Fluid Shear Stress Research Articles

Abstract P369: The Role Of Primary Cilia In The Pathogenesis And Therapy Of Hypertension In Polycystic Kidney Disease.

Primary cilia are sensory organelles, extending from the surface of vascular endothelialcells. Primary cilia dysfunctions have been linked to numerous genetic disorders,including polycystic kidney disease (PKD). Although PKD is characterized by fluid-filledcystic kidneys, cardiovascular complications such as hypertension (HTN) are the leadingcause of death in PKD patients. We demonstrated that primary cilia sense and transmitexternal mechanical stimuli such as fluid shear stress into internal biochemical reactionssuch as the release of nitric oxide (NO). This idea has only been investigated in ECs invitro . However, the importance of the vascular primary cilia in the long-term regulationof BP has not been investigated. NO-induced vasodilation is also produced in response tostimulation of eNOS by muscarinic acetylcholine receptor 3 (AChM3R) activation byacetylcholine (ACh). Using immunofluorescence staining, we generated new andsurprising data showing that AChM3R, and its signaling components, PIP2 are localizedto primary cilia and can modulate cilia function. We hypothesize that primary ciliacontribute to BP regulation in PKD through AChM3R. We showed that both, selective(cevimeline) and non-selective (ACh, CCh) activation of AChM3R led to an increase incilia length and cilia sensory function in terms of p-eNOS expression. We also generatedendothelial-specific ( Tie2Cre and VECre ) AChM3R KO mouse lines, in which AChM3R was deleted from the vascular endothelia. These mice developed high BP, as measured bytail cuff and telemetry blood pressure monitoring devices, associated with attenuated NOproduction and impaired vascular relaxation in response to ACh stimulation. Thesestudies demonstrated the physiological significance of primary cilia-derived NO in thelong-term control of vascular hemodynamics.

Permanent Solutions for MHD Motions of Generalized Burgers’ Fluids Adjacent to an Unbounded Plate Subjected to Oscillatory Shear Stresses

Closed-form expressions have been obtained to characterize the non-dimensional velocity and corresponding non-trivial shear stress in the context of two magnetohydrodynamic (MHD) motions exhibited by incompressible generalized Burgers’ fluids. These motions occur over an infinite plate, which subjects the fluid to oscillatory shear stresses. The obtained solutions represent the first exact analytical solutions for MHD motions of such fluids under the condition of shear stress prescribed along the boundary. The establishment of these solutions relies upon the utilization of a perfect symmetry existing between the governing equations of fluid velocity and shear stress. To validate the results, a comprehensive analysis has been undertaken using two distinct methods. This validation process is further substantiated through graphical representation, demonstrating the congruence between the obtained solutions. Additionally, the convergence of the initial solutions, obtained through numerical techniques, towards their corresponding permanent counterparts has been visually established. This graphical depiction not only substantiates the accuracy of the solutions but also provides insights into the temporal evolution of the system toward its permanent state. An insight to characterize the non-dimensional shear stresses in the context of two values of the magnetic parameter is to identify that the permanent state is reached at an earlier time and the absolute magnitude of fluid velocity is reduced in the presence of an applied magnetic field.

Integrating Chemical Profiling, In Vivo Study, and Network Pharmacology to Explore the Anti-inflammatory Effect of Pterocarpus dalbergioides Fruits and Its Correlation with the Major Phytoconstituents.

