Comparative bone healing with induced membrane technique (IMT) versus empty defects in septic and aseptic conditions in a novel rabbit humerus model.

BACKGROUND: Long bone defects resulting from primary trauma or secondary to debridement of fracture-related infection (FRI) remain a major clinical challenge. One approach often used is the induced membrane technique (IMT). The effectiveness of the IMT in infected versus non-infected settings remains to be definitively established. In this study we present a new rabbit humerus model and compare the IMT approach between animals with prior infection and non-infected equivalents. METHODS: A 5 mm defect was created in the humerus of New Zealand White rabbits (n = 53) and fixed with a 2.5 mm stainless steel plate. In the non-infected groups, the defect was either left empty (n = 6) or treated using the IMT procedure (PMMA spacer for 3 weeks, n = 6). Additionally, both approaches were applied in animals that were inoculated with Staphylococcus aureus 4 weeks prior to defect creation (n = 5 and n = 6, respectively). At the first and second revision surgeries, infected and necrotic tissues were debrided and processed for bacteriological quantification. In the IMT groups, the PMMA spacer was removed 3 weeks post implantation and replaced with a beta-tricalcium phosphate scaffold and bone healing observed for a further 10 weeks. Infected groups also received systemic antibiotic therapy. The differences in bone healing between the groups were evaluated radiographically using a modification of the radiographic union score for tibial fractures (RUST) and by semiquantitative histopathology on Giemsa-Eosin-stained sections. RESULTS: The presence of S. aureus infection at revision surgery was required for inclusion to the second stage. At the second revision surgery all collected samples were culture negative confirming successful treatment. In the empty defect group, bone healing was increased in the previously infected animals compared with non-infected controls as revealed by radiography with significantly higher RUST values at 6 weeks (p = 0.0281) and at the end of the study (p = 0.0411) and by histopathology with increased cortical bridging (80% and 100% in cis and trans cortical bridging in infected animals compared to 17% and 67% in the non-infected animals). With the IMT approach, both infected and non-infected animals had positive healing assessments. CONCLUSION: We successfully developed an in vivo model of bone defect healing with IMT with and without infection. Bone defects can heal after an infection with even better outcomes compared to the non-infected setting, although in both cases, the IMT achieved better healing.

Periodontal tissue engineering using an apatite/collagen scaffold obtained by a plasma- and precursor-assisted biomimetic process.

BACKGROUND AND OBJECTIVES: In the treatment of severe periodontal destruction, there is a strong demand for advanced scaffolds that can regenerate periodontal tissues with adequate quality and quantity. Recently, we developed a plasma- and precursor-assisted biomimetic process by which a porous collagen scaffold (CS) could be coated with low-crystalline apatite. The apatite-coated collagen scaffold (Ap-CS) promotes cellular ingrowth within the scaffold compared to CS in rat subcutaneous tissue. In the present study, the osteogenic activity of Ap-CS was characterized by cell culture and rat skull augmentation tests. In addition, the periodontal tissue reconstruction with Ap-CS in a beagle dog was compared to that with CS. METHODS: The plasma- and precursor-assisted biomimetic process was applied to CS to obtain Ap-CS with a low-crystalline apatite coating. The effects of apatite coating on the scaffold characteristics (i.e., surface morphology, water absorption, Ca release, protein adsorption, and enzymatic degradation resistance) were assessed. Cyto-compatibility and the osteogenic properties of Ap-CS and CS were assessed in vitro using preosteoblastic MC3T3-E1 cells. In addition, we performed in vivo studies to evaluate bone augmentation and periodontal tissue reconstruction with Ap-CS and CS in a rat skull and canine furcation lesion, respectively. RESULTS: As previously reported, the plasma- and precursor-assisted biomimetic process generated a low-crystalline apatite layer with a nanoporous structure that uniformly covered the Ap-CS surface. Ap-CS showed significantly higher water absorption, Ca release, lysozyme adsorption, and collagenase resistance than CS. Cell culture experiments revealed that Ap-CS was superior to CS in promoting the osteoblastic differentiation of MC3T3-E1 cells while suppressing their proliferation. Additionally, Ap-CS significantly promoted (compared to CS) the augmentation of the rat skull bone and showed the potential to regenerate alveolar bone in a dog furcation defect. CONCLUSION: Ap-CS fabricated by the plasma- and precursor-assisted biomimetic process provided superior promotion of osteogenic differentiation and bone neoformation compared to CS.

