Chestnut-Inspired Hollow Hydroxyapatite 3D Printing Scaffolds Accelerate Bone Regeneration by Recruiting Calcium Ions and Regulating Inflammation.

This study aims to overcome the drawbacks associated with hydroxyapatite (HAP) dense structures after sintering, which often result in undesirable features such as large grain size, reduced porosity, high crystallinity, and low specific surface area. These characteristics hinder osseointegration and limit the clinical applicability of the material. To address these issues, a new method involving the preparation of hollow hydroxyapatite (hHAP) microspheres has been proposed. These microspheres exhibit distinctive traits including weak crystallization, high specific surface area, and increased porosity. The weak crystallization aligns more closely with early mineralization products found in the human body and animals. Moreover, the microspheres' high specific surface area and porosity offer advantages for protein loading and facilitating osteoblast attachment. This innovative approach not only mitigates the limitations of conventional HAP structures but also holds the potential for improving the effectiveness of hydroxyapatite in biomedical applications, particularly in enhancing osseointegration. Three-dimensional printed hHAP/chitosan (CS) scaffolds with different hHAP concentration gradients were manufactured, and the physical and biological properties of each group were systematically evaluated. In vitro and in vivo experiments show that the hHAP/CS scaffold has excellent performance in bone remodeling. Furthermore, in-scaffold components, hHAP and CS were cocultured with bone marrow mesenchymal stem cells to explore the regulatory role of hHAP and CS in the process of bone healing and to reveal the cell-level specific regulatory network activated by hHAP. Enrichment analysis showed that hHAP can promote bone regeneration and reconstruction by recruiting calcium ions and regulating inflammatory reactions.

DLP fabrication of HA scaffold with customized porous structures to regulate immune microenvironment and macrophage polarization for enhancing bone regeneration.

The immune microenvironment plays a pivotal role in osteoanagenesis. Biomaterials can modulate osteogenic efficacy by inducing specific local immune reactions. As 3D-printing technology advances, digital light projection printing has emerged as a promising method for creating large scale, high-precision biomaterial scaffolds. By adjusting the solid content and the sintering conditions during printing, the pore size of biomaterials can be meticulously controlled. Yet, the systematic influence of pore size on the immune microenvironment remains uncharted. We fabricated 3D-printed hydroxyapatite bioceramic scaffolds with three distinct pore sizes: 400 µm, 600 µm, and 800 µm. Our study revealed that scaffolds with a pore size of 600 µm promote macrophage M2 polarization, which is achieved by upregulating interferon-beta and HIF-1α production. When these materials were implanted subcutaneously in rats and within rabbit skulls, we observed that the 600 µm scaffolds notably improved the long-term inflammatory response, fostered vascular proliferation, and augmented new bone growth. This research paves the way for innovative therapeutic strategies for treating large segmental bone defects in clinical settings.

The association between basal metabolic rate and osteoarthritis: a Mendelian randomization study.

BACKGROUND: The role of the basal metabolic rate (BMR) in osteoarthritis (OA) remains unclear, as previous retrospective studies have produced inconsistent results. Therefore, we performed a Mendelian randomization (MR) study to systematically investigate the causal relationship between the BMR and OA. METHODS: Single-nucleotide polymorphism (SNP) data related to BMR and OA were collected in a genome-wide association study. Using OA as the outcome variable and BMR as the exposure factor, SNPs with strong correlation with the BMR as the tool variable were screened. The correlation between the BMR and OA risk was evaluated using the inverse-variance weighted method, and heterogeneity and pleiotropy were evaluated using a sensitivity analysis. RESULTS: There was a potential causal relationship between the BMR and OA risk (odds ratio [OR], 1.014; 95% confidence interval [CI], 1.008-1.020; P = 2.29e - 6). A causal relationship was also revealed between the BMR and knee OA (OR, 1.876; 95% CI, 1.677-2.098; P = 2.98e - 28) and hip OA (OR, 1.475; 95% CI, 1.290-1.686; P = 1.26e - 8). Sensitivity analysis confirmed the robustness of these results. CONCLUSION: Here, we identified a latent causal relationship between the BMR and the risk of OA. These results suggest that the risk of OA in the hip or knee joint may be reduced by controlling the BMR.

Hollow Hydroxyapatite Microspheres Loaded with rhCXCL13 to Recruit BMSC for Osteogenesis and Synergetic Angiogenesis to Promote Bone Regeneration in Bone Defects.

