bluuebunny/crossref_metadata_2025 huggingface dataset:
Risk factors for hip fracture in european women: The MEDOS study
Authors: Johnell Olof , Gullberg Bo , Kanis John A. , Allander Erik , Elffors Lars , Dequeker Jan , Dilsen Guzin , Gennari Carlo , Vaz Lopes Antonio , Lyritis George , Mazzuoli Gianfranco , Miravet Livia , Passeri Mario , Cano Perez Ramon , Rapado Aurelio , Ribot Claude
Published: February 2010

The aims of this study were to determine common international risk factors for hip fracture in women aged 50 years or more. We studied women aged 50 years or more who sustained a hip fracture in 14 centers from Portugal, Spain, France, Italy, Greece, and Turkey over a 1-year period. Women aged 50 years or more selected from the neighborhood or population registers served as controls. Cases and controls were interviewed using a structured questionnaire on work, physical activity, exposure to sunlight, reproductive history and gynecologic status, height, weight, mental score, and consumption of tobacco, alcohol, calcium, coffee, and tea. Significant risk factors identified by univariate analysis included low body mass index (BMI), short fertile period, low physical activity, lack of sunlight exposure, low milk consumption, no consumption of tea, and a poor mental score. No significant adverse effects of coffee or smoking were observed. Moderate intake of spirits was a protective factor in young adulthood, but otherwise no significant effect of alcohol intake was observed. For some risks, a threshold effect was observed. A low BMI and milk consumption were significant risks only in the lowest 50% and 10% of the population, respectively. A late menarche, poor mental score, low BMI and physical activity, low exposure to sunlight, and a low consumption of calcium and tea remained independent risk factors after multivariate analysis, accounting for 70% of hip fractures. Excluding mental score and age at menarche (not potentially reversible), the attributable risk was 56%. Thus, about half of the hip fractures could be explained on the basis of the potentially reversible risk factors sought. In contrast, the use of risk factors to “predict” hip fractures had moderate sensitivity and specificity. We conclude that variations in lifestyle factors are associated with significant differences in the risk of hip fracture, account for a large component of the total risk, and may be of some value in selecting individuals at high risk.
Transmenopausal change of trabecular bone density and structural pattern assessed by peripheral quantitative computed tomography in Japanese women
Authors: Takagi Yasuyuki , Fujii Yoshio , Miyauchi Akimitsu , Goto Bunrei , Takahashi Keiichi , Fujita Takuo
Published: February 2010

Trabecular bone pattern, related to connectivity, was analyzed along with a separate measurement of cortical and trabecular bone mineral density (BMD) at the distal radius by peripheral quantitative computed tomography (pQCT) in 48 perimenopausal women, consisting of 25 premenopausal women aged 41 to 52 (mean 46.6 ± 2.9 years) and 23 early postmenopausal women aged 46 to 59 (mean 53.2 ± 3.2 years) within 5 years of the menopause (mean 2.7 ± 1.5 years). No significant difference was found in either cortical or trabecular bone density between premenopausal and postmenopausal women despite a significant difference in age (premenopause vs postmenopause: 46.7 ± 2.9 years vs 53.2 ± 3.1 years, p < 0.00001), indicating a slow change of BMD, if any, before and within 5 years of the menopause. However, analysis of trabecular fragments and perforation revealed a significant increase of the number of perforations in postmenopausal compared with premenopausal women (premenopausal vs postmenopausal: 0.9 ± 1.6 vs 2.9 ± 2.3, p < 0.002), indicating that disconnectivity has already increased before a significant reduction of BMD. Furthermore, chi-square analysis showed that even postmenopausal women with trabecular BMD more than 160 mg/cm3 were about 11 times more likely to have three or more perforations than premenopausal ones (odds ratio: 11.42, F = 0.030). These data suggest that trabecular bone connectivity is more sensitive than BMD in the detection of the early changes of postmenopausal osteoporosis.
Bone fragility in transgenic mice expressing a mutated gene for type I procollagen (COL1A1) parallels the age-dependent phenotype of human osteogenesis imperfecta
Authors: Pereira Ruth F. , Hume Eric L. , Halford Kenneth W. , Prockop Darwin J.
Published: February 2010

An inbred strain of transgenic mice that expressed a mutated gene for type I procollagen and that developed spontaneous fractures was used to study the effects of age on the phenotype of fragile bones. The mutated gene has been shown to cause depletion of type I collagen in the transgenic mice because it generated shortened proα1(I) chains that bound to and produced degradation of normal proα1(I) chains synthesized from the endogenous mouse COL1A1 gene. For this study, femurs from transgenic mice ranging in age from 0.5–24 months were examined. The results demonstrated that the level of expression of the transgene was independent of age. Femurs from the transgenic mice were more fragile than controls at 0.5 and 1.5 months, they were biomechanically normal at 6 months, and then they were more fragile at 24 months. The normal biomechanical properties of the bones from the transgenic mice at 6 months were accompanied by periosteal thickening of the bones together with an increase in the collagen content that was not associated with a proportional increase in mineral content. The results indicated that the effects of age, mechanical stress, and hormonal action produced a biological compensation for the mutated gene by either increasing collagen synthesis of bone, decreasing collagen degradation, or both. The biological compensation was apparently lost by 24 months when the outer diameters of the femurs were again less than in controls, the cortical thickness was about the same as in controls, and both the collagen and mineral contents were less than controls. The results demonstrated that bone fragility in the transgenic mice paralleled the age-dependent phenotype of human osteogenesis imperfecta. Therefore the transgenic mice appeared to be useful models for osteogenesis imperfecta. They also may be useful models for some forms of osteoporosis.
PTH/PTHrP receptor expression on osteoblasts and osteocytes but not resorbing bone surfaces in growing rats
Authors: Dr. Fermor Beverley , Skerry Timothy M.
Published: February 2010

