Characteristics Of Bone Tissue Research Articles

Features of the state of bone tissue in children with cerebral palsy. Part 1. Etiological aspects. A literature review

BACKGROUND: The growth of the human body is the most significant period of development of the bone tissue, because it is during this period that the size, shape, and architectonics of bone are formed against the background of increasing body weight and increasing physical exertion. Considering a number of pathological factors of the underlying disease (alimentary, neurological, hormonal, stress, and physical), bone tissue in children with cerebral palsy grows and develops with deviations from the norm. АIM: To present up-to-date generalized information about the features of bone tissue in children with cerebral palsy to orthopedic traumatologists, neurologists, and physical therapy specialists. MATERIALS AND METHODS: Studies on the problem of bone tissue condition in patients with cerebral palsy were analyzed. Data published over the past 20 years were searched in the scientific databases PubMed, Google Scholar, Cochrane Library, Crossref, and eLibrary without language restrictions. RESULTS: In the last 20 years, the number of studies about pediatric osteoporosis has increased. The gold standard for determining the level of bone mineral density is dual-energy X-ray absorptiometry. However, its use in children has presented some difficulties and limitations. In children, the relationship between bone mineral density values and the risk of fractures has not been well studied, which does not allow us to discuss about osteoporosis based on densitometric bone mineral density data alone. In patients with cerebral palsy, a decrease in bone mineral density and bone mass during growth was found. Previous studies showed that the main factors associated with a decrease in bone mineral density in this group of patients include neuroendocrine causes due to growth retardation against the background of CNS damage, alimentary factors, decreased calcium and vitamin D concentrations, systemic use of glucocorticoids, intake of antiepileptic drugs, decreased motor activity, and low muscle mass. Increasing serum vitamin D concentrations does not have a positive effect on bone mass, although increasing serum calcium concentrations is associated with an increase in bone mineral density. CONCLUSIONS: Identifying and correcting factors leading to decreased bone mineral density in children with cerebral palsy can improve bone health in this group of patients. The absence of a relationship between bone mineral density values and the risk of fractures in children with cerebral palsy does not allow us to discuss about osteoporosis based only on bone mineral density densitometric data. There may be more factors leading to an increased risk of bone fractures in children with cerebral palsy that require further study.

Ultrasound propagation characteristics within the bone tissue of miniature ultrasound probes: implications for the spinal navigation of pedicle screw placement.

The accuracy of pedicle screw fixation is crucial for patient safety. Traditional navigation methods based on computed tomography (CT) imaging have several limitations. Therefore, this study aimed to investigate the ultrasonic propagation characteristics of bone tissue and their relationship with CT imaging results, as well as the potential application of ultrasound navigation in pedicle screw fixation. The study used three bovine spine specimens (BSSs) and five human vertebral allograft bones (HABs) to progressively decrease the thickness of the cancellous bone layer, simulating the process of pedicle screw perforation. Five unfocused miniature ultrasound probes with frequencies of 2.2, 2.5, 3, 12, and 30 MHz were employed for investigating the ultrasonic propagation characteristics of cancellous and cortical bone through ultrasound transmission and backscatter experiments. The CT features of the bone tissue was obtained with the Skyscan 1174 micro-CT scanner (Bruker, Billerica, MA, USA). The experimental results demonstrated that low-frequency (2-3 MHz) ultrasound effectively penetrated the cancellous bone layer up to a depth of approximately 5 mm, with an attenuation coefficient below 10 dB/cm. Conversely, high-frequency (12 MHz) ultrasound exhibited significant signal attenuation in cancellous bone, reaching up to 55.8 dB/cm. The amplitude of the backscattered signal at the cancellous bone interface exhibited a negative correlation with the bone sample thickness (average r=-0.84), meaning that as the thickness of the cancellous bone layer on the cortical bone decreases, the backscattered signal amplitude gradually increases (P<0.05). Upon reaching the cortical bone interface, there was a rapid surge in echo signal amplitude, up to 8 times higher. Meanwhile, the statistical results indicated a significant correlation between the amplitude of the echo signal and the micro-CT scanning results of bone trabecular structure. Theoretically, using multiple ultrasonic probes (≥3) and regions of interest (ROIs) (≥5) has the potential to provide surgeons with early warning signals for pedicle perforation based on three or more successive increases in echo signal amplitude or a sudden substantial increase. The statistical results indicate a significant correlation between the amplitude of the echo signal and the micro-CT scanning results of bone trabeculae, suggesting the potential use of ultrasound as opposed to CT for real-time intraoperative bone navigation.

