bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hypothalamic Control of Bone Formation: Distinct Actions of Leptin and Y2 Receptor Pathways
Authors: Baldock Paul A , Sainsbury Amanda , Allison Susan , Lin En-Ju D , Couzens Michelle , Boey Dana , Enriquez Ronaldo , During Matthew , Herzog Herbert , Gardiner Edith M 
Published: April 2006

Abstract
Leptin and Y2 receptors on hypothalamic NPY neurons mediate leptin effects on energy homeostasis; however, their interaction in modulating osteoblast activity is not established. Here, direct testing of this possibility indicates distinct mechanisms of action for leptin anti-osteogenic and Y2−/− anabolic pathways in modulating bone formation.
Introduction: Central enhancement of bone formation by hypothalamic neurons is observed in leptin-deficient ob/ob and Y2 receptor null mice. Similar elevation in central neuropeptide Y (NPY) expression and effects on osteoblast activity in these two models suggest a shared pathway between leptin and Y2 receptors in the central control of bone physiology. The aim of this study was to test whether the leptin and Y2 receptor pathways regulate bone by the same or distinct mechanisms.
Materials and Methods: The interaction of concomitant leptin and Y2 receptor deficiency in controlling bone was examined in Y2−/−ob/ob double mutant mice, to determine whether leptin and Y2 receptor deficiency have additive effects. Interaction between leptin excess and Y2 receptor deletion was examined using recombinant adeno-associated viral vector overproduction of NPY (AAV-NPY) to produce weight gain and thus leptin excess in adult Y2−/− mice. Cancellous bone volume and bone cell function were assessed.
Results: Osteoblast activity was comparably elevated in ob/ob, Y2−/−, and Y2−/−ob/ob mice. However, greater bone resorption in ob/ob and Y2−/−ob/ob mice reduced cancellous bone volume compared with Y2−/−. Both wildtype and Y2−/− AAV-NPY mice exhibited marked elevation of white adipose tissue accumulation and hence leptin expression, thereby reducing osteoblast activity. Despite this anti-osteogenic leptin effect in the obese AAV-NPY model, osteoblast activity in Y2−/− AAV-NPY mice remained significantly greater than in wildtype AAV-NPY mice.
Conclusions: This study suggests that NPY is not a key regulator of the leptin-dependent osteoblast activity, because both the leptin-deficient stimulation of bone formation and the excess leptin inhibition of bone formation can occur in the presence of high hypothalamic NPY. The Y2−/− pathway acts consistently to stimulate bone formation; in contrast, leptin continues to suppress bone formation as circulating levels increase. As a result, they act increasingly in opposition as obesity becomes more marked. Thus, in the absence of leptin, the cancellous bone response to loss of Y2 receptor and leptin activity can not be distinguished. However, as leptin levels increase to physiological levels, distinct signaling pathways are revealed.
Continuous PTH and PTHrP Infusion Causes Suppression of Bone Formation and Discordant Effects on 1,25(OH)2Vitamin D
Authors: Horwitz Mara J , Tedesco Mary Beth , Sereika Susan M , Syed Mushtaq A , Garcia-Ocaña Adolfo , Bisello Alessandro , Hollis Bruce W , Rosen Clifford J , Wysolmerski John J , Dann Pamela , Gundberg Caren , Stewart Andrew F 
Published: April 2006

