Bone formation of a porous Gelatin-Pectin-biphasic calcium phosphate composite in presence of BMP-2 and VEGF

Calcium Phosphates: A Key to Next-Generation In Vitro Bone Modeling

The replication of bone physiology under laboratory conditions is a prime target behind the development of in vitro bone models. The model should be robust enough to elicit an unbiased response when stimulated experimentally, giving reproducible outcomes. In vitro bone tissue generation majorly requires the availability of cellular components, the presence of factors promoting cellular proliferation and differentiation, efficient nutrient supply, and a supporting matrix for the cells to anchor - gaining predefined topology. Calcium phosphates (CaP) are difficult to ignore while considering the above requirements of a bone model. Therefore, the current review focuses on the role of CaP in developing an in vitro bone model addressing the prerequisites of bone tissue generation. Special emphasis is given to the physico-chemical properties of CaP that promote osteogenesis, angiogenesis and provide sufficient mechanical strength for load-bearing applications. Finally, the future course of action is discussed to ensure efficient utilization of CaP in the in vitro bone model development field.

Development of Composite Sponge Scaffolds Based on Carrageenan (CRG) and Cerium Oxide Nanoparticles (CeO2 NPs) for Hemostatic Applications

In this study, a novel absorbable hemostatic agent was developed using carrageenan (CRG) as a natural polymer and cerium oxide nanoparticles (CeO2 NPs). CRG-CeO2-0.5 and CRG-CeO2-1 composites were prepared by compositing CeO2 to CRG + CeO2 at a weight ratio of 0.5:100 and 1:100, respectively. The physicochemical and structural properties of these compounds were studied and compared with pristine CRG. Upon incorporation of CeO2 nanoparticles into the CRG matrix, significant reductions in hydrogel degradation were observed. In addition, it was noted that CRG-CeO2 exhibited better antibacterial and hemostatic properties than CRG hydrogel without CeO2 NPs. The biocompatibility of the materials was tested using the NIH 3T3 cell line, and all samples were found to be nontoxic. Particularly, CRG-CeO2-1 demonstrated superior hemostatic effects, biocompatibility, and a lower degradation rate since more CeO2 NPs were present in the CRG matrix. Therefore, CRG-CeO2-1 has the potential to be used as a hemostatic agent and wound dressing.

Scaffold Guided Bone Regeneration for the Treatment of Large Segmental Defects in Long Bones

Bone generally displays a high intrinsic capacity to regenerate. Nonetheless, large osseous defects sometimes fail to heal. The treatment of such large segmental defects still represents a considerable clinical challenge. The regeneration of large bone defects often proves difficult, since it relies on the formation of large amounts of bone within an environment impedimental to osteogenesis, characterized by soft tissue damage and hampered vascularization. Consequently, research efforts have concentrated on tissue engineering and regenerative medical strategies to resolve this multifaceted challenge. In this review, we summarize, critically evaluate, and discuss present approaches in light of their clinical relevance; we also present future advanced techniques for bone tissue engineering, outlining the steps to realize for their translation from bench to bedside. The discussion includes the physiology of bone healing, requirements and properties of natural and synthetic biomaterials for bone reconstruction, their use in conjunction with cellular components and suitable growth factors, and strategies to improve vascularization and the translation of these regenerative concepts to in vivo applications. We conclude that the ideal all-purpose material for scaffold-guided bone regeneration is currently not available. It seems that a variety of different solutions will be employed, according to the clinical treatment necessary.

Nanoparticles based composite coatings with tunable vascular endothelial growth factor and bone morphogenetic protein-2 release for bone regeneration

Bone healing is a complex cascade involving precisely coordinated spatiotemporal presentation of multiple growth factors (GFs), including osteogenic and angiogenic GFs, and each stage of bone healing requires varying types and content of GFs. In this study, we fabricated a composite nanocoating with tunable vascular endothelial growth factor (VEGF) and bone morphogenetic protein-2 (BMP-2) that was coated on the surface of a polydopamine (PDA)-decorated tertiary calcium phosphate (TCP) scaffold using VEGF-loaded chitosan/bovine serum albumin nanoparticles (CS/BSA-NPs) and BMP-2-loaded poly-L-lysine/oxidized alginate nanoparticles (PLL/OALG-NPs). It was found that VEGF could be efficiently released to promote vascularization in early bone repair stages due to the rapid biodegradation of CS/BSA-NPs, while bone formation can be promoted by a sustained release of BMP-2 from the slowly degrading PLL/OALG-NPs. The composite coating and TCP scaffold can be conjugated due to the excellent adhesive property of PDA. The composite coating can achieve the rapid release of VEGF and sustained release of BMP-2, which can activate GFs for accelerating bone healing.

Potential of pectin for biomedical applications: a comprehensive review

Pectin is a polysaccharide extracted from various plants, such as apples, oranges, lemons, and it possesses some beneficial effects on human health, including being hypoglycemic and hypocholesterolemic. Therefore, pectin is used in various pharmaceutical and biomedical applications. Meanwhile, its low mechanical strength and fast degradation rate limit its usage as drug delivery devices and tissue engineering scaffolds. To enhance these properties, it can be modified or combined with other organic molecules or polymers and/or inorganic compounds. These materials can be prepared as nano sized drug carriers in the form of spheres, capsules, hydrogels, self assamled micelles, etc., for treatment purposes (mostly cancer). Different composites or blends of pectin can also be produced as membranes, sponges, hydrogels, or 3D printed matrices for tissue regeneration applications. This review is concentrated on the properties of pectin based materials and focus especially on the utilization of these materials as drug carriers and tissue engineering scaffolds, including 3D printed and 3D bioprinted systems covering the studies in the last decade and especially in the last 5 years.

Can zaprinast and avanafil induce the levels of angiogenesis, bone morphogenic protein 2, 4 and 7 in kidney of ovariectomised rats?

OBJECTIVE

This study investigated effects of zaprinast and avanafil on angiogenesis, vascular endothelial growth factor (VEGF), bone morphogenic protein (BMP) 2, 4 and 7.

METHODS

Female rats were randomly divided into four groups (n = 6). Sham; abdomen was approximately 2 cm opened and closed. Ovariectomised (OVX); abdomen was opened 2 cm and the ovaries were cut. OVX + zaprinast and OVX + avanafil groups; after the same procedure with OVX, 10 mg/kg zaprinast and avanafil were orally administered for 2 month, respectively. Angiogenesis and the levels of VEGF, BMP2, 4 and 7 were determined.

RESULTS

VEGF, BMP2, 4 and 7 levels in OVX + zaprinast and especially OVX + avanafil groups were higher than the sham and OVX (p < .05). However, only VEGF and BMP2 levels in OVX + zaprinast group were significant according to sham (p < .05). Also, angiogenesis in OVX + zaprinast and OVX + avanafil groups was dominant according to sham and OVX (p < .05).

