bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stimulation of Smad1 Transcriptional Activity by Ras-Extracellular Signal-Regulated Kinase Pathway: A Possible Mechanism for Collagen-Dependent Osteoblastic Differentiation
Authors: Suzawa Miyuki , Tamura Yasuhiro , Fukumoto Seiji , Miyazono Kohei , Fujita Toshiro , Kato Shigeaki , Takeuchi YASUHIRO 
Published: April 2006

Abstract
Signals from bone morphogenetic protein receptors (BMPRs) and cell adhesion to type I collagen are both important for osteoblastic differentiation and functions. BMP signals are mediated mostly by Smad and collagen signals are transduced by integrins to activate focal adhesion kinase (FAK) and its downstream molecules. This study was undertaken to clarify how extracellular matrix collagen signals converge with BMP actions. We show that integrin activation by collagen was involved in BMP signals because disruption of either collagen synthesis or collagen-α2β1-integrin binding inhibited the stimulatory effect of BMP-2 on osteoblastic MC3T3-E1 cells. Downstream signals of collagen-integrin might be FAK-Ras-extracellular signal-regulated kinase (ERK) in osteoblastic cells. We further show that Ras-ERK signals enhanced the transcriptional activity of Smad1 in response to BMP in these cells transiently transfected with expression plasmids for a constitutively active mutant RasV12, a dominant negative mutant RasN17, and an ERK phosphatase CL100. Ras-ERK signals did not augment the transcriptional activity of Smad3 in response to transforming growth factor β (TGF-β) receptor activation but that of Smad1 in response to BMPR activation as examined in COS-1 cells. These observations suggest that the Ras-ERK pathway downstream of integrin-FAK is involved in Smad1 signals activated by BMP and provide a possible mechanism for cooperation between intracellular signals activated by integrin and BMPRs in osteoblastic cells.
Platelet-Derived Growth Factor BB Secreted From Osteoclasts Acts as an Osteoblastogenesis Inhibitory Factor
Authors: Kubota Kazuishi , Sakikawa Chisa , Katsumata Mutsumi , Nakamura Takemichi , Wakabayashi Kenji 
Published: April 2006

Abstract
Osteoclasts and osteoblasts are responsible for strict bone maintenance with a balance between bone formation and resorption by interacting with each other. Recently, it has been revealed that osteoblasts/stromal cells regulate differentiation of osteoclasts/hematopoietic cells by two factors, the receptor activator of nuclear factor-κB (NF-κB) ligand (RANKL) on the plasma membrane, and secreted osteoprotegerin (OPG). However, no factors have yet been reported by which osteoclasts/hematopoietic cells regulate osteoblasts/stromal cells. To elucidate the possibility of signal transduction from osteoclasts to osteoblasts, we studied the conditioned medium of mouse osteoclast-like myeloma cell line RAW264.7 treated with RANKL. We found that this medium contains a factor that inhibits differentiation of mouse osteoblast precursor-like cell line MC3T3-E1 to osteoblasts induced by bone morphogenetic protein 4 (BMP-4) and named this factor osteoblastogenesis inhibitory factor (OBIF). OBIF was purified by successive three-step chromatography by heparin affinity, anion exchange, and reversed-phase columns. Osteoblastogenesis inhibitory activity made one peak in each chromatography step, showing the factor is a single entity. Active fractions were loaded on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and bands of proteins were excised, digested by trypsin, and analyzed by liquid chromatography equipped with tandem mass spectrometry (LC/MS/MS). Consequently, we have identified this factor to be platelet-derived growth factor BB (PDGF BB) homodimer. Furthermore, this identification of PDGF BB as OBIF was confirmed by neutralization of the inhibitory activity of the medium with anti-PDGF antibody. These results show, for the first time, that osteoclasts regulate osteoblasts directly and suggest that PDGF BB is a key factor in bone remodeling.
The Assembly and Remodeling of the Extracellular Matrix in the Growth Plate in Relationship to Mineral Deposition and Cellular Hypertrophy: An In Situ Study of Collagens II and IX and Proteoglycan
Authors: Mwale Fackson , Tchetina Elena , Wu C. William , Poole A. Robin 
Published: April 2006

