Bone mineral crystal size

Fabrication of strontium ions substituted hydroxyapatite from the shells of the golden apple snail (Pomacea canaliculate L) with enhanced osteoconductive and improved biological properties

The use of biogenic calcium ions for the source of hydroxyapatite (HAp or HA) are very common and have been being explored extensively. However, it usually results high crystalline HA, due to high reaction and decomposition temperatures. In this study, strontium (Sr2+) doped HA from the golden apple snail shells (Pomacea canaliculate L) was successfully synthesized. It was indicated that Sr ions completely replaced calcium (Ca) ions, increased the lattice constant, and consecutively reduced HA crystallinity. Smaller crystal size and β-type carbonate (CO32-) ions substitution with Ca/P close to 1.67 molar ratio that mimic bone crystals were observed in Sr-doped HA, with significant increased rate of MC3T3-E1 cells viability and higher IC50 values. It was proven that Sr ions substitution resolved challenges on the use of biogenic sources for HA fabrication. Further in vivo study is needed to continue to valorise the results into real biomedical and clinical applications.

Emerging Roles of Natural Compounds in Osteoporosis: Regulation, Molecular Mechanisms and Bone Regeneration

Bone health is a critical aspect of overall well-being, and disorders such as osteoporosis pose significant challenges worldwide. East Asian Herbal Medicine (EAHM), with its rich history and holistic approach, offers promising avenues for enhancing bone regeneration. In this critical review article, we analyze the intricate mechanisms through which EAHM compounds modulate bone health. We explore the interplay between osteogenesis and osteoclastogenesis, dissect signaling pathways crucial for bone remodeling and highlight EAHM anti-inflammatory effects within the bone microenvironment. Additionally, we emphasize the promotion of osteoblast viability and regulation of bone turnover markers by EAHM compounds. Epigenetic modifications emerge as a fascinating frontier where EAHM influences DNA methylation and histone modifications to orchestrate bone regeneration. Furthermore, we highlight EAHM effects on osteocytes, mesenchymal stem cells and immune cells, unraveling the holistic impact in bone tissue. Finally, we discuss future directions, including personalized medicine, combinatorial approaches with modern therapies and the integration of EAHM into evidence-based practice.

Raman spectroscopic analysis for osteoporosis identification in humans with hip fractures

Osteoporosis is a significant health concern. While multiple techniques have been utilized to diagnose this condition, certain limitations still persist. Raman spectroscopy has shown promise in predicting bone strength in animal models, but its application to humans requires further investigation. In this study, we present an in vitro approach for predicting osteoporosis in 10 patients with hip fractures using Raman spectroscopy. Raman spectra were acquired from exposed femoral heads collected during surgery. Employing a leave-one-out cross-validated linear discriminant analysis (LOOCV-LDA), we achieved accurate classification (90 %) between osteoporotic and osteopenia groups. Additionally, a LOOCV partial least squares regression (PLSR) analysis based on the complete Raman spectra demonstrated a significant prediction (r2 = 0.84, p < 0.05) of bone mineral density as measured by dual X-ray absorptiometry (DXA). To the best of our knowledge, this study represents the first successful demonstration of Raman spectroscopy correlating with osteoporotic status in humans.

Effect of borate, fluoride and strontium ions on biomimetic nucleation of calcium phosphate studied using solid-state nuclear magnetic resonance and X-ray diffraction

OBJECTIVES

Apatite minerals can have various anions and cations in their crystal structure in addition to phosphate ion (PO₄³⁻) and calcium ion (Ca2+). The aim of this study is to investigate effects of the borate, fluoride and strontium ions on biomimetic nucleation of calcium phosphate.

METHODS

Nano-crystalline hydroxyapatite (H-Ap) was obtained from a supersaturated buffered solution containing 4.12 mM HPO42- and 5.88 mM Ca2+ (H-Ap). Four additives were used in solid solution methods: (i) 0.588 mM F- (F-Ap), (ii) 5.88 mM Sr2+ (Sr-Ap), (iii) 4.12 mM BO33- (BO3-Ap), and (iv) a surface pre-reacted glass ionomer (S-PRG) filler eluate that contained 0.17 mM Sr2+, 0.588 mM F-, 11.1 mM BO33-- (SPRG-Ap). Apatite crystallization was investigated using a solid-state magic-angle spinning NMR spectroscopy and X-ray diffraction (XRD) with the Rietveld analysis.

RESULTS

A 2D 1H-31P heteronuclear-correlation NMR showed F- ion incorporation in the apatite structure of the F-Ap and SPRG-Ap. The peaks on the 31P axis of the F-Ap, Sr-Ap, and BO3-Ap were different from that of the H-Ap, and the full width at half maximum increased in the following order: H-Ap∼F-Ap∼BO3-Ap< SPRG-Ap< Sr-Ap, suggesting the incorporation of the F-, Sr2+ and BO33-. The incorporation of F and BO3 was further confirmed by 19F and 11B NMR. The XRD revealed that Sr2+ was preferentially incorporated into the CaII site.

SIGNIFICANCE

The F-, Sr2+ and BO33-ions might be involved in modifying the crystallization of apatite precipitation, producing a variety of apatite. S-PRG filler that release these ions may have an effect on remineralization, i.e., the reformation of apatite lost due to caries.

Bone samples' behavior in sunlight, IR light, and temperature increase with FEM simulation

Biological and environmental factors produce biochemical processes that modify the bone structure. A few studies have attempted to show the adverse biological effects of sun radiation. The bone tissue exposures to infrared and sunlight radiation are analyzed by using focused sound, characterization spectroscopy techniques, and image processing. The study is complemented with a finite element method simulation on temperature behaviors. The crystal morphology on the bone hydroxyapatite and functional groups was characterized by X-ray diffraction and infrared spectroscopy. The infrared spectra confirmed the hydroxyl group of bovine hydroxyapatite, amines, and lipids are also correlated with modifications of the hydroxyapatite. The diffractograms showed the characteristic peaks of hydroxyapatite, with the main intensity at 2θ = 32.02°. Bone samples exposed to sun radiation presented a peak at 2θ = 27.5°, evidencing the possible formation of β-TCP y α-TCP. The analysis with the spectroscopy techniques about the structural changes in the samples suggests interpreting an increase of sound obtained by expanding the exposure time. It is possible to verify that there are some structural changes in the bone samples due to exposure to non-ionizing radiation. These results show an increase in the registered intensity sound correlated with the interpretation of the structural changes of bone. Thanks to the different novel analysis techniques established in the present study, it could establish the changes that experienced the bone structure under different sources of radiation, which will help to better detect scenarios of bone deficiency.

Intelligent Vascularized 3D/4D/5D/6D-Printed Tissue Scaffolds

Blood vessels are essential for nutrient and oxygen delivery and waste removal. Scaffold-repairing materials with functional vascular networks are widely used in bone tissue engineering. Additive manufacturing is a manufacturing technology that creates three-dimensional solids by stacking substances layer by layer, mainly including but not limited to 3D printing, but also 4D printing, 5D printing and 6D printing. It can be effectively combined with vascularization to meet the needs of vascularized tissue scaffolds by precisely tuning the mechanical structure and biological properties of smart vascular scaffolds. Herein, the development of neovascularization to vascularization to bone tissue engineering is systematically discussed in terms of the importance of vascularization to the tissue. Additionally, the research progress and future prospects of vascularized 3D printed scaffold materials are highlighted and presented in four categories: functional vascularized 3D printed scaffolds, cell-based vascularized 3D printed scaffolds, vascularized 3D printed scaffolds loaded with specific carriers and bionic vascularized 3D printed scaffolds. Finally, a brief review of vascularized additive manufacturing-tissue scaffolds in related tissues such as the vascular tissue engineering, cardiovascular system, skeletal muscle, soft tissue and a discussion of the challenges and development efforts leading to significant advances in intelligent vascularized tissue regeneration is presented.