Abstract
Osteoblast activity and plasma 1,25(OH)2vitamin D are increased in HPT but suppressed in HHM. To model HPT and HHM, we directly compared multiday continuous infusions of PTH versus PTHrP in humans. Continuous infusion of both PTH and PTHrP results in marked and prolonged suppression of bone formation; renal 1,25(OH)2D synthesis was stimulated effectively by PTH but poorly by PTHrP.
Introduction: PTH and PTH-related protein (PTHrP) cause primary hyperparathyroidism (HPT) and humoral hypercalcemia of malignancy (HHM), respectively. Whereas HHM and HPT resemble one another in many respects, osteoblastic bone formation and plasma 1,25(OH)2vitamin D are increased in HPT but reduced in HHM.
Materials and Methods: We performed 2- to 4-day continuous infusions of escalating doses of PTH and PTHrP in 61 healthy young adults, comparing the effects on serum calcium and phosphorus, renal calcium and phosphorus handling, 1,25(OH)2vitamin D, endogenous PTH(1-84) concentrations, and plasma IGF-1 and markers of bone turnover.
Results: PTH and PTHrP induced comparable effects on renal calcium and phosphorus handling, and both stimulated IGF-1 and bone resorption similarly. Surprisingly, PTH was consistently more calcemic, reflecting a selectively greater increase in renal 1,25(OH)2 vitamin D production by PTH. Equally surprisingly, continuous infusion of both peptides markedly, continuously, and equivalently suppressed bone formation.
Conclusions: PTHrP and PTH produce markedly different effects on 1,25(OH)2vitamin D homeostasis in humans, leading to different calcemic responses. Moreover, both peptides produce profound suppression of bone formation over multiple days, contrasting with events in HPT, but mimicking HHM. These findings underscore the facts that the mechanisms underlying the anabolic skeletal response to PTH and PTHrP in humans is poorly understood, as are the signal transduction mechanisms that link the renal PTH receptor to 1,25(OH)2vitamin D synthesis. These studies emphasize that much remains to be learned regarding the normal regulation of vitamin D metabolism and bone formation in response to PTH and PTHrP in humans.
Effect of Testosterone Replacement on Trabecular Architecture in Hypogonadal Men
Authors: Benito Maria , Vasilic Branimir , Wehrli Felix W , Bunker Benjamin , Wald Michael , Gomberg Bryon , Wright Alexander C , Zemel Babette , Cucchiara Andrew , Snyder Peter J 
Published: April 2006

Abstract
We evaluated the effect of testosterone treatment on trabecular architecture by μMRI in 10 untreated severely hypogonadal men. After 2 years, μMRI parameters of trabecular connectivity improved significantly, suggesting the possibility that testosterone improves trabecular architecture.
Introduction: Osteoporosis, characterized by low BMD and diminished bone quality, is a significant public health problem in men. Hypogonadal men have decreased BMD and deteriorated trabecular architecture compared with eugonadal men, and testosterone treatment improves their BMD. We tested the hypothesis that testosterone replacement in hypogonadal men would also improve their trabecular architecture.
Materials and Methods: We selected 10 untreated severely hypogonadal men and treated them with a testosterone gel for 24 months to maintain their serum testosterone concentrations within the normal range. Each subject was assessed before and after 6, 12, and 24 months of testosterone treatment by magnetic resonance microimaging (μMRI) of the distal tibia and by DXA of the spine and hip. The μMRI parameters reflect the integrity of the trabecular network and include the ratio of all surface voxels (representing plates) to curve voxels (representing rods) and the topological erosion index, a ratio of topological parameters expected to increase on trabecular deterioration to those expected to decrease. The higher the surface-to-curve ratio and the lower the topological erosion index, the more intact the trabecular network.
Results: Serum testosterone concentrations increased to midnormal after 3 months of treatment and remained normal thereafter. After 24 months of testosterone treatment, BMD of the spine increased 7.4% (p &lt; 0.001), and of the total hip increased 3.8% (p = 0.008). Architectural parameters assessed by μMRI also changed: the surface-to-curve ratio increased 11% (p = 0.004) and the topological erosion index decreased 7.5% (p = 0.004).
Conclusions: These results suggest the possibility that testosterone replacement of hypogonadal men improves trabecular architecture.
Identification of Osteopenic Women at High Risk of Fracture: The OFELY Study
Authors: Sornay-Rendu Elisabeth , Munoz Françoise , Garnero Patrick , Duboeuf François , Delmas Pierre D 
Published: April 2006

