Regulation of cell motile behavior by crosstalk between cadherin- and integrin-mediated adhesions

The Plasma Membrane and Mechanoregulation in Cells

Cells inhabit a mechanical microenvironment that they continuously sense and adapt to. The plasma membrane (PM), serving as the boundary of the cell, plays a pivotal role in this process of adaptation. In this Review, we begin by examining well-studied processes where mechanoregulation proves significant. Specifically, we highlight examples from the immune system and stem cells, besides discussing processes involving fibroblasts and other cell types. Subsequently, we discuss the common molecular players that facilitate the sensing of the mechanical signal and transform it into a chemical response covering integrins YAP/TAZ and Piezo. We then review how this understanding of molecular elements is leveraged in drug discovery and tissue engineering alongside a discussion of the methodologies used to measure mechanical properties. Focusing on the processes of endocytosis, we discuss how cells may respond to altered membrane mechanics using endo- and exocytosis. Through the process of depleting/adding the membrane area, these could also impact membrane mechanics. We compare pathways from studies illustrating the involvement of endocytosis in mechanoregulation, including clathrin-mediated endocytosis (CME) and the CLIC/GEEC (CG) pathway as central examples. Lastly, we review studies on cell-cell fusion during myogenesis, the mechanical integrity of muscle fibers, and the reported and anticipated roles of various molecular players and processes like endocytosis, thereby emphasizing the significance of mechanoregulation at the PM.

MSLN induced EMT, cancer stem cell traits and chemotherapy resistance of pancreatic cancer cells

Chemoresistance is one of the main reasons for poor prognosis of pancreatic cancer. The effects of mesothelin (MSLN) on chemoresistance in pancreatic cancer are still unclear. We aim to investigate potential roles of MSLN in chemoresistance and its relationship with proliferation, epithelial-mesenchymal transition (EMT) and cancer stemness of pancreatic cancer cells. Human pancreatic cancer cell lines ASPC-1 and Mia PaCa-2 with high and low expression of MSLN, respectively, were selected. The ASPC-1 with MSLN knockout (KO) and Mia PaCa-2 of MSLN overexpression (OE) were generated. The effects of MSLN on cell phenotypes, expression of EMT-related markers, clone formation, tumor sphere formation, and pathologic role of MSLN in tumorigenesis were detected. Sensitivity of tumor cells to gemcitabine was evaluated. The results showed that adhesion, proliferation, migration and invasion were decreased significantly in ASPC-1 with MSLN KO, whereas increased significantly in Mia PaCa-2 with MSLN OE. The size and the number of clones and tumor spheres were decreased in ASPC-1 with MSLN KO, and increased in Mia PaCa-2 with MSLN OE. In xenograft model, tumor volume was decreased (tumor grew slower) in MSLN KO group compared to control group, while increased in MSLN OE group. Mia PaCa-2 with MSLN OE had a higher IC50 of gemcitabine, while ASPC-1 with MSLN KO had a lower IC50. We concluded that MSLN could induce chemoresistance by enhancing migration, invasion, EMT and cancer stem cell traits of pancreatic cancer cells. Targeting MSLN could represent a promising therapeutic strategy for reversing EMT and chemoresistance in pancreatic cancer cells.

Integrin-based adhesions promote cell-cell junction and cytoskeletal remodelling to drive embryonic wound healing

Embryos repair wounds rapidly, with no inflammation or scarring. Embryonic wound healing is driven by the collective movement of the cells around the lesion. The cells adjacent to the wound polarize the cytoskeletal protein actin and the molecular motor non-muscle myosin II, which accumulate at the wound edge forming a supracellular cable around the wound. Adherens junction proteins, including E-cadherin, are internalized from the wound edge and localize to former tricellular junctions at the wound margin, in a process necessary for cytoskeletal polarity. We found that the cells adjacent to wounds in the Drosophila embryonic epidermis polarized Talin, a core component of cell-extracellular matrix (ECM) adhesions, which preferentially accumulated at the wound edge. Integrin knockdown and inhibition of integrin binding delayed wound closure and reduced actin polarization and dynamics around the wound. Additionally, disrupting integrins caused a defect in E-cadherin reinforcement at tricellular junctions along the wound edge, suggesting crosstalk between integrin-based and cadherin-based adhesions. Our results show that cell-ECM adhesion contributes to embryonic wound repair and reveal an interplay between cell-cell and cell-ECM adhesion in the collective cell movements that drive rapid wound healing.

E-cadherin biomaterials reprogram collective cell migration and cell cycling by forcing homeostatic conditions

Cells attach to the world through either cell-extracellular matrix adhesion or cell-cell adhesion, and traditional biomaterials imitate the matrix for integrin-based adhesion. However, materials incorporating cadherin proteins that mimic cell-cell adhesion offer an alternative to program cell behavior and integrate into living tissues. We investigated how cadherin substrates affect collective cell migration and cell cycling in epithelia. Our approach involved biomaterials with matrix proteins on one-half and E-cadherin proteins on the other, forming a "Janus" interface across which we grew a single sheet of cells. Tissue regions over the matrix side exhibited normal collective dynamics, but an abrupt behavior shift occurred across the Janus boundary onto the E-cadherin side, where cells attached to the substrate via E-cadherin adhesions, resulting in stalled migration and slowing of the cell cycle. E-cadherin surfaces disrupted long-range mechanical coordination and nearly doubled the length of the G0/G1 phase of the cell cycle, linked to the lack of integrin focal adhesions on the E-cadherin surface.

Machine learning interpretable models of cell mechanics from protein images

Cellular form and function emerge from complex mechanochemical systems within the cytoplasm. Currently, no systematic strategy exists to infer large-scale physical properties of a cell from its molecular components. This is an obstacle to understanding processes such as cell adhesion and migration. Here, we develop a data-driven modeling pipeline to learn the mechanical behavior of adherent cells. We first train neural networks to predict cellular forces from images of cytoskeletal proteins. Strikingly, experimental images of a single focal adhesion (FA) protein, such as zyxin, are sufficient to predict forces and can generalize to unseen biological regimes. Using this observation, we develop two approaches-one constrained by physics and the other agnostic-to construct data-driven continuum models of cellular forces. Both reveal how cellular forces are encoded by two distinct length scales. Beyond adherent cell mechanics, our work serves as a case study for integrating neural networks into predictive models for cell biology.

Vinculin is essential for sustaining normal levels of endogenous forces at cell-cell contacts

Transmission of cell-generated (i.e., endogenous) tension at cell-cell contacts is crucial for tissue shape changes during morphogenesis and adult tissue repair in tissues such as epithelia. E-cadherin-based adhesions at cell-cell contacts are the primary means by which endogenous tension is transmitted between cells. The E-cadherin-β-catenin-α-catenin complex mechanically couples to the actin cytoskeleton (and thereby the cell's contractile machinery) both directly and indirectly. However, the key adhesion constituents required for substantial endogenous force transmission at these adhesions in cell-cell contacts are unclear. Due to the role of α-catenin as a mechanotransducer that recruits vinculin at cell-cell contacts, we expected α-catenin to be essential for sustaining normal levels of force transmission. Instead, using the traction force imbalance method to determine the inter-cellular force at a single cell-cell contact between cell pairs, we found that it is vinculin that is essential for sustaining normal levels of endogenous force transmission, with absence of vinculin decreasing the inter-cellular tension by over 50%. Our results constrain the potential mechanical pathways of force transmission at cell-cell contacts and suggest that vinculin can transmit forces at E-cadherin adhesions independent of α-catenin, possibly through β-catenin. Furthermore, we tested the ability of lateral cell-cell contacts to withstand external stretch and found that both vinculin and α-catenin are essential to maintain cell-cell contact stability under external forces.

