Cell Spreading Activity Research Articles

Co-Electrospun Poly(ε-Caprolactone)/Zein Articular Cartilage Scaffolds.

Osteoarthritis scaffold-based grafts fail because of poor integration with the surrounding soft tissue and inadequate tribological properties. To circumvent this, we propose electrospun poly(ε-caprolactone)/zein-based scaffolds owing to their biomimetic capabilities. The scaffold surfaces were characterized using Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, static water contact angles, and profilometry. Scaffold biocompatibility properties were assessed by measuring protein adsorption (Bicinchoninic Acid Assay), cell spreading (stained F-actin), and metabolic activity (PrestoBlue™ Cell Viability Reagent) of primary bovine chondrocytes. The data show that zein surface segregation in the membranes not only completely changed the hydrophobic behavior of the materials, but also increased the cell yield and metabolic activity on the scaffolds. The surface segregation is verified by the infrared peak at 1658 cm-1, along with the presence and increase in N1 content in the survey XPS. This observation could explain the decrease in the water contact angles from 125° to approximately 60° in zein-comprised materials and the decrease in the protein adsorption of both bovine serum albumin and synovial fluid by half. Surface nano roughness in the PCL/zein samples additionally benefited the radial spreading of bovine chondrocytes. This study showed that co-electrospun PCL/zein scaffolds have promising surface and biocompatibility properties for use in articular-tissue-engineering applications.

GPCR/endocytosis/ERK signaling/S2R is involved in the regulation of the internalization, mitochondria-targeting and -activating properties of human salivary histatin 1

Human salivary histatin 1 (Hst1) exhibits a series of cell-activating properties, such as promoting cell spreading, migration, and metabolic activity. We recently have shown that fluorescently labeled Hst1 (F-Hst1) targets and activates mitochondria, presenting an important molecular mechanism. However, its regulating signaling pathways remain to be elucidated. We investigated the influence of specific inhibitors of G protein-coupled receptors (GPCR), endocytosis pathways, extracellular signal-regulated kinases 1/2 (ERK1/2) signaling, p38 signaling, mitochondrial respiration and Na+/K+-ATPase activity on the uptake, mitochondria-targeting and -activating properties of F-Hst1. We performed a siRNA knockdown (KD) to assess the effect of Sigma-2 receptor (S2R) /Transmembrane Protein 97 (TMEM97)—a recently identified target protein of Hst1. We also adopted live cell imaging to monitor the whole intracellular trafficking process of F-Hst1. Our results showed that the inhibition of cellular respiration hindered the internalization of F-Hst1. The inhibitors of GPCR, ERK1/2, phagocytosis, and clathrin-mediated endocytosis (CME) as well as siRNA KD of S2R/TMEM97 significantly reduced the uptake, which was accompanied by the nullification of the promoting effect of F-Hst1 on cell metabolic activity. Only the inhibitor of CME and KD of S2R/TMEM97 significantly compromised the mitochondria-targeting of Hst1. We further showed the intracellular trafficking and targeting process of F-Hst1, in which early endosome plays an important role. Overall, phagocytosis, CME, GPCR, ERK signaling, and S2R/TMEM97 are involved in the internalization of Hst1, while only CME and S2R/TMEM97 are critical for its subcellular targeting. The inhibition of either internalization or mitochondria-targeting of Hst1 could significantly compromise its mitochondria-activating property.

Biological properties of direct grafting by ultraviolet irradiation of vinyl benzyl phosphonic acid onto titanium surfaces

