Cell migration: integrating signals from front to back

Emergence of multiple collective motility modes in a physical model of cell chains

Collective cell migration is central to processes like development and cancer metastasis. While mechanisms of collective motility are increasingly understood, their classification remains incomplete. Here, we study the migration of small cell chains, namely cohesive pairs. Experiments with Dictyostelium discoideum (Dd) revealed two motility modes: the individual contributor (IC) mode, where each cell generates its own traction dipole, and the supracellular (S) mode, characterized by a single dipole. Dd pairs favored the IC mode, while Madin-Darby canine kidney (MDCK) doublets predominantly used the S mode. A 2D biophysical model recapitulated many experimental observations; the IC mode emerged naturally in ameboid Dd doublets when both cells exerted similar traction stresses, while the S mode dominated with stronger leaders. Contrary to amebas, MDCK-like cell chains showed a bias towards the IC mode when increasing cell-cell adhesion. Extending the model to longer chains, we show its potential for understanding emergent migration patterns across cell types and scales.

Nanoscale structural dynamics of cell edges in breast tumour cells revealed by scanning ion conductance microscopy

Cell migration plays a critical role in biological processes such as embryonic development, wound healing, cancer metastasis, and immune response. While the molecular mechanisms regulating cell movement are well-studied, bridging the gap between these mechanisms and macroscopic cell behaviour remains a significant challenge due to the disparity in scale. At the subcellular level, an intermediate scale between molecular and cellular scales, cell membranes exhibit complex structural dynamics that are difficult to quantify and poorly understood. In this study, we utilized time-lapse scanning ion conductance microscopy to visualise subcellular nanoscale structural dynamics at the edges of breast cancer cells. Through quantitative analysis, we successfully identified three key features: (1) dynamic edges with abundant filopodia, (2) an inverse relationship between the local cell migration rate and lamellipodia thickness, and (3) changes in the length and distance between cytoskeleton-filament-related structures following a Poisson process. These findings provide new insights into cell migration dynamics and contribute to bridging the gap between macroscopic and microscopic cellular motion.

Matrix Remodeling Associated Genes (MXRAs): structural diversity, functional significance, and therapeutic potential in tumor microenvironments

The Matrix Remodeling Associated Genes (MXRAs) family, comprising eight distinct members (MXRA1-8), plays a crucial role in the development and maintenance of higher vertebrate cells. These proteins are primarily involved in the regulation of intercellular adhesion and the remodeling of the extracellular matrix (ECM). Recent investigations have highlighted the significant roles of MXRAs in the modulation of tumor growth and progression, establishing them as vital components in the oncogenic landscape. Notably, each MXRA member exhibits unique structural characteristics and functional properties, contributing to a diverse array of regulatory effects within the tumor context. This review seeks to provide a comprehensive analysis of the structural attributes, functional contributions, and activities of MXRAs within the tumor microenvironment. By elucidating the underlying mechanisms of action, this paper aims to offer novel insights and strategic approaches for the identification of early diagnostic biomarkers, as well as potential therapeutic targets that may facilitate molecular interventions aimed at inhibiting tumor development.

Competing signaling pathways controls electrotaxis

Understanding how cells follow exogenous cues is a key question for biology, medicine, and bioengineering. Growing evidence shows that electric fields represent a precise and programmable method to control cell migration. Most data suggest that the polarization of membrane proteins and the following downstream signaling are central to electrotaxis. Unfortunately, how these multiple mechanisms coordinate with the motile machinery of the cell is still poorly understood. Here, we develop a mechanistic model that explains electrotaxis across different cell types. Using the zebrafish proteome, we identify membrane proteins directly related to migration signaling pathways that polarize anodally and cathodally. Further, we show that the simultaneous and asymmetric distribution of these membrane receptors establish multiple cooperative and competing stimuli for directing the anodal and cathodal migration of the cell. Using electric fields, we enhance, cancel, or switch directed cell migration, with clear implications in promoting tissue regeneration or arresting tumor progression.

Cell deformations generated by stochastic actomyosin waves drive in vivo random-walk swimming migration

Amoeboid cell migration drives many developmental and disease-related processes, including immune responses and cancer metastasis. Swimming migration is a subtype of amoeboid migration that is observed in cells in suspension ex vivo. However, the mechanism underlying swimming migration in vivo is unknown. Using Drosophila fat body cells (FBCs) as a model, we show that FBCs actively swim to patrol the pupa by random walk. Their migration is powered through actomyosin waves that exert compressive forces as they travel to the cell rear, causing cell deformations. Unlike in other types of amoeboid migration, Rho1 (the Drosophila orthologue of RhoA), Cdc42 and Rac1 are all required for regulation of formin-driven actin polymerization during FBC migration. We find that Rho1 at the cell rear induces actomyosin contractions via Rho kinase and myosin II. We show that contractile actin waves display a stochastic behaviour, inducing either cell elongation or rounding, suggesting that non-reciprocal cell deformations drive locomotion. Importantly, our work in a physiological system reveals that stochastic actomyosin waves promote random-walk swimming migration to enable fast, long-range cell dispersal. We propose that this individualist migration behaviour collectively allows patrolling of the pupal body.

Integration of focal adhesion morphogenesis and polarity by DOCK5 promotes YAP/TAZ-driven drug resistance in TNBC

YAP and TAZ are transcriptional co-activators that are inhibited by sequestration in the cytoplasm. Cellular signalling pathways integrate soluble, mechanical (cytoskeleton, adhesion), and geometric (cell size, morphology) cues to regulate the translocation of YAP/TAZ to the nucleus. In triple-negative breast cancer (TNBC) cells, both signalling and morphogenesis are frequently rewired, leading to increased YAP/TAZ translocation, which drives proliferation, invasion, and drug resistance. However, whether this increased YAP/TAZ translocation is due to alterations in upstream signalling events or changes in cell morphology remains unclear. To gain insight into YAP/TAZ regulation in TNBC cells, we performed multiplexed quantitative genetic screens for YAP/TAZ localisation and cell shape, enabling us to determine whether changes in YAP/TAZ localisation following gene knockdown could be explained by alterations in cell morphology. These screens revealed that the focal adhesion (FA)-associated RhoGEF DOCK5 is essential for YAP/TAZ nuclear localisation in TNBC cells. DOCK5-defective cells exhibit defects in FA morphogenesis and fail to generate a stable, polarised leading edge, which we propose contributes to impaired YAP/TAZ translocation. Mechanistically, we implicate DOCK5's ability to act as a RacGEF and as a scaffold for NCK/AKT as key to its role in FA morphogenesis. Importantly, DOCK5 is essential for promoting the resistance of LM2 cells to the clinically used MEK inhibitor Binimetinib. Taken together, our findings suggest that DOCK5's role in TNBC cell shape determination drives YAP/TAZ upregulation and drug resistance.

TGFβ1 and RGD Cooperatively Regulate SMAD2/3-Mediated Oncogenic Effects in Prostate Cancer Cells in Bio-Orthogonally Constructed Hydrogels

To recapitulate prostate cancer metastasis, DU145 cells were cultured in a hyaluronic acid-based, bio-orthogonally constructed, protease-degradable hydrogels. In the presence of a covalently conjugated integrin-binding peptide (GRGDSP), DU145 cells formed tumoroids and exhibited small protrusions. Upon addition of soluble transforming growth factor beta 1 (TGFβ1), cells underwent morphological changes to form extended interconnected cellular networks. Contrarily, in RGD-free hydrogels, cells maintained spherical structures even in the presence of TGFβ1. In RGD-conjugated hydrogels, TGFβ1 induced nuclear localization of SMAD2/3, upregulating a wide range of TGFβ1 target genes and proteins. Prolonged exposure to TGFβ1 led to matrix remodeling and induced epithelial-to-mesenchymal transition in DU145 cells, with loss of epithelial markers and gain of mesenchymal markers. A pharmacological inhibitor of TGFβRI/ALK5, SB-431542, attenuated TGFβ1-induced morphological changes, abrogated nuclear localization of SMAD2/3, and restored the expression of key epithelial markers. Our findings highlight the cooperative role of TGFβ1 signaling and integrin-binding peptide in the acquisition of an aggressive phenotype and the promotion of tumor progression.

