Cell-substrate Adhesion Research Articles

TMIC-17. TARGETING THE FLUIDIC FORCE-SENSING MECHANISM TO TREAT BRAIN TUMOR METASTASIS

Abstract Biofluid flow generates fluid shear stress (FSS), a mechanical force widely present in tissue microenvironment. How brain tumor growth alters the conduit of biofluid, thereby impacting FSS-regulated cancer progression is unknown. Medulloblastoma (MB) is the most common malignant brain tumor in children. Dissemination of MB cells into the cerebrospinal fluid (CSF) initiates metastasis within the central nervous system. By simulating CSF dynamics based on magnetic resonance imaging of MB patients, we discovered that FSS is elevated at the cervicomedullary junction. Strikingly, we found that MB-relevant FSS promotes metastasis along mouse spinal cords. Mechanistically, FSS induces metastatic cell behaviours, including weakened cell-substrate adhesion, increased motility, cell clustering, and plasma membrane localization of glucose transporter 1 (GLUT1) to enhance glucose uptake. FSS is perceived by mechanosensitive ion channel PIEZO2, which drives actomyosin contractility-dependent GLUT1 recruitment at the plasma membrane. Genetic targeting of PIEZO2 or pharmacologic inhibition of GLUT1 mitigates metastasis. Collectively, these findings define a targetable FSS-activated mechano-metastatic cascade for the treatment of MB metastasis.

Two-step global sensitivity analysis of a non-local integro-differential model for Cancer-on-Chip experiments

The present work focuses on a non-local integro-differential model reproducing Cancer-on-chip experiments where tumor cells, treated with chemotherapy drugs, secrete chemical signals stimulating the immune response. The reliability of the model in reproducing the phenomenon of interest is investigated through a global sensitivity analysis, rather than a local one, to have global information about the role of parameters, and by examining potential non-linear effects in greater detail. Focusing on a region in the parameter space, the effect of 13 model parameters on the in silico outcome is investigated by considering 11 different target outputs, properly selected to monitor the spatial distribution and the dynamics of immune cells along the period of observation. In order to cope with the large number of model parameters to be investigated and the computational cost of each numerical simulation, a two-step global sensitivity analysis is performed. First, the screening Morris method is applied to rank the effect of the 13 model parameters on each target output and it emerges that all the output targets are mainly affected by the same 6 parameters. The extended Fourier Amplitude Sensitivity Test (eFAST) method is then used to quantify the role of these 6 parameters. As a result, the proposed analysis highlights the feasibility of the considered space of parameters, and indicates that the most relevant parameters are those related to the chemical field and cell-substrate adhesion. In turn, it suggests how to possibly improve the model description as well as the calibration procedure, in order to better capture the observed phenomena and, at the same time, reduce the complexity of the simulation algorithm. On one hand, the model could be simplified by neglecting cell–cell alignment effects unless clear empirical evidences of their importance emerge. On the other hand, the best way to increase the accuracy and reliability of our model predictions would be to have experimental data/information to reduce the uncertainty of the more relevant parameters.

A theoretical model for focal adhesion and cytoskeleton formation in non-motile cells

To function and survive cells need to be able to sense and respond to their local environment through mechanotransduction. Crucially, mechanical and biochemical perturbations initiate cell signalling cascades, which can induce responses such as growth, apoptosis, proliferation and differentiation. At the heart of this process are actomyosin stress fibres (SFs), which form part of the cell cytoskeleton, and focal adhesions (FAs), which bind this cytoskeleton to the extra-cellular matrix (ECM). The formation and maturation of these structures (connected by a positive feedback loop) is pivotal in non-motile cells, where SFs are generally of ventral type, interconnecting FAs and producing isometric tension. In this study we formulate a one-dimensional bio-chemo-mechanical continuum model to describe the coupled formation and maturation of ventral SFs and FAs. We use a set of reaction–diffusion–advection equations to describe three sets of biochemical events: the polymerisation of actin and subsequent bundling into activated SFs; the formation and maturation of cell–substrate adhesions; and the activation of signalling proteins in response to FA and SF formation. The evolution of these key proteins is coupled to a Kelvin–Voigt viscoelastic description of the cell cytoplasm and the ECM. We employ this model to understand how cells respond to external and intracellular cues in vitro and are able to reproduce experimentally observed phenomena including non-uniform cell striation and cells forming weaker SFs and FAs on softer substrates.