Biomineralization in Three-Dimensional Scaffolds Based on Bacterial Nanocellulose for Bone Tissue Engineering: Feature Characterization and Stem Cell Differentiation

Bacterial nanocellulose (BNC) has a negative surface charge in physiological environments, which allows the adsorption of calcium ions to initiate the nucleation of different calcium phosphate phases. The aim of this study was to investigate different methods of mineralization in three-dimensional microporous bacterial nanocellulose with the intention of mimicking the composition, structure, and biomechanical properties of natural bone. To generate the 3D microporous biomaterial, porogen particles were incorporated during BNC fermentation with the Komagataeibacter medellinensis strain. Calcium phosphates (CPs) were deposited onto the BNC scaffolds in five immersion cycles, alternating between calcium and phosphate salts in their insoluble forms. Scanning electron microscopy (SEM) showed that the scaffolds had different pore sizes (between 70 and 350 µm), and their porous interconnectivity was affected by the biomineralization method and time. The crystals on the BNC surface were shown to be rod-shaped, with a calcium phosphate ratio similar to that of immature bone, increasing from 1.13 to 1.6 with increasing cycle numbers. These crystals also increased in size with an increasing number of cycles, going from 25.12 to 35.9 nm. The main mineral phase observed with X-ray diffraction was octacalcium dihydrogen hexakis phosphate (V) pentahydrate (OCP). In vitro studies showed good cellular adhesion and high cell viability (up to 95%) with all the scaffolds. The osteogenic differentiation of human bone marrow mesenchymal stem cells on the scaffolds was evaluated using bone expression markers, including alkaline phosphatase, osteocalcin, and osteopontin. In conclusion, it is possible to prepare 3D BNC scaffolds with controlled microporosity that allow osteoblast adhesion, proliferation, and differentiation.

Mineralized Collagen Fibrils: An Essential Component in Determining the Mechanical Behavior of Cortical Bone

Bone comprises mechanically different materials in a specific hierarchical structure. Mineralized collagen fibrils (MCFs), represented by tropocollagen molecules and hydroxyapatite nanocrystals, are the fundamental unit of bone. The mechanical characterization of MCFs provides the unique adaptive mechanical competence to bone to withstand mechanical load. The structural and mechanical role of MCFs is critical in the deformation mechanisms of bone and the marvelous strength and toughness possessed by bone. However, the role of MCFs in the mechanical behavior of bone across multiple length scales is not fully understood. In the present study, we shed light upon the latest progress regarding bone deformation at multiple hierarchical levels and emphasize the role of MCFs during bone deformation. We propose the concept of hierarchical deformation of bone to describe the interconnected deformation process across multiple length scales of bone under mechanical loading. Furthermore, how the deterioration of bone caused by aging and diseases impairs the hierarchical deformation process of the cortical bone is discussed. The present work expects to provide insights on the characterization of MCFs in the mechanical properties of bone and lays the framework for the understanding of the multiscale deformation mechanics of bone.

Association between nanoscale strains and tissue level nanoindentation properties in age-related hip-fractures

Measurement of the properties of bone as a material can happen in various length scales in its hierarchical and composite structure. The aim of this study was to test the tissue level properties of clinically-relevant human bone samples which were collected from donors belonging to three groups: ageing donors who suffered no fractures (Control); untreated fracture patients (Fx-Untreated) and patient who experienced hip fracture despite being treated with bisphosphonates (Fx-BisTreated). Tissue level properties were assessed by (a) nanoindentation and (b) synchrotron tensile tests (STT) where strains were measured at the 'tissue', 'fibril' and 'mineral' levels by using simultaneous Wide-angle - (WAXD) and Small angle- X-ray diffraction (SAXD). The composition was analysed by thermogravimetric analysis and material level endo- and exo-thermic reactions by differential scanning calorimetry (TGA/DSC3+). Irrespective of treatment fracture donors exhibited significantly lower tissue, fibril and mineral strain at the micro and nanoscale respectively and had a higher mineral content than controls. In nanoindentation only nanohardness was significantly greater for Controls and Fx-BisTreated versus Fx-Untreated. The other nanoindentation parameters did not vary significantly across the three groups. There was a highly significant positive correlation (p < 0.001) between organic content and tissue level strain behaviour. Overall hip-fractures were associated with lower STT nanostrains and it was behaviour measured by STT which proved to be a more effective approach for predicting fracture risk because evidently it was able to demonstrate the mechanical deficit for the bone tissue of the donors who had experienced fractures.

A brief review and clinical evidences of teriparatide therapy for atypical femoral fractures associated with long-term bisphosphonate treatment

The risk of bisphosphonate (BP)-associated atypical femur fracture (AFF) has markedly increased over recent decades due to suppression of bone turnover, accumulation of structural micro-damage and reduction of bone remodeling consequent to long-term BP treatment. These medications further delay bone union and result in challenging clinical management. Teriparatide (TPTD), a synthetic human parathyroid hormone, exhibits unique anabolic effects and can increase bone remodeling and improve bone microarchitecture, further promoting fracture healing and reducing the rate of bone non-union. In this study, we briefly define AFF as well as the effects of BPs on AFFs, detailed the role of TPTD in AFF management and the latest clinical therapeutic findings. We have confirmed that TPTD positively promotes the healing of AFFs by reducing the time to bone union and likelihood of non-union. Thus, teriparatide therapy could be considered as an alternative treatment for AFFs, however, further research is required for the establishment of effective clinical guidelines of TPTD use in the management of AFF.

Raman microscopic spectroscopy as a diagnostic tool to detect Staphylococcus epidermidis in bone grafts

INTRODUCTION

Raman microscopic spectroscopyis a new approach for further characterization and detection of molecular features in many pathological processes. This technique has been successfully applied to scrutinize the spatial distribution of small molecules and proteins within biological systems by in situ analysis. This study uses Raman microscopic spectroscopyto identify any in-depth benefits and drawbacks in diagnosing Staphylococcus epidermidis in human bone grafts.

MATERIAL AND METHODS

40 non-infected human bone samples and 10 human bone samples infected with Staphylococcus epidermidis were analyzed using Raman microscopic spectroscopy. Reflectance data were collected between 200 cm^-1 and 3600 cm^-1 with a spectral resolution of 4 cm^-1 using a Senterra II microscope (Bruker, Ettlingen, Germany). The acquired spectral information was used for spectral and unsupervised classification, such as principal component analysis.

RESULTS

Raman measurements produced distinct diagnostic spectra that were used to distinguish between non-infected human bone samples and Staphylococcus epidermidis infected human bone samples by spectral and principal component analyses. A substantial loss in bone quality and protein conformation was detected by human bone samples co-cultured with Staphylococcus epidermidis. The mineral-to-matrix ratio using the phosphate/Amide I ratio (p = 0.030) and carbonate/phosphate ratio (p = 0.001) indicates that the loss of relative mineral content in bones upon bacterial infection is higher than in non-infected human bones. Also, an increase of alterations in the collagen network (p = 0.048) and a decrease in the structural organization and relative collagen in infected human bone could be detected. Subsequent principal component analyses identified Staphylococcus epidermidis in different spectral regions, respectively, originating mainly from CH₂ deformation (wagging) of protein (at 1450 cm^-1) and bending and stretching modes of C-H groups (∼2800-3000 cm^-1).

CONCLUSION

Raman microscopic spectroscopyis presented as a promising diagnostic tool to detect Staphylococcus epidermidis in human bone grafts. Further studies in human tissues are warranted.

Gradient Magnesium Content Affects Nanomechanics via Decreasing the Size and Crystallinity of Nanoparticles of Pseudoosteodentine of the Pacific Cutlassfish, Trichiurus lepturus Teeth

The formation of biomaterials such as enamel, dentin, and bone is important for many organisms, and the mechanical properties of biomaterials are affected by a wide range of structural and chemical factors. Special dentins exist in extant aquatic gnathostomes, and many more are present in fossils. When a layer of compact orthodentine surrounds the porous osteodentine core in the crown, the composite dentin is called pseudoosteodentine. Using various high-resolution analytical techniques, including micro-computed tomography (micro-CT), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Raman spectroscopy, and nanoindentation, we analyzed the micro- and nanostructures, chemical composition, and mechanical properties of pseudoosteodentine in the Pacific cutlassfish, Trichiurus lepturus teeth. Nanoscale oval-shaped hydroxyapatite (HA) crystals were distributed in a disordered manner in the pseudoosteodentine, and a cross-sectional analysis showed that the mineral crystallinity and crystalline particle size of the outer orthodentine were greater than those of middle and inner osteodentine. Moreover, the outer orthodentine comprised a mixture of smaller crystals and larger, more mature crystals. The nano-hardness and nano-stiffness of outer orthodentine were significantly higher than those of middle and inner osteodentine along a radical direction. The hardness and stiffness of pseudoosteodentine were inversely proportional to its magnesium (Mg) content. These data are consistent with the concept that Mg delays crystal maturation. The crystal size, crystallinity, nano-hardness, and nano-stiffness of pseudoosteodentine all decreased commensurately with the increase of its Mg concentration. The pseudoosteodentine of T. lepturus also can be regarded as a functional gradient material (FGM) because its mechanical properties are closely related to its chemical composition and nanostructure. Special pseudoosteodentine may therefore serve as a design standard for biomimetic synthetic mineral composites.

