bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of Mouse Atp6i Gene, the Gene Promoter, and the Gene Expression
Authors: Deng Wenjie , Stashenko Philip , Chen Wei , Liang Yuqiong , Shimizu Ken , Li Y.-P. 
Published: April 2006

Abstract
Solubilization of bone mineral by osteoclasts depends on the formation of an acidic extracellular compartment through the action of a V-type ATPase. We previously cloned a gene encoding a putative osteoclast-specific proton pump subunit, termed OC-116 kDa, approved mouse Atp6i (ATPase, H+ transporting, [vacuolar proton pump] member I). The function of Atp6i as osteoclast-specific proton pump subunit was confirmed in our mouse knockout study. However, the transcription regulation of Atp6i remains largely unknown. In this study, the gene encoding mouse Atp6i and the promoter have been isolated and completely sequenced. In addition, the temporal and spatial expressions of Atp6i have been characterized. Intrachromosomal mapping studies revealed that the gene contains 20 exons and 19 introns spanning ∼11 kilobases (kb) of genomic DNA. Alignment of the mouse Atp6i gene exon sequence and predicted amino acid sequence to that of the human reveals a strong homology at both the nucleotide (82%) and the amino acid (80%) levels. Primer extension assay indicates that there is one transcription start site at 48 base pairs (bp) upstream of the initiator Met codon. Analysis of 4 kb of the putative promoter region indicates that this gene lacks canonical TATA and CAAT boxes and contains multiple putative transcription regulatory elements. Northern blot analysis of RNAs from a number of mouse tissues reveals that Atp6i is expressed predominantly in osteoclasts, and this predominant expression was confirmed by reverse-transcription polymerase chain reaction (RT-PCR) assay and immunohistochemical analysis. Whole-mount in situ hybridization shows that Atp6i expression is detected initially in the headfold region and posterior region in the somite stage of mouse embryonic development (E8.5) and becomes progressively restricted to anterior regions and the limb bud by E9.5. The expression level of Atp6i is largely reduced after E10.5. This is the first report of the characterizations of Atp6i gene, its promoter, and its gene expression patterns during mouse development. This study may provide valuable insights into the function of Atp6i, its osteoclast-selective expression, regulation, and the molecular mechanisms responsible for osteoclast activation.
Bone Strength and Related Traits in HcB/Dem Recombinant Congenic Mice
Authors: Yershov Yevgeniy , Baldini Todd H. , Villagomez Seagram , Young Todd , Martin Melissa L. , Bockman Richard S. , Peterson Margaret G. E. , Blank Robert D. 
Published: April 2006

Abstract
Fracture susceptibility depends jointly on bone mineral content (BMC), gross bone anatomy, and bone microarchitecture and quality. Overall, it has been estimated that 50-70% of bone strength is determined genetically. Because of the difficulty of performing studies of the genetics of bone strength in humans, we have used the HcB/Dem series of recombinant congenic (RC) mice to investigate this phenotype. We performed a comprehensive phenotypic analysis of the HcB/Dem strains including morphological analysis of long bones, measurement of ash percentage, and biomechanical testing. Body mass, ash percentage, and moment of inertia each correlated moderately but imperfectly with biomechanical performance. Several chromosome regions, on chromosomes 1, 2, 8, 10, 11, and 12, show sufficient evidence of linkage to warrant closer examination in further crosses. These studies support the view that mineral content, diaphyseal diameter, and additional nonmineral material properties contributing to overall bone strength are controlled by distinct sets of genes. Moreover, the mapping data are consistent with the existence of pleiotropic loci for bone strength-related phenotypes. These findings show the importance of factors other than mineral content in determining skeletal performance and that these factors can be dissected genetically.
Col1a1-Driven Transgenic Markers of Osteoblast Lineage Progression
Authors: Dacic S. , Kalajzic I. , Visnjic D. , Lichtler A. C. , Rowe D. W. 
Published: April 2006

