Collagen and non-collagenous proteins molecular crosstalk in the pathophysiology of osteoporosis

Using network pharmacology and molecular docking technology, proteomics and experiments were used to verify the effect of Yigu decoction (YGD) on the expression of key genes in osteoporotic mice

BACKGROUND

Yigu decoction (YGD) is a traditional Chinese medicine prescription for the treatment of osteoporosis, although many clinical studies have confirmed its anti-OP effect, but the specific mechanism is still not completely clear.

METHODS

In this study, through the methods of network pharmacology and molecular docking, the material basis and action target of YGD in preventing and treating OP were analyzed, and the potential target and mechanism of YGD in preventing and treating OP were clarified by TMT quantitative protein and experiment.

RESULTS

Network pharmacology and molecular docking revealed that the active components of YGD were mainly stigmasterol and flavonoids. Molecular docking mainly studied the strong binding ability of stigmasterol to the target. Animal proteomics verified the related mechanism of YGD in preventing and treating OP. Based on the KEGG enrichment of network pharmacology and histology, our animal experiments in vivo verified that YGD may play a role in the treatment of OP by mediating hif1- α/vegf/glut1 signal pathway.

CONCLUSIONS

YGD prevention and treatment of OP may be achieved by interfering with multiple targets. This study confirmed that it may promote osteoblast proliferation and protect osteoblast function by up-regulating the expression of proteins related to HIF signal pathway.

Epimedin B protects against bone loss and inflammation in diabetic osteoporosis rats by regulating OPG/RANKL pathway

BACKGROUND

Diabetes is a common disease contributing to osteoporosis. Epimedin B (EB), a major ingredient of Herba Epimedii, has been found to be effective in preventing osteoporosis in mice. However, the potential of EB to ameliorate diabetic osteoporosis (DOP) remains elusive. In this study, our goal is to investigate the functions and underlying mechanisms of EB in the progression of DOP.

METHODS

A DOP rat model was established via a high-fat diet combined with intraperitoneal injection of streptozotocin (STZ). DOP rats were daily administered with EB or vehicle via intragastric administration for 8 weeks. Body weights and blood glucose levels were measured every 4 weeks during the drug administration period. Blood samples and femoral tissues were collected for further analysis. Bone parameters and bone histopathological changes were detected. Bone formation and resorption markers as well as inflammatory factors were detected using enzyme-linked immunosorbent assay kits. Reverse-transcription quantitative polymerase chain reaction and western blotting were conducted to measure the expression of osteoprotegerin (OPG) and Rev-Erbα, receptor activator of NF-κB ligand (RANKL).

RESULTS

EB improved weight loss and lowered blood glucose of DOP rats. EB promoted the formation of bone trabeculae and altered several bone microstructure parameters in DOP rats. EB ameliorated improved bone structure, restored histological abnormalities of femoral bone, and reduced the number of bone marrow adipocytes in DOP rats. EB inhibited excessive bone resorption and inflammation and increased bone formation in DOP rats. EB regulated the OPG/RANKL axis in DOP rats.

CONCLUSION

EB attenuates STZ-induced DOP in rats by maintaining the balance between bone formation and resorption and inhibiting inflammation through regulating the OPG/RANKL axis.

Anti-cancer potential of chitosan-starch selenium Nanocomposite: Targeting osteoblastoma and insights of molecular docking

Nanotechnology has emerged as a promising approach in the realm of cancer therapy, primarily due its remarkable ability to target tumor cells with a high degree of specificity. In this study, a novel polymeric selenium nanocomposite (CS/S/SeNC) was synthesized using a co-precipitation method, and characterized through UV-vis spectroscopy, FTIR, and XRD to confirms its structural and morphological properties. CS/S/SeNC acts as a potential anti-cancer agent, specifically targeting osteoblastoma cells was evaluated for anti-cancer activity using in-vitro studies MTT assay, Alkaline Phosphatase (ALP) assays, and Alizarin Red Staining to assess cell viability, osteogenic differentiation, and mineralization, respectively. The results revealed that nanocomposite has a strong ability to inhibit cancer cell proliferation in a dose-dependent manner, and induce apoptosis via ROS- mediated mechanism. Molecular docking studies revealed strong interactions between chitosan, a key component of the nanocomposite, and cancer related protein osteocalcin, with a binding affinity of -12.6 kcal/mol. Furthermore, the biocompatibility of CS/S/SeNC was confirmed through its interaction with the endogenous protein Decorin, thereby augmenting its potential as a therapeutic agent for the treatment of bone cancer. These findings suggest that CS/S/SeNC has great potential for targeted cancer therapies.

Relationships among osteoporosis, redox homeostasis, and alcohol addiction: Importance of the brain-bone axis

Overabundance of reactive oxygen species (oxidative distress) leads to redox homeostasis disturbance and is associated with many pathological conditions. Accumulating evidence suggests that oxidative distress may contribute to osteoporosis. This review thoroughly outlines the relationships among osteoporosis, redox homeostasis, and alcohol addiction, since these relations are not sufficiently known and subsequently summarized. The brain-bone axis plays a crucial role in alcohol-induced damage to the nervous and skeletal systems. Alterations in the nervous system can lead to osteoporosis because the central nervous system is involved in bone remodeling through various neural pathways. Conversely, as an endocrine organ, bone secretes a number of bone-derived factors (osteokines), which can influence brain function and behavior. As a result, osteoporosis is more common in individuals with neurological disorders, and sudden neurological events can rapidly increase the risk of osteoporosis. Excessive alcohol consumption is linked to many neurological complications, as well as osteoporosis, which are manifested by disrupted redox homeostasis, inflammation, neurodegeneration, inhibition of neurogenesis, decreased bone mineral density, impaired bone microarchitecture, altered mineral homeostasis, raising fracture risk, hormonal dysregulation, and altered gut microbiota composition. Compared to men, alcohol dependence has more negative consequences for women, including an increased risk of liver, cardiovascular, metabolic, mental disorders, and breast cancer. Abstinence has been demonstrated to improve bone and brain health in alcohol addiction. The discovery of the brain-bone axis may lead to the development of new therapeutic approaches for alcohol and other substance addictions. Further research is needed in this direction, as many questions remain unanswered.

Long-term effects of s-KL treatment in wild-type mice: Enhancing longevity, physical well-being, and neurological resilience

Aging is a major risk factor for pathologies including sarcopenia, osteoporosis, and cognitive decline, which bring suffering, disability, and elevated economic and social costs. Therefore, new therapies are needed to achieve healthy aging. The protein Klotho (KL) has emerged as a promising anti-aging molecule due to its pleiotropic actions modulating insulin, insulin-like growth factor-1, and Wnt signaling pathways and reducing inflammatory and oxidative stress. Here, we explored the anti-aging potential of the secreted isoform of this protein on the non-pathological aging progression of wild-type mice. The delivery of an adeno-associated virus serotype 9 (AAV9) coding for secreted KL (s-KL) efficiently increased the concentration of s-KL in serum, resulting in a 20% increase in lifespan. Notably, KL treatment improved physical fitness, related to a reduction in muscle fibrosis and an increase in muscular regenerative capacity. KL treatment also improved bone microstructural parameters associated with osteoporosis. Finally, s-KL-treated mice exhibited increased cellular markers of adult neurogenesis and immune response, with transcriptomic analysis revealing induced phagocytosis and immune cell activity in the aged hippocampus. These results show the potential of elevating s-KL expression to simultaneously reduce the age-associated degeneration in multiple organs, increasing both life and health span.

Collagen peptides alleviate estrogen deficiency-induced osteoporosis by enhancing osteoblast differentiation and mineralization

BACKGROUND

Osteoporosis is a systemic skeletal disorder characterized by decreased bone mass and impaired bone microarchitecture because of an imbalance between bone resorption and formation. Existing pharmacological treatments often have significant side effects and mainly focus on inhibiting bone resorption. Other than inhibiting osteoclast-mediated bone resorption, the present study also investigates the potential role of sheepskin collagen peptide (SSCP) in bone formation by promoting osteoblast proliferation, differentiation and mineralization.

RESULTS

SSCP improved bone mineral density in ovariectomized mice by improving bone volume, trabecular thickness and trabecular number. Histological analysis and tartrate-resistant acid phosphatase (TRAP) staining revealed denser trabeculae and decreased osteoclast activity, accompanied by a normalized receptor activator of nuclear factor kappa-B ligand/osteoprotegerin ratio and reduced serum TRAP levels. SSCP promotes the proliferation, differentiation and mineralization of MC3T3-E1 osteoblast cells by upregulating osteogenic markers such as bone morphogenetic protein (BMO)-2, runt-related transcription factor (RUNX)-2 and β-catenin. SSCP enhanced bone formation and suppressed bone resorption by activating the WNT/β-catenin and BMP/Smad signaling pathways.

CONCLUSION

SSCP offers a dual modulatory approach to bone health, addressing both bone formation and resorption. Its activation of key osteogenic pathways and improvement in bone structural integrity highlight its therapeutic potential for managing osteoporosis and enhancing skeletal health. By activating key osteogenic pathways and normalizing bone metabolism markers, SSCP presents a promising therapeutic candidate for osteoporosis and other bone-related conditions. Further clinical studies are needed to confirm these findings and explore its potential applications. © 2024 Society of Chemical Industry.

