Icariin-loaded porous scaffolds for bone regeneration through the regulation of the coupling process of osteogenesis and osteoclastic activity

3D-Printed Biomimetic Hydroxyapatite Composite Scaffold Loaded with Curculigoside for Rat Cranial Defect Repair

The treatment of various large bone defects has remained a challenge for orthopedic surgeons for a long time. Recent research indicates that curculigoside (CUR) extracted from the curculigo plant exerts a positive influence on bone formation, contributing to fracture healing. In this study, we employed emulsification/solvent evaporation techniques to successfully fabricate poly(ε-caprolactone) nanoparticles loaded with curculigoside (CUR@PM). Subsequently, using three-dimensional (3D) printing technology, we successfully developed a bioinspired composite scaffold named HA/GEL/SA/CUR@PM (HGSC), chemically cross-linked with calcium chloride, to ensure scaffold stability. Further characterization of the scaffold's physical and chemical properties revealed uniform pore size, good hydrophilicity, and appropriate mechanical properties while achieving sustained drug release for up to 12 days. In vitro experiments demonstrated the nontoxicity, good biocompatibility, and cell proliferative properties of HGSC. Through alkaline phosphatase (ALP) staining, Alizarin Red S (ARS) staining, cell migration assays, tube formation assays, and detection of angiogenic and osteogenic gene proteins, we confirmed the HGSC composite scaffold's significant angiogenic and osteoinductive capabilities. Eight weeks postimplantation in rat cranial defects, Micro-computed tomography (CT) and histological observations revealed pronounced angiogenesis and new bone growth in areas treated with the HGSC composite scaffold. These findings underscore the scaffold's exceptional angiogenic and osteogenic properties, providing a solid theoretical basis for clinical bone repair and demonstrating its potential in promoting vascularization and bone regeneration.

Engineering approaches to manipulate osteoclast behavior for bone regeneration

Extensive research has delved into the multifaceted roles of osteoclasts beyond their traditional function in bone resorption in recent years, uncovering their significant influence on bone formation. This shift in understanding has spurred investigations into engineering strategies aimed at leveraging osteoclasts to not only inhibit bone resorption but also facilitate bone regeneration. This review seeks to comprehensively examine the mechanisms by which osteoclasts impact bone metabolism. Additionally, it explores various engineering methodologies, including the modification of bioactive material properties, localized drug delivery, and the introduction of exogenous cells, assessing their potential and mechanisms in aiding bone repair by targeting osteoclasts. Finally, the review proposes current limitations and future routes for manipulating osteoclasts through biological and material cues to facilitate bone repair.

Promoting osteogenesis and bone regeneration employing icariin-loaded nanoplatforms

There is an increasing demand for innovative strategies that effectively promote osteogenesis and enhance bone regeneration. The critical process of bone regeneration involves the transformation of mesenchymal stromal cells into osteoblasts and the subsequent mineralization of the extracellular matrix, making up the complex mechanism of osteogenesis. Icariin's diverse pharmacological properties, such as anti-inflammatory, anti-oxidant, and osteogenic effects, have attracted considerable attention in biomedical research. Icariin, known for its ability to stimulate bone formation, has been found to encourage the transformation of mesenchymal stromal cells into osteoblasts and improve the subsequent process of mineralization. Several studies have demonstrated the osteogenic effects of icariin, which can be attributed to its hormone-like function. It has been found to induce the expression of BMP-2 and BMP-4 mRNAs in osteoblasts and significantly upregulate Osx at low doses. Additionally, icariin promotes bone formation by stimulating the expression of pre-osteoblastic genes like Osx, RUNX2, and collagen type I. However, icariin needs to be effectively delivered to bone to perform such promising functions.Encapsulating icariin within nanoplatforms holds significant promise for promoting osteogenesis and bone regeneration through a range of intricate biological effects. When encapsulated in nanofibers or nanoparticles, icariin exerts its effects directly at the cellular level. Recalling that inflammation is a critical factor influencing bone regeneration, icariin's anti-inflammatory effects can be harnessed and amplified when encapsulated in nanoplatforms. Also, while cell adhesion and cell migration are pivotal stages of tissue regeneration, icariin-loaded nanoplatforms contribute to these processes by providing a supportive matrix for cellular attachment and movement. This review comprehensively discusses icariin-loaded nanoplatforms used for bone regeneration and osteogenesis, further presenting where the field needs to go before icariin can be used clinically.

