Repair of a rat calvaria defect with injectable strontium (Sr)-doped polyphosphate dicalcium phosphate dehydrate (P-DCPD) ceramic bone grafts.

The trace element strontium (Sr) enhances new bone formation. However, delivering Sr, like other materials, in a sustained manner from a ceramic bone graft substitute (BGS) is difficult. We developed a novel ceramic BGS, polyphosphate dicalcium phosphate dehydrate (P-DCPD), which delivers embedded drugs in a sustained pattern. This study assessed the in vitro and in vivo performance of Sr-doped P-DCPD. In vitro P-DCPD and 10%Sr-P-DCPD were nontoxic and eluents from 10%Sr-P-DCPD significantly enhanced osteoblastic MC3T3 cell differentiation. A sustained, zero-order Sr release was observed from 10%Sr-P-DCPD for up to 70 days. When using this BGS in a rat calvaria defect model, both P-DCPD and 10% Sr-P-DCPD were found to be biocompatible and biodegradable. Histologic data from decalcified and undecalcified tissue showed that 10%Sr-P-DCPD had more extensive new bone formation compared with P-DCPD 12-weeks after surgery and the 10%Sr-P-DCPD had more organized new bone and much less fibrous tissue at the defect margins. The new bone was formed on the surface of the degraded ceramic debris within the bone defect area. P-DCPD represented a promising drug-eluting BGS for repair of critical bone defects.

Comparison of the Volume and Histological Properties of Newly Formed Bone after the Application of Three Types of Bone Substitutes in Critical-Sized Bone Defects.

This study aimed to compare the volume and quality of the newly formed bone following application of two types of xenografts and one synthetic material in bone defects in rabbit calvaria from histological and micro-CT aspects. Four 8-mm defects were created in 12 rabbit calvaria. Three defects were filled with bone substitutes and one was left unfilled as the control group. The newly formed bone was evaluated histologically and also by micro-CT at 8 and 12 weeks after the intervention. The percentage of osteogenesis was comparable in histomor-phometric assessment and micro-CT. Histological analysis showed that the percentage of the newly formed bone was 10.92 ± 5.17%, 14.70 ± 11.02%, 11.47 ± 7.04%, and 9.45 ± 5.18% in groups bovine 1, bovine 2, synthetic, and negative control, respectively after 8 weeks. These values were 33.70 ± 11.48%, 26.30 ± 18.05%, 22.92 ± 6.30%, and 14.82 ± 8.59%, respectively at 12 weeks. The difference in the percentage of the new bone formation at 8 and 12 weeks was not significant in any group (P > 0.05) except for bovine 1 group (P < 0.05). Micro-CT confirmed new bone formation in all groups but according to the micro-CT results, the difference between the control and other groups was significant in this respect (P < 0.05). All bone substitutes enhanced new bone formation compared with the control group. Micro-CT assessment yielded more accurate and different results compared with histological assessment.

Improving bone defect healing using magnesium phosphate granules with tailored degradation characteristics.

OBJECTIVES: Dental implant placement frequently requires preceding bone augmentation, for example, with hydroxyapatite (HA) or ß-tricalcium phosphate (ß-TCP) granules. However, HA is degraded very slowly in vivo and for ß-TCP inconsistent degradation profiles from too rapid to rather slow are reported. To shorten the healing time before implant placement, rapidly resorbing synthetic materials are of great interest. In this study, we investigated the potential of magnesium phosphates in granular form as bone replacement materials. METHODS: Spherical granules of four different materials were prepared via an emulsion process and investigated in trabecular bone defects in sheep: struvite (MgNH4PO4·6H2O), K-struvite (MgKPO4·6H2O), farringtonite (Mg3(PO4)2) and ß-TCP. RESULTS: All materials except K-struvite exhibited promising support of bone regeneration, biomechanical properties and degradation. Struvite and ß-TCP granules degraded at a similar rate, with a relative granules area of 29% and 30% of the defect area 4 months after implantation, respectively, whereas 18% was found for farringtonite. Only the K-struvite granules degraded too rapidly, with a relative granules area of 2% remaining, resulting in initial fibrous tissue formation and intermediate impairment of biomechanical properties. SIGNIFICANCE: We demonstrated that the magnesium phosphates struvite and farringtonite have a comparable or even improved degradation behavior in vivo compared to ß-TCP. This emphasizes that magnesium phosphates may be a promising alternative to established calcium phosphate bone substitute materials.