Roles of the Dbl family of RhoGEFs in mechanotransduction - a review.

Rho guanine nucleotide exchange factors (RhoGEFs) comprise a wide range of proteins with a common domain responsible for the activation of the Rho family of small GTPases and various domains in other regions. The evolutionary divergence of RhoGEFs enables actin cytoskeletal reorganization, leading to complex cellular responses in higher organisms. In this review, we address the involvement of RhoGEFs in the mechanical stress response of mammalian cells. The cellular mechanical stress response is essential for the proper and orderly regulation of cell populations, including the maintenance of homeostasis, tissue morphogenesis, and adaptation to the mechanical environment. In particular, this review focuses on the recent findings regarding the Dbl family of RhoGEFs involved in mechanical stress responses at the cell-cell and cell-substrate adhesion sites, and their molecular mechanisms underlying actin cytoskeleton remodeling and signal transduction.

Elucidating the unexpected cell adhesive properties of agarose substrates. The effect of mechanics, fetal bovine serum and specific peptide sequences

2D agarose substrates have recently been surprisingly shown to be permissive for cell adhesion, depending on their mechanics and the use of the adhesive proteins of fetal bovine serum (FBS) in the cell culture medium. Here, we elucidate how the cells exhibit two anchoring mechanisms depending on the amount of FBS. Under low FBS conditions, the cells recognize the surface-coupled adhesive sequences of fibronectin via the binding of the heterodimer α5β1 integrin. Functionality of the actomyosin axis and mechanoactivation of focal adhesion kinase (FAK) are essential for the stretching of the protein, thereby accessing the “synergy” PPSRN site and enhancing cell adhesion in combination with the downstream RGD motif. Under high FBS conditions, the specific peptide sequences are much less relevant as the adsorbed serum proteins conceal the coupled fibronectin and the cells recognize the adhesive protein vitronectin, which is constitutively present in FBS, via the binding of the heterodimer αvβ3 integrin. Similarly, the intracellular tension and FAK activity are decisive, which collectively indicate that the cells stretch the partially cryptic RGD site of vitronectin and thus make it more accessible for integrin binding. Both anchoring mechanisms only work properly if the agarose substrate is mechanically compliant in terms of linear stress-strain response, unraveling a critical balance between the mechanics of the agarose substrate and the presentation of the adhesive peptides. Statement of significanceIn the context of biomaterial design, agarose hydrogels are known to lack intrinsic cell-adhesive peptide motifs and are therefore commonly used for the development of non-permissive 2D substrates. However, we unexpectedly found that agarose hydrogels can become permissive substrates for cell adhesion, depending on a compliant mechanical response of the substrate and the use of fetal bovine serum (FBS) as protein reservoir in the cell culture medium. We describe here two anchoring mechanisms that cells harness to adhere to agarose substrates, depending on the amount of FBS. Our results will have a major impact on the field of mechanobiology and shed light on the central role of FBS as a natural source of adhesive proteins that could promote cell anchoring.

Novel readthrough agent suppresses nonsense mutations and restores functional type VII collagen and laminin 332 in epidermolysis bullosa

Recessive Dystrophic Epidermolysis Bullosa (RDEB) and Junctional Epidermolysis Bullosa (JEB) are lethal blistering skin disorders resulting from mutations in genes coding for type VII collagen (COL7A1) and laminin 332 (LAMA3, LAMB3, or LAMC2), respectively. In RDEB, 25% of patients harbor nonsense mutations causing premature termination codons (PTCs). In JEB, a majority of mutations in LAMB3 are nonsense mutations (80%). ELX-02, an aminoglycoside analog, has demonstrated superior PTC readthrough activity and lower toxicity compared to gentamicin in various genetic disorders. This study investigated ELX-02's ability to suppress PTCs and promote the expression of C7 and laminin 332 in primary RDEB keratinocytes/fibroblasts and primary JEB keratinocytes harboring nonsense mutations. ELX-02 induced a dose-dependent production of C7 or laminin β3 that surpassed the results achieved with gentamicin. ELX-02 reversed RDEB and JEB cellular hypermotility and improved poor cell-substratum adhesion in JEB cells. Importantly, ELX-02-induced C7 and laminin 332 localized to the dermal-epidermal junction. This is the first study demonstrating that ELX-02 can induce PTC readthrough and restore functional C7 and laminin 332 in RDEB and JEB caused by nonsense mutations. Therefore, ELX-02 may offer a novel and safe therapy for RDEB, JEB, and other inherited skin diseases caused by nonsense mutations.

