Chitosan nanofiber scaffold improves bone healing via stimulating trabecular bone production due to upregulation of the Runx2/osteocalcin/alkaline phosphatase signaling pathway

In vitro/ in vivo evaluation of double crosslinked bone glue with different degrees

Successful bone fragment fixation is a crucial factor in bone fracture healing, the fixation of crushed bone fragments could hinder bone fracture healing. Thus, ideal bone glues to effectively adhere and splice comminuted bone fragments are needed in clinical. Herein, an osteoinductive and biodegradable double cross-linked bone glue (GelMA-oDex-AMBGN) was constructed through Schiff's base reaction between commercial GelMA (with different substitution degrees of amino groups) and Odex mixed with amine-modified mesoporous bioactive glass nanoparticles (AMBGN), followed by crosslink with blue light irradiation. The GelMA-oDex-AMBGN bone glue successfully adhered and spliced the comminuted bone fragments of isolated rat skulls. GelMA-oDex-AMBGN promoted the proliferation of 3T3 cells and enhanced the expression of osteogenic proteins Runx2 and OCN in vitro. In rat cranial critical-sized defect models, GelMA-oDex-AMBGNs with different substitution degrees significantly increased the new bone contents at the fracture defect sites and promoted bone tissue regeneration in vivo. In conclusion, the double cross-linked bone glue (GelMA-oDex-AMBGN) was successfully constructed and can induce bone regeneration. Additionally, there was no significant difference in osteogenic activity among GelMA-oDex-AMBGNs with different substitution degrees and the equal content of AMBGN.

Effects of using collagen and aloe vera grafted fibroin scaffolds on osteogenic differentiation of rat bone marrow mesenchymal stem cells in SBF-enriched cell culture medium

In the study, collagen and aloe vera were grafted onto silk fibroin with two different methods, and 3D-microporous scaffolds (1F5C4A1 and 2F5C4A1) were formed by lyophilization. Three osteogenic cultures were started by seeding rat bone marrow mesenchymal stem cells (MSCs) and pre-induced MSC (osteoblast (OB)) on biopolymeric scaffolds. The osteogenic medium was enriched with 10% (v/v) simulated body fluid (SBF) to promote mineralization and osteogenic differentiation in one of the MSC cultures and the OB culture. X-ray diffraction (XRD), scanning electron microscopy (SEM), scanning electron microscopy- energy dispersive spectrum (SEM-EDS) analyses on cellular samples and histochemical (alizarin red, safranin-O, alcian blue) and immunohistochemical (anti-collagen-1, anti-osteocalcin, anti-osteopontin) staining showed that bone-like mineralization was occurred by both chemically and cellular activity. In addition, pre-osteogenic induction of MSCs in 2D-cultured was found to promote osteogenesis more rapidly when started 3D-cultured. These results indicated that enrichment of the cell culture medium with SBF is sufficient forin vitromineralization rather than using high concentrations of SBF. The findings showed that OB cells on the 2F5C4A1 scaffold obtained the best osteogenic activity. Still, other culture media with 10% SBF content could be used for bone tissue engineering under osteogenic induction.

Mechanobiology-informed biomaterial and tissue engineering strategies for influencing skeletal stem and progenitor cell fate

Skeletal stem and progenitor cells (SSPCs) are the multi-potent, self-renewing cell lineages that form the hematopoietic environment and adventitial structures of the skeletal tissues. Skeletal tissues are responsible for a diverse range of physiological functions because of the extensive differentiation potential of SSPCs. The differentiation fates of SSPCs are shaped by the physical properties of their surrounding microenvironment and the mechanical loading forces exerted on them within the skeletal system. In this context, the present review first highlights important biomolecules involved with the mechanobiology of how SSPCs sense and transduce these physical signals. The review then shifts focus towards how the static and dynamic physical properties of microenvironments direct the biological fates of SSPCs, specifically within biomaterial and tissue engineering systems. Biomaterial constructs possess designable, quantifiable physical properties that enable the growth of cells in controlled physical environments both in-vitro and in-vivo. The utilization of biomaterials in tissue engineering systems provides a valuable platform for controllably directing the fates of SSPCs with physical signals as a tool for mechanobiology investigations and as a template for guiding skeletal tissue regeneration. It is paramount to study this mechanobiology and account for these mechanics-mediated behaviors to develop next-generation tissue engineering therapies that synergistically combine physical and chemical signals to direct cell fate. Ultimately, taking advantage of the evolved mechanobiology of SSPCs with customizable biomaterial constructs presents a powerful method to predictably guide bone and skeletal organ regeneration.

