Biodegradable Chitosan-graft-Poly(l-lactide) Copolymers For Bone Tissue Engineering

The design and synthesis of new biomaterials with adjustable physicochemical and biological properties for tissue engineering applications have attracted great interest. In this work, chitosan-graft-poly(l-lactide) (CS-g-PLLA) copolymers were prepared by chemically binding poly(l-lactide) (PLLA) chains along chitosan (CS) via the "grafting to" approach to obtain hybrid biomaterials that present enhanced mechanical stability, due to the presence of PLLA, and high bioactivity, conferred by CS. Two graft copolymers were prepared, CS-g-PLLA(80/20) and CS-g-PLLA(50/50), containing 82 wt % and 55 wt % CS, respectively. Degradation studies of compressed discs of the copolymers showed that the degradation rate increased with the CS content of the copolymer. Nanomechanical studies in the dry state indicated that the copolymer with the higher CS content had larger Young modulus, reduced modulus and hardness values, whereas the moduli and hardness decreased rapidly following immersion of the copolymer discs in alpha-MEM cell culture medium for 24 h. Finally, the bioactivity of the hybrid copolymers was evaluated in the adhesion and growth of MC3T3-E1 pre-osteoblastic cells. In vitro studies showed that MC3T3-E1 cells exhibited strong adhesion on both CS-g-PLLA graft copolymer films from the first day in cell culture, whereas the copolymer with the higher PLLA content, CS-g-PLLA(50/50), supported higher cell growth.

GPR39 agonist TC-G 1008 promotes osteoblast differentiation and mineralization in MC3T3-E1 cells

Osteoporosis-related bone fracture and falls have a severe impact on patients' daily lives. Osteoblasts are bone-building cells that play a vital role in bone formation and remodeling. Imbalanced osteoblast differentiation could lead to osteoporosis. GPR39 is an orphan G protein-coupled receptor that mediates metabolic pathways. In this study, we show that GPR39 is expressed in MC3T3-E1 cells. Osteoblast differentiation culture media induces GPR39, suggesting that GPR39 is a differentiation-responsive factor. Activation of GPR39 using its selective agonist TC-G 1008 induces alkaline phosphatase (ALP), osteocalcin (OCN), and type I collagen (Col-I) expression, and increases cellular ALP activity and calcium deposition, implying that GPR activation promotes cells toward osteoblast differentiation. Treatment with TC-G 1008 also increases Runx-2 expression and AMPK activation. However, the inhibition of AMPK by Compound C abolished TC-G 1008-mediated ALP, OCN, and Col-I induction, and reduces ALP activity and cellular calcium deposition as well as Runx-2 induction. These data indicate that TC-G 1008-mediated GPR39 activation involves AMPK-mediated Runx-2 induction. In summary, our study uncovers a new role of GPR39 activation in osteoblast differentiation, implying that GPR39 could be a promising therapeutic target for osteoporosis.

Activating transcription factor 4 is required for high glucose inhibits proliferation and differentiation of MC3T3-E1 cells

Activating transcription factor 4 (ATF4) promotes bone formation in human bone marrow mesenchymal stem cells. However, the underlying mechanisms of ATF4 in high glucose-induced injury of osteoblast still remain unclear. Small interfering RNA and plasmid targeting ATF4 were used to transfect MC3T3-E1 cells to knock down and overexpress ATF4 using Lipofectamin 3000. Cell viability, alkaline phosphatase (ALP) activity and levels were determined by MTT, ALP kit assay, quantitative real-time (qRT)-PCR and Western blot. Osteocalcin (OCN) expression was determined by ELISA, PCR and Western blot. The mRNA and protein levels of ATF4, glucose regulated protein 78 kDa (GRP78) and C/EBP homologous protein (CHOP) were detected by PCR and Western blot. In the current study, viabilities of MC3T3-E1 cells were inhibited by high glucose. Meanwhile, the mRNA and protein levels of ATF4 were effectively up-regulated in high glucose-incubated MC3T3-E1 cells. By conducting functional experiments, silencing ATF4 induced by small interfering RNA partially reversed the inhibitory effects of high glucose on viabilities of MC3T3-E1 cells. We also found that the expressions of ER stress-related proteins (ATF4, GRP78 and CHOP) were higher in high glucose-treated MC3T3-E1 cells but were inhibited by siATF4. However, overexpression of AFT4 had opposite results, and high glucose attenuated the protein levels of osteogenic marker genes ALP and OCN, which were further inhibited by ATF4 knockout gene. Thus, ATF4 was a necessary gene for high glucose to inhibit the proliferation and differentiation of MC3T3-E1 cells.