Adaptively multi-scale microstructure characterization of cancellous bone via photoacoustic signal decomposition

Osteoporosis is a systemic disease with a high incidence in the elderly and seriously affects the quality of life of patients. Photoacoustic (PA) technology, which combines the advantages of light and ultrasound, can provide information about the physiological structure and chemical information of biological tissues in a non-invasive and non-radiative way. Due to the complex structural characteristics of bone tissue, PA signals generated by bone tissue are non-stationary and nonlinear. However, conventional PA signal processing methods are not effective for non-stationary signal processing. In this study, an empirical mode decomposition (EMD)-based Hilbert-Huang transform (HHT) PA signal analysis method, called HHT PA signal analysis (HPSA), was developed to assess the microstructure information of bone tissue, which is closely related to bone health. The feasibility of the HPSA method in bone health assessment was proven by numerical simulation and experimental studies on animal samples with different bone volume/total volume (BV/TV) and bone mineral densities. First, based on adaptive EMD, the different modes correlated with multi-scale information were mined from the PA signal, the correlations between different intrinsic mode function (IMF) modes and BV/TVs were analyzed, and the optimal mode for more efficient PA time–frequency analysis was selected. Second, multi-wavelength HPSA was used to assess the changes in the chemical components of the bone tissue. The results demonstrate that the HPSA method can distinguish bones with different BV/TVs and microstructure conditions adaptively with high efficiency. They further emphasize the potential of PA techniques in characterizing biological tissues in bones for early and rapid detection of bone diseases.

Nanotechnology's Applications and Potential in Various Fields.

Since ancient times, several sorts of nanoparticles have been employed in the quickly expanding field of nanotechnology. These features include size, shape, and chemical as well as physical properties.Because of their small size and huge surface area, carbon-based nanoparticles, including fullerenes, carbon nanotubes, graphene, graphene oxide, and carbon-based quantum dots, have attracted a lot of attention in a variety of sectors, including biomedical applications. Lipid bilayers form the spherical vesicles known as liposomes. Magnetic resonance imaging (MRI) contrast agents are iron oxide nanoparticles. These materials are perfect for drug and delivery of genes, bioimaging, and bone repair because of their remarkable mechanical, electrical, visual, and chemical properties. However, concerns about potential asbestos-related diseases have arisen due to their length-to-width aspect ratio. Ceramic nanoparticles, on the other hand, are a common material in daily life and play a crucial role in bone repair, multiscale hybridisation, and aerospace structures. These nanoparticles can enhance osseointegration and bone development by mimicking the nanocomposition and nanoscale characteristics of bone tissue and enhance osteoconductive and osteoinductive capacities. Ceramic nanoparticles, however, have the potential to generate oxidative stress, which can result in irritation of the reticuloendothelial system, cytotoxicity to the heart, liver, and lungs, as well as toxicity to the cells that are attached. Additionally, oxidative stress, cell damage, and genotoxicity might result from the generation of free radicals by ceramic nanoparticles. Metal nanoparticles exhibit linear optical properties similar to molecular systems but arise from a different physical process. Semiconductor nanocrystals (NCs) are made from various compounds, such as silicon and germanium. Polyandry nanoparticles are particles approximately 10 and 10000 nanometers (nm) in size that can contain active substances. They have applications in vaccine delivery, gene therapy, and polymer nanoparticles (nanomedicine) for therapeutic applications.

