bluuebunny/crossref_metadata_2025_split huggingface dataset:
Further Characterization of Cells Expressing STRO-1 in Cultures of Adult Human Bone Marrow Stromal Cells
Authors: Stewart Karina , Walsh Susan , Screen Joanne , Jefferiss Carolyn M. , Chainey Jonathan , Jordan Grant R. , Beresford Jon N. 
Published: April 2006

Abstract
Primitive cells of the osteoblast lineage are not well characterized but are known to be present within the STRO-1+ fraction of adult human bone and marrow. A survey of human osteosarcoma cell lines revealed that STRO-1 is expressed by MG-63 but not SaOS-2. Among murine cell lines tested, expression of STRO-1 was detected in the bipotential (adipocyte/osteoblast) line BMS-2 but not the committed osteoblast precursor MC3T3-E1. A proportion of cultured adult human bone marrow stromal cells (BMSCs) consistently expressed the STRO-1 antigen. The expression of a range of cell surface antigens was studied in relation to STRO-1 by flow cytometry and several, including the bone/liver/kidney isoform of alkaline phosphatase (ALP), were found to subtype the STRO-1+ population of BMSCs. Further, BMSCs dual-labeled with antibodies recognizing STRO-1 and ALP could be assigned to one of four fractions: STRO-1−/ALP−, STRO-1+/ALP−, STRO-1+/ALP+, and STRO-1−/ALP+. Cells from each fraction could be isolated in high purity and, when recultured, remained viable and exhibited a limited degree of phenotypic stability. Using reverse transcriptase-polymerase chain reaction, cells in the four fractions were found to express different levels of transcripts for the parathyroid hormone receptor (PTHr) and bone sialoprotein (BSP). The expression of transcripts for the nuclear transcription factor core-binding factor alpha 1/osteoblast-specific factor-2 (CBFA1/OSF2) was restricted to those fractions expressing STRO-1 and/or ALP. Treatment with 10 nM dexamethasone consistently increased the proportion of cells present in those fractions which expressed the highest levels of transcripts for PTHr and BSP (STRO-1+/ALP+ and STRO-1−/ALP+) while simultaneously decreasing the proportion present in the STRO-1+/ALP− fraction. In conclusion, the expression of STRO-1 in vitro remains a characteristic of less well differentiated cells of the osteoblast lineage; in cultures of BMSCs and in established human osteosarcoma cell lines, there is an inverse association between the expression of STRO-1 and ALP; dual labeling of BMSCs with monoclonal antibodies recognizing STRO-1 and ALP permits the identification and isolation of cells of the osteoblast lineage at different stages of differentiation.
Biochemical Markers as Predictors of Rates of Bone Loss After Menopause
Authors: Rogers A. , Hannon R. A. , Professor Eastell R. 
Published: April 2006

Abstract
Biochemical markers of bone turnover may correlate with rates of bone loss in a group of postmenopausal women, but it is uncertain how useful they are in predicting rates of bone loss in the individual. The aim of this study was to determine the value of measurements of biochemical markers for the prediction of rates of bone loss in the individual. We studied 60 postmenopausal women (ages, 49–62 years), 43 of whom had gone through a natural menopause 1–20 years previously and 17 of whom had undergone hysterectomy 3–22 years ago. Lumbar spine bone mineral density (BMD) was measured using dual-energy X-ray absorptiometry (DXA) over 2–4 years. Bone formation markers (bone-specific alkaline phosphatase [ibAP] and amino terminal of type I collagen [PINP] and osteocalcin [OC]) were measured in serum. Bone resorption markers (N-telopeptide of type 1 collagen [NTx] and immunoreactive free deoxypyridinoline [iFDpd]) were measured in urine and corrected for creatinine (Cr). Rates of bone loss were calculated as percent change per year. We found significant negative correlations (Spearman rank) between all measured biochemical markers and rate of change in bone density with r values ranging from −0.35 to −0.52. When markers and rates of bone loss were divided into tertiles, prediction of bone loss in an individual was poor (κ &lt; 0.2). There was an exponential relationship between rate of bone loss and years since menopause (YSM) in the 43 women having a natural menopause (r2 = 0.44; p = 0.008) indicating higher rates of loss in the early postmenopausal period. Levels of NTx, iFDpd, and PINP also showed a significant negative correlation with YSM. We conclude that there is a strong relationship between rates of spinal bone loss and levels of bone turnover markers. Although this is a small study, the results also suggest that using DXA measurements of the lumbar spine as the “gold standard,” it is not possible to use biochemical markers to predict rate of bone loss in the individual.
The Hormonal Milieu in Early Stages of Bone Cell Differentiation Modifies the Subsequent Sex-Specific Responsiveness of the Developing Bone to Gonadal Steroids
Authors: Berger E. , Bleiberg I. , Weisman Y. , Lifschitz-Mercer B. , Leider-Trejo L. , Harel A. , Kaye A. M. , Somjen D. 
Published: April 2006