Applications of Chitosan in Surgical and Post-Surgical Materials

The continuous advances in surgical procedures require continuous research regarding materials with surgical applications. Biopolymers are widely studied since they usually provide a biocompatible, biodegradable, and non-toxic material. Among them, chitosan is a promising material for the development of formulations and devices with surgical applications due to its intrinsic bacteriostatic, fungistatic, hemostatic, and analgesic properties. A wide range of products has been manufactured with this polymer, including scaffolds, sponges, hydrogels, meshes, membranes, sutures, fibers, and nanoparticles. The growing interest of researchers in the use of chitosan-based materials for tissue regeneration is obvious due to extensive research in the application of chitosan for the regeneration of bone, nervous tissue, cartilage, and soft tissues. Chitosan can serve as a substance for the administration of cell-growth promoters, as well as a support for cellular growth. Another interesting application of chitosan is hemostasis control, with remarkable results in studies comparing the use of chitosan-based dressings with traditional cotton gauzes. In addition, chitosan-based or chitosan-coated surgical materials provide the formulation with antimicrobial activity that has been highly appreciated not only in dressings but also for surgical sutures or meshes.

bFGF-Loaded Mesoporous Silica Nanoparticles Promote Bone Regeneration Through the Wnt/β-Catenin Signalling Pathway

Background

Bone defects remain an unsolved clinical problem due to the lack of effective osteogenic induction protocols. Nanomaterials play an important role in bone defect repair by stimulating osteogenesis. However, constructing an effective bioactive nanomaterial remains a substantial challenge.

Methods

In this study, mesoporous silica nanoparticles (MSNs) were prepared and used as nanocarriers for basic fibroblast growth factor (bFGF). The characteristics and biological properties of the synthetic bFGF@MSNs were tested. The osteogenic effects of the particles on the behavior of MC3T3-E1 cells were investigated in vitro. In addition, the differentially expressed genes during induction of osteogenesis were analyzed by transcriptomic sequencing. Radiological and histological observations were carried out to determine bone regeneration capability in a distal femur defect model.

Results

Achieving bFGF sustained release, bFGF@MSNs had uniform spherical morphology and good biocompatibility. In vitro osteogenesis induction experiments showed that bFGF@MSNs exhibited excellent osteogenesis performance, with upregulation of osteogenesis-related genes (RUNX2, OCN, Osterix, ALP). Transcriptomic sequencing revealed that the Wnt/β-catenin signalling pathway could be activated in regulation of biological processes. In vivo, bone defect repair experiments showed enhanced bone regeneration, as indicated by radiological and histological analysis, after the application of bFGF@MSNs.

Conclusion

bFGF@MSNs can promote bone regeneration by activating the Wnt/β-catenin signalling pathway. These particles are expected to become a potential therapeutic bioactive material for clinical application in repairing bone defects in the future.

Chitosan-Based Biomaterial Scaffolds for the Repair of Infected Bone Defects

The treatment of infected bone defects includes infection control and repair of the bone defect. The development of biomaterials with anti-infection and osteogenic ability provides a promising strategy for the repair of infected bone defects. Owing to its antibacterial properties, chitosan (an emerging natural polymer) has been widely studied in bone tissue engineering. Moreover, it has been shown that chitosan promotes the adhesion and proliferation of osteoblast-related cells, and can serve as an ideal carrier for bone-promoting substances. In this review, the specific molecular mechanisms underlying the antibacterial effects of chitosan and its ability to promote bone repair are discussed. Furthermore, the properties of several kinds of functionalized chitosan are analyzed and compared with those of pure chitosan. The latest research on the combination of chitosan with different types of functionalized materials and biomolecules for the treatment of infected bone defects is also summarized. Finally, the current shortcomings of chitosan-based biomaterials for the treatment of infected bone defects and future research directions are discussed. This review provides a theoretical basis and advanced design strategies for the use of chitosan-based biomaterials in the treatment of infected bone defects.

CYT387, a JAK-Specific Inhibitor Impedes Osteoclast Activity and Oophorectomy-Induced Osteoporosis via Modulating RANKL and ROS Signaling Pathways

Osteoclasts are of hematopoietic lineage and have the ability to degrade mineralized bone tissues. Abnormalities in osteoclastic activity under certain pathological conditions are common in bone diseases such as osteoporosis, osteosclerosis, and arthritis. Although many kinds of drugs are currently used to treat osteoporosis, they have obvious adverse reactions and limitations. CYT387 is a new small-molecule Janus kinase (JAK) inhibitor involved in hematopoiesis, immune modulation, fertility, lactation, and embryonic development. However, it has remained unclear whether CYT387 functionally impacts osteoclast formation. Our study demonstrated through osteoclast formation assay in vitro, that the use of CYT387 is a potential drug candidate for treating osteoclast-associated bone disease. The effects of CYT387 on osteoclast formation, bone resorption, NFATc1 activation, and especially intracellular ROS levels were investigated in vitro. Further, we examined the preclinical prospects of CYT387 using an oophorectomy (OVX) mouse model of osteoporosis with its anti-osteoclast activity in vivo. On the whole, this study shows that CYT387 holds promise for treating osteoclast-related bone illnesses including osteoporosis.

