bluuebunny/crossref_metadata_2025_split huggingface dataset:
Deletion of Membrane-Bound Steel Factor Results in Osteopenia in Mice
Authors: Lotinun Sutada , Evans Glenda L , Turner Russell T , Oursler Merry Jo 
Published: April 2006

Abstract
To examine the functional role of membrane-bound SLF, we evaluated the growing skeletons of WT and SLF mutant (Sl/Sld) mice that do not produce this protein using DXA, bone histomorphometry, cell culture, and flow cytometry. Deletion of membrane-bound SLF delays bone growth, decreases bone mass and BMD, impairs osteoblast function, and increases osteoclast surface in young mice.
Introduction: Mutations at the murine steel locus lead to a defect in the development of hematopoietic stem cells, mast cells, and germ cells. Two isoforms of steel factor (SLF), soluble and membrane-associated, have been reported. Soluble SLF increases osteoclast formation and activity in cell culture. The effects of deletion of membrane-bound SLF on bone metabolism in mice have yet to be determined and are the subject of this study.
Materials and Methods: Five-, 7-, and 12-week-old male and 5-week-old female WCB6F1/J-KitlSl/KitlSl-d (Sl/Sld) mice and wildtype (WT) littermates were used. BMD and bone mass, growth, architecture, and turnover were evaluated by DXA (males and females) and histomorphometry (males only). Primary osteoblasts isolated from humeri of 5-week-old male WT and Sl/Sld mice were used to determine osteoblast function, and bone marrow cells from tibias and femurs of these mice were analyzed to determine cell surface expression of osteoclast precursors.
Results and Conclusions: Young Sl/Sld mice grew more slowly, had a reduced bone mass, and had shorter bones than WT littermates. Male mutants had significantly decreased whole body BMD in all age groups, largely because of a reduction in BMC. Tibial cross-sectional, cortical, and marrow area of cortical bone and cancellous bone volume was reduced in the mutants at all ages. The osteopenia in Sl/Sld was caused by increased osteoclast surface at all ages and decreased osteoblast surface at 5 weeks of age. [3H]thymidine incorporation studies showed that proliferation of osteoblasts derived from mutant mice was significantly suppressed (56%). Moreover, a decrease in mineralization was observed in Sl/Sld osteoblast culture. Fluorescence-activated cell sorting analysis of bone marrow cells from Sl/Sld mice revealed a 65% increase in the percentage of c-Fms+CD11b+RANK+ cells compared with WT controls. These findings suggest that membrane-bound SLF/c-Kit signaling plays a role in the regulation of peak bone mass.
Production of Prostaglandin D2 by Human Osteoblasts and Modulation of Osteoprotegerin, RANKL, and Cellular Migration by DP and CRTH2 Receptors
Authors: Gallant Maxime A , Samadfam Rana , Hackett Josette A , Antoniou John , Parent Jean-Luc , de Brum-Fernandes Artur J 
Published: April 2006

Abstract
Human osteoblasts produce PGD2, which acts on the DP receptor to decrease osteoprotegerin production and on the CRTH2 receptor to decrease RANKL expression and to induce osteoblast chemotaxis. These results indicate that activation of CRTH2 may lead to an anabolic response in bone.
Introduction: Whereas the actions of prostaglandin (PG)E2 as a modulator of bone and osteoblast function are relatively well characterized, little is known about PGD2 and bone metabolism. The objectives of this study were to determine if human osteoblasts can produce PGD2, which prostaglandin D2 synthases are implicated in this synthesis, to identify the PGD2 receptors (DP and CRTH2) on these cells and to characterize the biological effects resulting from their activation.
Materials and Methods: RT-PCR analysis and immunohistochemistry were used to detect PGD2 receptor and synthases in cultured human osteoblasts. Immunohistochemistry was used to identify the synthases and receptors in human bone tissue. Intracellular cAMP and calcium levels were determined to verify receptor activation. The cells were stimulated with PGD2 or the specific agonists BW 245C (DP) and DK-PGD2 (CRTH2), and the resulting effects on osteoprotegerin (OPG) secretion, RANKL expression, and chemotaxis were determined. Osteoblast production of PGD2 was evaluated by measuring PGD2 in the culture supernatants after stimulation with interleukin (IL)-1, TNF-α, PTH, vascular endothelial growth factor (VEGF), and insulin-like growth factor I (IGF-I).
Results: Human osteoblasts in culture generated PGD2 when stimulated. Both osteoblasts in culture and in situ present the lipocalin-type PGD2 synthase only. Both DP and CRTH2 receptors were present in human osteoblasts in culture and in situ. Stimulation of DP resulted in an increase in cAMP, whereas CRTH2 increased the intracellular calcium level. OPG production was reduced by 60% after DP receptor stimulation, whereas CRTH2 receptor stimulation decreased RANKL expression on human osteoblasts. As reported for other cell types, CRTH2 was a potent inducer of chemotaxis for human osteoblasts in culture.
Conclusions: Human osteoblasts in culture produce PGD2 under biologically relevant stimuli through the lipocalin-type PGD2 synthase (L-PGDS) pathway. As an autacoid, PGD2 can act on DP and CRTH2 receptors, both present on these cells. Specific activation of CRTH2 could lead directly and indirectly to an anabolic response in bone.
Non-Isomerized C-Telopeptide Fragments Are Highly Sensitive Markers for Monitoring Disease Activity and Treatment Efficacy in Paget's Disease of Bone
Authors: Alexandersen Peter , Peris Pilar , Guañabens Nuria , Byrjalsen Inger , Alvarez Luisa , Solberg Helene , Cloos Paul AC 
Published: April 2006