Physicochemical Properties and Surface Characteristics of Ground Human Teeth

Enamel, dentin and cementum apatite has a complex composition. The lack of complete reports on the chemical composition of all tooth tissues together and the need to create a modern biomaterial that reproduces the correct ratio of individual tooth mineral components prompted the authors to undertake the research. A detailed evaluation of the micro- and macro-elements of tooth powder, using various methods of chemical analysis was conducted. All four groups of human sound teeth were crushed using the grinder. A fine powder was implemented for the FTIR (Fourier Transform Infrared Spectroscopy), ICP (Inductively Coupled Plasma Optical Emission Spectometry) and for the potentiometric titration, SEM and mercury porosimetry analyses. The obtained studies indicate that there is no significant correlation in chemical composition between the different teeth types. This proves that every removed, crushed tooth free of microorganisms can be a suitable material for alveolar augmentation. It is essential to know the chemical profiles of different elements in teeth to develop a new class of biomaterials for clinical applications.

Techniques for Bone Assessment and Characterization: Porcine Hard Palate Case Study

The hard palate plate has an important structural function that separates the nasal cavity and the nasopharynx. Incomplete regeneration of palatal fistulae in children with a cleft palate deformity after primary palatoplasty is a relatively common complication. To date, the information about the physicochemical bone features of this region is deficient, due to the low availability of human samples. Swine and human bone share anatomical similarities. Specifically, pig bones are widely used as experimental animal models in dental, orthopedic, or surgical techniques. The aim of this study was to show different techniques to evaluate and characterize alternative properties of pig hard palate bone, compared to commercial hydroxyapatite, one of the most used biomaterials for bone tissue regeneration. Chemical analyses by Energy dispersive spectroscopy (EDS) and X-ray fluorescence (XRF) showed calcium and phosphate ions as the main constituents of bone, while magnesium, iron, sodium, potassium, and zinc ions were minor constituents. The calcium phosphate molar ratio (Ca/P) in the bone was low (1.1 ± 0.2) due to the very young specimen sample used. The FTIR spectrum shows the presence of phosphates ions (PO₄^3-) and the main characteristics of collagen type I. The XRD results showed that the hard palate bone has a mixture of calcium, octacalcium dihydrogen phosphate (OCP), and apatite, where OCP is the predominant phase. Besides, this research demonstrated that the young bone has low crystallinity and small crystal size compared with commercial hydroxyapatite (HA). The palatine process of maxilla density and porosity data reported, suggest that the palate bone is getting closer to the compact bone with a 52.78 ± 2.91% porosity and their mechanical properties depend on the preparation conditions and the area of the bone analyzed.

Assessing bone maturity: Compositional and mechanical properties of rib cortical bone at different ages

Understanding what maturity entails for bone, when it arrives, and its pre- and post-maturity traits and properties are very important for understanding its evolution and physiology. There is a clear but fine distinction between the chronological age of bone (the age of its donor) and the tissue age of the bone packets it comprises at the microscopic level. Whole bone fragility changes with age due to mass and architecture effects, but so do the properties of bone at the tissue level. Tissue age and tissue-level properties are therefore increasingly attracting a great deal of attention recently. The present study investigated compositional and material changes in the hydroxyapatite crystals, the collagenous phase, changes in bone matrix composition and its nanoindentation properties and their decline with chronological age in later life. The aim was to track the age threshold at which cortical bone arrives at maturity and what happens following that threshold. To do so FTIR, DSC/TGA, XRD, nanoindentation and microindentation were used to investigate rib cortical bone material across a cohort of 86 individuals from one ethnic group with age spanning between 17 and 82 years. Results of this cross-sectional study showed a clear increase in mineral content relative to the organic and water contents across all ages. Furthermore, an increase in crystal size and consequent decrease in strain (coherence length) was detected associated with secondary mineralisation and an increase in carbonate substitution. Overall, we observe a number of modifications which contribute to a typical functional behaviour of bone showing an increase in both indentation modulus and hardness until the age of about 35 after which both of these properties decline gradually and concomitantly to other physicochemical changes and seemingly until the end of one's life.

Induction of somatopause in adult mice compromises bone morphology and exacerbates bone loss during aging

Somatopause refers to the gradual declines in growth hormone (GH) and insulin‐like growth factor‐1 throughout aging. To define how induced somatopause affects skeletal integrity, we used an inducible GH receptor knockout (iGHRKO) mouse model. Somatopause, induced globally at 6 months of age, resulted in significantly more slender bones in both male and female iGHRKO mice. In males, induced somatopause was associated with progressive expansion of the marrow cavity leading to significant thinning of the cortices, which compromised bone strength. We report progressive declines in osteocyte lacunar number, and increases in lacunar volume, in iGHRKO males, and reductions in lacunar number accompanied by ~20% loss of overall canalicular connectivity in iGHRKO females by 30 months of age. Induced somatopause did not affect mineral/matrix ratio assessed by Raman microspectroscopy. We found significant increases in bone marrow adiposity and high levels of sclerostin, a negative regulator of bone formation in iGHRKO mice. Surprisingly, however, despite compromised bone morphology, osteocyte senescence was reduced in the iGHRKO mice. In this study, we avoided the confounded effects of constitutive deficiency in the GH/IGF‐1 axis on the skeleton during growth, and specifically dissected its effects on the aging skeleton. We show here, for the first time, that induced somatopause compromises bone morphology and the bone marrow environment.

Removal of glycosaminoglycans affects the in situ mechanical behavior of extrafibrillar matrix in bone

Previous studies have shown that glycosaminoglycans (GAGs) in bone matrix, coupling with water in bone matrix, may play a significant role in toughening bone tissues. Since GAGs are most likely present only in the extrafibrillar matrix (EFM) of bone, we hypothesized that GAGs in EFM would have a major impact on bone tissue toughness. To confirm this conjecture, we removed GAGs ex vivo from human cadaveric bone samples using a protein deglycosylation mix kit and then examined the in situ mechanical behavior of mineralized collagen fibrils (MCFs) and the surrounding EFM of the samples, using a high-resolution atomic force microscopy (AFM). By testing the bone samples before and after removal of GAGs, we found that under the wet condition removal of GAGs resulted in an increase in the elastic modulus of both EFM and MCFs, whereas a significant decrease in plastic energy dissipation was observed mainly in EFM. In contrast, under the dry condition the removal of GAGs had little effects on the mechanical properties of either MCFs or EFM. These results suggest that both MCFs and EFM contribute to the plastic energy dissipation of bone, whereas in the presence of matrix water removal of GAGs significantly reduces the capacity of EFM in plastic energy dissipation, but not MCFs. In addition, GAGs may affect the elastic modulus of both EFM and MCFs. These findings give rise to new understanding to the underlying mechanism of GAGs in toughening of bone tissues.

LDN Protects Bone Property Deterioration at Different Hierarchical Levels in T2DM Mice Bone

Type 2 diabetes mellitus (T2DM) commonly affects bone quality at different hierarchical levels and leads to an increase in the risk of bone fracture. Earlier, some anti-diabetic drugs showed positive effects on bone mechanical properties. Recently, we have investigated that low-dose naltrexone (LDN), a TLR4 antagonist treatment, improves glucose tolerance in high-fat diet (HFD)-induced T2DM mice and also gives protection against HFD-induced weight gain. However, effects on bone are still unknown. In this study, the effects of LDN on the bone properties at different hierarchical levels in T2DM mice bone were investigated. In order to investigate these, four different groups of bone (divided based on diet and treatment) were considered in this present study. These are (a) normal control diet treated with saline water, (b) normal control diet treated with LDN, (c) HFD treated with saline water, and (d) HFD treated with LDN. Bone properties were measured in terms of fracture toughness, nano-Young's modulus, hardness, mineral crystal size, bone composition, and bulk mineral to matrix ratio. Results indicated that fracture toughness, nano-Young's modulus, and hardness were decreased in T2DM bone as compared to normal bone, and interestingly, treatment with the LDN increases these material properties in T2DM mice bone. Similarly, as compared to the normal bone, decrease in the mineral crystal size and bulk mineral-to-matrix ratio was observed in the T2DM bone, whereas LDN treatment protects these alterations in the T2DM mice bone. The bone size (bone geometry) was increased in the case of HFD-induced T2DM bone; however, LDN cannot protect to increase the bone size in the T2DM mice bone. In conclusion, LDN can be used to control the T2DM-affected bone properties at different hierarchical levels.

