bluuebunny/crossref_metadata_2025 huggingface dataset:
Change in Bone Turnover and Hip, Non-Spine, and Vertebral Fracture in Alendronate-Treated Women: The Fracture Intervention Trial
Authors: Bauer Douglas C , Black Dennis M , Garnero Patrick , Hochberg Marc , Ott Susan , Orloff John , Thompson Desmond E , Ewing Susan K , Delmas Pierre D ,   for the Fracture Intervention Trial Study Group
Published: April 2006

We used data from the Fracture Intervention Trial to assess the relationship change in bone turnover after 1 year of alendronate or placebo treatment and subsequent hip, non-spine, and spine fracture risk among 6186 postmenopausal women. In the alendronate group (n = 3105), greater reductions in one or more biochemical marker were associated with a lower risk of fracture.

Introduction: There are few data on the relationship between short-term change in biochemical markers of bone turnover and non-spine fracture risk among bisphosphonate-treated women, and the clinical use of such measurements is unknown.

Materials and Methods: We measured biochemical markers of bone turnover (bone-specific alkaline phosphatase [bone ALP], intact N-terminal propeptide of type I collagen, and C-terminal crosslinked telopeptide of type 1 collagen) and BMD of the spine and hip at baseline and after 1 year of alendronate or placebo. During a mean follow-up of 3.6 years, 72 hip, 786 non-spine, and 336 vertebral fractures were documented.

Results and Conclusions: Each 1 SD reduction in 1-year change in bone ALP was associated with fewer spine (odds ratio = 0.74; CI: 0.63, 0.87), non-spine (relative hazard [RH] = 0.89; CI: 0.78, 1.00; p < 0.050), and hip fractures (RH = 0.61; CI: 0.46, 0.78). Alendronate-treated women with at least a 30% reduction in bone ALP had a lower risk of non-spine (RH = 0.72; CI: 0.55, 0.92) and hip fractures (RH = 0.26; CI: 0.08, 0.83) relative to those with reductions <30%. We conclude that greater reductions in bone turnover with alendronate therapy are associated with fewer hip, non-spine, and vertebral fractures, and the effect is at least as strong as that observed with 1-year change in BMD.
1α,25 Dihydroxyvitamin D3 Rapidly Regulates the Mouse Osteoprotegerin Gene Through Dual Pathways
Authors: Kondo Takeshi , Kitazawa Riko , Maeda Sakan , Kitazawa Sohei
Published: April 2006

1α,25(OH)2D3 rapidly and transiently suppressed OPG gene expression both by accelerating the degradation of mRNA and by suppressing promoter activity. The latter process was mediated through the AP-1 binding site by a reduction in the proportion of phospho-c-Jun in a JNK-independent manner.

Introduction: Osteoclastogenesis is regulated by an integrated network of numerous bone metabolic factors, among which 1α,25-dihydroxyvitamin D3 [1α,25(OH)2D3] promotes osteoclastogenesis by reciprocally upregulating the expression of RANKL and downregulating that of osteoprotegerin (OPG).

Materials and Methods: To analyze the mechanism by which 1α,25(OH)2D3 suppresses OPG, we characterized cis-acting elements of the mouse OPG gene and assessed the post-transcriptional modifications by actinomycin D assays.

Results: 1α,25(OH)2D3 rapidly and transiently suppressed OPG expression and shortened the half-life of OPG mRNA; additionally, the c-Jun homodimer bound to the AP-1 binding site (TGACTGA, −293/−287) and maintained steady-state transcription of the OPG gene. Furthermore, mutation of the AP-1 site negated 1α,25(OH)2D3-driven OPG suppression. Moreover, 1α,25(OH)2D3 treatment of ST2 cells decreased the amount of phosphorylated c-Jun protein (phospho-c-Jun), while the total amount of c-Jun remained constant; however, the amount of phosphorylated Jun N-terminal kinase (JNK) was nearly unchanged by 1α,25(OH)2D3 treatment.

Conclusion: Taken together with the observation that the OPG promoter has no consensus negative vitamin D-responsive elements, these data suggest that 1α,25(OH)2D3 transrepresses mouse OPG by reducing the proportion of phospho-c-Jun in a JNK-independent manner. Our data indicated that short-term treatment with 1α,25(OH)2D3 effectively downregulated OPG expression both by accelerating the degradation of OPG mRNA and by transrepressing the OPG gene through its AP-1 binding site in the catabolic phase. The OPG gene became insensitive to 1α,25(OH)2D3 treatment, however, and reverted to its steady-state expression level over time, leading to the anabolic phase of the effect of 1α,25(OH)2D3 on bone.
Serotonin Regulates Osteoclast Differentiation Through Its Transporter
Authors: Battaglino Ricardo , Fu Jia , Späte Ulrike , Ersoy Ulku , Joe Martha , Sedaghat Leela , Stashenko Philip
Published: April 2006

5-HTT mediates antidepressant-sensitive clearance of 5-HT after its release into neural synapses. We found increased expression of 5-HTT in RANKL-induced osteoclast-like cells. Fluoxetine, an inhibitor of 5-HTT, reduced osteoclast differentiation but not activation. Reserpine, an inhibitor of 5-HT intracellular transport, potentiated differentiation. These results indicate a role for 5-HTT in osteoclast function and suggest that commonly used antidepressive agents may affect bone mass.

Introduction: Interactions between the serotonergic and skeletal systems are suggested by various clinical observations but are poorly understood.

Materials and Methods: Using gene microarrays, we found that the serotonin transporter (5-HTT) was strongly expressed in RANKL-induced osteoclasts. Using RANKL stimulation of RAW264.7 cells and mouse bone marrow cells as a model system for osteoclast differentiation, we studied the possible role/s of the different components of the serotonin (5-HT) system on the differentiation process.