CONCLUSIONS

Zaprinast and avanafil induced BMP2, 4 and 7 levels synergistically with increased VEGF and angiogenesis in renal tissue.

Stimulating effects of vardenafil, tadalafil, and udenafil on vascular endothelial growth factor, angiogenesis, vitamin D3, bone morphogenic proteins in ovariectomized rats

OBJECTIVE

This study investigated the effect of vardenafil, tadalafil, and udenafil from phosphodiesterase-5 inhibitors (PDE-5Is) on bone morphogenic-protein (BMP)2 and 4 levels, along with angiogenesis in ovariectomized rat's kidney.

METHOD

Rats were randomly divided into five groups (n = 10). Sham: abdomen was opened, and closed. OVX: ovaries were removed. OVX + vardenafil, OVX + tadalafil, and OVX + udenafil groups: ovaries were removed and closed, and after 6 months from postoperative, 10 mg/kg of vardenafil, tadalafil, and udenafil were administrated as daily a single-dose for 60 days, respectively. Histopathologic and immunohistochemical examinations were performed for angiogenesis, and biochemical analysis for vascular endothelial growth-factor (VEGF), VitaminD₃, BMP2 and 4 levels in rat's kidney.

RESULTS

VEGF, BMP2 and 4, VitaminD₃, and angiogenesis were high in the all inhibitor groups compared with the sham and OVX (p < .05). However, BMP4 levels were only high in the OVX + tadalafil group (p < .05).

CONCLUSION

The results indicated that vardenafil, udenafil, and especially tadalafil increased VEGF, BMP2, and VitaminD₃ levels.

Preparation of Calcium Phosphate Compounds on Zirconia Surfaces for Dental Implant Applications

Titanium is widely used in medical implants despite the release of heavy metal ions over long-term use. Zirconia is very close to the color of teeth; however, its biological inertness hinders bonding with bone tissue. Alkaline treatment and coatings of calcium phosphate can be used to enhance bone regeneration adjacent to dental implants. This study examined the effects of alkaline treatment, calcium phosphate coatings, and sintering, on the physical properties of implant material. Our analysis confirmed that the calcium phosphate species were octacalcium phosphate (OCP). The sintering of calcium phosphate was shown to create B-type HAP, which is highly conducive toward the differentiation of mesenchymal stem cells (MSCs) into osteoblasts for the facilitation of bone integration. Conclusions: This study demonstrated the room-temperature fabrication of dental implants with superhydrophilic surfaces to enhance biocompatibility.

Lipid-Based Nano-Sized Cargos as a Promising Strategy in Bone Complications: A Review

Bone metastasis has been considered the fatal phase of cancers, which remains incurable and to be a challenge due to the non-availability of the ideal treatment strategy. Unlike bone cancer, bone metastasis involves the spreading of the tumor cells to the bones from different origins. Bone metastasis generally originates from breast and prostate cancers. The possibility of bone metastasis is highly attributable to its physiological milieu susceptible to tumor growth. The treatment of bone-related diseases has multiple complications, including bone breakage, reduced quality of life, spinal cord or nerve compression, and pain. However, anticancer active agents have failed to maintain desired therapeutic concentrations at the target site; hence, uptake of the drug takes place at a non-target site responsible for the toxicity at the cellular level. Interestingly, lipid-based drug delivery systems have become the center of interest for researchers, thanks to their biocompatible and bio-mimetic nature. These systems possess a great potential to improve precise bone targeting without affecting healthy tissues. The lipid nano-sized systems are not only limited to delivering active agents but also genes/peptide sequences/siRNA, bisphosphonates, etc. Additionally, lipid coating of inorganic nanomaterials such as calcium phosphate is an effective approach against uncontrollable rapid precipitation resulting in reduced colloidal stability and dispersity. This review summarizes the numerous aspects, including development, design, possible applications, challenges, and future perspective of lipid nano-transporters, namely liposomes, exosomes, solid lipid nanoparticles (SLN), nanostructured lipid carriers (NLC), and lipid nanoparticulate gels to treat bone metastasis and induce bone regeneration. Additionally, the economic suitability of these systems has been discussed and different alternatives have been discussed. All in all, through this review we will try to understand how far nanomedicine is from clinical and industrial applications in bone metastasis.

Local Application of Mineral-Coated Microparticles Loaded With VEGF and BMP-2 Induces the Healing of Murine Atrophic Non-Unions

Deficient angiogenesis and disturbed osteogenesis are key factors for the development of nonunions. Mineral-coated microparticles (MCM) represent a sophisticated carrier system for the delivery of vascular endothelial growth factor (VEGF) and bone morphogenetic protein (BMP)-2. In this study, we investigated whether a combination of VEGF- and BMP-2-loaded MCM (MCM + VB) with a ratio of 1:2 improves bone repair in non-unions. For this purpose, we applied MCM + VB or unloaded MCM in a murine non-union model and studied the process of bone healing by means of radiological, biomechanical, histomorphometric, immunohistochemical and Western blot techniques after 14 and 70 days. MCM-free non-unions served as controls. Bone defects treated with MCM + VB exhibited osseous bridging, an improved biomechanical stiffness, an increased bone volume within the callus including ongoing mineralization, increased vascularization, and a histologically larger total periosteal callus area consisting predominantly of osseous tissue when compared to defects of the other groups. Western blot analyses on day 14 revealed a higher expression of osteoprotegerin (OPG) and vice versa reduced expression of receptor activator of NF-κB ligand (RANKL) in bone defects treated with MCM + VB. On day 70, these defects exhibited an increased expression of erythropoietin (EPO), EPO-receptor and BMP-4. These findings indicate that the use of MCM for spatiotemporal controlled delivery of VEGF and BMP-2 shows great potential to improve bone healing in atrophic non-unions by promoting angiogenesis and osteogenesis as well as reducing early osteoclast activity.

Meeting the challenges and clinical requirements for dental regeneration; the New Zealand experience

Disease and trauma leading to tooth loss and destruction of supporting bone is a significant oral handicap, which may be addressed through surgical therapies that aim to regenerate the lost tissue. Whilst complete regeneration of teeth is still aspirational, regeneration of supporting structures (dental pulp, cementum, periodontal ligament, bone) is becoming commonplace, both for teeth and for titanium dental implants that are used to replace teeth. Most grafting materials are essentially passive, however the next generation of oral regenerative devices will combine non-antibiotic antimicrobials and/or osteogenic or inductive factors and/or appropriate multipotential stem cells. The review gives an overview of the approaches taken, including fabrication of novel scaffolds, incorporation of growth factors and cell-based therapies, and discusses the preclinical animal models we employ in the development pathway.