Biphasic calcium phosphate recruits Tregs to promote bone regeneration.

The use of bone substitute materials is crucial for the healing of large bone defects. Immune response induced by bone substitute materials is essential in bone regeneration. Prior research has mainly concentrated on innate immune cells, such as macrophages. Existing research suggests that T lymphocytes, as adaptive immune cells, play an indispensable role in bone regeneration. However, the mechanisms governing T cell recruitment and specific subsets that are essential for bone regeneration remain unclear. This study demonstrates that CD4+ T cells are indispensable for ectopic osteogenesis by biphasic calcium phosphate (BCP). Subsequently, the recruitment of CD4+ T cells is closely associated with the activation of calcium channels in macrophages by BCP to release chemokines Ccl3 and Ccl17. Finally, these recruited CD4+ T cells are predominantly Tregs, which play a significant role in ectopic osteogenesis by BCP. These findings not only shed light on the immune-regenerative process after bone substitute material implantation but also establish a theoretical basis for developing bone substitute materials for promoting bone tissue regeneration. STATEMENT OF SIGNIFICANCE: Bone substitute material implantation is essential in the healing of large bone defects. Existing research suggests that T lymphocytes are instrumental in bone regeneration. However, the specific mechanisms governing T cell recruitment and specific subsets that are essential for bone regeneration remain unclear. In this study, we demonstrate that activation of calcium channels in macrophages by biphasic calcium phosphate (BCP) causes them to release the chemokines Ccl3 and Ccl17 to recruit CD4+ T cells, predominantly Tregs, which play a crucial role in ectopic osteogenesis by BCP. Our findings provide a theoretical foundation for developing bone substitute material for bone tissue regeneration.

Effectiveness of a collagen matrix seal and xenograft in alveolar ridge preservation: an experimental study in dogs.

Majority of previous studies on alveolar ridge preservation (ARP) used collagen membranes as barrier membranes, and further evidence for ARP in dehiscent extraction sockets with a deproteinized bovine bone mineral (DBBM) and matrix is needed. The aim of this study is to assess the impact of non-cross linked collagen membranes (membrane) and crosslinked collagen matrices (matrix) on ARP using DBBM in extraction sockets with buccal dehiscence. In six mongrel dogs, the mesial roots of three mandibular premolars (P2, P3, and P4) were extracted 1 month after dehiscence defect induction. Two experimental groups were randomly assigned: (1) DBBM with a membrane (DBBM/membrane group) and (2) DBBM with a matrix (DBBM/matrix group). Three-dimensional (3D) volumetric, microcomputed tomography (µCT), and histologic analyses were performed to assess the ridge preservation. Both groups were effective to maintain the ridge width (p > 0.05), and the DBBM/matrix group showed more favorable soft tissue regeneration and bone quality in the histological analysis (p = 0.05). Based on these results, DBBM/matrix could be better choice for ARP in cases of buccal dehiscence defects.

Advanced Synthetic Scaffolds Based on 1D Inorganic Micro-/Nanomaterials for Bone Regeneration.

