bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes in Bone Structure and Mass With Advancing Age in the Male C57BL/6J Mouse
Authors: Halloran Bernard P. , Ferguson Virginia L. , Simske Steven J. , Burghardt Andrew , Venton Laura L. , Majumdar Sharmila
Published: April 2006

To determine whether the mouse loses bone with aging and whether the changes mimic those observed in human aging, we examined the changes in the tibial metaphysis and diaphysis in the male C57BL/6J mouse over its life span using microcomputed tomography (μCT). Cancellous bone volume fraction (BV/TV) decreased 60% between 6 weeks and 24 months of age. Loss was characterized by decreased trabecular number (Tb.N), increased trabecular spacing (Tb.Sp), and decreased connectivity. Anisotropy decreased while the structure model index increased with age. Cortical bone thickness increased between 6 weeks and 6 months of age and then decreased continuously to 24 months (−12%). Cortical bone area (Ct.Ar) remained constant between 6 and 24 months. Fat-free weight reached a peak at 12 months and gradually declined to 24 months. Total mass lost between 12 and 24 months reached 10%. Overall, the age-related changes in skeletal mass and architecture in the mouse were remarkably similar to those seen in human aging. Furthermore, the rapid early loss of cancellous bone suggests that bone loss is not just associated with old age in the mouse but rather occurs as a continuum from early growth. We conclude that the C57BL/6J male mouse maybe a useful model to study at least some aspects of age-related bone loss in humans.
The Effects of Growth Hormone Replacement Therapy on Bone Metabolism in Adult-Onset Growth Hormone Deficiency: A 2-Year Open Randomized Controlled Multicenter Trial
Authors: Bex Marie , Abs Roger , Maiter Dominique , Beckers Albert , Lamberigts Gerard , Bouillon Roger
Published: April 2006

Adult hypopituitary patients with growth hormone deficiency (GHD) show a significant decrease in bone mass and an increased fracture rate. Replacement therapy with GH increases bone turnover. Most of the long-term data on bone mineral content (BMC) and bone mineral density (BMD) have been acquired in open, noncontrolled trials involving limited numbers of patients. To determine whether long-term GH therapy is beneficial for bone despite the increased bone turnover, 100 patients (59 men and 41 women), aged 25-65 years (mean, 49.7 years) with adult-onset GHD were randomized to treatment with GH (40 men and 28 women; mean dose, 0.18 IU/kg per week) or to a nontreated control group (19 men and 13 women) for 24 months. Despite a similar increase in parameters of bone turnover (osteocalcin [OC], procollagen type I carboxy-terminal propeptide [PICP], and pyridinolines ([PYD]) in male and female GH-treated patients compared with controls, the effects on BMC and BMD as evaluated by dual-energy X-ray absorptiometry were gender specific. A significant increase in spine BMC and BMD and total hip BMD and a decrease in BMD at the ultradistal radius over time was observed in male GH-treated patients compared with the evolution in controls (mean ± SEM change at 24 months: +6.8 ± 1.1% and p = 0.009, +5.1 ± 0.8% and p = 0.005, +3.5 ± 0.7% and p = 0.02, and −2.6 ± 0.8% and p = 0.008, respectively). No significant treatment effects were observed in female patients. Despite the increase in the total remodeling space induced by GH treatment, prolonged GH therapy in adult-onset GHD has a positive effect on bone balance, maintaining bone mass in women, and even increasing it in men over a 2 year-period.
Tumor Necrosis Factor Modulates Apoptosis of Monocytes in Areas of Developmentally Regulated Bone Remodeling
Authors: Volejnikova S. , Marks S. C. , Graves D. T.
Published: April 2006

Tooth eruption is characterized by spatially segregated bone resorption along the path of eruption and bone formation in the opposite direction. Monocyte recruitment occurs in two distinct peaks in both areas of resorption and formation. Without such recruitment tooth eruption does not occur. The signals that regulate this recruitment are thought to involve the expression of cytokines and chemokines. One such cytokine is tumor necrosis factor (TNF), which can affect monocyte recruitment through the induction of chemokines and adhesion molecules and increase their lifespan by acting as antiapoptotic cell survival signals. We examined the latter by studying mice with targeted deletions of TNF receptors p55 and p75 (TNFRp55/p75). The results indicate that mice that lack functional TNF receptors have a significantly reduced number of monocytes in the apical area associated with bone formation. The reduced number of monocytes in this area can be accounted for by an increase in apoptosis in TNFRp55−/−/p75−/−. In contrast, the number of monocytes, the rate of monocyte apoptosis, and the formation of osteoclasts in the occlusal area associated with bone resorption occurred independently of TNF activity. These results suggest that TNF receptor signaling can affect tooth eruption by acting as a monocyte survival signal in some but not all areas of bone undergoing developmentally regulated remodeling.
Smad3 Promotes Alkaline Phosphatase Activity and Mineralization of Osteoblastic MC3T3-E1 Cells
Authors: Sowa Hideaki , Kaji Hiroshi , Yamaguchi Toru , Sugimoto Toshitsugu , Chihara Kazuo
Published: April 2006

