bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transcriptional Regulation of a BMP-6 Promoter by Estrogen Receptor α
Authors: Ong Delia B , Colley Shane M , Norman Michael R , Kitazawa Sohei , Tobias Jonathan H 
Published: April 2006

Abstract
The effects of 17β-estradiol (E2) and ICI 182,780 (ICI) on activity of a BMP-6 promoter were compared in osteoblast-like and breast cancer cells transiently transfected with ERα. E2 but not ICI stimulated BMP-6 reporter activity in breast cancer cells, whereas the opposite was observed in osteoblast-like cells, associated with lack of AF-2 dependence of the response, and absent intranuclear localization of ERα, suggesting the involvement of a distinct ERα-dependent response mechanism in osteoblasts.
Introduction: Previous studies suggest that the tissue-selective effect of antiestrogens on bone reflects the ability of these compounds to target certain osteoblast regulatory genes. To explore this hypothesis, we examined whether antiestrogens preferentially stimulate the bone morphogenetic protein 6 (BMP-6) promoter in bone cells, and if so, whether this activity is associated with a distinct estrogen receptor (ER)α-dependent response mechanism to that in other cell types.
Materials and Methods: We compared the effects of 17β-estradiol (E2) and ICI 182,780 (ICI) on activity of a 4.3-kb BMP-6 reporter construct in osteoblast-like cells (human MG63 and SaOS-2 cells and rat ROS 17/2.8 cells), human MCF-7 and T47-D breast cancer cell lines, and HepG2 hepatoma cells, after transient transfection with ERα, ERβ, and mutant ER constructs.
Results: E2, but not ICI, stimulated BMP-6 reporter activity by approximately 100% in MCF-7, T47-D cells, and HepG2 cells when transfected with ERα. In contrast, in ERα-transfected osteoblast-like cells, an increase in reporter activity of approximately 75% was observed after treatment with ICI but not E2. The response of MG63 cells to ICI and MCF-7 cells to E2 both required ERα as opposed to ERβ and the ERα activation function (AF)-1 activation domain. However, whereas the AF-2 domain was also required for E2 to stimulate reporter activity in MCF-7 cells, the response to ICI in MG63 cells was AF-2 independent. In further studies where we compared the intracellular distribution of ERα associated with these responses, E2-dependent stimulation of the BMP-6 reporter in MCF-7 cells was associated with intranuclear localization of ERα, whereas extranuclear localization was seen in rat osteosarcoma cells (ROS) cells treated with ICI.
Conclusions: Antiestrogens selectively stimulate BMP-6 reporter activity in osteoblast-like cells through a distinct ERα-dependent mechanism characterized by independence of the AF-2 domain and extranuclear localization of ERα.
Calcium Signaling Pathway Involving Calcineurin Regulates Interleukin-8 Gene Expression Through Activation of NF-κB in Human Osteoblast-Like Cells
Authors: Mitsuyama Hirohito , Kambe Fukushi , Murakami Ryuichiro , Cao Xia , Ishiguro Naoki , Seo Hisao 
Published: April 2006

