Bone substitutes: a review of their characteristics, clinical use, and perspectives for large bone defects management

Antimicrobial potency, prevention ability, and killing efficacy of daptomycin-loaded versus vancomycin-loaded β-tricalcium phosphate/calcium sulfate for methicillin-resistant Staphylococcus aureus biofilms

Growing evidence has shown that the efficacy of systemic administration of daptomycin for the treatment of methicillin-resistant Staphylococcus aureus (MRSA)-related infections is satisfactory. However, the clinical efficacy of the local administration of daptomycin for the management of osteoarticular infections remains unclear. This in vitro study compared the efficacy of daptomycin and vancomycin against MRSA biofilms. The elution kinetics of daptomycin and vancomycin, combined with gentamicin and loaded with either β-tricalcium phosphate/calcium sulfate or calcium sulfate, in the presence of MRSA infection, was assessed. Their efficacy in preventing biofilm formation and killing pre-formed biofilms was assessed using colony-forming unit count and confocal laser scanning microscopy. In addition, the efficacy of daptomycin, vancomycin, and gentamicin in prophylaxis and eradication of MRSA biofilms was also evaluated. Daptomycin + gentamicin and vancomycin + gentamicin displayed similar antimicrobial potency against MRSA, by either β-tricalcium phosphate/calcium sulfate or calcium sulfate. In the prevention assays, both daptomycin + gentamicin and vancomycin + gentamicin showed similar efficacy in preventing bacterial colony formation, with approximately 6 logs lower colony-forming units than those in the control group at both 1 and 3  days. The killing effect on pre-formed biofilms showed significant decreases of approximately 4 logs at 1 and 3  days following treatment with daptomycin + gentamicin and vancomycin + gentamicin. In addition, the confocal laser scanning microscopy results support the colony-forming unit data. Moreover, single use of vancomycin and gentamicin showed similar efficacies in preventing and killing MRSA biofilms, both of which were better than that of gentamicin. Our study demonstrated that vancomycin + gentamicin and daptomycin + gentamicin loaded with β-tricalcium phosphate/calcium sulfate or calcium sulfate showed similar prophylactic and killing effects on MRSA biofilms, implying a potential indication of local administration daptomycin for the treatment of MRSA-associated osteoarticular infections, especially if vancomycin administration presents limitations.

The effect of resolvin D1 on bone regeneration in a rat calvarial defect model

Resolvin D1 (RvD1) is a pro-resolving lipid mediator of inflammation, endogenously synthesized from omega-3 docosahexaenoic acid. The purpose of this study was to investigate the effect of RvD1 on bone regeneration using a rat calvarial defect model. Collagen 3D nanopore scaffold (COL) and Pluronic F127 hydrogel (F127) incorporated with RvD1 (RvD1-COL-F127 group) or COL and F127 (COL-F127 group) were implanted in symmetrical calvarial defects. After implantation, RvD1 was administrated subcutaneously every 7 days for 4 weeks. The rats were sacrificed at weeks 1 and 8 post-implantation. Tissue samples were analyzed by real-time reverse transcriptase-polymerase chain reaction and histology at week 1. Radiographical and histological analyses were done at week 8. At week 1, calvarial defects treated with RvD1 exhibited decreased numbers of inflammatory cells and tartrate-resistant acid phosphatase (TRAP) positive cells, greater numbers of newly formed blood vessels, upregulated gene expression of vascular endothelial growth factor and alkaline phosphatase, and downregulated gene expression of receptor activator of nuclear factor-κB ligand, interleukin-1β and tumor necrosis factor-α. At week 8, the radiographical results showed that osteoid area fraction of the RvD1-COL-F127 group was higher than that of the COL-F127 group, and histological examination exhibited enhanced osteoid formation and newly formed blood vessels in the RvD1-COL-F127 group. In conclusion, this study showed that RvD1 enhanced bone formation and vascularization in rat calvarial defects.

Impact of Different Preparations of Tooth Graft vs Xenogeneic Bone Graft on Bone Healing: An Experimental Study

AIM

This study aims to compare the effect of demineralized xenogeneic tooth graft in its two forms, particulate and block, with bovine xenograft in the healing of a rabbit tibial bone defect model.

MATERIALS AND METHODS

Two monocortical bony defects were made in the right tibias of 36 rabbits, and were divided into four groups. Group I defects were left empty, while group II, III, and IV were filled with bovine xenograft, demineralized particulate tooth graft, and demineralized perforated block tooth graft, respectively for evaluation of the bone healing process. Three rabbits from each group were euthanized at 2, 4, and 6 weeks after surgery. The bone specimens were processed and stained with hematoxylin and eosin (H&E) and osteopontin (OPN) immunohistochemical staining. The results were subjected to image analysis and quantitative evaluation.

RESULTS

Demineralized particulate tooth graft showed the best bone healing capacity compared to all other groups at all time points tested, as it showed a large amount of the formed bone, rapid closure of the defect with a significant increase in OPN expression, and the least amount of the residual grafted particles.

CONCLUSION

In comparison to bovine xenograft and demineralized dentin block graft, the demineralized particulate tooth grafting material is a promising bone grafting substitute as it proved to be osteoconductive, biocompatible, and bioresorbable.

CLINICAL SIGNIFICANCE

Demineralized tooth grafting material can aid in the regeneration of large bone defects, leading to improvement in the filling of the bone defects which can help in oral and maxillofacial reconstruction.

The efficacy of vancomycin-loaded biphasic calcium phosphate bone substitute in the promotion of new bone growth and the prevention of postoperative infection

Background: Due to the increasing need for suitable alternatives to bone grafts, artificial bones made of biphasic calcium phosphate (BCP) are currently being extensively researched. These porous bone substitutes have also demonstrated considerable incorporation with the host bone, and new bone is able to grow within the porous structure. They therefore offer a potential therapeutic approach for bone defects.

Methods: Vancomycin-loaded Bicera™, a BCP bone substitute, was investigated in order to prevent implant-associated osteomyelitis and postoperative infection after orthopedic surgery. The loading capacity of Bicera™ was measured to understand its potential antibiotic adsorption volume. An antibiotic susceptibility test was also carried out to analyze the effect of Bicera™ loaded with different concentrations of vancomycin on the growth inhibition of methicillin-resistant Staphylococcus aureus (MRSA). Vancomycin-loaded Bicera™ was implanted into rabbits with bone defects, and general gross, radiographic, and histological evaluation was undertaken at 4, 12, and 24 weeks after implantation.

Results: The maximum loading capacity of vancomycin-loaded Bicera™ was 0.9 ml of liquid regardless of the vancomycin concentration. Antibiotic susceptibility tests showed that vancomycin-loaded Bicera™ inhibited the growth of MRSA for 6 weeks. In addition, animal studies revealed that new bone grew into the vancomycin-loaded Bicera™. The percentage of new bone formation from 4 to 24 weeks after implantation increased from 17% to 36%.

Conclusion: Vancomycin-loaded Bicera™ could effectively inhibit the growth of MRSA in vitro. It was found to incorporate into the host bone well, and new bone was able to grow within the bone substitute. The results of this study indicate that vancomycin-loaded Bicera™ is a potential bone substitute that can prevent implant-associated osteomyelitis and postoperative infection.

Influence of the Components and Orientation of Hydroxyapatite Fibrous Substrates on Osteoblast Behavior

Synthetic hydroxyapatite has good biocompatibility, bioactivity and osteoconductive ability because its chemical properties and biological properties are similar to those of bioapatite in bone tissue. Strontium-substituted hydroxyapatite has better degradability than hydroxyapatite and can both promote osteogenesis and inhibit adipogenesis in mesenchymal stem cells. Hence, hydroxyapatite and strontium-substituted hydroxyapatite are widely used as bone graft materials, cell carriers and drug/gene delivery carriers. In addition, osteoblasts cultured on aligned nanofibrous substrates had higher expression of osteogenesis-related genes than did those cultured on random nanofibrous substrates. However, to date, no study has explored the effects of the components and orientation of hydroxyapatite nanofibrous substrates on osteoblastic behavior. In this study, a random hydroxyapatite nanofibrous substrate (R-HANF), a random strontium-substituted hydroxyapatite nanofibrous substrate (R-SrHANF), an aligned hydroxyapatite nanofibrous substrate (A-HANF) and an aligned strontium-substituted hydroxyapatite nanofibrous substrate (A-SrHANF) were successfully fabricated by using the electrospinning technique. The effect of fiber composition on osteoblast-like MG63 cells was assessed by evaluating cell morphology, cell proliferation and osteogenesis-related gene expression. The results showed that MG63 cells cultured on A-SrHANF had higher osteogenesis-related gene expression than those cultured on A-HANF. Additionally, MG63 cells were cultured on R-SrHANF and A-SrHANF to evaluate the effects of fiber orientation on cell behavior. On A-SrHANF, the cells aligned along the direction of the nanofibers, with typical bipolar morphologies, and exhibited higher osteogenesis-related gene expression than cells on R-SrHANF. Hence, the components and orientation of hydroxyapatite nanofibrous substrates are critical parameters affecting the osteogenesis process.