Jawbone quality classification in dental implant planning and placement studies. A scoping review.

Cone beam computed tomography has become an attractive method for implant planning. However, in most cases, not all the information is taken advantage of and often the radiographic evaluation of bone quality is based on subjective assessment by the individual clinician. Therefore, the aim of this study was to examine classifications of bone tissue characteristics and methods for assessing them in dental implant planning and placement studies. Three databases (Pubmed, Scopus, Web of Science) were searched using specific index terms: "Bone quality, bone quantity, bone density, cone-beam CT and cone-beam computed tomography". Three reviewers selected titles and analyzed abstracts according to inclusion and exclusion criteria. Some descriptions of bone tissue characteristics (bone quality, density, and quantity) used before or during dental implant placement were selected and categorized. The search yielded 442 titles. A total of 32 articles were selected and read in full text. Seventeen articles were considered relevant. Different classification systems were found to evaluate bone tissue characteristics as well as different examination protocols. Thirteen publications included in this review reported on bone quality and quantity using the Lekholm and Zarb classification. However, only four studies implemented and/or proposed modifications of the Lekholm and Zarb system. Four other publications described bone quality according to different classification systems such as Misch, University of California Los Angeles (UCLA), or Trisi and Rao. The assessment methods were often briefly described (or not described at all in one publication). Of the articles analyzed, five presented observer performance, whereas three presented diagnostic accuracy of the assessment method. Currently, there are different classification systems applied to dental implant planning and placement, particularly regarding whether bone quality or quantity affects treatment outcomes. However, most authors have not validated the diagnostic accuracy and reproducibility of the classification used. Therefore, it is necessary to develop a classification system consistent with characteristics of bone tissue, taking into consideration an adequate description of bone tissue assessment methods, their diagnostic accuracy, and observer performance.

3D printing nacre powder/sodium alginate scaffold loaded with PRF promotes bone tissue repair and regeneration.

Bone defects are a common complication of bone diseases, which often affect the quality of life and mental health of patients. The use of biomimetic bone scaffolds loaded with bioactive substances has become a focal point in the research on bone defect repair. In this study, composite scaffolds resembling bone tissue were created using nacre powder (NP) and sodium alginate (SA) through 3D printing. These scaffolds exhibit several physiological structural and mechanical characteristics of bone tissue, such as suitable porosity, an appropriate pore size, applicable degradation performance and satisfying the mechanical requirements of cancellous bone, etc. Then, platelet-rich fibrin (PRF), containing a mass of growth factors, was loaded on the NP/SA scaffolds. This was aimed to fully maximize the synergistic effect with NP, thereby accelerating bone tissue regeneration. Overall, this study marks the first instance of preparing a bionic bone structure scaffold containing NP by 3D printing technology, which is combined with PRF to further accelerate bone regeneration. These findings offer a new treatment strategy for bone tissue regeneration in clinical applications.

Rat bone responses to hindlimb unloading-reloading: Composition, BMD and mechanical properties

