Efficacy Of Bone Regeneration Research Articles

Platelet-Rich Plasma Contains High Concentrations of DKK1, A Potent Inhibitor of Wnt Signaling that Limits Bone Regeneration and Hair Growth

Platelet-rich plasma (PRP) is a popular autologous therapy in the tissue regenerative technology space based on its enriched milieu of platelet-released growth factors (GFs), including platelet-derived growth factor (PDGF) and vascular endothelial growth factor (VEGF). PRP is frequently used for hair restoration, wound healing, tendon and ligament repairs, and other soft-tissue settings, but PRP did not fulfill its original promise for enhancing bone grafts and bone augmentation in dentistry or orthopedics because it does not consistently promote osteogenesis. The effects of PRP on bone regeneration are often described as controversial, contradictory, and confusing, including evidence that greater platelet enrichment often leads to lesser osteogenic responses. The latter paradox suggests that limited PRP efficacy in bone regeneration may relate to platelet-derived factors that inhibit osteoblasts rather than inadequate GF concentrations. One candidate platelet-derived anti-osteogenic factor is Dickkopf-1 (DKK1), a potent soluble inhibitor of Wnt signaling that limits bone regeneration after bone damage. Recognizing that platelets store DKK1 in their alpha granules and rapidly release it upon platelet activation, we evaluated levels of DKK1, PDGF, and VEGF in human serum, plasma, platelet-poor plasma (PPP), and PRP. Sclerostin, another inhibitor of Wnt signaling that limits bone formation in undamaged bone, was also evaluated because platelets are not known to secrete sclerostin. We show that DKK1, PDGF, and VEGF concentrations are much higher in serum versus plasma, probably due to platelet activation during serum preparation. DKK1, PDGF, and VEGF concentrations were also higher in PRP versus plasma, and in plasma versus PPP. Activation of plasma or PRP with thrombin resulted in marked increases in DKK1, PDGF, and VEGF concentrations, with DKK1 levels in activated PRP being over 40-fold higher than the minimum concentration reported to inhibit osteogenesis in cell culture models. Conversely, sclerostin levels in plasma and PRP were unaffected by platelet activation and were significantly lower in serum versus standard plasma, providing new evidence that platelets do not secrete sclerostin. These results suggest that the beneficial effects of high GF levels in PRP may be limited by the presence of high levels of DKK1 released from the same platelet alpha granules.

Photo-crosslinked gelatin methacryloyl hydrogel strengthened with calcium phosphate-based nanoparticles for early healing of rabbit calvarial defects.

The aim of this study was to investigate the efficacy of photo-crosslinked gelatin methacryloyl (GelMa) hydrogel containing calcium phosphate nanoparticles (CNp) when applying different fabrication methods for bone regeneration. Four circular defects were created in the calvaria of 10 rabbits. Each defect was randomly allocated to the following study groups: 1) the sham control group, 2) the GelMa group (defect filled with crosslinked GelMa hydrogel), 3) the CNp-GelMa group (GelMa hydrogel crosslinked with nanoparticles), and 4) the CNp+GelMa group (crosslinked GelMa loaded with nanoparticles). At 2, 4, and 8 weeks, samples were harvested, and histological and micro-computed tomography analyses were performed. Histomorphometric analysis showed that the CNp-GelMa and CNp+GelMa groups at 2 weeks had significantly greater total augmented areas than the control group (P<0.05). The greatest new bone area was observed in the CNp-GelMa group, but without statistical significance (P>0.05). Crosslinked GelMa hydrogel with nanoparticles exhibited good biocompatibility with a minimal inflammatory reaction. There was no difference in the efficacy of bone regeneration according to the synthesized method of photo-crosslinked GelMa hydrogel with nanoparticles. However, these materials could remain within a bone defect up to 2 weeks and showed good biocompatibility with little inflammatory response. Further improvement in mechanical properties and resistance to enzymatic degradation would be needed for the clinical application.

Core-shell bioceramic fiber-derived biphasic granules with adjustable core compositions for tuning bone regeneration efficacy.

