Bone regeneration with BMP-2 and hydroxyapatite in critical-size calvarial defects in rats

Prevention of bone dehiscence associated with orthodontic tooth movement by prophylactic injection of bone anabolic agents in mice

Although bone dehiscence may occur during orthodontic tooth movement into the narrow alveolar ridge, a non-invasive prevention method is yet to be fully established. We show for the first time prevention of bone dehiscence associated with orthodontic tooth movement by prophylactic injection of bone anabolic agents in mice. In this study, we established a bone dehiscence mouse model by applying force application and used the granular type of scaffold materials encapsulated with bone morphogenetic protein (BMP)-2 and OP3-4, the receptor activator of NF-κB ligand (RANKL)-binding peptide, for the prophylactic injection to the alveolar bone. In vivo micro-computed tomography revealed bone dehiscence with decreased buccal alveolar bone thickness and height after force application, whereas no bone dehiscence was observed with the prophylactic injection after force application, and alveolar bone thickness and height were kept at similar levels as those in the control group. Bone histomorphometry analyses revealed that both bone formation and resorption parameters were significantly higher in the injection with force application group than in the force application without the prophylactic injection group. These findings suggest that the prophylactic local delivery of bone anabolic reagents can prevent bone dehiscence with increased bone remodelling activity.

Multifunctional Scaffolds Based on Emulsion and Coaxial Electrospinning Incorporation of Hydroxyapatite for Bone Tissue Regeneration

Tissue engineering is nowadays a powerful tool to restore damaged tissues and recover their normal functionality. Advantages over other current methods are well established, although a continuous evolution is still necessary to improve the final performance and the range of applications. Trends are nowadays focused on the development of multifunctional scaffolds with hierarchical structures and the capability to render a sustained delivery of bioactive molecules under an appropriate stimulus. Nanocomposites incorporating hydroxyapatite nanoparticles (HAp NPs) have a predominant role in bone tissue regeneration due to their high capacity to enhance osteoinduction, osteoconduction, and osteointegration, as well as their encapsulation efficiency and protection capability of bioactive agents. Selection of appropriated polymeric matrices is fundamental and consequently great efforts have been invested to increase the range of properties of available materials through copolymerization, blending, or combining structures constituted by different materials. Scaffolds can be obtained from different processes that differ in characteristics, such as texture or porosity. Probably, electrospinning has the greater relevance, since the obtained nanofiber membranes have a great similarity with the extracellular matrix and, in addition, they can easily incorporate functional and bioactive compounds. Coaxial and emulsion electrospinning processes appear ideal to generate complex systems able to incorporate highly different agents. The present review is mainly focused on the recent works performed with Hap-loaded scaffolds having at least one structural layer composed of core/shell nanofibers.

Enhanced Biocompatibility and Osteogenic Activity of Marine-Plankton-Derived Whitlockite Bone Granules through Bone Morphogenetic Protein 2 Incorporation

Whitlockite (WH) is a calcium-phosphate-based Mg-containing ceramic with good mechanical properties, rapid resorption, and good osteogenicity. Recently, we successfully synthesized highly porous WH granules using a marine plankton exoskeleton (MP-WH). In the present study, we improved the osteoinductive activity of MP-WH granules by bone morphogenetic protein2 (BMP2) (MP-WH/BMP2). The surface morphology and composition of the fabricated MP-WH/BMP2 granules were characterized using scanning electron microscopy (SEM), X-ray diffraction, and Fourier transform infrared (FT-IR) spectroscopy. The biocompatibility and osteogenic effects were evaluated using human mesenchymal stem cells (hMSCs). BMP2 was absorbed on the surfaces of the MP-WH/BMP2 granules. Immobilized BMP2 was released at a moderate rate over 30 days. hMSCs seeded on MP-WH/BMP2 granules became biocompatible, with a better proliferation and adhesion for MP-WH/BMP2, compared with MP-WH. Bone-specific markers Runx2, type I collagen, osteocalcin, and osteopontin were significantly upregulated following BMP2 incorporation. Similar observations were made regarding the alkaline phosphatase activity. This study suggests that BMP2 incorporation improves the osteoinductive activity of marine-plankton-derived WH granules for bone tissue repair.

BMP Gene-Immobilization to Dental Implants Enhances Bone Regeneration

For individuals who have experienced tooth loss, dental implants are an important treatment option for oral reconstruction. For these patients, alveolar bone augmentation and acceleration of osseointegration optimize implant stability. Traditional oral surgery often requires invasive procedures, which can result in prolonged treatment time and associated morbidity. It has been previously shown that chemical vapor deposition (CVD) polymerization of functionalized [2.2]paracyclophanes can be used to anchor gene encoding vectors onto biomaterial surfaces and local delivery of a bone morphogenetic protein (BMP)-encoding vector can increase alveolar bone volume and density in vivo. This study is the first to combine the use of CVD technology and BMP gene delivery on titanium for the promotion of bone regeneration and bone to implant contact in vivo. BMP-7 tethered to titanium surface enhances osteoblast cell differentiation and alkaline phosphatase activity in vitro and increases alveolar bone regeneration and % bone to implant contact similar to using high doses of exogenously applied BMP-7 in vivo. The use of this innovative gene delivery strategy on implant surfaces offers an alternative treatment option for targeted alveolar bone reconstruction.

