Are MG-63 and HOS TE85 human osteosarcoma cell lines representative models of the osteoblastic phenotype?

In Vitro Bone Cell Models: Impact of Fluid Shear Stress on Bone Formation

This review describes the role of bone cells and their surrounding matrix in maintaining bone strength through the process of bone remodeling. Subsequently, this work focusses on how bone formation is guided by mechanical forces and fluid shear stress in particular. It has been demonstrated that mechanical stimulation is an important regulator of bone metabolism. Shear stress generated by interstitial fluid flow in the lacunar-canalicular network influences maintenance and healing of bone tissue. Fluid flow is primarily caused by compressive loading of bone as a result of physical activity. Changes in loading, e.g., due to extended periods of bed rest or microgravity in space are associated with altered bone remodeling and formation in vivo. In vitro, it has been reported that bone cells respond to fluid shear stress by releasing osteogenic signaling factors, such as nitric oxide, and prostaglandins. This work focusses on the application of in vitro models to study the effects of fluid flow on bone cell signaling, collagen deposition, and matrix mineralization. Particular attention is given to in vitro set-ups, which allow long-term cell culture and the application of low fluid shear stress. In addition, this review explores what mechanisms influence the orientation of collagen fibers, which determine the anisotropic properties of bone. A better understanding of these mechanisms could facilitate the design of improved tissue-engineered bone implants or more effective bone disease models.

Methyl donor deficiency impairs bone development via peroxisome proliferator-activated receptor-γ coactivator-1α-dependent vitamin D receptor pathway

Deficiency in methyl donor (folate and vitamin B12) and in vitamin D is independently associated with altered bone development. Previously, methyl donor deficiency (MDD) was shown to weaken the activity of nuclear receptor coactivator, peroxisome proliferator-activated receptor-γ coactivator-1α (PGC1α), for nuclear signaling in rat pups, including estrogen receptor-α and estrogen-related receptor-α; its effect on vitamin D receptor (VDR) signaling, however, is unknown. We studied bone development under MDD in rat pups and used human MG-63 preosteoblast cells to better understand the associated molecular mechanism. In young rats, MDD decreased total body bone mineral density, reduced tibia length, and impaired growth plate maturation, and in preosteoblasts, MDD slowed cellular proliferation. Mechanistic studies revealed decreased expression of VDR, estrogen receptor-α, PGC1α, arginine methyltransferase 1, and sirtuin 1 in both rat proximal diaphysis of femur and in MG-63, as well as decreased nuclear VDR-PGC1α interaction in MG-63 cells. The weaker VDR-PGC1α interaction could be attributed to the reduced protein expression, imbalanced PGC1α methylation/acetylation, and nuclear VDR sequestration by heat shock protein 90 (HSP90). These together compromised bone development, which is reflected by lowered bone alkaline phosphatase and increased proadipogenic peroxisome proliferator-activated receptor-γ, adiponectin, and estrogen-related receptor-α expression. Of interest, under MDD, the bone development effects of 1,25-dihydroxyvitamin D3 were ineffectual and these could be rescued by the addition of S-adenosylmethionine, which restored expression of arginine methyltransferase 1, PGC1α, adiponectin, and HSP90. In conclusion, MDD inactivates vitamin D signaling via both disruption of VDR-PGC1α interaction and sequestration of nuclear VDR attributable to HSP90 overexpression. These data suggest that vitamin D treatment may be ineffective under MDD.-Feigerlova, E., Demarquet, L., Melhem, H., Ghemrawi, R., Battaglia-Hsu, S.-F., Ewu, E., Alberto, J.-M., Helle, D., Weryha, G., Guéant, J.-L. Methyl donor deficiency impairs bone development via peroxisome proliferator-activated receptor-γ coactivator-1α-dependent vitamin D receptor pathway.

Mechanical properties, biological behaviour and drug release capability of nano TiO2-HAp-Alginate composite scaffolds for potential application as bone implant material

Nanocomposite scaffolds of TiO2 and hydroxyapatite nanoparticles with alginate as the binding agent were fabricated using the freeze drying technique. TiO2, hydroxyapatite and alginate were used in the ratio of 1:1:4. The scaffolds were characterized using X-ray diffraction, fourier transform infrared spectroscopy, and scanning electron microscopy. The biocompatibility of the scaffolds was evaluated using cell adhesion and MTT assay on osteosarcoma (MG-63) cells. Scanning electron microscopy analysis revealed that cells adhered to the surface of the scaffolds with good spreading. The mechanical properties of the scaffolds were investigated using dynamic mechanical analysis. The swelling ability, porosity, in vitro degradation, and biomineralization of the scaffolds were also evaluated. The results indicated controlled swelling, limited degradation, and enhanced biomineralization. Further, drug delivery studies of the scaffolds using the chemotherapeutic drug methotrexate exhibited an ideal drug release profile. These scaffolds are proposed as potential candidates for bone tissue engineering and drug delivery applications.