Comparative evaluation of the physicochemical properties of nano-hydroxyapatite/collagen and natural bone ceramic/collagen scaffolds and their osteogenesis-promoting effect on MC3T3-E1 cells

The use of various types of calcium phosphate has been reported in the preparation of repairing materials for bone defects. However, the physicochemical and biological properties among them might be vastly different. In this study, we prepared two types of calcium phosphates, nano-hydroxyapatite (nHA) and natural bone ceramic (NBC), into 3D scaffolds by mixing with type I collagen (CoL), resulting in the nHA/CoL and NBC/CoL scaffolds. We then evaluated and compared the physicochemical and biological properties of these two calcium phosphates and their composite scaffold with CoL. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD) and compressive tests were used to, respectively, characterize the morphology, composition, distribution and the effect of nHA and NBC to collagen. Next, we examined the biological properties of the scaffolds using cytotoxicity testing, flow cytometry, immunofluorescence staining, biocompatibility testing, CCK-8 assays and RT-PCR. The results reflected that the Ca2+ released from nHA and NBC could bind chemically with collagen and affect its physicochemical properties, including the infrared absorption spectrum and compression modulus, among others. Furthermore, the two kinds of scaffolds could promote the expression of osteo-relative genes, but showed different gene induction properties. In short, NBC/CoL could promote the expression of early osteogenic genes, while nHA/CoL could upregulate late osteogenic genes. Conclusively, these two composite scaffolds could provide MC3T3-E1 cells with a biomimetic surface for adhesion, proliferation and the formation of mineralized extracellular matrices. Moreover, nHA/CoL and NBC/CoL had different effects on the period and extent of MC3T3-E1 cell mineralization.

Preparation of bioactive hydroxyapatite@halloysite and its effect on MC3T3-E1 osteogenic differentiation of chitosan film

Halloysite nanotubes (HNTs) are widely used in biomedical field due to their special tubular structure and high reinforcing ability, while hydroxyapatite (HAP) is generally used in tissue engineering owing to its excellent biocompatibility and biological activity. In this work, hydroxyapatite@halloysite nanotubes(HAP@HNTs) hybrid was synthesized via a facial hydrothermal reaction process. The morphology, particle size, specific surface area, and chemical composition of the hybrid were thoroughly characterized by different techniques. Rod-like HAP nanoparticles can be anchored on the outer surface of the clay tubes, which lead to a maximum increase of 4.7 m²/g in the specific surface area of HAP@HNTs over that of HNTs. HAP nanoparticles have little effect on the pores of HNTs, but diffraction peak strength of HNTs is covered by the HAP crystals. HAP@HNTs exhibit improved cytocompatibility and possess osteogenic differentiation ability towards MC3T3-E1 preosteoblasts. Chitosan/HAP@HNTs composite films were then prepared by doping of HAP@HNTs into chitosan by solution mixing. HAP@HNTs can serve as a functional phase which enhances mechanical properties of chitosan films and osteogenic differentiation of MC3T3-E1 cells. This work provides a facial synthesis routine of bioactive HAP@HNTs, which combines the osteogenic activity of HAP and the good mechanical properties of HNTs. HAP@HNTs can be used a novel bone regeneration biomaterial as local delivery systems with improved osteoinductive properties.

ATP6V1H facilitates osteogenic differentiation in MC3T3-E1 cells via Akt/GSK3β signaling pathway

Type 2 diabetes mellitus (T2DM) accounts for approximately 90% of all diabetic patients, and osteoporosis is one of the complications during T2DM process. ATP6V1H (V-type proton ATPase subunit H) displays crucial roles in inhibiting bone loss, but its role in osteogenic differentiation remains unknown. Therefore in this study, we aimed to explore the biological role of ATP6V1H in osteogenic differentiation. OM (osteogenic medium) and HG (high glucose and free fatty acids) were used to induce the MC3T3-E1 cells into osteogenic differentiation in a T2DM simulating environment. CCK8 assay was used to detect cell viability. Alizarin Red staining was used to detect the influence of ATP6V1H on osteogenic differentiation. ATP6V1H expression increased in OM-MC3T3-E1 cells, while decreased in OM+HG-MC3T3-E1 cells. ATP6V1H promoted osteogenic differentiation of OM+HG-MC3T3-E1 cells. Overexpression of ATP6V1H inhibited Akt/GSK3β signaling pathway, while knockdown of ATP6V1H promoted Akt/GSK3β signaling pathway. ATP6V1H overexpression promoted osteogenic differentiation of OM+HG-MC3T3-E1 cells. The role of ATP6V1H in osteogenic differentiation in a T2DM simulating environment involved in Akt/GSK3β signaling pathway. These data demonstrated that ATP6V1H could serve as a potential target for osteogenic differentiation in a T2DM simulating environment.