Inorganic nanoparticulate biomaterials, such as calcium phosphate and bioglass particles, with chemical compositions similar to that of the inorganic component of natural bone, and hence having excellent biocompatibility and bioactivity, are widely used for the fabrication of synthetic bone graft substitutes. Growing evidence suggests that structurally anisotropic, or 1D inorganic micro-/nanobiomaterials are superior to inorganic nanoparticulate biomaterials in the context of mechanical reinforcement and construction of self-supporting 3D network structures. Therefore, in the past decades, efforts have been devoted to developing advanced synthetic scaffolds for bone regeneration using 1D micro-/nanobiomaterials as building blocks. These scaffolds feature extraordinary physical and biological properties, such as enhanced mechanical properties, super elasticity, multiscale hierarchical architecture, extracellular matrix-like fibrous microstructure, and desirable biocompatibility and bioactivity, etc. In this review, an overview of recent progress in the development of advanced scaffolds for bone regeneration is provided based on 1D inorganic micro-/nanobiomaterials with a focus on their structural design, mechanical properties, and bioactivity. The promising perspectives for future research directions are also highlighted.

Preclinical evaluation of a new synthetic carbonate apatite bone substitute on periodontal regeneration in intrabony defects.

OBJECTIVE: To evaluate the potential of a novel synthetic carbonate apatite bone substitute (CO3 Ap-BS) on periodontal regeneration. BACKGROUND: The use of various synthetic bone substitutes as a monotherapy for periodontal regeneration mainly results in a reparative healing pattern. Since xenografts or allografts are not always accepted by patients for various reasons, a synthetic alternative would be desirable. METHODS: Acute-type 3-wall intrabony defects were surgically created in 4 female beagle dogs. Defects were randomly allocated and filled with CO3 Ap-BS (test) and deproteinized bovine bone mineral (DBBM) or left empty (control). After 8 weeks, the retrieved specimens were scanned by micro-CT, and the percentages of new bone, bone substitute, and soft tissues were evaluated. Thereafter, the tissues were histologically and histometrically analyzed. RESULTS: Healing was uneventful in all animals, and defects were present without any signs of adverse events. Formation of periodontal ligament and cementum occurred to varying extent in all groups without statistically significant differences between the groups. Residues of both bone substitutes were still present and showed integration into new bone. Histometry and micro-CT revealed that the total mineralized area or volume was higher with the use of CO3 Ap-BS compared to control (66.06 ± 9.34%, 36.11 ± 6.40%; p = .014, or 69.74 ± 2.95%, 42.68 ± 8.68%; p = .014). The percentage of bone substitute surface covered by new bone was higher for CO3 Ap-BS (47.22 ± 3.96%) than for DBBM (16.69 ± 5.66, p = .114). CONCLUSIONS: CO3 Ap-BS and DBBM demonstrated similar effects on periodontal regeneration. However, away from the root surface, more new bone, total mineralized area/volume, and higher osteoconductivity were observed for the CO3 Ap-BS group compared to the DBBM group. These findings point to the potential of CO3 Ap-BS for periodontal and bone regeneration.

Octacalcium phosphate phase forming cements as an injectable bone substitute materials: Preparation and in vitro structural study.

In the realm of regenerating damaged or degenerated bones through minimally invasive techniques, injectable materials have emerged as exceptionally promising. Among these, calcium phosphate bone cements (CPCs) have garnered significant interest due to their remarkable bioactivity, setting it apart from non-degradable alternatives such as polymethyl methacrylate cements. α-Tricalcium phosphate (α-TCP) is a widely used solid phase component in CPCs. It can transform into calcium-deficient hydroxyapatite (CDHAp) when it comes in contact with water. In this study, we aimed to create an injectable, self-setting bone cement using low-temperature synthesized α-TCP powder as a single precursor of the powder phase. We found that changes in the pH of the liquid phase (pH 6.0, pH 6.2, pH 7.0 and pH 7.4) significantly altered the cement's setting, handling, and mechanical properties. The formation of the octacalcium phosphate (OCP) phase was identified in our study, which positively affects the osteoblastic cell response. Hardened OCP-forming bone cements prepared using a liquid phase with pH 7.0 and 7.4 showed better osteogenic cell attachment and proliferation than those prepared with pH 6.0 and 6.2. Our study suggests that changes in the pH of the liquid phase can significantly affect the properties of α-TCP-based bone cement, and the presence of the OCP phase is crucial for optimal cement performance.

