Preparation and physicochemical characterization of whitlockite/PVA/Gelatin composite for bone tissue regeneration

This work used a straightforward solvent casting approach to synthesize bone whitlockite (WH) based PVA/Gelatin composites. WH nanoparticles (NPs) were synthesized using the wet precipitation method, followed by their addition into the PVA/Gelatin matrix at concentrations from 1% to 10%. The physicochemical characterization of the prepared PVA/Gelatin/WH composite was carried out using ATR-FTIR, Optical profilometry, a Goniometer, a Universal tensile testing machine (UTM), and scanning electron microscopy (SEM) techniques. The ATR-FTIR analysis confirmed the formation of noncovalent interactions between polymeric chains and WH NPs and the incorporation of WH NPs into the polymer cavities. SEM analysis demonstrated increased surface roughness with the addition of WH NPs, supporting the results obtained through optical profilometry analysis. The mechanical properties of the prepared composite showed an increase in the tensile strength with the addition of WH filler up to 7% loading. The prepared composite has demonstrated an excellent swelling ability and surface wettability. The reported results demonstrate the exceptional potential of the prepared composite for bone tissue regeneration.

Ultrastructure and Nanoporosity of Human Bone Shown with Correlative On-Axis Electron and Spectroscopic Tomographies

Mineralized collagen fibrils are the building block units of bone at the nanoscale. While it is known that collagen fibrils are mineralized both inside their gap zones (intra-fibrillar mineralization) and on their outer surfaces (extra-fibrillar mineralization), a clear visualization of this architecture in three dimensions (3D), combining structural and compositional information over large volumes, but without compromising the resolution, remains challenging. In this study, we demonstrate the use of on-axis Z-contrast electron tomography (ET) with correlative energy-dispersive X-ray spectroscopy (EDX) tomography to examine rod-shaped samples with diameters up to 700 nm prepared from individual osteonal lamellae in the human femur. Our work mainly focuses on two aspects: (i) low-contrast nanosized circular spaces ("holes") observed in sections of bone oriented perpendicular to the long axis of a long bone, and (ii) extra-fibrillar mineral, especially in terms of morphology and spatial relationship with respect to intra-fibrillar mineral and collagen fibrils. From our analyses, it emerges quite clearly that most "holes" are cross-sectional views of collagen fibrils. While this had been postulated before, our 3D reconstructions and reslicing along meaningful two-dimensional (2D) cross-sections provide a direct visual confirmation. Extra-fibrillar mineral appears to be composed of thin plates that are interconnected and span over several collagen fibrils, confirming that mineralization is cross-fibrillar, at least for the extra-fibrillar phase. EDX tomography shows mineral signatures (Ca and P) within the gap zones, but the signal appears weaker than that associated with the extra-fibrillar mineral, pointing toward the existence of dissimilarities between the two types of mineralization.

Osteomalacia

Osteomalacia with characteristic histomorphometric, radiographic, laboratory and clinical features is a prominent syndrome of disturbed bone mineralisation in adulthood. From an etiological point of view, osteomalacia is usually caused by substrate (calcium, phosphate) deficiency, presence of excess mineralization inhibitors or deficiency or ineffectivness of mineralization facilitator (vitamin D). In proportion to the high number of congenital and acquired causes of osteomalacia, its clinical and laboratory picture is heterogeneous and rarely fully expressed. The treatment of a particular case is determined by the cause of osteomalacia and may (but does not necessarily) include correction of the underlying disease, administration of calcium and various forms of vitamin D, as well as orthopaedic interventions. For some of the hereditary forms, biological or replacement therapy is prospectively available. The article attempts to cover the whole range of osteomalacia variants, mentioning a fact discussed only in recent years - the occurrence of oligosymptomatic, incompletely expressed forms.

Sport Activity Load and Skeletomuscular Robustness in Elite Youth Athletes

In an earlier report, bone mineral reference values for young athletes were developed. This study addressed variations in bone mineral parameters of young athletes participating in sports with different mechanical loads. The bone mineral status of 1793 male and female athletes, 11 to 20 years of age, in several sports was measured with DEXA. Specific bone mineral parameters were converted to z-scores relative to age- and sex-specific reference values specified by the DEXA software. Z-score profiles and principal components analyses were used to identify body structural components in the young athletes and to evaluate the associations between the identified component and type of sport defined by mechanical load. A unique skeletomuscular robusticity of male wrestlers, pentathletes, and cyclists was noted: wrestlers had significantly more developed skeletomuscular robusticity and bone mineral density compared to the age-group average among elite athletes, while pentathletes and cyclists had lower bone mineral parameters than the age-group references among elite athletes. Among female athletes, bone mineral parameters of both the trunk and extremities of rhythmic gymnasts and pentathletes were significantly lower compared to the age-group means for elite athletes. The bone mineral development of elite young athletes varies with the impact forces associated with their respective sports. The skeletal development of cyclists, pentathletes, and rhythmic gymnasts should be monitored regularly as their bone development lags behind that of their athlete peers and the reference for the general population.

Investigating pair distribution function use in analysis of nanocrystalline hydroxyapatite and carbonate-substituted hydroxyapatite

Hydroxyapatite (HA) is a complex material, which is often nanocrystalline when found within a biological setting. This work has directly compared the structural characteristics derived from data collected using a conventional laboratory-based X-ray diffractometer with those collected from a dedicated pair distribution function (PDF) beamline at Diamond Light Source. In particular, the application of PDF analysis methods to carbonated HA is evaluated. 20 synthetic samples were measured using both X-ray diffraction (XRD) and PDFs. Both Rietveld refinement (of laboratory XRD data) and real-space refinement (of PDF data) were used to analyse all samples. The results of Rietveld and real-space refinements were compared to evaluate their application to crystalline and nanocrystalline hydroxyapatite. Significant relationships were observed between real-space refinement parameters and increasing carbonate substitution. Understanding the local order of synthetic hydroxyapatite can benefit several fields, including both biomedical and clinical settings.