Titanium (Ti) and its alloys are the most effective metals for structural implantable device applications. However, Ti-based materials are passively integrated into the bone, resulting in a purely mechanical attachment. Consequently, the loss of osseointegration often leads to implant failure. Therefore, enhancing bone formation surrounding the implant is primordial. In previous investigations conducted in our laboratory, grafting bioactive polymers with sulfonate groups, such as poly(sodium styrene sulfonate) (polyNaSS), was demonstrated to increase the adherence and differentiation of osteoblast cells. In this context, this contribution proposes to functionalize Ti with a phosphonic acid-based polymer, poly(vinyl benzyl phosphonic acid) (poly(VBP)). A two-step UV-initiated grafting polymerization was developed to covalently graft VBP into Ti surfaces. The surfaces were characterized using colorimetry, Fourier-transformed infrared spectra recorded in an attenuated total reflection (FTIR-ATR), X-ray photoelectron spectroscopy (XPS) techniques, and water contact angle (WCA) measurements. The Ti substrates were evaluated for cell viability, spreading, alkaline phosphatase activity, and calcium formation using MC3T3-E1 osteoblast cells. The interaction of Ti grafted samples with osteoblast cells, was significantly improved as well as the cell/surface interaction. Together, these findings demonstrated that poly(VBP) grafted on Ti surfaces improved osteoblasts' early cell adhesion and spreading activities, crucial for osseointegration applications.

Design of RGDS Peptide-Immobilized Self-Assembling β-Strand Peptide from Barnacle Protein.

We designed three types of RGD-containing barnacle adhesive proteins using self-assembling peptides. In the present study, three types of RGD-containing peptides were synthesized by solid-phase peptide synthesis, and the secondary structures of these peptides were analyzed by CD and FT-IR spectroscopy. The mechanical properties of peptide hydrogels were characterized by a rheometer. We discuss the correlation between the peptide conformation, and cell attachment and cell spreading activity from the viewpoint of developing effective tissue engineering scaffolds. We created a peptide-coated cell culture substrate by coating peptides on a polystyrene plate. They significantly facilitated cell adhesion and spreading compared to a non-coated substrate. When the RGDS sequence was modified at N- or C-terminal of R-Y, it was found that the self-assembling ability was dependent on the strongly affects hydrogel formation and cell adhesion caused by its secondary structure.

Antimicrobial Activity and Biocompatibility of Antibiotic-Loaded Chitosan Hydrogels as a Potential Scaffold in Regenerative Endodontic Treatment

IntroductionThe objective of this study was to determine the effectiveness of several antibiotic-loaded hydrogel scaffolds against Enterococcus faecalis, as well as their ability to stimulate proliferation and mineralization of dental pulp stem cells. MethodsFibrin (Fg) or chitosan-fibrin hydrogels (Ch) were prepared using 12.5 mg/mL fibrinogen and 0.4% (w/v) chitosan. Triple antibiotics, clindamycin-modified triple antibiotic paste, or double antibiotics were loaded in gels (1 mg/mL). Antibacterial effect against E. faecalis biofilm was determined by using colony-forming units (CFUs) and confocal laser scanning microscope (CLSM). Cell viability and morphology were determined by loading cells into different gels at 7 and 14 days using the water-soluble tetrazolium salt-1 cell viability assay and Live & Dead cell analysis. Mineralization was detected by using alkaline phosphatase and alizarin red staining activity. ResultsAntibiotic-loaded Fg gel and Ch gel alone without antibiotics resulted in a significant reduction in CFUs compared with the positive control (P < .05). When antibiotics were loaded in Ch gel, there were no CFUs detected in any groups (P < .05). CLSM images showed dense red areas with mostly dead bacteria on the dentin surface in antibiotic-loaded Ch groups, which showed significantly less live bacteria compared with the other groups (P < .05). Triple antibiotic-loaded Fg and Ch gels resulted in a dramatic decrease in the mineralized nodule formation compared with all other gel groups (P < .05). Ch hydrogels resulted in round cell morphology up to 7 days. Ch alone or with double antibiotic paste showed more cell spreading with spindle-shaped morphology at 14 days and higher alkaline phosphatase activity compared with other antibiotic-loaded Ch groups (P > .05). ConclusionsDouble antibiotic-loaded Ch gel appears to enhance the antibacterial properties while maintaining higher cell viability, cell spreading, and mineralization activity, compared with all the other scaffolds investigated.

The laminin-211-derived PPFEGCIWN motif accelerates wound reepithelialization and increases phospho-FAK-Tyr397 and Rac1-GTP levels in a rat excisional wound splinting model.

