Naringin-inlaid silk fibroin/hydroxyapatite scaffold enhances human umbilical cord-derived mesenchymal stem cell-based bone regeneration

Inducing Osteogenesis in Human Pulp Stem Cells Cultured on Nano-Hydroxyapatite and Naringin-Coated 3D-Printed Poly Lactic Acid Scaffolds

BACKGROUND

Regeneration dentistry demonstrates significant challenges due to the complexity of different dental structures. This study aimed to investigate osteogenic differentiation of human pulp stem cells (hDPSCs) cultured on a 3D-printed poly lactic acid (PLA) scaffold coated with nano-hydroxyapatite (nHA) and naringin (NAR) as a model for a dental regenerative.

METHODS

PLA scaffolds were 3D printed into circular discs (10 × 1 mm) and coated with nHA, NAR, or both. Scaffolds were cultured with hDPTCs to identify cellular morphological changes and adhesion over incubation periods of 3, 7, and 21 days using SEM. Then, the osteogenic potential of PLA, PLA/nHA/NAR, or PLA scaffolds coated with MTA elutes (PLA/MTA scaffolds) were evaluated by measuring mineralized tissue deposition using calcium concentration assays and alizarin red staining (ARS). Also, immunofluorescence labelling of alkaline phosphatase (ALP) and dentine sialophosphoprotein (DSPP) within cultured cells were evaluated.

RESULTS

The highest cellular attachment was identified on the PLA/nHA/NAR scaffold, with morphological changes reflecting cellular differentiation. The highest calcium deposition and ARS were recognized in the PLA/nHA/NAR culture, with statistically significant difference (p < 0.05) compared to PLA/MTA. Also, ALP and DSPP markers showed statistically significantly higher (p < 0.05) immunoreactivity in cells cultured within PLA/nHA/NAR compared to PLA/MTA.

CONCLUSIONS

The results confirm the osteogenic potential of PLA scaffolds coated with nHA/NAR for future animal and human investigations.

Fibroin-Hybrid Systems: Current Advances in Biomedical Applications

Fibroin, a protein extracted from silk, offers advantageous properties such as non-immunogenicity, biocompatibility, and ease of surface modification, which have been widely utilized for a variety of biomedical applications. However, in vivo studies have revealed critical challenges, including rapid enzymatic degradation and limited stability. To widen the scope of this natural biomacromolecule, the grafting of polymers onto the protein surface has been advanced as a platform to enhance protein stability and develop smart conjugates. This review article brings into focus applications of fibroin-hybrid systems prepared using chemical modification of the protein with polymers and inorganic compounds. A selection of recent preclinical evaluations of these hybrids is included to highlight the significance of this approach.

Manipulation of signaling pathways in bone tissue engineering and regenerative medicine: Current knowledge, novel strategies, and future directions

During osteogenesis, a large number of bioactive molecules, macromolecules, cells, and cellular signals are activated to induce bone growth and development. The activation of molecular pathways leads to the occurrence of cellular events, ultimately resulting in observable changes. Therefore, in the studies of bone tissue engineering and regenerative medicine, it is essential to target fundamental events to exploit the mechanisms involved in osteogenesis. In this context, signaling pathways are activated during osteogenesis and trigger the activation of numerous other processes involved in osteogenesis. Direct influence of signaling pathways should allow to manipulate the signaling pathways themselves and impact osteogenesis. A combination of sequential cascades takes place to drive the progression of osteogenesis. Also, the occurrence of these processes and, more generally, cellular and molecular processes related to osteogenesis necessitate the presence of transcription factors and their activity. The present review focuses on outlining several signaling pathways and transcription factors influencing the development of osteogenesis, and describes various methods of their manipulation to induce and enhance bone formation.

Regulation of bone homeostasis by traditional Chinese medicine active scaffolds and enhancement for the osteoporosis bone regeneration

ETHNOPHARMACOLOGICAL RELEVANCE

The active ingredients of traditional Chinese medicine (TCM), such as naringin (NG), Eucommiol, isopsoralen, icariin, Astragalus polysaccharides, and chondroitin sulfate, contained in Drynariae Rhizoma, Eucommiae Cortex, Psoralea corylifolia, Herba Epimedii, Astragalus radix and deer antler, are considered promising candidates for enhancing the healing of osteoporotic defects due to their outstanding bone homeostasis regulating properties. They are commonly used to activate bone repair scaffolds.

AIM OF THE REVIEW

Bone repair scaffolds are inadequate to meet the demands of osteoporotic defect healing due to the lack of regulation of bone homeostasis. Therefore, selecting bone scaffolds activated with TCM to improve the therapeutic effect of repairing osteoporotic bone defects.