Promotion of angiogenesis toward transplanted ovaries using nitric oxide releasing nanoparticles in fibrin hydrogel

Transplantation of ovary is one method of facilitating fertility preservation to increase the quality of life of cancer survivors. Immediately after transplantation, ovaries are under ischemic conditions owing to a lack of vascular anastomosis between the graft and host tissues. The transplanted ovaries can suffer damage because of lack of oxygen and nutrients, resulting in necrosis and dysfunction. In the technique proposed in this paper, the ovary is encapsulated with nitric oxide-releasing nanoparticles (NO-NPs) in fibrin hydrogels, which form a carrying matrix to prevent ischemic damage and accelerate angiogenesis. The low concentration of NO released from mPEG-PLGA nanoparticles elicits blood vessel formation, which allows transplanted ovaries in the subcutis to recover from the ischemic period. In experiments with mice, the NO-NPs/fibrin hydrogel improved the total number and quality of ovarian follicles after transplantation. The intra-ovarian vascular density was 4.78 folds higher for the NO-NPs/fibrin hydrogel groups compared to that for the nontreated groups. Finally,in vitrofertilization revealed a successful blastocyst formation rate for NO-NPs/fibrin hydrogel coated ovaries. Thus, NO-NPs/fibrin hydrogels can provide an appropriate milieu to promote angiogenesis and be considered as adjuvant surgery materials for fertility preservation.

Implantation of nanofibrous silk scaffolds seeded with bone marrow stromal cells promotes spinal cord regeneration (6686 words)

Spinal cord injury (SCI) is a common pathology often resulting in permanent loss of sensory, motor, and autonomic function. Numerous studies in which stem cells have been transplanted in biomaterial scaffolds into animals have demonstrated their considerable potential for recovery from SCI. In the present study, a three-dimensional porous silk fibroin (SF) scaffold with a mean pore size of approximately 383 μm and nanofibrous structure was fabricated, the silk scaffold enabling the enhanced attachment and proliferation of bone marrow stromal cells (BMSCs). Investigation of its therapeutic potential was conducted by implantation of the nanofibrous SF scaffold seeded with BMSCs into a transected spinal cord model. Recovery of the damaged spinal cord was significantly improved after 2 months, compared with a non-nanofibrous scaffold, in combination with decreased glial fibrillary acidic protein (GFAP) expression and improved axonal regeneration at the site of injury. Furthermore, elevated Basso-Beattie-Bresnahan (BBB) scores indicated greatly improved hindlimb movement. Together, these results demonstrate that transplantation of neural scaffolds consisting of nanofibrous SF and BMSCs is an attractive strategy for the promotion of functional recovery following SCI.

Recent advances in utilization of pectins in biomedical applications: a review focusing on molecular structure-directing health-promoting properties

The numerous health benefits of pectins justify their inclusion in human diets and biomedical products. This review provides an overview of pectin extraction and modification methods, their physico-chemical characteristics, health-promoting properties, and pharmaceutical/biomedical applications. Pectins, as readily available and versatile biomolecules, can be tailored to possess specific functionalities for food, pharmaceutical and biomedical applications, through judicious selection of appropriate extraction and modification technologies/processes based on green chemistry principles. Pectin's structural and physicochemical characteristics dictate their effects on digestion and bioavailability of nutrients, as well as health-promoting properties including anticancer, immunomodulatory, anti-inflammatory, intestinal microflora-regulating, immune barrier-strengthening, hypercholesterolemia-/arteriosclerosis-preventing, anti-diabetic, anti-obesity, antitussive, analgesic, anticoagulant, and wound healing effects. HG, RG-I, RG-II, molecular weight, side chain pattern, and degrees of methylation, acetylation, amidation and branching are critical structural elements responsible for optimizing these health benefits. The physicochemical characteristics, health functionalities, biocompatibility and biodegradability of pectins enable the construction of pectin-based composites with distinct properties for targeted applications in bioactive/drug delivery, edible films/coatings, nano-/micro-encapsulation, wound dressings and biological tissue engineering. Achieving beneficial synergies among the green extraction and modification processes during pectin production, and between pectin and other composite components in biomedical products, should be key foci for future research.

Recent Progress on Polysaccharide-Based Hydrogels for Controlled Delivery of Therapeutic Biomolecules

A plethora of applications using polysaccharides have been developed in recent years due to their availability as well as their frequent nontoxicity and biodegradability. These polymers are usually obtained from renewable sources or are byproducts of industrial processes, thus, their use is collaborative in waste management and shows promise for an enhanced sustainable circular economy. Regarding the development of novel delivery systems for biotherapeutics, the potential of polysaccharides is attractive for the previously mentioned properties and also for the possibility of chemical modification of their structures, their ability to form matrixes of diverse architectures and mechanical properties, as well as for their ability to maintain bioactivity following incorporation of the biomolecules into the matrix. Biotherapeutics, such as proteins, growth factors, gene vectors, enzymes, hormones, DNA/RNA, and antibodies are currently in use as major therapeutics in a wide range of pathologies. In the present review, we summarize recent progress in the development of polysaccharide-based hydrogels of diverse nature, alone or in combination with other polymers or drug delivery systems, which have been implemented in the delivery of biotherapeutics in the pharmaceutical and biomedical fields.

Pectin in biomedical and drug delivery applications: A review

Natural macromolecules have attracted increasing attention due to their biocompatibility, low toxicity, and biodegradability. Pectin is one of the few polysaccharides with biomedical activity, consequently a candidate in biomedical and drug delivery Applications. Rhamnogalacturonan-II, a smaller component in pectin, plays a major role in biomedical activities. The ubiquitous presence of hydroxyl and carboxyl groups in pectin contribute to their hydrophilicity and, hence, to the favorable biocompatibility, low toxicity, and biodegradability. However, pure pectin-based materials present undesirable swelling and corrosion properties. The hydrophilic groups, via coordination, electrophilic addition, esterification, transesterification reactions, can contribute to pectin's physicochemical properties. Here the properties, extraction, and modification of pectin, which are fundamental to biomedical and drug delivery applications, are reviewed. Moreover, the synthesis, properties, and performance of pectin-based hybrid materials, composite materials, and emulsions are elaborated. The comprehensive review presented here can provide valuable information on pectin and its biomedical and drug delivery applications.

