Nanometer scale titanium surface texturing are detected by signaling pathways involving transient FAK and Src activations

The Action of Angiocrine Molecules Sourced from Mechanotransduction-Related Endothelial Cell Partially Explain the Successful of Titanium in Osseointegration

Since Branemark's findings, titanium-based alloys have been widely used in implantology. However, their success in dental implants is not known when considering the heterogenicity of housing cells surrounding the peri-implant microenvironment. Additionally, they are expected to recapitulate the physiological coupling between endothelial cells and osteoblasts during appositional bone growth during osseointegration. To investigate whether this crosstalk was happening in this context, we considered the mechanotransduction-related endothelial cell signaling underlying laminar shear stress (up to 3 days), and this angiocrine factor-enriched medium was harvested further to use exposing pre-osteoblasts (pOb) for up to 7 days in vitro. Two titanium surfaces were considered, as follows: double acid etching treatment (w_DAE) and machined surfaces (wo_DAE). These surfaces were used to conditionate the cell culture medium as recommended by ISO10993-5:2016, and this titanium-enriched medium was later used to expose ECs. First, our data showed that there is a difference between the surfaces in releasing Ti molecules to the medium, providing very dynamic surfaces, where the w_DAE was around 25% higher (4 ng/mL) in comparison to the wo_DAE (3 ng/mL). Importantly, the ECs took up some of this titanium content for up to 3 days in culture. However, when this conditioned medium was used to expose pOb for up to 7 days, considering the angiocrine factors released from ECs, the concentration of Ti was lesser than previously reported, reaching around 1 ng/mL and 2 ng/mL, respectively. Thereafter, pOb exposed to this angiocrine factor-enriched medium presented a significant difference when considering the mechanosignaling subjected to the ECs. Shear-stressed ECs showed adequate crosstalk with osteoblasts, stimulating the higher expression of the Runx2 gene and driving higher expressions of Alkaline phosphatase (ALP), bone sialoprotein (BSP), and osteocalcin. Mechanotransduction-related endothelial cell signaling as a source of angiocrine molecules also stimulated the higher expression of the Col3A1 gene in osteoblasts, which suggests it is a relevant protagonist during trabecular bone growth. In fact, we investigated ECM remodeling by first evaluating the expression of genes related to it, and our data showed a higher expression of matrix metalloproteinase (MMP) 2 and MMP9 in response to mechanosignaling-based angiocrine molecules, independent of considering w_DAE or the wo_DAE, and this profile reflected on the MMP2 and MMP9 activities evaluated via gelatin-based zymography. Complimentarily, the ECM remodeling seemed to be a very regulated mechanism in mature osteoblasts during the mineralization process once both TIMP metallopeptidase inhibitor 1 and 2 (TIMP1 and TIMP2, respectively) genes were significantly higher in response to mechanotransduction-related endothelial cell signaling as a source of angiocrine molecules. Altogether, our data show the relevance of mechanosignaling in favoring ECs' release of bioactive factors peri-implant, which is responsible for creating an osteogenic microenvironment able to drive osteoblast differentiation and modulate ECM remodeling. Taking this into account, it seems that mechanotransduction-based angiocrine molecules explain the successful use of titanium during osseointegration.

Recombinant sugarcane cystatin CaneCPI-5 promotes osteogenic differentiation

Cysteine proteases orchestrate bone remodeling, and are inhibited by cystatins. In reinforcing our hypothesis that exogenous and naturally obtained inhibitors of cysteine proteases (cystatins) act on bone remodeling, we decided to challenge osteoblasts with sugarcane-derived cystatin (CaneCPI-5) for up to 7 days. To this end, we investigated molecular issues related to the decisive, preliminary stages of osteoblast biology, such as adhesion, migration, proliferation, and differentiation. Our data showed that CaneCPI-5 negatively modulates both cofilin phosphorylation at Ser03, and the increase in cytoskeleton remodeling during the adhesion mechanism, possibly as a prerequisite to controlling cell proliferation and migration. This is mainly because CaneCPI-5 also caused the overexpression of the CDK2 gene, and greater migration of osteoblasts. Extracellular matrix remodeling was also evaluated in this study by investigating matrix metalloproteinase (MMP) activities. Our data showed that CaneCPI-5 overstimulates both MMP-2 and MMP-9 activities, and suggested that this cellular event could be related to osteoblast differentiation. Additionally, differentiation mechanisms were better evaluated by investigating Osterix and alkaline phosphatase (ALP) genes, and bone morphogenetic protein (BMP) signaling members. Altogether, our data showed that CaneCPI-5 can trigger biological mechanisms related to osteoblast differentiation, and broaden the perspectives for better exploring biotechnological approaches for bone disorders.

Adipogenesis-Related Metabolic Condition Affects Shear-Stressed Endothelial Cells Activity Responding to Titanium

PURPOSE

Obesity has increased around the world. Obese individuals need to be better assisted, with special attention given to dental and medical specialties. Among obesity-related complications, the osseointegration of dental implants has raised concerns. This mechanism depends on healthy angiogenesis surrounding the implanted devices. As an experimental analysis able to mimic this issue is currently lacking, we address this issue by proposing an in vitro high-adipogenesis model using differentiated adipocytes to further investigate their endocrine and synergic effect in endothelial cells responding to titanium.