Effect of different HA/ß-TCP coated 3D printed bioceramic scaffolds on repairing large bone defects in rabbits.

BACKGROUND: Treatment of large segmental bone defects is still a major clinical challenge, and bone grafting is the main method. The development of novel bone graft substitutes will help solve this problem. METHODS: Porous bioceramics hydroxyapatite (HA) scaffolds coated with different ratios of HA/ß-tricalcium phosphate (ß-TCP) were prepared by 3D printing. The scaffolds were sampled and tested in large segmental bone defect rabbit models. X-ray, micro-computed tomography (CT), hematoxylin and eosin (HE) staining, Van-Gieson staining, and type I collagen staining were performed to find the best scaffolds for large segmental bone defect treatment. RESULTS: The average length, diameter, compressive strength, and porosity of the bioceramics scaffolds were 15.05 ± 0.10 mm, 4.98 ± 0.06 mm, 11.11 ± 0.77 MPa, and 54.26 ± 5.38%, respectively. Postoperative lateral radiographs suggested the scaffold group got better bone healing and stability than the blank group. Micro-CT showed new bones grew into the scaffold from the two ends of the fracture along the scaffold and finally achieved bony union. The new bone volume around the scaffolds suggested the 3:7 HA/ß-TCP-coated bioceramic scaffolds were more favorable for the healing of large segmental bone defects. The results of HE, Van-Gieson, and type I collagen staining also suggested more new bone formation in 3:7 HA/ß-TCP-coated bioceramic scaffolds. CONCLUSION: 3:7 HA/ß-TCP-coated porous bioceramics scaffolds are more conducive to the repair of large bone defects in rabbits. The results of this study can provide some reference and theoretical support in this area.

Bone regeneration property of tooth-derived bone substitute prepared chairside for periodontal bone defects: an experimental study.

BACKGROUND: Periodontitis often leads to progressive destruction and loss of alveolar bone, the reconstruction of which remains difficult in periodontal therapy. As a novel bone graft material, tooth-derived bone substitute (TDBS) processed from extracted teeth has been previously reported about its osteoconductivity and promising results in bone regeneration. This study was to investigate the biological effects and bone regeneration properties of TDBS in vitro and in vivo using rat periodontal bone defect model. METHODS: Three groups of materials were used in the experiments: TDBS, TDBS treated with ethylene diamine tetraacetic acid (EDTA) (TDBS-E), and allogeneic bone materials. Calcium (Ca) and phosphate (P) ion dissolutions were quantified by spectrophotometer for seven days. The releases of bone morphogenetic protein-2 (BMP-2) and transforming growth factor-ß1 (TGF-ß1) were identified by enzyme-linked immunosorbent assay (ELISA). Human osteoblast proliferation, migration, and differentiation were detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, cell counting, alkaline phosphatase activity (ALP), and alizarin red staining (ARS), respectively. Furthermore, the osteogenic effects of TDBS on periodontal furcation bone defects were evaluated at eight weeks postoperatively using micro-computed tomography (Micro-CT) and histological analysis. RESULTS: The dissolution of both Ca and P ions in TDBS increased over time. The BMP-2 released from TDBS was significantly higher than that from TDBS-E and allografts, while the TGF-ß1 release from TDBS and TDBS-E groups was higher than that in the allografts. The TDBS-E group could induce the highest level of osteoblast proliferation compared to other groups. Cell migration with allografts co-culture was significantly induced compared to the blank control. However, all groups demonstrated similar positive effects on osteoblast differentiation. Furthermore, in the periodontal model, all materials could effectively enhance bone regeneration in the furcation defect. CONCLUSIONS: The TDBS prepared chairside as an autogenous bone graft, demonstrating osteoinductivity, which enhances the osteogenic biological characteristics. Therefore, TDBS is suggested as an economical and biocompatible material for periodontal bone regeneration.