Choice of osteoblast model critical for studying the effects of electromagnetic stimulation on osteogenesis in vitro

The clinical benefits of electromagnetic field (EMF) therapy in enhancing osteogenesis have been acknowledged for decades, but agreement regarding the underlying mechanisms continues to be sought. Studies have shown EMFs to promote osteoblast-like cell proliferation, or contrarily, to induce differentiation and enhance mineralization. Typically these disparities have been attributed to methodological differences. The present paper argues the possibility that the chosen osteoblast model impacts stimulation outcome. Phenotypically immature cells, particularly at low seeding densities, appear to be prone to EMF-amplified proliferation. Conversely, mature cells at higher densities seem to be predisposed to earlier onset differentiation and mineralization. This suggests that EMFs augment ongoing processes in cell populations. To test this hypothesis, mature SaOS-2 cells and immature MC3T3-E1 cells at various densities, with or without osteo-induction, were exposed to sinusoidal 50 Hz EMF. The exposure stimulated the proliferation of MC3T3-E1 and inhibited the proliferation of SaOS-2 cells. Baseline alkaline phosphatase (ALP) expression of SaOS-2 cells was high and rapidly further increased with EMF exposure, whereas ALP effects in MC3T3-E1 cells were not seen until the second week. Thus both cell types responded differently to EMF stimulation, corroborating the hypothesis that the phenotypic maturity and culture stage of cells influence stimulation outcome.

The influence of calcitonin gene-related peptide on markers of bone metabolism in MG-63 osteoblast-like cells co-cultured with THP-1 macrophage-like cells under virtually osteolytic conditions

Background

The neuropeptide calcitonin gene-related peptide (CGRP) has been described to have an inhibitory effect on endotoxin- and wear particle-induced inflammation in the early stages of periprosthetic osteolysis. In the present study, the crosstalk between immune cells and osteoblasts in osteolytic conditions treated with CGRP has been analyzed to evaluate whether the anti-inflammatory properties of the peptide also have a beneficial, i.e. an anti-resorptive and osteo-anabolic impact on bone metabolism.

Methods

MG-63 osteoblast-like cells were co-cultured with THP-1 macrophage-like cells stimulated with either ultra-high molecular weight polyethylene (UHMWPE) particles or different concentrations of bacterial lipopolysaccharides (LPS) and simultaneously treated with CGRP. Inflammation was monitored in terms of measuring the levels of tumor necrosis factor (TNF)-α secretion. Furthermore, the production of the osteoblast markers osteoprotegerin (OPG), receptor activator of nuclear factor κB ligand (RANKL), alkaline phosphatase (ALP) and osteopontin (OPN) was quantified. Also, ALP enzymatic activity was measured.

Results

Stimulation of co-cultured THP-1 macrophages with either high levels of LPS or UHMWPE induced the secretion of TNF-α which could be inhibited by CGRP to a great extent. However, no remarkable changes in the OPG/RANKL ratio or bone ALP activity were observed. Interestingly, OPN was exclusively produced by THP-1 cells, thus acting as a marker of inflammation. In addition, TNF-α production in THP-1 single cell cultures was found to be considerably higher than in co-cultured cells.

Conclusions

In the co-culture system used in the present study, no obvious relation between inflammation, its mitigation by CGRP, and the modulation of bone metabolism became evident. Nonetheless, the results suggest that during the onset of periprosthetic osteolysis the focus might lie on the modulation of inflammatory reactions. Possibly, implant-related inflammation might merely have an impact on osteoclast differentiation rather than on the regulation of osteoblast activity.

Electronic supplementary material

The online version of this article (doi:10.1186/s12891-016-1044-5) contains supplementary material, which is available to authorized users.

Fluorophosphonate-functionalised titanium via a pre-adsorbed alkane phosphonic acid: a novel dual action surface finish for bone regenerative applications

Enhancing vitamin D-induced human osteoblast (hOB) maturation at bone biomaterial surfaces is likely to improve prosthesis integration with resultant reductions in the need for revision arthroplasty consequent to aseptic loosening. Biomaterials that are less appealing to microorganisms implicated in implant failures through infection are also highly desirable. However, finding surfaces that enhance hOB maturation to active vitamin D yet deter bacteria remain elusive. In addressing this, we have sought to bio-functionalise titanium (Ti) with lysophosphatidic acid (LPA) and related, phosphatase-resistant, LPA analogues. The impetus for this follows our discovery that LPA co-operates with active vitamin D3 metabolites to secure hOB maturation in vitro including cells grown upon Ti. LPA has also been found, by others, to inhibit virulence factor production and biofilm formation of the human opportunistic pathogen Pseudomonas aeruginosa. Collectively, selected LPA species might offer potential dual-action surface finishes for contemporary bone biomaterials. In attaching a phosphatase-resistant LPA analogue to Ti we took advantage of the affinity of alkane phosphonic acids for TiO2. Herein, we provide evidence for the facile development of a dual-action Ti surface for potential orthopaedic and dental applications. Successful conjugation of an LPA analogue (3S)1-fluoro-3-hydroxy-4-(oleoyloxy)butyl-1-phosphonate (FHBP) to the Ti surface was supported through physiochemical characterisation using x-ray photoelectron spectroscopy and secondary ion mass spectrometry. hOB maturation to active vitamin D3 was enhanced for cells grown on FHBP-Ti whilst these same surfaces exhibited clear antiadherent properties towards a clinical isolate of Staphylococcus aureus.