Abstract
Involvement of aberrant IL-8 production by osteoblasts was demonstrated in pathogenesis of inflammatory joint diseases. We thus investigated intracellular signaling pathways leading to IL-8 expression in human osteoblast-like HOS-TE85 cells. It was demonstrated that Ca2+ signaling pathway involving calcineurin regulates IL-8 gene expression through activation of a transcription factor, NF-κB.
Introduction: Involvement of aberrant interleukin (IL)-8 production by osteoblasts was demonstrated in pathogenesis of inflammatory joint diseases. However, intracellular signaling pathways leading to IL-8 expression in osteoblasts have been poorly explored. Because a variety of external stimuli was shown to increase intracellular Ca2+ in osteoblasts, we investigated effects of Ca2+-ionophore and phorbol-myristate-acetate (Ion/PMA) on IL-8 expression in human osteoblast-like HOS-TE85 cells and compared the effects with those elicited by TNF-α.
Materials and Methods: HOS-TE85 cells were treated with Ion/PMA or TNF-α in the presence and absence of calcineurin inhibitors (CnI), cyclosporin A, and FK506. IL-8 mRNA levels and its promoter activities were examined by Northern blot and luciferase reporter analyses, respectively. Electrophoretic mobility shift assay (EMSA) was used to evaluate DNA binding activities of transcription factors such as NF-κB. Degradation of IκB, a cytoplasmic NF-κB-inhibitory protein, was examined by Western blot analysis.
Results: Ion/PMA and TNF-α induced IL-8 mRNA expression. Interestingly, CnI attenuated the induction by Ion/PMA, but not that by TNF-α. Promoter activity was also increased by both stimuli, and only the Ion/PMA-dependent increase was suppressed by CnI. Introduction of mutations in the promoter demonstrated that one NF-κB site was responsible for the suppression by CnI. EMSA revealed that this site binds with NF-κB containing p65 that was activated by Ion/PMA and TNF-α and that CnI inhibited only Ion/PMA-dependent NF-κB activation. Accordingly, CnI blocked only Ion/PMA-dependent degradation of IκB-α. In addition, the basal and Ion/PMA-dependent IL-8 promoter activities were enhanced by co-transfection of constitutively active calcineurin.
Conclusion: These results show that the Ca2+ signaling pathway involving calcineurin regulates IL-8 gene expression through activation of NF-κB in human osteoblast-like cells.
Estrogen Receptor β Polymorphisms Are Associated With Bone Mass in Women and Men: The Framingham Study
Authors: Shearman Amanda M , Karasik David , Gruenthal Kristen M , Demissie Serkalem , Cupples L Adrienne , Housman David E , Kiel Douglas P 
Published: April 2006

Abstract
ESR2 is expressed in bone cells, yet few studies have tested its variation for association with BMD, an important determinant of osteoporotic fractures. This was investigated in 723 men and 795 women from the Framingham study. Results show association of variation in this gene with BMD in both women and men.
Introduction: Osteoporotic fracture risk is highly dependent on bone density, a quantitative multifactorial trait with a substantial genetic component. In contrast to the growing body of evidence that estrogen receptor α (ESR1) plays a role in bone metabolism, few studies have examined the estrogen receptor β (ESR2) gene for association with BMD. An ESR2 CA repeat polymorphism, D14S1026, was associated with BMD in two small studies, each with &lt;200 women.
Materials and Methods: The objective of this investigation was to assess whether D14S1026 or four other intronic polymorphisms were associated with BMD in 723 men and 795 women (mean age, 60 years) from the offspring cohort of the population-based Framingham Study. BMD was measured at the femur (neck, trochanter, and Ward's area) and the lumbar spine (L2-L4).
Results: In both women and men, there was significant association of D14S1026 genotype with measures of femoral but not spinal BMD. In addition, genotypes of two common single nucleotide polymorphisms, rs1256031 and rs1256059, in strong linkage disequilibrium with one another but not with D14S1026, were associated with measures of femoral BMD in men. The rs1256031 genotypes had up to a 4.0% difference in mean femoral BMD. An inferred rs1256031-D14S1026-rs1256059 haplotype C-23CA-T was significantly associated with reduced femoral BMD in women (p = 0.03, 0.003, and 0.01 for neck, trochanter, and Ward's area, respectively). Haplotype-based BMD differences ranged from 3.0% to 4.3%.
Conclusions: We have observed significant association of common ESR2 variants with measures of femoral BMD in both men and women.
A Synthetic Peptide Fragment of Human MEPE Stimulates New Bone Formation In Vitro and In Vivo
Authors: Hayashibara Tetsuyuki , Hiraga Toru , Yi Bing , Nomizu Motoyoshi , Kumagai Yoshinari , Nishimura Riko , Yoneda Toshiyuki 
Published: April 2006