Treatment of tibial large bone defects: A comparative study of bone transport over an intramedullary nail in combination with antibiotic-impregnated calcium sulphate versus bone transport alone with antibiotic-impregnated calcium sulphate

PURPOSE

To compare the bone transport over an intramedullary nail in combination with antibiotic-impregnated calcium sulphate versus bone transport alone with antibiotic-impregnated calcium sulphate for the treatment of tibial large bone defects.

METHODS

A retrospective analysis was conducted by enroling 33 surgically treated patients with tibial large bone defects after the debridement for tibial infection or osteomyelitis who were admitted in Lower Limb Surgery Ward of Traumatic orthopaedic Department, Xi'an Honghui Hospital from January 2018 to January 2021. All the patients were categorized in Group A (transport over intramedullary nail, 12 cases) and Group B (transport alone, 21 cases) based on the surgery strategy. The collected clinical materials and data included gender, age, injury mechanism, smoking habits, comorbidity diseases, initial fracture type (open or close), bone defect size, surgical duration, intraoperative bleeding loss, resorption time of calcium sulphate, bone transport time, external fixation time, external fixation index, weight bearing time, complications and Paley bone and functional criteria.

RESULTS

Thirty-three patients were enroled and successfully followed up with an average time of 15.25±4.31 months ranged from 8 to 21 months in Group A and an average time of 17.09±5.64 months ranged from 9 to 31 months in Group B. No significantly statistical differences of the demographic data were discovered between the two groups. There were no significantly statistical differences of the average bone defect size, intraoperative bleeding loss, resorption time of calcium sulphate and bone transport time between the two groups. However, the average surgical duration (P = 0.002) was significantly longer in Group A than Group B and the average external fixation time (P<0.001), external fixation index(P = 0.002) and weight bearing time (P = 0.030) were significantly shorter in Group A than Group B. No significantly statistical difference of excellent and good rate of bone outcomes and complication rate was observed, however, the excellent and good rate of functional outcomes (P = 0.041) was significantly higher in Group A than Group B.

CONCLUSION

Compared with the conventional Ilizarov technique combining with antibiotic-impregnated calcium sulphate for large tibial bone defects, bone transport over an intramedullary nail in combination with antibiotic-impregnated calcium sulphate had favourable external fixation time, external fixation index, weight bearing time and clinical functional outcomes which effectively suppressed the infection and allowed patients earlier removal of the external fixator and weight bearing for rehabilitation.

A review on fabrication of 3D printed biomaterials using optical methodologies for tissue engineering applications

Human body comprises of different internal and external biological components. Human organs tend to fail due to continuous or sudden stress which leads to deterioration, failure, and dislocation. The choice of selection and fabrication of materials for tissue engineering play a key role in terms of suitability, sensitivity, and functioning with other organs as a replacement for failed organs. The progressive improvement of the additive manufacturing (AM) approach in healthcare made it possible to print multi-material and customized complex/intricate geometries in a layer-by-layer fashion. The customized or patient-specific implant fabrication can be easily produced with a high success rate due to the development of AM technologies with tailorable properties. The structural behavior of 3D printed biomaterials is a crucial factor in tissue engineering as they affect the functionality of the implants. Various techniques have been developed in appraising the important features and the effects of the subsequent design of the biomaterial implants. The behavior of the AM built biomaterial implants can be understood visually by an imaging system with a high spatial and spectral resolution. This review intends to present an overview of various biomaterials used in implants, followed by a detailed description of optical 3D printing procedures and evaluation of the performance of 3D printed biomaterials using optical characterization.

In Vivo Analysis of the Regeneration Capacity and Immune Response to Xenogeneic and Synthetic Bone Substitute Materials

Although various studies have investigated differences in the tissue reaction pattern to synthetic and xenogeneic bone substitute materials (BSMs), a lack of knowledge exists regarding the classification of both materials based on the DIN ISO 10993-6 scoring system, as well as the histomorphometrical measurement of macrophage subtypes within their implantation beds. Thus, the present study was conducted to analyze in vivo responses to both xenogeneic and synthetic bone substitute granules. A standardized calvaria implantation model in Wistar rats, in combination with established scoring, histological, histopathological, and histomorphometrical methods, was conducted to analyze the influence of both biomaterials on bone regeneration and the immune response. The results showed that the application of the synthetic BSM maxresorb^® induced a higher pro-inflammatory tissue response, while the xenogeneic BSM cerabone^® induced a higher anti-inflammatory reaction. Additionally, comparable bone regeneration amounts were found in both study groups. Histopathological scoring revealed that the synthetic BSM exhibited non-irritant scores at all timepoints using the xenogeneic BSM as control. Overall, the results demonstrated the biocompatibility of synthetic BSM maxresorb^® and support the conclusion that this material class is a suitable alternative to natural BSM, such as the analyzed xenogeneic material cerabone^®, for a broad range of indications.

Biphasic Calcium Phosphate Versus Demineralized Freeze-Dried Bone Allograft in the Treatment of Periodontal Disease: A Clinical and Radiographical Evaluation

 Aim

The study aimed to clinically and radiographically evaluate the effect of biphasic calcium phosphate (BCP) versus demineralized freeze-dried bone allograft (DFDBA) in treating periodontal disease.

Method

The study consisted of 44 patients. The sites were randomly assigned to receive one of two treatment modalities (BCP at site 1 and demineralized freeze-dried bone at site 2) by a computerized method. All the clinical data were measured with the help of a University of North Carolina-15 (UNC-15) probe at the baseline, three months, and six months postoperatively. Radiovisiographs were taken using a Rinn XCP® (Dentsply/Rinn Corp, Elgin, IL) system and an oral grid using the paralleling technique. A manual calculation of the defect area was undertaken at the end of six months and was compared with the other groups.

Result

The linear bone growth recorded for site 1 at the end of six months was 3.8 ± 1.14 mm, and site 2 was 4.6 ± 1.07 mm. The intergroup comparison showed more remarkable linear bone growth in site 2, which was statistically insignificant, with a mean difference of 0.8 ± 1.23 mm and a p-value of 0.07.

Conclusion

Improvements were observed on all the documented parameters. However, the sites treated with DFDBA showed better periodontal regeneration.

The Management of Aseptic Non-unions of Distal Femur Fractures with Anatomical Lateral Locking Plates

Background

Distal femoral non-unions are challenging, and frequently associated with short distal fragments, poor bone stock, and with issues from previous implants.

Materials and methods

A retrospective study of 31 patients admitted with distal femoral non-unions treated using anatomical lateral locking plates. Non-union scores were used. The Knee Society and Neer's scores were used for the comparison of results. The mean follow-up was 39.5 months (from 24 months to 60 months).

Results

Stable union was accomplished in all. There was a significant improvement in the average Neer's score (24 preoperative to 82 post-operatively at final follow-up), the Part 1 Knee Society score from an average of 46 preoperatively to 84 post-operatively, and Part 2 Knee Society score from 36 preoperatively to 80 post-operatively.

Conclusion

Optimal stability, good compression at the non-union site (either by lag screws or a compression device or both), maintaining the axial alignment strictly, freshening of bone ends, using an adequate amount of cortico-cancellous bone graft, respecting the biology along with the correct choice of the implant (including the size) are essential to achieve union at the fracture site.

