Bone substitutes: an update

Fully guided system for position-predictable autotransplantation of teeth: A randomized clinical trial

AIM

Autotransplantation of teeth (ATT) is a viable biological method for addressing dental defects. The objective was to achieve occlusal reconstruction-orientated ATT to enhance functionality and obtain optimal location and adjacency. This study proposes a new concept of a guide (a fully guided system) to achieve position-predictable ATT.

METHODOLOGY

This study included 30 transplants in 29 patients who were randomly divided into two groups during the initial examination using a single-blind method. The experimental group comprised 15 transplants in 14 patients who underwent surgery using a fully guided system. Fifteen transplants were performed on 15 patients in the control group using only a replica.

RESULTS

The mean number of repeated teeth autotransplantation attempts and mean preparation time exhibited no significant differences. The mean follow-up period was 1 year. Twenty-six transplants were followed up clinically, while four were only followed up by phone calls. The experimental group demonstrated a 100% success rate, whereas the control group exhibited a 70% success rate, with an overall 100% survival rate. 3D analysis: Deviation of both angle and distance was calculated for evaluation of accuracy. The mean centre deviation of teeth in experiment group was 0.79 mm (95% confidence interval [CI], 0.51-1.08) compared to 1.79 mm (95% CI, 1.10-2.47) in control group (p < .05). The mean of average index points distance deviation showed a significant difference. The mean angle deviation of long axis in experiment group was 3.87° (95% CI, 2.25-5.49) compared to 12.98° (95% CI, 8.64-17.31) in control group (p < .05). The angle deviation of long axis in mesio-distal direction, buccal-lingual direction and rotation showed a significant difference also.

CONCLUSIONS

The results of the analysis indicated that the fully guided system increased the predictability of achieving an ideal transplant position with intuitive data, establishing a solid foundation for optimal dental functional recovery and restoration. However, this study had limitations regarding the generalisability of the design of the optimal location for transplantation and the equipment requirements for clinical procedures. Therefore, further research on the screening of indications for guided systems and location planning is necessary.

CLINICAL TRIAL REGISTRATION

This study was registered on the Chinese Clinical Trial Registry (Registration Number: ChiCTR 2300074646).

The Role of Bone Grafting in Corrective Osteotomy of Distal Radius Malunions

Background  It remains unclear whether bone grafting is required during corrective osteotomy of the distal radius. The goal of this systematic review is to determine the union, revision, and complication rates of bone grafting techniques associated with extra-articular corrective osteotomy for dorsally malunited distal radius fractures treated with volar plating. Questions  Is bone grafting in distal radius corrective osteotomy associated with increased rates of bone union and reduced rates of revision surgery and complications? Materials and Methods  A comprehensive search of the MEDLINE, Embase, and Cumulative Index to Nursing and Allied Health Literature databases was completed for studies reporting clinical outcomes of extra-articular corrective osteotomy for dorsally malunited distal radius fractures treated with volar plating. Results  A total of 13 studies, with 14 intervention arms and 236 patients, were included. Bone grafting techniques consisted of autograft (6 studies, n  = 93), synthetic bone grafts (2 studies, n  = 38), allograft (1 study, n  = 14), or no grafting (5 studies, n  = 91). The overall union rate was 97%, and the mean time-to-union was 12.0 weeks. Larger corrections of dorsal tilt and ulnar variance were performed in the autograft and allograft groups. Complication and revision rates were highest in the synthetic group, 45 and 26.3% respectively. Conclusion  Grafting in extra-articular corrective osteotomy for dorsally angulated distal radius malunions treated with volar plating is not associated with an improved union rate in the literature. However, larger corrections were achieved in both the autograft and allograft groups compared to the no-graft and synthetic groups, resulting in similar union rates. Synthetic bone grafting was associated with the highest complication and revision rates. Future comparative prospective trials and proper documentation of whether cortical contact was present or absent are required to assess whether bone grafting warrants consideration in more advanced deformities. Level of Evidence  IV.

Distal femoral bone defect treatment using an engineered hydroxyapatite cylinder scaffold made from rattan wood

Distal femoral non-union presents significant challenges, often requiring complex treatment strategies to achieve bone healing. In this case, a young male patient with an open fracture of the distal femur developed an atrophic non-union, 9 months after initial fixation. The patient underwent surgical intervention with debridement, leading to a 2.2 cm bone defect and placement of a cylindrical synthetic bone graft (b.Bone), combined with bone marrow aspirate concentrate. This approach aimed to provide structural support and enhance biological healing. The choice of the cylindrical graft was due to its optimal fit and support for the anterior femoral cortex. Postoperative outcomes were favourable, with successful bone healing, confirmed radiologically, and restoration of function. This case demonstrates the potential of synthetic bone substitutes augmented with biological agents as a promising alternative to traditional grafts in managing complex non-unions.

Risk factors for non-union in foot and ankle arthrodesis: a population-based case-control study using registry data

BACKGROUND

Nonunion is a common complication following foot and ankle arthrodesis. This study endeavoured to determine the risk factors for nonunion in foot and ankle arthrodesis.

METHODS

This was a retrospective case-control study using the National Health Insurance Research Database. Patients who underwent foot and ankle arthrodesis with a minimum follow-up duration of 6 months were included. International Classification of Diseases codes were used to identify diagnoses and treatment. Patients with nonunion were matched by age and sex with patients with union at a ratio of 1:4. Logistic regression was performed to compare between patients with nonunion and controls with union to ascertain the effects of various risk factors.

RESULTS

A total of 107 joints were identified as nonunion, and 428 age- and sex-matched controls were selected. Patients with diabetes mellitus had a 1.710 times (95% CI = 1.060 - 2.756, p = 0.0278) higher risk of nonunion than those without. No significant differences were observed in the risk of nonunion in relation to which joint was treated; the presence of osteoarthritis, traumatic osteoarthritis, rheumatoid arthritis, osteoporosis, or open/arthroscopic arthrodesis; internal or external fixation; or the usage of a bone graft. For patients without diabetes mellitus, those who underwent arthrodesis in the tarsometatarsal joint had a 6.507 times (95% CI: 1.045 - 40.522, p = 0.0256) higher risk of nonunion compared to those who underwent arthrodesis in the ankle joint.

CONCLUSION

Diabetes mellitus increases the risk of nonunion among patients with and without diabetes mellitus. For those without diabetes mellitus, arthrodesis in the tarsometatarsal joint is associated with the highest risk of nonunion.

Fusion Rate of Biphasic Calcium Phosphate Bone Graft with Needle-Shaped Submicron Surface Topography in Interbody Lumbar Fusion for Degenerative Disc Disease: A Single-Center Retrospective Review

BACKGROUND

Calcium phosphate bone grafts are emerging as alternatives to autologous bone grafts in lumbar spinal fusion. This study evaluates the 12-month fusion rate and clinical outcomes of lumbar interbody fusion using synthetic biphasic calcium phosphate with submicron needle-shaped surface topography (BCP<μm).

METHODS

A retrospective review identified patients who underwent lumbar interbody arthrodesis with BCP<μm, with or without autograft. Fusion was assessed by an independent neuroradiologist using a computed tomography alphanumeric classification based on bridging bone on 12-month postoperative computed tomography. Secondary outcomes included changes in visual analog scale, length of stay, and fusion of all treated levels.

RESULTS

Fifty-five patients with 93 treated levels were analyzed (average age: 62.78 years; body mass index: 28.73 kg/m2). Patients had an average of 3 comorbidities and a median of 2 levels fused. Procedures included anterior (52 levels), transforaminal (22 levels), and lateral lumbar interbody fusion (19 levels). Fusion occurred in 95.70% of levels without evidence of fixation failure. Fusion rates were unaffected by procedure type (P = 0.965) or supplemental autograft use (P = 1.00). Complications were reported in 4 patients. Six-month postoperative visual analog scale improved by a mean of 25.10 (P < 0.0001).

CONCLUSIONS

This study demonstrates a high fusion rate (95.70%) and low complication rate in a diverse patient population with multiple comorbidities, suggesting BCP<μm is a viable graft material for lumbar interbody fusion.

Clinical challenges in bone tissue engineering - A narrative review

Bone tissue engineering (BTE) has emerged as a promising approach to address large bone defects caused by trauma, infections, congenital malformations, and tumors. This review focuses on scaffold design, cell sources, growth factors, and vascularization strategies, highlighting their roles in developing effective treatments. We explore the complexities of balancing mechanical properties, porosity, and biocompatibility in scaffold materials, alongside optimizing mesenchymal stem cell delivery methods. The critical role of growth factors in bone regeneration and the need for controlled release systems are discussed. Vascularization remains a significant hurdle, with strategies such as angiogenic factors, co-culture systems, and bioprinting under investigation. Mechanical challenges, tissue responses, and inflammation management are examined, alongside gene therapy's potential for enhancing osteogenesis and angiogenesis via both viral and non-viral delivery methods. The review emphasizes the impact of patient-specific factors on bone healing outcomes and the importance of personalized approaches. Future directions are described, emphasizing the necessity of interdisciplinary cooperation to advance the field of BTE and convert laboratory results into clinically feasible solutions.