Using in situ hybridization, we correlated the expression of mRNA for the parathyroid hormone/parathyroid hormone related peptide (PTH/PTHrP) receptor with bone formation and resorption in undecalcified serial sections of bones from growing rats. In addition we investigated the presence of biologically active receptors in the same locations using an in vivo autoradiographic technique. In the ulnae of growing rats, there are well defined zones of cortical bone formation and resorption. These contribute to the modeling drifts by which the bone achieves its adult shape. Forming surfaces incorporate fluorochrome labels, are lined with osteoid, and have a layer of cuboidal osteoblasts that have a high alkaline phosphatase activity. Resorbing surfaces have no fluorochrome incorporation, no osteoid, and are lined with resorbing cells with high tartrate-resistant acid phosphatase (TRAP) activity. PTH/PTHrP receptor mRNA was expressed predominantly on forming but not on resorbing bone surfaces and colocalized with sites of binding of radiolabeled PTH after intravenous injection. PTH/PTHrP mRNA expression on osteocytes was inconclusive but radiolabeled PTH bound to a proportion of osteocytes in all regions of the cortex although binding was not specifically related to areas of bone formation or resorption. These results suggest that in growing animals the actions of PTH or PTHrP are connected more with bone formation than resorption. Such a role may be linked to the ability of PTH to induce bone formation in adults but does not explain the actions of the hormone in regulating resorption. Binding of PTH to osteocytes increases the evidence for a physiological role for these cells.
Cranial sutures require tissue interactions with dura mater to resist osseous obliteration in vitro
Authors: Opperman Lynne A. , Passarelli Ralph W. , Morgan Ellen P. , Reintjes Mark , Dr. Ogle Roy C.
Published: February 2010

A chemically defined serum-free medium, which supports the development of bones and fibrous tissues of rat calvaria from nonmineralized mesenchymal precursor tissues, was employed to investigate tissue interactions between the dura mater and overlying tissues. Fetal calvarial rudiments from stages prior to bone and suture morphogenesis (fetal days 19 and 20) and neonatal calvarial rudiments with formed sutures (day 1) were cultured with and without associated dura mater. Removal of calvaria for in vitro culture allowed the examination of suture morphogenesis in the absence of tensional forces exerted on the sutures via fiber tracts in the dura mater originating in the cranial base. Ossification of frontal and parietal bones proceeded in a fashion comparable to development in vivo, but the cranial (coronal) sutures—primary sites for subsequent skull growth—were obliterated by osseous tissue union in the absence of dura mater. Bony fusion did not occur when rudiments were cocultured with dura mater on the opposite sides of 0.45 μm polycarbonate transwell filters, suggesting that the influence of dura mater on sutural obliteration was mediated by soluble factors rather than cell—cell or cell—matrix interactions. These results indicate that cell signaling mechanisms rather than biomechanical tensional forces are required for morphogenesis of the calvaria.
Effects of aluminum on bone surface ion composition
Authors: Bushinsky David A. , Sprague Stuart M. , Hallegot Philippe , Girod Chantal , Chabala Jan M. , Levi-Setti Riccardo
Published: February 2010

Aluminum induces net calcium efflux from cultured bone. To determine whether aluminum alters the bone surface ion composition in a manner consistent with predominantly cell-mediated resorption, a combination of cell-mediated resorption and physicochemical dissolution or physicochemical dissolution alone, we utilized an analytic high-resolution scanning ion microprobe with secondary ion mass spectroscopy to determine the effects of aluminum on bone surface ion composition. We cultured neonatal mouse calvariae with or without aluminum (10−7 M) for 24 h and determined the relative ion concentrations of 23Na, 27AI, 39K, and 40Ca on the bone surface and eroded subsurface. Control calvariae have a surface (depth ∼6 nm) that is rich in Na and K compared with Ca (Na/Ca = 24.4 + 1.4, mean + 95% confidence limit of counts per second of detected secondary ions, K/Ca = 13.2 + 0.9). Aluminum is incorporated into the bone and causes a depletion of surface Na and K relative to Ca (Na/Ca = 9.6 + 0.7, K/Ca = 4.9 + 0.4; each p < 0.001 versus control). After erosion (depth ∼50 nm), control calvariae have more Na and K than Ca (Na/Ca = 16.0 + 0.1, K/Ca = 7.5 + 0.1); aluminum again depleted Na and K relative to Ca (Na/Ca = 4.1 + 0.1, K/Ca = 1.9 + 0.1; each p < 0.001 versus control). Aluminum produced a greater net efflux of Ca (362 ± 53, mean ± SE, nmol/bone/24 h) than control (60 ± 30, p < 0.001). With aluminum, the fall in the ratios of both Na/Ca and K/Ca coupled with net Ca release from bone indicates that aluminum induces a greater efflux of Na and K than Ca from the bone surface and is consistent with an aluminum-induced removal of the bone surface. This alteration in surface ion concentration and calcium efflux is consistent with that observed when calcium is lost from bone through a combination of cell-mediated resorption and physicochemical dissolution.
Normal parathyroid hormone responsiveness of bone-derived cells from a patient with pseudohypoparathyroidism
Authors: Ish-Shalom Sophia , Rao Letitia G. , Levine Michael A. , Fraser Donald , Kooh Sang W. , Josse Robert G. , Mcbroom Robert , Wong Min-Min , Murray Timothy M.
Published: February 2010

