Mechanical confinement triggers spreading and migration of immobile cells by deforming nucleus

Cells in vivo are often subject to the challenge of spatial confinement from neighboring cells and extracellular matrix (ECM) that are usually adhesive and deformable. Here, we showed that confinement makes initially quiescent round cells on soft adhesive substrates spread and migrate, exhibiting a phenotype similar to that of cells on unconfined stiff substrates. Interestingly, the confinement-induced cell spreading and migration exist widely in many cell types, and depend on formins, cell contractility and endonuclear YAP-TEAD interaction. Finally, we demonstrated the nucleus is a mechanosensor independent of ECM rigidity, and its flattening alone is sufficient to trigger YAP nuclear translocation, assembly of focal adhesions and stress fibers, cell spreading and migration. Thus, our findings revealed a new inside-out mechanism through which the nucleus directly detects and responds to external mechanical confinement, and could have important implications for cell migration in crowded micro-environments during cancer metastasis, wound healing and embryonic development.

B cell mechanobiology in health and disease: emerging techniques and insights into therapeutic responses

Cells sense physical cues from their environment and convert them into biochemical responses through mechanotransduction. Unlike solid tumours, the role of such forces in haematological cancers is underexplored. In this context, immune cells experience dynamic mechanical stimuli as they migrate, extravasate and home to specific tissues. Understanding how these forces shape B-cell function and malignancy represents a groundbreaking area of research. This review examines the key mechanosensory pathways and molecules involved in lymphocyte mechanotransduction, beginning with mechanosensory proteins at the plasma membrane, followed by intracellular signal propagation through the cytoskeleton, eventually highlighting the nucleus as a 'signal actuator'. Subsequently, we cover some measurement approaches and advanced systems to investigate tumour biomechanics, highlighting their application in the context of B cells. Finally, we focus on the implications of mechanobiology in leukaemia, identifying molecules involved in B-cell malignancies that could serve as potential 'mechano-targets' for personalised therapies. This review emphasises the need to understand how lymphocytes generate, sense and respond to mechanical stimuli, which could open avenues for future biomedical innovations. Impact statement Our review is particularly valuable in highlighting the underexplored role of mechanobiology in B cell function and malignancies, while also discussing emerging techniques that can advance this research area. It bridges mechanotransduction, immunology, and cancer biology in a way that will be of interest to researchers across these three main fields.

Mechano-metabolism on the rise

Cells respond to the physical and geometrical tissue properties by multiple mechanotransduction mechanisms that can profoundly influence cells' decision-making, extending to cell metabolism. This review incorporates the most recent findings on this topic, organized along the idea that the mechano-metabolic connection serves three main functions, namely to inform systemic metabolism on the general functioning of a tissue/organ, to tune cells' energy production with the mechanical requirements imposed by their surroundings, and to coordinate cell metabolism with cell fate choices induced in response to mechanical cues. This connection highlights the pervasive influence of mechanical cues on cell activity, opens interesting questions on its physiological and pathological roles, and lays the foundations for exploiting the mechano-metabolism axis to design new therapeutic approaches.

Drosophila epidermal cells are intrinsically mechanosensitive and modulate nociceptive behavioral outputs

Somatosensory neurons (SSNs) that detect and transduce mechanical, thermal, and chemical stimuli densely innervate an animal's skin. However, although epidermal cells provide the first point of contact for sensory stimuli, our understanding of roles that epidermal cells play in SSN function, particularly nociception, remains limited. Here, we show that stimulating Drosophila epidermal cells elicits activation of SSNs including nociceptors and triggers a variety of behavior outputs, including avoidance and escape. Further, we find that epidermal cells are intrinsically mechanosensitive and that epidermal mechanically evoked calcium responses require the store-operated calcium channel Orai. Epidermal cell stimulation augments larval responses to acute nociceptive stimuli and promotes prolonged hypersensitivity to subsequent mechanical stimuli. Hence, epidermal cells are key determinants of nociceptive sensitivity and sensitization, acting as primary sensors of noxious stimuli that tune nociceptor output and drive protective behaviors.

Microdevice for confinement of T-cells on functionalized bio-interfaces

Mechanical stimuli are an integral part of the natural cellular microenvironment, influencing cell growth, differentiation, and survival, particularly in mechanically challenging environments like tumors. These stimuli are also crucial in the T-cell microenvironment, where they play a role in antigen recognition and pathogen detection. To study T-cell mechanobiology effectively, in vitro methods must replicate these mechanical stimuli induced by compression, tension or shear flow, in the presence of antigen-presenting cells (APCs). While custom-made microdevices and microfluidic chips have successfully observed bulk cell behavior under mechanical strain, no existing device fully replicated the T-cell mechanoenvironment comprehensively. In this study, we developed a microdevice that integrates the mechanoenvironmental aspects of an APC mimicry with compression under live-cell imaging conditions. This device allows for precise confinement of cells between two glass surfaces, which can be individually coated with functional bio-interfaces. The microdevice is reusable and enables presetting of confinement heights, manual seeding of cells and the assembly of components directly at the microscope. To validate our microdevice we confined primary mouse T-cells on different APC-mimicking supported lipid bilayers while monitoring their morphology and migratory behaviour over time. To study the effect of confinement on TCR signalling, we tracked intracellular calcium levels and quantified Erk1/2 phosphorylation by immunostaining. We observed that T-cell morphology and motility are affected by confinement but also by bilayer composition. Moreover our findings suggest that confinement, despite not interfering with T-cell activation, might increase TCR background signalling in resting T-cells. Importantly, our microdevice is not limited to T-cell research; it can also serve as a platform for studying mechanical stimulation in other cell types, cell aggregates like spheroids and organoids, or even tissue samples in the presence of various bio-interfaces.

Frictiotaxis underlies focal adhesion-independent durotaxis

Cells move directionally along gradients of substrate stiffness - a process called durotaxis. In the situations studied so far, durotaxis relies on cell-substrate focal adhesions to sense stiffness and transmit forces that drive directed motion. However, whether and how durotaxis can take place in the absence of focal adhesions remains unclear. Here, we show that confined cells can perform durotaxis despite lacking focal adhesions. This durotactic migration depends on an asymmetric myosin distribution and actomyosin retrograde flow. We propose that the mechanism of this focal adhesion-independent durotaxis is that stiffer substrates offer higher friction. We put forward a physical model that predicts that non-adherent cells polarise and migrate towards regions of higher friction - a process that we call frictiotaxis. We demonstrate frictiotaxis in experiments by showing that cells migrate up a friction gradient even when stiffness is uniform. Our results broaden the potential of durotaxis to guide any cell that contacts a substrate, and they reveal a mode of directed migration based on friction. These findings have implications for cell migration during development, immune response and cancer progression, which usually takes place in confined environments that favour adhesion-independent amoeboid migration.