Pym-18a, a novel pyrimidine derivative ameliorates glucocorticoid induced osteoblast apoptosis and promotes osteogenesis via autophagy and PINK 1/Parkin mediated mitophagy induction

Glucocorticoid-induced osteoporosis (GIOP) is the most common type of secondary osteoporosis, marked by reduced bone density and impaired osteoblast function. Current treatments have serious side effects, highlighting the need for new drug candidates. Pyrimidine derivatives have been noted for their potential in suppressing osteoclastogenesis, but their effects on osteogenesis and GIOP remain underexplored. Our recent study identified a novel pyrimidine derivative, Pym-18a, which enhances osteoblast functions. In this study, Pym-18a was found to mitigate the detrimental effects of Dexamethasone (Dex) in osteoblast cells and in GIOP in Balb/C mice. Pretreatment with Pym-18a followed by Dex (100 µM) for 24 h restored osteoblast alkaline phosphatase activity and viability. Pym-18a reduced Dex-induced apoptosis and reactive oxygen species (ROS) generation at cellular and mitochondrial levels and preserved mitochondrial membrane potential. Dex impaired autophagy and mitophagy, however but Pym-18a pretreatment increased expression of autophagy markers (LC3II) and mitophagy markers (PINK1, Parkin, TOM20) while decreasing P62 expression. The osteogenic effects of Pym-18a were diminished in the presence of 3-MA (an autophagy inhibitor). In silico studies showed mTOR inhibition by Pym-18a, corroborated by its suppression of Dex-induced mTOR activation. In vivo, Pym-18a (10 mg/kg) significantly improved bone microarchitecture, trabecular connectivity, and strength, and corrected P1NP and CTX levels altered by Dex. Pym-18a also promoted autophagy, mitophagy, and suppressed mTOR activation in GIOP mice. Overall, Pym-18a mitigates detrimental effect of Dex by modulating autophagy and PINK/Parkin-mediated mitophagy through mTOR inhibition, suggesting it as a potential novel therapeutic option for GIOP.

Impact of cathepsin K-induced proteoglycans degradation on dentin collagen

OBJECTIVES

This study aimed to investigate the effects of cathepsin K (catK) on proteoglycans (PGs) and the subsequent impacts on dentin collagen degradation.

MATERIALS AND METHODS

Demineralized dentin samples were prepared and divided into the following groups: deionized water (DW), 0.1 U/mL chondroitinase ABC (C-ABC), and 1 μM odanacatib (ODN). Then, they were immersed for 48 h and then incubated in 1 mL of PBS (pH=5.5) at 37 °C for 5 d. Glycosaminoglycan (GAG) were examined to explore the degradation of PGs by catK. To determine the effect of catK-mediated PGs on dentin collagen degradation, hydroxyproline (HYP) assays, assessment of the degree of dentin crosslinking, and scanning electron microscopy (SEM) were assessed. Statistical analysis was conducted using one-way ANOVA followed by Tukey's tests or Welch's ANOVA followed by Dunnett's tests at a significance level of 0.05.

RESULTS

The production of GAG was significantly lower in the ODN group than in the DW group (P < 0.05), revealing that PG degradation was reduced in dentin after ODN treatment. Additionally, ODN treatment minimized the gaps in collagen fibers, improved fiber arrangement, and significantly increased the degree of collagen crosslinking, subsequently reducing the total amount of collagen fiber degradation in the dentin (P < 0.05).

CONCLUSIONS

CatK-mediated degradation of PGs negatively impacted the stability of collagen fibers, promoted gaps, led to a less organized arrangement of dentin collagen fibers, ultimately increasing collagen degradation.

Endothelial BMAL1 decline during aging leads to bone loss by destabilizing extracellular fibrillin-1

The occurrence of aging is intricately associated with alterations in circadian rhythms that coincide with stem cell exhaustion. Nonetheless, the extent to which the circadian system governs skeletal aging remains inadequately understood. Here, we noticed that skeletal aging in male mice was accompanied by a decline in a core circadian protein, BMAL1, especially in bone marrow endothelial cells (ECs). Using male mice with endothelial KO of aryl hydrocarbon receptor nuclear translocator-like protein 1 (Bmal1), we ascertained that endothelial BMAL1 in bone played a crucial role in ensuring the stability of an extracellular structural component, fibrillin-1 (FBN1), through regulation of the equilibrium between the extracellular matrix (ECM) proteases thrombospondin type 1 domain-containing protein 4 (THSD4) and metalloproteinase with thrombospondin motifs 4 (ADAMTS4), which promote FBN1 assembly and breakdown, respectively. The decline of endothelial BMAL1 during aging prompted excessive breakdown of FBN1, leading to persistent activation of TGF-β/SMAD3 signaling and exhaustion of bone marrow mesenchymal stem cells. Meanwhile, the free TGF-β could promote osteoclast formation. Further analysis revealed that activation of ADAMTS4 in ECs lacking BMAL1 was stimulated by TGF-β/SMAD3 signaling through an ECM-positive feedback mechanism, whereas THSD4 was under direct transcriptional control by endothelial BMAL1. Our investigation has elucidated the etiology of bone aging in male mice by defining the role of ECs in upholding the equilibrium within the ECM, consequently coordinating osteogenic and osteoclastic activities and retarding skeletal aging.

The Influence of Juglans regia L. Extract and Ellagic Acid on Oxidative Stress, Inflammation, and Bone Regeneration Biomarkers

Bone regeneration is a highly dynamic and complex process that involves hematopoietic stem cells and mesenchymal cells, collagen fibers, non-collagenous proteins and biomolecules from extracellular matrices, and different cytokines and immune cells, as well as growth factors and hormones. Some phytochemicals due to antioxidant and anti-inflammatory effects can modulate the bone signaling pathways and improve bone healing and thus can be a good candidate for osteoregeneration. The aim of this study was to analyze the impact of Juglans regia L. extract compared to ellagic acid on bone neoformation in rats. The animals with a 5 mm calvaria defect were divided into four groups (n = 10): group 1 was treated with ellagic acid 1% (EA), group 2 was treated with Juglans regia L. extract 10% (JR), group 3 was treated with a biphasic mix of hydroxyapatite and tricalcium phosphate (Ceraform), and group 4 was treated with vehicle inert gel with carboxymethylcellulose (CMC). After 3 weeks of treatment, blood samples were collected for oxidative stress and inflammation assessment. Additionally, the receptor activator of nuclear factor kappa-Β ligand (RANKL) and hydroxyproline levels were quantified in blood. The skull samples were analyzed by scanning electron microscopy in order to detect the modifications in the four groups. The results suggested that JR extract had relevant anti-oxidant effect and bone protective activity and generated the accumulation of Ca and P, demonstrating the potential therapeutic abilities in bone regeneration.

Recent development and applications of electrodeposition biocoatings on medical titanium for bone repair

Bioactive coatings play a crucial role in enhancing the osseointegration of titanium implants for bone repair. Electrodeposition offers a versatile and efficient technique to deposit uniform coatings onto titanium surfaces, endowing implants with antibacterial properties, controlled drug release, enhanced osteoblast adhesion, and even smart responsiveness. This review summarizes the recent advancements in bioactive coatings for titanium implants used in bone repair, focusing on various electrodeposition strategies based on material-structure synergy. Firstly, it outlines different titanium implant materials and bioactive coating materials suitable for bone repair. Then, it introduces various electrodeposition methods, including electrophoretic deposition, anodization, micro-arc oxidation, electrochemical etching, electrochemical polymerization, and electrochemical deposition, discussing their applications in antibacterial, osteogenic, drug delivery, and smart responsiveness. Finally, it discusses the challenges encountered in the electrodeposition of coatings for titanium implants in bone repair and potential solutions.

Europium-Containing Nanospheres for Treating Ovariectomy-Induced Osteoporosis: Targeted Bone Remodeling and Macrophage Polarization Modulation

Purpose

Osteoporosis, characterized by reduced bone mass and structural deterioration, poses a significant healthcare challenge. Traditional treatments, while effective in reducing fracture risks, are often limited by side effects. This study introduces a novel nanocomplex, europium (Eu) ions-doped superparamagnetic iron oxide (SPIO) nanocrystals encapsulated in poly(lactic-co-glycolic acid) (PLGA) nanospheres, abbreviated as SPIO:Eu@PLGA nanospheres, as a potential therapeutic agent for osteoporosis by modulating macrophage polarization, enhancing osteoblast differentiation and inhibiting osteoclastogenesis.

Methods

SPIO and SPIO:Eu nanocrystals were synthesized through pyrolysis and encapsulated in PLGA using an emulsification method. To evaluate the impact of SPIO:Eu@PLGA nanospheres on macrophage reprogramming and reactive oxygen species (ROS) production, flow cytometry analysis was conducted. Furthermore, an ovariectomized (OVX) rat model was employed to assess the therapeutic efficacy of SPIO:Eu@PLGA nanospheres in preventing the deterioration of osteoporosis.

Results

In vitro, SPIO:Eu@PLGA nanospheres significantly attenuated M1 macrophage activation induced by lipopolysaccharides, promoting a shift towards the M2 phenotype. This action is linked to the modulation of ROS and the NF-κB pathway. Unlike free Eu ions, which do not achieve similar results when not incorporated into the SPIO nanocrystals. SPIO:Eu@PLGA nanospheres enhanced osteoblast differentiation and matrix mineralization while inhibiting RANKL-induced osteoclastogenesis. In vivo studies demonstrated that SPIO:Eu@PLGA nanospheres effectively targeted trabecular bone surfaces in OVX rats under magnetic guidance, preserving their structure and repairing trabecular bone loss by modulating macrophage polarization, thus restoring bone remodeling homeostasis. The study underscores the critical role of Eu doping in boosting the anti-osteoporotic effects of SPIO:Eu@PLGA nanospheres, evident at both cellular and tissue levels in vitro and in vivo.