Comparison of rhBMP-2 in Combination with Different Biomaterials for Regeneration in Rat Calvaria Critical-Size Defects

Regeneration of critical bone defects requires the use of biomaterials. The incorporation of osteoinductive agents, such as bone morphogenetic proteins (BMPs), improves bone formation. This study aimed to compare the efficacy of rhBMP-2 in combination with different materials for bone regeneration in critical-sized rat calvarial defects. This was an experimental animal study using 30 rats. In each rat, two 5-mm critical-size defects were made in the calvaria (60 bone defects in total) using a trephine. All rats were randomized to one of the six groups: control (C), autograft + rhBMP-2 (A), absorbable collagen sponge + rhBMP-2 (ACS), β-tricalcium phosphate + rhBMP-2 (B-TCP), bovine xenograft + rhBMP-2 (B), and hydroxyapatite + rhBMP-2 (HA). The outcome was assessed after 4 and 8 weeks using histological description and the histological bone healing scale. Statistical analysis was performed using the Kruskal-Wallis and Mann–Whitney U tests, with a p-value set at 0.05. The average bone healing scores per group were as follows: C group, 12.5; A group, 26.5; ACS group, 18.8; B-TCP group, 26.2; HA group, 20.9; and B group, 20.9. The C group showed a significant difference between weeks 4 and 8 (p = 0.032). Among the 4-week groups, the C group showed a significant difference compared to A (p = 0.001), ACS (p = 0.017), and B-TCP (p = 0.005) groups. The 8-week experimental group did not show any significant differences between the groups. The 5-mm critical size defect in rat calvaria requires the use of bone biomaterials to heal at 4 and 8 weeks. rhBMP-2, as applied in this study, showed no difference in new bone formation when combined with bovine, B-TCP, or HA biomaterials.

Periodontal Tissue as a Biomaterial for Hard-Tissue Regeneration following bmp-2 Gene Transfer

The application of periodontal tissue in regenerative medicine has gained increasing interest since it has a high potential to induce hard-tissue regeneration, and is easy to handle and graft to other areas of the oral cavity or tissues. Additionally, bone morphogenetic protein-2 (BMP-2) has a high potential to induce the differentiation of mesenchymal stem cells into osteogenic cells. We previously developed a system for a gene transfer to the periodontal tissues in animal models. In this study, we aimed to reveal the potential and efficiency of periodontal tissue as a biomaterial for hard-tissue regeneration following a bmp-2 gene transfer. A non-viral expression vector carrying bmp-2 was injected into the palate of the periodontal tissues of Wistar rats, followed by electroporation. The periodontal tissues were analyzed through bone morphometric analyses, including mineral apposition rate (MAR) determination and collagen micro-arrangement, which is a bone quality parameter, before and after a gene transfer. The MAR was significantly higher 3-6 d after the gene transfer than that before the gene transfer. Collagen orientation was normally maintained even after the bmp-2 gene transfer, suggesting that the bmp-2 gene transfer has no adverse effects on bone quality. Our results suggest that periodontal tissue electroporated with bmp-2 could be a novel biomaterial candidate for hard-tissue regeneration therapy.

Bone Morphogenetic Proteins, Carriers, and Animal Models in the Development of Novel Bone Regenerative Therapies

Bone morphogenetic proteins (BMPs) possess a unique ability to induce new bone formation. Numerous preclinical studies have been conducted to develop novel, BMP-based osteoinductive devices for the management of segmental bone defects and posterolateral spinal fusion (PLF). In these studies, BMPs were combined with a broad range of carriers (natural and synthetic polymers, inorganic materials, and their combinations) and tested in various models in mice, rats, rabbits, dogs, sheep, and non-human primates. In this review, we summarized bone regeneration strategies and animal models used for the initial, intermediate, and advanced evaluation of promising therapeutical solutions for new bone formation and repair. Moreover, in this review, we discuss basic aspects to be considered when planning animal experiments, including anatomical characteristics of the species used, appropriate BMP dosing, duration of the observation period, and sample size.

Synthesis and characterization of nano-hydroxyapatite from Sardinella longiceps fish bone and its effects on human osteoblast bone cells

Organic debris in the form of fish bone wastes account to several thousand tons annually. In recent years, researchers have turned attention towards the bioconversion of organic debris into materials with biomedical applications. Accordingly, the present study synthesized nano-Hydroxyapatite (n-HAP) from bones of discarded Sardinella longiceps by the alkaline hydrolysis method. The synthesized n-HAP was characterized by using the scanning electron microscope (SEM), X-ray diffraction (XRD), atomic force microscope (AFM), and Fourier transform infrared spectroscopy (FTIR). Crushed fish bone demonstrated an agglomerate of fine and rod-like crystals as observed in SEM, whereas n-HAP exhibited a structure of dense thick particles. FTIR spectral data confirmed the functional groups such as alkanes, esters, saturated aliphatic, and aromatic groups. XRD analysis exhibited strong diffraction peaks of HAP confirming its presence in synthesized n-HAP. AFM analysis affirmed that the synthesized particles had an average size of 19.65 nm. Cell viability was tested at different concentrations (10, 50, 100, 250 μg/mL) against human osteoblast bone cells (MG-63).The maximum cell viability (141.3 ± 3.1%) was observed at 100 μg/mL (24 h). Mineralization was evaluated using Alizarin red staining of osteoblast MG-63 cells treated with n-HAP at the concentration of 50 and 100 μg/mL (0.54 ± 0.03 and 0.99 ± 0.05%) which exhibited red color indicating good results. The size, morphology, functional groups, viability and mineralization of the synthesized n-HAP are favorable for its use in bone tissue engineering and other potential osteo and dental applications.