Clinical significance

Paying attention to the basic principles of management, good contact, stability and maintaining biology is essential in the treatment of non-union.

How to cite this article

Mukhopadhaya J, Ranjan R, Sinha AK, et al. The Management of Aseptic Non-unions of Distal Femur Fractures with Anatomical Lateral Locking Plates. Strategies Trauma Limb Reconstr 2022;17(3):137-143.

Spheroid co-culture of BMSCs with osteocytes yields ring-shaped bone-like tissue that enhances alveolar bone regeneration

Oral and maxillofacial bone defects severely impair appearance and function, and bioactive materials are urgently needed for bone regeneration. Here, we spheroid co-cultured green fluorescent protein (GFP)-labeled bone marrow stromal cells (BMSCs) and osteocyte-like MLO-Y4 cells in different ratios (3:1, 2:1, 1:1, 1:2, 1:3) or as monoculture. Bone-like tissue was formed in the 3:1, 2:1, and 1:1 co-cultures and MLO-Y4 monoculture. We found a continuous dense calcium phosphate structure and spherical calcium phosphate similar to mouse femur with the 3:1, 2:1, and 1:1 co-cultures, along with GFP-positive osteocyte-like cells encircled by an osteoid-like matrix similar to cortical bone. Flake-like calcium phosphate, which is more mature than spherical calcium phosphate, was found with the 3:1 and 2:1 co-cultures. Phosphorus and calcium signals were highest with 3:1 co-culture, and this bone-like tissue was ring-shaped. In a murine tooth extraction model, implantation of the ring-shaped bone-like tissue yielded more bone mass, osteoid and mineralized bone, and collagen versus no implantation. This tissue fabricated by spheroid co-culturing BMSCs with osteocytes yields an internal structure and mineral composition similar to mouse femur and could promote bone formation and maturation, accelerating regeneration. These findings open the way to new strategies in bone tissue engineering.

High resolution DLP stereolithography to fabricate biocompatible hydroxyapatite structures that support osteogenesis

Lithography based additive manufacturing techniques, specifically digital light processing (DLP), are considered innovative manufacturing techniques for orthopaedic implants because of their potential for construction of complex geometries using polymers, metals, and ceramics. Hydroxyapatite (HA) coupons, printed using DLP, were evaluated for biological performance in supporting viability, proliferation, and osteogenic differentiation of the human cell line U2OS and human mesenchymal stem cells (MSCs) up to 35 days in culture to determine feasibility for future use in development of complex scaffold geometries. Contact angle, profilometry, and scanning electron microscopy (SEM) measurements showed the HA coupons to be hydrophilic, porous, and having micro size surface roughness, all within favourable cell culture ranges. The study found no impact of leachable and extractables form the DLP printing process. Cells seeded on coupons exhibited morphologies comparable to conventional tissue culture polystyrene plates. Cell proliferation rates, as determined by direct cell count and the RealTime-Glo^TM MT Cell Viability Assay, were similar on HA coupons and standard tissue culture polystyrene plates). Osteogenic differentiation of human MSCs on HA coupons was confirmed using alkaline phosphatase, Alizarin Red S and von Kossa staining. The morphology of MSCs cultured in osteogenic medium for 14 to 35 days was similar on HA coupons and tissue culture polystyrene plates, with osteogenic (geometric, cuboidal morphology with dark nodules) and adipogenic (lipid vesicles and deposits) features. We conclude that the DLP process and LithaBone HA400 slurry are biocompatible and are suitable for osteogenic applications. Coupons served as an effective evaluation design in the characterization and visualization of cell responses on DLP printed HA material. Results support the feasibility of future technical development for 3D printing of sophisticated scaffold designs, which can be constructed to meet the mechanical, chemical, and porosity requirements of an artificial bone scaffold.

Advances in 3D bioprinting of tissues/organs for regenerative medicine and in-vitro models

Tissue/organ shortage is a major medical challenge due to donor scarcity and patient immune rejections. Furthermore, it is difficult to predict or mimic the human disease condition in animal models during preclinical studies because disease phenotype differs between humans and animals. Three-dimensional bioprinting (3DBP) is evolving into an unparalleled multidisciplinary technology for engineering three-dimensional (3D) biological tissue with complex architecture and composition. The technology has emerged as a key driver by precise deposition and assembly of biomaterials with patient's/donor cells. This advancement has aided in the successful fabrication of in vitro models, preclinical implants, and tissue/organs-like structures. Here, we critically reviewed the current state of 3D-bioprinting strategies for regenerative therapy in eight organ systems, including nervous, cardiovascular, skeletal, integumentary, endocrine and exocrine, gastrointestinal, respiratory, and urinary systems. We also focus on the application of 3D bioprinting to fabricated in vitro models to study cancer, infection, drug testing, and safety assessment. The concept of in situ 3D bioprinting is discussed, which is the direct printing of tissues at the injury or defect site for reparative and regenerative therapy. Finally, issues such as scalability, immune response, and regulatory approval are discussed, as well as recently developed tools and technologies such as four-dimensional and convergence bioprinting. In addition, information about clinical trials using 3D printing has been included.

Preparation of 3D Printing PLGA Scaffold with BMP-9 and P-15 Peptide Hydrogel and Its Application in the Treatment of Bone Defects in Rabbits

Objective

To prepare a three-dimensional (3D) printing polylactic acid glycolic acid (PLGA) scaffold with bone morphogenetic protein-9 (BMP-9) and P-15 peptide hydrogel and evaluate its application in treating bone defects in rabbits.

Methods

3D printing PLGA scaffolds were formed and scanned by electron microscopy. Their X-ray diffraction (XRD), in vitro degradation, and compressive strength were characterized. BMP-9 and P-15 hydrogels were prepared. Flow cytometry was used to detect apoptosis, and an electron microscope was used to evaluate cell adhesion to scaffolds. Alkaline phosphatase (ALP), type 1 collagen (Col-I), osteocalcin (OCN), runt-related transcription factor 2 (RUNX2), and osterix (SP7) were detected by western blotting. MicroCT was used to detect new bone formation, and bone tissue-related protein expressions were determined in the rabbit model with bone defects.

Results

The 3D printing scaffolds were cylindrical, and the inner diameter of the scaffolds was about 1 mm. The bread peak with wide distribution showed that the 3D printing only involved a physical change, which did not change the properties of the materials. The degradation rate of scaffolds was 9.38%, which met the requirements of properties of biological scaffolds. The water absorption of the support was about 9.09%, and the compressive strength was 15.83 N/mm². In the coculture of bone marrow mesenchymal stem cells (BMSCs) with scaffolds, the 2% polypeptide hydrogel showed the most obvious activity in promoting the differentiation of BMSCs. Flow cytometry showed that the 0% and 2% groups did not cause obvious apoptosis compared with the control group. Scaffolds with 2% and 4% polypeptide promoted the expression of ALP, COL-1, OCN, RUNX2, and Sp7 in BMSCs. In vivo experiments showed that the expression of ALP, COL-1, OCN, RUNX2, and Sp7 protein in the 2% polypeptide scaffold group increased significantly compared with the model group. MicroCT detection demonstrated that the 2% polypeptide scaffold had good bone repair ability.

Conclusion

The PLGA scaffolds combined with BMP-9 and P-15 peptide hydrogels had good biological and mechanical properties and could repair bone defects in rabbits.

Characterization and Evaluation of Composite Biomaterial Bioactive Glass-Polylactic Acid for Bone Tissue Engineering Applications

The limitations associated with the clinical use of autographs and allografts are driving efforts to develop relevant and applicable biomaterial substitutes. In this research, 3D porous scaffolds composed of bioactive glass (BG) obtained through the sol-gel technique and polylactic acid (PLA) synthesized via lactic acid (LA) ring-opening polymerization were prepared by the gel-pressing technique. Two different weight compositions were evaluated, namely, BG70-PLA30 and BG30-PLA70. The structure and morphology of the resulting scaffolds were analysed by FTIR, XRD, SEM, and under ASTM F1635 standard characterizations. The results confirmed that BG promotes the formation of a hydroxy-carbonated apatite (HAp) layer on composites when immersed in simulated body fluid (SBF). Biodegradability evaluations were carried out according to the ISO 10993-13:2010 standard. In addition, electrochemical evaluations were performed in both Hank's and SBF solutions at 37 °C in order to analyse the degradation of the material. This evaluation allowed us to observe that both samples showed an activation mechanism in the early stages followed by pseudo-passivation due to physical bioactive glass characteristics, suggesting an improvement in the formation of the HAp nucleation. The described composites showed excellent resistance to degradation and outstanding suitability for bone tissue engineering applications.