Conclusion

The inclusion of Eu into SPIO matrix suggests a novel approach for developing more effective osteoporosis treatments, particularly for conditions induced by OVX. This research provides essential insights into SPIO:Eu@PLGA nanospheres as an innovative osteoporosis treatment, addressing the limitations of conventional therapies through targeted delivery and macrophage polarization modulation.

Osteogenic Induction and Anti-Inflammatory Effects of Calcium-Chlorogenic Acid Nanoparticles Remodel the Osteoimmunology Microenvironment for Accelerating Bone Repair

Successful bone regeneration requires close cooperation between bone marrow mesenchymal stem cells (BMSCs) and macrophages, but the low osteogenic differentiation efficiency of stem cells and the excessive inflammatory response of immune cells hinder the development of bone repair. It is necessary to develop a strategy that simultaneously regulates the osteogenic differentiation of BMSCs and the anti-inflammatory polarization of macrophages for accelerating the bone regeneration. Herein, calcium-chlorogenic acid nanoparticles (Ca-CGA NPs) are synthesized by combining the small molecules of chlorogenic acid (CGA) with Ca2+. Ca-CGA NPs internalized by cells can be dissolved to release free CGA and Ca2+ under low pH conditions in lysosomes. In vitro results demonstrate that Ca-CGA NPs can not only enhance the osteogenic differentiation of BMSCs but also promote the phenotype transformation of macrophages from M1 to M2. Furthermore, in vivo experiments confirm that Ca-CGA NPs treatment facilitates the recovery of rat skull defect model through both osteoinduction and immunomodulation. This study develops a new Ca-CGA NPs-based strategy to induce the differentiation of BMSCs into osteoblasts and the polarization of macrophages into M2 phenotype, which is promising for accelerating bone repair.

Investigating the Role of Amino Acids in Short Peptides for Hydroxyapatite Binding and Osteogenic Differentiation of Mesenchymal Stem Cells to Aid Bone Regeneration

Bone defects show a slow rate of osteoconduction and imperfect reconstruction, and the current treatment strategies to treat bone defects suffer from limitations like immunogenicity, lack of cell adhesion, and the absence of osteogenic activity. In this context, bioactive supramolecular peptides and peptide gels offer unique opportunities to develop biomaterials that can play a dominant role in the biomineralization of bone tissues and promote bone formation. In this article, we have demonstrated the potential of six tetrapeptides for specific binding to hydroxyapatite (HAp), a major inorganic component of the bone, and their effect on the growth and osteogenic differentiation of mesenchymal stem cells (MSCs). We adopted a simplistic approach of rationally designing amphiphilic peptides by incorporating amino acids, Ser, pSer, Pro, Hyp, Asp, and Glu, which are present in either collagenous or noncollagenous proteins and render properties like antioxidant, calcification, and mineralization. A total of six tetrapeptides, Trp-Trp-His-Ser (WWHS), Trp-Trp-His-pSer (WWHJ), Trp-Trp-His-Pro (WWHP), Trp-Trp-His-Hyp (WWHO), Trp-Trp-His-Asp (WWHD), and Trp-Trp-His-Glu (WWHE), were synthesized. Four peptides were found to self-assemble into nanofibrillar gels resembling the extracellular matrix (ECM), and the remaining two peptides (WWHJ, WWHP) self-assembled into nanorods. The peptides showed excellent cell adhesion, encapsulation, proliferation, and migration and induced the differentiation of mesenchymal stem cells (MSCs), as evident from the enhanced mineralization, resulting from the upregulation of osteogenic markers, RUNX 2, COL I, OPN, and OCN, alkaline phosphatase (ALP) production, and calcium deposition. The peptides also induced the downregulation of inflammatory markers, TNF-α and iNOS, and the upregulation of the anti-inflammatory marker, IL-10, resulting in M2 macrophage polarization. RANKL and TRAP genes were downregulated in a coculture system of MC3T3-E1 and RAW 264.7 cells, implying that peptides promote osteogenesis and inhibit osteoclastogenesis. The peptide-based biomaterials developed in this work can enhance bone regeneration capacity and show strong potential as scaffolds for bone tissue engineering.

Dual cross-linked COL1/HAp bionic gradient scaffolds containing human amniotic mesenchymal stem cells promote rotator cuff tendon-bone interface healing

The tendon-bone interface heals through scar tissue, while the lack of a natural interface gradient structure and collagen fibre alignment leads to the occurrence of retearing. Therefore, the promotion of tendon healing has become the focus of regenerative medicine. The purpose of this study was to develop a gradient COL1/ hydroxyapatite (HAp) biomaterial loaded with human amniotic mesenchymal stem cells (hAMSCs). The performance of common cross-linking agents, Genipin, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide (EDC/NHS), and dual cross-linked materials were compared to select the best cross-linking mechanism to optimize the biological and mechanical properties of the scaffold. The optimal COL1/HAp-loaded with hAMSCs were implanted into the tendon-bone rotator cuff interfaces in rats and the effect on the tendon-bone healing was assessed by micro-CT, histological analysis, and biomechanical properties. The results showed that Genipin and EDC/NHS dual cross-linked COL1/HAp had good biological activity and mechanical properties and promoted the proliferation and differentiation of hAMSCs. Animal experiments showed that the group using a scaffold loaded with hAMSCs had excellent continuity and orientation of collagen fibers, increased fibrocartilage and bone formation, and significantly higher biomechanical functions than the control group at the interface at 12 weeks post operation. This study demonstrated that dual cross-linked gradient COL1/HAp-loaded hAMSCs could promote interface healing, thereby providing a feasible strategy for tendon-bone interface regeneration.

Insights and implications of sexual dimorphism in osteoporosis

Osteoporosis, a metabolic bone disease characterized by low bone mineral density and deterioration of bone microarchitecture, has led to a high risk of fatal osteoporotic fractures worldwide. Accumulating evidence has revealed that sexual dimorphism is a notable feature of osteoporosis, with sex-specific differences in epidemiology and pathogenesis. Specifically, females are more susceptible than males to osteoporosis, while males are more prone to disability or death from the disease. To date, sex chromosome abnormalities and steroid hormones have been proven to contribute greatly to sexual dimorphism in osteoporosis by regulating the functions of bone cells. Understanding the sex-specific differences in osteoporosis and its related complications is essential for improving treatment strategies tailored to women and men. This literature review focuses on the mechanisms underlying sexual dimorphism in osteoporosis, mainly in a population of aging patients, chronic glucocorticoid administration, and diabetes. Moreover, we highlight the implications of sexual dimorphism for developing therapeutics and preventive strategies and screening approaches tailored to women and men. Additionally, the challenges in translating bench research to bedside treatments and future directions to overcome these obstacles will be discussed.

Regulation of Immune Inflammation and Promotion of Periodontal Bone Regeneration by Irisin-Loaded Bioactive Glass Nanoparticles

Clinical solutions of bone defects caused by periodontitis involve surgical treatment and subsequent anti-infection treatment using antibiotics. Such a strategy faces a key challenge in that the excessive host immune response results in the damage of periodontal tissues. Consequently, it is of great importance to develop novel periodontitis treatment that allows the regulation of the host immune response and promotes the generation of periodontal tissues. Irisin has a good bone regeneration ability and could reduce the inflammatory reaction by regulating the differentiation of macrophages. In this study, we loaded irisin onto bioactive glass nanoparticles (BGNs) to prepare a composite, irisin-BGNs (IR-BGNs) with anti-inflammatory, bacteriostatic, and tissue regeneration functions, providing a novel idea for the design of ideal materials for repairing oral tissue defects caused by periodontitis. We also verified that the IR-BGNs had better anti-inflammatory properties on RAW264.7 cells compared to irisin and BGNs alone. Strikingly, when hPDLCs were stimulated with IR-BGNs, they exhibited increased expression of markers linked to osteogenesis, ALP activity, and mineralization ability in comparison to the negative control. Furthermore, on the basis of RNA sequencing results, we validated that the p38 pathway can contribute to the osteogenic differentiation of the IR-BGNs. This work may offer new thoughts on the design of ideal materials for repairing oral tissue defects.

OSTEO18, a novel urinary proteomic signature, associated with osteoporosis in heart transplant recipients

Background

Immunosuppressive treatment in heart transplant (HTx) recipient causes osteoporosis. The urinary proteomic profile (UPP) includes peptide fragments derived from the bone extracellular matrix. Study aims were to develop and validate a multidimensional UPP biomarker for osteoporosis in HTx patients from single sequenced urinary peptides identifying the parent proteins.

Methods

A single-center HTx cohort was analyzed. Urine samples were measured by capillary electrophoresis coupled with mass spectrometry. Cases with osteoporosis and matching controls were randomly selected from all available 389 patients. In derivation case-control dataset, 1576 sequenced peptides detectable in ≥30 % of patients. Applying statistical analysis on these, an 18-peptide multidimensional osteoporosis UPP biomarker (OSTEO18) was generated by support vector modeling. The 2 replication datasets included 118 and 94 patients. For further validation, the whole cohort was analyzed. Statistical methods included logistic regression and receiver operating characteristic curve (ROC) analysis.

