The research team, led by Meraj Ahmed, Lahcen Akerkouch and Trung Bao Le at North Dakota State University, together with colleagues at the University of North Dakota, tackled a problem that has long frustrated modelers. Most previous simulations represented cancer cells as idealized spheres or capsules, an assumption that bears little resemblance to the irregular, protrusion-covered geometries seen under the microscope. To break free of that limitation, the team cultured breast cancer cells of the MDA-MB-231 line on glass coverslips, fixed and stained them, and then imaged individual cells with a Leica Stellaris confocal microscope at an axial step size of half a micrometer. From these image stacks, four distinct three-dimensional cell geometries, labeled M-1 through M-4, were reconstructed and converted into triangulated surface meshes that preserved the experimentally observed irregularity.

The simulation framework itself is a hybrid of two computational worlds. The cell membrane and the nuclear envelope were modeled using dissipative particle dynamics, a mesoscopic technique in which the membranes are represented as networks of nonlinear springs obeying a Helmholtz free energy functional. That energy accounts for in-plane stretching through a Wormlike Chain-Power formulation, bending resistance, and the conservation of surface area and enclosed volume, with an additional short-range repulsive potential preventing the membrane and nucleus from unphysically overlapping. The surrounding blood plasma, by contrast, was treated as a continuous incompressible Newtonian fluid governed by the three-dimensional unsteady Navier-Stokes equations. The two descriptions were stitched together with a sharp-interface curvilinear immersed boundary method, so that forces generated by the deforming membranes are transferred to the fluid while the local fluid velocity is interpolated back to the membrane nodes. Each of the four geometries was then simulated under three stiffness combinations, in which the Young’s moduli of the membrane and nucleus were varied from 1.26 to 2.52 times ten to the minus five newtons per meter, yielding twelve cases in total.

Before any flow was applied, the reconstructed cells had to be brought to mechanical equilibrium. Because scanned geometries cannot generally be represented by equilateral triangles, the team ran shape relaxation simulations for 900 milliseconds under force-free conditions, temporarily removed the scanned nuclei, and then reintroduced them as spheres inside the relaxed cell volumes. Only then were the cells placed in a rectangular microchannel with plasma viscosity of 1.2 times ten to the minus six square meters per second and a bulk velocity of one millimeter per second, ramped up over half a millisecond. The simulations, run on 64 CPUs at North Dakota State University’s computing cluster with a physical time step of one microsecond, captured the first ten milliseconds of deformation in exquisite detail.

The first striking result is how fast everything happens. All four cell models exhibited a rapid deformation response within the first one to two milliseconds of flow onset, followed by shape evolution that depended strongly on both morphology and stiffness. To classify the ever-changing shapes, the researchers introduced a scheme based on two classical indices, sphericity and aspect ratio, partitioning the shape space into five categories: round or compact, amoeboid ellipsoidal, lobed, elongated, and streamer. Model M-1, which began highly elongated with an aspect ratio above ten, remained streamer-like throughout. Model M-2, the most compact, stayed amoeboid ellipsoidal with remarkable stability, its aspect ratio hovering between roughly 4.4 and 5.3 and its sphericity near 0.8. The transition-prone models M-3 and M-4 told a more dramatic story, switching between compact, elongated, lobed and streamer states as time progressed and as stiffness changed.

Stiffness, it turns out, does not act uniformly. Membrane stiffening dominated elongation and the loss of compactness, while nuclear stiffening mainly modulated the timing and amplitude of deformation excursions and the degree of partial recovery. The most vivid example came from model M-3, which was compact ellipsoidal for all stiffness cases at five milliseconds but, by ten milliseconds, had transitioned to a streamer state only under the stiffest membrane and nucleus combination, a stiffness-induced switch from compact deformation to tether-dominated elongation. Model M-4 underwent a clear temporal transition, starting elongated, briefly becoming streamer-like, and then converging to a folded, lobed configuration by ten milliseconds regardless of stiffness, indicating that lobing and folding, rather than continued stretching, dominated its loss of compactness.

Because the framework resolves the extracellular flow as well as the cell, the researchers could watch how these shape changes reorganized the surrounding fluid. When membrane stiffening did not substantially change the cell’s shape class, the wake vortices were merely stretched and pushed closer to the membrane as near-surface velocity gradients sharpened. But when stiffness drove a genuine shape transition, as in M-3’s shift from compact to streamer, the flow responded dramatically: separation and reattachment points moved, recirculation zones shifted, and some vortices were effectively washed away. Traction maps, which combine pressure and viscous shear on the membrane surface, told a complementary story. The compact M-2 showed the smoothest and most symmetric loading with weak stiffness sensitivity, while the deformation-prone models concentrated traction into hot spots at geometric constrictions, high-curvature protrusions, neck and tether regions, and surface folds, with membrane stiffening sharpening these gradients into smaller, more intense patches.