BMP4 micro-immunotherapy increases collagen deposition and reduces PGE2 release in human gingival fibroblasts and increases tissue viability of engineered 3D gingiva under inflammatory conditions

Background

We aimed to evaluate the effect of low doses (LD) bone morphogenetic protein‐2 (BMP2) and BMP4 micro‐immunotherapy (MI) in two in vitro models of periodontal wound healing/regeneration.

Methods

We first evaluated the effect of LD of BMP2 and BMP4 MI on a 2D cell culture using human gingival fibroblasts (hGF) under inflammatory conditions induced by IL1β. Biocompatibility, inflammatory response (Prostaglandin E2 (PGE2) release), collagen deposition and release of extracellular matrix (ECM) organization‐related enzymes (matrix metalloproteinase‐1 (MMP1) and metalloproteinase inhibitor 1 (TIMP1)) were evaluated after short (3 days) and long‐term (24 days) treatment with BMP2 or BMP4 MI. Then, given the results obtained in the 2D cell culture, LD BMP4 MI treatment was evaluated in a 3D cell culture model of human tissue equivalent of gingiva (GTE) under the same inflammatory stimulus, evaluating the biocompatibility, inflammatory response and effect on MMP1 and TIMP1 release.

Results

LD BMP4 was able to decrease the release of the inflammatory mediator PGE2 and completely re‐establish the impaired collagen metabolism induced by IL1β treatment. In the 3D model, LD BMP4 treatment improved tissue viability compared with the vehicle, with similar levels to 3D tissues without inflammation. No significant effects were observed on PGE2 levels nor MMP1/TIMP1 ratio after LD BMP4 treatment, although a tendency to decrease PGE2 levels was observed after 3 days.

Conclusions

LD BMP4 MI treatment shows anti‐inflammatory and regenerative properties on hGF, and improved viability of 3D gingiva under inflammatory conditions. LD BMP4 MI treatment could be used on primary prevention or maintenance care of periodontitis.

Development of a New Bone-Mimetic Surface Treatment Platform: Nanoneedle Hydroxyapatite (nnHA) Coating

The hierarchical structure of bone plays pivotal roles in driving cell behavior and tissue regeneration and must be considered when designing materials for orthopedic applications. Herein, it is aimed to recapitulate the native bone environment by using melt electrowriting to fabricate fibrous microarchitectures which are modified with plate-shaped (pHA) or novel nanoneedle-shaped (nnHA) crystals. Nuclear magnetic resonance spectroscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction demonstrate that these coatings replicate the nanostructure and composition of native bone. Human mesenchymal stem/stromal cell (MSC) mineralization is significantly increased fivefold with pHA scaffolds and 14-fold with nnHA scaffolds. Given the protein stabilizing properties of mineral, these materials are further functionalized with bone morphogenetic protein 2 (BMP2). nnHA treatment facilitates controlled release of BMP2 which further enhance MSC mineral deposition. Finally, the versatility of this nnHA treatment method, which may be used to coat different architectures/materials including fused deposition modeling (FDM) scaffolds and Ti6Al4V titanium, is demonstrated. This study thus outlines a method for fabricating scaffolds with precise fibrous microarchitectures and bone-mimetic nnHA extrafibrillar coatings which significantly enhance MSC osteogenesis and therapeutic protein delivery, and leverages these results to show how this surface treatment method may be applied to a wider field for multiple orthopedic applications.

KMN-159, a novel EP4 receptor selective agonist, stimulates osteoblastic differentiation in cultured whole rat bone marrow

KMN-159 is the lead compound from a series of novel difluorolactam prostanoid EP₄ receptor agonists aimed at inducing local bone formation while avoiding the inherent side effects of systemic EP₄ activation. KMN-159 is a potent, selective small molecule possessing pharmacokinetic properties amenable to local administration. Unfractionated rat bone marrow cells (BMCs) were treated once at plating with escalating doses of KMN-159 (1 pM to 10 μM). The resulting elevated alkaline phosphatase (ALP) levels measured 9 days post-dose are consistent with increased osteoblastic differentiation and exposure to KMN-159 at low nanomolar concentrations for as little as 30 min was sufficient to induce complete osteoblast differentiation of the BMCs from both sexes and regardless of age. ALP induction was blocked by an EP₄ receptor antagonist but not by EP₁ or EP₂ receptor antagonists and was not induced by EP₂ or EP₃ receptor agonists. Addition of BMCs to plates coated with KMN-159 24 days earlier resulted in ALP activation, highlighting the chemical stability of the compound. The expression of phenotype markers such as ALP, type I collagen, and osteocalcin was significantly elevated throughout the osteoblastic differentiation timecourse initiated by KMN-159 stimulation. An increased number of tartrate-resistant acid phosphatase-positive cells was observed KMN-159 or PGE₂ treated BMCs but only in the presence of exogenous receptor activator of nuclear factor kappa-Β ligand (RANKL). No change in the number of adipocytes was observed. KMN-159 also increased bone healing in a rat calvarial defect model with a healing rate equivalent to recombinant human bone morphogenetic protein-2. Our studies show that KMN-159 is able to stimulate osteoblastic differentiation with a very short time of exposure, supporting its potential as a therapeutic candidate for augmenting bone mass.