Transforming growth factor (TGF) β is abundantly stored in bone matrix and appears to regulate bone metabolism. Although the Smad family proteins are critical components of the TGF-β signaling pathways, the roles of Smad3 in the expression of osteoblastic phenotypes remain poorly understood. Therefore, this study was performed to clarify the roles of Smad3 in the regulation of proliferation, expression of bone matrix proteins, and mineralization in osteoblasts by using mouse osteoblastic cell line MC3T3-E1 cells stably transfected with Smad3. Smad3 significantly inhibited [3H]thymidine incorporation and fluorescent intensity of the MTT-dye assay, compared with empty vector. Moreover, Smad3 increased the levels of type I procollagen, osteopontin (OPN), and matrix Gla protein (MGP) mRNA in Northern blotting. These effects of Smad3 mimicked the effects of TGF-β on the same cells. On the other hand, Smad3 greatly enhanced ALP activity and mineralization of MC3T3-E1 cells compared with empty vector, although TGF-β inhibited ALP activity and mineralization of wild-type MC3T3-E1 cells. A type I collagen synthesis inhibitor L-azetidine-2-carboxylic acid, as well as osteocalcin (OCN), significantly antagonized Smad3-stimulated ALP activity and mineralization of MC3T3-E1 cells. In conclusion, this study showed that in mouse osteoblastic cells, Smad3 inhibited proliferation, but it also enhanced ALP activity, mineralization, and the levels of bone matrix proteins such as type I collagen (COLI), OPN, and MGP. We propose that Smad3 plays an important role in osteoblastic bone formation and might help to elucidate the transcriptional mechanism of bone formation and possibly lead to the development of bone-forming drugs.
Dietary Essential Amino Acid Supplements Increase Bone Strength by Influencing Bone Mass and Bone Microarchitecture in Ovariectomized Adult Rats Fed an Isocaloric Low-Protein Diet
Authors: Ammann P. , Laib A. , Bonjour J.-P. , Meyer J. M. , Rüegsegger P. , Rizzoli R.
Published: April 2006

This study was designed to investigate whether the administration of dietary essential amino acid supplements in adult rats made osteoporotic by estrogen deficiency and reduced protein intake could reverse the deleterious effects caused by these maneuvers. This animal model was selected to mimic the situation observed in elderly women in whom estrogen deficiency and/or low-protein intake (but also calcium and vitamin D deficiency) are known to contribute to the pathogenesis of osteoporosis. Six-month-old rats were ovariectomized (OVX) and fed an isocaloric 2.5% casein diet for 10 weeks or sham-operated (SHAM) and fed an isocaloric 15% casein diet. The animals fed the 2.5% casein diet were given isocaloric supplements of essential amino acids in similar relative proportion to that of casein at doses of 2.5% or 5% of total diet for an additional 16 weeks. Vertebrae, femur, and tibia bone mineral density (BMD); ultimate strength; and microtomographic histomorphometry were evaluated before and after dietary essential amino acid supplements. Essential amino acid supplements increased vertebrae, femur, and tibia bone strength in OVX rats fed a low-protein diet. The mechanical changes induced by this dietary isocaloric supplement were associated with the prevention of a further BMD decrease or even with some increases and changes in microarchitecture such as from a rod to a plate trabecular spacial configuration and increased cortical thickness. Higher insulin-like growth factor (IGF) I levels, as well as greater bone formation and reduced bone resorption as assessed by biochemical markers of bone remodeling, were found in rats receiving essential amino acid supplements. In conclusion, dietary essential amino acid supplements increased bone strength through modifications of BMD, trabecular architecture, and cortical thickness possibly by an IGF-I-mediated process.
Association Analysis of Single Nucleotide Polymorphisms in Cartilage-Specific Collagen Genes With Knee and Hip Osteoarthritis in the Japanese Population
Authors: Ikeda Toshiyuki , Mabuchi Akihiko , Fukuda Akira , Kawakami Akira , Yamada Ryo , Yamamoto Seizo , Miyoshi Kota , Haga Nobuhiko , Hiraoka Hisatada , Takatori Yoshio , Kawaguchi Hiroshi , Nakamura Kozo , Ikegawa Shiro
Published: April 2006

Osteoarthritis (OA) is one of the most common diseases in the elderly. Although its pathophysiology is complex and its molecular basis remains to be determined, much evidence suggests that OA has strong genetic determinants. To search for susceptibility loci of OA, we selected seven candidate genes encoding cartilage-specific collagens (type II, IX, X, and XI collagens) and performed association analysis for OA using single nucleotide polymorphisms (SNPs) in the coding region of these genes. Four hundred seventeen OA samples and 280 control samples were collected from the Japanese population, and 12 SNPs were genotyped. Our studies have identified two susceptibility loci of OA: COL2A1 and COL9A3. An SNP in COL9A3 showed significant association with knee OA (p = 0.002, odds ratio [OR] = 1.48). Haplotype analysis showed significant association between a specific haplotype of COL2A1 and hip OA (p = 0.024; OR = 1.30). Further analysis of these two genes will shed light on the molecular mechanisms of OA.
Hadju-Cheney Syndrome: Response to Therapy With Bisphosphonates in Two Patients
Authors: Drake WM , Hiorns MP , Kendler DL
Published: April 2006

Hadju-Cheney syndrome is characterized by short stature, distinctive facies, and a slowly progressive skeletal dysplasia including acro-osteolysis. Autosomal dominant inheritance is typical, but the genetic defect and molecular pathogenesis of the syndrome are unknown. Osteoporosis with atraumatic fracture is a frequent finding, and previous studies have documented biochemical and morphometric evidence of high bone turnover. Here, we report the clinical details and response to therapy with bisphosphonates in two patients (mother and son) with Hadju-Cheney syndrome and postulate that osteoclast-mediated bone resorption is important in the generalized osteoporosis commonly associated with this condition.
Regional Specificity of Exercise and Calcium During Skeletal Growth in Girls: A Randomized Controlled Trial
Authors: Iuliano-Burns Sandra , Saxon Leanne , Naughton Geraldine , Gibbons Kay , Bass Shona L
Published: April 2006

