen V. , Lindsay R. 
Published: February 2010

Abstract
The effects of acute pharmacologic steroid treatment on skeletal and mineral metabolism were assessed in 56 multiple sclerosis patients who were to receive 1 g intravenous methylprednisolone for 10 days, followed by a 4 day intravenous and 28 day oral glucocorticoid taper. Serum and urine samples were obtained at baseline and then within 3 days, 1, 2, and 3 weeks after beginning steroids. A subset of patients (n = 11) had sampling throughout the 6 weeks of steroid administration and up to 8 weeks afterward. All mean basal biochemistries were normal except 25(OH)D, which was in the “insufficient” range (25-50 nM) at 40 nM. During and after steroid administration, there were no changes in ionized calcium, 25(OH)D, urinary hydroxyproline, or pyridinoline. There was an increase in 1,25(OH)2D and a decrease in serum phosphorus, accompanied by an increase in urinary phosphate clearance, within 3 days of administration (p &lt; 0.006). Serum osteocalcin (BGP) decreased to below assay sensitivity limits within 3 days of steroid administration (p &lt; 0.0002), increasing thereafter but remaining at 50% of baseline by the third week. PTH(1-84) increased to a peak at week 2 (p &lt; 0.02), after both the 1,25(OH)2D peak and the serum phosphorus nadir. Tartrate-resistant acid phosphatase, urinary calcium, and urinary cyclic AMP all increased above baseline (p &lt; 0.05) with a pattern similar to that of PTH. To investigate further the immediate effects of steroid administration, serum samples were obtained at the same four times on both the day before and the day after the first intravenous methylprednisolone dose in a randomly chosen subset of patients (n = 9). Serum phosphorus fell (p &lt; 0.05) by 1 h after administration, associated with an immediate drop in the tubular maximum phosphate reabsorption concentration adjusted for glomerular filtration rate (TmP/GFR). Serum 1,25(OH)2D increased (p &lt; 0.04) and BGP decreased (p &lt; 0.0001) within 8 h after steroid administration. The decrease in serum phosphorus, increase in 1,25(OH)2D, and depression in BGP were all independent of PTH, which did not change during this time period. The profound drop in BGP was particularly significant given the rise in 1,25(OH)2D (a known stimulator of BGP synthesis). In conclusion, these studies support the theory that high-dose glucocorticoid administration causes primary depression of bone formation as well as primary effects on the kidney, including lowering the TmP/GFR and increasing 1,25(OH)2D, all before increasing PTH levels.
Hormonal regulation of Na+-Ca2+ exchange in osteoblast-like cells
Authors: Short Cynthia L. , Monk Rebeca D. , Bushinsky David A. , Krieger Nancy S. 
Published: February 2010

AbstractWe proposed a role for Na-Ca exchange in hormonally mediated bone resorption and recently characterized Na-dependent Ca transport in an osteoblast-like rat osteosarcoma cell line (UMR-106). To test whether calcemic agents alter Na+-Ca2+ exchange in osteoblasts, UMR cells were treated acutely or cultured in the absence or presence of calcemic agent for 24h. Cells were then loaded with the Ca-sensitive dye fura-2 in the presence of 140 mM NaCl, no Ca, and the absence or presence of 0.3 mM ouabain. Cells were resuspended at 22°C, and the fluorescence ratio at excitation wavelength of 340 and 380 nm was measured. An outward Na gradient was generated by removing extracellular Na and maintaining isotonicity with choline chloride. Na+-Ca2+ exchange was demonstrated by enhanced Ca uptake in ouabain-treated (Na-loaded) cells after the addition of 1.5 mM Ca. Acute addition of 10−7 M PTH or 10−6 M PGE2 had no effect on Na-dependent Ca uptake. However, 24 h treatment of cells with PTH, PGE2, or 1,25(OH)2D3 caused a dose-dependent inhibition of Na+-Ca2+ exchange. Using the Na-sensitive dye, SBFI, we also demonstrated that the effect was bidirectional; PTH inhibited Ca-dependent Na uptake comparably to its inhibition of Na-dependent Ca uptake. The effects of the calcemic agents were mimicked by 24 h treatment of the cells with 1 μM forskolin or 2 μM PMA. These results suggest that regulation of Na+-Ca2+ exchange by calcemic agents occurs downstream of signal transduction messengers and that alterations in Na+-Ca2+ exchange may play an integral role in their long-term regulation of osteoblast activity.
Parathyroid hormone fragments may stimulate bone growth in ovariectomized rats by activating adenylyl cyclase
Authors: Rixon Ray H. , Whitfield James F. , Gagnon Lyne , Isaacs Richard J. , Maclean Susanne , Chakravarthy Balu , Durkin Jon P. , Neugebauer Witold , Ross Virginia , Sung Wing , Willick Gordon E. 
Published: February 2010