Silicate-based biomaterials-clinically applied fillers and promising candidates-can act as a highly biocompatible substrate for osteostimulative osteogenic cell growth in vitro and in vivo. These biomaterials have been proven to exhibit a variety of conventional morphologies in bone repair, including scaffolds, granules, coatings and cement pastes. Herein, we aim to develop a series of novel bioceramic fiber-derived granules with core-shell structures which have a hardystonite (HT) shell layer and changeable core components-that is, the chemical compositions of a core layer can be tuned to include a wide range of silicate candidates (e.g., wollastonite (CSi)) with doping of functional ions (e.g., Mg, P, and Sr). Meanwhile, it is versatile to control the biodegradation and bioactive ion release sufficiently for stimulating new bone growth after implantation. Our method employs rapidly gelling ultralong core-shell CSi@HT fibers derived from different polymer hydrosol-loaded inorganic powder slurries through the coaxially aligned bilayer nozzles, followed by cutting and sintering treatments. It was demonstrated that the nonstoichiometric CSi core component could contribute to faster bio-dissolution and biologically active ion release in tris buffer in vitro. The rabbit femoral bone defect repair experiments in vivo indicated that core-shell bioceramic granules with an 8% P-doped CSi-core could significantly stimulate osteogenic potential favorable for bone repair. It is worth concluding that such a tunable component distribution strategy in fiber-type bioceramic implants may develop new-generation composite biomaterials endowed with time-dependent biodegradation and high osteostimulative activities for a range of bone repair applications in situ.

Antimicrobial and Pro-Osteogenic Coaxially Electrospun Magnesium Oxide Nanoparticles-Polycaprolactone /Parathyroid Hormone-Polycaprolactone Composite Barrier Membrane for Guided Bone Regeneration

An antibacterial and pro-osteogenic coaxially electrospun nanofiber guided bone regeneration (GBR) membrane was fabricated to satisfy the complicated and phased requirements of GBR process. In this study, we synthesize dual-functional coaxially electrospun nanofiber GBR membranes by encapsulating parathyroid hormone (PTH) in the core layer and magnesium oxide nanoparticles (MgONPs) in the shell layer (MgONPs-PCL/PTH-PCL). Herein, the physicochemical characterization of MgONPs-PCL/PTH-PCL, the release rates of MgONPs and PTH, and antibacterial efficiency of the new membrane were evaluated. Furthermore, the pro-osteogenicity of the membranes was assessed both in-vitro and in-vivo. We successfully fabricated a coaxially electrospun nanofiber MgONPs-PCL/PTH-PCL membrane with the majority of nanofibers (>65%) ranged from 0.40~0.60μm in diameter. MgONPs-PCL/PTH-PCL showed outstanding antibacterial potential against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) through the release of MgONPs. We also discovered that the incorporation of MgONPs significantly prolonged the release of PTH. Furthermore, both the in-vivo and in-vitro studies demonstrated that high dosage of PTH promoted pro-osteogenicity of the membrane to improve bone regeneration efficacy with the presence of MgONPs. The new composite membrane is a promising approach to enhance bone regeneration in periodontitis or peri-implantitis patients with large-volume bone defects.

Characterization of a nanocomposite scaffold and assessment of its osteogenic influence in a rabbit mandibular bone defect model

ObjectiveBone is a complex tissue with a multifactorial healing process. Different scaffold materials have been tested for efficacy in bone regeneration. Polycaprolactone (PCL), alginate (Alg), and hydroxyapatite (HA) are materials with different properties that make them good candidates for scaffold fabrication for bone tissue engineering purposes. Composite scaffolds achieve better properties because they combine high mechanical strength of synthetic materials with biocompatibility and hydrophilicity of natural materials. This study was conducted to achieve in vitro and in vivo characterization of a composite nanofibrous material and test its osteogenic effect on mandibular bone defects. MethodsScaffolds were fabricated through electrospinning technique and coated through casting method. Characterization was conducted using scanning electron microscope (SEM), energy-dispersive X-ray (EDX), and Fourier transform infrared (FTIR). Mechanical tests were done. Weight loss and water absorption percentages were calculated in vitro. For in vivo tests, male New Zealand white rabbits were divided into two groups. Both groups had bilateral circular mandibular defects. The control group was left without further intervention while the experimental group had scaffolds implanted in the defects. After different time intervals, animals were euthanized, and histological evaluations with histomorphometric analyses were conducted. ResultsThe fabricated material showed proper biocompatibility and morphological, physical, chemical, and mechanical properties. The experimental group showed enhanced bone healing with more arranged and mature bone trabeculae. The area of new bone formation was significantly higher in the experimental than the control group. ConclusionsElectrospun nanocomposite [PCL/Alg/nano-HA (nHA)] represents a highly qualified material that can efficiently enhance bone regeneration.