Satb2 expression in Foxc1-promoted osteogenic differentiation of MC3T3-E1 cells is negatively regulated by microRNA-103-3p

The forkhead transcription factor C1 (Foxc1) is a cell-fate-determining factor that controls cranial bone development and osteogenic differentiation. Previously, it was demonstrated that various microRNAs (miRNAs) play important roles in osteogenesis and regulate the complex process of osteogenic differentiation. However, it remains unclear how miRNA expression changes during Foxc1-promoted osteogenic differentiation. In this study, we successfully overexpressed the Foxc1 gene in MC3T3-E1 cells and investigated the alterations in the miRNA expression profile on day 3 after osteogenic induction by using a miRNA microarray. Nine downregulated miRNAs and eight upregulated miRNAs were found to be differentially expressed. Among these miRNAs, miR-103-3p was consistently downregulated in the Foxc1-overexpressing MC3T3-E1 cells and was identified as a negative regulator of osteogenic differentiation by using a gain- and lose-of-function assay. The special AT-rich sequence-binding protein 2 (Satb2), a pivotal osteogenic transcription factor, was identified as the miR-103-3p targeting gene and was verified by real-time polymerase chain reaction, western blot analysis, and luciferase assay. Overexpression of miR-103-3p markedly inhibited the expression of Satb2 and attenuated Foxc1-promoted osteogenic differentiation. Taken together, our results elucidated the miRNA expression profiles of MC3T3-E1 cells in the early stage of Foxc1-promoted osteogenic differentiation and suggested that miR-103-3p acts as a negative regulator of the osteogenic differentiation of MC3T3-E1 cells by directly targeting Satb2.

Induction of Osteogenic MC3T3-E1 Cell Differentiation by Nacre and Flesh Lipids of Tunisian Pinctada radiata

The flesh of the Pinctada radiata pearl oyster from coastal Tunisia is considered as a high source of n-3 and n-6 and its shell nacre layer is a promising osteogenic biomaterial. Fatty acid (FA) analysis showed that the major components found in total FA (TFA) were 14:0, 16:0, and 18:0 saturated FA (SFA); 16:1, 18:1, and 20:1 monoenoic FA; 20:4n-6 (ARA), 22:5n-3 (DPA). Characteristically high levels of 20:5n-3 (EPA) and 22:6n-3 (DHA) (6.53-89.75 mg/100 g TFA) polyunsaturated FA (PUFA) were found, respectively, in the TFA of nacre and flesh. Evaluated the effects in vitro of lipids extracted from nacre (Ln) and from flesh (Lc) of P. radiata on growth and the differentiation of osteoblasts. Cytotoxicity tests (3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide [MTT] and lactic acid dehydrogenase c [LDH]) demonstrated that both extracts are nontoxic. Alizarin Red staining was used in an osteoblast differentiation model using the osteoblast MC3T3-E1 cell line. It showed that the FA of both extracts induced osteoblast differentiation leading to mineralization. Reverse transcription-polymerase chain reaction (RT-PCR) showed a significantly higher expression of osteocalcin (Bglap) and runt-related transcription (Runx2) in MC3T3-E1 cells in the presence of Ln. No difference of osteopontin (Spp1) and Collagen type I (Col1a1) genes compared to the control was observed. In conclusion, these results supported, obtained from our in vitro experimental model used, the interest/potential of lipids extracted from nacre and P. radiata flesh to stimulate bone formation.

