Application of scaffolds for bone regeneration strategies: current trends and future directions

Bone tissue regeneration by 58S bioactive glass scaffolds containing exosome: an in vivo study

Exosomes, the naturally secreted nanocarriers of cells, have recently been demonstrated to have therapeutic benefits in a variety of disease models where parent cells are not present. However, the use of exosomes in bone defect regeneration has been unusual, and little is documented about the underlying processes. In recent study we produced and characterized exosomes derived human endometrial mesenchymal stem stromal cells and 58S bioactive glass scaffolds; in following, in this research exosome loaded scaffolds synthetized and release of exosome, porosity and bioactivity of them were assessed. More over the effect of scaffolds on repair of critical-size bone defects in rat's calvaria was evaluated by histological examination and micro computed tomography (µ CT). The findings confirmed that constructed porous scaffolds consistently release exosomes; additionally, in vivo findings including Hematoxilin & Eosin staining, Immunohistochemistry, Masson's trichrome, histomorphometric analysis, and µ CT clarified that our implant has osteogenic properties. We discovered that Exo-treated scaffolds might promote osteogenesis especially compared to pure scaffolds, indicating that produced scaffolds containing exosomes could be a potential replacement in bone tissue engineering.

Mechano-driven intervertebral bone bridging via oriented mechanical stimulus in a twist metamaterial cage: An in silico study

Stiffer cages provide sufficient mechanical support but fail to promote bone ingrowth due to stress shielding. It remains challenging for fusion cage to satisfy both bone bridging and mechanical stability. Here we designed a fusion cage based on twist metamaterial for improved bone ingrowth, and proved its superiority to the conventional diagonal-based cage in silico. The fusion process was numerically reproduced via an injury-induced osteogenesis model and the mechano-driven bone remodeling algorithm, and the outcomes fusion effects were evaluated by the morphological features of the newly-formed bone and the biomechanical behaviors of the bone-cage composite. The twist-based cages exhibited oriented bone formation in the depth direction, in comparison to the diagonal-based cages. The axial stiffness of the bone-cage composites with twist-based cages was notably higher than that with diagonal-based cages; meanwhile, the ranges of motion of the twist-based fusion segment were lower. It was concluded that the twist metamaterial cages led to oriented bone ingrowth, superior mechanical stability of the bone-cage composite, and less detrimental impacts on the adjacent bones. More generally, metamaterials with a tunable displacement mode of struts might provide more design freedom in implant designs to offer customized mechanical stimulus for osseointegration.

Multifunctional dendrimer@nanoceria engineered GelMA hydrogel accelerates bone regeneration through orchestrated cellular responses

Bone defects in patients entail the microenvironment that needs to boost the functions of stem cells (e.g., proliferation, migration, and differentiation) while alleviating severe inflammation induced by high oxidative stress. Biomaterials can help to shift the microenvironment by regulating these multiple events. Here we report multifunctional composite hydrogels composed of photo-responsive Gelatin Methacryloyl (GelMA) and dendrimer (G3)-functionalized nanoceria (G3@nCe). Incorporation of G3@nCe into GelMA could enhance the mechanical properties of hydrogels and their enzymatic ability to clear reactive oxygen species (ROS). The G3@nCe/GelMA hydrogels supported the focal adhesion of mesenchymal stem cells (MSCs) and further increased their proliferation and migration ability (vs. pristine GelMA and nCe/GelMA). Moreover, the osteogenic differentiation of MSCs was significantly stimulated upon the G3@nCe/GelMA hydrogels. Importantly, the capacity of G3@nCe/GelMA hydrogels to scavenge extracellular ROS enabled MSCs to survive against H₂O₂-induced high oxidative stress. Transcriptome analysis by RNA sequencing identified the genes upregulated and the signalling pathways activated by G3@nCe/GelMA that are associated with cell growth, migration, osteogenesis, and ROS-metabolic process. When implanted subcutaneously, the hydrogels exhibited excellent tissue integration with a sign of material degradation while the inflammatory response was minimal. Furthermore, G3@nCe/GelMA hydrogels demonstrated effective bone regeneration capacity in a rat critical-sized bone defect model, possibly due to an orchestrated capacity of enhancing cell proliferation, motility and osteogenesis while alleviating oxidative stress.

Collagen membrane from bovine pericardium for treatment of long bone defect

The treatment of bone regeneration failures has been constantly improved with the study of new biomaterials. Techgraft® is a collagen membrane derived from bovine pericardium, which has been shown to have biocompatibility and effectiveness in tissue repair. However, its use in orthopedics has not yet been evaluated. Therefore, the purpose of this study was to characterize a bovine pericardium collagen membrane and evaluate the effects of its use in the regeneration of a bone defect in rat tibia. Scanning electron microscopy, atomic force microscopy, weight lost and water uptake tests, and mechanical test were performed. Afterwards, the membrane was tested in an experimental study, using 12 male Sprague Dawley rats. A bone defect was surgically made in tibiae of animals, which were assigned to two groups (n = 6): bone defect treated with collagen membrane (TG) and bone defect without treatment (CONT). Then, tibiae were submitted to micro-CT. The membranes preserved their natural collagen characteristics, presenting great strength, high water absorption, hydrophilicity, and almost complete dissolution in 30 days. In the experimental study, the membrane enhanced the growth of bone tissue in contact with its surface. A higher bone volume and trabeculae number and less trabecular space was observed in bone defects of the membrane group compared to the control group at 21 days. In conclusion, the Techgraft membrane seems to have favorable characteristics for treatment of long bone repair.

Exosome loaded hydroxyapatite (HA) scaffold promotes bone regeneration in calvarial defect: an in vivo study

In this study, hydroxyapatite (HA) scaffolds were synthesized and characterized, following the osteogenic and angiogenic effects of HA scaffolds with or without endometrial mesenchymal stem stromal cells (hEnSCs) derived Exosomes were investigated in rat animal model with calvaria defect. The X-ray diffraction (XRD) analysis of HA powder formation was confirmed with Joint Corporation of Powder Diffraction Standards (JCPDS) files numbers of 34-0010 and 24-0033A and Ball mill, and sintering manufactured Nano-size particles. Obtained results containing FE-SEM images presented that the surface of scaffolds has a rough and porous structure, which makes them ideal and appropriate for tissue engineering. Additionally, the XRD showed that these scaffolds exhibited a crystallized structure without undergoing phase transformation; meanwhile, manufactured scaffolds consistently release exosomes; moreover, in vivo findings containing hematoxylin-eosin staining, immunohistochemistry, Masson's trichrome staining, and histomorphometric analysis confirmed that our implant has an osteogenic and angiogenic characteristic. So prepared scaffolds containing exosomes can be proposed as a promising substitute in tissue engineering.