MATERIALS AND METHODS

To gather information on bone scaffold activated by traditional Chinese medicine, we conducted a thorough search of several scientific databases, including Google Scholar, Web of Science, Scifinder, Baidu Scholar, PubMed, and China National Knowledge Infrastructure (CNKI).

RESULTS

This review discusses the mechanism of TCM active ingredients in regulating bone homeostasis, including stimulating bone formation and inhibiting bone resorption process and the healing mechanism of traditional bone repair scaffolds activated by them for osteoporotic defect healing.

CONCLUSION

In general, the introduction of TCM active ingredients provides a novel therapeutic approach for modulating bone homeostasis and facilitating osteoporotic defect healing, and also offers a new strategy for design of other unconventional bone defect healing materials.

Developing Chinese herbal-based functional biomaterials for tissue engineering

The role of traditional Chinese medicine (TCM) in treating diseases is receiving increasing attention. Chinese herbal medicine is an important part of TCM with various applications and the active ingredients extracted from Chinese herbal medicines have physiological and pathological effects. Tissue engineering combines cell biology and materials science to construct tissues or organs in vitro or in vivo. TCM has been proposed by the World Health Organization as an effective treatment modality. In recent years, the potential use of TCM in tissue engineering has been demonstrated. In this review, the classification and efficacy of TCM active ingredients and delivery systems are discussed based on the TCM theory. We also summarized the current application status and broad prospects of Chinese herbal active ingredients in different specialized biomaterials in the field of tissue engineering. This review provides novel insights into the integration of TCM and modern Western medicine through the application of Chinese medicine in tissue engineering and regenerative medicine.

Flavonoid-Loaded Biomaterials in Bone Defect Repair

Skeletons play an important role in the human body, and can form gaps of varying sizes once damaged. Bone defect healing involves a series of complex physiological processes and requires ideal bone defect implants to accelerate bone defect healing. Traditional grafts are often accompanied by issues such as insufficient donors and disease transmission, while some bone defect implants are made of natural and synthetic polymers, which have characteristics such as good porosity, mechanical properties, high drug loading efficiency, biocompatibility and biodegradability. However, their antibacterial, antioxidant, anti-inflammatory and bone repair promoting abilities are limited. Flavonoids are natural compounds with various biological activities, such as antitumor, anti-inflammatory and analgesic. Their good anti-inflammatory, antibacterial and antioxidant activities make them beneficial for the treatment of bone defects. Several researchers have designed different types of flavonoid-loaded polymer implants for bone defects. These implants have good biocompatibility, and they can effectively promote the expression of angiogenesis factors such as VEGF and CD31, promote angiogenesis, regulate signaling pathways such as Wnt, p38, AKT, Erk and increase the levels of osteogenesis-related factors such as Runx-2, OCN, OPN significantly to accelerate the process of bone defect healing. This article reviews the effectiveness and mechanism of biomaterials loaded with flavonoids in the treatment of bone defects. Flavonoid-loaded biomaterials can effectively promote bone defect repair, but we still need to improve the overall performance of flavonoid-loaded bone repair biomaterials to improve the bioavailability of flavonoids and provide more possibilities for bone defect repair.

Resorbable Membranes for Guided Bone Regeneration: Critical Features, Potentials, and Limitations

Lack of horizontal and vertical bone at the site of an implant can lead to significant clinical problems that need to be addressed before implant treatment can take place. Guided bone regeneration (GBR) is a commonly used surgical procedure that employs a barrier membrane to encourage the growth of new bone tissue in areas where bone has been lost due to injury or disease. It is a promising approach to achieve desired repair in bone tissue and is widely accepted and used in approximately 40% of patients with bone defects. In this Review, we provide a comprehensive examination of recent advances in resorbable membranes for GBR including natural materials such as chitosan, collagen, silk fibroin, along with synthetic materials such as polyglycolic acid (PGA), polycaprolactone (PCL), polyethylene glycol (PEG), and their copolymers. In addition, the properties of these materials including foreign body reaction, mechanical stability, antibacterial property, and growth factor delivery performance will be compared and discussed. Finally, future directions for resorbable membrane development and potential clinical applications will be highlighted.

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.

Injectable rBMSCs-laden hydrogel microspheres loaded with naringin for osteomyelitis treatment

Osteomyelitis, caused by purulent bacteria invading bone tissue, often occurs in long bones and seriously affects the physical and mental health and working ability of patients; it can even endanger life. However, due to bone cavity structure, osteomyelitis tends to occur inside the bone and thus lacks an effective treatment; anti-inflammatory treatment and repair of bone defects are necessary. Here, we developed injectable hydrogel microspheres loaded with naringin and bone marrow mesenchymal stem cells, which have anti-inflammatory and osteogenic properties. These homogeneous microspheres, ranging from 200 to 1000μm, can be rapidly fabricated using an electro-assisted bio-fabrication method. Interestingly, it was found that microspheres with relatively small diameters (200μm) were more conducive to the initial cell attachment, growth, spread, and later osteogenic differentiation. The developed microspheres can effectively treat tibial osteomyelitis in rats within six weeks, proving their prospects for clinical application.

