The effect of substrate stiffness on cancer cell volume homeostasis.

Existing studies on the mechanism of cell volume regulation are mainly relevant to ion channels and osmosis in extracellular fluid. Recently, accumulating evidence has shown that cellular mechanical microenvironment also influences the cell volume. Herein, we investigated the regulation of substrate stiffness on the cell volume homeostasis of MCF-7 cells and their following migration behaviors. We found that cell volume increases with increasing substrate stiffness, which could be affected by blocking the cell membrane anion permeability and dopamine receptor. In addition, the cell migration is significantly inhibited by decreasing the cell volume using tamoxifen and such inhibition effect on migration is enhanced by increasing substrate stiffness. The cell membrane anion permeability might be the linker between cellular mechanical microenvironment and cellular volume homeostasis regulation. This work revealed the regulation of substrate stiffness on cell volume homeostasis for the first time, which would provide a new perspective into the understanding of cancer metastasis and a promising anti-cancer therapy through regulation of cell volume homeostasis.

Parametric Study on Electric Field-Induced Micro-/Nanopatterns in Thin Polymer Films.

Electric field-induced micro-/nanopatterns in thin polymer films, sometimes referred as electrohydrodynamic patterning, is a promising technique to fabricate micro-/nanostructures. Extensive attention has been attracted because of its advantages in microcontact (easy demolding) and low cost. Although considerable work has been done on this technique, including both experimental and theoretical ones, there still appears a requirement for understanding the mechanism of electrohydrodynamic patterning. Thus, we systematically studied the effect of different parameters on electrohydrodynamic patterning with a numerical phase field model. Previous researchers usually employed lubrication approximation (i.e., long-wave approximation) to simplify the numerical model. However, this approximation would lose its validity if the structure height is on the same scale or larger than the wavelength, which occurs in most cases. Thus, we abandoned the lubrication approximation and solved the full governing equations for fluid flow and electric field. In this model, the deformation of polymer film is described by the phase field model. As to the electric field, the leaky dielectric model is adopted in which both electrical permittivity and conductivity are considered. The fluid flow together with electric field is coupled together in the framework of phase field. By this model, the effect of physical parameters, such as external voltage, template structure height, and polymer conductivity, is studied in detail. After that, the governing equations are nondimesionalized to analyze the relationship between different parameters. A dimensionless parameter, electrical Reynolds number ER, is defined, for which, a large value would simplify the electric field to perfect dielectric model and a small value leads it to steady leaky model. These findings and results may enhance our understanding of electrohydrodynamic patterning and may be a meaningful guide for experiments.

The potential health challenges of TiO2 nanomaterials.

Titanium dioxide (TiO2 ) nanomaterials (NMs) have found widespread applications owing to their attractive physical and chemical properties. As a result, the potential adverse impacts of nano-TiO2 exposure on humans have become a matter of concern. This review presents the state-of-the-art advances on the investigations of the adverse effects of NMs, including the potential exposure routes of nano-TiO2 (e.g. respiratory system, skin absorption and digestive system), the physico-chemical characterizations of nano-TiO2 (e.g. crystal structure, shape,size, zeta potential, treatment media, aggregation and agglomeration tendency, surface characteristics and coatings), risk evaluation of nanotoxicity (e.g. cytotoxicity, ecotoxicity, phototoxicity, and phytotoxicity) and potential mechanisms of adverse effects (e.g. generation of reactive oxygen species, oxidative stress and organelle dysfunction). The review aims to facilitate scientific assessments of health risks to nano-TiO2 , which would guide the safe applications of NMs in our daily life.

Fabrication of a three-layer SU-8 mould with inverted T-shaped cavities based on a sacrificial photoresist layer technique.

A novel method for fabricating a three-layer SU-8 mould with inverted T-shaped cavities is presented. The first two SU-8 layers were spin coated and exposed separately, and simultaneously developed to fabricate the bottom and the horizontal part of the inverted T-shaped cavity. Then, a positive photoresist was filled into the cavity, and a wet lapping process was performed to remove the excess photoresist and make a temporary substrate. The third SU-8 layer was spin coated on the temporary substrate to make the vertical part of the inverted T-shaped cavity. The sacrificial photoresist layer can prevent the first two SU-8 layers from being secondly exposed, and make a temporary substrate for the third SU-8 layer at the same time. Moreover, the photoresist can be easily removed with the development of the third SU-8 layer. A polydimethylsiloxane (PDMS) microchip with arrays of T-shaped cantilevers for studying the mechanics of cells was fabricated by using the SU-8 mould.