Programmable and Reversible Integrin-Mediated Cell Adhesion Reveals Hysteresis in Actin Kinetics that Alters Subsequent Mechanotransduction

Dynamically evolving adhesions between cells and extracellular matrix (ECM) transmit time-varying signals that control cytoskeletal dynamics and cell fate. Dynamic cell adhesion and ECM stiffness regulate cellular mechanosensing cooperatively, but it has not previously been possible to characterize their individual effects because of challenges with controlling these factors independently. Therefore, a DNA-driven molecular system is developed wherein the integrin-binding ligand RGD can be reversibly presented and removed to achieve cyclic cell attachment/detachment on substrates of defined stiffness. Using this culture system, it is discovered that cyclic adhesion accelerates F-actin kinetics and nuclear mechanosensing in human mesenchymal stem cells (hMSCs), with the result that hysteresis can completely change how hMSCs transduce ECM stiffness. Results are dramatically different from well-known results for mechanotransduction on static substrates, but are consistent with a mathematical model of F-actin fragments retaining structure following loss of integrin ligation and participating in subsequent repolymerization. These findings suggest that cyclic integrin-mediated adhesion alters the mechanosensing of ECM stiffness by hMSCs through transient, hysteretic memory that is stored in F-actin.

Integrating Shear Flow and Trypsin Treatment to Assess Cell Adhesion Strength

Cell adhesion is of fundamental importance in cell and tissue organization, and for designing cell-laden constructs for tissue engineering. Prior methods to assess cell adhesion strength for strongly adherent cells using hydrodynamic shear flow either involved the use of specialized flow devices to generate high shear stress or used simpler implementations like larger height parallel plate chambers that enable multi-hour cell culture but generate low shear stress and are hence more applicable for weakly adherent cells. Here, we propose a shear flow assay for adhesion strength assessment of strongly adherent cells that employs off-the-shelf parallel plate chambers for shear flow as well as simultaneous trypsin treatment to tune down the adhesion strength of cells. We implement the assay with a strongly adherent cell type and show that shear stress in the 0.07 to 7 Pa range is sufficient to dislodge the cells with simultaneous trypsin treatment. Imaging of cells over a square centimeter area allows cell morphological analysis of hundreds of cells. We show that the cell area of cells that are dislodged, on average, does not monotonically increase with shear stress at the higher end of shear stresses used and suggest that this can be explained by the likely higher resistance of high circularity cells to trypsin digestion. The adhesion strength assay proposed can be easily adapted by labs to assess the adhesion strength of both weakly and strongly adherent cell types and has the potential to be adapted for substrate stiffness-dependent adhesion strength assessment in mechanobiology studies.

Breast Cancer Cell Type and Biomechanical Properties of Decellularized Mouse Organs Drives Tumor Cell Colonization

Tissue engineering has emerged as an indispensable tool for the reconstruction of organ-specific environments. Organ-derived extracellular matrices (ECM) and, especially, decellularized tissues (DCL) are recognized as the most successful biomaterials in regenerative medicine, as DCL preserves the most essential organ-specific ECM properties such as composition alongside biomechanics characterized by stiffness and porosity. Expansion of the DCL technology to cancer biology research, drug development, and nanomedicine is pending refinement of the existing DCL protocols whose reproducibility remains sub-optimal varying from organ to organ. We introduce a facile decellularization protocol universally applicable to murine organs, including liver, lungs, spleen, kidneys, and ovaries, with demonstrated robustness, reproducibility, high purification from cell debris, and architecture preservation, as confirmed by the histological and SEM analysis. The biomechanical properties of as-produced DCL organs expressed in terms of the local and total stiffness were measured using our facile methodology and were found well preserved in comparison with the intact organs. To demonstrate the utility of the developed DCL model to cancer research, we engineered three-dimensional tissue constructs by recellularization representative decellularized organs and collagenous hydrogel with human breast cancer cells of pronounced mesenchymal (MDA-MB-231) or epithelial (SKBR-3) phenotypes. The biomechanical properties of the DCL organs were found pivotal to determining the cancer cell fate and progression. Our histological and scanning electron microscopy (SEM) study revealed that the larger the ECM mean pore size and the smaller the total stiffness (as in lung and ovary), the more proliferative and invasive the mesenchymal cells became. At the same time, the low local stiffness ECMs (ranged 2.8-3.6 kPa) did support the epithelial-like SKBR-3 cells' viability (as in lung and spleen), while stiff ECMs did not. The total and local stiffness of the collagenous hydrogel was measured too low to sustain the proliferative potential of both cell lines. The observed cell proliferation patterns were easily interpretable in terms of the ECM biomechanical properties, such as binding sites, embedment facilities, and migration space. As such, our three-dimensional tissue engineering model is scalable and adaptable for pharmacological testing and cancer biology research of metastatic and primary tumors, including early metastatic colonization in native organ-specific ECM.

E-cadherin biointerfaces reprogram collective cell migration and cell cycling by forcing homeostatic conditions

Cells attach to the world around them in two ways-cell:extracellular-matrix adhesion and cell:cell adhesion-and conventional biomaterials are made to resemble the matrix to encourage integrin-based cell adhesion. However, interest is growing for cell-mimetic interfaces that mimic cell-cell interactions using cadherin proteins, as this offers a new way to program cell behavior and design synthetic implants and objects that can integrate directly into living tissues. Here, we explore how these cadherin-based materials affect collective cell behaviors, focusing specifically on collective migration and cell cycle regulation in cm-scale epithelia. We built culture substrates where half of the culture area was functionalized with matrix proteins and the contiguous half was functionalized with E-cadherin proteins, and we grew large epithelia across this 'Janus' interface. Parts of the tissues in contact with the matrix side of the Janus interface exhibited normal collective dynamics, but an abrupt shift in behaviors happened immediately across the Janus boundary onto the E-cadherin side, where cells formed hybrid E-cadherin junctions with the substrate, migration effectively froze in place, and cell-cycling significantly decreased. E-cadherin materials suppressed long-range mechanical correlations in the tissue and mechanical information reflected off the substrate interface. These effects could not be explained by conventional density, shape index, or contact inhibition explanations. E-cadherin surfaces nearly doubled the length of the G0/G1 phase of the cell cycle, which we ultimately connected to the exclusion of matrix focal adhesions induced by the E-cadherin culture surface.