Thermosensitive hydrogel coupled with sodium ascorbyl phosphate promotes human umbilical cord-derived mesenchymal stem cell-mediated skin wound healing in mice

Poor survival and restricted function of transplanted stem cells are regarded as limiting their efficacy in wound recovery greatly. Consequently, it is necessary to identify innovative therapeutic strategies to solve these issues. Firstly, the biological effect of PF-127 hydrogel alone and in combination with SAP on the survival, and migration of cultured HUCMSCs was assessed by cell viability, apoptosis, and scratch wound assays. S. aureus and E. coli were used to evaluate the antibacterial activity of PF-127 plus SAP combination. Further, the ability of HUCMSCs-conditioned medium (HUCMSCs-CM) to promote the angiogenesis and migration of human umbilical vein endothelial cells (HUVECs) in vitro was evaluated using tube formation and transwell migration assays. Finally, the HUCMSCs embedded in PF-127 plus SAP scaffold were administered onto mice's excisional cutaneous wound bed. Histological and immunohistochemical analyses were employed to investigate the wound healing capacity as well as cellular responses of PF-127/HUCMSCs/SAP hydrogel. PF-127 showed cytotoxicity on HUCMSCs, whereas the addition of SAP significantly promoted cell viability and alleviated apoptosis of HUCMSCs encapsulated in PF-127 hydrogel in vitro. SAP supplementation substantially abrogated the inhibiting effect of PF-127 on the migration of HUCMSCs in vitro. The combination of PF-127 and SAP exerted an obvious bacteriostatic function on S. aureus and E. coli. Moreover, the co-treatment with SAP could remarkably enhance the stimulative effect of HUCMSCs-CM on the angiogenesis and migration of HUVECs in vitro. PF-127 combined SAP-embedded HUCMSCs transplantation resulted in a potently accelerated wound healing process, promoted the number of proliferating cells and newly formed blood vessels, as well as enhanced expression of vascular endothelial growth factor. PF-127 coupled with SAP contributes to HUCMSCs-mediated traumatic wound closure in mice by promoting cell survival, antibacterial action, and angiogenesis. Our results offered a theoretical foundation for the clinical treatment of traumatic skin defects.

Biomimetic, biodegradable and osteoinductive treated dentin matrix/α-calcium sulphate hemihydrate composite material for bone tissue engineering

It is still a huge challenge for bone regenerative biomaterial to balance its mechanical, biological and biodegradable properties. In the present study, a new composite material including treated dentin matrix (TDM) and α-calcium sulphate hemihydrate (α-CSH) was prepared. The optimal composition ratio between TDM and α-CSH was explored. The results indicate that both components were physically mixed and structurally stable. Its compressive strength reaches up to 5.027 ± 0.035 MPa for 50%TDM/α-CSH group, similar to human cancellous bone tissues. Biological experiments results show that TDM/α-CSH composite exhibits excellent biocompatibility and the expression of osteogenic related genes and proteins (ALP, RUNX2, OPN) is significantly increased. In vivo experiments suggest that the addition of TDM for each group (10%, 30%, 50%) effectively promotes cell proliferation and osteomalacia. In addition, 50% of the TDM/α-CSH combination displays optimal osteoconductivity. The novel TDM/α-CSH composite is a good candidate for certain applications in bone tissue engineering.

Injectable Self-Setting Ternary Calcium-Based Bone Cement Promotes Bone Repair

Bone defects, especially large ones, are clinically difficult to treat. The development of new bone repair materials exhibits broad application prospects in the clinical treatment of trauma. Bioceramics are considered to be one of the most promising biomaterials owing to their good biocompatibility and bone conductivity. In this study, a self-curing bone repair material having a controlled degradation rate was prepared by mixing calcium citrate, calcium hydrogen phosphate, and semi-hydrated calcium sulfate in varying proportions, and its properties were comprehensively evaluated. In vitro cell experiments and RNA sequencing showed that the composite cement activated PI3K/Akt and MAPK/Erk signaling pathways to promote osteogenesis by promoting the proliferation and osteoblastic differentiation of mesenchymal stem cells. In a rat model with femoral condyle defects, the composite bone cement showed excellent bone repair effect and promoted bone regeneration. The injectable properties of the composite cement further improved its practical applicability, and it can be applied in bone repair, especially in the repair of irregular bone defects, to achieve superior healing.

