Cobalt-chromium-enriched medium ameliorates shear-stressed endothelial cell performance

Hypoxia modulates the phenotype of mechanically stressed endothelial cells responding to CoCr-enriched medium

Given the importance of the endothelial cell phenotype in dental peri-implant healing processes, the aim of this study was to better assess the involvement of endothelial cells responding to cobalt-chromium (CoCr)-enriched medium. Biologically, cobalt is widely used molecule to induce chemical experimental hypoxia because it stabilizes hypoxia inducible factors (HIF1α). The aplication of hypoxia models provides better experimental condition to allow its impact on cellular metabolism, by looking for biochemical and molecular issues. Thus, this study looks for understaing whether CoCr-based materials are able to modulate endothelial cells considering the hypoxic effect prmoted by cobalt. Firstly, our data shows there is a siginificant effect on endothelial phenotype by modulating the expression of VEGF and eNOS genes, whith low requirement of genes related with proteasome intracellular complex. Importantly, the data were validated using classical chemical modulators of hypoxia signaling [chrysin (5,7-dihydroxyflavone) and Dimethyloxalylglycine (DMOG)] in functional assays. Altogether, these data validate the hypothesis that hipoxya is important to maintain the phenotype of endothelial cells, and it is properly interesting during the tissue regeneration surrounding implants and so compromising osseointegration process. Finally, it is important to mention that the cobalt released from CoCr devices might contribute with an sufficient microenvironment surrounding implanted devices and it paviments new roads looking for more bioactive surfaces of implantable materials in human health.

Research progress of metal biomaterials with potential applications as cardiovascular stents and their surface treatment methods to improve biocompatibility

Facing the growing issue of cardiovascular diseases, metallic materials with higher tensile strength and fatigue resistance play an important role in treating diseases. This review lists the advantages and drawbacks of commonly used medical metallic materials for vascular stents. To avoid post-procedural threats such as thrombosis and in-stent restenosis, surface treatments, and coating methods have been used to further improve the biocompatibility of these materials. Surface treatments including laser, plasma treatment, polishing, oxidization, and fluorination can improve biocompatibility by modifying the surface charges, surface morphology, and surface properties of the material. Coating methods based on polymer coatings, carbon-based coatings, and drug-functional coatings can regulate the surface properties, and also serve as an effective barrier to the interaction of metallic biomaterial surfaces with biomolecules, which can be used to improve corrosion resistance and stability, as well as improve their biocompatibility. Biocompatibility serves as the most fundamental property of cardiovascular stents, and maintaining the excellent and stable biocompatibility of cardiovascular stent surfaces is a current research bottleneck. Few reviews have been published on metallic biomaterials as cardiovascular stents and their surface treatments. For the purpose of advancing research on cardiovascular stents, common metal biomaterials, surface treatment methods, and coating methods to improve biocompatibility and comprehensive properties of the materials are described in this review. Finally, we suggest future directions for stent development, including continuously improving the durability and stability of permanent stents, accelerating the development of biodegradable stents, and strengthening feedback to improve the safety and reliability of cardiovascular stents.

Combination of in silico and cell culture strategies to predict biomaterial performance: Effects of sintering temperature on the biological properties of hydroxyapatite

Advances in methodologies to evaluate biomaterials brought an explosive growth of data, ensuing computational challenges to better analyzing them and allowing for high-throughput profiling of biological systems cost-efficiently. In this sense, we have applied bioinformatics tools to better understand the biological effect of different sintering temperatures of hydroxyapatite (abbreviated HA; at 1100, 1150, and 1250°C) on osteoblast performance. To do, we have better analyzed an earlier deposited study, in which the access code is E-MTAB-7219, which the authors have explored different in silico tools on this purpose. In this study, differential gene expression analyses were performed using the gene set variation analysis (GSVA) algorithm from the transcriptomes respecting the thermal changes of HA, which were validated using exclusively in vitro strategies. Furthermore, in silico approaches elected biomarkers during cell behavior in response to different sintering temperatures of HA, and it was further validated using cell culture and qPCR technologies. Altogether, the combination of those strategies shows the capacity of sintered HA at 1250°C to present a better performance in organizing an adequate microenvironment favoring bone regeneration, angiogenesis and material resorption stimulus once it has promoted higher involvement of genes such as CDK2, CDK4 (biomarkers of cell proliferation), p15, Osterix gene (related with osteogenic differentiation), RANKL (related with osteoclastogenesis), VEGF gene (related with angiogenesis), and HIF1α (related with hypoxia microenvironment). Altogether, the combination of in silico and cell culture strategies shows the capacity of sintered HA at 1250°C in guaranteeing osteoblast differentiation and it can be related in organizing an adequate microenvironment favoring bone regeneration, angiogenesis, and material resorption stimulus.