Oxidative stress increased hepatotoxicity induced by nano-titanium dioxide in BRL-3A cells and Sprague-Dawley rats.

Extensive studies have shown that titanium dioxide (TiO2 ) nanomaterials (NMs) can cause toxicity in vitro and in vivo under normal conditions. However, an adverse effect induced by nano-TiO2 in many diseased conditions, typically characterized by oxidative stress (OS), remains unknown. We investigated the toxicity of nano-TiO2 in rat liver cells (BRL-3A) and Sprague-Dawley (SD) rat livers under OS conditions, which were generated using hydrogen peroxide (H2 O2 ) in vitro and alloxan in vivo, respectively. In vitro results showed that cell death ratios after nano-TiO2 exposure were significantly enhanced (up to 2.62-fold) in BRL-3A cells under OS conditions, compared with normal controls. Significant interactions between OS conditions and nano-TiO2 resulted in the rapid G0/G1 to S phase transition and G2/M arrest, which were opposite to G0/G1 phase arrest in cells after NMs exposure only. In vivo results showed that obvious pathological changes in rat livers and the increased activities of four enzymes (i.e. aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase and alkaline phosphatase) owing to liver damage after nano-TiO2 exposure under OS conditions, compared with their healthy controls. In addition, compared with increased hepatotoxicity after nano-TiO2 exposure, micro-TiO2 showed no adverse effects to cells and rat livers under OS conditions. Our results suggested that OS conditions synergistically increase nano-TiO2 induced toxicity in vitro and in vivo, indicating that the evaluation of nanotoxicity under OS conditions is essentially needed prior to various applications of NMs in foods, cosmetics and potential treatment of diseases.

Chronic stress dysregulates the Hippo/YAP/14-3-3η pathway and induces mitochondrial damage in basolateral amygdala in a mouse model of depression.

Rationale: Recent evidence highlights the pivotal role of mitochondrial dysfunction in mood disorders, but the mechanism involved remains unclear. We studied whether the Hippo/YAP/14-3-3η signaling pathway mediates mitochondrial abnormalities that result in the onset of major depressive disorder (MDD) in a mouse model. Methods: The ROC algorithm was used to identify a subpopulation of mice that were exposed to chronic unpredictable mild stress (CUMS) and exhibited the most prominent depressive phenotype (Dep). Electron microscopy, biochemical assays, quantitative PCR, and immunoblotting were used to evaluate synaptic and mitochondrial changes in the basolateral amygdala (BLA). RNA sequencing was used to explore changes in the Hippo pathway and downstream target genes. In vitro pharmacological inhibition and immunoprecipitation was used to confirm YAP/14-3-3η interaction and its role in neuronal mitochondrial dysfunction. We used virus-mediated gene overexpression and knockout in YAP transgenic mice to verify the regulatory effect of the Hippo/YAP/14-3-3η pathway on depressive-like behavior. Results: Transcriptomic data identified a large number of genes and signaling pathways that were specifically altered from the BLA of Dep mice. Dep mice showed notable synaptic impairment in BLA neurons, as well as mitochondrial damage characterized by abnormal mitochondrial morphology, compromised function, impaired biogenesis, and alterations in mitochondrial marker proteins. The Hippo signaling pathway was activated in Dep mice during CUMS, and the transcriptional regulatory activity of YAP was suppressed by phosphorylation of its Ser127 site. 14-3-3η was identified as an important co-regulatory factor of the Hippo/YAP pathway, as it can respond to chronic stress and regulate cytoplasmic retention of YAP. Importantly, the integrated Hippo/YAP/14-3-3η pathway mediated neuronal mitochondrial dysfunction and depressive behavior in Dep mice. Conclusion: The integrated Hippo/YAP/14-3-3η pathway in the BLA neuron is critical in mediating depressive-like behaviors in mice, suggesting a causal role for this pathway in susceptibility to chronic stress-induced depression. This pathway therefore may present a therapeutic target against mitochondrial dysfunction and synaptic impairment in MDD.