IntroductionBone loss in lower limbs under space microgravity condition can persist even after the astronauts return to Earth's gravitational environment. It is crucial to determine the extent and timing of bone recovery after spaceflight, especially for long-term flights. However, there is a lack of comprehensive descriptions of the recovery of various aspects of bone quality, particularly in terms of compositional characteristics that reflect changes in bone quality. Therefore, the objective of this study is to investigate the alterations in bone mineral density, composition characteristics, and mechanical properties of rat lower limbs during unloading (tail suspension) and the subsequent recovery loading period. MethodsRats were subjected to tail suspension for four weeks (TS4) followed by reloading for an additional four weeks. Bone mineral density (BMD) was measured by μ-CT and analyzed. The mechanical properties of the tibia were assessed by a three-point bending test, and the composition characteristics of bone tissue were evaluated using Raman spectroscopy. Regression analysis was performed to identify main component related to mechanical property. ResultsIn the metaphysis, BMD of the tibia significant decreased, particularly in trabecular bone. Upon reloading, only the cortical bone showed recovery. In the diaphysis, cortical bone remained unchanged during unloading but demonstrated delayed bone loss during the reloading period. Simultaneously, the mechanical properties of tibia experienced a substantial reduction after four weeks of unloading, The stiffness and maximum strength did not fully recover, though the elastic modulus and the ultimate strength were restored following the reloading process. Raman spectroscopy characterization found an increase in the carbonate substitution and crystal crystallinity of the diaphysis after 4 weeks of unloading. There was an intriguing alteration in the mineralized collagen ratio, that an increase was observed in the diaphysis while a decrease was observed in the metaphysis. During 4 weeks of reloading, the compositional characteristics of the diaphysis recovered earlier than those of the metaphysis, with the exception of crystallinity which remained unrecovered. Regression analysis indicated that carbonate replacement has a strong correlation to bone mechanical properties during the 4 weeks of unloading and subsequent 4 weeks of reloading. ConclusionsThe data obtained in this study highlight the incomplete recovery of bone mineral density, mechanical properties, and compositional characteristics during reloading in tail-suspended rats. These findings deepen our understanding of microgravity-induced bone loss and provide valuable information to develop interventions not only for astronauts but also for persons on earth during and after prolonged periods of unloading.

Three-dimensional spine reconstruction from biplane radiographs using convolutional neural networks

PurposeThe purpose of this study was to develop and evaluate a deep learning network for three-dimensional reconstruction of the spine from biplanar radiographs. MethodsThe proposed approach focused on extracting similar features and multiscale features of bone tissue in biplanar radiographs. Bone tissue features were reconstructed for feature representation across dimensions to generate three-dimensional volumes. The number of feature mappings was gradually reduced in the reconstruction to transform the high-dimensional features into the three-dimensional image domain. We produced and made eight public datasets to train and test the proposed network. Two evaluation metrics were proposed and combined with four classical evaluation metrics to measure the performance of the method. ResultsIn comparative experiments, the reconstruction results of this method achieved a Hausdorff distance of 1.85 mm, a surface overlap of 0.2 mm, a volume overlap of 0.9664, and an offset distance of only 0.21 mm from the vertebral body centroid. The results of this study indicate that the proposed method is reliable.

A Brief Review of Bone Cell Function and Importance.

This review focuses on understanding the macroscopic and microscopic characteristics of bone tissue and reviews current knowledge of its physiology. It explores how these features intricately collaborate to maintain the balance between osteoblast-mediated bone formation and osteoclast-mediated bone resorption, which plays a pivotal role in shaping not only our physical framework but also overall health. In this work, a comprehensive exploration of microscopic and macroscopic features of bone tissue is presented.

Bone Material Properties in Bone Diseases Affecting Children.

Metabolic and genetic bone disorders affect not only bone mass but often also the bone material, including degree of mineralization, matrix organization, and lacunar porosity. The quality of juvenile bone is moreover highly influenced by skeletal growth. This review aims to provide a compact summary of the present knowledge on the complex interplay between bone modeling and remodeling during skeletal growth and to alert the reader to the complexity of bone tissue characteristics in children with bone disorders. We describe cellular events together with the characteristics of the different tissues and organic matrix organization (cartilage, woven and lamellar bone) occurring during linear growth. Subsequently, we present typical alterations thereof in disorders leading to over-mineralized bone matrix compared to those associated with low or normal mineral content based on bone biopsy studies. Growth spurts or growth retardation might amplify or mask disease-related alterations in bone material, which makes the interpretation of bone tissue findings in children complex and challenging.

Midpalatal suture maturation in 15- to 35-year-olds: morphological assessment in the coronal plane using CBCT-an exploratory study.

