Bone grafts and bone graft substitutes in orthopaedic trauma surgery. A critical analysis

Mesenchymal stem cells in craniofacial reconstruction: a comprehensive review

Craniofacial reconstruction faces many challenges, including high complexity, strong specificity, severe injury, irregular and complex wounds, and high risk of bleeding. Traditionally, the "gold standard" for treating craniofacial bone defects has been tissue transplantation, which involves the transplantation of bone, cartilage, skin, and other tissues from other parts of the body. However, the shape of craniofacial bone and cartilage structures varies greatly and is distinctly different from ordinary long bones. Craniofacial bones originate from the neural crest, while long bones originate from the mesoderm. These factors contribute to the poor effectiveness of tissue transplantation in repairing craniofacial defects. Autologous mesenchymal stem cell transplantation exhibits excellent pluripotency, low immunogenicity, and minimally invasive properties, and is considered a potential alternative to tissue transplantation for treating craniofacial defects. Researchers have found that both craniofacial-specific mesenchymal stem cells and mesenchymal stem cells from other parts of the body have significant effects on the restoration and reconstruction of craniofacial bones, cartilage, wounds, and adipose tissue. In addition, the continuous development and application of tissue engineering technology provide new ideas for craniofacial repair. With the continuous exploration of mesenchymal stem cells by researchers and the continuous development of tissue engineering technology, the use of autologous mesenchymal stem cell transplantation for craniofacial reconstruction has gradually been accepted and promoted. This article will review the applications of various types of mesenchymal stem cells and related tissue engineering in craniofacial repair and reconstruction.

Bioinspired 3D scaffolds with antimicrobial, drug delivery, and osteogenic functions for bone regeneration

A major clinical challenge today is the large number of bone defects caused by diseases or trauma. The development of three-dimensional (3D) scaffolds with adequate properties is crucial for successful bone repair. In this study, we prepared biomimetic mesoporous bioactive glass (MBG)-based scaffolds with and without ceria addition (up to 3 mol %) to explore the biological structure and chemical composition of the marine sponge Spongia Agaricina (SA) as a sacrificial template. Micro-CT examination revealed that all scaffolds exhibited a highly porous structure with pore diameters primarily ranging from 143.5 μm to 213.5 μm, facilitating bone ingrowth. Additionally, smaller pores (< 75 μm), which are known to enhance osteogenesis, were observed. The undoped scaffold displayed the highest open porosity value of 90.83%. Cytotoxicity assessments demonstrated that all scaffolds were noncytotoxic and nongenotoxic toward osteoblast cells. Moreover, scaffolds with higher CeO2 content promoted osteogenic differentiation of dental pulp stem cells, stimulating calcium and osteocalcin secretion. The scaffolds also exhibited antimicrobial and antibiofilm effects against Staphylococcus aureus (S. aureus) as well as drug delivery ability. Our research findings indicated that the combination of MBG, natural biological structure, and the addition of Ce exhibited a synergistic effect on the structure and biological properties of scaffolds for applications in bone tissue engineering.

SLS 3D Printing To Fabricate Poly(vinyl alcohol)/Hydroxyapatite Bioactive Composite Porous Scaffolds and Their Bone Defect Repair Property

Poly(vinyl alcohol) (PVA) exhibits a wide range of potential applications in the biomedical field due to its favorable mechanical properties and biocompatibility. However, few studies have been carried out on selective laser sintering (SLS) of PVA due to its poor thermal processability. In this study, in order to impart PVA powder the excellent thermal processability, the molecular complexation technology was performed to destroy the strong hydrogen bonds in PVA and thus significantly reduced the PVA melting point and crystallinity to 190.9 °C and 27.9%, respectively. The modified PVA (MPVA) was then compounded with hydroxyapatite (HA) to prepare PVA/HA composite powders suitable for SLS 3D printing. The final SLS 3D-printed MPVA/HA composite porous scaffolds show high precision and interconnected pores with a porosity as high as 68.3%. The in vitro cell culture experiments revealed that the sintered composite scaffolds could significantly promote the adhesion and proliferation of osteoblasts and facilitate bone regeneration, and the quantitative real-time polymerase chain reaction results further demonstrate that the printed MPVA/20HA scaffold could significantly enhance the expression levels of both early osteogenic-specific marker of alkaline phosphatase stain and runt-related transcription factor 2. Meanwhile, in in vivo experiments, it is encouragingly found that the resultant MPVA/20HA SLS 3D-printed part has an obvious effect on promoting the growth of new bone tissue as well as a better bone regeneration capability. This work could provide a promising strategy for fabrication of PVA scaffolds through SLS 3D printing, exhibiting a great potential for clinical applications in bone tissue engineering.

Modified Masquelet Technique and Primary Tibial Metaphyseal Shortening for the Management of Proximal Tibial-infected Non-union in a Patient with Alcohol-induced Neuropathy: A Case Study

Aim

To highlight the role of the Masquelet technique as a limb salvage procedure for a neuropathic patient presenting with infected non-union of proximal tibia.

Background

The management of an infected non-union in neuropathic patients is most challenging; with various treatment options available, the prognosis is often guarded.

Case description

A 37-year-old male with chronic polyneuropathy, also possessing a contralateral midfoot Charcot arthropathy secondary to a history of alcohol abuse, developed infection after a proximal tibial osteotomy for a preceding mal-non-union of a proximal tibia fracture. The management included hardware removal, excision of necrotic bone, interim insertion of antibiotic-loaded bone cement followed by an acute shortening and revision of the internal fixation utilising a second surgical incision. Successful bone union and eradication of infection was achieved and maintained after 13 months follow-up.

Conclusion

A successful outcome was achieved for an infected non-union of a long bone in a neuropathic patient using the Masquelet technique which was then followed with a second-stage removal of the spacer and shortening. By performing the revision ORIF surgery utilising a different skin incision in the setting of complicated previous surgical scars proved to be a viable technique towards reducing risk of recurrence of infection and a good outcome.

Clinical significance

Utilisation of the Masquelet technique and limb shortening in a staged manner for the management of long bone infections in neuropathic patients has not been reported before and may be valuable in such demanding clinical situations.

How to cite this article

Mahmoud AN, Watson JT, Horwitz DS. Modified Masquelet Technique and Primary Tibial Metaphyseal Shortening for the Management of Proximal Tibial-infected Non-union in a Patient with Alcohol-induced Neuropathy: A Case Study. Strategies Trauma Limb Reconstr 2023;18(3):181-185.

Bone Grafting Outcomes in Smokers Undergoing High Tibial Osteotomy: A Systematic Review

This systematic review summarises the findings in the literature available to show outcomes of high tibial osteotomy (HTO) with bone grafting in smokers. It also studies the trend of complications, outcome measures used and overall outcomes like union, non-union or the need to perform revision surgeries. The aim is to find out if HTO done with bone grafting improves outcomes in smokers. Articles were shortlisted using Population, Intervention, Control, and Outcomes (PICO) search design and quality assessment was completed using Jadad, STROBE (Strengthening the Reporting of Observational studies in Epidemiology), Delphi, and Critical Appraisal Skills Program (CASP) followed by data extraction by two independent authors. There was union in 97.6% of smokers who received HTO with bone grafting. A case of non-union was treated with removal of metalwork and distraction osteogenesis. Three cases of unknown demographics had arthroplasty in the time frame from HTO with bone grafting to follow up. The commonest complication post surgery was metalwork causing soft tissue irritation and lateral proximal tibial cortex fracture. Following this review we can conclude that HTO with bone grafting could be considered as an option to achieve better outcomes in smokers. Bone grafting helps healing across osteotomy sites in smokers whose healing potential is poor. Autogenous Iliac crest bone grafting is ideal due to its osteoinductive and osteoconductive properties, but has the disadvantage of donor site morbidity.

