Bone architecture: collagen structure and calcium/phosphorus maps

Self-Assembly of Cyclic-Bending Collagen Fibrils by Polyimide Films

The cyclic-bending morphologies of the fibrils formed by the self-assembly of type I collagen (Col) are closely related to the mechanisms of various diseases. Therefore, studies that allow the self-assembly of Col molecules to form cyclic-bending fibrils in vitro are vitally important. In this study, we successfully achieved the cyclic-bending shapes (specifically, a regular hexagonal shape) of Col molecules by controlling the steric structures of polyimide (PI) molecular chains through the film formation process. Specifically, when a single layer of PI film was baked, the PI molecular chains within the film bent in the direction parallel to the substrate surface plane. Repeating the layering and baking processes resulted in 3D structures of the PI molecular chains, which were oriented in the direction perpendicular to the substrate surface plane. This three-dimensional bending would result from the PI molecular chain interactions between the upper and lower layers. When the Col molecules were reacted on these film surfaces, they recognized the structures of the PI molecular chains and self-assembled to form cyclic-bending Col fibrils. Especially, in PI films subjected to three cycles of layering and baking, hemicircular-shaped Col fibrils were observed to be regularly arrayed. Additionally, these regularly cyclic-bending fibrils were aligned in the uniaxial direction through a uniaxial rubbing treatment of the PI films. This successful research is significant both as a method for controlling the morphologies of Col fibrils and as a study that explores the biomedical implications of Col fibril cyclic-bending in the living body.

The Ways of Forming and the Erosion/Decay/Aging of Bioapatites in the Context of the Reversibility of Apatites

This study primarily focused on the acid erosion of enamel and dentin. A detailed examination of the X-ray diffraction data proves that the products of the acid-caused decay of enamel belong to the family of isomorphic bioapatites, especially calcium-deficient hydroxyapatites. They are on a trajectory towards less and less crystallized substances. The increase in Bragg's parameter d and the decrease in the energy necessary for the changes were coupled with variability in the pH. This was valid for the corrosive action of acid solutions with a pH greater than 3.5. When the processes of natural tooth aging were studied by X-ray diffraction, a clear similarity to the processes of the erosion of teeth was revealed. Scarce data on osteoporotic bones seemed to confirm the conclusions derived for teeth. The data concerning the bioapatite decays were confronted with the cycles of apatite synthesis/decay. The chemical studies, mainly concerning the Ca/P ratio in relation to the pH range of durability of popular compounds engaged in the synthesis/decay of apatites, suggested that the process of the formation of erosion under the influence of acids was much inverted in relation to the process of the formation of apatites, starting from brushite up to apatite, in an alkaline environment. Our simulations showed the shift between the family of bioapatites versus the family of apatites concerning the pH of the reaction environment. The detailed model stoichiometric equations associated with the particular stages of relevant processes were derived. The synthesis processes were alkalization reactions coupled with dehydration. The erosion processes were acid hydrolysis reactions. Formally, the alkalization of the environment during apatite synthesis is presented by introducing Ca(OH)2 to stoichiometric equations.

Design considerations when creating a high throughput screen-compatible in vitro model of osteogenesis

Inducing osteogenic differentiation in vitro is useful for the identification and development of bone regeneration therapies as well as modelling bone disorders. To couple in vitro models with high throughput screening techniques retains the assay's relevance in research while increasing its therapeutic impact. Miniaturizing, automating and/or digitalizing in vitro assays will reduce the required quantity of cells, biologic stimulants, culture/output assay reagents, time and cost. This review highlights the design and workflow considerations for creating a high throughput screen-compatible model of osteogenesis, comparing and contrasting osteogenic cell type, assay fabrication and culture methodology, osteogenic induction approach and repurposing existing output techniques.

Immunoengineering Biomaterials for Musculoskeletal Tissue Repair across Lifespan

Musculoskeletal diseases and injuries are among the leading causes of pain and morbidity worldwide. Broad efforts have focused on developing pro-regenerative biomaterials to treat musculoskeletal conditions; however, these approaches have yet to make a significant clinical impact. Recent studies have demonstrated that the immune system is central in orchestrating tissue repair and that targeting pro-regenerative immune responses can improve biomaterial therapeutic outcomes. However, aging is a critical factor negatively affecting musculoskeletal tissue repair and immune function. Hence, understanding how age affects the response to biomaterials is essential for improving musculoskeletal biomaterial therapies. This review focuses on the intersection of the immune system and aging in response to biomaterials for musculoskeletal tissue repair. The article introduces the general impacts of aging on tissue physiology, the immune system, and the response to biomaterials. Then, it explains how the adaptive immune system guides the response to injury and biomaterial implants in cartilage, muscle, and bone and discusses how aging impacts these processes in each tissue type. The review concludes by highlighting future directions for the development and translation of personalized immunomodulatory biomaterials for musculoskeletal tissue repair.

Artificial keloid skin models: understanding the pathophysiological mechanisms and application in therapeutic studies

Keloid is a type of scar formed by the overexpression of extracellular matrix substances from fibroblasts following inflammation after trauma. The existing keloid treatment methods include drug injection, surgical intervention, light exposure, cryotherapy, etc. However, these methods have limitations such as recurrence, low treatment efficacy, and side effects. Consequently, studies are being conducted on the treatment of keloids from the perspective of inflammatory mechanisms. In this study, keloid models are created to understand inflammatory mechanisms and explore treatment methods to address them. While previous studies have used animal models with gene mutations, chemical treatments, and keloid tissue transplantation, there are limitations in fully reproducing the characteristics of keloids unique to humans, and ethical issues related to animal welfare pose additional challenges. Consequently, studies are underway to create in vitro artificial skin models to simulate keloid disease and apply them to the development of treatments for skin diseases. In particular, herein, scaffold technologies that implement three-dimensional (3D) full-thickness keloid models are introduced to enhance mechanical properties as well as biological properties of tissues, such as cell proliferation, differentiation, and cellular interactions. It is anticipated that applying these technologies to the production of artificial skin for keloid simulation could contribute to the development of inflammatory keloid treatment techniques in the future.

Reassociation of Skeletal Remains Using Laser-Induced Breakdown Spectroscopy

A major challenge in forensic anthropology and bioarcheology is the development of fast and effective methods for sorting commingled remains. This study assesses how portable laser-induced breakdown spectroscopy (LIBS) can be used to group skeletal remains based on their elemental profiles. LIBS spectra were acquired from the remains of 45 modern skeletons, with a total data set of 8388 profiles from 1284 bones. Spectral feature selection was conducted to reduce the spectral profiles to the peaks exhibiting the highest variation among individuals. Emission lines corresponding to 9 elements (Ca, P, C, K, Mg, Na, Al, Ba, and Sr) were found important for classification. Linear discriminant analysis (LDA) was concurrently used to classify each spectral profile. From the 45 individuals, each LIBS spectrum was successfully sorted to its corresponding skeleton with an average accuracy of 87%. These findings indicate that variation exists among the LIBS profiles of individuals' skeletal remains, highlighting the potential for portable LIBS technology to aid in the sorting of commingled remains.

Targeted silencing of GNAS in a human model of osteoprogenitor cells results in the deregulation of the osteogenic differentiation program

Introduction

The dysregulation of cell fate toward osteoprecursor cells associated with most GNAS-based disorders may lead to episodic de novo extraskeletal or ectopic bone formation in subcutaneous tissues. The bony lesion distribution suggests the involvement of abnormal differentiation of mesenchymal stem cells (MSCs) and/or more committed precursor cells. Data from transgenic mice support the concept that GNAS is a crucial factor in regulating lineage switching between osteoblasts (OBs) and adipocyte fates. The mosaic nature of heterotopic bone lesions suggests that GNAS genetic defects provide a sensitized background for ectopic osteodifferentiation, but the underlying molecular mechanism remains largely unknown.