Abstract
The modular organization of the type I collagen promoter allows creation of promoter-reporter constructs with preferential activity in different type I collagen-producing tissues that might be useful to mark cells at different stages of osteoblastic differentiation. Primary marrow stromal cell (MSC) and mouse calvarial osteoblast (mCOB) cultures were established from transgenic mice harboring different Col1a1 promoter fragments driving chloramphenicol acetyltransferase (CAT). In these models, Col1a1 messenger RNA (mRNA) and alkaline phosphatase (ALP) are the first markers of differentiation appearing soon after the colonies develop. Bone sialoprotein (BSP) is detected 2-3 days later, followed by osteocalcin (OC) expression and nodule mineralization. A 3.6 Col1a1 fragment (ColCAT3.6) initiated activity concomitant with ALP staining and type I collagen mRNA expression. In contrast, a 2.3 Col1a1 fragment (ColCAT2.3) became active coincident with BSP expression. The pattern of transgene expression assessed by immunostaining was distinctly different. ColCAT3.6 was expressed within and at the periphery of developing nodules whereas the ColCAT2.3 expression was restricted to the differentiated nodules. The feasibility of using green fluorescent protein (GFP) as a marker of osteoblast differentiation was evaluated in ROS17/2.8 cells. A 2.3-kilobase (kb) Col1a1 promoter driving GFP (pOB4Col2.3GLP) was stably transfected into the cell line and positive clones were selected. Subcultures lost and then regained GFP expression that was localized in small clusters of cells throughout the culture. This suggests that expression from the 2.3-kb Col1A1 fragment is determined by the state of differentiation of the ROS17/2.8 cells. Col1a1 transgenes should be useful in appreciating the heterogeneity of a primary or immortalized culture undergoing osteoblastic differentiation.
Continuous Parathyroid Hormone and Estrogen Administration Increases Vertebral Cancellous Bone Volume and Cortical Width in the Estrogen-Deficient Rat
Authors: Zhou H. , Shen V. , Dempster D. W. , Lindsay R. 
Published: April 2006

Abstract
Generally, it is believed that intermittent administration of parathyroid hormone (PTH) has an anabolic effect on the skeleton, whereas continuous administration is catabolic. However, there is evidence that continuous exposure to PTH may have an anabolic effect, for example, in patients with mild primary hyperparathyroidism (PHPT). The possibility of delivering PTH continuously may have important implications for the treatment of osteoporosis. Furthermore, estrogen treatment may be useful in the medical management of PHPT. Therefore, we examined the skeletal effects of continuous administration of PTH, with or without estrogen, in the estrogen-deficient rat with established osteopenia. Forty 7-month-old SD rats were divided into four ovariectomy (OVX) groups and one sham-operated group. Eight weeks post-OVX, three groups received subcutaneous implants of Alzet mini pumps loaded with PTH(1-34) (30 μg/kg per day), 17β-estradiol (10 μg/kg per day) pellet, or both PTH and 17β-estradiol separately for 4 weeks. OVX and sham control groups were given the mini pumps loaded with vehicle. Two doses of calcein (10 mg/kg) were given subcutaneously to all rats 2 days and 8 days before death. Histomorphometry was performed on cancellous and cortical bone of the fourth lumbar vertebra. At 3 months, post-OVX rats displayed bone loss with high bone turnover. Estrogen reversed OVX-mediated high turnover without restoring cancellous bone volume (BV/TV). PTH infusion further increased bone turnover and partially restored BV/TV. However, PTH infusion increased cortical porosity. Estrogen inhibited PTH-mediated cancellous bone resorption and substantially increased BV/TV above sham control. The combined treatment was associated with a significant increase in peritrabecular fibrosis and woven bone formation. The combined treatment of PTH infusion and estrogen replacement enhanced cortical width but estrogen did not prevent the PTH-induced cortical tunneling. We conclude that continuous administration of PTH and estrogen increases cortical porosity but has substantial beneficial effects on vertebral cancellous bone volume and cortical width in OVX rats.
Ultrasonic Backscatter and Transmission Parameters at the Os Calcis in Postmenopausal Osteoporosis
Authors: Roux Christian , Roberjot Valéry , Porcher Raphaël , Kolta Sami , Dougados Maxime , Laugier Pascal 
Published: April 2006

