Segmental bone repair by tissue-engineered periosteal cell transplants with bioresorbable fleece and fibrin scaffolds in rabbits

Use of Fibrin Glue as a Surgical Adjunct in Bone Grafting of Fracture Non-unions

Introduction

Non-union of long bones is a common challenge in the treatment of fractures. Bone grafting is commonly used to treat atrophic non-union, but mechanical displacement of the graft may occur, resulting in delay or failure of treatment. Fibrin glue has demonstrated positive results in management of bone defects in neurosurgery and oromaxillary facial surgery, however, there has yet to be any study on its use in long bone fractures.

Materials and Methods

We conducted a prospective randomised controlled trial at a single tertiary centre involving adult patients with long bone fractures that had undergone non-union and requiring bone grafting only. Autologous iliac crest bone graft was applied to the debrided non-union site, with additional fibrin glue applied for the intervention arm. Patients were followed-up with serial radiographs until clinical and radiographical union.

Results

Ten patients (3 male, 7 female), of mean age 41.7 (19 - 63) were recruited over five years, with one drop out. Eight out of nine fractures united after treatment. One patient underwent hypertrophic non-union requiring re-fixation and bone grafting. There was no difference in the time to union for patients in the fibrin glue group (19.5 weeks) versus the control group (18.75 weeks) (p=0.86). There were no complications sustained from usage of fibrin glue.

Conclusion

Fibrin glue appears to be a safe adjunct for treatment of non-union of long bone fractures across varying fracture sites by holding the bone graft in place despite not demonstrating a faster time to union.

Sequestration and Involucrum: Understanding Bone Necrosis and Revascularization in Pediatric Orthopedics

Sequestration, a condition where a section of bone becomes necrotic due to a loss of vascularity or thrombosis, can be a challenging complication of osteomyelitis. This review explores the pathophysiology of sequestration, highlighting the role of the periosteum in forming involucrum and creeping substitution which facilitate revascularization and bone formation. The authors also discuss the induced membrane technique, a two-stage surgical procedure for cases of failed healing of sequestration. Future directions include the potential use of prophylactic anticoagulation and novel drugs targeting immunocoagulopathy, as well as the development of advanced imaging techniques and single-stage surgical procedures.

Potential of periosteal cells in bone and cartilage regeneration: a systematic review

Introduction: The unavailability of adequate human primary cells presents multiple challenges in terms of bone and cartilage regeneration and disease modeling experiments in vitro. Periosteal cells (PCs), which represent promising skeletal stem cell sources, could be a promising strategy in tissue engineering. The present study aimed to summarize the characteristics of PCs to investigate the efficacy of these cells in bone and cartilage regeneration in different models, paying special attention to the comparison of bone marrow stromal cells (BMSCs). Methods: A comprehensive literature search was conducted in Embase, PubMed/MEDLINE, Web of Science, and Scopus for articles published in English until April 2023. Only original researches in which PCs were employed for bone or cartilage regeneration experiments were included. Results: A total of 9140 references were retrieved. After screening the results, 36 publications were considered to be eligible for inclusion in the present literature review. Overall, PCs demonstrated beneficial bone and cartilage regenerative efficacy compared to the bare scaffold since almost all included studies reported positive results. The 9 studies assessing the differences in bone formation capacity between PCs and BMSCs indicated that PCs exhibited stronger in vivo osteogenic differentiation capabilities compared to BMSCs, while the other study demonstrated stronger chondrogenic potential of BMSCs. Discussion: PCs demonstrated beneficial to bone regenerative efficacy compared to the bare scaffold with a low risk of most studies included. However, the cartilage formation capacity of BMSCs still needs to be investigated due to the limited research available and the certain risk of bias. PCs exhibited higher osteogenic capabilities compared to BMSCs in combination with various scaffolds in vivo with good evidence. Further researches are needed to elucidate the comparative benefits of cartilage regeneration. Systematic Review Registration: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42023411522, CRD42023411522.

The enhancer landscape predetermines the skeletal regeneration capacity of stromal cells

Multipotent stromal cells are considered attractive sources for cell therapy and tissue engineering. Despite numerous experimental and clinical studies, broad application of stromal cell therapeutics is not yet emerging. A major challenge is the functional diversity of available cell sources. Here, we investigated the regenerative potential of clinically relevant human stromal cells from bone marrow (BMSCs), white adipose tissue, and umbilical cord compared with mature chondrocytes and skin fibroblasts in vitro and in vivo. Although all stromal cell types could express transcription factors related to endochondral ossification, only BMSCs formed cartilage discs in vitro that fully regenerated critical-size femoral defects after transplantation into mice. We identified cell type-specific epigenetic landscapes as the underlying molecular mechanism controlling transcriptional stromal differentiation networks. Binding sites of commonly expressed transcription factors in the enhancer and promoter regions of ossification-related genes, including Runt and bZIP families, were accessible only in BMSCs but not in extraskeletal stromal cells. This suggests an epigenetically predetermined differentiation potential depending on cell origin that allows common transcription factors to trigger distinct organ-specific transcriptional programs, facilitating forward selection of regeneration-competent cell sources. Last, we demonstrate that viable human BMSCs initiated defect healing through the secretion of osteopontin and contributed to transient mineralized bone hard callus formation after transplantation into immunodeficient mice, which was eventually replaced by murine recipient bone during final tissue remodeling.

Bone regeneration materials and their application over 20 years: A bibliometric study and systematic review

Bone regeneration materials (BRMs) bring us new sights into the clinical management bone defects. With advances in BRMs technologies, new strategies are emerging to promote bone regeneration. The aim of this study was to comprehensively assess the existing research and recent progress on BRMs, thus providing useful insights into contemporary research, as well as to explore potential future directions within the scope of bone regeneration therapy. A comprehensive literature review using formal data mining procedures was performed to explore the global trends of selected areas of research for the past 20 years. The study applied bibliometric methods and knowledge visualization techniques to identify and investigate publications based on the publication year (between 2002 and 2021), document type, language, country, institution, author, journal, keywords, and citation number. The most productive countries were China, United States, and Italy. The most prolific journal in the BRM field was Acta Biomaterialia, closely followed by Biomaterials. Moreover, recent investigations have been focused on extracellular matrices (ECMs) (370 publications), hydrogel materials (286 publications), and drug delivery systems (220 publications). Research hotspots related to BRMs and extracellular matrices from 2002 to 2011 were growth factor, bone morphogenetic protein (BMP)-2, and mesenchymal stem cell (MSC), whereas after 2012 were composite scaffolds. Between 2002 and 2011, studies related to BRMs and hydrogels were focused on BMP-2, in vivo, and in vitro investigations, whereas it turned to the exploration of MSCs, mechanical properties, and osteogenic differentiation after 2012. Research hotspots related to BRM and drug delivery were fibroblast growth factor, mesoporous materials, and controlled release during 2002–2011, and electrospinning, antibacterial activity, and in vitro bioactivity after 2012. Overall, composite scaffolds, 3D printing technology, and antibacterial activity were found to have an important intersection within BRM investigations, representing relevant research fields for the future. Taken together, this extensive analysis highlights the existing literature and findings that advance scientific insights into bone tissue engineering and its subsequent applications.

