Bone Matrix Research Articles

Bone tissue condition in early dates of restoration after thermic exposure

BACKGROUND: Thermoablation is a promising method for treating bone tumors. It is important to select the optimal mode (dose/time) of high-temperature exposure to fully realize the potential of this method.AIM: to study in vivo the reaction of rabbits’ bone tissue (BT) in the dynamics of early (3-7 days) recovery after local intraoperative hyperthermic ablation in the temperature range in the bone marrow canal of 55-60℃.METHODS: The study involved 6 mongrel rabbits aged 15 weeks, weighing 3-4 kg. The animals were derived from the experiment on the 3rd and 7th days after local thermoablation of the femoral diaphysis. Histological assay of BT included overall examination (HE staining), assessment of the area of immature BT (Mallory staining), optical density and area of osteoblasts and osteocytes (Einarson staining). Statistical data processing was performed in the R programming language.RESULTS: HE staining showed no signs of pathological changes after high-temperature exposure of BT. Mallory staining revealed no negative effects of local thermoablation on the intercellular bone matrix. Morphometric analysis showed an overshoot in the area of osteoblasts by the 7th day against the background of reduced synthetic activity starting from the 3rd day of the experiment. By the 3rd day, there is also a decrease in the area and optical density of osteocytes in the diaphyses of bones subjected to thermoablation. However, by the 7th day, the area of mature bone cells doesn`t differ from the corresponding value in the contralateral limb.CONCLUSION: Local intraoperative thermoablation of rabbit femoral diaphyses at an intramedullary temperature of 55-60℃ significantly reduces the optical density of osteoblasts and osteocytes in the dynamics of early (3-7 days) recovery after extreme exposure, which suggests a violation of metabolic processes and intracellular organelles (nucleus, ribosomes) of bone cells. At the same time, signs of remodeling of the damaged area were noted, presumably through the mechanism of osteoconduction of endosteal and periosteal cells from metaphyses that were not subjected to direct hyperthermia. The results obtained may be useful in thermoablation of BT tumors with the condition of higher sensitivity of malignant cells to heating.

Determination of individual age and ontogenetic stages of fossil tetrapods using paleohistological methods

The determination of individual age and ontogenetic stage (juvenile, subadult, adult) of fossil vertebrates is important for the initial determination of taxonomic affiliation, as well as for further evolutionary and paleobiological interpretations. Determination of individual age and ontogenetic stage (= relative age) is carried out by various methods, including paleohistological analysis. The study of thin sections of tetrapod bones allows us to assume how many years the animal lived (skeletochronological method) and to determine the ontogenetic stage according to a set of age-related histological markers: change in the type of bone matrix and vascularization, change in the distance between growth marks, formation of the external fundamental system (EFS), formation of the inner (endosteal) and outer (periosteal) circumferential layers (OCL, ICL), occurrences of secondary remodeling – Haversian substitution and formation of trabeculae. Depending on the phylogenetic position and biological peculiarities of the study group of tetrapods, the set of age “histologic markers” may be different.

Tales of Cancer-Induced Bone Disease from the Senescent Osteocyte Crypt

Cancer-induced bone disease greatly diminishes the quality of life for patients with bone metastatic breast cancer, resulting in painful skeletal-related events including bone loss and fracture. Improved understanding of the roles of osteoblasts and osteoclasts, and how tumors alter their biology, has led to blockbuster therapies that significantly reduce skeletal-related events, but the disease remains incurable. However, emerging technologies and tools for studying the role of other stromal and immune components in controlling tumor–host interactions have begun to reveal new insights that may yield tractable therapeutic targets to further mitigate the painful effects of bone metastases. In this issue of Cancer Research, Kaur and colleagues study osteocytes, which are terminally differentiated osteoblasts and entombed within the bone matrix, from established bone metastatic breast cancer and report how the disease ages them as characterized by a senescence-associated secretory phenotype. This premature development of osteocyte senescence in turn enhances bone destruction and osteoclastogenic potential. Targeting senescent cells using senolytics suppressed bone resorption and preserved bone mass. Collectively, these findings underscore osteocyte involvement in the “vicious cycle” of bone metastasis, and targeting senescent osteocytes represents a new avenue for managing cancer-induced bone disease.See related article by Kaur et al., p. 3936

A Composite Foam of Dermal Matrix-Demineralized Bone Matrix for Enhanced Bone Regeneration.

