Bone defects caused by trauma, severe infection, tumor resection and skeletal abnormalities are common osteoporotic conditions and major challenges in orthopedic surgery, and there is still no effective solution to this problem. Consequently, new treatments are needed to develop regeneration procedures without side effects. Exosomes secreted by mesenchymal stem cells (MSCs) derived from human induced pluripotent stem cells (hiPSCs, hiPSC-MSC-Exos) incorporate the advantages of both MSCs and iPSCs with no immunogenicity. However, there are no reports on the application of hiPSC-MSC-Exos to enhance angiogenesis and osteogenesis under osteoporotic conditions. HiPSC-MSC-Exos were isolated and identified before use. The effect of hiPSC-MSC-Exos on the proliferation and osteogenic differentiation of bone marrow MSCs derived from ovariectomized (OVX) rats (rBMSCs-OVX) in vitro were investigated. In vivo, hiPSC-MSC-Exos were implanted into critical size bone defects in ovariectomized rats, and bone regeneration and angiogenesis were examined by microcomputed tomography (micro-CT), sequential fluorescent labeling analysis, microfil perfusion and histological and immunohistochemical analysis. The results in vitro showed that hiPSC-MSC-Exos enhanced cell proliferation and alkaline phosphatase (ALP) activity, and up-regulated mRNA and protein expression of osteoblast-related genes in rBMSCs-OVX. In vivo experiments revealed that hiPSC-MSC-Exos dramatically stimulated bone regeneration and angiogenesis in critical-sized calvarial defects in ovariectomized rats. The effect of hiPSC-MSC-Exos increased with increasing concentration. In this study, we showed that hiPSC-MSC-Exos effectively stimulate the proliferation and osteogenic differentiation of rBMSCs-OVX, with the effect increasing with increasing exosome concentration. Further analysis demonstrated that the application of hiPSC-MSC-Exos+β-TCP scaffolds promoted bone regeneration in critical-sized calvarial defects by enhancing angiogenesis and osteogenesis in an ovariectomized rat model.

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Exosomes Secreted by Human-Induced Pluripotent Stem Cell-Derived Mesenchymal Stem Cells Repair Critical-Sized Bone Defects through Enhanced Angiogenesis and Osteogenesis in Osteoporotic Rats.

Mitochondrial dysfunction and oxidative stress damage are hallmarks of osteoarthritis (OA). Mesenchymal stem cell (MSC)-derived exosomes are important in intercellular mitochondria communication. However, the use of MSC exosomes for regulating mitochondrial function in OA has not been reported. This study aimed to explore the therapeutic effect of MSC exosomes in a three dimensional (3D) printed scaffold for early OA therapeutics. Methods: We first examined the mitochondria-related proteins in normal and OA human cartilage samples and investigated whether MSC exosomes could enhance mitochondrial biogenesis in vitro. We subsequently designed a bio-scaffold for MSC exosomes delivery and fabricated a 3D printed cartilage extracellular matrix (ECM)/gelatin methacrylate (GelMA)/exosome scaffold with radially oriented channels using desktop-stereolithography technology. Finally, the osteochondral defect repair capacity of the 3D printed scaffold was assessed using a rabbit model. Results: The ECM/GelMA/exosome scaffold effectively restored chondrocyte mitochondrial dysfunction, enhanced chondrocyte migration, and polarized the synovial macrophage response toward an M2 phenotype. The 3D printed scaffold significantly facilitated the cartilage regeneration in the animal model. Conclusion: This study demonstrated that the 3D printed, radially oriented ECM/GelMA/exosome scaffold could be a promising strategy for early OA treatment.

Desktop-stereolithography 3D printing of a radially oriented extracellular matrix/mesenchymal stem cell exosome bioink for osteochondral defect regeneration.

Hydroxyapatite (HA), the traditional bone tissue replacement material was widely used in the clinical treatment of bone defects because of its excellent biocompatibility. However, the processing difficulty and poor osteoinductive ability greatly limit the application of HA. Although many strategies have been reported to improve the machinability and osteointegration ability, the performance including mechanical strength, porosity, cell adhesion, etc. of material still can not meet the requirements. In this work, a soft template method was developed and a porous scaffold with hierarchical pore structure, nano surface morphology, suitable porosity and pore size, and good biomechanical strength was successfully prepared. The hierarchical pore structure is beneficial for cell adhesion, fluid transfer, and cell ingrowth. Moreover, the loaded reduced graphene oxide (rGO) can improve the adhesion and promote the proliferation and spontaneous osteogenic differentiation bone marrow mesenchymal stem cells. The scaffold is then crushed, degraded and wrapped by the newly formed bone and the newly formed bone gradually replaces the scaffold. The degradation rate of the scaffold well matches the rate of the new bone formation. The hierarchical porous HA/rGO composite scaffolds can greatly accelerate the bone ingrowth in the scaffold and bone repair in critical bone defects, thus providing a clinical potential candidate for large segment bone tissue engineering.