Development of cobalt (Co)-doped monetites for bone regeneration

Cobalt-doped monetite powders were synthesized by coprecipitation method under a cobalt nominal content between 2 and 20 mol % of total cation. Structural characterization of samples was performed by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy. XRD results indicated that the Co-doped samples exhibited a monetite single-phase with the cell parameters and crystallite size dependent on the amount of substitutional element incorporated into the triclinic crystalline structure. Cell viability and adhesion assays using pre-osteoblastic cells showed there is no toxicity and the RTqPCR analysis showed significant differences in the expression for osteoblastic phenotype genes, showing a potential material for the bone regeneration.

Mechanosignaling-related angiocrine factors drive osteoblastic phenotype in response to zirconia

BACKGROUND

The growing use of zirconia as a ceramic material in dentistry is attributed to its biocompatibility, mechanical properties, esthetic appearance, and reduced bacterial adhesion. These favorable properties make ceramic materials a viable alternative to commonly used titanium alloys. Mimicking the physiological properties of blood flow, particularly the mechanosignaling in endothelial cells (ECs), is crucial for enhancing our understanding of their role in the response to zirconia exposure.

METHODS

In this study, EC cultures were subjected to shear stress while being exposed to zirconia for up to 3 days. The conditioned medium obtained from these cultures was then used to expose osteoblasts for a duration of 7 days. To investigate the effects of zirconia on osteoblasts, we examined the expression of genes associated with osteoblast differentiation, including Runx2, Osterix, bone sialoprotein, and osteocalcin genes. Additionally, we assessed the impact of mechanosignaling-related angiocrine factors on extracellular matrix (ECM) remodeling by measuring the activities of matrix metalloproteinases 2 and 9 (MMP2 and MMP9) during the acquisition of the osteogenic phenotype, which precedes mineralization.

RESULTS

Our data revealed that mechanosignaling-related angiocrine factors play a crucial role in promoting an osteoblastic phenotype in response to zirconia exposure. Specifically, exposed osteoblasts exhibited significantly higher expression levels of genes associated with osteoblast differentiation, such as Runx2, Osterix, bone sialoprotein, and osteocalcin genes. Furthermore, the activities of MMP2 and MMP9, which are involved in ECM remodeling, were modulated by mechanosignaling-related angiocrine factors. This modulation is likely an initial event preceding the mineralization phase.

CONCLUSION

Based on our findings, we propose that mechanosignaling drives the release of angiocrine factors capable of modulating the osteogenic phenotype at the biointerface with zirconia. This process creates a microenvironment that promotes wound healing and osseointegration. Moreover, these results highlight the importance of considering the mechanosignaling of endothelial cells in the modulation of bone healing and osseointegration in the context of blood vessel effects. Our data provide new insights and open avenues for further investigation into the influence of mechanosignaling on bone healing and the osseointegration of dental devices.

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.

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.

Toxicological Risks of the Cobalt-Chromium Alloys in Dentistry: A Systematic Review

Background: The toxicological risk of Co-Cr dental alloys is actually a sensitive subject with the European regulatory changes, namely regulation (EU) 2017/745 and annex VI to the CLP regulation (EC) 1972/2008. Objectives: The objective of this review is to conduct a rigorous analysis of the cytocompatibility of cobalt-chromium (Co-Cr) dental alloys. Considering various parameters such as cytotoxicity, type IV hypersensitivity reaction, sensitization, and irritation, we investigated evidence of toxicity of Co-Cr in human dental applications. Data sources: Specific search strategies were performed in three electronic databases, namely Medline, Embase, and Web of Science, using a main restriction in the search regarding the publication date (1995-2022). Study selection: Out of a total of 836 articles, only 21 studies were selected and analyzed according to PRISMA methodology. Results: Among them, 10 in vitro studies using human samples and 11 in vivo studies on human patients were distinguished. Most of the in vitro studies confirmed that Co-Cr alloys have a good cytocompatibility compared to Ni alloys. Regarding the in vivo studies, it appeared that Co-Cr could rarely cause sensitization, irritation, and allergic reactions. Reactions were mainly observed for people allergic to Co or Cr. Nevertheless, titanium-based materials showed better results. Conclusions: This study proposes a new state of the art on Co-Cr dental alloys and will thus be very useful for carrying out additional studies. Relevance: This review will help practitioners in their daily clinical choice.