MARK2 regulates Golgi apparatus reorientation by phosphorylation of CAMSAP2 in directional cell migratio

The reorientation of the Golgi apparatus is crucial for cell migration and is regulated by multipolarity signals. A number of non-centrosomal microtubules anchor at the surface of the Golgi apparatus and play a vital role in the Golgi reorientation, but how the Golgi are regulated by polarity signals remains unclear. Calmodulin-regulated spectrin-associated protein 2 (CAMSAP2) is a protein that anchors microtubules to the Golgi, a cellular organelle. Our research indicates that CAMSAP2 is dynamically localized at the Golgi during its reorientation processing. Further research shows that CAMSAP2 is potentially regulated by a polarity signaling molecule called MARK2, which interacts with CAMSAP2. We used mass spectrometry to find that MARK2 phosphorylates CAMSAP2 at serine-835, which affects its interaction with the Golgi-associated protein USO1 but not with CG-NAP or CLASPs. This interaction is critical for anchoring microtubules to the Golgi during cell migration, altering microtubule polarity distribution, and aiding Golgi reorientation. Our study reveals an important signaling pathway in Golgi reorientation during cell migration, which can provide insights for research in cancer cell migration, immune response, and targeted drug development.

Cell signaling facilitates apical constriction by basolaterally recruiting Arp2/3 via Rac and WAVE

Apical constriction is a critical cell shape change that drives cell internalization and tissue bending. How precisely localized actomyosin regulators drive apical constriction remains poorly understood. Caenorhabditis elegans gastrulation provides a valuable model to address this question. The Arp2/3 complex is essential in C. elegans gastrulation. To understand how Arp2/3 is locally regulated, we imaged embryos with endogenously tagged Arp2/3 and its nucleation-promoting factors (NPFs). The three NPFs-WAVE, WASP, and WASH-controlled Arp2/3 localization at distinct subcellular locations. We exploited this finding to study distinct populations of Arp2/3 and found that only WAVE depletion caused penetrant gastrulation defects. WAVE localized basolaterally with Arp2/3 and controlled F-actin levels near cell-cell contacts. WAVE and Arp2/3 localization depended on CED-10/Rac. Establishing ectopic cell contacts recruited WAVE and Arp2/3, identifying the contact as a symmetry-breaking cue for localization of these proteins. These results suggest that cell-cell signaling via Rac activates WAVE and Arp2/3 basolaterally and that basolateral Arp2/3 makes an important contribution to apical constriction.

Exploring the spatio-temporal dynamics in activator-inhibitor systems through a dual approach of analysis and computation

Real-world mathematical models often manifest as systems of non-linear differential equations, which presents challenges in obtaining closed-form analytical solutions. In this paper, we study the diffusion-driven instability of an activator-inhibitor-type reaction-diffusion (RD) system modeling the GEF-Rho-Myosin signaling pathway linked to cellular contractility. The mathematical model we study is formulated from first principles using experimental observations. The model formulation is based on the biological and mathematical assumptions. The novelty is the incorporation of Myo9b as a GAP for RhoA, leading to a new mathematical model that describes Rho activity dynamics linked to cell contraction dynamics. Assuming mass conservation of molecular species and adopting a quasi-steady state assumption based on biological observations, model reduction is undertaken and leads us to a system of two equations. We adopt a dual approach of mathematical analysis and numerical computations to study the spatiotemporal dynamics of the system. First, in absence of diffusion, we use a combination of phase-plane analysis, numerical bifurcation and simulations to characterize the temporal dynamics of the model. In the absence of spatial variations, we identified two sets of parameters where the model exhibit different transition dynamics. For some set of parameters, the model transitions from stable to oscillatory and back to stable, while for another set, the model dynamics transition from stable to bistable and back to stable dynamics. To study the effect of parameter variation on model solutions, we use partial rank correlation coefficient (PRCC) to characterize the sensitivity of the model steady states with respect to parameters. Second, we extend the analysis of the model by studying conditions under which a uniform steady state becomes unstable in the presence of spatial variations, in a process known as Turing diffusion-driven instability. By exploiting the necessary conditions for diffusion-driven instability and the sufficient conditions for pattern formation we carry out, numerically, parameter estimation through the use of mode isolation. To support theoretical and computational findings, we employ the pdepe solver in one-space dimension and the finite difference method in two-space dimension.

Nanofibrous Guidance Conduits with Multiple Gradient Cues for Spinal Cord Repair

Spinal cord injury (SCI) is a debilitating condition that leads to severe disabilities and imposes significant economic and social burdens. Current therapeutic strategies primarily focus on symptom management, with limited success in promoting full neurological recovery. In response to this challenge, the design of novel guidance conduits incorporating multiple gradient cues, inspired is reported by biological processes, to enhance spinal cord repair. These conduits are fabricated using electrospinning and masked coaxial electrospraying, a simple yet effective method that integrates topological, haptotactic, and chemotactic cues into a single scaffold. The synergy of these cues significantly promoted cell migration, neural stem cell differentiation into neurons, and axonal extension, resulting in substantial improvements in spinal cord regeneration and functional recovery in a rat model. Single-nucleus RNA sequencing further demonstrated that the guidance conduit inhibited fibroblast proliferation, preserved microglial homeostasis, restored cellular proportions, and facilitated the regeneration of neuronal axons, dendrites, and synapses. This work presents an innovative, versatile platform for fabricating tissue scaffolds that integrate multiple gradient cues, offering a promising strategy for SCI treatment and broader tissue regeneration applications.

Disrupting Cdc42 activation-driven filopodia formation with low-intensity ultrasound and microbubbles: A novel strategy to block ovarian cancer metastasis

Metastasis is a primary cause of mortality and treatment failure in ovarian cancer, with limited effective therapeutic strategies. Low-intensity ultrasound (LIUS) and microbubbles (MBs) has been demonstrated as an adjunctive technique capable of enhancing drug delivery and suppressing tumor metastasis. However, the underlying mechanisms remain incompletely understood. In this study, we aimed to investigate whether LIUS + MBs alone could suppress tumor metastasis and to explore its mechanism of action through disruption of the cytoskeletal remodeling in filopodia, an essential structure in the early stages of cancer cell dissemination. Based on cell-based experiments to determine the optimal parameters, our results showed LIUS + MBs significantly inhibited the migration and invasion of ovarian cancer cells. In vivo, LIUS + MBs treatment markedly suppressed the overall metastasis in the orthotopic ovarian cancer model, and in both the intraperitoneal and hematogenous metastatic models established by injecting pretreated cells. Morphologically, such treatment led to a notable reduction in the length and number of filopodia, while the number of lamellipodia remained unaffected. At the molecular level, LIUS + MBs disturbed filopodia formation and the metastatic potential of ovarian cancer cells by suppressing the activation of Cdc42, a key regulator of cytoskeletal dynamics. The inhibitory effect was reversed by the overexpression of Cdc42CA. Further proteomic and bioinformatics analysis implied that LIUS + MBs may reduce Cdc42 activity by upregulating the expression of GTPase-activating proteins (GAPs). Our research provides novel insight into the mechanism by which LIUS + MBs can inhibit tumor metastasis, highlighting its role in disturbing the Cdc42-mediated cytoskeletal remodelling of filopodia.

In Situ "Confocal" Electrochemiluminescence 3D Imaging: From Cell to Tissue Section

Endowing electrochemiluminescence (ECL) imaging technique with three-dimensional (3D) resolution to investigate specimens at varying axial depths poses a challenging yet significant objective. Herein, a "confocal" 3D ECL imaging method was developed using luminol as ECL probe, in which excited luminophore was formed in the vicinity of electrode surface through homogeneous chemical reactions between oppositely diffusing ECL precursors, luminol diazaquinone intermediate (L), and hydrogen peroxide (H2O2), confining the ECL emission in a thin plane (ECL focal plane) parallel to electrode surface at their intersection. The regulating ability of electrochemical method on the reaction fluxes of L and H2O2 was validated, regulating the axial location of the ECL focal plane from 0 to 63 µm, which can even extend to 400 µm by using the stable coreactant of ClO-. Leveraging the optical sectioning capability of the ECL focal plane, the "confocal" 3D ECL imaging method was applied to bioimaging, from cells to tissue sections. It revealed cellular morphology changes during cell polarity establishment and the heterogeneous distribution of complex tubule structure in kidney tissue sections. The optical sectioning capability of "confocal" 3D ECL imaging makes it a powerful tool for studying complex biological samples.