Allogenic demineralized bone matrix (DBM) is widely used for bone repair and regeneration due to its osteoinductivity and osteoconductivity. The present study utilized acellular dermis microfibers to improve the DBM's clinical handling properties and to enhance bone regeneration. Donated human cadaver skin was de-epidermized and decellularized to be acellular dermal matrix (ADM), which was further processed into microfibers. Donated human bone was micronized and partially demineralized (∼30% calcium removal) for optimal bone regeneration. A flexible ADM/DBM composite foam was fabricated with ADM microfibers and DBM particles. Structural analysis found that the ADM/DBM composite foam had proper porosity with interconnected micropores and rapid wettability, and good stability upon cyclic compressions, whereas cytotoxicity test, in vitro collagenase degradation, and rat subcutaneous implantation showed good biocompatibility and biodegradability. The composite foam, used for in vitro coculture, significantly increased the alkaline phosphatase activity of C2C12 cells and upregulated the expression of osteogenesis-related genes of human umbilical cord mesenchymal stem cells. Using the rat Φ8 mm calvarium defect repair model, the ADM/DBM composite foam demonstrated superior osteogenicity by rapidly inducing new bone formation and achieving complete closure of the bone defects, as compared with the commercially available bone graft for skull repair (SkuHeal). Therefore, the ADM/DBM composite foam holds promise as a superior DBM-based product for repairing critical bone defects.

Osteogenic tailoring of oriented bone matrix organization using on/off micropatterning for osteoblast adhesion on titanium surfaces.

Titanium (Ti) implants are well known for their mechanical reliability and chemical stability, crucial for successful bone regeneration. Various shape control and surface modification techniques to enhance biological activity have been developed. Despite the crucial importance of the collagen/apatite bone microstructure for mechanical function, antimicrobial properties, and biocompatibility, precise and versatile pattern control for regenerating the microstructure remains challenging. Here, we developed a novel osteogenic tailoring stripe-micropatterned MPC-Ti substrate that induces genetic-level control of oriented bone matrix organization. This biomaterial was created by micropatterning 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer onto a titanium (Ti) surface through a selective photoreaction. The stripe-micropatterned MPC-Ti substrate establishes a distinct interface for cell adhesion, robustly inducing osteoblast cytoskeleton alignment through actin cytoskeletal alignment, and facilitating the formation of a bone-mimicking-oriented collagen/apatite tissue. Moreover, our study revealed that this bone alignment process is promoted through the activation of the Wnt/β-catenin signaling pathway, which is triggered by nuclear deformation induced by strong cellular alignment guidance. This innovative material is essential for personalized next-generation medical devices, offering high customizability and active restoration of the bone microstructure. STATEMENT OF SIGNIFICANCE: This study demonstrates a novel osteogenic tailoring stripe-micropatterned MPC-Ti substrate that induces osteoblast alignment and bone matrix orientation based on genetic mechanism. By employing a light-reactive MPC polymer, we successfully micropatterned the titanium surface, creating a biomaterial that stimulates unidirectional osteoblast alignment and enhances the formation of natural bone-mimetic anisotropic microstructures. The innovative approach of regulating cell adhesion and cytoskeletal alignment activates the Wnt/β-catenin signaling pathway, crucial for both bone differentiation and orientation. This study presents the first biomaterial that artificially induces the construction of mechanically superior anisotropic bone tissue, and it is expected to promote functional bone regeneration by enhancing bone differentiation and orientation-targeting both the quantity and quality of bone tissue.