We previously reported that the PPFEGCIWN motif (Ln2-LG3-P2-DN3), residues 2678-2686 of the human laminin α2 chain, promotes cell attachment of normal human epidermal keratinocytes (NHEKs) and dermal fibroblasts (NHDFs); however, its in vivo effects on cutaneous wound healing have not yet been examined. In this study, we sought to determine whether Ln2-LG3-P2-DN3 could promote full-thickness cutaneous wound healing by accelerating wound reepithelialization and wound closure in vivo. Ln2-LG3-P2-DN3 had significantly higher cell attachment and spreading activities than vehicle or scrambled peptide control in both NHEKs and NHDFs in vitro. The wound area was significantly smaller in rats treated with Ln2-LG3-P2-DN3 than in those treated with vehicle or scrambled peptide in the early phase of wound healing. Furthermore, Ln2-LG3-P2-DN3 significantly accelerated wound reepithelialization relative to vehicle or scrambled peptide and promoted FAK-Tyr397 phosphorylation and Rac1 activation. Collectively, our findings suggest that the PPFEGCIWN motif has potential as a therapeutic agent for cutaneous regeneration via the acceleration of wound reepithelization and wound closure.

Mg/Ag ratios induced in vitro cell adhesion and preliminary antibacterial properties of TiN on medical Ti-6Al-4V alloy by Mg and Ag implantation

Titanium alloy (Ti-6Al-4V) has been extensively applied in joint replacements, orthopedic prostheses, dental implants, and so on, because of their good biocompatibilities and mechanical properties. However, the inferior antibacterial activity and biological inert of titanium alloy limit its application in the field of hard tissue repair. Therefore, the surface modification to Ti-6Al-4V is well method. In this paper, titanium nitride (TiN) was first deposited on the surface of Ti-6Al-4V alloy. Then magnesium (Mg) and silver (Ag) ions with different ratios (Mg:Ag = 0.5:1; 1:1; 3:1) were implanted into TiN via a plasma immersion ion implantation (PIII) system to explore the effects of Mg/Ag ratios on the cell adhesion and the preliminary antibacterial properties. Structure characteristics and compositions of Mg/Ag implanted TiN were analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD). X-ray photoelectron spectrometer (XPS) proved the presence of Mg and Ag on the surface of Mg/Ag-TiN. The results of water contact angle and protein adsorption proved that the wettability and protein adsorption energy of the materials increased significantly with the increase of Mg content. Moreover, in vitro investigations indicated that Mg/Ag (1/1)-TiN exhibited the best cell adhesion and spreading activity, and ideal proliferation, as well as preliminary antibacterial activities, which made it has a good application prospect in orthopedic material.

Supported Membrane Platform to Assess Surface Interactions between Extracellular Vesicles and Stromal Cells.

Extracellular vesicles (EVs) are membrane-encapsulated particles secreted by eukaryotic cells that stimulate cell communication and horizontal cargo exchange. EV interactions with stromal cells can result in molecular changes in the recipient cell and, in some cases, lead to disease progression. However, mechanisms leading to these changes are poorly understood. A few model systems are available for studying the outcomes of surface interactions between EV membranes with stromal cells. Here, we created a hybrid supported bilayer incorporating EVs membrane material, called an extracellular vesicle supported bilayer, EVSB. Using EVSBs, we investigated the surface interactions between breast cancer EVs and adipose-derived stem cells (ADSCs) by culturing ADSCs on EVSBs and analyzing cell adhesion, spreading, viability, vascular endothelial growth factor (VEGF) secretion, and myofibroblast differentiation. Results show that cell viability, adhesion, spreading, and proangiogenic activity were enhanced, conditions that promote oncogenic activity, but cell differentiation was not. This model system could be used to develop therapeutic strategies to limit EV-ADSC interactions and proangiogenic conditions. Finally, this model system is not limited to the study of cancer but can be used to study surface interactions between EVs from any origin and any target cell to investigate EV mechanisms leading to cellular changes in other diseases.