Guiding bone formation using semi-onlay calcium phosphate implants in an ovine calvarial model

The restoration of cranio‐maxillofacial deformities often requires complex reconstructive surgery in a challenging anatomical region, with abnormal soft tissue structures and bony deficits. In this proof‐of‐concept, the possibility of vertical bone augmentation was explored by suspending hemispherically shaped titanium‐reinforced porous calcium phosphate (CaP) implants (n = 12) over the frontal bone in a sheep model (n = 6). The animals were euthanized after week 13 and the specimens were subject to micro‐computed tomography (μCT) and comprehensive histological analysis. Histology showed that the space between implant and the recipient bone was filled with a higher percentage of newly formed bone (NFB) versus soft tissue with a median of 53% and 47%, respectively. Similar results were obtained from the μ‐CT analysis, with a median of 56% NFB and 44% soft tissue filling the void. Noteworthy, significantly higher bone‐implant contact was found for the CaP (78%, range 14%–94%) versus the Titanium (29%, range 0%–75%) portion of the implant exposed to the surrounding bone. The histological analysis indicates that the CaP replacement by bone is driven by macrophages over time, emphasized by material‐filled macrophages found in close vicinity to the CaP with only a small number of single osteoclasts found actively remodeling the NFB. This study shows that CaP based implants can be assembled with the help of additive manufacturing to guide vertical bone formation without decortification or administration of growth factors. Furthermore, it highlights the potential disadvantage of a seamless fit between the implant and the recipient's bone.

Delivery of synthetic mRNAs for tissue regeneration

In recent years, nucleic acid-based therapeutics have gained increasing importance as novel treatment options for disease prevention and treatment. Synthetic messenger RNAs (mRNAs) are promising nucleic acid-based drugs to transiently express desired proteins that are missing or defective. Recently, synthetic mRNA-based vaccines encoding viral proteins have been approved for emergency use against COVID-19. Various types of vehicles, such as lipid nanoparticles (LNPs) and liposomes, are being investigated to enable the efficient uptake of mRNA molecules into desired cells. In addition, the introduction of novel chemical modifications into mRNAs increased the stability, enabled the modulation of nucleic acid-based drugs, and increased the efficiency of mRNA-based therapeutic approaches. In this review, novel and innovative strategies for the delivery of synthetic mRNA-based therapeutics for tissue regeneration are discussed. Moreover, with this review, we aim to highlight the versatility of synthetic mRNA molecules for various applications in the field of regenerative medicine and also discuss translational challenges and required improvements for mRNA-based drugs.

Modern approaches on stem cells and scaffolding technology for osteogenic differentiation and regeneration

The process of bone repair has always been a natural mystery. Although bones do repair themselves, supplemental treatment is required for the initiation of the self-regeneration process. Predominantly, surgical procedures are employed for bone regeneration. Recently, cell-based therapy for bone regeneration has proven to be more effective than traditional methods, as it eliminates the immune risk and painful surgeries. In clinical trials, various stem cells, especially mesenchymal stem cells, have shown to be more efficient for the treatment of several bone-related diseases, such as non-union fracture, osteogenesis imperfecta, osteosarcoma, and osteoporosis. Furthermore, the stem cells grown in a suitable three-dimensional scaffold support were found to be more efficient for osteogenesis. It has been shown that the three-dimensional bioscaffolds support and simulate an in vivo environment, which helps in differentiation of stem cells into bone cells. Bone regeneration in patients with bone disorders can be improved through modification of stem cells with several osteogenic factors or using stem cells as carriers for osteogenic factors. In this review, we focused on the various types of stem cells and scaffolds that are being used for bone regeneration. In addition, the molecular mechanisms of various transcription factors, signaling pathways that support bone regeneration and the senescence of the stem cells, which limits bone regeneration, have been discussed.

Osseointegration Improvement of Co-Cr-Mo Alloy Produced by Additive Manufacturing

Cobalt-base alloys (Co-Cr-Mo) are widely employed in dentistry and orthopedic implants due to their biocompatibility, high mechanical strength and wear resistance. The osseointegration of implants can be improved by surface modification techniques. However, complex geometries obtained by additive manufacturing (AM) limits the efficiency of mechanical-based surface modification techniques. Therefore, plasma immersion ion implantation (PIII) is the best alternative, creating nanotopography even in complex structures. In the present study, we report the osseointegration results in three conditions of the additively manufactured Co-Cr-Mo alloy: (i) as-built, (ii) after PIII, and (iii) coated with titanium (Ti) followed by PIII. The metallic samples were designed with a solid half and a porous half to observe the bone ingrowth in different surfaces. Our results revealed that all conditions presented cortical bone formation. The titanium-coated sample exhibited the best biomechanical results, which was attributed to the higher bone ingrowth percentage with almost all medullary canals filled with neoformed bone and the pores of the implant filled and surrounded by bone ingrowth. It was concluded that the metal alloys produced for AM are biocompatible and stimulate bone neoformation, especially when the Co-28Cr-6Mo alloy with a Ti-coated surface, nanostructured and anodized by PIII is used, whose technology has been shown to increase the osseointegration capacity of this implant.

Development of collagen/nanohydroxyapatite scaffolds containing plant extract intended for bone regeneration

In this study scaffolds of nanohydroxyapatite (nHA) and anionic collagen (C) combined with plant extracts intended for bone tissue repair were developed. Grape seed (P), pomegranate peel (R) and jabuticaba peel (J) extracts were used as collagen crosslinker agents in order to improve the materials properties. All crude extracts were effective against Staphylococcus aureus, but only for CR scaffold inhibition zone was noticed. The extracts acted as crosslinking agents, increasing enzymatic resistance and thermal stability of collagen. The extracts showed cytotoxicity at the concentrations tested, while nHA increased cell viability. The scaffolds presented porosity and pore size appropriate for bone growth. CR, CnHAP, CnHAR and CnHAJ increased the cell viability after 24 h. The combination of collagen, nHA and plant extracts offers a promising strategy to design novel biomaterials for bone tissue regeneration.

In-situ analysis of the hydration ability of bone graft material using a synchrotron radiation X-ray micro-CT

The conventional micro-computed tomography (μCT) is a non-destructive imaging technique used for obtaining 2D and 3D information for scaffolds. The main composition and internal structure are important in mimicking and designing the characteristics of natural bone. This study was three-dimensional evaluating the external or internal structures and the hydration effects of bone graft materials by using the in-situ image technique. Synchrotron radiation micro-computed tomography (SR-μCT) was used to extract information on the geometry of two biphasic calcium phosphates (BCP) with identical chemicals and different micro-macro porosity, pore size distribution, and pore interconnection pathways. Volume analysis by hydration was used to measure the two bone graft materials at 0, 5, and 10-min intervals. The SR-μCT image was achieved with information regarding the internal pore structure and hydration effects evaluated under 3D visualization. Both types of bone graft materials showed structures suitable for tissue engineering applications. The SR-μCT in-situ techniques with 3D information provided a detailed view of the structures. Thus, SR-μCT could be an available, unbiased 3D alternative to in-situ analysis.

