bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nuclear Localization of Type I Parathyroid Hormone/Parathyroid Hormone-Related Protein Receptors in Deer Antler Osteoclasts: Evidence for Parathyroid Hormone-Related Protein and Receptor Activator of NF-κB-Dependent Effects on Osteoclast Formation in Regenerating Mammalian Bone
Authors: Faucheux C. , Horton M. A. , Price J. S. 
Published: April 2006

Abstract
Parathyroid hormone-related protein (PTHrP) is not required for osteoclastogenesis during embryonic development; however, after birth it has been shown to regulate osteoclast formation during tooth eruption. Our study explores the hypothesis that PTHrP also may regulate osteoclast differentiation in the regenerating skeletal tissues of deer antlers, bones capable of complete regeneration. Osteoclast-like multinucleated cells (MNCs) formed spontaneously in micromass cultures derived from antler cartilage and these cells had the phenotypic characteristics of osteoclasts. PTHrP and receptor activator of NF-κB ligand (RANKL) stimulated antler osteoclast formation although the effect of RANKL was less marked than that of PTHrP. The addition of osteoprotegerin (OPG) only partially decreased (by ∼65%) the number of osteoclasts in PTHrP-treated cultures. To determine whether PTHrP also potentially could have direct effects on antler osteoclasts, we studied, by confocal microscopy, the expression of the type I PTH/PTHrP receptor (PTH1R) in MNCs cultured on glass and found the receptor protein to have a nuclear localization. In situ hybridization showed that antler MNCs also expressed PTH1R and PTHrP messenger RNAs (mRNAs). PTHrP was immunolocalized in MNCs cultured on glass but was undetectable in cells resorbing a dentine substrate. In tissue sections of antler cartilage, PTHrP and PTH1R were expressed in vitronectin receptor-positive (VNR+) osteoclast-like cells localized in the perivascular stroma. Thus, these data show that PTHrP plays a role in the regulation of osteoclast differentiation in regenerating skeletal tissues and that PTHrP can have effects on osteoclastogenesis that are independent of RANKL synthesis. Ours is the first study to describe the expression of the type I PTH/PTHrP receptor in mammalian osteoclasts at a protein and mRNA level, which indicates that PTHrP also may have a direct effect on osteoclasts. This also is the first study to show a nuclear localization of the PTHIR in cells of the osteoclast lineage, although the functional significance of this observation has yet to be established.
Incidence and Natural History of Paget's Disease of Bone in England and Wales
Authors: Van Staa T. P. , Selby P. , Leufkens H. G. M. , Lyles K. , Sprafka J. M. , Prof. Cooper C. 
Published: April 2006

Abstract
This study used a large, primary care, record-linkage resource (the General Practice Research Database [GPRD]) to evaluate the incidence, clinical presentation, and natural history of Paget's disease of bone in England and Wales. Between 1988 and 1999, we identified 2465 patients with the recorded diagnosis of Paget's disease of bone, within the five million subjects ≥18 years old who were registered in the GPRD. The validity of diagnostic recording was assessed by questionnaire to individual general practitioners (GPs) in 150 patients; the diagnosis was confirmed in 93.8% of responders. The mean age of patients with Paget's disease was 75 years and 51% were men. The prevalence of the disorder was 0.3% among men and women aged ≥55 years; incidence rates for clinically diagnosed Paget's disease rose steeply with age (men, 5 per 10,000 person-years; women, 3 per 10,000 person-years at the age of 75 years). Over the 11-year period of the study, the age- and sex-adjusted incidence rate of clinically diagnosed Paget's disease declined from 1.1 per 10,000 person-years to 0.7 per 10,000 person-years. Each patient with Paget's disease was matched to three controls matched by age, gender, and general practice. Cases had a greater risk of back pain (relative risk [RR], 2.1; 95% CI, 1.9-2.3), osteoarthritis (OA; RR, 1.7; 95% CI, 1.5-1.9), hip arthroplasty (RR, 3.1; 95% CI, 2.4-4.1), knee arthroplasty (RR, 1.6; 95% CI, 1.0-2.6), fracture (RR, 1.2; 95% CI, 1.0-1.5), and hearing loss (RR, 1.6; 95% CI, 1.3-1.9). Seven patients with Paget's disease developed a malignant bone neoplasm (0.3%). Using life table methodology, the estimated number of people who died within 5 years of follow-up was 32.7% among the patients with Paget's disease and 28.0% among the control patients.
Nuclear Magnetic Resonance Spin-Spin Relaxation of the Crystals of Bone, Dental Enamel, and Synthetic Hydroxyapatites
Authors: Wu Yaotang , Ackerman Jerome L. , Kim Hyun-Man , Rey Christian , Barroug Allal , Glimcher Melvin J. 
Published: April 2006