Results

In derivation dataset, the AUC, sensitivity and specificity of OSTEO18 were 0.83 (95 % CI: 0.76-0.90), 74.3 % and 87.1 %, respectively. In replication datasets, results were confirmatory. In the whole cohort (154 osteoporotic patients [39.6 %]), the ORs for osteoporosis increased (p < 0.0001) across OSTEO18 quartiles from 0.39 (95 % CI: 0.25-0.61) to 3.14 (2.08-4.75). With full adjustment for known osteoporosis risk factors, OSTEO18 improved AUC from 0.708 to 0.786 (p = 0.0003) for OSTEO18 categorized (optimized threshold: 0.095) and to 0.784 (p = 0.0004) for OSTEO18 as continuously distributed classifier.

Conclusion

OSTEO18 is a clinically meaningful novel biomarker indicative of osteoporosis in HTx recipients and is being certified as in-vitro diagnostic.

NOVEL HIGH-STRENGTH POLYESTER COMPOSITE SCAFFOLDS FOR BONE REGENERATION

Repair of critical sized bone defects, particularly in load-bearing areas, is a major clinical problem that requires surgical intervention and implantation of biological or engineered grafts. For load-bearing sites, it is essential to use engineered grafts that have both sufficient mechanical strength and appropriate pore properties to support bone repair and tissue regeneration. Unfortunately, the mechanical properties of such grafts are often compromised due to the creation of pores required to facilitate tissue ingrowth following implantation. To overcome the limitations associated with porous scaffolds and their reduced mechanical strength, we have developed a methodology for creating a solid structure that retains its bulk mechanical properties while also evolving into a porous structure in a biological environment through degradation and erosion. In this study, we utilized polyesters that have been approved by the FDA, including poly (lactic acid) (PLA), poly(glycolic acid) (PGA), their copolymer PLGA (PLGA, with a ratio of 85:15 and 50:50 of PLA:PGA), and poly(caprolactone) (PCL). These polymers and their ceramic composites with tricalcium phosphate (TCP) were compression molded into solid forms, which exhibited mechanical properties with compressive modulus as high as 2745 ± 364 MPa within the range of human trabecular bone and in the lower range of human cortical bone. The use of fast-degrading PLGA (50:50) and PGA as porogens allowed the formation of pores within the solid structures due to their degradation, and the TCP acts as a buffering agent to neutralize their acidic degradation byproducts. These scaffolds facilitated the growth of new blood vessels and tissue ingrowth in a subcutaneous implantation model. In addition, in a rat critical-sized mandibular bone defects these scaffolds supported bone growth with 70% of new bone volume fraction. Furthermore, the extent of bone regeneration was found to be higher for the scaffolds with bone morphogenic proteins (BMP2), indicating their suitability for bone repair and regeneration.

Additional Insights Into the Role of Osteocalcin in Osteoblast Differentiation and in the Early Steps of Developing Alveolar Process of Rat Molars

This study investigated whether osteocalcin (OCN) is present in osteoblast precursors and its relationship with initial phases of alveolar process formation. Samples of maxillae of 16-, 18-, and 20-day-old rat embryos (E16, E18, and E20, respectively), and 05-, 10-, and 15-day-old postnatal rats (P05, P10, and P15, respectively) were fixed and embedded in paraffin or araldite. Immunohistochemistry for osterix (Osx), alkaline phosphatase (ALP), and OCN detection was performed and the number of immunolabelled cells was computed. Non-decalcified sections were subjected to the von Kossa method combined with immunohistochemistry for Osx or OCN detection. For OCN immunolocalization, samples were fixed in 0.5% glutaraldehyde/2% formaldehyde and embedded in LR White resin. The highest number of ALP- and OCN-immunolabelled cells was observed in dental follicle of E16 specimens, mainly in basal portions of dental alveolus. In corresponding regions, osteoblasts in differentiation adjacent to von Kossa-positive bone matrix exhibited Osx and OCN immunoreactivity. Ultrastructural analysis revealed OCN immunoreactive particles inside osteoblast in differentiation, and in bone matrix associated with collagen fibrils and within matrix vesicles, at early stages of alveolar process formation. Our results indicate that OCN plays a role in osteoblast differentiation and may regulate calcium/phosphate precipitation during early mineralization of the alveolar process.

The mechanism of biomineralization: Progress in mineralization from intracellular generation to extracellular deposition

Biomineralization is a highly regulated process that results in the deposition of minerals in a precise manner, ultimately producing skeletal and dental hard tissues. Recent studies have highlighted the crucial role played by intracellular processes in initiating biomineralization. These processes involve various organelles, such as the endoplasmic reticulum(ER), mitochondria, and lysosomes, in the formation, accumulation, maturation, and secretion of calcium phosphate (CaP) particles. Particularly, the recent in-depth study of the dynamic process of the formation of amorphous calcium phosphate(ACP) precursors among organelles has made great progress in the development of the integrity of the biomineralization chain. However, the precise mechanisms underlying these intracellular processes remain unclear, and they cannot be fully integrated with the extracellular mineralization mechanism and the physicochemical structure development of the mineralization particles. In this review, we aim to focus on the recent progress made in understanding intracellular mineralization organelles' processes and their relationship with the physicochemical structure development of CaP and extracellular deposition of CaP particles.

Metabolomics analysis of the potential mechanism of Yi-Guan-Jian decoction to reverse bone loss in glucocorticoid-induced osteoporosis

BACKGROUND

Glucocorticoid-induced osteoporosis (GIOP) is a disease in which long-term use of glucocorticoid causes bone loss, deterioration of bone microstructure and fracture. Currently, clinical drugs targeting this disease have certain side effects. There is still a need to find effective drugs with fewer side effects. The theory of traditional Chinese medicine suggests that YGJ has therapeutic effect on GIOP, but it has not been explained. Therefore, this study aims to explore the protective effect of YGJ on GIOP mouse models and elucidate the underlying mechanism through LC-MS-based metabolomics analysis.

METHODS

The general condition of 8 week age male C57BL/6J mice was recorded after 8 weeks of treatment with dexamethasone (DEX) and YGJ. Bone-related parameters and bone morphology were determined by Micro-CT. HE staining was used to observe the pathological changes of bone tissue. Serum levels of bone metabolism markers were detected by ELISA. Liver metabolomics analysis was conducted to search for the significant markers of anti-GIOP of YGJ and the metabolic pathway affecting it.

RESULTS

After treatment, YGJ significantly reversed the weight loss caused by DEX; increase the number of bone trabecular in ROI region, significantly improve the bone-related parameters of GIOP mice, and increase the levels of alkaline phosphatase and osteocalcin. In the study of metabolic mechanism, YGJ reversed 24 potential markers in GIOP mice. These included cortisol, 3-hydroxybutyric acid, taurine, esculin and uric acid, which are closely associated with osteoporosis. Topological analysis results showed that YGJ had the most significant effect on taurine and hypotaurine metabolism, with - log10 (P) > 2.0 and Impact > 0.4.

CONCLUSIONS

Yi-Guan-Jian decoction can increase bone density and improve bone microstructure by regulating the levels of alkaline phosphatase and osteocalcin and reverse bone loss in GIOP mouse model. The underlying metabolic mechanism may be related to taurine and hypotaurine metabolic pathway.

β-TCP/S53P4 Scaffolds Obtained by Gel Casting: Synthesis, Properties, and Biomedical Applications

The objective of this study was to investigate the osteogenic and antimicrobial effect of bioactive glass S53P4 incorporated into β-tricalcium phosphate (β-TCP) scaffolds in vitro and the bone neoformation in vivo. β-TCP and β-TCP/S53P4 scaffolds were prepared by the gel casting method. Samples were morphologically and physically characterized through X-ray diffraction (XRD) and scanning electron microscope (SEM). In vitro tests were performed using MG63 cells. American Type Culture Collection reference strains were used to determine the scaffold's antimicrobial potential. Defects were created in the tibia of New Zealand rabbits and filled with experimental scaffolds. The incorporation of S53P4 bioglass promotes significant changes in the crystalline phases formed and in the morphology of the surface of the scaffolds. The β-TCP/S53P4 scaffolds did not demonstrate an in vitro cytotoxic effect, presented similar alkaline phosphatase activity, and induced a significantly higher protein amount when compared to β-TCP. The expression of Itg β1 in the β-TCP scaffold was higher than in the β-TCP/S53P4, and there was higher expression of Col-1 in the β-TCP/S53P4 group. Higher bone formation and antimicrobial activity were observed in the β-TCP/S53P4 group. The results confirm the osteogenic capacity of β-TCP ceramics and suggest that, after bioactive glass S53P4 incorporation, it can prevent microbial infections, demonstrating to be an excellent biomaterial for application in bone tissue engineering.

Extraction, Characterization and Osteogenic Activity of a Type I Collagen from Starfish (Asterias amurensis)

Outbreaks of starfish (Asterias amurensis) pose a major threat to aquaculture and marine ecosystems in Qingdao, China, and no effective methods have been found to control them. A comprehensive study of collagen in starfish could be an alternative to high efficient utilization. Based on this, collagen was firstly extracted from Qingdao A. amurensis. Then, its protein pattern, amino acid composition, secondary structure, microstructure and thermal stability were investigated. The results showed that the A. amurensis collagen (AAC) is a type I collagen composed of α₁, α₂, and β chains. Glycine, hydroxyproline, and alanine were the major amino acids. The melting temperature was 57.7 °C. From FTIR, UV spectra and CD chromatography, the AAC had an intact triple helix and secondary structure, and microstructural analysis showed that the AAC had a loose, fibrous porous structure. Next, the osteogenic differentiation effect of AAC on Mouse bone marrow stem cells (BMSCs) was investigated, and the results showed that AAC induced osteogenic differentiation of cells by promoting the proliferation of BMSCs, enhancing alkaline phosphatase (ALP) activity, promoting cell mineralization nodules and upregulating the expression of mRNA of relevant osteogenic genes. These results suggest that AAC might have the potential application to bone health-related functional foods.