Critical-sized mandibular defect reconstruction using human dental pulp stem cells in a xenograft model-clinical, radiological, and histological evaluation

PURPOSE

This research evaluated clinical, histological, and radiological osseous regeneration in a critical-sized bilateral cortico-medullary osseous defect in model rabbits from New Zealand after receiving a hydroxyapatite matrix and polylactic polyglycolic acid (HA/PLGA) implanted with human dental pulp stem cells (DPSCs).

METHODS

Eight New Zealand rabbits with bilateral mandibular critical-sized defects were performed where one side was treated with an HA/PLGA/DPSC matrix and the other side only with an HA/PLGA matrix for 4 weeks.

RESULTS

An osseointegration was clinically observed as well as a reduction of 70% of the surgical lumen on one side and a 35% on the other. Histologically, there was neo-bone formation in HA/PLGA/DPSC scaffold and angiogenesis. A bone radiodensity (RD) of 80% was radiologically observed achieving density levels similar to mandibular bone, while the treatment with HA/PLGA matrix achieves RD levels of 40% on its highest peaks.

CONCLUSIONS

HA/PLGA/DPSC scaffold was an effective in vivo method for mandibular bone regeneration in critical-sized defects induced on rabbit models.

Study on osteogenesis of zinc-loaded carbon nanotubes/chitosan composite biomaterials in rat skull defects

Chitosan with hydroxyapatite composition, a natural polymer, may be a biomaterial of importance for bone regeneration. Carbon nanotube, a nanoscale material, has been another focus for bone restoration. Zinc, an essential trace element, contributes to the development and growth of skeletal system. The purpose of the current research was to investigate the effects of Zinc-loaded Carbon Nanotubes/Chitosan composite biomaterials in the restoration of rat skull defects, and to verify the hypothesis that these zinc ions of appropriate concentration would strengthen the osteogenesis of rat defects. Four different groups of composite biomaterials were fabricated from no Zinc Carbon nanotubes/Chitosan (GN), 0.2% Zinc-Carbon nanotubes/Chitosan (GL), 1% Zinc-Carbon nanotubes/Chitosan (GM) and 2% Zinc-Carbon nanotubes/Chitosan (GH). After characterizations, these composite biomaterials were then transplanted into rat skull defects. The experimental animals were executed at 12 weeks after transplanted surgeries, and the rat skull defects were removed for related analyses. The results of characterizations suggested the Zinc-loaded composite biomaterials possessed good mechanical and osteoinductive properties. An important finding was that the optimal osteogenic effect appeared in rat skull defects transplanted with 1% Zinc-Carbon nanotubes/Chitosan. Overall, these composite biomaterials revealed satisfactory osteogenesis, nevertheless, there was a requirement to further perfect the zinc ion concentrations to achieve the better bone regeneration.

Enhanced Osteoconductivity and Osseointegration in Calcium Polyphosphate Bioceramic Scaffold via Lithium Doping for Bone Regeneration

Calcium polyphosphate (CPP) is a novel bioceramic bone substitute, which is favored because its composition is highly similar to natural bone. According to previous studies, doping ions into CPP is an effective and convenient method for overcoming the shortcomings, such as poor osteoconductivity of CPP. Lithium (Li) is a fairly new additive to bone substitutes that brought attention due to its role in osteogenesis. The present study was conducted to assess whether doping Li into CPP could influence the microstructure, degradation, and osteoinductivity of CPP. The results found that both CPP and Li-doped CPP (LiCPP) had a single beta-CPP phase, indicating that Li did not affect the crystallized phase. SEM images revealed that both scaffolds were porous, while the surface of LiCPP was rougher and more uneven compared to CPP. Also, a better degradation property of LiCPP was observed via weight loss and ion release tests. In vitro study found that LiCPP extracts had advantages of promoting osteoblasts' proliferation and differentiation over CPP extracts. In vivo study on rabbit's cranial defects was also conducted. Microcomputed tomography and histological staining showed that LiCPP had better osteoconductivity than CPP. This study proved that doping Li into CPP is a feasible modification method, and LiCPP might be a suitable bioceramic for bone tissue engineering.

Nano hydroxyapatite induces glioma cell apoptosis by suppressing NF-κB signaling pathway

Nano-sized hydroxyapatite (nHA) particles have been demonstrated to exert anti-cancer effects on multiple cancer cell lines and animal models of cancer biology. However, the molecular mechanism underlying the effects of nHA particles on glioma cells remains unclear. The present study aimed to examine the effects of nHA on the behavior of glioma cells and investigate its underlying molecular mechanism. Rat glioma C6 cells and human glioma U87MG ATCC cells were exposed to nHA (20–100 µg/ml), and its effects on cell morphology, viability, apoptosis, cell cycle, invasion and nuclear factor (NF)-κB signaling were analyzed. Exposure of C6 and U87MG ATCC cells to 20 µg/ml nHA for 24 h caused cell detachment. Viability of C6 and U87MG ATCC cells were significantly reduced by nHA in a dose-dependent manner (P<0.05). Nuclear staining with Hoechst 33258 exhibited clear chromatin condensation in C6 cells following 24 h exposure to ≥25 µg/ml nHA. Flow cytometry revealed that nHA (20–100 µg/ml) significantly induced apoptosis and cell cycle G2/M arrest in C6 and U87MG ATCC cells (P<0.05). Transwell invasion assay demonstrated that nHA (20–60 µg/ml) significantly inhibited invasion of U87MG ATCC cells (P<0.05). Furthermore, western blotting and confocal immunofluorescence microscopy revealed that nHA (20–100 µg/ml) decreased NF-κB p65 protein expression and blocked NF-κB p65 nuclear translocation in C6 cells. The protein expression of NF-κB target molecules, such as B cell lymphoma 2, cyclooxygenase-2 and survivin, were also significantly reduced by nHA in a dose-dependent manner in both C6 and U87MG ATCC cells (P<0.05). In conclusion, it was demonstrated that the inhibitory effect of nHA on glioma cells is likely associated with the downregulation of NF-κB signaling.

Effects of Silicon Compounds on Biomineralization, Osteogenesis, and Hard Tissue Formation

Bioinspired stem cell-based hard tissue engineering includes numerous aspects: The synthesis and fabrication of appropriate scaffold materials, their analytical characterization, and guided osteogenesis using the sustained release of osteoinducing and/or osteoconducting drugs for mesenchymal stem cell differentiation, growth, and proliferation. Here, the effect of silicon- and silicate-containing materials on osteogenesis at the molecular level has been a particular focus within the last decade. This review summarizes recently published scientific results, including material developments and analysis, with a special focus on silicon hybrid bone composites. First, the sources, bioavailability, and functions of silicon on various tissues are discussed. The second focus is on the effects of calcium-silicate biomineralization and corresponding analytical methods in investigating osteogenesis and bone formation. Finally, recent developments in the manufacturing of Si-containing scaffolds are discussed, including in vitro and in vivo studies, as well as recently filed patents that focus on the influence of silicon on hard tissue formation.

