Actin stabilization by jasplakinolide affects the function of bone marrow-derived late endothelial progenitor cells

Therapeutic Potential of Marine-Derived Cyclic Peptides as Antiparasitic Agents

Parasitic diseases still compromise human health. Some of the currently available therapeutic drugs have limitations considering their adverse effects, questionable efficacy, and long treatment, which have encouraged drug resistance. There is an urgent need to find new, safe, effective, and affordable antiparasitic drugs. Marine-derived cyclic peptides have been increasingly screened as candidates for developing new drugs. Therefore, in this review, a systematic analysis of the scientific literature was performed and 25 marine-derived cyclic peptides with antiparasitic activity (1-25) were found. Antimalarial activity is the most reported (51%), followed by antileishmanial (27%) and antitrypanosomal (20%) activities. Some compounds showed promising antiparasitic activity at the nM scale, being active against various parasites. The mechanisms of action and targets for some of the compounds have been investigated, revealing different strategies against parasites.

Respiratory syncytial virus disrupts the airway epithelial barrier by decreasing cortactin and destabilizing F-actin

Respiratory syncytial virus (RSV) infection is the leading cause of acute lower respiratory tract infection in young children worldwide. Our group recently revealed that RSV infection disrupts the airway epithelial barrier in vitro and in vivo. However, the underlying molecular pathways were still elusive. Here, we report the critical roles of the filamentous actin (F-actin) network and actin-binding protein cortactin in RSV infection. We found that RSV infection causes F-actin depolymerization in 16HBE cells, and that stabilizing the F-actin network in infected cells reverses the epithelial barrier disruption. RSV infection also leads to significantly decreased cortactin in vitro and in vivo. Cortactin-knockout 16HBE cells presented barrier dysfunction, whereas overexpression of cortactin protected the epithelial barrier against RSV. The activity of Rap1 (which has Rap1A and Rap1B forms), one downstream target of cortactin, declined after RSV infection as well as in cortactin-knockout cells. Moreover, activating Rap1 attenuated RSV-induced epithelial barrier disruption. Our study proposes a key mechanism in which RSV disrupts the airway epithelial barrier via attenuating cortactin expression and destabilizing the F-actin network. The identified pathways will provide new targets for therapeutic intervention toward RSV-related disease. This article has an associated First Person interview with the first author of the paper.

Measuring expression heterogeneity of single-cell cytoskeletal protein complexes

Multimeric cytoskeletal protein complexes orchestrate normal cellular function. However, protein-complex distributions in stressed, heterogeneous cell populations remain unknown. Cell staining and proximity-based methods have limited selectivity and/or sensitivity for endogenous multimeric protein-complex quantification from single cells. We introduce micro-arrayed, differential detergent fractionation to simultaneously detect protein complexes in hundreds of individual cells. Fractionation occurs by 60 s size-exclusion electrophoresis with protein complex-stabilizing buffer that minimizes depolymerization. Proteins are measured with a ~5-hour immunoassay. Co-detection of cytoskeletal protein complexes in U2OS cells treated with filamentous actin (F-actin) destabilizing Latrunculin A detects a unique subpopulation (~2%) exhibiting downregulated F-actin, but upregulated microtubules. Thus, some cells may upregulate other cytoskeletal complexes to counteract the stress of Latrunculin A treatment. We also sought to understand the effect of non-chemical stress on cellular heterogeneity of F-actin. We find heat shock may dysregulate filamentous and globular actin correlation. In this work, our assay overcomes selectivity limitations to biochemically quantify single-cell protein complexes perturbed with diverse stimuli.

Molecular Profiling and Gene Banking of Rabbit EPCs Derived from Two Biological Sources