Chitosan scaffolds with mesoporous hydroxyapatite and mesoporous bioactive glass

Bone regeneration is one of the most well-known fields in tissue regeneration. The major focus concerns polymeric/ceramic composite scaffolds. In this work, several composite scaffolds based on chitosan (CH), with low and high molecular weights, and different concentrations of ceramics like mesoporous bioactive glass (MBG), mesoporous hydroxyapatite (MHAp) and both MBG and MHAp (MC) were produced by lyophilization. The purpose is to identify the best combination regarding optimal morphology and properties. The tests of the scaffolds present a highly porous structure with interconnected pores. The compression modulus increases with ceramic concentration in the scaffolds. Furthermore, the 75%MBG (835 ± 160 kPa) and 50%MC (1070 ± 205 kPa) samples are the ones that mostly enhance increases in mechanical properties. The swelling capacity increases with MBG and MC, respectively, to 700% and 900% and decreases to 400% when MHAp concentration increases. All scaffolds are non-cytotoxic at 12.5 mg/mL. The CHL scaffolds improve cell adhesion and proliferation compared to CHH, and the MC scaffold samples, show better results than those produced with just MBG or MHAp. The composite scaffolds of chitosan with MBG and MHAp, have revealed to be the best combination due to their enhanced performance in bone tissue engineering.

A Medical-Grade Polycaprolactone and Tricalcium Phosphate Scaffold System With Corticoperiosteal Tissue Transfer for the Reconstruction of Acquired Calvarial Defects in Adults: Protocol for a Single-Arm Feasibility Trial

Background

Large skull defects present a reconstructive challenge. Conventional cranioplasty options include autologous bone grafts, vascularized bone, metals, synthetic ceramics, and polymers. Autologous options are affected by resorption and residual contour deformities. Synthetic materials may be customized via digital planning and 3D printing, but they all carry a risk of implant exposure, failure, and infection, which increases when the defect is large. These complications can be a threat to life. Without reconstruction, patients with cranial defects may experience headaches and stigmatization. The protection of the brain necessitates lifelong helmet use, which is also stigmatizing.

Objective

Our clinical trial will formally study a hybridized technique's capacity to reconstruct large calvarial defects.

Methods

A hybridized technique that draws on the benefits of autologous and synthetic materials has been developed by the research team. This involves wrapping a biodegradable, ultrastructured, 3D-printed scaffold made of medical-grade polycaprolactone and tricalcium phosphate in a vascularized, autotransplanted periosteum to exploit the capacity of vascularized periostea to regenerate bone. In vitro, the scaffold system supports cell attachment, migration, and proliferation with slow but sustained degradation to permit host tissue regeneration and the replacement of the scaffold. The in vivo compatibility of this scaffold system is robust—the base material has been used clinically as a resorbable suture material for decades. The importance of scaffold vascularization, which is inextricably linked to bone regeneration, is underappreciated. A variety of methods have been described to address this, including scaffold prelamination and axial vascularization via arteriovenous loops and autotransplanted flaps. However, none of these directly promote bone regeneration.

Results

We expect to have results before the end of 2023. As of December 2020, we have enrolled 3 participants for the study.

Conclusions

The regenerative matching axial vascularization technique may be an alternative method of reconstruction for large calvarial defects. It involves performing a vascularized free tissue transfer and using a bioresorbable, 3D-printed scaffold to promote and support bone regeneration (termed the regenerative matching axial vascularization technique). This technique may be used to reconstruct skull bone defects that were previously thought to be unreconstructable, reduce the risk of implant-related complications, and achieve consistent outcomes in cranioplasty. This must now be tested in prospective clinical trials.

Trial Registration

Australian New Zealand Clinical Trials Registry ACTRN12620001171909; https://tinyurl.com/4rakccb3

International Registered Report Identifier (IRRID)

DERR1-10.2196/36111

Cell-Laden Composite Hydrogel Bioinks with Human Bone Allograft Particles to Enhance Stem Cell Osteogenesis

There is a growing demand for bone graft substitutes that mimic the extracellular matrix properties of the native bone tissue to enhance stem cell osteogenesis. Composite hydrogels containing human bone allograft particles are particularly interesting due to inherent bioactivity of the allograft tissue. Here, we report a novel photocurable composite hydrogel bioink for bone tissue engineering. Our composite bioink is formulated by incorporating human allograft bone particles in a methacrylated alginate formulation to enhance adult human mesenchymal stem cell (hMSC) osteogenesis. Detailed rheology and printability studies confirm suitability of our composite bioinks for extrusion-based 3D bioprinting technology. In vitro studies reveal high cell viability (~90%) for hMSCs up to 28 days of culture within 3D bioprinted composite scaffolds. When cultured within bioprinted composite scaffolds, hMSCs show significantly enhanced osteogenic differentiation as compared to neat scaffolds based on alkaline phosphatase activity, calcium deposition, and osteocalcin expression.

(Bio)manufactured Solutions for Treatment of Bone Defects with Emphasis on US-FDA Regulatory Science Perspective

Bone defects, with second highest demand for surgeries around the globe, may lead to serious health issues and negatively influence patient lives. The advances in biomedical engineering and sciences have led to the development of several creative solutions for bone defect treatment. This review provides a brief summary of bone graft materials, an organized overview of top-down and bottom-up (bio)manufacturing approaches, plus a critical comparison between advantages and limitations of each method. We specifically discuss additive manufacturing techniques and their operation mechanisms in detail. Next, we review the hybrid methods and promising future directions for bone grafting, while giving a comprehensive US-FDA regulatory science perspective, biocompatibility concepts and assessments, and clinical considerations to translate a technology from a research laboratory to the market. The topics covered in this review could potentially fuel future research efforts in bone tissue engineering, and perhaps could also provide novel insights for other tissue engineering applications.

Top 50 Cited Bone Graft Orthopedic Papers

The purpose of this research is to recognize the highest 50 most-mentioned articles in the literature concentrating on bone grafts. That has been accomplished with the use of the Scopus database and the search slogan "bone grafts," and we inquired for the 50 most-cited articles on bone grafting. The study was completed in September 2020. We investigated the articles issued between 1970 and 2020. The articles were organized and classified based on the total number of citations. We appraised the following information relating to each article: first author, year of publication, journal, and title.

A total of 1,580 studies matched our search standards, of which the 50 most-cited extended between 1,862 and 403 citations. Seven articles were cited more than 1,000 times. The article by Marx et al. was the maximum-cited article, with 1,862 citations, followed by Younger et al.'s with 1,461 and Giannoudis et al.'s with 1,245. The majority of the studies originated from the United States (n = 30) and were published in the 2000s. Biomaterials was the most regular destination journal (n = 8), followed by the Journal of Bone and Joint Surgery American series (n = 7). A maximum of the articles focused on the different types of bone grafts and their alternatives including bone tissue engineering (n=29). Our investigation of the highest 50 articles linking to bone grafting has emphasized the most significant papers in the field. These cover a wide-ranging variety of topics including types, management, and mechanism of action of bone grafts. To recognize the present treatment guidelines and how the use of bone grafting has grown, it is vital to know the most-cited articles relating to this grafting.

Development of Intracorporeal Differentiation of Stem Cells to Induce One-Step Mastoid Bone Reconstruction during Otitis Media Surgeries

Mastoidectomy is a surgical procedure for the treatment of chronic otitis media. This study investigated the ability of rat stromal vascular fraction cells (rSVF) in combination with polycaprolactone (PCL) scaffolds and osteogenic differentiation-enhancing blood products to promote the regeneration of mastoid bone defect. Twenty male Sprague Dawley rats were randomly divided according to obliteration materials: (1) control, (2) PCL scaffold only, (3) rSVFs + PCL, (4) rSVFs + PCL + platelet-rich plasma, and (5) rSVFs + PCL + whole plasma (WP). At 7 months after transplantation, the rSVFs + PCL + WP group showed remarkable new bone formation in the mastoid. These results indicate that SVFs, PCL scaffolds, and blood products accelerate bone regeneration for mastoid reconstruction. Autologous SVF cells with PCL scaffolds and autologous blood products are promising composites for mastoid reconstruction which can be easily harvested after mastoidectomy. With this approach, the reconstruction of mastoid bone defects can be performed right after mastoidectomy as a one-step procedure which can offer efficiency in the clinical field.

Evaluation of biocompatibility, osteointegration and biomechanical properties of the new Calcemex® cement: An <em>in vivo</em> study

The mixture of polymethylmethacrylate (PMMA) and β-tricalciumphospate (β-TCP) is the most widely used bone graft. Common features of bone cement are the biocompatibility, bioactivity, mechanical stability and ability to fuse with the host's bone tissue. However, there are still few studies that have evaluated these characteristics in vivo. Our study aims to acquire these parameters, using an animal model with functional characteristics similar to those of humans. The analyzed cement is Calcemex^®, evaluated both in compact and fluid formulation. The chosen animal models were 5 pigs, treated with femoral and tibial implants of Calcemex^® samples. After one year, the pigs were sacrificed and the specimens explanted for morphological, histological, ultrastructural and mechanical evaluations. For both formulations, the investigation highlighted the absence of foreign body reactions in the host, the histological integration with the surrounding tissues and the preservation of mechanical compression resistance.

