Growth Factors For Bone Regeneration Research Articles

Concentrated Growth Factor (CGF): A Potential New Player in Periodontal Regeneration

Regenerative procedures have become a key focus in contemporary rehabilitation therapies. In dentistry, research on growth factors for bone regeneration has identified autologous growth factors as the most effective stimuli for tissue regeneration and healing. These bioactive proteins play a crucial role in wound healing. Concentrated growth factor (CGF) is a recent advancement in 2 nd generation platelet concentrates. The use of different centrifugation speeds helps to obtain a significantly dense fibrin. Also, it contains more amount of growth factors than the other platelet concentrates available.

Plasma Rich in Growth Factors in Bone Regeneration: The Proximity to the Clot as a Differential Factor in Osteoblast Cell Behaviour.

The osteogenic differentiation process, by which bone marrow mesenchymal stem cells and osteoprogenitors transform into osteoblasts, is regulated by several growth factors, cytokines, and hormones. Plasma Rich in Growth Factors (PRGF) is a blood-derived preparation consisting of a plethora of bioactive molecules, also susceptible to containing epigenetic factors such as ncRNAs and EVs, that stimulates tissue regeneration. The aim of this study was to investigate the effect of the PRGF clot formulation on osteogenic differentiation. Firstly, osteoblast cells were isolated and characterised. The proliferation of bone cells cultured onto PRGF clots or treated with PRGF supernatant was determined. Moreover, the gene expression of Runx2 (ID: 860), SP7 (ID: 121340), and ALPL (ID: 249) was analysed by one-step real-time quantitative polymerase chain reaction (RT-qPCR). Additionally, alkaline phosphatase (ALPL) activity determination was performed. The highest proliferative effect was achieved by the PRGF supernatant in all the study periods analysed. Concerning gene expression, the logRGE of Runx2 increased significantly in osteoblasts cultured with PRGF formulations compared with the control group, while that of SP7 increased significantly in osteoblasts grown on the PRGF clots. On the other hand, despite the fact that the PRGF supernatant induced ALPL up-regulation, significantly higher enzyme activity was detected for the PRGF clots in comparison with the supernatant formulation. According to our results, contact with the PRGF clot could promote a more advanced phase in the osteogenic process, associated to higher levels of ALPL activity. Furthermore, the PRGF clot releasate stimulated a higher proliferation rate in addition to reduced SP7 expression in the cells located at a distant ubication, leading to a less mature osteoblast stage. Thus, the spatial relationship between the PRGF clot and the osteoprogenitors cells could be a factor that influences regenerative outcomes.

The Evolution and Application of a Novel DNA Aptamer Targeting Bone Morphogenetic Protein 2 for Bone Regeneration.

Recombinant human bone morphogenetic protein 2 (rhBMP-2) is an FDA-approved growth factor for bone regeneration and repair in medical practice. The therapeutic effects of rhBMP-2 may be enhanced through specific binding to extracellular matrix (ECM)-like scaffolds. Here, we report the selection of a novel rhBMP-2-specific DNA aptamer, functionalization of the aptamer in an ECM-like scaffold, and its application in a cellular context. A DNA aptamer BA1 was evolved and shown to have high affinity and specificity to rhBMP-2. A molecular docking model demonstrated that BA1 was probably bound to rhBMP-2 at its heparin-binding domain, as verified with experimental competitive binding assays. The BA1 aptamer was used to functionalize a type I collagen scaffold, and fraction ratios were optimized to mimic the natural ECM. Studies in the myoblast cell model C2C12 showed that the aptamer-enhanced scaffold could specifically augment the osteo-inductive function of rhBMP-2 in vitro. This aptamer-functionalized scaffold may have value in enhancing rhBMP-2-mediated bone regeneration.

The Delivery and Activation of Growth Factors Using Nanomaterials for Bone Repair

Bone regeneration is a comprehensive process that involves different stages, and various growth factors (GFs) play crucial roles in the entire process. GFs are currently widely used in clinical settings to promote bone repair; however, the direct application of GFs is often limited by their fast degradation and short local residual time. Additionally, GFs are expensive, and their use may carry risks of ectopic osteogenesis and potential tumor formation. Nanomaterials have recently shown great promise in delivering GFs for bone regeneration, as they can protect fragile GFs and control their release. Moreover, functional nanomaterials can directly activate endogenous GFs, modulating the regeneration process. This review provides a summary of the latest advances in using nanomaterials to deliver exogenous GFs and activate endogenous GFs to promote bone regeneration. We also discuss the potential for synergistic applications of nanomaterials and GFs in bone regeneration, along with the challenges and future directions that need to be addressed.