MACC1-induced migration in tumors: Current state and perspective

Malignant tumors are still a global, heavy health burden. Many tumor types cannot be treated curatively, underlining the need for new treatment targets. In recent years, metastasis associated in colon cancer 1 (MACC1) was identified as a promising biomarker and drug target, as it is promoting tumor migration, initiation, proliferation, and others in a multitude of solid cancers. Here, we will summarize the current knowledge about MACC1-induced tumor cell migration with a special focus on the cytoskeletal and adhesive systems. In addition, a brief overview of several in vitro models used for the analysis of cell migration is given. In this context, we will point to issues with the currently most prevalent models used to study MACC1-dependent migration. Lastly, open questions about MACC1-dependent effects on tumor cell migration will be addressed.

Characterization of recombinant humanized collagen type III and its influence on cell behavior and phenotype

Collagen made a tremendous impact in the field of regenerative medicine as a bioactive material. For decades, collagen has been used not only as a scaffolding material but also as an active component in regulating cells' biological behavior and phenotype. However, animal-derived collagen as a major source suffered from problems of immunogenicity, risk of viral infection, and the unclear relationship between bioactive sequence and function. Recombinant humanized collagen (rhCol) provided alternatives for regenerative medicine with more controllable risks. However, the characterization of rhCol and the interaction between rhCol and cells still need further investigation, including cell behavior and phenotype. The current study preliminarily demonstrated that recombinant humanized collagen type III (rhCol III) conformed to the theoretical amino acid sequence and had an advanced structure resembling bovine collagen. Furthermore, rhCol III could facilitate basal biological behaviors of human skin fibroblasts, such as adhesion, proliferation and migration. rhCol III was beneficial for some extracellular matrix-expressing cell phenotypes. The study would shed light on the mechanism research of rhCol and cell interactions and further understanding of effectiveness in tissue regeneration.

Graphical abstract

ZO-1 Guides Tight Junction Assembly and Epithelial Morphogenesis via Cytoskeletal Tension-Dependent and -Independent Functions

Formation and maintenance of tissue barriers require the coordination of cell mechanics and cell-cell junction assembly. Here, we combined methods to modulate ECM stiffness and to measure mechanical forces on adhesion complexes to investigate how tight junctions regulate cell mechanics and epithelial morphogenesis. We found that depletion of the tight junction adaptor ZO-1 disrupted junction assembly and morphogenesis in an ECM stiffness-dependent manner and led to a stiffness-dependant reorganisation of active myosin. Both junction formation and morphogenesis were rescued by inhibition of actomyosin contractility. ZO-1 depletion also impacted mechanical tension at cell-matrix and E-cadherin-based cell-cell adhesions. The effect on E-cadherin also depended on ECM stiffness and correlated with effects of ECM stiffness on actin cytoskeleton organisation. However, ZO-1 knockout also revealed tension-independent functions of ZO-1. ZO-1-deficient cells could assemble functional barriers at low tension, but their tight junctions remained corrupted with strongly reduced and discontinuous recruitment of junctional components. Our results thus reveal that reciprocal regulation between ZO-1 and cell mechanics controls tight junction assembly and epithelial morphogenesis, and that, in a second, tension-independent step, ZO-1 is required to assemble morphologically and structurally fully assembled and functionally normal tight junctions.

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

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

Integrating shear flow and trypsin treatment to assess cell adhesion strength

Cell adhesion is of fundamental importance in cell and tissue organization and for designing cell-laden constructs for tissue engineering. Prior methods to assess cell adhesion strength for strongly adherent cells using hydrodynamic shear flow either involved the use of specialized flow devices to generate high shear stress or used simpler implementations like larger height parallel plate chambers that enable multihour cell culture but generate low wall shear stress and are, hence, more applicable for weakly adherent cells. Here, we propose a shear flow assay for adhesion strength assessment of strongly adherent cells that employs off-the-shelf parallel plate chambers for shear flow as well as simultaneous trypsin treatment to tune down the adhesion strength of cells. We implement the assay with a strongly adherent cell type and show that wall shear stress in the 0.07-7 Pa range is sufficient to dislodge the cells with simultaneous trypsin treatment. Imaging of cells over a square centimeter area allows cell morphological analysis of hundreds of cells. We show that the cell area of cells that are dislodged, on average, does not monotonically increase with wall shear stress at the higher end of wall shear stresses used and suggest that this can be explained by the likely higher resistance of high circularity cells to trypsin digestion. The adhesion strength assay proposed can be used to assess the adhesion strength of both weakly and strongly adherent cell types and has the potential to be adapted for substrate stiffness-dependent adhesion strength assessment in mechanobiology studies.

Quantitative Analysis of Collective Migration by Single-Cell Tracking Aimed at Understanding Cancer Metastasis

Metastasis is a major complication of cancer treatments. Studies of the migratory behavior of cells are needed to investigate and control metastasis. Metastasis is based on the epithelial–mesenchymal transition, in which epithelial cells acquire mesenchymal properties and the ability to leave the population to invade other regions of the body. In collective migration, highly migratory “leader” cells are found at the front of the cell population, as well as cells that “follow” these leader cells. However, the interactions between these cells are not well understood. We examined the migration properties of leader–follower cells during collective migration at the single-cell level. Different mixed ratios of “leader” and “follower” cell populations were compared. Collective migration was quantitatively analyzed from two perspectives: cell migration within the colony and migration of the entire colony. Analysis of the effect of the cell mixing ratio on migration behavior showed that a small number of highly migratory cells enhanced some of the migratory properties of other cells. The results provide useful insights into the cellular interactions in collective cell migration of cancer cell invasion.

Epithelial Cell-Like Elasticity Modulates Actin-Dependent E-Cadherin Adhesion Organization

E-cadherin adhesions are essential for cell-to-cell cohesion and mechanical coupling between epithelial cells and reside in a microenvironment that comprises the adjoining epithelial cells. While E-cadherin has been shown to be a mechanosensor, it is unknown if E-cadherin adhesions can differentially sense stiffness within the range of that of epithelial cells. A survey of literature shows that epithelial cells' Young's moduli of elasticity lie predominantly in the sub-kPa to few-kPa range, with cancer cells often being softer than noncancerous ones. Here, we devised oriented E-cadherin-coated soft silicone substrates with sub-kPa or few-kPa elasticity but with similar viscous moduli and found that E-cadherin adhesions differentially organize depending on the magnitude of epithelial cell-like elasticity. Our results show that the actin cytoskeleton organizes E-cadherin adhesions in two ways─by supporting irregularly shaped adhesions at localized regions of high actin density and linear shaped adhesions at the end of linear actin bundles. Linearly shaped E-cadherin adhesions associated with radially oriented actin─but not irregularly shaped E-cadherin adhesions associated with circumferential actin foci─were much more numerous on 2.4 kPa E-cadherin substrates compared to 0.3 kPa E-cadherin substrates. However, the total amount of E-cadherin in both types of adhesions taken together was similar on the 0.3 and 2.4 kPa E-cadherin substrates across many cells. Our results show how the distribution of E-cadherin adhesions, supported by actin density and architecture, is modulated by epithelial cell-like elasticity and have significant implications for disease states like carcinomas characterized by altered epithelial cell elasticity.