Results: Osteoclast 5-HTT exhibited typical 5-HT uptake activity that was inhibitable by fluoxetine (Prozac). Fluoxetine reduced osteoclast differentiation but did not inhibit the activation of preformed osteoclasts, whereas the addition of 5-HT itself enhanced differentiation. Fluoxetine-treated osteoclast precursors had reduced NF-κB activation and elevated inhibitory protein κBα (IκBα) levels compared with untreated cells. 5-HT, on the other hand, resulted in activation of NF-κB. Reserpine inhibition of intracellular transport of 5-HT into cytoplasmic vesicles potentiated RANKL-induced osteoclast formation, suggesting the importance of intracellular 5-HT in regulating osteoclast differentiation. Reserpine also modestly enhanced the expression of the osteoclast marker TRACP in the absence of RANKL.

Conclusions: Taken together, these data suggest that the 5-HT system plays an important role in bone homeostasis through effects on osteoclast differentiation and implies that commonly used antidepressive agents may affect bone mass.
HMG-CoA Reductase Inhibitors and the Risk of Vertebral Fracture
Authors: Schoofs Mariette WCJ , Sturkenboom Miriam CJM , van der Klift Marjolein , Hofman Albert , Pols Huibert AP , Stricker Bruno HCh
Published: April 2006

Statins inhibit an enzyme in the mevalonate pathway and therefore may affect bone. In this first study on both symptomatic and nonsymptomatic vertebral fractures in the elderly (N = 3469), we show that long-term statin use is significantly associated with a 50% lower vertebral fracture risk. Randomized trials on statins and fractures, carried out in populations at risk for fractures, are needed.

Introduction: Statins are cholesterol-lowering agents that could potentially affect bone. Previous studies on statin use and fracture risk reported contradictory results and did not include both symptomatic and nonsymptomatic vertebral fractures.

Materials and Methods: To examine the association between statin use, vertebral fractures, and lumbar spine BMD, we performed a prospective population-based cohort study in men and women (N = 3469) ≥55 years of age. These individuals had both baseline and follow-up spinal X-rays available. Statin use was obtained from detailed computerized pharmacy data, and the total number of days of exposure before second X-ray was calculated. A multivariate logistic regression model was fitted to calculate odds ratios and CIs.

Results: During a mean follow-up of 6.5 years, 176 incident vertebral fractures occurred. There were 508 statin users and 16 exposed cases. The adjusted relative risk for incident vertebral fracture in users of statins (compared with nonusers) was 0.58 (95% CI, 0.34-0.99). The relative risk decreased on higher cumulative use to 0.52 (95% CI, 0.28-0.97) for use for more than 365 days during the study period. Use of (the hydrophilic statin) pravastatin and use of nonstatin cholesterol-lowering drugs was not significantly associated with vertebral fracture risk. Statin use was not significantly associated with lumbar spine BMD.

Conclusion: Statin use is associated with a lower risk of vertebral fracture. Randomized clinical trials in a population at risk for fracture are needed to examine this association.
Comparison of TGF-β/BMP Pathways Signaled by Demineralized Bone Powder and BMP-2 in Human Dermal Fibroblasts
Authors: Zhou Shuanhu , Glowacki Julie , Yates Karen E
Published: April 2006

Demineralized bone induces chondrogenic differentiation of human dermal fibroblasts in vitro. Analyses of signaling gene expression showed that DBP and BMP-2 regulate common and distinct pathways. Although BMP-2 was originally isolated as a putative active factor in DBP, rhBMP-2 and DBP do not affect all the same genes or in the same ways.

Introduction: Demineralized bone powder (DBP) induces chondrogenic differentiation of human dermal fibroblasts (hDFs) in 3D culture, but the initiating mechanisms have not been identified. We tested the hypotheses that DBP would affect expression of signaling genes and that DBP's effects would differ from the effects of bone morphogenetic proteins (BMPs).

Materials and Methods: A chondroinduction model was used in which hDFs were cultured with and without DBP in a porous collagen sponge. BMP-2 was delivered in a square of absorbable collagen felt inserted into a collagen sponge. Total RNA was isolated after 3 days of culture, a time that precedes expression of the chondrocyte phenotype. Gene expression was evaluated with two targeted macroarray screens. Effects of DBP and rhBMP-2 were compared by macroarray, RT-PCR, and Northern hybridization analysis of selected genes in the transforming growth factor (TGF)-β/BMP signaling pathways.

Results: By macroarray analysis of 16 signal transduction pathways, the following pathways were modulated in hDFs by DBP: TGF-β, insulin/LDL, hedgehog, PI3 kinase/AKT, NF-κB, androgen, retinoic acid, and NFAT. There was convergence and divergence in DBP and rhBMP-2 regulation of genes in the TGF-β/BMP signaling pathway. Smad target genes were the predominant group of DBP- or rhBMP-2-regulated genes. Several genes (IGF-BP3, ID2, and ID3) showed similar responses (increased expression) to DBP and rhBMP-2. In contrast, many of the genes that were greatly upregulated by DBP (TGFBI/βig-h3, Col3A1, TIMP1, p21/Waf1/Cip1) were barely affected by rhBMP-2.