Preparation of microfluidic-based pectin microparticles loaded carbon dots conjugated with BMP-2 embedded in gelatin-elastin-hyaluronic acid hydrogel scaffold for bone tissue engineering application

The controlled delivery of the bone morphogenetic protein-2 (BMP-2) with tracking ability would overcome most of the side effects linked to the burst release and uncontrolled delivery of this growth factor for bone regeneration. Herein, BMP-2-conjugated carbon dots (CDs) was used as noninvasive detection platforms to deliver BMP-2 for therapeutic applications where osteogenesis and bioimaging are both required. With this in mind, the present work aimed to develop a controlled BMP-2-CDs release system using composite scaffolds containing BMP-2-CDs loaded pectin microparticles, which had been optimized for bone regeneration. By using microfluidic approach, we encapsulated BMP-2-CDs in pectin microparticles with narrow size distribution and then incorporated into composite scaffolds composed of gelatin, elastin, and hyaluronic acid. The BMP-2-CDs was released from the composite scaffolds in a sustained fashion for up to 21 days exhibited a high controlled delivery capacity. When tested in vitro with MG-63 cells, these extraction mediums showed the intercellular uptake of BMP-2-CDs and enhanced biological properties and pro-osteogenic effect. By utilizing the pectin microparticles carrying BMP-2-CDs as promising bioimaging agents for growth factor delivery and by tuning the composition of the scaffolds, this platform has immense potential in the field of bone tissue regeneration.

Individualized plasticity autograft mimic with efficient bioactivity inducing osteogenesis

Mineralized tissue regeneration is an important and challenging part of the field of tissue engineering and regeneration. At present, autograft harvest procedures may cause secondary trauma to patients, while bone scaffold materials lack osteogenic activity, resulting in a limited application. Loaded with osteogenic induction growth factor can improve the osteoinductive performance of bone graft, but the explosive release of growth factor may also cause side effects. In this study, we innovatively used platelet-rich fibrin (PRF)-modified bone scaffolds (Bio-Oss^®) to replace autograft, and used cytokine (BMP-2) to enhance osteogenesis. Encouragingly, this mixture, which we named “Autograft Mimic (AGM)”, has multiple functions and advantages. (1) The fiber network provided by PRF binds the entire bone scaffold together, thereby shaping the bone grafts and maintaining the space of the defect area. (2) The sustained release of BMP-2 from bone graft promoted bone regeneration continuously. (3) AGM recruited bone marrow mesenchymal stem cells (BMSCs) and promote their proliferation, migration, and osteogenic differentiation. Thus, AGM developed in this study can improve osteogenesis, and provide new guidance for the development of clinical bone grafts.

A partially demineralized allogeneic bone graft: in vitro osteogenic potential and preclinical evaluation in two different intramembranous bone healing models

In skeletal surgical procedures, bone regeneration in irregular and hard-to-reach areas may present clinical challenges. In order to overcome the limitations of traditional autologous bone grafts and bone substitutes, an extrudable and easy-to-handle innovative partially demineralized allogenic bone graft in the form of a paste has been developed. In this study, the regenerative potential of this paste was assessed and compared to its clinically used precursor form allogenic bone particles. Compared to the particular bone graft, the bone paste allowed better attachment of human mesenchymal stromal cells and their commitment towards the osteoblastic lineage, and it induced a pro-regenerative phenotype of human monocytes/macrophages. The bone paste also supported bone healing in vivo in a guide bone regeneration model and, more interestingly, exhibited a substantial bone-forming ability when implanted in a critical-size defect model in rat calvaria. Thus, these findings indicate that this novel partially demineralized allogeneic bone paste that combines substantial bone healing properties and rapid and ease-of-use may be a promising alternative to allogeneic bone grafts for bone regeneration in several clinical contexts of oral and maxillofacial bone grafting.

Sustained release of epigallocatechin-3-gallate from chitosan-based scaffolds to promote osteogenesis of mesenchymal stem cell

Epigallocatechin-3-gallate (EGCG) is a kind of flavonoids and has the ability to promote differentiation of mesenchymal stem cells (MSCs) into osteoblasts. However, the EGCG is easily metabolized by cells during cell culture, which reduces its bioavailability. Therefore, in this paper, EGCG-loaded chitosan nanoparticles (ECN) were fabricated and entrapped into chitosan/alginate (CS/Alg) scaffolds to form CS/Alg-ECN scaffolds for improving the bioavailability of EGCG. The human umbilical cord mesenchymal stem cells (HUMSCs) were cultured on CS/Alg-ECN scaffolds to induce osteogenic differentiation. The results indicated that the CS/Alg-ECN scaffolds continuously released EGCG for up to 16 days. Besides, these results suggested that CS/Alg-ECN scaffolds promoted osteoblast differentiation through activating Wnt/β-catenin signaling pathway. Collectively, this study demonstrated that the entrapment ECN into CS/Alg scaffolds was a promising strategy for promoting osteogenesis of MSCs.

Vascular endothelial growth factor for in vivo bone formation: A systematic review

BACKGROUND

To achieve optimal bone formation one of the most influential parameters has been mentioned to be adequate blood supply. Vascular endothelial growth factor (VEGF) is hereby of particular interest in bone regeneration, because of its primary ability to induce neovascularization and chemokine affection for endothelial cells (EC), and is considered to be the main regulator of vascular formation. However, the growth factor has yet to be implemented in a clinical setting in orthopaedic intervention surgery. We hypothesised that the development of VEGF in vivo for bone formation in the last decade had progressed towards clinical application since the latest systematic review from 2008.

OBJECTIVE

This systematic review recapped the last 13 years of in vivo bone regeneration using vascular endothelial growth factor (VEGF).

METHOD

A total of 1374 articles were identified using the PubMed search string (vegf or "vascular endothelial growth factor") and (osteogen∗ or "bone formation" or "bone regeneration"). By 3 selection phases 24 published articles were included by the criteria of being in vivo, using only VEGF for bone formation, published after 2007 and written in English. Articles in vitro, written in different languages than English and older than 2007 was excluded. The most recent systematic review on this subject was published in 2008, with the latest included study from 01 to 11-2007. All included studies were classified based on animal, type of defect, scaffold, control group, type of VEGF, release rate, dosage of VEGF, time of evaluation and results. Each study was evaluated for risk of bias by modified CAMARADES quality assessment for the use in experimental animal studies. The score was calculated by peer review journal publication, use of control group, randomisation of groups, justified VEGF dosage, blinding of results, details on animal model, sample size calculation, comply with ethics and no conflict of interest.

RESULTS

No clinical trials or human application studies were obtained from our search. Experimentally, 11 articles using solely VEGF for bone formation had a group or a timepoint significantly better than the corresponding control group. 18 articles revealed no significant difference of VEGF compared to the control group and 1 article reported a significant decreased bone growth using VEGF compared to control.

CONCLUSION

Based on these results no clinical studies have yet been performed. However, indications in the best use of VEGF from experimental studies could be made towards that the optimal release is within the first three weeks, in defect models, with the best effect before eight weeks. Future designs should incorporate this with standardised and reproducible models for verification towards clinical practice.

THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE

This systematic review aims to assess the existing literature to focus on methodologies and outcomes that can provide future knowledge regarding the solitary use of VEGF for bone regeneration in a clinical setting.