Abstract
Matrix extracellular phosphoglycoprotein (MEPE) was proposed as a candidate for the phosphaturic hormone phosphatonin. We found that a synthetic peptide fragment of MEPE containing the RGD and SGDG sequence stimulated new bone formation in vitro and in vivo.
Introduction: Matrix extracellular phosphoglycoprotein (MEPE) was recently identified as a candidate for the phosphaturic hormone phosphatonin, which has been implicated in disturbed phosphate metabolism, rickets, and osteomalacia associated with X-linked hypophosphatemic rickets (XLH) and oncogenic hypophosphatemic osteomalacia (OHO). MEPE expression was predominantly found in osteoblasts, and mice deficient in a homolog of MEPE showed increased bone density, suggesting that MEPE produced in osteoblasts negatively regulates bone formation. In this study, we examined the effects of a synthetic 23mer peptide fragment of MEPE (AC-100, region 242–264) containing the RGD (integrin-binding) and SGDG (glycosaminoglycan-attachment) motif on bone formation in vitro and in vivo.
Materials and Methods: The osteogenic activity of AC-100 was examined in organ cultures of neonatal mouse calvariae and in vivo by injecting AC-100 onto the calvariae of mice.
Results: Histomorphometric examination showed that AC-100 stimulated new bone formation with increased numbers of osteoblasts in neonatal mouse calvariae in organ culture. In contrast, synthetic MEPE fragment peptides without either the RGD or SGDG motif failed to increase new bone formation. Repeated daily subcutaneous injections of AC-100 onto the calvariae in mice increased bone thickness and stimulated new bone formation as determined by the calcein double-labeling technique. However, peptides in which the RGD or SGDG sequence was scrambled did not stimulate new bone formation in vivo. AC-100 increased cell proliferation and alkaline phosphatase activity and activated focal adhesion kinase (FAK) and extracellular signal-regulated protein kinase (ERK) in human primary osteoblasts.
Conclusion: Our results show that a synthetic peptide corresponding with the sequence of human MEPE fragment stimulates new bone formation with increased number of osteoblasts. The results also suggest that the RGD and SGDG motifs are critical to the osteogenic activity of AC-100, presumably through activating integrin signaling pathways in osteoblasts. The anabolic effects of AC-100 may be beneficial for bone diseases associated with decreased bone formation.
Genetically Based Influences on the Site-Specific Regulation of Trabecular and Cortical Bone Morphology
Authors: Judex Stefan , Garman Russell , Squire Maria , Donahue Leah-Rae , Rubin Clinton 
Published: April 2006

Abstract
The degree of site-specificity by which genes influence bone quantity and architecture was investigated in the femur of three strains of mice. Morphological indices were highly dependent on both genetic makeup as well as anatomical location showing that the assessment of bone structure from a single site cannot be extrapolated to other sites even within a single bone.
Introduction: The identification of genes responsible for establishing peak BMD will yield critical information on the regulation of bone quantity and quality. Whereas such knowledge may eventually uncover novel molecular drug targets or enable the identification of individuals at risk of osteoporosis, the site-specificity by which putative genotypes cause low or high bone mass (and effective bone morphology) is essentially unknown.
Materials and Methods: μCT was used to determine morphological and microarchitectural features of the femora harvested from three genetically distinct strains of 4-month-old female mice, each with distinct skeletal mass (low: C57BL/6J [B6], medium: BALB/cByJ [BALB], high: C3H/HeJ [C3H]). Two trabecular regions (distal epiphysis and metaphysis) were considered in addition to four cortical regions within the metaphysis and diaphysis.
Results and Conclusions: Comparing morphological properties of the different trabecular and cortical femoral regions between the three strains of mice, it was apparent that high or low values of specific parameters of bone morphology could not be consistently attributed to the same genetic strain. Trabecular metaphyseal bone volume, for instance, was 385% larger in C3H mice than in B6 mice, yet the two strains displayed similar bone volume fractions in the epiphysis. Similarly, BALB mice had 48% more trabecular bone than C3H mice in the epiphysis, but there were no strain-specific differences in cortical bone area at the diaphysis. These data suggest that the genetic control of bone mass and morphology, even within a given bone, is highly site-specific and that a comprehensive search for genes that are indicative of bone quantity and quality may also have to occur on a very site-specific basis.
Comparison of Cross-Sectional Geometry of the Proximal Femur in White and Black Women from Detroit and Johannesburg
Authors: Nelson Dorothy A , Pettifor John M , Barondess David A , Cody Dianna D , Uusi-Rasi Kirsti , Beck Thomas J 
Published: April 2006