Functionalized cell-free scaffolds for bone defect repair inspired by self-healing of bone fractures: A review and new perspectives

Studies have demonstrated that scaffolds, a component of bone tissue engineering, play an indispensable role in bone repair. However, these scaffolds involving ex-vivo cultivated cells seeded have disadvantages in clinical practice, such as limited autologous cells, time-consuming cell expansion procedures, low survival rate and immune-rejection issues. To overcome these disadvantages, recent focus has been placed on the design of functionalized cell-free scaffolds, instead of cell-seeded scaffolds, that can reduplicate the natural self-healing events of bone fractures, such as inflammation, cell recruitment, vascularization, and osteogenic differentiation. New approaches and applications in tissue engineering and regenerative medicine continue to drive the development of functionalized cell-free scaffolds for bone repair. In this review, the self-healing processes were highlighted, and approaches for the functionalization were summarized. Also, ongoing efforts and breakthroughs in the field of functionalization for bone defect repair were discussed. Finally, a brief summery and new perspectives for functionalization strategies were presented to provide guidelines for further efforts in the design of bioinspired cell-free scaffolds.

Use of collagen/chitosan sponges mineralized with hydroxyapatite for the repair of cranial defects in rats

In traumatology, we encounter several clinical challenges that involve extensive bone loss primarily related to trauma, conditions that can be treated with autologous grafts. A good alternative is the use of synthetic biomaterials as substitutes. These polymers provide a suitable environment for the growth of new bone and vascular tissue, which are essential for repair. Collagen/hydroxyapatite composites have proven to be biocompatible and to behave mechanically. Furthermore, the addition of chitosan contributes to the formation of a three-dimensional structure that permits cell adhesion and proliferation, thus improving osteogenesis. The aim of this study was to evaluate bone formation during the repair of bone defects experimentally induced in the skull of rats and grafted with a polymer blend consisting of bovine tendon collagen and chitosan combined with hydroxyapatite. Thirty animals were used for the creation of a defect in the left parietal bone and were divided into three groups of 10 animals each: a control group without biomaterial implantation, a group receiving the blend of collagen and chitosan, and a group receiving this blend combined with hydroxyapatite. Each group was subdivided and the animals were sacrificed 3 or 8 weeks after surgery. After sacrifice, the skulls were removed for macroscopic photodocumentation and radiographic examination. The samples were processed for histological evaluation of new bone formation at the surgical site. Macroscopic and radiographic analysis demonstrated the biocompatibility of the blends. Histologically, the formation of new bone occurred in continuity with the edges of the defect, with the observation of higher volumes in the grafted groups compared to control. Mineralization of sponges did not stimulate bone neoformation, with bone repair being incomplete over the experimental period. In conclusion, mineralization by the addition of hydroxyapatite should be better studied. However, the collagen/chitosan sponges used in this study are suitable to stimulate osteogenesis in cranial defects, although this process is slow and not sufficient to achieve complete bone regeneration over a short period of time.

Construction of vascularized tissue-engineered bone with a double-cell sheet complex

A double-cell sheet (DCS) complex composed of an osteogenic cell sheet and a vascular endothelial cell sheet with osteogenesis and blood vessel formation potential was developed in this study. The osteogenic and vascular endothelial cell sheets were obtained after induced culture of rabbit adipose-derived mesenchymal stem cells. The osteogenic cell sheet showed positive alizarin red, von Kossa, and alkaline phosphatase (ALP) staining. The vascular endothelial cell sheet exhibited visible W-P bodies in the cells, the expression of CD31 was positive, and a vascular mesh structure was spontaneously formed in a Matrigel matrix. The subcutaneous transplantation results for four groups of DCS and DCS-coral hydroxyapatite (CHA) complexes, and the CHA scaffold group in nude mice revealed mineralization of collagen fibers and vascularization in each group at 12 weeks, but the degrees of mineralization and vascularization showed differences among groups. The pattern involving endothelial cell sheets covered with osteogenic cell sheets, group B, exhibited the best results. In addition, the degree of mineralization of the DCS-CHA complexes was more mature than those of the same group of DCS complexes and the CHA scaffold, and the capillary number was greater than those of the same group of DCS complexes and the CHA scaffold. Therefore, the CHA scaffold strengthened the osteogenesis and blood vessel formation potential of the DCS complexes. Meanwhile, the DCS complexes also promoted the osteogenesis and blood vessel formation potential of the CHA scaffold. This study will provide a basis for building vascularized tissue-engineered bone for bone defect therapy.

STATEMENT OF SIGNIFICANCE

This study developed a double-cell sheet (DCS) complex composed of an osteogenic cell sheet and a vascular endothelial cell sheet with osteogenesis and blood vessel formation potential. Osteogenic and vascular endothelial cell sheets were obtained after induced culture of rabbit adipose-derived mesenchymal stem cells. The DCS complex and DCS-CHA complex exhibited osteogenic and blood vessel formation potential in vivo. CHA enhanced the osteogenesis and blood vessel formation abilities of the DCS complexes in vivo. Meanwhile, the DCS complexes also promoted the osteogenesis and blood vessel formation potential of the CHA scaffold. Group B of the DCS complexes and DCS-CHA complexes exhibited the best osteogenesis and blood vessel formation abilities.

Note on the use of different approaches to determine the pore sizes of tissue engineering scaffolds: what do we measure?

Background

Collagen-based scaffolds provide a promising option for the treatment of bone defects. One of the key parameters of such scaffolds consists of porosity, including pore size. However, to date, no agreement has been found with respect to the methodology for pore size evaluation. Since the determination of the exact pore size value is not possible, the comparison of the various methods applied is complicated. Hence, this study focuses on the comparison of two widely-used methods for the characterization of porosity—scanning electron microscopy (SEM) and micro-computed tomography (micro-CT).

Methods

7 types of collagen-based composite scaffold models were prepared by means of lyophilization and collagen cross-linking. Micro-CT analysis was performed in 3D and in 2D (pore size parameters were: major diameter, mean thickness, biggest inner circle diameter and area-equivalent circle diameter). Afterwards, pore sizes were analyzed in the same specimens by an image analysis of SEM microphotographs. The results were statistically evaluated. The comparison of the various approaches to the evaluation of pore size was based on coefficients of variance and the semi-quantitative assessment of selected qualities (e.g. the potential for direct 3D analysis, whole specimen analysis, non-destructivity).

Results

The pore size values differed significantly with respect to the parameters applied. Median values of pore size values were ranging from 20 to 490 µm. The SEM values were approximately 3 times higher than micro-CT 3D values for each specimen. The Mean thickness was the most advantageous micro-CT 2D approach. Coefficient of variance revealed no differences among pore size parameters (except major diameter). The semi-quantitative comparison approach presented pore size parameters in descending order with regard to the advantages thereof as follows: (1) micro-CT 3D, (2) mean thickness and SEM, (3) biggest inner circle diameter, major diameter and area equivalent circle diameter.

Conclusion

The results indicated that micro-CT 3D evaluation provides the most beneficial overall approach. Micro-CT 2D analysis (mean thickness) is advantageous in terms of its time efficacy. SEM is still considered as gold standard for its widespread use and high resolution. However, exact comparison of pore size analysis in scaffold materials remains a challenge.