The regulatory challenges of innovative customized combination products

Background/aims

Combination products are therapeutic and/or diagnostic products that can combine drugs and medical devices and which increasing complexity has raised new regulatory framework challenges. To reach the market, a combination product must be classified based on the principal mode of action (PMOA). However, research and technological progress has been leading to the development of novel combination products with no clearly defined PMOA, emphasizing the lack of a systematization process, thus challenging the correct classification of these products. To illustrate the regulatory challenge, two case studies are discussed: innovative combination products with PMOA that can change due to an external stimulus, specifically custom-made 3D-printed scaffolds with incorporated medicinal substances.

Methods

Data was collected through computational search engines, regulatory agencies and equally relevant associations. The analysis of the data resulted on this state-of-the-art review, a description of the decision-making process by the regulatory authorities, and case studies analysis that culminated in the proposal of a decision-tree scheme.

Findings

Current regulations do not fully address complex combination products namely personalized 3D-printed scaffolds. Two merged regulatory approaches are suggested along with the schematization of the rational assisted by a decision-tree tool.

Conclusion

Combination products have become increasingly sophisticated, which has furthered the need to develop multidisciplinary collaborations within the health sector to adapt to these innovative healthcare solutions as well as with regulators to overcome the challenges posed for their classification.

Challenges and tissue engineering strategies of periodontal guided tissue regeneration

Periodontitis is a chronic infectious oral disease with a high prevalence rate in the world, and is a major cause of tooth loss. Nowadays, people have realized that the local microenvironment that includes proteins, cytokines, and extracellular matrix has a key influence on the functions of host immune cells and periodontal ligament stem cells during a chronic infectious disease such as periodontitis. The above pathological process of periodontitis will lead to a defect of periodontal tissues. Through the application of biomaterials, biological agents, and stem cells therapy, guided tissue regeneration (GTR) makes it possible to reconstruct healthy periodontal ligament tissue after local inflammation control. To date, substantial advances have been made in periodontal guided tissue regeneration. However, the process of periodontal remodeling experiences complex microenvironment changes, and currently periodontium regeneration still remains to be a challenging feat. In this review, we summarized the main challenges in each stage of periodontal regeneration, and try to put forward appropriate biomaterial treatment mechanisms or potential tissue engineering strategies that provide a theoretical basis for periodontal tissue engineering regeneration research.

Current status and prospects of metal-organic frameworks for bone therapy and bone repair

With the development of society, traumatic bone defects caused by accidents, diseases and surgeries have become common, eventually resulting in an increase in bone defects. The treatment of bone defects is characterized by a long period of treatment, high cost and uncontrollable outcomes. Also, it results in complications such as infection and bone discontinuity. Hence, due to this situation, the physical, mental and financial aspects of the patient are severely affected. What's more, such outcomes pose a challenge to orthopaedic surgeons. As a result, bone therapy and bone repair have become a hot topic of interest. In repairing bone defects, materials other than autogenous bone are still unable to provide good biocompatibility, osteogenesis, osteoconductivity and osteoinduction properties at the same time. In addition, the scarcity of autologous bone sources has forced the search for new autologous bone replacement materials. Metal organic frameworks (MOFs) are a new class of developed functional materials that have been widely used in the biomedical field during the recent years due to their porous nature, large specific surface area and diverse structures. With the progress in the investigation into bone treatment and repair, more and more investigators are using MOFs in bone therapy and bone repair. With these viewpoints, in the present perspective, the use of MOFs in bone therapy and bone repair has been summarized, and an insight into the future of MOFs in bone therapy and bone repair has been provided.

A Bibliometric Analysis of Electrospun Nanofibers for Dentistry

Electrospun nanofibers have been widely used in dentistry due to their excellent properties, such as high surface area and high porosity, this bibliometric study aimed to review the application fields, research status, and development trends of electrospun nanofibers in different fields of dentistry in recent years. All of the data were obtained from the Web of Science from 2004 to 2021. Origin, Microsoft Excel, VOSviewer, and Carrot² were used to process, analyze, and evaluate the publication year, countries/region, affiliations, authors, citations, keywords, and journal data. After being refined by the year of publication, document types and research fields, a total of 378 publications were included in this study, and an increasing number of publications was evident. Through linear regression calculations, it is predicted that the number of published articles in 2022 will be 66. The most published journal about electrospun dental materials is Materials Science & Engineering C-Materials for Biological Applications, among the six core journals identified, the percent of journals with Journal Citation Reports (JCR) Q1 was 60%. A total of 17.60% of the publications originated from China, and the most productive institution was the University of Sheffield. Among all the 1949 authors, the most productive author was Marco C. Bottino. Most electrospun dental nanofibers are used in periodontal regeneration, and Polycaprolactone (PCL) is the most frequently used material in all studies. With the global upsurge in research on electrospun dental materials, bone regeneration, tissue regeneration, and cell differentiation and proliferation will still be the research hotspots of electrospun dental materials in recent years. Extensive collaboration and citations among authors, institutions and countries will also reach a new level.

Proteomics reveals differential adsorption of angiogenic platelet lysate proteins on calcium phosphate bone substitute materials

Protein adsorption on biomaterials for bone substitution, such as calcium phosphates (CaP), evokes biological responses and shapes the interactions of biomaterials with the surrounding biological environment. Proteins adsorb when CaP materials are combined with growth factor-rich hemoderivatives prior to implantation to achieve enhanced angiogenesis and stimulate new bone formation. However, the identification of the adsorbed proteins and their angiogenic effect on bone homeostasis remain incompletely investigated. In this study, we analyzed the adsorbed complex protein composition on CaP surfaces when using the hemoderivatives plasma, platelet lysate in plasma (PL), and washed platelet lysate proteins (wPL). We detected highly abundant, non-regenerative proteins and anti-angiogenic proteins adsorbed on CaP surfaces after incubation with PL and wPL by liquid chromatography and mass spectrometry (LC–MS) proteomics. Additionally, we measured a decreased amount of adsorbed pro-angiogenic growth factors. Tube formation assays with human umbilical endothelial cells demonstrated that the CaP surfaces only stimulate an angiogenic response when kept in the hemoderivative medium but not after washing with PBS. Our results highlight the necessity to correlate biomaterial surfaces with complex adsorbed protein compositions to tailor the biomaterial surface toward an enrichment of pro-angiogenic factors.

Improving Vascularization of Biomaterials for Skin and Bone Regeneration by Surface Modification: A Narrative Review on Experimental Research

Artificial tissue substitutes are of great interest for the reconstruction of destroyed and non-functional skin or bone tissue due to its scarcity. Biomaterials used as scaffolds for tissue regeneration are non-vascularized synthetic tissues and often based on polymers, which need ingrowth of new blood vessels to ensure nutrition and metabolism. This review summarizes previous approaches and highlights advances in vascularization strategies after implantation of surface-modified biomaterials for skin and bone tissue regeneration. The efficient integration of biomaterial, bioactive coating with endogenous degradable matrix proteins, physiochemical modifications, or surface geometry changes represents promising approaches. The results show that the induction of angiogenesis in the implant site as well as the vascularization of biomaterials can be influenced by specific surface modifications. The neovascularization of a biomaterial can be supported by the application of pro-angiogenic substances as well as by biomimetic surface coatings and physical or chemical surface activations. Furthermore, it was confirmed that the geometric properties of the three-dimensional biomaterial matrix play a central role, as they guide or even enable the ingrowth of blood vessels into a biomaterial.