Nuclear Deformation and Stiffness-Dependent Traction Force Generation Dictate the Migration of Cells under Confinement

Cells need to migrate through confined spaces during processes such as embryo development and cancer metastasis. However, the fundamental question of how confinement size and surrounding rigidity collectively regulate the migration capability of cells remains unclear. Here, by utilizing maskless photolithography with a digital micromirror device (DMD), a microchannel with precisely controlled width and wall stiffness (similar to those exhibited by natural tissues) is fabricated. We find that increasing the rigidity of the confining wall leads to a more reduced nuclear volume but has no detectable influence on the myosin expression level in the cells. More interestingly, a biphasic trend of the cell speed is observed, with the migration velocity reaching its minimum at an intermediate wall rigidity of ∼10 kPa. A motor-clutch-based pulling race model is then proposed, which suggests that such biphasic dependence is due to the fact that a very soft channel wall will result in small deformation of the nucleus and consequently reduced cell-wall friction, while larger myosin-based crawling force can be triggered by a stiff confining boundary, both leading to a relatively high migration speed. These findings could provide critical insights into novel strategies for controlling the movement of cells and the design of high-performance biological materials.

The activation of INF2 by Piezo1/Ca2+ is required for mesenchymal-to-amoeboid transition in confined environments

To invade tissues, cells may undergo a mesenchymal-to-amoeboid transition (MAT). However, the mechanisms regulating this transition are poorly defined. In melanoma cells, we demonstrate that intracellular [Ca2+] increases with the degree of confinement in a Piezo1-dependent fashion. Moreover, Piezo1/Ca2+ is found to drive amoeboid and not mesenchymal migration in confined environments. Consistent with a model in which Piezo1 senses tension at the plasma membrane, the percentage of cells using amoeboid migration is further increased in undulating microchannels. Surprisingly, amoeboid migration was not promoted by myosin light-chain kinase (MLCK), which is sensitive to intracellular [Ca2+]. Instead, we report that Piezo1/Ca2+ activates inverted formin-2 (INF2) to induce widespread actin cytoskeletal remodeling. Strikingly, the activation of INF2 promotes de-adhesion, which in turn facilitates migration across micropatterned surfaces. Thus, we reveal a novel Piezo1/Ca2+/INF2 signaling cascade that regulates MAT, enabling cancer cells to adapt their migration mode in response to varying mechanochemical environments.

Tissue geometry spatiotemporally drives bacterial infections

Epithelial tissues serve as the first line of host against bacterial infections. The self-organization of epithelial tissues continuously adapts to the architecture and mechanics of microenvironments, thereby dynamically impacting the initial niche of infections. However, the mechanism by which tissue geometry regulates bacterial infection remains poorly understood. Here, we showed geometry-guided infection patterns of bacteria in epithelial tissues using bioengineering strategies. We discovered that cellular traction forces play a crucial role in the regulation of bacterial invasive sites and marginal infection patterns in epithelial monolayers through triggering co-localization of mechanosensitive ion channel protein Piezo1 with bacteria. Further, we developed precise mechanobiology-based strategies to potentiate the antibacterial efficacy in animal models of wound and intestinal infection. Our findings demonstrate that tissue geometry exerts a key impact on mediating spatiotemporal infections of bacteria, which has important implications for the discovery and development of alternative strategies against bacterial infections.

Autonomous learning of pathologists' cancer grading rules

Deep learning (DL) algorithms have demonstrated remarkable proficiency in histopathology classification tasks, presenting an opportunity to discover disease-related features escaping visual inspection. However, the "black box" nature of DL obfuscates the basis of the classification. Here, we develop an algorithm for interpretable Deep Learning (IDL) that sheds light on the links between tissue morphology and cancer biology. We make use of a generative model trained to represent images via a combination of a semantic latent space and a noise vector to capture low level image details. We traversed the latent space so as to induce prototypical image changes associated with the disease state, which we identified via a second DL model. Applied to a dataset of clear cell renal cell carcinoma (ccRCC) tissue images the AI system pinpoints nuclear size and nucleolus density in tumor cells (but not other cell types) as the decisive features of tumor progression from grade 1 to grade 4 - mirroring the rules that have been used for decades in the clinic and are taught in textbooks. Moreover, the AI system posits a decrease in vasculature with increasing grade. While the association has been illustrated by some previous reports, the correlation is not part of currently implemented grading systems. These results indicate the potential of IDL to autonomously formalize the connection between the histopathological presentation of a disease and the underlying tissue architectural drivers.

3D Mechanical Confinement Directs Muscle Stem Cell Fate and Function

Muscle stem cells (MuSCs) play a crucial role in skeletal muscle regeneration, residing in a niche that undergoes dimensional and mechanical changes throughout the regeneration process. This study investigates how 3D confinement and stiffness encountered by MuSCs during the later stages of regeneration regulate their function, including stemness, activation, proliferation, and differentiation. An asymmetric 3D hydrogel bilayer platform is engineered with tunable physical constraints to mimic the regenerating MuSC niche. These results demonstrate that increased 3D confinement maintains Pax7 expression, reduces MuSC activation and proliferation, inhibits differentiation, and is associated with smaller nuclear size and decreased H4K16ac levels, suggesting that mechanical confinement modulates both nuclear architecture and epigenetic regulation. MuSCs in unconfined 2D environments exhibit larger nuclei and higher H4K16ac expression compared to those in more confined 3D conditions, leading to progressive activation, expansion, and myogenic commitment. This study highlights the importance of 3D mechanical cues in MuSC fate regulation, with 3D confinement acting as a mechanical brake on myogenic commitment, offering novel insights into the mechano-epigenetic mechanisms that govern MuSC behavior during muscle regeneration.