Selenium Nano Particles versus Nano Vitamin D3 in Modulating Anastrozole-Induced Osteoporosis on the Mandibular Alveolar Bone of Albino Rats

Aim: Compare the efficiency of selenium nanoparticles (SeNPs) and Nano vitamin D3 in modulating alveolar bone osteoporosis induced by anastrozole in albino rats. Materials and Methods: 28 female albino rats were randomly divided into 4 groups (7/group); Control group (GP I): rats were received distilled water orally. Anastrozole group (GP II): rats were orally given anastrozole (1 mg/kg/day) dissolved in distilled water. SeNP treated Anastrozole group (GP III): rats were orally given anastrozole with SeNP (0.5 mg/kg/day). Nano vitamin D3 treated Anastrozole group (GP IV): rats were orally given anastrozole with Nano vitamin D3 (40 IU/kg/day). After 4 weeks of drugs administration, mandibles were prepared and stained with hematoxylin & eosin, Masson trichrome and anti-osteocalcin antibody. New collagen area% in Masson trichrome and positive anti-osteocalcin osteoblasts count were measured and statistically analyzed. Results: Deleterious changes in the alveolar bone were detected in Gp II, while being markedly improved in treated groups. Moreover, GP II demonstrated large areas of old collagen, with positive anti-osteocalcin immunoreactivity in some osteoblasts and few osteocytes, meanwhile, control and treated groups showed more predominant newly formed collagen with positive immunoreactivity in nearly all osteoblasts, osteocytes, and some areas of bone matrix. Statistically, Gp III and Gp IV showed the significantly highest newly formed collagen mean area% and positive osteoblasts count, then Gp I, while Gp II represented the least recorded data. Conclusions: SeNPs and Nano Vitamin D3 improve the structural and cellular quality of mandibular alveolar bone in anastrozole-induced osteoporosis of albino rats.

Surface modification of 3D-printed polycaprolactone- human decellularized bone matrix composite scaffold by plasma for bone tissue engineering

BackgroundBone tissue engineering is a revolutionary field focused on creating viable bone substitutes using advanced materials and techniques. Utilizing 3D printing, precise and customizable bone scaffolds can be produced. A notable composite material in this domain is a composite of polycaprolactone (PCL) and human decellularized bone matrix (hDBM), which combines synthetic and natural elements for enhanced functionality. To further improve cell attachment and growth, cold plasma surface modification is employed, optimizing scaffold surfaces. These innovations collectively hold great potential for improving bone repair and regeneration outcomes. MethodsScaffold architecture was designed through CAD software, and the composite of PCL and hDBM was printed using FDM technology. Surface modification was achieved by exposing the scaffolds to Argon-Oxygen (Ar-O₂) plasma radiation for 1 and 3 minutes. Both treated and untreated scaffolds were characterized, including measurements of surface roughness, hydrophilicity, and cellular activity. ResultsAlmost all groups showed non-toxic effect on cellular behavior during cell culture. Plasma-treated scaffolds showed a significant increase in surface roughness, with roughness values (Ra) increasing from 10.45 nm (untreated) to 62.75 nm after 3 minutes of plasma exposure. Contact angle measurements decreased from approximately 66.5° in untreated scaffolds to 31.4° in those treated for 3 minutes, indicating enhanced hydrophilicity. Plasma-treated scaffolds demonstrated excellent cytocompatibility, significantly enhancing cell proliferation, osteogenic differentiation, and mineralization compared to untreated scaffolds. After 7 days, scaffolds treated for 1 and 3 minutes showed 35% and 60% increases in cell proliferation, respectively, highlighting the role of plasma treatment in creating a bioactive surface conducive to cell adhesion, growth, and improved osteogenic properties, with longer exposure times further amplifying these effects. ConclusionsThe current study demonstrates the efficacy of Ar+O₂ plasma treatment in enhancing the surface properties of PCL-hDBM scaffolds, making them more conducive to osteogenesis. This study suggests that plasma-treated PCL-hDBM scaffolds are a promising option for bone tissue engineering applications.

Self-Assembled Nanoparticles with Well-Defined Oligosaccharide Promote Osteogenesis by Regulating Golgi Stress Response.