Combining exercise with calcium supplementation may produce additive or multiplicative effects at loaded sites; thus, we conducted a single blind, prospective, randomized controlled study in pre- and early-pubertal girls to test the following hypotheses. (1) At the loaded sites, exercise and calcium will produce greater benefits than exercise or calcium alone. (2) At non-loaded sites, exercise will have no benefit, whereas calcium with or without exercise will increase bone mass over that in exercise alone or no intervention. Sixty-six girls aged 8.8 ± 0.1 years were randomly assigned to one of four study groups: moderate-impact exercise with or without calcium or low-impact exercise with or without calcium. All participants exercised for 20 minutes, three times a week and received Ca-fortified (434 ± 19 mg/day) or non-fortified foods for 8.5 months. Analysis of covariance (ANCOVA) was used to determine interaction and main effects for exercise and calcium on bone mass after adjusting for baseline bone mineral content and growth in limb lengths. An exercise-calcium interaction was detected at the femur (7.1%, p < 0.05). In contrast, there was no exercise-calcium interaction detected at the tibia-fibula; however, there was a main effect of exercise: bone mineral content increased 3% more in the exercise than non-exercise groups (p < 0.05). Bone mineral content increased 2–4% more in the calcium-supplemented groups than the non-supplemented groups at the humerus (12.0% vs. 9.8%, respectively, p < 0.09) and radius-ulna (12.6% vs. 8.6%, respectively, p < 0.01). In conclusion, greater gains in bone mass at loaded sites may be achieved when short bouts of moderate exercise are combined with increased dietary calcium, the former conferring region-specific effects and the latter producing generalized effects.
Osteosarcoma of Bone in a Patient With Primary Hyperparathyroidism: A Case Report
Authors: Betancourt M , Wirfel KL , Raymond AK , Yasko AW , Lee J , Vassilopoulou-Sellin R
Published: April 2006

A 69-year-old woman was diagnosed with a malignant tumor of the right proximal femur. She had primary hyperparathyroidism and chronic elevation of parathyroid hormone levels (PTH > 1000 pg/ml). She underwent resection of the bone lesion; histological analysis showed a high-grade fibroblastic osteosarcoma. In addition, she underwent curative resection of a large left superior parathyroid adenoma. To our knowledge, this is the third reported clinical case of osteosarcoma arising in association with hyperparathyroidism.
Costs and Strategies in Minority Recruitment for Osteoporosis Research
Authors: Marquez Miriam A , Muhs Joan M , Tosomeen Ann , Riggs B Lawrence , Melton L Joseph
Published: April 2006

To meet expectations for the participation of minority populations in research, we committed to enroll 140 minority subjects in addition to a random sample of Olmsted County, Minnesota residents (90% white) for a study of risk factors for age-related bone loss and fractures. We successfully enrolled 597 additional minority subjects but encountered specific problems with respect to identification of potential subjects, recruitment, obtaining informed consent, transportation to the study site, and collecting study data. These problems were resolved by observing the tenets of outreach to a diverse study population, namely (1) understand the target population; (2) establish explicit recruitment goals; (3) agree on research plans between study staff and minority communities; (4) continuously evaluate the recruitment process; and (5) maintain lines of communication. Success depended especially on the recruitment of cultural advisors from the different ethnic groups. These special efforts increased the recruitment cost substantially; the total expense of $122,000 for recruiting 550 Asian, Hispanic, and Somali subjects was almost 5-fold higher than the $26,000 required to recruit 699 mostly white study subjects from the population who were contacted by mail. Although it is not impossible to recruit minority subjects, investigators (and grant reviewers) should recognize that significant resources are required to gain access to ethnic communities for research. These results should contribute to more realistic budgets for recruiting minority subjects into clinical research studies.
Induction of Human Osteoprogenitor Chemotaxis, Proliferation, Differentiation, and Bone Formation by Osteoblast Stimulating Factor-1/Pleiotrophin: Osteoconductive Biomimetic Scaffolds for Tissue Engineering
Authors: Yang Xuebin , Tare Rahul S , Partridge Kris A , Roach Helmtrud I , Clarke Nicholas MP , Howdle Steven M , Shakesheff Kevin M , Oreffo Richard OC
Published: April 2006

The process of bone growth, regeneration, and remodeling is mediated, in part, by the immediate cell-matrix environment. Osteoblast stimulating factor-1 (OSF-1), more commonly known as pleiotrophin (PTN), is an extracellular matrix-associated protein, present in matrices, which act as targets for the deposition of new bone. However, the actions of PTN on human bone progenitor cells remain unknown. We examined the effects of PTN on primary human bone marrow stromal cells chemotaxis, differentiation, and colony formation (colony forming unit-fibroblastic) in vitro, and in particular, growth and differentiation on three-dimensional biodegradable porous scaffolds adsorbed with PTN in vivo. Primary human bone marrow cells were cultured on tissue culture plastic or poly(DL-lactic acid-co-glycolic acid) (PLGA; 75:25) porous scaffolds with or without addition of recombinant human PTN (1 pg-50 ng/ml) in basal and osteogenic conditions. Negligible cellular growth was observed on PLGA scaffold alone, generated using a super-critical fluid mixing method. PTN (50 μg/ml) was chemotactic to human osteoprogenitors and stimulated total colony formation, alkaline phosphatase-positive colony formation, and alkaline phosphatase-specific activity at concentrations as low as 10 pg/ml compared with control cultures. The effects were time-dependent. On three-dimensional scaffolds adsorbed with PTN, alkaline phosphatase activity, type I collagen formation, and synthesis of cbfa-1, osteocalcin, and PTN were observed by immunocytochemistry and PTN expression by in situ hybridization. PTN-adsorbed constructs showed morphologic evidence of new bone matrix and cartilage formation after subcutaneous implantation as well as within diffusion chambers implanted into athymic mice. In summary, PTN has the ability to promote adhesion, migration, expansion, and differentiation of human osteoprogenitor cells, and these results indicate the potential to develop protocols for de novo bone formation for skeletal repair that exploit cell-matrix interactions.
In Vitro Acoustic Waves Propagation in Human and Bovine Cancellous Bone
Authors: Cardoso Luis , Teboul Frédéric , Sedel Laurent , Oddou Christian , Meunier Alain
Published: April 2006