Conclusion: These findings indicate that multiple signaling pathways are regulated in fibroblasts by DBP, that one of the major pathways involves Smad target genes, and that DBP and rhBMP-2 elicit different gene expression responses in hDFs. Although BMP-2 was originally isolated as a putative inductive factor in DBP, rhBMP-2 and DBP do not affect all the same genes or in the same ways.
Human Bone Marrow Stromal Cells Protect Prostate Cancer Cells From TRAIL-Induced Apoptosis
Authors: Nyambo Rachel , Cross Neil , Lippitt Jenny , Holen Ingunn , Bryden Gorden , Hamdy Freddie C , Eaton Colby L
Published: April 2006

Tumor-derived OPG has recently been shown to protect prostate cancer cells from apoptosis. This study has confirmed that bone marrow stromal cell-derived OPG also suppresses cytokine-induced apoptosis in this tumor type, suggesting that it may be the presence of bone-derived OPG that is responsible for the observed preference of these cells in colonizing the skeleton.

Introduction: Metastasis to the skeleton occurs in around 70% of patients with advanced prostate cancer (CaP), suggesting that the bone microenvironment may provide factors that favor the growth and survival of prostate cancer cells. Osteoprotegerin (OPG) is a molecule involved in bone remodeling, where it acts as an inhibitor of osteoclastogenesis, but it is also a decoy receptor for TRAIL/Apo 2L, a member of the TNF family of pro-apoptotic cytokines. The aim of this study was to determine whether OPG produced by human bone marrow stromal cells could protect prostate cancer cells from TRAIL-induced apoptosis.

Materials and Methods: Human bone marrow stromal cell cultures were generated from bone biopsies taken from newly diagnosed untreated CaP patients with (M1) or without (M0) bony metastasis. The stromal origin of these cells was confirmed by Western blot analysis using antibodies raised to stromal and epithelial markers. Media were conditioned over the cultures of these cells for 4 days, and levels of OPG were determined using an ELISA. The human prostate cancer cell line PC3 was challenged with TRAIL (50 ng/ml) in fresh media or in media supplemented with 50% conditioned media, and apoptosis was assessed using DAPI stain. The effects of specific removal of OPG activity by immunoprecipitation or by co-treatment of cultures with an alternative ligand for OPG (RANKL) were also tested.

Results and Conclusions: The presence of stromal cell conditioned media in PC3 culture significantly reduced TRAIL-induced apoptosis. All stromal cell lines isolated were shown to express OPG and to release this protein into the conditioned media. Immunoprecipitation of OPG and co-treatment of cultures with sRANKL reversed the protective effects of the conditioned media. These data suggest that at least part of the survival advantage gained by CaP cells in colonizing bone may be caused by the production of OPG by tumor-associated stromal cells.
An Improved Segmentation Method for In Vivo μCT Imaging
Authors: Waarsing Jan H , Day Judd S , Weinans Harrie
Published: April 2006

Image segmentation methods for μCT can influence the accuracy of bone morphometry calculations. A new automated segmentation method is introduced, and its performance is compared with standard segmentation methods. The new method can improve the results of in vivo μCT, where the need to keep radiation dose low limits scan quality.

Introduction: An important topic for μCT analysis of bone samples is the segmentation of the original reconstructed grayscale data sets to separate bone from non-bone. Problems like noise, resolution limitations, and beam-hardening make this a nontrivial issue. Inappropriate segmentation methods will reduce the potential power of μCT and may introduce bias in the architectural measurements, in particular, when new in vivo μCT with its inherent limitations in scan quality is used. Here we introduce a new segmentation method using local thresholds and compare its performance to standard global segmentation methods.

Material and Methods: The local threshold method was validated by comparing the result of the segmentation with histology. Furthermore, the effect of choosing this new method versus standard segmentation methods using global threshold values was investigated by studying the sensitivity of these methods to signal to noise ratio and resolution.

Results: Using the new method on high-quality scans yielded accurate results and virtually no differences between histology and the segmented data sets could be observed. When prior knowledge about the volume fraction of the bone was available the global threshold also resulted in appropriate results. Degrading the scan quality had only minor effects on the performance of the new segmentation method. Although global segmentation methods were not sensitive to noise, it was not possible to segment both lower mineralized thin trabeculae and the higher mineralized cortex correctly with the same threshold value.

Conclusion: At high resolutions, both the new local and conventional global segmentation methods gave near exact representations of the bone structure. When scanned samples are not homogenous (e.g., thick cortices and thin trabeculae) and when resolution is relatively low, the local segmentation method outperforms global methods. It maximizes the potential of in vivo μCT by giving good structural representation without the need to use longer scanning times that would increase absorption of harmful X-ray radiation by the living tissue.
Transient Retention of Endochondral Cartilaginous Matrix With Bisphosphonate Treatment in a Long-Term Rabbit Model of Distraction Osteogenesis
Authors: Smith Elisabeth J , McEvoy Anthony , Little David G , Baldock Paul A , Eisman John A , Gardiner Edith M
Published: April 2006

Bisphosphonates induce major increases in strength of callus in distraction osteogenesis in the short term. Poor understanding of the underlying mechanism, however, raises concerns about long-term consequences. In this long-term study in 32 rabbits, zoledronic acid transiently increased trabeculae by delayed temporal progression of endochondral bone remodeling but did not prevent radiographic completion of bone repair.

Introduction: We hypothesized that bisphosphonate inhibition of osteoclast-mediated resorption would retain bone during repair, producing a larger callus in the short term. However, if remodeling was not restored, completion of the bone repair process in the long term could be jeopardized.

Materials and Methods: Juvenile rabbits underwent right tibial osteotomy and 2 weeks of distraction, followed by a period of consolidation. Animals received saline (controls) or zoledronic acid (ZA; 0.1 mg/kg at surgery and again 2 weeks later), and distracted tibias were examined by radiograph, DXA, histology, and histomorphometry at 2, 4, 6, 18, and 44 weeks after surgery.