Partial-Insulation HTS Magnet for Reduction of Quench-Induced Peak Currents.

The No-insulation-like (NI) coil's turn-to-turn current paths prevent local heating by forcing the current to bypass into nearby turns when a hot spot appears in a coil. However, the changing direction of the current by bypassing will change the magnetic flux, which generates unwanted induced currents in the adjacent coils in a multiply-stacked HTS magnet. This induced current can temporarily exceed the designed maximum currents in the NI coils, damaging the magnet. A partial-insulation (PI) coil, in which a single or multiple insulated, with a polyimide-like material or a thin ceramic film, is inserted between windings to hinder the current paths, can reduce the peak induced currents in the NI HTS coil's current paths. In this paper, we present the results of a simulation study on the peak-induced current upon a quench of the PI HTS magnet with a double pancake. The study shows that the peak-induced current varies with the number of insulated turns. We also discuss the induced current turn-by-turn simulation. According to the simulation result, the PI effectively reduces overall induced current, especially insulation applied every two turns.

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.

Activated Carbon Fiber Cloth/Biomimetic Apatite: A Dual Drug Delivery System.

A biomaterial that is both bioactive and capable of controlled drug release is highly attractive for bone regeneration. In previous works, we demonstrated the possibility of combining activated carbon fiber cloth (ACC) and biomimetic apatite (such as calcium-deficient hydroxyapatite (CDA)) to develop an efficient material for bone regeneration. The aim to use the adsorption properties of an activated carbon/biomimetic apatite composite to synthetize a biomaterial to be used as a controlled drug release system after implantation. The adsorption and desorption of tetracycline and aspirin were first investigated in the ACC and CDA components and then on ACC/CDA composite. The results showed that drug adsorption and release are dependent on the adsorbent material and the drug polarity/hydrophilicity, leading to two distinct modes of drug adsorption and release. Consequently, a double adsorption approach was successfully performed, leading to a multifunctional and innovative ACC-aspirin/CDA-tetracycline implantable biomaterial. In a second step, in vitro tests emphasized a better affinity of the drug (tetracycline or aspirin)-loaded ACC/CDA materials towards human primary osteoblast viability and proliferation. Then, in vivo experiments on a large cortical bone defect in rats was carried out to test biocompatibility and bone regeneration ability. Data clearly highlighted a significant acceleration of bone reconstruction in the presence of the ACC/CDA patch. The ability of the aspirin-loaded ACC/CDA material to release the drug in situ for improving bone healing was also underlined, as a proof of concept. This work highlights the possibility of bone patches with controlled (multi)drug release features being used for bone tissue repair.

Hot-Spot Modeling of REBCO NI Pancake Coil: Analytical and Experimental Approaches.

The No-Insulation (NI) winding provides intrinsic bypassing current paths that enable self-protection from overheating. The self-protection of the NI coil is one of the most promising protection techniques for the high field high-temperature superconductor (HTS) magnet applications. Since the additional paths are valid for an HTS magnet with a thinner matrix, the self-protection mechanism is applicable even for the higher current density magnet with reduced matrix thickness inside the HTS tape. However, reducing the matrix can cause damage to the magnet by producing excessive heat during the quench. This research introduces a new modeling method to investigate the hot-spot characteristics in the REBCO NI pancake coil. The model is also validated with a sample NI HTS coil experiment result. Radial direction Normal Zone Propagation (NZP) velocity of the sample coil is estimated based on the suggested model. The calculated radial direction NZP velocity is applied to calculate the center field drop of the NI HTS coil, and the result is well-matched with the experiment result. We also introduce one example of the model applications. The maximum current density that will not exceed a given reference temperature in the adiabatic cooling condition is estimated using the model.

Bevacizumab Improves Achilles Tendon Repair in a Rat Model.