Poly-ε-Caprolactone/Fibrin-Alginate Scaffold: A New Pro-Angiogenic Composite Biomaterial for the Treatment of Bone Defects

We hypothesized that a composite of 3D porous melt-electrowritten poly-ɛ-caprolactone (PCL) coated throughout with a porous and slowly biodegradable fibrin/alginate (FA) matrix would accelerate bone repair due to its angiogenic potential. Scanning electron microscopy showed that the open pore structure of the FA matrix was maintained in the PCL/FA composites. Fourier transform infrared spectroscopy and differential scanning calorimetry showed complete coverage of the PCL fibres by FA, and the PCL/FA crystallinity was decreased compared with PCL. In vitro cell work with osteoprogenitor cells showed that they preferentially bound to the FA component and proliferated on all scaffolds over 28 days. A chorioallantoic membrane assay showed more blood vessel infiltration into FA and PCL/FA compared with PCL, and a significantly higher number of bifurcation points for PCL/FA compared with both FA and PCL. Implantation into a rat cranial defect model followed by microcomputed tomography, histology, and immunohistochemistry after 4- and 12-weeks post operation showed fast early bone formation at week 4, with significantly higher bone formation for FA and PCL/FA compared with PCL. However, this phenomenon was not extrapolated to week 12. Therefore, for long-term bone regeneration, tuning of FA degradation to ensure syncing with new bone formation is likely necessary.

Polymer microcapsules and microbeads as cell carriers for in vivo biomedical applications

Polymer microcarriers are being extensively explored as cell delivery vehicles in cell-based therapies and hybrid tissue and organ engineering. Spherical microcarriers are of particular interest due to easy fabrication and injectability. They include microbeads, composed of a porous matrix, and microcapsules, where matrix core is additionally covered with a semipermeable membrane. Microcarriers provide cell containment at implantation site and protect the cells from host immunoresponse, degradation and shear stress. Immobilized cells may be genetically altered to release a specific therapeutic product directly at the target site, eliminating side effects of systemic therapies. Cell microcarriers need to fulfil a number of extremely high standards regarding their biocompatibility, cytocompatibility, immunoisolating capacity, transport, mechanical and chemical properties. To obtain cell microcarriers of specified parameters, a wide variety of polymers, both natural and synthetic, and immobilization methods can be applied. Yet so far, only a few approaches based on cell-laden microcarriers have reached clinical trials. The main issue that still impedes progress of these systems towards clinical application is limited cell survival in vivo. Herein, we review polymer biomaterials and methods used for fabrication of cell microcarriers for in vivo biomedical applications. We describe their key limitations and modifications aiming at improvement of microcarrier in vivo performance. We also present the main applications of polymer cell microcarriers in regenerative medicine, pancreatic islet and hepatocyte transplantation and in the treatment of cancer. Lastly, we outline the main challenges in cell microimmobilization for biomedical purposes, the strategies to overcome these issues and potential future improvements in this area.

Ceramic Scaffolds in a Vacuum Suction Handle for Intraoperative Stromal Cell Enrichment

During total joint replacement, high concentrations of mesenchymal stromal cells (MSCs) are released at the implantation site. They can be found in cell–tissue composites (CTC) that are regularly removed by surgical suction. A surgical vacuum suction handle was filled with bone substitute granules, acting as a filter allowing us to harvest CTC. The purpose of this study was to investigate the osteopromotive potential of CTC trapped in the bone substitute filter material during surgical suction. In the course of 10 elective total hip and knee replacement surgeries, β-tricalcium-phosphate (TCP) and cancellous allograft (Allo) were enriched with CTC by vacuum suction. Mononuclear cells (MNC) were isolated from the CTC and investigated towards cell proliferation and colony forming unit (CFU) formation. Furthermore, MSC surface markers, trilineage differentiation potential and the presence of defined cytokines were examined. Comparable amounts of MNC and CFUs were detected in both CTCs and characterized as MSC‰ of MNC with 9.8 ± 10.7‰ for the TCP and 12.8 ± 10.2‰ for the Allo (p = 0.550). CTCs in both filter materials contain cytokines for stimulation of cell proliferation and differentiation (EGF, PDGF-AA, angiogenin, osteopontin). CTC trapped in synthetic (TCP) and natural (Allo) bone substitute filters during surgical suction in the course of a joint replacement procedure include relevant numbers of MSCs and cytokines qualified for bone regeneration.

Fibrin Scaffold Incorporating Platelet Lysate Enhance Follicle Survival and Angiogenesis in Cryopreserved Preantral Follicle Transplantation

Background:

Transplantation of cryopreserved follicles can be regarded as a promising strategy for preserving fertility in cancer patients under chemotherapy and radiotherapy by reducing the risk of cancer recurrence. The present study aimed to evaluate whether fibrin hydrogel supplemented with platelet lysate (PL) could be applied to enhance follicular survival, growth, and angiogenesis in cryopreserved preantral follicle grafts.

Materials and Methods:

Preantral follicles were extracted from 15 four-week-old NMRI mice, cryopreserved by cryotop method, and encapsulated in fibrin-platelet lysate for subsequent heterotopic (subcutaneous) auto-transplantation into the neck. Transplants were assessed in three groups including fresh follicles in fibrin-15%PL, cryopreserved follicles in fibrin-15%PL, and cryopreserved follicles in fibrin-0% PL. Two weeks after transplantation, histological, and immunohistochemistry (CD31) analysis were applied to evaluate follicle morphology, survival rate, and vascular formation, respectively.

Results:

Based on the results, fibrin-15% PL significantly increased neovascularization and survival rate (SR) both in cryopreserved (SR=66.96%) and fresh follicle (SR=90.8%) grafts, compared to PL-less fibrin cryopreserved transplants (SR=28.46%). The grafts supplemented with PL included a significantly higher percentage of preantral and antral follicles. Also, no significant difference was observed in the percentage of preantral follicles between cryopreserved and fresh grafts of fibrin-15% PL. However, a significantly lower (P=0.03) percentage of follicles (23.37%) increased to the antral stage in cryopreserved grafts of fibrin-15%PL, compared to fresh grafts (35.01%).

Conclusion:

The findings demonstrated that fibrin-PL matrix could be a promising strategy to improve cryopreserved follicle transplantation and preserve fertility in cancer patients at the risk of ovarian failure.

Bone Substitutes in Orthopaedic Surgery: Current Status and Future Perspectives

Bone replacement materials have been successfully supplied for a long time. But there are cases, especially in critical sized bone defects, in which the therapy is not sufficient. Nowadays, there are multiple bone substitutes available. Autologous bone grafts remain the "gold standard" in bone regeneration. Yet, donor-site morbidity and the available amount of sufficient material are limitations for autologous bone grafting. This study aimed to provide information about the current status in research regarding bone substitutes. We report on the advantages and drawbacks of several bone substitutes. At the end, we discuss the current developments of combining ceramic substitutes with osteoinductive substances.

