Assessment of the Release of Vascular Endothelial Growth Factor from 3D-Printed Poly-ε-Caprolactone/Hydroxyapatite/Calcium Sulfate Scaffold with Enhanced Osteogenic Capacity

Multidimensional 3D-Printed Scaffolds and Regeneration of Intrabony Periodontal Defects: A Systematic Review

BACKGROUND

The utilization of regenerative techniques in periodontology involves tailoring tissue engineering principles to suit the oral cavity's unique environment. Advancements in computer-assisted technology, specifically utilizing cone beam computed tomography (CBCT), enabled the fabrication of 3D-printed scaffolds. The current review aims to explore whether 3D-printed scaffolds are effective in promoting osteogenesis in patients with periodontal defects.

METHODS

A thorough exploration was undertaken across seven electronic databases (PubMed, Scopus, ScienceDirect, Google Scholar, Cochrane, Web of Science, Ovid) to detect pertinent research in accordance with specified eligibility criteria, aligning with the PRISMA guidelines. Two independent reviewers undertook the screening and selection of manuscripts, executed data extraction, and evaluated the bias risk using the Newcastle-Ottawa Scale for non-randomized clinical trials and SYRCLE's risk of bias tool for animal studies.

RESULTS

Initially, 799 articles were identified, refined by removing duplicates. After evaluating 471 articles based on title and abstract, 18 studies remained for full-text assessment. Eventually, merely two manuscripts fulfilled all the eligibility criteria concerning human trials. Both studies were prospective non-randomized clinical trials. Moreover, 11 animal studies were also included.

CONCLUSIONS

The use of multidimensional, 3D-printed, customized scaffolds appears to stimulate periodontal regeneration. While the reported results are encouraging, additional studies are required to identify the ideal characteristics of the 3D scaffold to be used in the regeneration of periodontal tissue.

Polydopamine-Functionalized Strontium Alginate/Hydroxyapatite Composite Microhydrogel Loaded with Vascular Endothelial Growth Factor Promotes Bone Formation and Angiogenesis

Critical-size bone defects are a common and intractable clinical problem that typically requires filling in with surgical implants to facilitate bone regeneration. Considering the limitations of autologous bone and allogeneic bone in clinical applications, such as secondary damage or immunogenicity, injectable microhydrogels with osteogenic and angiogenic effects have received considerable attention. Herein, polydopamine (PDA)-functionalized strontium alginate/nanohydroxyapatite (Sr-Alg/nHA) composite microhydrogels loaded with vascular endothelial growth factor (VEGF) were prepared using microfluidic technology. This composite microhydrogel released strontium ions stably for at least 42 days to promote bone formation. The PDA coating can release VEGF in a controlled manner, effectively promote angiogenesis around bone defects, and provide nutritional support for new bone formation. In in vitro experiments, the composite microhydrogels had good biocompatibility. The PDA coating greatly improves cell adhesion on the composite microhydrogel and provides good controlled release of VEGF. Therefore, this composite microhydrogel effectively promotes osteogenic differentiation and vascularization. In in vivo experiments, composite microhydrogels were injected into critical-size bone defects in the skull of rats, and they were shown by microcomputed tomography and tissue sections to be effective in promoting bone regeneration. These findings demonstrated that this novel microhydrogel effectively promotes bone formation and angiogenesis at the site of bone defects.

Functionalization of Osteoplastic Material with Human Placental Growth Factor and Assessment of Biocompatibility of the Resulting Material In Vitro

This article provides the results of a study of the interaction of placental growth factor with adipose-derived stem cells (ASCs) of various origins, as well as the possibility of generating osteoplastic material based on xenogeneic matrix functionalization with human placental growth factor (PLGF). It is demonstrated that the greatest release of this factor from the functionalized material into the medium occurs during the first 3 h of contact with the model medium, but then the levels of the factor being released fall sharply, although release did continue throughout the 7 days of observation. The modified material was not cytotoxic, and its surface provided good cell adhesion. During 3 days of cultivation, the ASCs proliferated and migrated more actively on the surfaces of the modified material than on the surfaces of the control material. This study can serve as the basis for the development of original methods to functionalize such osteoplastic material by increasing PLGF immobilization by creating stronger bonds in order to regulate both factor dosage and the dynamics of the factor release into the environment. Further studies in experimental animals should facilitate assessment of the effectiveness of the functionalized materials. Such studies will be useful in the development of osteoplastic materials with new properties resulting from the inclusion of growth factors and in research on their biological activity.

