Human gingival fibroblast integrin subunit expression on titanium implant surfaces

Substrate Stiffness of Bone Microenvironment Controls Functions of Pre-Osteoblasts and Fibroblasts In Vitro

The formation of bone in a bone defect is accomplished by osteoblasts, while the over activation of fibroblasts promotes fibrosis. However, it is not clear how the extracellular matrix stiffness of the bone-regeneration microenvironment affects the function of osteoblasts and fibroblasts. This study aim to investigate the effect of bone-regeneration microenvironment stiffness on cell adhesion, cell proliferation, cell differentiation, synthesizing matrix ability and its potential mechanisms in mechanotransduction, in pre-osteoblasts and fibroblasts. Polyacrylamide substrates mimicking the matrix stiffness of different stages of the bone-healing process (15 kPa, mimic granulation tissue; 35 kPa, mimic osteoid; 150 kPa, mimic calcified bone matrix) were prepared. Mouse pre-osteoblasts MC3T3-E1 and mouse fibroblasts NIH3T3 were plated on three types of substrates, respectively. There were significant differences in the adhesion of pre-osteoblasts and fibroblasts on different polyacrylamide substrates. Runx2 expression increased with increasing substrate stiffness in pre-osteoblasts, while no statistical differences were found in the Acta2 expression in fibroblasts on three substrates. OPN expression in pre-osteoblasts, as well as Fn1 and Col1a1 expression in fibroblasts, decreased with increasing stiffness. The difference between the cell traction force generated by pre-osteoblasts and fibroblasts on substrates was also found. Our results indicated that substrate stiffness is a potent regulator of pre-osteoblasts and fibroblasts with the ability of promoting osteogenic differentiation of pre-osteoblasts, while having no effect on myofibroblast differentiation of fibroblasts.

Focal adhesion formation of primary human gingival fibroblast on hydrothermally and in-sol-made TiO2 -coated titanium

Optimal cell adhesion of the gingival fibroblasts to dental implants is important for maintaining good implant integration. The aim of this study was to discover, if the nanoporous TiO₂ -coating on titanium alloy substrates is able to increase the cell adhesion of the human gingival fibroblasts (HGF). The study consisted of three differently produced titanium groups: hydrothermally produced TiO₂ -coating (HT), novel TiO₂ -coating made in sol (SOL), and noncoated control group. Primary HGF cells were initiated from gingival biopsies from patients having a third molar extraction. HGF were cultivated on titanium discs for 2 and 24 h to determine the initial attachment with confocal microscope. The cell spreading and adhesion protein signals were measured. In addition, expression of adhesion proteins vinculin, paxillin, and focal adhesion kinase (FAK) were measured after 3 days of cultivation by using Western Blotting. Higher protein levels of paxillin, vinculin, and FAK were induced on both coated discs compared to noncoated discs. The difference was statistically significant (p < 0.05) concerning expression of paxillin. The cell spreading was significantly larger on SOL discs after 2 and 24 h when comparing to noncoated controls. The confocal microscope analyses revealed significantly higher adhesion protein signals on both HT- and SOL-coated titanium compared to control group. This study showed, that both methods to produce TiO₂ -coatings are able to increase HGF adhesion protein expression and cell spreading on titanium surface. Accordingly, the coatings can potentially improve the gingival attachment to titanium implant surfaces.

Peptides for Coating TiO2 Implants: An In Silico Approach

Titanium is usually used in the manufacturing of metal implants due to its biocompatibility and high resistance to corrosion. A structural and functional connection between the living bone and the surface of the implant, a process called osseointegration, is mandatory for avoiding prolonged healing, infections, and tissue loss. Therefore, osseointegration is crucial for the success of the implantation procedure. Osseointegration is a process mediated by bone-matrix progenitor cells' proteins, named integrins. In this study, we used an in silico approach to assemble and test peptides that can be strategically used in sensitizing TiO₂ implants in order to improve osseointegration. To do so, we downloaded PDB structures of integrins α5β1, αvβ3, and αIIbβ3; their biological ligands; and low-cost proteins from the Protein Data Bank, and then we performed a primary (integrin-protein) docking analysis. Furthermore, we modeled complex peptides with the potential to bind to the TiO₂ surface on the implant, as well as integrins in the bone-matrix progenitor cells. Then we performed a secondary (integrin-peptide) docking analysis. The ten most promising integrin-peptide docking results were further verified by molecular dynamics (MD) simulations. We recognized 82 peptides with great potential to bind the integrins, and therefore to be used in coating TiO₂ implants. Among them, peptides 1 (GHTHYHAVRTQTTGR), 3 (RKLPDATGR), and 8 (GHTHYHAVRTQTLKA) showed the highest binding stability during the MD simulations. This bioinformatics approach saves time and more effectively directs in vitro studies.