Methods

The effect of GNAS silencing in the presence and/or absence of osteoblastic stimuli was evaluated in the human L88/5 MSC line during osteodifferentiation. A comparison of the data obtained with data coming from a bony lesion from a GNAS-mutated patient was also provided.

Results

Our study adds some dowels to the current fragmented notions about the role of GNAS during osteoblastic differentiation, such as the premature transition of immature OBs into osteocytes and the characterization of the differences in the deposed bone matrix.

Conclusion

We demonstrated that our cell model partially replicates the in vivo behavior results, resulting in an applicable human model to elucidate the pathophysiology of ectopic bone formation in GNAS-based disorders.

Sequential trypsin and ProAlanase digestions unearth immunological protein biomarkers shrouded by skeletal collagen

This study investigates the efficacy of proteomic analysis of human remains to identify active infections in the past through the detection of pathogens and the host response to infection. We advance leprosy as a case study due to the sequestering of sufferers in leprosaria and the suggestive skeletal lesions that can result from the disease. Here we present a sequential enzyme extraction protocol, using trypsin followed by ProAlanase, to reduce the abundance of collagen peptides and in so doing increase the detection of non-collagenous proteins. Through our study of five individuals from an 11th to 18th century leprosarium, as well as four from a contemporaneous non-leprosy associated cemetery in Barcelona, we show that samples from 2 out of 5 leprosarium individuals extracted with the sequential digestion methodology contain numerous host immune proteins associated with modern leprosy. In contrast, individuals from the non-leprosy associated cemetery and all samples extracted with a trypsin-only protocol did not. Through this study, we advance a palaeoproteomic methodology to gain insights into the health of archaeological individuals and take a step toward a proteomics-based method to study immune responses in past populations.

Amino acid-based supramolecular chiral hydrogels promote osteogenesis of human dental pulp stem cells via the MAPK pathway

Critical-size defects (CSDs) of the craniofacial bones cause aesthetic and functional complications that seriously impact the quality of life. The transplantation of human dental pulp stem cells (hDPSCs) is a promising strategy for bone tissue engineering. Chirality is commonly observed in natural biomolecules, yet its effect on stem cell differentiation is seldom studied, and little is known about the underlying mechanism. In this study, supramolecular chiral hydrogels were constructed using L/d-phenylalanine (L/D-Phe) derivatives. The results of alkaline phosphatase expression analysis, alizarin red S assay, as well as quantitative real-time polymerase chain reaction and western blot analyses suggest that right-handed D-Phe hydrogel fibers significantly promoted osteogenic differentiation of hDPSCs. A rat model of calvarial defects was created to investigate the regulation of chiral nanofibers on the osteogenic differentiation of hDPSCs in vivo. The results of the animal experiment demonstrated that the D-Phe group exhibited greater and faster bone formation on hDPSCs. The results of RNA sequencing, vinculin immunofluorescence staining, a calcium fluorescence probe assay, and western blot analysis indicated that L-Phe significantly promoted adhesion of hDPSCs, while D-Phe nanofibers enhanced osteogenic differentiation of hDPSCs by facilitating calcium entry into cells and activate the MAPK pathway. These results of chirality-dependent osteogenic differentiation offer a novel therapeutic strategy for the treatment of CSDs by optimising the differentiation of hDPSCs into chiral nanofibers.

Osteocyte-mediated mechanical response controls osteoblast differentiation and function

Low bone mass is a pervasive global health concern, with implications for osteoporosis, frailty, disability, and mortality. Lifestyle factors, including sedentary habits, metabolic dysfunction, and an aging population, contribute to the escalating prevalence of osteopenia and osteoporosis. The application of mechanical load to bone through physical activity and exercise prevents bone loss, while sufficient mechanical load stimulates new bone mass acquisition. Osteocytes, cells embedded within the bone, receive mechanical signals and translate these mechanical cues into biological signals, termed mechano-transduction. Mechano-transduction signals regulate other bone resident cells, such as osteoblasts and osteoclasts, to orchestrate changes in bone mass. This review explores the mechanisms through which osteocyte-mediated response to mechanical loading regulates osteoblast differentiation and bone formation. An overview of bone cell biology and the impact of mechanical load will be provided, with emphasis on the mechanical cues, mechano-transduction pathways, and factors that direct progenitor cells toward the osteoblast lineage. While there are a wide range of clinically available treatments for osteoporosis, the majority act through manipulation of the osteoclast and may have significant disadvantages. Despite the central role of osteoblasts to the deposition of new bone, few therapies directly target osteoblasts for the preservation of bone mass. Improved understanding of the mechanisms leading to osteoblastogenesis may reveal novel targets for translational investigation.

Artificial Dermis and Human Recombinant Epidermal Growth Factor Application for the Management of Critical Size Calvarial Defect

Restoration of the 3-dimensional structure of the facial and calvarial skeleton after trauma or ablative oncologic surgeries serves as a framework for soft tissue reconstruction. In the present study, the authors aimed to evaluate the osteogenic effect of artificial dermis and epidermal growth factor treatment in critical-sized calvarial defects, which cannot be healed spontaneously. 8 mm calvarial defects were created in 28 male rats and filled with the artificial dermis, the artificial dermis and growth factor, growth factor or left untreated. Atomic absorption spectrometry was used to determine the amount of calcium, scanning electron microscopy was used to show the bone tissue in 3 dimensions, and immunohistochemistry was used to assess the bone formation and cell density. Histologic evaluation at 6 weeks showed incomplete bone regeneration in all groups. No statistical differences were found between the groups with regard to their scores for the following: inflammation, new bone formation, osteocyte density, resorption of bone at the edges of the defect, or fibrous tissue formation in the defect area. In conclusion, the predictability of bone formation in critical-size defects is not clear. Contrary to popular belief, the combined use of epidermal growth factor with artificial dermis or alone did not enhance the potential for osseous healing.

Effects of pseudoephedrine on rat fetal bone development: evaluation by three different methods

Pseudoephedrine (PSE) is an agent that is contained in common cold medications. The agent, which is used to treat cold and cough, is the fourth most prescribed drug group in some countries. During pregnancy, expectant mothers use PSE for colds and other reasons. One out of every four expectant mothers use PSE alone or in combination with other medicines for various reasons. This study was aimed to investigate effects of PSE on long bones development in rat during fetal growth. Pregnant rats were divided into five groups: control and four experimental groups (25 mg/kg, 50 mg/kg, 100 mg/kg, 200 mg/kg PSE). Between 1 and 20 days of pregnancy, PSE was given to them by gavage. Weights and heights of fetuses isolated by cesarean on the 21st day were measured. Ossification of femur and humerus was examined by three different methods mentioned earlier. Depending on the dose increase, all morphometric data, ossification rate and bone length of the fetuses were decreased. Besides, it was determined that the amount of Calcium in the bone tissue decreased in the analyzes made with SEM-EDX Analysis. The data obtained from this study reveal that the use of PSE during pregnancy disrupts the existing balance in the bone and negatively affects ossification due to the dose increase. In conclusion, we present descriptive and novel data on the effects of PSE use during pregnancy on the bone development of rat fetal long bones.