The purpose of this study is to explore the anti-inflammatory activity of Pterocarpus dalbergioides fruit extract (PFE) and the underlying mechanism. Chemical profiling using ultraperformance liquid chromatography/mass spectrometry identified 28 compounds in PFE (12 flavonoids, 5 fatty acids, 4 phenolic compounds, 3 alkaloids, 2 sesquiterpenes, and 2 xanthophylls). PFE (2 g/kg) significantly inhibited carrageenan-induced rat paw edema after 4 h of administration (42% inhibition). A network-based strategy and molecular docking studies were utilized to uncover the anti-inflammatory mechanism. Out of the identified compounds, 16 compounds with DL ≥ 0.18 and F ≥ 30% were selected using bioavailability (F) and drug-likeness (DL) metrics. The network analysis revealed that 90 genes are considered key targets for the selected compounds and linked to the anti-inflammatory effect. Among all compounds, linoleic acid was found to be the top-most active constituent as it targets maximum genes. Four targets (TNF, IL6, AKT1, and CCL2) among the top 10 genes were found to be the main target genes that may contribute to the anti-inflammatory potential of PFE. Furthermore, KEGG (Kyoto encyclopedia of genes and genomes) pathway analysis revealed that PFE might regulate inflammation through five pathways: neuroactive ligand-receptor interaction, lipid and atherosclerosis, fluid shear stress and atherosclerosis, TNF signaling pathway, and rheumatoid arthritis. The docking study predicted the significant binding affinity between the top four active constituents (linoleic acid, 9-octadecenoic acid, 11,12,13-trihydroxy-9-octadecenoic acid, and rhamnetin-3-O-rhamnoside) and the selected target proteins (TNF and AKT1). The findings highlight PFE as a promising drug lead for controlling inflammation.

Visualization of thermal removal mechanism of paraffin deposits: Providing guidelines for minimum temperature requirements

Active heating is increasingly explored as a cost-effective strategy for managing wax deposition in production flowlines. While active heating is widely used across the industry to maintain or raise the temperature of the production fluid above the wax appearance temperature (WAT), there exists no clear understanding of the mechanism and guidelines for wax removal using active heating technology. Currently, operators tend to aim for temperatures far above the WAT to ensure removal. There is an interest in the finding of the actual temperature targets. If these can be defined, lowering current operational targets, reducing energy requirements, and therefore reducing costs becomes possible. To this end, a novel dynamic microscopic visualization technique is employed to understand the removal mechanism as the deposit is exposed to varying removal temperatures. As the removal temperature is raised to WAT + 54 % the deposit underwent 100 % removal, while increasing it to WAT + 12 % resulted in 97 % removal throughout the experiment. Raising the removal temperature to WAT − 7 % resulted in no removal.A mechanism for thermal removal is proposed based on visual evidence for a counter-diffusion process preceding detachment. During removal, the deposit becomes less dense with wax crystals over time, lowering its yield stress until a point where shear forces from the flow can strip and carry away large chunks of wax deposit. Higher removal temperatures require less time for detachment to occur. Increasing the coolant temperature to WAT + 54 % required only 8 min for detachment to occur, while increasing it to WAT + 12 % extended this time to 46 min. Deposit yield stress and fluid shear stresses are used to determine the minimum removal temperature for active heating. The pipe wall needs to be raised at least to this temperature for removal to occur. The higher the wall temperature is raised above this value, the faster the removal will occur. Understanding this mechanism can inform the development of accurate removal models and improve production economics.

Multimodal investigation reveals the neuroprotective mechanism of Angong Niuhuang pill for intracerebral hemorrhage: Converging bioinformatics, network pharmacology, and experimental validation