A ceramic microbridge microfluidic chip to study osteogenic differentiation of mesenchymal stem cells in bioactive ceramic immune microenvironment

Bioactive ceramics have been used in bone tissue repair and regeneration. However, because of the complex in vivo osteogenesis process, long cycle, and difficulty of accurately tracking, the mechanism of interaction between materials and cells has yet to be fully understood, hindering its development. The ceramic microbridge microfluidic chip system may solve the problem and provide an in vitro method to simulate the microenvironment in vivo. Nevertheless, the complex microenvironment parameters of the chip system need to be studied in detail. Computer simulation bionics can provide clues for the setting of microenvironment parameters. This study used a computational bionic model to simulate the bone growth process in the presence of immune-related factors. The osteoblast differentiation of mesenchymal stem cells of calcium phosphate ceramics in a macrophage-dominated immune microenvironment was studied using a microfluidic chip system. The computational biomimetic model and microfluidic chip findings were basically consistent with the reported results of the animal experiments. These findings suggest that studying the osteogenic behavior of calcium phosphate ceramics using a microfluidic chip model is feasible. The method model provided in this study can be extended to other biomaterials, providing a viable path for their research and evaluation.

Supercritical CO2 With Enzymatic Posttreatment Enhances Mechanical and Biological Properties of Cancellous Bovine Bone Block Grafts

Bone loss resulting in large bony defects presents a significant challenge for surgeons. In cases requiring reconstruction, bone "block" grafts that have the key attributes of both physical robustness and biocompatibility are required to facilitate bone healing and regeneration. Current technologies employed for the development of block grafts often result in constructs with suboptimal strength and integration. This study aimed to develop a bovine-derived bone block graft using the process of supercritical fluid (SCF) extraction to maintain mechanical strength and biocompatibility. Bone blocks were prepared from the condyles of bovine femurs. After optimization, the blocks were divided into six groups; Group 1: Raw bone, Group 2: SCF-CO2, Groups 3: SCF-CO2-H2O2, and Group 4: SCF-CO2-H2O2 + Pepsin. Characterization of the constructs included analysis of organic material (thermogravimetric analysis, TGA), crystallinity using x-ray diffraction (XRD), surface topography with scanning electron microscopy (SEM), and chemical composition using Fourier-transform infrared (FTIR) spectroscopy. Mechanical strength was assessed using compression testing, and clinically relevant handling was investigated with a bench-top drill test. Biological testing was carried out in vitro using human bone marrow-derived mesenchymal stem cells (hBMSCs). The SCF-treated bone blocks showed promising results with enhanced mechanical strength (raw bone [mean = 23.01 8.9 MPa], SCF-CO2-H2O2 [mean = 48.9 ± 11.6 MPa], p < 0.0001) reduced organic content (raw bone = 17.6%, SCF-CO2-H2O2 + Pepsin = 12.4%), and significantly higher hBMSCs' metabolic activity on the SCF-CO2 and SCF-CO2 + H2O2 compared to Bio-Oss at 24, 48, 72, and 96 h (p < 0.05). SEM photomicrographs showed reduced debris in trabecular structures with open pores after SCF-CO2 treatment, especially in SCF-CO2-H2O2 + Pepsin blocks. Moreover, the bench-top clinical handling test demonstrated the ease of block fixation with surgical screws. Overall, the SCF-CO2 and posttreatments of bovine block grafts showed potential for clinical application.

Enhanced osteogenic capacity of octacalcium phosphate involving adsorption of stromal-derived factor-1 in a standardized defect of a rat femur

This study investigated whether octacalcium phosphate (OCP) enhances bone regeneration through its synergistic effect with stromal-derived factor-1 (SDF-1). Recombinant SDF-1 (0.5-5.0 μg) was combined with OCP granules through lyophilization. OCP/SDF-1 granules were implanted into a rat femoral standardized defect for 2 and 4 weeks and subjected to histomorphometry, C-X-C motif chemokine receptor 4 (CXCR4) and osteocalcin immunohistomorphometry, and tartrate-resistant acid phosphatase (TRAP) staining. Calcium-deficient hydroxyapatite (CDHA) was used as a control for in vitro analyses. Mesenchymal stem cell (MSC) migration was estimated using a Transwell system with OCP/SDF-1. SDF-1 release from OCP/SDF-1 into the supernatant was determined without cells. SDF-1 adsorption in 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid buffer onto OCP, the chemical structure of OCP immersed in the medium using Fourier transform infrared spectroscopy, and the degree of supersaturation of the medium were determined. Bone regeneration and OCP degradation were enhanced the most by 1.0 μg of OCP/SDF-1 at 2 weeks after implantation by CT analysis and increasing CXCR4-positive, osteocalcin-positive, and TRAP-positive cells accumulation around the OCP. MSC migration increased until 48 h in the following order: SDF-1 only, CDHA/SDF-1, and OCP/SDF-1, with the greatest effect with 1.0 μg of SDF-1 than from OCP. CDHA promoted a greater release than OCP at 48 h. The physicochemical analyses indicated that SDF-1 interacted with OCP through Freundlich-type adsorption and that the adsorption controlled SDF-1 release from OCP during the hydrolysis into CDHA. Therefore, leveraging its molecular affinity for the OCP surface, OCP/SDF-1 facilitates MSC migration and enhances bone formation by ensuring the controlled, sustained release of SDF-1 from OCP.

Freeze-Cast Composites of Alginate/Pyrophosphate-Stabilized Amorphous Calcium Carbonate: From the Nanoscale Structuration to the Macroscopic Properties

Pyrophosphate-stabilized amorphous calcium carbonates (PyACC) are promising compounds for bone repair due to their ability to release calcium, carbonate, and phosphate ions following pyrophosphate hydrolysis. However, shaping these metastable and brittle materials using conventional methods remains a challenge, especially in the form of macroporous scaffolds, yet essential to promote cell colonization. To overcome these limitations, this article describes for the first time the design and multiscale characterization of freeze-cast alginate (Alg)-PyACC nanocomposite scaffolds. The study initially focused on the synthesis of Alg-PyACC powder through in situ coprecipitation. The presence of alginate chains in the vicinity of the PyACC was shown to affect both the powder reactivity and the release of calcium ions when placed in water (XRD, chemical titrations). In vitro cellular assays confirmed the biocompatibility of Alg-PyACC powder, supporting its use as a filler in scaffolds for bone substitutes. In a second step, the freeze-casting process was carried out using these precursor powders with varying rates of inorganic fillers. The resulting scaffolds were compared in terms of pore size and gradient (via SEM, X-ray microtomography, and mercury intrusion porosimetry). All scaffolds exhibited a pore size gradient oriented along the solidification axis, featuring unidirectional, lamellar, and interconnected pores. Interestingly, we found that the pore size and wall thickness could be controlled by the filler rate. This effect was attributed to the in situ cross-linking of alginate chains by released Ca2+ ions from the fillers, which increased viscosity, affecting temperature-driven segregation during the freezing step. Different multiscale organizations of the porosity and spatial distribution of fillers (FEG-SEM) were correlated with changes in the scaffold mechanical properties (tested via uniaxial compression). With such tunable porous and mechanical properties, Alg-PyACC composite scaffolds present attractive opportunities for specific bone substitute applications.

Bone Fillers with Balance Between Biocompatibility and Antimicrobial Properties

Millions of people request bone regeneration every year, and the market for bone grafting materials has a positive trend. The most used biomaterials applied to replace and regenerate bone are based on collagen and different types of ceramics in order to mimic natural bone matrix. However, there are a lot of implant-associated infections after surgery, or the implants are rejected because of reduced biocompatibility, and this is why the research into graft bone materials is still a challenge. This study aims to develop and characterize novel biomimetic bone fillers which have simultaneously both antimicrobial properties and biocompatibility with human bone marrow-derived mesenchymal stem cells (BMSCs). Type I collagen and calcium triphosphate in a ratio of 1:1 were used as a control, according to our previous studies, and ZnO, functionalized with different percentages of Satureja thymbra L. essential oils, was added as an antimicrobial, promoting bone growth, mineralization, and formation. The bone fillers were obtained by freeze-drying in spongious forms and characterized by Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), water uptake, biodegradability over time, antimicrobial activity against Staphylococcus aureus and Escherichia coli and viability and proliferation of human BMSCs. The graft material showed a higher porosity with interconnected pores, gradual resorption over time and a balance between antimicrobial properties and biocompatibility and was chosen as an ideal bone filler.