Fabrication and Properties of the Montmorillonite/Nanobioglass Hybrid Reinforcement from Agroindustrial Waste for Bone Regeneration

Nowadays, bone systems have a series of consequences that compromise the quality of life mainly due to wear and decreased bioactivity, generally in elderly people and children. In this context, the combination of montmorillonite (MMT-NPs) in a vitreous system such as nanobioglass facilitates the adsorption of biomolecules on the surface and within the interlamellar spaces, enabling the entry of ions by a cation exchange process focusing on increasing the rate of bone formation. This work aims to synthesize and characterize an eco-friendly hybrid reinforcement containing MMT-NPs with nanobioglass doped with magnesium nanoparticles (MgNPs-BV). In this way, MMT-NPs@MgNPs-BV was synthesized by the impregnation method, where an experimental design was used to verify the synthesis conditions. The ideal condition by experimental design was carried out in terms of the characterization and biological activity, where we demonstrated MMT-NPs of 30% w w-1, MgNPs-BV of 6% w w-1, and a calcination temperature of 1273.15 K with a cell viability around 66.87%, an average crystallite diameter of 12.5 nm, and a contact angle of 17.7°. The characterizations confirmed the impregnation method with an average particle size of 51.4 ± 13.1 nm. The mechanical tests showed a hardness of 2.6 GPa with an apparent porosity of 22.2%, similar to human bone. MMT-NPs@MgNPs-BV showed a cell proliferation of around 96% in osteoblastic cells (OFCOL II), with the formation of the apatite phase containing a relation of Ca/P of around 1.63, a biodegradability of 82%, and rapid release of ions with a Ca/P ratio of 1.42. Therefore, the eco-friendly hybrid reinforcement with MMT-NPs and MgNPs-BV shows potential for application with a matrix for biocompatible nanocomposites for bone regeneration.

ICA/SDF-1α/PBMSCs loaded onto alginate and gelatin cross-linked scaffolds promote damaged cartilage repair

A three-dimensional alginate-coated scaffold (GAIS) was constructed in the present study to showcase the multidifferentiation potential of peripheral blood mesenchymal stem cells (PBMSCs) and to investigate the role and mechanism by which Icariin (ICA)/stromal cell-derived factor (SDF-1α)/PBMSCs promote damaged articular repair. In addition, the ability of ICA, in combination with SDF-1α, to promote the migration and proliferation of stem cells was validated through the utilization of CCK-8 and migration experiments. The combination of ICA and SDF-1α inhibited the differentiation of PBMSCs into cartilage, as demonstrated by in vivo experiments and histological staining. Both PCR and western blot experiments showed that GAIS could upregulate the expression of particular genes in chondrocytes. In comparison to scaffolds devoid of alginate (G0), PBMSCs seeded into GAIS scaffolds exhibited a greater rate of proliferation, and the conditioned medium derived from scaffolds containing SDF-1α enhanced the capacity for cell migration. Moreover, after a 12-week treatment period, GAIS, when successfully transplanted into osteochondral defects of mice, was found to promote cartilage regeneration and repair. The findings, therefore, demonstrate that GAIS enhanced the in vitro capabilities of PBMSCs, including proliferation, migration, homing and chondrogenic differentiation. In addition, ICA and SDF-1α effectively collaborated to support cartilage formation in vivo. Thus, the ICA/SDF-1α/PBMSC-loaded biodegradable alginate-gelatin scaffolds showcase considerable potential for use in cartilage repair.

Dual-functional 3D-printed porous bioactive scaffold enhanced bone repair by promoting osteogenesis and angiogenesis

The treatment of bone defects is a difficult problem in orthopedics. The excessive destruction of local bone tissue at defect sites destroys blood supply and renders bone regeneration insufficient, which further leads to delayed union or even nonunion. To solve this problem, in this study, we incorporated icariin into alginate/mineralized collagen (AMC) hydrogel and then placed the drug-loaded hydrogel into the pores of a 3D-printed porous titanium alloy (AMCI/PTi) scaffold to prepare a bioactive scaffold with the dual functions of promoting angiogenesis and bone regeneration. The experimental results showed that the ACMI/PTi scaffold had suitable mechanical properties, sustained drug release function, and excellent biocompatibility. The released icariin and mineralized collagen (MC) synergistically promoted angiogenesis and osteogenic differentiation in vitro. After implantation into a rabbit radius defect, the composite scaffold showed a satisfactory effect in promoting bone repair. Therefore, this composite dual-functional scaffold could meet the requirements of bone defect treatment and provide a promising strategy for the repair of large segmental bone defects in clinic.