Pseudohypoparathyroidism (PHP) is characterized by a lack of response to parathyroid hormone (PTH); however, normal skeletal responsiveness to PTH in some patients with PHP type la was previously suggested on the basis of clinical observations. To test this hypothesis, we measured cyclic adenosine monophosphate (cAMP) production in response to various agonists in bone-derived osteoblast-like (OBL) cells from trabecular explants obtained from an iliac crest biopsy of a 25-year-old woman with PHP. The patient was proved to have PHP type la on the basis of Albright's hereditary osteodystrophy and decreased activity of stimulatory guanine nucleotide-binding protein (Gs) in erythrocytes. Responsiveness of the patient's OBL cells was compared with OBL cells from eight subjects aged 18–39 years who had no evidence of metabolic bone disease. OBL cells from the patient responded to the following agonists (expressed in multiples of elevation of cAMP, stimulated/basal, mean ± SE, n = 3): PTH, 3.8 ± 0.3; forskolin, 8.2 ± 0.2; and cholera toxin, 56.8 ± 10.0. These responses were not significantly different from those of control OBL cells: PTH, 4.5 ± 1.1 (range 2.4–7.5); forskolin, 7.7 ± 1.4; and cholera toxin, 57.9 ± 16.2. The normal cholera toxin response indicated the presence of functional Gs. Bone cells from patients with PHP type la may exhibit a normal PTH receptor-coupled adenylyl cyclase system in vitro despite clinical evidence of impaired hormone-responsive adenylyl cyclase in other tissues, including the kidney. Skeletal responsiveness to PTH may explain the long periods of spontaneous normocalcemia observed in this patient.
Osteoblast hydraulic conductivity is regulated by calcitonin and parathyroid hormone
Authors: Hillsley Mechteld V. , Frangos John A.
Published: February 2010

It is our hypothesis that osteoblasts play a major role in regulating bone (re)modeling by regulating interstitial fluid (ISF) flow through individual bone compartments. We hypothesize that osteoblasts of the blood-bone membrane lining the bone surfaces are capable of regulating transosseous fluid flow. This regulatory function of the osteoblasts was tested in vitro by culturing a layer of rat calvarial osteoblasts on porous membranes. Such a layer of osteoblasts subjected to 7.3 mm Hg of hydrostatic pressure posed a significant resistance to fluid flow across the cell layer similar in magnitude to the resistance posed by endothelial monolayers in vitro. The hydraulic conductivity, the volumetric fluid flux per unit pressure drop, of the osteoblast layer was altered in response to certain hormones. Hydraulic conductivity decreased approximately 40% in response to 33 nM parathyroid hormone, while it exhibited biphasic behavior in response to calcitonin: increased 40% in response to 100 nM calcitonin and decreased 40% in response to 1000 nM calcitonin. Further, activation of adenylate cyclase by forskolin dramatically increased the hydraulic conductivity, while elevation of intracellular calcium, [Ca2+]i, by the calcium ionophore A23187 initially decreased the hydraulic conductivity at 5 minutes before increasing conductivity by 30 minutes. These results suggest that cyclic adenosine monophosphate (cAMP) and [Ca2+]i may mediate changes in the osteoblast hydraulic conductivity. The increase in hydraulic conductivity in response to 100 nM calcitonin and the decrease in response to PTH suggest that the stimulatory and inhibitory effects on bone formation of calcitonin and parathyroid hormone, respectively, may be due in part to alterations in bone fluid flow.
Maintaining bone mass by bisphosphonate incadronate disodium (YM175) sequential treatment after discontinuation of intermittent human parathyroid hormone (1-34) administration in ovariectomized rats
Authors: Takano Yuichi , Tanizawa Tatsuhiko , Mashiba Tasuku , Endo Naoto , Nishida Saburo , Takahashi Hideaki E.
Published: February 2010

Intermittent treatment with human parathyroid hormone (1-34) [hPTH(1-34)] stimulates bone formation and increases cancellous bone mass in ovariectomized (OVX) rats. But PTH-induced cancellous bone rapidly disappears upon cessation of treatment. The fate of cortical bone treated by PTH has not been well characterized. Incadronate disodium (disodium cycloheptylaminomethylenedisphosphonate monohydrate, YM175) was expected to be antiresorptive without inhibiting bone formation. The purposes of this study were to determine (1) whether PTH treatment increases new cancellous and cortical bone mass and bone formation, (2) whether the new bone could be maintained by YM175 sequential treatment, and (3) whether the maintenance effect is persistent after YM175 withdrawal. Eighty-eight 11-week-old Sprague-Dawley rats were divided into sham operation and OVX groups. The OVX rats were treated for 8 weeks with the subcutaneous intermittent injection of 30 μ/kg of hPTH(1–34) three times a week beginning 4 weeks after surgery, then PTH treatment was withdrawn and YM175 (10 μ/kg) was injected subcutaneously three times a week for 4 weeks. YM175 treatment was withdrawn for the last 8 weeks of the protocol. The results of microstructural assessment in proximal tibial metaphysis and bone mineral density in distal and proximal femur demonstrated that PTH treatment for 8 weeks restored bone mass to the sham control level. However, after cessation of PTH treatment, the PTH-induced tibial cancellous bone mass showed a decrease at 4 weeks and almost totally disappeared after 12 weeks. Conversely, YM175 treatment maintained the PTH-induced tibial cancellous bone mass, and the bone continued to be maintained after 8 weeks of withdrawal of the YM175. Cortical bone was not lost during PTH treatment. YM175 maintained the PTH-induced new tibial cancellous bone in OVX rats by suppressing remodeling.
Induction of apoptosis in murine clonal osteoblasts expressed by human T-cell leukemia virus type I tax by NF-κPB and TNF-α
Authors: Kitajima Isao , Nakajima Toshihiro , Imamura Takeshi , Takasaki Ikuko , Kawahara Koichi , Okano Toshihiro , Tokioka Takeshi , Soejima Yasuko , Abeyama Kazuhiro , Maruyama Ikuro
Published: February 2010