Abstract
About one-half of women with incident fractures have BMD above the WHO diagnostic threshold of osteoporosis. In the OFELY study, low BMD, increased markers of bone turnover, and prior fracture could be used to identify, within osteopenic women, those at high risk of fracture.
Introduction: Recent data suggest that about one-half of women with incident fractures have BMD above the World Health Organization (WHO) diagnostic threshold of osteoporosis (T score ≤ −2.5). We aimed to identify, within osteopenic women, those at high risk of fracture.
Materials and Methods: In the 671 postmenopausal women (mean age: 62 years) belonging to the Os des Femmes de Lyon (OFELY) population-based prospective cohort, we measured at baseline BMD by DXA at the spine and total hip, bone turnover markers (BTM) and clinical risk factors for osteoporosis. All fragility vertebral or nonvertebral fractures, confirmed by radiographs, were assessed during a median follow-up of 9.1 years (IQ: 2.3).
Results: 158 incident fractures were recorded in 116 women: 8% in normal, 48% in osteopenic, and 44% in osteoporotic women. Among osteopenic women, low BMD (−2.5 &lt; T score ≤ −2.0) was associated with an increased fracture risk with an age-adjusted hazard ratio (HR) of 2.5 (1.3-4.6). In addition, age, prior fracture, and high BTM—but not other risk factors—were independently associated with an increased fracture risk with an age-adjusted HR of 2.2 (1.2-4.3) for prior fractures and 2.2 (1.4-3.8) for bone alkaline phosphatase (BALP) in the highest quartile. In the whole group of osteopenic women, a large majority of incident fractures occurred in those with a low BMD, prior fractures, or BALP in the highest quartile, with an age-adjusted HR of 5.3 (2.3-11.8). The 10-year probability of fracture in osteopenic women was 26% if at least one predictor was present, contrasting with 6% in those without any of the three risk factors.
Conclusions: In postmenopausal women with osteopenia, low BMD, increased BTM, and prior fracture are associated with an increased risk of fracture in the subsequent 10 years. Their assessment may play an important role in identifying women at high risk of fracture who could not be adequately detected by BMD measurement alone and who may benefit from a therapeutic intervention.
Biglycan Modulates Osteoblast Differentiation and Matrix Mineralization
Authors: Parisuthiman Duenpim , Mochida Yoshiyuki , Duarte Wagner R , Yamauchi Mitsuo 
Published: April 2006

Abstract
MC3T3-E1 cell-derived clones expressing higher (S) or lower (AS) levels of biglycan were generated and characterized. The processes of cell differentiation and matrix mineralization were accelerated in S but delayed in AS, indicating that BGN modulates osteoblastic cell differentiation.
Introduction: Biglycan (BGN), a member of the small leucine-rich proteoglycan family, is one of the major proteoglycans found in bone and has been implicated in bone formation. In this study, the effects of over- or underexpression of BGN on osteoblastic cell phenotypes and matrix mineralization were studied.
Materials and Methods: MC3T3-E1 cells were transfected with vectors containing the BGN cDNA in a sense or antisense orientation to generate clones expressing higher (S clones) or lower (AS clones) levels of BGN. MC3T3-E1 cells and those transfected with an empty vector (EV) were used as controls. The levels of BGN synthesized by these clones were evaluated by Western blot analysis. Cell growth was analyzed by cell counting and cell differentiation by the gene expression patterns of several osteoblastic markers using quantitative real-time PCR. The abilities of these clones to form mineralized matrices were evaluated by in vitro and in vivo mineralization assays. Furthermore, the clones were treated with BMP-4 and their responsiveness was assessed.
Results: The cell growth in these clones was unaffected; however, osteoblast differentiation was significantly accelerated in S clones and suppressed in AS clones. The in vitro matrix mineralization in S clones was significantly enhanced but severely impaired in AS clones. When transplanted into immunodeficient mice, S clone transplants exhibited larger areas of lamellar bonelike matrices, whereas only minute amounts of woven bone-type structure was found in AS transplants. The response to BMP-4 was higher in S clones but poorer in AS clones compared with that of controls.
Conclusions: BGN modulates osteoblast differentiation, possibly by regulating BMP signaling, and consequently matrix mineralization.
Critical Role of β3 Integrin in Experimental Postmenopausal Osteoporosis
Authors: Zhao Haibo , Kitaura Hideki , Sands Mark S , Ross F Patrick , Teitelbaum Steven L , Novack Deborah Veis 
Published: April 2006