Hormone-Related and Drug-Induced Osteoporosis: A Cellular and Molecular Overview

Osteoporosis resulting from an imbalance of bone turnover between resorption and formation is a critical health issue worldwide. Estrogen deficiency following a nature aging process is the leading cause of hormone-related osteoporosis for postmenopausal women, while glucocorticoid-induced osteoporosis remains the most common in drug-induced osteoporosis. Other medications and medical conditions related to secondary osteoporosis include proton pump inhibitors, hypogonadism, selective serotonin receptor inhibitors, chemotherapies, and medroxyprogesterone acetate. This review is a summary of the cellular and molecular mechanisms of bone turnover, the pathophysiology of osteoporosis, and their treatment. Nuclear factor-κβ ligand (RANKL) appears to be the critical uncoupling factor that enhances osteoclastogenesis. In contrast, osteoprotegerin (OPG) is a RANKL antagonist secreted by osteoblast lineage cells. Estrogen promotes apoptosis of osteoclasts and inhibits osteoclastogenesis by stimulating the production of OPG and reducing osteoclast differentiation after suppression of IL-1 and TNF, and subsequent M-CSF, RANKL, and IL-6 release. It can also activate the Wnt signaling pathway to increase osteogenesis, and upregulate BMP signaling to promote mesenchymal stem cell differentiation from pre-osteoblasts to osteoblasts rather than adipocytes. Estrogen deficiency leads to the uncoupling of bone resorption and formation; therefore, resulting in greater bone loss. Excessive glucocorticoids increase PPAR-2 production, upregulate the expression of Dickkopf-1 (DKK1) in osteoblasts, and inhibit the Wnt signaling pathway, thus decreasing osteoblast differentiation. They promote osteoclast survival by enhancing RANKL expression and inhibiting OPG expression. Appropriate estrogen supplement and avoiding excessive glucocorticoid use are deemed the primary treatment for hormone-related and glucocorticoid-induced osteoporosis. Additionally, current pharmacological treatment includes bisphosphonates, teriparatide (PTH), and RANKL inhibitors (such as denosumab). However, many detailed cellular and molecular mechanisms underlying osteoporosis seem complicated and unexplored and warrant further investigation.

The influence on surface characteristic and biocompatibility of nano-SnO2-modified titanium implant material using atomic layer deposition technique

BACKGROUND/PURPOSE

To investigate the surface characteristics of titanium (Ti) implant materials, which were coated with different thicknesses of nanoscale tin oxide (SnO₂) using the atomic layer deposition technique, and evaluated its biological performance on human embryonic palatal mesenchyme (HEPM) cells.

METHODS

The thickness of the coating layer on Ti was 0 (Ti0), 20 nm (Ti20), 50 nm (Ti50), and 100 nm (Ti100), respectively. The surface morphology was observed with an SEM and AFM. The root mean square roughness of micron-scale (mRq) and nanoroughness (nRq) of Ti discs' surface were measured. The Alamar blue (AB) assay and F-actin fluorescence staining were used to evaluate the biocompatibility, and the osteocalcin (OCN) was measured to clarify the differentiation of HEPM cells on materials.

RESULTS

In the coating groups, the mRq was decreased, but the nRq was increased. The spreading and polygonal morphology of HEPMs was apparent in coating groups. On Day 4, the survival rate of HEPM cells on Ti0 was higher than on Ti20 and Ti50. There was no significant difference on Day 7, Day 10, and Day 14. The OCN was significantly higher on Day 14 in all the coating groups than Ti0.

CONCLUSION

The results showed that the cell growth was intensified with rough surfaces. However, the OCN and morphology change was prominent when the nanoroughness was increased, which meant the increased nanoroughness might enhance OCN production and improve the tendency of osseointegration. The nanoscale SnO₂ coating could increase the ability of bone formation but not cell growth.

Oxidative Stress and Inflammation in Osteoporosis: Molecular Mechanisms Involved and the Relationship with microRNAs

Osteoporosis is characterized by the alteration of bone homeostasis due to an imbalance between osteoclastic bone resorption and osteoblastic bone formation. Estrogen deficiency causes bone loss and postmenopausal osteoporosis, the pathogenesis of which also involves oxidative stress, inflammatory processes, and the dysregulation of the expression of microRNAs (miRNAs) that control gene expression at post-transcriptional levels. Oxidative stress, due to an increase in reactive oxygen species (ROS), proinflammatory mediators and altered levels of miRNAs enhance osteoclastogenesis and reduce osteoblastogenesis through mechanisms involving the activation of MAPK and transcription factors. The present review summarizes the principal molecular mechanisms involved in the role of ROS and proinflammatory cytokines on osteoporosis. Moreover, it highlights the interplay among altered miRNA levels, oxidative stress, and an inflammatory state. In fact, ROS, by activating the transcriptional factors, can affect miRNA expression, and miRNAs can regulate ROS production and inflammatory processes. Therefore, the present review should help in identifying targets for the development of new therapeutic approaches to osteoporotic treatment and improve the quality of life of patients.

Advances in biomimetic collagen mineralisation and future approaches to bone tissue engineering

With an ageing world population and ~20% of adults in Europe being affected by bone diseases, there is an urgent need to develop advanced regenerative approaches and biomaterials capable to facilitate tissue regeneration while providing an adequate microenvironment for cells to thrive. As the main components of bone are collagen and apatite mineral, scientists in the tissue engineering field have attempted in combining these materials by using different biomimetic approaches to favour bone repair. Still, an ideal bone analogue capable of mimicking the distinct properties (i.e., mechanical properties, degradation rate, porosity, etc.) of cancellous bone is to be developed. This review seeks to sum up the current understanding of bone tissue mineralisation and structure while providing a critical outlook on the existing biomimetic strategies of mineralising collagen for bone tissue engineering applications, highlighting where gaps in knowledge exist.

Osteogenic differentiation and proliferation potentials of human bone marrow and umbilical cord-derived mesenchymal stem cells on the 3D-printed hydroxyapatite scaffolds

Mesenchymal stem cells (MSCs) are a promising candidate for bone repair. However, the maintenance of MSCs injected into the bone injury site remains inefficient. A potential approach is to develop a bone-liked platform that incorporates MSCs into a biocompatible 3D scaffold to facilitate bone grafting into the desired location. Bone tissue engineering is a multistep process that requires optimizing several variables, including the source of cells, osteogenic stimulation factors, and scaffold properties. This study aims to evaluate the proliferation and osteogenic differentiation potentials of MSCs cultured on 2 types of 3D-printed hydroxyapatite, including a 3D-printed HA and biomimetic calcium phosphate-coated 3D-printed HA. MSCs from bone marrow (BM-MSCs) and umbilical cord (UC-MSCs) were cultured on the 3D-printed HA and coated 3D-printed HA. Scanning electron microscopy and immunofluorescence staining were used to examine the characteristics and the attachment of MSCs to the scaffolds. Additionally, the cell proliferation was monitored, and the ability of cells to differentiate into osteoblast was assessed using alkaline phosphatase (ALP) activity and osteogenic gene expression. The BM-MSCs and UC-MSCs attached to a plastic culture plate with a spindle-shaped morphology exhibited an immunophenotype consistent with the characteristics of MSCs. Both MSC types could attach and survive on the 3D-printed HA and coated 3D-printed HA scaffolds. The MSCs cultured on these scaffolds displayed sufficient osteoblastic differentiation capacity, as evidenced by increased ALP activity and the expression of osteogenic genes and proteins compared to the control. Interestingly, MSCs grown on coated 3D-printed HA exhibited a higher ALP activity and osteogenic gene expression than those cultured on the 3D-printed HA. The finding indicated that BM-MSCs and UC-MSCs cultured on the 3D-printed HA and coated 3D-printed HA scaffolds could proliferate and differentiate into osteoblasts. Thus, the HA scaffolds could provide a suitable and favorable environment for the 3D culture of MSCs in bone tissue engineering. Additionally, biomimetic coating with octacalcium phosphate may improve the biocompatibility of the bone regeneration scaffold.

Bone fragility: conceptual framework, therapeutic implications, and COVID-19-related issues

Bone fragility is the susceptibility to fracture even for common loads because of structural, architectural, or material alterations of bone tissue that result in poor bone strength. In osteoporosis, quantitative and qualitative changes in density, geometry, and micro-architecture modify the internal stress state predisposing to fragility fractures. Bone fragility substantially depends on the structural behavior related to the size and shape of the bone characterized by different responses in the load-deformation curve and on the material behavior that reflects the intrinsic material properties of the bone itself, such as yield and fatigue. From a clinical perspective, the measurement of bone density by DXA remains the gold standard for defining the risk of fragility fracture in all population groups. However, non-quantitative parameters, such as macro-architecture, geometry, tissue material properties, and microcracks accumulation can modify the bone's mechanical strength. This review provides an overview of the role of different contributors to bone fragility and how these factors might be influenced by the use of anti-osteoporotic drugs and by the COVID-19 pandemic.

