bluuebunny/crossref_metadata_2025_split huggingface dataset:
Activation of Protease-Activated Receptor-2 Leads to Inhibition of Osteoclast Differentiation
Authors: Smith Rosealee , Ransjö Maria , Tatarczuch Liliana , Song Shu-Jun , Pagel Charles N , Morrison John R , Pike Robert N , Mackie Eleanor J 
Published: April 2006

Abstract
PAR-2 is expressed by osteoblasts and activated by proteases present during inflammation. PAR-2 activation inhibited osteoclast differentiation induced by hormones and cytokines in mouse bone marrow cultures and may protect bone from uncontrolled resorption.
Introduction: Protease-activated receptor-2 (PAR-2), which is expressed by osteoblasts, is activated specifically by a small number of proteases, including mast cell tryptase and factor Xa. PAR-2 is also activated by a peptide (RAP) that corresponds to the “tethered ligand” created by cleavage of the receptor's extracellular domain. The effect of activating PAR-2 on osteoclast differentiation was investigated.
Materials and Methods: Mouse bone marrow cultures have been used to investigate the effect of PAR-2 activation on osteoclast differentiation induced by parathyroid hormone (PTH), 1,25 dihydroxyvitamin D3 [1,25(OH)2D3], and interleukin-11 (IL-11). Expression of PAR-2 by mouse bone marrow, mouse bone marrow stromal cell-enriched cultures, and the RAW264.7 osteoclastogenic cell line was demonstrated by RT-PCR.
Results: RAP was shown to inhibit osteoclast differentiation induced by PTH, 1,25(OH)2D3, or IL-11. Semiquantitative RT-PCR was used to investigate expression of mediators of osteoclast differentiation induced by PTH, 1,25(OH)2D3, or IL-11 in mouse bone marrow cultures and primary calvarial osteoblast cultures treated simultaneously with RAP. In bone marrow and osteoblast cultures treated with PTH, 1,25(OH)2D3, or IL-11, RAP inhibited expression of RANKL and significantly suppressed the ratio of RANKL:osteoprotegerin expression. Activation of PAR-2 led to reduced expression of prostaglandin G/H synthase-2 in bone marrow cultures treated with PTH, 1,25(OH)2D3, or IL-11. RAP inhibited PTH- or 1,25(OH)2D3-induced expression of IL-6 in bone marrow cultures. RAP had no effect on osteoclast differentiation in RANKL-treated RAW264.7 cells.
Conclusion: These observations indicate that PAR-2 activation inhibits osteoclast differentiation by acting on cells of the osteoblast lineage to modulate multiple mediators of the effects of PTH, 1,25(OH)2D3, and IL-11. Therefore, the role of PAR-2 in bone may be to protect it from uncontrolled resorption by limiting levels of osteoclast differentiation.
Bilateral Femoral Head Osteonecrosis After Septic Shock and Multiorgan Failure
Authors: Bolland Mark J , Hood Gill , Bastin Sonja T , King Alan R , Grey Andrew 
Published: April 2006

Abstract
A case of bilateral femoral head osteonecrosis after septic shock is presented. We suggest that the osteonecrosis was caused by ischemic insults to the proximal femora. The association between septic shock and osteonecrosis has not been previously reported.
Introduction: Osteonecrosis is an uncommon disorder characterized by the in situ death of bone. A diverse range of conditions has been associated with osteonecrosis. We present a case of bilateral femoral head osteonecrosis that occurred after an episode of septic shock.
Materials and Methods: A 66-year-old woman presented with a left-sided renal stone and a urinary tract infection. Her condition rapidly progressed to a life-threatening illness with septic shock complicated by multiorgan failure, which necessitated prolonged intensive care and inotropic support. She made a full recovery but 3 months later developed bilateral osteonecrosis of the femoral heads requiring bilateral total hip joint replacement.
Results and Conclusions: We propose that the osteonecrosis was caused by ischemic insults to the femoral heads as a result of the widespread systemic ischemia that occurred during her initial illness. To our knowledge, septic shock has not been previously described as a cause of osteonecrosis. Clinicians should be aware of this association, particularly in patients presenting with bone pain after episodes of sepsis.
Megakaryocyte-Osteoblast Interaction Revealed in Mice Deficient in Transcription Factors GATA-1 and NF-E2
Authors: Kacena Melissa A , Shivdasani Ramesh A , Wilson Kimberly , Xi Yougen , Troiano Nancy , Nazarian Ara , Gundberg Caren M , Bouxsein Mary L , Lorenzo Joseph A , Horowitz Mark C 
Published: April 2006