Biodegradable engineered fiber scaffolds fabricated by electrospinning for periodontal tissue regeneration

Considering the specificity of periodontium and the unique advantages of electrospinning, this technology has been used to fabricate biodegradable tissue engineering materials for functional periodontal regeneration. For better biomedical quality, a continuous technological progress of electrospinning has been performed. Based on property of materials (natural, synthetic or composites) and additive novel methods (drug loading, surface modification, structure adjustment or 3 D technique), various novel membranes and scaffolds that could not only relief inflammation but also influence the biological behaviors of cells have been fabricated to achieve more effective periodontal regeneration. This review provides an overview of the usage of electrospinning materials in treatments of periodontitis, in order to get to know the existing research situation and find treatment breakthroughs of the periodontal diseases.

Design and evaluation of collagen-inspired mineral-hydrogel nanocomposites for bone regeneration

Bone loss due to trauma and tumors remains a serious clinical concern. Due to limited availability and disease transmission risk with autografts and allografts, calcium phosphate bone fillers and growth factor-based substitute bone grafts are currently used in the clinic. However, substitute grafts lack bone regeneration potential when used without growth factors. When used along with the added growth factors, they lead to unwanted side effects such as uncontrolled bone growth. Collagen-based hydrogel grafts available on the market fail to provide structural guidance to native cells due to high water-solubility and faster degradation. To overcome these limitations, we employed bioinspired material design and fabricated three different hydrogels with structural features similar to native collagen at multiple length-scales. These hydrogels fabricated using polyionic complexation of oppositely charged natural polysaccharides exhibited multi-scale architecture mimicking nanoscale banding pattern, and microscale fibrous structure of native collagen. All three hydrogels promoted biomimetic apatite-like mineral deposition in vitro elucidating crystalline structure on the surface while amorphous calcium phosphate inside the hydrogels resulting in mineral-hydrogel nanocomposites. When evaluated in a non-load bearing critical size mouse calvaria defect model, chitosan - kappa carrageenan mineral-hydrogel nanocomposites enhanced bone regeneration without added growth factors compared to empty defect as well as widely used marketed collagen scaffolds. Histological assessment of the regenerated bone revealed improved healing and tissue remodeling with mineral-hydrogel nanocomposites. Overall, these collagen-inspired mineral-hydrogel nanocomposites showed multi-scale hierarchical structure and can potentially serve as promising bioactive hydrogel to promote bone regeneration. STATEMENT OF SIGNIFICANCE: Hydrogels, especially collagen, are widely used in bone tissue engineering. Collagen fibrils play arguably the most important role during natural bone development. Its multi-scale hierarchical structure to form fibers from fibrils and electrostatic charges enable mineral sequestration, nucleation, and growth. However, bulk collagen hydrogels exhibit limited bone regeneration and are mostly used as carriers for highly potent growth factors such as bone morphogenic protein-2, which increase the risk of uncontrolled bone growth. Thus, there is an unmet clinical need for a collagen-inspired biomaterial that can recreate structural hierarchy, mineral sequestration ability, and stimulate recruitment of host progenitor cells to facilitate bone regeneration. Here, we propose collagen-inspired bioactive mineral-hydrogel nanocomposites as a growth factor-free approach to guide and enhance bone regeneration.

Advancements in Hydrogel-Based Drug Sustained Release Systems for Bone Tissue Engineering

Bone defects caused by injury, disease, or congenital deformity remain a major health concern, and efficiently regenerating bone is a prominent clinical demand worldwide. However, bone regeneration is an intricate process that requires concerted participation of both cells and bioactive factors. Mimicking physiological bone healing procedures, the sustained release of bioactive molecules plays a vital role in creating an optimal osteogenic microenvironment and achieving promising bone repair outcomes. The utilization of biomaterial scaffolds can positively affect the osteogenesis process by integrating cells with bioactive factors in a proper way. A high water content, tunable physio-mechanical properties, and diverse synthetic strategies make hydrogels ideal cell carriers and controlled drug release reservoirs. Herein, we reviewed the current advancements in hydrogel-based drug sustained release systems that have delivered osteogenesis-inducing peptides, nucleic acids, and other bioactive molecules in bone tissue engineering (BTE).

VEGF-loaded mineral-coated microparticles improve bone repair and are associated with increased expression of epo and RUNX-2 in murine non-unions

A poor vascular supply of the fracture gap is a key factor for the development of atrophic non-unions. Mineral-coated microparticles (MCM) represent a sophisticated carrier system for the delivery of vascular endothelial growth factor (VEGF). Hence, we investigated whether VEGF-loaded MCM improve bone repair in non-unions. For this purpose, we analyzed binding and release kinetics of MCM for VEGF in vitro. Moreover, we applied VEGF-loaded or -unloaded MCM in a murine non-union model in vivo and studied the process of bone healing by means of biomechanical, radiological, histomorphometric, and Western blot techniques. MCM-free non-unions served as controls. The binding efficiency of MCM for VEGF was 46 ± 3% and the release profile revealed an initial minor burst release followed by a sustained release over a 50-day study period, thus, mimicking the physiological expression profile of VEGF during bone healing. In vivo, bone defects treated with VEGF-loaded MCM exhibited a higher bending stiffness, a higher fraction of bone volume/tissue volume and a larger callus area on days 14 and 70 when compared to the other groups. Western blot analyses on day 14 revealed a higher expression of VEGF, erythropoietin (EPO), and runt-related transcription factor 2, but not of EPO-receptor in bone defects treated with VEGF-loaded MCM. These findings demonstrate that the use of MCM for VEGF delivery shows great potential due to the ability to maintain protein stability and functionality in vivo. Moreover, the application of VEGF-loaded MCM represent a promising strategy for the treatment of non-unions. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Bioactive calcium phosphate materials and applications in bone regeneration

BACKGROUND

Bone regeneration involves various complex biological processes. Many experiments have been performed using biomaterials in vivo and in vitro to promote and understand bone regeneration. Among the many biomaterials, calcium phosphates which exist in the natural bone have been conducted a number of studies because of its bone regenerative property. It can be directly contributed to bone regeneration process or assist in the use of other biomaterials. Therefore, it is widely used in many applications and has been continuously studied.

MAINBODY

Calcium phosphate has been widely used in bone regeneration applications because it shows osteoconductive and in some cases osteoinductive features. The release of calcium and phosphorus ions regulates the activation of osteoblasts and osteoclasts to facilitate bone regeneration. The control of surface properties and porosity of calcium phosphate affects cell/protein adhesion and growth and regulates bone mineral formation. Properties affecting bioactivity vary depending on the types of calcium phosphates such as HAP, TCP and can be utilized in various applications because of differences in ion release, solubility, stability, and mechanical strength. In order to make use of these properties, different calcium phosphates have been used together or mixed with other materials to complement their disadvantages and to highlight their advantages. Calcium phosphate has been utilized to improve bone regeneration in ways such as increasing osteoconductivity for bone ingrowth, enhancing osteoinductivity for bone mineralization with ion release control, and encapsulating drugs or growth factors.