Surgical Site-Released Tissue Is Potent to Generate Bone onto TCP and PCL-TCP Scaffolds In Vitro

There is evidence that surgical site tissue (SSRT) released during orthopedic surgery has a strong mesenchymal regenerative potential. Some data also suggest that this tissue may activate synthetic or natural bone substitute materials and can thus upgrade its osteopromoting properties. In this comparative in vitro study, we investigate the composition of SSRT during total hip replacement (n = 20) harvested using a surgical suction handle. In addition, the osteopromoting effect of the cells isolated from SSRT is elucidated when incubated with porous beta-tricalcium phosphate (β-TCP) or 80% medical-grade poly-ε-caprolactone (PCL)/20% TCP composite material. We identified multiple growth factors and cytokines with significantly higher levels of PDGF and VEGF in SSRT compared to peripheral blood. The overall number of MSC was 0.09 ± 0.12‱ per gram of SSRT. A three-lineage specific differentiation was possible in all cases. PCL-TCP cultures showed a higher cell density and cell viability compared to TCP after 6 weeks in vitro. Moreover, PCL-TCP cultures showed a higher osteocalcin expression but no significant differences in osteopontin and collagen I synthesis. We could demonstrate the high regenerative potential from SSRT harvested under vacuum in a PMMA filter device. The in vitro data suggest advantages in cytocompatibility for the PCL-TCP composite compared to TCP alone.

Intelligent Vascularized 3D/4D/5D/6D-Printed Tissue Scaffolds

Blood vessels are essential for nutrient and oxygen delivery and waste removal. Scaffold-repairing materials with functional vascular networks are widely used in bone tissue engineering. Additive manufacturing is a manufacturing technology that creates three-dimensional solids by stacking substances layer by layer, mainly including but not limited to 3D printing, but also 4D printing, 5D printing and 6D printing. It can be effectively combined with vascularization to meet the needs of vascularized tissue scaffolds by precisely tuning the mechanical structure and biological properties of smart vascular scaffolds. Herein, the development of neovascularization to vascularization to bone tissue engineering is systematically discussed in terms of the importance of vascularization to the tissue. Additionally, the research progress and future prospects of vascularized 3D printed scaffold materials are highlighted and presented in four categories: functional vascularized 3D printed scaffolds, cell-based vascularized 3D printed scaffolds, vascularized 3D printed scaffolds loaded with specific carriers and bionic vascularized 3D printed scaffolds. Finally, a brief review of vascularized additive manufacturing-tissue scaffolds in related tissues such as the vascular tissue engineering, cardiovascular system, skeletal muscle, soft tissue and a discussion of the challenges and development efforts leading to significant advances in intelligent vascularized tissue regeneration is presented.

Simulation of Cortical and Cancellous Bone to Accelerate Tissue Regeneration

Different tissues have complex anisotropic structures to support biological functions. Mimicking these complex structures in vitro remains a challenge in biomaterials designs in support of tissue regeneration. Here, inspired by different types of silk nanofibers, a composite materials strategy was pursued towards this challenge. A combination of fabrication methods was utilized to achieve separate control of amorphous and beta-sheet rich silk nanofibers in the same solution. Aqueous solutions containing these two structural types of silk nanofibers were then simultaneously treated with an electric field and with ethylene glycol diglycidyl ether (EGDE). Under these conditions, the beta-sheet rich silk nanofibers in the mixture responded to the electric field while the amorphous nanofibers were active in the crosslinking process with the EGDE. As a result, cryogels with anisotropic structures were prepared, including mimics for cortical- and cancellous-like bone biomaterials as a complex osteoinductive niche. In vitro studies revealed that mechanical cues of the cryogels induced osteodifferentiation of stem cells while the anisotropy inside the cryogels influenced immune reactions of macrophages. These bioactive cryogels also stimulated improved bone regeneration in vivo through modulation of inflammation, angiogenesis and osteogenesis responses, suggesting an effective strategy to develop bioactive matrices with complex anisotropic structures beneficial to tissue regeneration.