The Impact of Whole-Body Vibration Training on Bone Minerals and Lean Mass in Children and Adolescents with Motor Disabilities: A Systematic Review and Meta-Analysis

Whole-body vibration training (WBVT) offers a potential auxiliary treatment method for the rehabilitation of motor disabilities to address a reduction in bone minerals and lean mass caused by motor-disability rehabilitation. The aim of this review was to analyze the efficacy of WBVT in muscle-bone rehabilitation. In order to investigate the potential effect of WBVT on children and adolescents with motor disabilities, a meta-analysis was carried out. From January 2006 to June 2021, studies that met certain criteria were searched for in the Scopus, PubMed, Web of Science, and EBSCO databases. An analysis of standardized mean differences was performed using the STATA 15.1 software with a 95% confidence interval (PROSPERO registration number: CRD42021258538). Eight studies were selected that included 179 male and 139 female children and adolescents suffering from motor disabilities. The results of the meta-analysis showed that WBVT significantly improved femur bone-mineral density ((p < 0.01, z = 2.66), standardized mean difference (SMD) (95% CI) = 0.41 (0.11, 0.72)), total body-bone mineral content ((p < 0.01, z = 3.08), SMD (95% CI) = 0.26 (0.10, 0.43)), and lean mass ((p < 0.01, z = 2.63), SMD (95% CI) = 0.22 (0.06, 0.39)). In addition, there was no significant effect of WBVT on lumbar spine bone mineral density in the disabled children and adolescents ((p = 0.21, z = 1.25), SMD (95% CI) = 0.17 (-0.10, 0.43)). WBVT can improve femur bone density, total body bone mineral content, and lean mass in children and adolescents suffering from motor disabilities, while there is no effect on lumbar-spine bone density. WBVT can be used as a potential program to improve bone minerals in children and adolescents with motor disabilities.

Reproducibility of Densitometric and Biomechanical Assessment of the Mouse Tibia From In Vivo Micro-CT Images

Interventions for bone diseases (e.g. osteoporosis) require testing in animal models before clinical translation and the mouse tibia is among the most common tested anatomical sites. In vivo micro-Computed Tomography (microCT) based measurements of the geometrical and densitometric properties are non-invasive and therefore constitute an important tool in preclinical studies. Moreover, validated micro-Finite Element (microFE) models can be used for predicting the bone mechanical properties non-invasively. However, considering that the image processing pipeline requires operator-dependant steps, the reproducibility of these measurements has to be assessed. The aim of this study was to evaluate the intra- and inter-operator reproducibility of several bone parameters measured from microCT images. Ten in vivo microCT images of the right tibia of five mice (at 18 and 22 weeks of age) were processed. One experienced operator (intra-operator analysis) and three different operators (inter-operator) aligned each image to a reference through a rigid registration and selected a volume of interest below the growth plate. From each image the following parameters were measured: total bone mineral content (BMC) and density (BMD), BMC in 40 subregions (ten longitudinal sections, four quadrants), microFE-based stiffness and failure load. Intra-operator reproducibility was acceptable for all parameters (precision error, PE < 3.71%), with lowest reproducibility for stiffness (3.06% at week 18, 3.71% at week 22). The inter-operator reproducibility was slightly lower (PE < 4.25%), although still acceptable for assessing the properties of most interventions. The lowest reproducibility was found for BMC in the lateral sector at the midshaft (PE = 4.25%). Densitometric parameters were more reproducible than most standard morphometric parameters calculated in the proximal trabecular bone. In conclusion, microCT and microFE models provide reproducible measurements for non-invasive assessment of the mouse tibia properties.

Improving the Management of Patients with Osteoporosis Undergoing Spinal Fusion: The Need for a Bone Mineral Density-Matched Interbody Cage

With an increasingly aging population globally, a confluence has emerged between the rising prevalence of degenerative spinal disease and osteoporosis. Fusion of the anterior spinal column remains the mainstay surgical intervention for many spinal degenerative disorders. However, decreased vertebral bone mineral density (BMD), quantitatively measured by dual x-ray absorptiometry (DXA), complicates treatment with surgical interbody fusion as weak underlying bone stock increases the risk of post-operative implant-related adverse events, including cage subsidence. There is a necessity for developing cages with advanced structural designs that incorporate bioengineering and architectural principles to tailor the interbody fusion device directly to the patient’s BMD status. Specifically, lattice-designed cages that mimic the web-like structure of native cancellous bone have demonstrated excellent resistance to post-operative subsidence. This article provides an introductory profile of a spinal interbody implant designed intentionally to simulate the lattice structure of human cancellous bone, with a similar modulus of elasticity, and specialized to match a patient’s bone status across the BMD continuum. The implant incorporates an open pore design where the degree of pore compactness directly corresponds to the patient’s DXA-defined BMD status, including patients with osteoporosis.

Single-nucleotide polymorphism rs10036727 in the SLIT3 gene is associated with osteoporosis at the femoral neck in older Mexican postmenopausal women

AIMS

Osteoporosis (OP) remains a major public health problem worldwide. The most serious complications of this disease are fragility fractures, which increase morbidity and mortality. Management of OP represents an economic burden for health systems. Therefore, it is necessary to develop new screening strategies to identify the population at risk and implement preventive measures. We previously identified the SNPs rs3801387 in WNT16, rs7108738 in SOX6, rs10036727 in SLIT3 and rs7584262 in PKDCC as associated with bone mineral density in postmenopausal women through a genome-wide association study. The aim of this study was to validate those SNPs in two independent cohorts of non-related postmenopausal women.