We investigated the effects of various cytokines in the presence of human T-cell leukemia virus type I (HTLV-I) tax protein in murine clonal osteoblasts, MC3T3-E1 cells. Skeletal remodeling by osteoclasts and osteoblasts is coordinated by cytokines, which are activated by HTLV-I tax protein via nuclear factor-κB (NF-κB). MC3T3-E1 cells were cocultured with an irradiated HTLV-I-producing lymphocyte cell line, MT-2. After coculture, the tumor necrosis factor-α (TNF-α) level in the medium was markedly elevated during the 7 days of culture, and MC3T3-E1 cells underwent apoptotic cell death. Marked apoptosis was also observed in MC3T3-E1 cells treated with MT-2 culture medium and in HTLV-I tax-expressing MC3T3-E1 clones, which both expressed high levels of TNF-α. This apoptosis was prevented by treatment with neutralizing anti-TNF-α antibody (αTNF). HTLV-I tax protein and TNF-α induced activation of NF-κB in apoptotic MC3T3-E1 cells. Decreased NF-κB activation was observed in HTLV-I tax-expressing MC3T3-E1 cells treated with αTNF. Our results suggest that HTLV-I tax activated NF-κB and subsequently TNF-α, leading to apoptosis of osteoblasts.
Exercise effects on bone mass in postmenopausal women are site-specific and load-dependent
Authors: Kerr Deborah , Morton Alan , Dick Ian , Prince Richard
Published: February 2010

It is considered that skeletal mass in humans may respond to loading or the number of loading cycles. The aim of this study was to examine the effect of a 1 year progressive resistance training program on the bone mass of 56 postmenopausal women. Assignment was by block randomization to one of two resistance training groups: a strength trained group (3 × 8 repetition maximum) or an endurance group (3 × 20 repetition maximum). The resistance exercises were selected to stress the ipsilateral forearm and hip region. The exercising side was randomly assigned with one side exercised while the alternate side acted as the nonexercise control. Bone mineral density (BMD) was measured every 3 months at the radial forearm and four hip sites using the Hologic QDR 2000 bone densitometer. A linear regression function was fitted for each individual's bone density results, and the slope was compared for the exercise and control side using paired t-tests. The bone mass increase with the strength regimen was significantly greater at the trochanteric hip site (control -0.6 + 2.2%, exercise 1.7 + 4.1%,p < 0.01), at the intertrochanteric hip site (control -0.1 + 2.1%, exercise 1.5 + 3.0%,p < 0.05), Ward's triangle (control 0.8 + 5.2%, exercise 23 + 4.0%,p < 0.05), and at the ultradistal radial site (control -1.4 + 2.3%, exercise 2.4 + 4.3%. p < 0.01). There was no significant increase in BMD with the endurance regimen except at the radius midsite (control -1.0 + 23%, exercise 0.1 + 1.4%, p < 0.01). In both the endurance and the strength group, muscle strength, tested by a one-repetition maximum (IRM) test, increased significantly for all 10 exercises (p < 0.01) and to a similar degree in the two groups. In the strength group but not the endurance group there were significant correlations between the slope of the change in BMD and the percentage increase in strength as follows: trochanter with leg press; intertrochanter with leg press (p < 0.05); and Ward's triangle with hip extension and hip adduction (p < 0.05). Thus these results support the notion of a site-specific response of bone to maximal loading from resistance exercise in that although the trochanter and intertrochanteric bone density was elevated by the resistance exercises undertaken, there was no effect on the femoral neck value. Postmenopausal bone mass can be significantly increased by a strength regimen that uses high-load low repetitions but not by an endurance regimen that uses low-load high repetitions. We conclude that the peak load is more important than the number of loading cycles in increasing bone mass in early postmenopausal women.
Bone mineral mass consolidation in young British adults
Authors: Parsons Tessa J. , Prentice Ann , Smith Elisabeth A. , Cole Tim J. , Compston Juliet E.
Published: February 2010

