Evaluation of dense polylactic acid/beta-tricalcium phosphate scaffolds for bone tissue engineering

Effects of ceramic additives and bioactive coatings on the degradation of polylactic acid-based bone scaffolds under hydrolytic conditions

Polylactic acid (PLA) has been extensively used for the manufacturing of scaffolds in bone tissue engineering applications. Due to the low hydrophilicity and the acidic degradation process of this biomaterial, different strategies have been proposed to increase the biofunctionality of the support structure. The use of ceramic particles is a generally preferred option to increase the osteoconductivity of the base material, while acting as buffers to maintain the pH level of the surroundings tissues. Surface modification is another approach to overcome the limitations of PLA for tissue engineering applications. In this work, the degradation profile of 3D-printed PLA scaffolds containing beta-tricalcium phosphate (β-TCP) and calcium carbonate (CaCO3 ) particles has been studied under hydrolytic conditions. Composite samples treated with plasma and coated with Aloe vera extracts were also studied to evaluate the effect of this surface modification method. The characterization of the 3D structures included its morphological, calorimetric and mechanical evaluation. According to the results obtained, the proposed composite scaffolds allowed an adequate maintenance of the pH level of the surrounding medium, with no effects observed on the morphology and mechanical properties of these structures. Hence, these samples showed potential to be further investigated as candidates for bone tissue regeneration.

The Role of Growth Factors in Bioactive Coatings

With increasing obesity and an ageing population, health complications are also on the rise, such as the need to replace a joint with an artificial one. In both humans and animals, the integration of the implant is crucial, and bioactive coatings play an important role in bone tissue engineering. Since bone tissue engineering is about designing an implant that maximally mimics natural bone and is accepted by the tissue, the search for optimal materials and therapeutic agents and their concentrations is increasing. The incorporation of growth factors (GFs) in a bioactive coating represents a novel approach in bone tissue engineering, in which osteoinduction is enhanced in order to create the optimal conditions for the bone healing process, which crucially affects implant fixation. For the application of GFs in coatings and their implementation in clinical practice, factors such as the choice of one or more GFs, their concentration, the coating material, the method of incorporation, and the implant material must be considered to achieve the desired controlled release. Therefore, the avoidance of revision surgery also depends on the success of the design of the most appropriate bioactive coating. This overview considers the integration of the most common GFs that have been investigated in in vitro and in vivo studies, as well as in human clinical trials, with the aim of applying them in bioactive coatings. An overview of the main therapeutic agents that can stimulate cells to express the GFs necessary for bone tissue development is also provided. The main objective is to present the advantages and disadvantages of the GFs that have shown promise for inclusion in bioactive coatings according to the results of numerous studies.

Additive manufacturing of PLA-based scaffolds intended for bone regeneration and strategies to improve their biological properties

Polylactic acid (PLA) is one of the most commonly used materials in the biomedical sector because of its processability, mechanical properties and biocompatibility. Among the different techniques that are feasible to process this biomaterial, additive manufacturing (AM) has gained attention recently, as it provides the possibility of tuning the design of the structures. This flexibility in the design stage allows the customization of the parts in order to optimize their use in the tissue engineering field. In the recent years, the application of PLA for the manufacture of bone scaffolds has been especially relevant, since numerous studies have proven the potential of this biomaterial for bone regeneration. This review contains a description of the specific requirements in the regeneration of bone and how the state of the art have tried to address them with different strategies to develop PLA-based scaffolds by AM techniques and with improved biofunctionality.

Effectiveness of Surface Treatment with Amine Plasma for Improving the Biocompatibility of Maxillofacial Plates

To date, no products have been presented for the surface treatment of metal plates used for repairing maxillofacial defects caused by trauma. Plasma surface treatment is a useful technique for chemically modifying the surfaces of biomaterials. Amine plasma-polymerization is an efficient way to prepare bioactive thin film polymers terminated with nitrogen-containing functional groups. The purpose of this study was to investigate the improvement in biocompatibility of titanium (Ti) plates treated with amine plasma-polymerization, and analyze their surfaces characteristics. To compare biocompatibility levels, in vitro test and animal study were performed using an amine plasma-polymerized Ti plate and an untreated Ti plate. After amine plasma-polymerization, the hydrophilicity of the Ti surface was remarkably improved. Biocompatibility was also improved for the Ti plates treated with amine plasma. The clinical application of this technique will not only shorten the time required for osseointegration, but will also improve the regeneration of bone.

