Intrinsic Bone Material Properties Research Articles

Skeletal cell YAP and TAZ combinatorially promote bone development.

The functions of the paralogous transcriptional coactivators Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) in bone are controversial. Each has been observed to promote or inhibit osteogenesis in vitro, with reports of both equivalent and divergent functions. Their combinatorial roles in bone physiology are unknown. We report that combinatorial YAP/TAZ deletion from skeletal lineage cells, using Osterix-Cre, caused an osteogenesis imperfecta-like phenotype with severity dependent on allele dose and greater phenotypic expressivity with homozygous TAZ vs. YAP ablation. YAP/TAZ deletion decreased bone accrual and reduced intrinsic bone material properties through impaired collagen content and organization. These structural and material defects produced spontaneous fractures, particularly in mice with homozygous TAZ deletion and caused neonatal lethality in dual homozygous knockouts. At the cellular level in vivo, YAP/TAZ ablation reduced osteoblast activity and increased osteoclast activity, in an allele dose-dependent manner, impairing bone accrual and remodeling. Transcriptionally, YAP/TAZ deletion and small-molecule inhibition of YAP/TAZ interaction with the transcriptional coeffector TEAD reduced osteogenic and collagen-related gene expression, both in vivo and in vitro. These data demonstrate that YAP and TAZ combinatorially promote bone development through regulation of osteoblast activity, matrix quality, and osteoclastic remodeling.-Kegelman, C. D., Mason, D. E., Dawahare, J. H., Horan, D. J., Vigil, G. D., Howard, S. S., Robling, A. G., Bellido, T. M., Boerckel, J. D. Skeletal cell YAP and TAZ combinatorially promote bone development.

Doses effects of zoledronic acid on mineral apatite and collagen quality of newly-formed bone in the rat's calvaria defect

Due to their inhibitory effects on resorption, bisphosphonates are widely used in the treatment of diseases associated to an extensive bone loss. Yet, little is known about bisphosphonates effects on newly-formed bone quality. In the present study, adult male Sprague-Dawley rats (n=80) with a bone defect calvaria area were used and short-term effects of zoledronic acid (ZA) were studied on the healing bone area. Three ZA treatments were tested by using either: 1°) a low single dose (120μgZA/kg, n=10; equivalent to human osteoporosis treatment), 2°) a low fractionated doses (20μgZA/kg daily for 6days either a total of 120μg/kg, n=15), and 3°) a high fractionated doses, (100μgZA/kg weekly for 6weeks, n=15; equivalent to 6months of human bone metastasis treatment). For each treatment, a control “vehicle” treatment was performed (with an identical number of rats). After ZA administration, the intrinsic bone material properties were evaluated by quantitative backscattered electron imaging (qBEI) and Raman microspectroscopy. Neither single nor fractionated low ZA doses modify the intrinsic bone material properties of the newly-formed bone compared to their respective control animals. On the opposite, the high ZA treatment resulted in a significant decrease of the crystallinity (−25%, P< 0.05) and of the hydroxyproline-to-proline ratio (−30%, P<0.05) in newly-formed bones. Moreover, with the high ZA treatment, the crystallinity was positively correlated with the hydroxyproline-to-proline ratio (ρ=0.78, P<0.0001). The present data highlight new properties for ZA on bone formation in a craniofacial defect model. As such, ZA at high doses disrupted the apatite crystal organization. In addition, we report here for the first time that high ZA doses decreased the hydroxyproline-to-proline ratio suggesting that ZA may affect the early collagen organization during the bone healing.

Dietary restrictions, bone density, and bone quality.

Caloric restriction (CR), protein restriction (PR), and specific amino acid restriction (e.g., methionine restriction (MR)) are different dietary interventions that have been confirmed with regard to their comprehensive benefits to metabolism and health. Based on bone densitometric measurements, weight loss induced by dietary restriction is known to be accompanied by reduced areal bone mineral density, bone mass, and/or bone size, and it is considered harmful to bone health. However, because of technological advancements in bone densitometric instruments (e.g., high-resolution X-ray tomography), dietary restrictions have been found to cause a reduction in bone mass/size rather than volumetric bone mineral density. Furthermore, when considering bone quality, bone health consists of diverse indices that cannot be fully represented by densitometric measurements alone. Indeed, there is evidence that moderate dietary restrictions do not impair intrinsic bone material properties, despite the reduction in whole-bone strength because of a smaller bone size. In the present review, we integrate research evidence from traditional densitometric measurements, metabolic status assays (e.g., energy metabolism, oxidative stresses, and inflammatory responses), and biomaterial analyses to provide revised conclusions regarding the effects of CR, PR, and MR on the skeleton.