Abstract
Ultrasound technology has emerged as a new tool in the assessment of osteoporosis. Ultrasound parameters usually are measured in transmission; there is a potential for the analysis of backscattered signals to provide information on bone microarchitecture. The aim of this study was to explore a new technological development of the method, adding backscatter coefficient to transmission parameters, and to examine the appropriate thresholds to identify postmenopausal osteoporotic women. We examined 210 postmenopausal women (including 60 with osteoporotic fractures) and 30 healthy premenopausal controls. They had lumbar spine and hip bone mineral density (BMD) measurement and quantitative ultrasound (QUS) evaluation at the os calcis, measured in transmission (broadband ultrasound attenuation [BUA], speed of sound [SOS], ratio of transit time [dt] to BUA [dt/BUA], and “strength” index [STI]) and reflexion (broadband ultrasound backscattering [BUB]). The standardized CVs (sCVs) were between 2.27% and 3.40% for QUS measured in transmission and 4.41% for BUB. The odds ratio (OR) for fracture discrimination adjusted for age was 2.77 for hip BMD and between 1.6 and 2.9 for QUS. After adjustment for hip BMD, ORs were still highly significant for SOS, STI, and dt/BUA. According to hip BMD T score, prevalence of osteoporosis in our population was 39%. To detect the same prevalence, T scores ranged between −0.95 and −1.42 for QUS. QUS parameters have adequate ability to discriminate osteoporotic patients from controls. The World Health Organization (WHO) threshold for diagnosis of osteoporosis does not apply to this technology. The clinical utility of BUB at the os calcis, in addition to usual ultrasound parameters, is not yet proven. However, BUB evaluation, which does not require two transducers and may be implemented in conventional reflection mode systems, warrants further studies.
Colocalization of Glucocorticoid and Mineralocorticoid Receptors in Human Bone
Authors: Beavan Siân , Horner Alan , Bord Sharyn , Ireland Deborah , Compston Juliet 
Published: April 2006

Abstract
Osteoporosis is a poorly understood but common complication of glucocorticoid therapy. The actions of glucocorticoids are mediated via glucocorticoid receptors (GRs), but in vitro, glucocorticoids also can bind to mineralocorticoid receptors (MRs). It is not known if MR protein is present in human bone and little is known of GR isoform expression (GRα and GRβ). GR and MR protein expression and possible sites of action were investigated in neonatal rib and adult iliac crest biopsy specimens using antibodies specific for MR, GRα, and GRαβ. Colocalization [MR GRα] [MR GRαβ] was performed using fluorescent-conjugated secondary antibodies. GRα, GRβ, and MR show distinct but overlapping patterns of expression, suggesting important functions for each receptor type. Osteoclasts showed no staining for GRα but strong staining for GRαβ, indicating expression of GRβ and a specific role in addition to antagonizing the transcriptional activity of GRα. MR also was observed in osteoclasts and colocalized with GRαβ. Coexpression of MR, GRα, and GRαβ was seen in osteoblasts. Reverse-transcription-polymerase chain reaction (RT-PCR) of cultured osteoblast RNA confirmed expression of both GRα and GRβ. Osteocytes stained with MR, GRα, and GRαβ antibodies but to a lesser degree than osteoblasts. In the neonatal rib cartilage, staining for GRα, GRαβ, and MR was present in approximately one-half of the resting and hypertrophic chondrocytes and in most of proliferating chondrocytes and chondrocytes within the mineralizing matrix. Identification of MR raises the possibility that the physiological and pharmacologic effects of glucocorticoids on bone may be mediated via MR as well as GR and that GRα, GRβ, and MR synergize to influence corticosteroid metabolism in human bone.
Digital Topological Analysis of In Vivo Magnetic Resonance Microimages of Trabecular Bone Reveals Structural Implications of Osteoporosis
Authors: Wehrli Felix W. , Gomberg Bryon R. , Saha Punam K. , Song Hee Kwon , Hwang Scott N. , Snyder Peter J. 
Published: April 2006