Cellular properties of human gingival fibroblasts on novel and conventional implant-abutment materials

OBJECTIVES

To characterize human-gingival-fibroblast-(HGFs) viability, proliferation and adhesion on polymer-infiltrated-ceramic-network-(PICN), polyetheretherketone-(PEEK), hydroxyapatite-reinforced-polyetheretherketone-(HA-PEEK), polyetherketoneketone-(PEKK), as well as conventional titanium-(Ti) and zirconia ceramic-(Zr) implant materials in-vitro.

METHODS

Six materials (n = 40/group, 240 specimens) were standardized for surface roughness, assessed employing water contact angle measurements (WCA) and loaded with HGFs. HGF viability and proliferation were assessed at 24 and 72 h. Cell adhesion strength was evaluated after 24 h exposure to lateral shear forces using a shaking-device at 320 and 560-rpm.and qualitatively tested by scanning-electron-microscopy-(SEM) at 3, 24 and 72 h.

RESULTS

PICN demonstrated the lowest mean WCA (48.2 ± 6.3º), followed by Zr (73.8 ± 5.1º), while HA-PEEK showed the highest WCA (87.2 ± 1.5º; p ≤ 0.05). After 24 h, Zr showed the highest mean HGFs-viability rate (88 ± 14%), while PEKK showed the lowest one (78 ± 7%). At 72 h, Zr continued to show the highest HGF-viability (80 ± 6%) compared to PEKK (67.5 ± 6%) and PEEK (67%±5). SEM did not reveal differences between different materials with respect to cell attachment at 3, 24 or 72 h. At 320 rpm shaking, HGFs showed to be best attached to PICN (mean%-of-detached-cells ± SD; 26 ± 11%) and worst to PEEK (54 ± 18%). At 560 rpm shaking, Zr showed the least detached cells (32 ± 4%), while HA-PEEK revealed the highest number of detached cells (58 ± 3%; ANOVA/Tukey-post-hoc-test, differences not statistically significant).

SIGNIFICANCE

Dental implant abutment materials and their wettability strongly affect HGF proliferation and adhesion properties. Although, PICN showed the best wettability properties, Zr exhibited the strongest adhesion strength at high shaking. Within the current study's limitations, Zr remains the most biocompatible abutment material.

Engineering of Bio-Adhesive Ligand Containing Recombinant RGD and PHSRN Fibronectin Cell-Binding Domains in Fusion with a Colored Multi Affinity Tag: Simple Approach for Fragment Study from Expression to Adsorption

Engineering of biomimetic motives have emerged as promising approaches to improving cells’ binding properties of biomaterials for tissue engineering and regenerative medicine. In this study, a bio-adhesive ligand including cell-binding domains of human fibronectin (FN) was engineered using recombinant protein technology, a major extracellular matrix (ECM) protein that interacts with a variety of integrins cell-surface’s receptors and other ECM proteins through specific binding domains. 9th and 10th fibronectin type III repeat containing Arginine-Glycine-Aspartic acid (RGD) and Pro-His-Ser-Arg-Asn (PHSRN) synergic site (FNIII9-10) were expressed in fusion with a Colored Multi Affinity Tag (CMAT) to develop a simplified production and characterization process. A recombinant fragment was produced in the bacterial system using E. coli with high yield purified protein by double affinity chromatography. Bio-adhesive surfaces were developed by passive coating of produced fragment onto non adhesive surfaces model. The recombinant fusion protein (CMAT-FNIII9/10) demonstrated an accurate monitoring capability during expression purification and adsorption assay. Finally, biological activity of recombinant FNIII9/10 was validated by cellular adhesion assay. Binding to α5β1 integrins were successfully validated using a produced fragment as a ligand. These results are robust supports to the rational development of bioactivation strategies for biomedical and biotechnological applications.