Spatial confinement toward creating artificial living systems

Lifeforms are regulated by many physicochemical factors, and these factors could be controlled to play a role in the construction of artificial living systems. Among these factors, spatial confinement is an important one, which mediates biological behaviors at multiscale levels and participates in the biomanufacturing processes accordingly. This review describes how spatial confinement, as a fundamental biological phenomenon, provides cues for the construction of artificial living systems. Current knowledge about the role of spatial confinement in mediating individual cell behavior, collective cellular behavior, and tissue-level behavior are categorized. Endeavors on the synthesis of biomacromolecules, artificial cells, engineered tissues, and organoids in spatially confined bioreactors are then emphasized. After that, we discuss the cutting-edge applications of spatially confined artificial living systems in biomedical fields. Finally, we conclude by assessing the remaining challenges and future trends in the context of fundamental science, technical improvement, and practical applications.

The Galapagos Chip Platform for High-Throughput Screening of Cell Adhesive Chemical Micropatterns

In vivo cells reside in a complex extracellular matrix (ECM) that presents spatially distributed biochemical and -physical cues at the nano- to micrometer scales. Chemical micropatterning is successfully used to generate adhesive islands to control where and how cells attach and restore cues of the ECM in vitro. Although chemical micropatterning has become a powerful tool to study cell-material interactions, only a fraction of the possible micropattern designs was covered so far, leaving many other possible designs still unexplored. Here, a high-throughput screening platform called "Galapagos chip" is developed. It contains a library of 2176 distinct subcellular chemical patterns created using mathematical algorithms and a straightforward UV-induced two-step surface modification. This approach enables the immobilization of ligands in geometrically defined regions onto cell culture substrates. To validate the system, binary RGD/polyethylene glycol patterns are prepared on which human mesenchymal stem cells are cultured, and the authors observe how different patterns affect cell and organelle morphology. As proof of concept, the cells are stained for the mechanosensitive YAP protein, and, using a machine-learning algorithm, it is demonstrated that cell shape and YAP nuclear translocation correlate. It is concluded that the Galapagos chip is a versatile platform to screen geometrical aspects of cell-ECM interaction.

Integrin-Mediated Tumorigenesis and Its Therapeutic Applications

Integrins, a family of adhesion molecules generally exist on the cell surface, are essential for regulating cell growth and its function. As a bi-directional signaling molecule, they mediate cell-cell and cell-extracellular matrix interaction. The recognitions of their key roles in many human pathologies, including autoimmunity, thrombosis and neoplasia, have revealed their great potential as a therapeutic target. This paper focuses on the activation of integrins, the role of integrins in tumorigenesis and progression, and advances of integrin-dependent tumor therapeutics in recent years. It is expected that understanding function and signaling transmission will fully exploit potentialities of integrin as a novel target for tumors.

Improved epithelial cell-cell adhesion using molecular mobility of supramolecular surfaces

Cells can sense the surrounding microenvironmental properties including contact with biomaterials. Although in vitro cell fates in response to the physical properties of cell-adhesive materials have been widely reported, their influence on cell-cell adhesion is unclear. Here, we investigated the role of molecular mobility on polyrotaxane surfaces in epithelial cell-cell adhesion. Polyrotaxane surfaces with high mobility induced cytoplasmic yes-associated protein (YAP) localization in epithelial cells, whereas those with low mobility induced nuclear YAP localization, suggesting that YAP localization is switched by the mobility of the polyrotaxane surface. The cytoplasmic YAP localization increased the expression of tight junction-associated genes. A scratch assay revealed that although the epithelial cells on the low mobile surface rapidly initiated their migration, the cells on the highly mobile surface delayed their migration. Thus, this finding suggests that polyrotaxane surfaces with higher mobility induce cytoplasmic YAP localization, leading to stronger cell-cell adhesion. The polyrotaxane biointerface is promising as a powerful tool to improve the physical immune system and repair biological tissues.

Sticking together: Harnessing cadherin biology for tissue engineering

Directing cell behavior and building a tissue for therapeutic impact is the main goal of regenerative medicine, for which scientists need to modulate the interaction of cells with biomaterials. The focus of the field thus far has been on the incorporation of cues from the extracellular matrix but we propose that scientists take lessons from cell-cell adhesion proteins, more specifically cadherin biology, as these proteins make multicellularity possible. In this perspective, we re-examine cadherins through the lens of a tissue engineer for the purpose of advancing regenerative medicine. Furthermore, we summarize exciting developments in biomaterials inspired by cadherins and discuss some challenges and opportunities for the future. STATEMENT OF SIGNIFICANCE: Tissue engineers need tools to direct cell behavior. To date, tissue engineers have designed many sophisticated materials to positively influence cell behavior but are faced with the challenge where these materials sometimes work and sometimes fail. This uncertainty is a big unanswered question that challenges the community. We propose that tissue engineering could be more successful if they would take lessons from cell-cell adhesion proteins, more specifically cadherin biology. In the article, we discuss key structural and functional characteristics that make cadherins ideal for tissue engineering approaches. Furthermore, by providing a state-of-the-art overview of exemplary studies that have used cadherins to influence cell behavior, we show tissue engineers that they already have the tools necessary to incorporate this knowledge.

Tissue engineered bovine saphenous vein extracellular matrix scaffolds produced via antigen removal achieve high in vivo patency rates

Diseases of small diameter blood vessels encompass the largest portion of cardiovascular diseases, with over 4.2 million people undergoing autologous vascular grafting every year. However, approximately one third of patients are ineligible for autologous vascular grafting due to lack of suitable donor vasculature. Acellular extracellular matrix (ECM) scaffolds derived from xenogeneic vascular tissue have potential to serve as ideal biomaterials for production of off-the-shelf vascular grafts capable of eliminating the need for autologous vessel harvest. A modified antigen removal (AR) tissue process, employing aminosulfabetaine-16 (ASB-16) was used to create off-the-shelf small diameter (< 3 mm) vascular graft from bovine saphenous vein ECM scaffolds with significantly reduced antigenic content, while retaining native vascular ECM protein structure and function. Elimination of native tissue antigen content conferred graft-specific adaptive immune avoidance, while retention of native ECM protein macromolecular structure resulted in pro-regenerative cellular infiltration, ECM turnover and innate immune self-recognition in a rabbit subpannicular model. Finally, retention of the delicate vascular basement membrane protein integrity conferred endothelial cell repopulation and 100% patency rate in a rabbit jugular interposition model, comparable only to Autograft implants. Alternatively, the lack of these important basement membrane proteins in otherwise identical scaffolds yielded a patency rate of only 20%. We conclude that acellular antigen removed bovine saphenous vein ECM scaffolds have potential to serve as ideal off-the-shelf small diameter vascular scaffolds with high in vivo patency rates due to their low antigen content, retained native tissue basement membrane integrity and preserved native ECM structure, composition and functional properties. STATEMENT OF SIGNIFICANCE: The use of autologous vessels for the treatment of small diameter vascular diseases is common practice. However, the use of autologous tissue poses significant complications due to tissue harvest and limited availability. Developing an alternative vessel for use for the treatment of small diameter vessel diseases can potentially increase the success rate of autologous vascular grafting by eliminating complications related to the use of autologous vessel and increased availability. This manuscript demonstrates the potential of non-antigenic extracellular matrix (ECM) scaffolds derived from xenogeneic vascular tissue as off-the-shelf vascular grafts for the treatment of small diameter vascular diseases.