In Vitro Analysis of Fibronectin-Modified Titanium Surfaces

Background

Glow discharge plasma (GDP) procedure is an effective method for grafting various proteins, including albumin, type I collagen, and fibronectin, onto a titanium surface. However, the behavior and impact of titanium (Ti) surface modification is yet to be unraveled.

Purpose

The purpose of this study is to evaluate and analyze the biological properties of fibronectin-grafted Ti surfaces treated by GDP.

Materials and Methods

Grade II Ti discs were initially cleaned and autoclaved to obtain original specimens. Subsequently, the specimens were GDP treated and grafted with fibronectin to form Ar-GDP (Argon GDP treatment only) and GDP-fib (fibronectin coating following GDP treatment) groups. Blood coagulation test and MG-63 cell culture were performed to evaluate the biological effects on the specimen.

Results

There was no significant difference between Ar-GDP and GDP-fib groups in blood compatibility analysis. While in the MTT test, cellular proliferation was benefited from the presence of fibronectin coating. The numbers of cells on Ar-GDP and GDP-fib specimens were greater than those in the original specimens after 24 h of culturing.

Conclusions

GDP treatment combined with fibronectin grafting favored MG-63 cell adhesion, migration, and proliferation on titanium surfaces, which could be attributed to the improved surface properties.

Dual Action of Lysophosphatidate-Functionalised Titanium: Interactions with Human (MG63) Osteoblasts and Methicillin Resistant Staphylococcus aureus

Titanium (Ti) is a widely used material for surgical implants; total joint replacements (TJRs), screws and plates for fixing bones and dental implants are forged from Ti. Whilst Ti integrates well into host tissue approximately 10% of TJRs will fail in the lifetime of the patient through a process known as aseptic loosening. These failures necessitate revision arthroplasties which are more complicated and costly than the initial procedure. Finding ways of enhancing early (osseo)integration of TJRs is therefore highly desirable and continues to represent a research priority in current biomaterial design. One way of realising improvements in implant quality is to coat the Ti surface with small biological agents known to support human osteoblast formation and maturation at Ti surfaces. Lysophosphatidic acid (LPA) and certain LPA analogues offer potential solutions as Ti coatings in reducing aseptic loosening. Herein we present evidence for the successful bio-functionalisation of Ti using LPA. This modified Ti surface heightened the maturation of human osteoblasts, as supported by increased expression of alkaline phosphatase. These functionalised surfaces also deterred the attachment and growth of Staphylococcus aureus, a bacterium often associated with implant failures through sepsis. Collectively we provide evidence for the fabrication of a dual-action Ti surface finish, a highly desirable feature towards the development of next-generation implantable devices.

Continuous cellularization of calcium phosphate hybrid scaffolds induced by plasma polymer activation

The generation of hybrid materials based on β-tricalcium phosphate (TCP) and various biodegradable polymers like poly(l-lactide-co-d,l-lactide) (PLA) represents a common approach to overcoming the disadvantages of pure TCP devices. These disadvantages lie in TCP's mechanical properties, such as brittleness. The positive characteristic of PLA - improvement of compressive strength of calcium phosphate scaffolds - is diametrically opposed to its cell attractiveness. Therefore, the objective of this work was to optimize osteoblast migration and cellularization inside a three-dimensionally (3D) printed, PLA polymer stabilized TCP hybrid scaffold by a plasma polymer process depositing amino groups via allylamine. MG-63 osteoblastic cells inside the 10mm hybrid scaffold were dynamically cultivated for 14days in a 3D model system integrated in a perfusion reactor. The whole TCP/PLA hybrid scaffold was continuously colonized due to plasma polymerized allylamine activation inducing the migration potential of osteoblasts.

Cyclic mechanical stretch promotes energy metabolism in osteoblast-like cells through an mTOR signaling-associated mechanism

Energy metabolism is essential for maintaining function and substance metabolism in osteoblasts. However, the role of cyclic stretch in regulating osteoblastic energy metabolism and the underlying mechanisms remain poorly understood. In this study, we found that cyclic stretch (10% elongation at 0.1 Hz) significantly enhanced glucose consumption, lactate levels (determined using a glucose/lactate assay kit), intracellular adenosine triphosphate (ATP) levels (quantified using rLuciferase/Luciferin reagent) and the mRNA expression of energy metabolism-related enzymes [mitochondrial ATP synthase, L-lactate dehydrogenase A (LDHA) and enolase 1; measured by RT-qPCR], and increased the phosphorylation levels of Akt, mammalian target of rapamycin (mTOR) and p70s6k (measured by western blot analysis) in human osteoblast‑like MG‑63 cells. Furthermore, the inhibition of Akt or mTOR with an antagonist (wortmannin or rapamycin) suppressed the stretch-induced increase in glucose consumption, lactate levels, intracellular ATP levels and the expression of mitochondrial ATP synthase and LDHA, indicating the significance of the Akt/mTOR/p70s6k pathway in regulating osteoblastic energy metabolism in response to mechanical stretch. Thus, we concluded that cyclic stretch regulates energy metabolism in MG‑63 cells partially through the Akt/mTOR/p70s6k signaling pathway. The present findings provide novel insight into osteoblastic mechanobiology from the perspective of energy metabolism.