Osteoclasts degrade fibrinogen scaffolds and induce mesenchymal stem/stromal osteogenic differentiation

Fibrinogen (Fg) is a pro-inflammatory protein with pro-healing properties. Previous work showed that fibrinogen 3D scaffolds (Fg-3D) promote bone regeneration, but the cellular players were not identified. Osteoclasts are bone resorbing cells that promote bone remodeling in close crosstalk with osteoblasts. Herein, the capacity of osteoclasts differentiated on Fg-3D to degrade the scaffolds and promote osteoblast differentiation was evaluated in vitro. Fg-3D scaffolds were prepared by freeze-drying and osteoclasts were differentiated from primary human peripheral blood monocytes. Results obtained showed osteoclasts expressing the enzymes cathepsin K and tartrate resistant acid phosphatase colonizing Fg-3D scaffolds. Osteoclasts were able to significantly degrade Fg-3D, reducing the scaffold's area, and increasing D-dimer concentration, a Fg degradation product, in their culture media. Osteoclast conditioned media from the first week of differentiation promoted significantly stronger human primary mesenchymal stem/stromal cell (MSC) osteogenic differentiation, evaluated by alkaline phosphatase activity. Moreover, week 1 osteoclast conditioned media promoted earlier MSC osteogenic differentiation, than chemical osteogenesis inductors. TGF-β1 was found increased in osteoclast conditioned media from week 1, when compared to week 3 of differentiation. Taken together, our results suggest that osteoclasts are able to differentiate and degrade Fg-3D, producing factors like TGF-β1 that promote MSC osteogenic differentiation.

Core-shell fibrous membranes of PVDF-Ba0.9Ca0.1TiO3/PVA with osteogenic and piezoelectric properties for bone regeneration

The goal of this research was to promote the bioactivity and osteogenic characteristics of polyvinylidene fluoride(PVDF) fibrous membrane, while preserving its piezoelectric property for bone regeneration. In this regard, core-shell fibrous membrane of PVDF-Ba_0.9Ca_0.1TiO₃/polyvinyl alcohol(PVA) was developed via emulsion electrospinning approach. While PVA was in the outer layer of fibers with thickness of 53 ± 18 nm, the Ba_0.9Ca_0.1TiO₃ nanoparticles was uniformly dispersed in the PVDF core. The formation of PVA shell resulted in significant improvement of its hydrophilicity (3 times) and degradation rate, while piezoelectricity did noticeably modulate. In addition, incorporation of Ba_0.9Ca_0.1TiO₃ nanopowder remarkably improved bioactivity, protein adsorption and mechanical properties of PVDF/PVA fibrous membranes. Finally, the osteogenic differentiation of mesenchymal stem cells on the nanocomposite fibrous membranes, in the absence of osteogenic supplements, was also observed. Overall, the results confirmed the promising potential of PVDF-Ba_0.9Ca_0.1TiO₃/PVA fibrous membrane containing 1-2 wt% nanopowder for bone regeneration.

Autologous mesenchymal stem cell implantation, hydroxyapatite, bone morphogenetic protein-2, and internal fixation for treating critical-sized defects: a translational study

INTRODUCTION

Critical-sized defect (CSD) is one of the most challenging cases for orthopaedic surgeons. We aim to explore the therapeutic potential of the combination of bone marrow-derived mesenchymal stem cells (BM-MSCs), hydroxyapatite (HA) granules, bone morphogenetic protein-2 (BMP-2), and internal fixation for treating CSDs.

METHODS

This was a translational study performed during the period of January 2012 to 2016. Subjects were patients diagnosed with CSDs who had previously failed surgical attempts. They were treated with the combination of autologous BM-MSCs, HA granules, BMP-2, and mechanical stabilization. Post-operative pain level, functional outcome, defect volume, and radiological healing were evaluated after a minimum follow-up of 12 months.

RESULTS

A total of six subjects were recruited in this study. The pain was significantly reduced in all cases; with the decrease of mean preoperative visual analog scale (VAS) from 4 ± 2.2 to 0 after six month follow-up. Clinical functional outcome percentage increased significantly from 25 ± 13.7 to 70.79 ± 19.5. Radiological healing assessment using Tiedemann score also showed an increase from 0.16 ± 0.4 to 8 ± 3 at one year follow-up. No immunologic nor neoplastic side effects were found.

CONCLUSIONS

The combination of autologous BM-MSCs, HA granules, and BMP-2 is safe and remains to be a good option for the definitive treatment for CSD with previous failed surgical attempts. Further studies with a larger sample size are required to be done.

Comparison of the regenerative effect of adipose-derived stem cells, fibrin glue scaffold, and autologous bone graft in experimental mandibular defect in rabbit

BACKGROUND/AIMS

One of the main concerns for maxillofacial and orthopedic surgeons is finding a method to improve regeneration of large craniofacial bone defects. The aim of this study was to investigate the healing and regenerative effects of fibrin glue associated with adipose-derived stem cells (ADSCs) and fibrin glue scaffold alone with autologous bone grafts in experimental mandibular defects of the rabbit.

METHODS

Bilateral uni-cortical osteotomies were performed in the mandible of 20 male Dutch rabbits. The animals were randomly divided into 2 equal groups. In one group, the defect on the right side was treated by fibrin glue associated with ADSCs and the defect on the other side remained as the control. In another group, the defect on the right side was treated with fibrin glue and on the left side with autologous bone graft. After 28 and 56 days, five rabbits from each group were evaluated by computed tomography (CT) and histopathological examinations.

RESULTS

Coronal CT showed a remarkable reconstruction of cortical bone in the fibrin glue associated with ADSCs group at 28 and 56 days post-surgery. Histopathologically, new cortical bony bridge formation was seen increasingly in the fibrin glue, fibrin glue associated with ADSCs, and autologous bone graft groups after 28 days. Statistical analysis of the thickness of new cortical bone in the treatment versus control groups showed a significant difference between fibrin glue alone and fibrin glue associated with ADSCs groups (P = 0.02). No significant difference was found between the fibrin glue associated with ADSCs and the autologous bone graft groups (P > 0.05).

CONCLUSIONS

The healing process had a significant increase in the thickness of new cortical bone when fibrin glue scaffold associated with ADSCs was used.