Chitosan, Gelatin, and Collagen Hydrogels for Bone Regeneration

Hydrogels are versatile biomaterials characterized by three-dimensional, cross-linked, highly hydrated polymeric networks. These polymers exhibit a great variety of biochemical and biophysical properties, which allow for the diffusion of diverse molecules, such as drugs, active ingredients, growth factors, and nanoparticles. Meanwhile, these polymers can control chemical and molecular interactions at the cellular level. The polymeric network can be molded into different structures, imitating the structural characteristics of surrounding tissues and bone defects. Interestingly, the application of hydrogels in bone tissue engineering (BTE) has been gathering significant attention due to the beneficial bone improvement results that have been achieved. Moreover, essential clinical and osteoblastic fate-controlling advances have been achieved with the use of synthetic polymers in the production of hydrogels. However, current trends look towards fabricating hydrogels from biological precursors, such as biopolymers, due to the high biocompatibility, degradability, and mechanical control that can be regulated. Therefore, this review analyzes the concept of hydrogels and the characteristics of chitosan, collagen, and gelatin as excellent candidates for fabricating BTE scaffolds. The changes and opportunities brought on by these biopolymers in bone regeneration are discussed, considering the integration, synergy, and biocompatibility features.

The Reliability of PCL/Anti-VEGF Electrospun Scaffolds to Support Limbal Stem Cells for Corneal Repair

Since only few reported studies propose anti-vascular endothelial growth factor (anti-VEGF) delivery through electrospun scaffolds, this study greatly contributes to the potential prevention of patient's vision loss, as it explores electrospun polycaprolactone (PCL) coated with anti-VEGF for the blockage of abnormal cornea vascularization. In terms of physicochemical properties, the biological component increased the PCL scaffold fiber diameter (by ~24%) and pore area (by ~82%), while ut slightly reduced its total porosity as the anti-VEGF solution filled the voids of the microfibrous structure. The addition of the anti-VEGF increased the scaffold stiffness almost three-fold at both strains of 5 and 10%, as well as its biodegradation rate (~36% after 60 days) with a sustained release profile after Day 4 of phosphate buffered saline incubation. In terms of scaffold application function, the PCL/Anti-VEGF scaffold proved to be more favorable for the adhesion of cultured limbal stem cells (LSCs); this was confirmed by the SEM images, where the cells showed flat and elongated conformations. Further support of the LSC growth and proliferation was confirmed by the identified p63 and CK3 markers after cell staining. These results demonstrate the advantageous effect of the surface-adsorbed anti-VEGF to stop vision loss and help damaged corneal tissue repair.

Nano-Hydroxyapatite Composite Scaffolds Loaded with Bioactive Factors and Drugs for Bone Tissue Engineering

Nano-hydroxyapatite (n-HAp) is similar to human bone mineral in structure and biochemistry and is, therefore, widely used as bone biomaterial and a drug carrier. Further, n-HAp composite scaffolds have a great potential role in bone regeneration. Loading bioactive factors and drugs onto n-HAp composites has emerged as a promising strategy for bone defect repair in bone tissue engineering. With local delivery of bioactive agents and drugs, biological materials may be provided with the biological activity they lack to improve bone regeneration. This review summarizes classification of n-HAp composites, application of n-HAp composite scaffolds loaded with bioactive factors and drugs in bone tissue engineering and the drug loading methods of n-HAp composite scaffolds, and the research direction of n-HAp composite scaffolds in the future is prospected.

3D-Printing for Critical Sized Bone Defects: Current Concepts and Future Directions

The management and definitive treatment of segmental bone defects in the setting of acute trauma, fracture non-union, revision joint arthroplasty, and tumor surgery are challenging clinical problems with no consistently satisfactory solution. Orthopaedic surgeons are developing novel strategies to treat these problems, including three-dimensional (3D) printing combined with growth factors and/or cells. This article reviews the current strategies for management of segmental bone loss in orthopaedic surgery, including graft selection, bone graft substitutes, and operative techniques. Furthermore, we highlight 3D printing as a technology that may serve a major role in the management of segmental defects. The optimization of a 3D-printed scaffold design through printing technique, material selection, and scaffold geometry, as well as biologic additives to enhance bone regeneration and incorporation could change the treatment paradigm for these difficult bone repair problems.