Enhancement of the mechanical and biological properties on Zn/Ag co-implanted TiN via ions contents regulation

Most orthopedic and dental implants are made of Ti and its alloys due to the excellent biocompatibility and machinability. However, low hardness, biologically inert and poor antibacterial property block its application in the field of hard tissue repair. Therefore, in this study, TiN co-implanted with Zn and Ag (Zn/Ag-TiN) with different contents using the plasma immersion ion implantation system was modified on the surface of titanium alloy to evaluate the mechanical properties, biological properties and antibacterial activities. X-ray photoelectron spectrometer was used to determine the chemical state and composition of samples. The tests of hardness, elastic modulus and scratch of different samples were performed by the nano indenter XP system. Biocompatibility and antibacterial properties were evaluated by MC3T3-E1 cells, bovine serum albumin (BSA) and Escherichia coli (E. coli) in vitro. Results indicate that Zn/Ag(1.5 h)-TiN with the largest content of Zn and Ag exhibits the strongest hardness and adhesion strength, the highest protein adsorption capacity, the best cell adhesion and spreading activity, and ideal proliferation, as well as antibacterial activities, which makes it have great application prospects in orthopedic materials.

All-trans retinoic acid and human salivary histatin-1 promote the spreading and osteogenic activities of pre-osteoblasts invitro.

Cell‐based bone tissue engineering techniques utilize both osteogenic cells and biomedical materials, and have emerged as a promising approach for large‐volume bone repair. The success of such techniques is highly dependent on cell adhesion, spreading, and osteogenic activities. In this study, we investigated the effect of co‐administration of all‐trans retinoic acid (ATRA) and human salivary peptide histatin‐1 (Hst1) on the spreading and osteogenic activities of pre‐osteoblasts on bio‐inert glass surfaces. Pre‐osteoblasts (MC3T3‐E1 cell line) were seeded onto bio‐inert glass slides in the presence and absence of ATRA and Hst1. Cell spreading was scored by measuring surface areas of cellular filopodia and lamellipodia using a point‐counting method. The distribution of fluorogenic Hst1 within osteogenic cells was also analyzed. Furthermore, specific inhibitors of retinoic acid receptors α, β, and γ, such as ER‐50891, LE‐135, and MM‐11253, were added to identify the involvement of these receptors. Cell metabolic activity, DNA content, and alkaline phosphatase (ALP) activity were assessed to monitor their effects on osteogenic activities. Short‐term (2 h) co‐administration of 10 μm ATRA and Hst1 to pre‐osteoblasts resulted in significantly higher spreading of pre‐osteoblasts compared to ATRA or Hst1 alone. ER‐50891 and LE‐135 both nullified these effects of ATRA. Co‐administration of ATRA and Hst1 was associated with significantly higher metabolic activity, DNA content, and ALP activity than either ATRA or Hst1 alone. In conclusion, co‐administration of Hst1 with ATRA additively stimulated the spreading and osteogenicity of pre‐osteoblasts on bio‐inert glass surfaces in vitro.

Phosphorylated fibronectin enhances cell attachment and upregulates mechanical cell functions.

A large number of extracellular matrix proteins have been found in phosphorylated states, yet little is known about how the phosphorylation of extracellular matrix proteins might affect cell functions. We thus tested the hypothesis whether the phosphorylation of fibronectin, a major adhesion protein, affects cell behavior. Controlled in vitro phosphorylation of fibronectin by a casein kinase II (CKII) significantly upregulated cell traction forces and total strain energy generated by fibroblasts on nanopillar arrays, and consequently other elementary cell functions including cell spreading and metabolic activity. Mass spectrometry of plasma fibronectin from healthy human donors then identified a constitutively phosphorylated site in the C-terminus, and numerous other residues that became phosphorylated by the CKII kinase in vitro. Our findings open up novel strategies for translational applications including targeting diseased ECM, or to develop assays that probe the phosphorylation state of the ECM or blood as potential cancer markers.