Enzymatically Cross-Linked Silk Fibroin-Based Hierarchical Scaffolds for Osteochondral Regeneration

Osteochondral (OC) regeneration faces several limitations in orthopedic surgery, owing to the complexity of the OC tissue that simultaneously entails the restoration of articular cartilage and subchondral bone diseases. In this study, novel biofunctional hierarchical scaffolds composed of a horseradish peroxidase (HRP)-cross-linked silk fibroin (SF) cartilage-like layer (HRP-SF layer) fully integrated into a HRP-SF/ZnSr-doped β-tricalcium phosphate (β-TCP) subchondral bone-like layer (HRP-SF/dTCP layer) were proposed as a promising strategy for OC tissue regeneration. For comparative purposes, a similar bilayered structure produced with no ion incorporation (HRP-SF/TCP layer) was used. A homogeneous porosity distribution was achieved throughout the scaffolds, as shown by micro-computed tomography analysis. The ion-doped bilayered scaffolds presented a wet compressive modulus (226.56 ± 60.34 kPa) and dynamic mechanical properties (ranging from 403.56 ± 111.62 to 593.56 ± 206.90 kPa) superior to that of the control bilayered scaffolds (189.18 ± 90.80 kPa and ranging from 262.72 ± 59.92 to 347.68 ± 93.37 kPa, respectively). Apatite crystal formation, after immersion in simulated body fluid (SBF), was observed in the subchondral bone-like layers for the scaffolds incorporating TCP powders. Human osteoblasts (hOBs) and human articular chondrocytes (hACs) were co-cultured onto the bilayered structures and monocultured in the respective cartilage and subchondral bone half of the partitioned scaffolds. Both cell types showed good adhesion and proliferation in the scaffold compartments, as well as adequate integration of the interface regions. Osteoblasts produced a mineralized extracellular matrix (ECM) in the subchondral bone-like layers, and chondrocytes showed GAG deposition. The gene expression profile was different in the distinct zones of the bilayered constructs, and the intermediate regions showed pre-hypertrophic chondrocyte gene expression, especially on the BdTCP constructs. Immunofluorescence analysis supported these observations. This study showed that the proposed bilayered scaffolds allowed a specific stimulation of the chondrogenic and osteogenic cells in the co-culture system together with the formation of an osteochondral-like tissue interface. Hence, the structural adaptability, suitable mechanical properties, and biological performance of the hierarchical scaffolds make these constructs a desired strategy for OC defect regeneration.

Antimicrobial photodynamic active biomaterials for periodontal regeneration

OBJECTIVE

Biomaterials for periodontal regeneration may have insufficient mechanical and antimicrobial properties or are difficult to apply under clinical conditions. The aim of the present study was to develop a polymeric bone grafting material of suitable physical appearance and antimicrobial photodynamic activity.

METHODS

Two light curable biomaterials based on urethane dimethacrylate (BioM1) and a tri-armed oligoester-urethane methacrylate (BioM2) that additionally contained a mixture of β-tricalcium phosphate microparticles and 20wt% photosensitizer mTHPC (PS) were fabricated and analyzed by their compressive strength, flexural strength and modulus of elasticity. Cytotoxicity was observed by incubating eluates and in direct-contact to MC3T3-E1 cells. Antimicrobial activity was ascertained on Porphyromonas gingivalis and Enterococcus faecalis upon illumination with laser light (652nm, 1×100J/cm², 2×100J/cm²).

RESULTS

The compressive strength, flexural strength and elastic modulus were, respectively, 311.73MPa, 22.81MPa and 318.85MPa for BioM1+PS and 742.37MPa, 7.58MPa and 406.23MPa for BioM2+PS. Both materials did not show any cytotoxic behavior. Single laser-illumination (652nm) caused total suppression of P. gingivalis (BioM2+PS), while repeated irradiation reduced E. faecalis by 3.7 (BioM1+PS) and 3.1 (BioM2+PS) log-counts.