Electronic supplementary material

The online version of this article (10.1186/s12938-018-0543-z) contains supplementary material, which is available to authorized users.

Development and biological evaluation of fluorophosphonate-modified hydroxyapatite for orthopaedic applications

There is an incentive to functionalise hydroxyapatite (HA) for orthopaedic implant use with bioactive agents to encourage superior integration of the implants into host bone. One such agent is (3S) 1-fluoro-3-hydroxy-4-(oleoyloxy) butyl-1-phosphonate (FHBP), a phosphatase-resistant lysophosphatidic acid (LPA) analogue. We investigated the effect of an FHBP-HA coating on the maturation of human (MG63) osteoblast-like cells. Optimal coating conditions were identified and cell maturation on modified and unmodified, control HA surfaces was assessed. Stress tests were performed to evaluate coating survivorship after exposure to mechanical and thermal insults that are routinely encountered in the clinical environment. MG63 maturation was found to be three times greater on FHBP-modified HA compared to controls (p < 0.0001). There was no significant loss of coating bioactivity after autoclaving (P = 0.9813) although functionality declined by 67% after mechanical cleaning and reuse (p < 0.0001). The bioactivity of modified disks was significantly greater than that of controls following storage for up to six months (p < 0.001). Herein we demonstrate that HA can be functionalised with FHBP in a facile, scalable manner and that this novel surface has the capacity to enhance osteoblast maturation. Improving the biological performance of HA in a bone regenerative setting could be realised through the simple conjugation of bioactive LPA species in the future. Depicted is a stylised summary of hydroxyapatite (HA) surface modification using an analogue of lysophosphatidic acid, FHBP. a HA surfaces are simply steeped in an aqueous solution of 2 μM FHBP. b The polar head group of some FHBP molecules react with available hydroxyl residues at the mineral surfaces forming robust HA-O-P bonds leaving acyl chain extensions perpendicular to the HA surface. These fatty acyl chains provide points of integration for other FHBP molecules to facilitate their self-assembly. This final surface finish enhanced the human osteoblast maturation response to calcitriol, the active vitamin D3 metabolite.

A Decellularized Porcine Xenograft-Derived Bone Scaffold for Clinical Use as a Bone Graft Substitute: A Critical Evaluation of Processing and Structure

BACKGROUND

Bone grafts are used in approximately one half of all musculoskeletal surgeries. Autograft bone is the historic gold standard but is limited in supply and its harvest imparts significant morbidity to the patient. Alternative sources of bone graft include allografts, synthetics and, less commonly, xenografts which are taken from animal species. Xenografts are available in unlimited supply from healthy animal donors with controlled biology, avoiding the risk of human disease transmission, and may satisfy current demand for bone graft products.

METHODS

In the current study, cancellous bone was harvested from porcine femurs and subjected to a novel decellularization protocol to derive a bone scaffold.

RESULTS

The scaffold was devoid of donor cellular material on histology and DNA sampling (p < 0.01). Microarchitectural properties important for osteoconductive potential were preserved after decellularization as shown by high resolution imaging modalities. Proteomics data demonstrated similar profiles when comparing the porcine bone scaffold against commercially available human demineralized bone matrix approved for clinical use.

CONCLUSION

We are unaware of any porcine-derived bone graft products currently used in orthopaedic surgery practice. Results from the current study suggest that porcine-derived bone scaffolds warrant further consideration to serve as a potential bone graft substitute.

Recent Advances in Laser-Ablative Synthesis of Bare Au and Si Nanoparticles and Assessment of Their Prospects for Tissue Engineering Applications

Driven by surface cleanness and unique physical, optical and chemical properties, bare (ligand-free) laser-synthesized nanoparticles (NPs) are now in the focus of interest as promising materials for the development of advanced biomedical platforms related to biosensing, bioimaging and therapeutic drug delivery. We recently achieved significant progress in the synthesis of bare gold (Au) and silicon (Si) NPs and their testing in biomedical tasks, including cancer imaging and therapy, biofuel cells, etc. We also showed that these nanomaterials can be excellent candidates for tissue engineering applications. This review is aimed at the description of our recent progress in laser synthesis of bare Si and Au NPs and their testing as functional modules (additives) in innovative scaffold platforms intended for tissue engineering tasks.

Biomaterial granules used for filling bone defects constitute 3D scaffolds: porosity, microarchitecture and molecular composition analyzed by microCT and Raman microspectroscopy

Biomaterials are used in the granular form to fill small bone defects. Granules can be prepared with a grinder from trabecular bone samples or provided as synthetic biomaterials by industry. Granules occupy the 3D-space and create a macroporosity allowing invasion of vascular and bone cells when the inter-granular pores are larger than 300 µm. We compared the 3D-porosity of granule stacks obtained or prepared with nine biomaterials Osteopure^® , Lubboc^® , Bio-Oss^® , CopiOs^® , TCP Dental^® , TCP Dental HP^® , KeraOs^® , and TCH^® in comparison with that of human trabecular bone. For each biomaterial, two sizes of granules were analyzed: 250-1000 and 1000-2000 µm. Microcomputed tomography determined porosity and microarchitectural characteristics of granular stacks and Raman microspectroscopy was used to analyze their composition. Stacks of 250-1000 µm granules had a much lower porosity than 1000-2000 µm granules and the maximum frequency of pores was always centered at 200-250 µm. One biomaterial contained substantial amount of cortical bone (Bio-Oss^® ). The highest porosity and pore size was obtained with TCP Dental HP. Raman spectroscopy found differences in biomaterials of the same composition. Stacks of granules represent 3D scaffolds resembling trabecular bone with an interconnected porous microarchitecture. Small granules have created pores <300 µm in diameter; this can interfere with vascular colonization. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 107B: 415-423, 2019.

Natural and Synthetic Biodegradable Polymers: Different Scaffolds for Cell Expansion and Tissue Formation

The formation of tissue produced by implanted cells is influenced greatly by the scaffold onto which they are seeded. In the long term it is often preferable to use a biodegradable material scaffold so that all the implanted materials will disappear, leaving behind only the generated tissue. Research in this area has identified several natural biodegradable materials. Among them, hydrogels are receiving increasing attention due to their ability to retain a great quantity of water, their good biocompatibility, their low interfacial tension, and the minimal mechanical and frictional irritation that they cause. Biocompatibility is not an intrinsic property of materials; rather it depends on the biological environment and the tolerability that exists with respect to specific polymer-tissue interactions. The most often utilized biodegradable synthetic polymers for 3D scaffolds in tissue engineering are saturated poly-a-hydroxy esters, including poly(lactic acid) (PLA) and poly(glycolic acid) (PGA), as well as poly(lactic-co-lycolide) (PLGA) copolymers. Hard materials provide compressive and torsional strength; hydrogels and other soft composites more effectively promote cell expansion and tissue formation. This review focuses on the future potential for understanding the characteristics of the biomaterials considered evaluated for clinical use in order to repair or to replace a sizable defect by only harvesting a small tissue sample.