Platelet-rich fibrin increases the osteoprotegerin/receptor activator of nuclear factor-κB ligand ratio in osteoblasts

Platelet-rich fibrin (PRF) is a platelet concentrate derived from complete autologous blood rich in growth factors in the fibrin matrix. Although PRF has been used during oral surgery to optimize wound healing in soft and hard tissue, the precise role of PRF in bone healing remains unclear. The present study assessed the role of PRF in bone remodeling. PRF was prepared from whole blood by low speed centrifugation without any anti-coagulants. Culture of MC3T3-E1 cells with PRF induced the expression of osteoprotegerin (OPG), but had no effect on the expression of receptor activator of nuclear factor-κB ligand (RANKL), increasing the OPG/RANKL ratio. Expression of other osteoblastic differentiation makers, including BMP-2 and −4 and RUNX2, was not affected. PRF filling of a hole defect in the mental foramen bone of rats increased OPG positivity and decreased tartrate-resistant acid phosphatase positivity compared with unfilled control. In conclusion, PRF increased the OPG/RANKL ratio by inducing OPG expression, suggesting that PRF enhances early stage osteogenesis by optimizing osteoblastic differentiation. The present study provides a scientific basis for clinical findings showing that PRF can enhance bone regeneration such as sinus lift.

Regulation of MC3T3-E1 differentiation by actin cytoskeleton through lipid mediators reflecting the cell differentiation stage

Actin cytoskeleton is reported to be related in various functions of osteoblast, bone-forming cell. However the function of actin cytoskeleton in osteoblasts is not fully understood, since bone formation is derived from extracellular interactions of functional proteins produced from osteoblasts, including osteocalcin (Ocn), and it is a result of closely and complex organized sequence of biochemical events. In this study, we showed that actin cytoskeleton of MC3T3-E1 cells functioned in recognition of cell condition and regulation of extracellular matrix mineralization, bone formation. Maturation of MC3T3-E1 cells by 14 days of culture reduced F-actin filaments, while induced expression of Ocn mRNA known as late stage differentiation marker and matrix mineralization, terminal stage of cell differentiation. The disruption of actin cytoskeleton with Cyto D in immature MC3T3-E1 cells significantly increased expression of Ocn mRNA in 24 h. Both PTX-induced inhibition of signal transduction through GPCRs and celecoxib-induced suppression of lipid mediators in immature MC3T3-E1 cells reduced actin filaments and suppressed matrix mineralization. Furthermore, addition of lipid mediators extracted from culture mediums of differentiated MC3T3-E1 cells by Bligh-Dyer method induced actin cytoskeleton reorganization and matrix mineralization change in MC3T3-E1 cells. Taken together, our data suggest that actin cytoskeleton of MC3T3-E1 cells regulates activation of developmental pathway reflecting cell differentiation stages through lipid mediators. The function we identified is important for bone formation tightly regulated by mechanical stress, since actin cytoskeleton is also known as a mechanosensor of osteoblasts.

Bactericidal and Biocompatible Properties of Plasma Chemical Oxidized Titanium (TiOB®) with Antimicrobial Surface Functionalization

Coating of plasma chemical oxidized titanium (TiOB^®) with gentamicin-tannic acid (TiOB^® gta) has proven to be efficient in preventing bacterial colonization of implants. However, in times of increasing antibiotic resistance, the development of alternative antimicrobial functionalization strategies is of major interest. Therefore, the aim of the present study is to evaluate the antibacterial and biocompatible properties of TiOB^® functionalized with silver nanoparticles (TiOB^® SiOx Ag) and ionic zinc (TiOB^® Zn). Antibacterial efficiency was determined by agar diffusion and proliferation test on Staphylocuccus aureus. Cytocompatibility was analyzed by direct cultivation of MC3T3-E1 cells on top of the functionalized surfaces for 2 and 4 d. All functionalized surfaces showed significant bactericidal effects expressed by extended lag phases (TiOB^® gta for 5 h, TiOB^® SiOx Ag for 8 h, TiOB^® Zn for 10 h). While TiOB^® gta (positive control) and TiOB^® Zn remained bactericidal for 48 h, TiOB^® SiOx Ag was active for only 4 h. After direct cultivation for 4 d, viable MC3T3-E1 cells were found on all surfaces tested with the highest biocompatibility recorded for TiOB^® SiOx Ag. The present study revealed that functionalization of TiOB^® with ionic zinc shows bactericidal properties that are comparable to those of a gentamicin-containing coating.