Effect of lentivirus-mediated BMP2 from autologous tooth on the proliferative and osteogenic capacity of human periodontal ligament cells

BACKGROUND AND OBJECTIVE

Periodontitis is a chronic progressive inflammation that invades periodontal supporting tissues, in which periodontal tissue regeneration engineering offers new hope for prevention and treatment, including seed cells, scaffolds, and growth factors. In recent years, scholars have shown that autologous teeth can be used as new bone tissue repair materials for periodontal regeneration and bone tissue repair. The aim of this study was to establish a human periodontal ligament cell line that expresses the human bone morphogenetic protein 2 gene (BMP2) in a stable manner using lentiviral mediation in order to explore the effect of BMP2 from autologous tooth on the proliferative and osteogenic capacity of human periodontal ligament cells (hPDLCs).

MATERIALS AND METHODS

Human periodontal ligament cells were cultured, subcultured, and identified, and then homologous recombinant lentivirus plasmid plv-BMP2 was constructed and transfected into the third passage (P₃ ) hPDLCs. After that, the effect of BMP2 on its proliferation was detected by CCK-8, at the same time, the osteogenic induction of hPDLCs was carried out at 7, 14, and 21 days, and then the effect of BMP2 on its osteogenic ability was detected by alizarin red staining, alkaline phosphatase activity determination, and the mRNA expression levels of osteogenic-related genes using real-time fluorescence quantitative PCR, including alkaline phosphatase, runt-related transcription factor 2, bone sialoprotein, osteocalcin, osteopontin, and collagen I. Finally, spss26.0 software was used for statistical processing.

RESULTS

The results showed that cells transfected with the homologous recombinant lentiviral plasmid pLV-BMP2 had a similar morphology to normal hPDLCs, showing a typical radial arrangement; the cell proliferative capacity of the pLV-BMP2 group as measured by CCK-8 was enhanced compared with the control group and the pLV-puro group (p < .05); alizarin red staining and alkaline phosphatase activity assay showed that the osteogenic ability of pLV-BMP2 was significantly enhanced compared with the control and pLV-puro groups (p < .01), and the findings of real-time fluorescence-based quantitative PCR showed high expression of osteogenic-related genes in pLV-BMP2 group (p < .01).

CONCLUSION

In conclusion, a stable periodontal ligament cell line overexpressing BMP2 was successfully established by a lentivirus-mediated method, which proved that BMP2 has a strong ability to promote the proliferation and osteogenesis of hPDLCs, thereby providing an opportunity for the study of periodontal tissue regeneration as well as providing an experimental basis for the application of autologous teeth as a new type of bone repair material for periodontal therapy and even for maxillofacial bone tissue repair.

Engineering Biomimetic Extracellular Matrix with Silica Nanofibers: From 1D Material to 3D Network

Biomaterials at nanoscale is a fast-expanding research field with which extensive studies have been conducted on understanding the interactions between cells and their surrounding microenvironments as well as intracellular communications. Among many kinds of nanoscale biomaterials, mesoporous fibrous structures are especially attractive as a promising approach to mimic the natural extracellular matrix (ECM) for cell and tissue research. Silica is a well-studied biocompatible, natural inorganic material that can be synthesized as morpho-genetically active scaffolds by various methods. This review compares silica nanofibers (SNFs) to other ECM materials such as hydrogel, polymers, and decellularized natural ECM, summarizes fabrication techniques for SNFs, and discusses different strategies of constructing ECM using SNFs. In addition, the latest progress on SNFs synthesis and biomimetic ECM substrates fabrication is summarized and highlighted. Lastly, we look at the wide use of SNF-based ECM scaffolds in biological applications, including stem cell regulation, tissue engineering, drug release, and environmental applications.

Engineering biomaterials to 3D-print scaffolds for bone regeneration: practical and theoretical consideration

There are more than 2 million bone grafting procedures performed annually in the US alone. Despite significant efforts, the repair of large segmental bone defects is a substantial clinical challenge which requires bone substitute materials or a bone graft. The available biomaterials lack the adequate mechanical strength to withstand the static and dynamic loads while maintaining sufficient porosity to facilitate cell in-growth and vascularization during bone tissue regeneration. A wide range of advanced biomaterials are being currently designed to mimic the physical as well as the chemical composition of a bone by forming polymer blends, polymer-ceramic and polymer-degradable metal composites. Transforming these novel biomaterials into porous and load-bearing structures via three-dimensional printing (3DP) has emerged as a popular manufacturing technique to develop engineered bone grafts. 3DP has been adopted as a versatile tool to design and develop bone grafts that satisfy porosity and mechanical requirements while having the ability to form grafts of varied shapes and sizes to meet the physiological requirements. In addition to providing surfaces for cell attachment and eventual bone formation, these bone grafts also have to provide physical support during the repair process. Hence, the mechanical competence of the 3D-printed scaffold plays a key role in the success of the implant. In this review, we present various recent strategies that have been utilized to design and develop robust biomaterials that can be deployed for 3D-printing bone substitutes. The article also reviews some of the practical, theoretical and biological considerations adopted in the 3D-structure design and development for bone tissue engineering.

Antiosteoporotic Nanohydroxyapatite Zoledronate Scaffold Seeded with Bone Marrow Mesenchymal Stromal Cells for Bone Regeneration: A 3D In Vitro Model

Background: Bisphosphonates are widely employed drugs for the treatment of pathologies with high bone resorption, such as osteoporosis, and display a great affinity for calcium ions and apatitic substrates. Here, we aimed to investigate the potentiality of zoledronate functionalized hydroxyapatite nanocrystals (HAZOL) to promote bone regeneration by stimulating adhesion, viability, metabolic activity and osteogenic commitment of human bone marrow derived mesenchymal stromal cells (hMSCs). Methods: we adopted an advanced three-dimensional (3D) in vitro fracture healing model to study porous scaffolds: hMSCs were seeded onto the scaffolds that, after three days, were cut in halves and unseeded scaffolds were placed between the two halves. Scaffold characterization by X-ray diffraction, transmission and scanning electron microscopy analyses and cell morphology, viability, osteogenic differentiation and extracellular matrix deposition were evaluated after 3, 7 and 10 days of culture. Results: Electron microscopy showed a porous and interconnected structure and a uniform cell layer spread onto scaffolds. Scaffolds were able to support cell growth and cells progressively colonized the whole inserts in absence of cytotoxic effects. Osteogenic commitment and gene expression of hMSCs were enhanced with higher expressions of ALPL, COL1A1, BGLAP, RUNX2 and Osterix genes. Conclusion: Although some limitations affect the present study (e.g., the lack of longer experimental times, of mechanical stimulus or pathological microenvironment), the obtained results with the adopted experimental setup suggested that zoledronate functionalized scaffolds (GHAZOL) might sustain not only cell proliferation, but positively influence osteogenic differentiation and activity if employed in bone fracture healing.

Notoginsenoside R1 Promotes Migration, Adhesin, Spreading, and Osteogenic Differentiation of Human Adipose Tissue-Derived Mesenchymal Stromal Cells

Cellular activities, such as attachment, spreading, proliferation, migration, and differentiation are indispensable for the success of bone tissue engineering. Mesenchymal stromal cells (MSCs) are the key precursor cells to regenerate bone. Bioactive compounds from natural products had shown bone regenerative potential. Notoginsenoside R1 (NGR1) is a primary bioactive natural compound that regulates various biological activities, including cardiovascular protection, neuro-protection, and anti-cancer effects. However, the effect of NGR1 on migration, adhesion, spreading, and osteogenic differentiation of MSCs required for bone tissue engineering application has not been tested properly. In this study, we aimed to analyze the effect of NGR1 on the cellular activities of MSCs. Since human adipose-derived stromal cells (hASCs) are commonly used MSCs for bone tissue engineering, we used hASCs as a model of MSCs. The optimal concentration of 0.05 μg/mL NGR1 was biocompatible and promoted migration and osteogenic differentiation of hASCs. Pro-angiogenic factor VEGF expression was upregulated in NGR1-treated hASCs. NGR1 enhanced the adhesion and spreading of hASCs on the bio-inert glass surface. NGR1 robustly promoted hASCs adhesion and survival in 3D-printed TCP scaffold both in vitro and in vivo. NGR1 mitigated LPS-induced expression of inflammatory markers IL-1β, IL-6, and TNF-α in hASCs as well as inhibited the RANKL/OPG expression ratio. In conclusion, the biocompatible NGR1 promoted the migration, adhesion, spreading, osteogenic differentiation, and anti-inflammatory properties of hASCs.