MATERIALS AND METHODS

We included 1160 women classifying them as normal, osteopenic or osteoporotic and a group with hip fragility fracture. Genotyping was performed using predesigned TaqMan assays.

RESULTS

The variants rs10036727 and rs7108738 showed a significant association with BMD at the femoral neck. SLIT3 has been previously proposed as a potential biomarker and therapeutic resource.

CONCLUSIONS

Our results provide new evidence regarding a possible involvement of SLIT3 in bone metabolisms and encourage the development of more studies in different populations to support these observations.

Synthesis, Characterization and Process Optimization of Bone Whitlockite

Whitlockite, being the second most abundant bio-mineral in living bone, finds huge applications in tissue regeneration and implants and its synthesis into its pure form has remained a challenge. Although precipitation of whitlockite phase has been reported recently in many publications, effects of various parameters to control such phase as well as conditions for the bulk preparation of this extremely important bio-mineral have not been investigated so far. In this work, we report the precipitation of pure whitlockite phase using common precursors. As reported in the literature, whitlockite is stable in a narrow pH range, therefore; optimization of pH for the stabilization of whitlockite phase has been investigated. Additionally, in order to narrow down the optimum conditions for the whitlockite precipitation, effect of temperature and heating conditions has also been studied. The obtained solids were characterized using powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). From PXRD analysis, it was observed that heating the precursor's mixture at 100 °C with subsequent aging at the optimized pH resulted in the precipitation of pure whitlockite phase. These results were further confirmed by TGA, SEM and Raman spectroscopy analysis and it was confirmed that the conditions reported here favor whitlockite precipitation without formation of any secondary phase. These reaction conditions were further confirmed by changing all the parameters like aging, heating time, feed rate of precursors one by one. From PXRD analysis of these samples, it was concluded that not only pH but temperature, heating time, aging time and feed rate effect simultaneously on the precipitation of pure whitlockite phase and a subtle change in any of these parameters could lead to the formation of undesired stable secondary calcium phosphate phases.

Association of Vitamin D Gene Polymorphisms and Bone Mineral Density in Healthy young Saudi Females

BACKGROUND

Osteoporosis is a systemic skeletal disease characterized by low bone mineral density. Vitamin D metabolism may play a pivotal role in its pathophysiology.

OBJECTIVES

To determine the association between Vitamin D receptor gene polymorphisms and bone density, as well as its relation to biochemical markers of bone turnover, in a healthy Saudi female population.

METHODS

A cross-sectional study was carried out at Taibah University, Madinah Region, Kingdom of Saudi Arabia. After receiving informed consent, blood samples from 300 subjects were collected to measure calcium, phosphorus, alkaline phosphatase, parathyroid hormone osteocalcin, and 1,25-OHD and perform genetic analysis of SNPs in vitamin D receptors (VDR) rs2228570, rs731236, and rs11568820.

RESULTS

There were significant differences between the CC, CT, and TT alleles of VDR rs2228570. Carrying the TT allele was associated with increased risks of decreased bone density and the presence of osteopenia with lower vitamin D3 levels (p≤0.001). The VDR rs731236 gene showed that CC allele carriers had significant risk of osteopenia. The AA genotype of rs11568820 showed lower levels of physical activity, bone mineral density, Z scores, serum osteocalcin, phosphorus, and parathyroid hormones.

CONCLUSION

The presence of the TT allele of the SNP rs2228570 of the VDR gene and the SNP rs731236 of the CC genotype was associated with the presence of osteopenia and decreased bone mineral density alongside malfunctions of vitamin D.

Bone Mineral Reference Values for Athletes 11 to 20 Years of Age

Objectives. Training for sport is associated with the development of bone minerals, and the need for reference data based on athletes is often indicated. The purpose of this study was to develop a reference for bone mineral density (BMD) and content (BMC) specific for youth athletes of both sexes participating in several sports. Methods DEXA (dual energy X-ray absorptiometry) was used for total body measurements of bone minerals in 1385 athletes 11 to 20 years, 1019 males and 366 females. The athletes were training in several sports at Hungarian academies. Reference values for total bone mineral density and bone mineral content, and also BMD excluding the head (total body less head, TBLH) were developed using the LMS chartmaker pro version 2.3. Results. The centile distributions for BMD and BMC of the athletes differed significantly from those of the age- and sex-specific references for the general population. The youth athletes had higher BMD and BMC than those of the reference for the general population. Conclusion. The potential utility of the DEXA reference for male and female youth athletes may assist in monitoring changes in the BMC and BMD associated with normal growth and maturation, and perhaps more importantly, may be useful in monitoring changes specific to different phases of sport-specific training protocols.