Osteogenic Enhancement Between Icariin and Bone Morphogenetic Protein 2: A Potential Osteogenic Compound for Bone Tissue Engineering

Icariin, a typical flavonol glycoside, is the main active component of Herba Epimedii, which was used to cure bone-related diseases in China for centuries. It has been reported that Icariin can be delivered locally by biomaterials and it has an osteogenic potential for bone tissue engineering. Biomimetic calcium phosphate (BioCaP) bone substitute is a novel drug delivery carrier system. Our study aimed to evaluate the osteogenic potential when Icariin was internally incorporated into the BioCaP granules. The BioCaP combined with Icariin and bone morphogenetic protein 2 (BMP-2) was investigated in vitro using an MC3T3-E1 cell line. We also investigated its efficacy to repair 8 mm diameter critical size bone defects in the skull of SD male rats. BioCaP was fabricated according to a well-established biomimetic mineralization process. In vitro, the effects of BioCaP alone or BioCaP with Icariin and/or BMP-2 on cell proliferation and osteogenic differentiation of MC3T3-E1 cells were systematically evaluated. In vivo, BioCaP alone or BioCaP with Icariin and/or BMP-2 were used to study the bone formation in a critical-sized bone defect created in a rat skull. Samples were retrieved for Micro-CT and histological analysis 12 weeks after surgery. The results indicated that BioCaP with or without the incorporation of Icariin had a positive effect on the osteogenic differentiation of MC3T3-E1. BioCaP with Icariin had better osteogenic efficiency, but had no influence on cell proliferation. BioCap + Icariin + BMP-2 showed better osteogenic potential compared with BioCaP with BMP-2 alone. The protein and mRNA expression of alkaline phosphatase and osteocalcin and mineralization were higher as well. In vivo, BioCaP incorporate internally with both Icariin and BMP-2 induced significantly more newly formed bone than the control group and BioCaP with either Icariin or BMP-2 did. Micro-CT analysis revealed that no significant differences were found between the bone mineral density induced by BioCaP with icariin and that induced by BioCaP with BMP-2. Therefore, co-administration of Icariin and BMP-2 was helpful for bone tissue engineering.

MicroRNA-590-5p antagonizes the inhibitory effect of high glucose on osteoblast differentiation by suppressing Smad7 in MC3T3-E1 cells

Objective

MicroRNA-590-5p (miR-590-5p) has been reported to stimulate osteoblast differentiation; however, its effect in diabetic osteoporosis remains unknown. This study investigated the effect of miR-590-5p on high glucose (HG)-suppressed osteoblast differentiation.

Methods

The effect of HG on MC3T3-E1 cell survival was assessed using the MTT assay. The expression levels and activities of osteoblastic proteins were evaluated by quantitative reverse transcription polymerase chain reaction (qRT-PCR), alkaline phosphatase (ALP) assay, and immunoblotting assay. Tumor growth factor-β (TGF-β) signaling in MC3T3-E1 cells was assessed using luciferase assay, qRT-PCR, and immunoblotting. Mineralized nodule formation in MC3T3-E1 cells was examined by using the mineralization assay.

Results

When MC3T3-E1 cells were exposed to HG conditions, there was significant downregulation of miR-590-5p and osteoblastic proteins (e.g., collagen I, Runx2, and ALP); in contrast, Smad7 was upregulated. Furthermore, miR-590-5p targeted Smad7 and inhibited its expression. Additionally, overexpression of miR-590-5p significantly promoted osteoblast growth and differentiation by upregulating TGF-β signaling in HG-treated MC3T3-E1 cells.

Conclusions

Collectively, the results showed that miR-590-5p was involved in osteogenesis; moreover, miR-590-5p may represent a potential target for the treatment of diabetic osteoporosis.

Nephronectin Expression is Inhibited by Inorganic Phosphate in Osteoblasts

Nephronectin (Npnt), an extracellular matrix protein, is known to be a ligand of integrin α8β1, and it has also been known to play critical roles as various organs. In the present study, elevated extracellular inorganic phosphate (Pi) strongly inhibited the expression of Npnt in MC3T3-E1 cells, while the existence of extracellular calcium (Ca) was indispensable for its effect. Furthermore, Pi-induced inhibition of Npnt gene expression was recovered by inhibitors of both sodium-dependent Pi transporter (Pit) and fibroblast growth factor receptors (Fgfrs). These results demonstrated that Npnt gene expression is regulated by extracellular Pi via Pit and Fgfrs.