The acoustic behavior of cancellous bone with regard to its complex poroelastic nature has been investigated. The existence of two longitudinal modes of propagation is demonstrated in both bovine and human cancellous bone. Failure to take into account the presence of these two waves may result in inaccurate material characterization.

Introduction: Acoustic wave propagation is now a commonly used nondestructive method for cancellous bone characterization. However, wave propagation in this material may be affected by fluid-solid interactions inherent to its poroelastic nature, resulting in two different longitudinal waves. This phenomenon has been demonstrated in previous studies and is in agreement with Biot's theory. The purpose of this paper is to extend these findings to human trabecular bone and to thoroughly investigate these two waves.

Materials and Methods: Sixty human and 14 bovine cancellous bone cubic specimens were tested in vitro in three different directions using an immersion acoustic transmission method. Original procedures were developed to quantify both velocity and attenuation characteristics of each wave. In term of attenuation, a modified broadband ultrasound attenuation (BUA), describing the rate of change of the frequency-dependent attenuation, was defined for each wave (FDUA).

Results: Both waves were identified in most of the specimens. The fast wave velocities demonstrated a negative linear correlation with porosity (1500–2300 m/s, R2 = 0.44, p < 10−3), whereas the slow wave velocities exhibited two different behaviors: (1) a first set of data clearly dependent on porosity showing a positive linear correlation (1150–1450 m/s, R2 = 0.26, p < 10−3) and (2) a second group independent on porosity. The fast wave FDUA (20–140 dB/cmMHz) showed a parabolic behavior and reached a maximum for 75% porosity (second degree relationship R2 = 0.41, p < 10−3), whereas a positive linear behavior was observed for the slow wave FDUA (15–40 dB/cmMHz; R2 = 0.15, p < 10−2).

Conclusions: Existence of two wave propagation modes were demonstrated in human cancellous bone. Our data suggest that, in some cases, the amplitude of the slow wave is much larger than the amplitude of the fast wave. For this reason, care should be taken when using measurement systems that incorporate simple threshold detection because the fast wave could remain undetected. Moreover, failure to consider the presence of these two waves could result in an inaccurate quantification of cancellous bone physical properties.
Tartrate-Resistant Acid Phosphatase Knockout Mice
Authors: Hayman Alison R , Cox Timothy M
Published: April 2006

TRACP is a lysosomal enzyme found in diverse tissues, where it is expressed in dendritic cells as well as osteoclasts and macrophages. To investigate the function of TRACP in vivo, we have generated mice in which the gene-encoding TRACP has been selectively disrupted by targeted homologous recombination in murine embryonic stem cells. Homozygous TRACP “knockout” mice have progressive foreshortening and deformity of the long bones and axial skeleton suggesting a role for TRACP in endochondral ossification. There is increased mineralization reflecting a mild osteopetrosis caused by reduced osteoclast modeling activity. These knockout mice also display an impairment of macrophage function with abnormal immunomodulatory cytokine responses. Superoxide formation and nitrite production were enhanced in stimulated macrophages lacking TRACP as was the secretion of the proinflammatory cytokines TNF-α, interleukin (IL)-1β, and IL-12. TRACP knockout mice showed delayed clearance of the microbial pathogen Staphylococcus aureus after sublethal intraperitoneal inoculation. The macrophages lacking TRACP showed an increase in tartrate-sensitive lysosomal acid phosphatase activity (LAP). The TRACP knockout mice were bred with mice lacking LAP. Mice lacking both TRACP and LAP had even shorter bones than the TRACP single knockouts. Osteopontin, identical to the T-cell cytokine η-1, accumulated adjacent to actively resorbing osteoclasts suggesting that both phosphatases are important for processing this protein. We propose that TRACP may be an important regulator of osteopontin/η-1 activity common to both the immune system and skeleton.
Disease-Specific Expression of Tartrate-Resistant Acid Phosphatase Isoforms
Authors: Janckila Anthony J , Nakasato Yuri R , Neustadt David H , Yam Lung T
Published: April 2006