BACKGROUND/AIMS: Effective wound-healing generally requires efficient re-vascularization after injury, ensuring sufficient supply with oxygen, nutrients, and various cell populations. While this applies to most tissues, tendons are mostly avascular in nature and harbor relatively few cells, probably contributing to their poor regenerative capacity. Considering the minimal vascularization of healthy tendons, we hypothesize that controlling angiogenesis in early tendon healing is beneficial for repair tissue quality and function. METHODS: To address this hypothesis, Bevacizumab, a monoclonal antibody blocking VEGF-A signaling, was locally injected into the defect area of a complete tenotomy in rat Achilles tendon. At 28 days post-surgery, the defect region was investigated using immunohistochemistry against vascular and lymphatic epitopes. Polarization microscopy and biomechanical testing was used to determine tendon integrity and gait analysis for functional testing in treated vs non-treated animals. RESULTS: Angiogenesis was found to be significantly reduced in the Bevacizumab treated repair tissue, accompanied by significantly reduced cross sectional area, improved matrix organization, increased stiffness and Young's modulus, maximum load and stress. Further, we observed an improved gait pattern when compared to the vehicle injected control group. CONCLUSION: Based on the results of this study we propose that reducing angiogenesis after tendon injury can improve tendon repair, potentially representing a novel treatment-option.

Periodontal regeneration induced by porous alpha-tricalcium phosphate with immobilized basic fibroblast growth factor in a canine model of 2-wall periodontal defects.

We evaluated the effect of porous alpha-tricalcium phosphate (α-TCP) with immobilized basic fibroblast growth factor (bFGF) on periodontal regeneration in a canine model of 2-wall periodontal defects. Identical bone defects were made in the canine mandible; six defects in each animal were filled with porous α-TCP with bFGF bound via heparin (bFGF group), and the remaining defects were filled with unmodified porous α-TCP (control group). Micro-computed tomography and histological evaluation were performed at 2, 4, and 8 weeks post-implantation. The bone mineral content of the bFGF group was higher than that of the control group at 2 and 4 weeks (p < 0.05). Histological evaluation at 2 weeks post-implantation revealed degradation of the porous α-TCP, and bone had formed on the surface of α-TCP particles in the bFGF group. Some of these collagen fibers connected the newly formed cementum with the alveolar bone, revealing the formation of new periodontal ligaments with Sharpey's fibers. At 8 weeks, continuous cortical bone with a Haversian structure covered the top of the bone defects in the bFGF group. These findings indicate that porous α-TCP with immobilized bFGF could promote periodontal regeneration at the early regeneration phase in a canine model of 2-wall periodontal defects.

Acid ceramidase treatment enhances the outcome of autologous chondrocyte implantation in a rat osteochondral defect model.

OBJECTIVE: The overall aim of this study was to evaluate how supplementation of chondrocyte media with recombinant acid ceramidase (rhAC) influenced cartilage repair in a rat osteochondral defect model. METHODS: Primary chondrocytes were grown as monolayers in polystyrene culture dishes with and without rhAC (added once at the time of cell plating) for 7 days, and then seeded onto Bio-Gide® collagen scaffolds and grown for an additional 3 days. The scaffolds were then introduced into osteochondral defects created in Sprague-Dawley rat trochlea by a microdrilling procedure. Analysis was performed 6 weeks post-surgery macroscopically, by micro-CT, histologically, and by immunohistochemistry. RESULTS: Treatment with rhAC led to increased cell numbers and glycosaminoglycan (GAG) production (∼2 and 3-fold, respectively) following 7 days of expansion in vitro. Gene expression of collagen 2, aggrecan and Sox-9 also was significantly elevated. After seeding onto Bio-Gide®, more rhAC treated cells were evident within 4 h. At 6 weeks post-surgery, defects containing rhAC-treated cells exhibited more soft tissue formation at the articular surface, as evidenced by microCT, as well as histological evidence of enhanced cartilage repair. Notably, collagen 2 immunostaining revealed greater surface expression in animals receiving rhAC treated cells as well. Collagen 10 staining was not enhanced. CONCLUSION: The results further demonstrate the positive effects of rhAC treatment on chondrocyte growth and phenotype in vitro, and reveal for the first time the in vivo effects of the treated cells on cartilage repair.