The Development of a Magnesium-Releasing and Long-Term Mechanically Stable Calcium Phosphate Bone Cement Possessing Osteogenic and Immunomodulation Effects for Promoting Bone Fracture Regeneration

Bone grafts are commonly used for the treatment of critical sized bone defects. Since the supply of autologous bone is insufficient, allogeneic bone grafts have been used most of the time. However, the poor osteogenic property of allogeneic bone grafts after pretreatment results in delayed union, non-union, or even occasional deformity. Calcium phosphate cement (CPC) is one of the most promising bone filling materials due to its good biocompatibility and similar chemical components as natural bone. However, clinical applications of CPC were hampered by limited osteogenic effects, undesired immune response which results in resorption, and poor mechanical stability in vivo. Magnesium (Mg) has been proven to trigger bone regeneration through modulating cell behaviors of mesenchymal stem cells and macrophages significantly. Unfortunately, the degradation raters of pure Mg and Mg oxide are extremely fast, resulting in early collapse of Mg contained CPC. In this study, we developed a novel magnesium contained calcium phosphate bone cement (Mg-CPC), possessing long-term mechanical stability and osteogenic effects through sustained release of Mg. Furthermore, in vitro studies showed that Mg-CPC had no cytotoxic effects on hBMMSCs and macrophage RAW 264.7, and could enhance the osteogenic differentiation as determined by alkaline phosphate (ALP) activity and calcium nodule staining, as well as suppress the inflammatory as determined by expression of anti-inflammatory cytokine IL-1RA. We also found that Mg-CPC promoted new bone formation and bone maturation in vivo. These results suggest that Mg-CPC should be a good substitute material for bone grafts in clinical use.

Scaffold-guided bone regeneration in large volume tibial segmental defects

Large volume losses in weight bearing long bones are a major challenge in clinical practice. Despite multiple innovations over the last decades, significant limitations subsist in current clinical treatment options which is driving a strong clinical demand for clinically translatable treatment alternatives, including bone tissue engineering applications. Despite these shortcomings, preclinical large animal models of large volume segmental bone defects to investigate the regenerative capacity of bone tissue engineering strategies under clinically relevant conditions are rarely described in literature. We herein present a newly established preclinical ovine animal model for the treatment of XL volume (19 cm³) segmental tibial defects. In eight aged male Merino sheep (age > 6 years) a mid-diaphyseal tibial segmental defect was created and stabilized with a 5.6 mm Dynamic Compression Plate (DCP). We present short-term (3 months) and long-term (12-15 months) results of a pilot study using medical grade Polycaprolactone-Tricalciumphosphate (mPCL-TCP) scaffolds combined with a dose of 2 mg rhBMP-7 delivered in Platelet-Rich- Plasma (PRP). Furthermore, detailed analyses of the mechanical properties of the scaffolds as well as interfragmentary movement (IFM) and DCP-surface strain in vitro and a comprehensive description of the surgical and post-surgery protocol and post-mortem analysis is given.

Biocompatible Customized 3D Bone Scaffolds Treated with CRFP, an Osteogenic Peptide

BACKGROUND

Currently used synthetic bone graft substitutes (BGS) are either too weak to bear the principal load or if metallic, they can support loading, but can lead to stress shielding and are unable to integrate fully. In this study, we developed biocompatible, 3D printed scaffolds derived from µCT images of the bone that can overcome these issues and support the growth of osteoblasts.

METHODS

Cylindrical scaffolds were fabricated with acrylonitrile butadiene styrene (ABS) and Stratasys^® MED 610 (MED610) materials. The 3D-printed scaffolds were seeded with Mus musculus calvaria cells (MC3T3). After the cells attained confluence, osteogenesis was induced with and without the addition of calcitonin receptor fragment peptide (CRFP) and the bone matrix production was analyzed. Mechanical compression testing was carried out to measure compressive strength, stiffness, and elastic modulus.

RESULTS

For the ABS scaffolds, there was a 9.8% increase in compressive strength (p < 0.05) in the scaffolds with no pre-coating and the treatment with CRFP, compared to non-treated scaffolds. Similarly, MED610 scaffolds treated with CRFP showed an 11.9% (polylysine pre-coating) and a 20% (no pre-coating) increase (p < 0.01) in compressive strength compared to non-treated scaffolds.

CONCLUSIONS

MED610 scaffolds are excellent BGS as they support osteoblast growth and show enhanced bone growth with enhanced compressive strength when augmented with CRFP.

Preliminary outcomes of the combination of demineralized bone matrix and platelet Rich plasma in the treatment of long bone non-unions

Background

A variety of bone graft substitutes have been introduced into the treatment of bone non-unions. However, clinical outcomes from current evidences are various and conflicting. This study aimed to present the preliminary outcomes of a treatment protocol in which the combination of demineralized bone matrix (DBM) and platelet rich plasma (PRP) was used as a bone graft substitute for long bone non-unions.

Methods

Data of this retrospective study were reviewed and collected from a consecutive case series involving 43 patients who presented with a long bone non-union and were treated in our department from October 2018 to May 2019. The combination of DMB and PRP was applied as a bone defect filler in 16 patients, whilst the other 27 patients were treated with iliac bone autografting. Patients’ demographics, postoperative complications and the result of bone union were compared and evaluated.

Results

The demographic data between the two groups were comparable. No significant difference was found with regard to the incidence of postoperative complications. No graft rejection, heterotopic ossification or other complications were noted. The distribution of bony healing time was rather scattered but did not differ significantly between the groups (7.533 ± 3.357 months vs. 6.625 ± 2.516 months; P=0.341). Union was identified radiographically in 15 of 16 patients in the DBM+PRP group and in 24 of 27 patients in autograft group.

Conclusions

The present study identified that low incidence of postoperative complications and satisfactory bony healing rate could be achieved in the treatment of long bone non-unions augmented with the combination of DBM and PRP. Although these findings might indicate the promising future of this treatment protocol, larger and higher quality studies should also be executed to assess its routine use.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04840-2.

Decision-Making and Management of Proximal Humerus Nonunions

Proximal humerus fracture nonunions are heterogenous group of posttraumatic sequelae in both the operatively and nonoperatively treated proximal humerus fracture. The management of these fractures is largely based on the residual morphology. Understanding the relationship of the nonunited and malunited fragments, anatomic location of the fracture, and viability of the residual bone stock will allow for better surgical planning. Patient optimization with nonoperative care, open reduction internal fixation, intramedullary nailing, and shoulder arthroplasty, all have a role in the treatment of proximal humerus fracture nonunions.

An In Vitro and In Vivo Comparison of Osteogenic Differentiation of Human Mesenchymal Stromal/Stem Cells

The use of stem cells in regenerative medicine, including tissue engineering and transplantation, has generated a great deal of enthusiasm. Mesenchymal stromal/stem cells (MSCs) can be isolated from various tissues, most commonly, bone marrow but more recently adipose tissue, dental pulp, and Wharton's jelly, to name a few. MSCs display varying phenotypic profiles and osteogenic differentiating capacity depending and their site of origin. MSCs have been successfully differentiated into osteoblasts both in vitro an in vivo but discrepancies exist when the two are compared: what happens in vitro does not necessarily happen in vivo, and it is therefore important to understand why these differences occur. The osteogenic process is a complex network of transcription factors, stimulators, inhibitors, proteins, etc., and in vivo experiments are helpful in evaluating the various aspects of this osteogenic process without distractions and confounding variables. With that in mind, the results of in vitro experiments need to be carefully considered and interpreted with caution as they do not perfectly replicate the conditions found within living organisms. This is where in vivo experiments help us better understand interactions that might occur in the osteogenic process that cannot be replicated in vitro. Potentially, these differences could also be exploited to develop an optimal MSC cell therapeutic product that can be used for bone disorders. There are many bone disorders, most of which cause a great deal of discomfort. Clinically acceptable protocols could be developed in which MSCs are used to aid in bone regeneration providing relief for patients with chronic pain. The aim of this review is to examine the differences between studies conducted in vitro and in vivo with regard to the osteogenic process to better define the gaps in current osteogenic research. By better understanding osteogenic differentiation, we can better define treatment strategies for various bone disorders.