Carbonate apatite versus ß-tricalcium phosphate for rat vertical bone augmentation: A comparison of bioresorbable bone substitutes using polytetrafluoroethylene tubes.

This study radiologically and histologically compared two bioresorbable bone substitutes with different compositions carbonate apatite (Cytrans® Granules; CGs) and ß-tricalcium phosphate (ß-TCP) for vertical bone augmentation on a rat skull using a polytetrafluoroethylene (PTFE) tubes. This PTFE tube was placed at the center of the skull, fixed with Super Bond, and augmented with CGs or ß-TCP granules. Specimens with surrounding tissue were harvested at 4, 8, and 12 weeks postoperatively, and radiological and histological evaluations were performed. The bone volume to total volume ratio (BV/TV) of the ß-TCP-implanted group was markedly higher than that of the CG-implanted group at 4 and 12 weeks postoperatively. Compared to CGs, ß-TCP exhibited the ability to form blood vessels into the graft material for a short period after transplantation, as well as an elevated production of collagen into ß-TCP granules during the bone formation process.

Bioactive Bone Substitute in a Rabbit Ulna Model: Preclinical Study.

BACKGROUND: Current therapies to effectively treat long-bone defects and extensive bone tissue loss remains limited. In this study, we created a new bone substitute by integrating advanced technologies such as structure patterning, controlled release of a bone growth factor and conjugation system for clinically effective bone regeneration. This novel bioactive bone substitute was evaluated for its safety and efficacy using a rabbit ulna model. METHODS: A three dimensional bone patterned cylindrical structure with 1.5 cm in length and 5 mm in diameter was printed using poly(L-lactic acid)(PLLA) as a weight-bearing support and space-filling scaffold. And a bone morphogenetic protein 2 (BMP2) was employed to enhance bone regeneration, and coated to a 3D PLLA using alginate catechol and collagen to prolong the release kinetics. This novel bone substitute (BS)was evaluated for its physico-chemical and biological properties in vitro, and histological analysis and radiographical analysis such as X-ray, CT and micro-CT image analysis were performed to evaluate new bone formation in vivo. RESULTS: The BS possesses an ideal shape and mechanically suitable proeperties for clinical use, with an easy-to-grab and break-resistant design at both ends, 80 ± 10 MPa of compression strength, and BMP2 release for two months. Histological analysis demonstrated the biocompability of BS with minimal inflammation and immune response, and X-ray, CT and micro-CT demonstrated effective new bone formation in rabbit ulna defect model. CONCLUSION: The preclinical study of a novel bioactive bone substitute has shown its safe and effective properties in an animal model suggesting its clinical potential.

Efficacy of positive space acquiring membrane and antimicrobial membrane combined with granular bone substitute implantation in guiding oral bone regeneration.

Augmentation of the alveolar bone is important before oral implantation. For large bone defects, it becomes necessary to apply guided bone regeneration (GBR) materials, accompanied by filling defect sites with autologous or allogeneic bone, or bone substitutes such as acellular bone powder. In this study, we tested a granular bone substitute and GBR membrane combination therapy in treating MC3T3-E1 and L929 cells in vitro and rat calvarial and alveolar defects in vivo. The recovery conditions of bone defects were monitored by micro-CT, and 3D reconstruction of the CT images was applied to evaluate the bone augmentation semi-quantitatively. Test GBR materials could support the proliferation of MC3T3-E1 cells, poly (p-dioxanone-co-L-phenylalanine) (PDPA)-based membrane could induce apoptosis of L929 cells. Among GBR membranes applied groups, the regeneration condition of defected calvarial defects of PDPA based membrane applied group was the best and this may be caused by its excellent positive space acquiring effect. However, in a complex bacteriogenic environment, the oral bone regeneration-guided efficacy of the PDPA membrane decreased in the post-repair stage with the aggravation of infections. By contrast, the antimicrobial membrane combined with the PDPA membrane exhibited continually increasing GBR efficacy at the later stage of repair owing to its multifunctional properties, which are infection-inhibiting and positive space acquiring. Therefore, multifunctional GBR membranes are preferable for GBR in complex oral environments, and further research should be conducted to determine their efficacy in other models.