Rapid maxillary expansion (RME) is used in patients presenting transverse maxillary deficiency. However, RME may be unpredictable after late adolescence if the midpalatal sutural maturation stage (MPMS) is in late stage. Since MPMS evaluation is influenced by the expertise of the operator and image quality, this classification method could be complemented. Therefore, this study aimed to analyze the morphology of the midpalatal suture (MPS) and its surrounding bone in the coronal plane using cone beam computed tomography (CBCT) images of adolescents and young adults and to correlate the findings with their respective MPMS status. CBCT scans of 200 patients aged 15-35years of both sexes were evaluated. MPS and surrounding bone tissue characteristics in the coronal and axial sections were analyzed, and MPMS was evaluated (A to E). Six categories were identified for the coronal evaluation, analyzing it in 2 standardized locations. Sutural morphology: I, hypodense sutural line limited by 2 hyper-dense para-sutural lines; II, hypodense sutural line; and III, suture not visible. The presence of para-sutural cancellous bone: CB0, compact bone; CB1, dense cancellous tissue; CB2, spaced cancellous bone. Midpalatal bone thickness (MBTh) was also measured. ANOVA-Bonferroni, chi-square, logistic regression and t-tests were used. MPMS increased with age. Sutural morphology I and CB0 bone were the most prevalent. Here we show that sutural morphology, para-sutural bone characteristics, and MPSM were significantly associated. The coronal evaluation of the MPS can complement the information from the MPSM assessment, allowing the identification of patent MPS even in the presence of late MPSM.

Bone Tissue Evaluation Indicates Abnormal Mineralization in Patients with Autoimmune Polyendocrine Syndrome Type I: Report on Three Cases

Autoimmune polyendocrine syndrome type-1 (APS1) is characterized by autoimmune manifestations affecting different organs from early childhood on. Immunological abnormalities, the resulting endocrinopathies, and their treatments may compromise bone health. For the first time in APS1, we analyzed transiliac bone biopsy samples by bone histomorphometry and quantitative backscattered electron imaging in three adult patients (female P1, 38 years; male P2, 47 years; male P3, 25 years). All had biallelic mutations in the autoimmune regulator gene and in addition to endocrinopathies, also significant bone fragility. Histomorphometry showed bone volume in the lower normal range for P1 (BV/TV, − 0.98 SD) and P3 (− 1.34 SD), mainly due to reduced trabecular thickness (TbTh, − 3.63 and − 2.87 SD). In P1, osteoid surface was low (OS/BS, − 0.96 SD); active osteoblasts and double labeling were seen only on cortical bone. P3 showed a largely increased bone turnover rate (BFR/BV, + 4.53 SD) and increased mineralization lag time (Mlt, + 3.40 SD). Increased osteoid surface (OS/BS, + 2.03 and + 4.71 SD for P2 and P3) together with a large proportion of lowly mineralized bone area (Trab CaLow, + 2.22 and + 9.81 SD for P2 and P3) and focal mineralization defects were consistent with abnormal mineralization. In all patients, the density and area of osteocyte lacunae in cortical and trabecular bone were similar to healthy adults. The bone tissue characteristics were variable and included decreased trabecular thickness, increased amount of osteoid, and abnormal mineralization which are likely to contribute to bone fragility in patients with APS1.

Toward 3D Bioprinting of Osseous Tissue of Predefined Shape Using Single-Matrix Cell-Bioink Constructs.

Engineering living bone tissue of defined shape on-demand has remained a challenge. 3D bioprinting (3DBP), a biofabrication process capable of yielding cell constructs of defined shape, when combined with developmental engineering can provide a possible path forward. Through the development of a bioink possessing appropriate rheological properties to carry a high cell load and concurrently yield physically stable structures, printing of stable, cell-laden, single-matrix constructs of anatomical shapes is realized without the need for fugitive or support phases. Using this bioink system, constructs of hypertrophic cartilage of predesigned geometry are engineered in vitro by printing human mesenchymal stromal cells at a high density to drive spontaneous condensation and implanted in nude mice to evoke endochondral ossification. The implanted constructs retain their prescribed shape over a 12-week period and undergo remodeling to yield ossicles of the designed shape with neovascularization. Microcomputed tomography, histological, and immunohistochemistry assessments confirm bone tissue characteristics and the presence of human cells. These results demonstrate the potential of 3DBP to fabricate complex bone tissue for clinical application.