Alterations of mineralized matrix by lead exposure in osteoblast (MC3T3-E1) culture

The present study investigated the effect of lead (Pb) on bone ultrastructure and chemistry using an in vitro bone model. MC3T3-E1 preosteoblasts were differentiated and treated with lead acetate at 0.4, 2, 10, and 50 μM. No abnormalities in either cell growth or bone nodule formation were observed with the treated dose of lead acetate. However, Pb treatments could significantly increase Pb accumulation in differentiated osteoblast cultures and upregulate expression of Divalent metal transporter 1 (Dmt1) in a dose dependent manner. Pb treatments also altered the expression of osteogenic genes, including secreted phosphoprotein 1, osteocalcin, type I collagen, and osteoprotegerin. Moreover, in mineralized osteoblast cultures, Pb was found to be mainly deposited as Pb salts and oxides, respectively. Ultrastructure analysis revealed Pb localizing with calcium and phosphorus in the mineralized matrix. In mineralizing osteoblast cells, Pb was found in the intracellular calcified vesicles which is one of the bone mineralization mechanisms. Pb was also present in mineral deposits with various shapes and sizes, such as small and large globular or needle-like mineral deposits representing early to mature stages of mineral deposits. Furthermore, Pb was found more in the globular deposits than the needle shaped mineral crystals. Taken together, our observations revealed how Pb incorporates into bone tissue, and showed a close association with bone apatite.

[Determination of flavonoids constituents in epimedium total flavone capsule and research on its anti-osteoporosis activity]

To develop a rapid resolution liquid chromatography (RRLC) method for the simultaneous determination of epimedoside A, epimedin A1, epimedin A, epimedin B, epimedin C, icariin, baohuosideⅡ, icarisideⅠ, sagittatoside B, 2"-O-rhamnosyl icarisideⅡ, and baohuosideⅠin epimedium total flavone capsule. At the same time, the effects of the above 11 compounds on osteogenic differentiation of MC3T3-E1 cells were investigated by detecting the content of alkaline phosphatase (AKP). The results showed that baohuoside Ⅱ had the highest activities, and both the activities of baohuoside Ⅱ and icariside Ⅰ were stronger than those of icariin.In this study, the content determination method of flavonoid glycosides was established, and the anti-osteoporosis effect of monomers was compared, providing technical support for the study of the pharmacodynamic and mechanism of Epimedium total flavone capsule.

Heterodimeric BMP-2/7 exhibits different osteoinductive effects in human and murine cells

As robust osteoinductive cytokines, bone morphogenetic proteins (BMPs) play a significant role in bone tissue engineering. Constituted of two different polypeptides, heterodimeric BMPs are more effective than the homodimers in bone formation. While most studies focused on the murine cell lines, such as murine preosteoblasts MC3T3-E1, the role of heterodimeric BMPs in the osteogenic differentiation of human cells remains uncertain, which hinders their application to practical treatment. In this study, we compared the osteoinductive effects of BMP-2/7 heterodimer in human adipose-derived stem cells (hASCs) with their homodimers BMP-2 and BMP-7, in which MC3T3-E1 cells were utilized as a positive control. The results indicated that BMP-2/7 was not a stronger inducer during the osteogenic differentiation of hASCs as that for MC3T3-E1, and extracellular-signal-regulated kinase signaling played a role in the different effects of BMP-2/7 between hASCs and MC3T3-E1. Our study demonstrates the osteoinductive effects of heterodimeric BMP-2/7 present in a cell-specific pattern and cautions should be taken when applying heterodimeric BMP-2/7 to clinical practice.

Synergistic effects of titania nanotubes and silicon to enhance the osteogenic activity

In this study, titania nanotubes (TNTs) incorporating silicon (Si) were formed on Ti disks using anodization and electron beam evaporation (EBE) technology to improve the osteogenic activity. The amount of Si was exquisitely adjusted by controlling the duration of EBE to optimize the biofunctionality. As the Si was incorporated, the samples exhibited hydrophilic surfaces. Long lasting and controllable Si release was observed from the EBE-modified samples without cytotoxicity. Moreover, initial cell adhesion, spreading, proliferation and osteogenic differentiation of MC3T3-E1 cells were evaluated. The results showed a notable enhancement of spreading, osteogenesis and differentiation of cells on silicon-coated TNTs (Si-TNTs). In particular, samples with highest amount of silicon (∼5.93% Si) displayed greatest augmentation of ALP activity, osteogenic-related gene expression and mineralization compared to the others in the present study. It was indicated that the modification with TNTs and appropriated Si content resulted in enhanced osteoblastic spreading, proliferation and differentiation, and therefore has the potential for future applications in the field of orthopedics.