The association between elevated serum type 5 TRACP activity and metabolic bone diseases has been recognized for many years. However, serum type 5 TRACP exists as two related isoforms: 5a and 5b. Only isoform 5b is osteoclast-derived; the origin and significance of isoform 5a has hardly been explored. We have used simultaneous immunoassays for type-5 TRACP activity and total type-5 TRACP protein in conjunction with non-denaturing gel electrophoresis and column chromatography to investigate the nature and significance of TRACP isoforms 5a and 5b in end-stage renal disease (ESRD) and rheumatoid arthritis (RA). Our studies have shown that TRACP activity and protein are elevated in ∼50% of sera from ESRD patients, which is caused by osteoclastic isoform 5b. We have also shown that total TRACP protein, but not TRACP activity, is elevated in ∼30% of sera from RA patients, which is caused by non-osteoclastic isoform 5a. When macrophages or dendritic cells (DC) were cultured in vitro, abundant TRACP 5a was secreted into the culture medium, whereas TRACP 5b was retained intracellularly by both cell types. This implicates macrophages and DC as potential sources of elevated TRACP 5a in RA. Because TRACP isoform expression may be disease-specific, it is important to be able to distinguish TRACP 5a from 5b. There are four criteria by which to do so: (1) TRACP 5a bears sialic acid residues while TRACP 5b does not; (2) the pH optimum for TRACP 5a is 5.2 while that for TRACP 5b is 5.8; (3) the specific activity of TRACP 5a is significantly lower than that of TRACP 5b; and (4) TRACP 5a is as an uncleaved polypeptide, whereas TRACP 5b is a proteolytically nicked disulfide-linked “heterodimer.” The differences in biochemical properties and disease-specific expression of TRACP isoforms 5a and 5b suggest that they are regulated differently and perform separate functions in a tissue-specific manner.
Rapid Loss of Bone Mineral Density of the Femoral Neck After Cessation of Ice Hockey Training: A 6-Year Longitudinal Study in Males
Authors: Gustavsson Anna , Olsson Tommy , Nordström Peter
Published: April 2006

The aim of this study was to evaluate the effect of training and reduced training on BMD in young ice hockey players during 6 years of follow-up. We found BMD gains in the femoral neck in the ice hockey group compared with controls. However, these gains were lost with reduced activity after cessation of career.

Introduction: It has been suggested that increasing bone mass by intense physical activity during childhood and adolescence may decrease the risk of osteoporosis later in life.

Materials and Methods: In this longitudinal study, 43 ice hockey players (16.7 ± 0.6 years) and 25 control subjects (16.8 ± 0.3 years) were studied at baseline and after a mean period of 30 and 70 months. The groups did not differ in weight or height. Bone mineral density (BMD; g/cm2) was measured for total body, femoral neck, and spine using DXA. Volumetric BMD (vBMD; mg/cm3) of the femoral neck was estimated.

Results: The ice hockey players were found to have gained significantly more femoral neck BMD than controls (0.07 versus 0.03 g/cm2, p = 0.04) and to have gained femoral neck vBMD, whereas the controls did not (16 versus 0 mg/cm3, p = 0.049) between baseline and the first follow-up. At the first follow-up, the ice hockey players were found to have significantly higher BMD at the femoral neck and total body versus controls (p < 0.05). Between the first and second follow-ups, 21 ice hockey players stopped their active sports career. During this time period, these subjects lost significantly more femoral neck BMD (0.10 versus 0.02 g/cm2, p < 0.001) and femoral neck vBMD (38 versus 4 mg/cm3, p < 0.001) compared with the 22 ice hockey players who continued training. The former ice hockey players also lost significantly more neck vBMD (38 versus 14 mg/cm3, p = 0.009) compared with the controls during the same period. At the second follow-up, only the 22 ice hockey players who had continued their training were found to have significantly higher BMD at the femoral neck (p = 0.01), total body (p = 0.04), and spine (p = 0.02) compared with the controls. The former athletes were found to have intermediate BMD at all sites.

Conclusion: In summary, we have demonstrated fast BMD loss at the femoral neck after decreased physical activity in young men. We conclude that ice hockey training during childhood and adolescence may not prevent the development of osteoporosis of the femoral neck later in life if the activity is not maintained.
Racial Differences in the Effect of Early Milk Consumption on Peak and Postmenopausal Bone Mineral Density
Authors: Opotowsky Alexander R , Bilezikian John P
Published: April 2006

Studies of the effect of milk consumption on bone density have focused on white women. The applicability to other races is unclear. This study of 4316 women found a racial difference in the effect of early milk consumption on bone. Further study is required to evaluate the etiology of this difference.

Introduction: Early milk consumption has been found to influence bone mineral density positively throughout life. Previous studies leading to this finding focused on white women; there are no data to support the view that black women also gain an equivalent benefit from early milk consumption.

Materials and Methods: Using data from the Third National Health and Nutrition Examination Survey (NHANES III), we analyzed the relationship between reported childhood and teenage milk consumption and current hip bone mineral density at four sites (femoral neck, trochanter, intertrochanter, and total hip) among postmenopausal and 20- to 39-year-old non-Hispanic white (NHW) and black (NHB) women. Potential confounding variables were accounted for in the analysis.

Results: Controlling for age and body mass index, teenage milk consumption was significantly associated with higher bone mineral density at all four sites among both postmenopausal and 20- to 39-year-old white women, but was not associated with bone mineral density at any site among black women. A similar pattern was observed for childhood milk intake. The interaction between race and teenage milk consumption significantly explained postmenopausal bone mineral density at all sites, whereas the interaction between race and teenage milk consumption was significant at two of the four sites among the 20- to 39-year-old women.