The Development of Naringin for Use against Bone and Cartilage Disorders

Bone and cartilage disorders are the leading causes of musculoskeletal disability. There is no absolute cure for all bone and cartilage disorders. The exploration of natural compounds for the potential therapeutic use against bone and cartilage disorders is proving promising. Among these natural chemicals, naringin, a flavanone glycoside, is a potential candidate due to its multifaceted pharmacological activities in bone and cartilage tissues. Emerging studies indicate that naringin may promote osteogenic differentiation, inhibit osteoclast formation, and exhibit protective effects against osteoporosis in vivo and in vitro. Many signaling pathways, such as BMP-2, Wnt/β-catenin, and VEGF/VEGFR, participate in the biological actions of naringin in mediating the pathological development of osteoporosis. In addition, the anti-inflammatory, anti-oxidative stress, and anti-apoptosis abilities of naringin also demonstrate its beneficial effects against bone and cartilage disorders, including intervertebral disc degeneration, osteoarthritis, rheumatoid arthritis, bone and cartilage tumors, and tibial dyschondroplasia. Naringin exhibits protective effects against bone and cartilage disorders. However, more efforts are still needed due to, at least in part, the uncertainty of drug targets. Further biological and pharmacological evaluations of naringin and its applications in bone tissue engineering, particularly its therapeutic effects against osteoporosis, might result in developing potential drug candidates.

Electrospun naringin-loaded microsphere/sucrose acetate isobutyrate system promotes macrophage polarization toward M2 and facilitates osteoporotic bone defect repair

Repairing osteoporotic bone defects is still a major clinical challenge. Recent studies have revealed that immune response is also essential in osteogenesis. The intrinsic inflammatory response of the host, especially the M1/M2 polarization status and inflammatory secretory function of macrophages, can directly affect osteogenic differentiation. Therefore, in this study, an electrospun naringin-loaded microspheres/sucrose acetate isobutyrate (Ng-m-SAIB) system was constructed to investigate its effect on the polarization of macrophage and osteoporotic bone defects. The results of both in vitro and in vivo experiments showed that Ng-m-SAIB had good biocompatibility and could promote the polarization of macrophage toward M2, thereby forming a favorable microenvironment for osteogenesis. The animal experiments also showed that Ng-m-SAIB could promote the osteogenesis of critical size defects in the skull of the osteoporotic model mouse (the senescence-accelerated mouse-strain P6). Together, these results collectively suggested that Ng-m-SAIB might be a promising biomaterial to treat osteoporotic bone defects with favorable osteo-immunomodulatory effects.

The role of PIWI-interacting RNA in naringin pro-angiogenesis by targeting HUVECs

Angiogenesis is a biological process in which resting endothelial cells start proliferating, migrating and forming new blood vessels. Angiogenesis is particularly important in the repair of bone tissue defects. Naringin (NG) is the main active monomeric component of traditional Chinese medicine, which has various biological activities, such as anti-osteoporosis, anti-inflammatory, blood activation and microcirculation improvement. At present, the mechanism of naringin in the process of angiogenesis is not clear. PIWI protein-interacting RNA (piRNA) is a small noncoding RNA (sncRNA) that has the functions of regulating protein synthesis, regulating the structure of chromatin and the genome, stabilizing mRNA and others. Several studies have demonstrated that piRNAs can mediate the angiogenesis process. Whether naringin can interfere with the process of angiogenesis by regulating piRNAs and related target genes deserves further exploration. Thus, the purpose of this study was to validate the potential angiogenic and bone regeneration properties and related mechanisms of naringin both in vivo and in vitro.

Application of Hydrogels as Sustained-Release Drug Carriers in Bone Defect Repair

Large bone defects resulting from trauma, infection and tumors are usually difficult for the body's repair mechanisms to heal spontaneously. Generally, various types of bones and orthopedic implants are adopted to enhance bone repair and regeneration in the clinic. Due to the limitations of traditional treatments, bone defect repair is still a compelling challenge for orthopedic surgeons. In recent years, bone tissue engineering has become a potential option for bone repair and regeneration. Amidst the various scaffolds for bone tissue engineering applications, hydrogels are considered a new type of non-toxic, non-irritating and biocompatible materials, which are widely used in the biomedicine field currently. Some studies have demonstrated that hydrogels can provide a three-dimensional network structure similar to a natural extracellular matrix for tissue regeneration and can be used to transport cells, biofactors, nutrients and drugs. Therefore, hydrogels may have the potential to be multifunctional sustained-release drug carriers in the treatment of bone defects. The recent applications of different types of hydrogels in bone defect repair were briefly reviewed in this paper.