Metallic powder-bed based 3D printing of cellular scaffolds for orthopaedic implants: A state-of-the-art review on manufacturing, topological design, mechanical properties and biocompatibility

Metallic cellular scaffold is one of the best choices for orthopaedic implants as a replacement of human body parts, which could improve life quality and increase longevity for the people needed. Unlike conventional methods of making cellular scaffolds, three-dimensional (3D) printing or additive manufacturing opens up new possibilities to fabricate those customisable intricate designs with highly interconnected pores. In the past decade, metallic powder-bed based 3D printing methods emerged and the techniques are becoming increasingly mature recently, where selective laser melting (SLM) and selective electron beam melting (SEBM) are the two representatives. Due to the advantages of good dimensional accuracy, high build resolution, clean build environment, saving materials, high customisability, etc., SLM and SEBM show huge potential in direct customisable manufacturing of metallic cellular scaffolds for orthopaedic implants. Ti-6Al-4V to date is still considered to be the optimal materials for producing orthopaedic implants due to its best combination of biocompatibility, corrosion resistance and mechanical properties. This paper presents a state-of-the-art overview mainly on manufacturing, topological design, mechanical properties and biocompatibility of cellular Ti-6Al-4V scaffolds via SLM and SEBM methods. Current manufacturing limitations, topological shortcomings, uncertainty of biocompatible test were sufficiently discussed herein. Future perspectives and recommendations were given at the end.

Calcium-phosphate ceramics and polysaccharide-based hydrogel scaffolds combined with mesenchymal stem cell differently support bone repair in rats

Research in bone tissue engineering is focused on the development of alternatives to autologous bone grafts for bone reconstruction. Although multiple stem cell-based products and biomaterials are currently being investigated, comparative studies are rarely achieved to evaluate the most appropriate approach in this context. Here, we aimed to compare different clinically relevant bone tissue engineering methods and evaluated the kinetic repair and the bone healing efficiency supported by mesenchymal stem cells and two different biomaterials, a new hydrogel scaffold and a commercial hydroxyapatite/tricalcium phosphate ceramic, alone or in combination.Syngeneic mesenchymal stem cells (5 × 10⁵) and macroporous biphasic calcium phosphate ceramic granules (Calciresorb C35^®, Ceraver) or porous pullulan/dextran-based hydrogel scaffold were implanted alone or combined in a drilled-hole bone defect in rats. Using quantitative microtomography measurements and qualitative histological examinations, their osteogenic properties were evaluated 7, 30, and 90 days after implantation. Three months after surgery, only minimal repair was evidenced in control rats while newly mineralized bone was massively observed in animals treated with either hydrogels (bone volume/tissue volume = 20%) or ceramics (bone volume/tissue volume = 26%). Repair mechanism and resorption kinetics were strikingly different: rapidly-resorbed hydrogels induced a dense bone mineralization from the edges of the defect while ceramics triggered newly woven bone formation in close contact with the ceramic surface that remained unresorbed. Delivery of mesenchymal stem cells in combination with these biomaterials enhanced both bone healing (>20%) and neovascularization after 1 month, mainly in hydrogel.Osteogenic and angiogenic properties combined with rapid resorption make hydrogels a promising alternative to ceramics for bone repair by cell therapy.

Composite biopolymers for bone regeneration enhancement in bony defects

For the past century, various biomaterials have been used in the treatment of bone defects and fractures. Their role as potential substitutes for human bone grafts increases as donors become scarce. Metals, ceramics and polymers are all materials that confer different advantages to bone scaffold development. For instance, biocompatibility is a highly desirable property for which naturally-derived polymers are renowned. While generally applied separately, the use of biomaterials, in particular natural polymers, is likely to change, as biomaterial research moves towards mixing different types of materials in order to maximize their individual strengths. This review focuses on osteoconductive biocomposite scaffolds which are constructed around natural polymers and their performance at the in vitro/in vivo stages and in clinical trials.

Simple and economic elaboration of high purity CaCO3 particles for bone graft applications using a spray pyrolysis technique

CaCO₃ particles obtained using spray pyrolysis possess all the requirements to constitute promising multi-purpose materials for bone graft applications.

The potential impact of bone tissue engineering in the clinic

Bone tissue engineering (BTE) intends to restore structural support for movement and mineral homeostasis, and assist in hematopoiesis and the protective functions of bone in traumatic, degenerative, cancer, or congenital malformation. While much effort has been put into BTE, very little of this research has been translated to the clinic. In this review, we discuss current regenerative medicine and restorative strategies that utilize tissue engineering approaches to address bone defects within a clinical setting. These approaches involve the primary components of tissue engineering: cells, growth factors and biomaterials discussed briefly in light of their clinical relevance. This review also presents upcoming advanced approaches for BTE applications and suggests a probable workpath for translation from the laboratory to the clinic.

Corrosion resistance characteristics of a Ti-6Al-4V alloy scaffold that is fabricated by electron beam melting and selective laser melting for implantation in vivo

The purpose of this study is to determine the corrosion resistance of Ti-6Al-4V alloy fabricated with electron beam melting and selective laser melting for implantation in vivo. Ti-6Al-4V alloy specimens were fabricated with electron beam melting (EBM) and selective laser melting (SLM). A wrought form of Ti-6Al-4V alloy was used as a control. Surface morphology observation, component analysis, corrosion resistance experimental results, electrochemical impedance spectroscopy, crevice corrosion resistance experimental results, immersion test and metal ions precipitation analysis were processed, respectively. The thermal stability of EBM specimen was the worst, based on the result of open circuit potential (OCP) result. The result of electrochemical impedance spectroscopy indicated that the corrosion resistance of the SLM specimen was the best under the low electric potential. The result of potentiodynamic polarization suggested that the corrosion resistance of the SLM specimen was the best under the low electric potential (<1.5V) and EBM specimen was the best under the high electric potential (>1.5V).The crevice corrosion resistance of the EBM specimen was the best. The corrosion resistance of SLM specimen was the best, based on the result of immersion test. The content of Ti, Al and V ions of EBM, SLM and wrought specimens was very low. In general, the scaffolds that were fabricated with EBM and SLM had good corrosion resistance, and were suitable for implantation in vivo.

Multilayer scaffolds in orthopaedic tissue engineering

PURPOSE

The purpose of this study was to summarize the recent developments in the field of tissue engineering as they relate to multilayer scaffold designs in musculoskeletal regeneration.

METHODS

Clinical and basic research studies that highlight the current knowledge and potential future applications of the multilayer scaffolds in orthopaedic tissue engineering were evaluated and the best evidence collected. Studies were divided into three main categories based on tissue types and interfaces for which multilayer scaffolds were used to regenerate: bone, osteochondral junction and tendon-to-bone interfaces.

