bluuebunny/crossref_metadata_2025_split huggingface dataset:
Expression Patterns of Matrix Metalloproteinases and Vascular Endothelial Growth Factor During Epiphyseal Ossification
Authors: Álvarez Jesús , Costales Lorena , Serra Rosa , Balbín Milagros , López José M 
Published: April 2006

Abstract
In situ hybridization studies allowed for the localization of three MMPs and the angiogenic factor VEGF during secondary ossification. MMPs were widely expressed during ossification of the secondary center, whereas expression of VEGF was restricted to later stages.
Introduction: The spatiotemporal expression patterns of the matrix metalloproteinases gelatinase-B (MMP-9), collagenase-3 (MMP-13), and membrane-type 1 metalloproteinase (MMP-14) and the angiogenic peptide vascular endothelial growth factor (VEGF) were studied during development of the proximal epiphysis of the rat tibia.
Materials and Methods: Cell expression was analyzed by in situ hybridization. Studies on osteoclastic activity, matrix mineralization, cell proliferation, and vascular progression were also performed.
Results: MMP-9, MMP-13, and MMP-14 were expressed in discrete perichondrial cells that gave way to sites of intrachondral canal formation. High expression levels for the three MMPs were found at the blind ends of advancing intrachondral canals and at the expanding borders of the marrow space. Signals for MMP-9 and MMP-13 were in close proximity but did not overlap, whereas MMP-14 was expressed in both MMP-9+ and MMP-13+ cells. VEGF was not expressed during formation of intrachondral vascular canals but was observed in hypertrophic chondrocytes during formation of the bone marrow cavity.
Conclusions: Expression of MMPs and VEGF are constant events during development of the secondary ossification center. We propose that MMPs are involved in targeting proteolytic activity during epiphyseal development. VEGF is not expressed during early formation of vascular canals, but it may have a role in the formation of the bone marrow cavity.
Annexin II Stimulates RANKL Expression Through MAPK
Authors: Li Fanghong , Chung HoYeon , Reddy Sakamuri V , Lu Ganwei , Kurihara Noriyoshi , Zhao Allan Z , Roodman G David 
Published: April 2006

Abstract
We report that AX-II, in addition to inducing GM-CSF expression, also increases membrane-bound RANKL synthesis by marrow stromal cells and does so through a previously unreported MAPK-dependent pathway. Thus, both GM-CSF and RANKL are required for AX-II stimulation of OCL formation.
Introduction: Annexin II (AX-II) is an autocrine/paracrine factor secreted by osteoclasts (OCLs) that stimulates human OCL formation and bone resorption in vitro by inducing bone marrow stromal cells and activated CD4+ T cells to produce granulocyte-macrophage colony-stimulating factor (GM-CSF). GM-CSF in turn increases OCL precursor proliferation and further enhances OCL formation. However, the induction of GM-CSF by AX-II cannot fully explain its effects on OCL formation. In this study, we tested the capacity of AX-II to induce the expression of RANKL and the corresponding signaling pathways AX-II employs in human marrow stromal cells to induce RANKL. We also showed that both GM-CSF and RANKL are required for OCL formation induced by AX-II.
Materials and Methods: Real-time RT-PCR and Western blot analysis were used to detect RANKL and osteoprotegerin (OPG) mRNA and protein expression in unfractionated human bone marrow mononuclear cells stimulated with AX-II. Soluble RANKL in the conditioned medium was analyzed by ELISA. Activation of the MAPK pathway by AX-II was tested by Western blot. The effects of OPG and anti-GM-CSF on AX-II-induced OCL formation were also examined.
Results and Conclusion: In addition to upregulating GM-CSF mRNA, AX-II increased RANKL mRNA expression dose-dependently in unfractionated human bone marrow mononuclear cells and modestly increased soluble RANKL in unfractionated human bone marrow mononuclear cell conditioned medium. However, AX-II markedly increased membrane-bound RANKL on human bone marrow stromal cells. Treatment of marrow stromal cells with AX-II activated MAP-kinase (ERKs) and PD 98059 abolished the effect but did not block the increase in GM-CSF. Interestingly, OPG, a natural decoy receptor for RANKL, or anti-GM-CSF partially inhibited OCL formation by AX-II in human bone marrow cells, and the combination of OPG and anti-GM-CSF completely blocked AX-II-induced OCL formation. These data show that AX-II stimulates both the proliferation and differentiation of OCL precursors through production of GM-CSF and RANKL respectively.
TOPGAL Mice Show That the Canonical Wnt Signaling Pathway Is Active During Bone Development and Growth and Is Activated by Mechanical Loading In Vitro
Authors: Hens Julie R , Wilson Kimberly M , Dann Pamela , Chen Xuesong , Horowitz Mark C , Wysolmerski John J 
Published: April 2006