Transcriptomic Analysis Reveals the Heterogeneous Role of Conducting Films Upon Electrical Stimulation.

Central nervous system (CNS) injuries and neurodegenerative diseases have markedly poor prognoses and can result in permanent dysfunction due to the general inability of CNS neurons to regenerate. Differentiation of transplanted stem cells has emerged as a therapeutic avenue to regenerate tissue architecture in damaged areas. Electrical stimulation is a promising approach for directing the differentiation outcomes and pattern of outgrowth of transplanted stem cells, however traditional inorganic bio-electrodes can induce adverse effects such as inflammation. This study demonstrates the implementation of two organic thin films, a polymer/reduced graphene oxide nanocomposite (P(rGO)) and PEDOT:PSS, that have favorable properties for implementation as conductive materials for electrical stimulation, as well as an inorganic indium tin oxide (ITO) conductive film. Transcriptomic analysis reveals that electrical stimulation improves neuronal differentiation of SH-SY5Y cells on all three films, with the greatest effect for P(rGO). Unique material- and electrical stimuli-mediated effects are observed, associated with differentiation, cell-substrate adhesion, and translation. The work demonstrates that P(rGO) and PEDOT:PSS are highly promising organic materials for the development of biocompatible, conductive scaffolds that will enhance electrically-aided stem cell therapeutics for CNS injuries and neurodegenerative diseases.

Bulky glycocalyx drives cancer invasiveness by modulating substrate-specific adhesion.

The majority of the eukaryotic cell surface is decorated with a layer of membrane-attached polysaccharides and glycoproteins collectively referred to as the glycocalyx. While the formation of a bulky glycocalyx has been associated with the cancer progression, the mechanisms by which the glycocalyx regulates cancer invasiveness are incompletely understood. We address this question by first documenting subtype-specific expression of the major glycocalyx glycoprotein Mucin-1 (MUC1) in breast cancer patient samples and breast cancer cell lines. Strikingly, glycocalyx disruption led to inhibition of 2D motility, loss of 3D invasion, and reduction of clonal scattering in breast cancer cells at the population level. Tracking of 2D cell motility and 3D invasiveness of MUC1-based sorted subpopulations revealed the fastest motility and invasiveness in intermediate MUC1-expressing cells, with glycocalyx disruption abolishing these effects. While differential sensitivity in 2D motility is attributed to a nonmonotonic dependence of focal adhesion size on MUC1 levels, higher MUC1 levels enhance 3D invasiveness via increased traction generation. In contrast to inducing cell rounding on collagen-coated substrates, high MUC1 level promotes cell adhesion and confers resistance to shear flow on substrates coated with the endothelial surface protein E-selectin. Collectively, our findings illustrate how MUC1 drives cancer invasiveness by differentially regulating cell-substrate adhesion in a substrate-dependent manner.

Machine learning and bioinformatics analysis of diagnostic biomarkers associated with the occurrence and development of lung adenocarcinoma.

