A Biomimetic Material with a High Bio-responsibility for Bone Reconstruction and Tissue Engineering

Current and Future Perspectives of Bioactive Glasses as Injectable Material

This review covers recent compositions of bioactive glass, with a specific emphasis on both inorganic and organic materials commonly utilized as matrices for injectable materials. The major objective is to highlight the predominant bioactive glass formulations and their clinical applications in the biomedical field. Previous studies have highlighted the growing interest among researchers in bioactive glasses, acknowledging their potential to yield promising outcomes in this field. As a result of this increased interest, investigations into bioactive glass have prompted the creation of composite materials and, notably, the development of injectable composites as a minimally invasive method for administering the material within the human body. Injectable materials have emerged as a promising avenue to mitigate various challenges. They offer several advantages, including minimizing invasive surgical procedures, reducing patient discomfort, lowering the risk of postoperative infection and decreasing treatment expenses. Additionally, injectable materials facilitate uniform distribution, allowing for the filling of defects of any shape.

Quercetin-loaded mesoporous nano-delivery system remodels osteoimmune microenvironment to regenerate alveolar bone in periodontitis via the miR-21a-5p/PDCD4/NF-κB pathway

BACKGROUND

Impaired osteo-/angiogenesis, excessive inflammation, and imbalance of the osteoimmune homeostasis are involved in the pathogenesis of the alveolar bone defect caused by periodontitis. Unfortunately, there is still a lack of ideal therapeutic strategies for periodontitis that can regenerate the alveolar bone while remodeling the osteoimmune microenvironment. Quercetin, as a monomeric flavonoid, has multiple pharmacological activities, such as pro-regenerative, anti-inflammatory, and immunomodulatory effects. Despite its vast spectrum of pharmacological activities, quercetin's clinical application is limited due to its poor water solubility and low bioavailability.

RESULTS

In this study, we fabricated a quercetin-loaded mesoporous bioactive glass (Quercetin/MBG) nano-delivery system with the function of continuously releasing quercetin, which could better promote the bone regeneration and regulate the immune microenvironment in the alveolar bone defect with periodontitis compared to pure MBG treatment. In particular, this nano-delivery system effectively decreased injection frequency of quercetin while yielding favorable therapeutic results. In view of the above excellent therapeutic effects achieved by the sustained release of quercetin, we further investigated its therapeutic mechanisms. Our findings indicated that under the periodontitis microenvironment, the intervention of quercetin could restore the osteo-/angiogenic capacity of periodontal ligament stem cells (PDLSCs), induce immune regulation of macrophages and exert an osteoimmunomodulatory effect. Furthermore, we also found that the above osteoimmunomodulatory effects of quercetin via macrophages could be partially blocked by the overexpression of a key microRNA--miR-21a-5p, which worked through inhibiting the expression of PDCD4 and activating the NF-κB signaling pathway.

CONCLUSION

In summary, our study shows that quercetin-loaded mesoporous nano-delivery system has the potential to be a therapeutic approach for reconstructing alveolar bone defects in periodontitis. Furthermore, it also offers a new perspective for treating alveolar bone defects in periodontitis by inhibiting the expression of miR-21a-5p in macrophages and thereby creating a favorable osteoimmune microenvironment.

Hyaluronic acid as a bioactive component for bone tissue regeneration: Fabrication, modification, properties, and biological functions

Hyaluronic acid (HA) is widely distributed in the human body, and it is heavily involved in many physiological functions such as tissue hydration, wound repair, and cell migration. In recent years, HA and its derivatives have been widely used as advanced bioactive polymers for bone regeneration. Many medical products containing HA have been developed because this natural polymer has been proven to be nontoxic, noninflammatory, biodegradable, and biocompatible. Moreover, HA-based composite scaffolds have shown good potential for promoting osteogenesis and mineralization. Recently, many HA-based biomaterials have been fabricated for bone regeneration by combining with electrospinning and 3D printing technology. In this review, the polymer structures, processing, properties, and applications in bone tissue engineering are summarized. The challenges and prospects of HA polymers are also discussed.