RESULTS

In vitro and in vivo studies indicate that the use of stratified scaffolds composed of multiple layers with distinct compositions for regeneration of distinct tissue types within the same scaffold and anatomic location is feasible. This emerging tissue engineering approach has potential applications in regeneration of bone defects, osteochondral lesions and tendon-to-bone interfaces with successful basic research findings that encourage clinical applications.

CONCLUSIONS

Present data supporting the advantages of the use of multilayer scaffolds as an emerging strategy in musculoskeletal tissue engineering are promising, however, still limited. Positive impacts of the use of next generation scaffolds in orthopaedic tissue engineering can be expected in terms of decreasing the invasiveness of current grafting techniques used for reconstruction of bone and osteochondral defects, and tendon-to-bone interfaces in near future.

High-strength porous biomaterials for bone replacement: A strategy to assess the interplay between cell morphology, mechanical properties, bone ingrowth and manufacturing constraints

High-strength fully porous biomaterials built with additive manufacturing provide an exciting opportunity for load-bearing orthopedic applications. While factors controlling their mechanical and biological response have recently been the subject of intense research, the interplay between mechanical properties, bone ingrowth requirements, and manufacturing constraints, is still unclear. In this paper, we present two high-strength stretch-dominated topologies, the Tetrahedron and the Octet truss, as well as an intuitive visualization method to understand the relationship of cell topology, pore size, porosity with constraints imposed by bone ingrowth requirements and additive manufacturing. 40 samples of selected porosities are fabricated using Selective Laser Melting (SLM), and their morphological deviations resulting from SLM are assessed via micro-CT. Mechanical compression testing is used to obtain stiffness and strength properties, whereas bone ingrowth is assessed in a canine in vivo model at four and eight weeks. The results show that the maximum strength and stiffness ranged from 227.86±10.15 to 31.37±2.19MPa and 4.58±0.18 to 1.23±0.40GPa respectively, and the maximum 0.2% offset strength is almost 5 times stronger than that of tantalum foam. For Tetrahedron samples, bone ingrowth after four and eight weeks is 28.6%±11.6%, and 41.3%±4.3%, while for the Octet truss 35.5%±1.9% and 56.9%±4.0% respectively. This research is the first to demonstrate the occurrence of bone ingrowth into high-strength porous biomaterials which have higher structural efficiency than current porous biomaterials in the market.

STATEMENT OF SIGNIFICANCE

We present two stretch-dominated cell topologies for porous biomaterials that can be used for load-bearing orthopaedic applications, and prove that they encourage bone ingrowth in a canine model. We also introduce an intuitive method to visualize and understand the relationship of cell topology, pore size, porosity with constraints imposed by bone ingrowth requirements and additive manufacturing. We show this strategy helps to gain insight into the interaction of exogenous implant factors and endogenous system factors that can affect the success of load-bearing orthopaedic devices.

Calcium phosphate scaffolds combined with bone morphogenetic proteins or mesenchymal stem cells in bone tissue engineering

Objective:

The purpose of this study was to review the current status of calcium phosphate (CaP) scaffolds combined with bone morphogenetic proteins (BMPs) or mesenchymal stem cells (MSCs) in the field of bone tissue engineering (BTE).

Date Sources:

Data cited in this review were obtained primarily from PubMed and Medline in publications from 1979 to 2014, with highly regarded older publications also included. The terms BTE, CaP, BMPs, and MSC were used for the literature search.

Study Selection:

Reviews focused on relevant aspects and original articles reporting in vitro and/or in vivo results concerning the efficiency of CaP/BMPs or CaP/MSCs composites were retrieved, reviewed, analyzed, and summarized.

Results:

An ideal BTE product contains three elements: Scaffold, growth factors, and stem cells. CaP-based scaffolds are popular because of their outstanding biocompatibility, bioactivity, and osteoconductivity. However, they lack stiffness and osteoinductivity. To solve this problem, composite scaffolds of CaP with BMPs have been developed. New bone formation by CaP/BMP composites can reach levels similar to those of autografts. CaP scaffolds are compatible with MSCs and CaP/MSC composites exhibit excellent osteogenesis and stiffness. In addition, a CaP/MSC/BMP scaffold can repair bone defects more effectively than an autograft.

Conclusions:

Novel BTE products possess remarkable osteoconduction and osteoinduction capacities, and exhibit balanced degradation with osteogenesis. Further work should yield safe, viable, and efficient materials for the repair of bone lesions.

Feasibility study of collagen membranes derived from bovine pericardium and intestinal serosa for the repair of cranial defects in ovariectomised rats

The indication of biomaterials has increased substantially in the regenerative therapy of bone defects. However, in addition to evaluating the physicochemical properties of biomaterials, the quality of the recipient tissue is also essential for the osseointegration of implants, as abnormalities in bone metabolism, such as gonadal hormone deficiency, can influence bone healing. This study evaluated the osteoregenerative capacity of collagen membranes derived from bovine pericardium and intestinal serosa in the repair of cranial defects in ovariectomised rats. Thirty female Wistar rats were submitted to surgical creation of a 5-mm cranial bone defect. The rats were divided into a control group (not ovariectomised) and an ovariectomised group. The non-ovariectomised group was divided into three subgroups: control (G1) in which the defect was not filled with the biomaterial, and two subgroups (G2 and G3) that received the bovine pericardium- and serosa-derived collagen membranes, respectively. The ovariectomised group was divided into the same subgroups (G4, G5, and G6). The animals were sacrificed 8 weeks after surgery. The calvaria were removed for macroscopic and radiographic photodocumentation and processed for histomorphometric analysis of bone healing at the surgical site. Macroscopic, radiological, and microscopic analyses demonstrated the biocompatibility of the implanted collagen membranes, as indicated by the absence of infiltration and signs of inflammation at the surgical site. Histologically, discrete immature bone neoformation projecting from the margins of the defect was observed at the surgical site in ovariectomised groups when compared to the non-ovariectomised groups. The volume of newly formed bone was significantly higher in the non-ovariectomised groups (G1: 7.83%±1.32; G2: 21.33%±1.96; and G3: 22.83%±0.98) compared to the respective ovariectomised subgroups (G4: 3.16%±0.75; G5: 16.83%±0.98; and G6: 16.16%±0.75), thus demonstrating the deleterious effects of ovariectomy on bone homeostasis. Higher volumes of newly formed bone were observed in the groups receiving the membrane grafts (G2, G3, G5, and G6) compared to the control groups (G1 and G4). In conclusion, the bilateral ovariectomy compromises the ability to repair bone lesions grafted with osteoconductive biomaterials as in the case of collagen membranes derived from both bovine pericardium and intestinal serosa.