Abstract
Mice deficient in GATA-1 or NF-E2 have a 200–300% increase in bone volume and formation parameters. Osteoblasts and osteoclasts generated in vitro from mutant and control animals were similar in number and function. Osteoblast proliferation increased up to 6-fold when cultured with megakaryocytes. A megakaryocyte-osteoblast interaction plays a role in the increased bone formation in these mice.
Introduction: GATA-1 and NF-E2 are transcription factors required for the differentiation of megakaryocytes. Mice deficient in these factors have phenotypes characterized by markedly increased numbers of immature megakaryocytes, a concomitant drastic reduction of platelets, and a striking increased bone mass. The similar bone phenotype in both animal models led us to explore the interaction between osteoblasts and megakaryocytes.
Materials and Methods: Histomorphometry, μCT, and serum and urine biochemistries were used to assess the bone phenotype in these mice. Wildtype and mutant osteoblasts were examined for differences in proliferation, alkaline phosphatase activity, and osteocalcin secretion. In vitro osteoclast numbers and resorption were measured. Because mutant osteoblasts and osteoclasts were similar to control cells, and because of the similar bone phenotype, we explored the interaction between cells of the osteoblast lineage and megakaryocytes.
Results: A marked 2- to 3-fold increase in trabecular bone volume and bone formation indices were observed in these mice. A 20- to 150-fold increase in trabecular bone volume was measured for the entire femoral medullary canal. The increased bone mass phenotype in these animals was not caused by osteoclast defects, because osteoclast number and function were not compromised in vitro or in vivo. In contrast, in vivo osteoblast number and bone formation parameters were significantly elevated. When wildtype or mutant osteoblasts were cultured with megakaryocytes from GATA-1- or NF-E2-deficient mice, osteoblast proliferation increased over 3- to 6-fold by a mechanism that required cell-to-cell contact.
Conclusions: These observations show an interaction between megakaryocytes and osteoblasts, which results in osteoblast proliferation and increased bone mass, and may represent heretofore unrecognized anabolic pathways in bone.
Association of a Common Polymorphism in the Methylenetetrahydrofolate Reductase (MTHFR) Gene With Bone Phenotypes Depends on Plasma Folate Status
Authors: McLean Robert R , Karasik David , Selhub Jacob , Tucker Katherine L , Ordovas Jose M , Russo Giuseppina T , Cupples L Adrienne , Jacques Paul F , Kiel Douglas P 
Published: April 2006

Abstract
A study of a polymorphism in the MTHFR gene, plasma folate, and bone phenotypes in 1632 individuals revealed that the genotype effect on BMD and quantitative ultrasound was dependent on the level of folate. Our findings support the hypothesis that the association between an MTHFR polymorphism and bone phenotypes depends on folate status.
Introduction: Genome-wide screens using quantitative ultrasound (QUS) and BMD phenotypes have shown suggestive linkage on chromosome 1pter-1p36.3, a region containing the methylenetetrahydrofolate reductase (MTHFR) gene. Individuals homozygous (TT) for the MTHFR C677T polymorphism who have low plasma folate concentrations exhibit elevated plasma homocysteine (tHcy) concentrations that may compromise bone quality. We hypothesized that folate status might modify an association between the C677T polymorphism and bone, possibly by influencing homocysteine concentrations.
Materials and Methods: QUS (broadband ultrasound attenuation [BUA], speed of sound, and quantitative ultrasound index) of the heel and BMD of the hip and spine were measured in 1632 male and female members of the Framingham Offspring Study (1996–2001). Participants were assessed for plasma folate concentration and genotyped for the MTHFR C677T polymorphism. TT participants were compared with individuals in the CC + CT group using analysis of covariance.
Results: Adjusted mean QUS and BMD measures did not differ between C677T groups. Although all participants with plasma folate concentrations ≥4 ng/ml had ∼2% higher QUS and BMD than those with folate &lt;4 ng/ml, the association disappeared after controlling for tHcy. Suggestive interactions between folate status and the C677T group (CC + CT versus TT) were found for hip BMD (p ≤ 0.05) and BUA (p = 0.11). Compared with CC + CT participants, TT individuals had lower mean BUA (p = 0.06) and Ward's area BMD (p = 0.08) within the folate &lt;4 ng/ml group and significantly higher hip BMD (p ≤ 0.05) within the folate ≥4 ng/ml group. For both folate groups, TT participants had higher age-adjusted mean plasma tHcy versus CC + CT participants. Controlling for tHcy in these models did not affect the statistical significance of the interaction effects.
Conclusions: Our findings support the hypothesis that the association between the C677T MTHFR polymorphism and bone phenotypes depends on folate status. The mechanism mediating the association, however, remains unclear, but may be partially caused by homocysteine effects on bone.
Fracture Incidence in Polyostotic Fibrous Dysplasia and the McCune-Albright Syndrome
Authors: Leet Arabella I , Chebli Caroline , Kushner Harvey , Chen Clara C , Kelly Marilyn H , Brillante Beth A , Robey Pamela G , Bianco Paolo , Wientroub Shlomo , Collins Michael T 
Published: April 2006