Abstract
We have established previously that rat bone tissue, as well as rat and human-derived bone cells in culture, show a sex-specific response to gonadal steroids in stimulation of the specific activity of the BB isozyme of creatine kinase (CK) and DNA synthesis. This response could be modified by manipulation of the endocrine environment during early stages in rat development. To further examine the influence of changing hormonal steroid milieu and vitamin D status on the action of gonadal steroids in developing bone tissue, we used two models of ectopic bone formation: demineralized tooth matrix (DTM) implanted under the skin, and femoral bone marrow (BM) transplanted under the kidney capsule of a syngeneic recipient mouse. The response to gonadal steroids in ossicles developed from implanted DTM depended on the recipient's gender; injection of estradiol 17β (E2; 5 μg) into young female mice 21 days after DTM implantation increased, 24 h later, CK activity in the newly formed ossicles by ∼60%, whereas injection of dihydrotestosterone (DHT; 50 μg) had no effect on CK activity. In contrast, in male mice, DHT but not E2 increased CK activity in the ossicles by ∼50%. This sex-specific response was abolished in gonadectomized mice resulting in a similar response of the ossicles to both E2 and DHT. When DTM was implanted into vitamin D-deficient female mice, there was a lower basal CK activity and a significantly diminished response to E2 in the newly formed bone tissues. When BM, which contains mesenchymal and stromal cells and committed osteoprogenitor cells, was transplanted into 6-week-old intact or gonadectomized female or male mice, the response of the newly formed bone ossicles, 21 days after transplantation, to E2 or to DHT was according to the gender of the donor. Bone formed from BM obtained from female mice responded to E2 only and those formed from male BM responded to DHT only. Ossicles developed from BM obtained from gonadectomized mice showed lack of response to either gonadal steroid. Furthermore, only ∼25% of the BM transplants obtained from castrated (CAST) male donors developed into ossicles. Ossicles formed from BM obtained from vitamin D-deficient female donors showed lack of response to gonadal steroids. These findings suggest that the manipulation of the hormonal milieu in early stages of the differentiation sequence of bone cells modifies the subsequent selective responsiveness of the developing bone tissue to gonadal steroids.
Expression of a P2X7 Receptor by a Subpopulation of Human Osteoblasts
Authors: Gartland A. , Hipskind R. A. , Gallagher J. A. , Bowler W. B. 
Published: April 2006

Abstract
There is now conclusive evidence that extracellular nucleotides acting via cell surface P2 receptors are important local modulators of bone cell function. Multiple subtypes of P2 receptors have been localized to bone, where their activation modulates multiple processes including osteoblast proliferation, osteoblast-mediated bone formation, and osteoclast formation and resorptive capacity. Locally released nucleotides also have been shown to sensitize surrounding cells to the action of systemic factors such as parathyroid hormone (PTH). In nonskeletal tissue recent attention has focused on one particular P2 receptor, the P2X7 receptor (previously termed P2Z), and its ability to form nonselective aqueous pores in the plasma membrane on prolonged stimulation. Expression of this receptor originally was thought to be restricted to cells of hemopoietic origin, in which it has been implicated in cell fusion, apoptosis, and release of proinflammatory cytokines. However, recent reports have indicated expression of this receptor in cells of stromal origin. In this study, we investigated the expression of the P2X7 receptor in two human osteosarcoma cell lines, as well as several populations of primary human bone-derived cells (HBDCs) at the levels of messenger RNA (mRNA) and protein. We found that there is a subpopulation of osteoblasts that expresses the P2X7 receptor and that these receptors are functional as assessed by monitoring ethidium bromide uptake following pore formation. Inhibition of delayed lactate dehydrogenase (LDH) release in response to the specific agonist 2′,3′-(4-benzoyl)-benzoyl-adenosine triphosphate (BzATP) by the nonspecific P2X receptor antagonist PPADS confirmed a receptor-mediated event. After treatment with BzATP SaOS-2 cells exhibited dramatic morphological changes consistent with those observed after P2X7-mediated apoptosis in hemopoietic cells. Dual staining with terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labeling (TUNEL) and a P2X7-specific monoclonal antibody confirmed the induction of apoptosis in osteoblasts expressing the P2X7 receptor. These data show for the first time the expression of functional P2X7 receptors in a subpopulation of osteoblasts, activation of which can result in ATP-mediated apoptosis.
Bone Formation by Transplanted Human Osteoblasts Cultured Within Collagen Sponge with Dexamethasone In Vitro
Authors: Yamanouchi Kouji , Satomura Kazuhito , Gotoh Yuji , Kitaoka Eiichiro , Tobiume Satoru , Kume Keiko , Nagayama Masaru 
Published: April 2006

