A Combinatorial effect of carboxymethyl cellulose based scaffold and microRNA-15b on osteoblast differentiation

Study on the Effects of Low-Intensity Pulsed Ultrasound and Iron Ions for Proliferation and Differentiation of Osteoblasts

OBJECTIVE

This study involved the proliferation and differentiation of osteoblasts treated with low-intensity pulsed ultrasound (LIPUS) and iron (Fe3+) ions, respectively. The biological effects of LIPUS and Fe3+ ions on the proliferation and differentiation of osteoblasts were also evaluated.

METHODS

MC3T3-E1 cells were seeded in six-well plates with the medium, which contained different concentrations of Fe3+ (0, 100, 200, 300, 400, 500, 600 and 700 μg L-1, respectively). LIPUS treatment was directed at the bottom of the plate for 20 min at an intensity of 80 mW cm-2 every day.

RESULTS

Viability results showed that a dose of 400 μg L-1 Fe3+ ions had the best effect at promoting osteogenic proliferation in cell culture. The results of alkaline phosphatase staining and mineralization indicated that the differentiation of osteoblasts was promoted by LIPUS and Fe3+ ions. Fluorescence staining results showed that the number of cell nuclei in the LIPUS, Fe3+ and LIPUS-Fe groups increased by 37.20%, 55.81% and 89.76%, respectively. Migration data indicated that migration and proliferation rates were increased by LIPUS and Fe3+, and the results of protein expression indicated that LIPUS and Fe3+ may increase the expression of Wnt, β-catenin, and Runx2, hence promoting normal bone regeneration and development.

CONCLUSION

The combination of LIPUS (1.5 MHz, 80 mW cm-2) and Fe3+ accelerates the proliferation and differentiation of osteoblasts significantly compared with single-factor treatment (stimulated by LIPUS and Fe3+ ions, respectively). This study could establish a foundation for LIPUS-responsive biomaterials in the repair and regeneration of bone tissues.

MicroRNA-15b promotes cardiac ischemia injury by the inhibition of Mitofusin 2/PERK pathway

MicroRNA and mitofusin-2 (Mfn2) play an important role in the myocardial apoptosis induced by acute myocardial infarction (AMI). However, the target relationship and underlying mechanism associated with interorganelle interaction between endoplasmic reticulum (ER) and mitochondria under ischemic condition is not completely clear. MI-induced injury, Mfn2 expression, Mfn2-mediated mitochondrial function and ER stress, and target regulation by miRNA-15b (miR-15b) were evaluated by animal MI and cellular hypoxic models with advanced molecular techniques. The results confirmed that Mfn2 was down-regulated and miR-15b was up-regulated upon the target binding profile under ischemic/hypoxic condition. Our data showed that miR-15b caused cardiac apoptotic injury that was reversed by rAAV9-anti-miR-15b or AMO-15b. The damage effect of miR-15b on Mfn2 expression and mitochondrial function was observed and rescued by rAAV9-anti-miR-15b or AMO-15b. The targeted regulation of miR-15b on Mfn2 was verified by luciferase reporter and microRNA-masking. Importantly, miR-15b-mediated Mfn2 suppression activated PERK/CHOP pathway, by which leads to ER stress and mitochondrial dysfunction, and cardiac apoptosis eventually. In conclusion, our research, for the first time, revealed the missing molecular link in Mfn2 and apoptosis and elucidated that pro-apoptotic miR-15b plays crucial roles during the pathogenesis of AMI through down-regulation of Mfn2 and activation of PERK-mediated ER stress. These findings may provide an opportunity to develop new therapies for prophylaxis and treatment of ischemic heart disease.

Cross Talk Between Cells and the Current Bioceramics in Bone Regeneration: A Comprehensive Review

The conventional approach for addressing bone defects and stubborn non-unions typically involves the use of autogenous bone grafts. Nevertheless, obtaining these grafts can be challenging, and the procedure can lead to significant morbidity. Three primary treatment strategies for managing bone defects and non-unions prove resistant to conventional treatments: synthetic bone graft substitutes (BGS), a combination of BGS with bioactive molecules, and the use of BGS in conjunction with stem cells. In the realm of synthetic BGS, a multitude of biomaterials have emerged for creating scaffolds in bone tissue engineering (TE). These materials encompass biometals like titanium, iron, magnesium, and zinc, as well as bioceramics such as hydroxyapatite (HA) and tricalcium phosphate (TCP). Bone TE scaffolds serve as temporary implants, fostering tissue ingrowth and the regeneration of new bone. They are meticulously designed to enhance bone healing by optimizing geometric, mechanical, and biological properties. These scaffolds undergo continual remodeling facilitated by bone cells like osteoblasts and osteoclasts. Through various signaling pathways, stem cells and bone cells work together to regulate bone regeneration when a portion of bone is damaged or deformed. By targeting signaling pathways, bone TE can improve bone defects through effective therapies. This review provided insights into the interplay between cells and the current state of bioceramics in the context of bone regeneration.