Regulation of cell migration by extracellular matrix mechanics at a glance

Cell migration occurs throughout development, tissue homeostasis and regeneration, as well as in diseases such as cancer. Cells migrate along two-dimensional (2D) surfaces or interfaces, within microtracks, or in confining three-dimensional (3D) extracellular matrices. Although the basic mechanisms of 2D migration are known, recent studies have elucidated unexpected migration behaviors associated with more complex substrates and have provided insights into their underlying molecular mechanisms. Studies using engineered biomaterials for 3D culture and microfabricated channels to replicate cell confinement observed in vivo have revealed distinct modes of migration. Across these contexts, the mechanical features of the surrounding microenvironment have emerged as major regulators of migration. In this Cell Science at a Glance article and the accompanying poster, we describe physiological contexts wherein 2D and 3D cell migration are essential, report how mechanical properties of the microenvironment regulate individual and collective cell migration, and review the mechanisms mediating these diverse modes of cell migration.

Analytical methods in studying cell force sensing: principles, current technologies and perspectives

Mechanical stimulation plays a crucial role in numerous biological activities, including tissue development, regeneration and remodeling. Understanding how cells respond to their mechanical microenvironment is vital for investigating mechanotransduction with adequate spatial and temporal resolution. Cell force sensing-also known as mechanosensation or mechanotransduction-involves force transmission through the cytoskeleton and mechanochemical signaling. Insights into cell-extracellular matrix interactions and mechanotransduction are particularly relevant for guiding biomaterial design in tissue engineering. To establish a foundation for mechanical biomedicine, this review will provide a comprehensive overview of cell mechanotransduction mechanisms, including the structural components essential for effective mechanical responses, such as cytoskeletal elements, force-sensitive ion channels, membrane receptors and key signaling pathways. It will also discuss the clutch model in force transmission, the role of mechanotransduction in both physiology and pathological contexts, and biomechanics and biomaterial design. Additionally, we outline analytical approaches for characterizing forces at cellular and subcellular levels, discussing the advantages and limitations of each method to aid researchers in selecting appropriate techniques. Finally, we summarize recent advancements in cell force sensing and identify key challenges for future research. Overall, this review should contribute to biomedical engineering by supporting the design of biomaterials that integrate precise mechanical information.

Cell compression - relevance, mechanotransduction mechanisms and tools

From border cell migration during Drosophila embryogenesis to solid stresses inside tumors, cells are often compressed during physiological and pathological processes, triggering major cell responses. Cell compression can be observed in vivo but also controlled in vitro through tools such as micro-channels or planar confinement assays. Such tools have recently become commercially available, allowing a broad research community to tackle the role of cell compression in a variety of contexts. This has led to the discovery of conserved compression-triggered migration modes, cell fate determinants and mechanosensitive pathways, among others. In this Review, we will first address the different ways in which cells can be compressed and their biological contexts. Then, we will discuss the distinct mechanosensing and mechanotransducing pathways that cells activate in response to compression. Finally, we will describe the different in vitro systems that have been engineered to compress cells.

The mechanobiology of biomolecular condensates

The central goal of mechanobiology is to understand how the mechanical forces and material properties of organelles, cells, and tissues influence biological processes and functions. Since the first description of biomolecular condensates, it was hypothesized that they obtain material properties that are tuned to their functions inside cells. Thus, they represent an intriguing playground for mechanobiology. The idea that biomolecular condensates exhibit diverse and adaptive material properties highlights the need to understand how different material states respond to external forces and whether these responses are linked to their physiological roles within the cell. For example, liquids buffer and dissipate, while solids store and transmit mechanical stress, and the relaxation time of a viscoelastic material can act as a mechanical frequency filter. Hence, a liquid-solid transition of a condensate in the force transmission pathway can determine how mechanical signals are transduced within and in-between cells, affecting differentiation, neuronal network dynamics, and behavior to external stimuli. Here, we first review our current understanding of the molecular drivers and how rigidity phase transitions are set forth in the complex cellular environment. We will then summarize the technical advancements that were necessary to obtain insights into the rich and fascinating mechanobiology of condensates, and finally, we will highlight recent examples of physiological liquid-solid transitions and their connection to specific cellular functions. Our goal is to provide a comprehensive summary of the field on how cells harness and regulate condensate mechanics to achieve specific functions.

Measuring age-dependent viscoelasticity of organelles, cells and organisms with time-shared optical tweezer microrheology

Quantifying the mechanical response of the biological milieu (such as the cell's interior) and complex fluids (such as biomolecular condensates) would enable a better understanding of cellular differentiation and aging and accelerate drug discovery. Here we present time-shared optical tweezer microrheology to determine the frequency- and age-dependent viscoelastic properties of biological materials. Our approach involves splitting a single laser beam into two near-instantaneous time-shared optical traps to carry out simultaneous force and displacement measurements and quantify the mechanical properties ranging from millipascals to kilopascals across five decades of frequency. To create a practical and robust nanorheometer, we leverage both numerical and analytical models to analyse typical deviations from the ideal behaviour and offer solutions to account for these discrepancies. We demonstrate the versatility of the technique by measuring the liquid-solid phase transitions of MEC-2 stomatin and CPEB4 biomolecular condensates, and quantify the complex viscoelastic properties of intracellular compartments of zebrafish progenitor cells. In Caenorhabditis elegans, we uncover how mutations in the nuclear envelope proteins LMN-1 lamin A, EMR-1 emerin and LEM-2 LEMD2, which cause premature aging disorders in humans, soften the cytosol of intestinal cells during organismal age. We demonstrate that time-shared optical tweezer microrheology offers the rapid phenotyping of material properties inside cells and protein blends, which can be used for biomedical and drug-screening applications.

Nucleating amoeboid cancer cell motility with Diaphanous related formins

The tissue invasive capacity of cancer cells is determined by their phenotypic plasticity. For instance, mesenchymal to amoeboid transition has been found to facilitate the passage of cancer cells through confined environments. This phenotypic transition is also heavily regulated by the architecture of the actin cytoskeleton, which may increase myosin contractility and the intracellular pressure that is known to drive bleb formation. In this review, we highlight several Diaphanous related formins (DRFs) that have been found to promote or suppress bleb formation in cancer cells, which is a hallmark of amoeboid migration. Based on the work discussed here, the role of the DRFs in cancer(s) is worthy of further scrutiny in animal models, as they may prove to be therapeutic targets.