Effect of Pore Size and Porosity on the Biomechanical Properties and Cytocompatibility of Porous NiTi Alloys

Five types of porous Nickel-Titanium (NiTi) alloy samples of different porosities and pore sizes were fabricated. According to compressive and fracture strengths, three groups of porous NiTi alloy samples underwent further cytocompatibility experiments. Porous NiTi alloys exhibited a lower Young’s modulus (2.0 GPa ~ 0.8 GPa). Both compressive strength (108.8 MPa ~ 56.2 MPa) and fracture strength (64.6 MPa ~ 41.6 MPa) decreased gradually with increasing mean pore size (MPS). Cells grew and spread well on all porous NiTi alloy samples. Cells attached more strongly on control group and blank group than on all porous NiTi alloy samples (p < 0.05). Cell adhesion on porous NiTi alloys was correlated negatively to MPS (277.2 μm ~ 566.5 μm; p < 0.05). More cells proliferated on control group and blank group than on all porous NiTi alloy samples (p < 0.05). Cellular ALP activity on all porous NiTi alloy samples was higher than on control group and blank group (p < 0.05). The porous NiTi alloys with optimized pore size could be a potential orthopedic material.

Nanostructured gellan and xanthan hydrogel depot integrated within a baghdadite scaffold augments bone regeneration

Controlled delivery of biological cues through synthetic scaffolds to enhance the healing capacity of bone defects is yet to be realized clinically. The purpose of this study was development of a bioactive tissue-engineered scaffold providing the sustained delivery of an osteoinductive drug, dexamethasone disodium phosphate (DXP), encapsulated within chitosan nanoparticles (CN). Porous baghdadite (BD; Ca₃ ZrSi₂ O₉ ) scaffolds, a zirconia-modified calcium silicate ceramic, was coated with DXP-encapsulated CN nanoparticles (DXP-CN) using nanostructured gellan and xanthan hydrogel (GX). Crosslinker and GX polymer concentrations were optimized to achieve a homogeneous distribution of hydrogel coating within BD scaffolds. Dynamic laser scattering indicated an average size of 521 ± 21 nm for the DXP-CN nanoparticles. In vitro drug-release studies demonstrated that the developed DXP-CN-GX hydrogel-coated BD scaffolds (DXP-CN-GX-BD) resulted in a sustained delivery of DXP over the 5 days (78 ± 6% of drug release) compared with burst release over 1 h, seen from free DXP loaded in uncoated BD scaffolds (92 ± 8% release in 1 h). To estimate the influence of controlled delivery of DXP from the developed scaffolds, the effect on MG 63 cells was evaluated using various bone differentiation assays. Cell culture within DXP-CN-GX-BD scaffolds demonstrated a significant increase in the expression of early and late osteogenic markers of alkaline phosphatase activity, collagen type 1 and osteocalcin, compared to the uncoated BD scaffold. The results suggest that the DXP-releasing nanostructured hydrogel integrated within the BD scaffold caused sustained release of DXP, improving the potential for osteogenic differentiation. Copyright © 2015 John Wiley & Sons, Ltd.

IL-4 and IL-13 inhibit IL-1β and TNF-α induced kinin B1 and B2 receptors through a STAT6-dependent mechanism

BACKGROUND AND PURPOSE

Bone resorption induced by interleukin-1β (IL-1β) and tumour necrosis factor (TNF-α) is synergistically potentiated by kinins, partially due to enhanced kinin receptor expression. Inflammation-induced bone resorption can be impaired by IL-4 and IL-13. The aim was to investigate if expression of B1 and B2 kinin receptors can be affected by IL-4 and IL-13.

EXPERIMENTAL APPROACH

We examined effects in a human osteoblastic cell line (MG-63), primary human gingival fibroblasts and mouse bones by IL-4 and IL-13 on mRNA and protein expression of the B1 and B2 kinin receptors. We also examined the role of STAT6 by RNA interference and using Stat6(-/-) mice.

KEY RESULTS

IL-4 and IL-13 decreased the mRNA expression of B1 and B2 kinin receptors induced by either IL-1β or TNF-α in MG-63 cells, intact mouse calvarial bones or primary human gingival fibroblasts. The burst of intracellular calcium induced by either bradykinin (B2 agonist) or des-Arg(10) -Lys-bradykinin (B1 agonist) in gingival fibroblasts pretreated with IL-1β was impaired by IL-4. Similarly, the increased binding of B1 and B2 ligands induced by IL-1β was decreased by IL-4. In calvarial bones from Stat6-deficient mice, and in fibroblasts in which STAT6 was knocked down by siRNA, the effect of IL-4 was decreased.