Abstract
A new resorption assay measuring non-isomerized collagen type I C-telopeptide fragments (α-α CTX) was evaluated in a cohort comprising 32 Pagetic patients and 48 healthy controls. α-α CTX was found to be a sensitive marker for assessing disease activity and monitoring treatment efficacy in Paget's disease of bone compared with isomerized CTX (β-β CTX) and a number of other established bone turnover markers.
Introduction: Collagen type I fragments are generated by resorbing osteoclasts, and some of them can be measured using a C-telopeptide (CTX) immunoassay. The C-telopeptide of collagen type I comprises a DG-motif susceptible to isomerization. In newly synthesized collagen, this motif is in the native form denoted α, but spontaneously converts to an isomerized form (β) during aging of bone. CTX fragments composed of at least two α CTX chains (α-α CTX) originating from degradation of newly formed bone can be determined in the urine using a newly developed sandwich ELISA. The aim of this study was to assess the ability of this marker to monitor disease activity and treatment efficacy in patients with Paget's disease compared with established bone turnover markers.
Materials and Methods: A total of 32 patients diagnosed with Paget's disease of bone was included in the study. All received 400 mg/day of oral tiludronate for 3 months. Urinary α-α CTX (U α-α CTX) was measured at baseline and at 1 and 6 months after discontinuation of therapy and in 48 untreated age-matched and healthy controls. Other markers of bone turnover, including urinary β-β CTX, N-terminal cross-linking telopeptide of type I collagen, and deoxypyridinoline, were also measured for comparison.
Results and Conclusions: The U α-α CTX marker showed a marked reduction (−82% and −77% at 1 and 6 months of treatment, respectively) in response to antiresorptive therapy in patients with Paget's disease. The response to treatment in this marker exceeded that of the other markers (p &lt; 0.01). The α-α CTX marker also provided a high correlation (r = 0.89) to disease activity as assessed by scintigraphic activity index. In conclusion, α-α CTX seems to be a sensitive marker for assessing disease activity and monitoring treatment efficacy in Paget's disease.
Highly Ordered Interstitial Water Observed in Bone by Nuclear Magnetic Resonance
Authors: Wilson Erin E , Awonusi Ayorinde , Morris Michael D , Kohn David H , Tecklenburg Mary MJ , Beck Larry W 
Published: April 2006