Impact of Implant Surface Material and Microscale Roughness on the Initial Attachment and Proliferation of Primary Human Gingival Fibroblasts

Due to the rising demand for zirconia (Zr) based implant systems, it is important to understand the impact of Zr and titanium (Ti) implants and particularly their topography on soft tissue healing. As human gingival fibroblasts (hGFs) are the predominant cells in peri-implant soft tissue, we focused on examining the effect of implant material and surface roughness on hGFs' initial attachment, growth and the expression of proteins involved in the focal adhesion. hGFs isolated from eight healthy donors were cultured on the following surfaces: smooth titanium machined surface (TiM), smooth zirconia machined surface (ZrM), moderately rough titanium surface (SLA), or moderately rough zirconia surface (ZLA) for up to 14 days. The initial attachment of hGFs was evaluated by scanning electron microscopy. Cell proliferation/viability was assessed by cell counting kit 8. Focal adhesion and cytoskeleton were visualized by a focal adhesion staining kit. The gene expression of focal adhesion kinase (FAK), α-smooth muscle actin (α-SMA), and integrin subunits ITG-β1, ITG-β4, ITG-α4, ITG-α5, ITG-α6, was evaluated by qPCR. Cell proliferation/viability was slightly decreased by moderately rough surfaces, whereas no effect of surface material was observed. Cell morphology was strikingly different between differently treated surfaces: on machined surfaces, cells had elongated morphology and were attached along the grooves, whereas on moderately rough surfaces, cells were randomly attached. Surface roughness had a more pronounced effect on the gene expression compared to the surface material. The expression of FAK, α-SMA, ITG-β4, ITG-α5, and ITG-α6 was enhanced by moderately rough surfaces compared to smooth surfaces. Within the limitations of this in vitro study, it can be concluded that the behavior of primary hGFs is primarily affected by surface structure, whereas no apparent advantage of Zr over Ti could be observed.

Effect of implant surface material and roughness to the susceptibility of primary gingival fibroblasts to inflammatory stimuli

OBJECTIVES

The impact of the implant surface material and roughness on inflammatory processes in peri-implantitis is not entirely clear. Hence, we investigated how titanium and zirconia surfaces with different roughness influence the susceptibility of primary human gingival fibroblasts to different inflammatory stimuli.

METHODS

Primary human gingival fibroblasts were isolated from 8 healthy individuals and cultured on following surfaces: smooth titanium machined surface (TiM), smooth zirconia machined surface (ZrM), moderately rough titanium surface (SLA), or moderately rough zirconia surface (ZLA). Subsequently, stimulation with one of the following stimuli was performed: Porphyromonas gingivalis lipopolysaccharide (LPS), tumor necrosis factor (TNF)-α, interleukin (IL)-1β. The resulting production of IL-6, IL-8, and monocyte chemoattractant protein (MCP)-1 was measured by qPCR and ELISA.

RESULTS

P. gingivalis LPS induced IL-6 and MCP-1 production was slightly higher on titanium surfaces compared to zirconia surfaces. IL-1β induced IL-6 production was not affected by any surface characteristic. The production of MCP-1 in response to IL-1β was higher on smooth compared to rough surfaces and was not affected by the material. The production of IL-6 and MCP-1 in response to TNF-α was most strongly affected by surface characteristics. Higher production of these cytokine was observed on smooth compared to rough surfaces and on titanium compared to zirconia surfaces. Surface characteristics had only minor effects on IL-8 production.

SIGNIFICANCE

The susceptibility of primary gingival fibroblasts to inflammation depends on various factors, such as surface material, surface roughness and the nature of inflammatory stimuli. All these factors might determine susceptibility to peri-implantitis.

A proof of concept gene-activated titanium surface for oral implantology applications

Dental implants are very successful medical devices, yet implant failures do occur due to biological and mechanical complications. Peri-implantitis is one such biological complication that is primarily caused by bacteria and their products at the implant soft tissue interface. Bacterial infiltration can be prevented by the formation of a reliable soft tissue seal encircling dental implants. Platelet-derived growth factor-BB (PDGF-BB) has significant chemotactic and proliferative effects on various mesenchymal cell types, including fibroblasts, and therefore can be an effective molecule to enhance the peri-implant soft tissue seal. To overcome the limitations of the recombinant protein form of PDGF-BB, such as cost and the need for supraphysiological doses, we have developed and characterized a titanium surface that is rendered bioactive by coating it with polyethylenimine-plasmid DNA (pDNA) nanoplexes in the presence of sucrose. Human embryonic kidney 293T (HEK293T) cells and human primary gingival fibroblasts (GFs) were successfully transfected in culture with enhanced green fluorescent protein (EGFP)-encoding pDNA or platelet-derived growth factor subunit B (PDGFB)-encoding pDNA loaded into nanoplexes and coated onto titanium disks in a dose-dependent manner. GFs were shown to secrete PDGF-BB for at least 7 days after transfection and displayed both minimal viability loss and increased integrin-α2 expression 4 days posttransfection.