Forty males and 40 females, ages 18–21 years, were recruited into a prospective study to investigate the consolidation of bone mineral after cessation of linear growth and the influences of calcium intake, lifestyle factors, physical activity, and body composition on bone. Three sets of bone measurements were made annually at the spine, hip, and whole body (dual-energy X-ray absorptiometry) and at the wrist and midshaft radius (single photon absorptiometry). At baseline, the bone mineral content (BMC) was significantly greater in males than females at all sites (p < 0.004). After adjustment for scan area (BA), height, weight, and age, male BMC was significantly greater than female BMC at the midshaft radius (+7.4%; p < 0.01) but lower at the spine (-10.9%; p < 0.001) with no difference at the wrist, hip, or whole body. Positive effects of leanness on bone were observed in females but not in males. Dietary calcium, nutrient intakes, and physical activity levels were not size-independent determinants of BMC at any site. Significant increases in whole-body BMC were observed within individuals over the study period of 670 (SD 51) days, +13% in males and +2.1% in females (p < 0.01), mirrored by increases in BMC and BA at most skeletal sites. After allowing for changes in BA, significant increases (p < 0.01) were observed in adjusted BMC for the whole body (males, +1.1%; females, +0.6%), lumbar spine (males, +1.5%; females, +1.1%), and midshaft radius (males, +1.9%; females, +2.0%). No lifestyle or anthropometric factors were identified that influenced these longitudinal increases in bone mineral.
Trabecular bone morphology from micro-magnetic resonance imaging
Authors: Hipp John A. , Jansujwicz Alan , Simmons Craig A. , Snyder Brian D.
Published: February 2010

Micro-magnetic resonance imaging (micro-MRI) is potentially a widely available tool to image and quantify the three-dimensional structure of trabecular bone. However, it has not been demonstrated that the same quantitative measurements can be obtained using micro-MRI as would be obtained from conventional light microscope images. Bovine trabecular bone from several anatomic sites was imaged with both optical and micro-MRI methods. The six faces of approximately cubic trabecular bone specimens were examined with the light microscope, and the volume of bone internal to these faces was then imaged using an 8.6 T 25 mm bore magnet. Three-dimensional measures of bone morphology were calculated from both the optical and micro-MR images using the method of directed secants. Quantitative measures from the two imaging methods were compared by paired f-tests. Volume fractions (BV/TV) measured by micro-MRI were linearly related to (r2 = 0.81) and did not differ statistically from (p = 0.96) similar measurements from optical images. The trabecular plate number (Tb.N) measured by micro-MRI also was linearly related to (r2 = 0.53) and did not differ statistically from (p = 0.17) similar measurements from optical images. The orientation of trabeculae predicted from micro-MRI was within 6° of that calculated from optical images in 10 out of 16 specimens. The micro-MRI morphology measurements are relatively easy to perform, and since several hundred small-bore high-field strength MRI systems are available, this technique could be used widely to quantify the morphology of trabecular bone.
Editorial
Authors: Drezner Marc K.
Published: February 2010

“For this is not [that] which we can hope, that no grievance ever should arise …; but when complaints are freely heard, deeply considered, and speedily reformed then is the utmost bound … attained that wise men look for.” —Areopagitica (1644)
Constitutive in vivo mRNA expression by osteocytes of β-actin, osteocalcin, connexin-43, IGF-I, c-fos and c-jun, but not TNF-α nor tartrate-resistant acid phosphatase
Authors: Mason Deborah J. , Hillam Richard A. , Dr. Skerry Timothy M.
Published: February 2010

Osteocytes have been proposed to be the cells primarily responsible for sensing the effects of mechanical loading in bone. Osteocytes respond to loading in vivo, and have been shown to express osteotropic agents and their receptors, and cell/matrix adhesion molecules in vitro, but the functional significance of such findings is not clear. One obstacle to increased understanding of the role of osteocytes in the regulation of bone mass is that the cells are not easily accessible for study. In situ studies are difficult, and although it is possible to extract and culture osteocytes from neonatal bones, the responses of such cells might be very different from those in older bones in situ. We have developed a technique to investigate osteocyte gene expression in vivo, using the reverse transcriptase linked polymerase chain reaction (PCR), and have shown that they express mRNA for β-actin (β-ACT), osteocalcin (OC), connexin-43 (Cx43), insulin-like growth factor I (IGF-I), c-fos, and c-jun, but not tumor necrosis factor alpha (TNF-α) or tartrate-resistant acid phosphatase (TRAP). The principle behind the method is that after removal of the periosteum, tangential cryostat sections of a tubular bone contain RNA only from osteocytes and a very small number of endothelial cells as long as the marrow cavity is not broached. Using this method, we have investigated gene expression in cells from rat ulnar cortical bone under forming and resorbing bone surfaces. In addition, we have investigated the effect on gene expression of mechanical loading which, if repeated daily, initiates new bone formation on quiescent or resorbing surfaces. Although the expression of the genes we have studied in osteocytes is different from those expressed by the periosteal surfaces overlying the cortex, we have not detected loading-related changes in osteocyte gene expression in any cortical bones. This may be because of the extreme sensitivity of the PCR technique which can only resolve large differences in expression. The use of quantitative methods in the future may allow demonstration of regulated gene expression in osteocytes.
Interleukin-4 inhibits prostaglandin G/H synthase-2 and cytosolic phospholipase A2 induction in neonatal mouse parietal bone cultures
Authors: Kawaguchi Hiroshi , Nemoto Ken , Raisz Lawrence G. , Harrison John R. , Voznesensky Olga S. , Alander Cynthia B. , Pilbeam Carol C.
Published: February 2010

