bluuebunny/crossref_metadata_2025_split huggingface dataset:
Runx1/AML1/Cbfa2 Mediates Onset of Mesenchymal Cell Differentiation Toward Chondrogenesis
Authors: Wang YongJun , Belflower Ruth M , Dong Yu-Feng , Schwarz Edward M , O'Keefe Regis J , Drissi Hicham 
Published: April 2006

Abstract
Runx proteins mediate skeletal development. We studied the regulation of Runx1 during chondrocyte differentiation by real-time RT-PCR and its function during chondrogenesis using overexpression and RNA interference. Runx1 induces mesenchymal stem cell commitment to the early stages of chondrogenesis.
Introduction: Runx1 and Runx2 are co-expressed in limb bud cell condensations that undergo both cartilage and bone differentiation during murine development. However, the cooperative and/or compensatory effects these factors exert on skeletal formation have yet to be elucidated.
Materials and Methods: Runx1/Cbfa2 and Runx2/Cbfa1 were examined at different stages of embryonic development by immunohistochemistry. In vitro studies used mouse embryonic limb bud cells and assessed Runx expressions by immunohistochemistry and real-time RT-PCR in the presence and absence of TGFβ and BMP2. Runx1 was overexpressed in mesenchymal cell progenitors using retroviral infection.
Results: Immunohistochemistry showed that Runx1 and Runx2 are co-expressed in undifferentiated mesenchyme, had similar levels in chondrocytes undergoing transition from proliferation to hypertrophy, and that there was primarily Runx2 expression in hypertrophic chondrocytes. Overall, the expression of Runx1 remained significantly higher than Runx2 mRNA levels during early limb bud cell maturation. Treatment of limb bud micromass cultures with BMP2 resulted in early induction of both Runx1 and Runx2. However, upregulation of Runx2 by BMP2 was sustained, whereas Runx1 decreased in later time-points when type X collagen was induced. Although TGFβ potently inhibits Runx2 and type X collagen, it induces type II collagen mRNA and mildly but significantly inhibits Runx1 isoforms in the early stages of chondrogenesis. Virus-mediated overexpression of Runx1 in mouse embryonic mesenchymal cells resulted in a potent induction of the early chondrocyte differentiation markers but not the hypertrophy marker, type X collagen. Knockdown or Runx1 potently inhibits type II collagen, alkaline phosphatase, and Runx2 and has a late inhibitory effect on type X collagen.
Conclusion: These findings show a distinct and sustained role for Runx proteins in chondrogenesis and subsequent chondrocyte maturation. Runx1 is highly expressed during chondrogenesis in comparison with Runx2, and Runx1 gain of functions stimulated this process. Thus, the Runx genes are uniquely expressed and have distinct roles during skeletal development.
Contribution of Hip Strength Indices to Hip Fracture Risk in Elderly Men and Women
Authors: Ahlborg Henrik G , Nguyen Nguyen D , Nguyen Tuan V , Center Jacqueline R , Eisman John A 
Published: April 2006

Abstract
In this prospective, case-control study, femoral neck diameter, cross-sectional moment of inertia, or section modulus was an independent predictor of hip fracture risk after adjustment for BMD. However, the contribution of each of these indices to hip fracture prediction was modest in the presence of BMD.
Introduction: The relative contribution of measures of hip strength to hip fracture prediction is unclear. This study was designed to characterize the association between hip strength indices and hip fracture risk in relation to BMD in elderly men and women.
Materials and Methods: Seventy-one women and 25 men ≥60 years of age, who sustained a hip fracture during the study period of 1989–2003, were selected from the prospective, population-based Dubbo Osteoporosis Epidemiology Study. These fracture cases were randomly matched for age and sex in a 1:2 ratio with nonfracture individuals. BMD at the femoral neck was measured before the fracture event by DXA (Lunar DPX-L). Hip strength indices, including femoral neck diameter (FND), cross-sectional moment of inertia (CSMI), and section modulus (Z), were estimated by reanalysis of the image files using hip strength analysis software.
Results: In women, after adjustment for BMD, increased risk of hip fracture was associated with smaller FND (OR, 1.6; 95% CI, 1.0, 2.7), lower CSMI (OR, 1.8; 95% CI, 1.0, 3.2), or Z (OR, 1.6; 95% CI, 1.1, 5.1). In men, none of these hip strength indices were significant predictors of fracture risk. However, using the results in women as a prior distribution, it was estimated that the BMD-adjusted OR for FND (OR, 1.5; 95% CI, 1.0, 2.3), CSMI (OR, 1.6; 95% CI, 1.0, 2.5), or Z (OR, 2.3; 95% CI, 1.4, 3.9) was each significantly associated with hip fracture risk in men. In the logistic regression model, BMD alone accounted for 32% and 16% of the variance of fracture liability in women and men, respectively. The addition of FND, CSMI, or Z to the model increased the respective variance proportion to 34% and 19%.
Conclusions: These data suggest that smaller FND and lower CSMI or Z is an independent risk factor for hip fracture in both women and men. However, the contribution of these measures to hip fracture prediction over and above BMD is likely modest.
Identification of High‐Risk Individuals for Hip Fracture: A 14‐Year Prospective Study
Authors: Nguyen Nguyen D , Pongchaiyakul Chatlert , Center Jacqueline R , Eisman John A , Nguyen Tuan V 
Published: April 2006