A Non-thermal Biocompatible Plasma-Modified Chitosan Scaffold Enhances Osteogenic Differentiation in Bone Marrow Stem Cells

Non-thermal biocompatible plasma (NBP) was considered as an efficient tool in tissue engineering to modify the surface of biomaterials. Three-dimensional chitosan scaffolds have been extensively used in different ways because it holds some remarkable properties, including biodegradability and biocompatibility. In this study, we evaluated the osteogenic potential of NBP-treated chitosan scaffolds using two different plasma sources: a dielectric barrier discharge (NBP-DBD) and a soft jet (NBP-J). The surface modification of the scaffold was evaluated using scanning electron microscopy. For osteogenic differentiation of cells, proliferation and differentiation were tested by using bone marrow-derived stem cells (BMSCs). We observed that cell viability using NBP-DBD and NBP-J treated chitosan scaffolds yielded significant improvements in cell viability and differentiation. The results obtained with MTT and live/dead assays showed that NBP-modified scaffold increases cell metabolic by MTT assay and live/dead assay. It also observed that the NBP treatment is more effective at 5 min with DBD and was selected for further investigations. Enhanced osteogenic differentiation was observed using NBP-treated scaffolds, as reflected by increased alkaline phosphatase activity. Our findings showed that NBP is an innovative and beneficial tool for modifying chitosan scaffolds to increase their activity, making them suitable as biocompatible materials and for bone tissue engineering.

Assessment of Mineralization, Oxidative Stress, and Inflammation Mechanisms in the Pulp of Primary Teeth

Inflammation in primary teeth (PT) is commonly associated with a lower sensibility to painful stimuli, compared to permanent teeth, and usually leads to late presentation for dental treatment. Data obtained on the molecular assessments of dental pulp and clinical examinations could guide practitioners to conduct precise diagnoses and correct treatments. The aim of our pilot study was to assess the levels of several biomarkers (e.g., mineralization, oxidative stress, and inflammation) in primary teeth. The research included 46 dental pulp specimens collected from the primary teeth of children and adolescents between the ages of 6 and 12. The experimental groups consisted of 18 samples collected from primary teeth with acute pulpitis and 15 samples from chronically inflamed pulp tissues. The control group was represented by 13 specimens acquired from clinically healthy primary teeth. The enzyme-linked immunosorbent assay (ELISA) technique was used to determine the protein expression of tumor necrosis factor-α (TNF-α), superoxide dismutase-3 (SOD-3), osteocalcin, and transforming growth factor-β1 (TGF-β1) in the lysates. Our results revealed that all of the studied parameters presented statistically significant (p ≤ 0.05) increased levels in both experimental groups compared to the control samples. Furthermore, osteocalcin presented statistically significant increased concentrations in chronically- versus acute-inflamed pulp samples (p ≤ 0.05). The studied molecules may have an influential role in acute and chronic pulp inflammation in primary teeth.

Mineralization in a Critical Size Bone-Gap in Sheep Tibia Improved by a Chitosan-Calcium Phosphate-Based Composite as Compared to Predicate Device

Deacetylated chitin derivatives have been widely studied for tissue engineering purposes. This study aimed to compare the efficacy of an injectable product containing a 50% deacetylated chitin derivative (BoneReg-Inject™) and an existing product (chronOS Inject^®) serving as a predicate device. A sheep model with a critical size drill hole in the tibial plateau was used. Holes of 8 mm diameter and 30 mm length were drilled bilaterally into the proximal area of the tibia and BoneReg-Inject™ or chronOS Inject^® were injected into the right leg holes. Comparison of resorption and bone formation in vivo was made by X-ray micro-CT and histological evaluation after a live phase of 12 weeks. Long-term effects of BoneReg-Inject™ were studied using a 13-month live period. Significant differences were observed in (1) amount of new bone within implant (p < 0.001), higher in BoneReg-Inject^TM, (2) signs of cartilage tissue (p = 0.003), more pronounced in BoneReg-Inject^TM, and (3) signs of fibrous tissue (p < 0.001), less pronounced in BoneReg-Inject^TM. Mineral content at 13 months postoperative was significantly higher than at 12 weeks (p < 0.001 and p < 0.05, for implant core and rim, respectively). The data demonstrate the potential of deacetylated chitin derivatives to stimulate bone formation.