Bone regeneration after maxillary sinus floor augmentation with different ratios of autogenous bone and deproteinized bovine bone mineral an in vivo experimental study.

OBJECTIVE: Test the hypothesis of no difference in bone regeneration after maxillary sinus floor augmentation (MSFA) with different ratios of iliac or mandibular autogenous bone (AB) graft and deproteinized bovine bone mineral (DBBM). MATERIALS AND METHODS: Forty minipigs were randomly allocated to bilateral MSFA using: (A) 100% AB, (B) 75% AB and 25% DBBM, (C) 50% AB and 50% DBBM, (D) 25% AB and 75% DBBM, or (E) 100% DBBM. The animals were euthanized 12 weeks after surgery. Percentage of bone, non-mineralized tissue, and residual DBBM were estimated by histomorphometric analysis in a randomly selected region of interest and summarized as mean percentage with 95% confidence interval (CI). RESULTS: Mean percentage of bone following MSFA with iliac or mandibular AB graft was: (A) 55.5% and 64.2%, (B) 60.3% and 61.6%, (C) 54.4% and 52.1%, (D) 51.8% and 53.1%, and (E) 47.6%, respectively. There was a significant trend toward a higher percentage of bone, with a higher ratio of AB within the graft (p < .01), regardless of the origin of AB graft (iliac or mandible). CONCLUSIONS: The hypothesis was rejected since percentage of bone was significantly increased with larger proportions of AB within the graft. Consequently, AB or a mixture of AB and diminutive quantities of DBBM seem to be the preferred graft for MSFA based solely on histomorphometric assessment. However, it should be emphasized that newly formed bone and residual AB graft particles could not be distinguished by the applied histologic procedure.

The Interplay of Raloxifene and Sonochemical Bio-Oss in Early Maxillary Sinus Bone Regeneration: A Histological and Immunohistochemical Analysis in Rabbits.

The study aimed to assess the efficacy of using Raloxifene with ultrasonic processing to enhance Bio-Oss®, a bone graft substitute, for maxillary sinus bone height reconstruction. A total of 24 rabbit maxillary sinuses were distributed into three groups, each receiving different treatments: Bio-Oss® only, sonicated Bio-Oss, and sonicated Bio-Oss® with Raloxifene. Surgical procedures and subsequent histomorphometric and immunohistochemistry analyses were conducted to evaluate the bone formation, connective tissue, and remaining biomaterial, as well as the osteoblastic differentiation and maturation of collagen fibers. Results indicated that the sonicated Bio-Oss® and Bio-Oss® groups showed similar histological behavior and bone formation, but the Raloxifene group displayed inflammatory infiltrate, low bone formation, and disorganized connective tissue. The statistical analysis confirmed significant differences between the groups in terms of bone formation, connective tissue, and remaining biomaterial. In conclusion, the study found that while sonicated Bio-Oss® performed comparably to Bio-Oss® alone, the addition of Raloxifene led to an unexpected delay in bone repair. The findings stress the importance of histological evaluation for accurate bone repair assessment and the necessity for further investigation into the local application of Raloxifene. Future research may focus on optimizing bone substitutes with growth factors to improve bone repair.

Combination of leukocyte and platelet-rich fibrin and demineralized bovine bone graft enhanced bone formation and healing after maxillary sinus augmentation: a randomized clinical trial.