Abstract
In patients with polyostotic fibrous dysplasia of bone, the peak incidence of fractures is during the first decade of life, followed by a decrease thereafter. Phosphaturia is associated with an earlier incidence and increased frequency of fractures.
Introduction: Fibrous dysplasia (FD) is a disorder involving either one (monostotic) or several bones (polyostotic FD [PFD] and sometimes is associated with cafe-au-lait hyperpigmentation of the skin and one or more hyperfunctioning endocrinopathies (McCune-Albright syndrome [MAS]). Both PFD and MAS are often associated with phosphaturia. Although fractures occur frequently in PFD/MAS, fracture incidence and the effect of age and co-existing metabolic abnormalities (endocrinopathy and/or phosphaturia) on fractures are ill defined.
Materials and Methods: We reviewed the medical records and examined the endocrine and phosphorus metabolism of 35 patients with PFD/MAS. We report on the age at which extremity fractures occurred and their location and treatment. The results of endocrine and phosphorus metabolism testing and associations between age of first fractures, number of fractures, fracture rate, and metabolic abnormalities were noted.
Results: The average follow-up was 14.2 years (range, 2–39 years), during which 172 fractures occurred. The number and sites of fractures were 103 femoral, 25 tibial, 33 humeral, and 11 forearm. Twenty-seven patients had PFD with one or more endocrinopathies and/or phosphaturia, and eight had PFD alone. The endocrinopathies included precocious puberty (n = 19), hyperthyroidism (n = 9), growth hormone excess (n = 6), and one patient each with Cushing syndrome and primary hyperparathyroidism. Twelve patients had phosphaturia. The peak rate of fractures occurred between 6 and 10 years of age and decreased thereafter. Patients with metabolic abnormalities sustained their first fracture at an earlier age (6.9 versus 16.6 years, p &lt; 0.005) and had a higher lifetime rate of fractures (0.29 versus 0.08 fractures/year), relative to patients with PFD alone. Phosphaturia was the single metabolic dysfunction associated with both an earlier age of first fracture (5.1 versus 16.6 years, p &lt; 0.05) and a greater lifetime fracture rate (0.35 versus 0.08 fractures/year, p &lt; 0.05).
Conclusions: The occurrence of extremity fractures in FD peaks between 6 and 10 years of age and declines thereafter. Fractures occur earlier and more frequently in the presence of phosphaturia. These data have implications for long-term prognosis, clinical management, and interpretation of therapeutic interventions.
FGF-23 Is a Potent Regulator of Vitamin D Metabolism and Phosphate Homeostasis
Authors: Shimada Takashi , Hasegawa Hisashi , Yamazaki Yuji , Muto Takanori , Hino Rieko , Takeuchi Yasuhiro , Fujita Toshiro , Nakahara Kazuhiko , Fukumoto Seiji , Yamashita Takeyoshi 
Published: April 2006