Endothelial progenitor cells (EPCs) have been broadly studied for several years due to their outstanding regenerative potential. Moreover, these cells might be a valuable source of genetic information for the preservation of endangered animal species. However, a controversy regarding their characterization still exists. The aim of this study was to isolate and compare the rabbit peripheral blood- and bone marrow-derived EPCs with human umbilical vein endothelial cells (HUVECs) in terms of their phenotype and morphology that could be affected by the passage number or cryopreservation as well as to assess their possible neuro-differentiation potential. Briefly, cells were isolated and cultured under standard endothelial conditions until passage 3. The morphological changes during the culture were monitored and each passage was analyzed for the typical phenotype using flow cytometry, quantitative real–time polymerase chain reaction (qPCR) and novel digital droplet PCR (ddPCR), and compared to HUVECs. The neurogenic differentiation was induced using a commercial kit. Rabbit cells were also cryopreserved for at least 3 months and then analyzed after thawing. According to the obtained results, both rabbit EPCs exhibit a spindle-shaped morphology and high proliferation rate. The both cell lines possess same stable phenotype: CD14⁻CD29⁺CD31⁻CD34⁻CD44⁺CD45⁻CD49f⁺CD73⁺CD90⁺CD105⁺CD133⁻CD146⁻CD166⁺VE-cadherin⁺VEGFR-2⁺SSEA-4⁺MSCA-1⁻vWF⁺eNOS⁺AcLDL⁺ALDH⁺vimentin⁺desmin⁺α-SMA⁺, slightly different from HUVECs. Moreover, both induced rabbit EPCs exhibit neuron-like morphological changes and expression of neuronal markers ENO2 and MAP2. In addition, cryopreserved rabbit cells maintained high viability (>85%) and endothelial phenotype after thawing. In conclusion, our findings suggest that cells expanded from the rabbit peripheral blood and bone marrow are of the endothelial origin with a stable marker expression and interesting proliferation and differentiation capacity.

Jasplakinolide Attenuates Cell Migration by Impeding Alpha-1-syntrophin Protein Phosphorylation in Breast Cancer Cells

BACKGROUND

Alpha-1-syntrophin (SNTA1) is emerging as a novel modulator of the actin cytoskeleton. SNTA1 binds to F-actin and regulates intracellular localization and activity of various actin organizing signaling molecules. Aberration in syntrophin signaling has been closely linked with deregulated growth connected to tumor development/metastasis and its abnormal over expression has been observed in breast cancer. In the present work the effect of jasplakinolide, an actin-binding cyclodepsipeptide, on the SNTA1 protein activity and SNTA1 mediated downstream cellular events was studied in MDA-MB-231 breast cancer cell line.

METHODS

SNTA1 protein levels and phosphorylation status were determined in MDA-MB-231 cells post jasplakinolide exposure using western blotting and immunoprecipitation techniques respectively. MDA-MB-231 cells were transfected with WT SNTA1 and DM SNTA1 (Y^215/229 phospho mutant) and simultaneously treated with jasplakinolide. The effect of jasplakinolide and SNTA1 protein on cell migration was determined using the boyden chamber assay.

RESULTS

Jasplakinolide treatment decreases proliferation of MDA-MB-231 cells in both dose and time dependent manner. Results suggest that subtoxic doses of jasplakinolide induce morphological changes in MDA-MB-231 cells from flat spindle shape adherent cells to round weakly adherent forms. Mechanistically, jasplakinolide treatment was found to decrease SNTA1 protein levels and its tyrosine phosphorylation status. Moreover, migratory potential of jasplakinolide treated cells was significantly inhibited in comparison to control cells.

CONCLUSION

Our results demonstrate that jasplakinolide inhibits cell migration by impairing SNTA1 functioning in breast cancer cells.

Targeting and extending the eukaryotic druggable genome with natural products: cytoskeletal targets of natural products

Covering: 2014-2019We review recent progress on natural products that target cytoskeletal components, including microtubules, actin, intermediate filaments, and septins and highlight their demonstrated and potential utility in the treatment of human disease. The anticancer efficacy of microtubule targeted agents identified from plants, microbes, and marine organisms is well documented. We highlight new microtubule targeted agents currently in clinical evaluations for the treatment of drug resistant cancers and the accumulating evidence that the anticancer efficacy of these agents is not solely due to their antimitotic effects. Indeed, the effects of microtubule targeted agents on interphase microtubules are leading to their potential for more mechanistically guided use in cancers as well as neurological disease. The discussion of these agents as more targeted drugs also prompts a reevaluation of our thinking about natural products that target other components of the cytoskeleton. For instance, actin active natural products are largely considered chemical probes and non-selective toxins. However, studies utilizing these probes have uncovered aspects of actin biology that can be more specifically targeted to potentially treat cancer, neurological disorders, and infectious disease. Compounds that target intermediate filaments and septins are understudied, but their continued discovery and mechanistic evaluations have implications for numerous therapeutic indications.

Oscillatory shear stress induces the transition of EPCs into mesenchymal cells through ROS/PKCζ/p53 pathway

AIMS

Studies indicate that the pattern of shear stress determines the direction of endothelial progenitor cells (EPCs) differentiation. However, the mechanism remains largely unknown. Herein, we try to identify the role of oscillatory shear stress (OSS) in the transdifferentiation of EPCs into mesenchymal cells and the mechanism involved.