Ethnopharmacological relevanceAngong Niuhuang Pill (ANP) is a traditional Chinese medicine formula that has been used clinically for many years in the treatment of cerebral hemorrhage. It is composed of ingredients such as calculus bovis, moschus, and others. Ancient texts have documented that ANP's multiple components possess properties such as heat-clearing, detoxification, and sedation, which can be effective in treating conditions such as coma and stroke. However, the underlying mechanisms of ANP's potential actions are still under investigation. Aim of the studyANP is a Chinese medicine widely utilized for the treatment of intracerebral hemorrhage (ICH). However, the precise mechanism underlying the therapeutic effects remains largely elusive. The present study aims to unravel the effects and pharmacological molecular mechanisms of ANP in combatting ICH, employing a comprehensive network pharmacology approach and experimental validation. Materials and methodsThe molecular targets of ANP and ICH were obtained from various databases, followed by the construction of protein-protein interaction (PPI) networks using the STRING database. Further, gene ontology (GO) enrichment and Kyoto encyclopedia of genes and genomes (KEGG) analyses were conducted using the Metascape database and Cytoscape, respectively. Finally, molecular docking was performed. We performed a series of behavioral tests, immunohistochemical staining, TUNEL staining, and Western Blot to verify the effects of ANP. ResultsIL-6, JUN, MMP9, IL-1β, VEGFA were the main candidate targets and were associated with fluid shear stress and atherosclerosis, TNF signaling pathway, etc. It is suggested that the potential mechanism of ANP against ICH may be mainly related to pyroptosis, inflammation. In vivo validation showed that ANP treatment significantly reduced the number of TUNEL-positive cells and ANP inhibited the activation of Iba-1 positive neurons, and suppressed the expression of inflammatory factors and pyroptosis indicators. In addition, ANP improved the cognitive level and motor ability of ICH mice. ConclusionThe results of the study combined with virtual screening and experimental validation showed that ANP has an important contribution in protecting the brain from neuronal damage by regulating the pathways of inflammation and pyroptosis, laying the foundation and innovative ideas for future studies.

The myosin and RhoGAP MYO9B influences osteocyte dendrite growth and responses to mechanical stimuli.

Introduction: Myosin IXB (MYO9B) is an unconventional myosin with RhoGAP activity and thus is a regulator of actin cytoskeletal organization. MYO9B was previously shown to be necessary for skeletal growth and health and to play a role in actin-based functions of both osteoblasts and osteoclasts. However, its role in responses to mechanical stimulation of bone cells has not yet been described. Therefore, experiments were undertaken to determine the role of MYO9B in bone cell responses to mechanical stress both in vitro and in vivo. Methods: MYO9B expression was knocked down in osteoblast and osteocyte cell lines using RNA interference and the resulting cells were subjected to mechanical stresses including cyclic tensile strain, fluid shear stress, and plating on different substrates (no substrate vs. monomeric or polymerized collagen type I). Osteocytic cells were also subjected to MYO9B regulation through Slit-Robo signaling. Further, wild-type or Myo9b -/- mice were subjected to a regimen of whole-body vibration (WBV) and changes in bone quality were assessed by micro-CT. Results: Unlike control cells, MYO9B-deficient osteoblastic cells subjected to uniaxial cyclic tensile strain were unable to orient their actin stress fibers perpendicular to the strain. Osteocytic cells in which MYO9B was knocked down exhibited elongated dendrites but were unable to respond normally to treatments that increase dendrite length such as fluid shear stress and Slit-Robo signaling. Osteocytic responses to mechanical stimuli were also found to be dependent on the polymerization state of collagen type I substrates. Wild-type mice responded to WBV with increased bone tissue mineral density values while Myo9b -/- mice responded with bone loss. Discussion: These results demonstrate that MYO9B plays a key role in mechanical stress-induced responses of bone cells in vitro and in vivo.

Design and manufacturing of biomimetic scaffolds for bone repair inspired by bone trabeculae

Porous scaffold (PorS) implants, particularly those that mimic the structural features of natural cancellous bone (NCanB), are increasingly essential for the treatment of large-area bone defects. However, the mechanical properties of NCanB-based bionic bone scaffold (BioS) and its performance as a bone repair material have not been fully explored. This study investigates the effect of bionic structure parameters on the mechanical properties and bone reconstruction performance of BioS. Using laser powder bed fusion (L-PBF) technology, different BioS with various structural parameters were created and evaluated using Micro-CT, compression testing, Finite Element (FE) Simulation, and computational fluid dynamics (CFD), and compared to commonly used clinical PorS. Assess the capacity of the BioS scaffold to support and enhance bone reconstruction following implantation through the evaluation of its mechanical properties, permeability, and fluid shear stress (FSS). BioS-85-90 and BioS-80-50 showed suitable mechanical properties, performed well in FE simulation of implantation, demonstrated outstanding abilities for osteoinductive ingrowth and bone tissue differentiation, and proved to be reliable materials for the reconstruction of bone defects. Therefore, BioS shows significant potential for clinical application as a bone reconstruction material, providing a solid foundation for the integration of tissue engineering and bionic design.