MATERIALS AND METHODS

Firstly, adipocytes (3T3-L1 cell line) were differentiated under two experimental conditions: Ctrl (normal glucose concentration) and High-Glucose Medium (50 mM of glucose), which was validated using Oil Red O Staining and inflammatory markers gene expression by qPCR. Further, the adipocyte-conditioned medium was enriched by two types of titanium-related surfaces: Dual Acid-Etching (DAE) and Nano-Hydroxyapatite blasted surfaces (nHA) for up to 24 h. Finally, the endothelial cells (ECs) were exposed in those conditioned media under shear stress mimicking blood flow. Important genes related to angiogenesis were then evaluated by using RT-qPCR and Western blot.

RESULTS

Firstly, the high-adipogenicity model using 3T3-L1 adipocytes was validated presenting an increase in the oxidative stress markers, concomitantly with an increase in intracellular fat droplets, pro-inflammatory-related gene expressions, and also the ECM remodeling, as well as modulating mitogen-activated protein kinases (MAPKs). Additionally, Src was evaluated by Western blot, and its modulation can be related to EC survival signaling.

CONCLUSION

Our study provides an experimental model of high adipogenesis in vitro by establishing a pro-inflammatory environment and intracellular fat droplets. Additionally, the efficacy of this model to evaluate the EC response to titanium-enriched mediums under adipogenicity-related metabolic conditions was analyzed, revealing significant interference with EC performance. Altogether, these data gather valuable findings on understanding the reasons for the higher percentage of implant failures in obese individuals.

Titanium-Enriched Medium Promotes Environment-Induced Epigenetic Machinery Changes in Human Endothelial Cells

It is important to understand whether endothelial cells are epigenetically affected by titanium-enriched media when angiogenesis is required during bone development and it is expected to be recapitulated during osseointegration of biomaterials. To better address this issue, titanium-enriched medium was obtained from incubation of titanium discs for up to 24 h as recommended by ISO 10993-5:2016, and further used to expose human umbilical vein endothelial cells (HUVECs) for up to 72 h, when the samples were properly harvested to allow molecular analysis and epigenetics. In general, our data show an important repertoire of epigenetic players in endothelial cells responding to titanium, reinforcing protein related to the metabolism of acetyl and methyl groups, as follows: Histone deacetylases (HDACs) and NAD-dependent deacetylase sirtuin-1 (Sirt1), DNA methyltransferases (DNMTs) and ten-eleven translocation (TET) methylcytosine dioxygenases, which in conjunction culminate in driving chromatin condensation and the methylation profile of DNA strands, respectively. Taking our data into consideration, HDAC6 emerges as important player of this environment-induced epigenetic mechanism in endothelial cells, while Sirt1 is required in response to stimulation of reactive oxygen species (ROS) production, as its modulation is relevant to vasculature surrounding implanted devices. Collectively, all these findings support the hypothesis that titanium keeps the surrounding microenvironment dynamically active and so affects the performance of endothelial cells by modulating epigenetics. Specifically, this study shows the relevance of HDAC6 as a player in this process, possibly correlated with the cytoskeleton rearrangement of those cells. Furthermore, as those enzymes are druggable, it opens new perspectives to consider the use of small molecules to modulate their activities as a biotechnological tool in order to improve angiogenesis and accelerate bone growth with benefits of a fast recovery time for patients.

Epigenetic Differences Arise in Endothelial Cells Responding to Cobalt–Chromium

Cobalt–chromium (Co-Cr)-based alloys are emerging with important characteristics for use in dentistry, but the knowledge of epigenetic mechanisms in endothelial cells has barely been achieved. In order to address this issue, we have prepared a previously Co-Cr-enriched medium to further treat endothelial cells (HUVEC) for up to 72 h. Our data show there is important involvement with epigenetic machinery. Based on the data, it is believed that methylation balance in response to Co-Cr is finely modulated by DNMTs (DNA methyltransferases) and TETs (Tet methylcytosine dioxygenases), especially DNMT3B and both TET1 and TET2. Additionally, histone compaction HDAC6 (histone deacetylase 6) seems to develop a significant effect in endothelial cells. The requirement of SIRT1 seems to have a crucial role in this scenario. SIRT1 is associated with a capacity to modulate the expression of HIF-1α in response to hypoxia microenvironments, thus presenting a protective effect. As mentioned previously, cobalt is able to prevent HIF1A degradation and maintain hypoxia-related signaling in eukaryotic cells. Together, our results show, for the first time, a descriptive study reporting the relevance of epigenetic machinery in endothelial cells responding to cobalt–chromium, and it opens new perspectives to better understand their repercussions as prerequisites for driving cell adhesion, cell cycle progression, and angiogenesis surrounding this Co-Cr-based implantable device.