MATERIALS AND METHODS

OSS was applied to EPCs using the flow chamber system in vitro. Matrigel, Boyden chamber, and healing assay were used to observe the changes in EPCs function. Further, 2',7'-dichlorofluorescein diacetate (DCFH-DA) probe and/or western blot were performed to detect the expression of reactive oxygen species (ROS), p53 and PKCζ in EPCs. EPCs transduced with Lentivirus carrying Tp53 were implanted into the arterial vessel in the balloon injured rat model, and neointimal thickening was verified by HE staining.

KEY FINDINGS

OSS enhanced the expression of mesenchymal cell markers alpha-smooth muscle actin (α-SMA) and smooth muscle 22 alpha (SM22α) on EPCs. In the meantime, OSS time-dependently decreased p53 expression in EPCs, which was partially abolished by treatment with ROS scavenger N-acetylcysteine (NAC) or protein kinase C zeta (PKCζ) inhibitor Go6983. Moreover, the p53 agonist tenovin-1 attenuated the changes of OSS-mediated the mesenchymal cell markers and EPCs function. Besides, we also found that transplanting EPCs transfected with LV-Tp53 significantly inhibited neointimal thickening and promoted reendothelialization in vivo.

SIGNIFICANCE

This study demonstrates OSS-induced EPC transdifferentiation into mesenchymal cells and ROS/PKCζ/p53 pathway play an essential role in it. It may serve as a promising therapeutic target for cardiovascular disease in the future.

Function of Krüppel‑like factor 2 in the shear stress‑induced cell differentiation of endothelial progenitor cells to endothelial cells

The present study aimed to evaluate the effects of Krüppel‑like factor 2 (KLF2) on the differentiation of endothelial progenitor cells (EPCs) to endothelial cells (ECs) induced by shear stress, and to investigate the corresponding mechanisms. Cultured rat late EPCs were exposed to shear stress (12 dyn/cm2) for different lengths of time. Reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) was used to measure the initial KLF2 mRNA levels in each group. Subsequently, the EPCs were treated with anti‑integrin β1 or β3 antibodies to block integrin β1 and β3, respectively, or cytochalasin D to destroy F‑actin, and the subsequent expression levels of KLF2 in EPCs were measured. Then, KLF2 small interfering RNAs (siRNAs) were transfected into EPCs, and RT‑qPCR was used to measure the mRNA expression level of KLF2. Additionally, flow cytometry was applied to evaluate the protein levels of cluster of differentiation 31 (CD31) and the von Willebrand factor (vWF), and the regulatory effects of KLF2 in the promoter region of vWF were determined via a luciferase assay. High shear stress upregulated KLF2 expression, while blocking integrin β1/β3 or destroying F‑actin resulted in a corresponding decrease in KLF2 expression. Downregulation of KLF2 expression by siKLF2 inhibited the differentiation of EPCs to ECs under shear stress conditions, while the expression of EC‑specific markers decreased, including CD31 and vWF. Various lengths of the vWF promoter region induced vWF expression, and EPCs co‑transfected with KLF2 significantly increased the vWF expression levels compared with the group treated with vWF alone (P<0.01). In conclusion, shear stress may upregulate KLF2 expression, which may be associated with the integrin‑actin cytoskeleton system. Most importantly, the shear stress‑induced differentiation of EPCs may be mediated by KLF2.

Zerumbone, a Cyclic Sesquiterpene from Zingiber zerumbet Induces Apoptosis, Cell Cycle Arrest, and Antimigratory Effects in SW480 Colorectal Cancer Cells

Zerumbone isolated from the rhizomes of Zingiber zerumbet was investigated for the mechanisms by which it exhibits antiproliferative activity in colorectal cancer cells (SW480). The results indicated that the zerumbone suppressed cell growth and enhanced cell apoptosis. Exposure to zerumbone induced generation of reactive oxygen species, reduced the cellular antioxidant status, decreased mitochondrial membrane potential, and activated caspase 3, caspase 8, and caspase 9 (p < 0.001). It was also found that there was a decrease in the expression of Bcl 2 and elevation of Bax (p < 0.001) on exposure to zerumbone. Furthermore, treatment with 50, 75, and 100 μM zerumbone resulted in cell cycle arrest at the G2/M phase with a value of 17.2 ± 0.1, 19.63 ± 0.25, and 26.66 ± 0.25, respectively, and also distorted the microfilament network and effectively inhibited cellular migration.