Combined Effects of Polydopamine-Assisted Copper Immobilization on 3D-Printed Porous Ti6Al4V Scaffold for Angiogenic and Osteogenic Bone Regeneration

Numerous studies have demonstrated that biological compounds and trace elements such as dopamine (DA) and copper ions (Cu) could be modified onto the surfaces of scaffolds using a one-step immersion process which is simple, inexpensive and, most importantly, non-cytotoxic. The development and emergence of 3D printing technologies such as selective laser melting (SLM) have also made it possible for us to fabricate bone scaffolds with precise structural designs using metallic compounds. In this study, we fabricated porous titanium scaffolds (Ti) using SLM and modified the surface of Ti with polydopamine (PDA) and Cu. There are currently no other reported studies with such a combination for osteogenic and angiogenic-related applications. Results showed that such modifications did not affect general appearances and microstructural characteristics of the porous Ti scaffolds. This one-step immersion modification allowed us to modify the surfaces of Ti with different concentrations of Cu ions, thus allowing us to fabricate individualized scaffolds for different clinical scenarios. The modification improved the hydrophilicity and surface roughness of the scaffolds, which in turn led to promote cell behaviors of Wharton’s jelly mesenchymal stem cells. Ti itself has high mechanical strength, therefore making it suitable for surgical handling and clinical applications. Furthermore, the scaffolds were able to release ions in a sustained manner which led to an upregulation of osteogenic-related proteins (bone alkaline phosphatase, bone sialoprotein and osteocalcin) and angiogenic-related proteins (vascular endothelial growth factor and angiopoietin-1). By combining additive manufacturing, Ti6Al4V scaffolds, surface modification and Cu ions, the novel hybrid 3D-printed porous scaffold could be fabricated with ease and specifically benefited future bone regeneration in the clinic.

Multiple growth factors accommodated degradable submicron calcium sulfate hemihydrate/porous hydroxyapatite for dentin-pulp regeneration

Vital pulp therapy (VPT) has gained significant consideration by utilizing the natural healing capacity of the inflamed pulp in healing process. However, the protective pulp capping materials that facilitate this healing process are still under investigation for the successful promotion of dentin-pulp regeneration. Herein, we developed a bioactive and biodegradable pulp capping material (denoted as sCSHA-GFs) by synthesizing inorganic submicron calcium sulfate hemihydrate (sCS)/porous hydroxyapatite (HA) loaded with growth factors (GFs) such as transforming growth factor-beta 1 (TGF-β1), fibroblast growth factor-2 (FGF-2) and vascular endothelial growth factor (VEGF). Physiochemical characteristics of submicron CSHA-GFs (sCSHA-GFs) cement were determined. Human dental pulp stem cells (hDPSCs) were used for analyzing their biocompatibility and bioactivity for dentin mineralization. To evaluate the efficacy of sCSHA-GFs, we compared it with a commercial material, mineral trioxide aggregate (MTA), the reference standard used clinically on pulp capping. Our results showed that sCSHA-GFs cement presented good biodegradability with dissolution properties for sustained release of calcium (Ca²⁺) ions and GFs, and facilitated attachment, proliferation, differentiation and migration of hDPSCs. In addition, sCSHA-GFs cement was found to be more effective than MTA at prolonged incubation time in inducing the mRNA expression levels of odontoblastic differentiation markers, dentin sialophosphoprotein (DSPP) and dentin matrix protein (DMP-1), leading to increased mineralization (with calcium deposits) along with increased alkaline phosphatase (ALP) expressions, evident from Alizarin Red S and ALP staining assays. Our findings suggest that sCSHA-GFs cement may act as a suitable material in VPT for dentin-pulp regeneration.

Additive Manufacturing Technologies for Fabrication of Biomaterials for Surgical Procedures in Dentistry: A Narrative Review

PURPOSE

To screen and critically appraise available literature regarding additive manufacturing technologies for bone graft material fabrication in dentistry.

MATERIAL AND METHODS

PubMed and Scopus were searched up to May 2021. Studies reporting the additive manufacturing techniques to manufacture scaffolds for intraoral bone defect reconstruction were considered eligible. A narrative review was synthesized to discuss the techniques for bone graft material fabrication in dentistry and the biomaterials used.

RESULTS

The databases search resulted in 933 articles. After removing duplicate articles (128 articles), the titles and abstracts of the remaining articles (805 articles) were evaluated. A total of 89 articles were included in this review. Reading these articles, 5 categories of additive manufacturing techniques were identified: material jetting, powder bed fusion, vat photopolymerization, binder jetting, and material extrusion.