Binding-induced fibrillogenesis peptide inhibits RANKL-mediated osteoclast activation against osteoporosis

Osteoporosis is primarily driven by an imbalance between bone resorption and formation, stemming from enhanced osteoclast activity during bone remodeling. At the crux of this mechanism lies the pivotal RANK-RANKL-OPG axis. In our study, we designed two binding-induced fibrillogenesis (BIF) peptides, namely BIFP and BIFY, targeting RANK and RANKL, respectively. These BIF peptides, with distinct hydrophilic and hydrophobic characteristics, assemble into nanoparticles (NPs) in aqueous solution. Through specific ligand-receptor interactions, these NPs efficiently target and bind to specific proteins, resulting in the formation of fibrous networks that effectively inhibit the RANK-RANKL associations. Experiments have confirmed the potent inhibitory effects of peptides on both osteoclast differentiation and function. Compared with the +RANKL controls, BIFP and BIFY demonstrated a more remarkable reduction in tartrate resistant acid phosphatase (TRAP)-positive cells, achieving an impressive decline of 82.8% and 70.7%, respectively. Remarkably, the administration of BIFP led to a substantial reduction in bone resorption pit area by 17.4%, compared to a significant increase of 92.4% in the +RANKL groups. In vivo experiments on an ovariectomized mouse model demonstrated that the BIFP treated group exhibited an impressive 2.6-fold elevation in bone mineral density and an astounding 4.0-fold enhancement in bone volume/total volume as against those of the PBS-treated group. Overall, BIF peptides demonstrate remarkable abilities to impede osteoclast differentiation, presenting promising prospects for the treatment of osteoporosis.

Mechanism of regulating macrophages/osteoclasts in attenuating wear particle-induced aseptic osteolysis

Joint replacement surgery is the most effective treatment for end-stage arthritis. Aseptic loosening caused by periprosthetic osteolysis is a common complication after joint replacement. Inflammation induced by wear particles derived from prosthetic biomaterials is a major cause of osteolysis. We emphasize that bone marrow-derived macrophages and their fusion-derived osteoclasts play a key role in this pathological process. Researchers have developed multiple intervention approaches to regulate macrophage/osteoclast activation. Aiming at wear particle-induced periprosthetic aseptic osteolysis, this review separately discusses the molecular mechanism of regulation of ROS formation and inflammatory response through intervention of macrophage/osteoclast RANKL-MAPKs-NF-κB pathway. These molecular mechanisms regulate osteoclast activation in different ways, but they are not isolated from each other. There is also a lot of crosstalk among the different mechanisms. In addition, other bone and joint diseases related to osteoclast activation are also briefly introduced. Therefore, we discuss these new findings in the context of existing work with a view to developing new strategies for wear particle-associated osteolysis based on the regulation of macrophages/osteoclasts.

Fabrication of a three-dimensional printed gelatin/sodium alginate/nano-attapulgite composite polymer scaffold loaded with leonurine hydrochloride and its effects on osteogenesis and vascularization

Bone tissue engineering scaffolds have made significant progress in treating bone defects in recent decades. However, the lack of a vascular network within the scaffold limits bone formation after implantation in vivo. Recent research suggests that leonurine hydrochloride (LH) can promote healing in full-thickness cutaneous wounds by increasing vessel formation and collagen deposition. Gelatin and Sodium Alginate are both polymers. ATP is a magnesium silicate chain mineral. In this study, a Gelatin/Sodium Alginate/Nano-Attapulgite composite hydrogel was used as the base material first, and the Gelatin/Sodium Alginate/Nano-Attapulgite composite polymer scaffold loaded with LH was then created using 3D printing technology. Finally, LH was grafted onto the base material by an amide reaction to construct a scaffold loaded with LH to achieve long-term LH release. When compared to pure polymer scaffolds, in vitro results showed that LH-loaded scaffolds promoted the differentiation of BMSCs into osteoblasts, as evidenced by increased expression of osteogenic key genes. The results of in vivo tissue staining revealed that the drug-loaded scaffold promoted both angiogenesis and bone formation. Collectively, these findings suggest that LH-loaded Gelatin/Sodium Alginate/Nano-Attapulgite composite hydrogel scaffolds are a potential therapeutic strategy and can assist bone regeneration.

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.

Synthetic Calcium-Phosphate Materials for Bone Grafting

Synthetic bone grafting materials play a significant role in various medical applications involving bone regeneration and repair. Their ability to mimic the properties of natural bone and promote the healing process has contributed to their growing relevance. While calcium-phosphates and their composites with various polymers and biopolymers are widely used in clinical and experimental research, the diverse range of available polymer-based materials poses challenges in selecting the most suitable grafts for successful bone repair. This review aims to address the fundamental issues of bone biology and regeneration while providing a clear perspective on the principles guiding the development of synthetic materials. In this study, we delve into the basic principles underlying the creation of synthetic bone composites and explore the mechanisms of formation for biologically important complexes and structures associated with the various constituent parts of these materials. Additionally, we offer comprehensive information on the application of biologically active substances to enhance the properties and bioactivity of synthetic bone grafting materials. By presenting these insights, our review enables a deeper understanding of the regeneration processes facilitated by the application of synthetic bone composites.