A biomaterial with a channel-like pore architecture induces endochondral healing of bone defects

Biomaterials developed to treat bone defects have classically focused on bone healing via direct, intramembranous ossification. In contrast, most bones in our body develop from a cartilage template via a second pathway called endochondral ossification. The unsolved clinical challenge to regenerate large bone defects has brought endochondral ossification into discussion as an alternative approach for bone healing. However, a biomaterial strategy for the regeneration of large bone defects via endochondral ossification is missing. Here we report on a biomaterial with a channel-like pore architecture to control cell recruitment and tissue patterning in the early phase of healing. In consequence of extracellular matrix alignment, CD146+ progenitor cell accumulation and restrained vascularization, a highly organized endochondral ossification process is induced in rats. Our findings demonstrate that a pure biomaterial approach has the potential to recapitulate a developmental bone growth process for bone healing. This might motivate future strategies for biomaterial-based tissue regeneration.

Microcapsule Technology for Controlled Growth Factor Release in Musculoskeletal Tissue Engineering

Tissue engineering strategies have relied on engineered 3-dimensional (3D) scaffolds to provide architectural templates that can mimic the native cell environment. Among the several technologies proposed for the fabrication of 3D scaffold, that can be attractive for stem cell cultivation and differentiation, moulding or bioplotting of hydrogels allow the stratification of layers loaded with cells and with specific additives to obtain a predefined microstructural organization. Particularly with bioplotting technology, living cells, named bio-ink, and additives, such as biopolymer microdevices/nanodevices for the controlled delivery of growth factors or biosignals, can be organized spatially into a predesigned 3D pattern by automated fabrication with computer-aided digital files. The technologies for biopolymer microcarrier/nanocarrier fabrication can be strategic to provide a controlled spatiotemporal delivery of specific biosignals within a microenvironment that can better or faster address the stem cells loaded within it. In this review, some examples of growth factor-controlled delivery by biopolymer microdevices/nanodevices embedded within 3D hydrogel scaffolds will be described, to achieve a bioengineered 3D interactive microenvironment for stem cell differentiation. Conventional and recently proposed technologies for biopolymer microcapsule fabrication for controlled delivery over several days will also be illustrated and critically discussed.

Nonstoichiometric wollastonite bioceramic scaffolds with core-shell pore struts and adjustable mechanical and biodegradable properties

Controllable mechanical strength and biodegradation of bioceramic scaffolds is a great challenge to treat the load-bearing bone defects. Herein a new strategy has been developed to fabricate porous bioceramic scaffolds with adjustable component distributions based on varying the core-shell-structured nozzles in three-dimensional (3D) direct ink writing platform. The porous bioceramic scaffolds composed of different nonstoichiometic calcium silicate (nCSi) with 0%, 4% or 10% of magnesium-substituting-calcium ratio (CSi, CSi-Mg4, CSi-Mg10) was fabricated. Beyond the mechanically mixed composite scaffolds, varying the different nCSi slurries through the coaxially aligned bilayer nozzle makes it easy to create core-shell bilayer bioceramic filaments and better control of the different nCSi distribution in pore strut after sintering. It was evident that the magnesium substitution in CSi contributed to the increase of compressive strength for the single-phasic scaffolds from 11.2 MPa (CSi), to 39.4 MPa (CSi-Mg4) and 80 MPa (CSi-Mg10). The nCSi distribution in pore struts in the series of core-shell-strut scaffolds could significantly adjust the strength [e.g. CSi@CSi-Mg10 (58.9 MPa) vs CSi-Mg10@CSi (30.4 MPa)] and biodegradation ratio in Tris buffer for a long time stage (6 weeks). These findings demonstrate that the nCSi components with different distributions in core or shell layer of pore struts lead to tunable strength and biodegradation inside their interconnected macropore architectures of the scaffolds. It is possibly helpful to develop new bioactive scaffolds for time-dependent tailoring mechanical and biological performances to significantly enhance bone regeneration and repair applications, especially in some load-bearing bone defects.

Isolation of Mesenchymal Stem Cells from Human Alveolar Periosteum and Effects of Vitamin D on Osteogenic Activity of Periosteum-derived Cells

Mesenchymal stem cells (MSCs) are present in a variety of tissues and can be differentiated into numerous cell types, including osteoblasts. Among the dental sources of MSCs, the periosteum is an easily accessible tissue, which has been identified to contain MSCs in the cambium layer. However, this source has not yet been widely studied. Vitamin D3 and 1,25-(OH)2D3 have been demonstrated to stimulate in vitro differentiation of MSCs into osteoblasts. In addition, vitamin C facilitates collagen formation and bone cell growth. However, no study has yet investigated the effects of Vitamin D3 and Vitamin C on MSCs. Here, we present a method of isolating MSCs from human alveolar periosteum and examine the hypothesis that 1,25-(OH)2D3 may exert an osteoinductive effect on these cells. We also investigate the presence of MSCs in the human alveolar periosteum and assess stem cell adhesion and proliferation. To assess the ability of vitamin C (as a control) and various concentrations of 1,25-(OH)2D3 (10^-10, 10^-9, 10^-8, and 10^-7 M) to alter key mRNA biomarkers in isolated MSCs mRNA expression of alkaline phosphatase (ALP), bone sialoprotein (BSP), core binding factor alpha-1 (CBFA1), collagen-1, and osteocalcin (OCN) are measured using real-time polymerase chain reaction (RT-PCR).

Hemocompatible and Bioactive Heparin-Loaded PCL-α-TCP Fibrous Membranes for Bone Tissue Engineering

The combination of bioactive components such as calcium phosphates and fibrous structures are encouraging niche-mimetic keys for restoring bone defects. However, the importance of hemocompatibility of the membranes is widely ignored. Heparin-loaded nanocomposite poly(ε-caprolactone) (PCL)-α-tricalcium phosphate (α-TCP) fibrous membranes are developed to provide bioactive and hemocompatible constructs for bone tissue engineering. Nanocomposite membranes are optimized based on bioactivity, mechanical properties, and cell interaction. Consequently, various concentrations of heparin molecules are loaded within nanocomposite fibrous membranes. In vitro heparin release profiles reveal a sustained release of heparin over the period of 14 days without an initial burst. Moreover, heparin encapsulation enhances mesenchymal stem cell (MSC) attachment and proliferation, depending on the heparin content. It is concluded that the incorporation of heparin within TCP-PCL fibrous membranes provides the most effective cellular interactions through synergistic physical and chemical cues.