Biomimetic Calcium Phosphate Coatings for Bioactivation of Titanium Implant Surfaces: Methodological Approach and In Vitro Evaluation of Biocompatibility

Ti6Al4V as a common implant material features good mechanical properties and corrosion resistance. However, untreated, it lacks bioactivity. In contrast, coatings with calcium phosphates (CaP) were shown to improve cell-material interactions in bone tissue engineering. Therefore, this work aimed to investigate how to tailor biomimetic CaP coatings on Ti6Al4V substrates using modified biomimetic calcium phosphate (BCP) coating solutions. Furthermore, the impact of substrate immersion in a 1 M alkaline CaCl2 solution (pH = 10) on subsequent CaP coating formation was examined. CaP coatings were characterized via scanning electron microscopy, x-ray diffraction, energy-dispersive x-ray spectroscopy, and laser-scanning microscope. Biocompatibility of coatings was carried out with primary human osteoblasts analyzing cell morphology, proliferation, collagen type 1, and interleukin 6 and 8 release. Results indicate a successful formation of low crystalline hydroxyapatite (HA) on top of every sample after immersion in each BCP coating solution after 14 days. Furthermore, HA coating promoted cell proliferation and reduced the concentration of interleukins compared to the uncoated surface, assuming increased biocompatibility.

Prediction of mechanical properties of trabecular bone in patients with type 2 diabetes using damage based finite element method

Type-2 diabetic (T2D) and osteoporosis (OP) suffered patients are more prone to fragile fracture though the nature of alteration in areal bone mineral density (aBMD) in these two cases are completely different. Therefore, it becomes crucial to compare the effect of T2D and OP on alteration in mechanical and structural properties of femoral trabecular bone. This study investigated the effect of T2D, OP, and osteopenia on bone structural and mechanical properties using micro-CT, nanoindentation and compression test. Further, a nanoscale finite element model (FEM) was developed to predict the cause of alteration in mechanical properties. Finally, a damage-based FEM was proposed to predict the pathological related alteration of bone's mechanical response. The obtained results demonstrated that the T2D group had lower volume fraction (-18.25%, p = 0.023), young's modulus (-23.47%, p = 0.124), apparent modulus (-37.15%, p = 0.02), and toughness (-40%, p = 0.001) than the osteoporosis group. The damage-based FE results were found in good agreement with the compression experiment results for all three pathological conditions. Also, nanoscale FEM results demonstrated that the elastic and failure properties of mineralised collagen fibril decreases with increase in crystal size. This study reveals that T2D patients are more prone to fragile fracture in comparison to OP and osteopenia patients. Also, the proposed damage-based FEM can help to predict the risk of fragility fracture for different pathological conditions.

Mineral and organic matrix composition at bone forming surfaces in postmenopausal women with osteoporosis treated with either teriparatide or zoledronic acid

The ability of bone to resist fracture is dependent on the composite nature of its mineral and organic matrix content. Teriparatide (TPTD) and zoledronic acid (ZOL) are approved anabolic and antiresorptive therapies, respectively, to reduce fracture risk in women with postmenopausal osteoporosis. In the SHOTZ study, postmenopausal women with osteoporosis were treated with TPTD (20 μg daily, subcutaneous) or ZOL (5 mg/year, intravenous infusion) for 24 months. Iliac crest biopsies were obtained at 6 months and again at 24 months from approximately one third of the original study cohort. To investigate the early effects of these two drugs on the quality of newly formed bone, we used vibrational spectroscopic techniques to analyze tetracycline-labelled transiliac biopsies obtained from participants at the 6-month time point. Raman spectra were acquired at forming trabecular and intra-cortical surfaces (identified by fluorescent double labels), to determine mineral, organic matrix, glycosaminoglycan, and tissue water content, as well as mineral maturity/crystallinity at three specific tissue ages (1-5, 15, and ≥25 days). Fourier transformed infrared microspectroscopy was used to determine pyridinoline/divalent collagen cross-link ratios. At 6 months, treatment with TPTD versus ZOL resulted in lower mineral and higher organic matrix content, increased tissue water content, and lower mineral/matrix, mineral maturity/crystallinity, glycosaminoglycan content, and pyridinoline/divalent enzymatic collagen cross-link ratio. Our results suggest that TPTD and ZOL have differential effects on material properties of newly formed bone at individual remodeling sites, highlighting their different mechanisms of action.

Raman spectroscopic determination of bone matrix quantity and quality augments prediction of human cortical bone mechanical properties

Being independent contributors to bone mechanical resistance at the apparent level, quality and quantity of bone primary constituents are essential factors in better fracture risk assessment. Raman spectroscopy (RS) holds great potential for being a clinical tool with providing quality and quantity measurements of the bone mineralized matrix. Beyond mineral quality and quantity, recent years have revealed newly developed RS-derived bone compositional measurements focusing on organic matrix and water though their associations with bone mechanics have not been fully established yet. Herein, the author reported first thorough characterization study investigating associations between twenty different RS-derived measurements and mechanical properties of human cortical bone (i.e., yield and ultimate strength, elastic modulus, toughness, post-yield toughness, and post-yield strain). Forty-five rectangular human cortical beams harvested from all four anatomical quadrants of two male donors were tested under three-point bending. Raman spectra of each specimen were collected at the spectral range of 800 to 4000 cm^-1. While correlations were tested among RS-derived measurements via Spearman's rank correlations, multivariate linear regression using mixed effects were used to determine the best RS-derived measurement or the combination of RS-derived measurements in predicting various mechanical properties of human cortical bone. Most of the RS-derived measurements were associated with the mechanical properties (Rm² ranges from 8.9 to 68.3%, p < 0.05). The various linear combinations of six RS-derived measurements focusing on different aspects of bone matrix (i.e., ν₁PO₄/Amide I, ν₁PO₄/Amide III, Carbonate/ν₁PO₄, ~I₁₆₇₀/I₁₆₄₀, ~I₃₄₅₃/I₂₉₄₉, ~I₃₅₈₄/I₂₉₄₉) improved the prediction (Rm² = 43.5 to 70.2%, p < 0.05). While a causal relationship still needs to be investigated, RS has a great potential to establish a robust patient-specific fracture risk prediction with the latest advances in technologies.

Applications of Vibrational Spectroscopy for Analysis of Connective Tissues

Advances in vibrational spectroscopy have propelled new insights into the molecular composition and structure of biological tissues. In this review, we discuss common modalities and techniques of vibrational spectroscopy, and present key examples to illustrate how they have been applied to enrich the assessment of connective tissues. In particular, we focus on applications of Fourier transform infrared (FTIR), near infrared (NIR) and Raman spectroscopy to assess cartilage and bone properties. We present strengths and limitations of each approach and discuss how the combination of spectrometers with microscopes (hyperspectral imaging) and fiber optic probes have greatly advanced their biomedical applications. We show how these modalities may be used to evaluate virtually any type of sample (ex vivo, in situ or in vivo) and how "spectral fingerprints" can be interpreted to quantify outcomes related to tissue composition and quality. We highlight the unparalleled advantage of vibrational spectroscopy as a label-free and often nondestructive approach to assess properties of the extracellular matrix (ECM) associated with normal, developing, aging, pathological and treated tissues. We believe this review will assist readers not only in better understanding applications of FTIR, NIR and Raman spectroscopy, but also in implementing these approaches for their own research projects.