Nanoporous diopside modulates biocompatibility, degradability and osteogenesis of bioactive scaffolds of gliadin-based composites for new bone formation

INTRODUCTION

It is predicted that with increased life expectancy in the whole world, there will be a greater demand for synthetic biomedical materials to repair or regenerate lost, injured or diseased tissues. Natural polymers, as biomedical materials, have been widely applied in the field of regenerative medicine.

MATERIALS AND METHODS

By incorporation of nanoporous diopside bioglass (nDPB) into glia-din (GL) matrix, macro-nanoporous scaffolds of nDPB/GL composites (DGC) were fabricated by method of solution compressing and particles leaching.

RESULTS

The results revealed that the DGC scaffolds possessed well-interconnected macropores of 200-500 μm and nanopores of 4 nm, and the porosity and degradability of DGC scaffolds remarkably increased with the increase in nDPB content. In addition, in vitro cell experiments revealed that the adhesion and growth of MC3T3-E1 cells on DGC scaffolds were significantly promoted, which depended on nDPB content. Moreover, the results of histological evaluations confirmed that the osteogenic properties and degradability of DGC scaffolds in vivo significantly improved, which were nDPB content dependent. Furthermore, the results of immunohistochemical analysis demonstrated that, with the increase in nDPB content, the type I collagen expression in DGC scaffolds in vivo obviously enhanced, indicating excellent osteogenesis.

DISCUSSION AND CONCLUSION

The results demonstrated that the DGC scaffolds containing 30 wt% nDPB (30nDGC) exhibited good biocompatibility and new bone formation ability, which might have a great potential for applications in bone regeneration.

Evaluation of osteoblast differentiation and function when cultured on mesoporous bioactive glass adsorbed with testosterone

Mesoporous bioactive glass (MBG), a kind of porous materials with great osteoconductive and osteoinductive ability, shows promising application in bone tissue engineering due to its high specific surface area, orderly channel structure, and large pore volume. Here we reported that the proliferation, differentiation, and mineralization were promoted in MC3T3-E1 cells cultured on MBG which adsorbed with testosterone (MBG/T). We found that transcriptional activity of Runx2 which is a critical transcription factor is increased in MC3T3-E1 cells cultured on MBG/T. Intriguingly, we observed that ERK phosphorylation was enhanced in MC3T3-E1 cells cultured on MBG/T. We showed that activated Runx2 in MC3T3-E1 cells cultured on MBG/T is through Erk1/2 phosphorylation. Consistent with this result, we also found that the expression of osteoblastic marker genes were increased. Therefore, we concluded that osteoblast differentiation and mineralization was enhanced after cells cultured on MBG/T through Erk1/2-activated Runx2 pathway. Our findings provided that MBG/T is a potential material in the process of bone repair.

Synthesis and Promotion of the Osteoblast Proliferation Effect of Morroniside Derivatives

Sambucus williamsii Hance has been used in fractures for thousands of years, but research on its active components, such as morroniside, until now had not been carried out. In this study, morroniside was taken as the leading compound, and fourteen derivatives were synthesized. The promotion of osteoblast proliferation effect of the derivatives was evaluated on MC3T3-E1 cells. Five derivatives (2, 3, 4, 5, and 14) showed a good proliferation effect on MC3T3-E1 cells, and their promoted expression effects on OC (Osteocalcin) and ALP (Alkaline phosphatase) in MC3T3-E1 cells were measured. Compound 3 was shown to have the strongest proliferation effect (EC₅₀ = 14.78 ± 1.17 μg/mL) and to significantly promote the expression of OC and ALP.

Necrostatin-1 inhibits the cell death of osteoblasts induced by glucocorticoid

Glucocorticoids have been shown to induce apoptosis in different cell types. Recent studies have indicated that apoptosis may not be the only form of death that is activated in osteoblasts in response to glucocorticoids. The aim of this study was to investigate whether necrostatin-1 could protect osteoblasts from glucocorticoid-induced cell death. Dexamethasone could induce both apoptotic and necrotic cell death in MC3T3-E1 cells, in a dose- and time-dependent manner. Necrotic cell death was induced by dexamethasone in MC3T3-E1 cells and was characterized by caspase independence, delayed externalization of phosphatidylserine, cellular swelling and plasma membrane disruption. Blockages of necroptotic induction by a special inhibitor (Necrostatin-1) succeed to protect cells against dexamethasone induced cell death. The levels of RIP-1 production and loss of mitochondrial membrane potential were also determined to assess the effects of dexamethasone. This study showed, for the first time, that high-doses of dexamethasone can induce necrotic-like cell death in osteoblastic MC3T3-E1 cells, and this induction could be inhibited by necrostatin-1.