Osteoporosis, a prevalent disease characterized by low bone density and increased fracture risk, poses significant health challenges for the elderly. Current treatments offer short-term benefits but are limited by long-term efficacy and adverse effects, highlighting the need for new strategies. Chondroitin sulfate polysaccharides (CS), a major component of the bone matrix, are crucial for bone and cartilage health. However, their role in osteoporosis is understudied due to the heterogeneity of natural CS. we found reduced CS levels in osteoporosis patients and developed CS4-NP, a self-assembled tetrasaccharide nanoparticle that mimics CS's structure. CS4-NP, which efficiently delivers the active CS4, significantly improves bone mass in ovariectomized osteoporosis models. It activates the Activating Transcription Factor 4-Cystathionine gamma-Lyase signaling axis in pre-osteoblasts, enhancing osteogenesis. our findings suggest that CS4-NP, an oligosaccharide-based nanomaterial, could address the limitations of current treatments and provide a viable strategy for osteoporosis.

Initial clinical evaluation of a novel integrative bone matrix (IBM) in foot and ankle fusion procedures

BackgroundFoot and ankle arthrodesis procedures are frequently performed in concert with the utilization of bone grafts. However, the availability of autologous bone is often limited, inaccessible, or not suitable, thus there is a need for bone graft substitutes with equally effective clinical outcomes. A next generation integrative bone matrix (IBM) has been developed that has intrinsic osteogenic, osteoconductive, and osteoinductive characteristics, and is a promising solution to mitigate complications such as nonunion and reduce the need for autologous bone graft harvest.MethodsThe charts of twenty subjects undergoing foot and ankle fusion procedures with INFLUX™ SPARC, a novel IBM, were retrospectively reviewed to determine initial clinical safety and efficacy of this next generation bone graft. Endpoints included the presence of complications or surgical reintervention, fusion rates as determined by standardized radiographic films, and patient-reported outcome measures at various time points up to 24 weeks.ResultsNo major complications or surgical reinterventions were observed in this study. Complete radiographic fusion was achieved in all subjects by 24 weeks, with a mean overall fusion time of 8.5 ± 4.8 weeks. Subjective pain, function, and quality of life outcomes showed consistent improvements throughout the follow-up period, and all subjects (100%) achieved the minimum clinically significant mean improvements for all measures by week 24.ConclusionsThis study supports the use of this new IBM as a promising alternative to autologous bone grafting, offering high fusion success rates, low complications, and clinically meaningful improvements in patient-reported outcomes, particularly in higher-risk patient populations. Future investigations are needed to confirm these findings in larger and longer-term studies, and to explore the broader applications of this innovative bone graft.

A hypothesis of mesenchymal stem cell osteogenic differentiation mediated by chelidonic acid through the calcium import: original research and computer simulation.

Chelidonic acid (ChA) is small molecule capable of inducing the differentiation of mesenchymal stem cells (MSCs) into osteoblasts and the formation of mineralized bone matrix (MBM) both in vitro and in vivo. However, the molecular mechanisms underlying these effects are unknown. Therefore, in silico modelling of potential molecular targets of ChA was performed. ChA was isolated from Saussurea controversa. The ability of ChA to induce in vitro differentiation MSCs into osteoblasts synthesizing MBM was detected using alizarin red staining. ChA osteogenic activity was studied in mice by in situ test of ectopic osteogenesis, using the subcutaneous implantation of syngeneic bone marrow on the calcium phosphate coated titanium plates. DIGEP-Pred web service was used to simulate in silico the effect of ChA on gene expression, and overrepresentation analysis to search for common ontologies and pathways. ChA linearly increased the number of single (R2 = 0.92, p = 0.039) and the total areas of MBM sites (R2 = 0.96, p = 0.019) in a 21-day MSC culture. Oral administration of ChA led to two to three times improved bone and bone marrow formation in situ. In silico modelling identified 306 genes (including 7 calcium import genes) and 9 signalling pathways potentially involved in ChA osteogenic effect and calcium metabolism in MSCs. In silico analysis revealed a list of key signalling pathways and genes for calcium influx into MSCs and their differentiation into osteoblasts as the first target candidates for studying real gene expression and molecular mechanisms of the ChA osteogenic effects.

Comparative Evaluation of Microleakage in Class II Composite Restorations Using Three Bulk-fill Composites with or without Resin-modified Glass Ionomer Cement Liner: A Stereomicroscopic Study.