Selected Nanomaterials' Application Enhanced with the Use of Stem Cells in Acceleration of Alveolar Bone Regeneration during Augmentation Process

Regenerative properties are different in every human tissue. Nowadays, with the increasing popularity of dental implants, bone regenerative procedures called augmentations are sometimes crucial in order to perform a successful dental procedure. Tissue engineering allows for controlled growth of alveolar and periodontal tissues, with use of scaffolds, cells, and signalling molecules. By modulating the patient's tissues, it can positively influence poor integration and healing, resulting in repeated implant surgeries. Application of nanomaterials and stem cells in tissue regeneration is a newly developing field, with great potential for maxillofacial bony defects. Nanostructured scaffolds provide a closer structural support with natural bone, while stem cells allow bony tissue regeneration in places when a certain volume of bone is crucial to perform a successful implantation. Several types of selected nanomaterials and stem cells were discussed in this study. Their use has a high impact on the efficacy of the current and future procedures, which are still challenging for medicine. There are many factors that can influence the regenerative process, while its general complexity makes the whole process even harder to control. The aim of this study was to evaluate the effectiveness and advantage of both stem cells and nanomaterials in order to better understand their function in regeneration of bone tissue in oral cavity.

Radiographic and histologic effects of bone morphogenetic protein-2/hydroxyapatite within bioabsorbable magnesium screws in a rabbit model

Background

Hydrogen gas formed by magnesium (Mg) screw corrosion can accumulate around the implant and create bone cysts, long-term osteolysis lesions, and bone healing delay. Thus, several authors currently do not recommend Mg implants for clinical use. In contrast, bone morphogenetic proteins (BMP)-2 have a very strong osteoinductive activity. The purpose of this study was to evaluate the effect of rhBMP-2/hydroxyapatite (HA) inside specially designed Mg cannulated screws in a rabbit femur model for hydrogen gas formation avoidance.

Methods

Fifteen rabbits underwent randomly different cannulated Mg screw implantation in both distal femora; 30 femora were divided into three groups depending on the materials fill in the cannulated Mg screw: control group (Mg screw with no treatment), HA group (Mg screw with HA), and BMP-2/HA group (Mg screw with a composite BMP-2/HA). Plain radiography, micro-CT, and histological analysis were accomplished, and the ability to release BMP-2 of the screws was evaluated by immersion of both the screw with no treatment and screw with a composite BMP-2/HA into the SBF for up to 7 days.

Results

X-ray assessment found the gas shadow around the implant was slightly smaller in the BMP-2/HA group than the HA and control groups at 8 weeks. Micro-CT analysis demonstrated statistically significant higher new bone formation in the BMP-2/HA group than the other groups, respectively, which also correlated with a decreased gas volume. Histological analysis showed higher osteointegration between implants and host femurs in the BMP-2/HA group than the HA and control groups at 12 weeks.

Conclusions

This study indicates that the combination of BMP-2/HA within Mg screws enhances new bone formation and therefore has the potential to decrease the complications of hydrogen gas formation around these implants.

Human amniotic membrane for guided bone regeneration of calvarial defects in mice

Due to its biological properties, human amniotic membrane (hAM) is widely studied in the field of tissue engineering and regenerative medicine. hAM is already very attractive for wound healing and it may be helpful as a support for bone regeneration. However, few studies assessed its potential for guided bone regeneration (GBR). The purpose of the present study was to assess the potential of the hAM as a membrane for GBR. In vitro, cell viability in fresh and cryopreserved hAM was assessed. In vivo, we evaluated the impact of fresh versus cryopreserved hAM, using both the epithelial or the mesenchymal layer facing the defect, on bone regeneration in a critical calvarial bone defect in mice. Then, the efficacy of cryopreserved hAM associated with a bone substitute was compared to a collagen membrane currently used for GBR. In vitro, no statistical difference was observed between the conditions concerning cell viability. Without graft material, cryopreserved hAM induced more bone formation when the mesenchymal layer covered the defect compared to the defect left empty. When associated with a bone substitute, such improved bone repair was not observed. These preliminary results suggest that cryopreserved hAM has a limited potential for GBR.

Histological Evaluation of Bone Repair with Hydroxyapatite: A Systematic Review

The aim of this study was to evaluate the morphological bone response in animal experiments by applying hydroxyapatite grafts in critical and non-critical size bone defects. Current report followed the guidelines established by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. Animal experiments were selected by assessing repair of bone defects with hydroxyapatite as bone graft and with blood clot only as control. Eight articles were identified in specialized literature and included in the meta-analysis. Statistical analysis was carried out with a random-effect model (p = 0.05). Subgroup analyses were further performed to investigate bone repair in critical and non-critical bone defects. Comprehensive analysis of bone repair outcome showed a statistically significant difference between hydroxyapatite and blood clot control (p < 0.05). Subgroup analyses showed statistically significant difference for critical bone defects (p < 0.05). No statistically significant difference was reported in non-critical bone defects (p > 0.05). Although animal studies revealed a high risk of bias and results should be interpreted with caution, the literature suggests that non-critical bone defects may heal spontaneously and without the need of a bone graft. Conversely, when critical-size defects are present, the use of hydroxyapatite bone graft improves the bone repair process.