Electreted Sandwich Membranes with Persistent Electrical Stimulation for Enhanced Bone Regeneration.

Physiologically relevant electrical microenvironments play an indispensable role in manipulating bone metabolism. Although implanted biomaterials that simulate the electrical properties of natural tissues using conductive or piezoelectric materials have been introduced in the field of bone regeneration, the application of electret materials to provide stable and persistent electrical stimulation has rarely been studied in biomaterial design. In this study, a silicon dioxide electret-incorporated poly(dimethylsiloxane) (SiO2/PDMS) composite electroactive membrane was designed and fabricated to explore its bone regeneration efficacy. SiO2 electrets were homogeneously dispersed in the PDMS matrix, and sandwich-like composite membranes were fabricated using a facile layer-by-layer blade-coating method. Following the encapsulation, electret polarization was conducted to obtain the electreted composite membranes. The surface potential of the composite membrane could be adjusted to a bone-promotive biopotential by tuning the electret concentration, and the prepared membranes exhibited favorable electrical stability during an observation period of up to 42 days. In vitro biological experiments indicated that the electreted SiO2/PDMS membrane promoted cellular activity and osteogenic differentiation of mesenchymal stem cells. In vivo, the electreted composite membrane remarkably facilitated bone regeneration through persistent endogenous electrical stimulation. These findings suggest that the electreted sandwich-like membranes, which maintain a stable and physiological electrical microenvironment, are promising candidates for enhancing bone regeneration.

P-41374722-198 - Comparative histomorphometric evaluation of synthetic and egg-shell derived hydroxyapatite for bone regeneration in Wistar rats

<h3>Purpose</h3> Various bone regenerative materials have been used for the healing of bone defects with varying success rates. Recently, our team has developed nanohydroxyapatite (nHAp) as a novel bone graft substitute. The material has been compared for its bone regeneration efficacy in calvarial defects of Wistar rats. <h3>Methodology</h3> A total of 40 adult male Wistar rats were included and grouped into two: Group A with collagen membrane and Group B without collagen membrane. Both the groups received commercially available Synthetic (G-bone from G-Surgiware, India.) and nHAp ( from eggshell calcium-carbonate using indigenous Microwave-synthesis) graft material randomly to fill the bilateral calvarial bone defects of 6mm each. The animals were followed up to observe healing and sacrificed on the 10th,30th, 60th, 90th, and 120th days post-surgery to evaluate the nature of bone regeneration using histomorphometry & MicroCT. <h3>Results</h3> The wound was well healed in both groups. New bone formation was observed from the periphery in both groups filled with nHAp. Bone growth was statistically significant, and the thickness of bone, density of the matrix was increased progressively with a decrease in fibrous connective tissue throughout the healing process in nHAp compared to the Synthetic group. Micro CT observations were consistent with histomorphometry. <h3>Conclusion</h3> Both materials showed the osteoconductive property. Irrespective of the presence of collagen membrane, nHAp group showed better bone regeneration compared to the Synthetic group. The thickness of the matured bone was more in nHAp on the 120th day and was consistent compared to Synthetic group at all timelines.

Use of stem cells in bone regeneration in cleft palate patients: review and recommendations.

This study was conducted to review the efficacy of different sources of stem cells in bone regeneration of cleft palate patients. The majority of previous studies focused on the transplantation of bone marrow mesenchymal stem cells. However, other sources of stem cells have also gained considerable attention, and dental stem cells have shown especially favorable outcomes. Additionally, approaches that apply the co-culture and co-transplantation of stem cells have shown promising results. The use of different types of stem cells, based on their accessibility and efficacy in bone regeneration, is a promising method in cleft palate bone regeneration. In this regard, dental stem cells may be an ideal choice due to their efficacy and accessibility. In conclusion, stem cells, despite the lengthy procedures required for culture and preparation, are a suitable alternative to conventional bone grafting techniques.