Strontium Effects on Human Gingival Fibroblasts

Strontium is a naturally occurring alkaline earth metal that has been shown to be useful not only in the treatment and prevention of osteoporosis but also in the treatment of dentinal hypersensitivity in the oral cavity; strontium is also an effective cariostatic, antiplaque, antigingivitis agent. Relatively little is known, however, about the effects of strontium on gingival fibroblasts. The purpose of the present investigation was to conduct in vitro studies on the potential for strontium to positively affect the activity of these cells such that it might be effective in the enhancement of gingival attachment to surfaces, such as healing abutments in implants in the oral cavity. The results indicate that strontium added as strontium citrate (0.5–1.0 mM), both in the absence and presence of a healing abutment, increases human gingival cell activity and decreases apoptosis in these cells. Scanning electron microscopy studies also reveal that the addition of strontium increases attachment of gingival fibroblasts to the surfaces of healing abutments. These studies provide the basis for further investigations on the use of strontium in the prevention and treatment of peri-implantitis by maximizing the formation of a peri-implant soft-tissue barrier.

Influence on proliferation and adhesion of human gingival fibroblasts from different titanium surface decontamination treatments: An in vitro study

OBJECTIVES

To investigate the effects of different decontamination treatments on microstructure of titanium (Ti) surface as well as proliferation and adhesion of human gingival fibroblasts (HGFs).

MATERIAL AND METHODS

Ti discs with machined (M) and sand blasted, acid etched (SAE) surfaces were treated with five different decontamination treatments: (1) stainless steel curette (SSC), ultrasonic system with (2) straight carbon fiber tip (UCF) or (3) metal tip (UM), (4) rotating Ti brush (RTB), and (5) Er:YAG laser (30 mJ/pulse at 30 Hz). Surface roughness was analyzed under optical interferometry. HGFs were cultured on each disc. Proliferation and adhesive strength were analyzed. qRT-PCR and ELISA were performed to detect the RNA and protein expression of FAK, ITGB1, COL1A1, and FN1 respectively from different Ti surfaces.

RESULTS

Surface roughness increased on M surface. Proliferation, adhesive strength and gene expression were higher on M surface than SAE surface. Decontamination treatments affected surface parameters significantly (P < 0.001), making M surface less smooth while SAE surface became less rough. SSC, UCF, UM and RTB decreased proliferation on M surfaces significantly (P < 0.05). UCF, RTB and laser increased proliferation on SAE surface significantly (P < 0.05). UM decreased adhesive strength on M surface significantly and laser increased adhesive strength on SAE surface significantly (P < 0.05). Gene expression increased with time and was altered by decontamination treatments significantly (P < 0.001).

CONCLUSIONS

Decontamination treatments influence surface roughness and cell behavior of HGFs. Laser might be an optimal decontamination treatment which has the least negative effect on M surface and the most positive effect on SAE surface.

Adhesion of living cells to abutment materials, dentin, and adhesive luting cement with different surface qualities

OBJECTIVE

We tested the adhesion properties of living gingival fibroblasts on three different implant abutment materials, adhesive resin used to bond bi-partite abutments, and human dentin.

METHODS

Discs of lithium disilicate (LS), zirconium dioxide (Zr), adhesive resin cement (AR), titanium (Ti), and human dentin (HD) were fabricated with three different levels of surface roughness (rough, machined, and polished). Ra and Rz, water contact angle, and cell detachment forces were measured. Cell detachment force was measured for single cells using single-cell force spectroscopy. Data were statistically analyzed using parametric tests (ANOVA, MANOVA, Bonferroni post-hoc tests).

RESULTS

Surface roughness significantly influenced the water contact angle for all materials (P≤0.05). Overall, HD showed the lowest contact angle, followed by LS, Ti, Zr, and AR (P≤0.05). Comparison of cell detachment forces between materials with rough and machined surfaces revealed no significant differences (P>0.05), with the exception of Zr compared to HD with rough surfaces (P=0.006). For polished surfaces, HD showed the highest detachment force (P≤0.0001), followed by Ti, AR, and Zr, which did not significantly differ from each other (P>0.05) and LS; Ti/AR was significantly different from LS (P≤0.05). Except for HD, where polished surfaces exhibited the highest cell detachment force (P≤0.002), most machined surfaces showed higher cell detachment forces than polished or rough surfaces.

SIGNIFICANCE

Implant abutments should ideally be provided with a machined like surface roughness for best cell adhesion.