Abstract
NMR was used to study the nanostructure of bone tissue. Distance measurements show that the first water layer at the surface of the mineral in cortical bone is structured. This water may serve to couple the mineral to the organic matrix and may play a role in deformation.
Introduction: The unique mechanical characteristics of bone tissue have not yet been satisfactorily connected to the exact molecular architecture of this complex composite material. Recently developed solid-state nuclear magnetic resonance (NMR) techniques are applied here to the mineral component to provide new structural distance constraints at the subnanometer scale.
Materials and Methods: NMR dipolar couplings between structural protons (OH− and H2O) and phosphorus (PO4) or carbon (CO3) were measured using the 2D Lee-Goldburg Cross-Polarization under Magic-Angle Spinning (2D LG-CPMAS) pulse sequence, which simultaneously suppresses the much stronger proton-proton dipolar interactions. The NMR dipolar couplings measured provide accurate distances between atoms, e.g., OH and PO4 in apatites. Excised and powdered femoral cortical bone was used for these experiments. Synthetic carbonate (∼2-4 wt%)-substituted hydroxyapatite was also studied for structural comparison.
Results: In synthetic apatite, the hydroxide ions are strongly hydrogen bonded to adjacent carbonate or phosphate ions, with hydrogen bond (O-H) distances of ∼1.96 Å observed. The bone tissue sample, in contrast, shows little evidence of ordered hydroxide. Instead, a very ordered (structural) layer of water molecules is identified, which hydrates the small bioapatite crystallites through very close arrangements. Water protons are ∼2.3-2.55 Å from surface phosphorus atoms.
Conclusions: In synthetic carbonated apatite, strong hydrogen bonds were observed between the hydroxide ions and structural phosphate and carbonate units in the apatite crystal lattice. These hydrogen bonding interactions may contribute to the long-range stability of this mineral structure. The biological apatite in cortical bone tissue shows evidence of hydrogen bonding with an ordered surface water layer at the faces of the mineral particles. This structural water layer has been inferred, but direct spectroscopic evidence of this interstitial water is given here. An ordered structural water layer sandwiched between the mineral and the organic collagen fibers may affect the biomechanical properties of this complex composite material.
Postmenopausal Bilateral Oophorectomy Is Not Associated With Increased Fracture Risk in Older Women
Authors: Antoniucci Diana M , Sellmeyer Deborah E , Cauley Jane A , Ensrud Kristine E , Schneider Jennifer L , Vesco Kimberly K , Cummings Steven R , Melton L Joseph 
Published: April 2006

Abstract
We studied whether oophorectomy performed after menopause is associated with an increased risk of hip or vertebral fractures in 6295 Study of Osteoporotic Fractures participants. There was no association between postmenopausal oophorectomy and the risk of hip or vertebral fractures.
Introduction: Bilateral oophorectomy after natural menopause has been associated with an increased risk of osteoporotic fractures, potentially because of a decline in serum estradiol and testosterone levels after the oophorectomy. We prospectively tested this hypothesis in the Study of Osteoporotic Fractures (SOF).
Materials and Methods: We studied 6295 white women ⩾65 years of age participating in the SOF who were not taking estrogen therapy at baseline. Hip fracture analyses included 708 hip fractures; vertebral fracture analyses included 267 incident vertebral fractures. Baseline serum estradiol and free testosterone values were available in a small subset of participants.
Results and Conclusion: There were no significant differences in age, weight, or BMD between the women who underwent postmenopausal oophorectomy (n = 583) and those who did not (n = 5712). Free testosterone levels were significantly lower among women who had a postmenopausal oophorectomy. A history of postmenopausal oophorectomy was not associated with an increased risk of hip (hazard ratio [HR] = 1.1; 95% CI = 0.9-1.5) or vertebral fracture (HR = 0.7; 95% CI = 0.5-1.2). The relationship between oophorectomy and hip fracture was not altered by adding serum estradiol level (HR = 1.3; 95% CI = 0.5-3.2) or serum free testosterone level (HR = 1.7; 95% CI = 0.8-3.7) to the model. In summary, postmenopausal oophorectomy was not associated with an increased risk of hip or vertebral fracture in this cohort. These results are in contrast to previous findings, suggesting that the relationship between postmenopausal oophorectomy and fractures is not fully elucidated and that incidental oophorectomy after menopause should still be considered carefully in each potential patient.
Adjusting Data to Body Size: A Comparison of Methods as Applied to Quantitative Trait Loci Analysis of Musculoskeletal Phenotypes
Authors: Lang Dean H , Sharkey Neil A , Lionikas Arimantas , Mack Holly A , Larsson Lars , Vogler George P , Vandenbergh David J , Blizard David A , Stout Joseph T , Stitt Joseph P , McClearn Gerald E 
Published: April 2006