Weaning, parturitions and illnesses are recorded in rhesus macaque (Macaca mulatta) dental cementum microstructure

Many open questions in evolutionary studies relate to species' physiological adaptations, including the evolution of their life history and reproductive strategies. There are few empirical methods capable of detecting and timing physiologically impactful events such as weaning, parturition and illnesses from hard tissue remains of either extant or extinct species. Cementum is an incremental tissue with post eruption annual periodicity, which covers the tooth root and functions as a recording structure of an animal's physiology. Here we test the hypothesis that it is possible to detect and time physiologically impactful events through the analysis of dental cementum microstructure. Our sample comprises 41 permanent and deciduous teeth from male and female rhesus macaques (Macaca mulatta) with known medical, lifestyle and life history information. We develop a semi-automated method of cementum histological analysis for the purpose of event detection and timing, aimed at significantly reducing the amount of intra- and interobserver errors typically associated with histological analyses. The results of our work show that we were able to detect known events including weaning, parturition, illness and physical trauma with high accuracy (false negative rate = 3.2%; n = 1), and to time them within an average absolute difference of 0.43 years (R²  = .98; p < .05). Nonetheless, we could not distinguish between the several types of stressful events underlying the changes in cementum microstructure. While this study is the first to identify a variety of life history events in macaque dental cementum, laying foundations for future work in conservation and evolutionary studies of both primates and toothed mammals at large, there are some limitations. Other types of analyses (possibly chemical ones) are necessary to tease apart the causes of the stressors.

Intrinsic properties of osteomalacia bone evaluated by nanoindentation and FTIRM analysis

Osteomalacia is a pathological bone condition consisting in a deficient primary mineralization of the matrix, leading to an accumulation of osteoid tissue and reduced bone mechanical strength. The amounts, properties and organization of bone constituents at tissue level, are known to influence its mechanical properties. It is then important to investigate the relationship between mechanical behavior and tissue composition at this scale in order to provide a better understanding of bone fragility mechanisms associates with this pathology. Our purpose was to analyze the links between ultra-structural properties and the mechanical behavior of this pathological bone tissue (osteomalacia) at tissue level (mineral and osteoid separately, or global). Four bone biopsies were taken from patients with osteomalacia, and subsequently embedded, sectioned, and polished. Then nanoindentation tests were performed to determine local elastic modulus E, contact hardness Hc and true hardness H for both mineralized and organic bone phases and for the global bone. The creep of the bone was also studied using a special indentation procedure in order to assess visco-elasto-plastic (creep) bone behavior. This allowed a detailed study of the rheological models adapted to the bone and to calculate the parameters associated to a Burgers model. Ultra-structural parameters were measured by Fourier Transform InfraRed Microspectroscopy (FTIRM) on the same position as the indents. The use of rheological models confirmed a significant contribution from the organic phase on the viscous character of bone tissue. The elastic E and the elasto-plastic H_c deformation were correlated to both collagen maturity and Mineral/Matrix. The pure plastic deformation H was only correlated to the mineral phase. Our data show that mineral phase greatly affects mechanical variables (moduli and viscosities) and that organic phase (as illustrated in osteoid tissue) may play an important role in the creep behavior of bone. In conclusion, this study brings mechanical and physicochemical values for osteoid and mineral phases.

Deciphering the Relevance of Bone ECM Signaling

Bone mineral density, a bone matrix parameter frequently used to predict fracture risk, is not the only one to affect bone fragility. Other factors, including the extracellular matrix (ECM) composition and microarchitecture, are of paramount relevance in this process. The bone ECM is a noncellular three-dimensional structure secreted by cells into the extracellular space, which comprises inorganic and organic compounds. The main inorganic components of the ECM are calcium-deficient apatite and trace elements, while the organic ECM consists of collagen type I and noncollagenous proteins. Bone ECM dynamically interacts with osteoblasts and osteoclasts to regulate the formation of new bone during regeneration. Thus, the composition and structure of inorganic and organic bone matrix may directly affect bone quality. Moreover, proteins that compose ECM, beyond their structural role have other crucial biological functions, thanks to their ability to bind multiple interacting partners like other ECM proteins, growth factors, signal receptors and adhesion molecules. Thus, ECM proteins provide a complex network of biochemical and physiological signals. Herein, we summarize different ECM factors that are essential to bone strength besides, discussing how these parameters are altered in pathological conditions related with bone fragility.

Bone tissue material composition is compromised in premenopausal women with Type 2 diabetes

Type 2 diabetes mellitus (T2DM) patients are at an increased risk of fracture despite normal to high bone mineral density (BMD) values. In this cross-sectional study we establish bone compositional properties in tetracycline labeled iliac crest biopsies from premenopausal women diagnosed with T2DM (N = 26). Within group comparisons were made as a function of tissue age (TA), presence of chronic complications (CC), glycosylated haemoglobin (HbA1c) levels, and morphometric fracture (MFx). We also compared these data at actively trabecular bone forming surfaces against sex- and age-matched healthy controls (N = 32). The bone quality indices determined by Raman microspectroscopic analysis were: mineral/matrix (MM), tissue water content (nanoporosity; NanoP), mineral maturity/crystallinity (MMC), and glycosaminoglycan (GAG), pyridinoline (Pyd), N-(carboxymethyl)lysine (CML), and pentosidine (PEN) content. Within the T2DM group, at the oldest tissue, CML and PEN contents were significantly elevated in the cancellous compared to cortical compartment. The outcomes were not dependent on MFx. On the other hand, both were significantly elevated in patients with CC, as well as those with HbA1c levels > 7%. At actively forming surfaces, the cortical compartment had higher NanoP compared to cancellous. Still within the T2DM group, patients with MFx had significantly elevated MM and GAGs compared to the ones that did not. At actively forming trabecular surfaces, compared to healthy women, T2DM patients had elevated GAGs content and MMC. The results of this study indicate increased AGEs in those with poor glycation control and chronic complications. Additionally, T2DM patients had elevated MMC and decreased GAGs content compared to healthy controls. These alterations may be contributing to the T2DM inherent elevated fracture risk and suggest a role for hyperglycemia on bone quality.

Black phosphorus-based 2D materials for bone therapy

Since their discovery, Black Phosphorus (BP)-based nanomaterials have received extensive attentions in the fields of electromechanics, optics and biomedicine, due to their remarkable properties and excellent biocompatibility. The most essential feature of BP is that it is composed of a single phosphorus element, which has a high degree of homology with the inorganic components of natural bone, therefore it has a full advantage in the treatment of bone defects. This review will first introduce the source, physicochemical properties, and degradation products of BP, then introduce the remodeling process of bone, and comprehensively summarize the progress of BP-based materials for bone therapy in the form of hydrogels, polymer membranes, microspheres, and three-dimensional (3D) printed scaffolds. Finally, we discuss the challenges and prospects of BP-based implant materials in bone immune regulation and outlook the future clinical application.

XRD and ATR-FTIR techniques for integrity assessment of gamma radiation sterilized cortical bone pretreated by antioxidants

Terminal sterilization of bone allograft by gamma radiation is required to reduce the risk of infection. Free radical scavengers could be utilized to minimize the deteriorating effects of gamma radiation on bone allograft mechanical properties. The objective of this research is to assess the changes in structural and chemical composition induced by hydroxytyrosol (HT) and alpha lipoic acid (ALA) free radical scavengers in gamma sterilized cortical bone. Bovine femurs specimens were soaked in different concentrations of HT and ALA for 7 and 3 days respectively before irradiation with 35 KGy gamma radiation. The attenuated total reflection-Fourier transform infrared spectroscopy and the X-ray diffraction techniques were utilized to analyze the changes in chemical composition induced by irradiation in the presence of free radical scavengers. A significant increase in the proportion of amide I and amide II to phosphate was noticed in the irradiated group, while in the pretreated groups with ALA and HT this effect was minimized. In addition, gamma radiation reduced the mature to immature cross links while ALA and HT alleviated this reduction. No significant changes were noticed in the mineral crystallinity or crystal size. Bone chemical structure has been changed due to gamma irradiation and these changes are mainly relevant to amide I, amide II proportions and collagen crosslinks. The deteriorating effects of gamma sterilization dose (35 kGy) on chemical structure of bone allograft can be alleviated by using (HT) and (ALA) free radical scavengers before irradiation.