Hierarchically Porous Hydroxyapatite Hybrid Scaffold Incorporated with Reduced Graphene Oxide for Rapid Bone Ingrowth and Repair

Mesoporous materials are ideal carriers for guest molecules and they have been widely used in analytical science. The unique mesoporous structure provides special properties including large specific surface area, tunable pore size, and excellent pore connectivity. The structural properties of mesoporous materials have been largely made use of to improve the performance of analytical methods. For instance, the large specific surface area of mesoporous materials can provide abundant active sites and increase the probability of contact between analytes and active sites to produce stronger signals, thus leading to the improvement of detection sensitivity. The connections between analytical performances and the structural properties of mesoporous materials have not been discussed previously. Understanding the “structure–performance relationship” is highly important for the development of analytical methods with excellent performance based on mesoporous materials. In this review, we discuss the structural properties of mesoporous materials that can be optimized to improve the analytical performance. The discussion is divided into five sections according to the analytical performances: (i) selectivity-related structural properties, (ii) sensitivity-related structural properties, (iii) response time-related structural properties, (iv) stability-related structural properties, and (v) recovery time-related structural properties.

New insights into the structure-performance relationships of mesoporous materials in analytical science.

Three-dimensional nanostructured graphene: Synthesis and energy, environmental and biomedical applications

The most common complication for patients with postmenopausal osteoporosis is bone-related defects and fractures. While routine medication has a high probability of undesirable side effects, new approaches have aimed to develop regeneration procedures that stimulate new bone formation while reversing bone loss. Recently, we have synthesized a new hybrid CaP/silk scaffold with a CaP-phase distribution and pore architecture better suited to facilitate cell differentiation and bone formation. The aim of the present study was to compare the involved remodeling process and therapeutic effect of porous CaP/silk composite scaffolds upon local implantation into osteoporotic defects. Wistar rats were used to induce postmenopausal osteoporotic model by bilateral ovariectomy. The pure silk and hybrid CaP/silk scaffolds were implanted into critical sized defects created in distal femoral epiphysis. After 14 and 28 days, the in vivo osteogenetic efficiency was evaluated by μCT analysis, hematoxylin and eosin staining, Safranin O staining, tartrate-resistant acid phosphatase staining, and immunohistochemical assessment. Animals with or without critical-sized defects were used as drill or blank controls, respectively. The osteoporotic defect model was well established with significantly decreased μCT parameters of BV/TV, Tb.N and increased Tb.Sp, porosity, combined with changes in histological observations. During the healing process, the critical-sized drill control defects failed to regenerate appreciable bone tissue, while more significantly increased bone formation and mineralization with dynamic scaffold degradation and decreased osteoclastic bone resorption could be detected within defects with hybrid CaP/silk scaffolds compared to pure silk scaffolds.

Porous CaP/silk composite scaffolds to repair femur defects in an osteoporotic model.

Development of a cell-free scaffold with excellent mechanical properties and osteoconductivity is of significant need for bone regeneration. Herein, a reduced graphene oxide (rGO) functionalized hierarchical macro–mesoporous bioactive glass scaffold integrated with an osteoblast-specific aptamer is rationally designed to recruit and induce the rapid differentiation of osteoblasts for bone regeneration. This scaffold exhibits a macroporous structure with fully interconnected open pores and shows excellent mechanical properties with a Young's modulus of ∼80 kPa, which provides a strong scaffold to support the growth of osteoblasts and bone tissue regeneration. Furthermore, the scaffold displays good performance in accelerating osteoblast differentiation and promoting new bone formation. The osteoblast recruitment is achieved since the osteoblast-specific aptamer can specifically target osteoblasts with strong binding affinity. Micro-computed tomography and histological tests confirmed that the large bone defects fully heal with new plate-like-pattern bone appearing both peripherally and centrally, suggesting the outstanding bone regeneration performance of this cell-free and graphene functionalized scaffold. Considering the promising bioapplications of the graphene functionalized bioactive glass scaffold with osteoblast recruitment capacity, our strategy paves a way for the design of new bioactive functional materials for tissue regeneration and shows attractive prospects in targeted therapy.

