bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanical Strain Stimulates Osteoblast Proliferation Through the Estrogen Receptor in Males as Well as Females
Authors: Damien E. , Price J. S. , Lanyon L. E. 
Published: April 2006

Abstract
Mechanical strain, testosterone, and estrogen all stimulate proliferation of primary cultures of male rat long bone (LOB)-derived osteoblast-like cells as determined by [3H]thymidine incorporation. The maximum proliferative effect of a single period of mechanical strain (3400 με, 1 Hz, and 600 cycles) is additional to that of testosterone (10−8 M) or estrogen (10−8 M). The cells' proliferative response to strain is abolished both by concentrations of tamoxifen that cause proliferation (10−8 M) and by those that have no effect (10−6 M). Strain-related proliferation also is reduced by the estrogen antagonist ICI 182,780 (10−8 M) but is unaffected by the androgen receptor antagonist hydroxyflutamide (10−7 M). Tamoxifen, ICI 182,780, and the aromatase inhibitor 4-dihydroandrostenedione, at concentrations that have no effect on basal proliferation, significantly reduce the proliferative effect of the aromatizable androgen testosterone but not that of the nonaromatizable androgen 5α-dihydrotestosterone. Hydroxyflutamide, at a concentration that has no effect on basal proliferation (10−7 M), eliminates the proliferative effect of 5α-dihydro-testosterone but had no significant effect on that caused by testosterone. Proliferation associated with strain is blocked by neutralizing antibody to insulin-like growth factor II (IGF-II) but not by antibody to IGF-I. Proliferation associated with testosterone is blocked by neutralizing antibody to IGF-I but is unaffected by antibody to IGF-II. These data suggest that in rat osteoblast-like cells from males, as from females, strain-related proliferation is mediated through the estrogen receptor (ER) in a manner that does not compete with estrogen but that can be blocked by ER modulators. Proliferation associated with testosterone appears to follow its aromatization to estrogen and is mediated through the ER, whereas proliferation associated with 5α-dihydrotestosterone is mediated by the androgen receptor. Strain-related proliferation in males, as in females, is mediated by IGF-II, whereas proliferation associated with estrogen and testosterone is mediated by IGF-I.
Cloning, Sequencing, and Functional Characterization of the Rat Homologue of Receptor Activator of NF-κB Ligand
Authors: Xu Jiake , Tan Jamie Wy , Huang Lin , Gao Xiu-Hui , Laird Rebecca , Liu Dan , Wysocki Stan , Zheng Ming H. 
Published: April 2006

Abstract
A complementary DNA (cDNA) encoding the rat homologue of receptor activator of NF-κB ligand/osteoprotegerin ligand/osteoclast differentiation factor/tumor necrosis factor (TNF)-related activation-induced cytokine (RANKL/OPGL/ODF/TRANCE) was cloned and sequenced from tibias of ovariectomized (OVX) rats. The predicted amino acid sequence of rat RANKL (rRANKL) has 84% and 96% identity to that of human and mouse RANKL, respectively, and 35% and 37% similarity to that of human and mouse TNF-related apoptosis-inducing ligand (TRAIL), respectively. RANKL transcripts were expressed abundantly in the thymus and bone tissues of OVX rats. rRANKL has a single hydrophobic region between residues 53 and 69, which is most likely to serve as a transmembrane domain. The long C-terminal region containing β-sheet-forming sequences of the TNF-like core is considered the extracellular region. Three truncated domains within the TNF-like core region were expressed as glutathione S-transferase (GST) fusion proteins and investigated for their ability to induce osteoclastogenesis. The results showed that GST-rRANKL (aa160-318) containing the full TNF-like core region had the highest capability to induce the formation of osteoclast-like cells from RAW264.7 cells. GST-rRANKL (aa239-318 and aa160-268) had lesser degrees of osteoclast inductivity. Furthermore, the GST-rRANKL (aa160-318) is capable of (1) inducing osteoclast formation from rat spleen cells in the presence of macrophage colony-stimulating factor (M-CSF), (2) stimulating mature rat osteoclast polarization and bone resorption ex vivo, and (3) inducing systemic hypercalcemia in vivo; thus the full TNF-like core region of rRANKL is an important regulator of calcium homeostasis and osteoclastic function.
Protein Kinase A Regulates Chondrogenesis of Mesenchymal Cells at the Post-Precartilage Condensation Stage via Protein Kinase C-α Signaling
Authors: Yoon Young-Mee , Oh Chun-Do , Kang Shin-Sung , Chun Jang-Soo 
Published: April 2006