A bioartificial and vasculomorphic bone matrix-based organoid mimicking microanatomy of flat and short bones

We engineered an in vitro model of bioartificial 3D bone organoid consistent with an anatomical and vascular microenvironment common to mammalian flat and short bones. To achieve this, we chose the decellularized-decalcified matrix of the adult male rat scapula, implemented with the reconstruction of its intrinsic vessels, obtained through an original intravascular perfusion with polylevolactic (PLLA), followed by coating of the PLLA-fabricated vascularization with rat tail collagen. As a result, the 3D bone and vascular geometry of the native bone cortical and cancellous compartments was reproduced, and the rat tail collagen-PLLA biomaterial could in vitro act as a surrogate of the perivascular extracellular matrix (ECM) around the wall of the biomaterial-reconstituted cancellous vessels. As a proof-of-concept of cell compatibility and site-dependent osteoinductive properties of this bioartificial 3D construct, we show that it in vitro leads to a time-dependent microtopographic positioning of rat mesenchymal stromal cells (MSCs), initiating an osteogenic fate in relation to the bone compartment. In addition, coating of PLLA-reconstructed vessels with rat tail collagen favored perivascular attachment and survival of MSC-like cells (mouse embryonic fibroblasts), confirming its potentiality as a perivascular stroma for triggering competence of seeded MSCs. Finally, in vivo radiographic topography of bone lesions in the human jaw and foot tarsus of subjects with primary osteoporosis revealed selective bone cortical versus cancellous involvement, suggesting usefulness of a human 3D bone organoid engineered with the same principles of our rat organoid, to in vitro investigate compartment-dependent activities of human MSC in flat and short bones under experimental osteoporotic challenge. We conclude that our 3D bioartificial construct offers a reliable replica of flat and short bones microanatomy, and promises to help in building a compartment-dependent mechanistic perspective of bone remodeling, including the microtopographic dysregulation of osteoporosis.

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.

A crosstalk between 'osteocyte lacunal-canalicular system' and metabolism

Considering the importance, bone physiology has long been studied to understand what systematic and cellular impact its cells and functions have. Exploring more questions is a substantially solid way to improve the understanding of bone physiological functions in/out sides. In adult bone, osteocytes (Ots) form about 95% of bone cells and live the longest lifespan inside their mineralized surroundings. Ots are the endocrine cells and originate from blood vessel's endothelial cells. In this work, we discussed the vital role of the "Ots". To determine the association between osteocytes' network with metabolic parameters in healthy mice, the experiments were performed on ten (10) adult C57BL6 male mice. Fasting blood and bone samples were collected weekly from mice for measurement of metabolic parameters and bone morphology. Scanning electron microscopy (SEM) revealed a 2D fine morphology of the bone which indicates a strong functional interconnection with bone nano/micro, and macro components of the organs. The long-branched canaliculi look like neurocytes in structure. The morphology and quantitative measurements of the osteocyte lacunal-canalicular system showed its wide spectrum spatial resolution of the positive and negative relationship within this system or metabolite parameters, confirming a strong cross connection between osteocyte lacunal-canalicular system and metabolism. We believe that the findings of this study can deliver a strategy about the potential roles of metabolic relation among osteocytes, insulin, and lipid in management of bone and metabolic diseases.

Transforming growth factor-beta superfamily regulates mesenchymal stem cell osteogenic differentiation: A microRNA linking

The ability to differentiate into cells of different lineages, such as bone cells, is the principal value of adult mesenchymal stem cells (MSCs), which can be used with the final aim of regenerating damaged tissue. Due to its potential use and importance in regenerative medicine and tissue engineering, several questions have been raised regarding the molecular mechanisms of MSC differentiation. As one of the crucial mediators in organism development, the transforming growth factor-beta (TGF-β) superfamily directs MSCs' commitment to selecting differentiation pathways. This review aims to give an overview of the current knowledge on the mechanisms of the TGF-β superfamily in MSCs bone differentiation, with additional insight into the mutual regulation of microRNAs and TGF-β in osteogenesis.

3D-Printed Antibacterial Scaffolds for the Regeneration of Alveolar Bone in Severe Periodontitis

Current clinical treatment of periodontitis alleviates periodontal symptoms and helps to keep the disease under control for extended periods. Despite this, a significant destruction of the tooth's underlying bone tissue often takes place progressively. Herein, we present a two-way therapeutic approach for local delivery of antibacterial agents and bone tissue regeneration, incorporating ~1% w/w tetracycline hydrochloride (TCH) into a 3D-printed scaffold composed of poly(ε-caprolactone) (PCL). Samples were assessed for their morphological, physicochemical, pharmacokinetic, and antibacterial properties. Furthermore, osteoprecursor cells (MC3T3-E1) were employed to evaluate the osteoinductive potential of the drug-loaded scaffolds. Cell proliferation, viability, and differentiation were determined on all cell-seeded scaffolds. At the end of the culture, PCL-TCH scaffolds promoted abundant collagen organic matrix, demonstrating augmented alkaline phosphatase (ALP) activity and areas of accumulated mineralised bone tissue, despite their belayed cell proliferation. Based on the observed effectiveness of the PCL-TCH scaffolds to inhibit Staphylococcus aureus, these constructs could serve as an alternative bioactive implant that supports bacterial inhibition and favours a 3D microenvironment for bone tissue regeneration in severe periodontitis.

Extracellular Mechanical Stimuli Alters the Metastatic Progression of Prostate Cancer Cells within 3D Tissue Matrix

This study aimed to understand extracellular mechanical stimuli's effect on prostate cancer cells' metastatic progression within a three-dimensional (3D) bone-like microenvironment. In this study, a mechanical loading platform, EQUicycler, has been employed to create physiologically relevant static and cyclic mechanical stimuli to a prostate cancer cell (PC-3)-embedded 3D tissue matrix. Three mechanical stimuli conditions were applied: control (no loading), cyclic (1% strain at 1 Hz), and static mechanical stimuli (1% strain). The changes in prostate cancer cells' cytoskeletal reorganization, polarity (elongation index), proliferation, expression level of N-Cadherin (metastasis-associated gene), and migratory potential within the 3D collagen structures were assessed upon mechanical stimuli. The results have shown that static mechanical stimuli increased the metastasis progression factors, including cell elongation (p < 0.001), cellular F-actin accumulation (p < 0.001), actin polymerization (p < 0.001), N-Cadherin gene expression, and invasion capacity of PC-3 cells within a bone-like microenvironment compared to its cyclic and control loading counterparts. This study established a novel system for studying metastatic cancer cells within bone and enables the creation of biomimetic in vitro models for cancer research and mechanobiology.

Tumor removal limits prostate cancer cell dissemination in bone and osteoblasts induce cancer cell dormancy through focal adhesion kinase

BACKGROUND

Disseminated tumor cells (DTCs) can enter a dormant state and cause no symptoms in cancer patients. On the other hand, the dormant DTCs can reactivate and cause metastases progression and lethal relapses. In prostate cancer (PCa), relapse can happen after curative treatments such as primary tumor removal. The impact of surgical removal on PCa dissemination and dormancy remains elusive. Furthermore, as dormant DTCs are asymptomatic, dormancy-induction can be an operational cure for preventing metastases and relapse of PCa patients.