Abstract
We identified cellular targets of canonical Wnt signaling within the skeleton, which included chondrocytes, osteoblasts, and osteocytes in growing bone, but only osteocytes and chondrocytes in the mature skeleton. Mechanical deformation induced Wnt signaling in osteoblasts in vitro.
Introduction: Genetic evidence in mice and humans has implicated the canonical Wnt signaling pathway in the control of skeletal development and bone mass. However, little is known of the details of Wnt signaling in the skeleton in vivo. We used Wnt indicator TOPGAL mice to identify which cells activated this pathway during bone development and in the mature skeleton.
Materials and Methods: We examined canonical Wnt signaling during embryonic and neonatal bone development in TOPGAL mice. The TOPGAL transgene consists of a β-galactosidase gene driven by a T cell factor (TCF)β-catenin responsive promoter so that canonical Wnt activity can be detected by X-gal staining. Expression of Wnt signaling components was examined in primary calvarial cell cultures by RT-PCR. The effect of mechanical deformation on Wnt signaling was examined in primary calvarial cells grown on collagen I and stretched using Flexercell Tension Plus System FX-4000T. Immunohistochemistry was used to examine the localization of β-catenin in cartilage, bone, and cultured calvarial cells exposed to physical deformation.
Results and Conclusions: Canonical Wnt signaling was active in several cell types in the fetal and neonatal skeleton, including chondrocytes, osteoblasts, and osteocytes. With age, activation of Wnt signaling became less prominent but persisted in chondrocytes and osteocytes. Although osteoblasts in culture expressed many different individual Wnt's and Wnt receptors, the TOPGAL transgene was not active in these cells at baseline. However, Wnt signaling was activated in these cells by physical deformation. Together with the activation of canonical Wnt signaling in osteocytes seen in vivo, these data suggest that Wnt signaling may be involved in the coupling of mechanical force to anabolic activity in the skeleton.
Overexpression of Human PHEX Under the Human β-Actin Promoter Does Not Fully Rescue the Hyp Mouse Phenotype
Authors: Erben Reinhold G , Mayer Dagmar , Weber Karin , Jonsson Kenneth , Jüppner Harald , Lanske Beate 
Published: April 2006

Abstract
XLH in humans and the Hyp phenotype in mice are caused by inactivating Phex mutations. Overexpression of human PHEX under the human β-actin promoter in Hyp mice rescued the bone phenotype almost completely, but did not affect phosphate homeostasis, suggesting that different, possibly independent, pathophysiological mechanisms contribute to hyperphosphaturia and bone abnormalities in XLH.
Introduction: Mutations in PHEX, a phosphate-regulating gene with homologies to endopeptidases on the X chromosome, are responsible for X-linked hypophosphatemia (XLH) in humans, and its mouse homologs, Hyp, PhexHyp-2J, PhexHyp-Duk, Gy and Ska1. PHEX is thought to inactivate a phosphaturic factor, which may be fibroblast growth factor 23 (FGF)-23. Consistent with this hypothesis, FGF-23 levels were shown to be elevated in most patients with XLH and in Hyp mice. The aim of this study was, therefore, to examine whether transgenic overexpression of PHEX under the human β-actin promoter would rescue the Hyp phenotype.
Materials and Methods: We tested this hypothesis by generating two mouse lines expressing human PHEX under the control of a human β-actin promoter (PHEX-tg). With the exception of brain, RT-PCR analyses showed transgene expression in all tissues examined. PHEX protein, however, was only detected in bone, muscle, lung, skin, and heart. To assess the role of the mutant PHEX, we crossed female heterozygous Hyp mice with male heterozygous PHEX-tg mice to obtain wildtype (WT), PHEX-tg, Hyp, and Hyp/PHEX-tg offspring, which were examined at 3 months of age.
Results: PHEX-tg mice exhibited normal bone and mineral ion homeostasis. Hyp mice showed the known phenotype with reduced body weight, hypophosphatemia, hyperphosphaturia, and rickets. Hyp/PHEX-tg mice had almost normal body weight relative to WT controls, showed a dramatic improvement in femoral BMD, almost normal growth plate width, and, despite remaining disturbances in bone mineralization, almost normal bone architecture and pronounced improvements of osteoidosis and of halo formation compared with Hyp mice. However, Hyp and Hyp/PHEX-tg mice had comparable reductions in tubular reabsorption of phosphate and were hypophosphatemic relative to WT controls.
Conclusion: Our data suggest that different, possibly independent, pathophysiological mechanisms contribute to renal phosphate wasting and bone abnormalities in Hyp and XLH.
Femoral Neck Bone Loss Predicts Fracture Risk Independent of Baseline BMD
Authors: Nguyen Tuan V , Center Jacqueline R , Eisman John A 
Published: April 2006