Electrically-stimulated cellular and tissue events are coordinated through ion channel-mediated calcium influx and chromatin modifications across the cytosol-nucleus space

Electrical stimulation (ES) through biomaterials and devices has been implicated in activating diverse cell behaviors while facilitating tissue healing process. Despite its significance in modulating biological events, the mechanisms governing ES-activated cellular phenomena remain largely elusive. Here, we demonstrated that millisecond-pulsed temporal ES profoundly impacted a spectrum of cellular events across the membrane-cytosol-nuclear space. These include activated ion channels, intracellular calcium influx, actomyosin contractility, cell migration and proliferation, and secretome release. Such events were coordinated mainly through ES-activated ion channels and calcium oscillation dynamics. Notably, ES increased the chromatin accessibility of genes, particularly those associated with the ES-activated cellular events, underscoring the significance of epigenetic changes in ES-induced behavioral outcomes. We identified histone acetylation (mediated by histone acetyltransferases), among other chromatin modifications, is key in reshaping the chromatin landscape upon ES. These observations were further validated through experiments involving ex vivo skin tissue samples, including activated ion channels and calcium influx, increased cell proliferation and actomyosin contractility, elevated secretome profile, and more accessible chromatin structure following ES. This work provides novel insights into the mechanisms underlying ES-activated cell and tissue events, ultimately guiding design principles for the development of electrical devices and materials effective for tissue repair and wound healing.

Immune cells adapt to confined environments in vivo to optimise nuclear plasticity for migration

Cells navigating in complex 3D microenvironments frequently encounter narrow spaces that physically challenge migration. While in vitro studies identified nuclear stiffness as a key rate-limiting factor governing the movement of many cell types through artificial constraints, how cells migrating in vivo respond dynamically to confinement imposed by local tissue architecture, and whether these encounters trigger molecular adaptations, is unclear. Here, we establish an innovative in vivo model for mechanistic analysis of nuclear plasticity as Drosophila immune cells transition into increasingly confined microenvironments. Integrating live in vivo imaging with molecular genetic analyses, we demonstrate how rapid molecular adaptation upon environmental confinement (including fine-tuning of the nuclear lamina) primes leukocytes for enhanced nuclear deformation while curbing damage (including rupture and micronucleation), ultimately accelerating movement through complex tissues. We find nuclear dynamics in vivo are further impacted by large organelles (phagosomes) and the plasticity of neighbouring cells, which themselves deform during leukocyte passage. The biomechanics of cell migration in vivo are thus shaped both by factors intrinsic to individual immune cells and the malleability of the surrounding microenvironment.

Feeling the force from within - new tools and insights into nuclear mechanotransduction

The ability of cells to sense and respond to mechanical signals is essential for many biological processes that form the basis of cell identity, tissue development and maintenance. This process, known as mechanotransduction, involves crucial feedback between mechanical force and biochemical signals, including epigenomic modifications that establish transcriptional programs. These programs, in turn, reinforce the mechanical properties of the cell and its ability to withstand mechanical perturbation. The nucleus has long been hypothesized to play a key role in mechanotransduction due to its direct exposure to forces transmitted through the cytoskeleton, its role in receiving cytoplasmic signals and its central function in gene regulation. However, parsing out the specific contributions of the nucleus from those of the cell surface and cytoplasm in mechanotransduction remains a substantial challenge. In this Review, we examine the latest evidence on how the nucleus regulates mechanotransduction, both via the nuclear envelope (NE) and through epigenetic and transcriptional machinery elements within the nuclear interior. We also explore the role of nuclear mechanotransduction in establishing a mechanical memory, characterized by a mechanical, epigenetic and transcriptomic cell state that persists after mechanical stimuli cease. Finally, we discuss current challenges in the field of nuclear mechanotransduction and present technological advances that are poised to overcome them.

Nuclear mechano-confinement induces geometry-dependent HP1α condensate alterations

Cells sense external physical cues through complex processes involving signaling pathways, cytoskeletal dynamics, and transcriptional regulation to coordinate a cellular response. A key emerging principle underlying such mechanoresponses is the interplay between nuclear morphology, chromatin organization, and the dynamic behavior of nuclear bodies such as HP1α condensates. Here, applying Airyscan super-resolution live cell imaging, we report a hitherto undescribed level of mechanoresponse triggered by cell confinement below their resting nuclear diameter, which elicits changes in the number, size and dynamics of HP1α nuclear condensates. Utilizing biophysical polymer models, we observe radial redistribution of HP1α condensates within the nucleus, influenced by changes in nuclear geometry. These insights shed new light on the complex relationship between external forces and changes in nuclear shape and chromatin organization in cell mechanoreception.

Crosstalk between renin and arachidonic acid (and its metabolites)

Renin plays a significant role in the regulation of blood pressure and fluid volume by modulating the renin‒angiotensin‒aldosterone (RAAS) system. Renin suppression reduces serum aldosterone levels and lowers blood pressure in addition to preserving renal function. However, exactly how renin synthesis and action are regulated and how renin suppression preserves renal function are not clear. We propose that arachidonic acid (AA) and its metabolites control renin synthesis, secretion, and action by virtue of its (AA) anti-inflammatory, cytoprotective actions and ability to regulate the secretion of renin. These findings suggest that direct renin suppression results in changes in AA metabolism. This proposal implies that AA and its metabolites may be developed as potential drugs to prevent and manage hypertension and preserve renal function.

The emerging roles of the endoplasmic reticulum in mechanosensing and mechanotransduction

Cells are continuously subjected to physical and chemical cues from the extracellular environment, and sense and respond to mechanical cues via mechanosensation and mechanotransduction. Although the role of the cytoskeleton in these processes is well known, the contribution of intracellular membranes has been long neglected. Recently, it has become evident that various organelles play active roles in both mechanosensing and mechanotransduction. In this Review, we focus on mechanosensitive roles of the endoplasmic reticulum (ER), the functions of which are crucial for maintaining cell homeostasis. We discuss the effects of mechanical stimuli on interactions between the ER, the cytoskeleton and other organelles; the role of the ER in intracellular Ca2+ signalling via mechanosensitive channels; and how the unfolded protein response and lipid homeostasis contribute to mechanosensing. The expansive structure of the ER positions it as a key intracellular communication hub, and we additionally explore how this may be leveraged to transduce mechanical signals around the cell. By synthesising current knowledge, we aim to shed light on the emerging roles of the ER in cellular mechanosensing and mechanotransduction.