Abstract
The recent development of new specific immunoassays has provided an opportunity to study the assembly and resorption of type II and IX collagens of the extracellular matrix in relationship to endochondral calcification in situ. Here, we describe how in the bovine fetal physis prehypertrophic chondrocytes deposit an extensive extracellular matrix that, initially, is rich in both type II and type IX collagens and proteoglycan (PG; principally, aggrecan). The majority of the α1(IX)-chains lack the NC4 domain consistent with our previous studies with cultured chondrocytes. During assembly, the molar ratio of type II/COL2 domain of the α1(IX)-chain varied from 8:1 to 25:1. An increase in the content of Ca2+ and inorganic phosphate (Pi) was initiated in the prehypertrophic zone when the NC4 domain was removed selectively from the α1(IX)-chain. This was followed by the progressive loss of the α1(IX) COL2 domain and type II collagen. In the hypertrophic zone, the Ca2+/Pi molar ratio ranged from 1.56 to a maximum of 1.74, closely corresponding to that of mature hydroxyapatite (1.67). The prehypertrophic zone had an average ratio Ca2+/Pi ranging from 0.25 to 1, suggesting a phase transformation. At hypertrophy, when mineral content was maximal, type II collagen was reduced maximally in content coincident with a peak of cleavage of this molecule by collagenase when matrix metalloproteinase 13 (MMP-13) expression was maximal. In contrast, PG (principally aggrecan) was retained when hydroxyapatite was formed consistent with the view that this PG does not inhibit and might promote calcification in vivo. Taken together with earlier studies, these findings show that matrix remodeling after assembly is linked closely to initial changes in Ca2+ and Pi to subsequent cellular hypertrophy and mineralization. These changes involve a progressive and selective removal of types II and IX collagens with the retention of the PG aggrecan.
The Effects of Dynamic Axial Loading on the Rat Growth Plate
Authors: Ohashi Naoko , Robling Alexander G. , Burr David B. , Turner Charles H. 
Published: April 2006

Abstract
Longitudinal bone growth can be suppressed by compressive loading. In this study, we applied three different magnitudes (17, 8.5, and 4N) of compressive force to growing rat ulnas 10 minutes/day for 8 days and investigated the effects on the distal growth plate biology. Further, to investigate growth rate recovery after cessation of loading, we examined rats 7 days after the loading period. Longitudinal growth of the ulna was suppressed in a dose-dependent manner by applied compressive force. In the 17N group, the longitudinal mineralization rate (LMR) at the distal growth plate was suppressed completely by loading and did not recover. However, in the 8.5N and 4N groups, LMR suppression recovered in 1 week. In the 17N group, growth plate height and hypertrophic zone height were significantly greater than control; the number of hypertrophic chondrocytes was increased; and some traumatic changes such as cracks in the growth plate were found. In addition, 17N loading suppressed cartilage mineralization and capillary invasion beneath the growth plate, although the number of chondrocytes synthesizing vascular endothelial growth factor (VEGF) was increased. Our study shows longitudinal growth suppression caused by axial loading of the ulna, which is proportional to the magnitude of load. Only the largest load (17N) caused morphological changes in the distal growth plate cartilage. There was no association found between mineralization and type X collagen localization or capillary invasion and VEGF expression.
Discriminatory Ability of Quantitative Ultrasound Parameters and Bone Mineral Density in a Population-Based Sample of Postmenopausal Women With Vertebral Fractures: Results of the Basel Osteoporosis Study
Authors: Hartl F. , Tyndall A. , Kraenzlin M. , Bachmeier C. , Gückel C. , Senn U. , Hans D. , Theiler R. 
Published: April 2006