Nanohydroxyapatite-Blasted Bioactive Surface Drives Shear-Stressed Endothelial Cell Growth and Angiogenesis

Nanosized crystalline hydroxyapatite coating (HAnano®) accelerates the osteointegration of dental implants which is hypothesized to drive angiogenesis. In order to test this hypothesis, we have subjected shear-stressed human umbilical vein endothelial cells (HUVECs) to a HAnano®-enriched medium, as well as to surface presenting dual acid etching (DAE) as a control. To note, the titanium implants were coated with 10 nm in diameter HA particles using the Promimic HAnano method. Our data reveals that HAnano® modulates higher expression of genes related with endothelial cell performance and viability, such as VEGF, eNOS, and AKT, and further angiogenesis in vitro by promoting endothelial cell migration. Additionally, the data shows a significant extracellular matrix (ECM) remodeling, and this finding seems developing a dual role in promoting the expression of VEGF and control endothelial cell growth during angiogenesis. Altogether, these data prompted us to further validate this phenomenon by exploring genes related with the control of cell cycle and in fact our data shows that HAnano® promotes higher expression of CDK4 gene, while p21 and p15 genes (suppressor genes) were significantly lower. In conjunction, our data shows for the first time that HAnano®-coated surfaces drive angiogenesis by stimulating a proliferative and migration phenotype of endothelial cells, and this finding opens novel comprehension about osseointegration mechanism considering nanosized hydroxyapatite coating dental implants.

Osteosphere Model to Evaluate Cell-Surface Interactions of Implantable Biomaterials

Successful biomaterials for bone tissue therapy must present different biocompatible properties, such as the ability to stimulate the migration and proliferation of osteogenic cells on the implantable surface, to increase attachment and avoid the risks of implant movement after surgery. The present work investigates the applicability of a three-dimensional (3D) model of bone cells (osteospheres) in the evaluation of osteoconductive properties of different implant surfaces. Three different titanium surface treatments were tested: machined (MA), sandblasting and acid etching (BE), and Hydroxyapatite coating by plasma spray (PSHA). The surfaces were characterized by Scanning Electron Microscopy (SEM) and atomic force microscopy (AFM), confirming that they present very distinct roughness. After seeding the osteospheres, cell–surface interactions were studied in relation to cell proliferation, migration, and spreading. The results show that BE surfaces present higher densities of cells, leaving the aggregates towards than titanium surfaces, providing more evidence of migration. The PSHA surface presented the lowest performance in all analyses. The results indicate that the 3D model allows the focal analysis of an in vitro cell/surfaces interaction of cells and surfaces. Moreover, by demonstrating the agreement with the clinical data observed in the literature, they suggest a potential use as a predictive preclinical tool for investigating osteoconductive properties of novel biomaterials for bone therapy.

Effect of supplemental acid-etching on the early stages of osseointegration: A preclinical model

PURPOSE

To evaluate the effect of two surface modifications on early osseointegration parameters of conical implants in a translational pre-clinical model.

MATERIALS AND METHODS

Conical implants with progressive trapezoidal threads and healing chambers were evaluated consisting of two different surface conditions: 1) Implacil surface (IMP Sur), and 2) Implacil surface + Supplemental Acid-etching (IMP Sur + AE). Surface characterization comprised of the evaluation of roughness parameters (S_a, S_q and S_dr), surface energy and contact angle. Subsequently, implants were installed in the ilium crest of nine female sheep (weighing ~65 kg). Torque out, histological and histomorphometric analyses were conducted after 3 and 6 weeks in-vivo. The percentage of bone to implant contact (%BIC) and bone area fraction occupancy within implant threads (%BAFO) were quantified, and the results were analyzed using a general linear mixed model analysis as function of surface treatment and time in-vivo.

RESULTS

Supplemental acid etching significantly increased S_a and S_q roughness parameters without compromising the surface energy or contact angle, and no significant differences with respect to S_dr. Torque-out testing yielded significantly higher values for IMP Sur + AE in comparison to the IMP Sur at 3- (62.78 ± 15 and 33.49 ± 15 N.cm, respectively) and 6-weeks (60.74 ± 15 and 39.80 ± 15 N.cm, respectively). Histological analyses depicted similar osseointegration features for both surfaces, where an intramembranous-type healing pattern was observed. At histomorphometric analyses, IMP Sur + AE implants yielded higher values of BIC in comparison to IMP Sur at 3- (40.48 ± 38 and 27.98 ± 38%, respectively) and 6-weeks (45.86 ± 38 and 34.46 ± 38%, respectively). Both groups exhibited a significant increase in %BAFO from 3 (~35%) to 6 weeks (~44%), with no significant differences between surface treatments.

CONCLUSION

Supplemental acid-etching and its interplay with implant thread design, positively influenced the BIC and torque-out resistance at early stages of osseointegration.

The molecular pathway triggered by zirconia in endothelial cells involves epigenetic control

The requirement to achieve natural looking restorations is one of the most challenging aspects in dentistry. Although zirconia has provided new opportunities for achieving superior aesthetics and physicochemical outcomes, very little has been achieved for its cellular and molecular performance, especially considering angiogenesis and osteogenesis. As angiogenesis is a secondary event and concomitant to osteogenesis, an indirect effect of dental implant on endothelial cells could be the release of active molecules such as those already reported affecting osteoblasts. To better address this issue, we challenged human endothelial cells (HUVECs) with zirconia-conditioned medium up to 72 h to allow analysis specific gene expression and protein pattern of mediators of epigenetic machinery in full. Our data shows involvement of zirconia in triggering intracellular signaling through MAPK-ERK activation, leading the signal to activate histone deacetylase HDAC6 likely with concomitant well-modulated DNA methylation profile by DNMTs and TETs. These signaling pathways seem to culminate in cytoskeleton rearrangement of endothelial cells, an important prerequisite to cell migration expected in angiogenesis. Collectively, this study demonstrates for the first time epigenetic-related molecular mechanism involved in endothelial cells responding to zirconia, revealing a repertoire of signaling molecules capable of executing the reprogramming process of gene expression, which are necessary to drive cell proliferation, migration, and consequently angiogenesis. This set of data can further studies using gene editing approaches to better elucidate functional roles.