Shear stress-mediated changes in the expression of complement regulatory protein CD59 on human endothelial progenitor cells by ECM-integrinαVβ3-F-actin pathway in vitro

Membrane regulatory proteins, such as CD46, CD55, and CD59, prevent excess complement activation and to protect cells from damage. Previous investigations confirmed that shear stress in the physiological range was more favorable for endothelial progenitor cells (EPCs) to repair injured vascular endothelial cells and operates mainly in atheroprotective actions. However, detailed events that contribute to shear stress-induced protection in EPCs, particularly the mechanisms of signal transduction, remain poorly understood. In this study, we observed shear stress-mediated changes in the expression of complement regulatory proteins CD46, CD55, and CD59 on human EPCs and focused on the mechanical transmission mechanism in transformed cells in response to the ECM-F-actin pathway in vitro. Shear stress was observed to promote the expression of complement regulatory protein CD59, but not CD46 or CD55, on EPCs. In addition, the shear stress-induced CD59 expression was confirmed to be associated with the ECM components and was alleviated in EPCs pretreated with GRGDSP, which inhibits ECM components-integrin interaction. Furthermore, shear stress also promotes the rearrangement and polymerization of F-actin. However, shear stress-induced CD59 expression was reduced when the F-actin stress fiber formation process was delayed by Gly-Arg-Gly-Asp-Ser-Pro (GRGDSP) or destroyed by cytochalasin D (Cyto D), while Jasplakinolide (JAS) reversed the expression of CD59 through promotion of F-actin polymerization and its stabilizing capacities. Our results indicates that shear stress is an important mediator in EPC expression of CD59 regulated by the ECM-F-actin pathway, which is a key factor in preventing membrane attack complex (MAC) -mediated cell autolysis.

Atorvastatin protects endothelial colony‑forming cells against H2O2‑induced oxidative damage by regulating the expression of annexin A2

Endothelial dysfunction and injury are central events in the pathogenesis of ischemic vascular disorders. Endothelial progenitor cells (EPCs) are mobilized from the bone marrow into the peripheral circulation, where they locate to sites of injured endothelium and are involved in endothelial repair and vascular regeneration. During these processes, EPCs are exposed to oxidative stress, a crucial pathological condition, which occurs during vascular injury and limits the efficacy of EPCs in the repair of injured endothelium. Statins are effective inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase, and are commonly used to manage and prevent ischemic vascular disease by reducing plasma cholesterol levels. In addition to lowering cholesterol, statins have also been reported to exert pleiotropic actions, including anti-inflammatory and anti-oxidative activities. The present study aimed to investigate the ability of atorvastatin to protect endothelial colony-forming cells (ECFCs), a homogeneous subtype of EPCs, from hydrogen peroxide (H₂O₂)-induced oxidative damage, and to determine the mechanism underlying this protective action. MTT assay, acridine orange/ethidium bromide staining, reactive oxygen species assay, western blot analysis and tube formation assay were employed. The results demonstrated that H₂O₂ induced cell death and decreased the tube-forming ability of the ECFCs, in a concentration-dependent manner; however, these effects were partially attenuated following administration of atorvastatin. The reversion of the quantitative and qualitative impairment of the H₂O₂-treated ECFCs appeared to be mediated by the regulation of annexin A2, as the expression levels of annexin A2 were decreased following treatment with H₂O₂ and increased following treatment with atorvastatin. These results indicated that annexin A2 may be involved in the H₂O₂-induced damage of ECFCs, and in the protective activities of atorvastatin in response to oxidative stress.

Actin stabilization induces apoptosis in cultured porcine epithelial cell rests of Malassez

AIM

To test whether actin stabilization by jasplakinolide induces inhibition of cell viability and apoptosis in epithelial cell rests of Malassez (ERM).

METHODOLOGY

ERM derived from porcine were spread in a 96-well dish (5 × 10(4) /well) using Dulbecco's modified Eagle's medium. The actin-specific stabilization reagent, jasplakinolide, was incorporated into the culture medium and incubated for 24 h. To evaluate cell viability, the WST-1 assay was carried out and absorption (450 nm) was measured. To detect apoptotic cells, monoclonal antibody to single-strand DNA (ssDNA) was used and absorption (405 nm) was measured. Actin stabilization and apoptosis induced by jasplakinolide were morphologically investigated by staining with Alexa Fluor 568 phalloidin and observed under a fluorescent microscope. As a negative control, DMSO was used instead of jasplakinolide. Differences between the jasplakinolide-treated group and the control group were analysed statistically using the Student's t-test.