Evaluating the bioactivity of a hydroxyapatite-incorporated polyetheretherketone biocomposite

BackgroundPolyetheretherketone (PEEK) exhibits stable chemical properties, excellent biocompatibility, and rational mechanical properties that are similar to those of human cortical bone, but the lack of bioactivity impedes its clinical application.MethodsIn this study, hydroxyapatite (HA) was incorporated into PEEK to fabricate HA/PEEK biocomposite using a compounding and injection-molding technique. The tensile properties of the prepared HA/PEEK composites (HA content from 0 to 40 wt%) were tested to choose an optimal HA content. To evaluate the bioactivity of the composite, the cell attachment, proliferation, spreading and alkaline phosphatase (ALP) activity of MC3T3-E1 cells, and apatite formation after immersion in simulated body fluid (SBF), and osseointegration in a rabbit cranial defect model were investigated. The results were compared to those from ultra-high molecular weight polyethylene (UHMWPE) and pure PEEK.ResultsBy evaluating the tensile properties and elastic moduli of PEEK composite samples/PEEK composites with different HA contents, the 30 wt% HA/PEEK composite was chosen for use in the subsequent tests. The results of the cell tests demonstrated that PEEK composite samples/PEEK composite exhibited better cell attachment, proliferation, spreading, and higher ALP activity than those of UHMWPE and pure PEEK. Apatite islands formed on the HA/PEEK composite after immersion in SBF for 7 days and grew continuously with longer time periods. Animal tests indicated that bone contact and new bone formation around the HA/PEEK composite were more obvious than those around UHMWPE and pure PEEK.ConclusionsThe HA/PEEK biocomposite created by a compounding and injection-molding technique exhibited enhanced osteogenesis and could be used as a candidate of orthopedic implants.

Peptide-modified methacrylated glycol chitosan hydrogels as a cell-viability supporting pro-angiogenic cell delivery platform for human adipose-derived stem/stromal cells.

Cell-based therapies involving the injection of adipose-derived stem/stromal cells (ASCs) within rationally designed biomaterials are a promising approach for stimulating angiogenesis. With this focus, the current work explored the effects of incorporating integrin-binding RGD or IKVAV peptides within in situ-gelling N-methacrylate glycol chitosan (MGC) hydrogels on the response of encapsulated human ASCs. Initial studies focused on hydrogel characterization to validate that the MGC, MGC-RGD, and MGC-IKVAV hydrogels had similar biomechanical properties. ASC viability following encapsulation and culture under 2% O2 was significantly impaired in the MGC-IKVAV group relative to the MGC and MGC-RGD groups. In contrast, sustained viability, along with enhanced cell spreading and metabolic activity were observed in the MGC-RGD group. Investigation of angiogenic transcription suggested that the incorporation of the peptide groups did not substantially alter the pro-angiogenic gene expression profile of the encapsulated ASCs after 7 days of culture under 2% O2. Consistent with the in vitro findings, preliminary in vivo characterization following subcutaneous implantation into NOD/SCID mice showed that ASC retention was enhanced in the MGC-RGD hydrogels relative to the MGC-IKVAV group at 14 days. Further, the encapsulated ASCs in the MGC and MGC-RGD groups promoted murine CD31+ endothelial cell recruitment to the peri-implant region. Overall, the results indicate that the MGC-RGD and MGC hydrogels are promising platforms for ASC delivery, and suggest that strategies that support long-term ASC viability can augment in vivo angiogenesis through paracrine mechanisms. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 571-585, 2019.

An RGD-Containing Peptide Derived from Wild Silkworm Silk Fibroin Promotes Cell Adhesion and Spreading.

Arginine-Glycine-Aspartate (RGD) tripeptide can promote cell adhesion when present in the amino acid of proteins such as fibronectin. In order to demonstrate the bioactivity of an RGD-containing silk protein, a gene encoding the RGD motif-containing peptide GSGAGGRGDGGYGSGSS (–RGD–) derived from nonmulberry silk was designed and cloned, then multimerised and inserted into a commercial pGEX expression vector for recombinant expression of (–RGD–)n peptides. Herein, we focus on two glutathione-S-transferase (GST)-tagged fusion proteins, GST–(–RGD–)4 and GST–(–RGD–)8, which were expressed in Escherichia coli BL21, purified by GST affinity chromatography, and analyzed with sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and mass spectrometry (MS). Target peptides (–RGD–)4 and (–RGD–)8 (6.03 and 11.5 kDa) were cleaved from the GST-tag by thrombin digestion, as verified with MS and SDS-PAGE. Isoelectric point analysis confirmed that target peptides were expressed and released in accordance with the original design. Target peptides self-assembled into a mainly α-helical structure, as determined by circular dichroism spectroscopy. Furthermore, (–RGD–)4 and (–RGD–)8 modified mulberry silk fibroin films were more effective for rapid cell adhesion, spreading and proliferative activity of L929 cells than some chemically synthesized RGD peptides modified and mulberry silk lacking the RGD motif.