Case Report: Formation of 3D Osteoblast Spheroid Under Magnetic Levitation for Bone Tissue Engineering

Skeletal reconstruction is necessary in cases of bone defects created by tumors, trauma, and abnormalities. Regeneration of bone defects remains a critical problem, and current approaches are based on biocompatible scaffolds. Spheroids represent a simple 3D system since no supporting material is required for cell growth. Different techniques are used to generate spheroids, such as hanging drop, low-attachment plates, and magnetic nanoparticles. The idea of using magnetic nanoparticles is to cross-link through cell membrane overnight to create complex 3D cellular spheroid by using magnets to guide the cellular response. Herein, the current study aimed to achieve 3D human fetal osteoblast (hFOB) spheroid under magnetic levitation. Formation of 3D spheroid culture under magnetic levitation was evaluated by cell viability at 3, 7, and 14 days. Morphology of the 3D hFOB spheroid was analyzed by SEM and fluorescence microscopy and the differentiation towards mineralized lineage by ALP assay, qPCR, and alizarin red staining. The cell viability indicated that the 3D hFOB spheroid still viable after 14 days of culture. ALP assay, qPCR analysis expression of Col1, ALP, and Itg-β1 molecules, and calcium deposition with alizarin red showed a high level of bioactivity of the 3D hFOB spheroid. SEM images allowed the morphological analysis of the 3D microtissue-like spheroid with the presence of matrix deposition. These results indicate that magnetic levitation culture enables 3D stable osteoblast spheroids and could be a promising strategy for engineering application in the 3D construct in surgery regeneration of mineralized tissue.

Simultaneous incorporation of PTH(1-34) and nano-hydroxyapatite into Chitosan/Alginate Hydrogels for efficient bone regeneration

Tissue regeneration based on the utilization of artificial soft materials is considered a promising treatment for bone-related diseases. Here, we report cranial bone regeneration promoted by hydrogels that contain parathyroid hormone (PTH) peptide PTH(1-34) and nano-hydroxyapatite (nHAP). A combination of the positively charged natural polymer chitosan (CS) and negatively charged sodium alginate led to the formation of hydrogels with porous structures, as shown by scanning electron microscopy. Rheological characterizations revealed that the mechanical properties of the hydrogels were almost maintained upon the addition of nHAP and PTH(1-34). In vitro experiments showed that the hydrogel containing nHAP and PTH(1-34) exhibited strong biocompatibility and facilitated osteogenic differentiation of rat bone marrow mesenchymal stem cells (rBMSCs) via the Notch signaling pathway, as shown by the upregulated expression of osteogenic-related proteins. We found that increasing the content of PTH(1-34) in the hydrogels resulted in enhanced osteogenic differentiation of BMSCs. Implantation of the complex hydrogel into a rat cranial defect model led to efficient bone regeneration compared to the rats treated with the hydrogel alone or with nHAP, indicating the simultaneous therapeutic effect of nHAP and PTH during the treatment process. Both the in vitro and in vivo results demonstrated that simultaneously incorporating nHAP and PTH into hydrogels shows promise for bone regeneration, suggesting a new strategy for tissue engineering and regeneration in the future.

Large-Pore Platelet-Rich Fibrin with a Mg Ring to Allow MC3T3-E1 Preosteoblast Migration and to Improve Osteogenic Ability for Bone Defect Repair

Platelet-rich fibrin (PRF) is a natural fibrin meshwork material with multiple functions that are suitable for tissue engineering applications. PRF provides a suitable scaffold for critical-size bone defect treatment due to its platelet cytokines and rich growth factors. However, the structure of PRF not only promotes cell attachment but also, due to its density, provides a pool for cell migration into the PRF to facilitate regeneration. In our study, we used repeated freeze drying to enlarge the pores of PRF to engineer large-pore PRF (LPPRF), a type of PRF that has expanded pores for cell migration. Moreover, a biodegradable Mg ring was used to provide stability to bone defects and the release of Mg ions during degradation may enhance osteoconduction and osteoinduction. Our results revealed that cell migration was more extensive when LPPRF was used rather than when PRF was used and that LPPRF retained the growth factors present in PRF. Moreover, the Mg ions released from the Mg ring during degradation significantly enhanced the calcium deposition of MC3T3-E1 preosteoblasts. In the present study, a bone substitute comprising LPPRF combined with a Mg ring was demonstrated to have much potential for critical-size bone defect repair.

More weighted cancellous bone can be harvested from the proximal tibia with less donor site pain than anterior iliac crest corticocancellous bone harvesting: retrospective review

Background

Iliac crest is the most preferred autogenous bone graft harvesting donor site while it has sorts of complications like prolonged pain, hematoma, and fracture. Harvesting cancellous bone from proximal tibia is also increasingly being used because of lower complications and less donor site pain. However, there are lack of studies to compare these two donor sites in detail. Thus, we proposed to investigate the available amount of autogenous bone graft from the proximal tibia.

Methods

Fifty-one patients who underwent simultaneous bone graft harvest from the PT and the AIC to fill up the given critical sized bone defects were enrolled in this study. We prospectively collected data including the weight of the harvested bone, donor site pain using the visual analog scale (VAS) score, and complications between the two sites.

Results

The mean weight of cancellous bone harvested from the PT was greater than AIC (33.2g vs. 27.4g, p = 0.001). The mean VAS score was significantly lesser in the PT up to 60 days after harvesting (p < 0.001). There was persistent pain up to 90 days in four PT patients and in seven AIC patients. The major complication was reported only in AIC patients (11.8%).

Conclusions

Harvesting cancellous bone from the PT is an acceptable alternative to the AIC for autogenous bone grafting owing to availability of more weighted graft bone and less donor site pain.

An Elastic Mineralized 3D Electrospun PCL Nanofibrous Scaffold for Drug Release and Bone Tissue Engineering

Complex shaped and critical-sized bone defects have been a clinical challenge for many years. Scaffold-based strategies such as hydrogels provide localized drug release while filling complex defect shapes, but ultimately possess weaknesses in low mechanical strength alongside a lack of macroporous and collagen-mimicking nanofibrous structures. Thus, there is a demand for mechanically strong, extracellular matrix (ECM) mimicking scaffolds that can robustly fit complex shaped critical sized defects and simultaneously provide localized, sustained, multiple growth factor release. We therefore developed a composite, bi-phasic PCL/hydroxyapatite (HA) 3D nanofibrous (NF) scaffold for bone tissue regeneration by using our innovative electrospun-based thermally induced self-agglomeration (TISA) technique. One intriguing feature of our ECM-mimicking TISA scaffolds is that they are highly elastic and porous even after evenly coated with minerals and can easily be pressed to fit different defect shapes. Furthermore, the bio-mimetic mineral deposition technique allowed us to simultaneously encapsulate different type of drugs, e.g., proteins and small molecules, on TISA scaffolds under physiologically mild conditions. Compared to scaffolds with physically surface-adsorbed phenamil, a BMP2 signaling agonist, incorporated phenamil composite scaffolds indicated less burst release and longer lasting sustained release of phenamil with subsequently improved osteogenic differentiation of cells in vitro. Overall, our study indicated that the innovative press-fit 3D NF composite scaffold may be a robust tool for multiple-drug delivery and bone tissue engineering.

Effect of surface topography on in vitro osteoblast function and mechanical performance of 3D printed titanium

Critical-sized defects remain a significant challenge in orthopaedics. 3D printed scaffolds are a promising treatment but are still limited due to inconsistent osseous integration. The goal of the study is to understand how changing the surface roughness of 3D printed titanium either by surface treatment or artificially printing rough topography impacts the mechanical and biological properties of 3D printed titanium. Titanium tensile samples and discs were printed via laser powder bed fusion. Roughness was manipulated by post-processing printed samples or by directly printing rough features. Experimental groups in order of increasing surface roughness were Polished, Blasted, As Built, Sprouts, and Rough Sprouts. Tensile behavior of samples showed reduced strength with increasing surface roughness. MC3T3 pre-osteoblasts were seeded on discs and analyzed for cellular proliferation, differentiation, and matrix deposition at 0, 2, and 4 weeks. Printing roughness diminished mechanical properties such as tensile strength and ductility without clear benefit to cell growth. Roughness features were printed on mesoscale, unlike samples in literature in which roughness on microscale demonstrated an increase in cell activity. The data suggest that printing artificial roughness on titanium scaffold is not an effective strategy to promote osseous integration.