The inhibitory effect of zoledronate on early-stage osteoinduction by recombinant human bone morphogenetic protein 2 in an osteoporosis model.

This study evaluated the effect of the combined treatment of intravenous zoledronic acid (ZA, 0.08 mg/kg) and rhBMP-2 (5 µg) on osteogenesis in a calvarial defect model of ovariectomized SD rats. New bone formation was evaluated 4 or 8 weeks after calvarial defect implantation using micro-CT and histology. Micro-CT results revealed that the rhBMP-2 group showed significantly higher calvarial defect coverage ratio compared with the ZA + rhBMP-2 group at 4 weeks. In addition, bone formation indices were significantly lower in ZA + rhBMP-2 group when compared with the rhBMP-2 group after 4 weeks, which indicates a negative effect of ZA on the initial bone formation and the bone quality. At 8 weeks, the negative effect induced by ZA treatment was alleviated as time passed. Histological examination showed similar results to the micro-CT measurements. In conclusion, although ZA treatment lowered the new bone formation induced by rhBMP-2 initially, as time passed, the negative effect was decreased.

Acemannan sponges stimulate alveolar bone, cementum and periodontal ligament regeneration in a canine class II furcation defect model.

BACKGROUND AND OBJECTIVE: Periodontal disease is a common infectious disease, found worldwide, causing the destruction of the periodontium. The periodontium is a complex structure composed of both soft and hard tissues, thus an agent applied to regenerate the periodontium must be able to stimulate periodontal ligament, cementum and alveolar bone regeneration. Recent studies demonstrated that acemannan, a polysaccharide extracted from Aloe vera gel, stimulated both soft and hard tissue healing. This study investigated effect of acemannan as a bioactive molecule and scaffold for periodontal tissue regeneration. MATERIAL AND METHODS: Primary human periodontal ligament cells were treated with acemannan in vitro. New DNA synthesis, expression of growth/differentiation factor 5 and runt-related transcription factor 2, expression of vascular endothelial growth factor, bone morphogenetic protein-2 and type I collagen, alkaline phosphatase activity, and mineralized nodule formation were determined using [(3)H]-thymidine incorporation, reverse transcription-polymerase chain reaction, enzyme-linked immunoabsorbent assay, biochemical assay and alizarin red staining, respectively. In our in vivo study, premolar class II furcation defects were made in four mongrel dogs. Acemannan sponges were applied into the defects. Untreated defects were used as a negative control group. The amount of new bone, cementum and periodontal ligament formation were evaluated 30 and 60 d after the operation. RESULTS: Acemannan significantly increased periodontal ligament cell proliferation, upregulation of growth/differentiation factor 5, runt-related transcription factor 2, vascular endothelial growth factor, bone morphogenetic protein 2, type I collagen and alkaline phosphatase activity, and mineral deposition as compared with the untreated control group in vitro. Moreover, acemannan significantly accelerated new alveolar bone, cementum and periodontal ligament formation in class II furcation defects. CONCLUSION: Our data suggest that acemannan could be a candidate biomolecule for periodontal tissue regeneration.

Rapid innervation and physiological epidermal regeneration by bioengineered dermis implanted in mouse.

Tissue-engineered skin substitutes are promising tools to cover large and deep skin defects. However, the lack of a synergic and fast regeneration of the vascular network, nerves, and skin appendages limits complete skin healing and impairs functional recovery. It has been highlighted that an ideal skin substitute should mimic the structure of the native tissue to enhance clinical effectiveness. Here, we produced a pre-vascularized dermis (PVD) comprised of fibroblasts embedded in their own extracellular matrix (ECM) and a capillary-like network. Upon implantation in a mouse full-thickness skin defect model, we observed a very early innervation of the graft in 2 weeks. In addition, mouse capillaries and complete epithelialization were detectable as early as 1 week after implantation and, skin appendages developed in 2 weeks. These anatomical features underlie the interaction with the skin nerves, thus providing a further cue for reinnervation guidance. Further, the graft displays mechanical properties, collagen density, and assembly features very similar to the host tissue. Taken together our data show that the pre-existing ECM components of the PVD, physiologically organized and assembled similarly to the native tissue, support a rapid regeneration of dermal tissue. Therefore, our results suggest a promising potential for PVD in skin regeneration.