BACKGROUND AND OBJECTIVE: The resorption of alveolar ridge bone and maxillary sinus pneumatization are challenges to implant-supported prosthetic rehabilitation. Bone regeneration using bone substitutes and growth factors are alternatives for maxillary sinus augmentation (MSA). Therefore, we sought to evaluate the effects of the association between leukocyte and platelet-rich fibrin (L-PRF) and deproteinized bovine bone mineral (DBBM) in MSA procedures. MATERIALS AND METHODS: Thirty-six maxillary sinuses from 24 individuals were included in this randomized clinical trial. The maxillary sinuses were randomly grafted with LPRF and DBBM (test group) or grafted only with DBBM (positive control). Dental implants were installed in the test group following two periods of evaluation: after 4 (DBBM+LPRF4) and 8 (DBBM+LPFR8) months of sinus graft healing, while the control group received implants only after 8 months. Cone beam computed tomography (CBCT) was taken 1 week after surgery (T1) and before implant placement (T2). Bone samples were collected during implant placement for histomorphometric and immunohistochemical (IHC) analysis. The primary implant stability was assessed by resonance frequency analysis. RESULTS: CBCT analysis demonstrated a significant decrease in bone volume from T1 to T2 in all groups without differences among them. Histologically, the test group showed significantly increase in bone neoformation in both periods of evaluation (LPRF+DBBM4: 44.70±14.01%; LPRF+DBBM8: 46.56±12.25%) compared to the control group (32.34±9.49%). The control group showed the highest percentage of residual graft. IHC analysis showed increased staining intensity of osteocalcin (OCN), vascular endothelial growth factor (VEGF), and runt related transcription factor 2 (RUNX-2) in LPRF+DBBM4 group, and osteopontin (OPN) in the L-PRF+DBBM8. Primary implant stability was successfully achieved (above 60 in implant stability quotient) in all the evaluated groups. CONCLUSION: Combination of L-PRF and DBBM increased and accelerated new bone formation allowing early implant placement probably due to the higher protein expression of RUNX2, VEGF, OCN, and OPN. These data suggest that the use of L-PRF might be an interesting alternative to use in combination with DBBM for augment the maxillary sinuses allowing the installation of appropriate length implants in shorter period of time. CLINICAL RELEVANCE: This study showed improvement in bone neoformation and accelerated healing when associating L-PRF and DBBM for maxillary sinus augmentation procedures. TRIAL REGISTRATION: This study was registered before participant recruitment in Brazilian Registry of Clinical Trials (ReBEC - RBR-95m73t).

Hierarchically Porous Implants Orchestrating a Physiological Viscoelastic and Piezoelectric Microenvironment for Bone Regeneration.

The extracellular matrix microenvironment of bone tissue comprises several physiological cues. Thus, artificial bone substitute materials with a single cue are insufficient to meet the demands for bone defect repair. Regeneration of critical-size bone defects remains challenging in orthopedic surgery. Intrinsic viscoelastic and piezoelectric cues from collagen fibers play crucial roles in accelerating bone regeneration, but scaffolds or implants providing integrated cues have seldom been reported. In this study, it is aimed to design and prepare hierarchically porous poly(methylmethacrylate)/polyethyleneimine/poly(vinylidenefluoride) composite implants presenting a similar viscoelastic and piezoelectric microenvironment to bone tissue via anti-solvent vapor-induced phase separation. The viscoelastic and piezoelectric cues of the composite implants for human bone marrow mesenchymal stem cell line stimulate and activate Piezo1 proteins associated with mechanotransduction signaling pathways. Cortical and spongy bone exhibit excellent regeneration and integration in models of critical-size bone defects on the knee joint and femur in vivo. This study demonstrates that implants with integrated physiological cues are promising artificial bone substitute materials for regenerating critical-size bone defects.

The immunomodulatory effect of IL-4 accelerates bone substitute material-mediated osteogenesis in aged rats via NLRP3 inflammasome inhibition.