Vascular Endothelial Growth Factor and Mesenchymal Stem Cells Revealed Similar Bone Formation to Allograft in a Sheep Model

Introduction

Mesenchymal stem cells (MSCs) and vascular endothelial growth factor (VEGF) are key factors in bone regeneration. Further stimulation should establish an enhanced cell environment optimal for vessel evolvement and hereby being able to attract bone-forming cells. The aim of this study was to generate new bone by using MSCs and VEGF, being able to stimulate growth equal to allograft.

Methods

Eight Texel/Gotland sheep had four titanium implants in a size of 10 × 12 mm inserted into bilateral distal femurs, containing a 2 mm gap. In the gap, autologous 3 × 10⁶ MSCs seeded on hydroxyapatite (HA) granules in combination with 10 ng, 100 ng, and 500 ng VEGF release/day were added. After 12 weeks, the implant-bone blocks were harvested, embedded, and sectioned for histomorphometric analysis. Bone formation and mechanical fixation were evaluated. Blood samples were collected for the determination of bone-related biomarkers and VEGF in serum at weeks 0, 1, 4, 8, and 12.

Results

The combination of 3 × 10⁶ MSCs with 10 ng, 100 ng, and 500 ng VEGF release/day exhibited similar amount of bone formation within the gap as allograft (P > 0.05). Moreover, no difference in mechanical fixation was observed between the groups (P > 0.05). Serum biomarkers showed no significant difference compared to baseline (all P > 0.05).

Conclusion

MSCs and VEGF exhibit significant bone regeneration, and their bone properties equal to allograft, with no systemic increase in osteogenic markers or VEGF with no visible side effects. This study indicates a possible new approach into solving the problem of insufficient allograft, in larger bone defects.

Biologization of Pcl-Mesh Using Platelet Rich Fibrin (Prf) Enhances Its Regenerative Potential In Vitro

INTRODUCTION

Resorbable synthetic scaffolds are promising for different indications, especially in the context of bone regeneration. However, they require additional biological components to enhance their osteogenic potential. In addition to different cell types, autologous blood-derived matrices offer many advantages to enhance the regenerative capacity of biomaterials. The present study aimed to analyze whether biologization of a PCL-mesh coated using differently centrifuged Platelet rich fibrin (PRF) matrices will have a positive influence on primary human osteoblasts activity in vitro. A polymeric resorbable scaffold (Osteomesh, OsteoporeTM (OP), Singapore) was combined with differently centrifuged PRF matrices to evaluate the additional influence of this biologization concept on bone regeneration in vitro. Peripheral blood of three healthy donors was used to gain PRF matrices centrifuged either at High (710× g, 8 min) or Low (44× g, 8 min) relative centrifugal force (RCF) according to the low speed centrifugation concept (LSCC). OP-PRF constructs were cultured with pOBs. POBs cultured on the uncoated OP served as a control. After three and seven days of cultivation, cell culture supernatants were collected to analyze the pOBs activity by determining the concentrations of VEGF, TGF-β1, PDGF, OPG, IL-8, and ALP- activity. Immunofluorescence staining was used to evaluate the Osteopontin expression of pOBs. After three days, the group of OP+PRFLow+pOBs showed significantly higher expression of IL-8, TGF-ß1, PDGF, and VEGF compared to the group of OP+PRFHigh+pOBs and OP+pOBs. Similar results were observed on day 7. Moreover, OP+PRFLow+pOBs exhibited significantly higher activity of ALP compared to OP+PRFHigh+pOBs and OP+pOBs. Immunofluorescence staining showed a higher number of pOBs adherent to OP+PRFLow+pOBs compared to the groups OP+PRFHigh+pOBs and OP+pOBs. To the best of our knowledge, this study is the first to investigate the osteoblasts activity when cultured on a PRF-coated PCL-mesh in vitro. The presented results suggest that PRFLow centrifuged according to LSCC exhibits autologous blood cells and growth factors, seem to have a significant effect on osteogenesis. Thereby, the combination of OP with PRFLow showed promising results to support bone regeneration. Further in vivo studies are required to verify the results and carry out potential results for clinical translation.

Bioactive glass S53P4 vs. autologous bone graft for filling defects in patients with chronic osteomyelitis and infected non-unions - a single center experience

Introduction: The goals of osteomyelitis therapy are successful control of infection and reconstruction of the bone. The gold standard for filling defects is the autologous bone graft. Bioactive glass S53P4 is an inorganic bone substitute. We compared the outcome of using bioactive glass (BAG) versus autologous bone graft (AB) in patients with infected non-union. Methods: Patients with chronic osteomyelitis and infected non-union who received either bioactive glass or autologous bone grafts between 2013 and 2017 were analyzed retrospectively. The primary endpoint was successful control of infection during follow-up. Secondary endpoints were bone healing, functional outcome, and occurrence of complications. Results: Eighty-three patients were analyzed (BAG n=51, AB n=32). Twenty-one patients experienced reinfection (BAG n=15, 29 %; AB n=6, 19 %). Seventy-eight patients achieved full weight bearing (BAG n=47, 92 %; AB n=31, 97 %). Sixty-four patients had complete bone healing at the end of the follow-up period (BAG n=39, 77 %; AB n=25, 78 %). There were no significant differences between the groups with respect to the primary or secondary endpoints. Patients with multidrug-resistant pathogens had a significantly higher rate of incomplete bone healing (p=0.033) and a 3-fold higher risk of complications in both groups. Conclusions: Bioactive glass appears to be a suitable bone substitute not only for successful control of infection and defect filling but also for bone healing in cases of infected non-union. In our study, bioactive glass was neither superior nor inferior to autologous bone graft with regard to the primary and secondary endpoints. Further studies with larger numbers of patients are required.

A Review of Bioactive Glass/Natural Polymer Composites: State of the Art

Collagen, gelatin, silk fibroin, hyaluronic acid, chitosan, alginate, and cellulose are biocompatible and non-cytotoxic, being attractive natural polymers for medical devices for both soft and hard tissues. However, such natural polymers have low bioactivity and poor mechanical properties, which limit their applications. To tackle these drawbacks, collagen, gelatin, silk fibroin, hyaluronic acid, chitosan, alginate, and cellulose can be combined with bioactive glass (BG) nanoparticles and microparticles to produce composites. The incorporation of BGs improves the mechanical properties of the final system as well as its bioactivity and regenerative potential. Indeed, several studies have demonstrated that polymer/BG composites may improve angiogenesis, neo-vascularization, cells adhesion, and proliferation. This review presents the state of the art and future perspectives of collagen, gelatin, silk fibroin, hyaluronic acid, chitosan, alginate, and cellulose matrices combined with BG particles to develop composites such as scaffolds, injectable fillers, membranes, hydrogels, and coatings. Emphasis is devoted to the biological potentialities of these hybrid systems, which look rather promising toward a wide spectrum of applications.

Supramolecular self-assembling peptides to deliver bone morphogenetic proteins for skeletal regeneration

Recombinant human bone morphogenetic proteins (BMPs) have shown clinical success in promoting bone healing, but they are also associated with unwanted side effects. The development of improved BMP carriers that can retain BMP at the defect site and maximize its efficacy would decrease the therapeutic BMP dose and thus improve its safety profile. In this review, we discuss the advantages of using self-assembling peptides, a class of synthetic supramolecular biomaterials, to deliver recombinant BMPs. Peptide amphiphiles (PAs) are a broad class of self-assembling peptides, and the use of PAs for BMP delivery and bone regeneration has been explored extensively over the past decade. Like many self-assembling peptide systems, PAs can be designed to form nanofibrous supramolecular biomaterials in which molecules are held together by non-covalent bonds. Chemical and biological functionality can be added to PA nanofibers, through conjugation of chemical moieties or biological epitopes to PA molecules. For example, PA nanofibers have been designed to bind heparan sulfate, a natural polysaccharide that is known to bind BMPs and potentiate their signal. Alternatively, PA nanofibers have been designed to synthetically mimic the structure and function of heparan sulfate, or to directly bind BMP specifically. In small animal models, these bio-inspired PA materials have shown the capacity to promote bone regeneration using BMP at doses 10-100 times lower than established therapeutic doses. These promising results have motivated further evaluation of PAs in large animal models, where their safety and efficacy must be established before clinical translation. We conclude with a discussion on the possiblity of combining PAs with other materials used in orthopaedic surgery to maximize their utility for clinical translation.