To compare the microleakage of three bulk-fill composite resins with or without resin-modified glass ionomer cement (RMGIC) liner. A total of 30 maxillary human 1st premolar teeth were selected. Two box preparations were made on the mesial and distal sides. Teeth were randomly divided into three groups of 10 teeth each. RMGIC liner with 1 mm thick were applied to the mesial box. The specimens were divided into three groups according to the type of bulk-fill composites used and restoration of the cavities were done according to manufacturer instructions and light cured. Finishing and polishing were done and stored for 1 week in distilled water at 37°C. Thermocycling was then performed in a thermocycling unit. The specimens were then immersed in 0.5% methylene blue for 8 hours at 37°C. All the specimens were sectioned longitudinally in a mesiodistal direction and analyzed under 20× magnification in a stereomicroscope. The degree of dye penetration was scored. Subgroup M showed comparatively less microleakage compared to subgroup D in all the groups which was statistically significant. When microleakage between the study group on mesial and distal sides was compared, group smart dentin replacement (SDR)-M showed less microleakage compared to group F-M and this difference was statistically significant. RMGIC is the recommended liner beneath the bulk-fill composites in class II cavities and SureFil SDR bulk-fill flowable can be the recommended composite resin for class II restorations. Bulk-fill composite is a time-saving material as it eliminates the incremental placement. RMGIC is always recommended beneath bulk-fill composites. SDR bulk-fill is the recommended composite restoration. Mundaragi VAC, Niranjan NT, Chandrashekhar KS, et al. Comparative Evaluation of Microleakage in Class II Composite Restorations Using Three Bulk-fill Composites with or without Resin-modified Glass Ionomer Cement Liner: A Stereomicroscopic Study. Int J Clin Pediatr Dent 2024;17(10):1146-1152.

Osteoplastic biomaterials from organic and mineral components of the bone matrix: a literature review

Introduction. The bones of the human and animal have a unique ability to remodel. The ability to constantly renew bone tissue determines the healing of fractures and the adaptation of bones to mechanical loads. However, the process of bone self-healing is effective only for defects of non-critical size. In segmental and critical defects, endogenous stimulation of bone tissue regeneration is required. In this regard, there remains a need to design osteoplastic biomaterials with improved pro-regenerative action. Every year, new data appear that expand our understanding of the methods and mechanisms for stimulating bone tissue restoration using artificial osteoplastic materials. Aim. Characteristics of modern methods of constructing biomimetic materials from organic and mineral components of bone matrix. Materials and methods. The literature review was conducted using the PubMed and ScienceDirect databases. Query dates — may–july 2024, query depth — 1965–2024. Main content of the review. Effective use of bone polymers for the creation of biomimetic osteoplastic materials is possible only with an understanding of the principles of molecular-cellular interaction of biopolymers with bone cells and tissues. By now, it has been established that the ability of collagen to influence the functional activity of cells involved in the reparative regeneration of bone tissue is due to the presence of special patterns in its structure - binding sites with cellular receptors, which are formed by a specific sequence of amino acids in the collagen polypeptide chain. In the case of inorganic bone material, the functionally significant elements are the chemical composition and crystal structure of calcium phosphate salts. A current trend in the design of osteoplastic materials is to impart biomimetic properties to them. At the molecular level, this approach is implemented using as intrafibrillar and extrafibrillar mineralization of collagen fibrils. At the tissue and organ level, biomimicry is achieved through the use of three-dimensional bioprinting technologies. Conclusion. Thus, thanks to advances in biology, physics, chemistry and engineering sciences, it was possible to develop new technologies for designing osteoplastic materials that imitate the structure and function of native bone tissue. The use of biomaterials created using biomimetics principles increases the efficiency of bone tissue damage restoration.