BFGF-incorporated composite biomaterial for bone regeneration

Injectable biomaterials obtain increasing attention for the repair of bone defect due to the advantage of defect margin adaptability and easy handling. Our previous studies found that RADA16 peptide hydrogel could significantly promote bone formation. In order to improve the mechanical force, RADA16 peptide hydrogel was used to fill the porous calciumsulfate/nano-hydroxyapatite(CaSO4/HA)cement biomaterial for the fabrication of RADA16/CaSO4/HA composite biomaterial. Especially, RADA16 peptide hydrogel had the ability to slowly release growth factors for bone regeneration. Here, RADA16/CaSO4/HA composite biomaterials afforded the controlled and sustainable release of basic fibroblast growth factor(bFGF) for more than 32 days. Compared to RADA16/CaSO4/HA biomaterial, RADA16 + bFGF/CaSO4/HA composite biomaterial could further improve in vitro osteogenic differentiation of MC3T3 cells as evidenced by the increased expression of osteogenic markers (i.e. runt-related transcription factor 2 [Runx2], osteocalcin [OCN] andalkaline phosphatase [ALP]) and in vivo bone formation of femoral condyle defects which were confirmed by histological staining and micro-CT analyses. These indicate that bFGF-incorporated RADA16/CaSO4/HA can further improve bone formation through the controlled release of bFGF, which provides a novel injectable biomaterial design to specifically release growth factors for bone defects.

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.

Development of a 3D Bioprinted Scaffold with Spatio-temporally Defined Patterns of BMP-2 and VEGF for the Regeneration of Large Bone Defects.

The local delivery of growth factors such as BMP-2 is a well-established strategy for the repair of bone defects. The limitations of such approaches clinically are well documented and can be linked to the need for supraphysiological doses and poor spatio-temporal control of growth factor release in vivo. Using bioprinting techniques, it is possible to generate implants that can deliver cytokines or growth factors with distinct spatiotemporal release profiles and patterns to enhance bone regeneration. Specifically, for bone healing, several growth factors, including vascular endothelial growth factor (VEGF) and bone morphogenic proteins (BMPs), have been shown to be expressed at different phases of the process. This protocol aims to outline how to use bioprinting strategies to deliver growth factors, both alone or in combination, to the site of injury at physiologically relevant dosages such that repair is induced without adverse effects. Here we describe: the printing parameters to generate the polymer mechanical backbone; instructions to generate the different bioinks and allow for the temporal control of both growth factors; and the printing process to develop implants with spatially defined patterns of growth factors for bone regeneration. The novelty of this protocol is the use of multiple-tool fabrication techniques to develop an implant with spatio-temporal control of growth factor delivery for bone regeneration. While the overall aim of this protocol was to develop an implant for bone regeneration, the technique can be modified and used for a variety of regenerative purposes. Graphic abstract: 3D Bioprinting Spatio-Temporally Defined Patterns of Growth Factors to Tightly Control Bone Tissue Regeneration.

Application of a New Type of Natural Calcined Bone Repair Material Combined with Concentrated Growth Factors in Bone Regeneration in Rabbit Critical-Sized Calvarial Defect.

Purpose This study is aimed at investigating bone regeneration in critical-sized defects in rabbit calvarium using a novel nano- (n-) hydroxyapatite hybrid scaffold with concentrated growth factors (CGFs). Methods Twenty-four male adult rabbits were chosen to establish a critical-sized bone defect model and randomly divided into two groups. Two defects of 15 mm diameter each were created in the parietal bone of each animal. Group A had n-hydroxyapatite hybrid scaffold placed in the experimental defect on the right, and the left defect was unfilled as blank. Group B had hydroxyapatite hybrid scaffold mixed with CGF placed in the right defect and CGF on the left. Six animals in each group were sacrificed after 6 and 12 weeks. Cone-beam computed tomography system scanning and hematoxylin and eosin (HE) staining were used to detect osteogenesis within the defects. Results The treatment with n-hydroxyapatite hybrid scaffold along with CGF resulted in a significantly higher amount of new bone at 6 and 12 weeks compared to the treatment with CGF alone and the controls. No apparent inflammation and foreign body reaction were observed through HE staining. Conclusions The new synthesized n-hydroxyapatite hybrid scaffold and CGF can be applied for bone defect regeneration to promote the process to a certain extent.