Osteoinductive porous biphasic calcium phosphate ceramic as an alternative to autogenous bone grafting in the treatment of mandibular bone critical-size defects

The bone-induction capacity of a porous biphasic calcium phosphate (pBCP) using heterotopic implantation in mouse (mHI-model) and its efficacy as substitute for autograft in mandibular critical-size defect in rabbit (rabMCSD-model) was investigated. In mHI-model, pBCP was implanted into the thigh muscles and bone formation was histomorphometrically and immunohistochemically evaluated. In rabMCSD-model, 13 mm bone defects were treated with pBCP or autograft and bone repair comparatively evaluated by radiographic and histomorphometric methods. In mHI-model, formed bone and immunolabeling for bone morphogenetic protein-2 and osteopontin were observed in 90% of pBCP implanted samples after 12 weeks. In rabMCSD-model neither statistically significant difference was found in newly formed bone between pBCP and autograft groups at 4 weeks (18.8 ± 5.5% vs 27.1 ± 5.6%), 8 weeks (22.3 ± 2.7% vs 26.2 ± 5.1), and 12 weeks (19.6 ± 4.7% vs 19.6 ± 2.3%). At 12 weeks, the stability and contour of the mandible were restored in both treatments. Near tooth remaining, pBCP particles were covered by small amount of mineralized tissue exhibiting perpendicular attachments of collagen fiber bundles with histological characteristic of acellular cementum. Within the limitations of this study, it was concluded that pBCP is osteoinductive and able to stimulate the new formation of bone and cementum-like tissues in rabMCSD-model, suggesting that it may be an alternative to treatment of large bone defect and in periodontal regenerative therapy. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1546-1557, 2018.

A review of fibrin and fibrin composites for bone tissue engineering

Tissue engineering has emerged as a new treatment approach for bone repair and regeneration seeking to address limitations associated with current therapies, such as autologous bone grafting. While many bone tissue engineering approaches have traditionally focused on synthetic materials (such as polymers or hydrogels), there has been a lot of excitement surrounding the use of natural materials due to their biologically inspired properties. Fibrin is a natural scaffold formed following tissue injury that initiates hemostasis and provides the initial matrix useful for cell adhesion, migration, proliferation, and differentiation. Fibrin has captured the interest of bone tissue engineers due to its excellent biocompatibility, controllable biodegradability, and ability to deliver cells and biomolecules. Fibrin is particularly appealing because its precursors, fibrinogen, and thrombin, which can be derived from the patient's own blood, enable the fabrication of completely autologous scaffolds. In this article, we highlight the unique properties of fibrin as a scaffolding material to treat bone defects. Moreover, we emphasize its role in bone tissue engineering nanocomposites where approaches further emulate the natural nanostructured features of bone when using fibrin and other nanomaterials. We also review the preparation methods of fibrin glue and then discuss a wide range of fibrin applications in bone tissue engineering. These include the delivery of cells and/or biomolecules to a defect site, distributing cells, and/or growth factors throughout other pre-formed scaffolds and enhancing the physical as well as biological properties of other biomaterials. Thoughts on the future direction of fibrin research for bone tissue engineering are also presented. In the future, the development of fibrin precursors as recombinant proteins will solve problems associated with using multiple or single-donor fibrin glue, and the combination of nanomaterials that allow for the incorporation of biomolecules with fibrin will significantly improve the efficacy of fibrin for numerous bone tissue engineering applications.

Induction of Ectopic Bone Formation by Using Human Periosteal Cells in Combination with a Novel Scaffold Technology

Due to their osteogenic germination potential, periosteum-derived osteoprogenitor cells are a potential source for tissue engineering a bone graft that could be used to regenerate skeletal defects. In this study we evaluated if ectopic bone formation could be induced by a construct made of human periosteal cells and a novel scaffold architecture whose mechanical properties are in the range of cancellous bone. Biopsies from human calvarial periosteum were harvested and cells were isolated from the inner cambial layer. Fifty thousand periosteal cells were seeded into the scaffolds measuring 6 × 6 × 2 mm. The cell–scaffold constructs were cultured for a period of 3 weeks prior to implantation into balb C nude mice. Mice were sacrificed and implants were analyzed 6 and 17 weeks postoperatively. Immunohistochemical analysis confirmed the osteoblastic phenotype of the seeded cells. Formation of focal adhesions and stress fibers could be observed in both scaffold architectures. Three-dimensional cell proliferation was observed after 2 weeks of culturing with centripetal growth pattern inside the pore network. The deposition of calcified extracellular matrix was observed after 3 weeks of culturing. In vivo, endochondral bone formation with osteoid production was detectable via von Kossa and Osteocalcin staining after 6 and 17 weeks. Histology and SEM revealed that the entire scaffold/bone grafts were penetrated by a vascular network. This study showed the potential of bone tissue engineering by using human periosteal cells in combination with a novel scaffold technology.

A Magnetically Actuated Microscaffold Containing Mesenchymal Stem Cells for Articular Cartilage Repair

This study proposes a magnetically actuated microscaffold with the capability of targeted mesenchymal stem cell (MSC) delivery for articular cartilage regeneration. The microscaffold, as a 3D porous microbead, is divided into body and surface portions according to its materials and fabrication methods. The microscaffold body, which consists of poly(lactic-co-glycolic acid) (PLGA), is formed through water-in-oil-in-water emulsion templating, and its surface is coated with amine functionalized magnetic nanoparticles (MNPs) via amino bond formation. The porous PLGA structure of the microscaffold can assist in cell adhesion and migration, and the MNPs on the microscaffold can make it possible to steer using an electromagnetic actuation system that provides external magnetic fields for the 3D locomotion of the microscaffold. As a fundamental test of the magnetic response of the microscaffold, it is characterized in terms of the magnetization curve, velocity, and 3D locomotion of a single microscaffold. In addition, its function with a cargo of MSCs for cartilage regeneration is demonstrated from the proliferation, viability, and chondrogenic differentiation of D1 mouse MSCs that are cultured on the microscaffold. For the feasibility tests for cartilage repair, 2D/3D targeting of multiple microscaffolds with the MSCs is performed to demonstrate targeted stem cell delivery using the microscaffolds and their swarm motion.

Assessment of tricalcium phosphate/collagen (TCP/collagene)nanocomposite scaffold compared with hydroxyapatite (HA) on healing of segmental femur bone defect in rabbits

Bone regeneration is an important objective in clinical practice and has been used for different applications. The aim of this study was to evaluate the effectiveness of nanocomposite tricalcium phosphate (TCP)/collagen scaffolds combined with hydroxyapatite scaffold for bone healing in surgery of femoral defects in rabbits. In this study, 45 mature male New Zealand white rabbits between 6 and 8 months old and weighting between 3 and 3.5 kg were examined. Rabbits were divided into three groups. Surgical procedures were performed after intramuscular injection of Ketamine 10% (ketamine hydrochloride, 50 mg/kg) and Rompun 5% (xylazine, 5 mg/kg). Then an approximately 6 mm diameter-5 mm cylinder bone defect was created in the femur of one of the hind limbs. After inducing the surgical wound, all rabbits were coloured and randomly divided into three experimental groups of 15 animals each. Group 1 received pure medical nanocomposite TCP/collagen granules, group 2 received hydroxyapatite, and third group was a control group which received no treatment. Histopathological evaluation was performed on days 15, 30, and 45 after surgery. On days 15, 30, and 45 after surgery, the quantity and the velocity of stages of bone formation at the healing site in nanocomposite TCP/collagen group were better than HA and control groups and the quantity of newly formed lamellar bone at the healing site in nanocomposite TCP/collagen group were better than onward compared with HA and control groups. In conclusion, it seems that TCP/collagen nanocomposite has a significant role in the reconstruction of bone defects and can be used as scaffold in bone fractures.