Development of HFD-Fed/Low-Dose STZ-Treated Female Sprague-Dawley Rat Model to Investigate Diabetic Bone Fragility at Different Organization Levels

Type 2 diabetes (T2D) adversely affects the normal functioning, intrinsic material properties, and structural integrity of many tissues, and bone fragility is one of them. To simulate human T2D and to investigate diabetic bone fragility, many rodent diabetic models have been developed. Still, an outbred genetically normal nonobese diabetic rat model is not available that can better simulate the disease characteristics of nonobese T2D patients, who have a high prevalence in Asia. In this study, we used a combination treatment of high-fat diet (4 weeks, 58% kcal as fat) and low-dose streptozotocin (STZ; 35 mg/kg i.p. at the end of the fourth week) to develop T2D in female Sprague-Dawley (SD) rats. After 8 weeks of the establishment of the T2D model, the femoral bones were excised after euthanizing rats (animal age approximately 21 to 22 weeks; n = 10 with T2D, n = 10 without diabetes). The bone microstructure (μCT), mechanical, and material properties (three-point bending, cyclic reference point indentation, nanoindentation), mean mineral crystallite size (XRD), bone composition (mineral-to-matrix ratio, nonenzymatic cross-link ratio [NE-xLR], Fourier transform-infrared microspectroscopy), and total fluorescent advanced glycation end products were analyzed. We found that diabetic bone had reduced whole-bone strength and compromised structural properties (μCT). The NE-xLRs were elevated in the T2D group, and strongly and negatively correlated with postyield displacement, which suggests bone fragility was caused by a lack of glycation control. Along with that, the decreased mineral-to-matrix ratio and modulus, increased indentation distance increase, and wider mineral crystallite size in the T2D group were evidence that the diabetic bone composition and material properties had changed, and bone became weaker with a tendency to easily fracture. Altogether, this model simulates the natural history and metabolic characteristics of late-stage T2D (insulin resistance and as disease progress develops, hypoinsulinemia) for nonobese young (and/or adolescent) T2D patients (Asians) and provides potential evidence of diabetic bone fragility at various organization levels. © 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Raman and Fourier transform infrared imaging for characterization of bone material properties

As the application of Raman spectroscopy to study bone has grown over the past decade, making it a peer technology to FTIR spectroscopy, it has become critical to understand their complimentary roles. Recent technological advancements have allowed these techniques to collect grids of spectra in a spatially resolved fashion to generate compositional images. The advantage of imaging with these techniques is that it allows the heterogenous bone tissue composition to be resolved and quantified. In this review we compare, for non-experts in the field of vibrational spectroscopy, the instrumentation and underlying physical principles of FTIR imaging (FTIRI) and Raman imaging. Additionally, we discuss the strengths and limitations of FTIR and Raman spectroscopy, address sample preparation, and discuss outcomes to provide researchers insight into which techniques are best suited for a given research question. We then briefly discuss previous applications of FTIRI and Raman imaging to characterize bone tissue composition and relationships of compositional outcomes with mechanical performance. Finally, we discuss emerging technical developments in FTIRI and Raman imaging which provide new opportunities to identify changes in bone tissue composition with disease, age, and drug treatment.

Advancements in composition and structural characterization of bone to inform mechanical outcomes and modelling

Advancements in imaging, computing, microscopy, chromatography, spectroscopy and biological manipulations of animal models, have allowed for a more thorough examination of the hierarchical structure and composition of the skeleton. The ability to map cellular and molecular changes to nano-scale chemical composition changes (mineral, collagen cross-links) and structural changes (porosity, lacuno-canalicular network) to whole bone mechanics is at the forefront of an exciting era of discovery. In addition, there is increasing ability to genetically mimic phenotypes of human disease in animal models to study these structural and compositional changes. Combined, these recent developments have increased the ability to understand perturbations at multiple length scales to better realize the structure-function relationship in bone and inform biomechanical models. The intent of this review is to describe the multiple scales at which bone can characterized, highlighting new techniques such that structural, compositional, and biological changes can be incorporated into biomechanical modeling.

Differing trabecular bone architecture in dinosaurs and mammals contribute to stiffness and limits on bone strain

The largest dinosaurs were enormous animals whose body mass placed massive gravitational loads on their skeleton. Previous studies investigated dinosaurian bone strength and biomechanics, but the relationships between dinosaurian trabecular bone architecture and mechanical behavior has not been studied. In this study, trabecular bone samples from the distal femur and proximal tibia of dinosaurs ranging in body mass from 23-8,000 kg were investigated. The trabecular architecture was quantified from micro-computed tomography scans and allometric scaling relationships were used to determine how the trabecular bone architectural indices changed with body mass. Trabecular bone mechanical behavior was investigated by finite element modeling. It was found that dinosaurian trabecular bone volume fraction is positively correlated with body mass similar to what is observed for extant mammalian species, while trabecular spacing, number, and connectivity density in dinosaurs is negatively correlated with body mass, exhibiting opposite behavior from extant mammals. Furthermore, it was found that trabecular bone apparent modulus is positively correlated with body mass in dinosaurian species, while no correlation was observed for mammalian species. Additionally, trabecular bone tensile and compressive principal strains were not correlated with body mass in mammalian or dinosaurian species. Trabecular bone apparent modulus was positively correlated with trabecular spacing in mammals and positively correlated with connectivity density in dinosaurs, but these differential architectural effects on trabecular bone apparent modulus limit average trabecular bone tissue strains to below 3,000 microstrain for estimated high levels of physiological loading in both mammals and dinosaurs.

Age related changes in the bone microstructure in patients with femoral neck fractures

BACKGROUND

The risk of femoral neck fracture progressively increases with age. However, the reasons behind this consistent increase in the fracture risk can't be completely justified by the decrease in the bone mineral density. The objective of this study was to analyze the correlation between various bone structural features and age.

STUDY DESIGN & METHODS

A total of 29 consecutive patients who suffered an intracapsular hip fracture and underwent joint replacement surgery between May 2012 and March 2013 were included in this study. A 2 cm × 1 cm Ø cylindrical trabecular bone sample was collected from the femoral heads and preserved in formaldehyde. Bone mineral density (BMD), microarchitecture, organic content and crystallography were analyzed using a Dual-energy X-ray absorptiometry scan, micro-CT scan, and high resolution magic-angle-spinning-nuclear magnetic resonance (MAS-NMR), respectively. Statistical correlations were made using Spearman´s or Pearson´s correlation tests depending on the distribution of the continuous variables.

RESULTS

The mean patient age was 79.83 ± 9.31 years. A moderate negative correlation was observed between age and the hydrogen content in bone (¹H), which is an indirect estimate to quantify the organic matrix (r = -0.512, p = 0.005). No correlations were observed between BMD, trabecular number, trabecular thickness, phosphorous content, apatite crystal size, and age (r = 0.06, p = 0.755; r = -0.008, p = 0.967; r = -0.046, p = 0.812; r = -0.152, p = 0.430, respectively). A weak positive correlation was observed between Charlson´s comorbidity index (CCI) and c-axis of the hydroxiapatite (HA) crystals (r = -0.400, p = 0.035).

CONCLUSION

The femoral head relative protein content progressively decreases with age. BMD was not correlated with other structural bone parameters and age. Patients with higher comorbidity scores had larger HA crystals. The present results suggest that the progressive increase in the hip fracture risk in elderly patients could be partially explained by the lower bone protein content in this age group.

Parturitions, menopause and other physiological stressors are recorded in dental cementum microstructure

The life history pattern of recent humans is uniquely derived in many of its aspects including an extended post-reproductive lifespan combined with short interbirth intervals. A number of theories have been proposed to explain the evolution of this unusual pattern. However most have been difficult to test due to the fragmentary nature of the hominin fossil record and the lack of methods capable of inferring such later life history events. In search of a method we tested the hypothesis that the physiologically impactful events of parturition and menopause are recorded in dental cementum microstructure. We performed histomorphological analyses of 47 teeth from 15 individuals with known life history events and were able to detect reproductive events and menopause in all females. Furthermore, we found that other stressful events such as systemic illnesses and incarceration are also detectable. Finally, through the development of a novel analytical method we were able to time all such events with high accuracy (R-squared = 0.92).

Compositional and mechanical properties of growing cortical bone tissue: a study of the human fibula

Human cortical bone contains two types of tissue: osteonal and interstitial tissue. Growing bone is not well-known in terms of its intrinsic material properties. To date, distinctions between the mechanical properties of osteonal and interstitial regions have not been investigated in juvenile bone and compared to adult bone in a combined dataset. In this work, cortical bone samples obtained from fibulae of 13 juveniles patients (4 to 18 years old) during corrective surgery and from 17 adult donors (50 to 95 years old) were analyzed. Microindentation was used to assess the mechanical properties of the extracellular matrix, quantitative microradiography was used to measure the degree of bone mineralization (DMB), and Fourier transform infrared microspectroscopy was used to evaluate the physicochemical modifications of bone composition (organic versus mineral matrix). Juvenile and adult osteonal and interstitial regions were analyzed for DMB, crystallinity, mineral to organic matrix ratio, mineral maturity, collagen maturity, carbonation, indentation modulus, indicators of yield strain and tissue ductility using a mixed model. We found that the intrinsic properties of the juvenile bone were not all inferior to those of the adult bone. Mechanical properties were also differently explained in juvenile and adult groups. The study shows that different intrinsic properties should be used in case of juvenile bone investigation.