Bilateral double site (calvarial and mandibular) critical-size bone defect model in rabbits for evaluation of a craniofacial tissue engineering constructs.

Most existing preclinical models for evaluating the biosafety and bone-regeneration efficacy of innovative bone substitute materials (BSMs) or tissue engineering (TE) constructs only consisted of a single-site defect and the anatomical locations of defect varied drastically. While the compelling evidence showed that the bone healing pattern is location-dependent, owing to developmental, structural, and functional differences of anatomical locations, this is particularly true for the craniofacial region. Taking this into account, the bone healing efficiency of a BSM shown at one anatomical defect location cannot ensure the same impact at another. This prompted us to develop, for the first time, a model of bilateral critical-sized defect (CSD) at two distinctly different locations (non-load-bearing parietal calvaria and load-bearing mandibular body) co-existing in one rabbit to reduce the number of animals needed and avoid the influence of interindividual variability and evaluation bias on comparisons.24 healthy adult male New Zealand White rabbits were randomly assigned to a group, either control, autograft (considered the “gold standard”) or a clinically relevant BSM (biphasic calcium phosphate granules) (BCPg, Mastergraft®, Medronics). The full-thickness cylindrical calvarial defect (ø10 mm) on frontoparietal region and mandibular composite defect (ø11 mm) on the body of the mandible were created bilaterally using low-speed drilling with saline irrigation. The defect on one side was filled with autograft debris or BCPg, and the other side was no graft (empty). Following the euthanasia of animals at the predetermined intervals (4w and 12w), the defect zones were examined macroscopically and then sampled and processed for microcomputed tomography (microCT) and histological analysis.All surgeries went uneventfully, and all rabbits recovered slowly but steadily. No symptoms of infection or inflammation associated with the defect were observed during the experiment. At 4w and 12w, macroscopic views of all defect sites were clean without any signs of necrosis or abscess, and no intraoral communication was found. The analysis of microCT and histological findings showed the non-healing nature of the empty defect, thereby both calvaria and mandible CSDs can be validated. The study of the application of BCPg in this defect model highlighted good osteointegration and excellent osteoconductive properties but compromised the osteoinductive properties of this material (compared with autograft).To conclude, this novel double-site CSD model holds great promise in the application for preclinical evaluation of BSMs, TE construct, etc. With a reduced number of animals in use, and lower interindividual variability and evaluation bias for comparisons.

Titanium alloy composited with dual-cytokine releasing polysaccharide hydrogel to enhance osseointegration via osteogenic and macrophage polarization signaling pathways.

Titanium alloy has been widely used in orthopedic surgeries as bone defect filling. However, the regeneration of high-quality new bones is limited due to the pro-inflammatory microenvironment around implants, resulting in a high occurrence rate of implant loosening or failure in osteological therapy. In this study, extracellular matrix-mimetic polysaccharide hydrogel co-delivering BMP-2 and interleukin (IL)-4 was composited with 3D printed titanium alloy to promote the osseointegration and regulate macrophage response to create a pro-healing microenvironment in bone defect. Notably, it is discovered from the bioinformatics data that IL-4 and BMP-2 could affect each other through multiple signal pathways to achieve a synergistic effect toward osteogenesis. The composite scaffold significantly promoted the osteoblast differentiation and proliferation of human bone marrow mesenchyme stem cells (hBMSCs). The repair of large-scale femur defect in rat indicated that the dual-cytokine-delivered composite scaffold could manipulate a lower inflammatory level in situ by polarizing macrophages to M2 phenotype, resulting in superior efficacy of mature new bone regeneration over the treatment of native titanium alloy or that with an individual cytokine. Collectively, this work highlights the importance of M2-type macrophages-enriched immune-environment in bone healing. The biomimetic hydrogel–metal implant composite is a versatile and advanced scaffold for accelerating in vivo bone regeneration, holding great promise in treating orthopedic diseases.