Abstract
There are known black-white differences in bone density measured by DXA but less is known about bone architecture. We compared cross-sectional geometric properties of the proximal femur in U.S. black (n = 86) and white (n = 151) and South African black (n = 60) and white (n = 48) postmenopausal women. Results are consistent with greater bone strength in the black groups in both countries.
Introduction: There are well-known ethnic differences in bone density, but little is known about ethnic differences in bone architecture between U.S. and South African blacks and whites.
Materials and Methods: We compared bone density and cross-sectional geometric properties of the proximal femur in 237 U.S. black (n = 86) and white (n = 151) and 108 South African black (n = 60) and white (n = 48) postmenopausal women. The proximal femur (neck, intertrochanteric region, and proximal shaft regions of interest) was measured with DXA and further analyzed with a hip structural analysis program. For each region, BMD, cross-sectional area, outer diameter, section modulus, endosteal diameter, average cortical thickness, and the buckling ratio were estimated.
Results and Conclusions: In the femoral neck, in both countries, the blacks had narrower endosteal diameters (mean difference, 2.6% and 5.1% in U.S. and South African women, respectively), thicker cortices (9.3% and 11.0%), and a lower buckling ratio (11.6% and 15.2%) despite a similar outer diameter. In the intertrochanteric region, the whites had a greater outer diameter (2.2% and 3.0% in U.S. and South African women, respectively), lower cross-sectional area (4.8% and 7.2%), and a higher buckling ratio (7.6% and 3.6%). There are fewer differences in the shaft. Compared with South African whites, U.S. whites had wider (mean difference 2.9%) femoral necks and a greater section modulus (6.4%) in the shaft. U.S. whites also had greater cross-sectional area in both the neck and shaft (5.2% and 4.6%, respectively). The U.S. blacks had significantly greater outer diameters, cross-sectional areas, endosteal diameters, and section moduli in the neck region compared with South African blacks. Our observations are consistent with greater bone strength in the black groups in both countries, and they also suggest that there are fewer differences between the same ethnic groups in the two countries than there are between different ethnic groups within a country.
A Novel Cation-Sensing Mechanism in Osteoblasts Is a Molecular Target for Strontium
Authors: Pi Min , Quarles L Darryl 
Published: April 2006

Abstract
Defining the molecular target for strontium in osteoblasts is important for understanding the anabolic effects of this cation on bone. The current studies demonstrate that a G-protein-mediated response to strontium persists in osteoblasts that lack CASR, suggesting a predominant role for a novel cation-sensing receptor in mediating the osseous response to strontium.
Introduction: Strontium has anabolic effects on bone and is currently being developed for the treatment of osteoporosis. The molecular target for strontium in osteoblasts has not been determined, but the existence of CASR, a G-protein-coupled receptor calcium-sensing receptor, raises the possibility that strontium actions on bone are mediated through this or a related receptor.
Materials and Methods: We used activation of a transfected serum response element (SRE)-luciferase reporter in HEK-293 cells to determine if CASR is activated by strontium. In addition, we examined strontium-mediated responses in MC3T3-E1 osteoblasts and osteoblasts derived from wild-type and CASR null mice to determine if other cation-sensing mechanisms are present in osteoblasts.
Results and Conclusions: We found that strontium stimulated SRE-luc activity in HEK-293 cells transfected with full-length CASR but not in cells expressing the alternatively spliced CASR construct lacking exon 5. In contrast, we found that MC3T3-E1 osteoblasts that lack CASR as well as osteoblasts derived from CASR null mice respond to millimolar concentrations of strontium. The response to strontium in osteoblasts was nonadditive to a panel of extracellular cations, including aluminum, gadolinium, and calcium, suggesting a common mechanism of action. In contrast, neither the CASR agonist magnesium nor the calcimimetic NPS-R568 activated SRE activity in osteoblasts, but the response to these agonists was imparted by transfection of CASR into these osteoblasts, consistent with the presence of distinct cation-sensing mechanisms. Co-expression of the dominant negative Gαq(305–359) minigene also inhibited cation-stimulated SRE activity in osteoblasts lacking known CASR. These findings are consistent with strontium activation of a novel Gαq-coupled extracellular cation-sensing receptor in osteoblasts with distinct cation specificity.
Oxysterols Regulate Differentiation of Mesenchymal Stem Cells: Pro-Bone and Anti-Fat
Authors: Kha Hoa Ton , Basseri Benjamin , Shouhed Daniel , Richardson Jennifer , Tetradis Sotirios , Hahn Theodore J , Parhami Farhad 
Published: April 2006