Abstract
We analyzed the effects of an FGF-23 injection in vivo. FGF-23 caused a reduction in serum 1,25-dihydroxyvitamin D by altering the expressions of key enzymes for the vitamin D metabolism followed by hypophosphatemia. This study indicates that FGF-23 is a potent regulator of the vitamin D and phosphate metabolism.
Introduction: The pathophysiological contribution of FGF-23 in hypophosphatemic diseases was supported by animal studies in which the long-term administration of recombinant fibroblast growth factor-23 reproduced hypophosphatemic rickets with a low serum 1,25-dihydroxyvitamin D [1,25(OH)2D] level. However, there is no clear understanding of how FGF-23 causes these changes.
Materials and Methods: To elucidate the molecular mechanisms of the FGF-23 function, we investigated the short-term effects of a single administration of recombinant FGF-23 in normal and parathyroidectmized animals.
Results: An injection of recombinant FGF-23 caused a reduction in serum phosphate and 1,25(OH)2D levels. A decrease in serum phosphate was first observed 9 h after the injection and was accompanied with a reduction in renal mRNA and protein levels for the type IIa sodium-phosphate cotransporter (NaPi-2a). There was no increase in the parathyroid hormone (PTH) level throughout the experiment, and hypophosphatemia was reproduced by FGF-23 in parathyroidectomized rats. Before this hypophosphatemic effect, the serum 1,25(OH)2D level had already descended at 3 h and reached the nadir 9 h after the administration. FGF-23 reduced renal mRNA for 25-hydroxyvitamin D-1α-hydroxylase and increased that for 25-hydroxyvitamin D-24-hydroxylase starting at 1 h. In addition, an injection of calcitriol into normal mice increased the serum FGF-23 level within 4 h.
Conclusions: FGF-23 regulates NaPi-2a independently of PTH and the serum 1,25(OH)2D level by controlling renal expressions of key enzymes of the vitamin D metabolism. In conclusion, FGF-23 is a potent regulator of phosphate and vitamin D homeostasis.
Meta-Analysis of Molecular Association Studies: Vitamin D Receptor Gene Polymorphisms and BMD as a Case Study
Authors: Thakkinstian Ammarin , D'Este Catherine , Eisman John , Nguyen Tuan , Attia John 
Published: April 2006

Abstract
With the rise of molecular and genetic epidemiology, molecular association studies are increasingly common; however, meta-analysis of these studies has been a neglected area. This study performed a meta-analysis of the association of the vitamin D receptor (VDR) gene polymorphisms and BMD. We also highlight methodological issues that need to be resolved.
Introduction: With the rise of molecular and genetic epidemiology, molecular association studies are increasingly common; however, meta-analysis of these studies has been a neglected area. This study performed a meta-analysis of the association of vitamin D receptor (VDR) gene polymorphisms and BMD/osteoporosis and highlights methodological issues.
Materials and Methods: Studies published from 1994 to 2001 were identified through Medline using PubMed software. The reference lists of the articles retrieved were also reviewed. Where eligible papers had insufficient information, we contacted authors by mail (up to three mailings) for additional information. Any observational study, which tested the association between VDR BsmI genotypes and either BMD or osteoporosis at the femoral neck or spine in adult women, was included in the review. Data were extracted independently by two reviewers (AT and JA) using a standardized data extraction form.
Results: The B allele was significantly associated with BMD at the spine; it seemed to follow a recessive model, with the BB genotype having lower BMD than Bb/bb genotypes at baseline, which led to greater bone mineral loss over time. Highlighted methodological lessons included the need to check Hardy-Weinberg equilibrium and the importance of exploring heterogeneity, pooling data in a manner that is sensitive to genetic models, and avoiding multiple comparisons.
Conclusion: With the proliferation of molecular association studies, there will be an increased need to quantify the magnitude of the risk associated with genetic polymorphisms. This will likely entail meta-analytic methods, and this meta-analysis highlights some of the methodological issues that will need to be resolved.
Converse Relationship Between In Vitro Osteogenic Differentiation and In Vivo Bone Healing Elicited by Different Populations of Muscle-Derived Cells Genetically Engineered to Express BMP4
Authors: Peng Hairong , Usas Arvydas , Gearhart Brian , Olshanski Anne , Shen Hsain-Chung , Huard Johnny 
Published: April 2006