Network pharmacology- and molecular docking-based analyses of the antihypertensive mechanism of Ilex kudingcha.

Herein, network pharmacology was used to identify the active components in Ilex kudingcha and common hypertension-related targets. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were conducted, and molecular docking was performed to verify molecular dynamic simulations. Six active components in Ilex kudingcha were identified; furthermore, 123 target genes common to hypertension were identified. Topological analysis revealed the strongly associated proteins, with RELA, AKT1, JUN, TP53, TNF, and MAPK1 being the predicted targets of the studied traditional Chinese medicine. In addition, GO enrichment analysis revealed significant enrichment of biological processes such as oxidative stress, epithelial cell proliferation, cellular response to chemical stress, response to xenobiotic stimulus, and wound healing. Furthermore, KEGG enrichment analysis revealed that the genes were particularly enriched in lipid and atherosclerosis, fluid shear stress and atherosclerosis, and other pathways. Molecular docking revealed that the key components in Ilex kudingcha exhibited good binding potential to the target genes RELA, AKT1, JUN, TP53, TNF, and IL-6. Our study results suggest that Ilex kudingcha plays a role in hypertension treatment by exerting hypolipidemic, anti-inflammatory, and antioxidant effects and inhibiting the transcription of atherosclerosis-related genes.

Fluid shear stress enhances natural killer cell's cytotoxicity toward circulating tumor cells through NKG2D-mediated mechanosensing.

Tumor cells metastasize to distant organs mainly via hematogenous dissemination, in which circulating tumor cells (CTCs) are relatively vulnerable, and eliminating these cells has great potential to prevent metastasis. In vasculature, natural killer (NK) cells are the major effector lymphocytes for efficient killing of CTCs under fluid shear stress (FSS), which is an important mechanical cue in tumor metastasis. However, the influence of FSS on the cytotoxicity of NK cells against CTCs remains elusive. We report that the death rate of CTCs under both NK cells and FSS is much higher than the combined death induced by either NK cells or FSS, suggesting that FSS may enhance NK cell's cytotoxicity. This death increment is elicited by shear-induced NK activation and granzyme B entry into target cells rather than the death ligand TRAIL or secreted cytokines TNF-α and IFN-γ. When NK cells form conjugates with CTCs or adhere to MICA-coated substrates, NK cell activating receptor NKG2D can directly sense FSS to induce NK activation and degranulation. These findings reveal the promotive effect of FSS on NK cell's cytotoxicity toward CTCs, thus providing new insight into immune surveillance of CTCs within circulation.

Examining the impact of fluid shear stress on cancer-fighting immune cells

Natural killer cells hunt rogue cancer cells in the bloodstream aided by increased fluid shear stress.

Knockdown of TRPV2 inhibits the migration of RAW264.7 cells toward low fluid shear stress region.

Our previous studies have demonstrated that macrophages (RAW264.7) have a special ability for sensing the gradient of fluid shear stress (FSS) and migrate toward the low-FSS region. However, the molecular mechanism regulating this phenomenon is still unclear. In this study, we examined the transcriptome genes in RAW264.7 cells, MC3T3-E1 osteoblasts, mesenchymal stem cells, canine renal epithelial cells, and periodontal ligament cells. The expression levels of genes related to cell migration, force transfer, and force sensitivity in the Ca2+ signaling pathway were analyzed. We observed that the transient receptor potential cation channel type 2 (TRPV2) was highly expressed in RAW264.7 cells. Furthermore, we used lentiviral transfection to knockdown TRPV2 expression in RAW264.7 cells and studied the effect of TRPV2 on the migration of RAW264.7 cells under a gradient FSS field. The results showed that compared with normal cells, TRPV2-knockdown cells had impaired ability for sensing FSS gradient to migrate toward the low-FSS region and lower intracellular calcium response to FSS stimulation. This study may reveal the molecular mechanism of regulating the directional migration of macrophages under a gradient FSS field.