Abstract
The discriminatory potential to classify subjects with or without vertebral fractures was tested cross-sectionally with different methods for the measurement of bone status in a population-based sample of postmenopausal women. Quantitative ultrasound (QUS) measurement at the calcaneus (Lunar Achilles, Hologic Sahara), the proximal phalanges (Igea Bone Profiler), and measurement of bone mineral density (BMD) with dual-energy X-ray absorptiometry (DXA; Lunar Expert) at several anatomic sites was performed in 500 postmenopausal women (aged 65-75 years) randomly selected from the population. In addition, 50 young female subjects (20-40 years old) had QUS measurements and served as controls to express QUS results as T-score values. Radiographs of the lumbar and thoracic spine were performed in the elderly women. Two independent radiologists reviewed the X-rays for the presence of vertebral fractures. Of 486 eligible study participants, no fracture was seen in 396 participants. Single vertebral fractures were observed in 71 subjects; 19 individuals presented multiple fractures. The overall prevalence of vertebral fractures was 18.5%. Participants without vertebral fractures were compared with subjects with vertebral fractures. Normal statistical distributions were found for all bone measurement results. Risk of vertebral fracture in subjects with no and multiple vertebral fracture was estimated using age adjusted odds ratios (ORs) for QUS and dual-energy X-ray absorptiometry (DXA) values. Each SD decrease in bone measurement increased the risk of multiple vertebral fracture by 3.0 (95% CI, 1.6-5.6) for the Achilles stiffness, by 3.8 (95% CI, 1.8-8.2) for the Sahara QUI, 2.1 (95% CI, 1.3-3.4) for the Bone Profiler amplitude-dependent speed of sound (AD-SOS), and 2.1 (95% CI, 1.2-3.9) and 2.4 (95% CI, 1.3-4.3) for DXA lumbar spine and for DXA total hip, respectively. Results of a discriminant analysis showed sensitivities between 84% and 58% and specificities between 72% and 58% for the respective DXA and QUS parameters. Optimum fracture thresholds for QUS measurements derived from this analysis were calculated also. Optimum T-score threshold values for QUS measurements tended to be higher than those for DXA measurements. However, the performance of QUS measurements is at least comparable with DXA measurements in identifying subjects with multiple vertebral fractures randomly selected from the population.
A Randomized School-Based Jumping Intervention Confers Site and Maturity-Specific Benefits on Bone Structural Properties in Girls: A Hip Structural Analysis Study
Authors: Petit M. A. , Mckay H. A. , Mackelvie K. J. , Heinonen A. , Khan K. M. , Beck T. J. 
Published: April 2006

Abstract
We compared 7-month changes in bone structural properties in pre- and early-pubertal girls randomized to exercise intervention (10-minute, 3 times per week, jumping program) or control groups. Girls were classified as prepubertal (PRE; Tanner breast stage 1; n = 43 for intervention [I] and n = 25 for control [C]) or early-pubertal (EARLY; Tanner stages 2 and 3; n = 43 for I and n = 63 for C). Mean ± SD age was 10.0 ± 0.6 and 10.5 ± 0.6 for the PRE and EARLY groups, respectively. Proximal femur scans were analyzed using a hip structural analysis (HSA) program to assess bone mineral density (BMD), subperiosteal width, and cross-sectional area and to estimate cortical thickness, endosteal diameter, and section modulus at the femoral neck (FN), intertrochanter (IT), and femoral shaft (FS) regions. There were no differences between intervention and control groups for baseline height, weight, calcium intake, or physical activity or for change over 7 months (p &gt; 0.05). We used analysis of covariance (ANCOVA) to examine group differences in changes of bone structure, adjusting for baseline weight, height change, Tanner breast stage, and physical activity. There were no differences in change for bone structure in the PRE girls. The more mature girls (EARLY) in the intervention group showed significantly greater gains in FN (+2.6%, p = 0.03) and IT (+1.7%, p = 0.02) BMD. Underpinning these changes were increased bone cross-sectional area and reduced endosteal expansion. Changes in subperiosteal dimensions did not differ. Structural changes improved section modulus (bending strength) at the FN (+4.0%, p = 0.04), but not at the IT region. There were no differences at the primarily cortical FS. These data provide insight into geometric changes that underpin exercise-associated gain in bone strength in early-pubertal girls.
The Secreted Protein Thrombospondin 2 Is an Autocrine Inhibitor of Marrow Stromal Cell Proliferation
Authors: Hankenson Kurt D. , Bornstein Paul 
Published: April 2006