PI3K/AKT signaling drives titanium-induced angiogenic stimulus

Although osseointegration and clinical success of titanium (Ti)-implanted materials depend on neovascularization in the reactional peri-implant tissue, very little has been achieved considering the Ti-molecules release on the behavior of endothelial cells. To address this issue, we challenged endothelial cells (HUVECs) with Ti-enriched medium obtained from two types of commercial titanium surfaces [presenting or not dual-acid etching (DAE)] up to 72 h to allow molecular machinery analysis. Our data show that the Ti-enriched medium provokes significant stimulus of angiogenesis-related machinery in endothelial cells by upexpressing VEGFR1, VEGFR2, VEGF, eNOS, and iNOS genes, while the PI3K/Akt signaling pathway was also significantly enhanced. As PI3K/AKT signaling was related to angiogenesis in response to vascular endothelial growth factor (VEGF), we addressed the importance of PI3K/Akt upon Ti-enriched medium responses by concomitantly treating the cells with wortmannin, a well-known PI3K inhibitor. Wortmannin suppressed the angiogenic factors, because VEGF, VEGFR1, and eNOS genes were downregulated in those cells, highlighting the importance of PI3K/AKT signaling on driving angiogenic phenotype and angiogenesis performance within the peri-implant tissue reaction. In conjunction, these data reinforce that titanium-implantable devices modify the metabolism of surrounding cells, such as endothelial cells, probably coupling osteogenesis and angiogenesis processes in peri-implant tissue and then contributing to successfully osseointegration of biomedical titanium-based devices.

Infraphysiological 17β-estradiol (E2) concentration compromises osteoblast differentiation through Src stimulation of cell proliferation and ECM remodeling stimulus

It has been shown that 17β-estradiol (E2) helps to prevent bone loss. This study was undertaken to verify whether E2 action in human osteoblasts involves changes in the transcriptional profile of the TNF-α, IFN-γ, NF-κB, TRAIL, TGF-β, MMP2, MMP9, RECK, TIMP1, TIMP2, CDK2, CDK4, SRC, RUNX2, and SHH genes. Infraphysiological doses of E2 elevated mRNAs in all genes except for INF-γ, TRAIL, and TGF-β. Importantly, a significant increase in the CDKs -2 and -4 genes was found, which strongly suggests cell cycle progression, with a potential dependency of Src involvement, as well as a suppression of the osteoblast differentiation machinery, with ECM remodeling being involved. These data suggest that E2 plays an important role in bone formation and remodeling, and Src seems to play a pivotal role in driving cell proliferation and ECM remodeling. Taken together, these findings contribute to an understanding of the effects of infraphysiological E2 on modulating bone homeostasis, favoring bone resorption, and leading to osteoporosis.

OsteoBLAST: Computational Routine of Global Molecular Analysis Applied to Biomaterials Development

For bone purposes, surface modifications are a common trend in biomaterials research aiming to reduce the time necessary for osteointegration, culminating in faster recovery of patients. In this scenario, analysis of intracellular signaling pathways have emerged as an important and reliable strategy to predict biological responses from in vitro approaches. We have combined global analysis of intracellular protein phosphorylation, systems biology and bioinformatics into an early biomaterial analysis routine called OsteoBLAST. We employed the routine as follows: the PamChip tyrosine kinase assay was applied to mesenchymal stem cells grown on three distinct titanium surfaces: machined, dual acid-etched and nanoHA. Then, OsteoBLAST was able to identify the most reliable spots to further obtain the differential kinome profile and finally to allow a comparison among the different surfaces. Thereafter, NetworKIN, STRING, and Cytoscape were used to build and analyze a supramolecular protein-protein interaction network, and DAVID tools identified biological signatures in the differential kinome for each surface.

The Impact of Bioactive Surfaces in the Early Stages of Osseointegration: An In Vitro Comparative Study Evaluating the HAnano® and SLActive® Super Hydrophilic Surfaces

There is an increased effort on developing novel and active surfaces in order to accelerate their osteointegration, such as nanosized crystalline hydroxyapatite coating (HAnano®). To better understand the biological behavior of osteoblasts grown on HAnano® surface, the set of data was compared with SLActive®, a hydrophilic sandblasted titanium surface. Methodologically, osteoblasts were seeded on both surfaces up to 72 hours, to allow evaluating cell adhesion, viability, and set of genes encoding proteins related with adhesion, proliferation, and differentiation. Our data shows HAnano® displays an interesting substrate to support cell adhesion with typical spread morphologic cells, while SLActive®-adhering cells presented fusiform morphology. Our data shows that the cellular adhesion mechanism was accompanied with upexpression of integrin β1, Fak, and Src, favoring the assembling of focal adhesion platforms and coupling cell cycle progression (upmodulating of Cdk2, Cdk4, and Cdk6 genes) in response to HAnano®. Additionally, both bioactive surfaces promoted osteoblast differentiation stimulus, by activating Runx2, Osterix, and Alp genes. Although both surfaces promoted Rankl gene expression, Opg gene expression was higher in SLActive® and this difference reflected on the Rankl/Opg ratio. Finally, Caspase1 gene was significantly upmodulated in response to HAnano® and it suggests an involvement of the inflammasome complex. Collectively, this study provides enough evidences to support that the nanohydroxyapatite-coated surface provides the necessary microenvironment to drive osteoblast performance on dental implants and these stages of osteogenesis are expected during the early stages of osseointegration.