Facile synthesis of in situ bismuth-doped calcium phosphate nanocomposite integrated injectable biopolymer hydrogel slurry for bone regeneration

The bionics of natural bone structures plays an essential role in the selection of materials for bone tissue engineering. Although the content of trace metallic elements in bone is low, they have significant effects on the process of bone growth and metabolism. Up to now, the applications of "green" heavy metals in bone regeneration are limited. Herein, in this study, we present a straightforward one-pot strategy for the synthesis of in situ bismuth-doped amorphous calcium phosphate nanocomposites (RBCP), effectively integrating the beneficial properties of each component. The characterization of these products can be readily optimized by adjusting reaction parameters. Our in vitro studies show that under coordination of each component, the RBCP biomaterial demonstrates distinguished biocompatibility and significantly accelerates vascular pattern formation within just 4 h by stimulating the expression of angiogenesis-related genes in human umbilical vein endothelial cells (HUVECs). In vivo experiments indicate that the incorporation of bismuth effectively enhances bone regeneration and osseointegration in a rat femur defect model. In conclusion, the as-prepared RBCP biomaterials hold promising prospects for treating segmental bone defects, owing to the facile, cost-effective, and eco-friendly preparation process, along with their remarkable capabilities.

Bone Tissue Engineering: From Biomaterials to Clinical Trials

Bone tissue engineering is a promising field that aims to rebuild the bone tissue using biomaterials, cells, and signaling molecules. Materials like natural and synthetic polymers, inorganic materials, and composite materials are used to create scaffolds that mimic the hierarchical microstructure of bone. Stem cells, particularly mesenchymal stem cells (MSCs), play a crucial role in bone tissue engineering by promoting tissue regeneration and modulating the immune response. Growth factors like bone morphogenetic proteins (BMPs), vascular endothelial growth factor (VEGF), and platelet-derived growth factor (PDGF) are utilized to accelerate bone regeneration. Clinical applications include treating nonunion and mal-union fractures, osteonecrosis, orthopedic surgery, dental applications, and spinal cord injuries. Recent advances in the field include nanotechnology, 3D printing, bioprinting techniques, gene editing technologies, and microfluidic devices for drug testing. However, challenges remain, such as standardization of protocols, large-scale biomaterial production, personalized medicine approaches, cost-effectiveness, and regulatory issues. Current clinical trials are investigating the safety and efficacy of various bone tissue engineering approaches, with the potential to modernize patient care by providing more adequate treatments for bone defects and injuries.

Teriparatide as a non-surgical salvage therapy for prolonged humerus fracture nonunion: A case report and literature review

BACKGROUND

Fracture nonunion represents a challenging complication during fracture repair, often necessitating surgical intervention. Teriparatide, a recombinant human parathyroid hormone, has demonstrated promise in enhancing fracture healing, although its efficacy in treating established nonunion remains under investigation.

CASE SUMMARY

We report a case of a 27-year-old male who presented with a right humerus fracture following a traffic accident. Despite undergoing open reduction and internal fixation, the fracture resulted in a delayed union and subsequent nonunion. After 4 years of conservative management, teriparatide treatment was initiated due to persistent nonunion. Teriparatide injections were administered daily for 6 months, resulting in complete fracture healing and resolution of pain.

CONCLUSION

Our case demonstrates the successful use of teriparatide in treating a prolonged nonunion of a humerus fracture. Teriparatide may provide a valuable therapeutic option for established bone nonunion, even in cases that have not responded to conservative treatments.

Bibliometric mapping of mesenchymal stem cell therapy for bone regeneration from 2013 to 2023

Mesenchymal stem cells (MSCs) have shown significant potential in bone regeneration and regenerative medicine in recent years. With the advancement of tissue engineering, MSCs have been increasingly applied in bone repair and regeneration, and their clinical application potential has grown through interdisciplinary approaches involving biomaterials and genetic engineering. However, there is a lack of systematic reviews summarizing their applications in bone regeneration. To address this gap, we analyzed the latest research on MSCs for bone regeneration published from 2013 to 2023. Using the Web of Science Core Collection, we conducted a literature search in December 2024 and employed bibliometric tools like CiteSpace and VOSviewer for a comprehensive analysis of the key research trends. Our findings focus on the development of cell engineering, highlighting the advantages, limitations, and future prospects of MSC applications in bone regeneration. These insights aim to enhance understanding of MSC-based bone regeneration, inspire new research directions, and facilitate the clinical translation of MSC research.

Long-Term Natural Hydroxyapatite and Synthetic Collagen Hydroxyapatite Enhance Bone Regeneration and Implant Fixation Similar to Allograft in a Sheep Model of Implant Integration

There is an increasing demand for a suitable bone substitute to replace current clinical gold standard autografts or allografts. Majority of previous studies have focused on the early effects of substitutes on bone formation, while information on their long-term efficacies remains limited. This study investigated the efficacies of natural hydroxyapatite (nHA) derived from oyster shells and synthetic hydroxyapatite mixed with collagen (COL/HA) or chitosan (CS/HA) on bone regeneration and implant fixation in sheep. Titanium implants were inserted into critical-size defects in distal femur condyles bilaterally, and circumferential gaps around implants were filled with substitute materials or allografts (as control). 14 or 24 weeks post-operatively, the implant-bone blocks were harvested and evaluated using microarchitectural, histomorphometric, and mechanical methods. The nHA and COL/HA groups showed significant bone formation at both 14 and 24 weeks. There was a pronounced increase in bone tissue volume and ingrowth into titanium implant's porous surfaces, significantly enhancing mechanical fixation strength at 24 weeks. CS/HA had a limited ability to induce bone formation and implant fixation. We conclude that nHA and COL/HA revealed long-term effects on enhancing bone formation and implant fixation that were at least as good as allograft after 24 weeks, and both nHA and COL/HA appear to be good alternative materials to bone allograft.

Impact of regenerative procedure on the healing process following surgical root canal treatment: A systematic review and meta-analysis

INTRODUCTION

Different Guided Tissue Regeneration (GTR) procedures, such as membranes, bone substitute materials, and Autologous Platelet Concentrates (APCs), have been applied after surgical root canal treatment (SRCT), which produce different outcomes. This study aimed to evaluate the impact of regenerative procedures on the healing process following SRCT.

METHODS

A comprehensive search of PubMed, Embase, Scopus, Cochrane, and the Web of Science found Randomized Controlled Trials (RCTs) published until February 25, 2024. Manual searches were also conducted. Our main outcome was SRCT success or failure after GTR procedures. The Risk Ratio (RR) and failure rate meta-analysis used a fixed effects model with a 95% confidence interval (CI). Subgroup analyses were conducted based on the use of different GTR procedures for varying lesion types in SRCT.

RESULTS

Out of 1,605 records, 16 studies with 690 lesions were included. Overall, GTR procedures significantly improved healing after SRCT in both 2D (RR: 0.50; 95% CI, 0.34-0.73; P < 0.001) and 3D evaluation methods (RR: 0.36; 95% CI, 0.15-0.90; P < 0.001) with no significant difference between the two methods.

CONCLUSION

GTR significantly improved SRCT healing regardless of the evaluation method used. Combining collagen membranes with bovine bone-derived hydroxyapatite significantly enhanced the healing process. Additionally, GTR procedures significantly improve healing in through-and-through lesions.

Cavalcante R, Ge C, Franceschi RT, Ma PX. Synthetic helical peptides on nanofibers to activate cell-surface receptors and synergistically enhance critical-sized bone defect regeneration

More than 500,000 bone grafting procedures are performed annually in the USA. Considering the significant limitations of available bone grafts, we previously invented a phase-separation technology to generate nanofibrous poly(l-lactic acid) (PLLA) scaffolds that mimic the bone matrix collagen in nanofiber geometry and enhance bone regeneration. Here we report the development of nanofibrous scaffolds with covalently attached synthetic peptides that mimic native collagen peptides to activate the two main collagen receptors in bone cells, discoidin domain receptor 2 (DDR2) and β1 integrins. We synthesized a PLLA-based graft-copolymer to enable covalent peptide conjugation via a click reaction. Using PLLA and the graft-copolymer, we developed 3D scaffolds with interconnected pores and peptides-containing nanofibers to activate DDR2 and β1 integrins of osteogenic cells. The degradation rate and mechanical properties of the scaffolds are tunable. The peptides-decorated nanofibrous scaffolds demonstrated 7.8 times more mineralized bone regeneration over the control scaffolds without the peptides in a critical-sized bone defect regeneration model after 8 weeks of implantation, showing a synergistic effect of the two peptides. This study demonstrates the power of scaffolds to mimic ECM at both nanometer and molecular levels, activating cell surface receptors to liberate the innate regenerative potential of host stem/progenitor cells.

A safe, novel and ingenious method for autogenous bone graft storage in spine surgery with constrained resources - operative site as the bone bank

BACKGROUND

The aim of our study is to establish whether the bone graft harvested and stored in the surgical wound by our novel technique is safe, reproducible and preserves the viability of the graft. In doing so, it promises successful bony fusion in spine and orthopaedic surgeries.

METHODS

A prospective clinical case series was conducted for autogenous bone graft storage in complex spine surgeries requiring staged procedures, in resource constrained settings. The bone graft harvested was morselized, wrapped in moist sterile gauze and stored in the paraspinal gutter within the operative site. Thereafter, the surgical wound was easily closed without tension. During the second stage surgery, the stored bone was retrieved and mixed with more autologous/allogenic bone (if necessary) and appropriately laid at fusion sites. Bacterial samples were sent before implantation.