SIGNIFICANCE

Both materials show excellent mechanical and cytocompatible properties. In addition, irradiation with 652nm induced significant bacterial suppression. The manufactured biomaterials might enable a more efficient cure of periodontal bone lesions. Due to the mechanical properties functional stability might be increased. Further, the materials are antimicrobial upon illumination with light that enables a trans-mucosal eradication of residual pathogens.

Overcoming physical constraints in bone engineering: ‘the importance of being vascularized’

Bone plays several physiological functions and is the second most commonly transplanted tissue after blood. Since the treatment of large bone defects is still unsatisfactory, researchers have endeavoured to obtain scaffolds able to release growth and differentiation factors for mesenchymal stem cells, osteoblasts and endothelial cells in order to obtain faster mineralization and prompt a reliable vascularization. Nowadays, the application of osteoblastic cultures spans from cell physiology and pharmacology to cytocompatibility measurement and osteogenic potential evaluation of novel biomaterials. To overcome the simple traditional monocultures in vitro, co-cultures of osteogenic and vasculogenic precursors were introduced with very interesting results. Increasingly complex culture systems have been developed, where cells are seeded on proper scaffolds and stimulated so as to mimic the physiological conditions more accurately. These bioreactors aim at enabling bone regeneration by incorporating different cells types into bio-inspired materials within a surveilled habitat. This review is focused on the most recent developments in the organomimetic cultures of osteoblasts and vascular endothelial cells for bone tissue engineering.

Repair of urethral defects with polylactid acid fibrous membrane seeded with adipose-derived stem cells in a rabbit model

AIM

The aim of this study is to evaluate the capacity of polylactid acid (PLA) fibrous membrane seeded with allogeneic rabbit adipose tissue-derived stem cells (ADSCs) to repair urethral defects in a rabbit model.

MATERIALS AND METHODS

Rabbit ADSCs were harvested and phenotypically characterized. Twenty-four New Zealand male rabbits with 5-mm urethral mucosal defects were randomly divided into two groups. They underwent urethroplasty either with PLA fibrous membrane seeded with ADSCs (group A) or blank PLA fibrous membrane (group B). At 4 and 6 weeks after urethroplasty, the urethral grafts were collected and analyzed grossly and histologically. The incidence rate of urethrostenosis was measured.

RESULTS

The adipose tissue-derived cells in monolayer culture showed a typical morphology of mesenchymal stem cells (MSCs). They were positive for the MSC marker CD44 but negative for lineage markers CD45 and CD105. Six weeks after surgery, the incidence rate of urethrostenosis in group A was significantly lower than that in group B (p < 0.05). In group A, the ADSC-seeded grafts showed a normal urethral architecture with a thickened muscle layer. In contrast, the newly developed urethra in group B demonstrated a fewer number of urothelial layers and scarce or no smooth muscle cells.

CONCLUSION

The PLA scaffold seeded with ADSCs is effective in urethral regeneration in a rabbit model. ADSCs may represent a promising source of seed cells for urethral tissue engineering.

Comparison and preparation of multilayered polylactic acid fabric strengthen calcium phosphate-based bone substitutes for orthopedic applications

An attempt to maintain the three-dimensional space into restorative sites through the conveniently pack porous fillers are general used strategy. Advancement in the manufacturing protective shells in the scaffolds, which would be filled with brittle ceramic grafts for the development of highly connective pores provides the approach to solve crack problem for generating the tissues. Therefore, multilayered braided and alkalized poly(lactic acid) (PLA) composites with calcium phosphate bone cement (CPC) were synthesized and compared. The PLA/CPC composites were divided into various groups according to a series of heat-treatment temperatures (100-190 °C) and periods (1-3 h) and then characterized. The effects of 24-h immersion on the strength decay resistance of the samples were compared. Results showed that the residual oil capped on the surfaces of alkalized PLA braid was removed, and the structure was unaltered. However, the reduced tensile stress of alkalized PLA braids was due to ester-group formation by hydrolysis. Mechanical test results of PLA/CPC composites showed that the strength significantly increased after heat treatment, except when the heating temperature was higher than the PLA melting point at approximately 160-170 °C. The degree of PLA after recrystallization became higher than that of unheated composites, thereby leading to reduced strength and toughness of the specimen. Braiding fibers of biodegradable PLA reinforced and toughened the structure particularly of the extra-brittle material of thin-sheet CPC after implantation.