Use Of PRP In Severe Bone Defects

Aim of the study is to demonstrate the influence of using growth factors in bone regeneration in advanced implantology cases, such as severe bone defects that involve maxillary sinus

Osteogenic-differentiated mesenchymal stem cell-secreted extracellular matrix as a bone morphogenetic protein-2 delivery system for ectopic bone formation

While human bone morphogenetic protein-2 (BMP-2) is a promising growth factor for bone regeneration, a major challenge in biomedical applications is finding an optimal carrier for its delivery at the site of injury. Because of their natural affinities for growth factors (including BMP-2) as well as their role in instructing cell function, cultured cell-derived extracellular matrices (ECM) are of special interest. We hereby hypothesized that a “bony matrix” containing mineralized, osteogenic ECM is a potential efficacious carrier of BMP-2 for promoting bone formation and, therefore, compared the efficacy of the decellularized ECM derived from osteogenic-differentiated human mesenchymal stem cells (hMSCs) to the one obtained from ECM from undifferentiated hMSCs. Our results provided evidence that both ECMs can bind BMP-2 and promote bone formation when implanted ectopically in mice. The osteoinductive potential of BMP-2, however, was greater when loaded within an osteogenic MSC-derived ECM; this outcome was correlated with higher sequestration capacity of BMP-2 over time in vivo. Interestingly, although the BMP-2 mainly bound onto the mineral crystals contained within the osteogenic MSC derived-ECM, these mineral components were not involved in the observed higher osteoinductivity, suggesting that the organic components were the critical components for the matrix efficacy as BMP-2 carrier.

Degradable Poly(Methyl Methacrylate)-co-Methacrylic Acid Nanoparticles for Controlled Delivery of Growth Factors for Bone Regeneration.

Bone tissue engineering strategies have been developed to address the limitations of the current gold standard treatment options for bone-related disorders. These systems consist of an engineered scaffold that mimics the extracellular matrix and provides an architecture to guide the natural bone regeneration process, and incorporated growth factors that enhance cell recruitment and ingress into the scaffold and promote the osteogenic differentiation of stem cells and angiogenesis. In particular, the osteogenic growth factor bone morphogenetic protein 2 (BMP-2) has been widely studied as a potent agent to improve bone regeneration. A key challenge in growth factor delivery is that the growth factors must reach their target sites without losing bioactivity and remain in the location for an extended period to effectively aid in the formation of new bone. Protein incorporation into nanoparticles can both protect protein bioactivity and enable its sustained release. In this study, a poly(methyl methacrylate-co-methacrylic acid) nanoparticle-based system was synthesized incorporating a custom poly(ethylene glycol) dimethacrylate crosslinker. It was demonstrated that the nanoparticle degradation rate can be controlled by tuning the number of hydrolytically degradable ester units along the crosslinker. We also showed that the nanoparticles had high affinity for a model protein for BMP-2, and optimal conditions for maximum protein loading efficiency were elucidated. Ultimately, the proposed system and its high degree of tunability can be applied to a wide range of growth factors and tissue engineering applications. Impact Statement In this study, we developed a novel method of synthesizing nanoparticles with tunable degradation rates through the incorporation of a custom synthesized, hydrolytically degradable crosslinker. In addition, we demonstrated the affinity of the synthesized nanoparticles for a model protein for bone morphogenetic protein 2 (BMP-2). The tunability of these nanoparticles can be used to develop complex tissue engineering systems, for example, for the delivery of multiple growth factors involved at different stages of the bone regeneration process.

Role of growth factors in bone regeneration

Regeneration of periodontal structures lost during periodontal diseases constitutes a complex biological process regulated among others by interactions between cells and growth factors. Growth factors are biologically active polypeptides affecting the proliferation, chemotaxis, and differentiation of cells from the epithelium, bone, and connective tissue.

Research progress on controlled release of various growth factors in bone regeneration

To summarize the research progress of controlled release of angiogenic factors and osteogenic factors in bone tissue engineering. The domestic and abroad literature on the controlled release structure of growth factors during bone regeneration in recent years was extensively reviewed and summarized. The sustained-release structure includes direct binding, microsphere-three-dimensional scaffold structure, core-shell structure, layer self-assembly, hydrogel, and gene carrier. A sustained-release system composed of different sustained-release structures combined with different growth factors can promote bone regeneration and angiogenesis. Due to its controllability and persistence, the growth factor sustained-release system has become a research hotspot in bone tissue engineering and has broad application prospects.