Probiotics promote cellular wound healing responses by modulating the PI3K and TGF-β/Smad signaling pathways

BACKGROUND

Skin wound healing represents a dynamic and intricate biological process involving the coordinated efforts of various cellular and molecular components to restore tissue integrity and functionality. Among the myriads of cellular events orchestrating wound closure, fibroblast migration and the regulation of fibrosis play pivotal roles in determining the outcome of wound healing. In recent years, probiotic therapy has emerged as a promising strategy for modulating wound healing and fibrosis. Here, we aim to investigate the effect of bacterial probiotics on cell migration and anti-fibrotic response of human dermal fibroblast (HDFs).

METHODS

Probiotic mixture BioK was co-cultured with HDFs in vitro to assess its impact on fibroblast migration, gene expression, and protein production associated with important processes in wound healing. Gene expression was investigated by transcriptomic analysis and confirmed by RT-qPCR. Protein levels of the identified genes were evaluated by ELISA. The role of lactic acid, produced by BioK, in mediating pH-related effects on fibroblast activity was further examined.

RESULTS

We observed that BioK effectively promoted HDFs migration in vitro, which was found to be related to the up-regulation of genes involved in the phosphoinositide 3-kinase (PI3K) signaling pathways such as Paxillin, PI3K, PKC and ITG-β1. Interestingly, we also found that BioK down-regulated the expression of Nox-4, α-SMA and Col-I in TGF-Smad signaling pathways, which are involved in the differentiation of fibroblasts to myofibroblasts, and extracellular matrix type I collagen production, demonstrating its potential in reducing formation of fibrosis and scars. One of the acting factors for such down-regulation was identified to be BioK-produced lactic acid, which is known to lower the surrounding pH and to play a major role in fibroblast activity and wound healing.

CONCLUSIONS

This study demonstrates BioK's beneficial effects on fibroblast migration and its potential to mitigate fibrosis through pH modulation and pathway-specific gene regulation. These findings enhance our understanding of probiotic action on wound healing and offer promising therapeutic insights for the reduction of scar formation.

CLINICAL TRIAL NUMBER

Not applicable.

The impact of common redox mediators on cellular health: a comprehensive study

Electrochemistry has become a key technique for studying biomolecular reactions and dynamics of living systems by using electron-transfer reactions to probe the complex interactions between biological redox molecules and their surrounding environments. To enable such measurements, redox mediators such as ferro/ferricyanide, ferrocene methanol, and tris(bipyridine) ruthenium(II) chloride are used. However, the impact of these exogeneous redox mediators on the health of cell cultures remains underexplored. Herein, we present the effects of three common redox mediators on the health of four of the most commonly used cell lines (Panc1, HeLa, U2OS, and MDA-MB-231) in biological studies. Cell health was assessed using three independent parameters: reactive oxygen species quantification by fluorescence flow cytometry, cell migration through scratch assays, and cell growth via luminescence assays. We show that as the concentration of mediator exceeds 1 mM, ROS increases in all cell types while cell viability plumets. In contrast, cell migration was only hindered at the highest concentration of each mediator. Our observations highlight the crucial role that optimized mediator concentrations play in ensuring accuracy when studying biological systems by electrochemical methods. As such, these findings provide a critical reference for selecting redox mediator concentrations for bioanalytical studies on live cells.

Interaction of Gαi2 with EB1 controls microtubule dynamics and Rac1 activity in Xenopus neural crest cell migration

Cell migration is crucial in embryonic development, tissue repair and cancer metastasis, driven by the actin and tubulin cytoskeletons that control cell shape, polarity, adhesion and movement in response to various cues. Although heterotrimeric G proteins are known to be involved in cell migration, the specific mechanisms, especially during development, remain elusive. This study examines the role of Gαi2, a heterotrimeric G-protein subunit, in cranial neural crest (NC) cell migration during Xenopus embryonic development. Our research reveals that Gαi2 interacts directly with the microtubule-associated protein EB1, regulating microtubule dynamics. We show that Gαi2 knockdown stabilizes microtubules, disrupts cell polarity and morphology, increases Rac1-GTP at the leading edge and cell-cell contacts, and impairs actin localization and focal adhesion disassembly. Additionally, RhoA-GTP is reduced at cell-cell contacts and concentrated at the leading edge in Gαi2 knockdown cells, providing evidence of a role for Gαi2 in polarity. Treatment with nocodazole, a microtubule-depolymerizing agent, reduces Rac1 activity, restoring cranial NC cell morphology, actin distribution and overall migration. Our findings highlight a crucial role for Gαi2 in cranial NC cell migration by modulating microtubule dynamics through EB1 and Rac1 activity.

The voltage-gated sodium channel β3 subunit modulates C6 glioma cell motility independently of channel activity

BACKGROUND

Voltage-gated sodium channels (VGSCs) initiate action potentials in nerve and muscle cells and are regulated by auxiliary β subunits. VGSC β subunits are also expressed in some cancer types, suggesting potential functions distinct from their role in electrophysiological excitability. This study investigated the occurrence and functional implications of the VGSC β3 subunit (the product of SCN3B gene) in glioma, focusing on the role of its extracellular immunoglobulin domain (β3 Ig).

METHODS

Data mining explored associations between β3 expression and glioma severity at patient, tissue, and single-cell levels. Using C6 glioma cells expressing β3 or β3 without its Ig domain, we examined the effects on cell viability, mobility, and actin-based cell protrusions. A single-chain variable fragment (scFv) antibody targeting the β3 Ig was selected by phage display to interfere with its functions. The interacting proteins with β3 Ig were identified by immunoprecipitation-mass spectrometry.

RESULTS

Data mining revealed negative correlations between β3 expression and glioma severity and aggressiveness. Expression of β3 in C6 cells reduced cell migration and invasion without affecting cell viability. Filopodia were significantly increased while lamellipodia/ruffles were decreased, producing striking cell morphological changes. These effects were abrogated by expression of the β3 subunit lacking the β3 Ig domain or exogenous application of an scFv targeting β3 Ig. Most of the plasma membrane-associated proteins immunoprecipitated with the β3 subunit are known regulators of actin polymerization.

CONCLUSION

Our data reveals a novel and unexpected role for the VGSC β3 subunit in orchestrating actin organization and negatively regulating cell migration in glioma cells which may potentially explain clinical correlations with glioma severity.

Cell polarity: cell type-specific regulators, common pathways, and polarized vesicle transport

Cell polarity, the asymmetric organization of cellular components, is evolutionarily conserved from unicellular and multicellular organisms and is crucial for many biological processes. Polarity is required to maintain cell and tissue integrity by regulating cell division, migration, orientation, cell-cell interactions, and morphogenesis. Impaired polarity leads to dysregulation of cellular functions and is associated with disease. Understanding how polarity is established, maintained, and regulated is thus critical to improving our knowledge of pathologies and devising novel therapies. Here, we explore the various manifestations of cell polarity across different model systems, tissues, and cell types and focus on known polarity mechanisms in hematopoietic stem and progenitor cells. We discuss how cells with vastly different functions utilize conserved molecular complexes to establish cell polarity while adapting polarity proteins to unique cell-type-specific functions. In this discussion, we attempt to extract common themes and concepts to improve our understanding of cell polarity in hematological malignancies and other diseases. Finally, we summarize, compare, and evaluate classical as well as recently developed methods to quantify cell polarity, highlight important advances in imaging and analytical techniques, and suggest critical next steps required to move the field forward.

Memory and Friction: From the Nanoscale to the Macroscale

Friction is a phenomenon that manifests across all spatial and temporal scales, from the molecular to the macroscopic scale. It describes the dissipation of energy from the motion of particles or abstract reaction coordinates and arises in the transition from a detailed molecular-level description to a simplified, coarse-grained model. It has long been understood that time-dependent (non-Markovian) friction effects are critical for describing the dynamics of many systems, but that they are notoriously difficult to evaluate for complex physical, chemical, and biological systems. In recent years, the development of advanced numerical friction extraction techniques and methods to simulate the generalized Langevin equation has enabled exploration of the role of time-dependent friction across all scales. We discuss recent applications of these friction extraction techniques and the growing understanding of the role of friction in complex equilibrium and nonequilibrium dynamic many-body systems.