A 3D graphene coated bioglass scaffold for bone defect therapy based on the molecular targeting approach

Osteoporosis is a disease characterized by a reduction in bone mass, poor bone strength, and microarchitectural deterioration primarily in postmenopausal women. With respect to periodontal disease, osteoporosis is thought to contribute to pre-existing alveolar degeneration although the association between both diseases is not fully characterized. The aim of the present study was to observe the initial changes in mandibular alveolar bone for sham-operated and ovariectomized (OVX) rats in ligature-induced experimental periodontitis. A total of 64 Wistar rats (7 weeks of age, 180–200 g) were used in this study (32 control sham-operated animals + ligature placement, 32 OVX animals + ligature placement). Following an 8-week period to induce an OVX model, micro-CT analysis was performed to calculate vertical and furcation bone loss of mandibular first molars at time points 0, 3, 7, and 11 days following ligature placement (six animals per group per time point). Furthermore, histological analysis was performed to calculate the loss of alveolar bone crest height from the cemento-enamel junction, and tartrate-resistant acid phosphatase (TRAP) staining was utilized to calculate the number of osteoclasts. The results from the present study demonstrate that OVX animals showed significant vertical bone loss at all time points when compared to control sham-operated animals. In the furcation area, no significant difference in bone loss was observed between sham-operated and OVX animals at 0, 3, and 7 days; however by 11 days, a significant decrease in bone volume/total volume and trabecular thickness was observed in the OVX group. The histological analysis also revealed that alveolar bone crest height was significantly reduced in OVX animals, and TRAP staining further revealed the greater number of multinucleated osteoclasts peaking at 3 days postligature placement. The results from the present study demonstrate a direct correlation between the osteoporotic phenotype and the progression of periodontal breakdown in a diseased-induced animal model. It may be suggested that an osteoporotic phenotype has the potential to speed periodontal breakdown and thus contributes to the overall degeneration of the periodontium in patients suffering from postmenopausal bone loss. Future research from human clinical studies are necessary to further understand the relationship between periodontal disease and osteoporosis.

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Initial changes in alveolar bone volume for sham-operated and ovariectomized rats in ligature-induced experimental periodontitis

Recombinant bone morphogenetic protein two (rhBMP2) has been utilised for a variety of clinical applications in orthopaedic surgery and dental procedures. Despite its widespread use, concerns have been raised regarding its short half-life and transient bioactivity in vivo. Recent investigation aimed at developing rhBMP2 synthesized from a shorter polypeptide chain (108 amino acids) has been undertaken. The osteopromotive properties of BMP2 were investigated on cell behaviour. Five concentrations of rhBMP2_108 including 10, 50, 100, 200 and 500 ng/ml were compared to a commercially available rhBMP2 (100 ng/ml). Each of the working concentrations of rhBMP2_108 were investigated on MC3T3-E1 osteoblasts for their ability to induce osteoblast recruitment, proliferation and differentiation as assessed by alkaline phosphatase (ALP) staining, alizarin red staining, and real-time PCR for genes encoding ALP, osteocalcin (OCN), collagen-1 (COL-1) and Runx2. The results demonstrate that all concentrations of rhBMP2_108 significantly improved cell recruitment and proliferation of osteoblasts at 5 days post seeding. Furthermore, rhBMP2_108 had the most pronounced effects on osteoblast differentiation. It was found that rhBMP2_108 had over a four fold significant increase in ALP activity at seven and 14 days post-seeding and the concentrations ranging from 50 to 200 ng/ml demonstrated the most pronounced effects. Analysis of real-time PCR for genes encoding ALP, OCN, COL-1 and Runx2 further confirmed dose-dependant increases at 14 days post-seeding. Furthermore, alizarin red staining demonstrated a concentration dependant increase in staining at 14 days. The results from the present study demonstrate that this shorter polypeptide chain of rhBMP2_108 is equally as bioactive as commercially available rhBMP2 for the recruitment of progenitor cells by facilitating their differentiation towards the osteoblast lineage. Future in vivo study are necessary to investigate its bioactivity.

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Characterization of a shorter recombinant polypeptide chain of bone morphogenetic protein 2 on osteoblast behaviour

Objectives
The purpose of this study was to evaluate the effect of early functional loading to plateaued implants on bone formation and implant stability in a dog model.

Jing Dai

Papers

Porous CaP/silk composite scaffolds to repair femur defects in an osteoporotic model.

A 3D graphene coated bioglass scaffold for bone defect therapy based on the molecular targeting approach

Initial changes in alveolar bone volume for sham-operated and ovariectomized rats in ligature-induced experimental periodontitis

Characterization of a shorter recombinant polypeptide chain of bone morphogenetic protein 2 on osteoblast behaviour

Effect of decreased implant healing time on bone (re)modeling adjacent to plateaued implants under functional loading in a dog model