Abstract
Chondrogenesis of mesenchymal cells during in vitro micromass culture requires the generation of cyclic adenosine monophosphate (cAMP) and subsequent activation of cAMP-dependent protein kinase A (PKA). In this study, we investigated the regulatory activity of PKA during chondrogenesis of chick limb bud mesenchymal cells. PKA activity was high in 1-day and 2-day cultures, which was followed by a slight decrease in 4-day and 5-day old cultures. Inhibition of PKA blocked chondrogenesis. It did not affect precartilage condensation, but it blocked the progression from the precartilage condensation stage to cartilage nodule formation. The PKA inhibition-induced blockage of chondrogenesis was accompanied by an altered expression of N-cadherin. Although expression of N-cadherin was detected during the early period of chondrogenesis, it became reduced as chondrogenesis proceeded. Still, inhibition of PKA maintained expression of N-cadherin throughout the micromass culture period. The inhibition of PKA did not affect expression of protein kinase C-α (PKCα), PKCϵ, PKCζ, and PKCλ/ι, which are the isoforms expressed in differentiating mesenchymal cells. However, PKA inhibition completely blocked activation of PKCα. Because PKC activity regulates N-cadherin expression and chondrogenesis, the PKA-mediated regulation of PKCα appears to be responsible for the PKA regulation of N-cadherin expression and chondrogenesis. Taken together, our results suggest that PKA regulates chondrogenesis by activating PKCα at the stage of post-precartilage condensation.
Expansile Skeletal Hyperphosphatasia: A New Familial Metabolic Bone Disease
Authors: Whyte Michael P. , Mills Barbara G. , Reinus William R. , Podgornik Michelle N. , Roodman G. David , Gannon Francis H. , Eddy Mark C. , Mcalister William H. 
Published: April 2006

Abstract
We describe a new familial metabolic bone disease characterized by expanding hyperostotic long bones, early onset deafness, premature tooth loss, and episodic hypercalcemia. The condition affects a mother and daughter studied at the age of 36 years and 11 years, respectively. Both individuals lost all hearing in early childhood and suffered premature shedding of teeth. Skeletal pains began just before puberty. Swelling and aching of most middle phalanges in the hands is an especially troublesome manifestation. The mother also had episodes of symptomatic hypercalcemia first documented in late childhood and subsequently during intercurrent illness and postpartum lactation. Radiographs show hyperostosis and/or osteosclerosis predominantly in the skull and appendicular skeleton. Long bones also are expanded considerably, especially the middle phalanges in the fingers. The mother's skeletal abnormalities are more severe. Biochemical parameters of bone turnover, including serum alkaline phosphatase (ALP) activity, are elevated substantially. In the proposita, dynamic histomorphometry of nondecalcified sections of iliac crest revealed rapid skeletal remodeling. In the mother, who had been treated with bisphosphonates, electron microscopy (EM) showed disorganized collagen bundles as well as necrotic and apoptotic bone cells but no osteocytic osteolysis. Measles virus gene transcripts were not detected in peripheral blood monocytes. Karyotyping was normal, 46,XX. Hyperphosphatasia with bone disease previously has been reported as either a sporadic or autosomal recessive condition. Expansile skeletal hyperphosphatasia (ESH) is probably inherited as an autosomal dominant trait with a high degree of penetrance.
Basic Fibroblast Growth Factor Stimulates Vascular Endothelial Growth Factor Release in Osteoblasts: Divergent Regulation by p42/p44 Mitogen-Activated Protein Kinase and p38 Mitogen-Activated Protein Kinase
Authors: Tokuda Haruhiko , Kozawa Osamu , Uematsu Toshihiko 
Published: April 2006