Results: Regenerated bone in ZA-treated animals was denser than controls on radiographs at 6 weeks and had more distinct radiodense trabeculae and retention of original cortices at 18 weeks. By 44 weeks, controls and ZA-treated animals were radiographically healed and indistinguishable. Regenerate BMD and BMC increased between 2 and 4 weeks in all animals, with a greater effect in ZA. At 6 weeks, BMD and BMC in ZA-treated animals were 1.6- and 2-fold greater, respectively, than controls (p < 0.01). From 6 to 44 weeks, the control values gradually increased and approached the ZA-treated values. Regenerate bone volume and trabecular number by histomorphometry were from 1.6- to 2-fold greater in ZA-treated animals at 6 and 18 weeks (p < 0.05). Endochondral cartilaginous matrix volume was up to 2.4-fold greater in ZA-treated animals at 2 and 4 weeks (p < 0.05). TRACP+ cells in ZA-treated animals were larger with more nuclei. Mineral apposition rate and osteoblast number and surface were lower in ZA-treated animals at 6 weeks (p < 0.01) but not at later times.

Conclusions: Disruption of TRACP+ cell function by ZA during bone regeneration seems to lead to an accretion of cancellous bone built on a larger endochondral cartilaginous matrix and increased bone mass, consistent with reported increases in short-term callus strength. This increase in bone mass, caused by a delay in remodeling, provided a transient advantage without preventing radiographic completion of the bone repair process in the long term. Noncontinuous treatment with nitrogen-containing bisphosphonates thus can have short-term beneficial effects without preventing long-term bone repair.
Bone Remodeling Increases Substantially in the Years After Menopause and Remains Increased in Older Osteoporosis Patients
Authors: Recker Robert , Lappe Joan , Davies K Michael , Heaney Robert
Published: April 2006

Bone remodeling rates (Ac.f) were measured in transilial biopsy specimens from 50 healthy premenopausal women before and 1 year after menopause, in 34 healthy women 13 years past menopause, and in 89 women with untreated osteoporosis. Ac.f nearly doubled 1 year after menopause, tripled 13 years after menopause, and remained elevated in women with osteoporosis.

Introduction: Increased bone remodeling rates are associated with increased skeletal fragility independent of bone mass, partially accounting for the age-related increase in fracture risk in women that is independent of bone loss. We examined bone remodeling rates before and after menopause and in women with osteoporosis by measurements of activation frequency (Ac.f, #/year) in transilial bone biopsy specimens.

Materials and Methods: We recruited 75 women, >46 years old, who had premenopausal estradiol and gonadotropin levels and regular menses. During 9.5 years of observation, 50 women experienced normal menopause and had 2 transilial bone biopsy specimens after tetracycline labeling, one at the beginning of observation and the second 12 months after the last menses, when serum follicle-stimulating hormone (FSH) was >75 mIU/ml and serum estradiol was <20 pg/ml. Ac.f was also computed for a group of older healthy postmenopausal women and a group of women with untreated osteoporosis studied earlier by the same biopsy (Bx) and labeling protocol.

Results: Median Ac.f rose from 0.13/year to 0.24/year (p < 0.001) across menopause and was greater still in the older normals (p < 0.008) than in the second Bx. Ac.f was not significantly greater in the osteoporosis patients than in the older postmenopausal normals.

Conclusion: Bone remodeling rates double at menopause, triple 13 years later, and remain elevated in osteoporosis. This change contributes to increases in age-related skeletal fragility in women.
Malignant Autosomal Recessive Osteopetrosis Caused by Spontaneous Mutation of Murine Rank
Authors: Kapur Raj P , Yao Zhenqiang , Iida Malissa HK , Clarke Christine M , Doggett Barbara , Xing Lianping , Boyce Brendan F
Published: April 2006

We report the first case of lethal autosomal recessive osteopetrosis in mice caused by a spontaneous 8-bp deletion in exon 2 of the Rank gene. The phenotype, including a block in RANKL-dependent osteoclast differentiation and lymph node agenesis, copies that of Rank−/− mice, which have been produced by targeted recombination.

Introduction: Commitment of osteoclast progenitors to the osteoclast lineage requires RANKL/RANK-mediated intercellular signals. Gene-targeted defects in this signaling pathway resulted in osteoclast deficiency and severe osteopetrosis in mice, but to date, there have been no reports of spontaneous mutations in Rankl or Rank resulting in osteopetrosis.

Materials and Methods: Mice with malignant osteopetrosis and absent lymph nodes appeared spontaneously in a highly inbred colony. Appropriate crosses were analyzed to establish the pattern of inheritance. Tissues from affected pups and littermates were evaluated grossly, histopathologically, and radiographically. Osteoclast development from splenocytes was tested in vitro under a variety of conditions, including after infection with RANK-encoding retrovirus. Rank mutational analysis was performed by direct sequencing of RT-PCR products and genomic DNA.

Results: The inheritance pattern was consistent with autosomal recessive inheritance, and the phenotype resembled that of either Rankl or Rank knockout mice with the exception of as yet unexplained death of most mice 2–3 weeks after weaning. Osteoclast precursors from the spleens of affected pups failed to form osteoclasts in vitro when stimulated with macrophage-colony stimulating factor (M-CSF) and RANKL, unless they were forced to express wildtype Rank cDNA. Molecular genetic studies identified an 8-bp deletion in exon 2 of the Rank gene. The resulting allele, termed Rankdel8, encodes only a small portion of the RANK extracellular domain, which is probably nonfunctional.