DHRS7 Integrates NADP+/NADPH Redox Sensing with Inflammatory Lipid Signalling via the Oxoeicosanoid Pathway

During the innate immune response at epithelial wound sites, oxidative stress acts microbicidal and-mechanistically less well understood-as an immune and resilience signal. The reversible sulfhydryl (SH) oxidation of kinases, phosphatases, and transcription factors constitute the perhaps best-known redox signalling paradigm, whereas mechanisms that transduce metabolic redox cues, such as redox cofactor balance, remain little explored. Here, using mammalian cells, microsomes, and live zebrafish, we identify DHRS7, a short-chain fatty acid dehydrogenase/reductase (SDR), as conserved, 5-hydroxyeicosanoid dehydrogenase (5-HEDH). Under oxidative stress, DHRS7 consumes NADP+ to convert arachidonic acid (AA)-derived 5(S)-HETE into the inflammatory lipid 5-KETE, which activates leukocyte chemotaxis via the OXER1 receptor. While Dhrs7 acts as a NADPH-dependent 5-KETE sink in unstressed, healthy tissue, it promotes rapid, 5-KETE dependent leukocytic inflammation in wounded zebrafish skin. Thus, DHRS7 epitomizes an underappreciated mode of redox signalling-beyond classic SH oxidation-that leverages NADPH metabolism to generate or quench a paracrine lipid signal. Metabolic redox sensors like DHRS7 might be promising therapeutic targets in diseases characterized by disturbed redox balance.

Cell tumbling enhances stem cell differentiation in hydrogels via nuclear mechanotransduction

Cells can deform their local niche in three dimensions via whole-cell movements such as spreading, migration or volume expansion. These behaviours, occurring over hours to days, influence long-term cell fates including differentiation. Here we report a whole-cell movement that occurs in sliding hydrogels at the minutes timescale, termed cell tumbling, characterized by three-dimensional cell dynamics and hydrogel deformation elicited by heightened seconds-to-minutes-scale cytoskeletal and nuclear activity. Studies inhibiting or promoting the cell tumbling of mesenchymal stem cells show that this behaviour enhances differentiation into chondrocytes. Further, it is associated with a decrease in global chromatin accessibility, which is required for enhanced differentiation. Cell tumbling also occurs during differentiation into other lineages and its differentiation-enhancing effects are validated in various hydrogel platforms. Our results establish that cell tumbling is an additional regulator of stem cell differentiation, mediated by rapid niche deformation and nuclear mechanotransduction.

At the nucleus of cancer: how the nuclear envelope controls tumor progression

Historically considered downstream effects of tumorigenesis-arising from changes in DNA content or chromatin organization-nuclear alterations have long been seen as mere prognostic markers within a genome-centric model of cancer. However, recent findings have placed the nuclear envelope (NE) at the forefront of tumor progression, highlighting its active role in mediating cellular responses to mechanical forces. Despite significant progress, the precise interplay between NE components and cancer progression remains under debate. In this review, we provide a comprehensive and up-to-date overview of how changes in NE composition affect nuclear mechanics and facilitate malignant transformation, grounded in the latest molecular and functional studies. We also review recent research that uses advanced technologies, including artificial intelligence, to predict malignancy risk and treatment outcomes by analyzing nuclear morphology. Finally, we discuss how progress in understanding nuclear mechanics has paved the way for mechanotherapy-a promising cancer treatment approach that exploits the mechanical differences between cancerous and healthy cells. Shifting the perspective on NE alterations from mere diagnostic markers to potential therapeutic targets, this review calls for further investigation into the evolving role of the NE in cancer, highlighting the potential for innovative strategies to transform conventional cancer therapies.

The Molecular Mechanism of Macrophages in Response to Mechanical Stress

Macrophages, a type of functionally diversified immune cell involved in the progression of many physiologies and pathologies, could be mechanically activated. The physical properties of biomaterials including stiffness and topography have been recognized as exerting a considerable influence on macrophage behaviors, such as adhesion, migration, proliferation, and polarization. Recent articles and reviews on the physical and mechanical cues that regulate the macrophage's behavior are available; however, the underlying mechanism still deserves further investigation. Here, we summarized the molecular mechanism of macrophage behavior through three parts, as follows: (1) mechanosensing on the cell membrane, (2) mechanotransmission by the cytoskeleton, (3) mechanotransduction in the nucleus. Finally, the present challenges in understanding the mechanism were also noted. In this review, we clarified the associated mechanism of the macrophage mechanotransduction pathway which could provide mechanistic insights into the development of treatment for diseases like bone-related diseases as molecular targets become possible.

Mechanical Force-Induced cGAS Activation in Carcinoma Cells Facilitates Splenocytes into Liver to Drive Metastasis

Liver metastasis is the main cause of cancer-related mortality. During the metastasis process, circulating carcinoma cells hardly pass through narrow capillaries, leading to nuclear deformation. However, the effects of nuclear deformation and its underlying mechanisms on metastasis need further study. Here, it is shown that mechanical force-induced nuclear deformation exacerbates liver metastasis by activating the cGAS-STING pathway, which promotes splenocyte infiltration in the liver. Mechanical force results in nuclear deformation and rupture of the nuclear envelope with inevitable DNA leakage. Cytoplasmic DNA triggers the activation of cGAS-STING pathway, enhancing the production of IL6, TNFα, and CCL2. Additionally, splenocyte recruitment by the proinflammatory cytokines support carcinoma cell survival and colonization in the liver. Importantly, both intervening activity of cGAS and blocking of splenocyte migration to the liver efficiently ameliorate liver metastasis. Overall, these findings reveal a mechanism by which mechanical force-induced nuclear deformation exacerbates liver metastasis by regulating splenocyte infiltration into the liver and support targeting cGAS and blocking splenocyte recruitment as candidate therapeutic approaches for liver metastasis.

Experimental tools and emerging principles of organellar mechanotransduction

Mechanotransduction is the process by which cells detect mechanical forces and convert them into biochemical or electrical signals. This process occurs across various cellular compartments, including the plasma membrane, cytoskeleton, and intracellular organelles. While research has focused mainly on force sensing at the plasma membrane, the mechanisms and significance of intracellular mechanotransduction are just beginning to be understood. This review summarizes current techniques for studying organellar mechanobiology, and highlights advances in our understanding of the mechanosensitive events occurring in organelles such as the endoplasmic reticulum (ER), Golgi apparatus, and endolysosomes. Additionally, some open questions and promising directions are identified for future research.

Invasion of glioma cells through confined space requires membrane tension regulation and mechano-electrical coupling via Plexin-B2

Glioblastoma (GBM) is a malignant brain tumor with diffuse infiltration. Here, we demonstrate how GBM cells usurp guidance receptor Plexin-B2 for confined migration through restricted space. Using live-cell imaging to track GBM cells negotiating microchannels, we reveal endocytic vesicle accumulation at cell front and filamentous actin assembly at cell rear in a polarized manner. These processes are interconnected and require Plexin-B2 signaling. We further show that Plexin-B2 governs membrane tension and other membrane features such as endocytosis, phospholipid composition, and inner leaflet surface charge, thus providing biophysical mechanisms by which Plexin-B2 promotes GBM invasion. Together, our studies unveil how GBM cells regulate membrane tension and mechano-electrical coupling to adapt to physical constraints and achieve polarized confined 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.