Interactions between dietary calcium and phosphorus level, and vitamin D source on bone mineralization, performance, and intestinal morphology of coccidia-infected broilers1

Coccidiosis penalizes calcium (Ca), phosphorus (P), and fat-soluble vitamin status, as well as bone mineralization in broiler chickens. We hypothesized that dietary vitamin D (VitD) supplementation in the form of 25-hydroxycholecalciferol (OHD), compared to cholecalciferol (D3), would improve bone mineralization in broilers receiving marginally deficient Ca/P diets, with more pronounced effects during malabsorptive coccidiosis. In a 2 VitD source × 2 Ca/P levels × 2 levels of infection factorial experiment (n = 6 pens per treatment, 6 birds/pen), Ross 308 broilers were assigned to an Aviagen-specified diet supplemented with 4,000 IU/kg of either OHD or D3 between days 11 and 24 of age. The diet contained adequate (A; 8.7:4.4 g/kg) or marginally deficient (M; 6.1:3.1 g/kg) total Ca and available (av)P levels. At day 12 of age, birds were inoculated with water (C) or 7,000 Eimeria maxima oocysts (I). Pen performance was measured over 12 days post-infection (pi). One bird per pen was assessed for parameters of bone mineralization and intestinal histomorphometric features (day 6 and 12 pi), as well as E. maxima replication and gross lesions of the small intestine (day 6 pi). There was no interaction between infection status and Ca/avP level on bone mineralization. Bone breaking strength (BS), ash weight (AW), and ash percentage (AP) were highest in broilers fed the OHD-supplemented A diets irrespective of infection status. Eimeria maxima infection impaired (P < 0.05) ADG and FCR pi; Ca and P status at day 6 pi; OHD status, BS, AW, and AP at day 12 pi; and intestinal morphology at day 6 and 12 pi. A- compared to M-fed broilers had higher BS, AW, and AP at day 6 pi, and AW at day 12 pi. VitD source affected only OHD status, being higher (P < 0.001) for OHD- than D3-fed broilers at day 6 and 12 pi. In conclusion, offering OHD and adequate levels of Ca and P improved bone mineralization, with no effect on performance. Dietary D3 and OHD supplemented at 4,000 IU/kg had similar effects on coccidiosis-infected and uninfected broilers, which led to the rejection of our hypothesis.

Age-dependent changes of the mandible bone throughout the lifespan in female F344/N rat

Age-dependent changes of the mandible bone in female F344/N rats, aged 22-1196 days, were analyzed using physiological bone properties and morphology. Bone weight, bone area, bone mineral components, and bone mineral density were assessed using dual-energy X-ray absorptiometry. The bone weight, bone area, bone mineral components, and bone mineral density increased rapidly until approximately 150 days of age, increased gradually thereafter, and then stabilized or decreased after 910 days of age. The ratio of bone mineral components to bone weight (bone mineral ratio) increased rapidly until approximately 43 days of age and stabilized thereafter. Size of the mandible, which was measured at 13 points on mandible surface, increased with age, and the rate of change showed a similar pattern to the other parameters. From a principal component analysis on morphometric measurements, principal component 1 (size factor) increased proportionally with age, whereas principal component 2 (shape factor) decreased until approximately 88 days of age and then increased after 365 days of age. As a result, the scatter plots for principal component 1 and principal component 2 were V-shaped, which indicates that the mandible developed in size, with deformation at younger ages, and recovered its original shape later in life. Our results revealed the occurrence of inflection points at approximately 43, 88, 150, 365, and 910 days of age. Some of these ages corresponded to transition points revealed by the age-dependent changes of the occlusal mandibular condyle and tooth wear in the same rat.

In vivo bone 31 P relaxation times and their implications on mineral quantification

PURPOSE

The intersubject variations in bone phosphorus-31 (³¹ P) T₁ and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:msubsup><mml:mi>T</mml:mi> <mml:mn>2</mml:mn> <mml:mo>*</mml:mo></mml:msubsup> </mml:mrow> </mml:math> , as well as the implications on in vivo ³¹ P MRI-based bone mineral quantification, were investigated at 3T field strength.

METHODS

A technique that isolates the bone signal from the composite in vivo ³¹ P spectrum was first evaluated via simulation and experiments ex vivo and subsequently applied to measure the T₁ of bone ³¹ P collectively with a spectroscopic saturation recovery sequence in a group of healthy subjects aged 26 to 76 years. <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:msubsup><mml:mi>T</mml:mi> <mml:mn>2</mml:mn> <mml:mo>*</mml:mo></mml:msubsup> </mml:mrow> </mml:math> was derived from the bone signal linewidth. The density of bone ³¹ P was derived for all subjects from ³¹ P zero TE images acquired in the same scan session using the measured relaxation times. Test-retest experiments were also performed to evaluate repeatability of this in vivo MRI-based bone mineral quantification protocol.

RESULTS

The T₁ obtained in vivo using the proposed spectral separation method combined with saturation recovery sequence is 38.4 ± 1.5 s for the subjects studied. Average ³¹ P density found was 6.40 ± 0.58 mol/L (corresponding to 1072 ± 98 mg/cm³ mineral density), in good agreement with an earlier study in specimens from donors of similar age range. Neither the relaxation times (P = 0.18 for T₁ , P = 0.99 for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:msubsup><mml:mi>T</mml:mi> <mml:mn>2</mml:mn> <mml:mo>*</mml:mo></mml:msubsup> </mml:mrow> </mml:math> ) nor ³¹ P density (P = 0.55) were found to correlate with subject age. Average coefficients of variation for the repeat study were 1.5%, 2.6%, and 4.4% for bone ³¹ P T₁ , <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:msubsup><mml:mi>T</mml:mi> <mml:mn>2</mml:mn> <mml:mo>*</mml:mo></mml:msubsup> </mml:mrow> </mml:math> , and density, respectively.

CONCLUSION

Neither ³¹ P T₁ nor <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:msubsup><mml:mi>T</mml:mi> <mml:mn>2</mml:mn> <mml:mo>*</mml:mo></mml:msubsup> </mml:mrow> </mml:math> varies significantly in healthy adults across a 50-year age range, therefore obviating the need for subject-specific measurements.

Preparation and bioavailability of calcium-chelating peptide complex from tilapia skin hydrolysates

BACKGROUND

With the continuous improvement in material life, the generation of fish by-products and the market demand for calcium supplements have been increasing in China. Therefore a calcium-chelating peptide complex (CPC) from tilapia skins was prepared and its effect on calcium (Ca)-deficient mice was investigated.