Abstract
To apply osteoblasts to bone reconstruction, we proved that transplanted osteoblasts possessed the differentiated osteoblastic function and formed bonelike tissue in vivo after transplantation. First, we confirmed that dexamethasone (Dex) promoted the expression of osteoblastic phenotype in human osteoblast culture using reverse-transcription-polymerase chain reaction (RT-PCR). These osteoblasts were cultured for 10 days within collagen sponge, which consists of denatured type I collagen, in the presence or absence of 10−7 M Dex. The osteoblasts along with collagen sponge were transplanted into the trapezius muscles of 8-week-old severe combined immunodeficiency (SCID) mice, and the transplants were harvested at 2, 4, 6, and 8 weeks. At 2 weeks, Dex-treated osteoblasts formed bonelike tissue, the quantity of which increased in a time-dependent manner to 8 weeks. This bonelike tissue was composed of mineralized collagen matrix newly synthesized by the transplanted osteoblasts. This mineralized matrix was separated from the osteoblasts by nonmineralized matrixlike osteoid. Furthermore, many osteocytic cells were observed in this mineralized matrix. A high expression of alkaline phosphatase (ALPase) and osteocalcin was detected in the transplanted cells surrounding the bonelike tissue. In situ hybridization for human-specific alu sequence indicated that newly formed bone was of donor origin. The transplants of nontreated cells failed to form bonelike tissue. The transplants of collagen sponge alone formed no bonelike tissue. These studies indicate that Dex-treated human osteoblasts possess the differentiated osteoblastic function and are able to form bone tissue in vivo. These new findings are of use in facilitating the application of osteoblasts to bone reconstruction.
A Common Promoter Variant in the Cytochrome P450c17α (CYP17) Gene Is Associated with Bioavailable Testosterone Levels and Bone Size in Men
Authors: Zmuda Joseph M. , Cauley Jane A. , Kuller Lewis H. , Ferrell Robert E. 
Published: April 2006

Abstract
Cytochrome P450c17α (CYP17) encodes an enzyme with 17α-hydroxylase and 17,20-lyase activities, which is essential for the normal production of adrenal and gonadal androgens. Because androgens have powerful effects on bone growth and metabolism, we determined whether a single base pair (bp) substitution (T → C) in the promoter region (−34 bp) of CYP17 is associated with sex hormone levels, stature, and femoral mass and size in 333 white men aged 51-84 years (mean ± SD; 66 ± 7 years). Femoral neck bone mineral content (BMC), cross-sectional area (CSA), and bone mineral density (BMD) were measured using dual-energy X-ray absorptiometry (DXA). Genotype frequencies did not deviate from Hardy-Weinberg expectations. Serum bioavailable testosterone levels were 20% or 0.5 SDs higher in men with the C/C compared with the T/T genotype, whereas heterozygous men had intermediate hormone levels (p = 0.019). Men with the C/C genotype also were nearly 3 cm taller and had 0.6 SD greater femoral neck CSA than men with the T/T genotype (p ≤ 0.01 for both). The association with CSA persisted after adjusting for age, height, and body weight. In contrast, CYP17 genotype was not associated with femoral neck BMC, areal BMD (g/cm2), or estimated volumetric BMD (g/cm3). These results suggest that allelic variation at the CYP17 locus may contribute to the genetic influence on stature and femoral size in men.
Effect of 16 Months of Treatment with Tibolone on Bone Mass, Turnover, and Biomechanical Quality in Mature Ovariectomized Rats
Authors: Ederveen A. G. H. , Spanjers C. P. M. , Quaijtaal J. H. M. , Kloosterboer H. J. 
Published: April 2006