Biofunctionalization of titanium surfaces with alendronate and albumin modulates osteoblast performance

BACKGROUND

Biofunctionalization of titanium surfaces can improve host responses, especially considering the time for osteointegration and patient recovery. This prompted us to modify titanium surfaces with alendronate and albumin and to investigate the behavior of osteoblasts on these surfaces.

METHODS

The biofunctionalization of titanium surfaces was characterized using classical physicochemical approaches and later used to challenge pre-osteoblast cells up to 24 h. Then their viability and molecular behavior were investigated using mitochondrial dehydrogenase activity and RTq-PCR technologies, respectively. Potential stimulus of extracellular remodeling was also investigated by zymography.

RESULTS

Our data indicates a differential behavior of cells responding to the surfaces, considering the activity of mitochondrial dehydrogenases. Molecularly, the differential expression of genes related with cell adhesion highlighted the importance of Integrin-β1, Fak, and Src. These 3 genes were significantly decreased in response to titanium surfaces modified with alendronate, but this behavior was reverted when alendronate was associated with albumin. Alendronate-modified surfaces promoted a significant increase on ECM remodeling, as well as culminating with greater gene activity related to the osteogenic phenotype (Runx2, Alp, Bsp).

CONCLUSION

Altogether, our study found interesting osteogenic behavior of cells in response to alendronate and albumin surfaces, which indicates the need for in vivo analyses to better consider these surfaces before clinical trials within the biomedical field.

A novel BSA immobilizing manner on modified titanium surface ameliorates osteoblast performance

Surface modification of medical and dental devices, to improve their biocorrosion resistance and biocompatibility, can be achieved with the multidisciplinary field of biomaterials. Nanostructured titanium dioxide (TiO₂) has been employed as surface modifier of titanium-based biomaterials because it can prevent the failure of the devices due to wear mechanisms. Moreover, this oxide surface is mostly terminated by hydroxyl groups (-OH) that can be directly functionalized with biomolecules to improve the biocompatibility of these devices. We explored the influence of 3-aminopropyltrimethoxysilane (APTMS) molecules as spacers in bovine serum albumin (BSA) protein immobilization on the physically hydroxylated surfaces of rutile phase TiO₂ films grown by reactive Radio Frequency (RF) magnetron sputtering. X-ray Photoelectron Spectroscopy (XPS) was used to examine the adsorption of BSA and APTMS on the hydroxylated surface of TiO₂ thin films. For biological tests, BSA was directly immobilized on the film surface and on the APTMS monolayer. Biological analysis found better osteoblast performance considering gene markers related to cell adhesion after interacting directly with the surface modified by the immobilization of BSA, especially on the surface where this protein was immobilized by APTMS. Additionally, we addressed the relevance of this biointerfaces on extracellular matrix remodeling by zymography analysis. Altogether, our data provides new insights about the cellular and molecular mechanisms covering the improved osteoblastic response of the proposed surface modification.

Effect of focal adhesion kinase inhibition on osteoblastic cells grown on titanium with different topographies

Objective

The present study aimed to investigate the participation of focal adhesion kinases (FAK) in interactions between osteoblastic cells and titanium (Ti) surfaces with three different topographies, namely, untreated (US), microstructured (MS), and nanostructured (NS).

Methodology

Osteoblasts harvested from the calvarial bones of 3-day-old rats were cultured on US, MS and NS discs in the presence of PF-573228 (FAK inhibitor) to evaluate osteoblastic differentiation. After 24 h, we evaluated osteoblast morphology and vinculin expression, and on day 10, the following parameters: gene expression of osteoblastic markers and integrin signaling components, FAK protein expression and alkaline phosphatase (ALP) activity. A smooth surface, porosities at the microscale level, and nanocavities were observed in US, MS, and NS, respectively.

Results

FAK inhibition decreased the number of filopodia in cells grown on US and MS compared with that in NS. FAK inhibition decreased the gene expression of Alp, bone sialoprotein, osteocalcin, and ALP activity in cells grown on all evaluated surfaces. FAK inhibition did not affect the gene expression of Fak, integrin alpha 1 ( Itga1 ) and integrin beta 1 ( Itgb1 ) in cells grown on MS, increased the gene expression of Fak in cells grown on NS, and increased the gene expression of Itga1 and Itgb1 in cells grown on US and NS. Moreover, FAK protein expression decreased in cells cultured on US but increased in cells cultured on MS and NS after FAK inhibition; no difference in the expression of vinculin was observed among cells grown on all surfaces.

Conclusions

Our data demonstrate the relevance of FAK in the interactions between osteoblastic cells and Ti surfaces regardless of surface topography. Nanotopography positively regulated FAK expression and integrin signaling pathway components during osteoblast differentiation. In this context, the development of Ti surfaces with the ability to upregulate FAK activity could positively impact the process of implant osseointegration.