Development of label-free cell tracking for discrimination of the heterogeneous mesenchymal migration

Image-based cell phenotyping is fundamental in both cell biology and medicine. As cells are dynamic systems, phenotyping based on static data is complemented by dynamic data extracted from time-dependent cell characteristics. We developed a label-free automatic tracking method for phase contrast images. We examined the possibility of using cell motility-based discrimination to identify different types of mesenchymal migration in invasive malignant cancer and non-cancer cells. These cells were cultured in plastic tissue culture vessels, using motility parameters from cell trajectories extracted with label-free tracking. Correlation analysis with these motility parameters identified characteristic parameters for cancer HT1080 fibrosarcoma and non-cancer 3T3-Swiss fibroblast cell lines. The parameter "sum of turn angles," combined with the "frequency of turns" at shallow angles and "migration speed," proved effective in highlighting the migration characteristics of these cells. It revealed differences in their mechanisms for generating effective propulsive forces. The requirements to characterize these differences included the spatiotemporal resolution of segmentation and tracking, capable of detecting polarity changes associated with cell morphological alterations and cell body displacement. With the segmentation and tracking method proposed here, a discrimination curve computed using quadratic discrimination analysis from the "sum of turn angles" and "frequency of turns below 30°" gave the best performance with a 94% sensitivity. Cell migration is a process related not only to cancer but also to tissue healing and growth. The proposed methodology is easy to use, enabling anyone without professional skills in image analysis, large training datasets, or special devices. It has the potential for application not only in cancer cell discrimination but also in a broad range of applications and basic research. Validating the expandability of this method to characterize cell migration, including the scheme of propulsive force generation, is an important consideration for future study.

Extracellular osmolarity regulates osteoblast migration through the TRPV4-Rho/ROCK signaling

For precise bone formation, osteoblasts need to accurately migrate to specific sites guided by various biochemical and mechanical cues. During this migration, fluctuations in extracellular osmolarity may arise from shifts in the surrounding fluid environment. However, as a main regulator of cell morphology and function, whether the extracellular osmolarity change may affect osteoblast migration remains unclear. Here, we provide evidence showing that changes in extracellular osmolarity significantly impact osteoblast migration, with a hypotonic environment enhancing it while a hypertonic environment inhibiting it. Further, our findings reveal that a hypotonic treatment increases intracellular pressure, activating the Transient Receptor Potential Vanilloid 4 (TRPV4) channel. This activation of TRPV4 modulates stress fibers, focal adhesions (FAs), and cell polarity through the Rho/ROCK signaling pathway, ultimately impacting osteoblast migration. Our findings provide valuable insights into the significant influence of extracellular osmolarity on osteoblast migration, which has potential implications for enhancing our understanding of bone remodeling.

Learning stochastic reaction-diffusion models from limited data using spatiotemporal features

Pattern-forming stochastic systems arise throughout biology, with dynamic molecular waves observed in biochemical networks regulating critical cellular processes. Modeling these reaction-diffusion systems using handcrafted stochastic partial differential equations (PDEs) requires extensive trial-and-error tuning. Data-driven approaches for improved modeling are needed but have been hindered by data scarcity and noise. Here, we present a solution to the inverse problem of learning stochastic reaction-diffusion models from limited data by optimizing two spatiotemporal features: (1) stochastic dynamics and (2) spatiotemporal patterns. Combined with sparsity enforcement, this method identifies novel activator-inhibitor models with interpretable structure. We demonstrate robust learning from simulations of excitable systems with varying data scarcity, as well as noisy live-cell imaging data with low temporal resolution and a single observed biomolecule. This generalizable approach to learning governing stochastic PDEs enhances our ability to model and understand complex spatiotemporal systems from limited, real-world data.

Engineering strategies for the construction of oriented and functional skeletal muscle tissues

The growth and formation of tissues, such as skeletal muscle, involve a complex interplay of spatiotemporal events, including cell migration, orientation, proliferation, and differentiation. With the continuous advancement ofin vitroconstruction techniques, many studies have contributed to skeletal muscle tissue engineering (STME). This review summarizes recent advances in the ordered construction of skeletal muscle tissues, and evaluates the impact of engineering strategies on cell behavior and maturation, including biomaterials, manufacturing methods and training means. Biomaterials are used as scaffolds to provide a good microenvironment for myoblasts, manufacturing methods to guide the alignment of myoblasts through construction techniques, and external stimulation to further promote the myoblast orientation and maturation after construction, resulting in oriented and functional skeletal muscle tissues. Subsequently, we critically examine recent advancements in engineered composite skeletal muscle constructs, with particular emphasis on essential functionalization strategies including skeletal muscle vascularization, innervation and others. Concurrently, we evaluate emerging applications of STME in diverse translational areas such as volumetric muscle loss treatment, muscle-related disease models, drug screening, biohybrid robots, and cultured meat. Finally, future perspectives are proposed to provide guidance for rational design based on engineering strategies in STME.

PIEZO1-dependent mode switch of neuronal migration in heterogeneous microenvironments in the developing brain

The migration of newborn neurons is essential for brain morphogenesis and circuit formation, yet controversy exists regarding how neurons generate the driving force against strong mechanical stresses in crowded neural tissues. We found that cerebellar granule neurons employ a mechanosensing mechanism to switch the driving forces to maneuver in irregular brain tissue. In two-dimensional (2D) cultures, actomyosin is enriched in the leading process, exerting traction force on the cell soma. In tissue or 3D confinement, however, actomyosin concentrates at the posterior cell membrane, generating contractile forces that assist passage through narrow spaces, working alongside the traction force in the leading process. The 3D migration is initiated by the activation of a mechanosensitive channel, PIEZO1. PIEZO1-induced calcium influx in the soma triggers the PKC-ezrin cascade, which recruits actomyosin and transmits its contractile force to the posterior plasma membrane. Thus, migrating neurons adapt their motility modes in distinct extracellular environments in the developing brain.

Adhesion strength of tumor cells predicts metastatic disease in vivo

Although only a fraction of tumor cells contribute to metastatic disease, no prognostic biomarkers currently exist to identify these cells. We show that a physical marker-adhesion strength-predicts metastatic potential in a mouse breast cancer model and that it may stratify human disease. Cells disseminating from murine mammary tumors are weakly adherent, and, when pre-sorted by adhesion, primary tumors created from strongly adherent cells exhibit fewer lung metastases than weakly adherent cells do. We demonstrate that admixed cancer lines can be separated by label-free adhesive signatures. When applied to murine metastatic tumors, adhesion retrospectively predicts metastatic disease with 100% specificity, 85% sensitivity, and area under the curve (AUC) of 0.94. Cells from human reduction mammoplasties have a higher adhesion strength versus resected human tumors, which may also be stratified between invasive and more indolent cancers. Thus, highly metastatic cells may have a distinct physical phenotype that may be a predictive marker of clinical outcomes.

Long-Term Real-Time Tracking of Morphology and Migration of Neuronal Cells under Oxidative Stress

Neuronal cells exhibit diverse morphologies that are crucial for their function within the neuronal network. Long-term quantitative analysis of both neuronal cell morphology and migration is essential in neuroscience research but remains challenging. Sodium arsenite, a known inducer of oxidative stress in neurons, affects both cell morphology and migration. To rapidly assess oxidative stress in HT22 neuronal cells, we developed a method for tracking key morphological features and migration trajectories of the individual cells. Three time-dependent parameters-velocity, circularity increment, and turn angle-are identified as rapid, direct indicators of the early stages of oxidative stress in neuronal cells. This method is then applied to investigate the effects of arsenite exposure on neuronal cells. Our approach provides a valuable tool for the rapid, label-free, and long-term real-time tracking of oxidative stress in neuronal cells, offering potential insights into cellular responses under stress conditions.

Large-scale control over collective cell migration using light-activated epidermal growth factor receptors

Receptor tyrosine kinases (RTKs) play key roles in coordinating cell movement at both single-cell and tissue scales. The recent development of optogenetic tools for controlling RTKs and their downstream signaling pathways suggests that these responses may be amenable to engineering-based control for sculpting tissue shape and function. Here, we report that a light-controlled epidermal growth factor (EGF) receptor (OptoEGFR) can be deployed in epithelial cells for precise, programmable control of long-range tissue movements. We show that in OptoEGFR-expressing tissues, light can drive millimeter-scale cell rearrangements to densify interior regions or produce rapid outgrowth at tissue edges. Light-controlled tissue movements are driven primarily by phosphoinositide 3-kinase (PI3K) signaling, rather than diffusible ligands, tissue contractility, or ERK kinase signaling as seen in other RTK-driven migration contexts. Our study suggests that synthetic, light-controlled RTKs could serve as a powerful platform for controlling cell positions and densities for diverse applications, including wound healing and tissue morphogenesis.