Effects of miRNAs, lncRNAs and circRNAs on osteoporosis as regulatory factors of bone homeostasis (Review)

Osteoporosis is a common metabolic bone disorder typically characterized by decreased bone mass and an increased risk of fracture. At present, the detailed molecular mechanism underlying the development of osteoporosis remains to be elucidated. Accumulating evidence shows that non-coding (nc)RNAs, such as microRNAs (miRNAs), long ncRNAs (lncRNAs) and circular RNAs (circRNAs), play significant roles in osteoporosis through the post-transcriptional regulation of gene expression as regulatory factors. Previous studies have demonstrated that ncRNAs participate in maintaining bone homeostasis by regulating physiological and developmental processes in osteoblasts, osteoclasts and bone marrow stromal cells. In the present review, the latest research investigating the involvement of miRNAs, lncRNAs and circRNAs in regulating the differentiation, proliferation, apoptosis and autophagy of cells that maintain the bone microenvironment in osteoporosis is summarized. Deeper insight into the aspects of osteoporosis pathogenesis involving the deregulation of ncRNAs could facilitate the development of therapeutic approaches for osteoporosis.

Bioactive Zinc(II) complex incorporated PCL/gelatin electrospun nanofiber enhanced bone tissue regeneration

Bone tissue regeneration is augmented by biocompatible nanofiber scaffolds, that supports reliable and enhanced bone formation. Zinc is an essential mineral that is vital for routine skeletal growth and it emerges to be able to improve bone regeneration. Phytochemicals, particularly flavonoids have achieved prominent interest for their therapeutic ability, they have demonstrated promising effects on bone by encouraging osteoblastogenesis, which finally leads to bone formation. In this study, we have synthesized bioactive zinc(II) quercetin complex material and used for nanofibers scaffold fabrication to enhance bone tissue regeneration property. Two derivatives of zinc(II) quercetin complexes [(Zn(quercetin) (H₂O)₂) (Zn+Q), and Zn(quercetin)(phenanthroline) (Zn+Q(PHt)) have been synthesized and characterized using UV-Visible spectrophotometer and Fourier Transform-IR spectroscopy. The UV-Visible absorption and IR spectra prove the B-ring chelation of the flavonoid quercetin to zinc(II) rather C-ring chelation. The potential ability of the above synthesized metal complexes on osteogenesis and angiogenesis have been studied. Besides the bioactivity of the metal complexes, the control quercetin has also been examined. The chick embryo chorioallantoic membrane (CAM) assay demonstrated that the angiogenic parameters were increased by the (Zn+Q(PHt)) complex. Amongst, (Zn+Q(PHt)) complex showed significant activity and thereby this complex has been further examined for the bone tissue activity by incorporating the complex into a nanofiber through electrospinning method. At the molecular level, Runx2, mRNA and protein, ALP and type 1 collagen mRNAs, and osteoblast-specific microRNA, pre-mir-15b were examined using real time RT-PCR and Western blot assay. Histology studies showed that the (PCL/gelatin/Zn+Q(PHt)) was biocompatibility in-ovo. Overall, the present study showed that quercetin-zinc complex (Zn+Q(PHt)) incorporated into PCL/gelatin nanofiber can act as a pharmacological agent for treating bone associated defects and promote bone regeneration.