Enhancement of Endothelialization by Topographical Features Is Mediated by PTP1B-Dependent Endothelial Adherens Junctions Remodeling

Endothelial Cells (ECs) form cohesive cellular lining of the vasculature and play essential roles in both developmental processes and pathological conditions. Collective migration and proliferation of endothelial cells (ECs) are key processes underlying endothelialization of vessels as well as vascular graft, but the complex interplay of mechanical and biochemical signals regulating these processes are still not fully elucidated. While surface topography and biochemical modifications have been used to enhance endothelialization in vitro, thus far such single-modality modifications have met with limited success. As combination therapy that utilizes multiple modalities has shown improvement in addressing various intractable and complex biomedical conditions, here, we explore a combined strategy that utilizes topographical features in conjunction with pharmacological perturbations. We characterized EC behaviors in response to micrometer-scale grating topography in concert with pharmacological perturbations of endothelial adherens junctions (EAJ) regulators. We found that the protein tyrosine phosphatase, PTP1B, serves as a potent regulator of EAJ stability, with PTP1B inhibition synergizing with grating topographies to modulate EAJ rearrangement, thereby augmenting global EC monolayer sheet orientation, proliferation, connectivity, and collective cell migration. Our data delineates the crosstalk between cell-ECM topography sensing and cell-cell junction integrity maintenance and suggests that the combined use of grating topography and PTP1B inhibitor could be a promising strategy for promoting collective EC migration and proliferation.

VE-cadherin-based matrix promoting the self-reconstruction of pro-vascularization microenvironments and endothelial differentiation of human mesenchymal stem cells

Regulating the secretion and endothelial differentiation of human mesenchymal stem cells (hMSCs) plays an important role in the vascularization in tissue engineering and regenerative medicine. In this study, a recombinant cadherin fusion protein consisting of a human vascular endothelial-cadherin extracellular domain and immunoglobulin IgG Fc region (hVE-cad-Fc) was developed as a bioartificial matrix for modulating hMSCs. The hVE-cad-Fc matrix significantly enhanced the secretion of angiogenic factors, activated the VE-cadherin-VEGFR2/FAK-AKT/PI3K signaling pathway in hMSCs, and promoted the endothelial differentiation of hMSCs even without extra VEGF. Furthermore, the hVE-cad-Fc matrix was applied for the surface modification of a poly (lactic-co-glycolic acid) (PLGA) porous scaffold, which significantly improved the hemocompatibility and vascularization of the PLGA scaffold in vivo. These results revealed that the hVE-cad-Fc matrix should be a superior bioartificial ECM for remodeling the pro-vascularization extracellular microenvironment by regulating the secretion of hMSCs, and showed great potential for the vascularization in tissue engineering.

Nesprins are mechanotransducers that discriminate epithelial-mesenchymal transition programs

LINC complexes are transmembrane protein assemblies that physically connect the nucleoskeleton and cytoskeleton through the nuclear envelope. Dysfunctions of LINC complexes are associated with pathologies such as cancer and muscular disorders. The mechanical roles of LINC complexes are poorly understood. To address this, we used genetically encoded FRET biosensors of molecular tension in a nesprin protein of the LINC complex of fibroblastic and epithelial cells in culture. We exposed cells to mechanical, genetic, and pharmacological perturbations, mimicking a range of physiological and pathological situations. We show that nesprin experiences tension generated by the cytoskeleton and acts as a mechanical sensor of cell packing. Moreover, nesprin discriminates between inductions of partial and complete epithelial–mesenchymal transitions. We identify the implicated mechanisms, which involve α-catenin capture at the nuclear envelope by nesprin upon its relaxation, thereby regulating β-catenin transcription. Our data thus implicate LINC complex proteins as mechanotransducers that fine-tune β-catenin signaling in a manner dependent on the epithelial–mesenchymal transition program.

Collective migration during a gap closure in a two-dimensional haptotactic model

The ability of cells to respond to substrate-bound protein gradients is crucial for many physiological processes, such as immune response, neurogenesis and cancer cell migration. However, the difficulty to produce well-controlled protein gradients has long been a limitation to our understanding of collective cell migration in response to haptotaxis. Here we use a photopatterning technique to create circular, square and linear fibronectin (FN) gradients on two-dimensional (2D) culture substrates. We observed that epithelial cells spread preferentially on zones of higher FN density, creating rounded or elongated gaps within epithelial tissues over circular or linear FN gradients, respectively. Using time-lapse experiments, we demonstrated that the gap closure mechanism in a 2D haptotaxis model requires a significant increase of the leader cell area. In addition, we found that gap closures are slower on decreasing FN densities than on homogenous FN-coated substrate and that fresh closed gaps are characterized by a lower cell density. Interestingly, our results showed that cell proliferation increases in the closed gap region after maturation to restore the cell density, but that cell–cell adhesive junctions remain weaker in scarred epithelial zones. Taken together, our findings provide a better understanding of the wound healing process over protein gradients, which are reminiscent of haptotaxis.

Positive effect of Astragaloside IV on neurite outgrowth via talin-dependent integrin signaling and microfilament force

Integrin plays a prominent role in neurite outgrowth by transmitting both mechanical and chemical signals. Integrin expression is closely associated with Astragaloside IV (AS-IV), the main component extracted from Astragali radix, which has a positive effect on neural-protection. However, the relationship between AS-IV and neurite outgrowth has not been studied exhaustively to date. The present study investigated the underlying mechanism of AS-IV on neurite outgrowth. Longer neurites have been observed in SH-SY5Y cells or cortical neurons after AS-IV treatment. Furthermore, AS-IV not only increased the expression of integrin β but also activated it. The AS-IV-induced increased integrin activity was attributed to the integrin-activating protein talin. Application of the actin force probe showed that AS-IV led to an increase in intracellular microfilament force during neurite growth. Furthermore, in response to AS-IV, the microfilament force was regulated by talin and integrin activity during neurite growth. These results suggest that AS-IV has the ability to increase intracellular structural force and facilitate neurite elongation by integrin signaling, which highlights its therapeutic potential for neurite outgrowth.

You Talking to Me? Cadherin and Integrin Crosstalk in Biomaterial Design

While much work has been done in the design of biomaterials to control integrin-mediated adhesion, less emphasis has been put on functionalization of materials with cadherin ligands. Yet, cell-cell contacts in combination with cell-matrix interactions are key in driving embryonic development, collective cell migration, epithelial to mesenchymal transition, and cancer metastatic processes, among others. This review focuses on the incorporation of both cadherin and integrin ligands in biomaterial design, to promote what is called the "adhesive crosstalk." First, the structure and function of cadherins and their role in eliciting mechanotransductive processes, by themselves or in combination with integrin mechanosensing, are introduced. Then, biomaterials that mimic cell-cell interactions, and recent applications to get insights in fundamental biology and tissue engineering, are critically discussed.

Antiangiogenic Effect of Isomalyngamide A Riboside CY01 in Breast Cancer Cells via Inhibition of Migration, Tube Formation and pVEGFR2/pAKT Signals

BACKGROUND

To block the metastatic and angiogenic pathways during the tumor progression arouses considerable pharmacological interests in the development of anticancer drugs.