Hybrid extracellular matrix design for cartilage-mediated bone regeneration

Recapitulating long bone repair through endochondral ossification (EO) is increasingly becoming a more popular approach. A successful EO Process depends greatly on the establishment of a healthy hypertrophic-cartilage template (HCT). The aim of this work is to design a hydrogel system, which closely mimics the extracellular matrix of HCT. We examined the combinatorial effect of two commonly used hydrogels for bone and cartilage regeneration strategies, hyaluronan (HA) and fibrin (FB), to induce HCT formation. Hydrogel combinations were evaluated using a clinically relevant cell source, human bone marrow mesenchymal stem cells (hBMSCs). The results establish that with increasing HA (50-90%) the chondrogenic and its subsequent hypertrophy trend improved, with 70:30 HA:FB combination showing the highest and most uniform expression of chondrogenic and hypertrophic stage specific markers. This combination also showed superior support for cell micro-aggregation and differentiation. Thus, 70:30 HA-FB matrix demonstrated a healthy formation of chondrogenic and hypertrophic stages with rich stage-specific ECM components. This study demonstrates that with the appropriate hydrogel design it is possible to develop effective tissue engineering therapies for bone defect repair and regeneration through endochondral ossification by establishing a healthy HCT. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 300-309, 2018.

[FGF-2/PELA/BMP-2 microcapsule scaffold promotes osteogenic differentiation of rat periosteum-derived stem cells in vitro]

OBJECTIVE

To observe the effect of a microencapsule scaffold capable of sustained release of fibroblast growth factor-2 (FGF-2) and bone morphogenetic protein-2 (BMP-2) in promoting the osteogenic differentiation of rat periosteum-derived stem cells (PDSCs) in vitro.

METHODS

PDSCs from 4-week-old SD rats, after identification of the surface markers using flow cytometry, were induced to differentiate into osteoblast, chondroblast, and adipocyte lineages. The differentiated cells were verified by staining with Alizarin red, toluidine blue, alcian blue, oil red O and by immunofluorescence assay. FGF-2/PELA/BMP-2, FGF-2/PELA, PELA/BMP-2 and PELA microcapsules were prepared, examined for surface morphologies using scanning electron microscopy (SEM), and tested for controlled release of FGF-2 and BMP-2 using ELISA. The third passage of PDSCs were cultured in the presence of the aqueous extracts of one of the 4 materials, and alkaline phosphatase (AKP) activity in the culture media was detected at 7 and 14 days of culture; the expression levels of osteogenesis-related genes were quantified with quantitative real-time PCR (qRT-PCR). The osteogenic differentiation ability of the PDSCs cultured with the extracts was compared.

RESULTS

The PDSCs, which expressed mesenchymal stem cell surface markers, were shown to have osteogenic, chondrogenic and adipogenic differentiation potentials. The cells cultured with the extract of FGF-2/PELA/BMP-2 microcapsules showed the highest AKP activity at 7 and 14 days of culture, and their expression levels of OCN and RunX-2 mRNA were the highest among the 4 groups; RunX-2 expression reached its peak level on day 14, and OCN mRNA expression level increased progressively as the culture time extended.

CONCLUSION

FGF-2/PELA/BMP-2 biomimetic controlled release microcapsules preserve the cytokine activities and are capable of promoting the osteogenic differentiation of rat PDSCs.

Effective Bone Engineering with Periosteum-derived Cells

Bone augmentation via tissue engineering has generated significant interest. We hypothesized that periosteum-derived cells could be used in place of bone marrow stromal cells (which are widely used) in bone engineering, but the differences in osteogenic potential between these 2 cell types are unclear. Here, we compared the osteogenic potential of these cells, and investigated the optimal osteoinductive conditions for periosteum-derived cells. Both cell types were induced, via bFGF and BMP-2, to differentiate into osteoblasts. Periosteal cells proliferated faster than marrow stromal cells, and osteogenic markers indicated that bone marrow stromal cells were more osteogenic than periosteal cells. However, pre-treatment with bFGF made periosteal cells more sensitive to BMP-2 and more osteogenic. Transplants of periosteal cells treated with BMP-2 after pre-treatment with bFGF formed more new bone than did marrow stromal cells. Analysis of these data suggests that combined treatment with bFGF and BMP-2 can make periosteum a highly useful source of bone regeneration.

Effects of local delivery of BMP2, zoledronate and their combination on bone microarchitecture, biomechanics and bone turnover in osteoporotic rabbits

The hip fracture is one major clinical challenge associated with osteoporosis, resulting in heavy socioeconomic burdens and high mortality. Systemic therapies of anti-osteoporosis drugs are expensive, time-consuming and also evoke substantial side effects, which fails to provide early protection from fractures. Accumulating evidence demonstrates the high bioavailability and therapeutic efficacy of local drug delivery in accelerating facture healing and bone defect repair. This study aims at investigating the effects of local delivery of BMP2 and zoledronate (two promising anabolic/anti-catobolic reagents) encapsulated by fibrin sealants into femoral necks on regulating bone quality and remodeling in osteoporotic rabbits subjected to combined ovariectomy and glucocorticoid injection. We show that 6-week BMP2 delivery exhibited more prominent effect on mitigating trabecular bone microarchitecture deterioration and mechanical strength reduction of femoral necks than local zoledronate treatment. BMP2 plus zoledronate showed more significant improvement of bone microstructure, mechanical strength and bone formation rate at 12 weeks post injection than single BMP2 or zoledronate delivery via μCT, biomechanical, histomorphometric and serum biochemical analyses. This study enriches our knowledge for understanding the availability of local drug delivery for improving bone quantity and quality, which may lead to earlier, safer and more efficient protection from osteoporosis-induced fractures in clinics.

Evaluation of the effect of adipose tissue-derived stem cells on the quality of bone healing around implants

PURPOSE/AIM

This study evaluates the efficacy of grafted adipose-derived stem cells (ADSCs) on blade-type implants in improving osseointegration in rat femurs using a low-density bone model.

MATERIALS AND METHODS

After isolating and expanding ADSCs, twice-passaged cells were seeded on blade-type implants on culture plates. Osteogenic induction of grafted cells began after attaching cells to the prepared titanium surfaces and it continued for 4 days. The scaffolds were then implanted in the femurs of Wistar rats. Osteogenic differentiation of these cells was confirmed using polymerase chain reaction (PCR) and alizarin red staining of the mineralized extracellular matrix. After 8 weeks, histological and histomorphometric evaluations of undecalcified resin sections (bone-implant contact [BIC] % and bone mineral index [BMI]) were performed using light microscopy and scanning electron microscopy.

RESULTS

Alizarin red staining in conjunction with gene expression results confirmed osteogenic differentiation. Histomorphometric assessment using scanning electron microscopy demonstrated improved BIC% and BMI near the treated surface compared with the untreated surface.