Conclusions: The phenotypic similarities between Rankdel8 and mice previously described with a combined insertion and deletion in Rank confirm the role of this receptor in osteoclastogenesis and lymph node development and suggest that some forms of malignant osteopetrosis in humans could result from a similar defect.
Possible Roles of Runx1 and Sox9 in Incipient Intramembranous Ossification
Authors: Yamashiro Takashi , Wang Xiu-Ping , Li Zhe , Oya Shinji , Åberg Thomas , Fukunaga Tomohiro , Kamioka Hiroshi , Speck Nancy A , Takano-Yamamoto Teruko , Thesleff Irma
Published: April 2006

We evaluated the detailed expression patterns of Runx1 and Sox9 in various types of bone formation, and determined whether Runx1 expression was affected by Runx2 deficiency and Runx2 expression by Runx1 deficiency. Our results indicate that both Runx1 and Sox9 are intensely expressed in the future osteogenic cell compartment and in cartilage. The pattern of Runx1 and Sox9 expression suggests that both genes could potentially be involved in incipient intramembranous bone formation during craniofacial development.

Introduction: Runx1, a gene essential for hematopoiesis, contains RUNX binding sites in its promoter region, suggesting possible cross-regulation with Runx2 and potential regulatory roles in bone development. On the other hand, Sox9 is essential for chondrogenesis, and haploinsufficiency of Sox9 leads to premature ossification of the skeletal system. In this study, we studied the possible roles of Runx1 and Sox9 in bone development.

Materials and Methods: Runx1, Runx2/Osf2, and Sox9 expression was evaluated by in situ hybridization in the growing craniofacial bones of embryonic day (E)12–16 mice and in the endochondral bone-forming regions of embryonic and postnatal long bones. In addition, we evaluated Runx2/Osf2 expression in the growing face of Runx1 knockout mice at E12.5 and Runx1 expression in Runx2 knockout mice at E14.5.

Results: Runx1 and Sox9 were expressed in cartilage, and the regions of expression expanded to the neighboring Runx2-expressing osteogenic regions. Expression of both Runx1 and Sox9 was markedly downregulated on ossification. Runx1 and Sox9 expression was absent in the regions of endochondral bone formation and in actively modeling or remodeling bone tissues in the long bones as well as in ossified craniofacial bones. Runx2 expression was not affected by gene disruption of Runx1, whereas the expression domains of Runx1 were extended in Runx2−/− mice compared with wildtype mice.

Conclusions: Runx1 and Sox9 are specifically expressed in the osteogenic cell compartments in the craniofacial bones and the bone collar of long bones, and this expression is downregulated on terminal differentiation of osteoblasts. Our results suggest that Runx1 may play a role in incipient intramembranous bone formation.
Bone Fragility and Collagen Cross-Links
Authors: Paschalis Eleftherios P , Shane Elizabeth , Lyritis George , Skarantavos Grigoris , Mendelsohn Richard , Boskey Adele L
Published: April 2006

Infrared imaging analysis of iliac crest biopsy specimens from patients with osteoporotic and multiple spontaneous fractures shows significant differences in the spatial variation of the nonreducible:reducible collagen cross-links at bone-forming trabecular surfaces compared with normal bone.

Introduction: Although the role of BMC and bone mineral quality in determining fracture risk has been extensively studied, considerably less attention has been paid to the quality of collagen in fragile bone.

Materials and Methods: In this study, the technique of Fourier transform infrared imaging (FTIRI) was used to determine the ratio of nonreducible:reducible cross-links, in 2- to 4-μm-thick sections, from human iliac crest biopsy specimens (N = 27) at bone-forming trabecular surfaces. The biopsy specimens were obtained from patients that had been diagnosed as high- or low-turnover osteoporosis, as well as premenopausal women <40 years of age, with normal BMD and biochemistry, who suffered multiple spontaneous fractures. The obtained values were compared with previously published analyses of trabecular bone from normal non-osteoporotic subjects (N = 14, 6 males and 8 females; age range, 51–70 years).

Results and Conclusions: Collagen cross-links distribution within the first 50 μm at forming trabecular surfaces in patients with fragile bone was markedly different compared with normal bone.
Epidemiology of Childhood Fractures in Britain: A Study Using the General Practice Research Database
Authors: Cooper Cyrus , Dennison Elaine M , Leufkens Herbert GM , Bishop Nicholas , van Staa Tjeerd P
Published: April 2006

A population-based British cohort study, including ∼6% of the population, was used to derive age- and sex-specific incidence rates of fractures during childhood. Fractures were more common among boys than girls, with peak incidences at 14 and 11 years of age, respectively. At childhood peak, incidence rates were only surpassed later in life at 85 years of age among women and never among men.

Introduction: Fractures account for 25% of accidents and injuries in childhood; however, the descriptive epidemiology of childhood fractures remains uncertain.

Materials and Methods: Age- and sex-specific incidence rates for fractures at various skeletal sites were derived from the General Practice Research Database (a population-based British cohort containing computerized medical records of ∼7,000,000 residents) between 1988 and 1998.

Results: A total of 52,624 boys and 31,505 girls sustained one or more fractures over the follow-up period, for a rate of 133.1/10,000 person-years. Fractures were more common in boys (161.6/10,000 person-years) than girls (102.9/10,000 person-years). The most common fracture in both sexes was that of the radius/ulna (30%). Fracture incidence was greater among boys than girls at all ages, with the peak incidence at 14 years of age among boys and 11 years of age among girls. Marked geographic variation was observed in standardized fracture incidence, with significantly (p < 0.01) higher rates observed in Northern Ireland, Wales, and Scotland compared with southeast England.