RESULTS

16 complex spinal deformity patients who underwent surgery in a resource constrained hospital over a period of 5 years were included. Duration between both stages was within 2 weeks. All patients showed successful fusion, with mean follow-up of 2.6 years. There were no cases of deep or systemic infection in our series. Surgeons found harvesting, storing and retrieval of graft to be straightforward.

CONCLUSION

The operative site provides an ideal, safe and reproducible location for bone graft storage for staged surgeries conducted in resource constrained situations. The osteogenic potential of the autogenous bone graft is retained. This technique can be extrapolated to other orthopaedic surgeries conducted under resource limited environments like in surgical camps or combat medical facilities.

Biomaterial Cues for Regulation of Osteoclast Differentiation and Function in Bone Regeneration

Tissue regeneration involves dynamic dialogue between and among different cells and their surrounding matrices. Bone regeneration is specifically governed by reciprocity between osteoblasts and osteoclasts within the bone microenvironment. Osteoclast-directed resorption and osteoblast-directed formation of bone are essential to bone remodeling, and the crosstalk between these cells is vital to curating a sequence of events that culminate in the creation of bone tissue. Among bone biomaterial strategies, many have investigated the use of different material cues to direct the development and activity of osteoblasts. However, less attention has been given to exploring features that similarly target osteoclast formation and activity, with even fewer strategies demonstrating or integrating biomaterial-directed modulation of osteoblast-osteoclast coupling. This review aims to describe various biomaterial cues demonstrated to influence osteoclastogenesis and osteoclast function, emphasizing those that enhance a material construct's ability to achieve bone healing and regeneration. Additionally discussed are approaches that influence the communication between osteoclasts and osteoblasts, particularly in a manner that takes advantage of their coupling. Deepening our understanding of how biomaterial cues may dictate osteoclast differentiation, function, and influence on the microenvironment may enable the realization of bone-replacement interventions with enhanced integrative and regenerative capacities.

Establishment of immortalized rabbit bone marrow mesenchymal stem cells and a preliminary study of their osteogenic differentiation capability

BACKGROUND

A stable and standardized source of mesenchymal stem cells is a prerequisite for bone repair tissue engineering research and application. We aimed to establish a stable cell line of bone marrow mesenchymal stem cells from New Zealand rabbits and explore their osteogenic differentiation capacity.

METHODS

Primary rabbit bone marrow mesenchymal stem cells (RBMSCs) were isolated and immortalized via retroviral expression of SV40 Large T antigen (LTA). To assess the osteogenic differentiation capacity of the cells in vitro, we studied the alkaline phosphatase (ALP) expression level and calcium deposition in bone morphogenetic protein 9 (BMP9)-induced immortalized cells using ALP staining and quantification, as well as alizarin red staining. Ectopic bone formation by the cells was assessed using micro-computed tomography (μCT) and histological examination.

RESULTS

The immortalized cell line we established using SV40 LTA, which we termed iRBMSCs, was non-tumorigenic and maintained long-term proliferative activity. We further discovered that BMP9 (MOI = 30) effectively induced the osteogenic differentiation capacity of iRBMSCs in vitro, and there was a synergy with GelMA hydrogel in inducing osteogenic differentiation of the iRBMSCs in vivo.

CONCLUSION

We confirmed that iRBMSCs are promising as a stable cell line source for bone defect repair engineering.

Programmable biomaterials for bone regeneration

Programmable biomaterials are distinguished by their ability to adjust properties and functions on demand, in a periodic, reversible, or sequential manner. This contrasts with traditional biomaterials, which undergo irreversible, uncontrolled changes. This review synthesizes key advances in programmable biomaterials, examining their design principles, functionalities and applications in bone regeneration. It charts the transition from traditional to programmable biomaterials, emphasizing their enhanced precision, safety and control, which are critical from clinical and biosafety standpoints. We then classify programmable biomaterials into six types: dynamic nucleic acid-based biomaterials, electrically responsive biomaterials, bioactive scaffolds with programmable properties, nanomaterials for targeted bone regeneration, surface-engineered implants for sequential regeneration and stimuli-responsive release materials. Each category is analyzed for its structural properties and its impact on bone tissue engineering. Finally, the review further concludes by highlighting the challenges faced by programmable biomaterials and suggests integrating artificial intelligence and precision medicine to enhance their application in bone regeneration and other biomedical fields.

Mineralized collagen plywood contributes to bone autograft performance

Autologous bone (AB) is the gold standard for bone-replacement surgeries1, despite its limited availability and the need for an extra surgical site. Traditionally, competitive biomaterials for bone repair have focused on mimicking the mineral aspect of bone, as evidenced by the widespread clinical use of bioactive ceramics2. However, AB also exhibits hierarchical organic structures that might substantially affect bone regeneration. Here, using a range of cell-free biomimetic-collagen-based materials in murine and ovine bone-defect models, we demonstrate that a hierarchical hybrid microstructure-specifically, the twisted plywood pattern of collagen and its association with poorly crystallized bioapatite-favourably influences bone regeneration. Our study shows that the most structurally biomimetic material has the potential to stimulate bone growth, highlighting the pivotal role of physicochemical properties in supporting bone formation and offering promising prospects as a competitive bone-graft material.

Biomechanical validation of a tibial critical-size defect model in minipigs

BACKGROUND

Autologous cancellous bone grafting still represents the gold standard for the therapy of non-healing bone defects. However, donor site morbidity and the restricted availability of autologous bone grafts have initiated scientists to look for promising alternatives to heal even large defects. The present study aimed to evaluate the biomechanical potential and failure properties of a previously developed metaphyseal critical-size defect model of the proximal tibia in minipigs for future comparisons of bone substitute materials.

METHODS

Fresh-frozen minipig tibiae were divided into two groups, with half undergoing the creation of critical-size defects. Specimens were subjected to biomechanical fatigue tests and load-to-failure tests. CT scans post-test verified bone damage. Statistical analysis compared the properties of defected and intact specimens.

FINDINGS

In this model, it was demonstrated that under uniaxial cyclic compression within the loading axis, the intact tibiae specimens (8708 ± 202 N) provided a significant (p = 0.014) higher compressive force to failure than the tibiae with the defect (6566 ± 1653 N).

INTERPRETATION

Thus, the used minipig model is suitable for comparing bone substitute materials regarding their biomechanical forces and bone regeneration capacity.

Advances in Bioceramics for Bone Regeneration: A Narrative Review

Large osseous defects resulting from trauma, tumor resection, or fracture render the inherent ability of the body to repair inadequate and necessitate the use of bone grafts to facilitate the recovery of both form and function of the bony defect sites. In the United States alone, a large number of bone graft procedures are performed yearly, making it an essential area of investigation and research. Synthetic grafts represent a potential alterative to autografts due to their patient-specific customizability, but currently lack widespread acceptance in the clinical space. Early in their development, non-autologous bone grafts composed of metals such as stainless steel and titanium alloys were favorable due to their biocompatibility, resistance to corrosion, mechanical strength, and durability. However, since their inception, bioceramics have also evolved as viable alternatives. This review aims to present an overview of the fundamental prerequisites for tissue engineering devices using bioceramics as well as to provide a comprehensive account of their historical usage and significant advancements over time. This review includes a summary of commonly used manufacturing techniques and an evaluation of their use as drug carriers and bioactive coatings-for therapeutic ion/drug release, and potential avenues to further enhance hard tissue regeneration.

Mechanically enhanced biodegradable scaffold based on SF microfibers for repairing bone defects in the distal femur of rats

Silk-based biodegradable materials play an important role in tissue engineering, especially in the field of bone regeneration. However, while optimizing mechanical properties and bone regeneration characteristics, modified silk fibroin (SF)-based materials also increase the complexity of scaffold systems, which is not conducive to clinical translation. In this study, we first added synthetic biomimetic mineralized collagen (MC) particles to SF-based materials to improve the bone regeneration properties of the scaffolds and simultaneously regulated the degradation rate of the scaffolds to match the bone regeneration rate. Second, SF microfibers were prepared by hydrolysis with alkaline heating and added to SFMC scaffolds with excellent osteogenic stimulation ability to prepare SF microfiber (mf)-modified SFMC-mf scaffolds with excellent mechanical properties, whose compression modulus increased from 4.58±0.23 MPa to 14.63±0.88 MPa. Finally, the SFMC-mf scaffold was implanted into the weight-bearing bone defect area of the distal femur of rats, and the results showed that the SFMC-mf scaffold significantly promoted functional recovery of the affected limb and increased the amount of new bone in the defect area compared with those in the SFC-mf group and the blank control group. In addition, the RNA-seq results suggested that the genes with upregulated expression in the SFMC-mf scaffold group were mainly enriched in vascular regeneration. In conclusion, this SF microfiber modification method effectively improved the mechanical properties of SFMC scaffolds without moving the SF scaffold system in the direction of compositional complexity, providing new insights for the subsequent development of more effective bionic repair materials for bone defects and assisting in their clinical translation.