Strontium- and calcium-containing, titanium-stabilised phosphate-based glasses with prolonged degradation for orthopaedic tissue engineering

Strontium- and calcium-releasing, titanium-stabilised phosphate-based glasses with a controlled degradation rate are currently under development for orthopaedic tissue engineering applications. Ca and/or Sr were incorporated at varying concentrations in quaternary phosphate-based glasses, in order to promote osteoinduction. Ti was incorporated at a fixed concentration in order to prolong degradation. Glasses of the general formula (P₂O₅)–(Na₂O)–(TiO₂)–(CaO)–(SrO) were prepared via the melt-quench technique. The materials were characterised by energy-dispersive X-ray spectroscopy, X-ray diffraction, ³¹P magic angle spinning nuclear magnetic resonance, Fourier transform infrared spectroscopy, differential thermal analysis and density determination. The dissolution rate in distilled water was determined by measuring mass loss, ion release and pH change over a two-week period. In addition, the cytocompatibility and alkaline phosphatase activity of an osteoblast-like cell line cultured on the surface of glass discs was assessed. The glasses were shown to be amorphous and contained Q¹, Q² and Q³ species. Fourier transform infrared spectroscopy revealed small changes in the glass structure as Ca was substituted with Sr and differential thermal analysis confirmed a decrease in crystallisation temperature with increasing Sr content. Degradation and ion release studies also showed that mass loss was positively correlated with Sr content. These results were attributed to the lower electronegativity of Sr in comparison to Ca favouring the formation of phosphate-based mineral phases. All compositions supported cell proliferation and survival and induced at least 2.3-fold alkaline phosphatase activity relative to the control. Glass containing 17.5 mol% Sr had 3.6-fold greater alkaline phosphatase activity than the control. The gradual release of Ca and Sr supported osteoinduction, indicating their potential suitability in orthopaedic tissue engineering applications.

Custom-Made Computer-Aided-Design/Computer-Aided-Manufacturing Biphasic Calcium-Phosphate Scaffold for Augmentation of an Atrophic Mandibular Anterior Ridge

This report documents the clinical, radiographic, and histologic outcome of a custom-made computer-aided-design/computer-aided-manufactured (CAD/CAM) scaffold used for the alveolar ridge augmentation of a severely atrophic anterior mandible. Computed tomographic (CT) images of an atrophic anterior mandible were acquired and modified into a 3-dimensional (3D) reconstruction model; this was transferred to a CAD program, where a custom-made scaffold was designed. CAM software generated a set of tool-paths for the manufacture of the scaffold on a computer-numerical-control milling machine into the exact shape of the 3D design. A custom-made scaffold was milled from a synthetic micromacroporous biphasic calcium phosphate (BCP) block. The scaffold closely matched the shape of the defect: this helped to reduce the time for the surgery and contributed to good healing. One year later, newly formed and well-integrated bone was clinically available, and two implants (AnyRidge, MegaGen, Gyeongbuk, South Korea) were placed. The histologic samples retrieved from the implant sites revealed compact mature bone undergoing remodelling, marrow spaces, and newly formed trabecular bone surrounded by residual BCP particles. This study demonstrates that custom-made scaffolds can be fabricated by combining CT scans and CAD/CAM techniques. Further studies on a larger sample of patients are needed to confirm these results.

Effect of lithium ions on cementoblasts in the presence of lipopolysaccharide in vitro

The applications of lithium ions as an agent to facilitate bone formation have been widely documented; however, the effect of lithium ions in the periodontitis model has not yet been elucidated. The aim of the present study, therefore, was to investigate the effect of single lithium ions in the presence of lipopolysaccharide (LPS). A periodontitis model was induced in cementoblasts using LPS. The cytotoxic effect of the lithium ions on the cementoblasts was studied through the MTT assay. Alkaline phosphatase analysis and alizarin red staining were performed to investigate the effect of the lithium ions on differentiation. To examine the effect of lithium ions on osteoclastogenesis, osteoprotegerin (OPG) and receptor activator of nuclear factor-κB ligand (RANKL) mRNA and protein expression levels were assessed using reverse transcription-polymerase chain reaction analysis and ELISA, respectively. Compared with the effect induced by lithium ions on normal cementoblasts, proliferation and differentiation were downregulated following the co-incubation of the cementoblasts with LPS and lithium ions. Furthermore, the lithium ions appeared to alter osteoclastogenesis by regulating the OPG/RANKL ratio. In conclusion, the present findings suggest that lithium ions can downregulate proliferation and differentiation in a periodontitis model. Further studies should be undertaken prior to the acceptance of lithium ions for use in the clinic.

Stem cell technology for bone regeneration: current status and potential applications

Continued improvements in the understanding and application of mesenchymal stem cells (MSC) have revolutionized tissue engineering. This is particularly true within the field of skeletal regenerative medicine. However, much remains unknown regarding the native origins of MSC, the relative advantages of different MSC populations for bone regeneration, and even the biologic safety of such unpurified, grossly characterized cells. This review will first summarize the initial discovery of MSC, as well as the current and future applications of MSC in bone tissue engineering. Next, the relative advantages and disadvantages of MSC isolated from distinct tissue origins are debated, including the MSC from adipose, bone marrow, and dental pulp, among others. The perivascular origin of MSC is next discussed. Finally, we briefly comment on pluripotent stem cell populations and their possible application in bone tissue engineering. While continually expanding, the field of MSC-based bone tissue engineering and regeneration shows potential to become a clinical reality in the not-so-distant future.

Muscle extracellular matrix scaffold is a multipotent environment

The multipotency of scaffolds is a new concept. Skeletal muscle acellular scaffolds (MAS) implanted at the interface of Tibialis Anterior/tibial bone and masseter muscle/mandible bone in a murine model were colonized by muscle cells near the host muscle and by bone-cartilaginous tissues near the host bone, thus highlighting the importance of the environment in directing cell homing and differentiation. These results unveil the multipotency of MAS and point to the potential of this new technique as a valuable tool in musculo-skeletal tissue regeneration.

Beta-tricalcium phosphate shows superior absorption rate and osteoconductivity compared to hydroxyapatite in open-wedge high tibial osteotomy

PURPOSE

The purpose of this study was to clinically and radiologically compare the utility, osteoconductivity, and absorbability of hydroxyapatite (HAp) and beta-tricalcium phosphate (TCP) spacers in medial open-wedge high tibial osteotomy (HTO).

METHODS

Thirty-eight patients underwent medial open-wedge HTO with a locking plate. In the first 19 knees, a HAp spacer was implanted in the opening space (HAp group). In the remaining 19 knees, a TCP spacer was implanted in the same manner (TCP group). All patients underwent clinical and radiological examinations before surgery and at 18 months after surgery.

RESULTS

Concerning the background factors, there were no statistical differences between the two groups. Post-operatively, the knee score significantly improved in each group. Concerning the post-operative knee alignment and clinical outcome, there was no statistical difference in each parameter between the two groups. Regarding the osteoconductivity, the modified van Hemert's score of the TCP group was significantly higher (p = 0.0009) than that of the HAp group in the most medial osteotomy zone. The absorption rate was significantly greater in the TCP group than in the HAp group (p = 0.00039).

CONCLUSIONS

The present study demonstrated that a TCP spacer was significantly superior to a HAp spacer concerning osteoconductivity and absorbability at 18 months after medial open-wedge HTO.

LEVEL OF EVIDENCE

Retrospective comparative study, Level III.