Estradiol and zinc-doped nano hydroxyapatite as therapeutic agents in the prevention of osteoporosis; oxidative stress status, inflammation, bone turnover, bone mineral density, and histological alterations in ovariectomized rats

Osteoporosis (OP) is a serious health problem, and the most popular therapeutic strategy for OP is hormone replacement (estrogen); however, it increases the risk of reproductive cancers. Hydroxyapatite (HA) nanoparticles have a similar chemical structure to the bone mineral component and can be used as a new remedy for OP. This study was designed to investigate the osteoporosis-protective potential of nano zinc hydroxyapatite (ZnHA-NPs) and/or estradiol (E2) combined therapy. A total of 35 adult female rats were assigned into five groups (n = 7): 1) control group; 2) ovariectomized group (OVX); 3) OVX received oral estradiol replacement therapy (OVX/E2); 4) OVX received ZnHA replacement therapy (OVX/ZnHA); and 5) OVX received both estradiol and ZnHA-NPs combined therapy (OVX/E2+ZnHA). After 3 months of treatment, serum bone markers and estrogen level, oxidative/antioxidant, and inflammatory cytokines were determined. Additionally, femoral expression of estrogen receptors alpha and beta (ESR1; ESR2), receptor activator of nuclear factor-kappa B (RANKL) ligand, osteoprotegerin (OPG), bone mineral density (BMD), histological alterations, and immunohistochemical expression of vascular endothelial growth factor (VEGF) and proliferating cell nuclear antigen (PCNA) were assessed. ALP, PINP, Ca, and P concentrations improved significantly (p < 0.05) in all treatment groups, especially in the OVX/E + ZnHA group. MDA and NO were higher in OVX rats, while SOD activity and GSH were lower (p < 0.05). E2 alone or with ZnHA-NPs restored the estimated antioxidant molecules and cytokines toward normal levels in OVX rats (p < 0.05). On the other hand, E2 and ZnHA increased OPG and OC expression in femurs while decreasing ESR1, ESR2, and NF-kB expression (p < 0.05). The combination treatment was superior in the restoration of normal femoral histoarchitecture and both cortical and trabecular BMD (p < 0.05). Overall, the combined therapy of OVX/E2+ZnHA was more effective than the individual treatments in attenuating excessive bone turnover and preventing osteoporosis.

Altered type I collagen networking in osteoporotic human femoral head revealed by histomorphometric and Fourier transform infrared imaging correlated analyses

Bone homeostasis is the equilibrium between organic and inorganic components of the extracellular matrix (ECM) and cells. Alteration of this balance has consequences on bone mass and architecture, resulting in conditions such as osteoporosis (OP). Given ECM protein mutual regulation and their effects on bone structure and mineralization, further insight into their expression is crucial to understanding bone biology under normal and pathological conditions. This study focused on Type I Collagen, which is mainly responsible for structural properties and mineralization of bone, and selected proteins implicated in matrix composition, mineral deposition, and cell-matrix interaction such as Decorin, Osteocalcin, Osteopontin, Bone Sialoprotein 2, Osteonectin and Transforming Growth Factor beta. We developed a novel multidisciplinary approach in order to assess bone matrix in healthy and OP conditions more comprehensively by exploiting the Fourier Transform Infrared Imaging (FTIRI) technique combined with histomorphometry, Sirius Red staining, immunohistochemistry, and Western Blotting. This innovatory procedure allowed for the analysis of superimposed tissue sections and revealed that the alterations in OP bone tissue architecture were associated with warped Type I Collagen structure and deposition but not with changes in the total protein amount. The detected changes in the expression and/or cooperative or antagonist role of Decorin, Osteocalcin, Osteopontin, and Bone Sialoprotein-2 indicate the deep impact of these NCPs on collagen features of OP bone. Overall, our strategy may represent a starting point for designing targeted clinical strategies aimed at bone mass preservation and sustain the FTIRI translational capability as upcoming support for traditional diagnostic methods.

Epigenetic Alterations in Sports-Related Injuries

It is a well-known fact that physical activity benefits people of all age groups. However, highly intensive training, maladaptation, improper equipment, and lack of sufficient rest lead to contusions and sports-related injuries. From the perspectives of sports professionals and those performing regular–amateur sports activities, it is important to maintain proper levels of training, without encountering frequent injuries. The bodily responses to physical stress and intensive physical activity are detected on many levels. Epigenetic modifications, including DNA methylation, histone protein methylation, acetylation, and miRNA expression occur in response to environmental changes and play fundamental roles in the regulation of cellular activities. In the current review, we summarise the available knowledge on epigenetic alterations present in tissues and organs (e.g., muscles, the brain, tendons, and bones) as a consequence of sports-related injuries. Epigenetic mechanism observations have the potential to become useful tools in sports medicine, as predictors of approaching pathophysiological alterations and injury biomarkers that have already taken place.

Molecular investigations of the prenucleation mechanism of bone-like apatite assisted by type I collagen nanofibrils: insights into intrafibrillar mineralization

Bone is a typical inorganic-organic composite material with a multilevel hierarchical organization. In the lowest level of bone tissue, inorganic minerals, which are mainly composed of hydroxyapatite, are mineralized within the type I collagen fibril scaffold. Understanding the crystal prenucleation mechanism and growth of the inorganic phase is particularly important in the design and development of materials with biomimetic nanostructures. In this study, we built an all-atom human type I collagen fibrillar model with a 67 nm overlap/gap D-periodicity. Arginine residues were shown to serve as the dominant cross-linker to stabilize the fibril scaffold. Subsequently, the prenucleation mechanism of collagen intrafibrillar mineralization was investigated using a molecular dynamics approach. Considering the physiological pH of the human body (i.e., ∼7.4), HPO₄^2- was initially used to simulate the protonation state of the phosphate ions. Due to the spatially constrained effects resulting from the overlap/gap structure of the collagen fibrils, calcium phosphate clusters formed mainly inside the hole zone but with different spatial distributions along the long axis direction; this indicated that the nucleation of calcium phosphate may be highly site-selective. Furthermore, the model containing both HPO₄^2- and PO₄^3- in the solution phase formed significantly larger clusters without any change in the nucleation sites. This phenomenon suggests that the existence of PO₄^3- is beneficial for the mineralization process, and so the conversion of HPO₄^2- to PO₄^3- was considered a critical step during mineralization. Finally, we summarize the nucleation mechanism for collagen intrafibrillar mineralization, which could contribute to the fabrication of mineralized collagen biomimetic materials.

Proteins, possibly human, found in World War II concentration camp artifact

Museums displaying artifacts of the human struggle against oppression are often caught in their own internal struggle between presenting factual and unbiased descriptions of their collections, or relying on testament of survivors. Often this quandary is resolved in favor of what can be verified, not what is remembered. However, with improving instrumentation, methods and informatic approaches, science can help uncover evidence able to reconcile memory and facts. Following World War II, thousands of small, cement-like disks with numbers impressed on one side were found at concentration camps throughout Europe. Survivors claimed these disks were made of human cremains; museums erred on the side of caution—without documentation of the claims, was it justifiable to present them as fact? The ability to detect species relevant biological material in these disks could help resolve this question. Proteomic mass spectrometry of five disks revealed all contained proteins, including collagens and hemoglobins, suggesting they were made, at least in part, of animal remains. A new protein/informatics approach to species identification showed that while human was not always identified as the top contributor, human was the most likely explanation for one disk. To our knowledge, this is the first demonstration of protein recovery from cremains. Data are available via ProteomeXchange with identifier PXD035267.

3D Printed Scaffold Based on Type I Collagen/PLGA_TGF-β1 Nanoparticles Mimicking the Growth Factor Footprint of Human Bone Tissue

In bone regenerative strategies, the controlled release of growth factors is one of the main aspects for successful tissue regeneration. Recent trends in the drug delivery field increased the interest in the development of biodegradable systems able to protect and transport active agents. In the present study, we designed degradable poly(lactic-co-glycolic)acid (PLGA) nanocarriers suitable for the release of Transforming Growth Factor-beta 1 (TGF-β1), a key molecule in the management of bone cells behaviour. Spherical TGF-β1-containing PLGA (PLGA_TGF-β1) nanoparticles (ca.250 nm) exhibiting high encapsulation efficiency (ca.64%) were successfully synthesized. The TGF-β1 nanocarriers were subsequently combined with type I collagen for the fabrication of nanostructured 3D printed scaffolds able to mimic the TGF-β1 presence in the human bone extracellular matrix (ECM). The homogeneous hybrid formulation underwent a comprehensive rheological characterisation in view of 3D printing. The 3D printed collagen-based scaffolds (10 mm × 10 mm × 1 mm) successfully mimicked the TGF-β1 presence in human bone ECM as assessed by immunohistochemical TGF-β1 staining, covering ca.3.4% of the whole scaffold area. Moreover, the collagenous matrix was able to reduce the initial burst release observed in the first 24 h from about 38% for the PLGA_TGF-β1 alone to 14.5%, proving that the nanocarriers incorporation into collagen allows achieving sustained release kinetics.

Comparison of Synthetic vs. Biogenic Polymeric Process-Directing Agents for Intrafibrillar Mineralization of Collagen

With the aging population, there is a growing need for mineralized tissue restoration and synthetic bone substitutes. Previous studies have shown that a polymer-induced liquid-precursor (PILP) process can successfully mineralize collagen substrates to achieve compositions found in native bone and dentin. This process also leads to intrafibrillar apatitic crystals with their [001] axes aligned roughly parallel to the long axis of the collagen fibril, emulating the nanostructural organization found in native bone and dentin. When demineralized bovine bone was remineralized via the PILP process using osteopontin (OPN), the samples were able to activate mouse marrow-derived osteoclasts to similar levels to those of native bone, suggesting a means for fabricating bioactive bone substitutes that could trigger remodeling through the native bone multicellular unit (BMU). In order to determine if OPN derived from bovine milk could be a cost-effective process-directing agent, the mineralization of type I collagen scaffolds using this protein was compared to the benchmark polypeptide of polyaspartic acid (sodium salt; pAsp). In this set of experiments, we found that OPN led to much faster and more uniform mineralization when compared with pAsp, making it a cheaper and commercially attractive alternative for mineralized tissue restorations.