The survey of bone allograft transplantation in a Japanese regional bone bank

BACKGROUND

In reconstructive surgery for large bone defects, the demand for bone allografts has increased over the years; however, it is unclear how the supply and demand in Japanese regional bone banks have evolved over time. This study investigated the 15-year supply and demand of bone allografts stored in a regional bone bank, along with assessing the screening process's effectiveness.

METHODS

The target period was 15 years from April 2005 to March 2020. The period was subdivided into three 5-year periods: first, second, and third. The study items included the number of bone allografts donated, the number of bone allografts used, donor and user facilities, surgical methods using bone allografts, and the number of bone allografts discarded. We used the Cochran-Armitage test for statistical analysis.

RESULTS

A total of 1852 bone allografts were donated to the bone bank, and a total of 1721 were used. A total of 677 bone allografts grafts were provided in the first period, 738 in the second period, and 525 in the third period, indicating a decreasing trend. The average number of allografts per surgery was 2.8 in the first, 3.1 in the second, and 1.7 in the third, showing a decreasing trend. Concerning the percentage of each surgery using bone allografts, spine fusion decreased in the third period but not significantly, whereas primary hip arthroplasty increased significantly in the third period. The total number of discarded bone allografts was 4.8% of the total number of donated bone allografts, largely because of a lack of screening tests.

CONCLUSION

Although the number of allogeneic bone surgeries has been increasing over time, the number of allogeneic bone donations has shown a decreasing trend, and there is a need to develop a system that can provide surgeons with sufficient bone allografts.

Enhancement of a one-step membrane technique for the treatment of large bone defects by pre-seeding the membrane with CD8 lymphocyte depleted bone marrow mononuclear cells in a rat femoral defect model

Background

The one-step membrane technique, using a human acellular dermal matrix (hADM), is an experimental method for treating large bone defects. This eliminates the need for the Masquelet membrane induction step, shortening the procedure while maintaining effectiveness. However, previous studies showed that colonizing hADM with bone marrow mononuclear cells (BMC) worsens healing, likely due to the presence of CD8+ lymphocytes, which negatively affect bone regeneration. This study aims to investigate whether the negative impact of BMC on bone healing in this technique is due to the CD8+ cell population.

Materials and methods

A 5 mm femoral defect was created in 25 male Sprague-Dawley rats, divided into three groups (G1-G3). BMC were isolated from syngenic donor rats, with CD8+ lymphocytes removed magnetically from the BMC fraction in one group. The defects were filled with bone chips and wrapped with differently treated hADM: G1 received native hADM, G2 received hADM+BMC, and G3 received hADM+BMC-CD8. After 8 weeks, the femurs were evaluated through radiological, biomechanical, and histological examinations.

Results

Bone defects and bone mineral density (BMD) were significantly improved in G3 (hADM+BMC-CD8) compared to G2 (hADM+BMC). Bone volume, bone formation, and median bending stiffness were higher in G3. Immunohistological analysis showed a significant decrease in CD8 cell count in G3, with a lower percentage of IFNγ-producing cells compared to G2.

Conclusion

Depleting CD8+ cells from BMC before colonizing hADM significantly improved bone healing, likely due to changes in the local mediator environment. This suggests that preoperative colonization with CD8+-depleted BMC could enhance the one-step membrane technique.

FixThePig: a custom 3D-printed femoral intramedullary nailing for preclinical research applications

Background

Critical-size bone defects (CSBDs) pose significant challenges in clinical orthopaedics and traumatology. Developing reliable preclinical models that accurately simulate human conditions is crucial for translational research. This study addresses the need for a reliable preclinical model by evaluating the design and efficacy of a custom-made 3D-printed intramedullary nail (IMN) specifically for CSBDs in minipigs. The study aims to answer the following questions: Can a custom-made 3D-printed IMN be designed for femoral osteosynthesis in minipigs? Does the use of the custom-made IMN result in consistent and reproducible surgical procedure, particularly in the creation and fixation of CSBDs? Can the custom-made IMN effectively treat and promote bone consolidation of CSBDs?

Hypothesis

The custom-made 3D-printed IMN can be designed to effectively create, fix and treat CSBDs in minipigs, resulting in consistent surgical outcomes.

Materials and Methods

The IMN was designed based on CT scans of minipig femurs, considering factors such as femoral curvature, length, and medullary canal diameters. It was 3D-printed in titanium and evaluated through both in vitro and in vivo testing. Female Aachen minipigs underwent bilateral femoral surgeries to create and fix CSBDs using the custom-made IMN. Post-operative follow-up included X-rays and CT scans every 2 weeks, with manual examination of explanted femurs to assess consolidation and mechanical stability after 3 months.

Results

The custom-made IMN effectively fitted the minipig femoral anatomy and facilitated reproducible surgical outcomes. Symmetric double osteotomies were successfully performed, and allografts showed minimal morphological discrepancies. However, proximal fixation faced challenges, leading to non-union in several cases, while most distal osteotomy sites achieved stable consolidation.

Discussion

The custom-made 3D-printed IMN demonstrated potential in modelling and treating CSBDs in minipigs. While the design effectively supported distal bone healing, issues with proximal fixation highlight the need for further refinements. Potential improvements include better screw placement, additional mechanical support, and adaptations such as a reduction clamp or a cephalic screw to enhance stability and distribute forces more effectively.

A conservative treatment of an involved molar tooth associated with dentigerous cyst: a case report and literature review

BACKGROUND

Dentigerous cysts (DCs) are among the most frequently odontogenic cysts in young and middle-aged individuals. Marsupialization and enucleation are the main treatment options in clinical practice. However, there are few reports on preserving molars severely involved by the cyst.

CASE PRESENTATION

A 35-year-old male patient with a large odontogenic cyst that was successfully treated using a multidisciplinary approach. The patient's chief complaint was discomfort during mastication in the lower left molar region for a month. Clinical examination revealed that teeth 36 and 37 were intact without pain upon percussion, while tooth 38 was unerupted. The radiology examination illustrated a typical well-defined oval radiolucent lesion surrounding the crown of unerupted tooth 38, extending to the distal root of tooth 37. The treatment was divided into two parts: removal of the cyst and the impacted third molar, followed by filling with collagen bone particles; and preserving the tooth 37 via hemisection, root canal treatment and crown restoration. Pathological examination indicated a dentigerous cyst. After 18 months of treatment, the bone defect completely recovered and tooth 37 functioned well following the hemisection.

CONCLUSIONS

Hemisection effectively preserves the cyst-associated molars and maintains oral function. This article underscores the significance of collaboration among various departments in the treatment of odontogenic cysts, ultimately aiming to achieve minimally invasive and functional surgery.

Recent trends of stem cell therapies in the management of orthopedic surgical challenges

Emerged health-related problems especially with increasing population and with the wider occurrence of these issues have always put the utmost concern and led medicine to outgrow its usual mode of treatment, to achieve better outcomes. Orthopedic interventions are one of the most concerning hitches, requiring advancement in several issues, that show complications with conventional approaches. Advanced studies have been undertaken to address the issue, among which stem cell therapy emerged as a better area of growth. The capacity of the stem cells to renovate themselves and adapt into different cell types made it possible to implement its use as a regenerative slant. Harvesting the stem cells, particularly mesenchymal stem cells (MSCs) is easier and can be further grown in vitro . In this review, we have discussed orthopedic-related issues including bone defects and fractures, nonunions, ligament and tendon injuries, degenerative changes, and associated conditions, which require further approaches to execute better outcomes, and the advanced strategies that can be tagged along with various ways of application of MSCs. It aims to objectify the idea of stem cells, with a major focus on the application of MSCs from different sources in various orthopedic interventions. It also discusses the limitations, and future scopes for further approaches in the field of regenerative medicine. The involvement of MSCs may transition the procedures in orthopedic interventions from predominantly surgical substitution and reconstruction to bio-regeneration and prevention. Nevertheless, additional improvements and evaluations are required to explore the effectiveness and safety of mesenchymal stem cell treatment in orthopedic regenerative medicine.

Advances in implants and bone graft types for lumbar spinal fusion surgery

The increasing prevalence of spinal disorders worldwide necessitates advanced treatments, particularly interbody fusion for severe cases that are unresponsive to non-surgical interventions. This procedure, especially 360° lumbar interbody fusion, employs an interbody cage, pedicle screw-and-rod instrumentation, and autologous bone graft (ABG) to enhance spinal stability and promote fusion. Despite significant advancements, a persistent 10% incidence of non-union continues to result in compromised patient outcomes and escalated healthcare costs. Innovations in lumbar stabilisation seek to mimic the properties of natural bone, with evolving implant materials like titanium (Ti) and polyetheretherketone (PEEK) and their composites offering new prospects. Additionally, biomimetic cages featuring precisely engineered porosities and interconnectivity have gained traction, as they enhance osteogenic differentiation, support osteogenesis, and alleviate stress-shielding. However, the limitations of ABG, such as harvesting morbidities and limited fusion capacity, have spurred the exploration of sophisticated solutions involving advanced bone graft substitutes. Currently, demineralised bone matrix and ceramics are in clinical use, forming the basis for future investigations into novel bone graft substitutes. Bioglass, a promising newcomer, is under investigation despite its observed rapid absorption and the potential for foreign body reactions in preclinical studies. Its clinical applicability remains under scrutiny, with ongoing research addressing challenges related to burst release and appropriate dosing. Conversely, the well-documented favourable osteogenic potential of growth factors remains encouraging, with current efforts focused on modulating their release dynamics to minimise complications. In this evidence-based narrative review, we provide a comprehensive overview of the evolving landscape of non-degradable spinal implants and bone graft substitutes, emphasising their applications in lumbar spinal fusion surgery. We highlight the necessity for continued research to improve clinical outcomes and enhance patient well-being.