RESULTS

The molecular weight distribution of CPC mainly ranged from 2000 to 180 Da, and its contents of complete amino acids and free amino acids were 85.30 and 8.67% (w/w) respectively. Scanning electron microscopy images and Fourier transform infrared data revealed that Ca crystals were bound with gelatin hydrolysates via interaction between Ca ions and NH/CN groups. When Ca-deficient mice were fed CPC and CaCO₃ respectively for 4 weeks, no significant differences in serum biochemistry or bone mineral density were found. However, the length, weight, Ca content and hydroxyproline content of the femur, Ca absorption and body weight gain of mice fed CPC were significantly higher than those of mice fed CaCO₃ .

CONCLUSION

It is concluded that the prepared CPC could promote bone formation via better bioavailability of Ca and an increase in bone collagen. © 2017 Society of Chemical Industry.

Raman and Fourier Transform Infrared (FT-IR) Mineral to Matrix Ratios Correlate with Physical Chemical Properties of Model Compounds and Native Bone Tissue

Raman and Fourier transform infrared (FT-IR) spectroscopic imaging techniques can be used to characterize bone composition. In this study, our objective was to validate the Raman mineral:matrix ratios (ν₁ PO₄:amide III, ν₁ PO₄:amide I, ν₁ PO₄:Proline + hydroxyproline, ν₁ PO₄:Phenylalanine, ν₁ PO₄:δ CH₂ peak area ratios) by correlating them to ash fraction and the IR mineral:matrix ratio (ν₃ PO₄:amide I peak area ratio) in chemical standards and native bone tissue. Chemical standards consisting of varying ratios of synthetic hydroxyapatite (HA) and collagen, as well as bone tissue from humans, sheep, and mice, were characterized with confocal Raman spectroscopy and FT-IR spectroscopy and gravimetric analysis. Raman and IR mineral:matrix ratio values from chemical standards increased reciprocally with ash fraction (Raman ν₁ PO₄/Amide III: P < 0.01, R²= 0.966; Raman ν₁ PO₄/Amide I: P < 0.01, R²= 0.919; Raman ν₁ PO₄/Proline + Hydroxyproline: P < 0.01, R²= 0.976; Raman ν₁ PO₄/Phenylalanine: P < 0.01, R²= 0.911; Raman ν₁ PO₄/δ CH₂: P < 0.01, R²= 0.894; IR P < 0.01, R²= 0.91). Fourier transform infrared mineral:matrix ratio values from native bone tissue were also similar to theoretical mineral:matrix ratio values for a given ash fraction. Raman and IR mineral:matrix ratio values were strongly correlated ( P < 0.01, R²= 0.82). These results were confirmed by calculating the mineral:matrix ratio for theoretical IR spectra, developed by applying the Beer-Lambert law to calculate the relative extinction coefficients of HA and collagen over the same range of wavenumbers (800-1800 cm^-1). The results confirm that the Raman mineral:matrix bone composition parameter correlates strongly to ash fraction and to its IR counterpart. Finally, the mineral:matrix ratio values of the native bone tissue are similar to those of both chemical standards and theoretical values, confirming the biological relevance of the chemical standards and the characterization techniques.

Fragility of Bone Material Controlled by Internal Interfaces

Bone material is built in a complex multiscale arrangement of mineralized collagen fibrils containing water, proteoglycans and some noncollagenous proteins. This organization is not static as bone is constantly remodeled and thus able to repair damaged tissue and adapt to the loading situation. In preventing fractures, the most important mechanical property is toughness, which is the ability to absorb impact energy without reaching complete failure. There is no simple explanation for the origin of the toughness of bone material, and this property depends in a complex way on the internal architecture of the material on all scales from nanometers to millimeters. Hence, fragility may have different mechanical origins, depending on which toughening mechanism is not working properly. This article reviews the toughening mechanisms described for bone material and attempts to put them in a clinical context, with the hope that future analysis of bone fragility may be guided by this collection of possible mechanistic origins.

Changes in thigh muscle volume predict bone mineral density response to lifestyle therapy in frail, obese older adults

We studied the relationships among strength, muscle mass, and bone mineral density (BMD) with lifestyle change. Lifestyle therapy consisted of exercise, diet, and diet plus exercise. Diet was by caloric restriction to induce and maintain a weight loss of 10 % from baseline body weight. Exercise attenuated weight loss-induced muscle and bone losses. Exercise improved strength despite muscle loss in patients on diet and exercise. Changes in strength did not correlate with changes in BMD. However, changes in thigh muscle volume correlated with, and predicted changes in hip BMD.

INTRODUCTION

Losses of hip BMD and lean body mass are major complications of lifestyle therapy in frail, obese older adults; however, the contribution of mechanical strain loss from muscle loss is poorly defined. We determined the effect of changes in thigh muscle volume and muscle strength on BMD in frail, obese older adults undergoing lifestyle therapy aimed at intentional weight loss with or without exercise.

METHODS

One hundred seven obese older adults were randomized to control, diet, exercise, and diet-exercise groups for 1 year. Thigh muscle volume was measured by magnetic resonance imaging, BMD by DXA, knee strength by dynamometry, total strength by one-repetition maximum (1-RM), and bone markers by immunoassay.