Abstract
We previously showed that basic fibroblast growth factor (bFGF) activates p38 mitogen-activated protein (MAP) kinase via Ca2+ mobilization, resulting in interleukin-6 (IL-6) synthesis in osteoblast-like MC3T3-E1 cells. In the present study, we investigated the effect of bFGF on the release of vascular endothelial growth factor (VEGF) in these cells. bFGF stimulated VEGF release dose dependently in the range between 10 and 100 ng/ml. SB203580, an inhibitor of p38 MAP kinase, markedly enhanced the bFGF-induced VEGF release. bFGF induced the phosphorylation of both p42/p44 MAP kinase and p38 MAP kinase. PD98059, an inhibitor of upstream kinase of p42/p44 MAP kinase, reduced the VEGF release. SB203580 enhanced the phosphorylation of p42/p44 MAP kinase induced by bFGF. The enhancement by SB203580 of the bFGF-stimulated VEGF release was suppressed by PD98059. The depletion of extracellular Ca2+ by [ethylenebis-(oxyethylenenitrilo)]tetracetic acid (EGTA) or 1,2-bis-(O-aminophinoxy)-ethane-N,N,N,N-tetracetic acid tetracetoxymethyl ester (BAPTA/AM), a chelator of intracellular Ca2+, suppressed the bFGF-induced VEGF release. A23187, a Ca ionophore, or thapsigargin, known to induce Ca2+ release from intracellular Ca2+ store, stimulated the release of VEGF by itself. A23187 induced the phosphorylation of p42/p44 MAP kinase and p38 MAP kinase. PD98059 suppressed the VEGF release induced by A23187. SB203580 had little effect on either A23187-induced VEGF release or the phosphorylation of p42/p44 MAP kinase by A23187. These results strongly suggest that bFGF stimulates VEGF release through p42/p44 MAP kinase in osteoblasts and that the VEGF release is negatively regulated by bFGF-activated p38 MAP kinase.
Caveolin-Enriched Membrane Signaling Complexes in Human and Murine Osteoblasts
Authors: Solomon Keith R. , Danciu Theodora E. , Adolphson Layla D. , Hecht Leah E. , Hauschka Peter V. 
Published: April 2006

Abstract
Osteoblasts receive regulatory signals from hormones, growth factors, calcium, extracellular matrix, and other cells through a variety of receptors that utilize an array of signaling pathways and cytoplasmic messengers. This article addresses the nonuniform distribution of important signaling molecules (platelet-derived growth factor receptors [PDGFRs], nonreceptor tyrosine kinases, tyrosine kinase adaptor proteins, G proteins, and nitric oxide synthases [NOSs]) in the surface membranes of human and murine osteoblasts. We show that particular inner leaflet signaling molecules (e.g., heterotrimeric G proteins and Src family tyrosine kinases) are clustered and concentrated in Triton X-100-insoluble membranes that are enriched in caveolin, the major structural component of caveolae (50- to 100-nm flask-shaped invaginations of the plasma membrane that apparently are organized by oligomers of the protein caveolin). In addition, we show that a subset of highly ligand-responsive PDGFRs and mitogen-activated protein (MAP) kinase pathway effectors are present in the caveolin-enriched membrane fraction of osteoblasts.
Sox-4 Messenger RNA Is Expressed in the Embryonic Growth Plate and Regulated via the Parathyroid Hormone/Parathyroid Hormone-Related Protein Receptor in Osteoblast-like Cells
Authors: Reppe Sjur , Rian Edith , Jemtland Rune , Olstad Ole K. , Gautvik Vigdis T. , Gautvik Kaare M. 
Published: April 2006

Abstract
Parathyroid hormone (PTH) and PTH-related protein (PTHrP) exert potent and diverse effects in cells of the osteoblastic and chondrocytic lineages. However, downstream mediators of these effects are characterized inadequately. We identified a complementary DNA (cDNA) clone encoding the 5′ end of the transcription factor Sox-4, using a subtracted cDNA library enriched in PTH-stimulated genes from the human osteoblast-like cell line OHS. The SOX-4 gene is a member of a gene family (SOX and SRY) comprising transcription factors that bind to DNA through their high mobility group (HMG)-type binding domain, and previous reports have implicated Sox proteins in various developmental processes. In situ hybridization of fetal and neonatal mouse hindlimbs showed that Sox-4 messenger RNA (mRNA) was expressed most intensely in the zone of mineralizing cartilage where chondrocytes undergo hypertrophy, and by embryonic day 17 (ED17), after the primary ossification center was formed, its expression was detected only in the region of hypertrophic chondrocytes. Sox-4 mRNA was detected in osteoblast-like cells of both human and rodent origin. In OHS cells, physiological concentrations (10−10–10−9 M) of human PTH 1-84 [hPTH(1-84)] and hPTH(1-34), but not hPTH(3-84), stimulated Sox-4 mRNA expression in a time-dependent manner, indicating involvement of the PTH/PTHrP receptor. Sox-4 transcripts also were detected in various nonosteoblastic human cell lines and tissues, in a pattern similar to that previously reported in mice. The presence of Sox-4 mRNA in hypertrophic chondrocytes within the mouse epiphyseal growth plate at sites that overlap or are adjacent to target cells for PTH and PTHrP, and its strong up-regulation via activated PTH/PTHrP receptors in OHS cells, makes it a promising candidate for mediating downstream effects of PTH and PTHrP in bone.
The Protective Effect of Hormone-Replacement Therapy on Fracture Risk Is Modulated by Estrogen Receptor α Genotype in Early Postmenopausal Women
Authors: Salmén Timo , Heikkinen Anna-Mari , Mahonen Anitta , Kröger Heikki , Komulainen Marja , Saarikoski Seppo , Honkanen Risto , Mäenpää Pekka H. 
Published: April 2006