METHODS

We used a PCa subcutaneous xenograft model and species-specific PCR to survey the DTCs in various organs at different time points of tumor growth and in response to tumor removal. We developed in vitro 2D and 3D co-culture models to recapitulate the dormant DTCs in the bone microenvironment. Proliferation assays, fluorescent cell cycle reporter, qRT-PCR, and Western Blot were used to characterize the dormancy phenotype. We performed RNA sequencing to determine the dormancy signature of PCa. A drug repurposing algorithm was applied to predict dormancy-inducing drugs and a top candidate was validated for the efficacy and the mechanism of dormancy induction.

RESULTS

We found DTCs in almost all mouse organs examined, including bones, at week 2 post-tumor cell injections. Surgical removal of the primary tumor reduced the overall DTC abundance, but the DTCs were enriched only in the bones. We found that osteoblasts, but not other cells of the bones, induced PCa cell dormancy. RNA-Seq revealed the suppression of mitochondrial-related biological processes in osteoblast-induced dormant PCa cells. Importantly, the mitochondrial-related biological processes were found up-regulated in both circulating tumor cells and bone metastases from PCa patients' data. We predicted and validated the dormancy-mimicking effect of PF-562,271 (PF-271), an inhibitor of focal adhesion kinase (FAK) in vitro. Decreased FAK phosphorylation and increased nuclear translocation were found in both co-cultured and PF-271-treated C4-2B cells, suggesting that FAK plays a key role in osteoblast-induced PCa dormancy.

CONCLUSIONS

Our study provides the first insights into how primary tumor removal enriches PCa cell dissemination in the bones, defines a unique osteoblast-induced PCa dormancy signature, and identifies FAK as a PCa cell dormancy gatekeeper.

Bioactive Materials for Bone Regeneration: Biomolecules and Delivery Systems

Novel tissue regeneration strategies are constantly being developed worldwide. Research on bone regeneration is noteworthy, as many promising new approaches have been documented with novel strategies currently under investigation. Innovative biomaterials that allow the coordinated and well-controlled repair of bone fractures and bone loss are being designed to reduce the need for autologous or allogeneic bone grafts eventually. The current engineering technologies permit the construction of synthetic, complex, biomimetic biomaterials with properties nearly as good as those of natural bone with good biocompatibility. To ensure that all these requirements meet, bioactive molecules are coupled to structural scaffolding constituents to form a final product with the desired physical, chemical, and biological properties. Bioactive molecules that have been used to promote bone regeneration include protein growth factors, peptides, amino acids, hormones, lipids, and flavonoids. Various strategies have been adapted to investigate the coupling of bioactive molecules with scaffolding materials to sustain activity and allow controlled release. The current manuscript is a thorough survey of the strategies that have been exploited for the delivery of biomolecules for bone regeneration purposes, from choosing the bioactive molecule to selecting the optimal strategy to synthesize the scaffold and assessing the advantages and disadvantages of various delivery strategies.

Nanotechnology enabled radioprotectants to reduce space radiation-induced reactive oxidative species

Interest in space exploration has seen substantial growth following recent launch and operation of modern space technologies. In particular, the possibility of travel beyond low earth orbit is seeing sustained support. However, future deep space travel requires addressing health concerns for crews under continuous, longer-term exposure to adverse environmental conditions. Among these challenges, radiation-induced health issues are a major concern. Their potential to induce chronic illness is further potentiated by the microgravity environment. While investigations into the physiological effects of space radiation are still under investigation, studies on model ionizing radiation conditions, in earth and micro-gravity conditions, can provide needed insight into relevant processes. Substantial formation of high, sustained reactive oxygen species (ROS) evolution during radiation exposure is a clear threat to physiological health of space travelers, producing indirect damage to various cell structures and requiring therapeutic address. Radioprotection toward the skeletal system components is essential to astronaut health, due to the high radio-absorption cross-section of bone mineral and local hematopoiesis. Nanotechnology can potentially function as radioprotectant and radiomitigating agents toward ROS and direct radiation damage. Nanoparticle compositions such as gold, silver, platinum, carbon-based materials, silica, transition metal dichalcogenides, and ceria have all shown potential as viable radioprotectants to mitigate space radiation effects with nanoceria further showing the ability to protect genetic material from oxidative damage in several studies. As research into space radiation-induced health problems develops, this review intends to provide insights into the nanomaterial design to ameliorate pathological effects from ionizing radiation exposure. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Nanotechnology Approaches to Biology > Cells at the Nanoscale Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

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.

Role of carboxylic organic molecules in interfibrillar collagen mineralization

Bone is a composite material made up of inorganic and organic counterparts. Most of the inorganic counterpart accounts for calcium phosphate (CaP) whereas the major organic part is composed of collagen. The interfibrillar mineralization of collagen is an important step in the biomineralization of bone and tooth. Studies have shown that synthetic CaP undergoes auto-transformation to apatite nanocrystals before entering the gap zone of collagen. Also, the synthetic amorphous calcium phosphate/collagen combination alone is not capable of initiating apatite nucleation rapidly. Therefore, it was understood that there is the presence of a nucleation catalyst obstructing the auto-transformation of CaP before entering the collagen gap zone and initiating rapid nucleation after entering the collagen gap zone. Therefore, studies were focused on finding the nucleation catalyst responsible for the regulation of interfibrillar collagen mineralization. Organic macromolecules and low-molecular-weight carboxylic compounds are predominantly present in the bone and tooth. These organic compounds can interact with both apatite and collagen. Adsorption of the organic compounds on the apatite nanocrystal governs the nucleation, crystal growth, lattice orientation, particle size, and distribution. Additionally, they prevent the auto-transformation of CaP into apatite before entering the interfibrillar compartment of the collagen fibril. Therefore, many carboxylic organic compounds have been utilized in developing CaP. In this review, we have covered different carboxylate organic compounds governing collagen interfibrillar mineralization.

Pathophysiological Investigation of Skeletal Deformities of Musculocontractural Ehlers–Danlos Syndrome Using Induced Pluripotent Stem Cells

Musculocontractural Ehlers–Danlos syndrome caused by mutations in the carbohydrate sulfotransferase 14 gene (mcEDS-CHST14) is a heritable connective tissue disorder characterized by multiple congenital malformations and progressive connective tissue fragility-related manifestations in the cutaneous, skeletal, cardiovascular, visceral, and ocular systems. Progressive skeletal deformities are among the most frequent and serious complications affecting the quality of life and activities of daily living in patients. After establishing induced pluripotent stem cells (iPSCs) from cultured skin fibroblasts of three patients with mcEDS-CHST14, we generated a patient iPSC-based human osteogenesis model and performed an in vitro assessment of the phenotype and pathophysiology of skeletal deformities. Patient-derived iPSCs presented with remarkable downregulation of osteogenic-specific gene expression, less alizarin red staining, and reduced calcium deposition compared with wild-type iPSCs at each stage of osteogenic differentiation, including osteoprogenitor cells, osteoblasts, and osteocytes. These findings indicated that osteogenesis was impaired in mcEDS-CHST14 iPSCs. Moreover, the decrease in decorin (DCN) expression and increase in collagen (COL12A1) expression in patient-derived iPSCs elucidated the contribution of CHST14 dysfunction to skeletal deformities in mcEDS-CHST14. In conclusion, this disease-in-a-dish model provides new insight into the pathophysiology of EDS and may have the potential for personalized gene or drug therapy.