Abstract
In this study, we compared the use of primary muscle-derived osteoprogenitor cells (PP6 cells) for the delivery of BMP4 to improve bone healing to that of muscle-derived non-osteoprogenitor cells (PP1 cells). Surprisingly, the use of PP1 cells resulted in an improved outcome because of the lack of adverse responses to BMP4 involving cell differentiation, proliferation, and apoptosis.
Introduction: Although researchers frequently opt to use osteogenic cells for osteogenic bone morphogenetic protein (BMP)-based ex vivo gene therapy to improve bone healing, it remains unclear whether the osteogenic potential of a cellular vehicle affects the outcome of bone healing applications. Here we compared the use of muscle-derived non-osteoprogenitor cells (PP1 cells) to that of primary muscle-derived osteoprogenitor cells (PP6 cells) for the delivery of BMP4 to improve the healing of bone defects.
Materials and Methods: Two distinct populations of primary rat muscle-derived cells—PP1 and PP6—were selected, transduced with retroviral vectors to express BMP4 or a marker gene (LacZ), and implanted into critical-sized calvarial defects created in syngeneic rats. The bone healing was monitored radiographically and histologically at 7 and 14 weeks after implantation. Cellular responses to BMP4 were evaluated by alkaline phosphatase histochemical staining and RT-PCR of another osteogenic marker to indicate osteogenic differentiation, a cell proliferation assay and BrdU (bromodeoxyuridine) labeling to assess cell proliferation, and the TUNEL assay to determine apoptosis.
Results and Conclusions: In all animals (nine rats per group), transduced PP1 cells expressing BMP4 demonstrated significantly advanced healing compared with PP6 cells expressing BMP4 and control cells expressing LacZ. We found that constitutive BMP4 expression negatively impacted the in vitro proliferation and in vivo survival rates of PP6 cells, but not PP1 cells. BMP4 exposure also directly inhibited the proliferation and induced the apoptosis of PP6 cells, but not PP1 cells. The impairment in PP6 cell proliferation was directly associated with the osteogenic differentiation of these cells. These results indicate that PP1 cells are better suited than osteoprogenitor cells for use as cellular vehicles to deliver osteogenic BMP4 to improve bone healing and that cellular behavior in response to a particular gene can be used to predict the cells' performance as delivery vehicles in ex vivo gene therapy.
Interactions of Interleukin-6 Promoter Polymorphisms With Dietary and Lifestyle Factors and Their Association With Bone Mass in Men and Women From the Framingham Osteoporosis Study
Authors: Ferrari Serge L , Karasik David , Liu Jun , Karamohamed Samev , Herbert Alan G , Cupples L Adrienne , Kiel Douglas P 
Published: April 2006

Abstract
Lifestyle and dietary factors may influence the association of IL-6 polymorphisms with bone mass. In 1574 unrelated men and women from the Framingham Offspring Cohort, we observed significant hip BMD differences between IL-6 −174 genotypes only in older women, those without estrogens, and those with a poor calcium intake. Hence, association of IL-6 polymorphisms with BMD may be limited to discrete population subgroups.
Introduction: Interleukin (IL)-6 plays a central role in the pathogenesis of osteoporosis. Two functional variants in the IL-6 promoter have previously been associated with IL-6 expression, bone resorption levels, and BMD in late postmenopausal women, but results were conflicting in different populations. We hypothesized that the association between IL-6 promoter alleles and BMD may be affected by interactions with lifestyle and dietary factors known to influence bone turnover.
Materials and Methods: Among the Offspring Cohort of the Framingham Heart Study, 1574 unrelated men and women were genotyped for IL-6 −572 and −174 alleles. Interaction analyses with years since menopause, estrogen status, physical activity, smoking, dietary calcium, vitamin D, and alcohol intake were based on BMD measurements at the hip.
Results and Conclusions: In models that considered only the main effects of IL-6 polymorphisms, no significant association with BMD was observed in either gender. In contrast, p values (0.003–0.096 by ANOVA) suggestive of an interaction between IL-6 −174 genotypes and years since menopause, estrogen status, dietary calcium, and vitamin D intake were observed in women (n = 819). In turn, BMD was significantly lower with genotype −174 GG compared with CC, and intermediate with GC, in women who were more than 15 years past menopause and in those without estrogens or with calcium intake &lt;940 mg/day. In estrogen-deficient women with poor calcium intake, BMD differences between genotypes CC and GG were 10.2% at femoral neck (p = 0.012), 12.0% at trochanter (p = 0.012), and 16.8% at Ward's area (p = 0.0014). In contrast, no such interactions were observed in men (n = 755). In conclusion, IL-6 genetic variation was prominently associated with hip BMD in late postmenopausal women, those without estrogen replacement therapy, and those with inadequate calcium intake. In contrast, IL-6 polymorphisms are unlikely to be significant determinants of bone mass in other women or men.