Abstract
We show that mice lacking β3 integrin are protected from OVX-induced bone loss. Using a lentiviral-based strategy to express β3 mutants in β3−/− mice, we also show that β3S752, but not β3Y747/Y759, is important for osteoclastic bone resorption in vivo.
Introduction: Mice lacking the β3 integrin have dysfunctional osteoclasts and therefore accumulate bone mass with age. Thus, the αvβ3 integrin is a potential anti-osteoporosis target. Identifying components of the β3 integrin that determine its function in vivo is essential for therapeutically exploiting the antiresorptive properties of αvβ3.
Materials and Methods: We used DXA and histomorphometry to assess bone loss after ovariectomy in wildtype and β3 integrin null mice. We used lentiviral vectors carrying various human β3 (hβ3) integrin constructs to transduce β3−/− bone marrow and reconstituted lethally irradiated β3−/− mice with the transduced marrow. The expressed constructs include the intact integrin and two mutants, namely hβ3Y747F/Y759F and hβ3S752P, each of which induces the bleeding dyscrasia, Glanzmann's thrombasthenia, in humans. Two months after transplantation, the expression of hβ3 was measured by flow cytometry of marrow-derived macrophages. Osteoclast differentiation and function were assessed ex vivo by TRACP and actin-ring staining, respectively. Reconstituted mice were ovariectomized, and bone loss was assessed by DXA, histomorphometry, and serum TRACP5b assay.
Results: β3−/− mice are protected from ovariectomy-induced bone loss, showing no difference in BMD compared with sham-operated controls. We successfully expressed hβ3 integrins in β3−/− hosts using lentiviral transduction of bone marrow. Two months after transplantation, 25–35% of marrow-derived macrophages expressed the hβ3 constructs. Similar to its effect in vitro, hβ3WT completely rescued the osteoclast and platelet phenotype of β3−/− mice. Whereas platelet function remained deranged in β3−/− mice overexpressing hβ3Y747F/Y759F, osteoclast function was fully restored. In contrast, β3−/− mice expressing hβ3S752P continued to exhibit prolonged bleeding times and dysfunctional osteoclasts in vitro and ex vivo. Most importantly, hβ3WT and hβ3Y747F/Y759F transplanted mice underwent equivalent ovariectomy-induced bone loss, whereas, like those bearing the control vector, hβ3S752P transplanted mice were protected.
Conclusions: Functional β3 integrin is required for ovariectomy-induced bone loss. β3S752, but not β3Y747/Y759, is critical for osteoclast function in vivo.
Relationship Between Changes in BMD and Nonvertebral Fracture Incidence Associated With Risedronate: Reduction in Risk of Nonvertebral Fracture Is Not Related to Change in BMD
Authors: Watts Nelson B , Geusens Piet , Barton Ian P , Felsenberg Dieter 
Published: April 2006

Abstract
Whether greater treatment-related changes in BMD result in greater decreases in fracture risk is controversial. We analyzed the relationship between BMD change and nonvertebral fracture risk in postmenopausal osteoporotic women from the risedronate fracture program. Change in BMD did not influence the magnitude of risedronate's effect on nonvertebral fractures; the incidence of nonvertebral fractures was equally low in treated patients whose BMD increased or decreased.
Introduction: In untreated patients, low BMD correlates with increased fracture risk. Whether greater increases in BMD induced by anti-osteoporosis drugs are related to greater decreases in vertebral fracture risk is controversial, and little has been written about the relationship between change in BMD and nonvertebral fracture risk. We analyzed the relationship between BMD change and nonvertebral fracture incidence using individual patient data from postmenopausal osteoporotic women receiving antiresorptive treatment with risedronate.
Materials and Methods: This posthoc analysis combined data from three pivotal risedronate fracture endpoint trials. Women received risedronate 2.5 or 5 mg (n = 2561) or placebo (n = 1418) daily for up to 3 years. BMD and nonvertebral fractures confirmed by radiograph (hip, wrist, pelvis, humerus, clavicle, and leg) were assessed periodically over 3 years.
Results: The incidence of nonvertebral fractures in risedronate-treated patients was not different between patients whose spine BMD decreased (7.8%) and those whose spine BMD increased (6.4%; hazard ratio to subgroup of patients who lost BMD [HR], 0.79; 95% CI, 0.50, 1.25) or between those whose femoral neck BMD decreased (7.6%) and those whose femoral neck BMD increased (7.5%; HR, 0.93; 95% CI, 0.68, 1.28). The changes in lumbar spine and femoral neck BMD explained only 12% (95% CI, 2%, 21%; p = 0.014) and 7% (95% CI, 2%, 13%; p = 0.005), respectively, of risedronate's nonvertebral fracture efficacy.
Conclusions: For patients treated with risedronate, changes in BMD as measured by DXA do not predict the degree of reduction in nonvertebral fractures.
DMP1 Depletion Decreases Bone Mineralization In Vivo: An FTIR Imaging Analysis
Authors: Ling Yunfeng , Rios Hector F , Myers Elizabeth R , Lu Yongbo , Feng Jian Q , Boskey Adele L 
Published: April 2006