Migration and retention of human osteosarcoma cells in bioceramic graft with open channel architecture designed for bone tissue engineering

The microstructure of a porous bioceramic bone graft, especially the pore architecture, plays a crucial role in the performance of the graft. Conventional bioceramic grafts typically feature a random, closed-pore structure, limiting biological activity to the periphery of the graft. This can lead to delay in full integration with the host site. Bioceramic forms with open through pores can perform better because their inner regions are accessible for natural bone remodeling. This study explores the influence of open through pores in a bioceramic graft on the migration and retention of the local cellsin vitro, which will correlate to the rate of healingin vivo.Hydroxyapatite ceramic forms with aligned channels were fabricated using slip casting technique, employing sacrificial fibers. The sorption characteristics across the graft were evaluated using human osteosarcoma cell line. Seven-day cultures showed viable cells within the channels, confirmed by live/dead assay, scanning electron microscope analysis, and cytoskeletal staining, indicating successful cell colonization. The channel architecture effectively enhances cell migration and retention throughout its entire structure, suggesting potential applications in bone tissue engineering based on the results obtained.

Evaluation of Biocomposite Cements for Bone Defect Repair in Rat Models

Repairing or reconstructing significant bone defects is typically challenging. In the present study, two composite cements were used as scaffolds in a sub-critical femoral defect in rats. A control group and two experimental batches were used to compare the outcomes. This research aimed to investigate the osteogenic potential and toxicological tolerance of the bioproducts through histopathology and computed tomography imaging analysis at 14, 28, 56, and 90 days post-implantation. The biomaterials used in the investigation consisted of a 65% bioactive salinized inorganic filler and a 25% weight organic matrix. The organic part of the biomaterial was composed of Bis-GMA (bisphenol A-glycidyl methacrylate), UDMA (urethane dimethacrylate), HEMA (2-Hydroxyethyl methacrylate), and TEGDMA (triethylene glycol dimethacrylate), while the inorganic filler was composed of silica, barium glass, hydroxyapatite, and fluor aluminosilicate glass. The first findings of this research are encouraging, revealing that there is a slight difference between the groups treated with biomaterials, but it might be an effective approach for managing bone abnormalities. Material C1 exhibited a faster bone defect healing time compared to material C2, where bone fractures occurred in some individuals. It is unclear if the fractures were caused by the presence of the biomaterial C2 or whether additional variables were to blame. By the end of the research, the mice appeared to tolerate the biomaterials without exhibiting any inflammatory or rejection responses.

Advances in autogenous dentin matrix graft as a promising biomaterial for guided bone regeneration in maxillofacial region: A review

Autogenous dentin matrix (ADM), derived from a patient's extracted tooth, can be repurposed as an autologous grafting material in reconstructive dentistry. Extracted teeth provide a source for ADM, which distinguishes itself with its low rejection rate, osteoinductive capabilities and ease of preparation. Consequently, it presents a viable alternative to autogenous bone. Animal studies have substantiated its effective osteoinductive properties, while its clinical applications encompass post-extraction site preservation, maxillary sinus floor augmentation, and guided bone tissue regeneration. Nevertheless, the long-term efficacy of ADM applied in bone regeneration remains underexplored and there is a lack of standardization in the preparation processes. This paper comprehensively explores the composition, mechanisms underlying osteoinductivity, preparation methods, and clinical applications of ADM with the aim of establishing a fundamental reference for future studies on this subject.

Fibrin-konjac glucomannan-black phosphorus hydrogel scaffolds loaded with nasal ectodermal mesenchymal stem cells accelerated alveolar bone regeneration

BACKGROUND

Effective treatments for the alveolar bone defect remain a major concern in dental therapy. The objectives of this study were to develop a fibrin and konjac glucomannan (KGM) composite hydrogel as scaffolds for the osteogenesis of nasal mucosa-derived ectodermal mesenchymal stem cells (EMSCs) for the regeneration of alveolar bone defect, and to investigate the osteogenesis-accelerating effects of black phosphorus nanoparticles (BPNs) embedded in the hydrogels.

METHODS

Primary EMSCs were isolated from rat nasal mucosa and used for the alveolar bone recovery. Fibrin and KGM were prepared in different ratios for osteomimetic hydrogel scaffolds, and the optimal ratio was determined by mechanical properties and biocompatibility analysis. Then, the optimal hydrogels were integrated with BPNs to obtain BPNs/fibrin-KGM hydrogels, and the effects on osteogenic EMSCs in vitro were evaluated. To explore the osteogenesis-enhancing effects of hydrogels in vivo, the BPNs/fibrin-KGM scaffolds combined with EMSCs were implanted to a rat model of alveolar bone defect. Micro-computed tomography (CT), histological examination, real-time quantitative polymerase chain reaction (RT-qPCR) and western blot were conducted to evaluate the bone morphology and expression of osteogenesis-related genes of the bone regeneration.

RESULTS

The addition of KGM improved the mechanical properties and biodegradation characteristics of the fibrin hydrogels. In vitro, the BPNs-containing compound hydrogel was proved to be biocompatible and capable of enhancing the osteogenesis of EMSCs by upregulating the mineralization and the activity of alkaline phosphatase. In vivo, the micro-CT analysis and histological evaluation demonstrated that rats implanted EMSCs-BPNs/fibrin-KGM hydrogels exhibited the best bone reconstruction. And compared to the model group, the expression of osteogenesis genes including osteopontin (Opn, p < 0.0001), osteocalcin (Ocn, p < 0.0001), type collagen (Col , p < 0.0001), bone morphogenetic protein-2 (Bmp2, p < 0.0001), Smad1 (p = 0.0006), and runt-related transcription factor 2 (Runx2, p < 0.0001) were all significantly upregulated.

CONCLUSIONS

EMSCs/BPNs-containing fibrin-KGM hydrogels accelerated the recovery of the alveolar bone defect in rats by effectively up-regulating the expression of osteogenesis-related genes, promoting the formation and mineralisation of bone matrix.

Imidazole functionalized photo-crosslinked aliphatic polycarbonate drug-eluting coatings on zinc alloys for osteogenesis, angiogenesis, and bacteriostasis in bone regeneration

Zinc (Zn) alloys have demonstrated significant potential in healing critical-sized bone defects. However, the clinical application of Zn alloys implants is still hindered by challenges including excessive release of zinc ions (Zn2+), particularly in the early stage of implantation, and absence of bio-functions related to complex bone repair processes. Herein, a biodegradable aliphatic polycarbonate drug-eluting coating was fabricated on zinc-lithium (Zn-Li) alloys to inhibit Zn2+ release and enhance the osteogenesis, angiogenesis, and bacteriostasis of Zn alloys. Specifically, the photo-curable aliphatic polycarbonates were co-assembled with simvastatin and deposited onto Zn alloys to produce a drug-loaded coating, which was crosslinked by subsequent UV light irradiation. During the 60 days long-term immersion test, the coating showed distinguished stable drug release and Zn2+ release inhibition properties. Benefiting from the regulated release of Zn2+ and simvastatin, the coating facilitated the adhesion, proliferation, and differentiation of MC3T3-E1 cells, as well as the migration and tube formation of EA.hy926 cells. Astonishingly, the coating also showed remarkable antibacterial properties against both S. aureus and E. coli. The in vivo rabbit critical-size femur bone defects model demonstrated that the drug-eluting coating could efficiently promote new bone formation and the expression of platelet endothelial cell adhesion molecule-1 (CD31) and osteocalcin (OCN). The enhancement of osteogenesis, angiogenesis, and bacteriostasis is achieved by precisely controlling of the released Zn2+ at an appropriate level, as well as the stable release profile of simvastatin. This tailored aliphatic polycarbonate drug-eluting coating provides significant potential for clinical applications of Zn alloys implants.