Naringin Release from a Nano-Hydroxyapatite/Collagen Scaffold Promotes Osteogenesis and Bone Tissue Reconstruction

Bone fractures and defects are a major health issue and have reportedly affected over 455 million individuals globally to date. Bone tissue engineering has gained great success in bone defect repair and bone reconstruction based on the use of nano-hydroxyapatite (nHA) or collagen (COL). Both nHA and COL exhibit osteogenic induction capacity to support bone tissue regeneration; however, the former suffers from poor flexibility and the latter lacks mechanical strength. Biological scaffolds created by combining nHA and COL (nHA/COL) can overcome the drawbacks imposed by individual materials and, therefore, have become widely applied in tissue engineering. The composite scaffolds can further promote tissue reconstruction by allowing the loading of various growth factors. Naringin (NG) is a natural flavonoid. Its molecular weight is 580.53 Da, lower than that of many growth factors, and it causes minimal immune responses when being introduced in vivo. In addition, naringin is safe, non-toxic, inexpensive to produce, and has superior bio-properties. In this study, we introduced NG into a nHA/COL scaffold (NG/nHA/COL) and exploited the potentials of the NG/nHA/COL scaffold in enhancing bone tissue regeneration. NG/nHA/COL scaffolds were fabricated by firstly combining nHA and collagen at different compositional ratios, followed by NG encapsulation. NG release tests showed that the scaffold with a nHA/COL mass ratio of 7:3 exhibited the optimal property. The in vitro cell study showed the desirable biocompatibility of the NG/nHA/COL scaffold, and its effective promotion for the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs), as proved by an increased alkaline phosphatase (ALP) activity, the formation of more calcium nodules, and a higher expression of osteogenic-related genes involving Osteocalcin (OCN), BMP-2, and Osteopontin (OPN), compared with the control and nHA/COL groups. When administered into rats with skull defects, the NG/nHA/COL scaffold significantly promoted the reconstruction of bone tissues and the early repair of skull defects, indicating the great potential of NG/nHA/COL scaffolds in bone tissue engineering.

Traditional Chinese medicine promotes bone regeneration in bone tissue engineering

Bone tissue engineering (BTE) is a promising method for the repair of difficult-to-heal bone tissue damage by providing three-dimensional structures for cell attachment, proliferation, and differentiation. Traditional Chinese medicine (TCM) has been introduced as an effective global medical program by the World Health Organization, comprising intricate components, and promoting bone regeneration by regulating multiple mechanisms and targets. This study outlines the potential therapeutic capabilities of TCM combined with BTE in bone regeneration. The effective active components promoting bone regeneration can be generally divided into flavonoids, alkaloids, glycosides, terpenoids, and polyphenols, among others. The chemical structures of the monomers, their sources, efficacy, and mechanisms are described. We summarize the use of compounds and medicinal parts of TCM to stimulate bone regeneration. Finally, the limitations and prospects of applying TCM in BTE are introduced, providing a direction for further development of novel and potential TCM.

Polyphenol-Enriched Composite Bone Regeneration Materials: A Systematic Review of In Vitro Studies

One of the possible alternatives for creating materials for the regeneration of bone tissue supporting comprehensive reconstruction is the incorporation of active substances whose controlled release will improve this process. This systematic review aimed to identify and synthesize in vitro studies that assess the suitability of polyphenolics as additives to polymer-ceramic composite bone regeneration materials. Data on experimental studies in terms of the difference in mechanical, wettability, cytocompatibility, antioxidant and anti-inflammatory properties of materials were synthesized. The obtained numerical data were compiled and analyzed in search of percentage changes of these parameters. The results of the systematic review were based on data from forty-six studies presented in nineteen articles. The addition of polyphenolic compounds to composite materials for bone regeneration improved the cytocompatibility and increased the activity of early markers of osteoblast differentiation, indicating a high osteoinductive potential of the materials. Polyphenolic compounds incorporated into the materials presumably give them high antioxidant properties and reduce the production of reactive oxygen species in macrophage cells, implying anti-inflammatory activity. The evidence was limited by the number of missing data and the heterogeneity of the data.

Angiogenic and Osteogenic Effects of Flavonoids in Bone Regeneration

Bone is a highly vascularised tissue that relies on a close spatial and temporal interaction between blood vessels and bone cells. As a result, angiogenesis is critical for bone formation and healing. The vascular system supports bone regeneration by delivering oxygen, nutrients, and growth factors, as well as facilitating efficient cell-cell contact. Most clinical applications of engineered bone grafts are hampered by insufficient vascularization after implantation. Over the last decade, a number of flavonoids have been reported to have osteogenic-angiogenic potential in bone regeneration because of their excellent bioactivity, low cost, availability, and minimal in vivo toxicity. During new bone formation, the osteoinductive nature of certain flavonoids is involved in regulating multiple signaling pathways contributing toward the osteogenic-angiogenic coupling. This review briefly outlines the osteogenic-angiogenic potential of those flavonoids and the mechanisms of their action in promoting bone regeneration. However, further studies are needed to investigate their delivery strategies and establish their clinical efficacy. This article is protected by copyright. All rights reserved.