Repair of segmental radial defect with autologous bone marrow aspirate and hydroxyapatite in rabbit radius: A clinical and radiographic evaluation

AIM

Finding an ideal bone substitute to treat large bone defects, delayed union and nonunions remain a challenge for orthopedic surgeons and researchers. Several studies have been conducted on bone regeneration; each has its own advantages and disadvantages. The aim of this study was to evaluate the effect of a combination of hydroxyapatite (HA) powder with autologous bone marrow (BM) aspirate on the repair of segmental radial defect in a rabbit model.

MATERIALS AND METHODS

A total of 36 male and adult New Zealand rabbit with a mean weight of 2.25 kg were used in this study. Approximately, 5 mm defect was created in the mid-shaft of the radius to be filled with HA powder in the control group "HA" (n=18) and with a combination of HA powder and autologous BM aspirate in the test group "HA+BM" (n=18). Animals were observed daily for healing by inspection of the surgical site, and six rabbits of each group were sacrificed at 30, 60, and 90 post-operative days to perform a radiographic evaluation of defect site.

RESULTS

Obtained results revealed a better and more rapid bone regeneration in the test group: Since the defect was rapidly and completely filled with mature bone tissue after 90 days.

CONCLUSION

Based on these findings, we could infer that adding a BM aspirate to HA is responsible of a better regeneration process leading to a complete filling of the defect.

Immunohistochemistry evaluation of BMP-2 with β-tricalcium phosphate matrix, polylactic and polyglycolic acid gel, and calcium phosphate cement in rats

PURPOSE

The installation of implants has become a routine procedure in the clinic. However, it takes time and adequate bone thickness, and for that, tissue engineering has made efforts to develop substitutes for autografts, in view of certain disadvantages of this material. The decision to choose the most suitable graft material for each case is an important step in the success of bone reconstruction. This study was to verify, by means of immunohistochemical study, that the addition of bone morphogenetic protein had some influence on biomaterials commercially available, taking into account the formation of mineralized tissue, bone replacement, and the amount of degradation of biomaterials.

METHODS

The sample consisted of 72 rats that were divided into eight treatment groups, in which two defects of 5 mm were made in each animal calvaria. Euthanasia was performed at 5, 15, and 30 days postop.

RESULTS

A histologic and histometric analysis was performed to quantitate the area of mineralized tissue formed, the area of newly formed bone, and the area of degradation of the biomaterials. Data were analyzed with multiple comparisons of means by Tukey contrasts, and significant difference was assigned at the level of P < 0.05. The proteins used for immunohistochemical analysis accounted for the process of formation, mineralization, and bone resorption and was performed using ordinal qualitative analysis, where from assigning scores.

CONCLUSIONS

Bone morphogenetic protein 2 was shown to be effective as an inducer of bone formation process independent biomaterial used mainly for accelerating the resorption process of the framework.

Effects of a buried magnetic field on cranial bone reconstruction in rats

The understanding of bone repair phenomena is a fundamental part of dentistry and maxillofacial surgery.

Injectable porous nano-hydroxyapatite/chitosan/tripolyphosphate scaffolds with improved compressive strength for bone regeneration

In this study we have fabricated porous injectable spherical scaffolds using chitosan biopolymer, sodium tripolyphosphate (TPP) and nano-hydroxyapatite (nHA). TPP was primarily used as an ionic crosslinker to crosslink nHA/chitosan droplets. We hypothesized that incorporating nHA into chitosan could support osteoconduction by emulating the mineralized cortical bone structure, and improve the Ultimate Compressive Strength (UCS) of the scaffolds. We prepared chitosan solutions with 0.5%, 1% and 2% (w/v) nHA concentration and used simple coacervation and lyophilization techniques to obtain spherical scaffolds. Lyophilized spherical scaffolds had a mean diameter of 1.33mm (n=25). Further, portion from each group lyophilized scaffolds were soaked and dried to obtain Lyophilized Soaked and Dried (LSD) scaffolds. LSD scaffolds had a mean diameter of 0.93mm (n=25) which is promising property for the injectability. Scanning Electron Microscopy images showed porous surface morphology and interconnected pore structures inside the scaffolds. Lyophilized and LSD scaffolds had surface pores <10 and 2μm, respectively. 2% nHA/chitosan LSD scaffolds exhibited UCS of 8.59MPa compared to UCS of 2% nHA/chitosan lyophilized scaffolds at 3.93MPa. Standardize UCS values were 79.98MPa and 357MPa for 2% nHA/chitosan lyophilized and LSD particles respectively. One-way ANOVA results showed a significant increase (p<0.001) in UCS of 1% and 2% nHA/chitosan lyophilized scaffolds compared to 0% and 0.5% nHA/chitosan lyophilized scaffolds. Moreover, 2% nHA LSD scaffolds had significantly increased (p<0.005) their mean UCS by 120% compared to 2% nHA lyophilized scaffolds. In a drawback, all scaffolds have lost their mechanical properties by 95% on the 2nd day when fully immersed in phosphate buffered saline. Additionally live and dead cell assay showed no cytotoxicity and excellent osteoblast attachment to both lyophilized and LSD scaffolds at the end of 14th day of in vitro studies. 2% nHA/chitosan scaffolds showed higher osteoblast attachment than 0% nHA/chitosan scaffolds.