CONCLUSIONS AND IMPLICATIONS

These data show, for the first time, that IL-4 and IL-13 decrease kinin receptors in a STAT6-dependent mechanism, which can be one important mechanism by which these cytokines exert their anti-inflammatory effects and impair bone resorption.

Role of glass structure in defining the chemical dissolution behavior, bioactivity and antioxidant properties of zinc and strontium co-doped alkali-free phosphosilicate glasses

We investigated the structure-property relationships in a series of alkali-free phosphosilicate glass compositions co-doped with Zn(2+) and Sr(2+). The emphasis was laid on understanding the structural role of Sr(2+) and Zn(2+) co-doping on the chemical dissolution behavior of glasses and its impact on their in vitro bioactivity. The structure of glasses was studied using molecular dynamics simulations in combination with solid state nuclear magnetic resonance spectroscopy. The relevant structural properties are then linked to the observed degradation behavior, in vitro bioactivity, osteoblast proliferation and oxidative stress levels. The apatite-forming ability of glasses has been investigated by X-ray diffraction, infrared spectroscopy and scanning electron microscopy-energy-dispersive spectroscopy after immersion of glass powders/bulk in simulated body fluid (SBF) for time durations varying between 1h and 14 days, while their chemical degradation has been studied in Tris-HCl in accordance with ISO 10993-14. All the glasses exhibit hydroxyapatite formation on their surface within 1-3h of their immersion in SBF. The cellular responses were observed in vitro on bulk glass samples using human osteosarcoma MG63 cell line. The dose-dependent cytoprotective effect of glasses with respect to the concentration of zinc and strontium released from the glasses is also discussed.

Interaction of human osteoblast-like Saos-2 and MG-63 cells with thermally oxidized surfaces of a titanium-niobium alloy

An investigation was made of the adhesion, growth and differentiation of osteoblast-like MG-63 and Saos-2 cells on titanium (Ti) and niobium (Nb) supports and on TiNb alloy with surfaces oxidized at 165°C under hydrothermal conditions and at 600°C in a stream of air. The oxidation mode and the chemical composition of the samples tuned the morphology, topography and distribution of the charge on their surfaces, which enabled us to evaluate the importance of these material characteristics in the interaction of the cells with the sample surface. Numbers of adhered MG-63 and Saos-2 cells correlated with the number of positively-charged (related with the Nb₂O₅ phase) and negatively-charged sites (related with the TiO₂ phase) on the alloy surface. Proliferation of these cells is correlated with the presence of positively-charged (i.e. basic) sites of the Nb₂O₅ alloy phase, while cell differentiation is correlated with negatively-charged (acidic) sites of the TiO₂ alloy phase. The number of charged sites and adhered cells was substantially higher on the alloy sample oxidized at 600°C than on the hydrothermally treated sample at 165°C. The expression values of osteoblast differentiation markers (collagen type I and osteocalcin) were higher for cells grown on the Ti samples than for those grown on the TiNb samples. This was more particularly apparent in the samples treated at 165°C. No considerable immune activation of murine macrophage-like RAW 264.7 cells on the tested samples was found. The secretion of TNF-α by these cells into the cell culture media was much lower than for either cells grown in the presence of bacterial lipopolysaccharide, or untreated control samples. Thus, oxidized Ti and TiNb are both promising materials for bone implantation; TiNb for applications where bone cell proliferation is desirable, and Ti for induction of osteogenic cell differentiation.

24,25-Dihydroxyvitamin D3 cooperates with a stable, fluoromethylene LPA receptor agonist to secure human (MG63) osteoblast maturation

Vitamin D receptor (VDR) agonists supporting human osteoblast (hOB) differentiation in the absence of bone resorption are attractive agents in a bone regenerative setting. One potential candidate fulfilling these roles is 24,25-dihydroxy vitamin D3 (24,25D). Over forty years ago it was reported that supraphysiological levels of 24,25D could stimulate intestinal calcium uptake and aid bone repair without causing bone calcium mobilisation. VDR agonists co-operate with certain growth factors to enhance hOB differentiation but whether 24,25D might act similarly in promoting cellular maturation has not been described. Given our discovery that lysophosphatidic acid (LPA) co-operated with VDR agonists to enhance hOB maturation, we co-treated MG63 hOBs with 24,25D and a phosphatase-resistant LPA analog. In isolation 24,25D inhibited proliferation and stimulated osteocalcin expression. When co-administered with the LPA analog there were synergistic increases in alkaline phosphatase (ALP). These are encouraging findings which may help realise the future application of 24,25D in promoting osseous repair.

In vitro biocompatibility of a dentine substitute cement on human MG63 osteoblasts cells: Biodentine™ versus MTA(®)

AIM

To compare the in vitro biocompatibility of Biodentine™ and White ProRoot(®) mineral trioxide aggregate (MTA(®) ) with MG63 osteoblast-like cells and to characterize the cement surface.