Metallic Implants Used in Lumbar Interbody Fusion

Over the last decade, pedicle fixation systems have evolved and modifications in spinal fusion techniques have been developed to increase fusion rates and improve clinical outcomes after lumbar interbody fusion (LIF). Regarding materials used for screw and rod manufacturing, metals, especially titanium alloys, are the most popular resources. In the case of pedicle screws, that biomaterial can be also doped with hydroxyapatite, CaP, ECM, or tantalum. Other materials used for rod fabrication include cobalt-chromium alloys and nitinol (nickel-titanium alloy). In terms of mechanical properties, the ideal implant used in LIF should have high tensile and fatigue strength, Young's modulus similar to that of the bone, and should be 100% resistant to corrosion to avoid mechanical failures. On the other hand, a comprehensive understanding of cellular and molecular pathways is essential to identify preferable characteristics of implanted biomaterial to obtain fusion and avoid implant loosening. Implanted material elicits a biological response driven by immune cells at the site of insertion. These reactions are subdivided into innate (primary cellular response with no previous exposure) and adaptive (a specific type of reaction induced after earlier exposure to the antigen) and are responsible for wound healing, fusion, and also adverse reactions, i.e., hypersensitivity. The main purposes of this literature review are to summarize the physical and mechanical properties of metal alloys used for spinal instrumentation in LIF which include fatigue strength, Young's modulus, and corrosion resistance. Moreover, we also focused on describing biological response after their implantation into the human body. Our review paper is mainly focused on titanium, cobalt-chromium, nickel-titanium (nitinol), and stainless steel alloys.

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.

Metabolic effects of CoCr-enriched medium on shear-stressed endothelial cell and osteoblasts: A possible mechanism involving a hypoxic condition on bone healing

Cobalt-chromium (CoCr)-based alloys have emerged as an interesting biomaterial within biomedical field, mainly considering their biocompatibility, resistance to corrosion and absence of magnetism; however, its effect on cell metabolism is barely known and this prompted us better evaluating whether CoCr-enriched medium affects the metabolism of both osteoblast and endothelial cells, and also if there is a coupling between them. This is also considered here the already-known effect of Cobalt (Co) as a hypoxic element. Firstly, discs of CoCr [subjecting (W) or not (Wo) to dual acid-etched (DAE)] were incubated into FBS-free cell culture medium up to 24 h (37 °C). This CoCr-enriched medium was further used to treat shear-stressed endothelial cells cultures up to 72 h. Thereafter, the conditioned medium containing metabolites of shear-stressed endothelial cells in response to CoCr-enriched medium was further used to subject osteoblast's cultures, when the samples were properly harvested to allow the analysis of the molecular issues. Our data shows that CoCr-enriched medium contains 1.5 ng-2.0 ng/mL of Co, which was captured by endothelial cells and osteoblasts in about 30% in amount and it seems modulate their metabolic pathways: shear-stressed endothelial cells expressed higher profile of HIF1α, VEGF and nNOS genes, while their global profile of protein carbonylation was lower than the control cultures, suggesting lower oxidative stress commitment. Additionally, osteoblasts responding to metabolites of CoCr-challenged endothelial cells show dynamic expression of marker genes in osteogenic differentiation, with alkaline phosphatase (ALP), osteocalcin, and bone sialoprotein (BSP) genes being significantly increased. Additionally, tensional shear-stress forces decrease the stimulus for ColA1gene expression in osteoblasts responding to endothelial cells metabolites, as well as modifying the extracellular matrix remodeling related genes. Analyzing the activities of matrix metalloproteinases (MMPs), the data shows that shear-stressed endothelial cells metabolites increase the activities of both MMP9 and MMP2 in osteoblasts. Altogether, our data shows for the first time that shear-stressed endothelial metabolites responding to CoCr discs contribute to osteogenic phenotype in vitro, and this predicts an active crosstalk between angiogenesis and osteogenesis during osseointegration of CoCr alloy and bone healing, maybe guided by the Co-induced hypoxic condition.

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.

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.

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.