Altered bone material properties in HLA-B27 rats include reduced mineral to matrix ratio and altered collagen cross-links.

Spondyloarthropathy and inflammatory bowel disease (IBD), which includes ulcerative colitis and Crohn's disease, are often associated with severe osteopenia/osteoporosis in both children and adults. HLA-B27 transgenic rats present a phenotype that includes severe colitis and severely accelerated alveolar bone loss. The purpose of this study was to evaluate long bone density status, systemic bone metabolic markers, and intrinsic bone material properties in HLA-B27 transgenic (TG) rats, and compare them with those of age- and sex-matched wild-type (WT) animals. The results indicate that in the HLA-B27 rat, an animal susceptible to both alveolar bone loss (ABL) and long bone osteopenia, there is a statistically significant negative correlation between ABL and long bone bone mineral density (BMD), as well as mineral/matrix ratio at active bone-forming trabecular surfaces. The TG animals had a lower mineral/matrix ratio and higher relative proteoglycan and advanced glycation end product (ϵ-N-Carboxymethyl-L-lysine) content and pyridinoline/divalent collagen cross-link ratio compared with WT. These results may provide better understanding of the interrelationship between osteoporosis and oral bone loss, the underlying causes of the inferior bone strength in the HLA-B27 transgenic animals, and could prove to be a useful model in the elucidation of the pathophysiology of spondyloarthropathy and IBD-associated osteopenia/osteoporosis and in the evaluation of pharmacological intervention(s) against such conditions.

Molecular alterations of bone quality in sequesters of bisphosphonates-related osteonecrosis of the jaws

Compared to healthy bone, the intrinsic bone materials properties in the pre-existing lamellar bone are altered in jaw bone sequesters of bisphosphonates (BP)-related osteonecrosis. The aim of this study was to evaluate the human jaw bone quality, especially intrinsic bone material properties among sequesters of osteonecrosis of the jaw (ONJ) induced by BP. Bone sequesters were obtained from 24 patients suffering from ONJ following a BP treatment. Within BP-exposed bone samples, benign-BP and malignant-BP groups were distinguished in relation to the underlying disease: osteoporosis and bone metastases or multiple myeloma, respectively. Healthy cadaveric cortical jaw bone samples were used as controls. The physicochemical parameters of bone samples - mineral/organic ratio, relative proteoglycan content, crystallinity, monohydrogen phosphate content, and type-B carbonate substitution - were evaluated by Raman microspectroscopy. Representative Raman spectral features of bones control and BP-exposed bone sequesters were identified with the Partial-Least-Square Discriminant Analysis (PLS-DA). BP-exposed bone sequesters are characterized by a significant increase of mineral to organic ratio (+12 %) and a significant decrease of relative proteoglycan content (-35 %), thus regulating initial collagen matrix mineral deposition. Structural changes on mineral components are revealed by a significant decrease of both crystallinity (-2 %) and mineral maturation (-41 %) in the BP-exposed bone sequesters compared to healthy bones. These modifications were also observed distinctly in both benign-BP and malignant-BP groups. In addition, a shift of the phosphate ν1 band was highlighted by PLS-DA between bones control and BP-exposed bone sequesters, revealing a disruption of the apatitic phosphate environment in the jaw bone sequesters. The present data show that jaw bone quality can be altered with an overmineralization and ultrastructural modifications of apatitic mineral in bone sequesters of BP-related ONJ.

Sclerosteosis patients have altered intrinsic bone material properties as assessed by Raman spectroscopy

Sclerosteosis patients have altered intrinsic bone material properties as assessed by Raman spectroscopy

Functional analysis of leukemia inhibitory factor in osteoblast differentiation of bone marrow stromal cells

Functional analysis of leukemia inhibitory factor in osteoblast differentiation of bone marrow stromal cells

Bone material properties in hypoparathyroidism

Bone material properties in hypoparathyroidism

Effects of alendronate and risedronate on bone material properties in actively forming trabecular bone surfaces