Abstract
Osteoporosis is a disease characterized by bone volume loss and architectural deterioration. The majority of work aimed at evaluating the structural implications of the disease has been performed based on stereologic analysis of histomorphometric sections. Only recently noninvasive imaging methods have emerged that provide sufficient resolution to resolve individual trabeculae. In this article, we apply digital topological analysis (DTA) to magnetic resonance microimages (μ-MRI) of the radius obtained at 137 × 137 × 350 μm3 voxel size in a cohort of 79 women of widely varying bone mineral density (BMD) and vertebral deformity status. DTA is a new method that allows unambiguous determination of the three-dimensional (3D) topology of each voxel in a trabecular bone network. The analysis involves generation of a bone volume fraction map, which is subjected to subvoxel processing to alleviate partial volume blurring, followed by thresholding and skeletonization. The skeletonized images contain only surfaces, profiles, curves, and their mutual junctions as the remnants of trabecular plates and rods after skeletonization. DTA parameters were compared with integral BMD in the lumbar spine and femur as well as MR-derived bone volume fraction (BV/TV). Vertebral deformities were determined based on sagittal MRIs of the spine with a semiautomatic method and the number of deformities counted after threshold setting. DTA structural indices were found the strongest discriminators of subjects with deformities from those without deformities. Subjects with deformities (n = 29) had lower topological surface (SURF) density (p &lt; 0.0005) and surface-to-curve ratio (SCR; a measure of the ratio of platelike to rodlike trabeculae; p &lt; 0.0005) than those without. Profile interior (PI) density, a measure of intact trabecular rods, was also lower in the deformity group (p &lt; 0.0001). These data provide the first in vivo evidence for the structural implications inherent in postmenopausal osteoporosis accompanying bone loss, that is, the conversion of trabecular plates to rods and disruption of rods due to repeated osteoclastic resorption.
Influence of the Upper Femur and Pelvic Geometry on the Risk and Type of Hip Fractures
Authors: Partanen Juha , Jämsä Timo , Jalovaara Pekka 
Published: April 2006

Abstract
The geometry of the upper femur has been reported to associate with the hip fracture risk in postmenopausal women. However, these associations seem to be partly conflicting, probably because of differences in measurement setup. Here, we compared the upper femur and pelvic geometries of 70 hip fracture patients (46 cervical and 24 trochanteric fractures) and 40 age-adjusted controls based on plain anteroposterior radiographs, eliminating the possible sources of inaccuracy as far as possible by using a standardized patient position and calibrated dimension measurements by digital image analysis. The femoral neck/shaft angle (NSA) was larger in the fracture patients compared with the controls (p &lt; 0.001). The fracture group had thinner cortices in the upper femur than the controls (p &lt; 0.001). The femoral shaft diameter (FSD; p &lt; 0.001), trochanter width (TW; p &lt; 0.01), and the pelvic dimensions, that is, the smallest outer pelvic diameter (SOPD; p &lt; 0.01) and the largest inner pelvic diameter (LIPD; p &lt; 0.05) were smaller in the fracture group. Comparing the fracture types, we found NSA larger in the cervical hip fracture patients than in the patients with a trochanteric fracture (p &lt; 0.01). The femoral neck/shaft cortex ratio was lower and the FSD was smaller in the cervical hip fracture group (p &lt; 0.05). Acetabular width (AW) was greater and the SOPD was wider in the cervical fracture patients (p &lt; 0.01). We concluded that the upper femur and pelvic dimensions as defined from calibrated and position-standardized plain radiographs are useful in the evaluation of hip fracture risk and fracture type.
Large-Scale Screening for Candidate Genes of Ossification of the Posterior Longitudinal Ligament of the Spine
Authors: Furushima Kozo , Shimo-Onoda Kazuki , Maeda Shingo , Nobukuni Takahiro , Ikari Katsunori , Koga Hiroaki , Komiya Setsuro , Nakajima Toshiaki , Harata Seiko , Inoue Ituro 
Published: April 2006

Abstract
Ossification of the posterior longitudinal ligament of the spine (OPLL) is the predominant myelopathy among Japanese, and is usually diagnosed by ectopic bone formation in the paravertebral ligament in Japanese and other Asians. To detect genetic determinants associated with OPLL, we performed an extensive nonparametric linkage study with 126 affected sib-pairs using markers for various candidate genes by distinct analyses, SIBPAL and GENEHUNTER. Eighty-eight candidate genes were selected by comparing the genes identified by complementary DNA (cDNA) microarray analysis of systematic gene expression profiles during osteoblastic differentiation of human mesenchymal stem cells with the genes known to be involved in bone metabolism. Of the 24 genes regulated during osteoblastic differentiation, only one, the alpha B crystalline gene, showed evidence of linkage (p = 0.016, nonparametric linkage [NPL] score = 1.83). Of 64 genes known to be associated with bone metabolism, 7 showed weak evidence of linkage by SIBPAL analysis (p &lt; 0.05): cadherin 13 (CDH13), bone morphogenetic protein 4 (BMP4), proteoglycan 1 (PRG1), transforming growth factor beta 3 (TGFb3), osteopontin (OPN), parathyroid hormone receptor 1 (PTHR1), and insulin-like growth factor 1 (IGF1). Among these genes, BMP4 (NPL = 2.23), CDH13 (NPL = 2.00), TGFb3 (NPL = 1.30), OPN (NPL = 1.15), and PTHR1 (NPL = 1.00) showed evidence of linkage by GENEHUNTER. Only BMP4 reached criteria of suggestive evidence of linkage. Because this gene is a well-known factor in osteogenetic function, BMP4 should be screened in further study for the polymorphism responsible.
Use of Type I Collagen Green Fluorescent Protein Transgenes to Identify Subpopulations of Cells at Different Stages of the Osteoblast Lineage
Authors: Kalajzic I. , Kalajzic Z. , Kaliterna M. , Gronowicz G. , Clark S. H. , Lichtler A. C. , Rowe D. 
Published: April 2006