Biomaterial and biomechanical considerations to prevent risks in implant therapy

This paper is aimed to present a biomaterials perspective in implant therapy that fosters improved bone response and long-term biomechanical competence from surgical instrumentation to final prosthetic rehabilitation. Strategies to develop implant surface texturing will be presented and their role as an ad hoc treatment discussed in light of the interplay between surgical instrumentation and implant macrogeometric configuration. Evidence from human retrieved implants in service for several years and from in vivo studies will be used to show how the interplay between surgical instrumentation and implant macrogeometry design affect osseointegration healing pathways, and bone morphologic and long-term mechanical properties. Also, the planning of implant-supported prosthetic rehabilitations targeted at long-term performance will be appraised from a standpoint where personal preferences (eg, cementing or screwing a prosthesis) can very often fail to deliver the best patient care. Lastly, the acknowledgement that every rehabilitation will have its strength degraded over time once in function will be highlighted, since the potential occurrence of even minor failures is rarely presented to patients prior to treatment.

Differential Effects of Nano TiO₂ and CeO₂ on Normal Human Lung Epithelial Cells In Vitro

Nano-TiO₂ and nano-CeO₂ are among the most widely used engineered nanoparticles (NPs). We investigated a variety of endpoints to assess the toxicity of eight of these NPs to induce potentially adverse health effects in an In Vitro human respiratory epithelial cell model. These endpoints include cytotoxicity, reactive oxygen species (ROS)/reactive nitrogen species (RNS) production, 8-hydroxy-2_-deoxyguanosine (8-oxo-dG), endogenous DNA adducts, Apurinic/apyrimidinic (AP) sites, 4-Hrdoxynonenal (4-HNE) protein adducts, Malondialdehyde (MDA) protein adducts, and genomics analysis on altered signaling pathways. Our results indicated that cytotoxicity assays are relatively insensitive, and we detected changes in other endpoints at concentrations much lower than those inducing cytotoxicity. Among the ROS-related endpoints, 8-oxo-dG is relatively more sensitive than other assays, and nano-TiO₂ induced more 8-oxo-dG formation than nano-CeO₂. Finally, there are many signaling pathways changes at concentrations at which no cytotoxicity was observed. These alterations in signaling pathways correlated well with In Vitro toxicity that was observed at higher concentrations, and with in vivo adverse outcome pathways caused by nano-TiO₂ and nano-CeO₂ in experimental animals.

Argon plasma modification promotes adipose derived stem cells osteogenic and chondrogenic differentiation on nanocomposite polyurethane scaffolds; implications for skeletal tissue engineering

Bone and cartilage craniofacial defects due to trauma or congenital deformities pose a difficult problem for reconstructive surgeons. Human adipose stem cells (ADSCs) can differentiate into bone and cartilage and together with suitable scaffolds could provide a promising system for skeletal tissue engineering. It has been suggested that nanomaterials can direct cell behavior depending on their surface nanotopographies. Thus, this study examined whether by altering a nanoscaffold surface using radiofrequency to excite gases, argon (Ar), nitrogen (N₂) and oxygen (O₂) with a single step technique, we could enhance the osteogenic and chondrogenic potential of ADSCs. At 24 h, Ar modification promoted the highest increase in ADSCs adhesion as indicated by upregulation of vinculin and focal adhesion kinase (FAK) expression compared to O₂ and N₂ scaffolds. Furthermore, ADSCs on Ar-modified nanocomposite polymer POSS-PCU scaffolds upregulated expression of bone markers, alkaline phosphatase, collagen I and osteocalcin after 3 weeks. Cartilage markers, aggrecan and collagen II, were also upregulated on Ar-modified scaffolds at the mRNA and protein level. Finally, all plasma treated scaffolds supported tissue ingrowth and angiogenesis after grafting onto the chick chorioallantoic membrane. Ar promoted greater expression of vascular endothelial growth factor and laminin in ovo compared to O₂ and N₂ scaffolds as shown by immunohistochemistry. This study provides an important understanding into which surface chemistries best support the osteogenic and chondrogenic differentiation of ADSCs that could be harnessed for regenerative skeletal applications. Argon surface modification is a simple tool that can promote ADSC skeletal differentiation that is easily amenable to translation into clinical practice.

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Bone and cartilage craniofacial defects due to trauma or congenital deformities pose a challenging problem for reconstructive surgeons.

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Nanomaterials can direct adipose derived stem cell (ADSC) differentiation depending on their surface nanotopographies.

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This study demonstrates that Argon surface modification improve the chondrogenesis and osteogenesis of ADSCs.

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Argon surface modification is a tool that can upregulate ADSC skeletal differentiation and is amenable to translation into clinical practice.