The Impact of Defect Size on Bone Healing in Critical-Size Bone Defects Investigated on a Rat Femur Defect Model Comparing Two Treatment Methods.

Critical-size bone defects up to 25 cm can be treated successfully using the induced membrane technique established by Masquelet. To shorten this procedure, human acellular dermis (HAD) has had success in replacing this membrane in rat models. The aim of this study was to compare bone healing for smaller and larger defects using an induced membrane and HAD in a rat model. Using our established femoral defect model in rats, the animals were placed into four groups and defects of 5 mm or 10 mm size were set, either filling them with autologous spongiosa and surrounding the defect with HAD or waiting for the induced membrane to form around a cement spacer and filling this cavity in a second operation with a cancellous bone graft. Healing was assessed eight weeks after the operation using µ-CT, histological staining, and an assessment of the progress of bone formation using an established bone healing score. The α-smooth muscle actin used as a signal of blood vessel formation was stained and counted. The 5 mm defects showed significantly better bone union and a higher bone healing score than the 10 mm defects. HAD being used for the smaller defects resulted in a significantly higher bone healing score even than for the induced membrane and significantly higher blood vessel formation, corroborating the good results achieved by using HAD in previous studies. In comparison, same-sized groups showed significant differences in bone healing as well as blood vessel formation, suggesting that 5 mm defects are large enough to show different results in healing depending on treatment; therefore, 5 mm is a viable size for further studies on bone healing.

Combination of Adipose-Derived Stromal/Stem Cells and Decellularized Adipose Tissue Hydrogel for Osteogenic Applications.

Adipose-derived stromal/stem cells (ASCs) and decellularized adipose tissue (DAT) are adipose tissue products obtained from individuals undergoing fat removal procedures like liposuction, lipectomy, or breast reduction. DAT hydrogel is prepared by removing the cells from the adipose tissue and digesting it to form a liquid material that forms a gel at physiological temperature. ASCs seeded on DAT have displayed osteogenic potential in vitro and in animal models of bone defects. Herein, we describe the methods for preparing DAT hydrogel, ASC seeding in DAT hydrogel, osteogenic differentiation of ASCs, creation of critical-sized femur defect model in mice, its treatment with ASC-DAT hydrogel, and analyses.

Cell sheet-basedin vitrobone defect model for long term evaluation of bone repair materials.

Development of tissue-engineeredin vitrohuman bone defect models for evaluation of bone repair materials (BRMs) is a promising approach for addressing both translational and ethical concerns regarding animal models. In this study, human bone marrow mesenchymal stem cell sheets were stacked to form a periosteum like tissue. HE staining showed a cell-dense, multilayered structure. BRMs were implanted in the defect area of the three-dimensional (3D) model. The CCK-8 test demonstrated that the 3D model was stronger in resisting the cytotoxicity of three kinds of commercial BRMs than the 2D culture model, which was consistent within vivoresults. After 28 d implantation in the 3D model, western blot and RT-qPCR showed that three materials induced increased expressions of RUNX2, OSX, OCN, OPN, while Materials B and C seemed to have stronger osteoinductivity than A.In vivoexperiments also confirmed the osteoinductivity of the BRMs after 28 and 182 d implantation. Alizarin red staining proved that the mineralized nodules of Materials B and C were more than that of A. The differences of osteogenic properties among three BMRs might be attributed to calcium ion release. This cell sheet-based bone tissue model can resist cytotoxicity of BRMs, demonstrating the priority of long-term evaluation of osteoinductivity of BRMs. Further, the osteoinduction results of the 3D model corresponded to that ofin vivoexperiments, suggesting this model may have a potential to be used as a novel tool for rapid, accurate evaluation of BRMs, and thus shorten their research and development process.

Wnt7b: Is It an Important Factor in the Bone Formation Process after Calvarial Damage?