CONCLUSION

Calcium phosphate has been used for bone regeneration in various forms such as coating, cement and scaffold based on its unique bioactive properties and bone regeneration effectiveness. Additionally, several studies have been actively carried out to improve the efficacy of calcium phosphate in combination with various healing agents. By summarizing the properties of calcium phosphate and its research direction, we hope that calcium phosphate can contribute to the clinical treatment approach for bone defect and disease.

Synergistic effect of Si-hydroxyapatite coating and VEGF adsorption on Ti6Al4V-ELI scaffolds for bone regeneration in an osteoporotic bone environment

The osteogenic and angiogenic responses to metal macroporous scaffolds coated with silicon substituted hydroxyapatite (SiHA) and decorated with vascular endothelial growth factor (VEGF) have been evaluated in vitro and in vivo. Ti6Al4V-ELI scaffolds were prepared by electron beam melting and subsequently coated with Ca₁₀(PO₄)_5.6(SiO₄)_0.4(OH)_1.6 following a dip coating method. In vitro studies demonstrated that SiHA stimulates the proliferation of MC3T3-E1 pre-osteoblastic cells, whereas the adsorption of VEGF stimulates the proliferation of EC₂ mature endothelial cells. In vivo studies were carried out in an osteoporotic sheep model, evidencing that only the simultaneous presence of both components led to a significant increase of new tissue formation in osteoporotic bone. STATEMENT OF SIGNIFICANCE: Reconstruction of bones after severe trauma or tumors extirpation is one of the most challenging tasks in the field of orthopedic surgery. This scenario is even more complicated in the case of osteoporotic patients, since their bone regeneration capability is decreased. In this work we present a porous implant that promotes bone regeneration even in osteoporotic bone. By coating the implant with osteogenic bioceramics such as silicon substituted hydroxyapatite and subsequent adsorption of vascular endothelial growth factor, these implants stimulate the bone ingrowth when they are implanted in osteoporotic sheep.

Composite Hydrogels with the Simultaneous Release of VEGF and MCP-1 for Enhancing Angiogenesis for Bone Tissue Engineering Applications

Rapid new microvascular network induction was critical for bone regeneration, which required the spatiotemporal delivery of growth factors and transplantation of endothelial cells. In this study, the linear poly(d,l-lactic-co-glycolic acid)-b-methoxy poly(ethylene glycol) (PLGA-mPEG) block copolymer microspheres were prepared for simultaneously delivering vascular endothelial growth factor (VEGF) and monocyte chemotactic protein-1 (MCP-1). Then, vascular endothelial cells (VECs) with growth factor loaded microspheres were composited into a star-shaped PLGA-mPEG block copolymer solution. After this, composite hydrogel (microspheres ratio: 5 wt%) was formed by increasing the temperature to 37 °C. The release profiles of VEGF and MCP-1 from composite hydrogels in 30 days were investigated to confirm the different simultaneous delivery systems. The VECs exhibited a good proliferation in the composite hydrogels, which proved that the composite hydrogels had a good cytocompatibility. Furthermore, in vivo animal experiments showed that the vessel density and the mean vessel diameters increased over weeks after the composite hydrogels were implanted into the necrosis site of the rabbit femoral head. The above results suggested that the VECs-laden hydrogel composited with the dual-growth factor simultaneous release system has the potential to enhance angiogenesis in bone tissue engineering.

Interpenetrating network gelatin methacryloyl (GelMA) and pectin-g-PCL hydrogels with tunable properties for tissue engineering

The design of new hydrogel-based biomaterials with tunable physical and biological properties is essential for the advancement of applications related to tissue engineering and regenerative medicine. For instance, interpenetrating polymer network (IPN) and semi-IPN hydrogels have been widely explored to engineer functional tissues due to their characteristic microstructural and mechanical properties. Here, we engineered IPN and semi-IPN hydrogels comprised of a tough pectin grafted polycaprolactone (pectin-g-PCL) component to provide mechanical stability, and a highly cytocompatible gelatin methacryloyl (GelMA) component to support cellular growth and proliferation. IPN hydrogels were formed by calcium ion (Ca2+)-crosslinking of pectin-g-PCL chains, followed by photocrosslinking of the GelMA precursor. Conversely, semi-IPN networks were formed by photocrosslinking of the pectin-g-PCL and GelMA mixture, in the absence of Ca2+ crosslinking. IPN and semi-IPN hydrogels synthesized with varying ratios of pectin-g-PCL to GelMA, with and without Ca2+-crosslinking, exhibited a broad range of mechanical properties. For semi-IPN hydrogels, the aggregation of microcrystalline cores led to formation of hydrogels with compressive moduli ranging from 3.1 to 10.4 kPa. For IPN hydrogels, the mechanistic optimization of pectin-g-PCL, GelMA, and Ca2+ concentrations resulted in hydrogels with comparatively higher compressive modulus, in the range of 39 kPa-5029 kPa. Our results also showed that IPN hydrogels were cytocompatible in vitro and could support the growth of three-dimensionally (3D) encapsulated MC3T3-E1 preosteoblasts in vitro. The simplicity, technical feasibility, low cost, tunable mechanical properties, and cytocompatibility of the engineered semi-IPN and IPN hydrogels highlight their potential for different tissue engineering and biomedical applications.

The 3D Printing of Calcium Phosphate with K-Carrageenan under Conditions Permitting the Incorporation of Biological Components-A Method

Critical-size bone defects are a common clinical problem. The golden standard to treat these defects is autologous bone grafting. Besides the limitations of availability and co-morbidity, autografts have to be manually adapted to fit in the defect, which might result in a sub-optimal fit and impaired healing. Scaffolds with precise dimensions can be created using 3-dimensional (3D) printing, enabling the production of patient-specific, 'tailor-made' bone substitutes with an exact fit. Calcium phosphate (CaP) is a popular material for bone tissue engineering due to its biocompatibility, osteoconductivity, and biodegradable properties. To enhance bone formation, a bioactive 3D-printed CaP scaffold can be created by combining the printed CaP scaffold with biological components such as growth factors and cytokines, e.g., vascular endothelial growth factor (VEGF), bone morphogenetic protein-2 (BMP-2), and interleukin-6 (IL-6). However, the 3D-printing of CaP with a biological component is challenging since production techniques often use high temperatures or aggressive chemicals, which hinders/inactivates the bioactivity of the incorporated biological components. Therefore, in our laboratory, we routinely perform extrusion-based 3D-printing with a biological binder at room temperature to create porous scaffolds for bone healing. In this method paper, we describe in detail a 3D-printing procedure for CaP paste with K-carrageenan as a biological binder.