Overexpression of NDST1 Attenuates Fibrotic Response in Murine Adipose-Derived Stem Cells

Adipose-derived stem cells (ADSCs) hold tremendous potential for treating diseases and repairing damaged tissues. Heparan sulfate (HS) plays various roles in cellular signaling mechanisms. The importance of HS in stem cell function has been reported and well documented. However, there has been little progress in using HS for therapeutic purposes. We focused on one of the sulfotransferases, NDST1, which influences overall HS chain extent and sulfation pattern, with the expectation to enhance stem cell function by increasing the N-sulfation level. We herein performed transfections of a green fluorescent protein-vector control and NDST1-vector into mouse ADSCs to evaluate stem cell functions. Overexpression of NDST1 suppressed the osteogenic differentiation of ADSCs. There was no pronounced effect observed on the stemness, inflammatory gene expression, nor any noticeable effect in adipogenic and chondrogenic differentiation. Under the tumor necrosis factor-alpha stimulation, NDST1 overexpression induced several chemokine productions that attract neutrophils and macrophages. Finally, we identified an antifibrotic response in ADSCs overexpressing NDST1. This study provides a foundation for the evaluation of HS-related effects in ADSCs undergoing ex vivo gene manipulation.

The Impact of Major and Trace Elements in Serum and Bone on Dual-Energy X-Ray Absorptiometry-Derived Hip Strength

The purpose of this study was to establish associations between both serum levels and bone content of a wide range of elements (Na, K, P, Ca, Mg, Zn, Cu, Cr, Mn, Fe, and Pb), with hip strength (HS) indices derived from dual-energy X-ray absorptiometry (DXA). The study population consisted of a number of male patients aged 56-77 years following hip replacement due to osteoarthritis of the hip. Bone specimens were taken from the femoral head and neck during arthroplasty. The elemental analyses were carried out using coupled plasma optical emission spectrometry. The following DXA-HS parameters were assessed: buckling ratio (BR), cross-sectional area (CSA) and its moment of inertia (CSMI), section modulus, and Femoral Strength Index (FSI). Age was positively correlated with Na, K, and Cu in the bone. Ca in the bone was positively associated with BR and negatively with SM and CSMI. Of all the DXA-HS parameters, the weakest associations of elements in the bone were found with FSI and the strongest with BR. Among the elements in the serum, the strongest negative associations were found for K, Cr, Mn, and Zn with CSA, while the majority of bone elements were associated either positively (Ca, P, Mg, Zn, and Cu) or negatively (Mn, Fe, Pb, and Cr) with BR. In conclusion, the interactions between individual elements in blood serum and bone with DXA-HS could not be unequivocally established.

Bone Mineralization in Electrospun-Based Bone Tissue Engineering

Increasing the demand for bone substitutes in the management of bone fractures, including osteoporotic fractures, makes bone tissue engineering (BTE) an ideal strategy for solving the constant shortage of bone grafts. Electrospun-based scaffolds have gained popularity in BTE because of their unique features, such as high porosity, a large surface-area-to-volume ratio, and their structural similarity to the native bone extracellular matrix (ECM). To imitate native bone mineralization through which bone minerals are deposited onto the bone matrix, a simple but robust post-treatment using a simulated body fluid (SBF) has been employed, thereby improving the osteogenic potential of these synthetic bone grafts. This study highlights recent electrospinning technologies that are helpful in creating more bone-like scaffolds, and addresses the progress of SBF development. Biomineralized electrospun bone scaffolds are also reviewed, based on the importance of bone mineralization in bone regeneration. This review summarizes the potential of SBF treatments for conferring the biphasic features of native bone ECM architectures onto electrospun-based bone scaffolds.

A humanised rat model of osteosarcoma reveals ultrastructural differences between bone and mineralised tumour tissue

Current xenograft animal models fail to accurately replicate the complexity of human bone disease. To gain translatable and clinically valuable data from animal models, new in vivo models need to be developed that mimic pivotal aspects of human bone physiology as well as its diseased state. Above all, an advanced bone disease model should promote the development of new treatment strategies and facilitate the conduction of common clinical interventional procedures. Here we describe the development and characterisation of an orthotopic humanised tissue-engineered osteosarcoma (OS) model in a recently genetically engineered x-linked severe combined immunodeficient (X-SCID) rat. For the first time in a genetically modified rat, our results show the successful implementation of an orthotopic humanised tissue-engineered bone niche supporting the growth of a human OS cell line including its metastatic spread to the lung. Moreover, we studied the inter- and intraspecies differences in ultrastructural composition of bone and calcified tissue produced by the tumour, pointing to the crucial role of humanised animal models.

A genome-wide meta-analysis identifies 50 genetic loci associated with carpal tunnel syndrome

Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy and has a largely unknown underlying biology. In a genome-wide association study of CTS (48,843 cases and 1,190,837 controls), we found 53 sequence variants at 50 loci associated with the syndrome. The most significant association is with a missense variant (p.Glu366Lys) in SERPINA1 that protects against CTS (P = 2.9 × 10^-24, OR = 0.76). Through various functional analyses, we conclude that at least 22 genes mediate CTS risk and highlight the role of 19 CTS variants in the biology of the extracellular matrix. We show that the genetic component to the risk is higher in bilateral/recurrent/persistent cases than nonrecurrent/nonpersistent cases. Anthropometric traits including height and BMI are genetically correlated with CTS, in addition to early hormonal-replacement therapy, osteoarthritis, and restlessness. Our findings suggest that the components of the extracellular matrix play a key role in the pathogenesis of CTS.

Silk Fibroin Microparticle Scaffold for Use in Bone Void Filling: Safety and Efficacy Studies

Silk fibroin (SF) is a natural biocompatible protein polymer extracted from cocoons of silkworm Bombyx mori. SF can be processed into a variety of different forms and shapes that can be used as scaffolds to support bone regeneration. Three-dimensional (3D) SF scaffolds have shown promise in bone-void-filling applications. In in vitro studies, it has been demonstrated that a microparticle-based SF (M-RSF) scaffold promotes the differentiation of stem cells into an osteoblastic lineage. The expression of differentiation markers was also significantly higher for M-RSF scaffolds as compared to other SF scaffolds and commercial ceramic scaffolds. In this work, we have evaluated the in vitro and in vivo biocompatibility of M-RSF scaffolds as per the ISO 10993 guidelines in a Good Laboratory Practice (GLP)-certified facility. The cytotoxicity, immunogenicity, genotoxicity, systemic toxicity, and implantation studies confirmed that the M-RSF scaffold is biocompatible. Further, the performance of the M-RSF scaffold to support bone formation was evaluated in in vivo bone implantation studies in a rabbit model. Calcium sulfate (CaSO₄) scaffolds were chosen as reference material for this study as they are one of the preferred materials for bone-void-filling applications. M-RSF scaffold implantation sites showed a higher number of osteoblast and osteoclast cells as compared to CaSO₄ implantation sites indicating active bone remodeling. The number density of osteocytes was double for M-RSF scaffold implantation sites, and these M-RSF scaffold implantation sites were characterized by enhanced collagen deposition, pointing toward a finer quality of the new bone formed. Moreover, the M-RSF scaffold implantation sites had a negligible incidence of secondary fractures as compared to the CaSO₄ implantation sites (∼50% sites with secondary fracture), implying a reduction in postsurgical complications. Thus, the study demonstrates that the M-RSF scaffold is nontoxic for bone-void-filling applications and facilitates superior healing of fracture defects as compared to commercial calcium-based bone void fillers.