Horizontal ridge augmentation in the anterior maxilla with in situ onlay bone grafting: a retrospective cohort study

OBJECTIVES

This study aimed to introduce a digitally guided in situ autogenous onlay grafting technique and compare its effectiveness with the conventional (ex situ) onlay technique in augmenting horizontal bone defects of the anterior maxilla.

MATERIALS AND METHODS

This retrospective cohort study included 24 patients who had received autogenous onlay bone grafts combined with guided bone regeneration (GBR) in the anterior maxilla. Fourteen patients were recruited into the in situ onlay grafting group (EG), and 10 were recruited into the ex situ onlay group (CG), defined by the donor sites. The clinical parameters, radiographic changes, micro-CT, and histological processes were evaluated after a mean follow-up period of 1.7 years.

RESULTS

The horizontal bone width reflected significant bone modeling over time (p < 0.001) in the first 6 months. Multivariable analysis showed that the treatment modality (grouping) was a critical factor positively associated with vertical bone height alteration. However, neither the alteration rate of horizontal bone width nor the bone volume was associated with the treatment modality. The number of periosteal screws per graft positively affected horizontal contour maintenance (p < 0.05). No significant differences were observed between the groups in the clinical parameters (complications, success rate, and peri-implant parameters). The micro-CT and histological outcomes were similar between the groups.

CONCLUSION

Despite the limitations of this study, in situ onlay grafting combined with GBR was an effective and reliable approach for horizontal bone augmentation in the anterior maxilla and appeared to demonstrate better stability in vertical bone remodeling.

CLINICAL RELEVANCE

This study introduces a modified and minimally invasive technique of onlay grafting for horizontal bone augmentation. This in situ onlay grafting demonstrates superior stability in vertical bone remodeling. The trial registration number is ChiCTR2100054683.

Tooth as graft material: Histologic study

Background

An effective regenerative protocol is key to reestablish and maintain the hard and soft tissue dimensions over time. The choice of the graft material and its properties also could have an impact on the results. To prevent alveolar ridge dimensional changes, since numerous graft materials have been suggested and in the past years, a growing interest in teeth material has been observed as a valuable alternative to synthetic biomaterials.

Aim

The aim of the study was to explore the histomorphometric outcomes of tooth derivative materials as used as bone substitute material in socket preservation procedure.

Methods

After alveolar socket preservation (ASP) procedures using autologous demineralized tooth as graft material prepared by means of an innovative device, was evaluated. A total of 101 histological samples, from 96 subjects, were analyzed by evaluating the total amount of bone (BV), residual tooth material (residual graft, TT), and vital bone (VB). The section from each sample was then split in nine subsections, resulting in 909 subsections, to allow statistical comparison between the different areas.

Results

It was not noticed a statistically significant difference between maxillary and mandibular sites, being the amount of VB in upper jaw sites 37.9 ± 21.9% and 38.0 ± 22.0% in lower jaw sites and the amount of TT was 7.7 ± 12.2% in maxilla and 7.0 ± 11.1% in mandibles. None of the other considered parameters, including defect type and section position, were statistically correlated to the results of the histomorphometric analysis.

Conclusions

ASP procedure using demineralized autologous tooth‐derived biomaterial may be a predictable procedure to produce new vital bone potentially capable to support dental implant rehabilitation.

Ultra-low binder content 3D printed calcium phosphate graphene scaffolds as resorbable, osteoinductive matrices that support bone formation in vivo

Bone regenerative engineering could replace autografts; however, no synthetic material fulfills all design criteria. Nanocarbons incorporated into three-dimensional printed (3DP) matrices can improve properties, but incorporation is constrained to low wt%. Further, unmodified nanocarbons have limited osteogenic potential. Functionalization to calcium phosphate graphene (CaPG) imparts osteoinductivity and osteoconductivity, but loading into matrices remained limited. This work presents ultra-high content (90%), 3DP-CaPG matrices. 3DP-CaPG matrices are highly porous (95%), moderately stiff (3 MPa), and mechanically robust. In vitro, they are cytocompatible and induce osteogenic differentiation of human mesenchymal stem cells (hMSCs), indicated by alkaline phosphatase, mineralization, and COL1α1 expression. In vivo, bone regeneration was studied using a transgenic fluorescent-reporter mouse non-union calvarial defect model. 3DP-CaPG stimulates cellular ingrowth, retains donor cells, and induces osteogenic differentiation. Histology shows TRAP staining around struts, suggesting potential osteoclast activity. Apparent resorption of 3DP-CaPG was observed and presented no toxicity. 3DP-CaPG represents an advancement towards a synthetic bone regeneration matrix.

Effectiveness of Calcium Sulfate and Hydroxyapatite Composite in Collapse Prevention in Osteonecrosis of Femoral Head

Introduction

Calcium-sulfate-hydroxyapatite bioceramics have been widely used as void fillers in bone. However, their effectiveness as void fillers in core decompression for osteonecrosis of the femoral head (ONFH) in preventing femoral head collapse prevention has limited evidence. The current study investigates the effectiveness of calcium-sulfate-hydroxyapatite bioceramics as a void filler in the core decompression procedure for ONFH.

Methods

We retrospectively reviewed the clinical and radiological records of ONFH patients that underwent core-decompression using either autologous iliac crest cancellous bone graft or calcium-sulfate-hydroxyapatite bioceramic paste as void fillers with at least one-year follow-up. The primary outcome of this study was the radiological progression of collapse in the last available standard anteroposterior (AP) radiographs of the hip. The collapse progression was compared between the two groups based on void fillers.

Results

This study included patient records with 44 hip joints that underwent core decompression. There were five female and 33 male patients. The mean age was 29.1±6.3 years. The mean follow-up duration was 21.4±3.4 months. No significant differences in collapse progression were observed between the two groups based on void fillers.

Conclusion

The use of calcium-sulfate-hydroxyapatite as a void filler in core decompress for ONFH is not superior to the autologous cancellous bone in terms of collapse prevention and mechanical support. Further modifications in the core decompression techniques and well-planned prospective studies would help establish sound recommendations.

Comparison of the osseointegration of implants placed in areas grafted with HA/TCP and native bone

This study evaluated the osseointegration of implants in areas grafted with biphasic ceramic based on hydroxyapatite/β-tricalcium phosphate (HA/TCP) and in native bone (NB). Twenty-eight rats were randomly assigned into two groups of 14 animals each: HA/TCP group: implants installed in areas grafted with HA/TCP and NB group: implants installed in areas of native bone. Bone defects were made in both tibiae of the rats belonging to the HA/TCP group and then filled with this bone substitute. After 60 days, the rats were submitted to surgical procedures for implant placement in grafted areas in both tibiae in the HA/TCP group while the implants were installed directly in native bone in the NB group. The animals were euthanized 15 and 45 days, respectively, after the implant placement. Biomechanical (removal torque), microtomographic (volume of mineralized tissues around the implants), and histomorphometric (Bone-Implant contact-%BIC and bone area between the implant threads-%BBT) analyzes were conducted to assess the osseointegration process. The HA/TCP group showed lower values of removal torque, volume of mineralized tissue around the implants, lower %BIC, and %BBT compared to the NB group in both experimental periods. Osseointegration of implants placed in grafted areas with HA/TCP was lower compared to the osseointegration observed in native bone areas.

Bone Using Stem Cells for Maxillofacial Bone Disorders: A Systematic Review and Meta-analysis

Due to economic, cultural, environmental, and social factors, the prevalence of maxillofacial bone disorders varies in different parts of the world. The present meta-analysis was conducted to assess the efficacy and safety of different type of stem cells-based scaffolds and their construction methods in maxillofacial bone disorders. We searched major indexing databases, including PubMed/Medline, ISI Web of Science, Scopus, Embase, and Cochrane Central without any language, study region, or type restrictions. A systematic search of articles published up to July 2021 was done. Of the 428 studies found through initial searches, 36 met the inclusion criteria. After applying the exclusion criteria, the main properties of 32 articles on 643 animals and 4 experimental studies on 52 patients (age range from 43 to 74 years) included in this meta-analysis. Our pooled analysis showed that stem cells-based scaffolds significantly improved the bone regeneration and formation in maxillofacial bone disorders (Prevalence: 0.54; 95% CI: 0.43, 0.64, P < 00001, I2 = 90 2). According to the results of these studies, in most studies, bone marrow-derived mesenchymal stem cells (BMSCs) have been used to regenerate bone, and these cells are still the gold standard in bone tissue engineering, a growth factor that is one of the three sides of the tissue engineering triangle. Bone morphogenetic proteins (BMP) especially BMP2 and platelet-rich plasma (PRP) are the most widely used growth factor and scaffold respectively. Platelet-rich plasma (PRP) is used as a scaffold and since it contains proteins, it also used as a growth factor and can be a stimulant of ossification. It seems that the future perspective of bone tissue engineering is to use the prototyping rapid method to build a composite and patient-specific scaffold from CT and MRI images, along with genetically modified stem cells.