Introduction: Bone tissue engineering is a promising method to treat bone defects. However, the current methods of preparing composite materials that mimic the complex structure and biological activity of natural bone are challenging for recruitment of bone marrow mesenchymal stem cells (BMSCs), which affects the application of these materials in situ bone regeneration. Hollow hydroxyapatite microspheres (HHMs) possess a natural porous bone structure, good adsorption, and slow release of chemokines, but have low ability to recruit BMSCs and induce osteogenesis. In this study, The HHM/chitosan (CS) and recombinant human C-X-C motif chemokine ligand 13 (rhCXCL13)-HHM/CS biomimetic scaffolds that optimize bone regeneration and investigated their mechanism of BMSC recruitment and osteogenesis through cell and animal experiments and transcriptomic sequencing. Methods: Evaluate the physical characteristics of the HHM/CS and rhCXCL13-HHM/CS biomimetic scaffolds through Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), and the cumulative release curve of rhCXCL13. Transwell migration experiments and co-culture with BMSCs were conducted to study the recruitment ability and osteogenic differentiation of the scaffolds. Transcriptomic sequencing was performed to analyze the osteogenic differentiation mechanism. The osteogenesis and bone healing performance were evaluated using a rabbit radial defect model. Results: SEM demonstrated that the rhCXCL13-HHM/CS scaffold comprised hydroxyapatite microspheres in a porous three-dimensional network. The rhCXCL13 showed excellent sustained release capability. The rhCXCL13-HHM/CS scaffold could recruit BMSCs and induce bone regeneration. Transcriptome sequencing and experimental results showed that the osteogenesis mechanism of rhCXCL13-HHM/CS was through the PI3K-AKT pathway. In vivo, the rhCXCL13-HHM/CS scaffold significantly promoted osteogenesis and angiogenesis at 12 weeks after surgery. Conclusion: The rhCXCL13-HHM/CS scaffold demonstrates excellent potential for BMSC recruitment, osteogenesis, vascularized tissue-engineered bone reconstruction, and drug delivery, providing a theoretical basis for material osteogenesis mechanism study and promising clinical applications for treating large bone defects.

Study on the influence of scaffold morphology and structure on osteogenic performance.

The number of patients with bone defects caused by various bone diseases is increasing yearly in the aging population, and people are paying increasing attention to bone tissue engineering research. Currently, the application of bone tissue engineering mainly focuses on promoting fracture healing by carrying cytokines. However, cytokines implanted into the body easily cause an immune response, and the cost is high; therefore, the clinical treatment effect is not outstanding. In recent years, some scholars have proposed the concept of tissue-induced biomaterials that can induce bone regeneration through a scaffold structure without adding cytokines. By optimizing the scaffold structure, the performance of tissue-engineered bone scaffolds is improved and the osteogenesis effect is promoted, which provides ideas for the design and improvement of tissue-engineered bones in the future. In this study, the current understanding of the bone tissue structure is summarized through the discussion of current bone tissue engineering, and the current research on micro-nano bionic structure scaffolds and their osteogenesis mechanism is analyzed and discussed.

Effect of basal metabolic rate on osteoporosis: A Mendelian randomization study.

Purpose: Basal metabolic rate may play a key role in the pathogenesis and progression of osteoporosis. We performed Mendelian random analysis to evaluate the causal relationship between basal metabolic rate and osteoporosis. Methods: Instrumental variables for the basal metabolic rate were selected. We used the inverse variance weighting approach as the main Mendelian random analysis method to estimate causal effects based on the summary-level data for osteoporosis from genome-wide association studies. Results: A potential causal association was observed between basal metabolic rate and risks of osteoporosis (odds ratio = 0.9923, 95% confidence interval: 0.9898-0.9949; P = 4.005e - 09). The secondary MR also revealed that BMR was causally associated with osteoporosis (odds ratio = 0.9939, 95% confidence interval: 0.9911-0.9966; P = 1.038e - 05). The accuracy and robustness of the findings were confirmed using sensitivity tests. Conclusion: Basal metabolic rate may play a causal role in the development of osteoporosis, although the underlying mechanisms require further investigation.

The mechanism research of non-Smad dependent TAK1 signaling pathway in the treatment of bone defects by recombination BMP-2-loaded hollow hydroxyapatite microspheres/chitosan composite.

AIMS: The present study aimed to evaluate whether the non-Smad dependent TAK1 signaling pathway (BMP-2-TAK1-p38-Osx signaling pathway) played an important role in bone repair mediated by hollow hydroxyapatite (HA) microspheres/chitosan (CS) composite. METHODS: Firstly, the biological activity of rhBMP-2 released from the complex was investigated. Then, differentiation test of osteoblasts including ALP activity and calcium deposition, X-ray scoring and three-point bending test were performed. Finally, the mRNAs expression of TAK1, p38, Osx and osteogenic markers was tested by reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: RhBMP-2 could be loaded and released from the complex in bioactive form. Additionally, the complex provided a prolonged period of time compared with HA/CS scaffolds. Serum ALP activity was significantly decreased in the TAK1 inhibitor group and p38 inhibitor group. In the X-ray radiography, bone callus was observed in rhBMP-2-loaded hollow HA microspheres/CS composite group. In the three-point bending test, load values in p38 inhibitor group decreased. In the animal model, the mRNA expression of BSP on day 90 was significantly decreased in the p38 inhibitor group and TAK1 inhibitor group. In MC3T3-E1 cells, the mRNA expression of OSX was remarkably up-regulated in both rhBMP-2 group or rhBMP-2-loaded hollow HA microspheres/CS composite group; while the mRNA expression of OSX was significantly down-regulated in TAK1 inhibitor group and p38 inhibitor group. CONCLUSION: The BMP-2-TAK1-p38-OSX signaling pathway may play an important role in bone formation and repair mediated by rhBMP-2-loaded hollow HA microspheres/CS composite.