Abstract
The role of DMP1 in mineralization was analyzed by comparing bone mineral and matrix properties in dmp1-null female mice to heterozygous and wildtype controls by FTIR imaging spectroscopy. The observed decreased mineral content in dmp1 null mice indicates a key role for dmp1 in bone mineralization. Indirect effects of DMP1 on other systems also determine the KO phenotype.
Introduction: Dentin matrix protein 1 (DMP1), an acidic phosphorylated extracellular matrix protein, is highly expressed in mineralized tissues. In vitro, DMP1 peptides can promote or inhibit mineralization depending on the extent of phosphorylation, the peptide size, and concentration. To clarify the biological function of DMP1 protein on in vivo mineralization, this study analyzed bone properties of dmp1 knockout (KO) mice compared with heterozygous (HET) and wildtype (WT) controls.
Materials and Methods: Tibias from dmp1 KO and age-, sex-, and background-matched HET and WT mice at 4 and 16 weeks (Ntotal = 60) were examined by Fourier transform infrared imaging (FTIRI), histology (n = 6 per genotype and age; N = 36), and geometry by μCT (n = 4 per genotype and age; N = 24). Serum ionic calcium and phosphate concentrations were also determined.
Results: The mineral-to-matrix ratios (spectroscopic parameter of relative mineral content) were significantly lower in dmp1 KO mice tibias compared with WT and HET at 4 and 16 weeks. The mineral crystallinity (crystal size/perfection) was significantly increased in dmp1 KO and HET mice relative to WT. Collagen cross-link ratios (a spectroscopic parameter related to the relative amounts of nonreducible/reducible collagen cross-links) in dmp1 KO were not significantly different from WT and HET. Based on μCT, cortical bone cross-sectional areas at 16 but not 4 weeks were significantly reduced in the KO compared with controls. Maximum, minimum, and polar cross-sectional moments of inertia were significantly lower in dmp1 KO than in HET at 16 weeks but not at 4 weeks. Histological analysis and μCT 3-D images suggested that dmp1 KO mice had osteomalacia. Dmp1 KO mice had significantly lower ionic calcium and phosphate concentrations relative to WT, whereas in the HET, values for phosphate were equivalent, and calcium values were decreased relative to WT values.
Conclusions: The findings of decreased mineral-to-matrix ratio and increased crystal size in bones of dmp1 KO mice suggest that DMP1 has multiple roles (both direct and indirect) in the regulation of postnatal mineralization. We suggest that direct effects on mineral formation, crystal growth, and indirect effects on regulation of Ca × P concentrations and matrix turnover all contribute to the dominant phenotype in the dmp1 KO mouse.
New Target Genes for NOV/CCN3 in Chondrocytes: TGF-β2 and Type X Collagen
Authors: Lafont Jerome , Jacques Claire , Le Dreau Gwenvael , Calhabeu Frederico , Thibout Helene , Dubois Catherine , Berenbaum Francis , Laurent Maryvonne , Martinerie Cecile 
Published: April 2006

Abstract
We studied the involvement of NOV/CCN3, whose function is poorly understood, in chondrocyte differentiation. NOV was found to upregulate TGF-β2 and type X collagen and to act as a downstream effector of TGF-β1 in ATDC5 and primary chondrocytes. Thus, NOV is a positive modulator of chondrogenesis.
Introduction: NOV/CCN3 is a matricellular protein that belongs to the CCN family. A growing body of evidence indicates that NOV could play a role in cell differentiation, particularly in chondrogenesis. During chick embryo development, NOV expression is tightly regulated in cartilage, and a high expression of NOV has been associated with cartilage differentiation in Wilms' tumors. However, a precise role for NOV and potential target genes of NOV in chondrogenesis are unknown.
Materials and Methods: ATDC5 cells and primary chondrocytes were either treated with NOV recombinant protein or transfected with a NOV-specific siRNA to determine, using quantitative RT-PCR, the effect of NOV on the expression of several molecules involved in chondrocyte differentiation. Stable ATDC5 clones expressing NOV were also established to show that NOV was a downstream effector of TGF-β1.
Results: We established that NOV/CCN3 expression increases in ATDC5 cells at early stages of chondrogenic differentiation and precedes the appearance of TGF-β2 and of several chondrocytic markers such as SOX9 or type X collagen. When exogenously administered, NOV recombinant protein up-regulates TGF-β2 and type X collagen mRNA levels both in ATDC5 cells and in primary mouse chondrocytes but does not influence SOX9 expression. This regulation also occurs at the endogenous level because downregulation of NOV expression is correlated with an inhibition of TGF-β2 and type X collagen in primary chondrocytes. Furthermore, we found that NOV expression is downregulated when chondrocytes are exposed to TGF-β1-dedifferentiating treatment in chondrocytes, further providing evidence that NOV may counteract TGF-β1 effects on chondrocytes.
Conclusions: This study provides the first characterization of two new targets of NOV involved in chondrocyte differentiation, shows that NOV acts with TGF-β1 in a cascade of gene regulation, and indicates that NOV is a positive modulator of chondrogenesis.