OBJECTIVE: Previous studies found that Wnt7b played a unique and indispensable role in the process of osteoblast differentiation and could accelerate the repair of bone loss. However, what is the role of Wnt7B in osteogenesis? Is it possible to increase the expression of Wnt7b to promote the repair of skull defects? This study intends to provide the basic data for the application of Wnt7b in the treatment of craniomaxillofacial bone repair. METHODS: A calvarial defect mouse model that could induce Wnt7b overexpression was established. Three days after the operation, the mice in each group were intraperitoneally injected with tamoxifen (TAM) or oil eight times every other day. There were three groups. The TAMc group (R26Wnt7b/Wnt7b) was injected with tamoxifen. The Oil group (3.2 kb Col1-Cre-ERT2; R26Wnt7b/Wnt7b) was injected with oil. The TAM group (3.2 kb Col1-Cre-ERT2; R26Wnt7b/Wnt7b) was injected with tamoxifen. Four weeks after the surgery, micro-CT scanning was utilized to observe new bone formation and compare the ability to form new bone around the defect area. RESULTS: Four weeks after the operation, bone healing conditions were measured by using micro-CT scanning. The defect area of the TAM group was smaller than that of the other groups. Similarly, the bone volume fraction (BV/TV) significantly increased (p < 0.05), the trabecular number (Tb.N) increased, and the trabecular separation (Tb.Sp) decreased. CONCLUSIONS: Wnt7b participates in the bone formation process after calvarial damage, indicating the important role of Wnt7b in osteogenesis.

Injectable hydrogel based on silk fibroin/carboxymethyl cellulose/agarose containing polydopamine functionalized graphene oxide with conductivity, hemostasis, antibacterial, and anti-oxidant properties for full-thickness burn healing.

Overcoming bacterial infections and promoting wound healing are significant challenges in clinical practice and fundamental research. This study developed a series of enzymatic crosslinking injectable hydrogels based on silk fibroin (SF), carboxymethyl cellulose (CMC), and agarose, with the addition of polydopamine functionalized graphene oxide (GO@PDA) to endow the hydrogel with suitable conductivity and antimicrobial activity. The hydrogels exhibited suitable gelation time, stable mechanical and rheological properties, high water absorbency, and hemostatic properties. Biocompatibility was also confirmed through various assays. After loading the antibiotic vancomycin hydrochloride, the hydrogels showed sustained release and good antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). The fast gelation time and desirable tissue-covering ability of the hydrogels allowed for a good hemostatic effect in a rat liver trauma model. In a rat full-thickness burn wound model, the hydrogels exhibited an excellent treatment effect, leading to significantly enhanced wound closure, collagen deposition, and granulation tissue formation, as well as neovascularization and anti-inflammatory effects. In conclusion, the antibacterial electroactive injectable hydrogel dressing, with its multifunctional properties, significantly promoted the in vivo wound healing process, making it an excellent candidate for full-thickness skin wound healing.

Bioessential Inorganic Molecular Wire-Reinforced 3D-Printed Hydrogel Scaffold for Enhanced Bone Regeneration.

Materials with physicochemical properties and biological activities similar to those of the natural extracellular matrix are in high demand in tissue engineering. In particular, Mo3 Se3 - inorganic molecular wire (IMW) is a promising material composed of bioessential minerals and possess nanometer-scale diameters, negatively charged surfaces, physical flexibility, and nanotopography characteristics, which are essential for interactions with cell membrane proteins. Here, an implantable 3D Mo3 Se3 - IMW enhanced gelatin-GMA/silk-GMA hydrogel (IMW-GS hydrogel) is developed for osteogenesis and bone formation, followed by biological evaluations. The mechanical properties of the 3D printed IMW-GS hydrogel are improved by noncovalent interactions between the Mo3 Se3 - IMWs and the positively charged residues of the gelatin molecules. Long-term biocompatibility with primary human osteoblast cells (HOBs) is confirmed using the IMW-GS hydrogel. The proliferation, osteogenic gene expression, collagen accumulation, and mineralization of HOBs improve remarkably with the IMW-GS hydrogel. In in vivo evaluations, the IMW-GS hydrogel implantation exhibits a significantly improved new bone regeneration of 87.8 ± 5.9% (p < 0.05) for 8 weeks, which is higher than that from the gelatin-GMA/silk-GMA hydrogel without Mo3 Se3 - IMW. These results support a new improved strategy with in vitro and in vivo performance of 3D IMW enhanced scaffolds in tissue engineering.