Abstract
Marrow stromal cells (MSCs) are obtained in increased number from mice in which the thrombospondin 2 (TSP2) gene is disrupted, and these cells show increased DNA synthesis in vitro. To examine more closely the role of TSP2 in the physiology and osteogenic differentiation of MSCs, an in-depth characterization of TSP2-null MSCs was conducted. Determination of TSP2 protein content by Western analysis and RNA levels by reverse-transcription polymerase chain reaction (RT-PCR) indicated that MSCs are the primary source of TSP2 in the marrow and secrete abundant TSP2 into culture medium. Morphologically, the TSP2-null and wild-type (WT) cell populations were similar and by flow cytometry contained equivalent numbers of CD44+, Mac1+, intercellular adhesion molecule-1 (ICAM-1+), and ScaI+ cells. TSP2-null cells showed delayed mineralization associated with an increased rate of proliferation. Consistent with this finding, there was a decrease in expression of collagen and osteocalcin RNA by TSP2-null MSCs on day 7 and increased osteopontin expression on day 7 and day 14. In add-back experiments, recombinant TSP2 produced a dose-dependent decrease in proliferation. This reduction was associated with an accumulation of TSP2-treated cells in the G1 phase of the cell cycle and did not result from an increase in apoptosis. When TSP2 treatment was terminated, the cell population reentered the S phase. We conclude that the increased endosteal bone formation observed in TSP2-null mice results primarily from the failure of TSP2 to regulate locally MSC cell cycle progression.
Thyroid Hormones Promote Chondrocyte Differentiation in Mouse ATDC5 Cells and Stimulate Endochondral Ossification in Fetal Mouse Tibias Through Iodothyronine Deiodinases in the Growth Plate
Authors: Miura Masako , Tanaka Kiyoshi , Komatsu Yasato , Suda Michio , Yasoda Akihiro , Sakuma Yoko , Ozasa Ami , Nakao Kazuwa 
Published: April 2006

Abstract
Thyroid hormones (THs), 3,3′,5-triiodo-L-thyronine (T3) and L-thyroxine (T4), are important for the normal development of the growth plate (GP); congenital TH deficiency leads to severe dwarfism. In mouse chondrogenic cell line, ATDC5, T3 enhanced differentiation and increased Alizarin red staining, but did not affect Alcian blue staining. In organ-cultured mouse tibias, THs stimulated the cartilage growth, especially in the hypertrophic zone. Interestingly, T4 was as equally potent as T3 in organ-cultured tibias, which suggests that T4 is metabolized locally to T3, because T4 is a prohormone and must be converted to T3 for its activity. Two enzymes catalyze the conversion; type I deiodinase (D1) and type II deiodinase (D2). D1 has a ubiquitous distribution and D2, with a high affinity for T4, is present where the maintenance of intracellular T3 concentration is critical. Messenger RNAs (mRNAs) for D1 and D2 were detected in neonatal mouse tibias and ATDC5 cells. The enzyme activity was unaffected by the D1 inhibitor 6-propyl-2-thiouracil, suggesting that D2 mainly catalyzes the reaction. D2 mRNA was detected in differentiated ATDC5 cells. In organ-cultured mouse tibias, D2 activity was greater at later stages. In contrast, thyroid hormone receptors (TRs) were expressed in neonatal mouse tibias and ATDC5 cells, but their expression levels in ATDC5 cells were stable throughout the culture periods. Therefore, increased T3 production at later stages by D2 is likely to contribute to the preferential effects of THs in the terminal differentiation of GP. This article is the first to show that T4 is activated locally in GP and enhances the understanding of TH effects in GP.
Regulation of Fibroblast Growth Factor 2 and Fibroblast Growth Factor Receptors by Transforming Growth Factor β in Human Osteoblastic MG-63 Cells
Authors: Sobue T. , Gravely T. , Hand A. , Min Y. K. , Pilbeam C. , Raisz L. G. , Zhang X. , Larocca D. , Florkiewicz R. , Hurley M. M. 
Published: April 2006