Three-Dimensional Architecture and Mechanical Properties of Bovine Bone Mixed with Autologous Platelet Liquid, Blood, or Physiological Water: An In Vitro Study.

In recent years, several techniques and material options have been investigated and developed for bone defect repair and regeneration. The progress in studies of composite graft materials and autologous platelet-derived growth factors for bone regeneration in dentistry and their biological and biomechanical properties has improved clinical strategies and results. The aim of this study was to evaluate the three-dimensional architecture and mechanical properties of three different combinations of composite bovine graft, adding autologous platelet liquid (APL), blood, or physiological water. One experimental group for each combination of biomaterials was created. In particular, in Group I, the bovine graft was mixed with APL; in Group II, it was mixed with blood, and in Group III, the biomaterial graft was combined with physiological water. Then, the composite biomaterials were evaluated by scanning electron microscopy (SEM), and a compression-loading test was conducted. The evaluation showed a statistical significance (p < 0.01) of the elastic regime of deformation resistance, in which the combination of APL with bone graft resulted in an 875% increase in the mechanical resistance. The protocol of APL mixed with bovine bone graft produced a composite sticky graft block that was capable of increasing the mechanical properties in order to improve its clinical use in the treatment of the maxillary bone defects.

Functionalization of PCL-3D electrospun nanofibrous scaffolds for improved BMP2-induced bone formation

Bone morphogenic protein 2 (BMP2) is a key growth factor for bone regeneration, possessing FDA approval for orthopedic applications. BMP2 is often required in supratherapeutic doses clinically, yielding adverse side effects and substantial treatment costs. Considering the crucial role of materials for BMPs delivery and cell osteogenic differentiation, we devote to engineering an innovative bone-matrix mimicking niche to improve low dose of BMP2-induced bone formation. Our previous work describes a novel technique, named thermally induced nanofiber self-agglomeration (TISA), for generating 3D electrospun nanofibrous (NF) polycaprolactone (PCL) scaffolds. TISA process could readily blend PCL with PLA, leading to increased osteogenic capabilities in vitro, however, these bio-inert synthetic polymers produced limited BMP2-induced bone formation in vivo. We therefore hypothesize that functionalization of NF 3D PCL scaffolds with bone-like hydroxyapatite (HA) and BMP2 signaling activator phenamil will provide a favorable osteogenic niche for bone formation at low doses of BMP2. Compared to PCL-3D scaffolds, PCL/HA-3D scaffolds demonstrated synergistically enhanced osteogenic differentiation capabilities of C2C12 cells with phenamil. Importantly, in vivo studies showed that this synergism was able to generate significantly increased new bone in an ectopic mouse model, suggesting that PCL/HA-3D scaffolds act as a favorable synthetic extracellular matrix for bone regeneration.

Colloidal Gels with Extracellular Matrix Particles and Growth Factors for Bone Regeneration in Critical Size Rat Calvarial Defects.

Colloidal gels encapsulating natural materials and exhibiting paste-like properties for placement are promising for filling complex geometries in craniofacial bone regeneration applications. Colloidal materials have demonstrated modest clinical outcomes as bone substitutes in orthopedic applications, but limited success in craniofacial applications. As such, development of a novel colloidal gel will fill a void in commercially available products for use in craniofacial reconstruction. One likely application for this technology is cranial reconstruction. Currently, traumatic brain injury (TBI) is often treated with a hemi-craniectomy, a procedure in which half the cranium is removed to allow the injured brain to swell and herniate beyond the enclosed cranial vault. The use of colloidal gels would allow for the design of a pliable material capable of expansion during brain swelling and facilitate cranial bone regeneration alleviating the need for a second surgery to replace the previously removed hemi-cranium. In the current study, colloidal nanoparticles of hydroxyapatite (HAp), demineralized bone matrix (DBM), and decellularized cartilage (DCC) were combined with hyaluronic acid (HA) to form colloidal gels with desirable rheological properties ([Formula: see text] ≥ 100Pa). BMP-2 and VEGF growth factors were included to assess extracellular matrix (ECM) contribution of DBM and DCC. The HA-HAp (BMP-2) and HA-HAp-DCC group had 89 and 82% higher bone regeneration compared to the sham group, respectively (p < 0.01). Material retention issues observed may be alleviated by implementing chemical crosslinking. Overall, DCC may be a promising material for bone regeneration in general, and colloidal gels may hold significant potential in craniofacial applications.