Abstract
Studies of the apatitic crystals of bone and enamel by a variety of spectroscopic techniques have established clearly that their chemical composition, short-range order, and physical chemical reactivity are distinctly different from those of pure hydroxyapatite. Moreover, these characteristics change with aging and maturation of the bone and enamel crystals. Phosphorus-31 solid state nuclear magnetic resonance (NMR) spin-spin relaxation studies were carried out on bovine bone and dental enamel crystals of different ages and the data were compared with those obtained from pure and carbonated hydroxyapatites. By measuring the31P Hahn spin echo amplitude as a function of echo time, Van Vleck second moments (expansion coefficients describing the homonuclear dipolar line shape) were obtained and analyzed in terms of the number density of phosphorus nuclei.31P magnetization prepared by a 90° pulse or by proton-phosphorus cross-polarization (CP) yielded different second moments and experienced different degrees of proton spin-spin coupling, suggesting that these two preparation methods sample different regions, possibly the interior and the surface, respectively, of bone mineral crystals. Distinct differences were found between the biological apatites and the synthetic hydroxyapatites and as a function of the age and maturity of the biological apatites. The data provide evidence that a significant fraction of the protonated phosphates (HPO4−2) are located on the surfaces of the biological crystals, and the concentration of unprotonated phosphates (PO4−3) within the apatitic lattice is elevated with respect to the surface. The total concentration of the surface HPO4−2 groups is higher in the younger, less mature biological crystals.
A Comparison of Type I Collagen, Fibronectin, and Vitronectin in Supporting Adhesion of Mechanically Strained Osteoblasts
Authors: Lacouture Mario E. , Schaffer Jonathan L. , Klickstein Lloyd B. 
Published: April 2006

Abstract
We used an adhesion assay for cells cultured under high dynamic strain to measure human osteoblast-like HOS cell adherence to immobilized type I collagen, fibronectin, and vitronectin. These conditions were designed to model the increased forces present at unstable fractures or loose joint prostheses. At a constant, low protein-coating density (1000 molecules/μm2) and 20% cyclic strain for 24 h, type I collagen, fibronectin, and vitronectin supported 24.6 ± 2%, 16.7 ± 3%, and 1.1 ± 1% adherence, respectively, which paralleled the relative number of integrin-binding sites in each protein. Thus, when the number of available binding sites was limited, strain resistance was proportional to the number of integrin-ligand interactions. In contrast, at high protein-coating densities (≥2,500 molecules/μm2), vitronectin supported greater adherence (45.7 ± 2%) when compared with type I collagen (37 ± 2%) or fibronectin (34.8 ± 2%) and directed constitutive expression of osteopontin (OPN), which suggested that there exist discrete signals on vitronectin receptor occupancy that promoted cell adherence and survival under strain. Integrin-mediated binding was necessary for resistance to strain, as evidenced by the low levels of strain resistance observed when cells were adherent in a nonintegrin-dependent manner. These findings support the utilization of at least two distinct mechanisms (i.e., tensegrity and integrin-mediated signal transduction) by HOS cells to remain adherent and viable on exposure to mechanical forces.
Noninvasive Loading of the Murine Tibia: An In Vivo Model for the Study of Mechanotransduction
Authors: Gross Ted S. , Srinivasan Sundar , Liu Chung C. , Clemens Thomas L. , Bain Steven D. 
Published: April 2006