Gentamicin-loaded ceramic-biopolymer dual layer coatings on the Ti with improved bioactive and corrosion resistance properties for orthopedic applications

In orthopedic surgery, osteomyelitis (bone infection) is one of the most serious complications in the last few decades and the resident drug delivery is the key strategy to overcome this issue. Combination of bioactive materials with antibiotics is broadly developed for the handling of osteomyelitis which plays a dual role as bone cell growth and as local drug delivery systems for antibiotic delivery. TiO₂-SiO₂ mixtures were fabricated on Ti alloy by anodization method. Chitosan-Lysine (CS-LY) biopolymers were coated on composites by electrodeposition method and followed by gentamicin sulfate (GS) which was loaded as a model drug. The layers were characterized by AT-FTIR, XRD, FE-SEM and EDX methods. The mechanical, anticorrosion, antimicrobial effects and biocompatibility of the glazes were considered. In addition, drug loading, continued and prolonged liberation behaviors of GS from the fabricated coating were studied. The apatite development ability and cell viability are outstanding for CS-LY-3 coated composites. In vitro cell experimentations indicate that osteoblasts show good adhesion and high growth rates for CS-LY-3 coated TiO₂-SiO₂ composite substrate. In conclusion, the surface modification of TiO₂-SiO₂/CS-LY-3 coated Ti alloy could be used as a carrier for GS, not only to eradicate the osteomyelitis caused by Gram-negative and Gram-positive bacteria, but also to repair the bone defect initiated by the infection owing to the tunable nanocomposite degradation.

Photoacoustic stimulation promotes the osteogenic differentiation of bone mesenchymal stem cells to enhance the repair of bone defect

The aim of this study was to evaluate the direct photoacoustic (PA) effect on bone marrow mesenchymal stem cells (BMSCs) which is a key cell source for osteogenesis. As scaffold is also an indispensable element for tissue regeneration, here we firstly fabricated a composited sheet using polylactic-co-glycolic acid (PLGA) mixing with graphene oxide (GO). BMSCs were seeded on the PLGA-GO sheets and received PA treatment in vitro for 3, 9 and 15 days, respectively. Then the BMSCs were harvested and subjected to assess alkaline phosphatase (ALP) activity, calcium content and osteopontin (OPN) on 3, 9 and 15 days. For in vivo study, PLGA-GO sheet seeded with BMSCs after in vitro PA stimulation for 9 days were implanted to repair the bone defect established in the femoral mid-shaft of Sprague-Dawley rat. PLGA-GO group with PA pretreatment showed promising outcomes in terms of the expression of ALP, OPN, and calcium content, thus enhanced the repair of bone defect. In conclusion, we have developed an alternative approach to enhance the repair of bone defect by making good use of the beneficial effect of PA.

Mechanical properties, structure, bioadhesion, and biocompatibility of pectin hydrogels

The surface structure, biocompatibility, textural, and adhesive properties of calcium hydrogels derived from 1, 2, and 4% solutions of apple pectin were examined in this study. An increase in the pectin concentration in hydrogels was shown to improve their stability toward elastic and plastic deformation. The elasticity of pectin hydrogels, measured as Young's modulus, ranged from 6 to 100 kPa. The mechanical properties of the pectin hydrogels were shown to correspond to those of soft tissues. The characterization of surface roughness in terms of the roughness profile (Ra) and the root-mean-square deviation of the roughness profile (Rq) indicated an increased roughness profile for hydrogels depending on their pectin concentration. The adhesion of AU2% and AU4% hydrogels to the serosa abdominal wall, liver, and colon was higher than that of the AU1% hydrogel. The adhesion of macrophages and the non-specific adsorption of blood plasma proteins were found to increase as the pectin concentration in the hydrogels increased. The rate of degradation of all hydrogels was higher in phosphate buffered saline (PBS) than that in DMEM and a fibroblast cell monolayer. The pectin hydrogel was also found to have a low cytotoxicity. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2572-2581, 2017.

In vitro and in vivo evaluation of effectiveness of a novel TEMPO-oxidized cellulose nanofiber-silk fibroin scaffold in wound healing

In this study, a novel TEMPO-oxidized cellulose nanofiber (TOCN)-silk fibroin scaffold was prepared using a cost effective freeze drying method. Fundamental physical characterizations were carried out by scanning electron microscopy (SEM), pore diameter determination, FT-IR. PBS uptake behavior of the scaffold showed that, silk fibroin can enhance the swelling capacity of TOCN. L929 primary fibroblast cell was selected for in vitro studies, which showed that the scaffolds facilitated growth of cells. In vivo evaluation of TOCN, TOCN-silk fibroin composites was examined using critical sized rat skin excisional model for one and two weeks. The results of rat wound model revealed that, compared to only TOCN scaffold, TOCN-silk fibroin scaffold successfully promoted wound healing by the expression of wound healing markers. TOCN-silk fibroin 2% has the fastest wound healing capacity. Thus, it appears that TOCN-silk fibroin composite scaffolds can be useful as wound healing material in clinical applications.

Physicochemical regulation of TGF and VEGF delivery from mesoporous calcium phosphate bone substitutes

Aim: Determination of the physicochemical parameters governing growth factors (GFs) adsorption and release from mesoporous calcium phosphate ceramics. Materials & methods: Six mesoporous calcium phosphate ceramics prepared by soft and hard templating were loaded with two different physiological concentrations of TGF-β1 or VEGF165 and their in vitro kinetics of adsorption/release were studied. Results: This low GF loading promotes adsorption on the highest binding sites. The usually encountered detrimental burst release is thus considerably reduced for samples prepared by hard-templating method. Conclusion: Our findings highlight that the strong affinity of GFs with the ceramic surfaces, demonstrated by a slow GFs release, is enhanced by the large surface area, confinement into mesopores of ceramics and high difference of surface charge between ceramic surfaces and GFs.

Incorporation of BMP-2 loaded collagen conjugated BCP granules in calcium phosphate cement based injectable bone substitutes for improved bone regeneration

The objective of the present study was to incorporate surface modified porous multichannel BCP granule into CPC to enhance its in vivo biodegradation and bone tissue growth. The multichannel BCP granule (15wt%) was first coated with collagen subsequent to BMP-2 loading (ccMCG-B). It was then embedded into CPC to form CPC-ccMCG-B system. The newly developed CPC-ccMCG-B system was then examined for SEM, EDX, XRD, setting time, compressive strength, injectability, pH change, BMP-2 release, in vitro as well as in vivo studies and further compared with CPC. Optimized CPC (0.45mL/g) was found based on setting time and compressive strength studies. In vivo studies exhibited improved new bone formation and better degradation of CPC after 2 and 4weeks of implantation as compared to CPC as resulted from effective BMP-2 signaling. Our results suggest that CPC-ccMCG-B system might be used as a promising injectable bone substitutes in clinical applications.