Robust Silk Protein Hydrogels Made by a Facile One-Step Method and Their Multiple Applications

Silk fibroin is a natural polymer that has various material forms and wide applications. Hydrogel is one of the most attractive silk materials because of its hydrophilicity, biocompatibility, and flexibility. However, its applications are still quite limited because they have a complicated preparation process and/or low mechanical strength. Herein, a simple way to prepare tough silk fibroin hydrogels via a solvent-exchange method is introduced. The degummed silk fiber was directly dissolved in a calcium chloride/formic acid solution and then water was used to replace the solvent. The silk fibroin hydrogel that was obtained using this facile method exhibited even better mechanical properties than most silk fibroin hydrogels that have been reported in the literature. Also, the silk fibroin hydrogel maintained biocompatibility that was as good as that prepared via other methods. Finally, the possibility of using this regenerated silk fibroin hydrogel as a multi-functional platform (such as a catalyst carrier, photothermal agent, and underwater adhesive) has been discussed. Therefore, such a natural, sustainable, robust, and good biocompatible silk fibroin hydrogel that is prepared by an improved method may have great potential for further applications.

Anisotropic silk nanofiber layers as regulators of angiogenesis for optimized bone regeneration

Osteogenesis-angiogenesis coupling processes play a crucial role in bone regeneration. Here, electric field induced aligned nanofiber layers with tunable thickness were coated on the surface of pore walls inside the deferoxamine (DFO)-laden silk fibroin (SF) and hydroxyapatite (HA) composite scaffolds to regulate the release of DFO to control vascularization dynamically. Longer electric field treatments resulted in gradually thickening layers to reduce the release rate of DFO where the released amount of DFO decreased gradually from 84% to 63% after 28 days. Besides the osteogenic capacity of HA, the changeable release of DFO brought different angiogenic behaviors in bone regeneration process, which provided a desirable niche with osteogenic and angiogenic cues. Anisotropic cues were introduced to facilitate cell migration inside the scaffolds. Changeable cytokine secretion from endothelial cells cultured in the different scaffolds revealed the regulation of cell responses related to vascularization in vitro. Peak expression of angiogenic factors appeared at days 7, 21 and 35 for endothelial cells cultured in the scaffolds with different silk nanofier layers, suggesting the dynamical regulation of angiogenesis. Although all of the scaffolds had the same silk and HA composition, in vitro cell studies indicated different osteogenic capacities for the scaffolds, suggesting that the regulation of DFO release also influenced osteogenesis outcomes in vitro. In vivo, the best bone regeneration occurred in defects treated with the composite scaffolds that exhibited the best osteogenic capacity in vitro. Using a rat bone defect model, healing was achieved within 12 weeks, superior to those treated with previous SF-HA composite matrices. Controlling angiogenic properties of bone biomaterials dynamically is an effective strategy to improve bone regeneration capacity.

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Anisotropic silk nanofiber layers with tunable thickness control the sustained release of DFO dynamically.

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Dynamical regulation of angiogenesis was achieved in bone regeneration process through tuning the release behaviors of DFO.

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Significantly improved bone regeneration through the synergistic effect of optimal vascularization and osteogenesis.

The Role of Flavonoids in the Osteogenic Differentiation of Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) play an important role in developing bone tissue engineered constructs due to their osteogenic and chondrogenic differentiation potential. MSC-based tissue engineered constructs are generally considered a safe procedure, however, the long-term results obtained up to now are far from satisfactory. The main causes of these therapeutic limitations are inefficient homing, engraftment, and directional differentiation. Flavonoids are a secondary metabolite, widely existed in nature and have many biological activities. For a long time, researchers have confirmed the anti-osteoporosis effect of flavonoids through in vitro cell experiments, animal studies. In recent years the regulatory effects of flavonoids on mesenchymal stem cells (MSCs) differentiation have been received increasingly attention. Recent studies revealed flavonoids possess the ability to modulate self-renewal and differentiation potential of MSCs. In order to facilitate further research on MSCs osteogenic differentiation of flavonoids, we surveyed the literature published on the use of flavonoids in osteogenic differentiation of MSCs, and summarized their pharmacological activities as well as the underlying mechanisms, aimed to explore their promising therapeutic application in bone disorders and bone tissue engineered constructs.