Abstract
Whereas low BMD is known to be a risk factor for fracture, it is not clear whether loss of BMD is also a risk factor. In elderly women, greater loss of BMD at the femoral neck was associated with increased risk of fracture, independent of baseline BMD and age.
Introduction: Baseline measurement of BMD predicts fracture risk. However, it is not clear whether short-term bone loss is an independent risk factor for fractures. This study was designed to investigate the relationship between changes in BMD and fracture risk in elderly women in the general population.
Materials and Methods: A total of 966 women ≥60 years of age (mean, 70 ± 6.7 [SD] years), who had been followed for an average of 10.7 years, were studied. Atraumatic fracture of the proximal femur (hip), symptomatic vertebral fracture, and other major fractures, excluding pathological fractures or those resulting from severe trauma, were recorded and confirmed by radiographs. Femoral neck and lumbar spine BMD was measured by DXA.
Results: During the follow-up period, 224 had sustained a fracture (including 43 hip, 71 symptomatic vertebrae, 37 proximal humerus, 46 forearm and wrist, and 27 rib and pelvis fractures). The annual rate of change in BMD in fracture women (−2.1 ± 4.2%) was significantly higher than that in nonfracture women (−0.8 ± 2.8%; p = 0.005). In the multivariable Cox's proportional hazards analysis, the following factors were significant predictors of fracture risk: femoral neck bone loss (relative hazard [RH], 1.4; 95% CI, 1.1-1.8 per 5% loss), baseline femoral neck BMD (RH, 2.0; 95% CI, 1.7-2.7 per SD), and advancing age (RH, 1.2; 95% CI, 1.1-1.4). The proportion of fractures attributable to the three factors was 45%. For hip fracture, the attributable risk fraction was ∼90%.
Conclusion: Bone loss at the femoral neck is a predictor of fracture risk in elderly women, independent of baseline BMD and age.
Angiogenesis Is Required for Successful Bone Induction During Distraction Osteogenesis
Authors: Fang Tony D , Salim Ali , Xia Wei , Nacamuli Randall P , Guccione Samira , Song HanJoon M , Carano Richard A , Filvaroff Ellen H , Bednarski Mark D , Giaccia Amato J , Longaker Michael T 
Published: April 2006