Lung adenocarcinoma poses a major global health challenge and is a leading cause of cancer-related deaths worldwide. This study is a review of three molecular biomarkers screened by machine learning that are not only important in the occurrence and progression of lung adenocarcinoma but also have the potential to serve as biomarkers for clinical diagnosis, prognosis evaluation and treatment guidance. Differentially expressed genes (DEGs) were identified using comprehensive GSE1987 and GSE18842 gene expression databases. A comprehensive bioinformatics analysis of these DEGs was conducted to explore enriched functions and pathways, relative expression levels, and interaction networks. Random Forest and LASSO regression analysis techniques were used to identify the three most significant target genes. The TCGA database and quantitative polymerase chain reaction (qPCR) experiments were used to verify the expression levels and receiver operating characteristic (ROC) curves of these three target genes. Furthermore, immune invasiveness, pan-cancer, and mRNA-miRNA interaction network analyses were performed. Eighty-nine genes showed increased expression and 190 genes showed decreased expression. Notably, the upregulated DEGs were predominantly associated with organelle fission and nuclear division, whereas the downregulated DEGs were mainly associated with genitourinary system development and cell-substrate adhesion. The construction of the DEG protein-protein interaction network revealed 32 and 19 hub genes with the highest moderate values among the upregulated and downregulated genes, respectively. Using random forest and LASSO regression analyses, the hub genes were employed to identify three most significant target genes.TCGA database and qPCR experiments were used to verify the expression levels and ROC curves of these three target genes, and immunoinvasive analysis, pan-cancer analysis and mRNA-miRNA interaction network analysis were performed. Three target genes identified by machine learning: BUB1B, CENPF, and PLK1 play key roles in LUAD development of lung adenocarcinoma.

Depletion of calpain2 accelerates epithelial barrier establishment and reduces growth factor-induced cell scattering

Calpain2 is a conventional member of the non-lysosomal calpain protease family that has been shown to affect the dynamics of focal and cell-cell adhesions by proteolyzing the components of adhesion complexes. Here, we inactivated calpain2 using CRISPR/Cas9 in epithelial MDCK cells. We show that depletion of calpain2 has multiple effects on cell morphology and function. Calpain2-depleted cells develop epithelial shape, however, they cover a smaller area, and cell clusters are more compact. Inactivation of calpain2 enhanced restoration of transepithelial electrical resistance after calcium switch, decreased cell migration, and delayed cell scattering induced by HGF/SF. In addition, calpain2 depletion prevented morphological changes induced by ERK2 overexpression. Interestingly, proteolysis of several calpain2 targets, including E-cadherin, β-catenin, talin, FAK, and paxillin, was not discernibly affected by calpain2 depletion. Taken together, these data suggest that calpain2 regulates the stability of cell-cell and cell-substratum adhesions indirectly without affecting the proteolysis of these adhesion complexes.

Polyploidy of MDA-MB-231 cells drives increased extravasation with enhanced cell-matrix adhesion.

Metastasis, the leading cause of cancer-related deaths, involves a complex cascade of events, including extravasation. Despite extensive research into metastasis, the mechanisms underlying extravasation remain unclear. Molecular targeted therapies have advanced cancer treatment, yet their efficacy is limited, prompting exploration into novel therapeutic targets. Here, we showed the association of polyploidy in MDA-MB-231 breast cancer cells and their extravasation, using microfluidic systems to reproduce the in vivo microvascular environment. We observed enhanced extravasation in polyploid cells alongside upregulated expression of genes involved in cell-substrate adhesion and cell mechanical dynamics. These findings offer insights into the relationship between polyploidy and extravasation, highlighting potential targets for cancer therapy.

Proteomics analysis of deep fascia in acute compartment syndrome.

Acute compartment syndrome (ACS) is a syndrome in which local circulation is affected due to increased pressure within the compartment. We previously found in patients with calf fractures, the pressure of fascial compartment could be sharply reduced upon the appearance of tension blisters. Deep fascia, as the important structure for compartment, might play key role in this process. Therefore, the aim of the present study was to examine the differences in gene profile in deep fascia tissue in fracture patients of the calf with or without tension blisters, and to explore the role of fascia in pressure improvement in ACS. Patients with lower leg fracture were enrolled and divided into control group (CON group, n = 10) without tension blister, and tension blister group (TB group, n = 10). Deep fascia tissues were collected and LC-MS/MS label-free quantitative proteomics were performed. Genes involved in fascia structure and fibroblast function were further validated by Western blot. The differentially expressed proteins were found to be mainly enriched in pathways related to protein synthesis and processing, stress fiber assembly, cell-substrate adhesion, leukocyte mediated cytotoxicity, and cellular response to stress. Compared with the CON group, the expression of Peroxidasin homolog (PXDN), which promotes the function of fibroblasts, and Leukocyte differentiation antigen 74 (CD74), which enhances the proliferation of fibroblasts, were significantly upregulated (p all <0.05), while the expression of Matrix metalloproteinase-9 (MMP9), which is involved in collagen hydrolysis, and Neutrophil elastase (ELANE), which is involved in elastin hydrolysis, were significantly reduced in the TB group (p all <0.05), indicating fascia tissue underwent microenvironment reconstruction during ACS. In summary, the ACS accompanied by blisters is associated with the enhanced function and proliferation of fibroblasts and reduced hydrolysis of collagen and elastin. The adaptive alterations in the stiffness and elasticity of the deep fascia might be crucial for pressure release of ACS.