Background: Bone defect repair by implanting bone substitute materials has been a common clinical treatment. With the understanding of substance-immune system interactions and increasing evidence indicating that the post-implantation immune response determines the fate of bone substitute materials, active modulation of host macrophage polarization is considered a promising strategy. However, whether the same regulatory effects exist when an individual immune system is altered with aging is unclear. Methods: In this study, we mechanistically investigated the effect of immunosenescence on the active regulation of macrophage polarization by establishing a cranial bone defect model in young and aged rats implanted with Bio-Oss®. Forty-eight young and 48 aged specific pathogen-free (SPF) male SD rats were randomly divided into two groups. In the experimental group, 20 µL of IL-4 (0.5 µg/mL) was injected locally on the third to seventh postoperative days, while an equal volume of PBS was injected in the control group. Specimens were collected at 1, 2, 6, and 12 weeks postoperatively, and bone regeneration at the defect site was evaluated by micro-CT, histomorphometry, immunohistochemistry, double-labeling immunofluorescence, and RT-qPCR. Results: The application of exogenous IL-4 reduced activation of NLRP3 inflammasomes by promoting the polarization of M1 macrophages to M2 macrophages, thus promoting bone regeneration at the site of bone defects in aged rats. However, this effect was gradually weakened after the IL-4 intervention was discontinued. Conclusion: Our data confirmed that a strategy to regulate macrophage polarization is also feasible under conditions of immunosenescence, i.e., the local inflammatory microenvironment can be regulated by reducing M1-type macrophages. However, further experiments are needed to determine an exogenous IL-4 intervention that can maintain a more sustained effect.

Impact of Octacalcium Phosphate/Gelatin (OCP/Gel) Composite on Bone Repair in Refractory Bone Defects.

In clinical settings, bone grafting is frequently used to treat bone defects. Therefore, the development of bone graft substitutes with superior bone formation ability is expected, instead of autogenous bone grafting. Octacalcium phosphate (OCP) has been developed as a bone graft substitute, and preclinical studies using OCP have reported superior bone formation ability compared with ß-tricalcium phosphate. Furthermore, OCP has been used in composite forms with natural polymers such as collagen and gelatin to improve the usability of OCP, and OCP/collagen composite forms have been clinically applied in the dental field because of their excellent usability and osteogenic potential. This review describes the development and preclinical results of OCP and OCP/gelatin (OCP/Gel) composites and prospects for future applications in orthopedics. The development of bone graft substitutes that achieve a high degree of biodegradability and strength will be needed for the clinical application of OCP composites in orthopedics in the future.

Investigation of Bone Regeneration Efficacy of New Bovine Bone Minerals in a Canine Mandibular Critical Defect Model.

This study aims to investigate the bone regeneration effect of bovine hydroxyapatite-processed biomaterials Bone-XB and S1-XB in a beagle mandibular defect model. A total of four saddle-type critical sizes (15 mm × 10 mm) bone defects are created in each dog: two defects in the left mandible and two defects in the right mandible. The defect control (DC) group is kept unfilled, and the other three defects are filled with three different biomaterials as follows: positive control Bio-Oss (Bio-Oss group), Bone-XB (XB group), and S1-XB (S1-XB group). Bone regeneration is evaluated by radiography, micro-computed tomography, and histological analysis. It is revealed that Bone-XB and S1-XB significantly increase newly formed bone, defect filling percentage, and bone healing score compared to the DC group, which is confirmed by bone microstructure augmentation (bone volume/total volume, trabecular number, and trabecular thickness). Interestingly, no significant differences are observed between the Bone-XB, S1-XB, and Bio-Oss groups. It is suggested that Bone-XB or S1-XB stimulates bone regeneration demonstrated by the increase in newly formed bone and bone microstructure, thereby improving bone defect filling, which is equivalent to the Bio-Oss. Therefore, bovine hydroxyapatite-processed Bone-XB or S1-XB can be considered effective biomaterials for correcting critical-size bone defects or fractures.