Conclusions: Fractures are a common problem in childhood, with around one-third of boys and girls sustaining at least one fracture before 17 years of age. Rates are higher among boys than girls, and male incidence rates peak later than those among females. At their childhood peak, the incidence of fractures (boys, 3%; girls, 1.5%) is only surpassed at 85 years of age among women and never among men. The most common site affected in both genders is the radius/ulna. Studies to clarify the pathogenesis of these fractures, emphasizing bone fragility, are now required.
Primary Prevention of Osteoporosis: Mass Screening Scenario or Prescreening With Questionnaires? An Economic Perspective
Authors: Richy Florent , Ethgen Olivier , Bruyere Olivier , Mawet Audrey , Reginster Jean-Yves
Published: April 2006

This study focuses on the controversy surrounding selective approaches to screen for osteoporosis. Seven screening approaches were compared in terms of cost-effectiveness and incremental cost-effectiveness ratios in a sample of 4035 postmenopausal women. Our results show that certain prescreening strategies are more efficient than DXA-based approaches. These results are of considerable value for health policy decision-makers and the scientific community.

Introduction: There is no general consensus on the most efficient strategy to use bone densitometry for osteoporosis screening. Two distinct approaches have progressively emerged: mass screening using DXA and prescreening strategies using user-friendly risk indices. This study was designed to compare the efficiency of these approaches.

Materials and Methods: A database of 4035 medical records from postmenopausal women above 45 years was analyzed. In the first scenario, women were systematically referred to DXA if above 45, 50, or 65 years of age. The second scenario involved the validated prescreening tools SCORE, ORAI, OST, and OSIRIS and assessed two separate ways of handling their results (theoretical and pragmatic). The cost of a DXA test was set as the median Belgian value: 40.14£. All strategies were compared in terms of cost exposed per osteoporotic patient detected and in terms of incremental cost-effectiveness ratios.

Results: In the systematic DXA strategies, the cost per patient detected ranged from 123£ when measuring all women >45 years of age to 91£ when focusing on women >65 years of age. The corresponding percentage of cases detected ranged from 100% (age > 45 years) to 50% (age > 65 years). When considering prescreening under the theoretical and pragmatic scenarios, the OSIRIS index provided the best efficiency, with costs of 74£ (theoretical) to 85£ (pragmatic) per case detected, followed by ORAI (75£ and 96£), OST (84£ and 94£), and SCORE (96£ and 103£). The corresponding percentage of cases detected ranged from 89% (SCORE) to 75% (OSIRIS). The cost-effectiveness analysis showed that mass screening strategies over 50 and 65 years of age and using ORAI were best.

Conclusions: Our study sets the grounds for considering, in a health economics perspective, prescreening tools as valuable, cost-effective, approaches to significantly reduce the economic burden of osteoporosis screening.
Decreased BMD and Limb Deformities in Mice Carrying Mutations in Both Lrp5 and Lrp6
Authors: Holmen Sheri L , Giambernardi Troy A , Zylstra Cassandra R , Buckner-Berghuis Bree D , Resau James H , Hess J Fred , Glatt Vaida , Bouxsein Mary L , Ai Minrong , Warman Matthew L , Williams Bart O
Published: April 2006

Humans and mice lacking Lrp5 have low BMD. To evaluate whether Lrp5 and Lrp6 interact genetically to control bone or skeletal development, we created mice carrying mutations in both Lrp5 and the related gene Lrp6. We found that compound mutants had dose-dependent deficits in BMD and limb formation, suggesting functional redundancy between these two genes in bone and limb development.

Introduction: Lrp5 and Lrp6 are closely related members of the low density lipoprotein receptor family and are co-receptors for Wnt ligands. While Lrp5 mutations are associated with low BMD in humans and mice, the role of Lrp6 in bone formation has not been analyzed.

Materials and Methods: To address whether Lrp5 and Lrp6 play complimentary roles in bone and skeletal development, we created mice with mutations in both genes. We inspected limbs of mice from the different genotypic classes of compound mutants to identify abnormalities. DXA and μCT were used to evaluate the effect of mutations in Lrp5 and Lrp6 on BMD and microarchitecture.

Results: Mice heterozygous for mutations in Lrp6 and either heterozygous or homozygous for a mutation in Lrp5 (Lrp6+/−;Lrp5+/− or Lrp6+/−;Lrp5−/−) display limb defects with incomplete penetrance and variable expression. DXA analysis showed that BMD decreased as mice progressively were more deficient in Lrp5 and Lrp6. Lrp6+/−;Lrp5−/− mice were more severely affected than Lrp6+/+;Lrp5−/− mice, whereas Lrp6+/−;Lrp5+/− mice had statistically higher BMD than Lrp6+/+;Lrp5−/− mice and lower BMD compared with wildtype mice and mice heterozygous for either mutation alone.

Conclusions: Lrp6 and Lrp5 genetically interact in limb development in mice. Furthermore, heterozygosity for an inactivating mutation in Lrp6 further reduces BMD in both male and female mice lacking Lrp5.
Whole Body BMC in Pediatric Crohn Disease: Independent Effects of Altered Growth, Maturation, and Body Composition
Authors: Burnham Jon M , Shults Justine , Semeao Edisio , Foster Bethany , Zemel Babette S , Stallings Virginia A , Leonard Mary B
Published: April 2006

Whole body BMC was assessed in 104 children and young adults with CD and 233 healthy controls. CD was associated with significant deficits in BMC and lean mass, relative to height. Adjustment for lean mass eliminated the bone deficit in CD. Steroid exposure was associated with short stature but not bone deficits relative to height.

Introduction: Children with Crohn disease (CD) have multiple risk factors for impaired bone accrual. The confounding effects of poor growth and delayed maturation limit the interpretation of prior studies of bone health in CD. The objective of this study was to assess BMC relative to growth, body composition, and maturation in CD compared with controls.