Osteogenic differentiation of mesenchymal stem cells modulated by a chemically modified super-hydrophilic titanium implant surface.

This study investigated the osteogenic functionality of multipotent mesenchymal stem cells (MSCs) modulated by a chemically modified super-hydrophilic titanium (Ti) bone implant surface to elucidate the biological mechanism underlying the bone healing capacity of this modified Ti surface. A microstructured Ti surface incorporating bioactive ions (in this study, phosphate (P) ions) was prepared by wet chemical treatment. The results showed that the hydrothermally obtained crystalline P-incorporated Ti surface (P surface) displayed long-term super-hydrophilicity (water contact angles <5°) during a 36-week observation period. The hydrophilic P surface enhanced early cellular functions and osteogenic differentiation of multipotent MSCs derived from mouse bone marrow and human adipose tissue. The expression of critical integrins affecting subsequent osteoblast function and osteoblast phenotype genes was notably upregulated in multipotent MSCs grown on the P surface compared with the commercially available grit-blasted microrough clinical oral implant surface. The P surface supported better cell spreading, focal adhesion and ALP activity of MSCs. These results indicate that a super-hydrophilic P-incorporated Ti surface accelerates implant bone healing by enhancing the early osteogenesis functions of multipotent MSCs.

Bioactive composite scaffolds of carboxymethyl chitosan-silk fibroin containing chitosan nanoparticles for sustained release of ascorbic acid

This study introduces and characterizes the biomimetic and bioactive scaffolds for bone regeneration based on silk fibroin (SF)-carboxymethyl chitosan (CMCh) incorporated with ascorbic acid (AA)-loaded chitosan nanoparticles (ChNPs). The ChNPs were prepared to encapsulate AA, as a simple and safe osteoinductive drug, through the ionic gelation process. CMCh was also prepared through chemical reaction with monochloroacetic acid under various temperature conditions (60–80 °C). The CMCh with higher carboxyl content (T = 80 °C) was chosen for further scaffolding. Then, the AA-loaded ChNPs were mixed with different ratios of SF: CMCh to prepare osteoconductive and osteoinductive scaffolds. As proved by scanning electron microscopy, all composites had well-interconnected porous structures. Larger pore size, higher porosity, and greater water uptake were obtained by increasing CMCh, while the opposite trend was observed for compressive modulus and strength. The in vitro release studies showed that the release of AA was controlled by Fickian diffusion and was faster in the scaffolds containing more CMCh. The mineralization study in simulated body fluid indicated that both CMCh and AA promote calcium phosphate deposition throughout all scaffolds, while the bioactivity enhanced with the increase of CMCh. Osteoblast-like cells (MG63) cultured on the scaffolds demonstrated that higher CMCh content enhanced cell spreading, proliferation, and alkaline phosphatase activity.

Beneficial effects of paeoniflorin on osteoporosis induced by high-carbohydrate, high-fat diet-associated hyperlipidemia in vivo