Potential application of titanium dioxide nanoparticles in the prevention of osteosarcoma and chondrosarcoma recurrence.

Osteosarcoma and chondrosarcoma are malignant bone tumors, and they significantly affect the life quality of patients including children and adults. The main treatment method is surgical amputation of the malignant lesion, despite that recurrence often occurs. Recently, it has been observed that TiO2 NPs killed HeLa cells effectively via photocatalysis in vitro, which indicates titanium dioxide (TiO2) nanoparticles (NPs) might be used to reduce the recurrence of osteosarcoma and chondrosarcoma by inducing cytotoxicity to bone tumor cells. In this study, we investigated the potential effects of TiO2 NPs in two cancer cell lines in vitro: U-2 OS (osteosarcoma) and SW 1353 (chondrosarcoma). We assessed cell viability, the levels of reactive oxygen species (ROS) and glutathione (GSH) after exposure to TiO2 NPs at different concentrations (0.1-100 microg/ml) for varying exposure periods (12-48 hours). Compared to the NP-free control, TiO2 NPs induced cell death in a dosage-dependent and time-dependent manner. The median inhibitory concentration (IC50) of TiO2 NPs at 24 hours was 211.3 +/- 15.2 microg/ml and 5408.8 +/- 45.9 microg/ml for SW 1353 and U-2 OS cell lines, respectively. TiO2 NPs concentrations above 1 microg/ml were more efficient to reduce the cell viability of SW 1353 than U-2 OS of NPs at all exposure times. The increased ROS and reduced GSH levels indicated that TiO2 NPs killed cancer cells through oxidative stress. These results suggested that the TiO2 NPs can be potentially used to minimize/prevent the recurrence of osteosarcoma and chondrosarcoma.

[Regulation of chondrosarcoma cell growth using synthesized hydrogels with different electric charges].

To develop standard in vitro chondrosarcoma models, we synthesized three hydrogels (i. e., PDMAAm, PNaAMPS and PMETAC) and investigated the influence of Young's modulus, swelling ratio and electric charges on the behavior of chondrosarcoma cells seeded on the hydrogels, including morphology, adhesion and aggregation. Results showed that the morphology of chondrosarcoma cells at 6h was dependent on the charges of hydrogels; cells present spindle-shaped and round-shaped morphology on negative charged and neutral hydrogel, respectively, while no cells spreaded on positive charged hydrogel. Chondrosarcoma cells formed aggregates on neutral PDMAAm after further culture. The hydrogels can be synthesized easily and has the characteristics of ease at use with defined components, which holds great potential for developing standard chondrosarcoma models in vitro.

Genome-wide association and follow-up replication studies identified ADAMTS18 and TGFBR3 as bone mass candidate genes in different ethnic groups.

To identify and validate genes associated with bone mineral density (BMD), which is a prominent osteoporosis risk factor, we tested 379,319 SNPs in 1000 unrelated white U.S. subjects for associations with BMD. For replication, we genotyped the most significant SNPs in 593 white U.S. families (1972 subjects), a Chinese hip fracture (HF) sample (350 cases, 350 controls), a Chinese BMD sample (2955 subjects), and a Tobago cohort of African ancestry (908 males). Publicly available Framingham genome-wide association study (GWAS) data (2953 whites) were also used for in silico replication. The GWAS detected two BMD candidate genes, ADAMTS18 (ADAM metallopeptidase with thrombospondin type 1 motif, 18) and TGFBR3 (transforming growth factor, beta receptor III). Replication studies verified the significant findings by GWAS. We also detected significant associations with hip fracture for ADAMTS18 SNPs in the Chinese HF sample. Meta-analyses supported the significant associations of ADAMTS18 and TGFBR3 with BMD (p values: 2.56 x 10(-5) to 2.13 x 10(-8); total sample size: n = 5925 to 9828). Electrophoretic mobility shift assay suggested that the minor allele of one significant ADAMTS18 SNP might promote binding of the TEL2 factor, which may repress ADAMTS18 expression. The data from NCBI GEO expression profiles also showed that ADAMTS18 and TGFBR3 genes were differentially expressed in subjects with normal skeletal fracture versus subjects with nonunion skeletal fracture. Overall, the evidence supports that ADAMTS18 and TGFBR3 might underlie BMD determination in the major human ethnic groups.