The miRNA-15b/USP7/KDM6B axis engages in the initiation of osteoporosis by modulating osteoblast differentiation and autophagy

Osteoporosis is a metabolic disease that results from oxidative stress or inflammation in renal disorders. microRNAs (miRNAs) are recently implicated to participate in osteoporosis, but the mechanism remains largely unexplored. Herein, we aimed to explore the potential role of miR-15b in osteoblast differentiation and autophagy in osteoporosis. We established osteoporosis models through ovariectomy and determined that miR-15b was highly expressed whereas USP7 and KDM6B were poorly expressed in tissue of osteoporosis mice. Treatment of silenced miR-15b resulted in the elevation of decreased bone mineral density (BMD), the maximum elastic stress and the maximum load of osteoporosis mice. In osteoblasts, miR-15 overexpression decreased proliferation but suppressed the cell differentiation and autophagy, accompanied with decreased expression of USP7. Mechanistically, miR-15 bound and inhibited USP7 expression, while overexpression of USP7 promoted autophagy of osteoblasts. USP7, importantly, strengthened the stability of KDM6B and promoted KDM6B expression. MG132 protease inhibitor increased KDM6B and USP7 expression in osteoblasts. Silencing of KDM6B reversed the promoting effect on autophagy and proliferation induced by overexpression of USP7. Taken altogether, miR-15b inhibits osteoblast differentiation and autophagy to aggravate osteoporosis by targeting USP7 to regulate KDM6B expression.

In Vitro and In Vivo Evaluation of Carboxymethyl Cellulose Scaffolds for Bone Tissue Engineering Applications

The present study involves the development of citric acid-cross-linked carboxymethyl cellulose (C3CA) scaffolds by a freeze-drying process. Scaffolds were fabricated at different freezing temperatures of -20, -40, or -80 °C to investigate the influence of scaffold pore size on bone regeneration. All three scaffolds were porous in structure, and the pore size was measured to be 74 ± 4, 55 ± 6, and 46 ± 5 μm for -20, -40, and -80 °C scaffolds. The pores were larger in scaffolds processed at -20 °C compared to -40 and -80 °C, indicating the reduction in pore size of the scaffolds with a decrease in freezing temperature. The cytocompatibility, cell proliferation, and differentiation in C3CA scaffolds were assessed with the Saos-2 osteoblast cell line. These scaffolds supported the proliferation and differentiation of Saos-2 cells with significant matrix mineralization in scaffolds processed at -40 °C. Subcutaneous implantation of C3CA scaffolds in the rat model was investigated for its ability of vascularization and new matrix tissue formation. The matrix formation was observed at the earliest of 14 days in the scaffolds when processed at -40 °C while it was observed only after 28 days of implantation with the scaffolds processed at -20 and -80 °C. These results suggest that the citric acid-cross-linked CMC scaffolds processed at -40 °C can be promising for bone tissue engineering application.

A simple approach to prepare self-assembled, nacre-inspired clay/polymer nanocomposites

Inspired by the relationship between the well-ordered architecture of aragonite crystals and biopolymers found in natural nacre, we present a facile strategy to construct large-scale organic/inorganic nacre-mimetics with hierarchical structure via a water-evaporation driven self-assembly process. We connect LAPONITE®-nanoclay platelets with each other using carboxymethyl cellulose, a cellulose derivative, thus creating thin, flexible films with a local brick-and-mortar architecture. The dried films show a pronounced resistance against tensile forces allowing for stronger thin films than nacre. In terms of functionalities, we report excellent glass-like transparency along with exceptional shape-persistent flame shielding. We also demonstrate that through metal ion-coordination we can further strengthen the interactions between the polymers and the nanoclays, and thus enhanced mechanical, and thermal properties as well as resistance against swelling and dissolution in aqueous environments. We believe that our simple pathway to fabricate such versatile polymer/clay nanocomposites can open avenues for inexpensive production of environmentally friendly, biomimetic materials in aerospace, wearable electrical devices, and in the food packaging industry.

Alkaline phosphatase: Structure, expression and its function in bone mineralization

Alkaline phosphatase (ALP) is highly expressed in the cells of mineralized tissue and plays a critical function in the formation of hard tissue. The existing status of this critical enzyme should be reviewed periodically. ALP increases inorganic phosphate local rates and facilitates mineralization as well as reduces the extracellular pyrophosphate concentration, an inhibitor of mineral formation. Mineralization is the production, inside matrix vesicles, of hydroxyapatite crystals that bud from the outermembrane of hypertrophic osteoblasts and chondrocytes. The expansion of hydroxyapatite formsinto the extracellular matrix and its accumulation between collagen fibrils is observed. Among various isoforms, the tissue-nonspecific isozyme of ALP (TNAP) is strongly expressed in bone, liver and kidney and plays a key function in the calcification of bones. TNAP hydrolyzes pyrophosphate and supplies inorganic phosphate to enhance mineralization. The biochemical substrates of TNAP are believed to be inorganic pyrophosphate and pyridoxal phosphate. These substrates concentrate in TNAP deficient condition which results in hypophosphatasia. The increased level of ALP expression and development in this environment would undoubtedly provide new and essential information about the fundamental molecular mechanisms of bone formation, offer therapeutic possibilities for the management of bone-related diseases.