Abstract
The role of angiogenesis during mechanically induced bone formation is incompletely understood. The relationship between the mechanical environment, angiogenesis, and bone formation was determined in a rat distraction osteogenesis model. Disruption of either the mechanical environment or endothelial cell proliferation blocked angiogenesis and bone formation. This study further defines the role of the mechanical environment and angiogenesis during distraction osteogenesis.
Introduction: Whereas successful fracture repair requires a coordinated and complex transcriptional program that integrates mechanotransductive signaling, angiogenesis, and osteogenesis, the interdependence of these processes is not fully understood. In this study, we use a system of bony regeneration known as mandibular distraction osteogenesis (DO) in which a controlled mechanical stimulus promotes bone induction after an osteotomy and gradual separation of the osteotomy edges to examine the relationship between the mechanical environment, angiogenesis, and osteogenesis.
Materials and Methods: Adult Sprague-Dawley rats were treated with gradual distraction, gradual distraction plus the angiogenic inhibitor TNP-470, or acute distraction (a model of failed bony regeneration). Animals were killed at the end of distraction (day 13) or at the end of consolidation (day 41) and examined with μCT, histology, and immunohistochemistry for angiogenesis and bone formation (n = 4 per time-point per group). An additional group of animals (n = 6 per time-point per group) was processed for microarray analysis at days 5, 9, 13, 21, and 41.
Results and Conclusions: Either TNP-470 administration or disruption of the mechanical environment prevented normal osteogenesis and resulted in a fibrous nonunion. Subsequent analysis of the regenerate showed an absence of angiogenesis by gross histology and immunohistochemical localization of platelet endothelial cell adhesion molecule in the groups that failed to heal. Microarray analysis revealed distinct patterns of expression of genes associated with osteogenesis, angiogenesis, and hypoxia in each of the three groups. Our findings confirm the interdependence of the mechanical environment, angiogenesis, and osteogenesis during DO, and suggest that induction of proangiogenic genes and the proper mechanical environment are both necessary to support new vasculature for bone induction in DO.
Ovariectomy-Induced Bone Loss Varies Among Inbred Strains of Mice
Authors: Bouxsein Mary L , Myers Kelly S , Shultz Kathryn L , Donahue Leah R , Rosen Clifford J , Beamer Wesley G 
Published: April 2006

Abstract
There is a subset of women who experience particularly rapid bone loss during and after the menopause. However, the factors that lead to this enhanced bone loss remain obscure. We show that patterns of bone loss after ovariectomy vary among inbred strains of mice, providing evidence that there may be genetic regulation of bone loss induced by estrogen deficiency.
Introduction: Both low BMD and increased rate of bone loss are risk factors for fracture. Bone loss during and after the menopause is influenced by multiple hormonal factors. However, specific determinants of the rate of bone loss are poorly understood, although it has been suggested that genetic factors may play a role. We tested whether genetic factors may modulate bone loss subsequent to estrogen deficiency by comparing the skeletal response to ovariectomy in inbred strains of mice.
Materials and Methods: Four-month-old mice from five inbred mouse strains (C3H/HeJ, BALB/cByJ, CAST/EiJ, DBA2/J, and C57BL/6J) underwent ovariectomy (OVX) or sham-OVX surgery (n = 6-9/group). After 1 month, mice were killed, and μCT was used to compare cortical and trabecular bone response to OVX.
Results: The effect of OVX on trabecular bone varied with mouse strain and skeletal site. Vertebral trabecular bone volume (BV/TV) declined after OVX in all strains (−15 to −24%), except for C3H/HeJ. In contrast, at the proximal tibia, C3H/HeJ mice had a greater decline in trabecular BV/TV (−39%) than C57BL/6J (−18%), DBA2/J (−23%), and CAST/EiJ mice (−21%). OVX induced declines in cortical bone properties, but in contrast to trabecular bone, the effect of OVX did not vary by mouse strain. The extent of trabecular bone loss was greatest in those mice with highest trabecular BV/TV at baseline, whereas cortical bone loss was lowest among those with high cortical bone parameters at baseline.
Conclusions: We found that the skeletal response to OVX varies in a site- and compartment-specific fashion among inbred mouse strains, providing support for the hypothesis that bone loss during and after the menopause is partly genetically regulated.
Differential Effects of Teriparatide and Alendronate on Bone Remodeling in Postmenopausal Women Assessed by Histomorphometric Parameters
Authors: Arlot Monique , Meunier Pierre J , Boivin Georges , Haddock Lillian , Tamayo Juan , Correa-Rotter Ricardo , Jasqui Salomón , Donley David W , Dalsky Gail P , Martin Javier San , Eriksen Erik Fink 
Published: April 2006