Lyophilized Platelet-Rich Fibrin Exudate-Loaded Carboxymethyl Chitosan/GelMA Hydrogel for Efficient Bone Defect Repair

Platelet-rich fibrin (PRF) is an autologous growth factor carrier that promotes bone tissue regeneration, but its effectiveness is restrained by poor storage capabilities, uncontrollable concentration of growth factors, unstable shape, etc. Herein, we developed a photocrosslinkable composite hydrogel by incorporating lyophilized PRF exudate (LPRFe) into the carboxymethyl chitosan methacryloyl (CMCSMA)/gelatin methacryloyl (GelMA) hydrogel to effectively solve the dilemma of PRF. The hydrogel possessed suitable physical properties and sustainable release ability of growth factors in LPRFe. The LPRFe-loaded hydrogel could improve the adhesion, proliferation, migration, and osteogenic differentiation of rat bone mesenchymal stem cells (BMSCs). Furthermore, the animal experiments demonstrated that the hydrogel possessed excellent biocompatibility and biodegradability, and the introduction of LPRFe in the hydrogel can effectively accelerate the bone healing process. Conclusively, the combination of LPRFe with CMCSMA/GelMA hydrogel may be a promising therapeutic approach for bone defects.

Polymeric and Composite Carriers of Protein and Non-Protein Biomolecules for Application in Bone Tissue Engineering

Conventional intake of drugs and active substances is most often based on oral intake of an appropriate dose to achieve the desired effect in the affected area or source of pain. In this case, controlling their distribution in the body is difficult, as the substance also reaches other tissues. This phenomenon results in the occurrence of side effects and the need to increase the concentration of the therapeutic substance to ensure it has the desired effect. The scientific field of tissue engineering proposes a solution to this problem, which creates the possibility of designing intelligent systems for delivering active substances precisely to the site of disease conversion. The following review discusses significant current research strategies as well as examples of polymeric and composite carriers for protein and non-protein biomolecules designed for bone tissue regeneration.

Bioactivity, Molecular Mechanism, and Targeted Delivery of Flavonoids for Bone Loss

Skeletal disabilities are a prominent burden on the present population with an increasing life span. Advances in osteopathy have provided various medical support for bone-related diseases, including pharmacological and prosthesis interventions. However, therapeutics and post-surgery complications are often reported due to side effects associated with modern-day therapies. Thus, therapies utilizing natural means with fewer toxic or other side effects are the key to acceptable interventions. Flavonoids constitute a class of bioactive compounds found in dietary supplements, and their pharmacological attributes have been well appreciated. Recently, flavonoids' role is gaining renowned interest for its effect on bone remodeling. A wide range of flavonoids has been found to play a pivotal role in the major bone signaling pathways, such as wingless-related integration site (Wnt)/β-catenin, bone morphogenetic protein (BMP)/transforming growth factor (TGF)-β, mitogen-activated protein kinase (MAPK), etc. However, the reduced bioavailability and the absorption of flavonoids are the major limitations inhibiting their use against bone-related complications. Recent utilization of nanotechnological approaches and other delivery methods (biomaterial scaffolds, micelles) to target and control release can enhance the absorption and bioavailability of flavonoids. Thus, we have tried to recapitulate the understanding of the role of flavonoids in regulating signaling mechanisms affecting bone remodeling and various delivery methods utilized to enhance their therapeutical potential in treating bone loss.

Sequential gastrodin release PU/n-HA composite scaffolds reprogram macrophages for improved osteogenesis and angiogenesis

Wound healing is a highly orchestrated process involving a variety of cells, including immune cells. Developing immunomodulatory biomaterials for regenerative engineering applications, such as bone regeneration, is an appealing strategy. Herein, inspired by the immunomodulatory effects of gastrodin (a bioactive component in traditional Chinese herbal medicine), a series of new immunomodulatory gastrodin-comprising biodegradable polyurethane (gastrodin-PU) and nano-hydroxyapatite (n-HA) (gastrodin-PU/n-HA) composites were developed. RAW 264.7 macrophages, rat bone marrow mesenchymal stem cells (rBMSCs), and human umbilical vein endothelial cells (HUVECs) were cultured with gastrodin-PU/n-HA containing different concentrations of gastrodin (0.5%, 1%, and 2%) to decipher their immunomodulatory effects on osteogenesis and angiogenesis in vitro. Results demonstrated that, compared with PU/n-HA, gastrodin-PU/n-HA induced macrophage polarization toward the M2 phenotype, as evidenced by the higher expression level of pro-regenerative cytokines (CD206, Arg-1) and the lower expression of pro-inflammatory cytokines (iNOS). The expression levels of osteogenesis-related factors (BMP-2 and ALP) in the rBMSCs and angiogenesis-related factors (VEGF and BFGF) in the HUVECs were significantly up-regulated in gastrodin-PU/n-HA/macrophage-conditioned medium. The immunomodulatory effects of gastrodin-PU/n-HA to reprogram macrophages from a pro-inflammatory (M1) phenotype to an anti-inflammatory and pro-healing (M2) phenotype were validated in a rat subcutaneous implantation model. And the 2% gastrodin-PU/n-HA significantly decreased fibrous capsule formation and enhanced angiogenesis. Additionally, 2% gastrodin-PU/n-HA scaffolds implanted in the rat femoral condyle defect model showed accelerated osteogenesis and angiogenesis. Thus, the novel gastrodin-PU/n-HA scaffold may represent a new and promising immunomodulatory biomaterial for bone repair and regeneration.