Advances in Soft Functional Materials Research

Advances in Soft Functional Materials Research

Biomaterials Act as Enhancers of Growth Factors in Bone Regeneration

Inspired by the physiological events of the “wound healing cascade”, the integration of biomaterials and growth factors is generally accepted as an emerging and powerful strategy for bone regenerative therapy. As a type of biological mediator, growth factors play a key role in functional bone regeneration. In this review, recent progress in the enhancement of bone‐related growth factors via a biomaterial strategy will be discussed. Two main reinforcing mechanisms, temporal regulation and efficacy manipulation, are described in detail, highlighting the potential capability of biomaterials to harness the interactions between growth factors and specific cells. The effects of biomaterials for promoting bone formation via growth factor‐mediated osteogenesis are further elucidated. Finally, an outlook of the prospects in terms of superior communication among growth factors, cells, and biomaterials in the microenvironment is presented, which might provide new directions for the design of medical devices for bone regeneration.

A mouse femoral defect model demonstrates the clinically relevant side effects of BMP-2

AIM: Bone morphogenetic protein-2 (BMP-2) is an FDA approved, osteoinductive growth factor for bone regeneration. However, increasing awareness of the side effects of BMP-2, including inflammation, bone resorption and fat formation, require the development of animal surgical models that replicate these adverse events. MATERIAL & METHODS: We devised a mouse femoral uni-cortical defect (UCD) model to study the clinical side effects of BMP-2. UCDs (3×1×1 mm) were drilled in one femur of mice and filled with poly(D,L-lactide-co-glycolide) (PLGA) scaffolding coated with PBS or rhBMP-2 (0.3mg/ml or 0.6mg/ml). Post mortem analyses were performed at four weeks post-surgery. RESULTS: 100% successful surgery was achieved in mouse femoral UCD without surgical complication. Micro-CT analyses of the high dose rhBMP-2 group revealed bone cyst formation with ~2.5 fold increase in bone volume and more than 50% decrease in bone mineral density and trabecular number compared to PBS control. Tartrate-resistant acid phosphatase (TRAP) staining revealed a significant increase in osteoclast number, while immunostaining for fatty acid binding protein 4 (FABP4) and peroxisome proliferator-activated receptor gamma (PPAR-γ) confirmed significant increases in adipocyte formation with rhBMP-2 in a dose dependent manner. Lastly, rhBMP-2 treatment caused significant increases in inflammation, as determined by immunostaining for tumor necrosis factor-α (TNF- α) and interleukin 6 (IL6). CONCLUSION: Here, we established a mouse UCD model that faithfully replicates the clinically reported side effects of rhBMP-2. This model may facilitate future studies to improve upon current efforts in rhBMP-2 based bone repair.

Hollow hydroxyapatite microspheres/chitosan composite as a sustained delivery vehicle for rhBMP-2 in the treatment of bone defects.

Composite scaffold comprised of hollow hydroxyapatite (HA) and chitosan (designated hHA/CS) was prepared as a delivery vehicle for recombinating human bone morphogenetic protein-2 (rhBMP-2). The in vitro and in vivo biological activities of rhBMP2 released from the composite scaffold were then investigated. The rhBMP-2 was firstly loaded into the hollow HA microspheres, and then the rhBMP2-loaded HA microspheres were further incorporated into the chitosan matrix. The chitosan not only served to bind the HA microspheres together and kept them at the implant site, but also effectively modified the release behavior of rhBMP-2. The in vitro release and bioactivity analysis confirmed that the rhBMP2 could be loaded and released from the composite scaffolds in bioactive form. In addition, the composite scaffolds significantly reduced the initial burst release of rhBMP2, and thus providing prolonged period of time (as long as 60 days) compared with CS scaffolds. In vivo bone regenerative potential of the rhBMP2-loaded composite scaffolds was evaluated in a rabbit radius defect model. The results revealed that the rate of new bone formation in the rhBMP2-loaded hHA/CS group was higher than that in both negative control and rhBMP2-loaded CS group. These observations suggest that the hHA/CS composite scaffold would be effective and feasible as a delivery vehicle for growth factors in bone regeneration and repair.