Electro-assembly of a dynamically adaptive molten fibril state for collagen

Collagen is a biological building block that is hierarchically assembled into diverse morphological structures that, in some cases, is dynamically adaptive in response to external cues and in other cases forms static terminal structures. Technically, there is limited capabilities to guide the emergence of collagen's hierarchical organization to recapitulate the richness of biological structure and function. Here, we report an electro-assembly pathway to create a dynamically adaptive intermediate molten fibril state for collagen. Structurally, this intermediate state is composed of partially aligned and reversibly associating fibrils with limited hierarchical structure. These molten fibrils can be reversibly reconfigured to offer dynamic properties such as stimuli-stiffening, stimuli-contracting, self-healing, and self-shaping. Also, molten fibrils can be guided to further assemble to recapitulate the characteristic hierarchical structural features of native collagen (e.g., aligned fibers with D-banding). We envision that the electro-assembly of collagen fibrils will provide previously unidentified opportunities for tailored collagen-based biomedical materials.

Methods of producing three dimensional electrospun scaffolds for bone tissue engineering: A review

Bone is a dynamic, living tissue that exists and renews itself continuously in a 3D manner. Nevertheless, complex clinical conditions require a bone substitute to replace the defective bone and/or accelerate bone healing. Bone tissue engineering aims to treat bone defects that fail to heal on their own. Electrospinning provides an opportunity to create nano- to micro-fibrous scaffolds that mimic the architecture of the natural extracellular matrix (ECM) with high porosity and large specific surface area. Despite these advantages, traditional electrospun meshes can only provide a 2D architecture for cell attachment and proliferation rather than the 3D attachment in native tissue. Fabrication of 3D electrospun scaffolds for bone tissue regeneration is a challenging task, which has attracted significant attention over the past couple of decades. This review highlights recent strategies used to produce 3D electrospun/co-electrospun scaffolds for bone tissue applications describing the materials and procedures. It also considers combining conventional and coaxial electrospinning with other scaffold manufacturing techniques to produce 3D structures which have the potential to engineer missing bone in the human body.Graphical abstract[Formula: see text].

Comparison capacity of collagen hydrogel, mix-powder and in situ hydroxyapatite/collagen hydrogelscaffolds with and without mesenchymal stem cells and platelet-rich plasma in regeneration of critical sized bone defect in a rabbit animal model

The aim of this study was to investigate the effect of developed collagen (Co) hydrogel (CH), powder-mixed hydroxyapatite/collagen (HA/Co) hydrogel and in situ synthesized HA/Co (In/HA/Co) hydrogel with or without mesenchymal stem cell (MSC) and platelet-rich plasma (PRP) on the regeneration of full-thickness critical size bone defect in the rabbit animal model. In the first step of this study, the scaffolds were synthesized and characterized using FTIR spectroscopy, X-ray diffraction, and scanning electron microcopy. In the second step or animal study, the radial bone defects were filled with the synthesized scaffolds with and without MSC and PRP. One hundred sixty one year-old New Zealand white male rabbits were randomly divided in 16 groups of 10 rabbits including control with bone defect without treatment, In/HA/Co, HA/Co, CH, PRP, MSC, CH + PRP, HA/Co, In/HA/Co + PRP, HA/Co + PRP, CH + MSC, In/HA/Co + MSC, HA/Co + MSC, CH + PRP + MSC, In/HA/Co + PRP + MSC, and HA/Co + PRP + MSC. The created defects were filled using the constructed scaffolds alone or seeded with MSCs, with and without PRP injection. The treatments were assessed using histopathological, immunohistochemical and rediographical analysis on days 14, 28, 42, 56 post-treatment. The plate-like HA particles were distributed homogeneously in the in situ HA/Co scaffold compared to the HA/Co scaffold and had a similar structure to bone with carbonated plate-like HA particles and nanofibrilated Co matrix. In situ HA/Co nanocomposite seeded with MSC and enriched by PRP can accelerate bone regeneration resulted from osteoblastic production of osteocalcin protein. Therefore, in situ HA/Co hydrogel seeded with MSC and PRP can be a new approach for bone tissue engineering.

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.

Intermediate Structural Hierarchy in Biological Networks Modulates the Fractal Dimension and Force Distribution of Percolating Clusters

Globular protein hydrogels are an emerging class of materials with the potential for rational design, and a generalized understanding of how their network properties emerge from the structure and dynamics of the building block is a key challenge. Here we computationally investigate the effect of intermediate (polymeric) nanoscale structure on the formation of protein hydrogels. We show that changes in both the cross-link topology and flexibility of the polymeric building block lead to changes in the force transmission around the system and provide insight into the dynamic network formation processes. The preassembled intermediate structure provides a novel structural coordinate for the hierarchical modulation of macroscopic network properties, as well as furthering our understanding of the general dynamics of network formation.

Congenital Metabolic Bone Disorders as a Cause of Bone Fragility

Bone fragility is a pathological condition caused by altered homeostasis of the mineralized bone mass with deterioration of the microarchitecture of the bone tissue, which results in a reduction of bone strength and an increased risk of fracture, even in the absence of high-impact trauma. The most common cause of bone fragility is primary osteoporosis in the elderly. However, bone fragility can manifest at any age, within the context of a wide spectrum of congenital rare bone metabolic diseases in which the inherited genetic defect alters correct bone modeling and remodeling at different points and aspects of bone synthesis and/or bone resorption, leading to defective bone tissue highly prone to long bone bowing, stress fractures and pseudofractures, and/or fragility fractures. To date, over 100 different Mendelian-inherited metabolic bone disorders have been identified and included in the OMIM database, associated with germinal heterozygote, compound heterozygote, or homozygote mutations, affecting over 80 different genes involved in the regulation of bone and mineral metabolism. This manuscript reviews clinical bone phenotypes, and the associated bone fragility in rare congenital metabolic bone disorders, following a disease taxonomic classification based on deranged bone metabolic activity.

Cage type and mineral nutrition had independent impact on skeletal development in Lohmann LSL-Lite pullets from hatch to 16 weeks of age

The effects of rearing cage type and dietary Ca, available P and vitamin D3 (VitD3) on body and skeletal development were studied. A total of 3,420 Lohmann LSL-Lite day-old chicks were reared in conventional (CON) or furnished cages (FUR) to 16 wk of age. Initially, 40 and 150 chicks/cage were placed in CON and FUR and transitioned to 20 and 75 chicks/cage at 8 wk of age, respectively. Three diets: Diet 1, Diet 1.5 and Diet 2 were formulated to meet nutrient specifications with Diet 1.5 and Diet 2 containing 1.5 and 2 times more Ca, P and VitD3 than Diet 1, respectively. Diets were allocated within cage type to give 6 replicates and fed in 3 feeding programs: starter, grower and developer. At 4, 12 and 16 wk of age, BW was recorded, and femur, tibia and blood samples for bone quality and related parameters. There were no interactions (P > 0.05) of cage type, diet and pullet age on BW, plasma Ca and inorganic P, femur and tibia morphometry, mineral density (MD), breaking strength (BS) and ash concentration (AC). Concentration of Ca, P and VitD3 linearly decreased BW (P < 0.001), relative femur (P = 0.010) and tibia weight (P = 0.013). A quadratic increase on femur MD (P = 0.03) and BS (P = 0.026) was observed with dietary concentration of Ca, P and VitD3. Femur (P = 0.031) was longer for CON than FUR pullets, however, femur for FUR pullets had higher (P = 0.003) AC. Cage had no effect (P ≥ 0.415) femoral MD and BS. Pullets reared in FUR cages exhibited higher tibial MD (P = 0.015), BS (P = 0.071), AC (P < 0.01) and whole-body mineral content (P < 0.01). In conclusion, cage type and diets showed independent effect on femur and tibia quality with FUR pullets exhibiting enhanced indices of mineralization. Feeding pullets twice the recommended Ca, P and VitD3 decreased BW, relative weight of leg bone but enhanced femoral strength with no effects on tibia attributes.