Improving the ability to eliminate wounds and pressure ulcers

Pressure ulcers can be initiated by as little as 2 hours of constant pressure on the ski, that blocks blood circulation causing the skin and underlying tissues to die, leading to an open wound that never heals, but continues to grow in diameter and depth, and frequently jeopardizes patients' lives. Despite the application of many diverse techniques, pressure ulcers remain exceptionally difficult to heal because many ulcer elimination techniques have minimal effects, and although other techniques may appear to be effective, the evidence supporting their efficacy is weak. However, increasing evidence indicates that other techniques, such as the application of platelet-rich plasma, vacuum assisted closure, electrical stimulation, and hyperbaric oxygen therapy are effective and should be substituted for the older techniques. This review describes different standard and novel techniques that have been tested for eliminating pressure ulcers and discusses the relative efficacy of these techniques.

Effects of Recombinant Human Bone Morphogenetic Protein-2 Dose and Ceramic Composition on New Bone Formation and Space Maintenance in a Canine Mandibular Ridge Saddle Defect Model

Treatment of mandibular osseous defects is a significant clinical challenge. Maintenance of the height and width of the mandibular ridge is essential for placement of dental implants and restoration of normal dentition. While guided bone regeneration using protective membranes is an effective strategy for maintaining the anatomic contour of the ridge and promoting new bone formation, complications have been reported, including wound failure, seroma, and graft exposure leading to infection. In this study, we investigated injectable low-viscosity (LV) polyurethane/ceramic composites augmented with 100 μg/mL (low) or 400 μg/mL (high) recombinant human bone morphogenetic protein-2 (rhBMP-2) as space-maintaining bone grafts in a canine mandibular ridge saddle defect model. LV grafts were injected as a reactive paste that set in 5-10 min to form a solid porous composite with bulk modulus exceeding 1 MPa. We hypothesized that compression-resistant LV grafts would enhance new bone formation and maintain the anatomic contour of the mandibular ridge without the use of protective membranes. At the rhBMP-2 dose recommended for the absorbable collagen sponge carrier in dogs (400 μg/mL), LV grafts maintained the width and height of the host mandibular ridge and supported new bone formation, while at suboptimal (100 μg/mL) doses, the anatomic contour of the ridge was not maintained. These findings indicate that compression-resistant bone grafts with bulk moduli exceeding 1 MPa and rhBMP-2 doses comparable to that recommended for the collagen sponge carrier support new bone formation and maintain ridge height and width in mandibular ridge defects without protective membranes.

Preparation of resorbable carbonate-substituted hollow hydroxyapatite microspheres and their evaluation in osseous defects in vivo

Hollow hydroxyapatite (HA) microspheres, with a high-surface-area mesoporous shell, can provide a unique bioactive and osteoconductive carrier for proteins to stimulate bone regeneration. However, synthetic HA has a slow resorption rate and a limited ability to remodel into bone. In the present study, hollow HA microspheres with controllable amounts of carbonate substitution (0-12 wt.%) were created using a novel glass conversion route and evaluated in vitro and in vivo. Hollow HA microspheres with ~12 wt.% of carbonate (designated CHA12) showed a higher surface area (236 m(2) g(-1)) than conventional hollow HA microspheres (179 m(2)g(-1)) and a faster degradation rate in a potassium acetate buffer solution. When implanted for 12 weeks in rat calvarial defects, the CHA12 and HA microspheres showed a limited capacity to regenerate bone but the CHA12 microspheres resorbed faster than the HA microspheres. Loading the microspheres with bone morphogenetic protein-2 (BMP2) (1 μg per defect) stimulated bone regeneration and accelerated resorption of the CHA12 microspheres. At 12 weeks, the amount of new bone in the defects implanted with the CHA12 microspheres (73±8%) was significantly higher than the HA microspheres (59±2%) while the amount of residual CHA12 microspheres (7±2% of the total defect area) was significantly lower than the HA microspheres (21±3%). The combination of these carbonate-substituted HA microspheres with clinically safe doses of BMP2 could provide promising implants for healing non-loaded bone defects.

A review on carrier systems for bone morphogenetic protein-2

Bone morphogenetic protein-2 (BMP-2) has unique bone regeneration property. The powerful osteoinductive nature makes it considered as second line of therapy in nonunion bone defect. A large number of carriers and delivery systems made up of different materials have been investigated for controlled and sustained release of BMP-2. The delivery systems are in the form of hydrogel, microsphere, nanoparticles, and fibers. The carriers used for the delivery are made up of metals, ceramics, polymers, and composites. Implantation of these protein-loaded carrier leads to cell adhesion, degradation which eventually releases the drug/protein at site specific. But, problems like ectopic growth, lesser protein delivery, inactivation of the protein are reported in the available carrier systems. Therefore, it is need of an hour to modify the available carrier systems as well as explore other biomaterials with desired properties. In this review, all the reported carrier systems made of metals, ceramics, polymers, composites are evaluated in terms of their processing conditions, loading capacity and release pattern of BMP-2. Along with these biomaterials, the attempts of protein modification by adding some functional group to BMP-2 or extracting functional peptides from the protein to achieve the desired effect, is also evaluated. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 904-925, 2017.