Reactivating Sleeping Intramedullary Nail in a 16-Year-Old Female with Polyostotic Fibrous Dysplasia: A Case Report on Complications and Potential Solutions

Background: Fibrous dysplasia (FD) is a rare condition in which normal spongy and cortical bone is replaced by non-neoplastic fibrous tissue, leading to weakened bone matrix and increased risk of pathological fractures and deformities. Treating these deformities poses a significant challenge for surgeons. While various cases of surgical stabilization and limb lengthening using intramedullary nails have been reported, there is limited evidence on the use of Motorized Intramedullary Limb-Lengthening Nails (MILLNs) in FD patients. This case report presents the clinical history of a patient with FD who underwent multiple surgical interventions to address severe lower limb length discrepancy (LLD) and angular deformity caused by multiple fractures. Case presentation: A sixteen-year-old Caucasian girl with polyostotic FD developed a severe post-traumatic LLD of 10 cm on the right side, associated with coxa vara, valgus knee, and patellar instability. The deformity of the proximal femur was addressed with a valgus and derotational femoral osteotomy. However, this procedure exacerbated the knee’s valgus deformity and only partially corrected the LLD, leading to the decision to proceed with femoral lengthening. A retrograde magnetic intramedullary nail (PRECICE, NuVasive) was utilized for this purpose. Approximately three months postoperatively, radiographs revealed the loosening of the proximal anchoring screw, while the nail had reached maximum distraction. We then proposed reactivating the previously implanted nail. Nine months after the final surgery, standing long-leg radiographs showed a residual shortening of 1 cm, with excellent healing at the fracture sites and the nail and screws remaining securely in place. The patient was monitored regularly, with the latest follow-up occurring four years and five months after the conclusion of the last lengthening procedure. Conclusions: This case report describes the reactivation of a MILLN in a patient with polyostotic fibrous dysplasia. While nail reactivation has been previously described in the literature, to our knowledge, it has not been reported for treating complications arising from FD. In cases of mechanical complications, this approach can equalize leg length discrepancies and correct deformities, avoiding additional invasive surgeries and reducing healthcare costs. As this is an off-label treatment, preoperative consent from both the patient and the parents is required.

Enhancing Fracture Healing with 3D Bioprinted Hif1a-Overexpressing BMSCs Hydrogel: A Novel Approach to Accelerated Bone Repair.

Addressing the urgent need for effective fracture treatments, this study investigates the efficacy of a 3D bioprinted biomimetic hydrogel, enriched with bone marrow mesenchymal stem cells (BMSCs) and targeted hypoxia-inducible factor 1 alpha (Hif1a) gene activation, in enhancing fracture healing. A photocross-linkable bioink, gelatin methacryloyl bone matrix anhydride (GBMA) is developed, and selected its 5% concentration for bioink formulation. Rat BMSCs are isolated and combined with GBMA to create the GBMA@BMSCs bioink. This bioink is then used in 3D bioprinting to fabricate a hydrogel for application in a rat femoral fracture model. Through transcriptome sequencing, WGCNA, and Venn analysis, the hypoxia-inducible factor Hif1a is identified as a critical gene in the fracture healing process. In vitro studies showed that Hif1a promoted BMSC proliferation, chondrogenic differentiation, and cartilage matrix stability. The in vivo application of the GBMA@BMSCs hydrogel with Hif1a overexpression significantly accelerated fracture healing, evidenced by early and enhanced cartilage callus formation. The study demonstrates that 3D bioprinting of GBMA@BMSCs hydrogel, particularly with Hif1a-enhanced BMSCs, offers a promising approach for rapid and effective fracture repair.

Genes involved in osteogenic differentiation induced by low‑intensity pulsed ultrasound in goldfish scales.