Polycystin-1 Enhances Stemmness Potential of Umbilical Cord Blood-Derived Mesenchymal Stem Cells

Polycystic Kidney Disease (PKD) is a disorder that affects the kidneys and other organs, and its major forms are encoded by polycystin-1 (PC1) and polycystin-2 (PC2), as PKD1 and PKD2. It is located sandwiched inside and outside cell membranes and interacts with other cells. This protein is most active in kidney cells before birth, and PC1 and PC2 work together to help regulate cell proliferation, cell migration, and interactions with other cells. The molecular relationship and the function between PKD1 and cancer is well known, such as increased or decreased cell proliferation and promoting or suppressing cell migration depending on the cancer cell type specifically. However, its function in stem cells has not been revealed. Therefore, in this study, we investigated the biological function of PC1 and umbilical cord blood-derived mesenchymal stem cell (UCB-MSC). Furthermore, we assessed how it affects cell migration, proliferation, and the viability of cells when expressed in the PKD1 gene. In addition, we confirmed in an ex vivo artificial tooth model generated by the three-dimension printing technique that the ability to differentiate into osteocytes improved according to the expression level of the stemness markers when PKD1 was expressed. This study is the first report to examine the biological function of PKD1 in UCB-MSC. This gene may be capable of enhancing differentiation ability and maintaining long-term stemness for the therapeutic use of stem cells.

Stem Cell-Friendly Scaffold Biomaterials: Applications for Bone Tissue Engineering and Regenerative Medicine

Bone is a dynamic organ with high regenerative potential and provides essential biological functions in the body, such as providing body mobility and protection of internal organs, regulating hematopoietic cell homeostasis, and serving as important mineral reservoir. Bone defects, which can be caused by trauma, cancer and bone disorders, pose formidable public health burdens. Even though autologous bone grafts, allografts, or xenografts have been used clinically, repairing large bone defects remains as a significant clinical challenge. Bone tissue engineering (BTE) emerged as a promising solution to overcome the limitations of autografts and allografts. Ideal bone tissue engineering is to induce bone regeneration through the synergistic integration of biomaterial scaffolds, bone progenitor cells, and bone-forming factors. Successful stem cell-based BTE requires a combination of abundant mesenchymal progenitors with osteogenic potential, suitable biofactors to drive osteogenic differentiation, and cell-friendly scaffold biomaterials. Thus, the crux of BTE lies within the use of cell-friendly biomaterials as scaffolds to overcome extensive bone defects. In this review, we focus on the biocompatibility and cell-friendly features of commonly used scaffold materials, including inorganic compound-based ceramics, natural polymers, synthetic polymers, decellularized extracellular matrix, and in many cases, composite scaffolds using the above existing biomaterials. It is conceivable that combinations of bioactive materials, progenitor cells, growth factors, functionalization techniques, and biomimetic scaffold designs, along with 3D bioprinting technology, will unleash a new era of complex BTE scaffolds tailored to patient-specific applications.

Biomimetic and osteogenic 3D silk fibroin composite scaffolds with nano MgO and mineralized hydroxyapatite for bone regeneration

Artificial bioactive materials have received increasing attention worldwide in clinical orthopedics to repair bone defects that are caused by trauma, infections or tumors, especially dedicated to the multifunctional composite effect of materials. In this study, a weakly alkaline, biomimetic and osteogenic, three-dimensional composite scaffold (3DS) with hydroxyapatite (HAp) and nano magnesium oxide (MgO) embedded in fiber (F) of silkworm cocoon and silk fibroin (SF) is evaluated comprehensively for its bone repair potential in vivo and in vitro experiments, particularly focusing on the combined effect between HAp and MgO. Magnesium ions (Mg²⁺) has long been proven to promote bone tissue regeneration, and HAp is provided with osteoconductive properties. Interestingly, the weak alkaline microenvironment from MgO may also be crucial to promote Sprague-Dawley (SD) rat bone mesenchymal stem cells (BMSCs) proliferation, osteogenic differentiation and alkaline phosphatase (ALP) activities. This SF/F/HAp/nano MgO (SFFHM) 3DS with superior biocompatibility and biodegradability has better mechanical properties, BMSCs proliferation ability, osteogenic activity and differentiation potential compared with the scaffolds adding HAp or MgO alone or neither. Similarly, corresponding meaningful results are also demonstrated in a model of distal lateral femoral defect in SD rat. Therefore, we provide a promising 3D composite scaffold for promoting bone regeneration applications in bone tissue engineering.