Materials and Methods: Whole body BMC and lean mass were assessed by DXA in 104 CD subjects and 233 healthy controls, 4–26 years of age. Multivariable linear regression models were developed to sequentially adjust for differences in skeletal size, pubertal maturation, and muscle mass. BMC-for-height z scores were derived to determine CD-specific covariates associated with bone deficits.

Results: Subjects with CD had significantly lower height z score, body mass index z score, and lean mass relative to height compared with controls (all p < 0.0001). After adjustment for group differences in age, height, and race, the ratio of BMC in CD relative to controls was significantly reduced in males (0.86; 95% CI, 0.83, 0.94) and females (0.91; 95% CI, 0.85, 0.98) with CD. Adjustment for pubertal maturation did not alter the estimate; however, addition of lean mass to the model eliminated the bone deficit. Steroid exposure was associated with short stature but not bone deficits.

Conclusion: This study shows the importance of considering differences in body size and composition when interpreting DXA data in children with chronic inflammatory conditions and shows an association between deficits in muscle mass and bone in pediatric CD.
Management of Bone Loss After Organ Transplantation
Authors: Cohen Adi , Sambrook Philip , Shane Elizabeth
Published: April 2006

Organ transplant recipients experience rapid bone loss and high fracture rates, particularly during the early post-transplant period. Early rapid bone loss occurs in the setting of uncoupled bone turnover with increased bone resorption and decreased bone formation. Because there are no clinical factors that reliably predict post-transplant bone loss and fractures in the individual patient, all transplant recipients should be considered candidates for early preventive therapy for osteoporosis. Long-term transplant recipients with densitometric osteoporosis and/or fractures should also receive treatment. Although active metabolites of vitamin D and bisphosphonates have both shown efficacy, data from clinical trials suggest that bisphosphonates are the safest and most consistently effective agents for the prevention and treatment of post-transplantation osteoporosis in adults. Kidney transplant recipients represent a special population, and more research is needed to delineate the risks and benefits of treating bone disease in these patients.
Regulation of Human Osteoclast Differentiation by Thioredoxin Binding Protein-2 and Redox-Sensitive Signaling
Authors: Aitken Cathy J , Hodge Jason M , Nishinaka Yumiko , Vaughan Tanya , Yodoi Junji , Day Christopher J , Morrison Nigel A , Nicholson Geoffrey C
Published: April 2006

Differential expression of TBP-2 and Trx-1 occurs during osteoclastogenesis. Adenoviral overexpression of TBP-2 in osteoclast precursors inhibits Trx-1 expression, osteoclast formation, and AP-1 binding activity. TBP-2 and Trx-1 are key regulators of osteoclastogenesis.

Introduction: Thioredoxin binding protein-2 (TBP-2) negatively regulates thioredoxin-1 (Trx-1), a key endogenous modulator of cellular redox and signaling. In gene array analysis, we found that TBP-2 expression was reduced during human osteoclast differentiation compared with macrophage differentiation. Our aim was to determine the roles of TBP-2 and Trx-1 in human osteoclastogenesis and RANKL signaling.

Materials and Methods: Osteoclasts or macrophages were generated from colony-forming unit-granulocyte macrophage (CFU-GM) precursors treated with sRANKL and macrophage-colony-stimulating factor (M-CSF), or M-CSF alone, respectively. Expression of TBP-2 and Trx-1 was quantified by real-time PCR and Western analysis. Adenoviral gene transfer was used to overexpress TBP-2 in precursors. NF-κB and activator protein 1 (AP-1) signaling was assessed with EMSA.

Results: In the presence of sRANKL, expression of TBP-2 was decreased, whereas Trx-1 expression was increased. The antioxidant N-acetylcysteine reversed this pattern and markedly inhibited osteoclastogenesis. Adenoviral overexpression of human TBP-2 in precursors inhibited osteoclastogenesis and Trx-1 expression, inhibited sRANKL-induced DNA binding of AP-1, but enhanced sRANKL-induced DNA binding of NF-κB.

Conclusions: These data support significant roles for TBP-2 and the Trx system in osteoclast differentiation that are mediated by redox regulation of AP-1 transcription. A likely mechanism of stress signal induction of bone resorption is provided. Modulators of the Trx system such as antioxidants have potential as antiresorptive therapies.
Decreased Bone Formation and Osteopenia in Mice Lacking α-Calcitonin Gene-Related Peptide
Authors: Schinke Thorsten , Liese Sarah , Priemel Matthias , Haberland Michael , Schilling Arndt F , Catala-Lehnen Philip , Blicharski Dagmar , Rueger Johannes M , Gagel Robert F , Emeson Ronald B , Amling Michael
Published: April 2006

We recently described an unexpected high bone mass phenotype in mice lacking the Calca gene that encodes CT and αCGRP. Here we show that mice specifically lacking αCGRP expression display an osteopenia caused by a decreased bone formation. These results show that αCGRP is a physiological activator of bone formation and that the high bone mass phenotype of the Calca-deficient mice is caused by the absence of CT.

Introduction: Calcitonin (CT) and α-calcitonin gene-related peptide (αCGRP) are two polypeptides without completely defined physiologic functions that are both derived from the Calca gene by alternative splicing. We have recently described an unexpected high bone mass phenotype in mice carrying a targeted deletion of the Calca gene. To uncover whether this phenotype is caused by the absence of CT or by the absence of αCGRP, we analyzed a mouse model, where the production of αCGRP is selectively abolished.

Materials and Methods: Bones from Calca−/− mice, αCGRP−/− mice, and their corresponding wildtype controls were analyzed using radiography, μCT imaging, and undecalcified histology. Cellular activities were assessed using dynamic histomorphometry and by measuring the urinary collagen degradation products. CT expression was determined using radioimmunoassay and RT-PCR. Immunohistochemistry was performed using an anti-CGRP antibody on decalcified bone sections.