AbstractIn this 14‐year prospective study, men and women were found to share a common set of risk factors for hip fracture: low BMD, postural instability and/or quadriceps weakness, a history of falls, and prior fracture. The combination of these risk factors accounted for 57% and 37% of hip fractures in women and men, respectively.Introduction: Risk factors for hip fracture, including low BMD, identified in women, have not been shown to be useful in men. It is also not known whether fall‐related factors (muscle strength and postural instability) predict hip fracture. This study examined the association between falls‐related factors and hip fractures in elderly men and women.Materials and Methods: This is an epidemiologic, community‐based prospective study, which included 960 women and 689 men ≥60 years of age who have been followed for a median of 12 years (interquartile range, 6–13). The number of person‐years was 9961 for women and 4463 for men. The outcome measure was incidence of hip fracture. Risk factors were femoral neck BMD (FNBMD), postural sway, quadriceps strength, prior fracture, and fall.Results: Between 1989 and 2003, 115 (86 women) sustained a hip fracture. The risk of hip fracture (as measured by hazards ratio [HR]) was increased by 3.6‐fold (95% CI: 2.6–4.5) in women and 3.4‐fold (95% CI: 2.5–4.6) in men for each SD (0.12 g/cm2) reduction in FNBMD. After adjusting for BMD, the risk of hip fracture was also increased in individuals with the highest tertile of postural sway (HR: 2.7; 95% CI: 1.6–4.5) and low tertiles of quadriceps strength (HR: 3.0; 95% CI: 1.3–6.8). Furthermore, a history of fall during the preceding 12 months and a history of fracture were independent predictors of hip fracture. For each level of BMD, the risk of hip fracture increased linearly with the number of non‐BMD risk factors. Approximately 57% and 37% of hip fracture cases in women and men, respectively, were attributable to the presence of risk factors, osteoporosis (BMD T score ≤ −2.5), and advancing age.Conclusions: Men and women had a common set of risk factors for hip fracture: low BMD, postural instability and/or quadriceps weakness, a history of falls, and prior fracture. Preventive strategies should simultaneously target reducing falls and improvement of bone strength in both men and women.
Increased Prevalence of Radiological Spinal Deformities in Active Acromegaly: A Cross-Sectional Study in Postmenopausal Women
Authors: Bonadonna Stefania , Mazziotti Gherardo , Nuzzo Monica , Bianchi Antonio , Fusco Alessandra , De Marinis Laura , Giustina Andrea 
Published: April 2006