Randomized Controlled Clinical Trial of Nanostructured Carbonated Hydroxyapatite for Alveolar Bone Repair

The properties of the biodegradation of bone substitutes in the dental socket after extraction is one of the goals of regenerative medicine. This double-blind, randomized, controlled clinical trial aimed to compare the effects of a new bioabsorbable nanostructured carbonated hydroxyapatite (CHA) with a commercially available bovine xenograft (Bio-Oss®) and clot (control group) in alveolar preservation. Thirty participants who required tooth extraction and implant placement were enrolled in this study. After 90 days, a sample of the grafted area was obtained for histological and histomorphometric evaluation and an implant was installed at the site. All surgical procedures were successfully carried out without complications and none of the patients were excluded. The samples revealed a statistically significant increase of new bone formation (NFB) in the CHA group compared with Bio-Oss® after 90 days from surgery (p < 0.05). However, the clot group presented no differences of NFB compared to CHA and Bio-Oss®. The CHA group presented less amount of reminiscent biomaterial compared to Bio-Oss®. Both biomaterials were considered osteoconductors, easy to handle, biocompatible, and suitable for alveolar filling. Nanostructured carbonated hydroxyapatite spheres promoted a higher biodegradation rate and is a promising biomaterial for alveolar socket preservation before implant treatment.

Novel bisphosphonate compound FYB-931 preferentially inhibits aortic calcification in vitamin D3-treated rats

In patients with chronic kidney disease (CKD) or those undergoing hemodialysis, pathological calcific deposition known as ectopic calcification occurs in soft tissue, resulting in a life-threatening disorder. A potent and effective inhibitor of ectopic calcification is eagerly expected. In the current study, the effects of FYB-931, a novel bisphosphonate compound synthesized for the prevention of ectopic calcification, were compared with those of etidronate using both in vitro and in vivo models. In vitro, FYB-931 inhibited calcification of human aortic smooth muscle cells induced by high phosphate medium in a concentration-dependent manner, and the effect was slightly more potent than that of etidronate. In vivo, rats were administered with three subcutaneous injections of vitamin D3 to induce vascular calcification, and were given FYB-931 (1.5, 5, or 10 mg/kg) or etidronate (9, 30, or 60 mg/kg) orally once daily for 14 days. The increased aortic phosphorus content as an index of vascular calcification was inhibited by both FYB-931 and etidronate in a dose-dependent manner; however, FYB-931 was 10 times more potent than etidronate. FYB-931 inhibited serum tartrate-resistant acid phosphatase (TRACP) activity as a bone resorption marker 5.2 times more potently than etidronate. FYB-931, but not etidronate, significantly decreased serum phosphorus levels. The preferential inhibition of aortic calcification by FYB-931 suggested that possible additional effect including a decline in serum phosphorus may lead to an advantage in terms of its efficacy.

Osteoporosis Changes Collagen/Apatite Orientation and Young's Modulus in Vertebral Cortical Bone of Rat

This study revealed the distinguished changes of preferential orientation of collagen and apatite and Young's modulus in two different types of osteoporotic bones compared with the normal bone. Little is known about the bone material properties of osteoporotic bones; therefore, we aimed to assess material properties in osteoporotic bones. 66 female Sprague-Dawley rats were used. We analyzed the volumetric bone mineral density, collagen/apatite orientation, and Young's modulus of fifth lumbar vertebral cortex for osteoporotic rats caused by ovariectomy (OVX), administration of low calcium and phosphate content (LCaP) diet, and their combination (OVX + LCaP), as well as sham-operated control. Osteocyte conditions were assessed by hematoxylin and eosin and immunohistochemical (matrix extracellular phosphoglycoprotein (MEPE) and dentin matrix protein 1 (DMP1)) staining. All osteoporotic animals showed bone loss compared with the sham-operated control. OVX improved craniocaudal Young's modulus by enhancing collagen/apatite orientation along the craniocaudal axis, likely in response to the elevated stress due to osteoporotic bone loss. Conversely, LCaP-fed animals showed either significant bone loss or degraded collagen/apatite orientation and Young's modulus. Osteocytes in LCaP and OVX + LCaP groups showed atypical appearance and MEPE- and DMP1-negative phenotype, whereas those in the OVX group showed similarity with osteocytes in the control group. This suggests that osteocytes are possibly involved in the osteoporotic changes in collagen/apatite orientation and Young's modulus. This study is the first to demonstrate that osteoporosis changes collagen/apatite orientation and Young's modulus in an opposite manner depending on the cause of osteoporosis in spite of common bone loss.

Anisotropic aspects of solubility behavior in the demineralization of cortical bone revealed by XRD analysis

Dissolution of cortical bone mineral under demineralization in 0.1 M HCl and 0.1 M EDTA solutions is studied by X-ray diffraction (XRD). The bone specimens (in the form of planar oriented pieces) were cut from a diaphysial fragment of a mature mammal bone so that a cross-section surface and a longitudinal section surface could be analyzed individually. This permitted to compare the dissolution behavior of bone apatite of different morphologies: crystals having the c-axis of the hexagonal unit-cell generally parallel to the long axis of the bone (major morphology) and those having the c-axis almost perpendicular to the bone axis (minor morphology). For these two types of morphology, the crystallite sizes in two mutually perpendicular directions (namely, [002] and [310]) were estimated by Scherrer formula in the initial and the stepwise-demineralized specimens. The data obtained reveal that the crystals belonging to the minor morphology dissolve faster than the crystals of the major morphological type, despite the fact that the crystallites of the minor morphology seem to be only a little smaller than those of the major morphology; the apatite crystallites irrespective of the morphology type are elongated in the c-axis direction. We hypothesize that the revealed difference in solubility may be caused by diverse chemical modifications of apatite of these two morphological types, since the solubility of apatite is strictly regulated by anionic and cationic substitutions in the lattice. The anisotropy effect in solubility of bone mineral seems to be functionally predetermined and this should be a crucial factor in the resorption and remodeling behavior of a bone. Some challenges arising at XRD examination of partially decalcified cortical bone blocks are discussed, as well as the limitations of estimation of bone crystallite size by XRD line-broadening analysis.

Age-Related Changes in Femoral Head Trabecular Microarchitecture

Osteoporosis is a prevalent bone condition, characterised by low bone mineral density and increased fracture risk. Currently, the gold standard for identifying osteoporosis and increased fracture risk is through quantification of bone mineral density using dual energy X-ray absorption. However, many studies have shown that bone strength, and consequently the probability of fracture, is a combination of both bone mass and bone 'quality' (architecture and material chemistry). Although the microarchitecture of both non-fracture and osteoporotic bone has been previously investigated, many of the osteoporotic studies are constrained by factors such as limited sample number, use of ovariectomised animal models, and lack of male and female discrimination. This study reports significant differences in bone quality with respect to the microarchitecture between fractured and non-fractured human femur specimens. Micro-computed tomography was utilised to investigate the microarchitecture of femoral head trabecular bone from a relatively large cohort of non-fracture and fracture human donors. Various microarchitectural parameters have been determined for both groups, providing an understanding of the differences between fracture and non -fracture material. The microarchitecture of non-fracture and fracture bone tissue is shown to be significantly different for many parameters. Differences between sexes also exist, suggesting differences in remodelling between males and females in the fracture group. The results from this study will, in the future, be applied to develop a fracture model which encompasses bone density, architecture and material chemical properties for both female and male tissues.