Lotus root and osteons-inspired channel structural scaffold mediate cell biomineralization and vascularized bone tissue regeneration.

The interconnectivity of porous scaffold is vital for cell and tissue infiltration, and vascular networks formation, determining the successful bone regeneration in large bone defects. Here, inspired by the lotus-root and Haversian system of natural bone, a nano-hydroxyapatite/polyurethane (n-HA/PU) lotus root-like scaffold inlaid with micro holes on the wall of the adjacent channel was utilized to mediate cell biomineralization and vascularized bone tissue regeneration. Such a particular lotus-type structure remarkably promoted cells to proliferate and infiltrate into the center of the entire scaffold, serving as a clue to account for regulating cell alignment and differentiation physically. In vitro studies suggested that apatite accumulated dramatically on the channel wall in the lotus-type scaffold, probably promoting specific osteogenic differentiation of cells by the orientated channels, even in the absence of osteogenic factors. In vivo creation of critical bone defects (15-mm segments) was done in the radius of rabbits and implanted with the scaffold of different geometry to assess the structural parameters on the efficacy of new bone regeneration. The more extensive positive staining of BMP-2, more considerable amount of infiltrated capillary, more robust new bone formation, particularly the biomechanical strength of lotus-type scaffold group could reach the level of the control group without surgery, indicating that the lotus-type scaffold was more favorable for new bone tissue formation along tube-like channels. These results highlighted the potential of this biomimetic scaffold for cell and tissue infiltration and thus repair large bony defects.

Allogeneic Bone-Marrow Mesenchymal Stem Cell with Moldable Cryogel for Craniofacial Bone Regeneration.

Allogeneic bone-marrow mesenchymal stem cells (BMSCs) can promote bone regeneration and substitute for autologous BMSCs if autologous sources are unavailable, but the efficacy of bone regeneration by allogeneic BMSCs is still inconsistent. A Lewis rat cranium defect model was used to investigate the efficacy of bone regeneration between autologous and allogeneic BMSCs in gelatin-nanohydroxyapatite cryogel scaffolds. BMSCs from Wistar rats served as the allogeneic cell lineage. The full-thickness cranium defects were treated by either blank control, cryogel only, allogeneic BMSC-seeded cryogel, or autologous BMSC-seeded cryogel (n = 5). Bone regeneration was monitored by micro-computed tomography and examined histologically at week 12. In addition, we assessed the immune responses in vitro by mixed lymphocyte reaction (MLR) assay and CD4+ immunochemistry staining ex vivo. The MLR showed that allogeneic BSMCs elicited a weak immune response on day 14 that progressively attenuated by day 28. In vivo, the bone regeneration in allogeneic BMSCs was inferior at week 4, but progressively matched the autologous BMSCs by week 12. Our results suggest that allogeneic BMSCs can serve as an alternative source for bone regeneration.

In Vivo Efficacy of Neutrophil-Mediated Bone Regeneration Using a Rabbit Calvarial Defect Model.

Reconstruction of bone due to surgical removal or disease-related bony defects is a clinical challenge. It is known that the immune system exerts positive immunomodulatory effects on tissue repair and regeneration. In this study, we evaluated the in vivo efficacy of autologous neutrophils on bone regeneration using a rabbit calvarial defect model. Methods: Twelve rabbits, each with two surgically created calvarial bone defects (10 mm diameter), were randomly divided into two groups; (i) single application of neutrophils (SA-NP) vs. SA-NP control, and (ii) repetitive application of neutrophils (RA-NP) vs. RA-NP control. The animals were euthanized at 4 and 8 weeks post-operatively and the treatment outcomes were evaluated by micro-computed tomography, histology, and histomorphometric analyses. Results: The micro-CT analysis showed a significantly higher bone volume fraction (bone volume/total volume) in the neutrophil-treated groups, i.e., median interquartile range (IQR) SA-NP (18) and RA-NP (24), compared with the untreated controls, i.e., SA-NP (7) and RA-NP (14) at 4 weeks (p < 0.05). Similarly, new bone area fraction (bone area/total area) was significantly higher in neutrophil-treated groups at 4 weeks (p < 0.05). Both SA-NP and RA-NP had a considerably higher bone volume and bone area at 8 weeks, although the difference was not statistically significant. In addition, immunohistochemical analysis at 8 weeks revealed a higher expression of osteocalcin in both SA-NP and RA-NP groups. Conclusions: The present study provides first hand evidence that autologous neutrophils may have a positive effect on promoting new bone formation. Future studies should be performed with a larger sample size in non-human primate models. If proven feasible, this new promising strategy could bring clinical benefits for bone defects to the field of oral and maxillofacial surgery.