CONCLUSIONS

The complex of differentiated grafted ADSCs and extracellular matrix and the macrodesign and microdesign of the implant can improve osseointegration in low-density bone.

Dental materials for cleft palate repair

Numerous bone and soft tissue grafting techniques are followed to repair cleft of lip and palate (CLP) defects. In addition to the gold standard surgical interventions involving the use of autogenous grafts, various allogenic and xenogenic graft materials are available for bone regeneration. In an attempt to discover minimally invasive and cost effective treatments for cleft repair, an exceptional growth in synthetic biomedical graft materials have occurred. This study gives an overview of the use of dental materials to repair cleft of lip and palate (CLP). The eligibility criteria for this review were case studies, clinical trials and retrospective studies on the use of various types of dental materials in surgical repair of cleft palate defects. Any data available on the surgical interventions to repair alveolar or palatal cleft, with natural or synthetic graft materials was included in this review. Those datasets with long term clinical follow-up results were referred to as particularly relevant. The results provide encouraging evidence in favor of dental and other related biomedical materials to fill the gaps in clefts of lip and palate. The review presents the various bones and soft tissue replacement strategies currently used, tested or explored for the repair of cleft defects. There was little available data on the use of synthetic materials in cleft repair which was a limitation of this study. In conclusion although clinical trials on the use of synthetic materials are currently underway the uses of autologous implants are the preferred treatment methods to date.

Uncovering the periosteum for skeletal regeneration: the stem cell that lies beneath

The cartilage- and bone-forming properties of the periosteum have long since been recognized. As one of the major sources of skeletal progenitor cells, the periosteum plays a crucial role not only in bone development and growth, but also during bone fracture healing. Aided by the continuous expansion of tools and techniques, we are now starting to acquire more insight into the specific role and regulation of periosteal cells. From a therapeutic point of view, the periosteum has attracted much attention as a cell source for bone tissue engineering purposes. This interest derives not only from the physiological role of the periosteum during bone repair, but is also supported by the unique properties and marked bone-forming potential of expanded periosteum-derived cells. We provide an overview of the current knowledge of periosteal cell biology, focusing on the cellular composition and molecular regulation of this remarkable tissue, as well as the application of periosteum-derived cells in regenerative medicine approaches. This article is part of a Special Issue entitled "Stem Cells and Bone".

Physical and biological characterization of ferromagnetic fiber networks: effect of fibrin deposition on short-term in vitro responses of human osteoblasts

Ferromagnetic fiber networks have the potential to deform in vivo imparting therapeutic levels of strain on in-growing periprosthetic bone tissue. 444 Ferritic stainless steel provides a suitable material for this application due to its ability to support cultures of human osteoblasts (HObs) without eliciting undue inflammatory responses from monocytes in vitro. In the present article, a 444 fiber network, containing 17 vol% fibers, has been investigated. The network architecture was obtained by applying a skeletonization algorithm to three-dimensional tomographic reconstructions of the fiber networks. Elastic properties were measured using low-frequency vibration testing, providing globally averaged properties as opposed to mechanical methods that yield only local properties. The optimal region for transduction of strain to cells lies between the ferromagnetic fibers. However, cell attachment, at early time points, occurs primarily on fiber surfaces. Deposition of fibrin, a fibrous protein involved in acute inflammatory responses, can facilitate cell attachment within this optimal region at early time points. The current work compared physiological (3 and 5 g·L(-1)) and supraphysiological fibrinogen concentrations (10 g·L(-1)), using static in vitro seeding of HObs, to determine the effect of fibrin deposition on cell responses during the first week of cell culture. Early cell attachment within the interfiber spaces was observed in all fibrin-containing samples, supported by fibrin nanofibers. Fibrin deposition influenced the seeding, metabolic activity, and early stage differentiation of HObs cultured in the fibrin-containing fiber networks in a concentration-dependant manner. While initial cell attachment for networks with fibrin deposited from low physiological concentrations was similar to control samples without fibrin deposition, significantly higher HObs attached onto high physiological and supraphysiological concentrations. Despite higher cell numbers with supraphysiological concentrations, cell metabolic activities were similar for all fibrinogen concentrations. Further, cells cultured on supraphysiological concentrations exhibited lower cell differentiation as measured by alkaline phosphatase activity at early time points. Overall, the current study suggests that physiological fibrinogen concentrations would be more suitable than supraphysiological concentrations for supporting early cell activity in porous implant coatings.

Human embryonic stem cells and macroporous calcium phosphate construct for bone regeneration in cranial defects in rats

Human embryonic stem cells (hESCs) are an exciting cell source as they offer an unlimited supply of cells that can differentiate into all cell types for regenerative medicine applications. To date, there has been no report on hESCs with calcium phosphate cement (CPC) scaffolds for bone regeneration in vivo. The objectives of this study were to: (i) investigate hESCs for bone regeneration in vivo in critical-sized cranial defects in rats; and (ii) determine the effects of cell seeding and platelets in macroporous CPC on new bone and blood vessel formation. hESCs were cultured to yield mesenchymal stem cells (MSCs), which underwent osteogenic differentiation. Four groups were tested in rats: (i) CPC control without cells; (ii) CPC with hESC-derived MSCs (CPC+hESC-MSC); (iii) CPC with hESC-MSCs and 30% human platelet concentrate (hPC) (CPC+hESC-MSC+30% hPC); and (iv) CPC+hESC-MSC+50% hPC. In vitro, MSCs were derived from embryoid bodies of hESCs. Cells on CPC were differentiated into the osteogenic lineage, with highly elevated alkaline phosphatase and osteocalcin expressions, as well as mineralization. At 12weeks in vivo, the groups with hESC-MSCs and hPC had three times as much new bone as, and twice the blood vessel density of, the CPC control. The new bone in the defects contained osteocytes and blood vessels, and the new bone front was lined with osteoblasts. The group with 30% hPC and hESC-MSCs had a blood vessel density that was 49% greater than the hESC-MSC group without hPC, likely due to the various growth factors in the platelets enhancing both new bone and blood vessel formation. In conclusion, hESCs are promising for bone tissue engineering, and hPC can enhance new bone and blood vessel formation. Macroporous CPC with hESC-MSCs and hPC may be useful for bone regeneration in craniofacial and orthopedic applications.

Biological functionalization of dental implants with fibronectin: a scanning electron microscopic study

OBJECTIVES

Early stages of peri-implant bone formation play an essential role in the osseointegration and long-term success of dental implants. Biological implant surface coatings are an emerging technology to enhance the attachment of the implant to the surrounding bone and stimulate bone regeneration. The purpose of this study was to determine the effect of coating the implant surface with fibronectin on osseointegration.

MATERIAL AND METHODS

The experiment was conducted on a total of twelve New Zealand white mature male rabbits, weight between 2.5-4 kg. Twenty four pure titanium implants were used in this study. Each rabbits received two implants, one implant in each tibia; the implant in the right limb was coated with fibronectin (experimental group), whilst on the contralateral side the implants were placed without coating (control group). Six rabbits were sacrificed for Scanning Electron Microscopic evaluation after 4 and 8 week healing periods.