Calcium Phosphate Bioceramics: A Review of Their History, Structure, Properties, Coating Technologies and Biomedical Applications

Calcium phosphate (CaP) bioceramics are widely used in the field of bone regeneration, both in orthopedics and in dentistry, due to their good biocompatibility, osseointegration and osteoconduction. The aim of this article is to review the history, structure, properties and clinical applications of these materials, whether they are in the form of bone cements, paste, scaffolds, or coatings. Major analytical techniques for characterization of CaPs, in vitro and in vivo tests, and the requirements of the US Food and Drug Administration (FDA) and international standards from CaP coatings on orthopedic and dental endosseous implants, are also summarized, along with the possible effect of sterilization on these materials. CaP coating technologies are summarized, with a focus on electrochemical processes. Theories on the formation of transient precursor phases in biomineralization, the dissolution and reprecipitation as bone of CaPs are discussed. A wide variety of CaPs are presented, from the individual phases to nano-CaP, biphasic and triphasic CaP formulations, composite CaP coatings and cements, functionally graded materials (FGMs), and antibacterial CaPs. We conclude by foreseeing the future of CaPs.

Biodegradable ceramic-polymer composites for biomedical applications: A review

The present work focuses on the state-of-the-art of biodegradable ceramic-polymer composites with particular emphasis on influence of various types of ceramic fillers on properties of the composites. First, the general needs to create composite materials for medical applications are briefly introduced. Second, various types of polymeric materials used as matrices of ceramic-containing composites and their properties are reviewed. Third, silica nanocomposites and their material as well as biological characteristics are presented. Fourth, different types of glass fillers including silicate, borate and phosphate glasses and their effect on a number of properties of the composites are described. Fifth, wollastonite as a composite modifier and its effect on composite characteristics are discussed. Sixth, composites containing calcium phosphate ceramics, namely hydroxyapatite, tricalcium phosphate and biphasic calcium phosphate are presented. Finally, general possibilities for control of properties of composite materials are highlighted.

The Use of Sequential VEGF- and BMP2-Releasing Biodegradable Scaffolds in Rabbit Mandibular Defects

PURPOSE

Promising developments have materialized in reconstructive surgical procedures with the applications of tissue engineering. In our study, we used tissue scaffolds fabricated from polylactic acid-polyethylene glycol (PLLA-PEG) copolymers to ensure different release rates of selective growth factors recombinant human bone morphogenetic protein 2 [rhBMP-2] and vascular endothelial growth factor (rhVEGF165) in the repair of mandibular bone defects.

MATERIALS AND METHODS

In our experimental study, 54 New Zealand rabbits were used. The rabbits were separated into 4 groups: group I (control group), PLLA-PEG scaffold only; group II, PLLA-PEG scaffold plus rhBMP-2 application; group III, PLLA-PEG scaffold plus VEGF165 application; and group IV, PLLA-PEG scaffold plus rhBMP-2 and VEGF165 applications. The rabbits were killed at 4 and 8 weeks postoperatively, and histopathologic and immunohistochemical assessments were performed.

RESULTS

The greatest bone volume was observed in rhBMP-2-containing groups, the greatest vessel volume was observed in VEGF165-containing groups; however, the scaffold containing rhBMP-2 and VEGF165 provided the best outcomes in conjunction with increased remodeling of the new bone.

CONCLUSIONS

The use of polymer tissue scaffolds that release rhVEGF165 and rhBMP-2 in coordination and mimic the natural healing process in the regeneration of especially complex tissues, such as bone, is a promising treatment alternative in the field of reconstructive surgery.

The performance of bone tissue engineering scaffolds in in vivo animal models: A systematic review

Bone tissue engineering is an excellent alternative for the regeneration of large bone defects caused by trauma or bone pathologies. Scaffolds, stem cells, and bioactive molecules are the three key components of bone regeneration. Although a wide range of biomaterials of various compositions and structures has been proposed in the literature, these materials are rarely used in clinical applications. Therefore, more standardized studies are required to design scaffolds that enable better bone regeneration and are suitable for clinical use. The aim of this systematic review was to compare the performance of scaffolds used in preclinical animal studies to determine which class of materials has achieved a higher rate of bone neoformation (osteoinduction and osteoconduction). The selected studies were divided into three groups according to the following experimental models: studies that used subcutaneous models, bone defects in calvaria, and bone defects in long bones. Despite the large number of parameters in the included studies, we generally concluded that biomaterials containing calcium phosphates had important osteoinductive effects and were essential for better performance of the materials. Furthermore, natural polymers generally had better performance than synthetic polymers did, especially when the materials were associated with stem cells. The combination of materials from different classes was the most promising strategy for bone tissue regeneration.

Comparative study of BMP-2 alone and combined with VEGF carried by hydrogel for maxillary alveolar bone regeneration

The effect of vascular endothelial growth factor (VEGF) combined with bone morphogenetic protein-2 (BMP-2) for bone regeneration is still controversial as to whether or not VEGF has a synergistic or additive effect. This study attempted to evaluate the synergistic effect of VEGF and BMP-2 compared to BMP-2 alone for maxillary alveolar bone regeneration using collagen sponge/hydrogel complex sheets in a canine model. After mixing BMP-2 and VEGF with a hyaluronic acid-based hydrogel (HAH), the collagen sponge/hydrogel complex was transplanted into maxillary alveolar bone defects (n=14) after the extraction of canine upper first molars on both sides. Bone regeneration was evaluated in three groups (control group without growth factors, experimental groups I and II with BMP-2 alone and BMP-2 and VEGF, respectively) using micro-computed tomography and histological staining. The total amount of new bone formations and bone mineral density were significantly higher in the group with BMP-2 only and the group with BMP-2 combined with VEGF than it in the control group. The area with positive staining of von Willebrand factor bone defect was significantly greater in the group with BMP-2 only and with dual growth factors than the control. BMP-2 released from the HAH promoted new bone formation. However, the combination of BMP-2 and VEGF did not show a synergistic or additive effect on bone regeneration at canine maxillary alveolar bone defects.

Effects of immobilized VEGF on endothelial progenitor cells cultured on silicon substituted and nanocrystalline hydroxyapatites

Immobilized VEGF effects on angiogenic cells cultured on silicon substituted and nanocrystalline hydroxyapatites.

Preparation and characterization of calcium phosphate/pectin scaffolds for bone tissue engineering

A calcium phosphate cement (CPC) scaffold has been used to repair bone defects, but its low compressive strength and poor osteogenesis greatly hinder its clinical application.