Nano-scale modification of titanium implant surfaces to enhance osseointegration

The main aim of this review study was to report the state of art on the nano-scale technological advancements of titanium implant surfaces to enhance the osseointegration process. Several methods of surface modification are chronologically described bridging ordinary methods (e.g. grit blasting and etching) and advanced physicochemical approaches such as 3D-laser texturing and biomimetic modification. Functionalization procedures by using proteins, peptides, and bioactive ceramics have provided an enhancement in wettability and bioactivity of implant surfaces. Furthermore, recent findings have revealed a combined beneficial effect of micro- and nano-scale modification and biomimetic functionalization of titanium surfaces. However, some technological developments of implant surfaces are not commercially available yet due to costs and a lack of clinical validation for such recent surfaces. Further in vitro and in vivo studies are required to endorse the use of enhanced biomimetic implant surfaces. STATEMENT OF SIGNIFICANCE: Grit-blasting followed by acid-etching is currently used for titanium implant modifications, although recent technological biomimetic physicochemical methods have revealed enhanced osteoconductive and anti-microbial outcomes. An improvement in wettability and bioactivity of titanium implant surfaces has been accomplished by combining micro and nano-scale modification and functionalization with protein, peptides, and bioactive compounds. Such morphological and chemical modification of the titanium surfaces induce the migration and differentiation of osteogenic cells followed by an enhancement of the mineral matrix formation that accelerate the osseointegration process. Additionally, the incorporation of bioactive molecules into the nanostructured surfaces is a promising strategy to avoid early and late implant failures induced by the biofilm accumulation.

Layered Double Hydroxides Are Promising Nanomaterials for Tissue Bioengineering Application

Layered double hydroxides (LDHs) have emerged as promising nanomaterials for human health and although it has achieved some progress on this matter, their application within bioengineering is not fully addressed. This prompted to subject fibroblasts to two compositions of LDHs (Mg₂ Al-Cl and Zn₂ Al-Cl), considering an acute response. First, LDH particles are addressed by scanning electron microscopy, and no significant effect of the cell culture medium on the shape of LDHs particles is reported although it seems to adsorb some soluble proteins as proposed by energy-dispersive X-ray analysis. These LDHs release magnesium, zinc, and aluminum, but there is no cytotoxic or biocompatibility effects. The data show interference to fibroblast adhesion by driving the reorganization of actin-based cytoskeleton, preliminarily to cell cycle progression. Additionally, these molecular findings are validated by performing a functional wound-healing assay, which is accompanied by a dynamic extracellular matrix remodeling in response to the LDHs. Altogether, the results show that LDHs nanomaterials modulate cell adhesion, proliferation, and migration, delineating new advances on the biomaterial field applied in the context of soft tissue bioengineering, which must be explored in health disorders, such as wound healing in burn injuries.

Differential inflammatory landscape stimulus during titanium surfaces obtained osteogenic phenotype

Molecular mechanism governing inflammatory scenario in response to titanium (Ti)-nanotexturing surfaces needs to be better addressed. Thus, we subjected pre-osteoblast to different Ti-texturing surfaces, as follows: machined (Mac), double acid-etching (DAE), and nanoscaled hydroxyapatite-blasted titanium surface (nHA), considering the cells chronically responding either directly (when the cells were cultured onto the surfaces) or indirectly (when the cells were challenged with the conditioned medium by the surfaces), up to 10 days. Our results showed that there is a dynamic requirement of inflammatory-related genes activation in response to nHA by up expressing IL1ß, IL6, IL10, and IL33 (direct condition) and IL6, IL10, IL18 (indirect condition). Importantly, our data show that there is inflammasome involvement, once NLRP3, ASC1, and CASP1 genes were also required. As we found a strong signal of IL10, an anti-inflammatory cytokine, we further investigated Sonic Hedgehog (Shh) signaling cascade. Surprisingly, Shh ligand and Smoothened (Smo) genes were up-modulated in response to nHA, while Patched (Ptc) was down-modulated. Finally, an interactome was built using bioinformatics reinforcing Shh signaling cascade on modulating IL10 transcripts by Src mediating this process and this prevalence of anti-inflammatory picture might explain the low profile of RANKL transcripts in response to nHA, compromising the osteoclastogenesis surrounding the implants. Taking our results into account, our data show that the inflammatory landscape promoted by nHA is strictly modulated by Shh signaling promoted anti-inflammatory pathways. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1597-1604, 2019.

Titanium-enriched medium drives low profile of ECM remodeling as a pre-requisite to pre-osteoblast viability and proliferative phenotype

Titanium is widely used for biomedical applications, but little information is being delivered regarding the cellular/molecular mechanisms explaining their efficacy, mainly considering the effects of the Ti-released trace elements on pre-osteoblasts. We addressed this issue by investigating decisive intracellular signal transduction able to modulate cytoskeleton rearrangement, proliferative phenotype and extracellular matrix (ECM) remodeling. We considered titanium grades IV and V, submitted or not to dual acid-etching (w/DAE or wo/DAE, respectively). Our results showed there is no cytotoxicity, preserving AKT involvement. Additionally, Ti-enriched medium promoted a diminution of the downstream signaling upon integrin activation (phosphorylating Rac1 and cofilin), guaranteeing a dynamic cytoskeleton rearrangement. Moreover, the low profile of ECM remodeling obtained in response to trace molecules released by Ti-based devices seems contributing to the osteoblast performance in mediating extracellular support to cell anchorage. This hypothesis was validated by the up-expression of ß1-integrin, src and Focal adhesion kinase (fak) genes, mainly in response to titanium grade V. Proliferative phenotype showed an unbalance between cyclin-dependent kinases (CDKs) and p15^INK4b/p21^Cip1. In conjunction, we showed for the first time that trace elements from Ti-based biomedical devices provoke important modulation of the osteoblast biology, driving cell anchoring, viability, and proliferative phenotype. Certainly, these biological outcomes compromise implant osseointegration.