Selective responses of human gingival fibroblasts and bacteria on carbon fiber reinforced polyetheretherketone with multilevel nanostructured TiO2

The long-term success of dental implants relies not only on stable osseointegration but also on the integration of implant surfaces with surrounding soft tissues. In our previous work, titanium plasma immersion ion implantation (PIII) technique was applied to modify the carbon-fiber-reinforced polyetheretherketone (CFRPEEK) surface, constructing a unique multilevel TiO2 nanostructure thus enhancing certain osteogenic properties. However, the interactions between the modified surface and soft-tissue cells are still not clear. Here, we fully investigate the biological behaviors of human gingival fibroblasts (HGFs) and oral pathogens on the structured surface, which determine the early peri-implant soft tissue integration. Scanning electron microscopy (SEM) shows the formation of nanopores with TiO2 nanoparticles embedded on both the sidewall and bottom. In vitro studies including cell adhesion, viability assay, wound healing assay, real-time PCR, western blot and enzyme-linked immunosorbent assay (ELISA) disclose improved adhesion, migration, proliferation, and collagen secretion ability of HGFs on the modified CFRPEEK. Moreover, the structured surface exhibits sustainable antibacterial properties towards Streptococcus mutans, Fusobacterium nucleatum and Porphyromonas gingivalis. Our results reveal that the multilevel TiO2 nanostructures can selectively enhance soft tissue integration and inhibit bacterial reproduction, which will further support and broaden the adoption of CFRPEEK materials in dental fields.

Characterization of Human Gingival Fibroblasts on Zirconia Surfaces Containing Niobium Oxide

It was indicated that tetragonal zirconia polycrystal (TZP) containing yttria (Y₂O₃) and niobium oxide (Nb₂O₅) ((Y,Nb)-TZP) could be an adequate dental material to be used at esthetically important sites. The (Y,Nb)-TZP was also proved to possess its osteogenic potential comparable with those conventional dental implant material, titanium (Ti). The objective of the current study was to characterize cellular response of human gingival fibroblasts (HGFs) to smooth and rough surfaces of the (Y,Nb)-TZP disc, which were obtained by polishing and sandblasting, respectively. Various microscopic, biochemical, and molecular techniques were used to investigate the disc surfaces and cellular responses for the experimental (Y,Nb)-TZP and the comparing Ti groups. Sandblasted rough (Y,Nb)-TZP (Zir-R) discs had the highest surface roughness. HGFs cultured on polished (Y,Nb)-TZP (Zir) showed a rounded cell morphology and light spreading at 6 h after seeding and its proliferation rate significantly increased during seven days of culture compared to other surfaces. The mRNA expressions of type I collagen, integrin α2 and β1 were significantly stimulated for the Zir group at 24 h after seeding. The current findings, combined with the previous results, indicate that (Y,Nb)-TZP provides appropriate surface condition for osseointegration at the fixture level and for peri-implant mucosal sealing at the abutment level producing a suitable candidate for dental implantation with an expected favorable clinical outcome.

Differentiation, apoptosis, and GM-CSF receptor expression of human gingival fibroblasts on a titanium surface treated by a dual acid-etched procedure

OBJECTIVES

Analysis of the effects of titanium surface properties on the biological behavior of human gingival fibroblasts (HGFs).

MATERIALS AND METHODS

HGFs were in vitro cultured on a titanium surface modified by a dual acid-etched procedure and on a control machined surface. Cell adhesion, proliferation, apoptosis, production of certain extracellular matrix (ECM) proteins, and expression of granulocyte macrophage-colony stimulating factor receptor (GM-CSFR) were investigated using in each experiment a total of 18 samples for each titanium surface.

RESULTS

Cell attachment at 3 h of culture was statistically significantly higher on the etched surface. HGF growth increased on both surfaces during the entire experimental period and at day 14 of culture cell proliferation was statistically significantly higher on the treated surface than on the control. No statistically significant differences in percentage of apoptosis events were observed between the surfaces. ECM protein production increased progressively over time on both surfaces. A statistically significant deposition was observed at day 7 and 14 for collagen I and only at day 14 for fibronectin and tenascin, when compared to the baseline. GM-CSFR registered a positive expression on both surfaces, statistically significant at day 14 on the etched surface in comparison with the machined one.

CONCLUSIONS

Data showed that titanium surface microtopography modulates in vitro cell response and phenotypical expression of HGFs. The etched surface promoted a higher cell proliferation and differentiation improving the biological behavior of HGFs.