OBJECTIVE

To develop alternative antiangiogenic and antimetastic agents, we designed and prepared a series of nature inspired isomalyngamide A analogs containing ribose conjugate with 1,2-diaminoethane or 1,3- diaminopropane linkers (1-8).

METHODS

The target glycosylated isomalyngamide A analogs 1-8 were constructed through condensation of the malonic acids 16-19 and the corresponding aminoethoxyl ribosides 20 and 21, using HBTU/DIPEA as the coupling agent. The cell growth inhibition assay, cell migration assay, transwell invasion assay, adhesion assay, tube formation assay and western blot analysis were used to validate the biological actions of compounds.

RESULTS

The most effective compound, isomalyngamide A riboside 1 (CY01), possessing a D-ribose core structure and a 1,3-diaminopropane linker, showed significant suppression of MDA-MB-231 cell migration and inhibited tube formation of Human Umbilical Vascular Endothelial Cells (HUVECs) in a dose-dependent manner. Effect of the latter is comparable to that of sorafenib, an orally active multikinase inhibitor and an inhibitor of angiogenesis. CY01 also showed slight inhibition on collagen type IV- and laminin-mediated cell adhesion. These actions may be regulated through the blockade of the VEGF/VEGFR2 signaling pathway by inhibiting the VEGF induced phosphorylation of p-VEGFR2 and p-AKT.

CONCLUSION

In this effort, we have discovered synthetic and glycosylated marine metabolites which may serve as an alternative antiangiogenic and antimetastic agent during multitherapy.

Harnessing Mechanobiology for Tissue Engineering

A primary challenge in tissue engineering is to recapitulate both the structural and functional features of whole tissues and organs. In vivo, patterning of the body plan and constituent tissues emerges from the carefully orchestrated interactions between the transcriptional programs that give rise to cell types and the mechanical forces that drive the bending, twisting, and extensions critical to morphogenesis. Substantial recent progress in mechanobiology-understanding how mechanics regulate cell behaviors and what cellular machineries are responsible-raises the possibility that one can begin to use these insights to help guide the strategy and design of functional engineered tissues. In this perspective, we review and propose the development of different approaches, from providing appropriate extracellular mechanical cues to interfering with cellular mechanosensing machinery, to aid in controlling cell and tissue structure and function.

Quantifying cellular forces: Practical considerations of traction force microscopy for dermal fibroblasts

Traction force microscopy (TFM) is a well-established technique traditionally used by biophysicists to quantify the forces adherent biological cells exert on their microenvironment. As image processing software becomes increasingly user-friendly, TFM is being adopted by broader audiences to quantify contractility of (myo)fibroblasts. While many technical reviews of TFM's computational mechanics are available, this review focuses on practical experimental considerations for dermatology researchers new to cell mechanics and TFM who may wish to implement a higher throughput and less expensive alternative to collagen compaction assays. Here, we describe implementation of experimental methods, analysis using open-source software and troubleshooting of common issues to enable researchers to leverage TFM for their investigations into skin fibroblasts.

Mapping transmembrane binding partners for E-cadherin ectodomains

We combine proximity labeling and single molecule binding assays to discover transmembrane protein interactions in cells. We first screen for candidate binding partners by tagging the extracellular and cytoplasmic regions of a "bait" protein with BioID biotin ligase and identify proximal proteins that are biotin tagged on both their extracellular and intracellular regions. We then test direct binding interactions between proximal proteins and the bait, using single molecule atomic force microscope binding assays. Using this approach, we identify binding partners for the extracellular region of E-cadherin, an essential cell-cell adhesion protein. We show that the desmosomal proteins desmoglein-2 and desmocollin-3, the focal adhesion protein integrin-α2β1, the receptor tyrosine kinase ligand ephrin-B1, and the classical cadherin P-cadherin, all directly interact with E-cadherin ectodomains. Our data shows that combining extracellular and cytoplasmic proximal tagging with a biophysical binding assay increases the precision with which transmembrane ectodomain interactors can be identified.

What makes leader cells arise: Intrinsic properties and support from neighboring cells

Cancer cells collectively invading as a cohesive and polarized group is termed collective invasion, which is a fundamental property of many types of cancers. In this multicellular unit, cancer cells are heterogeneous, consisting of two morphologically and functionally distinct subpopulations, leader cells and follower cells. Leader cells at the invasive front are responsible for exploring the microenvironment, paving the way, and transmitting information to follower cells. Here, in this review, we will describe the important role of leader cells in collective invasion and the emerging underlying mechanisms of leader cell formation including intrinsic properties and the support from neighboring cells. It will help us to elucidate the essence of collective invasion and provide new anticancer therapeutic clues.

Engineering Elastic Nano- and Micro-Patterns and Textures for Directed Cell Motility

We present a reproducible protocol for fabrication of polyacrylamide (PAA) hydrogel-based nano-patterns and nano-textures with a wide range of elastic rigidities to study fundamental cell behaviors, such as mechanosensitivity and motility. We explore the benefits of this protocol by successfully testing the compatibility of the PAA platforms with super-resolution microscopy, which is largely unavailable with platforms of nano-scale textures made from different polymers. We also utilized soft and rigid nano-textures to study the mechanosensing basis of T cell behavior and phenotype.

For complete information on the generation and use of this protocol, please refer to Tabdanov et al. (2018b).

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Contact guidance cues are critical for directed cell migration in health and disease

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Manufacturing nano- and micro- scale patterns and textures with a wide range of rigidities

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The engineered platforms can be used to study motility in a wide range of cell types

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Deformable nano-textures are compatible with super-resolution imaging

Cell-Cell Adhesion-Driven Contact Guidance and Its Effect on Human Mesenchymal Stem Cell Differentiation

Contact guidance has been extensively explored using patterned adhesion functionalities that predominantly mimic cell-matrix interactions. Whether contact guidance can also be driven by other types of interactions, such as cell-cell adhesion, still remains a question. Herein, this query is addressed by engineering a set of microstrip patterns of (i) cell-cell adhesion ligands and (ii) segregated cell-cell and cell-matrix ligands as a simple yet versatile set of platforms for the guidance of spreading, adhesion, and differentiation of mesenchymal stem cells. It was unprecedently found that micropatterns of cell-cell adhesion ligands can induce contact guidance. Surprisingly, it was found that patterns of alternating cell-matrix and cell-cell strips also induce contact guidance despite providing a spatial continuum for cell adhesion. This guidance is believed to be due to the difference between the potencies of the two adhesions. Furthermore, patterns that combine the two segregated adhesion functionalities were shown to induce more human mesenchymal stem cell osteogenic differentiation than monofunctional patterns. This work provides new insight into the functional crosstalk between cell-cell and cell-matrix adhesions and, overall, further highlights the ubiquitous impact of the biochemical anisotropy of the extracellular environment on cell function.