•

A new immunomodulatory gastrodin-PU/n-HA biomaterial has been developed.

•

The gastrodin-PU/n-HA triggered M2 macrophage polarization.

•

The osteogenesis and angiogenesis were enhanced in response to the local immune microenvironment.

•

The findings prove a therapeutic strategy in bone defect and other inflammatory osteoimmune disorders.

Calcium phosphate cement with icariin-loaded gelatin microspheres as a local drug delivery system for bone regeneration

BACKGROUND

Icariin (ICA), a main active ingredient of Herba Epimedium, could promote bone formation, inhibit bone resorption and alleviate inflammatory responses. The aim of this study was to investigate the effect of ICA on the inhibition of bacteria associated with peri-implantitis, and fabricate a calcium phosphate cement (CPC) with ICA-loaded gelatin microspheres (GMs) as a local drug delivery system efficiently promoting bone formation and alleviating inflammation.

RESULTS

In this study, ICA exhibited antibacterial activity against P. gingivalis with a MIC value of 1 × 10^-4 mol/L. When the concentration of ICA was 0.5 mM, the encapsulation efficiency of GMs reached the maximum value of 76.26 ± 3.97%. GMs with ICA revealed a controlled release profile, 0.5 mM ICA exhibited a higher ICA release profile than the other groups during a 21 d monitoring span. The results of SEM and XRD demonstrated successful fabrication of a calcium phosphate cement with ICA-loaded GMs. ICA released from CPC/GMs (ICA) was slower than ICA released from GMs within 10 days. CPC/GMs (ICA) exhibited antibacterial activity against P. gingivalis, but the antibacterial rate of CPC/GMs (ICA) was only 17.15 ± 6.06%. In addition, CPC/GMs (ICA) promoted the proliferation of BMSCs and significantly stimulated the differentiation and maturation of BMSCs. In vivo, H&E and Masson staining experiments demonstrated that CPC/GMs (ICA) exhibited better capacity for bone regeneration than CPC/GMs and CPC, and the expression of TNF-α and IL-1β in the tissue around CPC/GMs (ICA) was significantly lower than CPC/GMs and CPC in IHC staining (P < 0.05).

CONCLUSION

In this study, ICA exhibited limited antibacterial activity against bacteria associated with peri-implantitis. A composite material of calcium phosphate cement with ICA-loaded gelatin microspheres was developed, which not only promoting osteoinductivity and bone formation, but also alleviating inflammation, demonstrating its potential as a promising bone substitute material for treatment of peri-implantitis.

Multifunctional Scaffolds Based on Emulsion and Coaxial Electrospinning Incorporation of Hydroxyapatite for Bone Tissue Regeneration

Tissue engineering is nowadays a powerful tool to restore damaged tissues and recover their normal functionality. Advantages over other current methods are well established, although a continuous evolution is still necessary to improve the final performance and the range of applications. Trends are nowadays focused on the development of multifunctional scaffolds with hierarchical structures and the capability to render a sustained delivery of bioactive molecules under an appropriate stimulus. Nanocomposites incorporating hydroxyapatite nanoparticles (HAp NPs) have a predominant role in bone tissue regeneration due to their high capacity to enhance osteoinduction, osteoconduction, and osteointegration, as well as their encapsulation efficiency and protection capability of bioactive agents. Selection of appropriated polymeric matrices is fundamental and consequently great efforts have been invested to increase the range of properties of available materials through copolymerization, blending, or combining structures constituted by different materials. Scaffolds can be obtained from different processes that differ in characteristics, such as texture or porosity. Probably, electrospinning has the greater relevance, since the obtained nanofiber membranes have a great similarity with the extracellular matrix and, in addition, they can easily incorporate functional and bioactive compounds. Coaxial and emulsion electrospinning processes appear ideal to generate complex systems able to incorporate highly different agents. The present review is mainly focused on the recent works performed with Hap-loaded scaffolds having at least one structural layer composed of core/shell nanofibers.