Abstract
Transgenic and knockout mice present a unique opportunity to study mechanotransduction pathways in vivo, but the difficulty inherent with applying externally controlled loads to the small mouse skeleton has hampered this approach. We have developed a novel device that enables the noninvasive application of controlled mechanical loads to the murine tibia. Calibration of tissue strains induced by the device indicated that the normal strain environment was repeatable across loading bouts. Two in vivo studies were performed to show the usefulness of the device. Using C57Bl/6J mice, we found that dynamic but not static loading increased cortical bone area. This result is consistent with previous models of bone adaptation, and the lack of adaptation induced by static loading serves as a negative control for the device. In a preliminary study, transgenic mice selectively overexpressing insulin-like growth factor 1 (IGF-1) in osteoblasts underwent a low-magnitude loading regimen. Periosteal bone formation was elevated 5-fold in the IGF-1-overexpressing mice but was not elevated in wild-type littermates, showing the potential for synergism between mechanical loading and selected factors. Based on these data, we anticipate that the murine tibia-loading device will enhance assessment of mechanotransduction pathways in vivo and, as a result, has the potential to facilitate novel gene discovery and optimization of synergies between drug therapies and mechanical loading.
Reductions in Bone Mass, Structure, and Strength in Axial and Appendicular Skeletons Associated With Increased Turnover After Ovariectomy in Mature Cynomolgus Monkeys and Preventive Effects of Clodronate
Authors: Itoh Fumiaki , Kojima Masami , Furihata-Komatsu Hanako , Aoyagi Shigemi , Kusama Hiroshi , Komatsu Hidetada , Nakamura Toshitaka 
Published: April 2006

Abstract
Over 16 months, we evaluated the effects of ovariectomy (OVX) and bisphosphonate clodronate (CLO) on bone in 48 cynomolgus monkeys (9-15 years old) fed a normal calcium diet. We established three OVX groups(oral CLO at 0 [OVX control], 12, or 60 mg/kg per day) and one sham-operated (SHAM) group. At 16 months, the bone mineral density (BMD) values (percentage of group baseline; OVX control vs. SHAM) for lumbar bone (L3-L5), proximal femur, midfemur, radius, and tibia were −2.6% versus 11.2%, −3.5% versus 8.9%, −3.0% versus 9.0%, −5.5% versus 15.7%, and −6.7% versus 13.9%, respectively. In OVX control (i) tibia showed significant loss of bone mineral content (BMC; vs. baseline), (ii) urinary deoxypyridinoline (DPD) and serum osteocalcin (OC) levels increased (peak = 182% and 168%, respectively, of SHAM), (iii) in lumbar bone and midfemur, ultimate load (UL) was reduced (vs. SHAM), (iv) in lumbar bone, trabecular bone-formation rates (BFRs) were not changed significantly, but tibial endocortical and intracortical bone formation rates were significantly raised (vs. SHAM), (v) the volumetric BMD (vBMD) and geometry of the tibial cortex (measured by peripheral quantitative computed tomography [pQCT]) were significantly reduced (vs. SHAM). CLO, 60 mg/kg per day but not 12 mg/kg per day, significantly inhibited OVX-induced changes, age-dependent increases in bone mass, and ability to maintain structure. Thus, in OVX mature cynomolgus monkeys (possibly, a unique model of the cortical bone loss secondary to estrogen deficiency), the post-OVX increases in systemic bone markers were slight, but stimulation of local turnover in the cortical envelope was enough to cause bone loss (more so in tibia than in lumbar trabecular bone). High-dose CLO prevented these changes.
Two Different Pathways for the Maintenance of Trabecular Bone in Adult Male Mice
Authors: Lindberg Marie K. , Movérare Sofia , Skrtic Stanko , Alatalo Sari , Halleen Jussi , Mohan Subburaman , Gustafsson J-Å , Ohlsson Claes 
Published: April 2006

Abstract
Androgens may regulate the male skeleton either directly via activation of the androgen receptor (AR) or indirectly via aromatization of androgens into estrogen and, thereafter, via activation of estrogen receptors (ERs). There are two known estrogen receptors, ER-α and ER-β. The aim of this study was to investigate the relative roles of ER-α, ER-β, and AR in the maintenance of trabecular bone in male mice. Seven-month-old male mice, lacking ER-α (ERKO), ER-β (BERKO), or both receptors (DERKO), were orchidectomized (orx) and treated for 3 weeks with 0.7 μg/mouse per day of 17β-estradiol or vehicle. No reduction in trabecular bone mineral density (BMD) was seen in ERKO, BERKO, or DERKO mice before orx, showing that neither ER-α nor ER-β is required for the maintenance of a normal trabecular BMD in male mice. After orx, there was a pronounced decrease in trabecular BMD, similar for all groups, resulting in equal levels of trabecular BMD in all genotypes. This reduction was reversed completely in wild-type (WT) and BERKO mice treated with estrogen, and no significant effect of estrogen was found in ERKO or DERKO mice. In summary, the trabecular bone is preserved both by a testicular factor, presumably testosterone acting via AR and by an estrogen-induced activation of ER-α. These results indicate that AR and ER-α are redundant in the maintenance of the trabecular bone in male mice. In contrast, ER-β is of no importance for the regulation of trabecular bone in male mice.
Estrogen Receptor Isoform-Specific Induction of Progesterone Receptors in Human Osteoblasts
Authors: Rickard David J. , Waters Katrina M. , Ruesink Terry J. , Khosla Sundeep , Katzenellenbogen John A. , Katzenellenbogen Benita S. , Riggs B. Lawrence , Spelsberg Thomas C. 
Published: April 2006