CONCLUSIONS

Additive manufacturing technologies for bone graft material fabrication in dentistry, especially 3D bioprinting approaches, have been successfully used to fabricate bone graft material with distinct compositions.

Towards Induction of Angiogenesis in Dental Pulp Stem Cells Using Chitosan-Based Hydrogels Releasing Basic Fibroblast Growth Factor

Introduction. Chitosan is a natural biopolymer that attracted enormous attention in biomedical fields. The main components of regenerative endodontic procedures (REPs), as well as tissue engineering, are scaffolds, stem cells, and growth factors. As one of the basic factors in the REPs is maintaining vascularization, this study was aimed at developing basic fibroblast growth factor- (bFGF-) loaded scaffolds and investigating their effects on the angiogenic induction in human dental pulp stem cells (hDPSCs). Methods. Poly (ε-caprolactone) (PCL)/chitosan- (CS-) based highly porous scaffold (PCL/CS) was prepared and evaluated by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) analyses. The adhesion and survival potency of seeded cells were assessed by SEM and MTT assays, respectively. The amount of angiogenic markers was investigated in gene and protein levels by real-time PCR and western blotting assays, respectively. Results. Based on our findings, the SEM and FTIR tests confirmed the appropriate structure of synthesized scaffolds. Besides, the adhesion and survival rate of cells and the levels of VEGFR-2, Tie2, and Angiopoietin-1 genes were increased significantly in the PCL/CS/bFGF group. Also, the western blotting results showed the upregulation of these markers at protein levels, which were considerably higher at the PCL/CS/bFGF group ( $P<0.05$ ). Conclusions. On a more general note, this study demonstrates that the bFGF-loaded PCL/CS scaffolds have the potential to promote angiogenesis of hDPSCs, which could provide vitality of dentin-pulp complex as the initial required factor for regenerative endodontic procedures.

Bone Regeneration and Oxidative Stress: An Updated Overview

Bone tissue engineering is a complex domain that requires further investigation and benefits from data obtained over past decades. The models are increasing in complexity as they reveal new data from co-culturing and microfluidics applications. The in vitro models now focus on the 3D medium co-culturing of osteoblasts, osteoclasts, and osteocytes utilizing collagen for separation; this type of research allows for controlled medium and in-depth data analysis. Oxidative stress takes a toll on the domain, being beneficial as well as destructive. Reactive oxygen species (ROS) are molecules that influence the differentiation of osteoclasts, but over time their increasing presence can affect patients and aid the appearance of diseases such as osteoporosis. Oxidative stress can be limited by using antioxidants such as vitamin K and N-acetyl cysteine (NAC). Scaffolds and biocompatible coatings such as hydroxyapatite and bioactive glass are required to isolate the implant, protect the zone from the metallic, ionic exchange, and enhance the bone regeneration by mimicking the composition and structure of the body, thus enhancing cell proliferation. The materials can be further functionalized with growth factors that create a better response and higher chances of success for clinical use. This review highlights the vast majority of newly obtained information regarding bone tissue engineering, such as new co-culturing models, implant coatings, scaffolds, biomolecules, and the techniques utilized to obtain them.

The effects of a 3D-printed magnesium-/strontium-doped calcium silicate scaffold on regulation of bone regeneration via dual-stimulation of the AKT and WNT signaling pathways

Numerous studies have demonstrated that calcium silicate (CS) can be doped with various trace metal elements such as strontium (Sr) or magnesium (Mg). These studies have confirmed that such modifications promote bone regeneration. However, the development and emergence of 3D printing have further made it possible to fabricate bone grafts with precise structural designs using multi-bioceramics so as to better suit specific clinical requirements. We fabricated scaffolds using Mg-doped CS as the outer layer with Sr-doped CS in the center. In addition, PCL was used to improve printability of the scaffolds. This enhanced Mg and Sr architecture prevented premature degradation of the scaffolds during immersion while enabling the release of ions in a sustained manner in order to achieve the desired therapeutic goals. Even the capabilities of stem cells were shown to be enhanced when cultured on these scaffolds. Furthermore, the hybrid scaffolds were found to up-regulate the expression of bone-related proteins such as factors leading to differentiation-inducing pathways, including PI3K/Akt, Wnt, and TRPM7. The in vivo performance of the proposed scaffolds was assessed using micro-CT. The histological results revealed that the hybrid scaffolds were able to further enhance bone regeneration as compared to uni-bioceramics. By combining 3D printing, multi-ceramics, and trace metal elements, a novel hybrid scaffold could be fabricated with ease and specifically suited to future bone tissue engineering applications.