Synergistic anti-inflammatory and osteogenic n-HA/resveratrol/chitosan composite microspheres for osteoporotic bone regeneration

The development of functional materials for osteoporosis is ultimately required for bone remodeling. However, grafts were accompanied by increasing pro-inflammatory cytokines that impaired bone formation. In this work, nano-hydroxyapatite (n-HA)/resveratrol (Res)/chitosan (CS) composite microspheres were designed to create a beneficial microenvironment and help improve the osteogenesis by local sustained release of Res. Study of in vitro release confirmed the feasibility of n-HA/Res/CS microspheres for controlled Res release. Notably, microspheres had anti-inflammatory activity evidenced by the decreased expression of pro-inflammatory cytokines TNF-α, IL-1β and iNOS in RAW264.7 cells in a dose dependent manner. Further, enhanced adhesion and proliferation of BMSCs seeded onto microspheres demonstrated that composite microspheres were conducive to cell growth. The ability to enhance osteo-differentiation was supported by up-regulation of Runx2, ALP, Col-1 and OCN, and substantial mineralization in osteogenic medium. When implanted into bone defects in the osteoporotic rat femoral condyles, enhanced entochondrostosis and bone regeneration suggested that the n-HA/Res/CS composite microspheres were more favorable for impaired fracture healing. The results indicated that optimized n-HA/Res/CS composite microspheres could serve as promising multifunctional fillers for osteoporotic bone defect/fracture treatment.

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The microspheres with sustained Res release possessed obvious anti-inflammatory activity.

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The microspheres were favorable for cell growth and osteo-differentiation.

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Higher Res-loaded microspheres significantly improved entochondrostosis and bone remodeling.

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The microspheres are promising bone fillers for the healing of osteoporotic bone defects/fractures.

Innovative Molecular and Cellular Therapeutics in Cleft Palate Tissue Engineering

Clefts of the lip and/or palate are the most prevalent orofacial birth defects occurring in about 1:700 live human births worldwide. Early postnatal surgical interventions are extensive and staged to bring about optimal growth and fusion of palatal shelves. Severe cleft defects pose a challenge to correct with surgery alone, resulting in complications and sequelae requiring life-long, multidisciplinary care. Advances made in materials science innovation, including scaffold-based delivery systems for precision tissue engineering, now offer new avenues for stimulating bone formation at the site of surgical correction for palatal clefts. In this study, we review the present scientific literature on key developmental events that can go awry in palate development and the common surgical practices and challenges faced in correcting cleft defects. How key osteoinductive pathways implicated in palatogenesis inform the design and optimization of constructs for cleft palate correction is discussed within the context of translation to humans. Finally, we highlight new osteogenic agents and innovative delivery systems with the potential to be adopted in engineering-based therapeutic approaches for the correction of palatal defects. Impact statement Tissue-engineered scaffolds supplemented with osteogenic growth factors have attractive, largely unexplored possibilities to modulate molecular signaling networks relevant to driving palatogenesis in the context of congenital anomalies (e.g., cleft palate). Constructs that address this need may obviate current use of autologous bone grafts, thereby avoiding donor-site morbidity and other regenerative challenges in patients afflicted with palatal clefts. Combinations of biomaterials and drug delivery of diverse regenerative cues and biologics are currently transforming strategies exploited by engineers, scientists, and clinicians for palatal cleft repair.

Relationship between the morphological, mechanical and permeability properties of porous bone scaffolds and the underlying microstructure

Bone scaffolds are widely used as one of the main bone substitute materials. However, many bone scaffold microstructure topologies exist and it is still unclear which topology to use when designing scaffold for a specific application. The aim of the present study was to reveal the mechanism of the microstructure-driven performance of bone scaffold and thus to provide guideline on scaffold design. Finite element (FE) models of five TPMS (Diamond, Gyroid, Schwarz P, Fischer-Koch S and F-RD) and three traditional (Cube, FD-Cube and Octa) scaffolds were generated. The effective compressive and shear moduli of scaffolds were calculated from the mechanical analysis using the FE unit cell models with the periodic boundary condition. The scaffold permeability was calculated from the computational fluid dynamics (CFD) analysis using the 4×4×4 FE models. It is revealed that the surface-to-volume ratio of the Fischer-Koch S-based scaffold is the highest among the scaffolds investigated. The mechanical analysis revealed that the bending deformation dominated structures (e.g., the Diamond, the Gyroid, the Schwarz P) have higher effective shear moduli. The stretching deformation dominated structures (e.g., the Schwarz P, the Cube) have higher effective compressive moduli. For all the scaffolds, when the same amount of change in scaffold porosity is made, the corresponding change in the scaffold relative shear modulus is larger than that in the relative compressive modulus. The CFD analysis revealed that the structures with the simple and straight pores (e.g., Cube) have higher permeability than the structures with the complex pores (e.g., Fischer-Koch S). The main contribution of the present study is that the relationship between scaffold properties and the underlying microstructure is systematically investigated and thus some guidelines on the design of bone scaffolds are provided, for example, in the scenario where a high surface-to-volume ratio is required, it is suggested to use the Fischer-Koch S based scaffold.

Osteoporotic Goat Spine Implantation Study Using a Synthetic, Resorbable Ca/P/S-Based Bone Substitute

One primary purpose of the present study is to clarify whether the highly porous, resorbable Ca/P/S-based bone substitute used in this study would still induce an osteoporotic bone when implanted into the osteoporotic vertebral defects of ovariectomized (OVX) goats, or the newly-grown bone would expectantly be rather healthy bone. The bone substitute material used for the study is a synthetic, 100% inorganic, highly porous and fast-resorbable Ca/P/S-based material (Ezechbone^® Granule CBS-400). The results show that the OVX procedure along with a low calcium diet and breeding away from light can successfully induce osteoporosis in the present female experimental goats. The histological examination reveals a newly-formed trabecular bone network within the surgically-created defect of the CBS-400-implanted (OVX_IP) goat. This new trabecular bone network in the OVX_IP goat appears much denser than the OVX goat and comparable to the healthy control goat. Histomorphometry show that, among all the experimental goats, the OVX_IP goat has the highest trabecular thickness and lowest trabecular bone packet prevalence. The differences in trabecular plate separation, trabecular number and trabecular bone tissue area ratio between the OVX_IP goat and the control goat are not significant, indicating that the trabecular bone architecture of the OVX_IP goat has substantially recovered to the normal level in about 6 months after implantation without signs of osteoporosis-related delay in the bone maturing process. The quick and nicely recovered trabecular architecture parameters observed in the OVX_IP goat indicate that the present Ca/P/S-based bone substitute material has a high potential to treat osteoporotic fractures.

Single-stage treatment of chronic localized tibial osteomyelitis with local debridement and antibiotic-loaded calcium sulfate implantation: a retrospective study of 42 patients

Background

Although various methods have been introduced, the management of chronic tibial osteomyelitis remains a challenge. This study aims to assess a combined treatment method, local debridement combined with antibiotic-loaded calcium sulfate implantation, for the management of the local (Cierny-Mader type III) tibial osteomyelitis.

Methods

Forty-two patients (43 limbs) with type III tibial osteomyelitis, from January 2012 to December 2018, who received the treatment method mentioned above were included in the study. The infection remission rate, recurrence rate, complications rate, and bone healing rate were respectively analyzed.

Results

With a mean follow-up of 42.8 months, 38 limbs (37 patients) (88.4%, 38/43) achieved infection remission without recurrence. Among those patients pain, limitation of movement, sinus tracts, topical redness, and swelling were generally eliminated. Only 4 patients felt slight pain after a long-distance walk, while another 6 patients showed minor but acceptable discomfort in affected limbs. Five patients (11.6%) suffered from osteomyelitis recurrence that required secondary surgical and medical treatment, but no amputation was necessary to eliminate the infection. Prolonged aseptic drainage was the most frequent complication that was observed in 13 patients (30.0%). They were successfully managed by appropriate wound caring in 10 patients and by surgical intervention, months later, in 3 patients. According to the final X-ray examination, bone losses caused by local debridement were generally repaired, though the shape of the tibia was not well-restored to its initial form in 17 limbs. No fracture was recorded during follow-up.