Abstract
The aim of this study was to compare three methods of adjusting skeletal data for body size and examine their use in QTL analyses. It was found that dividing skeletal phenotypes by body mass index induced erroneous QTL results. The preferred method of body size adjustment was multiple regression.
Introduction: Many skeletal studies have reported strong correlations between phenotypes for muscle, bone, and body size, and these correlations add to the difficulty in identifying genetic influence on skeletal traits that are not mediated through overall body size. Quantitative trait loci (QTL) identified for skeletal phenotypes often map to the same chromosome regions as QTLs for body size. The actions of a QTL identified as influencing BMD could therefore be mediated through the generalized actions of growth on body size or muscle mass.
Materials and Methods: Three methods of adjusting skeletal phenotypes to body size were performed on morphologic, structural, and compositional measurements of the femur and tibia in 200-day-old C57BL/6J × DBA/2 (BXD) second generation (F2) mice (n = 400). A common method of removing the size effect has been through the use of ratios. This technique and two alternative techniques using simple and multiple regression were performed on muscle and skeletal data before QTL analyses, and the differences in QTL results were examined.
Results and Conclusions: The use of ratios to remove the size effect was shown to increase the size effect by inducing spurious correlations, thereby leading to inaccurate QTL results. Adjustments for body size using multiple regression eliminated these problems. Multiple regression should be used to remove the variance of co-factors related to skeletal phenotypes to allow for the study of genetic influence independent of correlated phenotypes. However, to better understand the genetic influence, adjusted and unadjusted skeletal QTL results should be compared. Additional insight can be gained by observing the difference in LOD score between the adjusted and nonadjusted phenotypes. Identifying QTLs that exert their effects on skeletal phenotypes through body size-related pathways as well as those having a more direct and independent influence on bone are equally important in deciphering the complex physiologic pathways responsible for the maintenance of bone health.
TRAF2 Is Essential for TNF-α-Induced Osteoclastogenesis
Authors: Kanazawa Kiyoshi , Kudo Akira 
Published: April 2006

Abstract
TRAF2-deficient mice show embryonic lethality, and we developed a new in vitro differentiation system to show the function of TRAF2 in osteoclastogenesis, in which osteoclast progenitors are derived from the fetal liver of TRAF2-deficient mice. Using this system, we showed that TRAF2 is required for TNF-α-induced osteoclastogenesis.
Introduction: TNF receptor-associated factor 2 (TRAF2) is a signal transducer for RANK and for two TNF receptor isotypes, TNFR1 and TNFR2. Because TRAF2-deficient mice show embryonic lethality, it has remained unclear whether TRAF2 is crucial in RANKL- or TNF-α-induced osteoclastogenesis.
Materials and Methods: Osteoclast progenitors derived from fetal liver were cultured in the presence of monocyte macrophage colony-stimulating factor (M-CSF), and flow cytometry for characterization of surface markers on these cells was performed. To examine the involvement of TRAF2 in osteoclast differentiation, we cultured osteoclast progenitors from TRAF2-deficient and wildtype mice with soluble RANKL or TNF-α in the presence of M-CSF, and counted the number of TRACP+ multinucleate cells formed. c-jun N-terminal kinase (JNK) and NF-κB activation in osteoclast progenitors was examined by Western blot analysis and electrophoretic mobility shift assay, respectively. Nuclear factor of activated T cells (NFATc1) expression and activation were analyzed by RT-PCR and immunofluorescence staining, respectively. To examine whether TRAF2 overexpression induced osteoclastogenesis, TRAF2 was overexpressed in osteoclast progenitors form wildtype bone marrow by retrovirus infection.
Results and Conclusions: Osteoclast progenitors from normal fetal liver, which were cultured with M-CSF, expressed surface molecules c-fms, Mac-1, and RANK, and could differentiate into TRACP+ multinucleate cells in the presence of soluble RANKL or TNF-α. RANKL-induced osteoclastogenesis gave a reduction of 20% in the progenitors from TRAF2-deficient mice compared with that of the cells from littermate wildtype mice, whereas TNF-α-induced osteoclastogenesis was severely impaired in the cells from the TRAF2-deficient mice. Only a few TRACP+ multinucleate cells were formed, and TNF-α-mediated activation of JNK, NF-κB, and NFATc1 was defective. TRAF2 overexpression induced differentiation of osteoclast progenitors from wildtype mice into TRACP+ multinucleate cells. These results suggest that TRAF2 plays an important role in TNF-α-induced osteoclastogenesis.
Relationship of Volumetric BMD and Structural Parameters at Different Skeletal Sites to Sex Steroid Levels in Men
Authors: Khosla Sundeep , Melton L Joseph , Robb Richard A , Camp Jon J , Atkinson Elizabeth J , Oberg Ann L , Rouleau Peggy A , Riggs B Lawrence 
Published: April 2006