Mechanical behavior of metastatic vertebrae are influenced by tissue architecture, mineral content, and organic feature alterations

Diminished vertebral mechanical behavior with metastatic involvement is typically attributed to modified architecture and trabecular bone content. Previous work has identified organic and mineral phase bone quality changes in the presence of metastases, yet limited work exists on the potential influence of such tissue level modifications on vertebral mechanical characteristics. This work seeks to determine correlations between features of bone (structural and tissue level) and mechanical behavior in metastatically involved vertebral bone. It is hypothesized that tissue level properties (mineral and organic) will improve these correlations beyond architectural properties and BMD alone. Twenty-four female athymic rats were inoculated with HeLa or Ace-1 cancer cells lines producing osteolytic (N = 8) or mixed (osteolytic/osteoblastic, N = 7) metastases, respectively. Twenty-one days post-inoculation L1-L3 pathologic vertebral motion segments were excised and μCT imaged. 3D morphometric parameters and axial rigidity of the L2 vertebrae were quantified. Sequential loading and μCT imaging measured progression of failure, stiffness and peak force. Relationships between mechanical testing (whole bone and tissue-level) and tissue-level material property modifications with metastatic involvement were evaluated utilizing linear regression models. Osteolytic involvement reduced vertebral trabecular bone volume, structure, CT-derived axial rigidity, stiffness and failure force compared to healthy controls (N = 9). Mixed metastases demonstrated similar trends. Previously assessed collagen cross-linking and proline-based residues were correlated to mechanical behavior and improved the predictive ability of the regression models. Similarly, collagen organization improved predictive regression models for metastatic bone hardness. This work highlights the importance of both bone content/architecture and organic tissue-level features in characterizing metastatic vertebral mechanics. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:3013-3022, 2018.

Raman Spectroscopy detects changes in Bone Mineral Quality and Collagen Cross-linkage in Staphylococcus Infected Human Bone

Diagnosis of osteomyelitis presents a formidable challenge. Lack of pathognomonic clinical sign(s) and diagnostic tests that can diagnose osteomyelitis at an early stage contribute to this difficulty. If the diagnosis is not made early, the disease becomes very difficult to eradicate and can lead to limb threatening and potentially life-threatening complications. Staphylococcus aureus is the most common organism causing osteomyelitis. Raman Spectroscopy provides information about molecular vibration that could potentially be harnessed as a spectral signature for cellular changes in specific pathologic conditions. In this study we describe a technique using Raman spectroscopy that could potentially be used to diagnose staphylococcal osteomyelitis. Human bone samples were co-cultured with Staphylococcus aureus (S. aureus) and the effects of bacterial growth on bone quality were then monitored using Raman spectroscopy. A major drop in the bone mineral quality and crystallinity was observed in the infected bones compared to the controls. S. aureus infection was also found to alter the collagen cross-linking. Our study shows that specific spectral signatures are present for the cause as well as the effect of staphylococcal osteomyelitis, opening the possibility of developing a useful diagnostic modality for early and rapid diagnosis of this condition.

The Role of Matrix Composition in the Mechanical Behavior of Bone

PURPOSE OF REVIEW

While thinning of the cortices or trabeculae weakens bone, age-related changes in matrix composition also lower fracture resistance. This review summarizes how the organic matrix, mineral phase, and water compartments influence the mechanical behavior of bone, thereby identifying characteristics important to fracture risk.

RECENT FINDINGS

In the synthesis of the organic matrix, tropocollagen experiences various post-translational modifications that facilitate a highly organized fibril of collagen I with a preferred orientation giving bone extensibility and several toughening mechanisms. Being a ceramic, mineral is brittle but increases the strength of bone as its content within the organic matrix increases. With time, hydroxyapatite-like crystals experience carbonate substitutions, the consequence of which remains to be understood. Water participates in hydrogen bonding with organic matrix and in electrostatic attractions with mineral phase, thereby providing stability to collagen-mineral interface and ductility to bone. Clinical tools sensitive to age- and disease-related changes in matrix composition that the affect mechanical behavior of bone could potentially improve fracture risk assessment.

The role of OPG/RANKL in the pathogenesis of diabetic cardiovascular disease

Cardiovascular (CV) disease is the leading cause of mortality in patients with type 2 diabetes mellitus. A major factor in the pathogenesis of CV disease is vascular calcification (VC), which is accelerated in type 2 diabetes mellitus. Calcification of the vessel wall contributes to vascular stiffness and left ventricular hypertrophy whereas intimal calcification may predispose to plaque rupture and CV death. The pathogenesis of VC is complex but appears to be regulated by the osteoprotegerin (OPG)/receptor activator of nuclear factor-κB ligand (RANKL) signaling pathway, which is involved in bone remodeling. Within the bone, OPG prevents RANKL from binding to receptor activator of nuclear factor-κB and inhibiting bone resorption. Outside of the bone, the clinical significance of OPG blocking RANKL is not well understood, but OPG knockout mice that lack OPG develop early and severe VC. This minireview outlines some of the research on OPG/RANKL in the pathogenesis of VC and discusses potential therapies, which may reduce VC and CV burden in humans.

The compositional and nano-structural basis of fracture healing in healthy and osteoporotic bone

Osteoporosis, a prevalent metabolic bone disorder, predisposes individuals to increased susceptibility to fractures. It is also, somewhat controversially, thought to delay or impair the regenerative response. Using high-resolution Fourier-transform infrared spectroscopy and small/wide-angle X-ray scattering we sought to answer the following questions: Does the molecular composition and the nano-structure in the newly regenerated bone differ between healthy and osteoporotic environments? And how do pharmacological treatments, such as bone morphogenetic protein 7 (BMP-7) alone or synergistically combined with zoledronate (ZA), alter callus composition and nano-structure in such environments? Cumulatively, on the basis of compositional and nano-structural characterizations of newly formed bone in an open-osteotomy rat model, the healing response in untreated healthy and ovariectomy-induced osteoporotic environments was fundamentally the same. However, the BMP-7 induced osteogenic response resulted in greater heterogeneity in the nano-structural crystal dimensions and this effect was more pronounced with osteoporosis. ZA mitigated the effects of the upregulated catabolism induced by both BMP-7 and an osteoporotic bone environment. The findings contribute to our understanding of how the repair processes in healthy and osteoporotic bone differ in both untreated and treated contexts and the data presented represents the most comprehensive study of fracture healing at the nanoscale undertaken to date.

Protein-crystal interface mediates cell adhesion and proangiogenic secretion

The nanoscale materials properties of bone apatite crystals have been implicated in breast cancer bone metastasis and their interactions with extracellular matrix proteins are likely involved. In this study, we used geologic hydroxyapatite (HAP, Ca10(PO4)6(OH)2), closely related to bone apatite, to investigate how HAP surface chemistry and nano/microscale topography individually influence the crystal-protein interface, and how the altered protein deposition impacts subsequent breast cancer cell activities. We first utilized Förster resonance energy transfer (FRET) to assess the molecular conformation of fibronectin (Fn), a major extracellular matrix protein upregulated in cancer, when it adsorbed onto HAP facets. Our analysis reveals that both low surface charge density and nanoscale roughness of HAP facets individually contributed to molecular unfolding of Fn. We next quantified cell adhesion and secretion on Fn-coated HAP facets using MDA-MB-231 breast cancer cells. Our data show elevated proangiogenic and proinflammatory secretions associated with more unfolded Fn adsorbed onto nano-rough HAP facets with low surface charge density. These findings not only deconvolute the roles of crystal surface chemistry and topography in interfacial protein deposition but also enhance our knowledge of protein-mediated breast cancer cell interactions with apatite, which may be implicated in tumor growth and bone metastasis.

Cortical Bone Mineralization in the Human Femoral Neck in Cases and Controls from Synchrotron Radiation Study

To compare the degree and distribution of mineralization in femoral neck cortex from 23 women with hip fractures (age 65-96 years) and 17 female controls (age 72-103 years), we obtained 3D data by synchrotron radiation microtomography (SRμCT). Variables were degree of mineralization of bone (DMB) in total cortex (cDMBSRMEAN), osteons (oDMBSRMEAN), and pure interstitial tissue (intDMBSRMEAN). The cortex on SRμCT images was divided into nine to twelve 50-μm zones from the periosteum to the endosteum; cDMBSRMEAN, oDMBSRMEAN, and intDMBSRMEAN were measured in each zone. We used descriptive statistics and t tests, general linear model analyses to compare DMBSR values across zones and individuals, one-way analysis of variance for within-group comparisons of zones. In patients, the variance of mineral content value was not different than in controls, but mean values of degree of mineralization varied across zones. These cross-sectional data suggest that bone fragility may be related to a greater heterogeneity of the distribution of mineralization in femoral neck cortex.