Abstract
Tibolone (Org OD14) is a tissue-specific steroid with estrogenic effects on the bone and vagina but not endometrium or breast and has been shown to prevent ovariectomy-induced bone loss in young and old rats. We evaluated the effect of long-term tibolone treatment on bone parameters in mature ovariectomized (OVX) rats. Six-month-old rats were allotted to one of six groups (n = 8). Sham-operated and control OVX groups received vehicle, whereas other groups (all OVX) received tibolone (125, 250, or 500 μg/day orally) or 17α-ethinylestradiol (EE; 24 μg/day orally) for 16 months. Treatment with tibolone prevented ovariectomy-induced bone loss in peripheral (femur and tibia) and axial (L1-L2 and L4) skeleton. In peripheral skeleton, tibolone and EE prevented loss of bone mass and quality to a similar extent. Tibolone dose-dependently inhibited trabecular bone volume loss in L1-L2 and tibia, and at 500 μg/day it inhibited 88% of L1-L2 and 55% of tibial volume loss (p ≤ 0.05 in each case). Tibolone, 500 μg, resulted in 10% greater cortical strength of femur (p ≤ 0.05) and 60% greater compressive strength of L4 (p ≤ 0.05) compared with vehicle-treated OVX rats. Tibolone and EE inhibited bone resorption and turnover, assessed by urinary deoxypyridinoline/creatinine and plasma osteocalcin, respectively. We conclude that 16 months of tibolone treatment prevents ovariectomy-induced deterioration of axial and peripheral skeleton and preserves cortical and trabecular bone strength by reducing bone resorption.
Neonatal Bone Mass: Influence of Parental Birthweight, Maternal Smoking, Body Composition, and Activity During Pregnancy
Authors: Godfrey Keith , Walker-Bone Karen , Robinson Sian , Taylor Pat , Shore Sarah , Wheeler Timothy , Cooper Cyrus 
Published: April 2006

Abstract
Evidence is accumulating that intrauterine growth and development may influence an individual's risk of osteoporosis in later adult life. To examine maternal and paternal influences on intrauterine skeletal growth, we used dual-energy X-ray absorptiometry to measure the neonatal bone mineral content (BMC) and bone mineral density (BMD) of 145 infants born at term. Independently of the infant's duration of gestation at birth, the birthweights of both parents and the height of the father were positively correlated with neonatal whole body BMC. Women who smoked during pregnancy had infants with a lower whole body BMC and BMD; overall, there was a 7.1-g (11%) average difference between whole body BMC of infants whose mothers did and did not smoke during pregnancy (p = 0.005). Women with thinner triceps skinfold thicknesses (reflecting lower fat stores) and those who reported a faster walking pace and more frequent vigorous activity in late pregnancy also tended to have infants with a lower BMC and BMD (p values for BMC; 0.02, 0.03, and 0.05, respectively). Maternal thinness and faster walking pace but not maternal smoking or parental birthweight also were associated with lower bone mineral apparent density (BMAD). The influences on skeletal growth and mineralization were independent of placental weight, a marker of the placental capacity to deliver nutrients to the fetus. These observations point to a combination of genetic and intrauterine environmental influences on prenatal skeletal development and suggest that environmental modulation, even at this early stage of life, may reduce the risk of osteoporosis in adulthood.
Milk Supplementation of the Diet of Postmenopausal Chinese Women on a Low Calcium Intake Retards Bone Loss
Authors: Lau E. M. C. , Woo J. , Lam V. , Hong A. 
Published: April 2006

Abstract
The Chinese diet is low in calcium (less than 500 mg/day on average), and previous observational studies have suggested an association between a low calcium intake and risk of hip and vertebral fracture. In this study, we randomly assigned 200 postmenopausal Chinese women (age range, 55–59 years) to receive 50 g of milk powder containing 800 mg of calcium per day or to a control group. The following are the mean percentage changes (and SEs) in height and bone mineral density (BMD) over 24 months: for height, −0.1 ± 0.2 cm in the milk supplementation group and −0.2 ± 0.1 cm in the control group; for BMD at the total hip, −0.06 ± 0.22% in the milk supplementation group and −0.88 ± 0.26% in the control group; for BMD at the spine (L1−L4), −0.56 ± 0.29% in the milk supplementation group and −1.5 ± 0.29% in the control group; for total body BMD, −0.32 ± 0.16% in the milk supplementation group and −1.2 ± 0.19% in the control group (p &lt; 0.05 by analysis of covariance [ANCOVA] for repeated measures for height and BMD at all sites). The milk supplementation group had less loss in terms of both height and BMD than the control group (p &lt; 0.05 by ANCOVA for repeated measures). Serum parathyroid hormone (PTH) concentration was lower and serum 25-hyroxyvitamin D [25(OH)D] level was higher in the milk supplementation group than the control group at 12 months (p &lt; 0.05 by paired t-test). We conclude that supplementing the diet of postmenopausal Chinese women with high calcium milk powder retards bone loss.
Inhibition of 1,25-Dihydroxyvitamin D3-Dependent Transcription by Synthetic LXXLL Peptide Antagonists that Target the Activation Domains of the Vitamin D and Retinoid X Receptors
Authors: Pathrose Peterson , Barmina Olga , Chang Ching-Yi , McDonnell Donald P. , Shevde Nirupama K. , Pike J. Wesley 
Published: April 2006