We have shown previously that prostaglandin (PG) production in 7-day-old neonatal mouse calvarial cultures is regulated largely by changes in prostaglandin G/H synthase-2 (PGHS-2) expression and to a lesser extent by changes in arachidonic acid (AA) release. In this study, we examined the effects of interleukin-4 (IL-4), and its interactions with other cytokines and with parathyroid hormone (PTH), on mRNA levels of PGHS-2, PGHS-1, and cytosolic phospholipase A2 (cPLA2) and on medium protaglandin E2 (PGE2) levels in calvarial cultures. IL-1 and tumor necrosis factor-α (TNF-α), both at 1–100 ng/ml, and PTH at 0.1-10 nM increased PGHS-2 and cPLA2 mRNA and medium PGE2 levels dose-dependently after 4 h of treatment. IL-6 and IL-11 at 1–100 ng/ml did not affect mRNA or PGE2 levels. IL-4 at 1–100 ng/ml decreased PGHS-2 and cPLA2 mRNA and PGE2 levels in control as well as IL-1, TNF-α, and PTH-stimulated cultures. The inhibition of PGHS-2 and cPLA2 mRNA expression by IL-4 (10 ng/ml) was present at 1 h, reached a maximum at 4 h, and persisted for 24 h. The effects were maintained in the presence of cycloheximide. IL-4 also decreased PGHS-2 protein levels in control and IL-1-stimulated cultures. PGHS-1 mRNA levels were not stimulated by any of the factors studied nor inhibited by IL-4. IL-4 partially inhibited control and PTH-stimulated 45Ca release from prelabeled mouse calvariae at 4 days. However, neither the inhibition of resorption by IL-4 nor the stimulation by IL-1 and PTH were altered by indomethacin (1 μM). We conclude that (1) IL-1, TNF-α, and PTH, but not IL-6 nor IL-11, can increase the expression of PGHS-2, cPLA2, and PGE2 production in cultured mouse calvariae; (2) IL-4 inhibits PGE2 production in both control and stimulated calvarial cultures by inhibiting PGHS-2 and cPLA2; and (3) IL-4 has an inhibitory effect on bone resorption which is independent of PG production.
1,25-Dihydroxyvitamin D3—mediated transforming growth factor-β release is impaired in cultured osteoblasts from patients with multiple pituitary hormone deficiencies
Authors: Sterck Jozien G. H. , Klein-Nulend Jenneke , Burger Elisabeth H. , Lips Paul
Published: February 2010

To evaluate the osteoblastic function in patients with multiple pituitary hormone deficiencies (M-PHD) and with isolated growth hormone deficiency (I-GHD), bone cells were cultured and the effects of 10−8 M 1,25-dihydroxyvitamin D3 (1,25[OH]2D3) on parameters of cell proliferation, osteoblastic differentiation, and local paracrine regulation were measured. Three days of 1,25(OH)2D3 treatment increased alkaline phosphatase activity and osteocalcin release but inhibited [3H]thymidine incorporation in all cell cultures from patients as well as from controls. In addition, 1,25(OH)2D3 increased the release of both total and active transforming growth factor-β (TGF-β) in bone cells from controls by, respectively, 4.9- and 3.2-fold and in bone cells from I-GHD by 5.1- and 1.5-fold, respectively. However, in bone cells from M-PHD, the stimulation of total TGF-β release was significantly lower (1.3-fold) than in control and I-GHD cells, and active TGF-β release was not stimulated at all. One year of supplementation with human growth hormone did not improve this deficient TGF-β release in bone cells from M-PHD. We conclude that cultured bone cells from I-GHD and M-PHD show a normal response to 1,25(OH)2D3 regarding cell proliferation and osteoblastic differentiation, which implicates a normal l,25(OH)2D3-receptor function. In cells from controls and I-GHD, 1,25(OH)2D3 enhanced both total and active TGF-β release. However, bone cells from M-PHD showed a deficient TGF-β response to 1,25(OH)2D3. These results suggest that the regulation of TGF-β production is a major paracrine factor involved in hypopituitarism.
The effect of impact direction on the structural capacity of the proximal femur during falls
Authors: Ford Catherine M. , Keaveny Tony M. , Hayes Wilson C.
Published: February 2010

As with any structure, the structural capacity of the proximal femur depends on the applied loads and these can vary as a function of impact direction during a fall. However, despite its potential importance in hip fracture risk assessment, the relative importance of impact direction is unknown. To investigate the role of impact direction in hip fracture, we developed a detailed finite element model of the proximal femur. We analyzed four loading configurations that represent a range of possible falls on the greater trochanter. Our results indicate that a change in the angle between the line of action of the applied force and the axis of the femoral neck from 0° (representing a direct lateral impact) to 45° (representing a posterolateral impact) reduced structural capacity by 26%. This weakening of the femur with changes in impact direction is comparable to the weakening associated with 2–3 decades of age-related bone loss. Our result elucidates the independent contribution of fall mechanics to hip fracture risk by identifying an aspect of the fall (the direction of impact) that is an important determinant of fall severity. The results can also be incorporated into a refined clinical method for assessment of hip fracture risk that accounts for the complex interactions between fall severity and bone fragility.
Contributions of vertebral fractures to stature loss among elderly Japanese-American women in Hawaii
Authors: Dr. Huang Chun , Ross Philip D. , Lydick Eva , Davis James W. , Wasnich Richard D.
Published: February 2010