Chromosome mis-segregation triggers cell cycle arrest through a mechanosensitive nuclear envelope checkpoint

Errors during cell division lead to aneuploidy, which is associated with genomic instability and cell transformation. In response to aneuploidy, cells activate the tumour suppressor p53 to elicit a surveillance mechanism that halts proliferation and promotes senescence. The molecular sensors that trigger this checkpoint are unclear. Here, using a tunable system of chromosome mis-segregation, we show that mitotic errors trigger nuclear deformation, nuclear softening, and lamin and heterochromatin alterations, leading to rapid p53/p21 activation upon mitotic exit in response to changes in nuclear mechanics. We identify mTORC2 and ATR as nuclear deformation sensors upstream of p53/p21 activation. While triggering mitotic arrest, the chromosome mis-segregation-induced alterations of nuclear envelope mechanics provide a fitness advantage for aneuploid cells by promoting nuclear deformation resilience and enhancing pro-invasive capabilities. Collectively, this work identifies a nuclear mechanical checkpoint triggered by altered chromatin organization that probably plays a critical role in cellular transformation and cancer progression.

Mechanical Remodeling of Nuclear Biomolecular Condensates

Organism health relies on cell proliferation, migration, and differentiation. These universal processes depend on cytoplasmic reorganization driven notably by the cytoskeleton and its force-generating motors. Their activity generates forces that mechanically agitate the cell nucleus and its interior. New evidence from reproductive cell biology revealed that these cytoskeletal forces can be tuned to remodel nuclear membraneless compartments, known as biomolecular condensates, and regulate their RNA processing function for the success of subsequent cell division that is critical for fertility. Both cytoskeletal and nuclear condensate reorganization are common to numerous physiological and pathological contexts, raising the possibility that mechanical remodeling of nuclear condensates may be a much broader mechanism regulating their function. Here, we review this newfound mechanism of condensate remodeling and venture into the contexts of health and disease where it may be relevant, with a focus on reproduction, cancer, and premature aging.

Cytoskeletal activation of NHE1 regulates mechanosensitive cell volume adaptation and proliferation

Mammalian cells rapidly respond to environmental changes by altering transmembrane water and ion fluxes, changing cell volume. Contractile forces generated by actomyosin have been proposed to mechanically regulate cell volume. However, our findings reveal a different mechanism in adherent cells, where elevated actomyosin activity increases cell volume in normal-like cells (NIH 3T3 and others) through interaction with the sodium-hydrogen exchanger isoform 1 (NHE1). This leads to a slow secondary volume increase (SVI) following the initial regulatory volume decrease during hypotonic shock. The active cell response is further confirmed by intracellular alkalinization during mechanical stretch. Moreover, cytoskeletal activation of NHE1 during SVI deforms the nucleus, causing immediate transcriptomic changes and ERK-dependent growth inhibition. Notably, SVI and its associated changes are absent in many cancer cell lines or cells on compliant substrates with reduced actomyosin activity. Thus, actomyosin acts as a sensory element rather than a force generator during adaptation to environmental challenges.

Nuclear Structure, Size Regulation, and Role in Cell Migration

The nucleus serves as a pivotal regulatory and control hub in the cell, governing numerous aspects of cellular functions, including DNA replication, transcription, and RNA processing. Therefore, any deviations in nuclear morphology, structure, or organization can strongly affect cellular activities. In this review, we provide an updated perspective on the structure and function of nuclear components, focusing on the linker of nucleoskeleton and cytoskeleton complex, the nuclear envelope, the nuclear lamina, and chromatin. Additionally, nuclear size should be considered a fundamental parameter for the cellular state. Its regulation is tightly linked to environmental changes, development, and various diseases, including cancer. Hence, we also provide a concise overview of different mechanisms by which nuclear size is determined, the emerging role of the nucleus as a mechanical sensor, and the implications of altered nuclear morphology on the physiology of diseased cells.

Amphipathic helices sense the inner nuclear membrane environment through lipid packing defects

Amphipathic helices (AHs) are ubiquitous protein motifs that modulate targeting to organellar membranes by sensing differences in bulk membrane properties. However, the adaptation between membrane-targeting AHs and the nuclear membrane environment that surrounds the genome is poorly understood. Here, we computationally screened for candidate AHs in a curated list of characterized and putative human inner nuclear membrane (INM) proteins. Cell biological and in vitro experimental assays combined with computational calculations demonstrated that AHs detect lipid packing defects over electrostatics to bind to the INM, indicating that the INM is loosely packed under basal conditions. Membrane tension resulting from hypotonic shock further promoted AH binding to the INM, whereas cell-substrate stretch did not enhance recruitment of membrane tension-sensitive AHs. Together, our work demonstrates the rules driving lipid-protein interactions at the INM, and its implications in the response of the nucleus to different stimuli.

Perivascular Macrophages Convert Physical Wound Signals Into Rapid Vascular Responses

Leukocytes detect distant wounds within seconds to minutes, which is essential for effective pathogen defense, tissue healing, and regeneration. Blood vessels must detect distant wounds just as rapidly to initiate local leukocyte extravasation, but the mechanism behind this immediate vascular response remains unclear. Using high-speed imaging of live zebrafish larvae, we investigated how blood vessels achieve rapid wound detection. We monitored two hallmark vascular responses: vessel dilation and serum exudation. Our experiments-including genetic, pharmacologic, and osmotic perturbations, along with chemogenetic leukocyte depletion-revealed that the cPla2 nuclear shape sensing pathway in perivascular macrophages converts a fast (~50 μm/s) osmotic wound signal into a vessel-permeabilizing, 5-lipoxygenase (Alox5a) derived lipid within seconds of injury. These findings demonstrate that perivascular macrophages act as physicochemical relays, bridging osmotic wound signals and vascular responses. By uncovering this novel type of communication, we provide new insights into the coordination of immune and vascular responses to injury.