The teleost scale is a unique calcified tissue that contains osteoclasts, osteoblasts, osteocytes and the bone matrix, similar to mammalian bone. Here, the effects of low-intensity pulsed ultrasound (LIPUS) on osteoblasts and osteoclasts in goldfish scales were investigated. Scales were treated with LIPUS, which is equivalent to use under clinical conditions (30 mW/cm2 for 20 min), then cultured at 15˚C. Alkaline phosphatase activity, a marker of osteoblasts, or tartrate-resistant acid phosphatase (TRAP) activity, a marker of osteoclasts was measured. The gene expression profile was examined using RNA-sequencing. Gene network and biological function analyses were performed using the Ingenuity® Pathways Knowledge Base. A single exposure of LIPUS significantly increased ALP activity but did not affect TRAP activity. These data indicated that LIPUS induced osteoblastic activation in goldfish scales. Using RNA-sequencing, numerous genes that were significantly and differentially expressed 3, 6, and 24 h after LIPUS exposure were observed. Ingenuity® pathway analysis demonstrated that three gene networks, GN-3h, GN-6h, and GN-24h, were obtained from upregulated genes at 3, 6 and 24 h culture, respectively, and included several genes associated with osteoblast differentiation, such as protein kinase D1, prostaglandin-endoperoxide synthase 2, TNFRSF11B (tumor necrosis factor receptor superfamily, member 11b) and WNT3A (Wnt family member 3A). A significant upregulation of expression levels of these genes in scales treated with LIPUS was confirmed by reverse transcription-quantitative polymerase chain reaction. These results contribute to elucidating the molecular mechanisms of osteoblast activation induced by LIPUS.

Multifunctional Scaffold Comprising Metal-Organic Framework, Hydrogel, and Demineralized Bone Matrix for the Treatment of Steroid-Induced Femoral Head Necrosis.

Overproduction of reactive oxygen species (ROS) results in oxidative stress, a critical factor in the pathogenesis of steroid-induced osteonecrosis of the femoral head (SONFH). Excess ROS not only hinders the osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs) but also impairs mitochondrial structure and function, resulting in irreversible cellular damage. Herein, a biomimetic multifunctional scaffold comprising Zn-modified metal-organic framework 818 (Zn-MOF-818) loaded with deferoxamine (DFO), gelatin methacryloyl (GelMA) hydrogel, and demineralized bone matrix (DBM) is shown to scavenge excess ROS, promote angiogenesis, and regulate immunity. Introduced Zn significantly enhances the superoxide dismutase- and catalase-like activities of MOF-818, which increases ROS-scavenging efficiency. Zn-MOF-818 disrupts the vicious intracellular cycle of mitochondrial dysfunction and ROS accumulation by enhancing mitophagy, stabilizing mitochondrial function, and upregulating antioxidant genes. Additionally, Zn-MOF-818 facilitates the polarization of macrophages toward the M2 phenotype and alleviates inflammation, creating an advantageous immune microenvironment for osteogenic differentiation of BMSCs. The release of DFO, an activator of the HIF-1α pathway, and Zn2+ from Zn-MOF-818, along with the secretion of various cytokines from DBM (such as bone morphogenetic proteins and vascular endothelial growth factors), enhances angiogenesis and osteogenesis. This scaffold targets multiple factors concurrently, offering a promising new approach for treating SONFH.

Fracture characteristics of human cortical bone influenced by the duration of in vitro glycation

Abstract Advanced glycation end products (AGEs) accumulate in various tissues, including bone, due to aging and conditions like diabetes mellitus. To investigate the effects of AGEs on bone material quality and biomechanical properties, an in vitro study utilized human tibia, sectioned into 90 beams, and randomly assigned to three mechanical test groups. Each test group included ribose (c=0.6 M) treatment at 7-, 14-, and 21-day, alongside control groups (n=5 per group). Fluorescent AGE (fAGE) and carboxymethyl-lysine (CML) levels were assessed through fluorometric analysis and mass spectrometry, while bone matrix composition was characterized using Fourier-transform infrared and Raman spectroscopy. Mechanical properties were determined through nanoindentation and three-point bending tests on non-notched and notched specimens. The results showed significant increases in fAGEs levels at 7-, 14-, and 21-day compared to controls (119%, 311%, 404%; p=0.008, p<0.0001, p<0.0001; respectively), CML levels also rose substantially compared to controls (383%, 503%, 647%, p<0.0001, p<0.0001, p<0.0001; respectively). Analysis of bone matrix composition showed greater sugars/Amide I ratio at 21-day glycation compared to controls, 7-day, and 14-day (p=0.001, 0.011, 0.006; respectively); and higher carbonate-to-phosphate ratios in the ribose treatment group compared to controls (p<0.05) in the interstitial bone area. Mechanical testing of notched specimens exhibited a higher yield force, pre-yield toughness, and growth toughness at 14-day glycation compared to controls and to both 7-day and 21-day glycation (p<0.05). Nanoindentation showed that the hardness was lower at 7-day glycation compared to the controls and 21-day glycation (p<0.05). In conclusion, the study found altered mechanical properties at 7 and 14 days of glycation, which then returned to control levels at 21 days, indicating a dynamic relationship between glycation duration and mechanical characteristics that deserves further exploration.