Loss of stature is a typical feature of osteoporosis and associated vertebral fractures. However, there have been few prospective population-based studies to estimate the magnitude of this association. Further, the separate contributions of different types of vertebral fractures to stature loss have not been evaluated using prospective data. In this study we investigated the extent to which stature loss could be explained by the number of different types of vertebral fractures (wedge, endplate, and crush fractures) after adjusting for other covariates. Longitudinal data on stature loss and vertebral fractures were collected among 504 postmenopausal Japanese-American women living in Hawaii with mean age 73.4 (SD 4.9) years. During an average of 7.7 years of follow-up, women with at least one incident vertebral fracture had an average of 2.1 cm of stature loss while the average stature loss among those without incident fractures was only 0.4 cm. The mean rate of stature loss was very slight (< 1 mm/year) for those without incident vertebral fractures even after age 80. Our analyses suggest that both the number of wedge and the number of crush fractures are strong predictors of stature loss. After adjusting for age and total height loss in the anterior dimension over T3-L5, the estimated stature loss resulting from each wedge and crush fracture was 0.86 and 1.08 cm, respectively. Endplate fractures did not show significant contributions to stature loss.
Effects of continuous calcitonin treatment on osteoclast-like cell development and calcitonin receptor expression in mouse bone marrow cultures
Authors: Ikegame Mika , Rakopoulos Maryann , Martin T. John , Moseley Jane M. , Dr. Findlay David M.
Published: February 2010

Continuous treatment with calcitonin (CT) to inhibit osteoclastic bone resorption results in acquired resistance. The mechanisms of this “escape” phenomenon are not yet established. The aim of this study was to examine the effects of continuous treatment with CT on the generation of osteoclasts and calcitonin receptor (CTR) expression in mouse bone marrow cultures. This was done by daily CT treatment of mouse bone marrow cultures from day 0, when only undifferentiated mononuclear precursors of osteoclast-like cells were present, or commencing from day 6, when differentiated osteoclast-like cells were abundant. The response to CT treatment was determined by quantitation of cells positive for tartrate-resistant acid phosphatase (TRAP) and binding of 125I-salmon CT. Calcitonin receptor and TRAP mRNA levels were determined using semi-quantitative reverse transcription/polymerase chain reaction. When cultures were treated with CT from day 0, TRAP-positive multinucleated cells appeared. These cells expressed only very low levels of CTR or CTR mRNA and were morphologically indistinguishable from osteoclast-like cells formed in control cultures. They also displayed the ability to resorb bone. Continuous CT treatment of cultures from day 6 rapidly reduced the CTR mRNA levels, with a t1/2 of 6 to 12 h, and these levels remained low thereafter. 125I-salmon CT binding capacity, as determined by autoradiography, was lost in parallel. These effects were specific for the CTR since there was no consistent effect on TRAP mRNA levels. Based on these data, we suggest that the “escape” phenomenon may result from a prolonged CT-induced loss of CT responsiveness due, at least in part, both to reduced synthesis of CTR, and to the appearance in bone of CTR-deficient osteoclasts.
Ectopic secretion of osteocalcin, the major non-collagenous bone protein, by the myeloma cell line NCI-H929
Authors: Barille Sophie , Pellat-Deceunynck Catherine , Bataille Regis , Amiot Martine
Published: February 2010

In this study we provide the first evidence that human non-osteoblastic cells secrete the bone-specific protein osteocalcin. We show that the myeloma cell line NCI-H929 constitutively produces low amounts of osteocalcin. Furthermore, we demonstrate that this production is strongly enhanced after 1,25(OH)2D3 stimulation. An amplification or a deregulation of the osteocalcin gene could be responsible for the observed phenomenon because NCI-H929 has the unusual characteristic of having at least three chromosomes 1, where the osteocalcin gene was mapped (1q25-q31). It is of interest to note that the patient in whom the NCI-H929 cell line originated never developed osteolytic lesions despite extensive disease apparent at autopsy. Although lytic bone lesions with low osteocalcin serum levels are a common feature of multiple myeloma (MM), a small subset of patients does not develop lytic bone lesions or even demonstrate osteosclerotic MM. This occurrence is associated with high osteocalcin serum levels of unknown origin. In this context, osteocalcin production by immortalized tumor lacking any osteolytic potential could be relevant to the pathophysiology of this particular type of MM.
A digital model of trabecular bone
Authors: Engelke K. , Song S.M. , Glüer C.C. , Genant H.K.
Published: February 2010

A 3D μCT dataset of bovine bone was used to create a digital 3D model simulating trabecular bone. The model serves a dual purpose: It allows for standard quantitative histomorphometric analysis and it approximates the reality e.g. of high resolution CT in vivo datasets of trabecular bone. Thus the model can potentially be used as a reference to develop 2D and 3D structural analysis algorithms applicable in vivo while it simultaneously allows verification of the results of these algorithms by standard histomorphometry. The model can be used as a standard to evaluate the impact of image processing techniques and of restrictions of imaging systems on the quantitative analysis of structural parameters describing a trabecular network. The model can be used for a comparison of 2D and 3D structural analysis methods and for an analysis of decreasing spatial resolution. The effects of segmentation and filtration can be studied separately and grayscale analysis is possible. As examples standard 2D histomorphometry and the analysis of topological parameters like node number and trabecular network length were applied to the model. The influence of spatial resolution was investigated by decreasing the spatial resolution of the digital model. The bone surface area determined by 3D surface triangulation was only 4% smaller than the surface area determined from the traditional 2D bone histomorphometric parameter bone surface/tissue volume (BS/TV) when 2D results were averaged over all slices of the 3D volume. However, BS/TV showed large (10%) variations among slices within the volume. Both histomorphometric and topological parameters were heavily influenced by spatial resolution and image segmentation. Our initial experience with the digital model indicates a need to investigate bone microstructure based on volume data or to average the 2D results of many slices.
Effects of unilateral strength training and detraining on bone mineral mass and estimated mechanical characteristics of the upper limb bones in young women
Authors: Heinonen Ari , Sievänen Harri , Kannus Pekka , Oja Pekka , Vuori Ilkka
Published: February 2010

