Project description:The molecular processes that are crucial for cell function, such as proliferation, migration and survival, are regulated by hydrogen peroxide (H2O2). Although environmental cues, such as growth factors, regulate redox signaling, it was still unknown whether the ECM, a component of the cell microenvironment, had a function in this process. Here, we showed that the extracellular matrix (ECM) differently regulated H2O2 consumption by endothelial cells and that this effect was not general for all types of cells. The analysis of biophysical properties of the endothelial cell membrane suggested that this modification in H2O2 consumption rates was not due to altered membrane permeability. Instead, we found that the ECM regulated GPx activity, a known H2O2 scavenger. Finally, we showed that the extent of PTEN oxidation was dependent on the ECM, indicating that the ECM was able to modulate H2O2-dependent protein oxidation. Thus, our results unraveled a new mechanism by which the ECM regulates endothelial cell function by altering redox balance. These results pinpoint the ECM as an important component of redox-signaling.
Project description:The extracellular matrix (ECM) is a crucial component of the stem cell microenvironment, or stem-cell niches, and contributes to the regulation of cell behavior and fate. Accumulating evidence indicates that different types of stem cells possess a large variety of molecules responsible for interactions with the ECM, mediating specific epigenetic rearrangements and corresponding changes in transcriptome profile. Signals from the ECM are crucial at all stages of ontogenesis, including embryonic and postnatal development, as well as tissue renewal and repair. The ECM could regulate stem cell transition from a quiescent state to readiness to perceive the signals of differentiation induction (competence) and the transition between different stages of differentiation (commitment). Currently, to unveil the complex networks of cellular signaling from the ECM, multiple approaches including screening methods, the analysis of the cell matrixome, and the creation of predictive networks of protein-protein interactions based on experimental data are used. In this review, we consider the existing evidence regarded the contribution of ECM-induced intracellular signaling pathways into the regulation of stem cell differentiation focusing on mesenchymal stem/stromal cells (MSCs) as well-studied type of postnatal stem cells totally depended on signals from ECM. Furthermore, we propose a system biology-based approach for the prediction of ECM-mediated signal transduction pathways in target cells. Video Abstract.
Project description:Extracellular matrix (ECM) production is critical to preserve the function and integrity of mature blood vessels. Toward the engineering of blood vessels, studies have centered on ECM production by supporting cells, whereas few studies implicate endothelial cells (ECs) with ECM synthesis. Here, we elucidate variations between cultured human arterial, venous, and progenitor ECs with respect to ECM deposition assembly, composition, and response to biomolecular and physiological factors. Our studies reveal that progenitor ECs, endothelial colony-forming cells (ECFCs), deposit collagen IV, fibronectin, and laminin that assemble to an organized weblike structure, as confirmed by decellularized cultures. Mature ECs only express these ECM proteins intracellularly. ECFC-derived ECM is abrogated in response to TGF? signaling inhibition and actin cytoskeleton disruption. Hypoxic (1%) and physiological (5%) O(2) tension stimulate ECM deposition from mature ECs. Interestingly, deposition of collagen I is observed only under 5% O(2) tension. ECM production from all ECs is found to be regulated by hypoxia-inducible factors 1? and 2? but differentially in the different cell lines. Collectively, we suggest that ECM deposition and assembly by ECs is dependent on maturation stage and oxygen supply and that these findings can be harnessed to advance engineered vascular therapeutics.