Abstract
An 18-month randomized double-blind study was conducted in postmenopausal women with osteoporosis to compare the effects of once-daily teriparatide 20 μg with alendronate 10 mg on bone histomorphometry. Biopsies were obtained from 42 patients. Indices of bone formation were significantly higher after 6 or 18 months of teriparatide compared with alendronate treatment.
Introduction: Alendronate and teriparatide increased BMD, assessed by DXA, by different mechanisms of action, supported by changes in biochemical markers of bone turnover. The purpose of this cross-sectional study was to explore the differential effects of these two osteoporosis treatments at the bone tissue level by examining bone histomorphometric parameters of bone turnover after either 6 or 18 months of treatment.
Materials and Methods: Patients were a cohort from a randomized parallel double-blind study conducted to compare the effects of once-daily teriparatide 20 μg and alendronate 10 mg in postmenopausal women with osteoporosis. Transiliac crest bone biopsies were obtained after tetracycline double labeling from 42 patients treated for 6 months (n = 23) or 18 months (n = 14); 5 additional patients were biopsied from contralateral sides at 6 and 18 months. Biopsy specimens adequate for quantitative analysis were analyzed by 2D histomorphometry from 17 patients at 6 months (teriparatide, n = 8; alendronate, n = 9) and 15 patients at 18 months (teriparatide, n = 8; alendronate, n = 7). Data were analyzed by two-sample tests.
Results: Histomorphometric indices of bone formation were significantly and markedly greater in the teriparatide group than in the alendronate group at 6 and 18 months, whereas indices of bone resorption were only significantly greater in the teriparatide group than in the alendronate group at 6 months. Bone formation and activation frequency were significantly lower at 18 months compared with 6 months in the teriparatide group, returning to levels comparable with untreated postmenopausal women. In the teriparatide group, the peak in histomorphometric bone formation indices coincided with peak levels for N-terminal propeptide of type I collagen, a biochemical marker of bone formation. The degree of mineralization was lower at 18 months than at 6 months with treatment in both groups but was not different between groups.
Conclusions: These results confirm the opposite mechanisms of action of teriparatide and alendronate on bone remodeling and confirm the bone formation effect of teriparatide.
Racial Differences in Rate of Decline in Bone Mass in Older Men: The Baltimore Men's Osteoporosis Study
Authors: Tracy J Kathleen , Meyer Walter A , Flores Raymond H , Wilson P David , Hochberg Marc C 
Published: April 2006

Abstract
Older black men have higher adjusted BMD than older white men. Using data from a longitudinal cohort study of older men followed for a mean of 18.8 ± 6.5 (SD) months, we found that older black men have a higher rate of decline in femoral neck and total hip BMD and femoral neck BMAD than older white men.
Introduction: Older black men have higher adjusted BMD compared with older white men. The difference in BMD may be caused by having attained higher peak bone mass as young adults and/or having a slower rate of decline in bone mass as adults. There are few published longitudinal data on change in bone mass in older white men and no published data for older black men.
Materials and Methods: Three hundred forty-nine white men and 119 black men ⩾65 of age (mean age, 75 ± 5.7 and 72 ± 5.6 years, respectively) who participated in the longitudinal component of the Baltimore Men's Osteoporosis Study returned for a second visit after a mean of 18.8 ± 6.5 (SD) months and were not taking medications used to treat low bone mass at either visit. BMD was measured at the femoral neck and total hip by Hologic-certified technicians using a QDR 2000 at the baseline visit (V1) and QDR 4500 at the first follow-up visit (V2). Participants also completed self-administered and interviewer-administered questionnaires and underwent standardized clinic examinations. Bone mineral apparent density (BMAD) at the femoral neck was calculated as an estimate of volumetric BMD. Annual crude and multiple variable adjusted percent changes in BMD and BMAD were calculated.
Results: In univariate analyses, black men had lower percent decline in femoral neck and total hip BMD and femoral neck BMAD than white men. In addition, older age at baseline, lower baseline weight, current smoking, and lower baseline BMD were associated with greater percent decline per year in femoral neck BMD; older age at baseline, current smoking, and lower baseline BMD were associated with greater percent decline per year in total hip BMD; and older age at baseline and lower baseline femoral neck BMAD were associated with greater percent decline per year in femoral neck BMAD. Racial differences in bone loss persisted in multiple variable models that controlled for other factors associated with change in BMD and BMAD.
Conclusions: Older black men seem to lose bone mass at a slower rate than older white men. These differences in the rate of bone loss may account, in part, for the racial disparities in BMD and BMAD and risk of osteoporotic fractures among older men.