The Effect of Low-Temperature Thermal Processing on Bovine Hydroxyapatite Bone Substitutes, toward Bone Cell Interaction and Differentiation

Ideal bone grafting scaffolds are osteoinductive, osteoconductive, and encourage osteogenesis through the remodeling processes of bone resorption, new bone formation, and successful integration or replacement; however, achieving this trifecta remains challenging. Production methods of bone grafts, such as thermal processing, can have significant effects on the degree of cell-surface interactions via wide-scale changes in the material properties. Here, we investigated the effects of small incremental changes at low thermal processing temperatures on the degree of osteoclast and osteoblast attachment, proliferation, and differentiation. Bovine bone scaffolds were prepared at 100, 130, 160, 190, and 220 °C and compared with a commercial control, Bio-Oss^®. Osteoclast attachment and activity were significantly higher on lower temperature processed bone and were not present ≥190 °C. The highest osteoblast proliferation and differentiation were obtained from treatments at 130 and 160 °C. Similarly, qRT²-PCR assays highlighted osteoblasts attached to bone processed at 130 and 160 °C as demonstrating the highest osteogenic gene expression. This study demonstrated the significant effects of small-scale processing changes on bone graft materials in vitro, which may translate to a tailored approach of cellular response in vivo.

Engineering hypertrophic cartilage grafts from lipoaspirate for critical‐sized calvarial bone defect reconstruction: An adipose tissue‐based developmental engineering approach

Developmental engineering of living implants from different cell sources capable of stimulating bone regeneration by recapitulating endochondral ossification (ECO) is a promising strategy for large bone defect reconstruction. However, the clinical translation of these cell‐based approaches is hampered by complex manufacturing procedures, poor cell differentiation potential, and limited predictive in vivo performance. We developed an adipose tissue‐based developmental engineering approach to overcome these hurdles using hypertrophic cartilaginous (HyC) constructs engineered from lipoaspirate to repair large bone defects. The engineered HyC constructs were implanted into 4‐mm calvarial defects in nude rats and compared with decellularized bone matrix (DBM) grafts. The DBM grafts induced neo‐bone formation via the recruitment of host cells, while the HyC pellets supported bone regeneration via ECO, as evidenced by the presence of remaining cartilage analog and human NuMA‐positive cells within the newly formed bone. However, the HyC pellets clearly showed superior regenerative capacity compared with that of the DBM grafts, yielding more new bone formation, higher blood vessel density, and better integration with adjacent native bone. We speculate that this effect arises from vascular endothelial growth factor and bone morphogenetic protein‐2 secretion and mineral deposition in the HyC pellets before implantation, promoting increased vascularization and bone formation upon implantation. The results of this study demonstrate that adipose‐derived HyC constructs can effectively heal large bone defects and present a translatable therapeutic option for bone defect repair.

Graphene Oxide Framework Structures and Coatings: Impact on Cell Adhesion and Pre-Vascularization Processes for Bone Grafts

Graphene oxide (GO) is a promising material for bone tissue engineering, but the validation of its molecular biological effects, especially in the context of clinically applied materials, is still limited. In this study, we compare the effects of graphene oxide framework structures (F-GO) and reduced graphene oxide-based framework structures (F-rGO) as scaffold material with a special focus on vascularization associated processes and mechanisms in the bone. Highly porous networks of zinc oxide tetrapods serving as sacrificial templates were used to create F-GO and F-rGO with porosities >99% consisting of hollow interconnected microtubes. Framework materials were seeded with human mesenchymal stem cells (MSC), and the cell response was evaluated by confocal laser scanning microscopy (CLSM), deoxyribonucleic acid (DNA) quantification, real-time polymerase chain reaction (RT-PCR), enzyme-linked immunosorbent assay (ELISA), and alkaline phosphatase activity (ALP) to define their impact on cellular adhesion, osteogenic differentiation, and secretion of vascular growth factors. F-GO based scaffolds improved adhesion and growth of MSC as indicated by CLSM and DNA quantification. Further, F-GO showed a better vascular endothelial growth factor (VEGF) binding capacity and improved cell growth as well as the formation of microvascular capillary-like structures in co-cultures with outgrowth endothelial cells (OEC). These results clearly favored non-reduced graphene oxide in the form of F-GO for bone regeneration applications. To study GO in the context of a clinically used implant material, we coated a commercially available xenograft (Bio-Oss® block) with GO and compared the growth of MSC in monoculture and in coculture with OEC to the native scaffold. We observed a significantly improved growth of MSC and formation of prevascular structures on coated Bio-Oss®, again associated with a higher VEGF binding capacity. We conclude that graphene oxide coating of this clinically used, but highly debiologized bone graft improves MSC cell adhesion and vascularization.

Influence of 3D Printing Parameters on the Mechanical Stability of PCL Scaffolds and the Proliferation Behavior of Bone Cells

Introduction The use of scaffolds in tissue engineering is becoming increasingly important as solutions need to be found for the problem of preserving human tissue, such as bone or cartilage. In this work, scaffolds were printed from the biomaterial known as polycaprolactone (PCL) on a 3D Bioplotter. Both the external and internal geometry were varied to investigate their influence on mechanical stability and biocompatibility. Materials and Methods: An Envisiontec 3D Bioplotter was used to fabricate the scaffolds. First, square scaffolds were printed with variations in the strand width and strand spacing. Then, the filling structure was varied: either lines, waves, and honeycombs were used. This was followed by variation in the outer shape, produced as either a square, hexagon, octagon, or circle. Finally, the internal and external geometry was varied. To improve interaction with the cells, the printed PCL scaffolds were coated with type-I collagen. MG-63 cells were then cultured on the scaffolds and various tests were performed to investigate the biocompatibility of the scaffolds. Results: With increasing strand thickness and strand spacing, the compressive strengths decreased from 86.18 + 2.34 MPa (200 µm) to 46.38 + 0.52 MPa (600 µm). The circle was the outer shape with the highest compressive strength of 76.07 + 1.49 MPa, compared to the octagon, which had the lowest value of 52.96 ± 0.98 MPa. Varying the external shape (toward roundness) geometry, as well as the filling configuration, resulted in the highest values of compressive strength for the round specimens with honeycomb filling, which had a value of 91.4 + 1.4 MPa. In the biocompatibility tests, the round specimens with honeycomb filling also showed the highest cell count per mm², with 1591 ± 239 live cells/mm2 after 10 days and the highest value in cell proliferation, but with minimal cytotoxic effects (9.19 ± 2.47% after 3 days).

Clinical Application of Adipose Derived Stem Cells for the Treatment of Aseptic Non-Unions: Current Stage and Future Perspectives-Systematic Review

Fracture non-union is a challenging orthopaedic issue and a socio-economic global burden. Several biological therapies have been introduced to improve traditional surgical approaches. Among these, the latest research has been focusing on adipose tissue as a powerful source of mesenchymal stromal cells, namely, adipose-derived stem cells (ADSCs). ADSC are commonly isolated from the stromal vascular fraction (SVF) of liposuctioned hypodermal adipose tissue, and their applications have been widely investigated in many fields, including non-union fractures among musculoskeletal disorders. This review aims at providing a comprehensive update of the literature on clinical application of ADSCs for the treatment of non-unions in humans. The study was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Only three articles met our inclusion criteria, with a total of 12 cases analyzed for demographics and harvesting, potential manufacturing and implantation of ADSCs. The review of the literature suggests that adipose derived cell therapy can represent a promising alternative in bone regenerative medicine for the enhancement of non-unions and bone defects. The low number of manuscripts reporting ADSC-based therapies for long bone fracture healing suggests some critical issues that are discussed in this review. Nevertheless, further investigations on human ADSC therapies are needed to improve the knowledge on their translational potential and to possibly achieve a consensus on their use for such applications.