Effect of simulated microgravity and ionizing radiation on expression profiles of miRNA, lncRNA, and mRNA in human lymphoblastoid cells

In space, multiple unique environmental factors, particularly microgravity and space radiation, pose a constant threat to astronaut health. MicroRNAs (miRNAs) and long noncoding RNAs (lncRNAs) are functional RNAs that play critical roles in regulating multiple cellular processes. To gain insight into the role of non-coding RNAs in response to radiation and microgravity, we analyzed RNA expression profiles in human lymphoblastoid TK6 cells incubated for 24 h under static or rotating conditions to stimulate microgravity in space, after 2-Gy γ-ray irradiation. The expression of 14 lncRNAs and 17 mRNAs (differentially-expressed genes, DEGs) was found to be significantly downregulated under simulated microgravity conditions. In contrast, irradiation upregulated 55 lncRNAs and 56 DEGs, whereas only one lncRNA, but no DEGs, was downregulated. Furthermore, two miRNAs, 70 lncRNAs, and 87 DEGs showed significantly altered expression in response to simulated microgravity after irradiation, and these changes were independently induced by irradiation and simulated microgravity. GO enrichment and KEGG pathway analyses indicated that the associated target genes showed similar patterns to the noncoding RNAs and were suggested to be involved in the immune/inflammatory response including LPS/TLR, TNF, and NF-κB signaling pathways. However, synergistic effects on RNA expression and cellular responses were also observed with a combination of simulated microgravity and irradiation based on microarray and RT-PCR analysis. Together, our results indicate that simulated microgravity and irradiation additively alter expression patterns but synergistically modulate the expression levels of RNAs and their target genes in human lymphoblastoid cells.

Comprehensive In Vitro Testing of Calcium Phosphate-Based Bioceramics with Orthopedic and Dentistry Applications

Recently, a large spectrum of biomaterials emerged, with emphasis on various pure, blended, or doped calcium phosphates (CaPs). Although basic cytocompatibility testing protocols are referred by International Organization for Standardization (ISO) 10993 (parts 1-22), rigorous in vitro testing using cutting-edge technologies should be carried out in order to fully understand the behavior of various biomaterials (whether in bulk or low-dimensional object form) and to better gauge their outcome when implanted. In this review, current molecular techniques are assessed for the in-depth characterization of angiogenic potential, osteogenic capability, and the modulation of oxidative stress and inflammation properties of CaPs and their cation- and/or anion-substituted derivatives. Using such techniques, mechanisms of action of these compounds can be deciphered, highlighting the signaling pathway activation, cross-talk, and modulation by microRNA expression, which in turn can safely pave the road toward a better filtering of the truly functional, application-ready innovative therapeutic bioceramic-based solutions.

Regulation of Runx2 by MicroRNAs in osteoblast differentiation

Bone is one of the most dynamic organs in the body that continuously undergoes remodeling through bone formation and resorption. A cascade of molecules and pathways results in the osteoblast differentiation that is attributed to osteogenesis, or bone formation. The process of osteogenesis is achieved through participation of the Wnt pathway, FGFs, BMPs/TGF-β, and transcription factors such as Runx2 and Osx. The activity and function of the master transcription factor, Runx2, is of utmost significance as it can induce the function of osteoblast differentiation markers. A number of microRNAs [miRNAs] have been recently identified in the regulation of Runx2 expression/activity, thus affecting the process of osteogenesis. miRNAs that target Runx2 corepressors favor osteogenesis, while miRNAs that target Runx2 coactivators inhibit osteogenesis. In this review, we focus on the regulation of Runx2 by miRNAs in osteoblast differentiation and their potential for treating bone and bone-related diseases.