Extreme wrinkling of the nuclear lamina is a morphological marker of cancer

Nuclear atypia is a hallmark of cancer. A recent model posits that excess surface area, visible as folds/wrinkles in the lamina of a rounded nucleus, allows the nucleus to take on diverse shapes with little mechanical resistance. Whether this model is applicable to normal and cancer nuclei in human tissues is unclear. We image nuclear lamins in patient tissues and find: (a) nuclear laminar wrinkles are present in control and cancer tissue but are obscured in hematoxylin and eosin (H&E) images, (b) nuclei rarely have a smooth lamina, and (c) wrinkled nuclei assume diverse shapes. Deep learning reveals the presence of extreme nuclear laminar wrinkling in cancer tissues, which is confirmed by Fourier analysis. These data support a model in which excess surface area in the nuclear lamina enables nuclear shape diversity in vivo. Extreme laminar wrinkling is a marker of cancer, and imaging the lamina may benefit cancer diagnosis.

Nuclear deformability facilitates apical nuclear migration in the developing zebrafish retina

Nuclear positioning is a crucial aspect of cell and developmental biology. One example is the apical movement of nuclei in neuroepithelia before mitosis, which is essential for proper tissue formation. While the cytoskeletal mechanisms that drive nuclei to the apical side have been explored, the influence of nuclear properties on apical nuclear migration is less understood. Nuclear properties, such as deformability, can be linked to lamin A/C expression levels, as shown in various in vitro studies. Interestingly, many nuclei in early development, including neuroepithelial nuclei, express only low levels of lamin A/C. Therefore, we investigated whether increased lamin A expression in the densely packed zebrafish retinal neuroepithelium affects nuclear deformability and, consequently, migration phenomena. We found that overexpressing lamin A in retinal nuclei increases nuclear stiffness, which in turn indeed impairs apical nuclear migration. Interestingly, nuclei that do not overexpress lamin A but are embedded in a stiffer lamin A-overexpressing environment also exhibit impaired apical nuclear migration, indicating that these effects can be cell non-autonomous. Additionally, in the less crowded hindbrain neuroepithelium, only minor effects on apical nuclear migration are observed. Together, this suggests that the material properties of the nucleus influence nuclear movements in a tissue-dependent manner.

Regulation of cytoskeleton dynamics and its interplay with force in plant cells

The plant cytoskeleton is an intricate network composed of actin filaments and microtubules. The cytoskeleton undergoes continuous dynamic changes that provide the basis for rapidly responding to intrinsic and extrinsic stimuli, including mechanical stress. Microtubules can respond to alterations of mechanical stress and reorient along the direction of maximal tensile stress in plant cells. The cytoskeleton can also generate driving force for cytoplasmic streaming, organelle movement, and vesicle transportation. In this review, we discuss the progress of how the plant cytoskeleton responds to mechanical stress. We also summarize the roles of the cytoskeleton in generating force that drive organelles and nuclear transportation in plant cells. Finally, some hypotheses concerning the link between the roles of the cytoskeleton in force response and organelle movement, as well as several key questions that remain to be addressed in the field, are highlighted.

Mechanobiology of 3D cell confinement and extracellular crowding

Cells and tissues are often under some level of confinement, imposed by the microenvironment and neighboring cells, meaning that there are limitations to cell size, volume changes, and fluid exchanges. 3D cell culture, increasingly used for both single cells and organoids, inherently impose levels of confinement absent in 2D systems. It is thus key to understand how different levels of confinement influences cell survival, cell function, and cell fate. It is well known that the mechanical properties of the microenvironment, such as stiffness and stress relaxation, are important in activating mechanosensitive pathways, and these are responsive to confinement conditions. In this review, we look at how low, intermediate, and high levels of confinement modulate the activation of known mechanobiology pathways, in single cells, organoids, and tumor spheroids, with a specific focus on 3D confinement in microwells, elastic, or viscoelastic scaffolds. In addition, a confining microenvironment can drastically limit cellular communication in both healthy and diseased tissues, due to extracellular crowding. We discuss potential implications of extracellular crowding on molecular transport, extracellular matrix deposition, and fluid transport. Understanding how cells sense and respond to various levels of confinement should inform the design of 3D engineered matrices that recapitulate the physical properties of tissues.

Sensing the squeeze: nuclear mechanotransduction in health and disease

The nucleus not only is a repository for DNA but also a center of cellular and nuclear mechanotransduction. From nuclear deformation to the interplay between mechanosensing components and genetic control, the nucleus is poised at the nexus of mechanical forces and cellular function. Understanding the stresses acting on the nucleus, its mechanical properties, and their effects on gene expression is therefore crucial to appreciate its mechanosensitive function. In this review, we examine many elements of nuclear mechanotransduction, and discuss the repercussions on the health of cells and states of illness. By describing the processes that underlie nuclear mechanosensation and analyzing its effects on gene regulation, the review endeavors to open new avenues for studying nuclear mechanics in physiology and diseases.

Mechanobiology of the nucleus during the G2-M transition

Cellular behavior is continuously influenced by mechanical forces. These forces span the cytoskeleton and reach the nucleus, where they trigger mechanotransduction pathways that regulate downstream biochemical events. Therefore, the nucleus has emerged as a regulator of cellular response to mechanical stimuli. Cell cycle progression is regulated by cyclin-CDK complexes. Recent studies demonstrated these biochemical pathways are influenced by mechanical signals, highlighting the interdependence of cellular mechanics and cell cycle regulation. In particular, the transition from G2 to mitosis (G2-M) shows significant changes in nuclear structure and organization, ranging from nuclear pore complex (NPC) and nuclear lamina disassembly to chromosome condensation. The remodeling of these mechanically active nuclear components indicates that mitotic entry is particularly sensitive to forces. Here, we address how mechanical forces crosstalk with the nucleus to determine the timing and efficiency of the G2-M transition. Finally, we discuss how the deregulation of nuclear mechanics has consequences for mitosis.

The mechanical journey of primordial germ cells

Primordial germ cells (PGCs) are the earliest progenitors of germline cells of the gonads in animals. The tissues that arise from primordial germ cells give rise to male and female gametes and are thus responsible for transmitting genetic information to subsequent generations. The development of gonads, from single cells to fully formed organs, is of great interest to the reproductive biology community. In most higher animals, PGCs are initially specified at a site away from the gonads. They then migrate across multiple tissue microenvironments to reach a mesodermal mass of cells called the genital ridge, where they associate with somatic cells to form sex-specific reproductive organs. Their migratory behavior has been studied extensively to identify which tissues they interact with and how this might affect gonad development. A crucial point overlooked by classical studies has been the physical environment experienced by PGCs as they migrate and the mechanical challenges they might encounter along the way. It has long been understood that migrating cells can sense and adapt to physical forces around them via a variety of mechanisms, and studies have shown that these mechanical signals can guide stem cell fate. In this review, we summarize the mechanical microenvironment of migrating PGCs in different organisms. We describe how cells can adapt to this environment and how this adaptation can influence cell fate. Finally, we propose that mechanical signals play a crucial role in the normal development of the germline and shed light on this unexplored area of developmental biology.