In vitro and in vivo investigation of bisphosphonate-loaded hydroxyapatite particles for peri-implant bone augmentation

Locally applied bisphosphonates, such as zoledronate, have been shown in several studies to inhibit peri-implant bone resorption and recently to enhance peri-implant bone formation. Studies have also demonstrated positive effects of hydroxyapatite (HA) particles on peri-implant bone regeneration and an enhancement of the anti-resorptive effect of bisphosphonates in the presence of calcium. In the present study, both hydroxyapatite nanoparticles (nHA) and zoledronate were combined to achieve a strong reinforcing effect on peri-implant bone. The nHA-zoledronate combination was first investigated in vitro with a pre-osteoclastic cell assay (RAW 264.7) and then in vivo in a rat model of postmenopausal osteoporosis. The in vitro study confirmed that the inhibitory effect of zoledronate on murine osteoclast precursor cells was enhanced by loading the drug on nHA. For the in vivo investigation, either zoledronate-loaded or pure nHA were integrated in hyaluronic acid hydrogel. The gels were injected in screw holes that had been predrilled in rat femoral condyles before the insertion of miniature screws. Micro-CT-based dynamic histomorphometry and histology revealed an unexpected rapid mineralization of the hydrogel in vivo through formation of granules, which served as scaffold for new bone formation. The delivery of zoledronate-loaded nHA further inhibited a degradation of the mineralized hydrogel as well as a resorption of the peri-implant bone as effectively as unbound zoledronate. Hyaluronic acid with zoledronate-loaded nHA, thanks to its dual effect on inducing a rapid mineralization and preventing resorption, is a promising versatile material for bone repair and augmentation. Copyright © 2015 John Wiley & Sons, Ltd.

Enhancement mechanisms of graphene in nano-58S bioactive glass scaffold: mechanical and biological performance

Graphene is a novel material and currently popular as an enabler for the next-generation nanocomposites. Here, we report the use of graphene to improve the mechanical properties of nano-58S bioactive glass for bone repair and regeneration. And the composite scaffolds were fabricated by a homemade selective laser sintering system. Qualitative and quantitative analysis demonstrated the successful incorporation of graphene into the scaffold without obvious structural damage and weight loss. The optimum compressive strength and fracture toughness reached 48.65 ± 3.19 MPa and 1.94 ± 0.10 MPa·m^1/2 with graphene content of 0.5 wt%, indicating significant improvements by 105% and 38% respectively. The mechanisms of pull-out, crack bridging, crack deflection and crack tip shielding were found to be responsible for the mechanical enhancement. Simulated body fluid and cell culture tests indicated favorable bioactivity and biocompatibility of the composite scaffold. The results suggest a great potential of graphene/nano-58S composite scaffold for bone tissue engineering applications.

Leveraging "raw materials" as building blocks and bioactive signals in regenerative medicine

Components found within the extracellular matrix (ECM) have emerged as an essential subset of biomaterials for tissue engineering scaffolds. Collagen, glycosaminoglycans, bioceramics, and ECM-based matrices are the main categories of "raw materials" used in a wide variety of tissue engineering strategies. The advantages of raw materials include their inherent ability to create a microenvironment that contains physical, chemical, and mechanical cues similar to native tissue, which prove unmatched by synthetic biomaterials alone. Moreover, these raw materials provide a head start in the regeneration of tissues by providing building blocks to be bioresorbed and incorporated into the tissue as opposed to being biodegraded into waste products and removed. This article reviews the strategies and applications of employing raw materials as components of tissue engineering constructs. Utilizing raw materials holds the potential to provide both a scaffold and a signal, perhaps even without the addition of exogenous growth factors or cytokines. Raw materials contain endogenous proteins that may also help to improve the translational success of tissue engineering solutions to progress from laboratory bench to clinical therapies. Traditionally, the tissue engineering triad has included cells, signals, and materials. Whether raw materials represent their own new paradigm or are categorized as a bridge between signals and materials, it is clear that they have emerged as a leading strategy in regenerative medicine. The common use of raw materials in commercial products as well as their growing presence in the research community speak to their potential. However, there has heretofore not been a coordinated or organized effort to classify these approaches, and as such we recommend that the use of raw materials be introduced into the collective consciousness of our field as a recognized classification of regenerative medicine strategies.