Theoretical Evidence of Osteoblast Self-Inhibition after Activation of the Genetic Regulatory Network Controlling Mineralization

Bone is a hard-soft biomaterial built through a self-assembly process under genetic regulatory network (GRN) monitoring. This paper aims to capture the behavior of the bone GRN part that controls mineralization by using a mathematical model. Here, we provide an advanced review of empirical evidence about interactions between gene coding (i) transcription factors and (ii) bone proteins. These interactions are modeled with nonlinear differential equations using Michaelis-Menten and Hill functions. Compared to empirical evidence, the two best systems (among 12⁶=2,985,984 possibilities) use factors of inhibition from the start of the activation of each gene. It reveals negative indirect interactions coming from either negative feedback loops or the recently depicted micro-RNAs. The difference between the two systems also lies in the BSP equation and two ways for activating and reducing its production. Thus, it highlights the critical role of BSP in the bone GRN that acts on bone mineralization. Our study provides the first theoretical evidence of a necessary genetic inhibition for bone mineralization with this work.

Degenerations in Global Morphometry of Cancellous Bone in Rheumatoid Arthritis, Osteoarthritis and Osteoporosis of Femoral Heads are Similar but More Severe than in Ageing Controls

We have recently revealed significant differences in microarchitectural properties (i.e. global and local morphometries) and mechanical properties between rheumatoid arthritis (RA), osteoarthritis (OA) and osteoporosis (OP) in cancellous bones. This study compared these properties with those of ageing controls by matching bone volume fraction (BV/TV), the most important determinant for bones' mechanical properties, to investigate whether these bones have similar properties and degenerative potentials. RA, OA and OP femoral heads were harvested from patients undergoing total hip replacement surgery. The selected patients were matched by similar cancellous bone BV/TV, with seven patients in each group. Four samples were prepared from each femoral head and scanned with micro-CT to quantify microarchitectural properties and compression tested to determine mechanical properties. In terms of global morphometry, no significant differences were observed between these diseased bones. In terms of local morphometry, the number of plates in the RA group was significantly greater than that of the OP and control groups. Plate volume density in the RA group was significantly greater than in the control group. Interestingly, the ultimate stresses in the three diseased groups were 77% to 195% lower than in the control group (p < 0.001). Degenerations of global morphometry of cancellous bones in these diseased femoral heads are similar but more severe than in ageing controls matched by BV/TV, as evidenced by pronounced reduction in bone strength. This phenomenon suggests that some local morphometric parameters, along with other factors, such as abnormal collagen, mineralisation, erosion and microdamage, may contribute to further compromising mechanical properties.

Nanoscale Imaging and Analysis of Bone Pathologies

Understanding the properties of bone is of both fundamental and clinical relevance. The basis of bone’s quality and mechanical resilience lies in its nanoscale building blocks (i.e., mineral, collagen, non-collagenous proteins, and water) and their complex interactions across length scales. Although the structure–mechanical property relationship in healthy bone tissue is relatively well characterized, not much is known about the molecular-level origin of impaired mechanics and higher fracture risks in skeletal disorders such as osteoporosis or Paget’s disease. Alterations in the ultrastructure, chemistry, and nano-/micromechanics of bone tissue in such a diverse group of diseased states have only been briefly explored. Recent research is uncovering the effects of several non-collagenous bone matrix proteins, whose deficiencies or mutations are, to some extent, implicated in bone diseases, on bone matrix quality and mechanics. Herein, we review existing studies on ultrastructural imaging—with a focus on electron microscopy—and chemical, mechanical analysis of pathological bone tissues. The nanometric details offered by these reports, from studying knockout mice models to characterizing exact disease phenotypes, can provide key insights into various bone pathologies and facilitate the development of new treatments.

Aesculetin Accelerates Osteoblast Differentiation and Matrix-Vesicle-Mediated Mineralization

The imbalance between bone resorption and bone formation in favor of resorption results in bone loss and deterioration of bone architecture. Osteoblast differentiation is a sequential event accompanying biogenesis of matrix vesicles and mineralization of collagen matrix with hydroxyapatite crystals. Considerable efforts have been made in developing naturally-occurring plant compounds, preventing bone pathologies, or enhancing bone regeneration. Coumarin aesculetin inhibits osteoporosis through hampering the ruffled border formation of mature osteoclasts. However, little is known regarding the effects of aesculetin on the impairment of matrix vesicle biogenesis. MC3T3-E1 cells were cultured in differentiation media with 1–10 μM aesculetin for up to 21 days. Aesculetin boosted the bone morphogenetic protein-2 expression, and alkaline phosphatase activation of differentiating MC3T3-E1 cells. The presence of aesculetin strengthened the expression of collagen type 1 and osteoprotegerin and transcription of Runt-related transcription factor 2 in differentiating osteoblasts for 9 days. When ≥1–5 μM aesculetin was added to differentiating cells for 15–18 days, the induction of non-collagenous proteins of bone sialoprotein II, osteopontin, osteocalcin, and osteonectin was markedly enhanced, facilitating the formation of hydroxyapatite crystals and mineralized collagen matrix. The induction of annexin V and PHOSPHO 1 was further augmented in ≥5 μM aesculetin-treated differentiating osteoblasts for 21 days. In addition, the levels of tissue-nonspecific alkaline phosphatase and collagen type 1 were further enhanced within the extracellular space and on matrix vesicles of mature osteoblasts treated with aesculetin, indicating matrix vesicle-mediated bone mineralization. Finally, aesculetin markedly accelerated the production of thrombospondin-1 and tenascin C in mature osteoblasts, leading to their adhesion to preformed collagen matrix. Therefore, aesculetin enhanced osteoblast differentiation, and matrix vesicle biogenesis and mineralization. These findings suggest that aesculetin may be a potential osteo-inductive agent preventing bone pathologies or enhancing bone regeneration.

Urinary peptidomic profiles to address age-related disabilities: a prospective population study

BACKGROUND

The Global Burden of Diseases, Injuries, and Risk Factors Study 2019 called for innovation in addressing age-related disabilities. Our study aimed to identify and validate a urinary peptidomic profile (UPP) differentiating healthy from unhealthy ageing in the general population, to test the UPP predictor in independent patient cohorts, and to search for targetable molecular pathways underlying age-related chronic diseases.

METHODS

In this prospective population study, we used data from participants in the Flemish Study on Environment, Genes and Health Outcomes (FLEMENGHO), done in northern Belgium from 1985 to 2019, and invited participants to a follow-up examination in 2005-10. Participants were eligible if their address was within 15 km of the examination centre and if they had not withdrawn consent in any of the previous examination cycles (1985-2004). All participants (2005-10) were also invited to an additional follow-up examination in 2009-13. Participants who took part in both the 2005-10 follow-up examination and in the additional 2009-13 follow-up visit constituted the derivation dataset, which included their 2005-10 data, and the time-shifted internal validation dataset, which included their 2009-13 data. The remaining participants who only had 2005-10 data constituted the synchronous internal validation dataset. Participants were excluded from analyses if they were incapacitated, had not undergone UPP, or had either missing or outlying (three SDs greater than the mean of all consenting participants) values of body-mass index, plasma glucose, or serum creatinine. The UPP was assessed by capillary electrophoresis coupled with mass spectrometry. The multidimensional UPP signature reflecting ageing was generated from the derivation dataset and validated in the time-shifted internal validation dataset and the synchronous validation dataset. It was further validated in patients with diabetes, COVID-19, or chronic kidney disease (CKD). In FLEMENGHO, the mortality endpoints were all-cause, cardiovascular, and non-cardiovascular mortality; other endpoints were fatal or non-fatal cancer and musculoskeletal disorders. Molecular pathway exploration was done using the Reactome and Kyoto Encyclopedia of Genes and Genomes databases.

FINDINGS

778 individuals (395 [51%] women and 383 [49%] men; aged 16·2-82·1 years; mean age 50·9 years [SD 15·8]) from the FLEMENGHO cohort had a follow-up examination between 2005 and 2010, of whom 559 participants had a further follow-up from Oct 28, 2009, to March 19, 2013, and made up the derivation (2005-10) and time-shifted internal validation (2009-13) datasets. 219 were examined once and constituted the synchronous internal validation dataset (2005-10). With correction for multiple testing and multivariable adjustment, chronological age was associated with 210 sequenced peptides mainly showing downregulation of collagen fragments. The trained model relating chronological age to UPP, derived by elastic net regression, included 54 peptides from 17 proteins. The UPP-age prediction model explained 76·3% (r=0·87) of chronological age in the derivation dataset, 54·4% (r=0·74) in the time-shifted validation dataset, and 65·3% (r=0·81) in the synchronous internal validation dataset. Compared with chronological age, the predicted UPP-age was greater in patients with diabetes (chronological age 50·8 years [SE 0·37] vs UPP-age 56·9 years [0·30]), COVID‑19 (53·2 years [1·80] vs 58·5 years [1·67]), or CKD (54·6 years [0·97] vs 62·3 years [0·85]; all p<0·0001). In the FLEMENGHO cohort, independent of chronological age, UPP-age was significantly associated with various risk markers related to cardiovascular, metabolic, and renal disease, inflammation, and medication use. Over a median of 12·4 years (IQR 10·8-13·2), total mortality, cardiovascular mortality, and osteoporosis in the population was associated with UPP-age independent of chronological age, with hazard ratios per 10 year increase in UPP-age of 1·54 (95% CI 1·22-1·95) for total mortality, 1·72 (1·20-2·47) for cardiovascular mortality, and 1·40 (1·06-1·85) for osteoporosis and fractures. The most relevant molecular pathways informed by the proteins involved deregulation of collagen biology and extracellular matrix maintenance.