Conclusion: The results show racial differences in the effect of early milk consumption on peak and postmenopausal bone mineral density.
Insulin-like Growth Factor-1 Rescues the Mutated FGF Receptor 3 (G380R) Expressing ATDC5 Cells From Apoptosis Through Phosphatidylinositol 3-Kinase and MAPK
Authors: Koike Mio , Yamanaka Yoshitaka , Inoue Masaru , Tanaka Hiroyuki , Nishimura Riko , Seino Yoshiki
Published: April 2006

An activated mutation in the FGFR3 gene causes ACH. To examine the effects of IGF-1, which is an important mediator of GH, on apoptosis, we analyzed a chondrogenic cell line expressing the FGFR3 mutants. Our findings that IGF-1 prevented the apoptosis through P13K and MAPK pathways may explain how GH treatment improves the disturbed bone growth in ACH.

Introduction: Achondroplasia (ACH), which is caused by a point mutation of the fibroblast growth factor receptor 3 (FGFR3) gene in the transmembrane domain (G380R), is one of the most common genetic forms of dwarfism. Recently, using a chondrogenic cell line, ATDC5, we have showed that the constitutively active FGFR3 mutants induced an apoptosis of chondrocytes. We have also reported that growth hormone (GH) treatment increased the growth rate in achondroplasia in parallel with the increment of serum levels of insulin-like growth factor (IGF)-1, suggesting an important role of IGF-1 in skeletal development. In this study, to clarify the mechanism by which GH treatment improved the phenotype of ACH patients, we examined the possible effects of IGF-1 on an apoptosis induced by FGFR3 mutant in ATDC5.

Materials and Methods: Using adenovirus vector, wildtype or mutant FGFR3 (G380R) was introduced into ATDC5. Analysis of apoptosis was estimated by TUNEL assay. Expression levels of apoptosis-related genes and activation of signaling molecules were analyzed by immunoblot.

Results: MTT assay showed that the cell number was reduced in ATDC5 cells expressing the mutant FGFR3 (G380R; ATDC5-mtR3 cells), suggesting that ATDC5-mtR3 cells might fall into apoptosis. IGF-1, which is an important mediator of GH, restored cell proliferation and reduced apoptosis in ATDC5-mtR3 cells. IGF-1 also decreased the ratio of Bax/Bcl-2 in the cells. To investigate which signaling cascade is responsible for antiapoptotic effects of IGF-1, we examined the role of phosphatidylinositol 3-kinase (PI3K) and MAPK in ATDC5-mtR3 cells. Specific inhibitors of PI3K or MAPK blocked the antiapoptotic effects of IGF-1 in ATDC5-mtR3 cells.

Conclusions: Our findings, showing IGF-1 prevents the apoptosis induced by FGFR3 mutation through the PI3K pathway and MAPK pathway, explain the mechanisms by which GH treatment improves the disturbed bone growth in ACH.
Activation of p38 Mitogen-Activated Protein Kinase and c-Jun-NH2-Terminal Kinase by BMP-2 and Their Implication in the Stimulation of Osteoblastic Cell Differentiation
Authors: Guicheux J , Lemonnier J , Ghayor C , Suzuki A , Palmer G , Caverzasio J
Published: April 2006

Signaling involved in osteoblastic cell differentiation remains largely unknown. This study further investigates mechanisms involved in BMP-2-induced osteoblastic cell differentiation. We report that BMP-2 can activate JNK and p38 in osteoblastic cells and provide evidences that these MAP kinases have distinct roles in regulating alkaline phosphatase and osteocalcin expression.

Introduction: Bone morphogenetic protein (BMP)-2 exerts many of its biological effects through activation of the Smad pathway. Cooperative interactions between the Smads and the stress-activated protein kinase (SAPK) p38 and c-Jun-NH2-terminal kinase (JNK) pathways have recently been observed in TGF-β signaling.

Materials and Methods: Activation of mitogen-activated protein (MAP) kinases by BMP-2 and the role of these signaling pathways for cell differentiation induced by BMP-2 was investigated in mouse MC3T3-E1 and primary cultured calvaria-derived osteoblastic cells using immunoprecipitation, in vitro kinase assay and Western blot analysis, as well as specific MAP kinase inhibitors.

Results: Associated with the rapid activation of Smads, BMP-2 barely affected extracellular-signal regulated kinase (ERK) activity, whereas it induced a transient activation of p38 and JNK. The role of p38 and JNK in mediating BMP-2-induced stimulation of osteoblastic cell differentiation was evaluated using the respective specific inhibitors SB203580 and SP600125. Inhibition of p38 by SB203580 was mainly associated with decreased alkaline phosphatase (ALP) activity, whereas inhibition of JNK by SP600125 was associated with a marked reduction in osteocalcin (OC) production induced by BMP-2. Corresponding alterations in ALP and OC mRNA levels were found in cells treated with BMP-2 and inhibitors, suggesting an implication of p38 and JNK pathways in BMP-2-induced osteoblastic cell differentiation at a transcriptional level.

Conclusion: Data presented in this study describe p38 and JNK as new signaling pathways involved in BMP-2-induced osteoblastic cell differentiation with evidences for a distinct role of each MAP kinase in the control of alkaline phosphatase and osteocalcin expression.
How Well Are Bones Designed to Resist Fracture?
Authors: Currey John D
Published: April 2006

Because bone is obviously in some way adapted to the loads falling on it and because fracture is usually the failure of mechanical competence of main clinical importance, it is often thought that bones are adapted to resist fracture. In this perspective, I consider that this may not be the case. Bones may be designed to be very stiff, and therefore highly mineralized, and therefore brittle; they may be adapted to normal loads, but not to the characteristic loads occurring in falls, or may be very poorly designed to stop cracks traveling once they have started. Bones may also potentially fail in completely contrasting modes, and therefore their design has to be a compromise that does not resist either mode completely successfully. The greatly differing fracture incidences in different bones seen in pre-senile adults suggest that safety factors have been adapted, over evolutionary time, to produce the best compromise for a host of different design constraints.
Bone Mass, Size, and Density in Children and Adolescents With Osteogenesis Imperfecta: Effect of Intravenous Pamidronate Therapy
Authors: Rauch Frank , Plotkin Horacio , Zeitlin Leonid , Glorieux Francis H
Published: April 2006