Stretch-induced damage in endothelial monolayers

Endothelial cells are constantly exposed to mechanical stimuli, of which mechanical stretch has shown various beneficial or deleterious effects depending on whether loads are within physiological or pathological levels, respectively. Vascular properties change with age, and on a cell-scale, senescence elicits changes in endothelial cell mechanical properties that together can impair its response to stretch. Here, high-rate uniaxial stretch experiments were performed to quantify and compare the stretch-induced damage of monolayers consisting of young, senescent, and aged endothelial populations. The aged and senescent phenotypes were more fragile to stretch-induced damage. Prominent damage was detected by immunofluorescence and scanning electron microscopy as intercellular and intracellular void formation. Damage increased proportionally to the applied level of deformation and, for the aged and senescent phenotype, induced significant detachment of cells at lower levels of stretch compared to the young counterpart. Based on the phenotypic difference in cell-substrate adhesion of senescent cells indicating more mature focal adhesions, a discrete network model of endothelial cells being stretched was developed. The model showed that the more affine deformation of senescent cells increased their intracellular energy, thus enhancing the tendency for cellular damage and impending detachment. Next to quantifying for the first-time critical levels of endothelial stretch, the present results indicate that young cells are more resilient to deformation and that the fragility of senescent cells may be associated with their stronger adhesion to the substrate.

RapB Regulates Cell Adhesion and Migration in Dictyostelium, Similar to RapA.

Ras small GTPases act as molecular switches in various cellular signaling pathways, including cell migration, proliferation, and differentiation. Three Rap proteins are present in Dictyostelium; RapA, RapB, and RapC. RapA and RapC have been reported to have opposing functions in the control of cell adhesion and migration. Here, we investigated the role of RapB, a member of the Ras GTPase subfamily in Dictyostelium, focusing on its involvement in cell adhesion, migration, and developmental processes. This study revealed that RapB, similar to RapA, played a crucial role in regulating cell morphology, adhesion, and migration. rapB null cells, which were generated by CRISPR/Cas9 gene editing, displayed altered cell size, reduced cell-substrate adhesion, and increased migration speed during chemotaxis. These phenotypes of rapB null cells were restored by the expression of RapB and RapA, but not RapC. Consistent with these results, RapB, similar to RapA, failed to rescue the phenotypes of rapC null cells, spread morphology, increased cell adhesion, and decreased migration speed during chemotaxis. Multicellular development of rapB null cells remained unaffected. These results suggest that RapB is involved in controlling cell morphology and cell adhesion. Importantly, RapB appears to play an inhibitory role in regulating the migration speed during chemotaxis, possibly by controlling cell-substrate adhesion, resembling the functions of RapA. These findings contribute to the understanding of the functional relationships among Ras subfamily proteins.