METHODOLOGY

A direct contact model for MG63 osteoblast-like cells with cements was used for 1, 3 and 5 days. Four end-points were investigated: (i) cement surface characterization by atomic force microscopy (AFM), (ii) cell viability by MTT assay, (iii) protein amount quantification by Bradford assay and (iv) cell morphology by SEM. Statistical analyses were performed by analysis of variance (anova) with a repetition test method.

RESULTS

The roughness of the cements was comparable as revealed by AFM analysis. The MTT test for Biodentine™ was similar to that of MTA(®) . Biodentine™ and MTA(®) induced a similar but slight decrease in metabolic activity. The amount of total protein was significantly enhanced at day three (P < 0.05) but slightly decreased at day five for both tested samples. Biodentine™ was tolerated as well as MTA(®) in all cytotoxicity assays. SEM observations showed improvement of cell attachment and proliferation on both material surfaces following the three incubation periods.

CONCLUSION

The biocompatibility of Biodentine™ to bone cells was comparable to MTA(®) .

Size control and biological properties of monodispersed mesoporous bioactive glass sub-micron spheres

Monodispersed mesoporous bioactive glass sub-micron spheres with a controllable size and good biocompatibility were fabricated by an improved sol–gel method.

A phenotypic comparison of osteoblast cell lines versus human primary osteoblasts for biomaterials testing

Immortalized cell lines are used more frequently in basic and applied biology research than primary bone-derived cells because of their ease of access and repeatability of results in experiments. It is clear that these cell models do not fully resemble the behavior of primary osteoblast cells. Although the differences will affect the results of biomaterials testing, they are not clearly defined. Here, we focused on comparing proliferation and maturation potential of three osteoblast cell lines, SaOs2, MG-63, and MC3T3-E1 with primary human osteoblast (HOb) cells to assess their suitability as in vitro models for biomaterials testing. We report similarities in cell proliferation and mineralization between primary cells and MC3T3-E1. Both, SaOs2 and MG-63 cells demonstrated a higher proliferation rate than HOb cells. In addition, SaOs2, but not MG-63, cells demonstrated similar ALP activity, mineralization potential and gene regulation to HOb's. Our results demonstrate that despite SaOs-2, MG63, and MC3T3 cells being popular choices for emulating osteoblast behavior, none can be considered appropriate replacements for HOb's. Nevertheless, these cell lines all demonstrated some distinct similarities with HOb's, thus when applied in the correct context are a valuable in vitro pilot model of osteoblast functionality, but should not be used to replace primary cell studies.

Mechanical and cytotoxicity testing of acrylic bone cement embedded with microencapsulated 2-octyl cyanoacrylate

The water-reactive tissue adhesive 2-octyl cyanoacrylate (OCA) was microencapsulated in polyurethane shells and incorporated into Palacos R bone cement. The tensile and compressive properties of the composite material were investigated in accordance with commercial standards, and fracture toughness of the capsule-embedded bone cement was measured using the tapered double-cantilever beam geometry. Viability and proliferation of MG63 human osteosarcoma cells after culture with extracts from Palacos R bone cement, capsule-embedded Palacos R bone cement, and OCA were also analyzed. Incorporating up to 5 wt % capsules had little effect on the compressive and tensile properties of the composite, but greater than 5 wt % capsules reduced these values below commercial standards. Fracture toughness was increased by 13% through the incorporation of 3 wt % capsules and eventually decreased below the toughness of the capsule-free controls at capsule contents of 15 wt % and higher. The effect on cell proliferation and viability in response to extracts prepared from capsule-embedded and commercial bone cements were not significantly different from each other, whereas extracts from OCA were moderately toxic to cells. Overall, the addition of lower wt % of OCA-containing microcapsules to commercial bone cement was found to moderately increase static mechanical properties without increasing the toxicity of the material.

Enhancement of fatty acid-based polyurethanes cytocompatibility by non-covalent anchoring of chondroitin sulfate

For tissue engineering purpose biopolymer chondroitin sulfate (CS), one of the major components of cartilage and bone extracellular matrix, was immobilized onto the surface of amino-functionalized polyurethane (PU) films derived from naturally occurring oleic and 10-undecenoic acids. The amino-functionalized PUs were prepared by aminolysis with 1,6-hexamethylenediamine of synthesized PUs containing methyl ester groups. FTIR-ATR, XPS, SEM, and water contact angle measurements were used to confirm the surface changes at each step of treatment, both in morphologies and chemical composition. Cytotoxicity and cell morphology analysis using osteoblast cell line MG63 showed that PU-CS films are suitable materials for cell growth, spreading, and differentiation.

The biological effects of fibrin-binding synthetic oligopeptides derived from fibronectin on osteoblast-like cells

Purpose

The aim of this study was to investigate the effects of synthetic fibronectin (FN) fragments, including fibrin binding sites from amino-terminal FN fragments containing type I repeats 1 to 5, on osteoblast-like cell activity.