Leucine reduces the proliferation of MC3T3-E1 cells through DNA damage and cell senescence

Leucine (Leu) is an essential branched-chain amino acid, present in dairy products, which has been investigated for its important role in cell signaling. The effects of Leu on several kinds of cells have been studied, altough little is known on its action upon bone cells and cell proliferation. Thus, the aim of this study is to investigate the effects of Leu supplementation on the proliferation of pre-osteoblasts from MC3T3-E1 lineage. MC3T3-E1 cells were kept in Alpha medium supplemented with 10% fetal bovine serum and 1% antibiotic-antimitotic. Cells were treated during 48h by adding 50μM of Leu, which corresponds to a 12.5% increase of the amino acid in the culture medium. The evaluation of viability and proliferation of cultured cells was performed using Trypan Blue dye. In order to identify the mechanisms related to the decreased cellular proliferation, assays were performed to assess cytotoxicity, apotosis, oxidative stress, inflammation, autophagy, senescence and DNA damage. Results showed that Leu supplementation decreased cell proliferation by 40% through mechanisms not related to cell necrosis, apoptosis, oxidative stress, autophagy or inhibition of the mTORC1 pathway. On the other hand, Leu supplementation caused DNA damage. In conclusion, Leu caused a negative impact on bone cell proliferation by inducing cell senescence through DNA damage.

Metformin promotes the proliferation and differentiation of murine preosteoblast by regulating the expression of sirt6 and oct4

Osteopenia, osteoporosis and bone salt metabolism disorder are common diseases in the aged and diabetics. From case reports of patients with T2DM, we have observed that metformin can decrease risk of bone fracture and promote bone formation. However, the underlying mechanism of metformin's effect on bone metabolism remains unknown. In our research, we show that metformin can promote proliferation of murine preosteoblast by regulating AMPK-mTORC2 and AKT-mTORC1 signaling axis. Furthermore, we have observed that metformin can promote SIRT6 expression before and during differentiation of murine preosteoblast. The interaction between SIRT6 and NF-κB is highly important in osteoblast differentiation just as the relationship between OPG and RANKL in the process of bone formation. During differentiation, we show that SIRT6 inhibits phosphorylation of NF-κB and that OPG increases while RANKL decrease in HG groups. In addition, ablation of sirt6 in mice causes phosphorylation of NF-κB at high-levels and RANKL increases slightly in femur bone cells. However, other bone formation marker proteins such as RUNX2, OSTERIX and OPG appear at low-levels in sirt6 KO mice. It has been confirmed that downregulation of OCT4 is critical incident in the differentiation of embryonic stem cells. Fortunately, we observe that SIRT6 can suppress OCT4 expression in murine preosteoblast and the expression of OCT4 is at high-level in sirt6 KO mice. Taken together, this study's results illuminate metformin's effect on bone metabolism under HG condition and help to elucidate why metformin can promote bone fracture healing of patients with T2DM.

Promoting Effect of Pinostrobin on the Proliferation, Differentiation, and Mineralization of Murine Pre-osteoblastic MC3T3-E1 Cells

Pinostrobin (PI), a natural flavonoid found in a variety of plants, is well known for its rich pharmacological activities. However, its osteogenic function remains unclear. The aim of this study is to evaluate the effect of PI on the proliferation, differentiation, and mineralization of murine pre-osteoblastic MC3T3-E1 cells in vitro using MTT, alkaline phosphatase (ALP) activity, the synthesis of collagen I (Col I) assay, and Von-Kossa staining, respectively. The expression of osteocalcin (OCN) mRNA in cells was detected by real-time PCR. The effect of PI on the differentiation of dexamethasone (DEX)-suppressed cells was also investigated. The results showed that PI greatly promoted the proliferation of MC3T3-E1 cells at 5–80 μg/mL (p < 0.05 or p < 0.01), and caused a significant elevation of ALP activity, Col I content, and mineralization of osteoblasts at 10–40 μg/mL (p < 0.05 or p < 0.01), and the expression levels of OCN gene were greatly upregulated after PI treatment (p < 0.01). Furthermore, PI could rescue the inhibition effect of cell differentiation induced by DEX. Taken together, these results indicated that PI could directly promote proliferation, differentiation, and mineralization of MC3T3-E1 cells and has potential for use as a natural treatment for osteoporosis.