RESULTS

Cell viability decreased in a concentration-dependent manner, and cell viability in the jasplakinolide-treated ERM was lower than that in nontreated ERM (n = 16, P < 0.01). Apoptotic cells in the jasplakinolide-treated ERM were more frequently detected compared to that in nontreated ERM (n = 16, P < 0.01). Morphologically, shrinkage, irregular forms and fragmentation of nuclei suggesting apoptotic bodies were observed in jasplakinolide-treated ERM, whilst actin filaments were extended in non-treated ERM.

CONCLUSION

Actin stabilization by jasplakinolide inhibited cell viability and induced apoptosis in epithelial cell rests of Malassez.

Association of annexin A2 with cancer development (Review)

Annexin A2 (ANXA2) is a well-known calcium-dependent phospholipid binding protein widely distributed in the nucleus, cytoplasm and extracellular surface of various eukaryotic cells. It has been recognized as a pleiotropic protein affecting a wide range of molecular and cellular processes. Dysregulation and abnormal expression of ANXA2 are linked to a large number of prevalent diseases, including autoimmune and neurodegenerative disease, antiphospholipid syndrome, inflammation, diabetes mellitus and a series of cancers. Accumulating data suggest that ANXA2 is aberrantly expressed in a wide spectrum of cancers, and exerts profound effects on tumor cell adhesion, proliferation, apoptosis, invasion and metastasis as well as tumor neovascularization via different modes of action. However, despite significant research, our knowledge of the mechanism by which ANXA2 participates in cancer development remains fragmented. The present review systematically summarizes the effects of ANXA2 on tumor progression, in an attempt to gain an improved understanding of the underlying mechanisms and to provide a potential effective target for cancer therapy.

Total syntheses and biological evaluation of miuraenamides

The miuraenamides, relatively simple representatives of a class of cyclodepsipeptides with high antitumor activity, can be easily and flexibly obtained by the concept of peptide modification. A reaction sequence consisting of an aldol reaction, oxidation, and methylation of the glycine subunit of the cyclodepsipeptides allows the incorporation of the unusual α,β-unsaturated dehydroamino acid in one of the last steps of the synthesis.

F‑actin cytoskeleton reorganization is associated with hepatic stellate cell activation

The activation of hepatic stellate cells (HSCs) is involved in the development of hepatic fibrosis. Previous studies have indicated that the acquisition of certain properties by activated HSCs is highly dependent on the reorganization of the actin cytoskeleton. However, direct evidence showing that the reorganization of the actin cytoskeleton is responsible for HSC activation is lacking. The aim of the present study was to investigate the role of cytoskeletal reorganization during HSC activation and to clarify the underlying mechanism. HSC-T6 cells were treated either with the F-actin stabilizer jasplakinolide (Jas) or the depolymerizer cytochalasin D (Cyto D). The actin cytoskeleton was evaluated via assessment of stress fiber formation. Furthermore, the activation properties of HSCs, including proliferation, adhesion, migration and the expression of α-smooth muscle actin (α-SMA) and collagen 1, were investigated in vitro. The results showed that Jas and Cyto D affected the actin distribution in HSC-T6 cells. Treatment with Jas resulted in thick actin bundles and a patchy appearance in the cytoplasm in HSC-T6 cells. In parallel, polymerization of actin microfilaments induced by Jas upregulated the expression of α-SMA and collagen 1, and also enhanced the migration and adhesion properties of HSC-T6 cells. Furthermore, the activation of HSC-T6 cells induced by the reorganization of the actin cytoskeleton was associated with the p38 mitogen-activated protein kinase (p38 MAPK) pathway. In conclusion, the present study suggests that the reorganization of the F-actin cytoskeleton is associated with HSC activation and that the p38 MAPK pathway is involved in this process. The inhibition of F-actin reorganization may thus be a potential key factor or molecular target for the control of liver fibrosis or cirrhosis.