CLINICAL RELEVANCE

Results suggest a possible beneficial effect of surface etching modification on peri-implant biological integration and soft tissue healing which is critical for the formation of a biological seal around the neck of dental implants.

Regulation of matrix remodelling phenotype in gingival fibroblasts by substratum topography

Gingival connective tissue often has a composition resembling that of scar surrounding dental implant abutments. Increased cell adhesion, α-smooth muscle actin (α-SMA) expression and increased extracellular matrix deposition are a hallmark of fibrotic cells, but how topographic features influence gingival fibroblast adhesion and adoption of the α-SMA positive myofibroblast phenotype associated with scarring is unknown. The purpose of the present study was to demonstrate whether implant topographies that limit adhesion formation would reduce myofibroblast differentiation and extracellular matrix deposition. Human gingival fibroblasts were cultured on PT (smooth) and SLA (roughened) titanium discs for varying time-points. At 1 and 2 weeks after seeding, incorporation of α-SMA into stress-fibre bundles and fibronectin deposition was significantly higher on PT than SLA surfaces indicating differentiation of the cells towards a myofibroblast phenotype. Analysis of adhesion formation demonstrated that cells formed larger adhesions and more stable adhesions on PT, with more nascent adhesions observed on SLA. Gene expression analysis identified up-regulation of 15 genes at 24 hrs on SLA versus PT associated with matrix remodelling. Pharmacological inhibition of Src/FAK signalling in gingival fibroblasts on PT reduced fibronectin deposition and CCN2 expression. We conclude that topographical features that reduce focal adhesion stability could be applied to inhibit myofibroblast differentiation in gingival fibroblasts.

Surface hydride on titanium by cathodic polarization promotes human gingival fibroblast growth

Connective tissue seal to dental abutment is crucial for peri-implant health. Several efforts have been made previously to optimize abutment surfaces, but no consensus has been reached regarding the optimal surface architecture and/or composition for soft tissue seal. Here, we report on experiments using cathodic polarization in organic acids to optimize titanium (Ti) surfaces for use as abutments. The three main factors affecting surface topography and chemistry were electrolyte composition, current density, and polarization time. Under identical conditions, oxalic acid created rougher surfaces than tartaric acid and acetic acid, and acetic acid produced more surface hydride. Surface hydride amount was suggested to first increase and then decrease with current density from 1 mA/cm(2) to 15 mA/cm(2) . The complexity of the surface topography and hydride production both increased with polarization time. Proliferation rate of human gingival fibroblasts (HGFs) was positively correlated with surface hydride content, suggesting the positive effect of surface hydride on connective tissue growth around dental abutment. Changes in surface topography and hydrophilicity did not significantly influence HGF growth.

Periodontal ligament cell behavior on different titanium surfaces

AIM

The purpose of this study was to investigate proliferation, morphology, mineralization and mRNA expressions of mineralized tissue associated proteins of PDL cells on smooth (S), sandblasted small-grit (SSG), sandblasted large-grit (SLG) and sodium titanate (NaTi) coated titanium alloys, in vitro.

METHODS AND MATERIALS

PDL cells were cultured with DMEM media containing 10% FBS on the S, SSG, SLG and NaTi titanium surfaces. PDL cell proliferation, mineralization and immunohistochemistry experiments for Bone Sialoprotein (BSP) were performed. The morphology of the PDL cells was examined using confocal and scanning electron microscopy (SEM). Gene expression profiles of cells were evaluated using a quantitative-polymerase chain reaction (Q-PCR) for type I collagen (COL I), Osteocalcin (OCN), osteopontin (OPN) and Runt-related transcription factor-2 (Runx2) on days 7 and 14.

RESULTS

Proliferation results on days 6 and 10 were similar in groups, while those of day 13 revealed a decrease in the NaTi group when compared to the S group. NaTi surface induced BSP mRNA expression which was correlated with mineralization tests and BSP immunostaining results. Increased Runx2 mRNA expression was also noted in the NaTi surface when compared to other surfaces.

CONCLUSIONS

This study considers the NaTi surface as a potential alternative to SSG and SLG surfaces. This surface might provide a promising environment for PDL ligament-anchored implants.