Genistein Improves Bone Healing via Triggering Estrogen Receptor Alpha-Mediated Expressions of Osteogenesis-Associated Genes and Consequent Maturation of Osteoblasts

Osteoporosis-associated fractures may cause higher morbidity and mortality. Our previous study showed the effects of genistein, a phytoestrogen, on the induction of estrogen receptor alpha (ERα) gene expression and stimulation of osteoblast mineralization. In this study, rat calvarial osteoblasts and an animal bone defect model were used to investigate the effects of genistein on bone healing. Treatment with genistein caused a time-dependent increase in alkaline phosphatase (ALP) activity in rat osteoblasts. Levels of cytosolic and nuclear ERα significantly augmented following exposure to genistein. Subsequently, genistein elevated levels of ALP mRNA and protein in rat osteoblasts. Moreover, genistein induced other osteogenesis-associated osteocalcin and Runx2 mRNA and protein expressions. Knocking-down ERα using RNA interference concurrently inhibited genistein-induced Runx2, osteocalcin, and ALP mRNA expression. Attractively, administration of ICR mice suffering bone defects with genistein caused significant increases in the callus width, chondrocyte proliferation, and ALP synthesis. Results of microcomputed tomography revealed that administration of genistein increased trabecular bone numbers and improved the bone thickness and volume. This study showed that genistein can improve bone healing via triggering ERα-mediated osteogenesis-associated gene expressions and subsequent osteoblast maturation.

The Bradykinin-BDKRB1 Axis Regulates Aquaporin 4 Gene Expression and Consequential Migration and Invasion of Malignant Glioblastoma Cells via a Ca2+-MEK1-ERK1/2-NF-κB Mechanism

Glioblastoma multiforme (GBM) is the most common form of brain tumor and is very aggressive. Rapid migration and invasion of glioblastoma cells are two typical features driving malignance of GBM. Bradykinin functionally prompts calcium influx via activation of bradykinin receptor B1/B2 (BDKRB1/2). In this study, we evaluated the roles of bradykinin in migration and invasion of glioblastoma cells and the possible mechanisms. Expressions of aquaporin 4 (AQP4) mRNA and protein were upregulated in human glioblastomas. Furthermore, exposure of human U87 MG glioblastoma cells to bradykinin specifically increased levels of BDKRB1. Successively, bradykinin stimulated influx of calcium, phosphorylation of MEK1 and extracellular signal-regulated kinase (ERK)1/2, translocation and transactivation of nuclear factor-kappaB (NF-κB), and expressions of AQP4 mRNA and protein. Concomitantly, migration and invasion of human glioblastoma cells were elevated by bradykinin. Knocking-down BDKRB1 concurrently decreased AQP4 mRNA expression and cell migration and invasion. The bradykinin-induced effects were further confirmed in murine GL261 glioblastoma cells. Therefore, bradykinin can induce AQP4 expression and subsequent migration and invasion through BDKRB1-mediated calcium influx and subsequent activation of a MEK1-ERK1/2-NF-κB pathway. The bradykinin-BDKRB1 axis and AQP4 could be precise targets for treating GBM patients.

Crosstalk between chitosan and cell signaling pathways

The field of tissue engineering (TE) experiences its most exciting time in the current decade. Recent progresses in TE have made it able to translate into clinical applications. To regenerate damaged tissues, TE uses biomaterial scaffolds to prepare a suitable backbone for tissue regeneration. It is well proven that the cell-biomaterial crosstalk impacts tremendously on cell biological activities such as differentiation, proliferation, migration, and others. Clarification of exact biological effects and mechanisms of a certain material on various cell types promises to have a profound impact on clinical applications of TE. Chitosan (CS) is one of the most commonly used biomaterials with many promising characteristics such as biocompatibility, antibacterial activity, biodegradability, and others. In this review, we discuss crosstalk between CS and various cell types to provide a roadmap for more effective applications of this polymer for future uses in tissue engineering and regenerative medicine.

Reconstruction of large segmental bone defects in rabbit using the Masquelet technique with α-calcium sulfate hemihydrate

Background

Large segmental bone defects can be repaired using the Masquelet technique in conjunction with autologous cancellous bone (ACB). However, ACB harvesting is severely restricted. α-calcium sulfate hemihydrate (α-CSH) is an outstanding bone substitute due to its easy availability, excellent biocompatibility, biodegradability, and osteoconductivity. However, the resorption rate of α-CSH is too fast to match the rate of new bone formation. The objective of this study was to investigate the bone repair capacity of the Masquelet technique in conjunction with isolated α-CSH or an α-CSH/ACB mix in a rabbit critical-sized defect model.

Methods

The rabbits (n = 28) were randomized into four groups: sham, isolated α-CSH, α-CSH/ACB mix, and isolated ACB group. A 15-mm critical-sized defect was established in the left radius, followed by filling with polymethyl methacrylate spacer. Six weeks after the first operation, the spacers were removed and the membranous tubes were grafted with isolated α-CSH, isolated ACB, α-CSH/ACB mix, or none. Twelve weeks later, the outcomes were evaluated by manual assessment, radiography, and spiral-CT. The histopathological and morphological changes were examined by H&E staining. The levels of alkaline phosphatase and osteocalcin were analyzed by immunohistochemistry and immunofluorescence staining.