The aims of this study were to examine the effects of 12 months unilateral high-resistance strength training and 8-month detraining on bone mineral content (BMC), density (BMD) and estimated mechanical characteristics of upper limb bones, and also to estimate consequent loading induced strains on forearm bone shafts. Thirteen female physiotherapy students (mean 23.8 ± 5.0 yrs, 166 ± 7 cm, 64.4 ± 13.3 kg) trained their left upper limbs with dumbbells on average 2.8 times per week for 12 months, followed by eight months detraining. Nineteen students served as controls (mean 25.7 ± 5.2 yrs, 16.5 ± 4 cm, 62.1 ± 7.0 kg). BMC, BMD, and bone width and estimated cortical wall thickness (CWT) were measured at five different sites in both upper extremities (proximal humerus, humeral shaft, radial shaft, ulnar shaft, and distal forearm) using dual energy x-ray absorptiometry (DXA) scanner. In addition, cross-sectional moment of inertia (CSMI) was estimated from DXA data. The maximal isometric strength of the upper extremities was measured with an arm flexion-extension dynamometer. The training increased significantly the flexion strength by 14% (p = 0.001). During the detraining period, all measured strength values in the training group decreased in both limbs with respect to values after training. Despite the clear effect on muscular strength, no significant intergroup differences were observed in BMC, BMD, bone width, CWT, or CSMI values at any measured site after the training or detraining period. The estimated loading-induced strains remained within customary loading, and the change in strain level was only 15%. In conclusion, this study indicated that using high-resistance strength training may not provide an effective osteogenic stimulus for bone formation and geometric changes in upper limb bones of young, healthy, adult women. The interaction of bones and muscles may play an important and relatively unrecognized role in the development of bone strength, suggesting that the entire biomechanical environment should be carefully considered when evaluating the osteogenic efficiency of physical loading.
Human protein tyrosine phosphatase-σ: Alternative splicing and inhibition by bisphosphonates
Authors: Endo Naoto , Rutledge Su Jane , Opas Evan E. , Vogel Robert , Rodan Gideon A. , Schmidt Azriel
Published: February 2010

Two forms of the transmembrane human protein tyrosine phosphatase (PTPσ), generated by alternative splicing, were identified by cDNA cloning and Northern hybridization with selective cDNA probes. The larger form of PTPσ is expressed in various human tissues, human osteosarcoma, and rat tibia. The hPTPσ cDNA codes for a protein of 1911 amino acid residues and is composed of a cytoplasmic region with two PTP domains and an extracellular region that can be organized into three tandem repeats of immunoglobulin-like domains and eight tandem repeats of fibronectin type III-like domains. In the brain, the major transcript of PTPσ is an alternatively spliced mRNA, in which the coding region for the fibronectin type III-like domains number four to seven are spliced out, thus coding for a protein of 1502 amino acid residues similar to the rat PTPσ and rat PTP-NE3. Using in situ hybridization, we assigned hPTPσ to chromosome 6, arm 6q and band 6q15. The bacterial-expressed hPTPσ exhibits PTPase activity that was inhibited by orthovanadate (IC50 = 0.02 μM) and by two bisphosphonates used for the treatment of bone diseases, alendronate (ALN) (IC50 = 0.5 μM) and etidronate (IC50 = 0.2 μM). In quiescent calvaria osteoblasts, micromolar concentrations of vanadate, ALN and etidronate stimulate cellular proliferation. These findings show tissue-specific alternative splicing of PTPσ and suggest that PTPs are putative targets of bisphosphonate action.
Expression of rat bone sialoprotein promoter in transgenic mice
Authors: Chen Jinkun , Thomas Huw F. , Jin Hangqing , Jiang Heping , Sodek Jaro
Published: February 2010

Bone sialoprotein (BSP) is a major protein of the mineralized bone extracellular matrix that has been implicated in the nucleation of hydroxyapatite crystals. Our previous studies have demonstrated that BSP mRNA is expressed by differentiated osteoblasts, odontoblasts, and cementoblasts involved in de novo mineralized tissue formation in a tissue-specific and developmentally regulated manner. To determine the basis of the selective expression of the BSP gene, we have generated four transgenic mouse lines in which ∼2.7 kb of the rat BSP promoter ligated to a luciferase reporter gene has been stably integrated into the mouse genome. Assays of luciferase activities in 5-day-old animals has revealed consistently high levels in bone tissues with negligible activities in various other organs including kidney, liver, stomach, intestine, and spleen. In some animals, variable expression was observed in brain and skin. Temporal analyses revealed the highest luciferase expression in neonatal bones, with expression decreasing markedly with subsequent growth and development, as observed previously for the endogenous gene in rats. Immunohistochemical analysis of luciferase activity and in situ hybridization of luciferase mRNA in bone tissues show that differentiated osteoblasts express the highest levels of luciferase, consistent with the induction of endogenous gene expression. These studies demonstrate that the regulation of the BSP gene during osteoblastic differentiation, together with its tissue-specific, developmentally regulated expression, is primarily mediated within the ∼2.7 kb region of the promoter.