Abstract
Green fluorescent protein (GFP)-expressing transgenic mice were produced containing a 3.6-kilobase (kb; pOBCol3.6GFPtpz) and a 2.3-kb (pOBCol2.3GFPemd) rat type I collagen (Col1a1) promoter fragment. The 3.6-kb promoter directed strong expression of GFP messenger RNA (mRNA) to bone and isolated tail tendon and lower expression in nonosseous tissues. The 2.3-kb promoter expressed the GFP mRNA in the bone and tail tendon with no detectable mRNA elsewhere. The pattern of fluorescence was evaluated in differentiating calvarial cell (mouse calvarial osteoblast cell [mCOB]) and in marrow stromal cell (MSC) cultures derived from the transgenic mice. The pOBCol3.6GFPtpz-positive cells first appeared in spindle-shaped cells before nodule formation and continued to show a strong signal in cells associated with bone nodules. pOBCol2.3GFPemd fluorescence first appeared in nodules undergoing mineralization. Histological analysis showed weaker pOBCol3.6GFPtpz-positive fibroblastic cells in the periosteal layer and strongly positive osteoblastic cells lining endosteal and trabecular surfaces. In contrast, a pOBCol2.3GFPemd signal was limited to osteoblasts and osteocytes without detectable signal in periosteal fibroblasts. These findings suggest that Col1a1GFP transgenes are marking different subpopulations of cells during differentiation of skeletal osteoprogenitors. With the use of other promoters and color isomers of GFP, it should be possible to develop experimental protocols that can reflect the heterogeneity of cell differentiation in intact bone. In primary culture, this approach will afford isolation of subpopulations of these cells for molecular and cellular analysis.
Bone Strength at Clinically Relevant Sites Displays Substantial Heterogeneity and Is Best Predicted From Site-Specific Bone Densitometry
Authors: Eckstein Felix , Lochmüller Eva-Maria , Lill Christoph A. , Kuhn Volker , Schneider Erich , Delling Günter , Müller Ralph 
Published: April 2006

Abstract
In this study we test the hypotheses that mechanical bone strength in elderly individuals displays substantial heterogeneity among clinically relevant skeletal sites, that ex situ dual-energy X-ray absorptiometry (DXA) provides better estimates of bone strength than in situ DXA, but that a site-specific approach of bone densitometry is nevertheless superior for optimal prediction of bone failure under in situ conditions. DXA measurements were obtained of the lumbar spine, the left femur, the left radius, and the total body in 110 human cadavers (age, 80.6 ± 10.5 years; 72 female, 38 male), including the skin and soft tissues. The bones were then excised, spinal and femoral DXA being repeated ex situ. Mechanical failure tests were performed on thoracic vertebra 10 and lumbar vertebra 3 (compressive loading of a functional unit), the left and right femur (side impact and vertical loading configuration), and the left and right distal radius (fall configuration, axial compression, and 3-point-bending). The failure loads displayed only very moderate correlation among sites (r = 0.39 to 0.63). Ex situ DXA displayed slightly higher correlations with failure loads compared with those of in situ DXA, but the differences were not significant and relatively small. Under in situ conditions, DXA predicted 50-60% of the variability in bone failure loads at identical (or closely adjacent) sites, but only around 20-35% at distant sites, advocating a site-specific approach of densitometry. These data suggest that mechanical competence in the elderly is governed by strong regional variation, and that its loss in osteoporosis may not represent a strictly systemic process.