Development of a Bone-Mimetic 3D Printed Ti6Al4V Scaffold to Enhance Osteoblast-Derived Extracellular Vesicles' Therapeutic Efficacy for Bone Regeneration.

Extracellular Vesicles (EVs) are considered promising nanoscale therapeutics for bone regeneration. To date, EVs are typically procured from cells on 2D tissue culture plastic, an artificial environment that limits cell growth and does not replicate in situ biochemical or biophysical conditions. This study investigated the potential of 3D printed titanium scaffolds coated with hydroxyapatite to promote the therapeutic efficacy of osteoblast-derived EVs. Ti6Al4V titanium scaffolds with different pore sizes (500 and 1000 µm) and shapes (square and triangle) were fabricated by selective laser melting. A bone-mimetic nano-needle hydroxyapatite (nnHA) coating was then applied. EVs were procured from scaffold-cultured osteoblasts over 2 weeks and vesicle concentration was determined using the CD63 ELISA. Osteogenic differentiation of human bone marrow stromal cells (hBMSCs) following treatment with primed EVs was evaluated by assessing alkaline phosphatase activity, collagen production and calcium deposition. Triangle pore scaffolds significantly increased osteoblast mineralisation (1.5-fold) when compared to square architectures (P ≤ 0.001). Interestingly, EV yield was also significantly enhanced on these higher permeability structures (P ≤ 0.001), in particular (2.2-fold) for the larger pore structures (1000 µm). Furthermore osteoblast-derived EVs isolated from triangular pore scaffolds significantly increased hBMSCs mineralisation when compared to EVs acquired from square pore scaffolds (1.7-fold) and 2D culture (2.2-fold) (P ≤ 0.001). Coating with nnHA significantly improved osteoblast mineralisation (>2.6-fold) and EV production (4.5-fold) when compared to uncoated scaffolds (P ≤ 0.001). Together, these findings demonstrate the potential of harnessing bone-mimetic culture platforms to enhance the production of pro-regenerative EVs as an acellular tool for bone repair.

A judicious approach of exploiting polyurethane-urea based electrospun nanofibrous scaffold for stimulated bone tissue regeneration through functionally nobbled nanohydroxyapatite

Complete natural healing of skeletal tissues may take several months or even years, depending on the type and size of defects owing to slow auto-osteogenesis. Numerous techniques have been explored to gear-up the bone-healing process, as bone tissue has complex nanohybrid hierarchical meshwork containing nano apatite layers. Healing of such tissues associates with risks of pathogenic infection and ectopic bone formation. Therefore, most of the approaches fail to meet the requisite criteria to adopt in clinical practice. Carbonaceous bone substitutes may trigger healing, but an excess of it may render many adverse effects. In the current study, nanohydroxyapatite (nHA) was prepared, doped with a minute amount (0.15%) of carboxyl functionalized multiwall carbon nanotube (CCNT). The hybrid nanomaterial (CCNTH) was introduced within the synthesized biomolecule tethered segmented polyurethane-urea (SP) through in-situ technique and scaffolds were fabricated by electrospinning technique. CCNT doping improves the tensile strength and the hardness of the nano-scaffold by 94.5% and 173.6%, respectively. In vitro MTT assay, FESEM and protein adsorption study indicated the excellent cytocompatibility of the nanohybrid scaffolds. The qRT-PCR study indicates the significant expression of the osteogenic bone marker, osteocalcin (OCN) and the alkaline phosphatase (ALP) of the CCNTH incorporated nanohybrid scaffolds compared to the SP scaffold. Furthermore, the in vivo rat tibia and skull model exhibit excellent bone regeneration efficacy compared to the control without showing any sign of organ toxicity. Thus, a minute amount of CCNT doped nHA incorporated SP based micro-porous nanohybrid scaffold can be used as an alternate suitable biomaterial for osteoinduction application.