Biological properties of bone marrow-derived early and late endothelial progenitor cells in different culture media

Ex vivo expansion of endothelial progenitor cells (EPCs) may be a promising strategy to overcome the clinical problem of limited cell numbers. As the culture medium is the key for the cell characteristics, the effects of different culture media on EPCs were investigated in the present study. Rat bone marrow mononuclear cells were cultured in different media, including M-199 media with 20% fetal bovine serum (FBS) and bovine pituitary extract (M1); M-199 media with 10% FBS, 20 ng/ml vascular endothelial growth factor (VEGF) and 10 ng/ml basic fibroblast growth factor (bFGF; M2) or epidermal growth medium (EGM)-2MV media. The cell morphology and biological functions, such as proliferation, adhesion, migration, tube formation and nitric oxide (NO) production were subsequently assayed in vitro. Moreover, endothelial biomarkers and apoptosis were also analyzed. The results showed that endothelial‑like cells appeared in all of the culture systems. First‑passage cells, namely early EPCs, tended to form colonies in M2 and EGM-2MV media but showed a fusiform shape in M1 media. The 3rd or 4th generation EPCs, namely late EPCs, cultured in EGM-2MV media exhibited increased adhesion, migration, tube formation and NO production as compared with EPCs in M1 or M2 media. Furthermore, late EPCs cultured in EGM-2MV expressed higher levels of endothelial cell markers, such as von Willibrand factor (vWF)and CD31, but relatively greater levels of apoptosis were observed. In conclusion, cell culture conditions, for example the medium used, affects the biological properties of bone marrow-derived early and late EPCs.

Modulating the actin cytoskeleton affects mechanically induced signal transduction and differentiation in mesenchymal stem cells

Mechanical interactions of mesenchymal stem cells (MSC) with the environment play a significant role in controlling the diverse biological functions of these cells. Mechanical forces are transduced by integrins to the actin cytoskeleton that functions as a scaffold to switch mechanical signals into biochemical pathways. To explore the significance of cytoskeletal mechanisms in human MSC we modulated the actin cytoskeleton using the depolymerising drugs cytochalasin D (CytD) and latrunculin A (LatA), as well as the stabilizing drug jasplakinolide (Jasp) and examined the activation of the signalling molecules ERK and AKT during mechanical loading. All three drugs provoked significant changes in cell morphology and organisation of the cytoskeleton. Application of mechanical forces to β1-integrin receptors using magnetic beads without deformation of the cell shape induced a phosphorylation of ERK and AKT. Of the two drugs that inhibited the cytoskeletal polymerization, LatA completely blocked the activation of ERK and AKT due to mechanical forces, whereas CytD inhibited the activation of AKT but not of ERK. Activation of both signalling molecules by integrin loading was not affected due to cell treatment with the cytoskeleton stabilizing drug Jasp. To correlate the effects of the drugs on mechanically induced activation of AKT and ERK with parameters of MSC differentiation, we studied ALP activity as a marker for osteogenic differentiation and examined the uptake of fat droplets as marker for adipogenic differentiation in the presence of the drugs. All three drugs inhibited ALP activity of MSC in osteogenic differentiation medium. Adipogenic differentiation was enhanced by CytD and Jasp, but not by LatA. The results indicate that modulation of the cytoskeleton using perturbing drugs can differentially modify both mechanically induced signal transduction and MSC differentiation. In addition to activation of the signalling molecules ERK and AKT, other cytoskeletal mechanisms are involved in MSC differentiation.

Shear stress regulates late EPC differentiation via mechanosensitive molecule-mediated cytoskeletal rearrangement

Background

Previous studies have demonstrated that endothelial progenitor cells (EPCs), in particular late EPCs, play important roles in endothelial maintenance and repair. Recent evidence has revealed shear stress as a key regulator for EPC differentiation. However, the underlying mechanisms regulating the shear stress–induced EPC differentiation have not been understood completely. The present study was undertaken to further investigate the effects of shear stress on the late EPC differentiation, and to elucidate the signal mechanism involved.

Methodology/Principal Finding

In vitro and in vivo assays revealed that cytoskeletal remodeling was involved in the shear stress-upregulated expression of endothelial markers vWF and CD31 in late EPCs, with subsequently increased in vivo reendothelialization after arterial injury. Moreover, shear stress activated several mechanosensitive molecules including integrin β₁, Ras, ERK1/2, paxillin and FAK, which were all involved in both cytoskeletal rearrangement and cell differentiation in response to shear stress in late EPCs.

Conclusions/Significance

Shear stress is a key regulator for late EPC differentiation into endothelial cells, which is important for vascular repair, and the cytoskeletal rearrangement mediated by the activation of the cascade of integrin β₁, Ras, ERK1/2, paxillin and FAK is crucial in this process.