Human mesenchymal stromal cells in adhesion to cell-derived extracellular matrix and titanium: Comparative kinome profile analysis

The extracellular matrix (ECM) physically supports cells and influences stem cell behaviour, modulating kinase‐mediated signalling cascades. Cell‐derived ECMs have emerged in bone regeneration as they reproduce physiological tissue‐architecture and ameliorate mesenchymal stromal cell (MSC) properties. Titanium scaffolds show good mechanical properties, facilitate cell adhesion, and have been routinely used for bone tissue engineering (BTE). We analyzed the kinomic signature of human MSCs in adhesion to an osteopromotive osteoblast‐derived ECM, and compared it to MSCs on titanium. PamChip kinase‐array analysis revealed 63 phosphorylated peptides on ECM and 59 on titanium, with MSCs on ECM exhibiting significantly higher kinase activity than on titanium. MSCs on the two substrates showed overlapping kinome profiles, with activation of similar signalling pathways (FAK, ERK, and PI3K signalling). Inhibition of PI3K signalling in cells significantly reduced adhesion to ECM and increased the number of nonadherent cells on both substrates. In summary, this study comprehensively characterized the kinase activity in MSCs on cell‐derived ECM and titanium, highlighting the role of PI3K signalling in kinomic changes regulating osteoblast viability and adhesion. Kinome profile analysis represents a powerful tool to select pathways to better understand cell behaviour. Osteoblast‐derived ECM could be further investigated as titanium scaffold‐coating to improve BTE.

Biomimetic Implant Surface Functionalization with Liquid L-PRF Products: In Vitro Study

Objective

Platelet-rich fibrin (PRF) clots and membranes are autologous blood concentrates widely used in oral surgical procedures; less is known, however, about the liquid formulations of such products. The aim of this in vitro study is to assess the behavior of different implant surfaces when in contact with two liquid leucocyte- and platelet-rich fibrin (L-PRF) products.

Methods

Six commercial pure titanium discs, of 9.5 mm diameter and 1.5 mm thickness, were used. Three of these samples had a micro/nano-rough surface; three were machined. Three different protocols were tested. Protocols involved the immersion of the samples in (1) a platelets, lymphocytes, and fibrinogen liquid concentrate (PLyF) for 10 minutes, (2) an exudate obtained from L-PRF clots rich in fibronectin and vitronectin for 5 minutes, and (3) the fibronectin/vitronectin exudate for 2 minutes followed by immersion in the PLyF concentrate for further 8 minutes. After these treatments, the samples were fixed and observed using a scanning electron microscope (SEM).

Results

Under microscopic observation, (1) the samples treated with the PLyF concentrate revealed a dense fibrin network in direct contact with the implant surface and a significant number of formed elements of blood; (2) in the samples treated with the fibronectin/vitronectin exudates, only a small number of white and red blood cells were detectable; and (3) in samples exposed to the combined treatment, there was an apparent increase in the thickness of the fibrin layer. When compared to the machined surface, the micro/nano-rough samples showed an overall increased retention of fibrin, leading to a thicker coating.

Conclusions

Liquid L-PRF products promote the formation of a dense fibrin clot on micro/nano-rough implant surfaces in vitro. The adjunctive treatment of surfaces with the fibronectin/vitronectin exudate could provide support to contact of the fibrin with the surface, though it is not essential for the clot formation. Further studies are necessary to better elucidate the properties and benefits of liquid L-PRF products.

Titanium-released from dental implant enhances pre-osteoblast adhesion by ROS modulating crucial intracellular pathways

It is important to understand the cellular and molecular events that occur at the cell-material interface of implants used for bone repair. The mechanisms involved in the initial stages of osteoblast interactions with the surface of the implant material must be decisive for cell fating surrounding them. In order to address this issue, we decided to investigate if conditioned medium for dental implants was able to modulate murine pre-osteoblast metabolism. First, we determined the concentration of titanium (Ti)-containing conditioned medium and found that it was 2-fold increased (p < 0.0001). We have reported that this conditioned medium significantly up-modulated pre-osteoblast adhesion up to 24 h (p < 0.0001). In parallel, our results showed that both phosphorylations of FAK (focal adhesion kinase) at Y397 (p < 0.0011) and Cofilin at Ser03 (p < 0.0053) were also up-modulated, as well as for Rac1 expression (p < 0.0175); both of them are involved with cell adaptation by rearranging cytoskeleton actin filaments. Thereafter, Ti-containing medium stimulated ROS (reactive oxygen species) production by pre-osteoblast cells, and it is very possible that ROS compromised PTP-1B (protein tyrosine phosphatase 1B) activation since PTP1B was down-phosphorylated (p < 0.0148). The low PTP activity guarantees the phosphorylation of FAK at Y-residue, causing better pre-osteoblast adhesion in response to Ti-containing medium. Altogether, these data indicate that ROS indirectly modulate FAK phosphorylation in response to Ti-released from dental implants. Taken the results in account, these data showed for the first time that the implanted dental device is able to dynamically affect surrounding tissues, mainly by promoting a better performance of the pre-osteoblast cells. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2968-2976, 2017.