RESULTS

Thigh muscle volume decreased in the diet group (-6.2 ± 4.8 %) and increased in the exercise group (2.7 ± 3.1 %), while it was not significantly different from the control in the diet-exercise group. Changes in hip BMD followed similar pattern as those in thigh muscle volume. Knee extension and flexion increased in the exercise group (23 ± 20 %; 25 ± 19 %) and diet-exercise group (20 ± 19 %; 20.6 ± 27 %) but were unchanged in the control and diet groups. Changes in thigh muscle volume correlated with changes in hip BMD (r = 0.55, P = <0.001) and were an independent predictor of changes in hip BMD (β = 0.12, P = 0.03) in the multiple regression analyses after accounting for demographic factors and changes in weight and physical activity. There were no correlations between BMD changes and knee strength, 1-RM, and sclerostin changes.

CONCLUSIONS

Changes in thigh muscle volume predict hip BMD changes in obese older patients undergoing lifestyle therapy. The effect of exercise in attenuating thigh muscle loss when added to diet may in part account for the reduction in weight loss-induced bone loss in the diet-exercise group.

Phage as a template to grow bone mineral nanocrystals

Phage display is a biotechnique that fuses functional peptides on the outer surface of filamentous phage by inserting DNA encoding the peptides into the genes of its coat proteins. The resultant peptide-displayed phage particles have been widely used as biotemplates for the synthesis of functional hybrid nanomaterials. Here, we describe the bioengineering of M13 filamentous phage to surface-display bone mineral (hydroxyapatite (HAP))-nucleating peptides derived from dentin matrix protein-1 and using the engineered phage as a biotemplate to grow HAP nanocrystals.

Optimal bone mechanical and material properties require a functional glucagon-like peptide-1 receptor

Bone is permanently remodeled by a complex network of local, hormonal, and neuronal factors that affect osteoclast and osteoblast biology. Among these factors, a role for gastrointestinal hormones has been proposed based on the evidence that bone resorption dramatically falls after a meal. Glucagon-like peptide-1 (GLP1) is one of these gut hormones, and despite several reports suggesting an anabolic effect of GLP1, or its stable analogs, on bone mass, little is known about the effects of GLP1/GLP1 receptor on bone strength. In this study, we investigated by three-point bending, quantitative X-ray microradiography, microcomputed tomography, qBEI, and FTIRI bone strength and bone quality in male Glp1r knockout (Glp1r KO) mice when compared with control WT animals. Animals with a deletion of Glp1r presented with a significant reduction in ultimate load, yield load, stiffness, and total absorbed and post-yield energies when compared with WT animals. Furthermore, cortical thickness and bone outer diameter were significantly decreased in deficient animals. The mineral quantity and quality were not significantly different between Glp1r KO and WT animals. On the other hand, the maturity of the collagen matrix was significantly reduced in deficient animals and associated with lowered material properties. Taken together, these data support a positive effect of GLP1R on bone strength and quality.

31P NMR relaxation of cortical bone mineral at multiple magnetic field strengths and levels of demineralization

Recent work has shown that solid-state (1) H and (31) P MRI can provide detailed insight into bone matrix and mineral properties, thereby potentially enabling differentiation of osteoporosis from osteomalacia. However, (31) P MRI of bone mineral is hampered by unfavorable relaxation properties. Hence, accurate knowledge of these properties is critical to optimizing MRI of bone phosphorus. In this work, (31) P MRI signal-to-noise ratio (SNR) was predicted on the basis of T1 and T2 * (effective transverse relaxation time) measured in lamb bone at six field strengths (1.5-11.7 T) and subsequently verified by 3D ultra-short echo-time and zero echo-time imaging. Further, T1 was measured in deuterium-exchanged bone and partially demineralized bone. (31) P T2 * was found to decrease from 220.3 ± 4.3 µs to 98.0 ± 1.4 µs from 1.5 to 11.7 T, and T1 to increase from 12.8 ± 0.5 s to 97.3 ± 6.4 s. Deuteron substitution of exchangeable water showed that 76% of the (31) P longitudinal relaxation rate is due to (1) H-(31) P dipolar interactions. Lastly, hypomineralization was found to decrease T1, which may have implications for (31) P MRI based mineralization density quantification. Despite the steep decrease in the T2 */T1 ratio, SNR should increase with field strength as B0 (0.4) for sample-dominated noise and as B0 (1.1) for coil-dominated noise. This was confirmed by imaging experiments.

A quantitative bioapatite/collagen calibration method using Raman spectroscopy of bone

Numerous calibration models were developed and tested for the quantitative analysis of collagen and bioapatite in bone using Raman spectroscopy. The ν1 phosphate vibration at 960 cm(-1) was used as indicator of the content of bioapatite while for collagen three markers were used: the C-H2 band at 2940 cm(-1) , the amide I band at 1667 cm(-1) and the vibrations of proline and hydroxyproline at 855 and 878 cm(-1) , respectively. Also a calibration model based on the PLS algorithm was developed, too. Validation of the derived calibration models indicated that the model that makes use of the height ratio of the peaks 960/(855+878) exhibits the best accuracy.

Fourier transform infrared spectroscopic imaging parameters describing acid phosphate substitution in biologic hydroxyapatite

Acid phosphate substitution into mineralized tissues is an important determinant of their mechanical properties and their response to treatment. This study identifies and validates Fourier transform infrared spectroscopic imaging (FTIRI) spectral parameters that provide information on the acid phosphate (HPO4) substitution into hydroxyapatite in developing mineralized tissues. Curve fitting and Fourier self-deconvolution were used to identify subband positions in model compounds (with and without HPO4). The intensity of subbands at 1127 and 1110 cm(-1) correlated with the acid phosphate content in these models. Peak height ratios of these subbands to the ν3 vibration at 1096 cm(-1) found in stoichiometric apatite were evaluated in the model compounds and mixtures thereof. FTIRI spectra of bones and teeth at different developmental ages were analyzed using these spectral parameters. Factor analysis (a chemometric technique) was also conducted on the tissue samples and resulted in factor loadings with spectral features corresponding to the HPO4 vibrations described above. Images of both factor correlation coefficients and the peak height ratios 1127/1096 and 1112/1096 cm(-1) demonstrated higher acid phosphate content in younger vs. more mature regions in the same specimen. Maps of the distribution of acid phosphate content will be useful for characterizing the extent of new bone formation, the areas of potential decreased strength, and the effects of therapies such as those used in metabolic bone diseases (osteoporosis, chronic kidney disease) on mineral composition. Because of the wider range of values obtained with the 1127/1096 cm(-1) parameter compared to the 1110/1096 cm(-1) parameter and the smaller scatter in the slope, it is suggested that this ratio should be the parameter of choice.