Abstract
PTH is regarded conventionally as a catabolic hormone that stimulates osteoclastic resorption of bone. However, it has been known since 1932 that intermittent pulses of PTH stimulate bone formation in animals and humans. PTH independently activates two signal mechanisms: one that stimulates adenylyl cyclase and one that stimulates protein kinase C (PKC). The goal of this study was to use the 3- to 5-month-old ovariectomized (OVX) rat model to determine which of the two signal mechanisms is responsible for the anabolic action of PTH on bone. OVX triggered a large loss of trabecular bone without significantly affecting the normal slow growth of cortical bone in the distal halves of the femora. Daily injections of human hPTH(1–34) fragment (1 nmol/100 g body weight), which stimulated both adenylyl cyclase and membrane-associated PKC activity in osteoblast-like ROS 17/2 rat osteosarcoma cells, stimulated the growth of both cortical and trabecular bone in the OVX rats. Daily injections of the same dose of hPTH(1–31), which stimulated adenylyl cyclase but not PKC in ROS 17/2 cells, stimulated trabecular bone growth in the OVX rats less effectively than hPTH(1–34), but it stimulated cortical bone growth as rapidly and as dramatically as hPTH(1–34). Injections of equimolar amounts of desamino-hPTH(1–34) [N-propionyl(2–3)hPTH-amide], which stimulated PKC as strongly as hPTH(1–34) in ROS 17/2 cells but had a drastically reduced ability to stimulate adenylyl cyclase, or injections of recombinant hPTH(8–84) which stimulated PKC only in the ROS 17/2 cells, did not stimulate cortical or trabecular bone growth in the OVX animals. Thus, cyclic AMP and cyclic AMP-dependent protein kinases may be the primary mediators of the anabolic action of intermittent pulses of PTH on bone in OVX rats.
Bone morphogenetic protein 2 stimulates osteogenesis but does not affect chondrogenesis in osteochondrogenic differentiation of periosteum-derived cells
Authors: Iwasaki Motoki , Nakahara Haruhiko , Nakase Takanobu , Kimura Tomoatsu , Takaoka Kunio , Caplan Arnold I. , Ono Keiro 
Published: February 2010

Abstract
The effects of recombinant human bone morphogenetic protein 2 (rhBMP-2) on osteochondrogenesis were examined in high-density cultures of periosteum-derived cells, which have the potential to differentiate into bone and hypertrophic cartilage in vitro. Proliferation of these cells was inhibited by treatment with rhBMP-2. The time course for alkaline phosphatase (ALP) expression was shortened and the mineralization of the culture was increased by supplementation with rhBMP-2. These stimulatory effects of rhBMP-2 were observed at doses of 10–100 ng/m. Bone Gla protein (BGP) was immunocytochemically detectable earlier in the culture treated with rhBMP-2, and the BGP-positive layer of the rhBMP-2-treated cultures was thicker than that of the control cultures. On the other hand, there was no difference in uronic acid content or the time course of α1 (II) collagen mRNA expression between the rhBMP-2-treated and the control cultures. These results indicate that rhBMP-2 shortens the time course of osteogenesis and increases the amount of bone formation, whereas chondrogenesis remains unaffected.
Hypertrophic chondrocytes undergo further differentiation to osteoblast-like cells and participate in the initial bone formation in developing chick embryo
Authors: Galotto Maria , Campanile Giuliano , Robino Grazia , Cancedda Fiorella Descalzi , Bianco Paolo , DR. Cancedda Ranieri 
Published: February 2010

Abstract
Differentiation of hypertrophic chondrocytes to an osteoblast-like phenotype occurs in vivo in the hypertrophic cartilage of chick embryo tibiae underneath early or prospective periosteum and in cartilage around vascular canals. Synthesis of type I collagen by hypertrophic chondrocytes was shown by immunolocalization of the C propeptide. By enzyme cytochemistry it was instead shown that, in vivo, further differentiating hypertrophic chondrocytes express alkaline phosphatase at the time of initial mineral deposition. Evidence that hypertrophic chondrocytes may resume proliferation was obtained by BrdU labeling. A monoclonal antibody (LA5) was isolated and characterized that recognizes a hypertrophic chondrocyte membrane protein. In addition to staining hypertrophic chondrocytes surrounded by a type II and type X collagen-stainable matrix, the LA5 antibodies also stained elongated chondrocytes at the cartilage/bone collar interface and cells incorporated in the first layer of bone and osteoid matrix.
Benefit of systemically administered rhIGF-I and rhIGF-I/IGFBP-3 on cancellous bone in ovariectomized rats
Authors: Bagi Cedo M. , Brommage Robert , Deleon Lita , Adams Steven , Rosen David , Sommer Andreas 
Published: February 2010

Abstract
The dose-related effects of systemically administered rhIGF-I and rhIGF-I/IGFBP-3 were monitored in the osteopenic rat skeleton at three different sites with cancellous bone: distal femoral metaphysis, epiphysis, and lumbar vertebral bodies. At the age of 16 weeks, rats were bilaterally ovariectomized (OVX) or sham operated (sham) and 8 weeks later divided into the control groups (sham OVX), and OVX groups treated with different doses of rhIGF-I or rhIGF-I/IGFBP-3 for 8 weeks. Fluorescent bone markers were given 9 and 2 days before necropsy. In addition, changes in designated bone sites as a result of ovariectomy alone were evaluated 8 and 16 weeks after surgery. High bone resorption, which dominates the postovariectomy remodeling process, resulted in a loss of cancellous bone at all measured sites. The highest trabecular bone loss was measured in the metaphyses (40%), compared with 22% in the lumbar vertebrae and 16% in the epiphyses. After 8 weeks of treatment with 7.5 mg/kg of rhIGF-I/IGFBP-3, bone formation rates were increased at all sites measured. Increased trabecular thickness was observed at the epiphyses and in the lumbar vertebral bodies. Increased bone resorption was restricted to the metaphyses of the rats that received the highest dose of rhIGF-I or rhIGF-I/IGFBP-3. Both formulations of rhIGF-I increased longitudinal bone growth similarly. This experiment demonstrates site-specific differences in cancellous bone reactions following ovariectomy. Epyphyses showed some advantages for cancellous bone histomorphometry over metaphyses and lumbar vertebral bodies. The data presented confirm the potential of rhIGF-I/IGFBP-3 complex to promote the bone formation process at various bone sites in osteoporotic rat skeleton.