INTERPRETATION

The UPP signature indicative of ageing reflects fibrosis and extracellular matrix remodelling and was associated with risk factors and adverse health outcomes in the population and with accelerated ageing in patients. Innovation in addressing disability should shift focus from the ontology of diseases to shared disease mechanisms, in particular ageing-related fibrotic degeneration.

FUNDING

European Research Council, Ministry of the Flemish Community, OMRON Healthcare.

Insights into oxidative stress in bone tissue and novel challenges for biomaterials

The presence of Reactive Oxygen Species (ROS) in bone can influence resident cells behaviour as well as the extra-cellular matrix composition and the tissue architecture. Aging, in addition to excessive overloads, unbalanced diet, smoking, predisposing genetic factors, lead to an increase of ROS and, if it is accompanied with an inappropriate production of scavengers, promotes the generation of oxidative stress that encourages bone catabolism. Furthermore, bone injuries can be triggered by numerous events such as road and sports accidents or tumour resection. Although bone tissue possesses a well-known repair and regeneration capacity, these mechanisms are inefficient in repairing large size defects and bone grafts are often necessary. ROS play a fundamental role in response after the implant introduction and can influence its success. This review provides insights on the mechanisms of oxidative stress generated by an implant in vivo and suitable ways for its modulation. The local delivery of active molecules, such as polyphenols, enhanced bone biomaterial integration evidencing that the management of the oxidative stress is a target for the effectiveness of an implant. Polyphenols have been widely used in medicine for cardiovascular, neurodegenerative, bone disorders and cancer, thanks to their antioxidant and anti-inflammatory properties. In addition, the perspective of new smart biomaterials and molecular medicine for the oxidative stress modulation in a programmable way, by the use of ROS responsive materials or by the targeting of selective molecular pathways involved in ROS generation, will be analysed and discussed critically.

Quantitative proteomics reveals the effect of Yigu decoction (YGD) on protein expression in bone tissue

Background

Osteoporosis (OP) is a systemic bone disease characterized by decreased bone mass, destruction of the bone tissue microstructure, increased bone brittleness and an increased risk of fracture. OP has a high incidence rate and long disease course and is associated with serious complications. Yigu decoction (YGD) is a compound prescription in traditional Chinese medicine that is used to treat OP. However, its mechanism in OP is not clear. This study used a tandem mass tag (TMT)quantitative proteomics method to explore the potential bone-protective mechanism of YGD in an osteoporotic rat model.

Materials and methods

A rat model of OP was established by ovariectomy. Eighteen 12-week-old specific-pathogen-free female Wistar rats weighing 220 ± 10 g were selected. The eighteen rats were randomly divided into 3 groups (n = 6 in each group): the normal, model and YGD groups. The right femurs from each group were subjected to quantitative biological analysis. TMT quantitative proteomics was used to analyze the proteins extracted from the bone tissue of rats in the model and YGD groups, and the differentially expressed proteins after intervention with YGD were identified as biologically relevant proteins of interest. Functional annotation correlation analysis was also performed to explore the biological function and mechanism of YGD.

Result

Compared with the model group, the YGD group showed significant upregulation of 26 proteins (FC > 1.2, P < 0.05) and significant downregulation of 39 proteins (FC < 0.833, P < 0.05). Four important targets involved in OP and 5 important signaling pathways involved in bone metabolism were identified.

Conclusions

YGD can significantly increase the bone mineral density (BMD) of osteoporotic rats and may play a therapeutic role by regulating target proteins involved in multiple signaling pathways. Therefore, these results improve the understanding of the OP mechanism and provide an experimental basis for the clinical application of YGD in OP treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12014-021-09330-0.

Optimization of Novel Human Acellular Dermal Dressing Sterilization for Routine Use in Clinical Practice

Gamma rays and electrons with kinetic energy up to 10 MeV are routinely used to sterilize biomaterials. To date, the effects of irradiation upon human acellular dermal matrices (hADMs) remain to be fully elucidated. The optimal irradiation dosage remains a critical parameter affecting the final product structure and, by extension, its therapeutic potential. ADM slides were prepared by various digestion methods. The influence of various doses of radiation sterilization using a high-energy electron beam on the structure of collagen, the formation of free radicals and immune responses to non-irradiated (native) and irradiated hADM was investigated. The study of the structure changes was carried out using the following methods: immunohistology, immunoblotting, and electron paramagnetic resonance (EPR) spectroscopy. It was shown that radiation sterilization did not change the architecture and three-dimensional structure of hADM; however, it significantly influenced the degradation of collagen fibers and induced the production of free radicals in a dose-dependent manner. More importantly, the observed effects did not disrupt the therapeutic potential of the new transplants. Therefore, radiation sterilization at a dose of 35kGy can ensure high sterility of the dressing while maintaining its therapeutic potential.

Transcriptome Analysis of Egg Yolk Sialoglycoprotein on Osteogenic Activity in MC3T3-E1 Cells

In this study, the effects of egg yolk sialoglycoprotein (EYG) on osteogenesis in MC3T3-E1 cells were investigated and the DEGs (differentially expressed genes) were explored by transcriptome analysis. The results found that EYG effectively increased cell proliferation, enhanced ALP activity, promoted the secretion of extracellular matrix protein COL-I and OCN, enhanced bone mineralization activity, exhibiting good osteogenic activity. Further study of the mechanism was explored through transcriptome analysis. Transcriptome analysis showed that 123 DEGs were triggered by EYG, of which 78 genes were downregulated and 45 genes were upregulated. GO (gene ontology) analysis showed that EYG mainly caused differences in gene expression of biological processes and cell composition categories in the top 30 most enriched items. KEGG (Kyoto Encyclopedia of Genes and Genomes) analysis showed that EYG inhibited inflammatory factors and downregulated inflammation-related pathways. The results also showed EYG regulated such genes as COL2A1, COL4A1 and COL4A2 to up-regulate pathways including ECM–receptor interaction, focal adhesion and protein digestion and absorption, enhancing the proliferation and differentiation of osteoblasts. Gene expression of COL-I, Runx2, BMP2 and β-catenin was determined by qRT-PCR for verification, which found that EYG significantly increased COL-I, Runx2, BMP2 and β-catenin gene expression, suggesting that BMP-2 mediated osteogenesis pathway was activated.

Triple Culture of Primary Human Osteoblasts, Osteoclasts and Osteocytes as an In Vitro Bone Model

In vitro evaluation of bone graft materials is generally performed by analyzing the interaction with osteoblasts or osteoblast precursors. In vitro bone models comprising different cell species can give specific first information on the performance of those materials. In the present study, a 3D co-culture model was established comprising primary human osteoblasts, osteoclasts and osteocytes. Osteocytes were differentiated from osteoblasts embedded in collagen gels and were cultivated with osteoblast and osteoclasts seeded in patterns on a porous membrane. This experimental setup allowed paracrine signaling as well as separation of the different cell types for final analysis. After 7 days of co-culture, the three cell species showed their typical morphology and gene expression of typical markers like ALPL, BSPII, BLGAP, E11, PHEX, MEPE, RANKL, ACP5, CAII and CTSK. Furthermore, relevant enzyme activities for osteoblasts (ALP) and osteoclasts (TRAP, CTSK, CAII) were detected. Osteoclasts in triple culture showed downregulated TRAP (ACP5) and CAII expression and decreased TRAP activity. ALP and BSPII expression of osteoblasts in triple culture were upregulated. The expression of the osteocyte marker E11 (PDPN) was unchanged; however, osteocalcin (BGLAP) expression was considerably downregulated both in osteoblasts and osteocytes in triple cultures compared to the respective single cultures.

Signaling Pathway and Transcriptional Regulation in Osteoblasts during Bone Healing: Direct Involvement of Hydroxyapatite as a Biomaterial

Bone defects and periodontal disease are pathological conditions that may become neglected diseases if not treated properly. Hydroxyapatite (HA), along with tricalcium phosphate and bioglass ceramic, is a biomaterial widely applied to orthopedic and dental uses. The in vivo performance of HA is determined by the interaction between HA particles with bone cells, particularly the bone mineralizing cells osteoblasts. It has been reported that HA-induced osteoblastic differentiation by increasing the expression of osteogenic transcription factors. However, the pathway involved and the events that occur in the cell membrane have not been well understood and remain controversial. Advances in gene editing and the discovery of pharmacologic inhibitors assist researchers to better understand osteoblastic differentiation. This review summarizes the involvement of extracellular signal-regulated kinase (ERK), p38, Wnt, and bone morphogenetic protein 2 (BMP2) in osteoblastic cellular regulation induced by HA. These advances enhance the current understanding of the molecular mechanism of HA as a biomaterial. Moreover, they provide a better strategy for the design of HA to be utilized in bone engineering.