Enhancement of aberrantly modified integrin‑mediated cell motility in multicellular tumor spheroids

Multicellular tumor spheroids (MTSs) of malignant cells can display cell‑cell and cell‑matrix interactions, different from monolayer cultures. The objective of the present study was to examine difference in intercellular and cell‑matrix interaction between monolayered cultures and spheroid cultures. Expression levels of cell adhesion molecules (CAMs) and epithelial‑mesenchymal transition (EMT) signaling molecules in monolayered cells and MTS cells were compared. The motility of single cells dispersed from each culture was evaluated using a live‑cell imaging device. The effect of an E‑cadherin neutralizing antibody, DECMA, was also compared between the two cultures. Among various CAMs, only E‑cadherin was increased in MTSs. The motility of single cells dispersed from MTSs was higher than that from monolayered cells. Compared with monolayered cells, the molecular weight (MW) of β1 integrin was decreased during MTS formation, particularly during the early stage. This notable reduction was maintained when DECMA was used to treat MTSs. Additionally, the expression levels of the EMT signaling molecules Snail and ILK increased more in MTSs than in monolayered cells. The blocking of E‑cadherin elicited increased expression levels of EMT molecules and cellular motility only in MTSs. In conclusion, the alteration of E‑cadherin expression and presence of low‑MW β1 integrin in MTS may enhance cell motility via the upregulation of EMT signaling molecules that may be intensified by blocking E‑cadherin.

Desmocollin-2 promotes intestinal mucosal repair by controlling integrin-dependent cell adhesion and migration

The intestinal mucosa is lined by a single layer of epithelial cells that forms a tight barrier, separating luminal antigens and microbes from underlying tissue compartments. Mucosal damage results in a compromised epithelial barrier that can lead to excessive immune responses as observed in inflammatory bowel disease. Efficient wound repair is critical to reestablish the mucosal barrier and homeostasis. Intestinal epithelial cells (IEC) exclusively express the desmosomal cadherins, Desmoglein-2 and Desmocollin-2 (Dsc2) that contribute to mucosal homeostasis by strengthening intercellular adhesion between cells. Despite this important property, specific contributions of desmosomal cadherins to intestinal mucosal repair after injury remain poorly investigated in vivo. Here we show that mice with inducible conditional knockdown (KD) of Dsc2 in IEC (Villin-Cre^ERT2; Dsc2 ^fl/fl) exhibited impaired mucosal repair after biopsy-induced colonic wounding and recovery from dextran sulfate sodium-induced colitis. In vitro analyses using human intestinal cell lines after KD of Dsc2 revealed delayed epithelial cell migration and repair after scratch-wound healing assay that was associated with reduced cell–matrix traction forces, decreased levels of integrin β1 and β4, and altered activity of the small GTPase Rap1. Taken together, these results demonstrate that epithelial Dsc2 is a key contributor to intestinal mucosal wound healing in vivo.

Small Diameter Xenogeneic Extracellular Matrix Scaffolds for Vascular Applications

Currently, despite the success of percutaneous coronary intervention (PCI), coronary artery bypass graft (CABG) remains among the most commonly performed cardiac surgical procedures in the United States. Unfortunately, the use of autologous grafts in CABG presents a major clinical challenge as complications due to autologous vessel harvest and limited vessel availability pose a significant setback in the success rate of CABG surgeries. Acellular extracellular matrix (ECM) scaffolds derived from xenogeneic vascular tissues have the potential to overcome these challenges, as they offer unlimited availability and sufficient length to serve as "off-the-shelf" CABGs. Unfortunately, regardless of numerous efforts to produce a fully functional small diameter xenogeneic ECM scaffold, the combination of factors required to overcome all failure mechanisms in a single graft remains elusive. This article covers the major failure mechanisms of current xenogeneic small diameter vessel ECM scaffolds, and reviews the recent advances in the field to overcome these failure mechanisms and ultimately develop a small diameter ECM xenogeneic scaffold for CABG. Impact Statement Currently, the use of autologous vessel in coronary artery bypass graft (CABG) is common practice. However, the use of autologous tissue poses significant complications due to tissue harvest and limited availability. Developing an alternative vessel for use in CABG can potentially increase the success rate of CABG surgery by eliminating complications related to the use of autologous vessel. However, this development has been hindered by an array of failure mechanisms that currently have not been overcome. This article describes the currently identified failure mechanisms of small diameter vascular xenogeneic extracellular matrix scaffolds and reviews current research targeted to overcoming these failure mechanisms toward ensuring long-term graft patency.

Tissue Regeneration from Mechanical Stretching of Cell-Cell Adhesion

Cell-cell adhesion complexes are macromolecular adhesive organelles that integrate cells into tissues. This mechanochemical coupling in cell-cell adhesion is required for a large number of cell behaviors, and perturbations of the cell-cell adhesion structure or related mechanotransduction pathways can lead to critical pathological conditions such as skin and heart diseases, arthritis, and cancer. Mechanical stretching has been a widely used method to stimulate the mechanotransduction process originating from the cell-cell adhesion and cell-extracellular matrix (ECM) complexes. These studies aimed to reveal the biophysical processes governing cell proliferation, wound healing, gene expression regulation, and cell differentiation in various tissues, including cardiac, muscle, vascular, and bone. This review explores techniques in mechanical stretching in two-dimensional settings with different stretching regimens on different cell types. The mechanotransduction responses from these different cell types will be discussed with an emphasis on their biophysical transformations during mechanical stretching and the cross talk between the cell-cell and cell-ECM adhesion complexes. Therapeutic aspects of mechanical stretching are reviewed considering these cellular responses after the application of mechanical forces, with a focus on wound healing and tissue regeneration. Impact Statement Mechanical stretching has been proposed as a therapeutic option for tissue regeneration and wound healing. It has been accepted that mechanotransduction processes elicited by mechanical stretching govern cellular response and behavior, and these studies have predominantly focused on the cell-extracellular matrix (ECM) sites. This review serves the mechanobiology community by shifting the focus of mechanical stretching effects from cell-ECM adhesions to the less examined cell-cell adhesions, which we believe play an equally important role in orchestrating the response pathways.

Primary cilium loss in mammalian cells occurs predominantly by whole-cilium shedding

The primary cilium is a central signaling hub in cell proliferation and differentiation and is built and disassembled every cell cycle in many animal cells. Disassembly is critically important, as misregulation or delay of cilia loss leads to cell cycle defects. The physical means by which cilia are lost are poorly understood but are thought to involve resorption of ciliary components into the cell body. To investigate cilium loss in mammalian cells, we used live-cell imaging to comprehensively characterize individual events. The predominant mode of cilium loss was rapid deciliation, in which the membrane and axoneme of the cilium was shed from the cell. Gradual resorption was also observed, as well as events in which a period of gradual resorption was followed by rapid deciliation. Deciliation resulted in intact shed cilia that could be recovered from culture medium and contained both membrane and axoneme proteins. We modulated levels of katanin and intracellular calcium, two putative regulators of deciliation, and found that excess katanin promotes cilia loss by deciliation, independently of calcium. Together, these results suggest that mammalian ciliary loss involves a tunable decision between deciliation and resorption.