Abstract
This cross-sectional study shows that high numbers of postmenopausal women with acromegaly develop vertebral fractures in relation to the activity of disease. In patients with active acromegaly, vertebral fractures occur even in presence of normal BMD, whereas in patients with controlled acromegaly, vertebral fractures are always accompanied by a pathological BMD.
Introduction: We studied the frequency of radiological vertebral fractures in a cohort of postmenopausal women with active or controlled acromegaly.
Materials and Methods: Thirty-six postmenopausal acromegalic patients (15 with active and 21 with controlled disease) were evaluated for BMD, bone metabolism (serum 25-hydroxyvitamin D, PTH, bone-specific alkaline phosphatase {BSALP}, and urinary deoxypyridinoline {Dpd}), and vertebral quantitative morphometry. Thirty-six nonacromegalic postmenopausal women, matched for age, were selected among the patients consulting the Bone Center as a control group for BMD evaluation and vertebral quantitative morphometry.
Results: Vertebral fractures were shown in 19 patients (52.8%) and 11 controls (30.6%; χ2: 3.7; p = 0.06). Fractured acromegalic women were older and had higher serum IGF-1, Dpd, and BSALP and lower T score and serum vitamin D values compared with nonfractured patients. Moreover, the fractured women had a longer diagnosis and were in the postmenopausal period for a longer period than the nonfractured women. The fracture rate was significantly higher in active than in controlled acromegaly (80% versus 33.3%; χ2: 7.6; p = 0.008). The patients with active acromegaly who fractured (12 cases) had significantly higher serum IGF-1 values (356 ng/ml; range: 212–950 versus 120 ng/ml; range: 84–217; p &lt; 0.001) and T scores (−1.3 SD, range: −2.9 to +1.3 versus −2.7 SD, range: −3.4 to −1.5, p = 0.04) compared with the fractured women whose disease was controlled (7 cases). All fractured women with controlled acromegaly had T scores &lt;−1.0 SD (57.1% of them had osteoporosis, and 42.9% were osteopenic). In contrast, 41.7% of women whose fractures were associated with active disease had a normal T score (&gt;−1.0 SD), whereas osteopenia and osteoporosis were found only in 33.3% and 25.0% of them, respectively.
Conclusions: This cross-sectional study shows that high numbers of postmenopausal women with acromegaly develop vertebral fractures in relation to the activity of disease. Furthermore, our study shows that, in patients with active acromegaly, vertebral fractures occur even in the presence of normal BMD, whereas in patients with controlled acromegaly, vertebral fractures are always accompanied by a pathological BMD.
A New Vitamin D Analog, 2MD, Restores Trabecular and Cortical Bone Mass and Strength in Ovariectomized Rats With Established Osteopenia
Authors: Ke Hua Zhu , Qi Hong , Crawford D Todd , Simmons Hollis A , Xu Gang , Li Mei , Plum Lori , Clagett-Dame Margaret , DeLuca Hector F , Thompson David D , Brown Thomas A 
Published: April 2006

Abstract
An orally active, highly potent analog of 1α,25-dihydroxyvitamin D3, 2MD, restores trabecular and cortical bone mass and strength by stimulating periosteal bone formation and decreasing trabecular bone resorption in OVX rats with established osteopenia.
Introduction: The purposes of this study were to determine the effects of long-term treatment with 2-methylene-19-nor-(20S)-1α,25(OH)2D3 (2MD) on restoring bone mass and bone strength in ovariectomized (OVX) rats with established osteopenia and 2MD effects on bone formation and bone resorption on trabecular and cortical bone surfaces.
Materials and Methods: Sprague-Dawley female rats were sham-operated (sham) or OVX at 4 months of age. Beginning at 8 weeks after OVX, OVX rats were orally dosed with 2MD at 0.5, 1, 2.5, 5, or 10 ng/kg/day for 16 weeks. Serum calcium was measured at 6, 13, and 16 weeks after treatment, and bone mass and structure, bone formation, bone resorption, and bone strength were determined at the end of the study.
Results: Serum calcium did not change significantly with 2MD at 0.5 or 1 ng/kg/day, whereas it significantly increased at 2.5, 5, or 10 ng/kg/day. 2MD significantly and dose-dependently increased total body BMD, total BMC, and stiffness of femoral shaft (FS), maximal load and stiffness of femoral neck, and toughness of the fifth lumbar vertebral body (L5) at all doses compared with OVX controls. In 2MD-treated OVX rats, there was a dose-dependent increase in total BMD and total BMC of the distal femoral metaphysis (DFM), trabecular bone volume of L3, ultimate strength and stiffness of L5, and maximal load of FS compared with OVX controls at dosages ≥1 ng/kg/day. At dosages &gt;2.5 ng/kg/day, most of the bone mass and bone strength related parameters were significantly higher in 2MD-treated OVX rats compared with sham controls. Bone histomorphometric analysis of L3 showed dose-dependent decreases in osteoclast number and osteoclast surface on trabecular bone surface and a dose-dependent increase in periosteal bone formation associated with 2MD treatment.
Conclusions: 2MD not only restored both trabecular and cortical bone mass but also added bone to the osteopenic OVX rats beyond that of sham controls by stimulating bone formation on the periosteal surface and decreasing bone resorption on the trabecular surface. 2MD increased bone mass and strength at doses that did not induced hypercalcemia.
Hepatocyte Growth Factor Contributes to Fracture Repair by Upregulating the Expression of BMP Receptors
Authors: Imai Yuuki , Terai Hidetomi , Nomura-Furuwatari Chizumi , Mizuno Shinya , Matsumoto Kunio , Nakamura Toshikazu , Takaoka Kunio 
Published: April 2006