Mapping cortical bone stiffness and mineralization from endosteal to periosteal surfaces of bovine mid-diaphyseal femur

INTRODUCTION

While bone literature abounds with correlations of mechanical stiffness to mineralization, such correlations are reported without relating the findings to specific intracortical locations. This study reports on mapping of stiffness and mineralization distributions in ring-shaped cortical bone samples sliced from mid-diaphyseal bovine femur. Stiffness and mineralization measurements were conducted at points across the intracortical thickness along radial lines emanating from the inner (endosteal) surface to the outer (periosteal) surface. Measurements were taken along approximately 4 mm distance of cortical bone thickness.

MATERIALS AND METHODS

Three experimental techniques were employed: Vickers microhardness (HV), energy-dispersive X-ray (EDX) spectroscopy, and computed tomography (CT). Stiffness values were extracted from the Vickers microhardness tests. Elemental mineralization values (calcium %wt. and phosphorus %wt.) were determined from EDX data. All measurements were repeated on three different femur bones taken from different bovines (collected fresh from butcher).

RESULTS

The study plots stiffness values and elemental mineralization (calcium %wt. and phosphorus %wt.) versus cortical thickness. Both stiffness and Ca %wt. and P %wt. are found to track and to linearly increase when plotted along the radial distance. The stiffness and mineralization trends collected from Vickers and EDX measurements were verified by employing the CT number (Hounsfield units, HU) via CT scans of the same bone samples. Data fitting via statistical methods revealed that all correlations were statistically significant.

CONCLUSION

Starting from endosteal to periosteal surfaces of mid-diaphyseal bovine femur, it was found that stiffness, mineralization, and HU values all exhibit increasing and correlating trends.

Elemental Composition in Female Dry Femora Using Portable X-Ray Fluorescence (pXRF): Association with Age and Osteoporosis

Pathophysiological conditions can modify the skeletal chemical concentration. This study analyzes the elemental composition in two anatomical regions from dry femoral bone using a portable X-Ray Fluorescence (pXRF) and evaluates its impact in the bone mineral density (BMD). The left femora of 97 female skeletons (21-95 years old individuals) from the Coimbra Identified Skeletal Collection were studied. Diagenetic biases were discarded at the outset and BMD was determined with Dual-energy X-ray absorptiometry. Chemical measurements were performed at the midpoint of the femoral neck and at the midshaft using a pXRF device, and comparisons were made considering the age and the BMD values. Only elements with a Technical Measurement Error ≤ 5% were selected: P, S, Ca, Fe, Zn, As, Sr, Pb and the Ca/P ratio. Statistically significant differences were found between regions, with higher concentrations of P, Ca, Zn and S at the midshaft, and the Ca/P ratio at the femoral neck. The concentration of P is higher in individuals < 50 years, while S and Ca/P ratio increase in individuals ≥ 50 years. The decrease of P with age can be simultaneously related to the decline of its concentration in osteoporosis. Decreased BMD is also associated with higher levels of S and Pb. Osteoporosis enhances the absorption of osteolytic elements in specific locations. This fast and non-destructive technique has proved effective for the comprehension of chemical changes related to bone mass loss. This study highlights the potential of identified skeletal collections to improve the knowledge about bone fragility.

Role of c-Met/β1 integrin complex in the metastatic cascade in breast cancer

Metastases cause 90% of human cancer deaths. The metastatic cascade involves local invasion, intravasation, extravasation, metastatic site colonization, and proliferation. Although individual mediators of these processes have been investigated, interactions between these mediators remain less well defined. We previously identified a complex between receptor tyrosine kinase c-Met and β1 integrin in metastases. Using cell culture and in vivo assays, we found that c-Met/β1 complex induction promoted intravasation and vessel wall adhesion in triple-negative breast cancer cells, but did not increase extravasation. These effects may have been driven by the ability of the c-Met/β1 complex to increase mesenchymal and stem cell characteristics. Multiplex transcriptomic analysis revealed upregulated Wnt and hedgehog pathways after c-Met/β1 complex induction. A β1 integrin point mutation that prevented binding to c-Met reduced intravasation. OS2966, a therapeutic antibody disrupting c-Met/β1 binding, decreased breast cancer cell invasion and mesenchymal gene expression. Bone-seeking breast cancer cells exhibited higher levels of c-Met/β1 complex than parental controls and preferentially adhered to tissue-specific matrix. Patient bone metastases demonstrated higher c-Met/β1 complex than brain metastases. Thus, the c-Met/β1 complex drove intravasation of triple-negative breast cancer cells and preferential affinity for bone-specific matrix. Pharmacological targeting of the complex may have prevented metastases, particularly osseous metastases.

Control Release of Adenosine Potentiate Osteogenic Differentiation within a Bone Integrative EGCG-g-NOCC/Collagen Composite Scaffold toward Guided Bone Regeneration in a Critical-Sized Calvarial Defect

The regeneration of critical-sized bone defects with biomimetic scaffolds remains clinically challenging due to avascular necrosis, chronic inflammation, and altered osteogenic activity. Two confounding mechanisms, efficacy manipulation, and temporal regulation dictate the scaffold's bone regenerative ability. Equally critical is the priming of the mesenchymal stromal cells (MSCs) toward lineage-specific differentiation into bone-forming osteoblast, which particularly depends on varied mechanochemical and biological cues during bone tissue regeneration. This study sought to design and develop an optimized osteogenic scaffold, adenosine/epigallocatechin gallate-N,O-carboxymethyl chitosan/collagen type I (AD/EGCG-g-NOCC@clgn I), having osteoinductive components toward swift bone regeneration in a calvarial defect BALB/c mice model. The ex vivo findings distinctly establish the pro-osteogenic potential of adenosine and EGCG, stimulating MSCs toward osteoblast differentiation with significantly increased expression of alkaline phosphatase, calcium deposits, and enhanced osteocalcin expression. Moreover, the 3D matrix recapitulates extracellular matrix (ECM) properties, provides a favorable microenvironment, structural support against mechanical stress, and acts as a reservoir for sustained release of osteoinductive molecules for cell differentiation, proliferation, and migration during matrix osteointegration observed. Evidence from in vivo experiments, micro-CT analyses, histology, and histomorphometry signify accelerated osteogenesis both qualitatively and quantitatively: effectual bone union with enhanced bone formation and new ossified tissue in 4 mm sized defects. Our results suggest that the optimized scaffold serves as an adjuvant to guide bone tissue regeneration in critical-sized calvarial defects with promising therapeutic efficacy.

Heat impact during laser ablation extraction of mineralised tissue micropillars

The underlying constraint of ultrashort pulsed laser ablation in both the clinical and micromachining setting is the uncertainty regarding the impact on the composition of material surrounding the ablated region. A heat model representing the laser-tissue interaction was implemented into a finite element suite to assess the cumulative temperature response of bone during ultrashort pulsed laser ablation. As an example, we focus on the extraction of mineralised collagen fibre micropillars. Laser induced heating can cause denaturation of the collagen, resulting in ultrastructural loss which could affect mechanical testing results. Laser parameters were taken from a used micropillar extraction protocol. The laser scanning pattern consisted of 4085 pulses, with a final radial pass being 22 [Formula: see text] away from the micropillar. The micropillar temperature was elevated to 70.58 [Formula: see text], remaining 79.42 [Formula: see text] lower than that of which we interpret as an onset for denaturation. We verified the results by means of Raman microscopy and Energy Dispersive X-ray Microanalysis and found the laser-material interaction had no effect on the collagen molecules or mineral nanocrystals that constitute the micropillars. We, thus, show that ultrashort pulsed laser ablation is a safe and viable tool to fabricate bone specimens for mechanical testing at the micro- and nanoscale and we provide a computational model to efficiently assess this.