Mechanism and Prospect of Gastrodin in Osteoporosis, Bone Regeneration, and Osseointegration

Gastrodin, a traditional Chinese medicine ingredient, is widely used to treat vascular and neurological diseases. However, recently, an increasing number of studies have shown that gastrodin has anti-osteoporosis effects, and its mechanisms of action include its antioxidant effect, anti-inflammatory effect, and anti-apoptotic effect. In addition, gastrodin has many unique advantages in promoting bone healing in tissue engineering, such as inducing high hydrophilicity in the material surface, its anti-inflammatory effect, and pro-vascular regeneration. Therefore, this paper summarized the effects and mechanisms of gastrodin on osteoporosis and bone regeneration in the current research. Here we propose an assumption that the use of gastrodin in the surface loading of oral implants may greatly promote the osseointegration of implants and increase the success rate of implants. In addition, we speculated on the potential mechanisms of gastrodin against osteoporosis, by affecting actin filament polymerization, renin-angiotensin system (RAS) and ferroptosis, and proposed that the potential combination of gastrodin with Mg2+, angiotensin type 2 receptor blockers or artemisinin may greatly inhibit osteoporosis. The purpose of this review is to provide a reference for more in-depth research and application of gastrodin in the treatment of osteoporosis and implant osseointegration in the future.

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.

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.

Jiawei Yanghe Decoction Regulates Bone-Lipid Balance through the BMP-SMAD Signaling Pathway to Promote Osteogenic Differentiation of Bone Mesenchymal Stem Cells

Background

The Jiawei Yanghe decoction (JWYHD) is a traditional Chinese medicine formula for the treatment of osteoporosis, but its therapeutic mechanism has not been fully elucidated, and the therapeutic target of the intervention disease needs to be further verified. The dysfunction of bone mesenchymal stem cells (BMSCs) is considered to be an important pathogenesis of postmenopausal osteoporosis (PMOP). The purpose of this study was to explore how JWYHD regulates BMSC differentiation through the BMP-SMAD signal pathway.

Methods

In the in vivo study, we used an ovariectomized PMOP rat (n = 36, 2-month-old, 200 ± 20 g) model and femur micro-CT analysis to study the effect of JWYHD on bone loss in rats. By immunofluorescence, the translocation expression of BMP2, a key protein in the pathway, was detected. Serum bone metabolism was detected by an enzyme-linked immunosorbent assay (ELISA). Alkaline phosphatase (ALP) activity was detected by alkaline phosphatase staining (ALPS), osteogenesis and matrix mineralization were detected by alizarin red staining (ARS), the adipogenic ability of BMSCs was detected by oil red staining (ORS), and CFU is used to detect the ability of cells to form colonies. The expression of related proteins was detected by western blotting.

Results

In vivo and in vitro, the OP phenotypes of SD rats induced by ovariectomy (OVX) included impaired bone mineral density and microstructure, abnormal bone metabolism, and impaired MSC differentiation potential. JWYHD treatment reversed this trend and restored the differentiation potential of MSCs. JWYHD medicated serum and direct intervention of drugs activated the BMP-SMAD signaling pathway, promoted the osteogenic differentiation of BMSCs, and inhibited their adipogenic differentiation.

Conclusions

Our data identified that JWYHD is an effective alternative drug for the treatment of PMOP that functions to stimulate the differentiation of BMSCs into osteoblasts in the BMP-SMAD signaling-dependent mechanism.

Degradation-Kinetics-Controllable and Tissue-Regeneration-Matchable Photocross-linked Alginate Hydrogels for Bone Repair

Photocross-linked alginate hydrogels, due to their biodegradability, biocompatibility, strong control for gelling kinetics in space and time, and admirable adaptability for in situ polymerization with a minimally invasive approach in surgical procedures, have created great expectations in bone regeneration. However, hydrogels with suitable degradation kinetics that can match the tissue regeneration process have not been designed, which limits their further application in bone tissue engineering. Herein, we finely developed an oxidation strategy for alginate to obtain hydrogels with more suitable degradation rates and comprehensively explored their physical and biological performances in vitro and in vivo to further advance the clinical application for the hydrogels in bone repair. The physical properties of the gels can be tuned via tailoring the degree of alginate oxidation. In particular, in vivo degradation studies showed that the degradation rates of the gels were significantly increased by oxidizing alginate. The activity, proliferation, initial adhesion, and osteogenic differentiation of rat and rabbit bone marrow stromal cells (BMSCs) cultured with/in the hydrogels were explored, and the results demonstrated that the gels possessed excellent biocompatibility and that the encapsulated BMSCs were capable of osteogenic differentiation. Furthermore, in vivo implantation of rabbit BMSC-loaded gels into tibial plateau defects of rabbits demonstrated the feasibility of hydrogels with appropriate degradation rates for bone repair. This study indicated that hydrogels with increasingly controllable and matchable degradation kinetics and satisfactory bioproperties demonstrate great clinical potential in bone tissue engineering and regenerative medicine and could also provide references for drug/growth-factor delivery therapeutic strategies for diseases requiring specific drug/growth-factor durations of action.