Abstract
Hepatocyte growth factor (HGF) is activated and the expression of BMP receptors (BMPRs) is induced around the fracture site during the early phase of fracture repair. HGF facilitates the expression of BMPRs in mesenchymal cells. This study suggests that HGF contributes to fracture repair by inducing the expression of BMPRs.
Introduction: The precise mechanisms that control the upregulation of BMP, BMPRs, and other molecules involved in bone repair are not completely understood. In this study, we hypothesized that HGF, activated through the action of thrombin on the HGF activator, may enhance BMP action through the local induction of BMP or BMPRs.
Materials and Methods: Callus samples from tibial fractures in mice were harvested for immunohistochemical analysis of HGF and phosphorylated c-Met, for in situ hybridization of BMPRs, and for real-time RT-PCR analysis for the expression of HGF, c-Met, and BMPRs. To study the changes in gene expression of BMPRs in response to HGF, C3H10T1/2 cells were cultured with or without HGF and harvested for real-time RT-PCR and for Western blot analysis. To evaluate the contribution of HGF to the biological action of BMP2, C3H10T1/2 cells and primary muscle-derived mesenchymal cells were precultured with HGF and cultured with BMP2. In addition, the expression of the luciferase gene linked to the Id1 promoter containing the BMP responsive element and alkaline phosphatase (ALP) activity were assayed.
Results: Positive immunostaining of HGF and phosphorylated c-Met was detected around the fracture site at 1 day after the fracture was made. mRNA expression of BMPRs was increased 1 day after fracture and localized in mesenchymal cells at the fracture site. From an in vitro study, the expression of mRNA for BMPRs was elevated by treatment with HGF, but the expression of BMP4 did not change. Western blot analysis also showed the upregulation of BMPR2 by HGF treatment. The results from the luciferase and ALP assays indicated increased responsiveness to BMPs by treating with HGF.
Conclusions: This study indicates that HGF is activated and expressed at the fracture site and that HGF induces the upregulation of BMPRs in mesenchymal cells. Furthermore, HGF may facilitate BMP signaling without altering the expression of BMP molecules.
RhoA and Cytoskeletal Disruption Mediate Reduced Osteoblastogenesis and Enhanced Adipogenesis of Human Mesenchymal Stem Cells in Modeled Microgravity
Authors: Meyers Valerie E , Zayzafoon Majd , Douglas Joanne T , McDonald Jay M 
Published: April 2006

Abstract
Spaceflight, aging, and disuse lead to reduced BMD. This study shows that overexpression of constitutively active RhoA restores actin cytoskeletal arrangement, enhances the osteoblastic phenotype, and suppresses the adipocytic phenotype of human mesenchymal stem cells cultured in modeled microgravity.
Introduction: Reduced BMD during spaceflight is partly caused by reduced bone formation. However, mechanisms responsible for this bone loss remain unclear. We have previously shown reduced osteoblastogenesis and enhanced adipogenesis of human mesenchymal stem cells (hMSCs) cultured in modeled microgravity (MMG). The small GTPase, RhoA, regulates actin stress fiber formation and has been implicated in the lineage commitment of hMSCs. We examined the effects of MMG on actin cytoskeletal organization and RhoA activity and the ability of constitutively active RhoA to reverse these effects.
Materials and Methods: hMSCs were seeded onto plastic microcarrier beads at a density of 106 and allowed to form aggregates in DMEM containing 10% FBS for 7 days. Aggregates were incubated in DMEM containing 2% FBS for 6 h with or without an adenoviral vector containing constitutively active RhoA at a multiplicity of infection (moi) of 500 and allowed to recover in 10% FBS for 24 h. Cells were transferred to the rotary cell culture system to model microgravity or to be maintained at normal gravity for 7 days in DMEM, 10% FBS, 10 nM dexamethasone, 10 mM β-glycerol phosphate, and 50 μM ascorbic acid 2-phosphate.
Results: F-actin stress fibers are disrupted in hMSCs within 3 h of initiation of MMG and are completely absent by 7 days, whereas monomeric G-actin is increased. Because of the association of G-actin with lipid droplets in fat cells, the observed 310% increase in intracellular lipid accumulation in hMSCs cultured in MMG was not unexpected. Consistent with these changes in cellular morphology, 7 days of MMG significantly reduces RhoA activity and subsequent phosphorylation of cofilin by 88 ± 2% and 77 ± 9%, respectively. Importantly, introduction of an adenoviral construct expressing constitutively active RhoA reverses the elimination of stress fibers, significantly increases osteoblastic gene expression of type I collagen, alkaline phosphatase, and runt-related transcription factor 2, and suppresses adipocytic gene expression of leptin and glucose transporter 4 in hMSCs cultured in MMG.
Conclusion: Suppression of RhoA activity during MMG represents a novel mechanism for reduced osteoblastogenesis and enhanced adipogenesis of hMSCs.
Downregulation of Wnt Signaling by Increased Expression of Dickkopf-1 and -2 is a Prerequisite for Late-Stage Osteoblast Differentiation of KS483 Cells
Authors: van der Horst Geertje , van der Werf Steffie M , Farih-Sips Hetty , van Bezooijen Rutger L , Löwik Clemens WGM , Karperien Marcel 
Published: April 2006