Platelet-Rich Plasma Promotes Axon Regeneration, Wound Healing, and Pain Reduction: Fact or Fiction

Platelet-rich plasma (PRP) has been tested in vitro, in animal models, and clinically for its efficacy in enhancing the rate of wound healing, reducing pain associated with injuries, and promoting axon regeneration. Although extensive data indicate that PRP-released factors induce these effects, the claims are often weakened because many studies were not rigorous or controlled, the data were limited, and other studies yielded contrary results. Critical to assessing whether PRP is effective are the large number of variables in these studies, including the method of PRP preparation, which influences the composition of PRP; type of application; type of wounds; target tissues; and diverse animal models and clinical studies. All these variables raise the question of whether one can anticipate consistent influences and raise the possibility that most of the results are correct under the circumstances where PRP was tested. This review examines evidence on the potential influences of PRP and whether PRP-released factors could induce the reported influences and concludes that the preponderance of evidence suggests that PRP has the capacity to induce all the claimed influences, although this position cannot be definitively argued. Well-defined and rigorously controlled studies of the potential influences of PRP are required in which PRP is isolated and applied using consistent techniques, protocols, and models. Finally, it is concluded that, because of the purported benefits of PRP administration and the lack of adverse events, further animal and clinical studies should be performed to explore the potential influences of PRP.

Natural-based nanocomposites for bone tissue engineering and regenerative medicine: a review

Tissue engineering and regenerative medicine has been providing exciting technologies for the development of functional substitutes aimed to repair and regenerate damaged tissues and organs. Inspired by the hierarchical nature of bone, nanostructured biomaterials are gaining a singular attention for tissue engineering, owing their ability to promote cell adhesion and proliferation, and hence new bone growth, compared with conventional microsized materials. Of particular interest are nanocomposites involving biopolymeric matrices and bioactive nanosized fillers. Biodegradability, high mechanical strength, and osteointegration and formation of ligamentous tissue are properties required for such materials. Biopolymers are advantageous due to their similarities with extracellular matrices, specific degradation rates, and good biological performance. By its turn, calcium phosphates possess favorable osteoconductivity, resorbability, and biocompatibility. Herein, an overview on the available natural polymer/calcium phosphate nanocomposite materials, their design, and properties is presented. Scaffolds, hydrogels, and fibers as biomimetic strategies for tissue engineering, and processing methodologies are described. The specific biological properties of the nanocomposites, as well as their interaction with cells, including the use of bioactive molecules, are highlighted. Nanocomposites in vivo studies using animal models are also reviewed and discussed.

Enhanced healing of rat calvarial critical size defect with selenium-doped lamellar biocomposites

A 3D porous lamellar selenium-containing nano-hydroxyapatite (SeHAN)/chitosan (CS) biocomposite was synthesized. The selenium-containing hydroxyapatite (HA) grains of 150~200 nm in length and 20~30 nm in width were observed by dynamic light scattering and transmission electron microscopy. A combination of X-ray diffraction, Fourier-transform infrared spectroscopy, and SEM indicated that HA particles were uniformly dispersed in chitosan matrix and there was a chemical interaction between chitosan and HA. Then, a standard critical size calvarial bone defect was created in Wistar rats. In group 1, no implant was made in the defect. In groups 2 and 3, HA nanoparticles (HAN)/CS biocomposite and SeHAN/CS biocomposite were implanted into the defect, respectively. After 4 weeks, the histological assessment clearly exhibited no significant changes, only found some living cells anchored in the periphery of the implants. After 8 and 12 weeks, most newly formed osteoid tissue was found in the SeHAN/CS implant group. Additionally, the newly formed osteoid tissue, both at the edge and in the center of implants, was bioactive and neovascularized. Microfocus computerized tomography measurements also confirmed the much better quality of the newly formed bone tissue in SeHAN/CS implant group than that in HAN/CS implant group (p < 0.01). Collectively, the SeHAN/CS biocomposite, as a bioactive bone grafting substitute, significantly enhanced the repair of bone defect.

Effect of Emdogain enamel matrix derivative and BMP-2 on the gene expression and mineralized nodule formation of alveolar bone proper-derived stem/progenitor cells

The objective of this study was to evaluate the effect of Emdogain (Enamel Matrix Derivative, EMD) and Bone Morphogenetic Protein-2 (BMP-2), either solely or in combination, on the gene expression and mineralized nodule formation of alveolar bone proper-derived stem/progenitor cells. Stem/progenitor cells were isolated from human alveolar bone proper, magnetically sorted using STRO-1 antibodies, characterized flowcytometrically for their surface markers' expression, and examined for colony formation and multilineage differentiation potential. Subsequently, cells were treated over three weeks with 100 μg/ml Emdogain (EMD-Group), or 100 ng/ml BMP-2 (BMP-Group), or a combination of 100 ng/ml BMP-2 and 100 μg/ml Emdogain (BMP/EMD-Group). Unstimulated stem/progenitor cells (MACS(+)-Group) and osteoblasts (OB-Group) served as controls. Osteogenic gene expression was analyzed using RTq-PCR after 1, 2 and 3 weeks (N = 3/group). Mineralized nodule formation was evaluated by Alizarin-Red staining. BMP and EMD up-regulated the osteogenic gene expression. The BMP Group showed significantly higher expression of Collagen-I, III, and V, Alkaline phosphatase and Osteonectin compared to MACS(+)- and OB-Group (p < 0.05; Two-way ANOVA/Bonferroni) with no mineralized nodule formation. Under in-vitro conditions, Emdogain and BMP-2 up-regulate the osteogenic gene expression of stem/progenitor cells. The combination of BMP-2 and Emdogain showed no additive effect and would not be recommended for a combined clinical stimulation.