Results

Our results suggest that the bone repair capacity of the α-CSH/ACB mix group was similar to the isolated ACB group, while the isolated α-CSH group was significantly decreased compared to the isolated ACB group.

Conclusion

These results highlighted a promising strategy in the healing of large segmental bone defect with the Masquelet technique in conjunction with an α-CSH/ACB mix (1:1, w/w) as they possessed the combined effects of sufficient supply and low resorption.

Bone remodeling effect of a chitosan and calcium phosphate-based composite

Chitosan is a biocompatible polymer that has been widely studied for tissue engineering purposes. The aim of this research was to assess bone regenerative properties of an injectable chitosan and calcium phosphate-based composite and identify optimal degree of deacetylation (%DDA) of the chitosan polymer. Drill holes were generated on the left side of a mandible in Sprague-Dawley rats, and the hole was either left empty or filled with the implant. The animals were sacrificed at several time points after surgery (7–22 days) and bone was investigated using micro-CT and histology. No significant new bone formation was observed in the implants themselves at any time points. However, substantial new bone formation was observed in the rat mandible further away from the drill hole. Morphological changes indicating bone formation were found in specimens explanted on Day 7 in animals that received implant. Similar bone formation pattern was seen in control animals with an empty drill hole at later time points but not to the same extent. A second experiment was performed to examine if the %DDA of the chitosan polymer influenced the bone remodeling response. The results suggest that chitosan polymers with %DDA between 50 and 70% enhance the natural bone remodeling mechanism.

Promotion of osteogenic differentiation by non-thermal biocompatible plasma treated chitosan scaffold

Non-thermal biocompatible plasma (NBP) has recently emerged as an attractive tool for surface modification of biomaterials in tissue engineering. Three dimensional chitosan scaffolds have been widely used in bone tissue engineering due to biodegradable and biocompatible properties. The present study aimed to evaluate osteogenic potential of NBP treated chitosan scaffold. The surface characteristics of scaffolds were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD), cell proliferation and differentiation was tested with osteoprogenitor cell line MC3T3-E1. The results show that NBP modified scaffold increase cell metabolic by MTT assay and live/dead assay. More importantly, we evidenced enhancement of osteogenic differentiation on NBP treated scaffolds by an increase of alkaline phosphatase (ALP) activity, high degree of extracellular mineralization and up-regulated osteogenic marker genes expression level. The findings in our study highlighted NBP as the innovative method to modified chitosan scaffold and to fine-tuning the scaffold a more suitable and beneficial biomaterial for in vivo bone tissue engineering and clinical bone defects therapies.

Electrospun PCL/mupirocin and chitosan/lidocaine hydrochloride multifunctional double layer nanofibrous scaffolds for wound dressing applications

Background

An ideal wound dressing should exhibit good biocompatibility, minimize pain and infection, absorb excess exudates, and maintain a moist environment. However, few clinical products meet all these needs. Therefore, the aim of this study was to fabricate a multifunctional double layer nanofibrous scaffolds (DLS) as a potential material for wound dressing.

Materials and methods

The scaffold was formed from mupirocin and lidocaine hydrochloride homogeneously incorporated into polycaprolactone as the first layer of scaffolds and chitosan as the second layer of scaffolds nanofibers through electrospinning. The fabricated nanofibrous scaffolds were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and measurement of swelling ratio, contact angle, drug release, and mechanical properties. Furthermore, antibacterial assessment, live/dead cell assays, and MTT assays were used to investigate the antibacterial activity and cytotoxicity of the nanofibrous scaffolds.

Results

The morphology of the nanofibrous scaffolds was studied by scanning electron microscopy, showing successful nanofibrous scaffolds. Fourier transform infrared spectroscopy demonstrated the successful incorporation of the material used to produce the produced nanofibrous scaffolds. Thermal studies with thermogravimetric analysis and differential scanning calorimetry indicated that the DLS had high thermal stability. The DLS also showed good in vitro characteristics in terms of improved swelling ratio and contact angle. The mechanical results revealed that the DLS had an improved tensile strength of 3.88 MPa compared with the second layer of scaffold (2.81 MPa). The release of drugs from the scaffold showed different profiles for the two drugs. Lidocaine hydrochlo ride exhibited an initial burst release (66% release within an hour); however, mupirocin exhibited only a 5% release. Furthermore, the DLS nanofibers displayed highly effective antibacterial activities against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa and were nontoxic to fibroblasts.

Conclusion

The fabricated DLS exhibited excellent hydrophilicity, cytocompatibility, sustained drug release, and antibacterial activity, which are favorable qualities for its use as a multifunctional material for wound dressing applications.