Programmable integrin and N-cadherin adhesive interactions modulate mechanosensing of mesenchymal stem cells by cofilin phosphorylation.

During mesenchymal development, the sources of mechanical forces transduced by cells transition over time from predominantly cell-cell interactions to predominantly cell-extracellular matrix (ECM) interactions. Transduction of the associated mechanical signals is critical for development, but how these signals converge to regulate human mesenchymal stem cells (hMSCs) mechanosensing is not fully understood, in part because time-evolving mechanical signals cannot readily be presented in vitro. Here, we established a DNA-driven cell culture platform that could be programmed to present the RGD peptide from fibronectin, mimicking cell-ECM interactions, and the HAVDI peptide from N-cadherin, mimicking cell-cell interactions, through DNA hybridization and toehold-mediated strand displacement reactions. The platform could be programmed to mimic the evolving cell-ECM and cell-cell interactions during mesenchymal development. We applied this platform to reveal that RGD/integrin ligation promoted cofilin phosphorylation, while HAVDI/N-cadherin ligation inhibited cofilin phosphorylation. Cofilin phosphorylation upregulated perinuclear apical actin fibers, which deformed the nucleus and thereby induced YAP nuclear localization in hMSCs, resulting in subsequent osteogenic differentiation. Our programmable culture platform is broadly applicable to the study of dynamic, integrated mechanobiological signals in development, healing, and tissue engineering.

Identification of 14-3-3 epsilon as a regulator of the neural apoptotic pathway for chronic-stress-induced depression.

Major depression is a prevalent and long-lasting psychiatric illness with severe functional impairment and high suicide rate. We have previously shown that the ventrolateral orbital cortex (VLO) plays a key role in the stress responses in mice, but the underlying mechanisms remains unclear. Here, we used proteomic method to identify differentially expressed proteins in VLO of chronic unpredictable mild stress (CUMS) mice. Of 4,953 quantified proteins, 45 proteins were differentially expressed following CUMS. The integrated pathway analyses identified 14-3-3ε and TrkB signaling as differentially downregulated in association with stress-induced depressive-like behaviors. 14-3-3ε overexpression in VLO relieved the depressive-like behaviors by rescue of Bad-mediated apoptosis. Moreover, treatment with the 14-3-3ε stabilizer FC-A precluded neuronal apoptotic signaling in VLO of depressed mice. Because 14-3-3ε provides significant protection against chronic stress, boosting 14-3-3ε expression, pharmacological stabilization of 14-3-3s (e.g. with FC-A) is identified as an exciting therapeutic target for major depression.

Mechanics-driven nuclear localization of YAP can be reversed by N-cadherin ligation in mesenchymal stem cells.

Mesenchymal stem cells adopt differentiation pathways based upon cumulative effects of mechanosensing. A cell's mechanical microenvironment changes substantially over the course of development, beginning from the early stages in which cells are typically surrounded by other cells and continuing through later stages in which cells are typically surrounded by extracellular matrix. How cells erase the memory of some of these mechanical microenvironments while locking in memory of others is unknown. Here, we develop a material and culture system for modifying and measuring the degree to which cells retain cumulative effects of mechanosensing. Using this system, we discover that effects of the RGD adhesive motif of fibronectin (representative of extracellular matrix), known to impart what is often termed "mechanical memory" in mesenchymal stem cells via nuclear YAP localization, are erased by the HAVDI adhesive motif of the N-cadherin (representative of cell-cell contacts). These effects can be explained by a motor clutch model that relates cellular traction force, nuclear deformation, and resulting nuclear YAP re-localization. Results demonstrate that controlled storage and removal of proteins associated with mechanical memory in mesenchymal stem cells is possible through defined and programmable material systems.

Impact of female cigarette smoking on circulating B cells in vivo: the suppressed ICOSLG, TCF3, and VCAM1 gene functional network may inhibit normal cell function.