The role of IL-8 in cancer development and its impact on immunotherapy resistance

Tumors are structures of high complexity. Plurality of their structural and functional components - heterogeneity, diversity, directionality, interdependence and integration of signaling pathways - seem to follow isolated local rules, whereby a superordinate structure remains largely unknown. Understanding the complexity of cancer is the mainstay in finding determinants and developing effective therapies. Interleukin 8 (IL-8) is a potent pro-inflammatory chemokine that is significantly elevated in many different tumor entities. In contrast to its initially postulated anti-tumor properties, an increasing number of studies have been published in recent years linking this chemokine with tumor-promoting features and poor prognosis. This review summarizes the current state and diversity of the role of IL-8 in the development of cancer.

Sos1 ablation alters focal adhesion dynamics and increases Mmp2/9-dependent gelatinase activity in primary mouse embryonic fibroblasts

BACKGROUND

Sos1 and Sos2 are guanine-nucleotide exchange factors for Ras and Rac small GTPases, which are involved in a wide range of cellular responses including proliferation and migration. We have previously shown that Sos1 and Sos2 have different effects on cell migration, but the underlying mechanisms are not clear.

METHODS

Using a 4-hydroxytamoxifen-inducible conditional Sos1KO mutation, here we evaluated the functional specificity or redundancy of Sos1 and Sos2 regarding the control of cell migration and dynamics of focal adhesions (FAs) in primary mouse embryonic fibroblasts (MEFs).

RESULTS

Functional analysis of the transcriptome of primary Sos1/2WT, Sos1KO, Sos2KO and Sos1/2DKO-MEFs revealed a specific, dominant role of Sos1 over Sos2 in transcriptional regulation. Sos1KO MEFs had an increased number and stability of focal adhesions (FAs) and curbed protrusion and spreading. Conversely, Sos2KO MEFs displayed unstable FAs with increased protrusion. Interestingly, Sos1, but not Sos2, ablation reduced the levels of GTP-bound Rac at the leading edge. In 3D, however, only Sos1/2KO MEFs showed increased invasion and matrix degradative capacity, which correlated with increased expression of the Mmp2 and Mmp9 gelatinases. Moreover, increased matrix degradation in Sos1/2KO MEFs was abrogated by treatment with Mmp2/9 inhibitors.

CONCLUSIONS

Our data demonstrate that Sos1 and Sos2 have different functions in FAs distribution and dynamics in 2D whereas in 3D they act together to regulate invasion and unveil a previously undescribed mechanistic connection between Sos1/2 and the regulation of Mmp2/9 expression in primary MEFs.

AP2A1 modulates cell states between senescence and rejuvenation

Aging proceeds with the accumulation of senescent cells in multiple organs. These cells exhibit increased size compared to young cells, which promotes further senescence and age-related diseases. Currently, the molecular mechanism behind the maintenance of such huge cell architecture undergoing senescence remains poorly understood. Here we focus on the reorganization of actin stress fibers induced upon replicative senescence in human fibroblasts, widely used as a senescent cell model. We identified, together with our previous proteomic study, that AP2A1 (alpha 1 adaptin subunit of the adaptor protein 2) is upregulated in senescent cells along the length of enlarged stress fibers. Knockdown of AP2A1 reversed senescence-associated phenotypes, exhibiting features of cellular rejuvenation, while its overexpression in young cells advanced senescence phenotypes. Similar functions of AP2A1 were identified in UV- or drug-induced senescence and were observed in epithelial cells as well. Furthermore, we found that AP2A1 is colocalized with integrin β1, and both proteins move linearly along stress fibers. With the observations that focal adhesions are enlarged in senescent cells and that this coincides with strengthened cell adhesion to the substrate, these results suggest that senescent cells maintain their large size by reinforcing their effective anchorage through integrin β1 translocation along stress fibers. This mechanism may work efficiently in senescent cells, compared with a case relying on random diffusion of integrin β1, given the enlarged cell size and resulting increase in travel time and distance for endocytosed vesicle transportation.

Spatiotemporal distribution of PKCα, PIP3, Moesin, Cdc42, MARCKS, Scriblle, and Arf6 before directed cell migration in monolayers

Protein kinase Cα (PKCα) has an important role in directed cell migration. After a mechanical wounding, PKCα rapidly accumulates at cell edges adjacent to the wounded cell and regulates cell migration. However, the proteins downstream of PKCα that mediate directed signaling remain unknown. In this study, we examined the spatiotemporal dynamics of PKCα, PIP3, Moesin, Cdc42, MARCKS, Scribble, and Arf6 before directed migration. After wounding, PIP3, Moesin, and Cdc42 accumulated at the cell edge near the wounded cells later than PKCα. In contrast, MARCKS moved away from the plasma membrane without polarization, and Scribble and Arf6 exhibited no significant translocation. The inhibition of PIP3 suppressed the accumulation of Moesin and Cdc42, suggesting that PIP3 regulates Moesin and Cdc42. In particular, the inhibition of PKCα completely inhibited the translocation of all factors, indicating that PKCα is a central regulator in early signaling after wounding and before directional migration.

The WASP/WAVE Protein Family in Breast Cancer and Their Role in the Metastatic Cascade

The Wiskott-Aldrich syndrome protein (WASP) and the WASP family verprolin-homologous protein (WAVE) family are essential molecules that connect GTPases to the actin cytoskeleton, thereby controlling actin polymerisation through the actin-related protein 2/3 complex. This control is crucial for forming actin-based membrane protrusions necessary for cell migration and invasion. The elevated expression of WASP/WAVE proteins in invasive breast cancer cells highlights their significant role in promoting cell motility and invasion. This review summarises the discovery, structural properties, and activation mechanisms of WASP/WAVE proteins, focuses on the contribution of the WASP/WAVE family to breast cancer invasion and migration, particularly synthesises the results of nearly a decade of research in this field since 2015. By exploring promising therapeutic strategies for breast cancer, including small molecule inhibitors and biological agents, this review stresses the potential for developing anticancer drugs that target the WASP/WAVE family and associated pathways, intending to improve the prognosis for patients with metastatic breast cancer.

EBP50 regulates senescence and focal adhesion in endometrial carcinoma

Ezrin-radixin-moesin (ERM)-binding phosphoprotein 50 (EBP50) is a multifunctional scaffold protein that is highly expressed in polarized epithelial cells. Here, we focused on the functional roles of EBP50 in endometrial carcinoma (Em Ca). We analyzed immunohistochemical sections from 121 Em Ca and 30 normal samples. We also characterized EBP50 overexpression or knockout (KO) Em Ca cell lines. High levels of membranous (Me) EBP50 expression were observed in endometrial tissues from normal menstrual cycles, in contrast to the transient upregulation of cytoplasmic (Cyt) EBP50 in tissues in the proliferative phase; this was probably in response to estrogenic effects. There was a significant stepwise reduction of Me-EBP50 expression from grade (G) 1 to G3 Em Cas, which was consistent with the loss of glandular structures. Conversely, Cyt-EBP50 levels increased with in the higher tumor grades. Low Me-EBP50 expression was significantly associated with tumor lymphovascular invasion and short overall survival. Whereas EBP50 KO led to senescence and reduced proliferation and motility, overexpression elicited the opposite phenotypes. Moreover, the number of focal adhesions (FAs), which mediate cell migration, was significantly increased in EBP50 overexpressing cells but decreased in the KO cells. In conclusion, Me- and/or Cyt-EBP50 expression contributes to acceleration of cell motility through enhancement of FA formation, and inhibits senescence to promote cytokinesis. Together, these effects contribute to Em Ca aggressiveness.