Exploring the therapeutic mechanism of Banxia Xiexin Decoction in mild cognitive impairment and diabetes mellitus: a network pharmacology approach.

The incidence of mild cognitive impairment (MCI) and diabetes mellitus (DM) is increasing year by year. Clinical findings show that Banxia Xiexin Decoction (BXD) can be combined to treat MCI and DM. However, the principle and mechanism of BXD in treating MCI and DM remain unclear. In this study, to explore the common mechanism of BXD in treating MCI and DM by using the method of network pharmacology.Traditional Chinese Medicine Systems Pharmacology Database (TCMSP) was used to screen the main active components of BXD, as well as to predict and screen its potential targets. Using Online Mendelian Inheritance in Man (OMIM), Therapeutic Target Database (TTD), DisGeNET, GeneCards to select the target proteins of two diseases, and intersecting the drug target and the disease target to obtain the common target of drug diseases, which is imported into cytoscape software to draw the network diagram of "drug components-target diseases" and the interaction network diagram between the common target proteins. According to the Database for Annotation, Visualization and Integrated Discovery (DAVID) database, we analyzed the common targets using two methods, gene ontology Kyoto Encyclopedia of Genes and Genomes (KEGG) biological pathway enrichment analysis and Gene Ontology (GO) function enrichment analysis, as well as studied the interaction mechanism of the two diseases, with the results validated using molecular docking.A total of 267 main active components of BXD were screened, together with the two diseases shared 233 common targets. The top five key targets identified by the topological analysis were TP53, AKT1, STAT3, TNF, and MAPK3. Go enrichment results indicated that it was primarily related to response to drug, extracellular space, enzyme binding, RNA polymerase II transcription factor activity, ligand-activated sequence-specific DNA binding. t KEGG enrichment pathway analysis identified 20 significant pathways, the majority of which are AGE-RAGE signaling pathways in diabetic complications, lipid and atherosclerosis, fluid shear stress and atherosclerosis, IL-17 signaling pathway, TNF signaling pathway, and so on. The results of molecular docking revealed that the key components of BXD, baicalein, licochalcone a, quercetin, and naringenin, had strong binding ability with core targets TP53, AKT1, STAT3, TNF, MAPK3.BXD can treat MCI and DM by multi-targets and multi-channels,and plays a role of "homotherapy for heteropathy" mainly through response to drug, positive regulation of gene expression, extracellular space and enzyme binding and other ways.

Association between Heavy Metals, Metalloids and Metabolic Syndrome: New Insights and Approaches.

Metabolic syndrome (MetS) is an important public health issue that affects millions of people around the world and is growing to pandemic-like proportions. This syndrome is defined by the World Health Organization (WHO) as a pathologic condition characterized by abdominal obesity, insulin resistance, hypertension, and hyperlipidemia. Moreover, the etiology of MetS is multifactorial, involving many environmental factors, including toxicant exposures. Several studies have associated MetS with heavy metals exposure, which is the focus of this review. Environmental and/or occupational exposure to heavy metals are a major risk, contributing to the development of chronic diseases. Of particular note, toxic metals such as mercury, lead, and cadmium may contribute to the development of MetS by altering oxidative stress, IL-6 signaling, apoptosis, altered lipoprotein metabolism, fluid shear stress and atherosclerosis, and other mechanisms. In this review, we discuss the known and potential roles of heavy metals in MetS etiology as well as potential targeted pathways that are associated with MetS. Furthermore, we describe how new approaches involving proteomic and transcriptome analysis, as well as bioinformatic tools, may help bring about an understanding of the involvement of heavy metals and metalloids in MetS.

Micromotion Derived Fluid Shear Stress Mediates Peri-Electrode Gliosis through Mechanosensitive Ion Channels.