Synergistically Promoting Bone Regeneration by Icariin-Incorporated Porous Microcarriers and Decellularized Extracellular Matrix Derived From Bone Marrow Mesenchymal Stem Cells

Multifunctionality has becoming essential for bone tissue engineering materials, such as drug release. In this study, icariin (ICA)-incorporated poly(glycolide-co-caprolactone) (PGCL) porous microcarriers were fabricated and then coated with decellularized extracellular matrix (dECM) which was derived from bone marrow mesenchymal stem cells (BMSC). The porous structure was generated due to the soluble gelatin within the microcarriers. The initial released ICA in microcarriers regulated osteogenic ECM production by BMSCs during ECM formation. The dECM could further synergistically enhance the migration and osteogenic differentiation of BMSCs together with ICA as indicated by the transwell migration assay, ALP and ARS staining, as well as gene and protein expression. Furthermore, in vivo results also showed that dECM and ICA exhibited excellent synergistic effects in repairing rat calvarial defects. These findings suggest that the porous microcarriers loaded with ICA and dECM coatings have great potential in the field of bone tissue engineering.

Dental pulp stem cell-derived extracellular matrix: autologous tool boosting bone regeneration

BACKGROUND AIMS

To facilitate artificial bone construct integration into a patient's body, scaffolds are enriched with different biologically active molecules. Among various scaffold decoration techniques, coating surfaces with cell-derived extracellular matrix (ECM) is a rapidly growing field of research. In this study, for the first time, this technology was applied using primary dental pulp stem cells (DPSCs) and tested for use in artificial bone tissue construction.

METHODS

Rat DPSCs were grown on three-dimensional-printed porous polylactic acid scaffolds for 7 days. After the predetermined time, samples were decellularized, and the remaining ECM detailed proteomic analysis was performed. Further, DPSC-secreated ECM impact to mesenchymal stromal cells (MSC) behaviour as well as its role in osteoregeneration induction were analysed.

RESULTS

It was identified that DPSC-specific ECM protein network ornamenting surface-enhanced MSC attachment, migration and proliferation and even promoted spontaneous stem cell osteogenesis. This protein network also demonstrated angiogenic properties and did not stimulate MSCs to secrete molecules associated with scaffold rejection. With regard to bone defects, DPSC-derived ECM recruited endogenous stem cells, initiating the bone self-healing process. Thus, the DPSC-secreted ECM network was able to significantly enhance artificial bone construct integration and induce successful tissue regeneration.

CONCLUSIONS

DPSC-derived ECM can be a perfect tool for decoration of various biomaterials in the context of bone tissue engineering.

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.

Implantation of stem cells on synthetic or biological scaffolds: an overview of bone regeneration

Humans are exposed to a wide range of bone tissue injuries. In severe cases, bone damages could be only treated with transplantation of autologous or allogeneic grafting.In recent years, tissue engineering has become a promising strategy for repairing damaged organs and tissues, providing a great opportunity to cure several diseases. Bone tissue engineering consists of three components: scaffold, cells, and growth factors. Current bone tissue engineering strategies combine the use of stem cells with biologically active materials and gene therapy to mimic the natural microenvironment of bone. The combination of the scaffold with growth factors and extracellular matrix protein molecules can promote cell attachment, proliferation, and induce osteogenesis, which could provide signals for cell migration to begin the healing process during repair and bone formation.This article reviews the principles of bone regeneration and the most current developments of bone tissue engineering related to bone growth factors, the biologically active materials, such as bacterial cellulose, and stem cells.

Fabrication of three dimensional bioactive Sr2+ substituted apatite scaffolds by gel-casting technique for hard tissue regeneration

This study aimed to fabricate three-dimensional (3D) bioactive Sr²⁺ -substituted apatite (Sr-HAP) scaffolds prepared by gel-casting with polymer sponge infiltration technique. 3D Sr-HAP scaffolds were prepared as engineering constructs with interconnected porous structure with a pore size of 200-600 μm ranging from a 10 × 10 × 6 mm size was designed. The characterization of X-ray diffraction, field emission scanning electron microscopy, and energy dispersion spectroscopy was utilized in order to evaluate the crystalline phase, structure, and morphology in the interconnected porous of the synthesized Sr-HAP scaffold. The bioactive and biocompatible of the resultant Sr-HAP scaffolds were analyzed by using simulated body fluid solution. Furthermore, the cytotoxicity and proliferation of MG-63 cell lines on the scaffolds were examined in 24 h culture. Furthermore, in vivo experiments demonstrated that the tibia bone defect with 4 mm diameter in rabbits was successfully healed by Sr-HAP porous scaffold after 45 days implantation. The histological images indicated the improved cell proliferation and new bone formation occurred in the porous scaffold treated group. The results indicated that the fabricated Sr-HAP scaffold is a promising capacity to infuse bone regeneration and promote in vivo tissue repair.