Direct reprogramming of human fibroblasts into hair-inducing dermal papilla cell-like cells by a single small molecule

Dermal papilla cells (DPCs) are a crucial subset of mesenchymal cells in the skin responsible for regulating hair follicle development and growth, making them invaluable for cell-based therapies targeting hair loss. However, obtaining sufficient DPCs with potent hair-inducing abilities remains a persistent challenge. In this study, the Food and Drug Administration (FDA)-approved drug library was utilized to screen small molecules capable of reprogramming readily accessible human skin fibroblasts into functional DPCs. In the initial screening, five candidate small molecules were identified from a pool of 1,817 compounds, and the small molecule peficitinib was further identified by the further hair follicle regeneration experiments. Following peficitinib treatment, fibroblasts derived from primary human foreskin and scalp exhibited the capability to induce hair growth and possessed a molecular profile highly similar to that of primary DPCs. We refer to these cells as dermal papilla cell-like cells (DPC-LCs). Furthermore, transcriptome analysis showed that the wingless/integrated (Wnt) signaling pathway and the transforming growth factor β (TGF-β) signaling pathway, both of which play crucial roles in hair follicle morphogenesis, are upregulated and enriched in these DPC-LCs. These functional DPC-LCs offer a promising avenue for obtaining a plentiful supply of hair-inducing cells, thereby advancing the development of therapeutic strategies for hair loss treatment.

Neutrophils exhibit flexible migration strategies and trail formation mechanisms on varying adhesive substrates

Substrate anchorage is essential for cell migration, and actin polymerization at cell front and myosin contractility at cell rear are known to govern cell forward movement. Yet their differential driving strategies for neutrophil migration on distinct adhesiveness substrates and their contributions to the migration-induced trail formation remain unclear. Here we explore the morphological changes, migration dynamics, and trail formation of neutrophils on ICAM-1 and PLL substrates, with a focus on the relationships among adhesive forces, traction forces, and out-of-plane forces. Results indicate that, on ICAM-1, neutrophil migration and trail formation rely on the coordinated interactions of Arp2/3 and myosin, along with biochemical regulation (via Syk and calpain) of adhesion and de-adhesion. This pattern leads to traction forces being concentrated at relatively fewer adhesive sites, facilitating cell forward migration. On PLL, however, neutrophils primarily depend on Arp2/3-mediated actin polymerization, resulting in a broader distribution of traction forces and weaker adhesions, which allows for higher leading-edge migrating velocities. Elevated membrane tension and out-of-plane forces generated by bleb protrusions on PLL reduce the reliance on myosin-driven contraction at the trailing edge, enabling easier tail detachment through elastic recoil. This work highlights the differential impact of substrate adhesiveness on neutrophil migration and trail formation and dynamics, providing new insights into cell migration mechanisms and potential therapeutic targets for inflammatory and immune-related disorders.

A novel mechanism of FTO modulating the progression of endometriosis through mediating the m6A methylation of GEF-H1 in a YTHDF1-dependent manner

BACKGROUND

Endometriosis (EMs) is a condition characterized by the growth of endometrial tissue outside the uterine cavity. Although this condition is benign, it has cancer-like features. N6-methyladenosine (m6A) is a common RNA modification involved in diverse biological processes, but its role in EMs remains unclear.

METHODS

A human endometrial stromal cell line (HESCs), primary eutopic endometrial stromal cells (Eu-ESCs), primary ectopic endometrial stromal cells (Ec-ESCs), and clinical samples were used in this study. A colorimetric assay was used to measure methylation levels in clinical and mouse EMs samples. Functional assays (CCK-8, EdU, Transwell, and wound healing) were used to evaluate phenotypic changes. m6A immunoprecipitation sequencing (MeRIP-seq) identified downstream targets. Mechanistic studies were conducted via qRT‒PCR, Western blot, RNA immunoprecipitation (RIP), dual-luciferase reporter, and RNA stability assays.

RESULTS

We detected aberrantly low levels of m6A within endometriotic lesions, which was attributed to increased expression of the m6A eraser fat mass and obesity-associated protein (FTO). Notably, estrogen and inflammatory factors, which are recognized as pathogenic agents in EMs amplify FTO expression while suppressing m6A levels. In vitro experiments demonstrated that overexpression of FTO in endometrial stromal cells leads to a reduction in m6A levels and concomitantly promotes their proliferation, migration, and invasion. Furthermore, both genetic deletion of Fto and chemical inhibition of FTO impeded the growth of ectopic endometrial lesions in vivo. By utilizing m6A-seq, we identified GEF-H1 (a Rho guanine nucleotide exchange factor) as a pivotal downstream target of FTO. Specifically, diminished m6A methylation at a certain site within the 3'UTR of GEF-H1 promotes its expression in a YTH N6-methyladenosine RNA-binding protein F1 (YTHDF1)-dependent manner, thereby activating the RhoA pathway. Subsequent experiments revealed that GEF-H1 mediates the effects of FTO in promoting migration and invasion.

CONCLUSIONS

This study revealed that FTO decreases the m6A level of GEF-H1, thereby increasing its stability, which in turn activates the GEF-H1-RhoA pathway to promote the migration and invasion of endometrial stromal cells, thereby inducing EMs. Our findings suggest potential therapeutic avenues for targeting FTO to alleviate EMs progression.

In Vitro Assessment of Gallium Nanoalloy Hydrogels for Antimicrobial and Wound Healing Applications

Chronic and recurring wounds pose a significant challenge in modern healthcare, leading to substantial morbidity. These wounds allow pathogens to colonize, potentially resulting in local and systemic infections. Current interventions need to be revised and become increasingly less reliable due to the emergence of antibiotic resistance. In the present study, we aim to address these issues by fabricating hydrogels impregnated with gallium-based nanoalloys for their antimicrobial activity. Gallium liquid metal nanoparticles (approximately 100 nm in diameter) were alloyed in different combinations with bismuth and silver ions through a galvanic replacement reaction. These multimetallic hydrogels showed favorable antibacterial activity against the Gram-positive Staphylococcus aureus and the Gram-negative Pseudomonas aeruginosa, as observed with fluorescence microscopy and inhibition assays. The multimetallic hydrogels showed no toxicity against murine macrophages or human dermal fibroblasts and enhanced in vitro wound healing. The development of these innovative gallium-based hydrogels represents a promising strategy to combat chronic wounds and their associated complications, offering an effective alternative to current antimicrobial treatments amidst rising antibiotic resistance.

Evaluation of Prenatal Transportation Stress on DNA Methylation (DNAm) and Gene Expression in the Hypothalamic-Pituitary-Adrenal (HPA) Axis Tissues of Mature Brahman Cows

Background/Objectives: The experience of prenatal stress results in various physiological disorders due to an alteration of an offspring's methylome and transcriptome. The objective of this study was to determine whether PNS affects DNA methylation (DNAm) and gene expression in the stress axis tissues of mature Brahman cows. Methods: Samples were collected from the paraventricular nucleus (PVN), anterior pituitary (PIT), and adrenal cortex (AC) of 5-year-old Brahman cows that were prenatally exposed to either transportation stress (PNS, n = 6) or were not transported (Control, n = 8). The isolated DNA and RNA samples were, respectively, used for methylation and RNA-Seq analyses. A gene ontology and KEGG pathway enrichment analysis of each data set within each sample tissue was conducted with the DAVID Functional Annotation Tool. Results: The DNAm analysis revealed 3, 64, and 99 hypomethylated and 2, 93, and 90 hypermethylated CpG sites (FDR < 0.15) within the PVN, PIT, and AC, respectively. The RNA-Seq analysis revealed 6, 25, and 5 differentially expressed genes (FDR < 0.15) in the PVN, PIT, and AC, respectively, that were up-regulated in the PNS group relative to the Control group, as well as 24 genes in the PIT that were down-regulated. Based on the enrichment analysis, several developmental and cellular processes, such as maintenance of the actin cytoskeleton, cell motility, signal transduction, neurodevelopment, and synaptic function, were potentially modulated. Conclusions: The methylome and transcriptome were altered in the stress axis tissues of mature cows that had been exposed to prenatal transportation stress. These findings are relevant to understanding how prenatal experiences may affect postnatal neurological functions.