Osteoporosis is linked to reduced bone mineral density (BMD) as a major risk factor for fragility fractures. Recent studies indicated an association between BMD and abnormally elevated lipid levels in blood as common indicators for hyperlipidemia. In this study, we assessed the protective effect of paeoniflorin, a phytochemical compound with multiple pharmacological activities, against hyperlipidemia-induced osteoporosis in rats fed a high-carbohydrate, high-fat diet (HCHF). The special diet-fed rats were subjected to an 8-week treatment with either paeoniflorin (20 mg/kg, daily) or vehicle. The control group received a normal diet during the entire study. At study conclusion, serum markers of lipid metabolism and bone turnover were measured. Bone strength was assessed by biomechanical testing, and femurs were scanned using micro-computed tomography to analyze trabecular and cortical bone structure. Interestingly, paeoniflorin controlled the serum lipid profile by significantly decreasing HCHF-induced high levels of total cholesterol, triglyceride, and low-density lipoprotein cholesterol. Paeoniflorin significantly improved trabecular and cortical parameters as well as femur length and width that were negatively affected by HCHF diet. Biomechanical strength testing showed that femurs of HCHF diet-fed rats endured significantly lower force but higher displacement and strain than those of control rats, whereas paeoniflorin reversed the negative effects. Moreover, paeoniflorin rescued osteoblast differentiation and cell spreading activities along with bone turnover markers. In conclusion, HCHF-induced hyperlipidemia caused adverse effects on the bone that were rescued by paeoniflorin treatment.

YAP regulates cell mechanics by controlling focal adhesion assembly

Hippo effectors YAP/TAZ act as on–off mechanosensing switches by sensing modifications in extracellular matrix (ECM) composition and mechanics. The regulation of their activity has been described by a hierarchical model in which elements of Hippo pathway are under the control of focal adhesions (FAs). Here we unveil the molecular mechanism by which cell spreading and RhoA GTPase activity control FA formation through YAP to stabilize the anchorage of the actin cytoskeleton to the cell membrane. This mechanism requires YAP co-transcriptional function and involves the activation of genes encoding for integrins and FA docking proteins. Tuning YAP transcriptional activity leads to the modification of cell mechanics, force development and adhesion strength, and determines cell shape, migration and differentiation. These results provide new insights into the mechanism of YAP mechanosensing activity and qualify this Hippo effector as the key determinant of cell mechanics in response to ECM cues.

Enhanced Bioactivity and Bacteriostasis of Surface Fluorinated Polyetheretherketone.

Although polyetheretherketone (PEEK) has been considered as a potential orthopedic and dental application material due to its similar elastic modulus as bones, inferior osseointegration and bacteriostasis of PEEK hampers its clinical application. In this work, fluorinated PEEK was constructed via plasma immersion ion implantation (PIII) followed by hydrofluoric acid treatment to ameliorate the osseointegration and antibacterial properties of PEEK. The surface microstructure, composition, and hydrophilicity of all samples were investigated. Rat bone mesenchymal stem cells (rBMSCs) were cultured on their surfaces to estimate bioactivity. The fluorinated PEEK can enhance the cell adhesion, cell spreading, proliferation, and alkaline phosphatase (ALP) activity compared to pristine PEEK. Furthermore, the fluorinated PEEK surface exhibits good bacteriostatic effect against Porphyromonas gingivalis, which is one of the major periodontal pathogens. In summary, we provide an effective route to introduce fluorine and the results reveal that the fluorinated PEEK can enhance the osseointegration and bacteriostasis, which provides a potential candidate for dental implants.

Influences of surface treatments with abrasive paper and sand-blasting on surface morphology, hydrophilicity, mineralization and osteoblasts behaviors of n-CS/PK composite

The surfaces of nano-calcium silicate (n-CS)/polyetheretherketone (PK) composites were treated with abrasive paper and sand-blasting, and the surfaces performances of the as-treated composites were studied. The results showed that the surface roughness, hydrophilicity and mineralization of the simulated body fluid (SBF) of the composites surfaces were significantly improved, and the properties of the composites treated by with sand-blasting were better than those treated with abrasive paper. Moreover, the treated composites significantly promoted osteoblasts responses, such as cell attachment, spreading, proliferation and alkaline phosphatase (ALP) activity, compared to un-treated composites, and the cellular responses to the composites treated with sand-blasting were better than those treated with abrasive paper. The results suggested that surface treatment with sand-blasting was an effective method to greatly improve the surface bioperformances of the n-CS/PK composite, and this treated composite with improved bioactivity and cytocompatibility might be a promising implant material for orthopedic applications.