We used Raman and Fourier transform infrared microspectroscopy (FTIRM) analysis to examine the intrinsic bone material properties at actively bone-forming trabecular surfaces in iliac crest biopsies from women with postmenopausal osteoporosis (PMO) who were treated with either alendronate (ALN) or risedronate (RIS). At eight study sites, women were identified who had postmenopausal osteoporosis (PMO), were at least 5 years postmenopause, and had been on long-term therapy (either 3-5 years or >5 years) with daily or weekly ALN or RIS. Following standard tetracycline labeling, biopsies were collected from 102 women (33 treated with ALN for 3-5 years [ALN-3], 35 with ALN for >5 years [ALN-5], 26 with RIS for 3-5 years [RIS-3], and 8 with RIS for >5 years [RIS-5]) and were analyzed at anatomical areas of similar tissue age in bone-forming areas (within the fluorescent double labels). The following outcomes were monitored and reported: mineral to matrix ratio (corresponding to ash weight), relative proteoglycan content (regulating mineralization commencement), mineral maturity (indicative of the mineral crystallite chemistry and stoichiometry, and having a direct bearing on crystallite shape and size), and the ratio of two of the major enzymatic collagen cross-links (pyridinoline/divalent). In RIS-5 there was a significant decrease in the relative proteoglycan content (-5.83% compared to ALN-5), while in both RIS-3 and RIS-5 there was significantly lower mineral maturity/crystallinity (-6.78% and -13.68% versus ALN-3 and ALN-5, respectively), and pyridinoline/divalent collagen cross-link ratio (-23.09% and -41.85% versus ALN-3 and ALN-5, respectively). The results of the present study indicate that ALN and RIS exert differential effects on the intrinsic bone material properties at actively bone-forming trabecular surfaces.

Effects of alendronate and risedronate on bone material properties in actively forming trabecular bone surfaces

We used Raman and Fourier transform infrared microspectroscopy (FTIRM) analysis to examine the intrinsic bone material properties at actively bone-forming trabecular surfaces in iliac crest biopsies from women with postmenopausal osteoporosis (PMO) who were treated with either alendronate (ALN) or risedronate (RIS). At eight study sites, women were identified who had postmenopausal osteoporosis (PMO), were at least 5 years postmenopause, and had been on long-term therapy (either 3-5 years or >5 years) with daily or weekly ALN or RIS. Following standard tetracycline labeling, biopsies were collected from 102 women (33 treated with ALN for 3-5 years [ALN-3], 35 with ALN for >5 years [ALN-5], 26 with RIS for 3-5 years [RIS-3], and 8 with RIS for >5 years [RIS-5]) and were analyzed at anatomical areas of similar tissue age in bone-forming areas (within the fluorescent double labels). The following outcomes were monitored and reported: mineral to matrix ratio (corresponding to ash weight), relative proteoglycan content (regulating mineralization commencement), mineral maturity (indicative of the mineral crystallite chemistry and stoichiometry, and having a direct bearing on crystallite shape and size), and the ratio of two of the major enzymatic collagen cross-links (pyridinoline/divalent). In RIS-5 there was a significant decrease in the relative proteoglycan content (-5.83% compared to ALN-5), while in both RIS-3 and RIS-5 there was significantly lower mineral maturity/crystallinity (-6.78% and -13.68% versus ALN-3 and ALN-5, respectively), and pyridinoline/divalent collagen cross-link ratio (-23.09% and -41.85% versus ALN-3 and ALN-5, respectively). The results of the present study indicate that ALN and RIS exert differential effects on the intrinsic bone material properties at actively bone-forming trabecular surfaces.

Viscoelastic properties of human cortical bone tissue depend on gender and elastic modulus

Bone exhibits rate-dependent failure behavior, suggesting that viscoelasticity is a factor in the damage and fracture of bone. Microdamage initiates at scales below the macroscopic porosity in bone, and, as such, is affected by the intrinsic viscoelasticity of the bone tissue. The viscoelasticity of the bone tissue can be measured by nanoindentation and recording the creep behavior at constant load. The viscoelastic properties have been used to assess differences in tissue behavior with respect to fracture healing, aging, and mouse strains. In this study, we compared the viscoelastic behavior of human cortical bone between genders by using nanoindentation at a fixed load of 10 mN to measure the creep time constant. Bones from females had a significantly greater time constant, indicating slower creep and relaxation, than bones from males. The creep time constants decreased with increasing tissue modulus. The mineralization, collagen content, and collagen cross-link density, which were bulk measurements, were analyzed to determine if the differences in viscoelastic behavior were explained by compositional differences in the bone. However, none of the parameters differed between genders, nor were they correlated to the viscoelastic time constant. As such, the difference must depend on other matrix proteins that we did not assess or differences in the microstructural organization. This is one of the only intrinsic bone material properties that has been found to differ between males and females, and it may be important for assessing differences in fracture risk, since crack propagation is generally sensitive to viscoelastic properties.