Cyclical intravenous therapy with pamidronate improves the clinical course in children and adolescents with osteogenesis imperfecta (OI). In this study, we evaluated the effect of this therapy on lumbar spine bone mass (bone mineral content [BMC]), size (bone volume [BV]), and density (volumetric bone mineral density [vBMD]). Results from 56 patients (age, 0.2–15.9 years; 25 girls) on long-term pamidronate treatment were compared with those of 167 patients who had not received pamidronate before densitometry. In all patients who received pamidronate, BMC, BV, and vBMD increased above levels expected for untreated patients (p < 0.001 in each case). After 4 years of treatment, BMC, BV, and vBMD were 154%, 44%, and 65% higher, respectively, in treated than in untreated patients who were matched for age and OI type. A multiple regression model showed that baseline BMC was negatively associated with the increase in BMC. In conclusion, the bone mass increase in pediatric OI patients receiving pamidronate is caused by increases in both bone size and density. Patients with larger deficits in bone mass at baseline have a more marked bone mass gain during therapy.
Leupaxin Is a Critical Adaptor Protein in the Adhesion Zone of the Osteoclast
Authors: Gupta Anandarup , Lee Beth S , Khadeer Mohammed A , Tang Zhihui , Chellaiah Meenakshi , Abu-Amer Yousef , Goldknopf Joshua , Hruska Keith A
Published: April 2006

Leupaxin is a cytoskeleton adaptor protein that was first identified in human macrophages and was found to share homology with the focal adhesion protein, paxillin. Leupaxin possesses several protein-binding domains that have been implicated in targeting proteins such as focal adhesion kinase (pp125FAK) to focal adhesions. Leupaxin can be detected in monocytes and osteoclasts, both cells of hematopoietic origin. We have identified leupaxin to be a component of the osteoclast podosomal signaling complex. We have found that leupaxin in murine osteoclasts is associated with both PYK2 and pp125FAK in the osteoclast. Treatment of osteoclasts with TNF-α and soluble osteopontin were found to stimulate tyrosine phosphorylation of both leupaxin and leupaxin-associated PYK2. Leupaxin was found to co-immunoprecipitate with the protein tyrosine phosphatase PTP-PEST. The cellular distribution of leupaxin, PYK2, and protein tyrosine phosphorylation-PEST co-localized at or near the osteoclast podosomal complex. Leupaxin was also found to associate with the ARF-GTPase-activating protein, paxillin kinase linker p95PKL, thereby providing a link to regulators of cytoskeletal dynamics in the osteoclast. Overexpression of leupaxin by transduction into osteoclasts evoked numerous cytoplasmic projections at the leading edge of the cell, resembling a motile phenotype. Finally, in vitro inhibition of leupaxin expression in the osteoclast led to a decrease in resorptive capacity. Our data suggest that leupaxin may be a critical nucleating component of the osteoclast podosomal signaling complex.
Receptor Tyrosine Kinases Inhibit Bone Morphogenetic Protein-Smad Responsive Promoter Activity and Differentiation of Murine MC3T3-E1 Osteoblast-like Cells
Authors: Nakayama Konosuke , Tamura Yasuhiro , Suzawa Miyuki , Harada Shun-Ichi , Fukumoto Seiji , Kato Mitsuyasu , Miyazono Kohei , Rodan Gideon A , Takeuchi Yasuhiro , Fujita Toshiro
Published: April 2006

Growth factors such as fibroblast growth factor-2 (FGF-2) and epidermal growth factor (EGF) that activate extracellular signal-regulated kinases (ERKs) through receptor tyrosine kinases (RTKs) stimulate proliferation but suppress differentiation of osteoblasts. To study the mechanism of this inhibitory action of these growth factors on osteoblastic differentiation, we evaluated Smad1 transactivity in MC3T3-E1 osteoblast-like cells by reporters of promoter activity of mouse Smad6, an early response gene to bone morphogenetic proteins (BMPs). FGF-2 and EGF inhibited alkaline phosphatase activity and Smad6 promoter activity stimulated by BMP-2. Overexpression of constitutively active MEK by adenovirus mimicked, but that of dominant negative Ras or treatment with a MEK1 inhibitor, PD098059, reversed, the inhibitory effects of these growth factors on both activities. These effects are mediated by BMP-responsive elements (BMPREs) on Smad6 promoter, because an artificial reporter driven by three tandem BMPREs gave similar results, and these effects were all abolished when the BMPREs were mutated. RTK-ERK activation inhibited the promoter activity even when BMP signal was mediated by a mutant Smad1, which lacks phosphorylation sites by ERKs, or by a Smad1 fused to Gal4 DNA binding domain, which constitutively localizes in the nucleus. These results show that the RTK-Ras-ERK pathway suppresses BMP signal by interfering with Smad1 transactivity. Because direct phosphorylation of Smad1 by ERKs is not required for the inhibition, other transcriptional factors that are phosphorylated by ERKs might be involved in the regulation of osteoblastic differentiation by ERKs.
Effect of 8-Month Vertical Whole Body Vibration on Bone, Muscle Performance, and Body Balance: A Randomized Controlled Study
Authors: Torvinen Saila , Kannus Pekka , Sievänen Harri , Järvinen Tero AH , Pasanen Matti , Kontulainen Saija , Nenonen Arja , Järvinen Teppo LN , Paakkala Timo , Järvinen Markku , Vuori Ilkka
Published: April 2006