Abstract
Estrogen induction of progesterone receptor (PR) expression may be important to bone physiology because progesterone has been implicated in the control of bone formation and resorption. Although PR gene expression can be induced in osteoblasts by estrogen signaling through the estrogen receptor (ER) α isoform, it is unknown whether the ER-β isoform is involved in this regulation. The effect of estrogen on PR expression was examined in human fetal osteoblast (hFOB) cell lines stably transfected with either ER-α or ER-β. Estrogen treatment of hFOB/ER-α cells induced PR messenger RNA (mRNA) steady-state levels after 24 h and protein levels after 48 h, as established by competitive reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blotting. Interestingly, no induction of PR expression was observed in the hFOB/ER-β cells during this period. However, PR mRNA was induced progressively after 48 h of treatment with estrogen with maximum levels achieved at 12 days posttreatment. ER protein also was increased after 12 days of treatment. Both A and B isoforms of PR (PRA and PRB) were induced by estrogen in the hFOB/ER-α cells as well as much later in hFOB/ER-β cells. The pure antiestrogen ICI 182,780 prevented PR induction by estrogen in both cell lines. An ER-β-selective antagonist R, R-tetrahydrochrysene (THC) abolished the induction of PR mRNA in hFOB/ER-β but not in hFOB/ER-α cells, verifying that the response in the former cell line was ER-β-mediated. Transient cotransfection of hFOB cells with ER-α or ER-β together with either a human PRA or PRB promoter linked to a reporter plasmid revealed that although the PRB promoter was stimulated equally by estrogen activation of either ER isoform, PRA was activated preferentially by ER-α. Together, these results show that although estrogen can up-regulate endogenous PR gene expression in osteoblasts via both ER isoforms, ER-α is the predominant inducer.
The Mode of Mechanical Integrin Stressing Controls Intracellular Signaling in Osteoblasts
Authors: Pommerenke Hagen , Schmidt Christian , Dürr Frieda , Nebe Barbara , Lüthen Frank , Müller Petra , Dr. Rychly Joachim 
Published: April 2006

Abstract
Following the idea that integrin receptors function as mechanotransducers, we applied defined physical forces to integrins in osteoblastic cells using a magnetic drag force device to show how cells sense different modes of physical forces. Application of mechanical stress to the β1-integrin subunit revealed that cyclic forces of 1 Hz were more effective to stimulate the cellular calcium response than continuous load. Cyclic forces also induced an enhanced cytoskeletal anchorage of tyrosine-phosphorylated proteins and increased activation of the focal adhesion kinase (FAK) and mitogen activated protein (MAP) kinase. These events were dependent on an intact cytoskeleton and the presence of intracellular calcium. Analyses of the intracellular spatial organization of the calcium responses revealed that calcium signals originate in a restricted region in the vicinity of the stressed receptors, which indicates that cells are able to sense locally applied stress on the cell surface via integrins. The calcium signals can spread throughout the cell including the nucleus, which shows that calcium also is a candidate to transmit mechanically induced information into different cellular compartments.
Cartilage Calcification Studied by Proton Nuclear Magnetic Resonance Microscopy
Authors: Potter K. , Leapman R. D. , Basser P. J. , Landis W. J. 
Published: April 2006