The Application of microRNAs in Biomaterial Scaffold-Based Therapies for Bone Tissue Engineering

In recent years, the application of microRNAs (miRNAs) or anti-microRNAs (anti-miRNAs) that can induce expression of the runt-related transcription factor 2 (RUNX2), a master regulator of osteogenesis, has been investigated as a promising alternative bone tissue engineering strategy. In this review, biomaterial scaffold-based applications that have been used to deliver cells expressing miRNAs or anti-miRNAs that induce expression of RUNX2 for bone tissue engineering are discussed. An overview of the components of the scaffold-based therapies including the miRNAs/anti-miRNAs, cell types, gene delivery vectors, and scaffolds that have been applied are provided. To date, there have been nine miRNAs/anti-miRNAs (i.e., miRNA-26a, anti-miRNA-31, anti-miRNA-34a, miRNA-135, anti-miRNA-138, anti-miRNA-146a, miRNA-148b, anti-miRNA-221, and anti-miRNA-335) that have been incorporated into scaffold-based bone tissue engineering applications and investigated in an in vivo bone critical-sized defect model. For all of the biomaterial scaffold-based miRNA therapies that have been developed thus far, cells that are transfected or transduced with the miRNA/anti-miRNA are loaded into the scaffolds and implanted at the site of interest instead of locally delivering the miRNA/anti-miRNAs directly from the scaffolds. Thus, future work may focus on developing biomaterial scaffolds to deliver miRNAs or anti-miRNAs into cells in vivo.

Syringic acid, a phenolic acid, promotes osteoblast differentiation by stimulation of Runx2 expression and targeting of Smad7 by miR-21 in mouse mesenchymal stem cells

Syringic acid (SA), a phenolic acid, has been used in Chinese and Indian medicine for treating diabetes but its role in osteogenesis has not yet been investigated. In the present study, at the molecular and cellular levels, we evaluated the effects of SA on osteoblast differentiation. At the cellular level, there was increased alkaline phosphatase (ALP) activity and calcium deposition by SA treatment in mouse mesenchymal stem cells (mMSCs). At the molecular level, SA treatment of these cells stimulated expression of Runx2, a bone transcription factor, and of osteoblast differentiation marker genes such as ALP, type I collagen, and osteocalcin. It is known that Smad7 is an antagonist of TGF-β/Smad signaling and is a negative regulator of Runx2. microRNAs (miRNAs) play a key role in the regulation of osteogenesis genes at the post-transcriptional level and studies have reported that Smad7 is one of the target genes of miR-21. We found that there was down regulation of Smad7 and up regulation of miR-21 in SA-treated mMSCs. We further identified that the 3'-untranslated region (UTR) of Smad7 was directly targeted by miR-21 in these cells. Thus, our results suggested that SA promotes osteoblast differentiation via increased expression of Runx2 by miR-21-mediated down regulation of Smad7. Hence, SA may have potential in orthopedic applications.

Chitosan based thermoresponsive hydrogel containing graphene oxide for bone tissue repair

Chitosan (CS), glycerophosphate (GP) based injectable hydrogels are explored for its implications in bone defect healing and regeneration. Both acellular and cell laden CS based hydrogels are widely investigated and improved through the inclusion of various nanoparticles, polymers and bioactive molecules. In order to improve its applicability for bone tissue repair, we developed an injectable, thermosensitive CS hydrogel containing graphene oxide (GO) and investigated its properties. The hydrogels were investigated for its porous architecture using scanning electron microscopy (SEM), swelling property, protein adsorption ability, degradation rate and exogenous biomineralization. GO addition improved the physico-chemical properties with notable betterment. The CS/GP/GO hydrogel was biocompatible to mesenchymal stem cells and they were metabolically active upon encapsulation. The hydrogel promoted osteogenic differentiation of mouse mesenchymal stem cells by upregualtion of Runt-related transcription factor 2 (Runx2), Alkaline phosphatase (ALP), Type -1 collagen (COL-1), and osteocalcin (OC) under osteogenic conditions. The hydrogel proves to be an amenable platform for carrying cells and exhibited suitable properties to be a potential candidate for bone tissue regeneration.