The development of bioelectronic neural implant technologies has advanced significantly over the past 5 years, particularlyin brain-machine interfaces and electronic medicine. However, neuroelectrode-based therapies require invasive neurosurgery and can subject neural tissues to micromotion-induced mechanical shear, leading to chronic inflammation, the formation of a peri-electrode void and the deposition of reactive glial scar tissue. These structures act as physical barriers, hindering electrical signal propagation and reducing neural implant functionality. Although well documented, the mechanisms behind the initiation and progression of these processes are poorly understood. Herein, in silico analysis of micromotion-induced peri-electrode void progression and gliosis is described. Subsequently, ventral mesencephalic cells exposed to milliscale fluid shear stress in vitro exhibited increased expression of gliosis-associated proteins and overexpression of mechanosensitive ion channels PIEZO1 (piezo-type mechanosensitive ion channel component 1) and TRPA1 (transient receptor potential ankyrin 1), effects further confirmed in vivo in a rat model of peri-electrode gliosis. Furthermore, in vitro analysis indicates that chemical inhibition/activation of PIEZO1 affects fluid shear stress mediated astrocyte reactivity in a mitochondrial-dependent manner. Together, the results suggest that mechanosensitive ion channels play a major role in the development of a peri-electrode void and micromotion-induced glial scarring at the peri-electrode region.

Network pharmacology and molecular docking analyses of the potential target proteins and molecular mechanisms underlying the anti-arrhythmic effects of Sophora Flavescens.

The objective was to investigate the potential cardiac arrhythmia-related target proteins and molecular mechanisms underlying the anti-arrhythmic effects of Sophora flavescens using network pharmacology and molecular docking. The bioactive ingredients and related target proteins of S flavescens obtained from the Traditional Chinese medicine systems pharmacology data platform, and gene names for target proteins were obtained from the UniProt database. Arrhythmia-related genes were identified by screening GeneCards and Online Mendelian inheritance in man databases. A Venn diagram was used to identify the key arrhythmia-related genes that are potentially targeted by the bioactive ingredients of S flavescens. Furthermore, CytoScape 3.7.2 software was used to construct an "ingredient-target" network diagram and the "drug-ingredient-target-disease" network diagram. We performed gene ontology and Kyoto encyclopedia of genes and genomes enrichment analysis in the Metascape database and performed the docking analysis using CB-Dock software. We identified 45 main bioactive ingredients, from S flavescens and 66 arrhythmia-related target proteins. Gene ontology and Kyoto encyclopedia of genes and genomes pathway enrichment analysis showed that these targets were related to the chemical carcinogenesis-receptor activation signaling pathway, lipid and atherosclerosis signaling pathway, and fluid shear stress and atherosclerosis signaling pathway. Molecular docking showed that the target protein had good binding power with the main active components of the compound of S flavescens. Our study demonstrated the synergistic effects of multiple bioactive components of S flavescens on multiple arrhythmia-related target proteins and identified potential therapeutic mechanisms underlying the anti-arrhythmic effects of S flavescens, providing new clinical ideas for arrhythmia treatment.

Fibroblast activation in response to TGFβ1 is modulated by co-culture with endothelial cells in a vascular organ-on-chip platform.

Background: Tissue fibrosis is a major healthcare burden that affects various organs in the body for which no effective treatments exist. An underlying, emerging theme across organs and tissue types at early stages of fibrosis is the activation of pericytes and/or fibroblasts in the perivascular space. In hepatic tissue, it is well known that liver sinusoidal endothelial cells (EC) help maintain the quiescence of stellate cells, but whether this phenomenon holds true for other endothelial and perivascular cell types is not well studied. Methods: The goal of this work was to develop an organ-on-chip microvascular model to study the effect of EC co-culture on the activation of perivascular cells perturbed by the pro-fibrotic factor TGFβ1. A high-throughput microfluidic platform, PREDICT96, that was capable of imparting physiologically relevant fluid shear stress on the cultured endothelium was utilized. Results: We first studied the activation response of several perivascular cell types and selected a cell source, human dermal fibroblasts, that exhibited medium-level activation in response to TGFβ1. We also demonstrated that the PREDICT96 high flow pump triggered changes in select shear-responsive factors in human EC. We then found that the activation response of fibroblasts was significantly blunted in co-culture with EC compared to fibroblast mono-cultures. Subsequent studies with conditioned media demonstrated that EC-secreted factors play at least a partial role in suppressing the activation response. A Luminex panel and single cell RNA-sequencing study provided additional insight into potential EC-derived factors that could influence fibroblast activation. Conclusion: Overall, our findings showed that EC can reduce myofibroblast activation of perivascular cells in response to TGFβ1. Further exploration of EC-derived factors as potential therapeutic targets in fibrosis is warranted.