Hypermineralized whale rostrum as the exemplar for bone mineral

Although bone is a nanocomposite of mineral and collagen, mineral has been the more elusive component of study. A standard for bone mineral is clearly needed. We hypothesized that the most natural, least-processed bone mineral could be retrieved from the most highly mineralized bone. We therefore studied the rostrum of the toothed whale Mesoplodon densirostris, which has the densest recognized bone. Essential to establishment of a standard for bone mineral is the documentation that the proposed tissue is bone-like in all properties except for its remarkably high concentration of mineral. Transmitted-light microscopy of unstained sections of rostral material shows normal bone morphology in osteon geometry, lacunae concentration, and vasculature development. Stained sections reveal extremely low density of thin collagen fibers in most of the bone, but enrichment of thicker collagen fibers around vascular holes and in a minority of osteons. Field-emission scanning electron microscopy shows the rostrum mostly consists of dense mineral prisms. Most rostral areas have the same chemical-structural features, i.e., Raman spectroscopically dominated by strong bands at ∼962 Δcm(-1) and weak bands at ∼2940 Δcm(-1). Spectral features indicate that the rostrum is composed mainly of the calcium phosphate mineral apatite and has only about 4 wt.% organic content. The degree of carbonate substitution (∼8.5 wt.% carbonate) in the apatite is in the upper range found in most types of bone. We conclude that, despite its enamel-like extraordinarily high degree of mineralization, the rostrum is in all other features bone-like. Its mineral component is the long-sought uncontaminated, unaltered exemplar of bone mineral.

Genetic analysis of serum osteocalcin and bone mineral in multigenerational Afro-Caribbean families

Osteocalcin is a major component of bone matrix. Concentrations of total, carboxylated, and uncarboxylated osteocalcin, are highly heritable and genetically correlated with bone mineral content (BMC) within African ancestry families.

INTRODUCTION

Osteocalcin (OC) is a protein constituent of bone matrix and a marker of bone formation. We characterized the heritability of serum OC measures and identified genomic regions potentially involved in the regulation of OC via high-density genome-wide linkage analysis in African ancestry individuals.

METHODS

African ancestry individuals (n = 459) were recruited, without regard to health status, from seven probands (mean family size = 66; 4,373 relative pairs). Residual heritability of serum OC measures was estimated and multipoint quantitative trait linkage analysis was performed using pedigree-based maximum likelihood methods.

RESULTS

Residual heritabilities of total OC, uncarboxylated OC, carboxylated OC and percent uncarboxylated OC were 0.74 ± 0.10, 0.89 ± 0.08, 0.46 ± 0.10 and 0.41 ± 0.09, respectively. All OC measures were genetically correlated with whole body BMC. We obtained strong evidence of bivariate linkage for percent uncarboxylated OC and whole body BMC on chromosome 17 (logarithm of the odds [LOD] = 3.15, 99 cM).

CONCLUSIONS

All forms of OC were highly heritable and genetically correlated with total body BMC in these African ancestry families. The identified linkage region contains several candidate genes for bone and energy metabolism including COL1A1 and TNFRSF11A. Further studies of this genomic region may reveal novel insight into the genetic regulation of OC and bone mineralization.

Phosphorus-31 MRI of hard and soft solids using quadratic echo line-narrowing

Magnetic resonance imaging (MRI) of solids is rarely attempted. One of the main reasons is that the broader MR linewidths, compared to the narrow resonance of the hydrogen ((1)H) in free water, limit both the attainable spatial resolution and the signal-to-noise ratio. Basic physics research, stimulated by the quest to build a quantum computer, gave rise to a unique MR pulse sequence that offers a solution to this long-standing problem. The "quadratic echo" significantly narrows the broad MR spectrum of solids. Applying field gradients in sync with this line-narrowing sequence offers a fresh approach to carry out MRI of hard and soft solids with high spatial resolution and with a wide range of potential uses. Here we demonstrate that this method can be used to carry out three-dimensional MRI of the phosphorus ((31)P) in ex vivo bone and soft tissue samples.

Mineral maturity and crystallinity index are distinct characteristics of bone mineral

The purpose of this study was to test the hypothesis that mineral maturity and crystallinity index are two different characteristics of bone mineral. To this end, Fourier transform infrared microspectroscopy (FTIRM) was used. To test our hypothesis, synthetic apatites and human bone samples were used for the validation of the two parameters using FTIRM. Iliac crest samples from seven human controls and two with skeletal fluorosis were analyzed at the bone structural unit (BSU) level by FTIRM on sections 2-4 mum thick. Mineral maturity and crystallinity index were highly correlated in synthetic apatites but poorly correlated in normal human bone. In skeletal fluorosis, crystallinity index was increased and maturity decreased, supporting the fact of separate measurement of these two parameters. Moreover, results obtained in fluorosis suggested that mineral characteristics can be modified independently of bone remodeling. In conclusion, mineral maturity and crystallinity index are two different parameters measured separately by FTIRM and offering new perspectives to assess bone mineral traits in osteoporosis.