Recent animal studies have given evidence that vibration loading may be an efficient and safe way to improve mass and mechanical competence of bone, thus providing great potential for preventing and treating osteoporosis. Randomized controlled trials on the safety and efficacy of the vibration on human skeleton are, however, lacking. This randomized controlled intervention trial was designed to assess the effects of an 8-month whole body vibration intervention on bone, muscular performance, and body balance in young and healthy adults. Fifty-six volunteers (21 men and 35 women; age, 19-38 years) were randomly assigned to the vibration group or control group. The vibration intervention consisted of an 8-month whole body vibration (4 min/day, 3-5 times per week). During the 4-minute vibration program, the platform oscillated in an ascending order from 25 to 45 Hz, corresponding to estimated maximum vertical accelerations from 2g to 8g. Mass, structure, and estimated strength of bone at the distal tibia and tibial shaft were assessed by peripheral quantitative computed tomography (pQCT) at baseline and at 8 months. Bone mineral content was measured at the lumbar spine, femoral neck, trochanter, calcaneus, and distal radius using DXA at baseline and after the 8-month intervention. Serum markers of bone turnover were determined at baseline and 3, 6, and 8 months. Five performance tests (vertical jump, isometric extension strength of the lower extremities, grip strength, shuttle run, and postural sway) were performed at baseline and after the 8-month intervention. The 8-month vibration intervention succeeded well and was safe to perform but had no effect on mass, structure, or estimated strength of bone at any skeletal site. Serum markers of bone turnover did not change during the vibration intervention. However, at 8 months, a 7.8% net benefit in the vertical jump height was observed in the vibration group (95% CI, 2.8-13.1%; p = 0.003). On the other performance and balance tests, the vibration intervention had no effect. In conclusion, the studied whole body vibration program had no effect on bones of young, healthy adults, but instead, increased vertical jump height. Future human studies are needed before clinical recommendations for vibration exercise.
Smoking May Impair the Bone Protective Effects of Nutritional Calcium: A Population-Based Approach
Authors: Sirola Joonas , Kröger Heikki , Honkanen Risto , Sandini Lorenzo , Tuppurainen Marjo , Jurvelin Jukka S , Saarikoski Seppo
Published: April 2006

Postmenopausal women were randomly selected to investigate the effects of smoking on prevention of bone loss with nutritional calcium. DXA was performed twice, and smoking and calcium intake habits were inquired through the mail in 954 women. Smoking dampened the bone protective effects of nutritional calcium. This may reflect the pathophysiology underlying smoking-induced bone loss postmenopause.

This study evaluated the effect of smoking on the bone protective properties of nutritional calcium. Of the random sample of 954 peri- and postmenopausal women selected from the Osteoporosis Risk Factor and Prevention (OSTPRE) study cohort (n = 13,100) in Kuopio, Finland, 182 had smoked at some time (ever smokers) and 772 had never smoked. Women were divided in tertiles according to self-reported dairy nutritional calcium intake (mg/day): <648 (1st), 648-927 (2nd), >927 (3rd). Bone mineral density at lumbar spine (LS) and femoral neck (FN) was measured with DXA at baseline in 1989-1991 and at the 5-year follow-up in 1994-1997. In a linear regression model, nutritional calcium intake did not predict annual bone loss in smokers. These results were similar in the subanalysis on 71 current smokers (at both baseline and 5-year measurements) and on 85 past smokers. In never smokers, a statistically significant linear trend was observed between calcium intake and annual bone loss at LS, but at FN only after adjustment for age, weight, hormone replacement therapy (HRT), and other covariates. In analysis of covariance (ANCOVA), no differences in bone loss rate were observed between calcium intake tertiles among smokers. In nonsmokers, the annual bone loss rate was lower in the second (−0.41%) and the third (−0.35%) tertile compared with the first tertile (−0.61%) at LS (p < 0.05) and lower in the third tertile (−0.55%) than in first tertile (−0.72%) at FN after adjustment for age, weight, HRT, and other covariates (p < 0.05). When smokers were added to the nonsmoker group, the differences in bone loss rate between calcium intake tertiles disappeared. In addition, in ANCOVA, the term of interaction between smoking and calcium intake was statistically significant at LS only. In conclusion, smoking seems to impair the bone protective effects of nutritional calcium in postmenopausal women, more clearly in LS than FN.
The Food and Drug Administration's Osteoporosis Guidance Document: Past, Present, and Future
Authors: Colman Eric G
Published: April 2006

In December 1979, the Food and Drug Administration's (FDA) Division of Metabolic and Endocrine Drug Products issued its Guidelines for the Clinical Evaluation of Drugs Used in the Treatment of Osteoporosis. The Guidance Document recommended study designs, patient populations for study, and techniques for evaluating skeletal mass and fracture frequency that were considered central to showing the efficacy and safety of drugs used to treat and prevent postmenopausal osteoporosis (PMO). In this paper, I discuss the evolution of the Osteoporosis Guidance as it relates to the pharmaceutical industry's efforts to develop effective and safe anti-osteoporosis drugs. Current regulatory policy on osteoporosis drugs and thoughts on the future direction of the Osteoporosis Guidance are also provided.