Biogenic gold nanoparticles synthesis mediated by Mangifera indica seed aqueous extracts exhibits antibacterial, anticancer and anti-angiogenic properties

During the last few decades, gold nanoparticles (AuNP's) have gained considerable attention in nanomedicine and expanded its application in clinical diagnosis and as therapeutics. Employing plant extract for synthesising gold nanoparticles proves to be an eco-friendly technology for large scale production. It is highly economical and suitable for biological applications by negating the use of chemicals involved in conventional route. In this study, AuNP's was prepared by a simple one step method of employing aqueous Mangifera indica seed extract as a reducing agent. Scanning electron microscopy and transmission electron microscopy revealed spherical shaped nanoparticles and dynamic light scattering analysis indicated the AuNP's to be approximately 46.8 nm in size. AuNP's efficiently inhibited the growth of E. coli and S. aureus by its inherent ability to generate reactive oxygen species (ROS) and exhibited detrimental effects towards the tested bacterial species. Biocompatibility assessment indicated the non-toxic nature of AuNP's towards mesenchymal stem cells at 25 μg/ml and interestingly, suppressed the growth of human gastric cancer cells under in vitro culture conditions. AuNP's significantly exhibited anti-angiogenic property in chick chorioallantoic membrane model (CAM) by downregulating Ang-1/Tie2 pathway. Overall, the synthesized AuNP's exhibited antibacterial and anti-angiogenic properties with high biocompatibility thereby supporting its candidature for various biomedical applications. It can be employed in suppressing tumor growth, combat inflammatory diseases that necessitate the involvement of angiogenesis suppression, and antibacterial activity is suitable for its clinical translation to negate surgery associated infections.

Chitosan/nano-hydroxyapatite/nano-zirconium dioxide scaffolds with miR-590-5p for bone regeneration

Bone tissue engineering (BTE) relies on biocomposite scaffolds and bioactive molecules for bone regeneration. The present study was aimed to synthesize and characterize biocomposite scaffolds containing chitosan (CS), nano-hydroxyapatite (nHAp) and nano‑zirconium dioxide (nZrO₂) along with microRNA (miRNA) for BTE applications. miRNAs act as post-transcriptional regulator of gene expression. The fabricated biocomposite scaffolds were characterized using SEM, FT-IR and XRD analyses. The effect of a bioactive molecule (miR-590-5p) with scaffolds was tested for osteoblast differentiation at the cellular and molecular levels using mouse mesenchymal stem cells (C3H10T1/2). The results showed that CS/nHAp/nZrO₂ scaffolds promoted osteoblast differentiation, and this effect was further increased in the presence of miR-590-5p in C3H10T1/2 cells. Thus, we suggested that CS/nHAp/nZrO₂ scaffolds with miR-590-5p would have potential towards the treatment of bone defects.

Scaffold-Based microRNA Therapies in Regenerative Medicine and Cancer

microRNA-based therapies are an advantageous strategy with applications in both regenerative medicine (RM) and cancer treatments. microRNAs (miRNAs) are an evolutionary conserved class of small RNA molecules that modulate up to one third of the human nonprotein coding genome. Thus, synthetic miRNA activators and inhibitors hold immense potential to finely balance gene expression and reestablish tissue health. Ongoing industry-sponsored clinical trials inspire a new miRNA therapeutics era, but progress largely relies on the development of safe and efficient delivery systems. The emerging application of biomaterial scaffolds for this purpose offers spatiotemporal control and circumvents biological and mechanical barriers that impede successful miRNA delivery. The nascent research in scaffold-mediated miRNA therapies translates know-how learnt from studies in antitumoral and genetic disorders as well as work on plasmid (p)DNA/siRNA delivery to expand the miRNA therapies arena. In this progress report, the state of the art methods of regulating miRNAs are reviewed. Relevant miRNA delivery vectors and scaffold systems applied to-date for RM and cancer treatment applications are discussed, as well as the challenges involved in their design. Overall, this progress report demonstrates the opportunity that exists for the application of miRNA-activated scaffolds in the future of RM and cancer treatments.

Mixed-ligand copper(II) complex of quercetin regulate osteogenesis and angiogenesis