The therapeutic effect of miR-125b is enhanced by the prostaglandin endoperoxide synthase 2/cyclooxygenase 2 blockade and hampers ETS1 in the context of the microenvironment of bone metastasis

Bone is the most common site for breast cancer spread. In the pro-metastatic cell line 1833, derived from MDA-MB-231 breast adenocarcinoma cells, both hypoxia and hepatocyte growth factor (HGF) influence the effect of miR-125b on ETS proto-oncogene 1 transcription factor (ETS1). The effect of hypoxia inducible factor 1 alpha subunit (HIF1A), known to promote metastatic spread by upregulating prostaglandin endoperoxide synthase 2 (PTGS2), may be dampened by miR-125b targeting PTGS2. Here, we investigated whether miR-125b plays a role in breast cancer metastasis by measuring its activity in response to the chemotherapeutic agent NS-398 in a xenograft model. NS-398 is typically used in the clinic to target PTGS2. We also aimed to describe the molecular mechanisms in vitro, since the enhancement of epithelial properties may favor the efficacy of therapies. We report that in the xenograft model, miR-125b reduced metastasis to the bone. We also report suppression of PTGS2 enhanced survival by decreasing HIF1A in cells within the bone marrow. In 1833 cells transfected with a miR-125b mimic we observed several phenotypic changes including enhancement of the epithelial marker E-cadherin, a reduction of mesenchymal-associated genes and a reduction of WNT-associated stem cell signaling. Our findings suggest that in vivo, key players of the bone microenvironment promoting breast cancer spread are regulated by miR-125b. In future, biological molecules imitating miR-125b may enhance the sensitivity of chemotherapeutic agents used to counteract bone metastases.

Estrogen/ERα signaling axis participates in osteoblast maturation via upregulating chromosomal and mitochondrial complex gene expressions

Estrogen deficiency usually leads to bone loss and osteoporosis in postmenopausal women. Osteoblasts play crucial roles in bone formation. However, osteoblast functions are influenced by mitochondrial bioenergetic conditions. In this study, we investigated the roles of the estrogen and estrogen receptor alpha (ERα) axis in mitochondrial energy metabolism and subsequent osteoblast mineralization. Exposure of rat calvarial osteoblasts to estradiol caused substantial improvements in alkaline phosphatase activities and cell calcification. In parallel, treatment of human osteoblast-like U2OS cells, derived from a female osteosarcoma patient, with estradiol specifically augmented ERα levels. Sequentially, estradiol stimulated translocation of ERα to nuclei in human osteoblasts and induced expressions of genomic respiratory chain complex NDUFA10, UQCRC1, cytochrome c oxidase (COX)8A, COX6A2, COX8C, COX6C, COX6B2, COX412, and ATP12A genes. Concurrently, estradiol stimulated translocation of ERα to mitochondria from the cytoplasm. A bioinformatic search found the existence of four estrogen response elements in the 5’-promoter region of the mitochondrial cox i gene. Interestingly, estradiol induced COX I mRNA and protein expressions in human osteoblasts or rat calvarial osteoblasts. Knocking-down ERα translation concurrently downregulated estradiol-induced COX I mRNA expression. Consequently, exposure to estradiol led to successive increases in the mitochondrial membrane potential, the mitochondrial enzyme activity, and cellular adenosine triphosphate levels. Taken together, this study showed the roles of the estradiol/ERα signaling axis in improving osteoblast maturation through upregulating the mitochondrial bioenergetic system due to induction of definite chromosomal and mitochondrial complex gene expressions. Our results provide novel insights elucidating the roles of the estrogen/ERα alliance in regulating bone formation.

Participation of GATA-3 in regulation of bone healing through transcriptional upregulation of bcl-xL expression

We have previously demonstrated the expression of GATA-DNA-binding protein (GATA)-3, a transcription factor, in osteoblasts and have verified its function in transducing cell survival signaling. This translational study was further designed to evaluate the roles of GATA-3 in regulating bone healing and to explore its possible mechanisms. A metaphyseal bone defect was created in the left femurs of male ICR mice. Analysis by micro-computed topography showed that the bone volume, trabecular bone number and trabecular thickness were augmented and that the trabecular pattern factor decreased. Interestingly, immunohistological analyses showed specific expression of GATA-3 in the defect area. In addition, colocalized expression of GATA-3 and alkaline phosphatase was observed at the wound site. As the fracture healed, the amounts of phosphorylated and non-phosphorylated GATA-3 concurrently increased. Separately, GATA-3 mRNA was induced during bone healing, and, levels of Runx2 mRNA and protein were also increased. The results of confocal microscopy and co-immunoprecipitation showed an association between nuclear GATA-3 and Runx2 in the area of insult. In parallel with fracture healing, Bcl-XL mRNA was significantly triggered. A bioinformatic search revealed the existence of a GATA-3-specific DNA-binding element in the promoter region of the bcl-xL gene. Analysis by chromatin immunoprecipitation assays further demonstrated transactivation activity by which GATA-3 regulated bcl-xL gene expression. Therefore, this study shows that GATA-3 participates in the healing of bone fractures via regulating bcl-xL gene expression, owing to its association with Runx2. In the clinic, GATA-3 may be used as a biomarker for diagnoses/prognoses or as a therapeutic target for bone diseases, such as bone fractures.