A multiscale dynamic model of cell–substrate interfaces

Cell–extracellular matrix (ECM) interactions play a pivotal role in many functions of cells, for example, sensing, signaling, migration, and gene expression. The spatial–temporal dynamic evolution of cell–substrate adhesions involves complicated mechano-bio-chemical coupling mechanisms of integrin, adaptor and signaling proteins, as well as the interplay between the cytoskeleton and ECM. In this paper, we establish a multiscale dynamic model of cell–substrate interfaces considering intermolecular force transmission pathways, i.e., intra- and extra-cellular bond dynamics, and mechanochemical coupling regulations. To illustrate its applications, this model is used to reproduce several adhesion-related experimental phenomena of cells, including substrate rigidity sensing, actin-assisted focal adhesion formation, and biphasic interface stress–actin speed relation. The results suggest that the cluster growth patterns are mediated by the intermolecular force transmission pathway and the actin flow speed, and that the integrin–ligand (IL) bond strengthening tends to inhibit the motion of clusters. We reveal that the monotonic-to-biphasic transition of force transmission and adhesion assembly is regulated by the bond rupture mechanosensitivity of integrin adhesion complexes (IACs). It is also demonstrated that this multiscale dynamic model can well describe the spatial–temporal evolutions of collective cell–substrate adhesions with the effects of actin flow and substrate deformation, and can also capture the morphological features of adhesion clusters and related interface force transmissions. This work provides a theoretical tool for studying mechano-biochemical mechanisms of cell–substrate interactions and for understanding various subcellular and cellular dynamic processes in, for example, tumors.

Imbalance between Actin Isoforms Contributes to Tumour Progression in Taxol-Resistant Triple-Negative Breast Cancer Cells.

The widespread occurrence of breast cancer and its propensity to develop drug resistance highlight the need for a comprehensive understanding of the molecular mechanisms involved. This study investigates the intricate pathways associated with secondary resistance to taxol in triple-negative breast cancer (TNBC) cells, with a particular focus on the changes observed in the cytoplasmic actin isoforms. By studying a taxol-resistant TNBC cell line, we revealed a shift between actin isoforms towards γ-actin predominance, accompanied by increased motility and invasive properties. This was associated with altered tubulin isotype expression and reorganisation of the microtubule system. In addition, we have shown that taxol-resistant TNBC cells underwent epithelial-to-mesenchymal transition (EMT), as evidenced by Twist1-mediated downregulation of E-cadherin expression and increased nuclear translocation of β-catenin. The RNA profiling analysis revealed that taxol-resistant cells exhibited significantly increased positive regulation of cell migration, hormone response, cell-substrate adhesion, and actin filament-based processes compared with naïve TNBC cells. Notably, taxol-resistant cells exhibited a reduced proliferation rate, which was associated with an increased invasiveness in vitro and in vivo, revealing a complex interplay between proliferative and metastatic potential. This study suggests that prolonged exposure to taxol and acquisition of taxol resistance may lead to pro-metastatic changes in the TNBC cell line.

Deletion of Dictyostelium tpc2 gene forms multi-tipped structures, regulates autophagy and cell-type patterning.

Two pore channels (TPCs) are voltage-gated ion channel superfamily members that release Ca2+ from acidic intracellular stores and are ubiquitously present in both animals and plants. Starvation initiates multicellular development in Dictyostelium discoideum. Increased intracellular calcium levels bias Dictyostelium cells towards the stalk pathway and thus we decided to analyze the role of TPC2 in development, differentiation, and autophagy. We showed TPC2 protein localizes in lysosome-like acidic vesicles and the in situ data showed stalk cell biasness. Deletion of tpc2 showed defective and delayed development with formation of multi-tipped structures attached to a common base, while tpc2OE cells showed faster development with numerous small-sized aggregates and wiry fruiting bodies. The tpc2OE cells showed higher intracellular cAMP levels as compared to the tpc2- cells while pinocytosis was found to be higher in the tpc2- cells. Also, TPC2 regulates cell-substrate adhesion and cellular morphology. Under nutrient starvation, deletion of tpc2 reduced autophagic flux as compared to Ax2. During chimera formation, tpc2- cells showed a bias towards the prestalk/stalk region while tpc2OE cells showed a bias towards the prespore/spore region. tpc2 deficient strain exhibits aberrant cell-type patterning and loss of distinct boundary between the prestalk/prespore regions. TPC2 is required for effective development and differentiation in Dictyostelium and supports autophagic cell death and cell-type patterning. Decreased calcium due to deletion of tpc2 inhibit autophagic flux.