E-modulus mapping at bone packet level: Combination of scanning acoustic microscopy in time of flight mode and back scattered electron imaging

E-modulus mapping at bone packet level: Combination of scanning acoustic microscopy in time of flight mode and back scattered electron imaging

Mineralization density distribution of postmenopausal osteoporotic bone is restored to normal after long-term alendronate treatment: qBEI and sSAXS data from the fracture intervention trial long-term extension (FLEX)

Long-term treatment studies showed that the therapeutic effects of alendronate (ALN) were sustained over a 10-year treatment period. However, data on the effects on intrinsic bone material properties by long-term reduction of bone turnover are still sparse. We analyzed transiliacal bone biopsies of a subgroup of 30 Fracture Intervention Trial Long-Term Extension (FLEX) participants (n = 6 were treated for 10 years with ALN at dose of 10 mg/day, n = 10 were treated for 10 years with ALN at dose of 5 mg/day, and n = 14 were treated for 5 years with ALN plus a further 5 years with placebo) by quantitative backscattered electron imaging (qBEI) and scanning small-angle X-ray scattering (sSAXS) to determine the bone mineralization density distribution (BMDD) and the mineral particle thickness parameter T. BMDD data from these FLEX participants were compared with those from a previously published healthy population (n = 52). Compared with 5 years of ALN plus 5 years of placebo 10 years of ALN treatment (independent of the dose given) did not produce any difference in any of the BMDD parameters: The weighted mean (Ca(mean)), the typical calcium concentration (Ca(peak)), the heterogeneity of mineralization (Ca(width)), the percentage of low-mineralized bone areas (Ca(low)), and the portion of highly mineralized areas (Ca(high)) were not different for the patients who continued ALN from those who stopped ALN after 5 years. Moreover, no significant differences for any of the BMDD parameters between the FLEX participants and the healthy population could be observed. In none of the investigated cases were abnormally high mineralization or changes in mineral particle thickness observed (Ca(high) and T were both in the normal range). The findings of this study support the recommendation that antiresorptive treatment with ALN should be maintained for 5 years. Even with longer treatment durations of up to 10 years, though, no negative effects on bone matrix mineralization were observed.

CRTAP deficiency leads to abnormally high bone matrix mineralization in a murine model and in children with osteogenesis imperfecta type VII

Cartilage-associated protein (CRTAP) is an essential cofactor for the proper post-translational chain modification and collagen folding. CRTAP mutations lead mice (Crtap−/− mice) and humans (OI type VII) to a severe/lethal osteochondrodystrophy; patients have fractures at birth, deformities of the lower extremities and impaired growth. The consequences of CRTAP deficiency on intrinsic bone material properties are still unknown. In the present study we evaluated bone quality based on quantitative backscattered electron imaging (qBEI) to assess bone mineralization density distribution (BMDD) in femurs from 12 weeks old Crtap−/− mice and transiliac bone biopsies from 4 children with hypomorphic mutations and having residual CRTAP expression.The analyses revealed in the bone matrix of Crtap−/− animals and OI type VII patients a significant increase in mean (CaMean) and most frequent mineral concentration (CaPeak) compared to wild-type littermates and control children, respectively. The heterogeneity of mineralization (CaWidth) was reduced in Crtap−/− mice but normal in OI type VII patients. The fraction of highly mineralized bone matrix (CaHigh) was remarkably increased in the patients: cancellous bone from 2.1 to 3.7 times and cortical bone from 7.6 to 25.5 times, associated with an increased persistence of primary bone. In conclusion, the BMDD data show that CRTAP deficiency results in a shift towards higher mineral content of the bone matrix similar to classical OI with collagen gene mutations. Our data further suggest altered mineralization kinetics resulting ultimately in an overall elevated tissue mineralization density. Finally, in OI type VII patients the increased portion of primary bone is most likely reflecting a disturbed bone development.