Long-duration type 1 diabetes is associated with deficient cortical bone mechanical behavior and altered matrix composition in human femoral bone.

Type 1 diabetes (T1D) is associated with an increased risk of hip fracture beyond what can be explained by reduced bone mineral density, possibly due to changes in bone material from accumulation of advanced glycation end products (AGEs) and altered matrix composition, though data from human cortical bone in T1D are limited. The objective of this study was to evaluate cortical bone material behavior in T1D by examining specimens from cadaveric femora from older adults with long-duration T1D (≥50years; n= 20) and age- and sex-matched non-diabetic controls (n= 14). Cortical bone was assessed by mechanical testing (4-point bending, cyclic reference point indentation, impact microindentation), AGE quantification (total fluorescent AGEs, pentosidine, carboxymethyl-lysine (CML)), and matrix composition via Raman spectroscopy. Cortical bone from older adults with T1D had diminished post-yield toughness to fracture (-30%, P=.036), elevated levels of AGEs (pentosidine, +17%, P=.039), lower mineral crystallinity (-1.4%, P=.010), greater proline hydroxylation (+1.9%, P=.009), and reduced glycosaminoglycan (GAG) content (-1.3%, P<.03) compared to non-diabetics. In multiple regression models to predict cortical bone toughness, cortical tissue mineral density (Ct.TMD), CML, and Raman spectroscopic measures of enzymatic collagen crosslinks and GAG content remained highly significant predictors of toughness, while diabetic status was no longer significant (adjusted R2> 0.60, P<.001). Thus, impairment of cortical bone to absorb energy following long-duration T1D is well explained by AGE accumulation and modifications to the bone matrix. These results provide novel insight into the pathogenesis of skeletal fragility in individuals with T1D.

Generation of BT-Amide, a Bone-Targeted Pyk2 Inhibitor, Effective via Oral Administration, for the Prevention of Glucocorticoid-Induced Bone Loss.

Glucocorticoid-induced osteoporosis (GIOP) is the leading cause of iatrogenic osteoporosis due to the widespread clinical use of glucocorticoids (GC) as immunosuppressants. Previous research identified the proline-rich tyrosine kinase 2, Pyk2, as a critical mediator of GC-induced bone loss, and that blocking Pyk2 could protect the skeleton from adverse GC actions. However, systemic administration of current Pyk2 inhibitors causes harmful side effects, such as skin lesions. To address this, we developed bone-targeted (BT) Pyk2 inhibitors by conjugating them with bisphosphonates (BP), ensuring adherence to the bone matrix and reducing impact on noncalcified tissues. We synthesized BT-Amide by linking a derivative of TAE-226, a Pyk2 inhibitor, with alendronic acid. Oral administration (gavage) of BT-Amide prevented GC-induced bone loss in mice without causing skin lesions, or elevation of any organ toxicity markers. These findings introduce BT-Amide as the first orally effective bone-targeted Pyk2 inhibitor for preventing GC-induced bone loss while minimizing off-target effects.

Molecular mechanism of bone metastasis in breast cancer.

Bone metastasis is a debilitating complication that frequently occurs in the advanced stages of breast cancer. However, the underlying molecular and cellular mechanisms of the bone metastasis remain unclear. Here, we elucidate how bone metastasis arises from tumor cells that detach from the primary lesions and infiltrate into the surrounding tissue, as well as how these cells disseminate to distant sites. Specifically, we elaborate how tumor cells preferentially grow within the bone micro-environment and interact with bone cells to facilitate bone destruction, characterized as osteoclastic bone metastasis, as well as new bone matrix deposition, characterized as osteoblastic bone metastasis. We also updated the current understanding of the molecular mechanisms underlying bone metastasis and reasons for relapse in breast cancer, and also opportunities of developing novel diagnostic approaches and treatment.