Solvent free production of porous PDLLA/calcium carbonate composite scaffolds improves the release of bone growth factors

PURPOSE

Incorporation of alkaline nano-/microparticles for neutralization of acidic degradation products into degradable polymer foams requires the use of organic solvents, which may compromise biocompatibility and may be associated with biological hazards. The aim of the present study was to develop and validate a solvent-free method to produce porous poly (DL-lactic acid)/calcium carbonate composite scaffolds (PDLLA/CaCO3) for controlled release of incorporated osteogenic growth factors.

METHODS

Composite PDLLA/CaCO3 granules were produced using a milling process and compared to composite material fabricated through a solution precipitation process using organic solvents. Particle size and mineral content were comparable in both groups. Supercritical carbon dioxide pressure was used to incorporate rhBMP2 into both composites.

RESULTS

Gas foaming resulted in comparable pore structures in both groups exhibiting a homogenous distribution of CaCO3 microparticles in the polymer scaffolds. The elasticity modulus of both types of scaffolds was not significantly different whereas the bending strength of the solvent-free produced scaffolds was significantly lower. The pH values remained constant between 6.90 and 7.25 during degradation of both composites. Release of BMP2 was significantly higher and the induction of alkaline phosphatase was more reliable in the group of scaffolds produced without organic solvents.

CONCLUSION

Solvent-free fabrication of composite PDLLA/CaCO3 scaffolds for controlled release of bone growth factors through gas foaming significantly enhances the release of growth factors and improves the biological efficacy of the incorporated growth factors.

Bone regeneration using a freeze-dried 3D gradient-structured scaffold incorporating OIC-A006-loaded PLGA microspheres based on β-TCP/PLGA

To reveal the latent capacity of the growth factor-like low-molecular-weight material OIC-A006 in tissue regeneration, it is essential to design a porous scaffold in order to concurrently accommodate cells and drug release in a controlled manner. Consequently, we fabricated poly (L-lactide-co-glycolide) (PLGA)-based microspheres with an OIC-A006-loaded gradient-structured β-TCP/PLGA scaffold by freeze-drying which could then be used for drug delivery and bone regeneration. The OIC-A006-loaded β-TCP/PLGA scaffold consisted of two parts which loaded different doses of OIC-A006 (6.25 μM, outside; 12.5 μM, inside). The porosity, compressive strength, SEM, degradation, and cumulative amount of drug release in vitro were characterized. Furthermore, we confirmed the incorporation of OIC-A006 into the PLGA-based microspheres within the scaffolds using UV-spectrophotometry, and the amount of drug remaining in the scaffold was maintained by 10 % for up to 28 days. The drug release was slower in the normal-structured drug-loaded scaffold. The OIC-A006 released action from the OIC-A006-loaded β-TCP/PLGA scaffold with ideal therapeutic prospects in tissue regeneration. In vitro cell culture results showed that this gradient-structured composite scaffold can induce the adhesion and proliferation of rat bone marrow stromal cells towards osteoblasts. These results showed that the newly developed OIC-A006-loaded scaffolds with gradient structure can be potentially applied to bone regeneration in clinical applications.

Bone formation in rabbit's leg muscle after autologous transplantation of bone marrow-derived mesenchymal stem cells expressing human bone morphogenic protein-2

BACKGROUND

To test whether autologous transplantation of bone marrow-derived mesenchymal stem cells (BM-MSCs) expressing human bone morphogenic protein-2 (hBMP-2) can produce bone in rabbit leg muscles.