Copper(II) complex of quercetin Cu+Q, mixed ligand complexes, quercetin-Cu(II)-phenanthroline [Cu+Q(PHt)] and quercetin-Cu(II)-neocuproine [Cu+Q(Neo)] have been synthesized and characterized. From the FT-IR spectroscopic studies, it was evident that C-ring of quercetin is involved in the metal chelation in all the three copper complexes. C-ring chelation was further proven by UV-Visible spectra and the presence of Cu(II) from EPR spectroscopic investigations. These complexes were found to have osteogenic and angiogenic properties, observed through in vitro osteoblast differentiation and chick embryo angiogenesis assay. In osteoblast differentiation, quercetin-Cu(II) complexes treatment increased calcium deposition and alkaline phosphatase activity (ALP) activity at the cellular level and stimulated Runx2 mRNA and protein, ALP mRNA and type 1 collagen mRNA expression at the molecular level. Among the complexes, Q+Cu(PHt) showed more effects on osteoblast differentiation when compared to that of other two copper complexes. Additionally, Q+Cu(Neo) showed more effect compared to Q+Cu. Furthermore, the effect of these complexes on osteoblast differentiation was confirmed by the expression of osteoblast specific microRNA, pre-mir-15b. The chick embryo angiogenesis assay showed that angiogenic parameters such as blood vessel length, size and junctions were stimulated by these complexes. Thus, the present study demonstrated that quercetin copper(II) complexes exhibit as a pharmacological agent for the orthopedic application.

Natural and synthetic polymers/bioceramics/bioactive compounds-mediated cell signalling in bone tissue engineering

Bone is a highly integrative and dynamic tissue of the human body. It is continually remodeled by bone cells such as osteoblasts, osteoclasts. When a fraction of a bone is damaged or deformed, stem cells and bone cells under the influence of several signaling pathways regulate bone regeneration at the particular locale. Effective therapies for bone defects can be met via bone tissue engineering which employs drug delivery systems with biomaterials to enhance cellular functions by acting on signaling pathways such as Wnt, BMP, TGF-β, and Notch. This review provides the current understanding of polymers/bioceramics/bioactive compounds as scaffolds in activation of signaling pathways for the formation of bone.

Alginate/Gelatin scaffolds incorporated with Silibinin-loaded Chitosan nanoparticles for bone formation in vitro

Silibinin is a plant derived flavonolignan known for its multiple biological properties, but its role in the promotion of bone formation has not yet been well studied. Moreover, the delivery of Silibinin is hindered by its complex hydrophobic nature, which limits its bioavailability. Hence, in this study, we fabricated a drug delivery system using chitosan nanoparticles loaded with Silibinin at different concentrations (20μM, 50μM, and 100μM). They were then incorporated into scaffolds containing Alginate and Gelatin (Alg/Gel) for the sustained and prolonged release of Silibinin. The Silibinin-loaded chitosan nanoparticles (SCN) were prepared using the ionic gelation technique, and the scaffolds (Alg/Gel-SCN) were synthesized by the conventional method of freeze drying. The scaffolds were subjected to physicochemical and material characterization studies. The addition of SCN did not affect the porosity of the scaffolds, yet increased the protein adsorption, degradation rates, and bio-mineralization. These scaffolds were biocompatible with mouse mesenchymal stem cells. The scaffolds loaded with 50μM Silibinin promoted osteoblast differentiation, which was determined at cellular and molecular levels. Recent studies indicated the role of microRNAs (miRNAs) in osteogenesis and we found that the Silibinin released from scaffolds regulated miRNAs that control the bone morphogenetic protein pathway. Hence, our results suggest the potential for sustained and prolonged release of Silibinin to promote bone formation and, thus, these Alg/Gel-SCN scaffolds may be candidates for bone tissue engineering applications.

Scaffolds containing chitosan, gelatin and graphene oxide for bone tissue regeneration in vitro and in vivo

Critical-sized bone defects are augmented with cell free and cell loaded constructs to bridge bone defects. Improving the properties of three-dimensional scaffolds with multiple polymers and others is of growing interest in recent decades. Chitosan (CS), a natural biopolymer has limitations for its use in bone regeneration, and its properties can be enhanced with other materials. In the present study, the composite scaffolds containing CS, gelatin (Gn) and graphene oxide (GO) were fabricated through freeze-drying. These scaffolds (GO/CS/Gn) were characterized by the SEM, Raman spectra, FT-IR, EDS, swelling, biodegradation, protein adsorption and biomineralization studies. The inclusion of GO in the CS/Gn scaffolds showed better physico-chemical properties. The GO/CS/Gn scaffolds were cyto-friendly to rat osteoprogenitor cells, and they promoted differentiation of mouse mesenchymal stem cells into osteoblasts. The scaffolds also accelerated bridging of the rat tibial bone defect with increased collagen deposition in vivo. Hence, these results strongly suggested the potential nature of GO/CS/Gn scaffolds for their application in bone tissue regeneration.