Abstract
The vitamin D receptor (VDR) is known to mediate the biological actions of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] through its ability to regulate cellular programs of gene expression. Although RXR appears to participate as a heterodimeric partner with the VDR, absolute evidence for its role remains equivocal in vivo. To test this role and to investigate the requirement for comodulator interaction, we identified VDR- and retinoid X receptor (RXR)-interacting LXXLL peptides and examined whether these molecules could block vitamin D and 9-cis retinoic acid (9-cis RA) response. We used a mammalian cell two-hybrid system to screen a series of nuclear receptor (NR)-reactive LXXLL peptides previously identified through phage display screening for hormone-dependent reactivity with either VDR or RXR. Three categories of peptides were identified: those reactive with both VDR and RXR, those selective for RXR, and those unreactive to either receptor. Peptide fusion proteins were then examined in MC3T3-E1 cells for their ability to block induction of the osteocalcin (OC) promoter by 1,25(OH)2D3 or stimulation of a retinoic acid response element-thymidine kinase (RARE-TK) reporter by 9-cis-RA. Peptides that interacted with both VDR and RXR blocked 1,25(OH)2D3-dependent transcription by up to 75%. Control LXXLL sequences derived from Src-1 and Grip also suppressed 1,25(OH)2D3-induced transactivation; peptides that interacted with RXR blocked 9-cis-RA-induced transcription. Interestingly, two RXR-interacting peptides were also found to block 1,25(OH)2D3 response effectively. These studies support the idea that comodulator recruitment is essential for VDR- and RXR-mediated gene expression and that RXR is required for 1,25(OH)2D3-induced OC gene transcription. This approach may represent a novel means of assessing the contribution of RXR in various endogenous biological responses to 1,25(OH)2D3.
Prediction of Fracture Risk in Postmenopausal White Women With Peripheral Bone Densitometry: Evidence From the National Osteoporosis Risk Assessment
Authors: Miller Paul D. , Siris Ethel S. , Barrett-Connor Elizabeth , Faulkner Kenneth G. , Wehren Lois E. , Abbott Thomas A. , Chen Ya-Ting , Berger Marc L. , Santora Arthur C. , Sherwood Louis M. 
Published: April 2006

AbstractLow bone mineral density (BMD) is a risk factor for fracture. Although the current “gold standard” test is DXA of the hip and spine, this method is not universally available. No large studies have evaluated the ability of new, less expensive peripheral technologies to predict fracture. We studied the association between BMD measurements at peripheral sites and subsequent fracture risk at the hip, wrist/forearm, spine, and rib in 149,524 postmenopausal white women, without prior diagnosis of osteoporosis. At enrollment, each participant completed a risk assessment questionnaire and had BMD testing at the heel, forearm, or finger. Main outcomes were new fractures of the hip, wrist/forearm, spine, or rib within the first 12 months after testing. After 1 year, 2259 women reported 2340 new fractures. Based on manufacturers' normative data and multivariable adjusted analyses, women who had T scores ≤ −2.5 SD were 2.15 (finger) to 3.94 (heel ultrasound [US]) times more likely to fracture than women with normal BMD. All measurement sites/devices predicted fracture equally well, and risk prediction was similar whether calculated from the manufacturers' young normal values (T scores) or using SDs from the mean age of the National Osteoporosis Risk Assessment (NORA) population. The areas under receiver operating characteristic (ROC) curves for hip fracture were comparable with those published using measurements at hip sites. We conclude that low BMD found by peripheral technologies, regardless of the site measured, is associated with at least a twofold increased risk of fracture within 1 year, even at skeletal sites other than the one measured.