Transcriptomics-based analysis of the mechanism by which Wang-Bi capsule alleviates joint destruction in rats with collagen-induced arthritis

BACKGROUND

Rheumatoid arthritis (RA) is a chronic autoimmune disease accompanied with joint destruction that often leads to disability. Wang-Bi capsule (WB), a traditional Chinese medicine-based herbs formula, has exhibited inhibition effect on joint destruction of collagen-induced arthritis (CIA) animal model in our previous study. But its molecular mechanisms are still obscure.

METHODS

CIA rats were treated intragastrical with WB for eight weeks, and the effect of joints protection were evaluated by hematoxylin and eosin (H&E) staining, safranin O fast green staining, tartrate-resistant acid phosphatase (TRAP) staining and micro‑CT scanning analysis. The transcriptomic of tarsal joints were used to investigate how WB alleviated joint destruction.

RESULTS

The histological examination of ankle joints showed WB alleviated both cartilage damage and bone destruction of CIA rats. This protective effect on joints were further evidenced by micro-CT analysis. The transcriptomic analysis showed that WB prominently changed 12 KEGG signaling pathways ("calcium signaling pathway", "cAMP signaling pathway", "cell adhesion molecules", "chemokine signaling pathway", "complement and coagulation cascades", "MAPK signaling pathway", "NF-kappa B signaling pathway", "osteoclast differentiation", "PI3K-Akt signaling pathway", "focal adhesion", "Gap junction" and "Rap1 signaling pathway") associated with bone or cartilage. Several genes (including Il6, Tnfsf11, Ffar2, Plg, Tnfrsf11b, Fgf4, Fpr1, Siglec1, Vegfd, Cldn1, Cxcl13, Chad, Arrb2, Fgf9, Egfr) regulating bone resorption, bone formation and cartilage development were identified by further analysis. Meanwhile, these differentially expressed genes were validated by real-time quantitative PCR.

CONCLUSIONS

Overall, the protective effect of WB treatment on joint were confirmed in CIA rats, and its basic molecular mechanisms may be associated with regulating some genes (including Il6, Tnfsf11, Ffar2 and Plg etc.) involved in bone resorption, bone formation and cartilage development.

The shared KEGG pathways between icariin-targeted genes and osteoporosis

Osteoporosis is a common metabolic bone disease that affects about 40% of postmenopausal women. Treatment options for osteoporosis are limited, however. Icariin is an herbal substance that has been shown to improve bone mass, but the mechanisms are largely unknown. Using bioinformatics analysis, we have identified the hub genes and KEGG pathways shared between icariin-targeted genes and osteoporosis. The top five shared KEGG pathways were the Toll-like receptor signaling pathway, adipocytokine pathway, neurotrophin signaling pathway, NOD-like receptor signaling, and B cell receptor signaling pathway; the hub genes were RELA, NFKBIA, and IKBKB, belonging to the NF-κB family. The identified icariin-targeted genes are involved in inflammation, insulin resistance, apoptosis, and immune responses, and regulate the PI3K-Akt, NF-κB, MAPK, and JNK signaling pathways. Our in vitro data show that icariin inhibits apoptosis in human mesenchymal stem cells by suppressing JNK/c-Jun signaling pathway. Together, these findings indicate that icariin exerts its anti-osteoporotic function by inhibiting JNK/c-Jun signaling pathway, and suggest that icariin may be a promising treatment option for osteoporosis.

Icariin controlled release on a silk fibroin/mesoporous bioactive glass nanoparticles scaffold for promoting stem cell osteogenic differentiation

The treatment of bone defects caused by various reasons is still a major problem in orthopedic clinical work. Many studies on osteogenic implant materials have used various biologically active factors such as osteogenic inducers, but these biologically active factors have various side effects. Therefore, in this study, silk fibroin (SF) was used as a scaffold material, mesoporous bioactive glass nanoparticles (MBGNs) as a sustained release carrier, and the traditional Chinese drug icariin (ICA) was loaded to promote bone formation. The experiments in this study have proven that SF/MBGNs-ICA scaffolds can successfully load and release ICA for a long time, and the sustained-release ICA can promote the proliferation and differentiation of BMSCs for a long time. This controlled-release ICA organic/inorganic two-component scaffold material is expected to become a new bone grafting solution.