Biphasic bone substitutes coated with PLGA incorporating therapeutic ions Sr2+ and Mg2+: cytotoxicity cascade and in vivo response of immune and bone regeneration

The incorporation of bioactive ions into biomaterials has gained significant attention as a strategy to enhance bone tissue regeneration on the molecular level. However, little knowledge exists about the effects of the addition of these ions on the immune response and especially on the most important cellular regulators, the macrophages. Thus, this study aimed to investigate the in vitro cytocompatibility and in vivo regulation of bone remodeling and material-related immune responses of a biphasic bone substitute (BBS) coated with metal ions (Sr2+/Mg2+) and PLGA, using the pure BBS as control group. Initially, two cytocompatible modified material variants were identified according to the in vitro results obtained following the DIN EN ISO 10993-5 protocol. The surface structure and ion release of both materials were characterized using SEM-EDX and ICP-OES. The materials were then implanted into Wistar rats for 10, 30, and 90 days using a cranial defect model. Histopathological and histomorphometrical analyses were applied to evaluate material degradation, bone regeneration, osteoconductivity, and immune response. The findings revealed that in all study groups comparable new bone formation were found. However, during the early implantation period, the BBS_Sr2+ group exhibited significantly faster regeneration compared to the other two groups. Additionally, all materials induced comparable tissue and immune responses involving high numbers of both pro-inflammatory macrophages and multinucleated giant cells (MNGCs). In conclusion, this study delved into the repercussions of therapeutic ion doping on bone regeneration patterns and inflammatory responses, offering insights for the advancement of a new generation of biphasic calcium phosphate materials with potential clinical applicability.

Role of Adipose-Derived Mesenchymal Stem Cells in Bone Regeneration

Bone regeneration involves multiple factors such as tissue interactions, an inflammatory response, and vessel formation. In the event of diseases, old age, lifestyle, or trauma, bone regeneration can be impaired which could result in a prolonged healing duration or requiring an external intervention for repair. Currently, bone grafts hold the golden standard for bone regeneration. However, several limitations hinder its clinical applications, e.g., donor site morbidity, an insufficient tissue volume, and uncertain post-operative outcomes. Bone tissue engineering, involving stem cells seeded onto scaffolds, has thus been a promising treatment alternative for bone regeneration. Adipose-derived mesenchymal stem cells (AD-MSCs) are known to hold therapeutic value for the treatment of various clinical conditions and have displayed feasibility and significant effectiveness due to their ease of isolation, non-invasive, abundance in quantity, and osteogenic capacity. Notably, in vitro studies showed AD-MSCs holding a high proliferation capacity, multi-differentiation potential through the release of a variety of factors, and extracellular vesicles, allowing them to repair damaged tissues. In vivo and clinical studies showed AD-MSCs favoring better vascularization and the integration of the scaffolds, while the presence of scaffolds has enhanced the osteogenesis potential of AD-MSCs, thus yielding optimal bone formation outcomes. Effective bone regeneration requires the interplay of both AD-MSCs and scaffolds (material, pore size) to improve the osteogenic and vasculogenic capacity. This review presents the advances and applications of AD-MSCs for bone regeneration and bone tissue engineering, focusing on the in vitro, in vivo, and clinical studies involving AD-MSCs for bone tissue engineering.

The Osteogenic Peptide P-15 for Bone Regeneration: A Narrative Review of the Evidence for a Mechanism of Action

Bone regeneration is a complex multicellular process involving the recruitment and attachment of osteoprogenitors and their subsequent differentiation into osteoblasts that deposit extracellular matrixes. There is a growing demand for synthetic bone graft materials that can be used to augment these processes to enhance the healing of bone defects resulting from trauma, disease or surgery. P-15 is a small synthetic peptide that is identical in sequence to the cell-binding domain of type I collagen and has been extensively demonstrated in vitro and in vivo to enhance the adhesion, differentiation and proliferation of stem cells involved in bone formation. These events can be categorized into three phases: attachment, activation and amplification. This narrative review summarizes the large body of preclinical research on P-15 in terms of these phases to describe the mechanism of action by which P-15 improves bone formation. Knowledge of this mechanism of action will help to inform the use of P-15 in clinical practice as well as the development of methods of delivering P-15 that optimize clinical outcomes.

Sustainably cultured coral scaffold supports human bone marrow mesenchymal stromal cell osteogenesis

The current gold standard grafting material is autologous bone due to its osteoinductive and osteoconductive properties. Autograft harvesting results in donors site morbidity. Coral scaffolds offer a natural autograft alternative, sharing the density and porosity of human bone. This study investigated the biocompatibility and osteogenic potential of a novel, sustainably grown Pocillopora scaffold with human bone marrow-derived mesenchymal stromal cells (MSCs). The coral-derived scaffold displays a highly textured topography, with concavities of uniform size and a high calcium carbonate content. Large scaffold samples exhibit compressive and diametral tensile strengths in the range of trabecular bone, with strengths likely increasing for smaller particulate samples. Following the in vitro seeding of MSCs adjacent to the scaffold, the MSCs remained viable, continued proliferating and metabolising, demonstrating biocompatibility. The seeded MSCs densely covered the coral scaffold with organized, aligned cultures with a fibroblastic morphology. In vivo coral scaffolds with MSCs supported earlier bone and blood vessel formation as compared to control constructs containing TCP-HA and MSCs. This work characterized a novel, sustainably grown coral scaffold that was biocompatible with MSCs and supports their in vivo osteogenic differentiation, advancing the current repertoire of biomaterials for bone grafting.

Efficacy and safety of autologous or allogeneic mesenchymal stromal cells from adult adipose tissue expanded and combined with tricalcium phosphate biomaterial for the surgical treatment of atrophic nonunion of long bones: a phase II clinical trial

BACKGROUND

Autologous bone grafting is the standard treatment for the surgical management of atrophic nonunion of long bones. Other solutions, such as bone marrow mesenchymal stem cells (BM-MSC) combined with phospho-calcium material, have also been used. Here we evaluate the safety and early efficacy of a novel procedure using autologous or allogenic adipose tissue mesenchymal stromal cells (AT-MSC) seeded in a patented tricalcium phosphate-based biomaterial for the treatment of bone regeneration in cases of atrophic nonunion.

METHODS

This was a prospective, multicentric, open-label, phase 2 clinical trial of patients with atrophic nonunion of long bones. Biografts of autologous or allogenic AT-MSC combined with a phosphate substrate were manufactured prior to the surgical procedures. The primary efficacy was measured 6 months after surgery, but patients were followed for 12 months after surgery and a further year out of the scope of the study. All adverse events were recorded. This cohort was compared with a historical cohort of 14 cases treated by the same research team with autologous BM-MSC.

RESULTS

A total of 12 patients with atrophic nonunion of long bones were included. The mean (SD) age was 41.2 (12.1) years and 66.7% were men. Bone healing was achieved in 10 of the 12 cases (83%) treated with the AT-MSC biografts, a percentage of healing similar (11 of the 14 cases, 79%) to that achieved in patients treated with autologous BM-MSC. Overall, two adverse events, in the same patient, were considered related to the procedure.

CONCLUSIONS

The results of this study suggest that AT-MSC biografts are safe for the treatment of bone regeneration in cases of atrophic nonunion and reach high healing rates.

TRIAL REGISTRATION

Study registered with EUDRA-CT (2013-000930-37) and ClinicalTrials.gov (NCT02483364).

Polydopamine-mediated immobilization of BMP-2 onto electrospun nanofibers enhances bone regeneration

Dealing with bone defects is a significant challenge to global health. Electrospinning in bone tissue engineering has emerged as a solution to this problem. In this study, we designed a PVDF-b-PTFE block copolymer by incorporating TFE, which induced a phase shift in PVDF fromαtoβ, thereby enhancing the piezoelectric effect. Utilizing the electrospinning process, we not only converted the material into a film with a significant surface area and high porosity but also intensified the piezoelectric effect. Then we used polydopamine to immobilize BMP-2 onto PVDF-b-PTFE electrospun nanofibrous membranes, achieving a controlled release of BMP-2. The scaffold's characters were examined using SEM and XRD. To assess its osteogenic effectsin vitro, we monitored the proliferation of MC3T3-E1 cells on the fibers, conducted ARS staining, and measured the expression of osteogenic genes.In vivo, bone regeneration effects were analyzed through micro-CT scanning and HE staining. ELISA assays confirmed that the sustained release of BMP-2 can be maintained for at least 28 d. SEM images and CCK-8 results demonstrated enhanced cell viability and improved adhesion in the experimental group. Furthermore, the experimental group exhibited more calcium nodules and higher expression levels of osteogenic genes, including COL-I, OCN, and RUNX2. HE staining and micro-CT scans revealed enhanced bone tissue regeneration in the defective area of the PDB group. Through extensive experimentation, we evaluated the scaffold's effectiveness in augmenting osteoblast proliferation and differentiation. This study emphasized the potential of piezoelectric PVDF-b-PTFE nanofibrous membranes with controlled BMP-2 release as a promising approach for bone tissue engineering, providing a viable solution for addressing bone defects.