Abstract
Pluripotent mesenchymal stem cells can undergo lineage-specific differentiation in adult organisms. However, understanding of the factors and mechanisms that drive this differentiation is limited. We show the novel ability of specific oxysterols to regulate lineage-specific differentiation of mesenchymal stem cells into osteogenic cells while inhibiting their adipogenic differentiation. Such effects may have important implications for intervention with osteoporosis.
Introduction: Oxysterols are products of cholesterol oxidation and are formed in vivo by a variety of cells including osteoblasts. Novel pro-osteogenic and anti-adipogenic effects of specific oxysterols on pluripotent mesenchymal cells are demonstrated in this report. Aging and osteoporosis are associated with a decrease in the number and activity of osteoblastic cells and a parallel increase in the number of adipocytic cells.
Materials and Methods: The M2–10B4 pluripotent marrow stromal cell line, as well as several other mesenchymal cell lines and primary marrow stromal cells, was used to assess the effects of oxysterols. All results were analyzed for statistical significance using ANOVA.
Results and Conclusion: Pro-osteogenic and anti-adipogenic effects of specific oxysterols were assessed by the increase in early and late markers of osteogenic differentiation, including alkaline phosphatase activity, osteocalcin mRNA expression and mineralization, and the decrease in markers of adipogenic differentiation including lipoprotein lipase and adipocyte P2 mRNA expression and adipocyte formation. Complete osteogenic differentiation of M2 cells into cells expressing early and late markers of differentiation was achieved only when using combinations of specific oxysterols, whereas inhibition of adipogenesis could be achieved with individual oxysterols. Oxysterol effects were in part mediated by extracellular signal-regulated kinase and enzymes in the arachidonic acid metabolic pathway, i.e., cyclo-oxygenase and phospholipase A2. Furthermore, we show that these specific oxysterols act in synergy with bone morphogenetic protein 2 in inducing osteogenic differentiation. These findings suggest that oxysterols may play an important role in the differentiation of mesenchymal stem cells and may have significant, previously unrecognized, importance in stem cell biology and potential therapeutic interventions.
Clodronate Reduces Vertebral Fracture Risk in Women With Postmenopausal or Secondary Osteoporosis: Results of a Double-Blind, Placebo-Controlled 3-Year Study
Authors: McCloskey Eugene , Selby Peter , Davies Mike , Robinson John , Francis Roger M , Adams Judith , Kayan Karthik , Beneton Monique , Jalava Tarja , Pylkkänen Liisa , Kenraali Juha , Aropuu Sakari , Kanis John A 
Published: April 2006

Abstract
The efficacy of oral clodronate 800 mg daily to reduce vertebral fractures was studied in 593 women with postmenopausal or secondary osteoporosis. The incidence of vertebral fractures was significantly reduced by 46%. The effect was not modified by the underlying cause of osteoporosis or other baseline factors including bone mineral density, QUS, weight, and smoking.
Introduction: This study aimed to determine if the bisphosphonate, clodronate (Bonefos), reduced the incidence of vertebral fractures in osteoporotic women.
Materials and Methods: Women fulfilling the WHO criteria for osteoporosis at the lumbar spine (T-score ≤ −2.5) and/or with at least one prevalent vertebral fracture were recruited to a 3-year double-blind, placebo-controlled study. A total of 593 patients were randomized to two strata comprised of women with postmenopausal osteoporosis (I, n = 483) and secondary osteoporosis (II, n = 110). They received either clodronate 800 mg daily orally (n = 292) or an identical placebo (n = 301). All patients received a calcium supplement of 500 mg daily. BMD was measured at 6, 12, 24, and 36 months, and lateral spine radiographs were obtained at baseline and annually thereafter for vertebral morphometry.
Results: Treatment with clodronate was associated with a significant increase in mean spine BMD over 3 years (percent change from baseline, 4.35 ± 6.34% versus 0.64 ± 6.02% in the placebo group, p &lt; 0.0001). At the hip, clodronate maintained total BMD, whereas a significant decrease was observed in the placebo group (percent change from baseline 0.70 ± 5.67% versus −3.03 ± 6.32% in the placebo group, p &lt; 0.0001). The changes at the spine and hip were similar in both strata. Incident vertebral fractures at 3 years were observed in 63 women in the placebo group and 33 patients receiving clodronate (relative risk, 0.54; 95% CI, 0.37–0.80; p = 0.001). Clodronate significantly reduced vertebral fracture risk in both strata and in women with or without prior vertebral fracture at baseline. Nonvertebral osteoporosis-associated fractures occurred in 21 women in the placebo group and in 14 women treated with clodronate. Treatment was well tolerated, with no significant difference in adverse event rates, including esophagitis, during clodronate treatment.
Conclusion: We conclude that clodronate 800 mg daily is a safe and effective treatment to reduce fracture risk in women with osteoporosis, regardless of causation.