Project description:Endostatin, a C-terminal fragment of collagen XVIII, binds to TG-2 (transglutaminase-2) in a cation-dependent manner. Recombinant human endostatin binds to TG-2 with an affinity in the nanomolar range (Kd=6.8 nM). Enzymatic assays indicated that, in contrast with other extracellular matrix proteins, endostatin is not a glutaminyl substrate of TG-2 and is not cross-linked to itself by the enzyme. Two arginine residues of endostatin, Arg27 and Arg139, are crucial for its binding to TG-2. They are also involved in the binding to heparin [Sasaki, Larsson, Kreuger, Salmivirta, Claesson-Welsh, Lindahl, Hohenester and Timpl (1999) EMBO J. 18, 6240-6248], and to alpha5beta1 and alphavbeta3 integrins [Faye, Moreau, Chautard, Jetne, Fukai, Ruggiero, Humphries, Olsen and Ricard-Blum (2009) J. Biol. Chem. 284, 22029-22040], suggesting that endostatin is not able to interact simultaneously with TG-2 and heparan sulfate, or with TG-2 and integrins. Inhibition experiments support the hypothesis that the GTP-binding site of TG-2 is a potential binding site for endostatin. Endostatin and TG-2 are co-localized in the extracellular matrix secreted by endothelial cells under hypoxia, which stimulates angiogenesis. This interaction, occurring in a cellular context, might participate in the concerted regulation of angiogenesis and tumorigenesis by the two proteins.
Project description:Endothelial cells derived from human pluripotent stem cells are a promising cell type for enhancing angiogenesis in ischemic cardiovascular tissues. However, our understanding of microenvironmental factors that modulate the process of endothelial differentiation is limited. We examined the role of combinatorial extracellular matrix (ECM) proteins on endothelial differentiation systematically using an arrayed microscale platform. Human pluripotent stem cells were differentiated on the arrayed ECM microenvironments for 5 days. Combinatorial ECMs composed of collagen IV?+?heparan sulfate?+?laminin (CHL) or collagen IV?+?gelatin?+?heparan sulfate (CGH) demonstrated significantly higher expression of CD31, compared to single-factor ECMs. These results were corroborated by fluorescence activated cell sorting showing a 48% yield of CD31+/VE-cadherin+ cells on CHL, compared to 27% on matrigel. To elucidate the signaling mechanism, a gene expression time course revealed that VE-cadherin and FLK1 were upregulated in a dynamically similar manner as integrin subunit ?3 (>50 fold). To demonstrate the functional importance of integrin ?3 in promoting endothelial differentiation, the addition of neutralization antibody inhibited endothelial differentiation on CHL-modified dishes by >50%. These data suggest that optimal combinatorial ECMs enhance endothelial differentiation, compared to many single-factor ECMs, in part through an integrin ?3-mediated pathway.
Project description:The generation of endothelial cells (ECs) from human pluripotent stem cells (PSCs) has been a promising approach for treating cardiovascular diseases for several years. Human PSCs, particularly induced pluripotent stem cells (iPSCs), are an attractive source of ECs for cell therapy. Although there is a diversity of methods for endothelial cell differentiation using biochemical factors, such as small molecules and cytokines, the efficiency of EC production varies depending on the type and dose of biochemical factors. Moreover, the protocols in which most EC differentiation studies have been performed were in very unphysiological conditions that do not reflect the microenvironment of native tissue. The microenvironment surrounding stem cells exerts variable biochemical and biomechanical stimuli that can affect stem cell differentiation and behavior. The stiffness and components of the extracellular microenvironment are critical inducers of stem cell behavior and fate specification by sensing the extracellular matrix (ECM) cues, adjusting the cytoskeleton tension, and delivering external signals to the nucleus. Differentiation of stem cells into ECs using a cocktail of biochemical factors has been performed for decades. However, the effects of mechanical stimuli on endothelial cell differentiation remain poorly understood. This review provides an overview of the methods used to differentiate ECs from stem cells by chemical and mechanical stimuli. We also propose the possibility of a novel EC differentiation strategy using a synthetic and natural extracellular matrix.
Project description:The construction of well-controllable in vitro models of physiological and pathological vascular endothelium remains a fundamental challenge in tissue engineering and drug development. Here, we present an approach for forming a synthetic endothelial extracellular matrix (ECM) that closely resembles that of the native structure by locally depositing basement membrane materials onto type 1 collagen nanofibers only in a region adjacent to the endothelial cell (EC) monolayer. Culturing the EC monolayer on this synthetic endothelial ECM remarkably enhanced its physiological properties, reducing its vascular permeability, and promoting a stabilized, quiescent phenotype. We demonstrated that the EC monolayer on the synthetic endothelial ECM neither creates non-physiological barriers to cell-cell or cell-ECM interactions, nor hinders molecular diffusion of growth factors and other molecules. The synthetic endothelial ECM and vascular endothelium on it may help us enter in a new phase of research in which various models of the biological barrier behavior can be tested experimentally.