Abstract
Genetic factors regulate bone mineral density (BMD) and possibly development of osteoporosis. It has been suggested that estrogen receptor α (ERα) genotype is associated with BMD, but the association between ERα genotype, fracture risk, and postmenopausal hormone replacement therapy (HRT) has not been studied. Therefore, we evaluated whether ERα polymorphism is associated with fracture risk in a 5-year trial with HRT in a population-based, randomized group of 331 early postmenopausal women. The participants consisted of two treatment groups: the HRT group (n = 151) received a sequential combination of 2 mg of estradiol valerate (E2Val) and 1 mg of cyproterone acetate with or without vitamin D3, 100-300 IU + 93 mg calcium as lactate per day; and the non-HRT group (n = 180) received 93 mg of calcium alone or in combination with vitamin D3, 100-300 IU/day. All new symptomatic, radiographically defined fractures were recorded. Pvu II restriction fragment length polymorphism of the ERα was determined using polymerase chain reaction (PCR). In all, 28 women sustained 33 fractures during the approximately 5.1-year follow-up. In the HRT group, the ERα genotype (PP, Pp, and pp) was not significantly associated with fracture risk (p = 0.138; Cox proportional hazards model). When the genotype was dichotomized (PP + Pp vs. pp), the incidence of new fractures in the HRT group was significantly reduced in women with the P allele (p = 0.046) with the relative risk (HR) of 0.25 (95% CI, 0.07-0.98), in comparison with the non-P allele group. After adjustment for time since menopause and previous fracture, the association between the dichotomous genotype and fracture risk persisted with HR of 0.24 (95% CI, 0.06-0.95; p = 0.042). In the non-HRT group, the ERα genotype was not significantly associated with fracture risk. During HRT, women with the pp genotype have a greater fracture risk than those with the P allele. The results suggest that the pp genotype is a relatively hormone-insensitive genotype, and it appears that women with the P allele may benefit more from the protective effect of HRT on fracture risk than women with the pp genotype.
Detraining Reverses Positive Effects of Exercise on the Musculoskeletal System in Premenopausal Women
Authors: Winters Kerri M. , Snow Christine M. 
Published: April 2006

Abstract
We studied the effects of a 6-month withdrawal of exercise after 12 months of progressive impact (jump) plus lower body resistance training on risk factors for hip fracture in premenopausal women (age, 30-45 years). Twenty-nine women completed the 12-month training and detraining programs and were compared with 22 matched controls. Bone mineral density (BMD) at the greater trochanter, femoral neck, lumbar spine, and whole body and body composition (% body fat) were measured by dual energy X-ray absorptiometry (DXA; Hologic QDR-1000/W). Knee extensor and hip abductor strength were assessed via isokinetic dynamometry (Kin-Com 500H); maximum leg power was tested using a Wingate Anaerobic Power test; and dynamic postural stability was measured on a stabilimeter (Biodex). All measurements were conducted at baseline, 12 months and 18 months with an additional midtraining measurement of BMD. Exercisers trained three times per week in a program of 100 jumps and 100 repetitions of resistance exercises at each session. Intensity was increased using weighted vests to final values of 10% and 13% of body weight (BW) for jump and resistance exercises, respectively. Differences between groups from training were analyzed by repeated measures analysis of covariance (ANCOVA), adjusted for baseline values. Detraining effects were analyzed by comparing the changes from training with the changes from detraining using repeated measures analysis of variance (ANOVA). Baseline values were not significantly different between exercisers and controls. Percent change over the training period was significantly greater in the exercise group than in the control group at the greater trochanter (2.7 ± 2.5% vs. 0.8 ± 0.8%, respectively; p &lt; 0.01) and approached significance at the femoral neck (1.2 ± 3.2% vs. −0.3 ± 1.9%, respectively; p = 0.06). Significant improvements also were observed in exercisers versus controls for strength and power with exercisers increasing 13-15% above controls, whereas stability was not different between groups. After 6 months of detraining, BMD and muscle strength and power decreased significantly toward baseline values, whereas control values did not change. We conclude that the positive benefits of impact plus resistance training on the musculoskeletal system in premenopausal women reverse when training is withdrawn. Therefore, continued training, perhaps at a reduced frequency and intensity, is required to maintain the musculoskeletal benefit from exercise that may lower fracture risk in later life.
Effect of Dietary Protein on Bone Loss in Elderly Men and Women: The Framingham Osteoporosis Study
Authors: Hannan Marian T. , Tucker Katherine L. , Dawson-Hughes Bess , Cupples L. Adrienne , Felson David T. , Kiel Douglas P. 
Published: April 2006