Results: Unlike the Calca-deficient mice, the αCGRP-deficient mice do not display a high bone mass phenotype. In contrast, they develop an osteopenia that is caused by a reduced bone formation rate. Serum levels and thyroid expression of CT are not elevated in αCGRP-deficient mice. While CGRP expression is detectable in neuronal cell close to trabecular bone structures, the components of the CGRP receptor are expressed in differentiated osteoblast cultures.

Conclusion: The discrepancy between the bone phenotypes of Calca−/− mice and αCGRP−/− mice show that the high bone mass phenotype of the Calca−/− mice is caused by the absence of CT. The osteopenia observed in the αCGRP−/− mice that have normal levels of CT further show that αCGRP is a physiologic activator of bone formation.
Population-Based Study of Age and Sex Differences in Bone Volumetric Density, Size, Geometry, and Structure at Different Skeletal Sites
Authors: Riggs B Lawrence , Melton L Joseph , Robb Richard A , Camp Jon J , Atkinson Elizabeth J , Peterson James M , Rouleau Peggy A , McCollough Cynthia H , Bouxsein Mary L , Khosla Sundeep
Published: April 2006

In a population-based, cross-sectional study, we assessed age- and sex-specific changes in bone structure by QCT. Over life, the cross-sectional area of the vertebrae and proximal femur increased by ∼15% in both sexes, whereas vBMD at these sites decreased by 39–55% and 34–46%, respectively, with greater decreases in women than in men.

Introduction: The changes in bone structure and density with aging that lead to fragility fractures are still unclear.

Materials and Methods: In an age- and sex-stratified population sample of 373 women and 323 men (age, 20–97 years), we assessed bone geometry and volumetric BMD (vBMD) by QCT at the lumbar spine, femoral neck, distal radius, and distal tibia.

Results: In young adulthood, men had 35–42% larger bone areas than women (p < 0.001), consistent with their larger body size. Bone area increased equally over life in both sexes by ∼15% (p < 0.001) at central sites and by ∼16% and slightly more in men at peripheral sites. Decreases in trabecular vBMD began before midlife and continued throughout life (p < 0.001), whereas cortical vBMD decreases began in midlife. Average decreases in trabecular vBMD were greater in women (−55%) than in men (−46%, p < 0.001) at central sites, but were similar (−24% and −26%, respectively) at peripheral sites. With aging, cortical area decreased slightly, and the cortex was displaced outwardly by periosteal and endocortical bone remodeling. Cortical vBMD decreased over life more in women (∼25%) than in men (∼18%, p < 0.001), consistent with menopausal-induced increases in bone turnover and bone porosity.

Conclusions: Age-related changes in bone are complex. Some are beneficial to bone strength, such as periosteal apposition with outward cortical displacement. Others are deleterious, such as increased subendocortical resorption, increased cortical porosity, and, especially, large decreases in trabecular vBMD that may be the most important cause of increased skeletal fragility in the elderly. Our findings further suggest that the greater age-related decreases in trabecular and cortical vBMD and perhaps also their smaller bone size may explain, in large part, why fragility fractures are more common in elderly women than in elderly men.
Upregulation of Osteopontin by Osteocytes Deprived of Mechanical Loading or Oxygen
Authors: Gross Ted S , King Katy A , Rabaia Natalia A , Pathare Pranali , Srinivasan Sundar
Published: April 2006

The pathway(s) by which disuse is transduced into locally mediated osteoclastic resorption remain unknown. We found that both acute disuse (in vivo) and direct hypoxia (in vitro) induced rapid upregulation of OPN expression by osteocytes. Within the context of OPN's role in osteoclast migration and attachment, hypoxia-induced osteocyte OPN expression may serve to mediate disuse-induced bone resorption.

Introduction: We have recently reported that disuse induces osteocyte hypoxia. Because hypoxia upregulates osteopontin (OPN) in nonconnective tissue cells, we hypothesized that both disuse and hypoxia would rapidly elevate expression of OPN by osteocytes.

Materials and Methods: The response of osteocytes to 24 h of disuse was explored by isolating the left ulna diaphysis of adult male turkeys from loading (n = 5). Cortical osteocytes staining positive for OPN were determined using immunohistochemistry and confocal microscopy. In vitro experiments were performed to determine if OPN expression was altered in MLO-Y4 osteocytes by direct hypoxia (3, 6, 24, and 48 h) or hypoxia (3 and 24 h) followed by 24 h of reoxygenation. A final in vitro experiment explored the potential of protein kinase C (PKC) to regulate hypoxia-induced osteocyte OPN mRNA alterations.

Results: We found that 24 h of disuse significantly elevated osteocyte OPN expression in vivo (145% versus intact bones; p = 0.02). We confirmed this finding in vitro, by observing rapid and significant upregulation of OPN protein expression after 24 and 48 h of hypoxia. Whereas 24 h of reoxygenation after 3 h of hypoxia restored normal osteocyte OPN expression levels, 24 h of reoxygenation after 24 h of hypoxia did not mitigate elevated osteocyte OPN expression. Finally, preliminary inhibitor studies suggested that PKC serves as a potent upstream regulator of hypoxia-induced osteocyte OPN expression.

Conclusions: Given the documented roles of OPN as a mediator of environmental stress (e.g., hypoxia), an osteoclast chemotaxant, and a modulator of osteoclastic attachment to bone, we speculate that hypoxia-induced osteocyte OPN expression may serve to mediate disuse-induced osteoclastic resorption. Furthermore, it seems that a brief window of time exists in which reoxygenation (as might be achieved by reloading bone) can serve to inhibit this pathway.