A Novel, Image-Based Method for Characterization of the Porosity of Additively Manufactured Bone Scaffolds With Complex Microstructures

Abstract Bone tissue engineering has emerged as a promising strategy for the treatment of osseous fractures, defects, and ultimately diseases caused by, for example, bone tumor resection, accident trauma, and congenital malformation. Additive fabrication of stem cell-seeded, osteoconductive porous scaffolds has been an effective method in clinical practice for the treatment of bone pathologies (such as osteoporosis, osteoarthritis, and rheumatic diseases). Porosity is known to be one of the main morphological characteristics of bone tissues, which affects the functional performance of an implanted bone scaffold. Hence, in situ detection and quantification of scaffold porosity implemented to ensure functional integrity prior to implantation/surgery is an unavoidable need. The objective of this research work is to introduce a robust, image-based method for identification and subsequently characterization of the surface porosity and dimensional accuracy of additively manufactured bone tissue scaffolds, with a focus on pneumatic micro-extrusion (PME) process. It was observed that the presented method would be capable of detecting complex individual pores based on a micrograph. Using the proposed method, not only were scaffold pores detected, but also scaffold porosity was characterized on the basis of various defined quality metrics/traits (such as the relative standard deviation of distance to the nearest pore). The proposed method was validated by contrasting its performance in “surface pore detection” against that of a standard method, tested on a complex benchmark in four different simulated lighting environments. Besides, the performance of the method in terms of “pore filling” was compared to that of a standard method, tested on a real PME-fabricated bone scaffold. It was observed that the proposed method had a better performance in pore filling, detection, and consolidation. Overall, the outcomes of this work pave the way for high-resolution fabrication of patient-specific, structurally complex, and porous bone scaffolds with easily validatable, functional, and medical properties for the treatment of bone pathologies.

Application of cytological research methods to solve the question of the organic origin of animal horns

Conducting forensic examinations is the leading evidentiary mechanism in the investigation and disclosure of poaching cases. During the investigation, animal derivatives (horns, hooves, and feathers) are found and seized from poachers in addition to clothing, crime instruments, and animal carcasses. Currently, the expensive horns of artiodactyls are of the greatest value for extraction, and their quality is largely determined by the correctness of processing from the remnants of blood, skin, and hair. Such processing precludes the use of biological methods of analysis to determine the organic origin of the seized derivatives, and genetic examination is complicated by the lack of proper laboratory equipment, appropriate reagents, and the high cost of analysis.&#x0D; The expert of the forensic biological department of the State Medical Institution of the Penza region should have established the organic origin of animal horns, presumably saiga, based on the decision on the examination appointment. The study included14 pieces of animal horns seized from persons suspected of poaching.&#x0D; Microparticles were obtained from the peripheral and central parts of the horns, from which pressed preparations were prepared, followed by their staining and microscopy during the study. Luminescent microscopy of preparations from solid plates of the central part of the horn stained with fluorochromes revealed osteocytes, which are cellular characteristics of bone tissue. Epithelial cells that form the basis of the horn cover were detected when azur-eosin stained small particles from the peripheral part of the horn.&#x0D; The identification of these cell types provides sufficient grounds to conclude the organic origin of the horns presented for research.