PDGF-metronidazole-encapsulated nanofibrous functional layers on collagen membrane promote alveolar ridge regeneration

This study aimed to develop a functionally graded membrane (FGM) to prevent infection and promote tissue regeneration. Poly(l-lactide-co-d,l-lactide) encapsulating platelet-derived growth factor (PDLLA-PDGF) or metronidazole (PDLLA-MTZ) was electrospun to form a nanofibrous layer on the inner or outer surface of a clinically available collagen membrane, respectively. The membrane was characterized for the morphology, molecule release profile, in vitro and in vivo biocompatibility, and preclinical efficiency for alveolar ridge regeneration. The PDLLA-MTZ and PDLLA-PDGF nanofibers were 800–900 nm in diameter, and the thicknesses of the functional layers were 20–30 μm, with sustained molecule release over 28 days. All of the membranes tested were compatible with cell survival in vitro and showed good tissue integration with minimal fibrous capsule formation or inflammation. Cell proliferation was especially prominent on the PDLLA-PDGF layer in vivo. On the alveolar ridge, all FGMs reduced wound dehiscence compared with the control collagen membrane, and the FGM with PDLLA-PDGF promoted osteogenesis significantly. In conclusion, the FGMs with PDLLA-PDGF and PDLLA-MTZ showed high biocompatibility and facilitated wound healing compared with conventional membrane, and the FGM with PDLLA-PDGF enhanced alveolar ridge regeneration in vivo. The design represents a beneficial modification, which may be easily adapted for future clinical use.

Local application of osteoprotegerin-chitosan gel in critical-sized defects in a rabbit model

BACKGROUND

Osteoprotegerin (OPG) is used for the systemic treatment of bone diseases, although it has many side effects. The aim of this study was to investigate a newly formulated OPG-chitosan gel for local application to repair bone defects. Recent studies have reported that immunodetection of osteopontin (OPN) and osteocalcin (OC) can be used to characterise osteogenesis and new bone formation.

METHODS

The osteogenic potential of the OPG-chitosan gel was evaluated in rabbits. Critical-sized defects were created in the calvarial bone, which were either left unfilled (control; group I), or filled with chitosan gel (group II) or OPG-chitosan gel (group III), with rabbits sacrificed at 6 and 12 weeks. Bone samples from the surgical area were decalcified and treated with routine histological and immunohistochemical protocols using OC, OPN, and cathepsin K (osteoclast marker) antibodies. The toxicity of the OPG-chitosan gel was evaluated by biochemical assays (liver and kidney function tests).

RESULTS

The mean bone growth in defects filled with the OPG-chitosan gel was significantly higher than those filled with the chitosan gel or the unfilled group (p < 0.05). At 6 and 12 weeks, the highest levels of OC and OPN markers were found in the OPG-chitosan gel group, followed by the chitosan gel group. The number of osteoclasts in the OPG-chitosan gel group was lower than the other groups. The results of the liver and kidney functional tests indicated no signs of harmful systemic effects of treatment. In conclusion, the OPG-chitosan gel has many characteristics that make it suitable for bone repair and regeneration, highlighting its potential benefits for tissue engineering applications.

The Regulatory Roles of MicroRNAs in Bone Remodeling and Perspectives as Biomarkers in Osteoporosis

MicroRNAs are involved in many cellular and molecular activities and played important roles in many biological and pathological processes, such as tissue formation, cancer development, diabetes, neurodegenerative diseases, and cardiovascular diseases. Recently, it has been reported that microRNAs can modulate the differentiation and activities of osteoblasts and osteoclasts, the key cells that are involved in bone remodeling process. Meanwhile, the results from our and other research groups showed that the expression profiles of microRNAs in the serum and bone tissues are significantly different in postmenopausal women with or without fractures compared to the control. Therefore, it can be postulated that microRNAs might play important roles in bone remodeling and that they are very likely to be involved in the pathological process of postmenopausal osteoporosis. In this review, we will present the updated research on the regulatory roles of microRNAs in osteoblasts and osteoclasts and the expression profiles of microRNAs in osteoporosis and osteoporotic fracture patients. The perspective of serum microRNAs as novel biomarkers in bone loss disorders such as osteoporosis has also been discussed.