Project description:Vascular endothelial growth factor (VEGF) can mediate endothelial cell migration, proliferation, and angiogenesis. During cancer progression, VEGF production is often increased to stimulate the growth of new blood vessels to supply growing tumors with the additional oxygen and nutrients they require. Extracellular matrix stiffening also occurs during tumor progression, however, the crosstalk between tumor mechanics and VEGF signaling remains poorly understood. Here, we show that matrix stiffness heightens downstream endothelial cell response to VEGF by altering VEGF receptor-2 (VEGFR-2) internalization, and this effect is influenced by cell confluency. In sub-confluent endothelial monolayers, VEGFR-2 levels, but not VEGFR-2 phosphorylation, are influenced by matrix rigidity. Interestingly, more compliant matrices correlated with increased expression and clustering of VEGFR-2; however, stiffer matrices induced increased VEGFR-2 internalization. These effects are most likely due to actin-mediated contractility, as inhibiting ROCK on stiff substrates increased VEGFR-2 clustering and decreased internalization. Additionally, increasing matrix stiffness elevates ERK 1/2 phosphorylation, resulting in increased cell proliferation. Moreover, cells on stiff matrices generate more actin stress fibers than on compliant substrates, and the addition of VEGF stimulates an increase in fiber formation regardless of stiffness. In contrast, once endothelial cells reached confluency, stiffness-enhanced VEGF signaling was no longer observed. Together, these data show a complex effect of VEGF and matrix mechanics on VEGF-induced signaling, receptor dynamics, and cell proliferation that is mediated by cell confluency.
Project description:We studied the three-dimensional cell-extracellular matrix interactions of endothelial cells that form multicellular structures called sprouts. We analyzed the data collected in-situ from angiogenic sprouting experiments and identified the differentiated interaction behavior exhibited by the tip and stalk cells. Moreover, our analysis of the tip cell lamellipodia revealed the diversity in their interaction behavior under certain conditions (e.g., when the heading of a sprout is switched approximately between the long-axis direction of two different lamellipodia). This study marks the first time that new characteristics of such interactions have been identified with shape changes in the sprouts and the associated rearrangements of collagen fibers. Clear illustrations of such changes are depicted in three-dimensional views.
Project description:Remodeling of extracellular matrix (ECM) components of endothelial cells is the main cause of retinal vascular basement membrane (BM) thickening, which leads to the initiation and perpetuation of microvasculopathy of diabetic retinopathy (DR). Excessive amounts of glucocorticoids (GCs) are related to the presence and severity of DR, however transcriptional effects of GCs on the biology of human retinal capillary endothelial cells (HRCECs) and its impacts on DR are still unclear. Here, we showed that GC (hydrocortisone) treatment induced ECM component [fibronectin (FN) and type IV collagen (Col IV)] expression and morphological changes in HRCECs via the glucocorticoid receptor (GR), which depended on the nuclear translocation of YAP coactivator. Mechanistically, GCs induced stress fiber formation in HRCECs, while blocking stress fiber formation inhibited GC-induced YAP nuclear translocation. Overexpression of FN, but not Col IV, activated YAP through the promotion of stress fiber formation via ECM-integrin signaling. Thus, a feedforward loop is established to sustain YAP activity. Using mRNA sequencing of HRCECs with overexpressed YAP or GC treatment, we found a similarity in Gene Ontology (GO) terms, differentially expressed genes (DEGs) and transcription factors (TFs) between the two RNA-seq datasets. In vivo, YAP was activated in retina vascular ECs of STZ-induced diabetic mice, and TF prediction analysis of published RNA-seq data of dermal vascular ECs from T2DM patients showed that GR and TEAD (the main transcription factor for YAP) were enriched. Together, GCs activate YAP and promote ECM component (FN and Col IV) remodeling in retinal capillary endothelial cells, and the underlying regulatory mechanism may provide new insights into the vascular BM thickening of the retina in the early pathogenesis of DR.