Surface Immobilized E-Cadherin Mimetic Peptide Regulates the Adhesion and Clustering of Epithelial Cells

Cadherin mimetic peptides are widely used in synthetic biomaterials to mimic cell-cell adhesion in cell microniches. This mimicry regulates various cell behaviors. Although the interaction between immobilized cadherin and cells is investigated in numerous studies, the exact manner of functioning of cadherin mimetic peptides is yet to be fully understood. Cadherin mimetic peptides mimic only the critical amino acid sequence of cadherin and are not equal to these proteins in function. Compared to the cadherin proteins, mimetic peptides are more stable, easier to fabricate, and exhibit a precise chemical composition. In this study the E-cadherin mimetic peptide His-Ala-Val (HAV) on material surfaces is immobilized and epithelial cell adhesion and clustering are studied. The results suggest that immobilized HAV peptides specifically interact with E-cadherin on the cell membrane, resulting in an increased expression of E-cadherin and its downstream signaling protein β-catenin. This interaction relocates E-cadherin-based adhesion from the cell-cell interface to the cell-materials interface, which promotes cell adhesion via mechanosensing and initiates a transition in the cell cluster from a solid-like to a fluid-like state. The study presents an overview of the interactions between E-cadherin mimetic peptide and epithelial cells to aid in the design of novel biomaterials.

Cadherin mechanotransduction in leader-follower cell specification during collective migration

Collective invasion drives the spread of multicellular cancer groups, into the normal tissue surrounding several epithelial tumors. Collective invasion recapitulates various aspects of the multicellular organization and collective migration that take place during normal development and repair. Collective migration starts with the specification of leader cells in which a polarized, migratory phenotype is established. Leader cells initiate and organize the migration of follower cells, to allow the group of cells to move as a cohesive and polarized unit. Leader-follower specification is essential for coordinated and directional collective movement. Forces exerted by cohesive cells represent key signals that dictate multicellular coordination and directionality. Physical forces originate from the contraction of the actomyosin cytoskeleton, which is linked between cells via cadherin-based cell-cell junctions. The cadherin complex senses and transduces fluctuations in forces into biochemical signals that regulate processes like cell proliferation, motility and polarity. With cadherin junctions being maintained in most collective movements the cadherin complex is ideally positioned to integrate mechanical information into the organization of collective cell migration. Here we discuss the potential roles of cadherin mechanotransduction in the diverse aspects of leader versus follower cell specification during collective migration and neoplastic invasion.

Remodeling the Microenvironment before Occurrence and Metastasis of Cancer

Tumorigenesis and progression of cancer are complex processes which transformed cells and stromal cells interact and co-evolve. Intrinsic and extrinsic factors cause the mutations of cells. The survival of transformed cells critically depends on the circumstances which they reside. The malignant transformed cancer cells reprogram the microenvironment locally and systemically. The formation of premetastatic niche in the secondary organs facilitates cancer cells survival in the distant organs. This review outlines the current understanding of the key roles of premalignant niche and premetastatic niche in cancer progression. We proposed that a niche facilitates survival of transformed cells is characteristics of senescence, stromal fibrosis and obese microenvironment. We also proposed the formation of premetastatic niche in secondary organs is critically influenced by primary cancer cells. Therefore, it suggested that strategies to target the niche can be promising approach to eradicate cancer cells.

Bimodal sensing of guidance cues in mechanically distinct microenvironments

Contact guidance due to extracellular matrix architecture is a key regulator of carcinoma invasion and metastasis, yet our understanding of how cells sense guidance cues is limited. Here, using a platform with variable stiffness that facilitates uniaxial or biaxial matrix cues, or competing E-cadherin adhesions, we demonstrate distinct mechanoresponsive behavior. Through disruption of traction forces, we observe a profound phenotypic shift towards a mode of dendritic protrusion and identify bimodal processes that govern guidance sensing. In contractile cells, guidance sensing is strongly dependent on formins and FAK signaling and can be perturbed by disrupting microtubule dynamics, while low traction conditions initiate fluidic-like dendritic protrusions that are dependent on Arp2/3. Concomitant disruption of these bimodal mechanisms completely abrogates the contact guidance response. Thus, guidance sensing in carcinoma cells depends on both environment architecture and mechanical properties and targeting the bimodal responses may provide a rational strategy for disrupting metastatic behavior.

Invasive cells respond to contact guidance cues during migration. Here, using micro- and nanopatterning with different ligands and varying stiffness, the authors find that cells can make cellular protrusions through both contractility-dependent and contractility-independent means.

Untangling the response of bone tumor cells and bone forming cells to matrix stiffness and adhesion ligand density by means of hydrogels

How cancer cells and their anchorage-dependent normal counterparts respond to the adhesion ligand density and stiffness of the same extracellular matrix (ECM) is still not very clear. Here we investigated the effects of ECM adhesion ligand density and stiffness on bone tumor cells (osteosarcoma cells) and bone forming cells (osteoblasts) by using poly (ethylene glycol) diacrylate (PEGDA) and methacrylated gelatin (GelMA) hydrogels. By independently changing the PEGDA and GelMA content in the hydrogels, we achieved crosslinked hydrogel matrix with independently tunable stiffness (1.6, 6 and 25 kPa for 5%, 10%, 15% PEDGA, respectively) and adhesion ligand density (low, medium and high for 0.05%, 0.2%, 0.5% GelMA respectively). By using a series of biochemical and cell biological characterizations as well as in vivo studies, we confirmed that osteosarcoma and osteoblastic cells responded differently to the stiffness and adhesion ligand density within 3D ECM. When cultured within the 3D PEGDA/GelMA hydrogel matrix, osteosarcoma cells are highly dependent on the matrix stiffness via regulating the integrin-mediated focal adhesion (FA) pathway, whereas osteoblasts are highly sensitive to the matrix adhesion ligand density through regulating the integrin-mediated adherens junction (AJ) pathway. However, when seeded on the 2D surface of the hydrogels, osteosarcoma cells behaved differently and became sensitive to the matrix adhesion ligand density because they were "forced" to attach to the substrate, similar to anchorage-dependent osteoblasts. This study might provide new insights into rational design of scaffolds for generating in vitro tumor models to test anticancer therapeutics and for regenerating tissue to repair defects.

Every step of the way: integrins in cancer progression and metastasis

Cell adhesion to the extracellular matrix is fundamental to tissue integrity and human health. Integrins are the main cellular adhesion receptors that through multifaceted roles as signalling molecules, mechanotransducers and key components of the cell migration machinery are implicated in nearly every step of cancer progression from primary tumour development to metastasis. Altered integrin expression is frequently detected in tumours, where integrins have roles in supporting oncogenic growth factor receptor (GFR) signalling and GFR-dependent cancer cell migration and invasion. In addition, integrins determine colonization of metastatic sites and facilitate anchorage-independent survival of circulating tumour cells. Investigations describing integrin engagement with a growing number of versatile cell surface molecules, including channels, receptors and secreted proteins, continue to lead to the identification of novel tumour-promoting pathways. Integrin-mediated sensing, stiffening and remodelling of the tumour stroma are key steps in cancer progression supporting invasion, acquisition of cancer stem cell characteristics and drug resistance. Given the complexity of integrins and their adaptable and sometimes antagonistic roles in cancer cells and the tumour microenvironment, therapeutic targeting of these receptors has been a challenge. However, novel approaches to target integrins and antagonism of specific integrin subunits in stringently stratified patient cohorts are emerging as potential ways forward.