Methods

Oligopeptides ranging from 9 to 20 amino acids, designated FF1, FF3, and FF5, were synthesized by a solid-phase peptide synthesizing system, and we investigated the effects of these peptides on cell attachment and extent of mineralization using confocal microscopy, 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays, and Alizarin red S staining.

Results

FF3 and FF5 peptides increased the number of attached human osteoblastic cells, and FF3 administration led to prominent cell spreading. Mineralization was increased in FF3 and FF5 compared to FF1 and the untreated control.

Conclusions

Taken together, it can be concluded that the fibrin-binding oligopeptides FF3 and FF5 enhanced cell attachment and mineralization on osteoblast-like cells. These results indicate that FF3 and FF5 have the potential to increase osteoblast-like cell activity. Performing an in vivo study may provide further possibilities for surface modification of biomimetic peptides to enhance osteogenesis, thus improving the regeneration of destroyed alveolar bone.

Attachment, spreading and short-term proliferation of human osteoblastic cells cultured on chitosan films with different degrees of acetylation

Chitosan (Ch) is being actively investigated as a non-protein template for the growth of an increasing number of anchorage-dependent cells, including chondrocytes and bone cells. In the present work, Ch films with degrees of N-acetylation (DAs) in the range of 4 to 49% were evaluated with respect to the attachment, spreading and short-term proliferation of osteoblasts, using human osteoblastic MG-63 cells. The films were characterized in terms of surface morphology and surface charge by atomic force microscopy and streaming potential measurements, respectively. Cell attachment was assessed after 3 and 24 h of cell culture. After 24 h of incubation, cell attachment was found to be dependent on the DA, lower DAs favouring cell adhesion. With time, cell spreading and cytoskeleton organization were only attained for DAs <or= 13%. Regarding cell proliferation, cells grown on films with the lowest DA (4%) revealed a higher specific growth rate as compared to those grown on films with higher DAs. Films with a DA of 49% failed to sustain cell proliferation. In addition, a longer lag-phase was observed on Ch, as compared to TCPS, in accordance to an observed delay of cell spreading. The present findings revealed that differences in the DA as small as 9% may be critical in terms of the osteoblast response to two-dimensional Ch-based matrices.

Effect of adsorbed fibronectin on the differential adhesion of osteoblast-like cells and Staphylococcus aureus with and without fibronectin-binding proteins

The influence of fibronectin (Fn) coated surfaces patterned with poly(ethylene glycol) microgels having inter-gel spacings between 0.5 and 3.0 μm on the adhesion of Staphylococcus aureus strains with and without Fn-binding proteins and cellular adhesion/spreading was investigated. Quantitative force measurements between a S. aureus cell and a patterned surface showed that the adhesion force between the bacterium and the patterned surface increased substantially after Fn adsorption, regardless of the strain used, but decreased with decreasing inter-gel spacing. In flow-chamber experiments, the Fn-binding strain adhered at a higher rate after Fn adsorption than the strain lacking Fn-binding proteins. In both cases, the adhesion rates decreased with decreasing inter-gel spacing. Osteoblast-like cells could bind to patterned surfaces despite the microgels, and adsorbed Fn substantially amplified this effect. Even under highly non-adhesive conditions associated with closely spaced microgels, adsorbed Fn preserves a window of inter-gel spacing around 1 μm where the adhesion of staphylococcal cells is hindered while cells can still adhere and spread.

Primary human osteoblast cultures

Osteoblast cultures can be used to investigate the mechanisms of bone formation, to probe the cellular and molecular basis of bone disease, and to screen for potential therapeutic agents that affect bone formation. Here, we describe the methods for establishing and characterising primary human osteoblast cultures.

Absence of glutamine supplementation prevents differentiation of murine calvarial osteoblasts to a mineralizing phenotype

Osteoblasts in vitro differentiate from a proliferating to a mineralizing phenotype upon transfer to a medium rich in beta-glycerophosphate and ascorbic acid. The nutritional requirements of the cells at different stages of this differentiation process are not known. In other cell types, nutritional supplementation during surgery can improve the outcome in terms of speed of patient recovery and prognosis. There is therefore the potential for supplementation at the site of fracture repair or bone grafting with critical osteoblast nutritional factors to potentially accelerate healing. In this study we investigate which common cell nutrients are required for the proliferating and mineralizing stages of osteoblast differentiation. Medium containing 5.5 mM glucose was sufficient to achieve maximal proliferation of primary calvarial osteoblasts and human osteoblast cell lines, with some added benefit of additional glutamine supplementation. However, when cells were stimulated to mineralize, glucose was insufficient to support their energetic requirements. Only when cells were supplemented with glucose together with glutamine were high levels of osteocalcin expression observed together with mineralized nodules in culture, suggesting that this would be a useful combination to assess in cultures of primary human osteoblasts to determine whether it may have beneficial effects during fracture surgery, bone grafting, and fixation of uncemented arthroplasty implants.