Precise in-situ release of microRNA from an injectable hydrogel induces bone regeneration

Critical bone defects are a common yet challenging orthopedic problem. Tissue engineering is an emerging and promising strategy for bone regeneration in large-scale bone defects. The precise on-demand release of osteogenic factors is critical for controlling the osteogenic differentiation of seed cells with the support of appropriate three dimensional scaffolds. However, most of the effective osteogenic factors are biomacromolecules with release behaviors that are difficult to control. Here, the cholesterol-modified non-coding microRNA Chol-miR-26a was used to promote the osteogenic differentiation of human mesenchymal stem cells (hMSCs). Chol-miR-26a was conjugated to an injectable poly(ethylene glycol) (PEG) hydrogel through an ultraviolet (UV)-cleavable ester bond. The injectable PEG hydrogel was formed by a copper-free click reaction between the terminal azide groups of 8-armed PEG and dibenzocyclooctyne-biofunctionalized PEG, into which UV-cleavable Chol-miR-26a was simultaneously conjugated via a Michael addition reaction. Upon UV irradiation, Gel-c-miR-26a (MLCaged) released Chol-c-miR-26a selectively and exhibited significantly improved efficacy in bone regeneration compared to the hydrogel without UV irradiation and UV-uncleavable MLControl. MLCaged significantly enhanced alkaline phosphatase activity and promoted calcium nodule deposition in vitro and repaired critical skull defects in a rat animal model, demonstrating that injectable implantation with the precise release of osteogenic factors has the potential to repair large-scale bone defects in clinical practice. Statement of significanceProvide a novel and practical strategy via hydrogel for efficient delivery and precisely controlled release of miRNAs into bone defect sites.The hydrogel is formed by polyethylene glycol (PEG), which is crosslinked by ‘click’ reaction.Cholesterol-modified miR-26a loading on the hydrogel is covalently patterned onto the fibers of hydrogel through a UV light-cleavable linker, which prevents undesired release of miRNA. This hydrogel could realize the controlled release of miRNA under light regulation both in vitro and in vivo, thus realize bone regeneration.

Dual mechanism design to enhance bone formation by overexpressed SDF-1 ADSCs in magnesium doped calcium phosphate scaffolds

BackgroundSDF-1/CXCR4 axis plays a critical role in the mobilization and regeneration of host-derived cells. Little is known around the role of SDF-1 gene on bone regeneration. This study was conceptualized to create a 2-in-1 strategy by identifying potential role of SDF-1 on promoting endogenous osteoblast migration and synergizing with magnesium doped calcium phosphate scaffold (MCPC) on osteogenic differentiation. MethodADSCs were transfected with Lenti-SDF-1. Cell proliferation, osteogenic gene expression and ALP/ARS staining were investigated. Osteoblast migration was studied. MCPC construct was employed as carrier of Lenti-SDF-1 ADSCs. Osteogenic gene expressions of BMSCs were determined in MCPC + ADSCs medium. MCPC + Lenti-SDF-1 ADSCs scaffolds were implanted into rats and bone regeneration efficacy was evaluated by micro-CT and histological analysis. ResultSDF-1 transduction neither impacted ADSCs' proliferation, nor osteogenic differentiation. Lenti-SDF-1 ADSCs promoted migration of BMSCs/osteoblasts. MCPC facilitated osteogenic differentiation of BMSCs. Bone formation was significantly increased in MCPC + Lenti-SDF-1 group. ConclusionOverexpressed SDF-1 gene promotes the homing of endogenous osteoblasts. MCPC + Lenti-SDF-1 facilitated robust in situ bone regeneration via dual mechanisms by recruiting endogenous BMSCs' and enhancing homing cell's differentiation. This advanced design combines gene therapy and osteoinductive tissue scaffolds, which is proved to be a promising strategy to achieve satisfied clinical bone repair efficacy.