Evaluating the efficacy of human dental pulp stem cells and scaffold combination for bone regeneration in animal models: a systematic review and meta-analysis.

INTRODUCTION: Human adult dental pulp stem cells (hDPSC) and stem cells from human exfoliated deciduous teeth (SHED) hold promise in bone regeneration for their easy accessibility, high proliferation rate, self-renewal and osteogenic differentiation capacity. Various organic and inorganic scaffold materials were pre-seeded with human dental pulp stem cells in animals, with promising outcomes in new bone formation. Nevertheless, the clinical trial for bone regeneration using dental pulp stem cells is still in its infancy. Thus, the aim of this systematic review and meta-analysis is to synthesise the evidence of the efficacy of human dental pulp stem cells and the scaffold combination for bone regeneration in animal bone defect models. METHODOLOGY: This study was registered in PROSPERO (CRD2021274976), and PRISMA guideline was followed to include the relevant full-text papers using exclusion and inclusion criteria. Data were extracted for the systematic review. Quality assessment and the risk of bias were also carried out using the CAMARADES tool. Quantitative bone regeneration data of the experimental (scaffold + hDPSC/SHED) and the control (scaffold-only) groups were also extracted for meta-analysis. RESULTS: Forty-nine papers were included for systematic review and only 27 of them were qualified for meta-analysis. 90% of the included papers were assessed as medium to low risk. In the meta-analysis, qualified studies were grouped by the unit of bone regeneration measurement. Overall, bone regeneration was significantly higher (p < 0.0001) in experimental group (scaffold + hDPSC/SHED) compared to the control group (scaffold-only) (SMD: 1.863, 95% CI 1.121-2.605). However, the effect is almost entirely driven by the % new bone formation group (SMD: 3.929, 95% CI 2.612-5.246) while % BV/TV (SMD: 2.693, 95% CI - 0.001-5.388) shows a marginal effect. Dogs and hydroxyapatite-containing scaffolds have the highest capacity in % new bone formation in response to human DPSC/SHED. The funnel plot exhibits no apparent asymmetry representing a lack of remarkable publication bias. Sensitivity analysis also indicated that the results generated in this meta-analysis are robust and reliable. CONCLUSION: This is the first synthesised evidence showing that human DPSCs/SHED and scaffold combination enhanced bone regeneration highly significantly compared to the cell-free scaffold irrespective of scaffold type and animal species used. So, dental pulp stem cells could be a promising tool for treating various bone diseases, and more clinical trials need to be conducted to evaluate the effectiveness of dental pulp stem cell-based therapies.

Improving the repair mechanism and miRNA expression profile of tibial defect in rats based on silent information regulator 7 protein analysis of mesenchymal stem cells.

The aim of this study was to verify the role of Silent Information Regulator 7 (SIRT7) in improving the repair mechanism of bone marrow mesenchymal stem cells (BMMSCs) and the expression of microribonucleic acid (miRNA). Human BMMSCs were extracted from patients with femoral fractures, and the proliferation activity of human BMMSCs before and after knockout SIRT7 and the expression levels of bone-related genes and proteins were compared. Thirty-two 8-week-old male Sprague-Dawley (SD) rats were randomly divided into a blank group, a chitosan scaffold group, a control group, and a silence information regulator knockout group 7 (n = 8). In addition to the blank group, the chitosan scaffold, the green fluorescent protein (GFP) transfected stem cell composite chitosan scaffold, and the SIRT7 knockout stem cell composite chitosan scaffold were implanted in the other three groups, respectively. The X-rays and small animal in vivo three-dimensional tomography (Micro-CT) were adopted to quantitatively analyze the volume fraction, the number of trabeculae, and the connection density. Compared with the other three groups, the bone defect was formed more in the medullary mesenchymal stem cell knockout group, and the bone volume fraction, number of trabeculae and connection density were significantly increased (P < 0.05). MiR-98-5p can significantly promote the formation of bone molecules and bone structure in rats (P < 0.05). Human BMMSCs combined with chitosan scaffold can accelerate the repair of tibial defects. MiR-98-5p targeting and regulating bone formation gene (CKIP-1) could significantly improve the process of osteogenesis in rats.