Conclusion

Local debridement combined with antibiotic-loaded calcium sulfate implantation is effective and safe in a single-stage treatment of chronic Cierny-Mader III tibial osteomyelitis.

Hybrid Bone Scaffold Induces Bone Bridging in Goat Calvarial Critical Size Defects Without Growth Factor Augmentation

Abstract

In the present study, a series of four different scaffolds were comparatively evaluated in a goat calvarial critical size defect model. Such studies are only rarely reported in the literature. In our work, E1001(1k), a member of a large combinational library of tyrosine-derived polycarbonates (TyrPC), was used to prepare two calcium phosphate hybrid, biodegradable bone scaffolds. In one formulation, the widely used β-tricalcium phosphate (β-TCP) was incorporated into the polymer scaffold. In the second formulation, a coating of dicalcium phosphate dihydrate (DCPD, also known as brushite) was used as the mineral phase. These scaffolds were evaluated for bone regeneration in goat calvarial 20-mm critical size defects (CSD) after 16 weeks. Results were compared with chronOS (a clinically used product) and E1001(1k)/β-TCP scaffolds, augmented with 400 μg of recombinant human bone morphogenetic protein-2 (rhBMP-2). Microcomputed tomography (micro-CT) and histomorphometry were used to assess bone regeneration within the defects. Histomorphometry showed that rhBMP-2-augmented E1001(1k)/β-TCP scaffolds completely healed the defect in all animals within 16 weeks. Among the hybrid scaffolds that were not augmented with rhBMP-2, the degree of bone regeneration within the defect area was low for the clinically used chronOS, which is a poly(lactide co-ε-caprolactone)/β-TCP hybrid scaffold. Similar results were obtained for E1001(1k)/β-TCP scaffolds, indicating that replacing poly(lactide co-ε-caprolactone) with E1001(1k) does not improve bone regeneration is this model. However, a statistically significant improvement of bone regeneration was observed for E1001(1k)/DCPD scaffolds. These scaffolds resulted in significant levels of bone regeneration in all animals and in complete bridging of the defect in three of six tests. This is the first report of a synthetic bone scaffold being able to heal a critical size calvarial defect in a large animal model without the addition of exogenous growth factors.

Lay Summary

Reconstruction of large bone defects is a significant clinical problem. The overwhelming majority of all research results are obtained in vitro or in small animal models (mouse, rat, rabbit) that cannot predict the clinical outcomes in humans. We address this problem by conducting our studies in a goat calvarial critical size defect model, which is widely regarded as predictive of human outcomes. Among the three rhBMP-2-free scaffolds tested, only one specific formulation, E1001(1k)/DCPD, resulted in massive bone ingrowth into the center of the defect in all animals and in complete bridging of the defect 50% of the animals. This is the first time, a synthetic bone scaffold was able to heal a critical size calvarial defect in a large animal model without the addition of biological growth factors. Given the high cost of biologically enhanced bone grafts and the regulatory complexities of their FDA market clearance, the development of E1001(1k)/DCPD hybrid scaffolds addresses a significant clinical need.

Injection Molding of 3-3 Hydroxyapatite Composites

The manufacturing of ideal implants requires fabrication processes enabling an adjustment of the shape, porosity and pore sizes to the patient-specific defect. To meet these criteria novel porous hydroxyapatite (HAp) implants were manufactured by combining ceramic injection molding (CIM) with sacrificial templating. Varied amounts (Φ = 0–40 Vol%) of spherical pore formers with a size of 20 µm were added to a HAp-feedstock to generate well-defined porosities of 11.2–45.2 Vol% after thermal debinding and sintering. At pore former contents Φ ≥ 30 Vol% interconnected pore networks were formed. The investigated Young’s modulus and flexural strength decreased with increasing pore former content from 97.3 to 29.1 GPa and 69.0 to 13.0 MPa, agreeing well with a fitted power-law approach. Additionally, interpenetrating HAp/polymer composites were manufactured by infiltrating and afterwards curing of an urethane dimethacrylate-based (UDMA) monomer solution into the porous HAp ceramic preforms. The obtained stiffness (32–46 GPa) and Vickers hardness (1.2–2.1 GPa) of the HAp/UDMA composites were comparable to natural dentin, enamel and other polymer infiltrated ceramic network (PICN) materials. The combination of CIM and sacrificial templating facilitates a near-net shape manufacturing of complex shaped bone and dental implants, whose properties can be directly tailored by the amount, shape and size of the pore formers.

Characterization of Naturally Occurring Bioactive Factor Mixtures for Bone Regeneration

In this study, the bone-regenerative potential of bioactive factors derived from adipose tissue, platelet-rich plasma (PRP) and conditioned medium from hypoxia-treated human telomerase immortalized bone-marrow-derived mesenchymal stem cells (hTERT-MSC) was investigated in vitro with the aim to develop cost-effective and efficient bone substitutes for optimized regeneration of bone defects. Adipose tissue was harvested from human donors undergoing reconstructive surgery, and adipose tissue extract (ATE) was prepared. Platelet lysates (PL) were produced by repeated freeze-thaw cycles of PRP, and hypoxia-conditioned medium (HCM) was obtained by culturing human telomerase immortalized bone-marrow-derived mesenchymal stromal cells for 5 days with 1% O2. Besides analysis by cytokine and angiogenesis arrays, ELISA was performed. Angiogenic potential was investigated in cocultures of bone-marrow-derived (BM)-MSC and human umbilical vein endothelial cells. Multiple angiogenic proteins and cytokines were detected in all growth factor mixtures. HCM and ATE contained high amounts of angiogenin and CCL2/MCP-1, whereas PL contained high amounts of IGFBP-1. Culturing cells with HCM and ATE significantly increased specific ALP activity of BM-MSC as well as tubule length and junctions of endothelial networks, indicating osteogenic and angiogenic stimulation. To achieve a synergism between chemoattractive potential and osteogenic and angiogenic differentiation capacity, a combination of different growth factors appears promising for potential clinical applications.

Randomized Controlled Clinical Trial of Nanostructured Carbonated Hydroxyapatite for Alveolar Bone Repair

The properties of the biodegradation of bone substitutes in the dental socket after extraction is one of the goals of regenerative medicine. This double-blind, randomized, controlled clinical trial aimed to compare the effects of a new bioabsorbable nanostructured carbonated hydroxyapatite (CHA) with a commercially available bovine xenograft (Bio-Oss^®) and clot (control group) in alveolar preservation. Thirty participants who required tooth extraction and implant placement were enrolled in this study. After 90 days, a sample of the grafted area was obtained for histological and histomorphometric evaluation and an implant was installed at the site. All surgical procedures were successfully carried out without complications and none of the patients were excluded. The samples revealed a statistically significant increase of new bone formation (NFB) in the CHA group compared with Bio-Oss^® after 90 days from surgery (p < 0.05). However, the clot group presented no differences of NFB compared to CHA and Bio-Oss^®. The CHA group presented less amount of reminiscent biomaterial compared to Bio-Oss^®. Both biomaterials were considered osteoconductors, easy to handle, biocompatible, and suitable for alveolar filling. Nanostructured carbonated hydroxyapatite spheres promoted a higher biodegradation rate and is a promising biomaterial for alveolar socket preservation before implant treatment.

Investigating the Osteoinductive Potential of a Decellularized Xenograft Bone Substitute

Bone grafting is the second most common tissue transplantation procedure worldwide. One of the alternative methods for bone repair under investigation is a tissue-engineered bone substitute. An ideal property of tissue-engineered bone substitutes is osteoinductivity, defined as the ability to stimulate primitive cells to differentiate into a bone-forming lineage. In the current study, we use a decellularization and oxidation protocol to produce a porcine bone scaffold and examine whether it possesses osteoinductive potential and can be used to create a tissue-engineered bone microenvironment. The decellularization protocol was patented by our lab and consists of chemical decellularization and oxidation steps using combinations of deionized water, trypsin, antimicrobials, peracetic acid, and triton-X100. To test if the bone scaffold was a viable host, preosteoblasts were seeded and analyzed for markers of osteogenic differentiation. The osteoinductive potential was observed in vitro with similar osteogenic markers being expressed in preosteoblasts seeded on the scaffolds and demineralized bone matrix. To assess these properties in vivo, scaffolds with and without preosteoblasts preseeded were subcutaneously implanted in mice for 4 weeks. MicroCT scanning revealed 1.6-fold increased bone volume to total volume ratio and 1.4-fold increase in trabecular thickness in scaffolds after implantation. The histological analysis demonstrates new bone formation and blood vessel formation with pentachrome staining demonstrating osteogenesis and angiogenesis, respectively, within the scaffold. Furthermore, CD31+ staining confirmed the endothelial lining of the blood vessels. These results demonstrate that porcine bone maintains its osteoinductive properties after the application of a patented decellularization and oxidation protocol developed in our laboratory. Future work must be performed to definitively prove osteogenesis of human mesenchymal stem cells, biocompatibility in large animal models, and osteoinduction/osseointegration in a relevant clinical model in vivo. The ability to create a functional bone microenvironment using decellularized xenografts will impact regenerative medicine, orthopedic reconstruction, and could be used in the research of multiple diseases.