Characterization of Porous β-Type Tricalcium Phosphate Ceramics Formed via Physical Foaming with Freeze-Drying

Porous β-tricalcium phosphate (Ca3(PO4)2; β-TCP) was prepared via freeze-drying and the effects of this process on pore shapes and sizes were investigated. Various samples were prepared by freezing β-TCP slurries above a liquid nitrogen surface at -180 °C with subsequent immersion in liquid nitrogen at -196 °C. These materials were then dried under reduced pressure in a freeze-dryer, after which they were sintered with heating. Compared with conventional heat-based drying, the resulting pores were more spherical, which increased both the mechanical strength and porosity of the β-TCP. These materials had a wide range of pore sizes from 50 to 200 µm, with the mean and median values both approximately 100 µm regardless of the freeze-drying conditions. Mercury porosimetry data showed that the samples contained small, interconnected pores with sizes of 1.24 ± 0.25 µm and macroscopic, interconnected pores of 25.8 ± 4.7 µm in size. The effects of nonionic surfactants having different hydrophilic/lipophilic balance (HLB) values on foaming and pore size were also investigated. Materials made with surfactants having lower HLB values exhibited smaller pores and lower porosity, whereas higher HLB surfactants gave higher porosity and slightly larger macropores. Even so, the pore diameter could not be readily controlled solely by adjusting the HLB value. The findings of this work indicated that high porosity (>75%) and good compressive strength (>2 MPa) can both be obtained in the same porous material and that foaming agents with HLB values between 12.0 and 13.5 were optimal.

Magnesium-oxide-enhanced bone regeneration: 3D-printing of gelatin-coated composite scaffolds with sustained Rosuvastatin release

Critical-size bone defects are one of the main challenges in bone tissue regeneration that determines the need to use angiogenic and osteogenic agents. Rosuvastatin (RSV) is a class of cholesterol-lowering drugs with osteogenic potential. Magnesium oxide (MgO) is an angiogenesis component affecting apatite formation. This study aims to evaluate 3D-printed Polycaprolactone/β-tricalcium phosphate/nano-hydroxyapatite/ MgO (PCL/β-TCP/nHA/MgO) scaffolds as a carrier for MgO and RSV in bone regeneration. For this purpose, PCL/β-TCP/nHA/MgO scaffolds were fabricated with a 3D-printing method and coated with gelatin and RSV. The biocompatibility and osteogenicity of scaffolds were examined with MTT, ALP, and Alizarin red staining. Finally, the scaffolds were implanted in a bone defect of rat's calvaria, and tissue regeneration was investigated after 3 months. Our results showed that the simultaneous presence of RSV and MgO improved biocompatibility, wettability, degradation rate, and ALP activity but decreased mechanical strength. PCL/β-TCP/nHA/MgO/gelatin-RSV scaffolds produced sustained release of MgO and RSV within 30 days. CT images showed that PCL/β-TCP/nHA/MgO/gelatin-RSV scaffolds filled approximately 86.83 + 4.9 % of the defects within 3 months and improved angiogenesis, woven bone, and osteogenic genes expression. These results indicate the potential of PCL/β-TCP/nHA/MgO/gelatin-RSV scaffolds as a promising tool for bone regeneration and clinical trials.

Time to full weight-bearing with the use of a calcium sulfate-calcium phosphate bone substitute as a bone void filler following extended curettage in the treatment of primary benign bone tumours

PURPOSE

The primary objective of this study was to determine time to full weight-bearing after the use of a calcium-sulfate-calcium phosphate bone substitute (CaSO4/CaPO4) as a bone void filler in the treatment of primary benign bone tumours following intralesional curettage. The secondary objectives were to determine surgical complications and recurrence rates.

METHODS

Retrospective review of patients identified from a surgeon-specific orthopaedic oncology database, who underwent curettage of benign bone tumours and subsequent bone void filling with CaSO4/CaPO4.

RESULTS

A total of 39 patients (20 males, 19 females) met inclusion criteria with an average age of 31 years (range: 13 to 62 years), a median follow-up of 3.7 years, and a maximum follow-up of 11 years. The most common tumour diagnosis was giant cell tumour of bone (GCT) (n = 19), and the most common location was the proximal tibia (n = 9). The mean volume of tumour excised was 74.1 cm3 including extraosseous bone expansion due to tumour growth, with a mean of volume of 21.4 mL of CaSO4/CaPO4 used to fill the intraosseous cavitary defects to restore normal bone anatomy. None of the lesions required additional internal fixation. The primary outcome measure, average time to full weight-bearing/full range of motion, was 11 weeks and 6 weeks for upper and lower extremity lesions, respectively. Secondary outcomes included tumour recurrence requiring reoperation in five patients and infection requiring reoperation in two patients.

CONCLUSION

This study demonstrates that CaSO4/CaPO4 is a viable option as a bone void filler in the reconstruction of cavitary defects following removal of primary benign bone tumours. CaSO4/CaPO4 provides sufficient bone regeneration early in the post-operative period to allow progression to full weight-bearing within weeks without the need for internal fixation. There were no graft-specific complications noted.

Effect of a synthetic hydroxyapatite-based bone grafting material compared to established bone substitute materials on regeneration of critical-size bone defects in the ovine scapula

Lately, the potential risk of disease transmission due to the use of bovine-derived bone substitutes has become obvious, demonstrating the urgent need for a synthetic grafting material with comparable bioactive behaviour and properties. Therefore, the effect of a synthetic hydroxyapatite (HA) (Osbone®) bone grafting material on bone regeneration was evaluated 2 weeks, 1 month, and 3, 6, 12 and 18 months after implantation in critical-size bone defects in the ovine scapula and compared to that of a bovine-derived HA (Bio-Oss®) and β-tricalcium phosphate (TCP) (Cerasorb® M). New bone formation and the biodegradability of the bone substitutes were assessed histomorphometrically. Hard tissue histology and immunohistochemical analysis were employed to characterize collagen type I, alkaline phosphatase, osteocalcin, as well as bone sialoprotein expression in the various cell and matrix components of the bone tissue to evaluate the bioactive properties of the bone grafting materials. No inflammatory tissue response was detected with any of the bone substitute materials studied. After 3 and 6 months, β-TCP (Cerasorb® M) showed superior bone formation when compared to both HA-based materials (3 months: β-TCP 55.65 ± 2.03% vs. SHA 49.05 ± 3.84% and BHA 47.59 ± 1.97%; p ≤ 0.03; 6 months: β-TCP 62.03 ± 1.58%; SHA: 55.83 ± 2.59%; BHA: 53.44 ± 0.78%; p ≤ 0.04). Further, after 12 and 18 months, a similar degree of bone formation and bone-particle contact was noted for all three bone substitute materials without any significant differences. The synthetic HA supported new bone formation, osteogenic marker expression, matrix mineralization and good bone-bonding behaviour to an equal and even slightly superior degree compared to the bovine-derived HA. As a result, synthetic HA can be regarded as a valuable alternative to the bovine-derived HA without the potential risk of disease transmission.

Safety of a Porous Hydroxyapatite Bone Substitute in Orthopedics and Traumatology: A Multi-Centric Clinical Study

The development of biomaterials in recent years has made it possible to broaden their use in the surgical field. Although iliac crest bone graft harvesting currently remains the gold standard as an autograft, the properties of hydroxyapatite bone substitutes appear to be beneficial. The first fundamental step to consider is the safety of using these devices. The purpose of this retrospective cohort study is to consider all the adverse events observed in our population and assess their relationships with the bone substitute device. The population analyzed consisted of patients undergoing trauma osteosynthesis with at least one implanted porous hydroxyapatite device. We considered a court of 114 patients treated at "Azienda Ospedaliera Universitaria di Ferrara-U.O. di Ortopedia e Traumatologia" in the period from January 2015 to December 2022. Upon analyzing our population, no adverse events related to the device emerged. Taking into consideration different study groups from other National Hospital Centers, no critical issues were detected except for three cases of extrusion of the biomaterial. It is necessary to clarify that bone substitutes cannot replace compliance with the correct principles linked to the biomechanics of osteosynthesis. This report outlines a safety profile for the use of these devices as bone substitutes in trauma orthopedic surgery.

Bone Tissue Engineering and Nanotechnology: A Promising Combination for Bone Regeneration

Large bone defects are the leading contributor to disability worldwide, affecting approximately 1.71 billion people. Conventional bone graft treatments show several disadvantages that negatively impact their therapeutic outcomes and limit their clinical practice. Therefore, much effort has been made to devise new and more effective approaches. In this context, bone tissue engineering (BTE), involving the use of biomaterials which are able to mimic the natural architecture of bone, has emerged as a key strategy for the regeneration of large defects. However, although different types of biomaterials for bone regeneration have been developed and investigated, to date, none of them has been able to completely fulfill the requirements of an ideal implantable material. In this context, in recent years, the field of nanotechnology and the application of nanomaterials to regenerative medicine have gained significant attention from researchers. Nanotechnology has revolutionized the BTE field due to the possibility of generating nanoengineered particles that are able to overcome the current limitations in regenerative strategies, including reduced cell proliferation and differentiation, the inadequate mechanical strength of biomaterials, and poor production of extrinsic factors which are necessary for efficient osteogenesis. In this review, we report on the latest in vitro and in vivo studies on the impact of nanotechnology in the field of BTE, focusing on the effects of nanoparticles on the properties of cells and the use of biomaterials for bone regeneration.