RESULTS

The results of the present study demonstrating the mean gap distance between the bone and implant was greater in the control group compared to fibronection group at both observation periods however, the difference between these two groups was not statistically significant.

CONCLUSION

Thus, it could be suggested that the biological functionalization of dental implants with fibronectin, may influence the integration or biocompatibility and bonding of the implant to the surrounding bone.

Tissue engineering and regenerative repair in wound healing

Wound healing is a highly evolved defense mechanism against infection and further injury. It is a complex process involving multiple cell types and biological pathways. Mammalian adult cutaneous wound healing is mediated by a fibroproliferative response leading to scar formation. In contrast, early to mid-gestational fetal cutaneous wound healing is more akin to regeneration and occurs without scar formation. This early observation has led to extensive research seeking to unlock the mechanism underlying fetal scarless regenerative repair. Building upon recent advances in biomaterials and stem cell applications, tissue engineering approaches are working towards a recapitulation of this phenomenon. In this review, we describe the elements that distinguish fetal scarless and adult scarring wound healing, and discuss current trends in tissue engineering aimed at achieving scarless tissue regeneration.

Exploring the complex mechanical properties of xanthan scaffolds by AFM-based force spectroscopy

The polysaccharide xanthan has been extensively studied owing to its potential application in tissue engineering. In this paper, xanthan scaffold structures were investigated by atomic force microscope (AFM) in liquid, and the mechanical properties of the complex xanthan structures were investigated by using AFM-based force spectroscopy (FS). In this work, three types of structures in the xanthan scaffold were identified based on three types of FS stretching events. The fact that the complex force responses are the combinations of different types of stretching events suggests complicated intermolecular interactions among xanthan fibrils. The results provide crucial information to understand the structures and mechanical properties of the xanthan scaffold.

Repair of segmental long bone defect in a rabbit radius nonunion model: comparison of cylindrical porous titanium and hydroxyapatite scaffolds

A segmental long bone defect in a rabbit radius nonunion model was repaired using cylindrical porous titanium (Ti) and hydroxyapatite (HA) scaffolds. Each scaffold was produced using the same method, namely, a slurry foaming method. Repairing ability was characterized using x-radiographic score 12 and 24 weeks postprocedure; failure load of the radius-ulna construct, under three-point bending, 12 weeks postprocedure; and the percentage of newly formed bone within the implant, 12 and 24 weeks after postprocedure. For each of these parameters, the difference in the results when porous Ti scaffold was used compared with when HA scaffolds were used was not significant; both porous scaffolds showed excellent repairing ability. Because the trabecular bone is a porous tissue, the interconnected porous scaffolds have the advantages of natural bone, and vasculature can grow into the porous structure to accelerate the osteoconduction and osteointegration between the implant and bone. The porous Ti scaffold not only enhanced the bone repair process, similar to porous HA scaffolds, but also has superior biomechanical properties. The present results suggest that porous Ti scaffolds may have promise for use in the clinical setting.

Preconditioned 70S30C bioactive glass foams promote osteogenesis in vivo

Bioactive glass scaffolds (70S30C; 70% SiO2 and 30% CaO) produced by a sol-gel foaming process are thought to be suitable matrices for bone tissue regeneration. Previous in vitro data showed bone matrix production and active remodelling in the presence of osteogenic cells. Here we report their ability to act as scaffolds for in vivo bone regeneration in a rat tibial defect model, but only when preconditioned. Pretreatment methods (dry, pre-wetted or preconditioned without blood) for the 70S30C scaffolds were compared against commercial synthetic bone grafts (NovaBone® and Actifuse®). Poor bone ingrowth was found for both dry and wetted sol-gel foams, associated with rapid increase in pH within the scaffolds. Bone ingrowth was quantified through histology and novel micro-CT image analysis. The percentage bone ingrowth into dry, wetted and preconditioned 70S30C scaffolds at 11 weeks were 10±1%, 21±2% and 39±4%, respectively. Only the preconditioned sample showed above 60% material-bone contact, which was similar to that in NovaBone and Actifuse. Unlike the commercial products, preconditioned 70S30C scaffolds degraded and were replaced with new bone. The results suggest that bioactive glass compositions should be redesigned if sol-gel scaffolds are to be used without preconditioning to avoid excess calcium release.

Recent developments of functional scaffolds for craniomaxillofacial bone tissue engineering applications

Autogenous bone grafting remains a gold standard for the reconstruction critical-sized bone defects in the craniomaxillofacial region. Nevertheless, this graft procedure has several disadvantages such as restricted availability, donor-site morbidity, and limitations in regard to fully restoring the complicated three-dimensional structures in the craniomaxillofacial bone. The ultimate goal of craniomaxillofacial bone reconstruction is the regeneration of the physiological bone that simultaneously fulfills both morphological and functional restorations. Developments of tissue engineering in the last two decades have brought such a goal closer to reality. In bone tissue engineering, the scaffolds are fundamental, elemental and mesenchymal stem cells/osteoprogenitor cells and bioactive factors. A variety of scaffolds have been developed and used as spacemakers, biodegradable bone substitutes for transplanting to the new bone, matrices of drug delivery system, or supporting structures enhancing adhesion, proliferation, and matrix production of seeded cells according to the circumstances of the bone defects. However, scaffolds to be clinically completely satisfied have not been developed yet. Development of more functional scaffolds is required to be applied widely to cranio-maxillofacial bone defects. This paper reviews recent trends of scaffolds for crania-maxillofacial bone tissue engineering, including our studies.

Reconstruction of critical-size mandibular defects in immunoincompetent rats with human adipose-derived stromal cells

In patients with bony defects, autologous bone grafts are the "gold standard" for reconstruction. In children, autologous bone harvesting is limited but tissue engineering offers an alternative. Next to bone marrow, adipose tissue is a source of mesenchymal stromal cells, and adipose-derived stromal cells (ADSC) can differentiate into osteocytes. The aim of this study was to evaluate the efficacy of bioactive implants (ADSC in fibrin glue) for repair of critical-size mandibular defects in athymic rats. Human adult ADSC embedded in fibrin glue were implanted into a critical-size defect in the rat mandible and their efficacy was compared to those of protected bone healing (pbh), autologous bone graft, and an empty defect. The newly formed bone was quantified using high-resolution flat-panel volumetric CT (fpvCT) during different observation times. After eight weeks, the specimens were assessed histologically and by micro-computed tomography (μ-CT). The radiographic examination demonstrated a significantly higher level of ossified defect area in the ADSC side compared with the pbh side. The autologous bone graft side showed significantly enhanced bone formation compared to the empty defect. The histological findings in the specimens with ADSC showed bony bridging of the defect. ADSC were capable of defect reconstruction under our experimental conditions.