MATERIALS AND METHODS

MSCs were isolated from BM of the iliac crest of rabbits and then infected with lentiviral vectors (LVs) bearing hBMP-2 and green fluorescent protein under the control of the cytomegalovirus (immediate early promoter). Differentiation of transduced MSCs to osteoblasts in vitro was evaluated with an alkaline phosphatase activity assay and immuohistochemistry against osteoblast specific markers. MSCs expressing hBMP-2 were placed in an absorbable gelatin sponge, which was then transplanted into the gastrocnemius of rabbits from which MSCs were isolated. Bone formation was examined by X-ray and histological analysis.

RESULTS

LVs efficiently mediated hBMP-2 gene expression in rabbit BM-MSCs. Ectopic expression of hBMP in these MSCs induced osteoblastic differentiation in vitro. Bone was formed after the MSCs expressing hBMP-2 were transplanted into rabbit muscles.

CONCLUSION

Ectopic expression of hBMP-2 in rabbit MSCs induces them to differentiate into osteoblasts in vitro and to form a bone in vivo.

The influence of prefreezing temperature on pore structure in freeze-dried beta-TCP scaffolds

A combined method of tricalcium phosphate (TCP) scaffold production, which comprised negative mold and scaffold fabrication, was reported in this study. The negative mold structure was designed by computer and fabricated by fused deposition modeling (FDM) technology, while the TCP scaffold was produced by freeze-drying technology under different prefreezing temperatures of -10 degrees C, -30 degrees C, and -86 degrees C and thermal treatment to get beta-TCP. The scaffold structure was evaluated with X-ray, scanning electron microscopy (SEM), compressive mechanical testing, and micro-computerized tomography (micro-CT). The cell-scaffold interaction was studied by culturing dog bone marrow stromal cells (BMSCs) on the scaffolds and assessing differentiated BMSC function by measuring cellular alkaline phosphatase (ALP) activity. The results showed good interconnectivity and good pore distribution with the pore size ranging from 50 to 250 microm and compressive modulus of 1.18 MPa at a prefreezing temperatures of -10 degrees C. In vitro cell culture results indicated that the porous scaffolds were not toxic to bone cells. These results demonstrate that rapid prototyping and freeze-drying technologies for creating beta-TCP scaffolds are promising for bone tissue engineering.

A minimal wrist arthroplasty for early wrist osteoarthritis

Background The most common forms of salvage surgery for wrist arthritis of any stage are four corner fusion and proximal row carpectomy. Younger, high demand patients with early arthritis may not be candidates for this type of salvage surgery. We describe a technique and preliminary case series of a minimal radiocarpal arthroplasty aimed at patients with initial and isolated wrist arthritis (stage 1). This procedure does not preclude any procedure that may become necessary in the future. Patients A series of nineteen male heavy laborers with scapholunate advanced collapse (SLAC grade 1-2) wrist osteoarthritis that felt the wrist arthritis was prohibiting their function enough to warrant surgery, but were unwilling to undergo a salvage procedure, were treated with the technique. The average age was 57.2 (± 7.7) years. The average follow up period was 40.3 months (9-63 months). All patients returned to heavy labor. No revision surgery was needed within the follow up period. Range of motion (ROM) and grip strength did not significantly improve. Patient satisfaction was high despite imperfect results. Conclusions Minimal arthroplasty as described may provide a temporary solution for active patients with symptomatic early wrist arthritis who are not candidates for salvage wrist surgery. Longer -term follow up as well as investigation of additional stabilization procedures is necessary.