As pivotal immune guardians, B cells were found to be directly associated with the onset and development of many smoking-induced diseases. However, the in vivo molecular response of B cells underlying the female cigarette smoking remains unknown. Using the genome-wide Affymetrix HG-133A GeneChip microarray, we firstly compared the gene expression profiles of peripheral circulating B cells between 39 smoking and 40 non-smoking healthy US white women. A total of 125 differential expressed genes were identified in our study, and 75.2% of them were down-regulated in smokers. We further obtained genotypes of 702 single nucleotide polymorphisms in those promising genes and assessed their associations with smoking status. Using a novel multicriteria evaluation model integrating information from microarray and the association studies, several genes were further revealed to play important roles in the response of smoking, including ICOSLG (CD275, inducible T-cell co-stimulator ligand), TCF3 (E2A immunoglobulin enhancer binding factors E12/E47), VCAM1 (CD106, vascular cell adhesion molecule 1), CCR1 (CD191, chemokine C-C motif receptor 1) and IL13 (interleukin 13). The differential expression of ICOSLG (p = 0.0130) and TCF3 (p = 0.0125) genes between the two groups were confirmed by real-time reverse transcription PCR experiment. Our findings support the functional importance of the identified genes in response to the smoking stimulus. This is the first in vivo genome-wide expression study on B cells at today's context of high prevalence rate of smoking for women. Our results highlight the potential usage of integrated analyses for unveiling the novel pathogenesis mechanism and emphasized the significance of B cells in the etiology of smoking-induced disease.

Genome-wide association study suggested copy number variation may be associated with body mass index in the Chinese population.

Obesity is a major public health problem characterized with high body mass index (BMI). Copy number variations (CNVs) have been identified to be associated with complex human diseases. The effect of CNVs on obesity is unknown. In this study, we explored the association of CNVs with BMI in 597 Chinese Han subjects using Affymetrix GeneChip Human Mapping 500K Array Set. We found that one CNV at 10q11.22 (from 46.36 Mb to 46.56 Mb) was associated with BMI (the raw P=0.011). The CNV contributed 1.6% of BMI variation, and it covered one important obesity gene-pancreatic polypeptide receptor 1(PPYR1). It was reported that PPYR1 was a key regulator of energy homeostasis. Our findings suggested that CNV might be potentially important for the BMI variation. In addition, our study suggested that CNV might be used as a genetic marker to locate genes associated with BMI in Chinese population.

A mechanoelectrical coupling model of neurons under stretching.

Neurons are situated in a microenvironment composed of various mechanical cues, where stretching is thought to have a major impact on neurons, resulting in microstructural changes in neural tissue and further leading to abnormal electrophysiological function. In spite of significant experimental efforts, the underlying mechanism remains elusive, more works are needed to provide a detailed description of the process that leads to the observed phenomena. Here, we developed a mechanoelectrical coupling model of central neurons under stretching and specially considered the plastic deformation of neurons. With the model, we showed that the increasing axial strain induces a decreased membrane action potential and a more frequent neuronal firing, which agree well with experimental observations reported in the literature. The simulation results also showed a faster electrophysiological signal conduction. Our model provides a reference for the prediction and regulation of neuronal function under simplified conditions of mechanical loadings.

Electrospun three-dimensional aligned nanofibrous scaffolds for tissue engineering.

Engineered tissue constructs rely on biomaterials as support structures for tissue repair and regeneration. Among these biomaterials, polyester biomaterials have been widely used for scaffold construction because of their merits such as ease in synthesis, degradable properties, and elastomeric characteristics. To mimic the aligned structures of native extracellular matrix (ECM) in tissues such as nerve, heart and tendon, various polyester materials have been fabricated into aligned fibrous scaffolds with fibers ranging from several nanometers to several micrometers in diameter by electrospinning in a simple and reproducible manner. These aligned fibrous scaffolds, especially the three-dimensional (3D) aligned nanofibrous scaffolds have emerged as a promising solution for tissue regeneration. Compared with two-dimensional (2D) scaffolds, the 3D aligned nanofibrous scaffolds provide another dimension for cell behaviors such as morphogenesis, migration and cell-cell interactions, which is important in regulating the stem cell fate and tissue regeneration. In this review, we provide an extensive overview on recent efforts for constructing 3D aligned polyester nanofibrous scaffolds by electrospinning, then the results of cell-specific functions dependent on such physical and chemical cues, and discuss their potentials in improving or restoring damaged tissues.