A Comparative Study of Two Bone Graft Substitutes–InterOss® Collagen and OCS-B Collagen®

Bone is a complex hierarchical tissue composed of organic and inorganic materials that provide structure, support, and protection to organs. However, there are some critical size defects that are unable to regenerate on their own and therefore require clinical repair. Bone graft substitutes allow repair by providing a temporary resorbable device. Among the common filler materials that aid in regeneration is hydroxyapatite particles of either animal or human origin which is used to fill or reconstruct periodontal and bony defects in the mouth. However, particulate graft substitutes suffer from localized migration away from the implantation site, necessitating the use of a barrier membrane. In this study, we designed InterOss Collagen, combining bovine hydroxyapatite granules with porcine-skin derived collagen to form a bone filler composite. Physiochemical properties of InterOss Collagen and a commercially available product, OsteoConductive Substitute-Bovine(OCS-B) Collagen, referred to as OCS-B Collagen, were examined. We found two bone graft substitutes to be mostly similar, though InterOss Collagen showed comparatively higher surface area and porosity. We conducted an in vivo study in rabbits to evaluate local tissue responses, percent material resorption and bone formation and showed that the two materials exhibited similar degradation profiles, inflammatory and healing responses following implantation. Based on these results, InterOss Collagen is a promising dental bone grafting material for periodontal and maxillofacial surgeries.

A Biofabrication Strategy for a Custom-Shaped, Non-Synthetic Bone Graft Precursor with a Prevascularized Tissue Shell

Critical-sized defects of irregular bones requiring bone grafting, such as in craniofacial reconstruction, are particularly challenging to repair. With bone-grafting procedures growing in number annually, there is a reciprocal growing interest in bone graft substitutes to meet the demand. Autogenous osteo(myo)cutaneous grafts harvested from a secondary surgical site are the gold standard for reconstruction but are associated with donor-site morbidity and are in limited supply. We developed a bone graft strategy for irregular bone-involved reconstruction that is customizable to defect geometry and patient anatomy, is free of synthetic materials, is cellularized, and has an outer pre-vascularized tissue layer to enhance engraftment and promote osteogenesis. The graft, comprised of bioprinted human-derived demineralized bone matrix blended with native matrix proteins containing human mesenchymal stromal cells and encased in a simple tissue shell containing isolated, human adipose microvessels, ossifies when implanted in rats. Ossification follows robust vascularization within and around the graft, including the formation of a vascular leash, and develops mechanical strength. These results demonstrate an early feasibility animal study of a biofabrication strategy to manufacture a 3D printed patient-matched, osteoconductive, tissue-banked, bone graft without synthetic materials for use in craniofacial reconstruction. The bone fabrication workflow is designed to be performed within the hospital near the Point of Care.

Clinical parameters and radiographic resorption of a novel magnesium based bone void filler

BACKGROUND

Bone voids can present challenging problems for the Orthopaedic surgeon, and are often treated with backfilling followed by structural stabilization. Recently, a magnesium based, and presumably resorbable, bone void filler (BVF) has been developed, but has limited longitudinal clinical data. Therefore, the purpose of this study was to investigate clinically relevant parameters and radiographic resorption characteristics of this novel magnesium based BVF (MgBVF) with long-term clinical data.

METHODS

All patients who underwent surgery by a single surgeon in which MgBVF was utilized from 2019 to 2020 were retrospectively reviewed. Clinical parameters including evidence of infection, wound breakdown, and wound drainage were reviewed. Radiographic resorption, evidence of joint extrusion of BVF, heterotopic ossification, and subsidence was assessed at each post-operative visit. Those with less than 6 month follow up were excluded from radiographic analysis of resorption. Postoperative images at two weeks were compared to each subsequent radiograph during follow up, and reviewed by each of the three authors in blinded fashion. Interval radiographs were assigned a grade of radiographic resorption which corresponded to estimated percent resorption: grade 1 (0-25%), grade 2 (25-50%), grade 3 (50-75%), or grade 4 (75-100%). After 2 weeks, this process was repeated, and both inter and intraobserver reliability scores were calculated.

RESULTS

Forty-two patients were identified for clinical review, and 18 for radiographic review. Average length of follow up was 209±113 days. Five patients experienced a postoperative complication: two wound infections, one delayed wound healing, one sterile serous drainage, and one catastrophic failure of the fixation construct. Four patients were noted to have postoperative joint subsidence of 2 mm or less. Average grade of resorption was found to be 1.5 ± 0.8, 1.7 ± 0.9, 2.9 ± 0.9, and 3.6 ± 0.6 at 6 weeks, 3 months, 6 months, and 1 year, respectively (p<0.001). Average kappa (intrarater reliability) was found to be 0.61, 0.41, 0.55, and 0.63 for each time interval, respectively. Interrater reliability increased form 0.19 at 6 weeks to 0.42 at 1 year.

CONCLUSION

This novel MgBVF demonstrates clinically relevant resorption, provides structural support in challenging bone voids, and does not appear to significantly increase risk of complications, setting it apart from previously described BVF's.

Macrophages and Bone Marrow-Derived Mesenchymal Stem Cells Work in Concert to Promote Fracture Healing: A Brief Review

Bone marrow-derived mesenchymal stem cell (BMSC)-based and macrophage-based cell therapy are regarded as promising strategies to promote fracture healing because of incredible osteogenic potential of BMSCs and typical immunomodulatory function of macrophages. Apart from their respective key roles, accumulative evidence has also demonstrated the importance of cross talk between these two cell types in fracture healing process. This review takes a deep insight into the recent research progress of the synergic performance of BMSCs and macrophages by discussing not only the cells own functions but also the relevant impact factors and mechanisms (ambient microenvironment stimulus, miRNAs, etc). The aim of this review is to provide some valuable cues and technique support for the macrophage- and BMSC-related research, which will be helpful to propel BMSC/macrophage-based combined cell therapy for bone fracture treatment.

Silk Fibroin Microparticle Scaffold for Use in Bone Void Filling: Safety and Efficacy Studies

Silk fibroin (SF) is a natural biocompatible protein polymer extracted from cocoons of silkworm Bombyx mori. SF can be processed into a variety of different forms and shapes that can be used as scaffolds to support bone regeneration. Three-dimensional (3D) SF scaffolds have shown promise in bone-void-filling applications. In in vitro studies, it has been demonstrated that a microparticle-based SF (M-RSF) scaffold promotes the differentiation of stem cells into an osteoblastic lineage. The expression of differentiation markers was also significantly higher for M-RSF scaffolds as compared to other SF scaffolds and commercial ceramic scaffolds. In this work, we have evaluated the in vitro and in vivo biocompatibility of M-RSF scaffolds as per the ISO 10993 guidelines in a Good Laboratory Practice (GLP)-certified facility. The cytotoxicity, immunogenicity, genotoxicity, systemic toxicity, and implantation studies confirmed that the M-RSF scaffold is biocompatible. Further, the performance of the M-RSF scaffold to support bone formation was evaluated in in vivo bone implantation studies in a rabbit model. Calcium sulfate (CaSO₄) scaffolds were chosen as reference material for this study as they are one of the preferred materials for bone-void-filling applications. M-RSF scaffold implantation sites showed a higher number of osteoblast and osteoclast cells as compared to CaSO₄ implantation sites indicating active bone remodeling. The number density of osteocytes was double for M-RSF scaffold implantation sites, and these M-RSF scaffold implantation sites were characterized by enhanced collagen deposition, pointing toward a finer quality of the new bone formed. Moreover, the M-RSF scaffold implantation sites had a negligible incidence of secondary fractures as compared to the CaSO₄ implantation sites (∼50% sites with secondary fracture), implying a reduction in postsurgical complications. Thus, the study demonstrates that the M-RSF scaffold is nontoxic for bone-void-filling applications and facilitates superior healing of fracture defects as compared to commercial calcium-based bone void fillers.