Biocomposites of pHEMA with HA/β -TCP (60/40) for bone tissue engineering: Swelling, hydrolytic degradation, and in vitro behavior

The field of bone and cartilage tissue engineering has a pressing need for novel, biocompatible, biodegradable biocomposites comprising polymers with bioceramics or bioglasses to meet numerous requirements for these applications. We created hydrolytically degradable hydrogel/bioceramic biocomposites, comprising poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogels and 50 wt% biphasic hydroxyapatite/β-tricalcium phosphate (60/40) through in situ polymerization. The hydrolytic degradation starts with hydrolysis of the cross-linker, N, O-dimethacryloyl hydroxylamine, which was synthesized in house. Swelling and degradation were examined in details at a phosphate buffered saline solution at 37 °C over a 12-week period of time. To vary degradability, a co-monomer, acrylic acid (AA) or 2-hydroxypropyl methacrylamide (HPMA), was introduced, coupled with altering the concentration of the cross-linker and of the bioceramic. The co-monomer HPMA was found to be more effective than AA in enhancing degradation, though AA led to greater swelling ratios. 33% of weight loss was achieved in some of the biocomposites containing HPMA. Porous structures were developed during swelling and degradation in biocomposites with AA but not in those containing HPMA, suggesting different degradation mechanisms: bulk erosion vs. bulk degradation. Good biocompatibility, as evidenced by attachment and proliferation of mouse-derived osteoblast precursor cells from the MC3T3-E1 lineage, was observed on these biomaterials, regardless of the type of the co-monomer. The rationale and approaches employed here open up new opportunities for creating novel, complex organic-inorganic biomaterials in orthopedic tissue engineering.

Stimulation of healing within a rabbit calvarial defect by a PCL/PLGA scaffold blended with TCP using solid freeform fabrication technology

The purpose of this study was to investigate the healing capacity within an 8-mm rabbit calvarial defect using a polycaprolactone (PCL)/poly(lactic-co-glycolic acid) (PLGA) scaffold blended with tri-calcium phosphate (TCP) that was constructed using solid freeform fabrication (SFF) technology. The PCL/PLGA/TCP scaffold showed a 37 % higher compressive strength and rougher surface than the PCL/PLGA scaffold. In animal experiments, new bone formation was analyzed using microcomputed tomography (micro-CT) and histological and histometric analyses. The PCL/PLGA/TCP groups had significantly greater neo-tissue areas as compared with the control groups at 4 and 8 weeks (P < 0.05). The PCL/PLGA/TCP group had significantly greater bone density as compared with the control and PCL/PLGA groups at 4 and 8 weeks (P < 0.005). The results of this study suggest that the PCL/PLGA/TCP scaffold fabricated using SFF technology is useful for recovering and enhancing new bone formation in bony defects in rabbits.

The influence of environmental factors on bone tissue engineering

Bone repair and regeneration are dynamic processes that involve a complex interplay between the substrate, local and systemic cells, and the milieu. Although each constituent plays an integral role in faithfully recreating the skeleton, investigators have long focused their efforts on scaffold materials and design, cytokine and hormone administration, and cell-based therapies. Only recently have the intangible aspects of the milieu received their due attention. In this review, we highlight the important influence of environmental factors on bone tissue engineering.

Leveraging "raw materials" as building blocks and bioactive signals in regenerative medicine

Components found within the extracellular matrix (ECM) have emerged as an essential subset of biomaterials for tissue engineering scaffolds. Collagen, glycosaminoglycans, bioceramics, and ECM-based matrices are the main categories of "raw materials" used in a wide variety of tissue engineering strategies. The advantages of raw materials include their inherent ability to create a microenvironment that contains physical, chemical, and mechanical cues similar to native tissue, which prove unmatched by synthetic biomaterials alone. Moreover, these raw materials provide a head start in the regeneration of tissues by providing building blocks to be bioresorbed and incorporated into the tissue as opposed to being biodegraded into waste products and removed. This article reviews the strategies and applications of employing raw materials as components of tissue engineering constructs. Utilizing raw materials holds the potential to provide both a scaffold and a signal, perhaps even without the addition of exogenous growth factors or cytokines. Raw materials contain endogenous proteins that may also help to improve the translational success of tissue engineering solutions to progress from laboratory bench to clinical therapies. Traditionally, the tissue engineering triad has included cells, signals, and materials. Whether raw materials represent their own new paradigm or are categorized as a bridge between signals and materials, it is clear that they have emerged as a leading strategy in regenerative medicine. The common use of raw materials in commercial products as well as their growing presence in the research community speak to their potential. However, there has heretofore not been a coordinated or organized effort to classify these approaches, and as such we recommend that the use of raw materials be introduced into the collective consciousness of our field as a recognized classification of regenerative medicine strategies.