Controlled delivery of bone morphogenic protein-2-related peptide from mineralised extracellular matrix-based scaffold induces bone regeneration

Ideal bone tissue engineering scaffolds composed of extracellular matrix (ECM) require excellent osteoconductive ability to imitate the bone environment. We developed a mineralised tissue-derived ECM-modified true bone ceramic (TBC) scaffold for the delivery of aspartic acid-modified bone morphogenic protein-2 (BMP-2) peptide (P28) and assessed its osteogenic capacity. Decellularized ECM from porcine small intestinal submucosa (SIS) was coated onto the surface of TBC, followed by mineralisation modification (mSIS/TBC). P28 was subsequently immobilised onto the scaffolds in the absence of a crosslinker. The alkaline phosphatase activity and other osteogenic differentiation marker results showed that osteogenesis of the P28/mSIS/TBC scaffolds was significantly greater than that of the TBC and mSIS/TBC groups. In addition, to examine the osteoconductive capability of this system in vivo, we established a rat calvarial bone defect model and evaluated the new bone area and new blood vessel density. Histological observation showed that P28/mSIS/TBC exhibited favourable bone regeneration efficacy. This study proposes the use of mSIS/TBC loaded with P28 as a promising osteogenic scaffold for bone tissue engineering applications.

Development of a decellularized porcine bone graft by supercritical carbon dioxide extraction technology for bone regeneration.

A series of novel decellularized porcine collagen bone graft (DPB) materials in a variety of shapes and sizes were developed by the supercritical carbon dioxide (SCCO2 ) extraction technique. The complete decellularization of DPB was confirmed by hematoxylin and eosin staining, 4,6-diamidino-2-phenylindole (DAPI) staining, and residual DNA analysis. The native intact collagen remained in the DPB after the SCCO2 process was confirmed by Masson trichrome staining. The physicochemical characteristics of DPB were investigated by scanning electron microscopy and x-ray diffraction. The cytotoxicity and biocompatibility tests according to ISO10993 and its efficacy for bone regeneration in osteochondral defects in rabbits were evaluated. The rabbit pyrogen test confirmed DPB was non-toxic. In vitro and in vivo biocompatibility tests of the DPB did not show any toxic or mutagenic effects. The bone regeneration potential of the DPB presented no significant histological differences compared to commercially available deproteinized bovine bone. In conclusion, DPB produced by SCCO2 exhibited similar chemical characteristics to human bone, no toxicity, good biocompatibility, and enhanced bone regeneration in rabbits comparable to that of deproteinized bovine bone. Results from this study could shed light on the potential application of the SCCO2 extraction technique to generate a native decellularized scaffold for bone tissue regeneration in human clinical trials.

Regenerative Treatment of Peri-Implantitis: A Systematic Revie.

Objectives:The aim of this systematic review was to assess the clinical efficacy of bone regeneration for treatment of peri-implantitis.Materials and Methods:Electronic search of the literature was performed to identify randomized clinical trials (RCTs) and case series on treatment of peri-implantitis using bone regeneration procedures with at least 6 months of follow-up. The guidelines of the Preferred Reporting Items for Systematic Reviews and Meta Analyses (PRISMA) were applied. The risk of bias was assessed using the Cochrane Collaboration’s Risk of Bias tool.Results:Two RCTs and 16 case series with a total of 520 treated patients (2002 implants) were included. Bone regenerative procedures showed controversial results regarding bone fill. Two studies reported statistically significant bone gain while four studies reported insignificant bone gain. Other studies reported bone gain with no P value. Pocket depth (PD) reduction varied among the studies since four studies reported a significant reduction in PD while four others reported insignificant reduction in PD. Other studies reported a reduction in PD with no P value. Bone regeneration procedures seemed to decrease bleeding on probing (BOP) but they did not seem conducive to increase the width of keratinized gingiva. Increased keratinized gingiva was noted in cases with subepithelial grafts.Conclusion:Evaluation of the effectiveness of bone regeneration techniques in this systematic review presented limitations related to heterogeneity in patient selection (age, history of periodontitis, smoking status and implant system), means of disinfection and decontamination, and variability of the materials used for treatment.