Molecular and Cellular Machinery of Lymphatic Metastasis in Breast Cancer

Breast cancer is one of the most common malignant tumours in women worldwide. A primary route for breast cancer cells to disseminate is through regional lymphatic vessels and nodes. Cancer cell-induced lymphangiogenesis plays a crucial role in lymphatic metastasis and is associated with poor survival of breast cancer. Advances in molecular biology have led to the identification of biomarkers associated with lymphangiogenesis and lymphatic metastasis, including lymphatic vessel endothelial cell (LVEC) markers and tumour microenvironment markers, such as vascular endothelial growth factor receptor 3 (VEGFR3), podoplanin (PDPN), and lymphatic endothelial hyaluronan receptor-1 (LYVE1). LVEC molecular markers play a profound role in both the formation of new lymphatic vessels and the invasive expansion of primary tumour. Abnormal expression of LVEC markers may contribute to lymphatic vessel disease and/or metastasis of cancer cells through the lymphatic system. These molecular markers may present a potential for targeted therapies and precision diagnostics for managing lymphatic metastasis in breast cancer. This review aims to provide a comprehensive summary of the current understanding of the molecular and cellular machinery underlying lymphatic metastasis in breast cancer, with a particular focus on the lymphangiogenic markers and their role in the lymphatic dissemination.

Trade-off movement between hydraulic resistance escape and shear stress escape by cancer cells

In the circulatory system, the microenvironment surrounding cancer cells is complex and involves multiple coupled factors. We selected two core physical factors, shear stress and hydraulic resistance, and constructed a microfluidic device with dual negative inputs to study the trade-off movement behavior of cancer cells when facing coupled factors. We detected significant shear stress escape phenomena in the MDA-MB-231 cell line and qualitatively explained this behavior using a cellular force model. Through the dual validation of substrate anti-cell-adhesion modification and employment of the MCF-7 cell line, we further substantiated the predictability and feasibility of our model. This study provides an explanation for the trade-off underlying the direction-choosing mechanism of cancer cells when facing environmental selection.

Pigment Epithelium-Derived Factor Inhibits Cell Motility and p-ERK1/2 Signaling in Intrahepatic Cholangiocarcinoma Cell Lines

Pigment epithelium-derived factor (PEDF) is a multifunctional soluble glycoprotein, primarily known for its potent anti-angiogenic properties. In recent years, its ability to counteract cell proliferation and motility has generated interest in PEDF as a potential tumor suppressor. In the intrahepatic Cholangiocarcinoma (iCCA), PEDF, Thrombospondin 1 (THBS1), and Thrombospondin 2 (THBS2) are expressed and released into the tumor microenvironment (TME), where they promote lymphangiogenesis at the expense of the neoangiogenic program, aiding the dissemination of cancer cells via lymphatic vessels. Recently, we demonstrated that THBS1 and THBS2 directly affect iCCA cells, exacerbating their malignant behavior, while the direct role of PEDF remains to be elucidated. In this study, through a cell-based assay and molecular analysis, we investigate the direct function of PEDF on two well-established iCCA cell lines. Our results show that PEDF affects cancer cell motility in a paracrine manner, reducing their migratory and invasive capabilities. Notably, our data suggest that the PEDF-induced inhibition of motility in iCCA cells occurs through the MAPK/ERK signaling pathway, as indicated by the reduced phosphorylation of ERK1/2. Overall, this study provides the first evidence of PEDF acting as a tumor suppressor in iCCA.

Spatiotemporal dissection of collective cell migration and tissue morphogenesis during development by optogenetics

Collective cell migration and tissue morphogenesis play a variety of important roles in the development of many species. Tissue morphogenesis often generates mechanical forces that alter cell shapes and arrangements, resembling collective cell migration-like behaviors. Genetic methods have been widely used to study collective cell migration and its like behavior, advancing our understanding of these processes during development. However, a growing body of research shows that collective cell migration during development is not a simple behavior but is often combined with other cellular and tissue processes. In addition, different surrounding environments can also influence migrating cells, further complicating collective cell migration during development. Due to the complexity of developmental processes and tissues, traditional genetic approaches often encounter challenges and limitations. Thus, some methods with spatiotemporal control become urgent in dissecting collective cell migration and tissue morphogenesis during development. Optogenetics is a method that combines optics and genetics, providing a perfect strategy for spatiotemporally controlling corresponding protein activity in subcellular, cellular or tissue levels. In this review, we introduce the basic mechanisms underlying different optogenetic tools. Then, we demonstrate how optogenetic methods have been applied in vivo to dissect collective cell migration and tissue morphogenesis during development. Additionally, we describe some promising optogenetic approaches for advancing this field. Together, this review will guide and facilitate future studies of collective cell migration in vivo and tissue morphogenesis by optogenetics.

Competing elastic and viscous gradients determine directional cell migration

Cell migration regulates central life processes including embryonic development, tissue regeneration, and tumor invasion. To establish the direction of migration, cells follow exogenous cues. Durotaxis, the directed cell migration towards elastic stiffness gradients, is the classical example of mechanical taxis. However, whether gradients of the relaxation properties in the extracellular matrix may also induce tactic responses (viscotaxis) is not well understood. Moreover, whether and how durotaxis and viscotaxis interact with each other has never been investigated. Here, we integrate clutch models for cell adhesions with an active gel theory of cell migration to reveal the mechanisms that govern viscotaxis. We show that viscotaxis is enabled by an asymmetric expression of cell adhesions that further polarize the intracellular motility forces to establish the cell front, similar to durotaxis. More importantly, when both relaxation and elastic gradients coexist, durotaxis appears more efficient in controlling directed cell migration, which we confirm with experimental results. However, the presence of opposing relaxation gradients to an elastic one can arrest or shift the migration direction. Our model rationalizes for the first time the mechanisms that govern viscotaxis and its competition with durotaxis through a mathematical model.

TRPC3-mediated NFATc1 calcium signaling promotes triple negative breast cancer migration through regulating glypican-6 and focal adhesion

Canonical transient receptor potential isoform 3 (TRPC3), a calcium-permeable non-selective cation channel, has been reported to be upregulated in breast cancers and a modulator of cell migration. Calcium-sensitive transcription factor NFATc1, which is important for cell migration, was shown to be frequently activated in triple negative breast cancer (TNBC) biopsy tissues. However, whether TRPC3-mediated calcium influx would activate NFATc1 and affect the migration of TNBC cells, and, if yes, the underlying mechanisms involved, remain to be investigated. By immunostaining followed by confocal microscopy, TNBC lines MDA-MB-231 and BT-549 were both found to express TRPC3 on their plasma membrane while ER+ line MCF-7 and HER2+ line SK-BR3 do not. Blockade of TRPC3 by pharmacological inhibitor Pyr3 or stable knockdown of TRPC3 by lentiviral vector both inhibited cell migration as measured by wound healing assay. Importantly, blocking TRPC3 by Pyr3 or knockdown of TRPC3 both caused the translocation of NFATc1 from the nucleus to the cytosol as revealed by confocal microscopy. Interestingly, NFATc1 was found to bind to the promoter of glypican 6 (GPC6) as determined by chromatin immunoprecipitation assay. Consistently, knockdown of TRPC3 decreased the expression of GPC6 as revealed by western blotting. Moreover, long-term knockdown of GPC6 by lentiviral vector also consistently decreased the migration of TNBC cells. Intriguingly, GPC6 proteins physically interact with vinculin in MDA-MB-231 as determined by co-immunoprecipitation. Blockade of TRPC3, knockdown of TRPC3 or knockdown of GPC6 all induced larger, stabilized actin-bound peripheral focal adhesion (FA) formations in TNBC cells as determined by co-staining of actin and vinculin followed by confocal microscopy. These large, stabilized actin-bound peripheral FAs indicated a defective FA turnover, and were reported to be responsible for impairing directed cell migration. Our results suggest that, in TNBC cells, calcium influx through TRPC3 channel positively regulates NFATc1 nuclear translocation and GPC6 expression, which maintains the dynamics of FA turnover and optimal cell migration. Our study reveals a novel TRPC3-NFATc1-GPC6-vinculin signaling cascade in maintaining the migration of TNBC cells.

E. Coli cytotoxic necrotizing factor-1 promotes colorectal carcinogenesis by causing oxidative stress, DNA damage and intestinal permeability alteration

BACKGROUND

Bacterial toxins are emerging as promising hallmarks of colorectal cancer (CRC) pathogenesis. In particular, Cytotoxic Necrotizing Factor 1 (CNF1) from E. coli deserves special consideration due to the significantly higher prevalence of this toxin gene in CRC patients with respect to healthy subjects, and to the numerous tumor-promoting effects that have been ascribed to the toxin in vitro. Despite this evidence, a definitive causal link between CNF1 and CRC was missing. Here we investigated whether CNF1 plays an active role in CRC onset by analyzing pro-carcinogenic key effects specifically induced by the toxin in vitro and in vivo.