Abstract
We examined the role of Wnt/β-catenin signaling in successive stages of osteoblast differentiation. It has been shown that Wnt signaling in mature osteoblasts needs to be downregulated to enable the formation of a mineralized matrix. Using RNA interference, we showed that this is, at least in part, accomplished by upregulation of the Wnt antagonists Dickkopf-1 and -2.
Introduction: The role of Wnt signaling in the initiation of osteoblast differentiation has been well studied. However, the role during late-stage differentiation is less clear. We have examined the role of Wnt/β-catenin signaling in successive stages of osteoblast differentiation.
Materials and Methods: We treated murine bone marrow and mesenchymal stem cell-like KS483 cells with either LiCl or Wnt3A during several stages of osteoblast differentiation. In addition, we generated stable KS483 cell lines silencing either the Wnt antagonist Dkk-1 or -2
Results: Activation of Wnt signaling by LiCl inhibits the formation of a mineralized bone matrix in both cell types. Whereas undifferentiated KS483 cells respond to Wnt3A by inducing nuclear β-catenin translocation, differentiated cells do not. This is at least in part accomplished by upregulated expression of Dkk-1 and -2 during osteoblast differentiation. Using RNA interference, we showed that Dkk-1 plays a crucial role in blunting the BMP-induced alkaline phosphatase (ALP) response and in the transition of an ALP+ osteoblast in a mineralizing cell. In contrast, Dkk-2 plays a role in osteoblast proliferation and the initiation of osteoblast differentiation.
Conclusions: Our data suggest that Wnt signaling in maturing osteoblasts needs to be downregulated to enable the formation of a mineralized bone matrix. Furthermore, they suggest that Dkk-1 and Dkk-2 may have distinct functions in osteoblast differentiation.
Vascular Endothelial Growth Factor Gene-Activated Matrix (VEGF165-GAM) Enhances Osteogenesis and Angiogenesis in Large Segmental Bone Defects
Authors: Geiger Florian , Bertram Helge , Berger Irina , Lorenz Helga , Wall Olga , Eckhardt Christina , Simank Hans-Georg , Richter Wiltrud 
Published: April 2006

Abstract
Healing of fractures is dependent on vascularization of bone, which is in turn promoted by VEGF. It was shown that 0.1 and 1 mg of pVEGF165-GAM led to a significant increase in vascularization and bone regeneration in defects that would otherwise have led to atrophic nonunions.
Introduction: One reason for lack of bone healing in nonunions is the absence of vascularization. In skeletogenesis, which is tightly linked to angiogenesis, vascular endothelial growth factor (VEGF) promotes the vascularization of the growth plate and transformation of cartilage to bone. We postulate that a gene-activated matrix (GAM), created with a plasmid coding for human VEGF165, coated on a collagen sponge could efficiently accelerate bone healing in large segmental defects.
Materials and Methods: Sixty New Zealand white rabbits received a 15-mm critical size defect on one radius, which was filled with either 0.1 or 1 mg plasmid-DNA as GAM. Radiographs were obtained every 3 weeks. After 6 or 12 weeks, animals were killed. New bone was measured by μCT scans. Vascularity was measured using anti-CD31 staining of endothelial cells in 18 regions of interest per implant.
Results: Scaffold and control plasmid showed no defect healing, whereas most of the animals in the VEGF groups showed partial or total bone regeneration. Significantly more bone was found in the VEGF groups, with no significant differences between the 0.1- and 1-mg groups. Immunohistochemical staining of endothelial cells revealed that the VEGF groups showed two to three times the number of vessels and a significantly larger endothelial area after 6 weeks. Twelve weeks after surgery, the amount of vascularization decreased, whereas more new bone was detectable.
Conclusions: The rabbit critical size defect was appropriate in size to produce atrophic nonunions. We showed that angiogenesis and osteogenesis can be promoted by a VEGF165-GAM that is an appropriate tool to induce bone healing in atrophic nonunions.