Abstract
Fibroblast growth factor 2 (FGF-2) and its receptors (FGFRs) are important regulators of bone cell function. Although FGF-2 is a major modulator of bone cell function, its expression and regulation in human osteoblasts have not been investigated. We examined FGF-2 messenger RNA (mRNA) expression and regulation in the human osteosarcoma MG-63 cells. Northern analysis revealed that MG-63 cells expressed FGF-2 mRNA transcripts of 7, 4, 2.2, and 1.3 kilobases (kb). In the absence of serum, treatment with transforming growth factor beta (TGF-β; 0.1-10 ng/ml) increased all FGF-2 mRNA transcripts. Maximal increase was seen with 1 ng/ml of TGF-β. TGF-β increased FGF-2 mRNA expression within 2 h and this was sustained for 24 h. Phorbal myristate acetate (PMA; 1 μM) also increased FGF-2 mRNA at 6 h. Time course studies showed that TGF-β did not significantly alter FGFR1 or FGFR2 mRNA expression in MG-63 cells. Western blotting with anti-human FGF-2 revealed that MG-63 cells synthesize three isoforms of FGF-2 protein of ∼18, 22/23, and 24 kDa, which were increased after either 6 h or 24 h of treatment with TGF-β. Increased FGF-2 mRNA and protein expression in response to TGF-β was markedly reduced by the protein kinase A (PKA) inhibitor H-89. Immunogold labeling of MG-63 cells treated with TGF-β showed increased labeling for FGF-2 and FGFR2 in the nuclei. In contrast, TGF-β treatment significantly decreased FGFR1 labeling in the nuclei. These data show that TGF-β regulates FGF-2 gene expression in human osteosarcoma cells. Furthermore, TGF-β modulates the cellular localization of FGF-2 and its receptors.
A Randomized Trial of Nasal Spray Salmon Calcitonin in Men With Idiopathic Osteoporosis: Effects on Bone Mineral Density and Bone Markers
Authors: Dr. Trovas G. P. , Lyritis G. P. , Galanos A. , Raptou P. , Constantelou E. 
Published: April 2006

AbstractIn a 12-month randomized, double-blind, placebo-controlled trial, we have studied the effects of intranasal salmon calcitonin (SCT) on bone mineral density (BMD) and biochemical markers of bone turnover. Twenty-eight men with idiopathic osteoporosis aged 27-74 years (mean, 52.4 years) were randomized to receive either nasal SCT (200 IU) or a nasal placebo daily for a period of 1 year. All the men received a daily supplement of 0.5 g of calcium. The men who received SCT had a mean (±SEM) increase in BMD of 7.1 ± 1.7% at the lumbar spine. In contrast, the men who received the placebo had an increase of 2.4 ± 1.5% (p &gt; 0.05) for the comparison with baseline. The increase in lumbar BMD in the calcitonin group was significantly greater than that in the placebo group (p &lt; 0.05). There were no significant changes in the femoral neck, trochanter, or Ward's triangle relative to both baseline and placebo after 12 months. Treatment with nasal SCT resulted in a significantly pronounced suppression of bone resorption markers (urinary deoxypyridinoline [DPD], type I cross-linked N-telopeptide [NTX], and type I cross-linked C-telopeptide [CTX]) and to a lesser extent in bone formation markers (serum bone-specific alkaline phosphatase [BALP], osteocalcin [OC], serum C-terminal procollagen type I extension peptides [PICP], and serum N-terminal procollagen type I extension peptides [PINP]), whereas the placebo did not. Therapy was tolerated well and there were no treatment-related adverse events. We conclude that intranasal SCT (200 IU daily) is safe and effective in increasing lumbar BMD and reducing bone turnover in men with idiopathic osteoporosis.
Does Hormone-Replacement Therapy Prevent Fractures in Early Postmenopausal Women?
Authors: Randell Kaisa M. , Honkanen Risto J. , Kröger Heikki , Saarikoski Seppo 
Published: April 2006

Abstract
The purpose of this population-based prospective cohort study was to examine the effect of hormone-replacement therapy (HRT) on the risk of fractures. The study population consisted of 7217 postmenopausal women aged 47-56 years (mean, 53.3 years) at baseline from data taken from the Kuopio Osteoporosis Risk Factor and Prevention Study (OSTPRE) in Finland. We compared fracture incidences between HRT users and nonusers. A total of 679 (9.4%) women recorded validated fractures during the 5-year follow-up. Of these, 268 (39%) women had a distal forearm fracture. Two thousand six hundred seventy women (37%) had used HRT &gt;6 months during the follow-up—one-half of them continuously. The relative risk, estimated as hazard ratio with Cox regression, was 0.69 (95% CI, 0.58-0.82) for any fracture and 0.49 (0.36-0.66) for distal forearm fracture among HRT users as compared with never-users. After adjusting for age, body mass index (BMI), number of chronic health disorders, fracture history, and time since menopause (independent risk factors) the corresponding risks were 0.67 (0.55-0.81) and 0.53 (0.37-0.74), respectively. The respective adjusted risks for continuous HRT users were 0.62 (0.48-0.79) and 0.41 (0.26-0.67). The adjusted risk of other than distal forearm fracture was 0.74 (0.55-0.98). The results suggest that HRT has a beneficial effect on prevention of fractures in general and on that of distal forearm fracture in particular in early postmenopausal women.