Abstract
In a population-based, cross-sectional study, we related age-associated changes in vBMD and in bone structural parameters to circulating bioavailable estradiol and testosterone levels in men. Associations between these bone mass/structural parameters and sex steroid levels were progressively stronger with age. Our previously postulated “threshold” for skeletal estrogen deficiency was most evident at cortical sites.
Introduction: Serum sex steroids, particularly estrogen levels, are associated with bone mass in men, and previous work has suggested that there may be a “threshold” bioavailable estradiol (bio E2) level below which the male skeleton becomes estrogen deficient. However, previous studies addressing this issue have exclusively used DXA, which cannot separate trabecular from cortical bone or provide information on bone geometry or structure.
Materials and Methods: In an age-stratified population sample of 314 men (age, 22-91 years), we assessed volumetric BMD (vBMD) and bone geometry by QCT at the lumbar spine, femoral neck, distal radius, and distal tibia and related these to circulating bio E2 and bio testosterone (T) levels.
Results: Compared with young men (age, 20-39 years), middle-aged men (age, 40-59 years) had significantly lower bio T (−26%, p &lt; 0.001) and bio E2 (−9%, p = 0.038) levels, and these decreases were even greater in the elderly men (age ≥ 60 years, −60% and −38% for bio T and bio E2, respectively, p &lt; 0.001 for both). Reflecting their intact gonadal status, vBMD/structural parameters were not related to sex steroid levels in young men, whereas bio E2 levels were associated consistently with vBMD and variably with bone geometric parameters in the elderly men; middle-aged men showed associations with bio E2 and bio T at some sites. At all cortical sites, vBMD was associated with bio E2 at low (&lt;30 pM, R = 0.27-0.41, p &lt; 0.05-0.001) but not high (≥30 pM, R = −0.003 to 0.12, p = not significant) levels; no such differences were evident at trabecular sites.
Conclusions: In men, bio E2 is the most consistent predictor of vBMD and some bone geometric variables as assessed by QCT. We also extend our previous findings on a possible “threshold” for skeletal estrogen deficiency by showing that this is most evident for cortical sites.
Population Trends in BMD Testing, Treatment, and Hip and Wrist Fracture Rates: Are the Hip Fracture Projections Wrong?
Authors: Jaglal Susan B , Weller Iris , Mamdani Muhammad , Hawker Gillian , Kreder Hans , Jaakkimainen Liisa , Adachi Jonathan D 
Published: April 2006

Abstract
A worldwide epidemic of hip fractures has been predicted. Time trends in BMD testing, bone-sparing medications and hip and wrist fractures in the province of Ontario, Canada, were examined. From 1996 to 2001, BMD testing and use of bone-sparing medications increased each year, whereas despite the aging of the population, wrist and hip fracture rates decreased.
Introduction: If patients with osteoporosis are being diagnosed and effective treatments used with increasing frequency in the population, rates of hip and wrist fractures will remain stable or possibly decrease. We report here time trends in BMD testing, prescriptions for bone-sparing medications, hip and wrist fracture rates, and population projections of fracture rates to 2005 in the province of Ontario, Canada.
Materials and Methods: Ontario residents have universal access to Medicare. To examine time trends in BMD testing, all physician claims for DXA from 1992 to 2001 were selected from the Ontario Health Insurance Plan (OHIP) database. Trends in prescribing were examined from 1996 to 2003 using data from the Ontario Drug Benefit plan, which provides coverage to persons ≥65 years of age. Actual numbers of hip and wrist fractures were determined for 1992-2000 and population projections for 2001-2005 using time-series analysis. Wrist fractures were identified in the OHIP database and hip fractures through hospital discharge abstracts.
Results: From 1992 to 2001, the number of BMD tests increased 10-fold. There has been a steady increase in the number of persons filling prescriptions for antiresorptives (12,298 in 1996 to 225,580 in 2003) and the majority were for etidronate. For women, the rate of decline for wrist fractures is greater than that for hip fractures. The rate of hip fracture was fairly constant around 41 per 10,000 women ≥50 years between 1992 and 1996. In 1997, the hip fracture rate began to decrease, and the population projections suggest that this downward trend will continue to a rate of 33.1 per 10,000 in 2005.
Conclusions: Our findings suggest that fracture rates may be on the decline, despite the aging of the population, because of increased patterns of diagnosis and treatment for osteoporosis.