Abstract
Few studies have evaluated protein intake and bone loss in elders. Excess protein may be associated with negative calcium balance, whereas low protein intake has been associated with fracture. We examined the relation between baseline dietary protein and subsequent 4-year change in bone mineral density (BMD) for 391 women and 224 men from the population-based Framingham Osteoporosis Study. BMD (g/cm2) was assessed in 1988-1989 and in 1992-1993 at the femur, spine, and radius. Usual dietary protein intake was determined using a semiquantitative food frequency questionnaire (FFQ) and expressed as percent of energy from protein intake. BMD loss over 4 years was regressed on percent protein intake, simultaneously adjusting for other baseline factors: age, weight, height, weight change, total energy intake, smoking, alcohol intake, caffeine, physical activity, calcium intake, and, for women, current estrogen use. Effects of animal protein on bone loss also were examined. Mean age at baseline (±SD) of 615 participants was 75 years (±4.4; range, 68-91 years). Mean protein intake was 68 g/day (±24.0; range, 14-175 g/day), and mean percent of energy from protein was 16% (±3.4; range, 7-30%). Proportional protein intakes were similar for men and women. Lower protein intake was significantly related to bone loss at femoral and spine sites (p ≤ 0.04) with effects similar to 10 lb of weight. Persons in the lowest quartile of protein intake showed the greatest bone loss. Similar to the overall protein effect, lower percent animal protein also was significantly related to bone loss at femoral and spine BMD sites (all p &lt; 0.01) but not the radial shaft (p = 0.23). Even after controlling for known confounders including weight loss, women and men with relatively lower protein intake had increased bone loss, suggesting that protein intake is important in maintaining bone or minimizing bone loss in elderly persons. Further, higher intake of animal protein does not appear to affect the skeleton adversely in this elderly population.
A Role for N-Cadherin in the Development of the Differentiated Osteoblastic Phenotype
Authors: Ferrari Serge L. , Traianedes Kathy , Thorne Marielle , Lafage-Proust Marie-Helene , Genever Paul , Cecchini Marco G. , Behar Vered , Bisello Alessandro , Chorev Michael , Rosenblatt Michael , Suva Larry J. 
Published: April 2006

Abstract
Cadherins are a family of cell surface adhesion molecules that play an important role in tissue differentiation. A limited repertoire of cadherins has been identified in osteoblasts, and the role of these molecules in osteoblast function remains to be elucidated. We recently cloned an osteoblast-derived N-cadherin gene from a rat osteoblast complementary DNA library. After in situ hybridization of rat bone and immunohistochemistry of human osteophytes, N-cadherin expression was localized prominently in well-differentiated (lining) osteoblasts. Northern blot hybridization in primary cultures of fetal rat calvaria and in human SaOS-2 and rat ROS osteoblast-like cells showed a relationship between N-cadherin messenger RNA expression and cell-to-cell adhesion, morphological differentiation, and alkaline phosphatase and osteocalcin gene expression. Treatment with a synthetic peptide containing the His-Ala-Val (HAV) adhesion motif of N-cadherin significantly decreased bone nodule formation in primary cultures of fetal rat calvaria and inhibited cell-to-cell contact in rat osteoblastic TRAB-11 cells. HAV peptide also regulated the expression of specific genes such as alkaline phosphatase and the immediate early gene zif268 in SaOS-2 cells. Transient transfection of SaOS-2 cells with a dominant-negative N-cadherin mutant (NCADΔC) significantly inhibited their morphological differentiation. In addition, aggregation of NCTC cells derived from mouse connective tissue stably transfected with osteoblast-derived N-cadherin was inhibited by either treatment with HAV or transfection with NCADΔC. Together, these results strongly support a role for N-cadherin, in concert with other previously identified osteoblast cadherins, in the late stages of osteoblast differentiation. (J Bone Miner Res 2000;15:198–208)