Recombinant Human Bone Morphogenetic Protein 7 Exerts Osteo-Catabolic Effects on Bone Grafts That Outweigh Its Osteo-Anabolic Capacity

This study aimed to investigate the effects of recombinant human bone morphogenetic protein (rhBMP-7) on human cancellous bone grafts (BGs) while differentiating between anabolic and catabolic events. Human BGs alone or supplemented with rhBMP-7 were harvested 14 weeks after subcutaneous implantation into NOD/Scid mice, and studied via micro-CT, histomorphometry, immunohistochemistry and flow cytometry. Immunohistochemical staining for human-specific proteins made it possible to differentiate between grafted human bone and newly formed murine bone. Only BGs implanted with rhBMP-7 formed an ossicle containing a functional hematopoietic compartment. The total ossicle volume in the BMP⁺ group was higher than in the BMP^- group (835 mm³ vs. 365 mm³, respectively, p < 0.001). The BMP⁺ group showed larger BM spaces (0.47 mm vs. 0.28 mm, p = 0.002) and lower bone volume-to-total volume ratio (31% vs. 47%, p = 0.002). Immunohistochemical staining for human-specific proteins confirmed a higher ratio of newly formed bone area (murine) to total area (0.12 vs. 0.001, p < 0.001) in the BMP+ group, while the ratio of grafted bone (human) area to total area was smaller (0.14 vs. 0.34, p = 0.004). The results demonstrate that rhBMP-7 induces BG resorption at a higher rate than new bone formation while creating a haematopoietic niche. Clinicians therefore need to consider the net catabolic effect when rhBMP-7 is used with BGs. Overall, this model indicates its promising application to further decipher BMPs action on BGs and its potential in complex bone tissue regeneration.

Tissue Engineering: What is New?

Soft and hard tissue engineering has expanded the frontiers of oral/maxillofacial augmentation. Soft tissue grafting enhancements include improving flap prevascularization and using stem cells and other cells to create not only the graft, but also the vascularization and soft tissue scaffolding for the graft. Hard tissue grafts have been enhanced by osteoinductive factors, such as bone morphogenic proteins, that have allowed the elimination of harvesting autogenous bone and thus decrease the need for other surgical sites. Advancements in bone graft scaffolds have developed via seeding with stem cells and improvement of the silica/calcium/phosphate composite to improve graft characteristics and healing.

Lysostaphin and BMP-2 co-delivery reduces S. aureus infection and regenerates critical-sized segmental bone defects

Staphylococcus aureus is the most common pathogen associated with bacterial infections in orthopedic procedures. Infections often lead to implant failure and subsequent removal, motivating the development of bifunctional materials that both promote repair and prevent failure due to infection. Lysostaphin is an anti-staphylococcal enzyme resulting in bacterial lysis and biofilm reduction. Lysostaphin use is limited by the lack of effective delivery methods to provide sustained, high doses of enzyme to infection sites. We engineered a BMP-2-loaded lysostaphin-delivering hydrogel that simultaneously prevents S. aureus infection and repairs nonhealing segmental bone defects in the murine radius. Lysostaphin-delivering hydrogels eradicated S. aureus infection and resulted in mechanically competent bone. Cytokine and immune cell profiling demonstrated that lysostaphin-delivering hydrogels restored the local inflammatory environment to that of a sterile injury. These results show that BMP-2-loaded lysostaphin-delivering hydrogel therapy effectively eliminates S. aureus infection while simultaneously regenerating functional bone resulting in defect healing.

Biomechanical Evaluation of Promising Different Bone Substitutes in a Clinically Relevant Test Set-Up

(1) Background: Bone substitutes are essential in orthopaedic surgery to fill up large bone defects. Thus, the aim of the study was to compare diverse bone fillers biomechanically to each other in a clinical-relevant test set-up and to detect differences in stability and handling for clinical use. (2) Methods: This study combined compressive strength tests and screw pullout-tests with dynamic tests of bone substitutes in a clinical-relevant biomechanical fracture model. Beyond well-established bone fillers (ChronOS^TM Inject and Graftys^® Quickset), two newly designed bone substitutes, a magnesium phosphate cement (MPC) and a drillable hydrogel reinforced calcium phosphate cement (CPC), were investigated. (3) Results: The drillable CPC revealed a comparable displacement of the fracture and maximum load to its commercial counterpart (Graftys^® Quickset) in the clinically relevant biomechanical model, even though compressive strength and screw pullout force were higher using Graftys^®. (4) Conclusions: The in-house-prepared cement allowed unproblematic drilling after replenishment without a negative influence on the stability. A new, promising bone substitute is the MPC, which showed the best overall results of all four cement types in the pure material tests (highest compressive strength and screw pullout force) as well as in the clinically relevant fracture model (lowest displacement and highest maximum load). The low viscosity enabled a very effective interdigitation to the spongiosa and a complete filling up of the defect, resulting in this demonstrated high stability. In conclusion, the two in-house-developed bone fillers revealed overall good results and are budding new developments for clinical use.

Adipose-derived stem cell sheets accelerate bone healing in rat femoral defects

In the present study, we investigated whether both adipose-derived stem cell (ADSC) and osteogenic-induced ADSC sheets could promote bone healing in a rat distal femoral metaphysis bone defect model. A through-hole defect of 1 mm diameter was drilled into each distal femur of 12 week old rats. Forty-five rats were randomly assigned to three groups: (1) control group; (2) ADSC sheet group; or (3) osteogenic-induced ADSC sheet group. We evaluated each group by analysis of computerized tomography scans every week after the surgery, histological analysis, and DiI labeling (a method of membrane staining for post implant cell tracing). Radiological and histological evaluations showed that a part of the hole persisted in the control group at four weeks after surgery, whereas the hole was restored almost completely by new bone formation in both sheet groups. The mean value of bone density (in Houndsfield units) for the bone defect area was significantly higher in both sheet groups than that in the control group (p = 0.05) at four weeks postoperative. A large number of osteocalcin positive osteoblasts were observed at the area of bone defect, especially in the osteogenic-induced ADCS sheet group. DiI labeling in the newly formed bone showed that each sheet had differentiated into bone tissue at four weeks after surgery. The ADSC and the osteogenic-induced ADSC sheets promoted significantly quicker bone healing in the bone defect. Moreover, the osteogenic-induced ADSC sheet may be more advantageous for bone healing than the ADSC sheet because of the higher number of osteocalcin positive osteoblasts via the transplantation.

A parameterised mathematical model to elucidate osteoblast cell growth in a phosphate-glass microcarrier culture

Tissue engineering has the potential to augment bone grafting. Employing microcarriers as cell-expansion vehicles is a promising bottom-up bone tissue engineering strategy. Here we propose a collaborative approach between experimental work and mathematical modelling to develop protocols for growing microcarrier-based engineered constructs of clinically relevant size. Experiments in 96-well plates characterise cell growth with the model human cell line MG-63 using four phosphate glass microcarrier materials. Three of the materials are doped with 5 mol% TiO₂ and contain 0%, 2% or 5% CoO, and the fourth material is doped only with 7% TiO₂ (0% CoO). A mathematical model of cell growth is parameterised by finding material-specific growth coefficients through data-fitting against these experiments. The parameterised mathematical model offers more insight into the material performance by comparing culture outcome against clinically relevant criteria: maximising final cell number starting with the lowest cell number in the shortest time frame. Based on this analysis, material 7% TiO₂ is identified as the most promising.