Anodized-hydrothermally treated titanium with a nanotopographic surface structure regulates integrin-α6β4 and laminin-5 gene expression in adherent murine gingival epithelial cells

PURPOSE

Peri-implant epithelium associated with the structure of the internal basal lamina is in contact with a transmucosal portion of the endosseous implant surface. This contact is important to protect the many complex factors required for the long-term stability and maintenance of the implant. This study investigated the effect of initial adhesion of gingival epithelial cells to anodized-hydrothermally treated commercially pure titanium with nanotopographic structure (SA-treated c.p.Ti). Changes in cell morphology and gene expression of integrin-α6β4 and laminin-5 were assessed.

METHODS

Murine immortalized gingival epithelial (GE1) cells were cultured for 1-3 days on c.p.Ti, anodic oxide (AO) c.p.Ti, and SA-treated c.p.Ti disks. Cell morphology was analyzed using scanning electron microscopy (SEM). Cell proliferation was analyzed using the WST-1 assay. Integrin-α6β4 and laminin-5 (α3, β3, γ2) mRNA levels were measured using real-time quantitative RT-PCR.

RESULTS

The GE1 cells appeared flattened with extensions on all disks by SEM analysis. Filopodium-like extensions were bound closely to the nanotopographic structure surface of SA-treated c.p.Ti especially at day 3 of culture. GE1 cell proliferation as well as the expression of integrin-α6β4 and laminin-5 (α3, β3, γ2) mRNAs was significantly higher on SA-treated c.p.Ti than on c.p.Ti and AO c.p.Ti disks after 3 days (P<0.05).

CONCLUSIONS

Gingival epithelial cells initially attach to a transmucosal portion of SA-treated c.p.Ti implant material and subsequently express the integrin-α6β4 adhesion molecule and the laminin-5 extracellular matrix molecule. This cell behavior may play a key role in maintaining the peri-implant oral mucosal tissue barrier.

The deep-sea natural products, biogenic polyphosphate (Bio-PolyP) and biogenic silica (Bio-Silica), as biomimetic scaffolds for bone tissue engineering: fabrication of a morphogenetically-active polymer

Bone defects in human, caused by fractures/nonunions or trauma, gain increasing impact and have become a medical challenge in the present-day aging population. Frequently, those fractures require surgical intervention which ideally relies on autografts or suboptimally on allografts. Therefore, it is pressing and likewise challenging to develop bone substitution materials to heal bone defects. During the differentiation of osteoblasts from their mesenchymal progenitor/stem cells and of osteoclasts from their hemopoietic precursor cells, a lineage-specific release of growth factors and a trans-lineage homeostatic cross-talk via signaling molecules take place. Hence, the major hurdle is to fabricate a template that is functioning in a way mimicking the morphogenetic, inductive role(s) of the native extracellular matrix. In the last few years, two naturally occurring polymers that are produced by deep-sea sponges, the biogenic polyphosphate (bio-polyP) and biogenic silica (bio-silica) have also been identified as promoting morphogenetic on both osteoblasts and osteoclasts. These polymers elicit cytokines that affect bone mineralization (hydroxyapatite formation). In this manner, bio-silica and bio-polyP cause an increased release of BMP-2, the key mediator activating the anabolic arm of the hydroxyapatite forming cells, and of RANKL. In addition, bio-polyP inhibits the progression of the pre-osteoclasts to functionally active osteoclasts. Based on these findings, new bioinspired strategies for the fabrication of bone biomimetic templates have been developed applying 3D-printing techniques. Finally, a strategy is outlined by which these two morphogenetically active polymers might be used to develop a novel functionally active polymer.

The biological seal of the implant-soft tissue interface evaluated in a tissue-engineered oral mucosal model

For dental implants, it is vital that an initial soft tissue seal is achieved as this helps to stabilize and preserve the peri-implant tissues during the restorative stages following placement. The study of the implant-soft tissue interface is usually undertaken in animal models. We have developed an in vitro three-dimensional tissue-engineered oral mucosal model (3D OMM), which lends itself to the study of the implant-soft tissue interface as it has been shown that cells from the three-dimensional OMM attach onto titanium (Ti) surfaces forming a biological seal (BS). This study compares the quality of the BS achieved using the three-dimensional OMM for four types of Ti surfaces: polished, machined, sandblasted and anodized (TiUnite). The BS was evaluated quantitatively by permeability and cell attachment tests. Tritiated water (HTO) was used as the tracing agent for the permeability test. At the end of the permeability test, the Ti discs were removed from the three-dimensional OMM and an Alamar Blue assay was used for the measurement of residual cells attached to the Ti discs. The penetration of the HTO through the BS for the four types of Ti surfaces was not significantly different, and there was no significant difference in the viability of residual cells that attached to the Ti surfaces. The BS of the tissue-engineered oral mucosa around the four types of Ti surface topographies was not significantly different.