The healing of critical-size calvarial bone defects in rat with rhPDGF-BB, BMSCs, and β-TCP scaffolds

Platelet-derived growth factor-BB (PDGF-BB) plays important roles in regenerating damaged tissue. In this study we investigated the effects of a tissue-engineered bone combined with recombinant human PDGF-BB (rhPDGF-BB), bone marrow stem cells (BMSCs) and β-tricalcium phosphate (β-TCP) to repair critical-size calvarial bone defects in rat. Proliferation and osteogenic differentiation of BMSCs treated with different concentration rhPDGF-BB (0, 10, and 50 ng/ml) was evaluated by MTT, alkaline phosphatase (ALP) activity, alizarin red staining and real-time quantitative PCR (RT-qPCR) analysis of osteogenic gene. BMSCs were then combined with rhPDGF-BB-loaded β-TCP and transplanted into 5 mm calvarial bone defects. The new bone formation and mineralization was evaluated by micro-computerized tomography (Micro-CT) and histological analysis at week 8 after operation. It was observed that the proliferation of BMSCs treated with rhPDGF-BB was enhanced with a time- and dose- dependent manner. There were increased ALP activity, mineralized deposition and elevated mRNA levels of osteogenic gene for BMSCs treated with rhPDGF-BB, particularly in the 50 ng/ml group. Histological analysis showed new bone formation and mineralization in the rhPDGF-BB/BMSCs/β-TCP group was significantly higher than BMSCs/β-TCP, rhPDGF-BB/β-TCP, and β-TCP alone group (P < 0.05). In conclusion, rhPDGF-BB/BMSCs/β-TCP is a promising tissue-engineered bone for craniofacial bone regeneration.

The impact of immobilization of BMP-2 on PDO membrane for bone regeneration

Poly(dioxanone) (PDO) is colorless, crystalline, a biodegradable synthetic polymers that is used for biomedical applications, such as surgical sutures, cardiovascular applications, orthopedics, and plastic surgery. Recently, bone morphogenetic protein-2 (BMP-2) is widely used for bone tissue engineering. For the first time we report here on the in vitro performance of an electrospun PDO membrane immobilized with BMP-2. Immobilized BMP-2 on PDO membrane enhanced ALPase activity, the osteogenic differentiation gene expressions as well as cell attachment, except cell proliferation when compared to that of PDO membrane alone. These results suggest that PDO membrane with BMP-2 is helpful to promote bone healing and regeneration.

Enhancing osteoconduction of PLLA-based nanocomposite scaffolds for bone regeneration using different biomimetic signals to MSCs

In bone engineering, the adhesion, proliferation and differentiation of mesenchymal stromal cells rely on signaling from chemico-physical structure of the substrate, therefore prompting the design of mimetic "extracellular matrix"-like scaffolds. In this study, three-dimensional porous poly-L-lactic acid (PLLA)-based scaffolds have been mixed with different components, including single walled carbon nanotubes (CNT), micro-hydroxyapatite particles (HA), and BMP2, and treated with plasma (PT), to obtain four different nanocomposites: PLLA + CNT, PLLA + CNTHA, PLLA + CNT + HA + BMP2 and PLLA + CNT + HA + PT. Adult bone marrow mesenchymal stromal cells (MSCs) were derived from the femur of orthopaedic patients, seeded on the scaffolds and cultured under osteogenic induction up to differentiation and mineralization. The release of specific metabolites and temporal gene expression profiles of marrow-derived osteoprogenitors were analyzed at definite time points, relevant to in vitro culture as well as in vivo differentiation. As a result, the role of the different biomimetic components added to the PLLA matrix was deciphered, with BMP2-added scaffolds showing the highest biomimetic activity on cells differentiating to mature osteoblasts. The modification of a polymeric scaffold with reinforcing components which also work as biomimetic cues for cells can effectively direct osteoprogenitor cells differentiation, so as to shorten the time required for mineralization.