Densitometric features of bone tissue in children during the growth spurt considering the VDR gene polymorphisms and vitamin D level

Background. The period of intensive growth in children is associated with active changes in the bone tissue architecture. A high level of bone mass accumulations was observed. Whether such processes are adequate depends on numerous factors, however, all of them are based on a genetic component. Gene expression affects all the processes in the body, including bone tissue. The BSML and Fokl polymorphisms of the VDR gene responsible for the activity of cell receptors for vitamin D is studied in association with bone pathology, autoimmune diseases, diseases of the central nervous, cardiovascular and other systems. Purpose – of the research is aimed at determining densitometric features of the structural and functional condition of bone tissue in children during the growth spurt, taking into account polymorphisms of BSML, FOKL gene VDR and vitamin D levels. Materials and Methods. The examination covered 205 healthy children aged 9–17, who were divided into groups depending on the presence or absence of growth spurt (GS) and its intensity. The examination presupposed analysis of the medical history, assessment of physical and sexual development, ultrasound (QUS) and X-ray (DXA) densitometry, determination of 25-(OH)-D levels, molecular diagnostics- definition of polymorphisms of BSML, FOKL gene VDR. Results. Ultrasound densitometry showed a decrease in bone mineral density (BMD) in 24 children of Group I (48.0%), Z-score: – 1.8 ± 0,56; 28 children in Group II (60.87%), Z-score: – 1.96 ± 0,27 and 43 children of Group III (39.45%), Z-score: – 1.68 ± 0,72. DXA was used for 32 children, 18 of them (56.25%) were diagnosed with a decreased BMD. Children of Group I with a reduced BMD had an average level of vitamin 25-(OH)-D at the value of 39.04 ± 11.84 nmol/l, while in children with a normal BMD it averaged – 42.43 ± 6.3 nmol/l. In children of group II BMD in which it was reduced, the average level of 25-(OH)-D was 45.68 ± 5.48 nmol/l, with normal BMD – 45.47 ± 4.69 nmol/l. Children of Group III with a reduced BMD had an average 25-(OH)-D level of 36.73 ± 8.94 nmol/l, those with a normal BMD showed the 25-(OH)-D level of 42.91 ± 9.1 nmol/l. A molecular study found that 48.76% of children did not have any mutations in the VDR gene BSML polymorphism, 41.32% of children showed a heterozygous mutation, and 9.92% of children revealed a homozygous mutation. 27.81% of children had no mutation of Fokl polymorphism in the VDR gene, 61.95% showed a heterozygous mutation and a homozygous mutation was detected in 10.24% of children. Conclusions. Decreased bone mineral density in children during growth spurt is due to insufficiency or deficiency of vitamin D and is determined genetically. However, the most significant factor in the BMD reduction is the retardation of bone mass accumulation processes against the background of an intensive linear growth of the skeleton.

Bone‐on‐a‐Chip: A Microscale 3D Biomimetic Model to Study Bone Regeneration

Organ‐on‐chip models, developed using microengineering and microfluidic technologies, aim to recreate physiological‐like microenvironments of organs or tissues as a tool to study (patho)physiological processes in vitro. On‐chip models of bone are relevant for the study of bone physiology, diseases and regenerative processes. While a few bone‐on‐a‐chip models exist, recapitulating the cellular components of bone, these models do not incorporate the chemical and structural characteristics of bone tissue. Herein, the development of a bone‐on‐a‐chip platform is reported that comprises a 3D structural model of bone. To build the platform, first, a 3D model of bone is produced in a polymer using two‐photon polymerization (2PP) from a 3D nano‐computed tomography scan of trabecular bone. This 3D model is then coated with a layer of bone mineral‐like calcium phosphate. Finally, the 3D bone model is integrated inside a microfluidic device suitable for cell culture. Human mesenchymal stromal cells, cultured inside the platform for up to 21 days, show high viability and extensive production of extracellular matrix, rich in collagen. This biomimetic bone‐on‐a‐chip platform can contribute to a better understanding of the processes related to bone formation and remodeling, which in turn can be used for the development of bone regeneration strategies.

Perfused Platforms to Mimic Bone Microenvironment at the Macro/Milli/Microscale: Pros and Cons.