Chemically induced proximity reveals a Piezo-dependent meiotic checkpoint at the oocyte nuclear envelope

Sexual reproduction relies on robust quality control during meiosis. Assembly of the synaptonemal complex between homologous chromosomes (synapsis) regulates meiotic recombination and is crucial for accurate chromosome segregation in most eukaryotes. Synapsis defects can trigger cell cycle delays and, in some cases, apoptosis. We developed and deployed a chemically induced proximity system to identify key elements of this quality control pathway in Caenorhabditis elegans. Persistence of the polo-like kinase PLK-2 at pairing centers-specialized chromosome regions that interact with the nuclear envelope-induced apoptosis of oocytes in response to phosphorylation and destabilization of the nuclear lamina. Unexpectedly, the Piezo1/PEZO-1 channel localized to the nuclear envelope and was required to transduce this signal to promote apoptosis in maturing oocytes.

Matrix stiffness drives drop like nuclear deformation and lamin A/C tension-dependent YAP nuclear localization

Extracellular matrix (ECM) stiffness influences cancer cell fate by altering gene expression. Previous studies suggest that stiffness-induced nuclear deformation may regulate gene expression through YAP nuclear localization. We investigated the role of the nuclear lamina in this process. We show that the nuclear lamina exhibits mechanical threshold behavior: once unwrinkled, the nuclear lamina is inextensible. A computational model predicts that the unwrinkled lamina is under tension, which is confirmed using a lamin tension sensor. Laminar unwrinkling is caused by nuclear flattening during cell spreading on stiff ECM. Knockdown of lamin A/C eliminates nuclear surface tension and decreases nuclear YAP localization. These findings show that nuclear deformation in cells conforms to the nuclear drop model and reveal a role for lamin A/C tension in controlling YAP localization in cancer cells.

A nuclear jamming transition in vertebrate organogenesis

Jamming of cell collectives and associated rigidity transitions have been shown to play a key role in tissue dynamics, structure and morphogenesis. Cellular jamming is controlled by cellular density and the mechanics of cell-cell contacts. However, the contribution of subcellular organelles to the physical state of the emergent tissue is unclear. Here we report a nuclear jamming transition in zebrafish retina and brain tissues, where physical interactions between highly packed nuclei restrict cellular movements and control tissue mechanics and architecture. Computational modelling suggests that the nuclear volume fraction and anisotropy of cells control the emerging tissue physical state. Analysis of tissue architecture, mechanics and nuclear movements during eye development show that retina tissues undergo a nuclear jamming transition as they form, with increasing nuclear packing leading to more ordered cellular arrangements, reminiscent of the crystalline cellular packings in the functional adult eye. Our results reveal an important role of the cell nucleus in tissue mechanics and architecture.

Physical effects of 3-D microenvironments on confined cell behaviors

Cell migration is a fundamental and functional cellular process, influenced by a complex microenvironment consisting of different cells and extracellular matrix. Recent research has highlighted that, besides biochemical cues from the microenvironment, physical cues can also greatly alter cellular behavior. However, due to the complexity of the microenvironment, little is known about how the physical interactions between migrating cells and surrounding microenvironment instructs cell movement. Here, we explore various examples of three-dimensional microenvironment reconstruction models in vitro and describe how the physical interplay between migrating cells and the neighboring microenvironment controls cell behavior. Understanding this mechanical cooperation will provide key insights into organ development, regeneration, and tumor metastasis.

Compressive stresses in cancer: characterization and implications for tumour progression and treatment

Beyond their many well-established biological aberrations, solid tumours create an abnormal physical microenvironment that fuels cancer progression and confers treatment resistance. Mechanical forces impact tumours across a range of biological sizes and timescales, from rapid events at the molecular level involved in their sensing and transmission, to slower and larger-scale events, including clonal selection, epigenetic changes, cell invasion, metastasis and immune response. Owing to challenges with studying these dynamic stimuli in biological systems, the mechanistic understanding of the effects and pathways triggered by abnormally elevated mechanical forces remains elusive, despite clear correlations with cancer pathophysiology, aggressiveness and therapeutic resistance. In this Review, we examine the emerging and diverse roles of physical forces in solid tumours and provide a comprehensive framework for understanding solid stress mechanobiology. We first review the physiological importance of mechanical forces, especially compressive stresses, and discuss their defining characteristics, biological context and relative magnitudes. We then explain how abnormal compressive stresses emerge in tumours and describe the experimental challenges in investigating these mechanically induced processes. Finally, we discuss the clinical translation of mechanotherapeutics that alleviate solid stresses and their potential to synergize with chemotherapy, radiotherapy and immunotherapies.

Applying Spatiotemporal Modeling of Cell Dynamics to Accelerate Drug Development

Cells act as physical computational programs that utilize input signals to orchestrate molecule-level protein-protein interactions (PPIs), generating and responding to forces, ultimately shaping all of the physiological and pathophysiological behaviors. Genome editing and molecule drugs targeting PPIs hold great promise for the treatments of diseases. Linking genes and molecular drugs with protein-performed cellular behaviors is a key yet challenging issue due to the wide range of spatial and temporal scales involved. Building predictive spatiotemporal modeling systems that can describe the dynamic behaviors of cells intervened by genome editing and molecular drugs at the intersection of biology, chemistry, physics, and computer science will greatly accelerate pharmaceutical advances. Here, we review the mechanical roles of cytoskeletal proteins in orchestrating cellular behaviors alongside significant advancements in biophysical modeling while also addressing the limitations in these models. Then, by integrating generative artificial intelligence (AI) with spatiotemporal multiscale biophysical modeling, we propose a computational pipeline for developing virtual cells, which can simulate and evaluate the therapeutic effects of drugs and genome editing technologies on various cell dynamic behaviors and could have broad biomedical applications. Such virtual cell modeling systems might revolutionize modern biomedical engineering by moving most of the painstaking wet-laboratory effort to computer simulations, substantially saving time and alleviating the financial burden for pharmaceutical industries.