Additive Manufacturing of Caffeic Acid-Inspired Mineral Trioxide Aggregate/Poly-ε-Caprolactone Scaffold for Regulating Vascular Induction and Osteogenic Regeneration of Dental Pulp Stem Cells

Mineral trioxide aggregate (MTA) is a common biomaterial used in endodontics regeneration due to its antibacterial properties, good biocompatibility and high bioactivity. Surface modification technology allows us to endow biomaterials with the necessary biological targets for activation of specific downstream functions such as promoting angiogenesis and osteogenesis. In this study, we used caffeic acid (CA)-coated MTA/polycaprolactone (PCL) composites and fabricated 3D scaffolds to evaluate the influence on the physicochemical and biological aspects of CA-coated MTA scaffolds. As seen from the results, modification of CA does not change the original structural characteristics of MTA, thus allowing us to retain the properties of MTA. CA-coated MTA scaffolds were shown to have 25% to 55% higher results than bare scaffold. In addition, CA-coated MTA scaffolds were able to significantly adsorb more vascular endothelial growth factors (p < 0.05) secreted from human dental pulp stem cells (hDPSCs). More importantly, CA-coated MTA scaffolds not only promoted the adhesion and proliferation behaviors of hDPSCs, but also enhanced angiogenesis and osteogenesis. Finally, CA-coated MTA scaffolds led to enhanced subsequent in vivo bone regeneration of the femur of rabbits, which was confirmed using micro-computed tomography and histological staining. Taken together, CA can be used as a potently functional bioactive coating for various scaffolds in bone tissue engineering and other biomedical applications in the future.

Synthetic Material for Bone, Periodontal, and Dental Tissue Regeneration: Where Are We Now, and Where Are We Heading Next?

Alloplasts are synthetic, inorganic, biocompatible bone substitutes that function as defect fillers to repair skeletal defects. The acceptance of these substitutes by host tissues is determined by the pore diameter and the porosity and inter-connectivity. This narrative review appraises recent developments, characterization, and biological performance of different synthetic materials for bone, periodontal, and dental tissue regeneration. They include calcium phosphate cements and their variants β-tricalcium phosphate (β-TCP) ceramics and biphasic calcium phosphates (hydroxyapatite (HA) and β-TCP ceramics), calcium sulfate, bioactive glasses and polymer-based bone substitutes which include variants of polycaprolactone. In summary, the search for synthetic bone substitutes remains elusive with calcium compounds providing the best synthetic substitute. The combination of calcium sulphate and β-TCP provides improved handling of the materials, dispensing with the need for a traditional membrane in guided bone regeneration. Evidence is supportive of improved angiogenesis at the recipient sites. One such product, (EthOss^® Regeneration, Silesden, UK) has won numerous awards internationally as a commercial success. Bioglasses and polymers, which have been used as medical devices, are still in the experimental stage for dental application. Polycaprolactone-TCP, one of the products in this category is currently undergoing further randomized clinical trials as a 3D socket preservation filler. These aforementioned products may have vast potential for substituting human/animal-based bone grafts.

Identification osteogenic signaling pathways following mechanical stimulation: A systematic review

INTRODUCTION

It has been shown that mechanical forces can induce or promote osteogenic differentiation as well as remodeling of the new created bone tissues. To apply this characteristic in bone tissue engineering, it is important to know which mechanical stimuli through which signaling pathway has a more significant impact on osteogenesis.

METHODS

In this systematic study, an electronic search was conducted using PubMed and Google Scholar databases. This study has been prepared and organized according to the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. Included studies were first categorized according to the in vivo and in vitro studies.

RESULTS

Six types of mechanical stresses were used in these articles and the most commonly used mechanical force and cell source were tension and bone marrow-derived mesenchymal stem cells (BMMSCs), respectively. These forces were able to trigger twelve signaling pathways in which Wnt pathway was so prominent.