In search of representative models of human bone-forming cells for cytocompatibility studies

Osteosarcoma-derived cells have been routinely used for studying osteoblastic functions, but it remains unclear to what extent they mimic the behavior of primary osteoblasts in the study of cells and materials interactions. This study reports comparatively on the responses of three human osteosarcoma cell lines, MG-63, Saos-2 and U-2 OS, and human primary osteoblasts cultured on Ti6Al4V surfaces or exposed to Ti particles. Phenotypic characterization of the cell lines revealed that Saos-2 cells and primary osteoblasts displayed similar expression patterns of Cbfa1, SP7 and osteocalcin. Unlike primary cells, the cell lines expressed markers of undifferentiated cells, had high proliferative rates and poor fibronectin matrix assembly. None of the three cell lines faithfully reproduced the adhesive behavior of primary osteoblasts when cultured on Ti6Al4V surfaces or exposed to Ti particles. Differences in cell growth between the cell lines and primary osteoblasts cultured on Ti6Al4V surfaces were also observed. Ti particles inhibited the growth of Saos-2 cells and primary osteoblasts to a similar extent, while no such effect was observed in U-2 OS and MG-63 cells. Saos-2 cells reproduced the alkaline phosphatase (ALP) activity profile of primary osteoblasts cultured on metallic surfaces or exposed to particles. Altogether, these results show that none of the osteoblast-like cells studied perfectly mimic the behavior of human osteoblast cells (hOB) on Ti6Al4V surfaces or exposed to Ti particles. Saos-2 cells reproduce some of the hOB responses such as the profile of enzymatic ALP activity when cultured on the surfaces or treated with particles as well as cell growth inhibition when exposed to Ti particles. Although in vitro cytocompatibility studies involve the evaluation of multiple parameters, Saos-2 cells may be used as representative of human osteoblasts when these standard tests are evaluated.

Differences in the pattern and regulation of mineral deposition in human cell lines of osteogenic and non-osteogenic origin

Bone marrow-derived mesenchymal stem cells (MSCs) are widely used as a cellular model of bone formation, and can mineralize in vitro in response to osteogenic medium (OM). It is unclear, however, whether this property is specific to cells of mesenchymal origin. We analysed the OM response in 3 non-osteogenic lines, HEK293, HeLa and NTera, compared to MSCs. Whereas HEK293 cells failed to respond to OM conditions, the 2 carcinoma-derived lines NTera and HeLa deposited a calcium phosphate mineral comparable to that present in MSC cultures. However, unlike MSCs, HeLa and NTera cultures did so in the absence of dexamethasone. This discrepancy was confirmed, as bone morphogenetic protein inhibition obliterated the OM response in MSCs but not in HeLa or NTera, indicating that these 2 models can deposit mineral through a mechanism independent of established dexamethasone or bone morphogenetic protein signalling.

Receptors and effects of gut hormones in three osteoblastic cell lines

Background

In recent years the interest on the relationship of gut hormones to bone processes has increased and represents one of the most interesting aspects in skeletal research. The proportion of bone mass to soft tissue is a relationship that seems to be controlled by delicate and subtle regulations that imply "cross-talks" between the nutrient intake and tissues like fat. Thus, recognition of the mechanisms that integrate a gastrointestinal-fat-bone axis and its application to several aspects of human health is vital for improving treatments related to bone diseases. This work analysed the effects of gut hormones in cell cultures of three osteoblastic cell lines which represent different stages in osteoblastic development. Also, this is the first time that there is a report on the direct effects of glucagon-like peptide 2, and obestatin on osteoblast-like cells.

Methods

mRNA expression levels of five gut hormone receptors (glucose-dependent insulinotropic peptide [GIP], glucagon-like peptide 1 [GLP-1], glucagon-like peptide 2 [GLP-2], ghrelin [GHR] and obestatin [OB]) were analysed in three osteoblastic cell lines (Saos-2, TE-85 and MG-63) showing different stages of osteoblast development using reverse transcription and real time polymerase chain reaction. The responses to the gut peptides were studied using assays for cell viability, and biochemical bone markers: alkaline phosphatase (ALP), procollagen type 1 amino-terminal propeptides (P1NP), and osteocalcin production.

Results

The gut hormone receptor mRNA displayed the highest levels for GIP in Saos-2 and the lowest levels in MG-63, whereas GHR and GPR39 (the putative obestatin receptor) expression was higher in TE-85 and MG-63 and lower in Saos-2. GLP-1 and GLP-2 were expressed only in MG-63 and TE-85. Treatment of gut hormones to cell lines showed differential responses: higher levels in cell viability in Saos-2 after GIP, in TE-85 and MG-63 after GLP-1, GLP-2, ghrelin and obestatin. ALP showed higher levels in Saos-2 after GIP, GHR and OB and in TE-85 after GHR. P1NP showed higher levels after GIP and OB in Saos-2. Decreased levels of P1NP were observed in TE-85 and MG-63 after GLP-1, GLP-2 and OB. MG-63 showed opposite responses in osteocalcin levels after GLP-2.

Conclusions

These results suggest that osteoblast activity modulation varies according to different development stage under different nutrition related-peptides.