Abstract
A three-dimensional (3D) mineralizing culture system using hollow fiber bioreactors has been developed to study the early stages of endochondral ossification by proton nuclear magnetic resonance (NMR) microscopy. Chondrocytes harvested from the cephalic half of the sterna from 17-day-old chick embryos were terminally differentiated with 33 nM of retinoic acid for 1 week and mineralization was initiated by the addition of 1% β-glycerophosphate to the culture medium. Histological sections taken after 6 weeks of development in culture confirmed calcification of the cartilage matrix formed in bioreactors. Calcium to phosphorus ratios (1.62-1.68) from X-ray microanalysis supported electron diffraction of thin tissue sections showing the presence of a poorly crystalline hydroxyapatite mineral phase in the cultures. After 4 weeks of culture, quantitative proton NMR images showed water proton magnetization transfer rate constants (km) were higher in premineralized cartilage compared with uncalcified cartilage, a result suggesting collagen enrichment of the matrix. Notably after 5 weeks mineral deposits formed in bioreactors principally in the collagen-enriched zones of the cartilage with increased km values. This caused marked reductions in water proton longitudinal (T1) and transverse (T2) relaxation times and water diffusion coefficients (D). These results support the hypothesis that mineralization proceeds in association with a collagen template. After 6 weeks of culture development, the water proton T2 values decreased by 13% and D increased by 7% in uncalcified areas, compared with the same regions of tissue examined 1 week earlier. These changes could be attributed to the formation of small mineral inclusions in the cartilage, possibly mediated by matrix vesicles, which may play an important role in cartilage calcification. In summary, NMR images acquired before and after the onset of mineralization of the same tissue provide unique insights into the matrix events leading to endochondral mineral formation.
Resistance to Unloading-Induced Three-Dimensional Bone Loss in Osteopontin-Deficient Mice
Authors: Ishijima Muneaki , Tsuji Kunikazu , Rittling Susan R. , Yamashita Teruhito , Kurosawa Hisashi , Denhardt David T. , Nifuji Akira , Noda Masaki 
Published: April 2006

Abstract
Recent development in three-dimensional (3D) imaging of cancellous bone has made possible true 3D quantification of trabecular architecture. This provides a significant improvement in the measures available to study and understand the mechanical functions of cancellous bone. We recently reported that the presence of osteopontin (OPN) was required for the effects of mechanical stress on bone as OPN-null (OPN−/−) mice showed neither enhancement of bone resorption nor suppression of bone formation when they were subjected to unloading by tail suspension. However, in this previous study, morphological analyses were limited to two-dimensional (2D) evaluation. Although bone structure is 3D and thus stress effect should be evaluated based on 3D parameters, no such 3D morphological features underlying the phenomenon have been known. To elucidate the role of OPN in mediating mechanical stress effect based on true quantitative examination of bone, we evaluated 3D trabecular structures of hindlimb bones of OPN−/− mice after tail suspension. Tail suspension significantly reduced 3D parameters of bone volume (BV/TV), trabecular number (Tb.N), trabecular thickness (Tb.Th), and anisotropy and increased 3D parameters on trabecular separation (Tb.Sp) in wild-type mice. In contrast, these 3D parameters were not altered after tail suspension in OPN−/− mice. These data provided evidence that OPN is required for unloading-induced 3D bone loss.
Transforming Growth Factor β2 Inhibits Adipocyte Differentiation Induced by Skeletal Unloading in Rat Bone Marrow Stroma
Authors: Ahdjoudj Souhila , Lasmoles Françoise , Holy Xavier , Zerath Erik , Marie Pierre J. 
Published: April 2006

Abstract
Skeletal unloading induced by hindlimb suspension in rats reduces bone formation and induces osteopenia, but its effect on adipogenesis is unknown. We assessed the effects of unloading and transforming growth factor (TGF) β2 on bone marrow stromal cell adipocyte differentiation in relation with osteoblast differentiation. Skeletal unloading rapidly (4-7 days) decreased osteoblast transcription factor Runx2, osteocalcin (OC), and type I collagen messenger RNA (mRNA) levels and reduced bone formation in the long bone metaphysis. Conversely, unloading increased expression of the adipocyte transcription factor peroxisome proliferator-activated receptor γ2 (PPARγ2) at 4 days and increased expression of the adipocyte differentiation genes lipoprotein lipase (LPL) and aP2 in the bone marrow stroma at 7 days. Consistently, unloading increased the number and volume of adipocytes in the bone marrow stroma. Continuous (0-7 days) and late (4-7 days) treatments with TGF-β2 corrected the abnormal expression of Cbfa1/Runx2, OC, and type I collagen mRNAs and normalized bone formation in unloaded metaphyseal bone. Moreover, both TGF-β2 treatments decreased PPARγ2 and C/EBPα mRNA levels at 4 days and normalized aP2 and LPL expression and adipocyte number and volume at 7 days. These results show that skeletal unloading increases adipocyte differentiation concomitantly with inhibition of osteoblast differentiation. These abnormalities are prevented and reversed by TGF-β2, suggesting a role for TGF-β in the control of adipogenic differentiation in the bone marrow stroma.