CONCLUSION

1) Although specific signaling pathways are induced through specific mechanical forces, Wnt signaling pathways are predominantly activated by almost all types of force/stimulation, 2) All signaling pathways regulate expression of RUNX2, which is known as a master regulator of osteogenesis, 3) In Tension force, the mode of force administration, i.e, continuous or non-continuous tension is more important than the percentage of elongation.

3D-Printed Ginsenoside Rb1-Loaded Mesoporous Calcium Silicate/Calcium Sulfate Scaffolds for Inflammation Inhibition and Bone Regeneration

Bone defects are commonly found in the elderly and athletic population due to systemic diseases such as osteoporosis and trauma. Bone scaffolds have since been developed to enhance bone regeneration by acting as a biological extracellular scaffold for cells. The main advantage of a bone scaffold lies in its ability to provide various degrees of structural support and growth factors for cellular activities. Therefore, we designed a 3D porous scaffold that can not only provide sufficient mechanical properties but also carry drugs and promote cell viability. Ginsenoside Rb1 (GR) is an extract from panax ginseng, which has been used for bone regeneration and repair since ancient Chinese history. In this study, we fabricated scaffolds using various concentrations of GR with mesoporous calcium silicate/calcium sulfate (MSCS) and investigated the scaffold’s physical and chemical characteristic properties. PrestoBlue, F-actin staining, and ELISA were used to demonstrate the effect of the GR-contained MSCS scaffold on cell proliferation, morphology, and expression of the specific osteogenic-related protein of human dental pulp stem cells (hDPSCs). According to our data, hDPSCs cultivated in GR-contained MSCS scaffold had preferable abilities of proliferation and higher expression of the osteogenic-related protein and could effectively inhibit inflammation. Finally, in vivo performance was assessed using histological results that revealed the GR-contained MSCS scaffolds were able to further achieve more effective hard tissue regeneration than has been the case in the past. Taken together, this study demonstrated that a GR-containing MSCS 3D scaffold could be used as a potential alternative for future bone tissue engineering studies and has good potential for clinical use.

Strategies for inclusion of growth factors into 3D printed bone grafts

There remains a critical need to develop new technologies and materials that can meet the demands of treating large bone defects. The advancement of 3-dimensional (3D) printing technologies has allowed the creation of personalized and customized bone grafts, with specific control in both macro- and micro-architecture, and desired mechanical properties. Nevertheless, the biomaterials used for the production of these bone grafts often possess poor biological properties. The incorporation of growth factors (GFs), which are the natural orchestrators of the physiological healing process, into 3D printed bone grafts, represents a promising strategy to achieve the bioactivity required to enhance bone regeneration. In this review, the possible strategies used to incorporate GFs to 3D printed constructs are presented with a specific focus on bone regeneration. In particular, the strengths and limitations of different methods, such as physical and chemical cross-linking, which are currently used to incorporate GFs to the engineered constructs are critically reviewed. Different strategies used to present one or more GFs to achieve simultaneous angiogenesis and vasculogenesis for enhanced bone regeneration are also covered in this review. In addition, the possibility of combining several manufacturing approaches to fabricate hybrid constructs, which better mimic the complexity of biological niches, is presented. Finally, the clinical relevance of these approaches and the future steps that should be taken are discussed.

Printing New Bones: From Print-and-Implant Devices to Bioprinted Bone Organ Precursors

Regenerating large bone defects remains a significant clinical challenge, motivating increased interest in additive manufacturing and 3D bioprinting to engineer superior bone graft substitutes. 3D bioprinting enables different biomaterials, cell types, and growth factors to be combined to develop patient-specific implants capable of directing functional bone regeneration. Current approaches to bioprinting such implants fall into one of two categories, each with their own advantages and limitations. First are those that can be 3D bioprinted and then directly implanted into the body and second those that require further in vitro culture after bioprinting to engineer more mature tissues prior to implantation. This review covers the key concepts, challenges, and applications of both strategies to regenerate damaged and diseased bone.

The synergistic effects of quercetin-containing 3D-printed mesoporous calcium silicate/calcium sulfate/poly-ε-caprolactone scaffolds for the promotion of osteogenesis in mesenchymal stem cells

BACKGROUND/PURPOSE

Several growth factors were proven to be effective in the treatment of bone defects and fractures and thus have great potential for bone regeneration applications. However, it needs low-temperature storage and transportation. This study aimed to investigate the herbal extract quercetin, a candidate for natural flavonoid compounds that have been reported to be involved in regulating inflammation and improving immunity and health.