Altered cell motility and attachment with titanium surface modifications

BACKGROUND

Titanium implants are widely used in dentistry to replace lost teeth. Various surface modifications have been used to improve implant retention and osseointegration. This study is designed to compare the ability of three titanium surfaces to promote cell attachment and cell motility of cells relevant to periodontal tissues.

METHODS

Three clinically relevant surfaces were tested: 1) machined titanium; 2) a titanium surface roughened through acid etching (dual thermal-etched titanium [DTET]); and 3) a titanium surface roughened with nanometer-scale calcium phosphate deposition (nanoscale calcium phosphate-impregnated titanium [NCPIT]). Cell attachment and migration were examined for four cell types: rat osteosarcoma cells, human osteoblasts, and gingival and periodontal ligament (PDL) fibroblasts.

RESULTS

All four cell types attached to each of the three titanium surfaces equally by 2 hours, and the PDL and gingival fibroblasts generally displayed less attachment than the osteosarcoma cells and osteoblasts. The cells displayed differential motility and long-term attachment to each of the titanium surfaces. Osteosarcoma cells displayed preferential motility on NCPIT, whereas PDL fibroblasts were more motile on machined titanium, and gingival fibroblasts moved more rapidly on both DTET and NCPIT. Osteoblasts displayed little motility on any of the titanium surfaces and lost viability on NCPIT after 24 hours. Gingival fibroblasts lost attachment to machined titanium.

CONCLUSIONS

Periodontal cells displayed differential motility and long-term attachment to titanium surfaces. Selective modification of titanium surface properties in various regions of an implant may be useful in guiding specific cell populations to specific locations where they might best aid in osseointegration and soft tissue remodeling.

Development of a novel model for the investigation of implant-soft tissue interface

BACKGROUND

In dental implant treatment, the long-term prognosis is dependent on the biologic seal formed by the soft tissue around the implant. The in vitro investigation of the implant-soft tissue interface is usually carried out using a monolayer cell-culture model that lacks a polarized-cell phenotype. This study developed a tissue-engineered three-dimensional oral mucosal model (3D OMM) to investigate the implant-soft tissue interface.

METHODS

A 3D OMM was constructed using primary human oral keratinocytes and fibroblasts cultured on a skin-derived scaffold at an air-liquid interface. A titanium implant was inserted into the engineered oral mucosa and further cultured to establish epithelial attachment. The 3D OMM was characterized using basic histology and immunostaining for cytokeratin (CK) 10 and CK13. Histomorphometric analyses of the implant-soft tissue interface were carried out using a light-microscopy (LM) examination of ground sections and semi-thin sections as well as scanning electron microscopy (SEM).

RESULTS

Immunohistochemistry analyses suggests that the engineered oral mucosa closely resembles the normal oral mucosa. The LM and SEM examinations reveal that the 3D OMM forms an epithelial attachment on the titanium surface.

CONCLUSION

The 3D OMM provided mimicking peri-implant features as seen in an in vivo model and has the potential to be used as a relevant alternative model to assess implant-soft tissue interactions.

Modulation of human gingival fibroblast adhesion, morphology, tyrosine phosphorylation, and ERK 1/2 localization on polished, grooved and SLA substratum topographies

Attachment of connective tissue to dental implants, which is influenced by surface topography, is an important determinant of implant success. Approaches employed to alter topography include acid etching or blasting to produce roughened surfaces, and production of precisely defined topographies using microfabrication techniques. The aim of this study was to assess the influence of polished, microgrooved, and sand-blasted, large grit, acid-etched (SLA) topographies on fibroblast adhesion, morphology, activation, and ERK 1/2 phosphorylation and localization. Human gingival fibroblasts (HGFs) spread on all tested surfaces within 2 h, and topography influenced the pattern of phosphotyrosine localization. Fibrillar adhesion formation was prominent in HGFs cultured on microgrooves and SLA at 24 h compared with smooth. No significant difference in ERK 1/2 phosphorylation was observed at 2 or 24 h, but nuclear localization depended on culture time and substratum topography. Nuclear localization of ERK 1/2 occurred at 2 h on polished surfaces, but was not evident at 1 week. In contrast, cells on SLA and grooved surfaces did not exhibit nuclear localization of ERK 1/2 at early times, but did at 1 week. The results of this study suggest that rough and microfabricated topographies influence fibroblast adhesion and intracellular signaling through focal adhesion/integrin-dependent mechanisms in a time-dependent manner.