Study of bone repair mediated by recombination BMP-2/ recombination CXC chemokine Ligand-13-loaded hollow hydroxyapatite microspheres/chitosan composite.

AIMS: The present study aimed to investigate the mechanism of bone repair mediated by recombination BMP-2 (rhBMP-2)/recombination CXC chemokine ligand-13 (rhCXCL13)-loaded hollow hydroxyapatite (HA) microspheres/chitosan (CS) composite. MATERIALS AND METHODS: Firstly, the biological activity of rhBMP-2 and rhCXCL13 released from the complex was investigated. Secondly, the effect of rhBMP-2 sustained release solution on ALP activity and rhCXCL13 sustained release solution on cell migration of rat bone marrow mesenchyme stem cells was tested. Thirdly, osteoblasts differentiation test, X-ray scoring and three-point bending test were performed. Finally, the mRNAs expression of osteogenic marker genes and the protein expression of Runx2 was tested by reverse transcription-polymerase chain reaction (RT-PCR) and western blotting (WB), respectively. KEY FINDINGS: RhBMP-2 could significantly promote the proliferation and differentiation, and RhCXCL13 could promote the migration of rat bone marrow MSCs. Detection of ALP activity and calcium salt deposition showed that rhBMP-2 and rhCXCL13 could significantly improve the biological activity and promote cell differentiation ability. X-ray scoring of radius and flexural strength test showed that rhBMP-2 and rhCXCL13 could promote bone healing and improve the bending resistance of bone tissue. The in vitro molecular experiments including RT-PCR and WB further demonstrated the roles of rhBMP-2 and rhCXCL13 in bone formation and bone repair. SIGNIFICANCE: Our results indicated that the hollow HA microspheres/CS composite could be effective as a delivery vehicle for rhBMP-2 and rhCXCL13 in bone regeneration and bone repair. In this process, rhBMP-2 may promote bone regeneration by regulating bone marrow MSCs cells recruited by rhCXCL13.

Bone repair scaffold coated with bone morphogenetic protein-2 for bone regeneration in murine calvarial defect model: Systematic review and quality evaluation.

To systematically assess the effects of hydroxyapatite bone repair scaffold coated with bone morphogenetic protein-2 on murine calvarial defect models and to determine the quality of studies according to the Animal Research Reporting in In Vivo Experiments guidelines. Internet search was performed in duplicate using PubMed, MEDLINE, Ovid and Embase databases (without restrictions on publication date). The Animal Research Reporting in In Vivo Experiments guidelines were used to evaluate the quality of selected studies. Following screening, 12 studies were eligible for the review. Studies with average quality coefficients predominated (66.67%), followed by poor (25%) and excellent (8.33%) quality coefficients. Minimum quality scores were assigned to the Animal Research Reporting in In Vivo Experiments guideline items: housing and husbandry (9), allocation (11), outcomes (12), interpretation (18) and generalizability (19). Sprague-Dawley rats were the most frequently used (50%) species, and most studies had a sample size of more than 30 (58.33%). A defect dimension of 5 mm was the most common (33.33%). The biological hydroxyapatite composite scaffold was common (50%), and the bioactive factors were bone morphogenetic protein-2 (50%) and recombinant human bone morphogenetic protein-2 (50%). Histomorphometric results showed that bone morphogenetic protein-2 enhanced the capacity to regenerate bone considerably. In addition, scaffolds with bone morphogenetic protein-2 resulted in a significant increase in the blood vessel in the new bone. The findings suggested that data on animal experiments of hydroxyapatite scaffold coated with bone morphogenetic protein-2 in murine calvarial defect models lack homogeneity. Animal experiment should follow the Animal Research Reporting in In Vivo Experiments guidelines to promote the high quality, integrity and reproducibility. This systematic review suggested that bone morphogenetic protein-2 enhanced the capacity to regenerate bone and the angiogenesis in the new bone.

Scaffolds for the repair of bone defects in clinical studies: a systematic review.

BACKGROUND: This systematic review aims to summarize the clinical studies on the use of scaffolds in the repair of bony defects. METHODS: The relevant articles were searched through PubMed database. The following keywords and search terms were used: "scaffolds," "patient," "clinic," "bone repair," "bone regeneration," "repairing bone defect," "repair of bone," "osteanagenesis," "osteanaphysis," and "osteoanagenesis." The articles were screened according to inclusion and exclusion criteria, performed by two reviewers. RESULTS: A total of 373 articles were obtained using PubMed database. After screening, 20 articles were identified as relevant for the purpose of this systematic review. We collected the data of biological scaffolds and synthetic scaffolds. There are eight clinical studies of biological scaffolds included collagen, gelatin, and cellular scaffolds for bone healing. In addition, 12 clinical studies of synthetic scaffolds on HAp, TCP, bonelike, and their complex scaffolds for repairing bone defects were involved in this systematic review. CONCLUSIONS: There are a lot of clinical evidences showed that application of scaffolds had a good ability to facilitate bone repair and osteogenesis. However, the ideal and reliable guidelines are insufficiently applied and the number and quality of studies in this field remain to be improved.