The effects of L-thyroxin replacement therapy on bone minerals and body composition in hypothyroid children

INTRODUCTION

Prolonged treatment with levothyroxine 4 (L-T4) is a well known risk factor for osteoporosis. Patients on L-T4 replacement occasionally have a subnormal TSH, which carries a risk of development of bone loss. Thyroid hormones directly affect bone cells, stimulating osteoclastic and osteoblastic activity with a predominance of bone resorption and decrease of bone mineral density (BMD).

MATERIAL AND METHODS

The study included 35 hypothyroid patients with mean age 11.57 ±5.06, while 26 age- and sex-matched children served as controls. Dual energy X-ray absorptiometry (DXA) was done to detect the bone mineral density (BMD), bone mineral content (BMC) and Z score in lumbar and femur neck regions. Body composition was also studied by DXA. Calcium, phosphorus, osteocalcin as a bone formation marker, osteoprotegerin as an indicator of osteoclast activity and urinary deoxypyridinoline as a bone collagen breakdown marker were assessed.

RESULTS

No significant differences were detected in lumbar Z score (-0.12 ±0.66) and femur Z score (-0.17 ±0.58) compared to controls (-0.33 ±0.74 and -0.21 ±0.53 respectively). Bone mineral density and BMC were not significantly different from controls. No significant difference was detected between cases and controls in body composition. A positive correlation was detected between BMD and age (r=0.857, p<0.01), and with the period of treatment (r=0.766, p<0.01). A positive correlation was found between BMD and total body fat (r=0.693, p<0.01), and with abdominal fat (r=0.667, p<0.01).

CONCLUSIONS

Levothyroxine 4 treatment in hypothyroid children does not alter bone metabolism and body composition.

Adiposity and TV viewing are related to less bone accrual in young children

OBJECTIVE

To examine the relation between baseline fat mass and gain in bone area and bone mass in preschoolers studied prospectively for 4 years, with a focus on the role of physical activity and TV viewing.

STUDY DESIGN

Children were part of a longitudinal study in which measures of fat, lean and bone mass, height, weight, activity, and diet were taken every 4 months from ages 3 to 7 years. Activity was measured by accelerometer and TV viewing by parent checklist. We included 214 children with total body dual energy x-ray absorptiometry (Hologic 4500A) scans at ages 3.5 and 7 years.

RESULTS

Higher baseline fat mass was associated with smaller increases in bone area and bone mass over the next 3.5 years (P < .001). More TV viewing was related to smaller gains in bone area and bone mass accounting for race, sex, and height. Activity by accelerometer was not associated with bone gains.

CONCLUSIONS

Adiposity and TV viewing are related to less bone accrual in preschoolers.

A comparison of the physical and chemical differences between cancellous and cortical bovine bone mineral at two ages

To assess possible differences between the mineral phases of cortical and cancellous bone, the structure and composition of isolated bovine mineral crystals from young (1-3 months) and old (4-5 years) postnatal bovine animals were analyzed by a variety of complementary techniques: chemical analyses, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and (31)P solid-state magic angle spinning nuclear magnetic resonance spectroscopy (NMR). This combination of methods represents the most complete physicochemical characterization of cancellous and cortical bone mineral completed thus far. Spectra obtained from XRD, FTIR, and (31)P NMR all confirmed that the mineral was calcium phosphate in the form of carbonated apatite; however, a crystal maturation process was evident between the young and old and between cancellous and cortical mineral crystals. Two-way analyses of variance showed larger increases of crystal size and Ca/P ratio for the cortical vs. cancellous bone of 1-3 month than the 4-5 year animals. The Ca/(P + CO(3)) remained nearly constant within a given bone type and in both bone types at 4-5 years. The carbonate and phosphate FTIR band ratios revealed a decrease of labile ions with age and in cortical, relative to cancellous, bone. Overall, the same aging or maturation trends were observed for young vs. old and cancellous vs. cortical. Based on the larger proportion of newly formed bone in cancellous bone relative to cortical bone, the major differences between the cancellous and cortical mineral crystals must be ascribed to differences in average age of the crystals.

Long term studies on bone mineral changes during different lactations in Swedish dairy cattle

Changes in the bone mineral content (BMG) during the first 4 lactations were continuously studied between July 1977 and February 1982 in a total number of 103 dairy cows of different breeds and rearing intensities. The BMG was measured by dichromatic photon absorptiometry in 2 coccygeal vertebrae. Although great individual variations were found, the changes in BMG during the lactation followed a typical pattern with high values during the dry period and low values after calving and during mid-lactation. The influence of body weight on the BMC value is discussed. The changes in BMC were more accentuated during the first lactation, as compared to the subsequent lactations. This could indicate a metabolically more active skeleton in younger cows. In this study no difference in BMC pattern was observed between cows affected or not affected by parturient paresis.

Crystallography of Tetracalcium Phosphate

Tetracalcium phosphate, Ca₄O(PO₄)2, has a monoclinic modification with the parameters a= 11.99, b = 9.48, and c = 6.97 A, α = 90.8°, z = 4, and space group P2₁ or P2₁/m. From a comparison with the work of Trömel and Zaminer, it is concluded that this salt has monoclinic and orthorhombic modifications with the most probable space groups being P2₁ and P2₁22₁, respectively. The results support the view that tetracalcium phosphate has a layer-type structural relationship to hydroxyapatite, Ca₅(OH)(PO₄)₃. This would account, in part, for variations in the compositions of apatitic materials in which the ratio Ca/P is greater than 10/6, and it suggests that tetracalcium phosphate may be present in the mineral of tooth and bone.