Podosome-Driven Defect Development in Lamellar Bone under the Conditions of Senile Osteoporosis Observed at the Nanometer Scale

The degradation mechanism of human trabecular bone harvested from the central part of the femoral head of a patient with a fragility fracture of the femoral neck under conditions of senile osteoporosis was investigated by high-resolution electron microscopy. As evidenced by light microscopy, there is a disturbance of bone metabolism leading to severe and irreparable damages to the bone structure. These defects are evoked by osteoclasts and thus podosome activity. Podosomes create typical pit marks and holes of about 300-400 nm in diameter on the bone surface. Detailed analysis of the stress field caused by the podosomes in the extracellular bone matrix was performed. The calculations yielded maximum stress in the range of few megapascals resulting in formation of microcracks around the podosomes. Disintegration of hydroxyapatite and free lying collagen fibrils were observed at the edges of the plywood structure of the bone lamella. At the ultimate state, the disintegration of the mineralized collagen fibrils to a gelatinous matrix comes along with a delamination of the apatite nanoplatelets resulting in a brittle, porous bone structure. The nanoplatelets aggregate to big hydroxyapatite plates with a size of up to 10 x 20 μm². The enhanced plate growth can be explained by the interaction of two mechanisms in the ruffled border zone: the accumulation of delaminated hydroxyapatite nanoplatelets near clusters of podosomes and the accelerated nucleation and random growth of HAP nanoplatelets due to a nonsufficient concentration of process-directing carboxylated osteocalcin cOC.

Challenges and Innovations in Osteochondral Regeneration: Insights from Biology and Inputs from Bioengineering toward the Optimization of Tissue Engineering Strategies

Due to the extremely high incidence of lesions and diseases in aging population, it is critical to put all efforts into developing a successful implant for osteochondral tissue regeneration. Many of the patients undergoing surgery present osteochondral fissure extending until the subchondral bone (corresponding to a IV grade according to the conventional radiographic classification by Berndt and Harty). Therefore, strategies for functional tissue regeneration should also aim at healing the subchondral bone and joint interface, besides hyaline cartilage. With the ambition of contributing to solving this problem, several research groups have been working intensively on the development of tailored implants that could promote that complex osteochondral regeneration. These implants may be manufactured through a wide variety of processes and use a wide variety of (bio)materials. This review aimed to examine the state of the art regarding the challenges, advantages, and drawbacks of the current strategies for osteochondral regeneration. One of the most promising approaches relies on the principles of additive manufacturing, where technologies are used that allow for the production of complex 3D structures with a high level of control, intended and predefined geometry, size, and interconnected pores, in a reproducible way. However, not all materials are suitable for these processes, and their features should be examined, targeting a successful regeneration.

Nutritional Supplements and Skeletal Health

PURPOSE OF REVIEW

Nutrition influences skeletal health throughout the lifespan, from the impact of maternal intakes during development, through the development of peak bone mass, to the rate of bone loss during aging. However, there are limited data available on the effects of nutritional supplements on bone density, let alone fracture risk. This review will assess the current literature, focusing on human studies, and emphasizing nutrients where bone density or fracture data are available.

RECENT FINDINGS

Calcium and vitamin D supplements, in combination, reduce fracture risk, particularly in populations with low intakes. Extensive recent analyses have supported the safety of these interventions at recommended intakes. There is growing evidence that specific isoflavones may improve bone density although fracture data are lacking. Multiple other nutrient supplements may benefit skeletal health, but data are limited. The effect size of nutrient interventions are relatively small, requiring large sample sizes for trials with bone outcomes, may be difficult to blind, and the impact of supplementation may depend on baseline intake. However, nutrition is the only intervention that can be implemented life long and on a population wide basis. Further investigation is needed into the potential benefits of nutritional supplements to determine in which settings supplements may add benefit in addition to dietary intakes.

Modeling Sympathetic Hyperactivity in Alzheimer's Related Bone Loss

BACKGROUND

A significant subset of patients with Alzheimer's disease (AD) exhibit low bone mineral density and are therefore more fracture-prone, relative to their similarly aged neurotypical counterparts. In addition to chronic immune hyperactivity, behavioral dysregulation of effector peripheral sympathetic neurons-which densely innervate bone and potently modulate bone remodeling-is implicated in this pathological bone reformation.

OBJECTIVE

Thus, there exists a pressing need for a robust in vitro model which allows interrogation of the paracrine interactions between the putative mediators of AD-related osteopenia: sympathetic neurons (SNs) and mesenchymal stem cells (MSCs).

METHODS

Toward this end, activated SN-like PC12 cells and bone marrow derived MSCs were cultured in poly(ethylene glycol) diacrylate (PEGDA) hydrogels in the presence or absence of the AD-relevant inflammatory cytokine tumor necrosis factor alpha (TNF-α) under mono- and co-culture conditions.

RESULTS

PC12s and MSCs exposed separately to TNF-α displayed increased expression of pro-inflammatory mediators and decreased osteopontin (OPN), respectively. These data indicate that TNF-α was capable of inducing a dysregulated state in both cell types consistent with AD. Co-culture of TNF-α-activated PC12s and MSCs further exacerbated pathological behaviors in both cell types. Specifically, PC12s displayed increased secretion of interleukin 6 relative to TNF-α stimulated monoculture controls. Similarly, MSCs demonstrated a further reduction in osteogenic capacity relative to TNF-α stimulated monoculture controls, as illustrated by a significant decrease in OPN and collagen type I alpha I chain.

CONCLUSION

Taken together, these data may indicate that dysregulated sympathetic activity may contribute to AD-related bone loss.

Development of a New Bone-Mimetic Surface Treatment Platform: Nanoneedle Hydroxyapatite (nnHA) Coating

The hierarchical structure of bone plays pivotal roles in driving cell behavior and tissue regeneration and must be considered when designing materials for orthopedic applications. Herein, it is aimed to recapitulate the native bone environment by using melt electrowriting to fabricate fibrous microarchitectures which are modified with plate-shaped (pHA) or novel nanoneedle-shaped (nnHA) crystals. Nuclear magnetic resonance spectroscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction demonstrate that these coatings replicate the nanostructure and composition of native bone. Human mesenchymal stem/stromal cell (MSC) mineralization is significantly increased fivefold with pHA scaffolds and 14-fold with nnHA scaffolds. Given the protein stabilizing properties of mineral, these materials are further functionalized with bone morphogenetic protein 2 (BMP2). nnHA treatment facilitates controlled release of BMP2 which further enhance MSC mineral deposition. Finally, the versatility of this nnHA treatment method, which may be used to coat different architectures/materials including fused deposition modeling (FDM) scaffolds and Ti6Al4V titanium, is demonstrated. This study thus outlines a method for fabricating scaffolds with precise fibrous microarchitectures and bone-mimetic nnHA extrafibrillar coatings which significantly enhance MSC osteogenesis and therapeutic protein delivery, and leverages these results to show how this surface treatment method may be applied to a wider field for multiple orthopedic applications.