METHODS

In this study, we prepared quercetin (Q)/mesoporous calcium silicate calcium sulfate (MSCS)/polycaprolactone (PCL) composite scaffolds using the 3D printing technique, where we immersed it in simulated body fluid (SBF) solution and soaked it for up to 60 days. The characteristics of quercetin scaffold were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), immunofluorescence, and Alizarin Red S staining.

RESULTS

We found precipitation of apatite on the surface of the scaffold. The in vitro results for cell proliferation, cytotoxicity, and immunofluorescence staining revealed that Wharton's jelly mesenchymal stem cells (WJMSCs) with a 2% quercetin (Q2) scaffold were significantly higher in number than with 1% quercetin (Q1) and MSCS scaffolds. The phalloidin staining of cell skeletons on the surface of Q2 revealed powerful cell-to-cell adhesion and high expression of green fluorescence. The Q2 scaffold also had the highest calcium deposit levels based on Alizarin Red S staining in all scaffolds. This indicated that quercetin was able to induce cell growth and mitosis, echoing the previous preliminary results.

CONCLUSION

Our initial results indicate that this natural herbal extract can be a good bone-based gene substitution for bone regeneration.

The synergistic effects of Xu Duan combined Sr-contained calcium silicate/poly-ε-caprolactone scaffolds for the promotion of osteogenesis marker expression and the induction of bone regeneration in osteoporosis

Osteoporosis and its related problems such as fractures are gradually becoming common due to an aging population. Current methods to treat osteoporosis include medical and surgical options such as bone implants. Recent developments in 3D printing and materials science technologies has allowed us to fabricate individualized scaffolds with desired properties. In this study, we mixed Xu Duan into strontium‑calcium silicate powder at 5% (XD5) and 10% (XD10) and fabricated 3D scaffolds with polycaprolactone. All scaffolds were assessed for its physical, mechanical, and biological properties to evaluated for its feasibility for bone tissue engineering in the osteoporosis model. Our results showed that such a scaffold could be fabricated using extrusion-based printing techniques and that addition of XD did not alter original structural properties of the SrCS. Furthermore, the XD5 and XD10 scaffolds were found to be non-toxic to cells and cells cultured on the scaffolds had significantly higher proliferation and secreted increased osteogenic-related proteins in in vitro studies as compared to the XD0 groups. Remarkably, the XD10 scaffolds could be used as substitutes for the critical-sized bone defect (7.0 mm diameter and 8.0 mm depth) in the osteoporotic rabbit model. The XD10 scaffolds can enhance bone ingrowth and accelerate new bone regeneration even in complex osteoporotic pathological environments. These results showed that such a Chinese medicine-contained scaffold had potential in osteoporosis bone tissue regeneration and could be considered as a promising tool for future clinical used applications.

Assessment of the Release Profile of Fibroblast Growth Factor-2-Load Mesoporous Calcium Silicate/Poly-ε-caprolactone 3D Scaffold for Regulate Bone Regeneration

Recent advances in three-dimensional printing technology enable facile and on-demand fabrication of patient-specific bone scaffolds. However, there is still an urgent need for printable biomaterials with osteoinductivity. In the present study, we propose an approach to synthesize fibroblast growth factor-2 loaded-mesoporous calcium silicate nanoparticles. The growth factor loaded-nanoparticles served as fillers of polycaprolactone and then the composite scaffolds with a controlled pore structure were obtained through a fused deposition modeling technique. To evaluate the feasibility of the composite scaffolds in bone tissue engineering, drug release kinetic, bioactivity, cell proliferation, differentiation, and animal study were conducted. Our findings illustrate that utilization of mesoporous calcium silicate allowed the introduction of fibroblast growth factor-2 into the composite scaffolds through a simple soaking process and then gradually released from the scaffold to facilitate proliferation and osteogenesis differentiation of human Wharton’s jelly mesenchymal stem cells. Additionally, the in vivo femur defect experiments also indicate that the co-existence of calcium silicate and fibrous growth factor-2 synergistically accelerated new bone formation. These results demonstrate that the fibroblast growth factor-2-loaded mesoporous calcium silicate nanoparticles/polycaprolactone composite scaffolds may serve as potential bone grafts for facilitating repair of defected bone tissues.