Distinct cellular microenvironment with cytotypic effects regulates orderly regeneration of vascular tissues

Regeneration of the architecturally complex blood vascular system requires precise temporal and spatial control of cell behaviours. Additional components must be integrated into the structure to achieve clinical success for in situ tissue engineering. Consequently, this study proposed a universal method for including any substrate type in vascular cell extracellular matrices (VCEM) via regulating selective adhesion to promote vascular tissue regeneration. The results uncovered that the VCEM worked as cell adhesion substrates, exhibited cell type specificity, and functioned as an address signal for recognition by vascular cells, which resulted in matching with the determined cells. The qPCR and immunofluorescence results revealed that a cell type-specific VCEM could be designed to promote or inhibit cell adhesion, consistenting with the expression patterns of eyes absent 3 (Eya3). In addition, a 3D vascular graft combined with VCEM which could recapitulate the vascular cell-like microenvironment was fabricated. The vascular graft revealed a prospective role for cellular microenvironment in the establishment of vascular cell distribution and tissue architecture, and potentiated the orderly regeneration and functional recovery of vascular tissues in vivo. The findings demonstrate that differential adhesion between cell types due to the cellular microenvironment is sufficient to drive the complex assembly of engineered blood vessel functional units, and underlies hierarchical organization during vascular regeneration.

An elastic-damaging cohesive law for cell–substrate adhesion with positive and negative durotaxis

Durotaxis of cells anchored to the extracellular matrix through focal adhesions has been systematically studied through both analytical and computational approaches. However, recent experiments have revealed the attitude of certain cells to unexpectedly migrate towards comparatively softer substrates, thus suggesting the possibility for negative durotaxis to manifest. Cell migration is possible because focal adhesions grow and disrupt, thus operating like adhesive structures undergoing a chemo-physical degradation process. In the present contribution, this degradation process is described through an elastic-damaging cohesive law deduced from a convex–concave pseudo-elastic potential, which confers a variational structure to the mechanical model of the adhesion structure and makes the derivation of analytical solutions possible. Furthermore, the obtained traction-separation cohesive law is amenable to a straightforward implementation into finite element codes. Finite elasticity of the cell body is considered while durotaxis is triggered by applying a contractile pre-stretch to the cell. It is shown that displacement- or force-driven degradation processes may lead to different kinds of durotaxis. The consistency and effectiveness of the proposed approach are showcased in one- and three-dimensional examples of cell–substrate systems.

Global Proteomics Analysis of Lysophosphatidic Acid Signaling in PC-3 Human Prostate Cancer Cells: Role of CCN1.

Cysteine-rich angiogenic factor 61 (CCN1/Cyr61) is a matricellular protein that is induced and secreted in response to growth factors. Our previous work showed that 18:1-lysophosphatidic acid (LPA), which activates the G protein-coupled receptor LPAR1, induces CCN1 between 2-4 h in PC-3 human prostate cancer cells in a manner than enhances cell-substrate adhesion. While the time course of induction suggests that CCN1 contributes to intermediate events in LPA action, the roles of CCN1 in LPA-mediated signal transduction have not been fully elucidated. This study utilized a comprehensive global proteomics approach to identify proteins up- or down-regulated in response to treatment of PC-3 cells with LPA for three hours, during the time of peak CCN1 levels. In addition, the effects of siRNA-mediated CCN1 knockdown on LPA responses were analyzed. The results show that, in addition to CCN1, LPA increased the levels of multiple proteins. Proteins up-regulated by LPA included metastasis-associated in colon cancer protein 1 (MACC1) and thrombospondin-1 (TSP1/THBS1); both MACC1 and TSP1 regulated cancer cell adhesion and motility. LPA down-regulated thioredoxin interacting protein (TXNIP). CCN1 knockdown suppressed the LPA-induced up-regulation of 30 proteins; these included MACC1 and TSP1, as confirmed by immunoblotting. Gene ontology and STRING analyses revealed multiple pathways impacted by LPA and CCN1. These results indicate that CCN1 contributes to LPA signaling cascades that occur during the intermediate phase after the initial stimulus. The study provides a rationale for the development of interventions to disrupt the LPA-CCN1 axis.