Retracted: Effects of Fluid Shear Stress on Human Intervertebral Disc Nucleus Pulposus Cells Based on Label-Free Quantitative Proteomics.

[This retracts the article DOI: 10.1155/2022/3860898.].

Force-induced motions of the PIEZO1 blade probed with fluorimetry

Mechanical forces are thought to activate mechanosensitive PIEZO channels by changing the conformation of a large transmembrane blade domain. Yet, whether different stimuli induce identical conformational changes in this domain remains unclear. Here, we repurpose a cyclic permuted green fluorescent protein as a conformation-sensitive probe to track local rearrangements along the PIEZO1 blade. Two independent probes, one inserted in an extracellular site distal to the pore and the other in a distant intracellular proximal position, elicit sizable fluorescence signals when the tagged channels activate in response to fluid shear stress of low intensity. Neither cellular indentations nor osmotic swelling of the cell elicit detectable fluorescence signals from either probe, despite the ability of these stimuli to activate the tagged channels. High-intensityflow stimuli are ineffective at eliciting fluorescence signals from either probe. Together, these findings suggest that low-intensity fluid shear stress causes a distinct form of mechanical stress to the cell.

Assessing effects of mechanical stimulation of fluid shear stress on inducing matrix Metalloproteinase-9 in cultured corneal epithelial cells

Blinking is regarded as mechanical stimulation of fluid shear stress on the corneal epithelial cells. Therefore, we evaluated whether fluid shear stress affects matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) in cultured human corneal epithelial cells (HCECs). No other study has shown the influence of fluid shear stress on HCECs regarding mRNA expression and the protein levels of MMPs. Cultured HCECs were exposed to shear stress (0, 1.2, 12 dyne/cm2) for 12 and 24 h with the parallel-plate type of flow chamber. Gene expression of MMPs and TIMPs was measured by real-time polymerase reaction. Concentrations of MMP-1 and MMP-9 in cell lysates were determined using bead-based amplified luminescent proximity homogenous assay-linked immunosorbent assay. The expression of MMP-9 and MMP-1 in HCECs exposed to low and high flow for 12 and 24 h, respectively, increased significantly compared with those under static conditions. The expression of MMP-9 in the cells exposed to high flow for 24 h increased significantly compared with those under static and low flow conditions. Levels of MMP-9 in cell lysates exposed to fluid flow for 24 h were elevated significantly with increasing shear stress. Fluid shear stress exerted on HCECs affected MMPs, which was associated with inflammation and pathogenesis. Mechanical stress induced by blinking might influence expression of MMPs on the ocular surface. Further studies are warranted to establish the molecular mechanism of shear stress-induced alternations of MMPs.

Synthetic Cell Armor Made of DNA Origami.

The bioengineering applications of cells, such as cell printing and multicellular assembly, are directly limited by cell damage and death due to a harsh environment. Improved cellular robustness thus motivates investigations into cell encapsulation, which provides essential protection. Here we target the cell-surface glycocalyx and cross-link two layers of DNA nanorods on the cellular plasma membrane to form a modular and programmable nanoshell. We show that the DNA origami nanoshell modulates the biophysical properties of cell membranes by enhancing the membrane stiffness and lowering the lipid fluidity. The nanoshell also serves as armor to protect cells and improve their viability against mechanical stress from osmotic imbalance, centrifugal forces, and fluid shear stress. Moreover, it enables mediated cell-cell interactions for effective and robust multicellular assembly. Our results demonstrate the potential of the nanoshell, not only as a cellular protection strategy but also as a platform for cell and cell membrane manipulation.