Localized delivery of brain-derived neurotrophic factor from PLGA microspheres promotes peripheral nerve regeneration in rats

Background

Repair of peripheral nerve defect presents a considerable challenge for reconstructive surgeons. The aim of this study is to develop a brain-derived neurotrophic factor (BDNF) from poly(D,L-lactide-co-glycolide) (PLGA) microspheres for the treatment of the peripheral nerve defect.

Method

BDNF microspheres were prepared by using an oil-in-water emulsification-solvent evaporation method. The morphology, particle size, encapsulation efficiency, drug loading and sustained release performance of microspheres was observed and calculated. Adipose mesenchymal stem cells (ADSCs) were isolated and expanded. ADSCs were divided into four groups: control, BDNF, blank microsphere and BDNF microsphere groups. Cell count kit-8 (CCK-8) assays were used to assess cell proliferation. Cell migration was determined by Transwell assays. Twenty-eight male Sprague–Dawley rats underwent transection damage model on the right sciatic nerve. The wet weight ratio of the gastrocnemius muscle was calculated by comparing the weight of the gastrocnemius muscle from the operated side to that of the normal side. Neuroelectrophysiological testing was performed to assess nerve function recovery. Nerve regeneration was evaluated by histological analysis and immunohistochemical staining.

Results

The microspheres were spherical and had uniform size (46.38 ± 1.00 μm), high encapsulation efficiency and high loading capacity. In vitro release studies showed that BDNF-loaded microspheres had good sustained release characteristics. The duration of BDNF release was extended to more than 50 days. BDNF or BDNF microsphere promote the proliferation and migration of ADSCs than control group (P < 0.05). Compared with control group, BDNF significantly decreased the nerve conduction velocity (NCV) and compound amplitude (AMP) (P < 0.05). The nerve fibers in the BDNF microsphere group were closely arranged and uniformly distributed than control group.

Conclusion

BDNF/PLGA sustained-release microsphere could promote the migration of ADSCs and promoted neural differentiation of ADSCs. Moreover, BDNF/PLGA sustained-release microsphere ameliorated nerve conduction velocity and prevented neuralgic amyotrophy.

Traditional Chinese Medicine Compound-Loaded Materials in Bone Regeneration

Bone is a dynamic organ that has the ability to repair minor injuries via regeneration. However, large bone defects with limited regeneration are debilitating conditions in patients and cause a substantial clinical burden. Bone tissue engineering (BTE) is an alternative method that mainly involves three factors: scaffolds, biologically active factors, and cells with osteogenic potential. However, active factors such as bone morphogenetic protein-2 (BMP-2) are costly and show an unstable release. Previous studies have shown that compounds of traditional Chinese medicines (TCMs) can effectively promote regeneration of bone defects when administered locally and systemically. However, due to the low bioavailability of these compounds, many recent studies have combined TCM compounds with materials to enhance drug bioavailability and bone regeneration. Hence, the article comprehensively reviewed the local application of TCM compounds to the materials in the bone regeneration in vitro and in vivo. The compounds included icariin, naringin, quercetin, curcumin, berberine, resveratrol, ginsenosides, and salvianolic acids. These findings will contribute to the potential use of TCM compound-loaded materials in BTE.

Sustained release of naringin from silk-fibroin-nanohydroxyapatite scaffold for the enhancement of bone regeneration

Bone defects are a common challenge in the clinical setting. Bone tissue engineering (BTE) is an effective treatment for the clinical problem of large bone defects. In this study, we fabricated silk fibroin (SF)/hydroxyapatite (HAp) scaffolds inlaid with naringin poly lactic-co-glycolic acid (PLGA) microspheres, investigating the feasibility of their application in BTE. Naringin PLGA microspheres were manufactured and adhered to the SF/HAp scaffold. Bone mesenchymal stem cells (BMSCs) were inoculated onto the SF/HAp scaffold containing naringin PLGA microsphere to examine the biocompatibility of the SF/HAp scaffolds. A rabbit femoral distal bone defect model was used to evaluate the in vivo function of the SF/HAp scaffolds containing naringin-loaded PLGA microspheres. The current study demonstrated that SF/HAp scaffolds containing naringin-loaded PLGA microspheres show promise as osteo-modulatory biomaterials for bone regeneration.