METHODS

Viability assays, confocal microscopy of γH2AX and 53BP1 molecules and cytogenetic analysis were carried out to assess CNF1-induced genotoxicity on non-neoplastic intestinal epithelial cells. Caco-2 monolayers and 3D Caco-2 spheroids were used to evaluate permeability alterations specifically induced by CNF1, either in the presence or in the absence of inflammation. In vivo, an inflammatory bowel disease (IBD) model was exploited to evaluate the carcinogenic potential of CNF1. Immunohistochemistry and immunofluorescence stainings of formalin-fixed paraffin-embedded (FFPE) colon tissue were carried out as well as fecal microbiota composition analysis by 16 S rRNA gene sequencing.

RESULTS

CNF1 induces the release of reactive oxidizing species and chromosomal instability in non-neoplastic intestinal epithelial cells. In addition, CNF1 modifies intestinal permeability by directly altering tight junctions' distribution in 2D Caco-2 monolayers, and by hindering the differentiation of 3D Caco-2 spheroids with an irregular arrangement of these junctions. In vivo, repeated intrarectal administration of CNF1 induces the formation of dysplastic aberrant crypt foci (ACF), and produces the formation of colorectal adenomas in an IBD model. These effects are accompanied by the increased neutrophilic infiltration in colonic tissue, by a mixed pro-inflammatory and anti-inflammatory cytokine milieu, and by the pro-tumoral modulation of the fecal microbiota.

CONCLUSIONS

Taken together, our results support the hypothesis that the CNF1 toxin from E. coli plays an active role in colorectal carcinogenesis. Altogether, these findings not only add new knowledge to the contribution of bacterial toxins to CRC, but also pave the way to the implementation of current screening programs and preventive strategies.

Biofunctionalized patterned platform as microarray biochip to supervise delivery and expression of pDNA nanolipoplexes in stem cells via mechanotransduction

Biochips are widely applied to manipulate the geometrical morphology of stem cells in recent years. Patterned antenna-like pseudopodia are also probed to explore the influence of pseudopodia formation on gene delivery and expression on biochips. However, how the antenna-like pseudopodia affect gene transfection is unsettled and the underlying trafficking mechanism of exogenous genes in engineered single cells is not announced. Therefore, the engineered microarray biochips were conceptualized and prepared by the synthesized photointelligent biopolymer to precisely manage geometric topological structures (cell size and antenna-like protrusion) of stem cells on biochips. The cytoskeleton could be regulated in engineered cells and large cells with more antennas assembled well-organized actin filaments to affect cell tension distribution. The stiffness and adhesion force were measured by atomic force microscope to reveal cell nanomechanics on microarray biochips. Cytoskeleton-mediated nanomechanics could be adjusted by actin filaments. Gene transfection efficiency was enhanced with increasing cell nanomechanics, which was also confirmed by the evaluation of cell internalization capacity of nanoparticles and DNA synthesis ability. This work will provide a new strategy to study functional biomaterials, microarray chips and internal mechanism of gene transfection in patterned stem cells on biochips.

Protocadherin-7 Regulates Monocyte Migration Through Regulation of Small GTPase RhoA and Rac1

Protocadherin-7 (Pcdh7) is a member of the non-clustered protocadherin δ1 subgroup within the cadherin superfamily. Pcdh7 has been shown to control osteoclast differentiation via the protein phosphatase 2A (PP2A)-glycogen synthase kinase-3β (GSK3β)-small GTPase signaling axis. As protocadherins serve multiple biological functions, a deeper understanding of Pcdh7's biological features is valuable. Using an in vitro mouse monocyte cell culture system, we demonstrate that Pcdh7 plays a role in regulating monocyte migration by modulating the small GTPases RhoA and Rac1. Pcdh7-deficient (Pcdh7-/-) bone marrow-derived monocytes exhibited impaired migration along with the reduced activation of RhoA and Rac1. This impaired migration was rescued by transduction with constitutively active forms of RhoA and Rac1. Treatment with the PP2A-specific activator DT-061 enhanced cell migration, whereas treatment with the GSK3β-specific inhibitor AR-A014418 inhibited migration in wild-type monocytes. In contrast, treatment with DT-061 failed to restore the impaired migration in Pcdh7-/- monocytes. These findings suggest the involvement of PP2A and GSK3β in monocyte migration, although the forced activation of PP2A alone is insufficient to restore impaired migration in Pcdh7-/- monocytes. Taken together, these results indicate that Pcdh7 regulates monocyte migration through the activation of RhoA and Rac1. Given the pivotal role of cell migration in both physiological and pathological processes, our findings provide a foundation for future research into therapeutic strategies targeting Pcdh7-regulated migration.

Confined cell migration along extracellular matrix space in vivo

Collective migration of cancer cells is often interpreted using concepts derived from the physics of active matter, but the experimental evidence is mostly restricted to observations made in vitro. Here, we study collective invasion of metastatic cancer cells injected into the mouse deep dermis using intravital multiphoton microscopy combined with a skin window technique and three-dimensional quantitative image analysis. We observe a multicellular but low-cohesive migration mode characterized by rotational patterns which self-organize into antiparallel persistent tracks with orientational nematic order. We analyze the deformations induced by the cells in the extracellular matrix and find broadly distributed strain bands with a prevalence of compression. A model of active nematic hydrodynamics is able to describe several statistical features of the experimentally observed flow, suggesting that collective cancer cell invasion can be interpreted as a nematic active fluid in the turbulent regime. Our results help elucidate the migration patterns of cancer cells in vivo and provide quantitative guidance for the development of realistic in vitro and in silico models for collective cell migration.

Polarity and migration of cranial and cardiac neural crest cells: underlying molecular mechanisms and disease implications

The Neural Crest cells are multipotent progenitor cells formed at the neural plate border that differentiate and give rise to a wide range of cell types and organs. Directional migration of NC cells and their correct positioning at target sites are essential during embryonic development, and defects in these processes results in congenital diseases. The NC migration begins with the epithelial-mesenchymal transition and extracellular matrix remodeling. The main cellular mechanisms that sustain this migration include contact inhibition of locomotion, co-attraction, chemotaxis and mechanical cues from the surrounding environment, all regulated by proteins that orchestrate cell polarity and motility. In this review we highlight the molecular mechanisms involved in neural crest cell migration and polarity, focusing on the role of small GTPases, Heterotrimeric G proteins and planar cell polarity complex. Here, we also discuss different congenital diseases caused by altered NC cell migration.

CD44 and Ezrin restrict EGF receptor mobility to generate a novel spatial arrangement of cytoskeletal signaling modules driving bleb-based migration

Cells under high confinement form highly polarized hydrostatic pressure-driven, stable leader blebs that enable efficient migration in low adhesion, environments. Here we investigated the basis of the polarized bleb morphology of metastatic melanoma cells migrating in non-adhesive confinement. Using high-resolution time-lapse imaging and specific molecular perturbations, we found that EGF signaling via PI3K stabilizes and maintains a polarized leader bleb. Protein activity biosensors revealed a unique EGFR/PI3K activity gradient decreasing from rear-to-front, promoting PIP3 and Rac1-GTP accumulation at the bleb rear, with its antagonists PIP2 and RhoA-GTP concentrated at the bleb tip, opposite to the front-to-rear organization of these signaling modules in integrin-mediated mesenchymal migration. Optogenetic experiments showed that disrupting this gradient caused bleb retraction, underscoring the role of this signaling gradient in bleb stability. Mathematical modeling and experiments identified a mechanism where, as the bleb initiates, CD44 and ERM proteins restrict EGFR mobility in a membrane-apposed cortical actin meshwork in the bleb rear, establishing a rear-to-front EGFR-PI3K-Rac activity gradient. Thus, our study reveals the biophysical and molecular underpinnings of cell polarity in bleb-based migration of metastatic cells in non-adhesive confinement, and underscores how alternative spatial arrangements of migration signaling modules can mediate different migration modes according to the local microenvironment.