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

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

Nanocomposites for bone tissue regeneration

Natural bone tissue possesses a nanocomposite structure that provides appropriate physical and biological properties. For bone tissue regeneration, it is crucial for the biomaterial to mimic living bone tissue. Since no single type of material is able to mimic the composition, structure and properties of native bone, nanocomposites are the best choice for bone tissue regeneration as they can provide the appropriate matrix environment, integrate desirable biological properties, and provide controlled, sequential delivery of multiple growth factors for the different stages of bone tissue regeneration. This article reviews the composition, structure and properties of advanced nanocomposites for bone tissue regeneration. It covers aspects of interest such as the biomimetic synthesis of bone-like nanocomposites, guided bone regeneration from inert biomaterials and bioactive nanocomposites, and nanocomposite scaffolds for bone tissue regeneration. The design, fabrication, and in vitro and in vivo characterization of such nanocomposites are reviewed.

A novel method of dental panoramic tomogram analysis: a perspective tool for a screening test for osteoporosis

OBJECTIVE

The purpose of this study was to test a new method of dental panoramic tomogram (DPT) analysis to show the differences of mandibular bone volume and relative bone density (RBD) in order to detect osteoporosis.

MATERIALS AND METHODS

A case-control study compared 62 women with osteoporosis (O) and 24 women with osteopenia (o) to a control group of 33 women with normal bone mineral density (N). DPTs were analyzed using an original method resulting in anatomic and RBD indexes as well as using previously described methods: panoramic mandibular index (PMI) and mandibular cortical width (MCW).

RESULTS

One anatomic and four RBD indexes differed statistically significantly between the group O and N and three RBD indexes differed statistically significantly between o and N. PMI did not show statistically significant differences between the groups. The MCW differed significantly at two measured sites between O and N.

CONCLUSIONS

Average values of RBD indexes were statistically significantly different between O and N and also between o and N. Important differences regarding RBD were confirmed using a new and original method of common DPT analysis. This method could serve as a screening tool for osteoporosis.

Effect of ozone therapy on autogenous bone graft healing in calvarial defects: a histologic and histometric study in rats

AIM

The purpose of this study was to analyze histologically the effect of ozone therapy in combination with autogenous bone graft on bone healing in rat calvaria.

METHODS

Critical size defects were created in calvaria of 27 male Wistar rats. The animals were divided into three groups of nine animals each: autogenous bone graft group (n = 9); autogenous bone graft with ozone therapy group (80%, 30 s 3 d for 2 wk, n = 9); non-treatment (control) group (n = 9). Animals were killed after 8 wk. Histomorphometric assessments, using image analysis software, and histological analyses were performed. Primary outcome was total bone area. Secondary outcomes (osteoblast number, new bone formation) were also measured.

RESULTS

Histomorphometrically, the total bone area in the autogenous bone graft with ozone therapy group (9.3 ± 2.2) were significantly higher than that of the autogenous bone graft group (5.1 ± 1.8) (p < 0.05). Also, the ozone therapy group significantly increased the percentage of total bone area compared to the autogenous bone graft group (p < 0.05). The osteoblast number significantly increased in the autogenous bone graft with the ozone therapy group (58 ± 12.3) compared to the autogenous bone graft group (9.3 ± 3.5) (p < 0.05). Also, it was observed that autogenous bone graft with ozone therapy group showed significant new bone formation when compared to the autogenous bone graft group (p < 0.05).

CONCLUSION

Ozone therapy enhances new bone formation by autogenous bone graft in the rat calvarial defect model.

Exploring anorganic bovine bone granules as osteoblast carriers for bone bioengineering: a study in rat critical-size calvarial defects

It is known that current trends on bone bioengineering seek ideal scaffolds and explore innovative methods to restore tissue function. In this way, the objective of this study was to evaluate the behavior of anorganic bovine bone as osteoblast carrier in critical-size calvarial defects. MC3T3-E1 osteoblast cells (1x10(5) cells/well) were cultured on granules of anorganic bovine bone in 24-well plates and after 24 h these granules were implanted into rat critical-size calvarial defects (group Biomaterial + Cells). In addition, other groups were established with different fillings of the defect: Blood Clot (negative control); Autogenous Bone (positive control); Biomaterial (only granules) and Cells (only MC3T3-E1 cells). After 30 days, the animals were euthanized and the calvaria were technically processed in order to allow histological and morphometric analysis. It was possible to detect blood vessels, connective tissue and newly formed bone in all groups. Particularly in the Biomaterial + Cells group, it was possible to observe a profile of biological events between the positive control group (autogenous bone) and the group in which only anorganic bovine granules were implanted. Altogether, the results of the present study showed that granules of anorganic bovine bone can be used as carrier to osteoblasts and that adding growth factors at the moment of implantation should maximize these results.