Heterostructured Silk-Nanofiber-Reduced Graphene Oxide Composite Scaffold for SH-SY5Y Cell Alignment and Differentiation.

Stem cell therapy is promising for treating traumatic injuries of the central nervous system, where a major challenge is to effectively differentiate neural stem cells into neurons with uniaxial alignment. Recently, controlling stem cell fate by modulating biophysical cues (e.g., stiffness, conductivity, and patterns) has emerged as an attractive approach. Herein, we report a new heterostructure composite scaffold to induce cell-oriented growth and enhance the neuronal differentiation of SH-SY5Y cells. The scaffold is composed of aligned electrospinning silk nanofibers coated on reduced graphene paper with high conductivity and good biocompatibility. Our experimental results demonstrate that the composite scaffold can effectively induce the oriented growth and enhance neuronal differentiation of SH-SY5Y cells. Our study develops a novel scaffold for enhancing the differentiation of SH-SY5Y cells into neurons, which holds great potential in the treatment of neurological diseases and injuries.

Comparison of simultaneous and sequential administration of fentanyl-propofol for surgical abortion: a randomized single-blinded controlled trial.

Propofol lipid emulsion (PLE) is a nanosized sedative, and it is used with a combination of salted antalgic prodrug, fentanyl citrate (FC). To illustrate the synergistic effect of mixing, we compared the sedation/analgesia resulting from simultaneous and sequential administration in surgically induced abortion (No. ChiCTR-IPC-15006153). Simultaneous group showed lower bispectral index, blood pressure, and heart rate, when cannula was inserted into the uterus. It also showed less frequency of hypertension, sinus tachycardia, movement, pain at the injection site, and additional FC. Therefore, premixing of PLE and FC enhanced the sedation and analgesia; stabilized the hemodynamics; lessened the incidence of movement and injection pain; and reduced the requirement of drugs.

Rapid and efficient crossing blood-brain barrier: Hydrophobic drug delivery system based on propionylated amylose helix nanoclusters.

A novel strategy of rapid transport across the blood-brain barrier (BBB) via phosphatidylethanolamine-triggered release is developed through both molecular dynamics (MD) simulation and experiments. Hydrophobic drugs, namely, propofol, iodine, and 1,1'-dioctadecyltetramethyl indotricarbocyanine iodide, were loaded with propionylated amylose helix (HLPAH) nanoclusters to form PLPAH, ILPAH, and DLPAH nanoclusters, respectively. These clusters were subjected to MD simulation, structure measurement, in vitro triggered study, in vivo DLPAH imaging, and analysis of PLPAH sedative effects on rabbits. Results indicated that HLPAH nanoclusters were initially located on the BBB, and the helix was unfolded to release the loaded hydrophobic drugs. The released drugs crossed the BBB and performed their functions in the central nervous system (CNS) through concentration gradient and hydrophobicity. This mechanism of HLPAH across the BBB featured high membrane permeability and specificity, rapid onset, short maintenance, rapid recovery, and lower dosage of drugs. Hence, this novel strategy is very meaningful for the development of CNS drug carriers and the proposed system could be used to improve the therapeutic effects of CNS diseases.

Coarse-grained molecular dynamics studies of the translocation mechanism of polyarginines across asymmetric membrane under tension.

Understanding interactions between cell-penetrating peptides and biomembrane under tension can help improve drug delivery and elucidate mechanisms underlying fundamental cellular events. As far as the effect of membrane tension on translocation, it is generally thought that tension should disorder the membrane structure and weaken its strength, thereby facilitating penetration. However, our coarse-grained molecular dynamics simulation results showed that membrane tension can restrain polyarginine translocation across the asymmetric membrane and that this effect increases with increasing membrane tension. We also analyzed the structural properties and lipid topology of the tensed membrane to explain the phenomena. Simulation results provide important molecular information on the potential translocation mechanism of peptides across the asymmetric membrane under tension as well as new insights in drug and gene delivery.