Construction of microenvironment onto titanium substrates to regulate the osteoblastic differentiation of bone marrow stromal cells in vitro and osteogenesis in vivo

To mimic the extracellular matrix of natural bone, apatite/gelatin composite was deposited onto nanostructured titanium substrates via a coprecipitation method, which was pretreated by potassium hydroxide and heat treatment to generate an anticorrosive nanostructured layer. The successful formation of the apatite/gelatin nanocomposite onto titanium surfaces was revealed by Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, atomic force microscopy (AFM), and thin film X-ray diffraction (TF-XRD) measurements, respectively. The immunofluorescence staining of vinculin revealed that the apatite/gelatin nanocomposite deposited titanium substrate was favorable for cell adhesion. More importantly, bone marrow stromal cells cultured onto the apatite/gelatin nanocomposite deposited titanium substrates displayed significantly higher (p < 0.05 or p < 0.01) proliferation and differentiation levels of alkaline phosphatase, mRNA expressions of osteocalcin (OC), osteopontin (OPN), and collagen type I (Col I), and OC content after culture for 7, 14, and 21 days, respectively, which was also revealed by the immunofluorescence analysis of OC and OPN expression. The deposition of apatite/gelatin nanocomposite improved bone density (p < 0.05) and bone-implant contact rate (p < 0.05), which was reflected by microcomputed tomography analysis and histological evaluation in vivo using a rabbit model. This work provides an approach to fabricate high-performance titanium-based implants with enhanced bone osseointegration.

Glycosaminoglycans enhance osteoblast differentiation of bone marrow derived human mesenchymal stem cells

Extracellular matrix plays an important role in regulating cell growth and differentiation. The biomimetic approach of cell-based tissue engineering is based on mirroring this in vivo micro environment for developing a functional tissue engineered construct. In this study, we treated normal tissue culture plates with selected extracellular matrix components consisting of glycosaminoglycans such as chondroitin-4-sulphate, dermatan sulphate, chondroitin-6-sulphate, heparin and hyaluronic acid. Mesenchymal stem cells isolated from adult human bone marrow were cultured on the glycosaminoglycan treated culture plates to evaluate their regulatory role in cell growth and osteoblast differentiation. Although no significant improvement on human mesenchymal stem cell adhesion and proliferation was observed on the glycosaminoglycan-treated tissue culture plates, there was selective osteoblast differentiation, indicating its potential role in differentiation rather than proliferation. Osteoblast differentiation studies showed high osteogenic potential for all tested glycosaminoglycans except chondroitin-4-sulphate. Osteoblast differentiation-associated genes such as osterix, osteocalcin, integrin binding sialoprotein, osteonectin and collagen, type 1, alpha 1 showed significant upregulation. We identified osterix as the key transcription factor responsible for the enhanced bone matrix deposition observed on hyaluronic acid, heparin and chondroitin-6-sulphate. Hyaluronic acid provided the most favourable condition for osteoblast differentiation and bone matrix synthesis. Our results confirm and emphasise the significant role of extracellular matrix in regulating cell differentiation. To summarise, glycosaminoglycans of extracellular matrix played a significant role in regulating osteoblast differentiation and could be exploited in the biomimetic approach of fabricating or functionalizing scaffolds for stem cell based bone tissue engineering.

Umbilical cord as a mesenchymal stem cell source for treating joint pathologies

Articular cartilage disorders and injuries often result in life-long chronic pain and compromised quality of life. Regrettably, the regeneration of articular cartilage is a continuing challenge for biomedical research. One of the most promising therapeutic approaches is cell-based tissue engineering, which provides a healthy population of cells to the injured site but requires differentiated chondrocytes from an uninjured site. The use of healthy chondrocytes has been found to have limitations. A promising alternative cell population is mesenchymal stem cells (MSCs), known to possess excellent proliferation potential and proven capability for differentiation into chondrocytes. The “immunosuppressive” property of human MSCs makes them an important candidate for allogeneic cell therapy. The use of allogeneic MSCs to repair large defects may prove to be an alternative to current autologous and allogeneic tissue-grafting procedures. An allogeneic cell-based approach would enable MSCs to be isolated from any donor, expanded and cryopreserved in allogeneic MSC banks, providing a readily available source of progenitors for cell replacement therapy. These possibilities have spawned the current exponential growth in stem cell research in pharmaceutical and biotechnology communities. Our objective in this review is to summarize the knowledge about MSCs from umbilical cord stroma and focus mainly on their applications for joint pathologies.