The post-processing temperature or humidity can importantly control the secondary structure and characteristics of silk fibroin films

Temperature and humidity (TH) are highly important factors that can control the secondary structure and characterization of silk fibroin (SF) biomaterials. In this study, the water stability, secondary structure, mechanical properties, surface morphology, and degradation of silk fibroin films (SFFs) with post-processing in different TH were investigated. Fourier transform infrared indicated that the SFF secondary structure did not change under low-relative humidity (RH) despite temperatures up to 180°C, while it transformed at 40°C with 100% RH in 10 min. A film with a higher tensile strength (42.1 ± 8.2 MPa) could be obtained after post-processing at 90°C/100% RH for 10 min. While a film with higher ductility (elongation at break: 198.8 ± 31.8%) was generated after post-processing at 40°C/100% RH for 10 min. Scanning electron microscope showed that the film presented a network structure of nanoparticles in series under certain TH post-treatment. Enzymatic hydrolysis proved that the SFFs containing a higher content of silk II structure degraded more slowly. Therefore, TH post-treatment is a relatively mild way to change the secondary structure and properties of SFFs, which can be widely used in loading drugs and maintaining the activity of drugs in SF biomaterials.

Total glycosides from Eucommia ulmoides seed promoted osteogenic differentiation of adipose-derived mesenchymal stem cells and bone formation in ovariectomized rats through regulating Notch signaling pathway

Background

Osteoporosis (OP) is a well-known chronic degenerative disease, with impaired mesenchymal stem cells (MSCs) function and suppressed osteogenic differentiation. Total glycosides from Eucommia ulmoides seed (TGEUS) was a Chinese medicine and have rich pharmacological effects. This study was designed to explore the mechanism of TGEUS in promoting osteogenic differentiation and bone formation in ovariectomized (OVX) rats.

Methods

Adipose‐derived mesenchymal stem cells (ADSCs) were isolated and treated with different concentration of TGEUS. Cell viability was assessed using cell counting kit-8 (CCK-8) assay. Osteogenic capacity was identified by ALP staining and ARS staining. Moreover, RNA sequencing between control and TGEUS treated ADSCs were further performed to reveal the mechanism of TGEUS in promoting osteogenic differentiation. The expression of Jag1, Lfng and Hey1 were measured using quantitative real-time polymerase chain reaction (qRTPCR). Osteogenic markers were further assessed by western blot. DAPT and NICD were further used to identify whether Notch signaling pathway involved into TGEUS promoting osteogenic differentiation of ADSCs. Ovariectomy-induced bone loss rats model was established and divided into three groups: sham, OVX and OVX + TGEUS groups. HE staining and immunohistochemical staining were further performed to identify whether TGEUS could promote bone formation.

Results

TGEUS treatment significantly enhanced the cell viability and ALP activity than control group, the optimal dose of TGEUS was 5 μM. We selected 5 μM TGEUS for further study. TGEUS significantly enhanced ALP activity and calcium deposition than that of control group. Activation of Notch signaling fully blocked TGEUS-induced osteogenic differentiation of ADSCs. Following TGEUS treatment, the trabecular bone of the rats was significantly increased, thickened, and more connected compared to the OVX group. With the treatment of TGEUS, the expression of Osterix (Osx), Osteocalcin (OCN) and RUNX Family Transcription Factor 2 (RUNX2) increased than OVX group.

Conclusion

TGEUS enhanced osteogenic differentiation of ADSCs and promoted bone formation in ovariectomy-induced bone loss rats. Our study broadened the understanding of TGEUS as a therapeutic target against osteoporosis.

Naringin-inlaid silk fibroin/hydroxyapatite scaffold enhances human umbilical cord-derived mesenchymal stem cell-based bone regeneration

OBJECTIVES

Large bone defects are a common, debilitating clinical condition that have substantial global health and economic burden. Bone tissue engineering technology has become one of the most promising approaches for regenerating defective bones. In this study, we fabricated a naringin-inlaid composite silk fibroin/hydroxyapatite (NG/SF/HAp) scaffold to repair bone defects.

MATERIALS AND METHODS

The salt-leaching technology was used to fabricate the NG/SF/HAp scaffold. The cytocompatibility of the NG/SF/HAp scaffold was assessed using scanning electron microscopy, live/dead cell staining and phalloidin staining. The osteogenic and angiogenic properties were assessed in vitro and in vivo.

RESULTS

The porous NG/SF/HAp scaffold had a well-designed biomimetic porous structure with osteoinductive and angiogenic activities. A gene microarray identified 854 differentially expressed genes between human umbilical cord-derived mesenchymal stem cells (hUCMSCs) cultured on SF-nHAp scaffolds and cells cultured on NG/SF/HAp scaffolds. The underlying osteoblastic mechanism was investigated using hUCMSCs in vitro. Naringin facilitated hUCMSC ingrowth into the SF/HAp scaffold and promoted osteogenic differentiation. The osteogenic and angiogenic capabilities of cells cultured in the NG/SF/HAp scaffold were superior to those of cells cultured in the SF/HAp scaffold.

CONCLUSIONS

The data indicate the potential of the SF/HAp composite scaffold incorporating naringin for bone regeneration.