As life expectancy increases, the population experiences progressive ageing. Ageing, in turn, is connected to an increase in bone-related diseases (i.e., osteoporosis and increased risk of fractures). Hence, the search for new approaches to study the occurrence of bone-related diseases and to develop new drugs for their prevention and treatment becomes more pressing. However, to date, a reliable in vitro model that can fully recapitulate the characteristics of bone tissue, either in physiological or altered conditions, is not available. Indeed, current methods for modelling normal and pathological bone are poor predictors of treatment outcomes in humans, as they fail to mimic the in vivo cellular microenvironment and tissue complexity. Bone, in fact, is a dynamic network including differently specialized cells and the extracellular matrix, constantly subjected to external and internal stimuli. To this regard, perfused vascularized models are a novel field of investigation that can offer a new technological approach to overcome the limitations of traditional cell culture methods. It allows the combination of perfusion, mechanical and biochemical stimuli, biological cues, biomaterials (mimicking the extracellular matrix of bone), and multiple cell types. This review will discuss macro, milli, and microscale perfused devices designed to model bone structure and microenvironment, focusing on the role of perfusion and encompassing different degrees of complexity. These devices are a very first, though promising, step for the development of 3D in vitro platforms for preclinical screening of novel anabolic or anti-catabolic therapeutic approaches to improve bone health.

Morphometric characteristics of bone tissue in the treatment of experimental tuberculous osteitis with anti-tuberculosis drugs and selective inhibitors of bisphosphonates

Introduction. The effect of bisphosphonates on bone recovery after surgical treatment of osteitis has not been fully understood. Aim: To study morphometric features of bone restoration when bisphosphonates are used after the surgical treatment of experimental tuberculous oste-itis. Material and methods. Experimental model of TB osteitis of distal femur was produced in 21 sexually ma-ture chinchilla male rabbits of distal epimetaphys of fem-oral bone. After resection of the locus and osteoplasty, 3 study arms have been formed depending on the medica-tion therapy: anti-TB drugs only, anti-TB drugs + bisphos-phonates (BF) and BF only. After the end of experiment, 3 and 5 months after surgery, material was harvested in autopsy and histological sections 3–5 microns thick were morphometrically studied on the basis of digital images of the preparations. Results. 3 months after the opera-tion, a greater thickness of the bone rods was noted in the group of rabbits treated with anti-TB drugs + BF, after 6 months — in those treated with BF only (p&lt;0.001). In all the studied groups, relief of specific TB inflammation was achieved in 50–75% of cases 6 months after surgical treatment. Conclusions: The use of BF in the treatment of experimental tuberculous osteitis does not impact the frequency of detection and the area of specific inflamma-tion, while providing the greatest thickness of the bone rods at 3 and 6 months after surgical treatment.

Titanium Implants and Local Drug Delivery Systems Become Mutual Promoters in Orthopedic Clinics.

Titanium implants have always been regarded as one of the gold standard treatments for orthopedic applications, but they still face challenges such as pain, bacterial infections, insufficient osseointegration, immune rejection, and difficulty in personalizing treatment in the clinic. These challenges may lead to the patients having to undergo a painful second operation, along with increased economic burden, but the use of drugs is actively solving these problems. The use of systemic drug delivery systems through oral, intravenous, and intramuscular injection of various drugs with different pharmacological properties has effectively reduced the levels of inflammation, lowered the risk of endophytic bacterial infection, and regulated the progress of bone tumor cells, processing and regulating the balance of bone metabolism around the titanium implants. However, due to the limitations of systemic drug delivery systems—such as pharmacokinetics, and the characteristics of bone tissue in the event of different forms of trauma or disease—sometimes the expected effect cannot be achieved. Meanwhile, titanium implants loaded with drugs for local administration have gradually attracted the attention of many researchers. This article reviews the latest developments in local drug delivery systems in recent years, detailing how various types of drugs cooperate with titanium implants to enhance antibacterial, antitumor, and osseointegration effects. Additionally, we summarize the improved technology of titanium implants for drug loading and the control of drug release, along with molecular mechanisms of bone regeneration and vascularization. Finally, we lay out some future prospects in this field.