Bone tissue engineering: current strategies and techniques--part I: Scaffolds

Bone repair and regeneration is a dynamic process that involves a complex interplay between the (1) ground substance, (2) cells, and (3) milieu. While each constituent is integral to the final product, it is often helpful to consider each component individually. Therefore, we created a two-part review to examine scaffolds and cells' roles in bone tissue engineering. In Part I, we review the myriad of materials use for in vivo bone engineering. In Part II, we discuss the variety cell types (e.g., osteocytes, osteoblasts, osteoclasts, chondrocytes, mesenchymal stem cells, and vasculogenic cells) that are seeded upon or recruited to these scaffolds. In Part III, we discuss the optimization of the microenvironment. The biochemical processes and sequence of events that guide matrix production, cellular activation, and ossification are vital to developing successful bone tissue engineering strategies and are thus succinctly reviewed herein.

Effect of polycaprolactone scaffold permeability on bone regeneration in vivo

Successful bone tissue engineering depends on the scaffold's ability to allow nutrient diffusion to and waste removal from the regeneration site, as well as provide an appropriate mechanical environment. Since bone is highly vascularized, scaffolds that provide greater mass transport may support increased bone regeneration. Permeability encompasses the salient features of three-dimensional porous scaffold architecture effects on scaffold mass transport. We hypothesized that higher permeability scaffolds will enhance bone regeneration for a given cell seeding density. We manufactured poly-ɛ-caprolactone scaffolds, designed to have the same internal pore design and either a low permeability (0.688×10(-7)m(4)/N-s) or a high permeability (3.991×10(-7)m(4)/N-s), respectively. Scaffolds were seeded with bone morphogenic protein-7-transduced human gingival fibroblasts and implanted subcutaneously in immune-compromised mice for 4 and 8 weeks. Micro-CT evaluation showed better bone penetration into high permeability scaffolds, with blood vessel infiltration visible at 4 weeks. Compression testing showed that scaffold design had more influence on elastic modulus than time point did and that bone tissue infiltration increased the mechanical properties of the high permeability scaffolds at 8 weeks. These results suggest that for polycaprolactone, a more permeable scaffold with regular architecture is best for in vivo bone regeneration. This finding is an important step toward the end goal of optimizing a scaffold for bone tissue engineering.

Teriparatide therapy and beta-tricalcium phosphate enhance scaffold reconstruction of mouse femoral defects

To investigate the efficacy of endocrine parathyroid hormone treatment on tissue-engineered bone regeneration, massive femoral defects in C57Bl/6 mice were reconstructed with either 100:0 or 85:15 poly-lactic acid (PLA)/beta-tricalcium phosphate (β-TCP) scaffolds (hereafter PLA or PLA/βTCP, respectively), which were fabricated with low porosity (<30%) to improve their structural rigidity. Experimental mice were treated starting at 1 week postop with daily subcutaneous injections of 40 μg/kg teriparatide until sacrifice at 9 weeks, whereas control mice underwent the same procedure but were injected with sterile saline. Bone regeneration was assessed longitudinally using planar X-ray and quantitative microcomputed tomography, and the reconstructed femurs were evaluated at 9 weeks either histologically or biomechanically to determine their torsional strength and rigidity. Teriparatide treatment increased bone volume and bone mineral content significantly at 6 weeks and led to enhanced trabeculated bone callus formation that appeared to surround and integrate with the scaffold, thereby establishing union by bridging bone regeneration across the segmental defect in 30% of the reconstructed femurs, regardless of the scaffold type. However, the bone volume and mineral content in the PLA reconstructed femurs treated with teriparatide was reduced at 9 weeks to control levels, but remained significantly increased in the PLA/βTCP scaffolds. Further, bridged teriparatide-treated femurs demonstrated a prototypical brittle bone torsion behavior, and were significantly stronger and stiffer than control specimens or treated specimens that failed to form bridging bone union. Taken together, these observations suggest that intermittent, systemic parathyroid hormone treatment can enhance bone regeneration in scaffold-reconstructed femoral defects, which can be further enhanced by mineralized (βTCP) particles within the scaffold.