The net hydrodynamic force on the membrane followed a common pattern across all models: a start-up rise within the first half millisecond followed by relaxation. Beyond that shared transient, morphology took over. The compact M-2 settled at the lowest and steadiest force levels, around 14 to 16 piconewtons, with the three stiffness curves nearly overlapping. M-1 stabilized near 18 to 20 piconewtons with mild unsteadiness. The deformation-prone models showed far richer behavior, including a compliant-case overshoot in M-3 reaching about 30 piconewtons at six to seven milliseconds, and late-time values up to 25 to 27 piconewtons in M-4 near ten milliseconds. Cross-sectional velocity and vorticity fields added the final piece, revealing a pronounced asymmetry about one lateral axis that produces a dominant hydrodynamic imbalance and drives lateral migration, with stiffness modulating the intensity of these features without changing their direction.

The clinical implications ripple outward in several directions. Highly deformable cells that adopt elongated or lobed configurations can pass through narrow capillaries more easily and are more likely to drift toward vessel walls, raising the probability of the adhesion and extravasation events that seed distant metastases, whereas stiffer cells tend to remain in the flow core. Cell deformability is increasingly recognized as a biophysical biomarker of malignancy, and the deformation-driven lateral migration described here could enable label-free microfluidic sorting of circulating tumor cells. Therapeutically, interventions that alter membrane or nuclear stiffness, such as cytoskeletal drugs or lamin-targeted strategies, might shift deformation pathways and reduce metastatic potential by limiting wall-ward transport. The authors caution that their simulations used periodic rather than no-slip lateral boundaries and did not include red blood cell collisions or the cell-free layer, effects they plan to incorporate in future work. They also note that the trends identified, with membrane stiffness controlling elongation and compactness and nuclear stiffness governing recovery and internal reorganization, are expected to hold qualitatively even in curved vessels and at higher velocities, even though exact transition thresholds may shift. For now, the study provides something the field has lacked: a mechanistic bridge linking what a cancer cell looks like, how stiff it is, and where the blood flow will carry it.

Subject of Research: Cancer cell deformation under shear flow as governed by cell morphology and membrane and nuclear elasticity

Article Title: Impacts of Morphology and Elasticity on Cancer Cell Deformation in Shear Flows

Article References: Ahmed, M., Akerkouch, L., Vanyo, A., Haage, A., & Le, T. B. (2026). Impacts of Morphology and Elasticity on Cancer Cell Deformation in Shear Flows. Annals of Biomedical Engineering. https://doi.org/10.1007/s10439-026-04363-8

Image Credits: AI Generated

DOI: 10.1007/s10439-026-04363-8

Keywords: circulating tumor cells, cancer cell deformation, shear flow, dissipative particle dynamics, immersed boundary method, membrane stiffness, nuclear stiffness, metastasis, mechanobiology, microfluidics, fluid-structure interaction, cell mechanics

Traction force microscopy, the foundational method behind CFM, has been a workhorse of mechanobiology for nearly two decades. In its classical form, cells are plated on a flat, elastic gel embedded with fluorescent beads. As a cell pulls and pushes on the gel, the beads shift, and by tracking those displacements researchers can computationally reconstruct the traction stresses the cell applies to its substrate. The approach has revealed how cancer cells turn mechanically aggressive, how stem cells sense the stiffness of their niche, and how fibroblasts remodel wound tissue. But its central limitation has always been geometry: real cells rarely live on open flat surfaces, and their force-generating machinery behaves differently when confined on multiple sides.

Confinement force microscopy addresses this gap with a microconfiner that can be dynamically tuned, positioned with precision and held stable over long imaging periods. The device brings a controlled, deformable ceiling down over cells resting on a soft elastic substrate, effectively sandwiching them in a defined three-dimensional space that mimics the physical confinement of a living tissue. Because the confining element is itself compliant and instrumented, the forces cells exert against it can be measured alongside the traction stresses they generate on the bottom surface. The result is a fuller, more faithful accounting of a single cell’s mechanical output under realistic compressive boundary conditions.

The dynamic character of the platform is one of its most significant advances. Earlier confinement approaches tended to be static, locking cells into a fixed geometry and leaving researchers unable to probe how cells respond as their mechanical environment changes. With CFM, the degree of confinement can be adjusted during an experiment. A cell can be observed in a relatively open state, then progressively constrained, then released, allowing researchers to map how traction stresses evolve as confinement tightens or relaxes in real time. This turns the microconfiner from a passive chamber into an active perturbation tool, capable of asking causal questions about how spatial restriction drives mechanotransduction.

Precision and stability, the other two pillars highlighted by the developers, matter because traction measurements are exquisitely sensitive to boundary conditions. Any drift in the position or compliance of a confining surface contaminates the displacement field on the underlying gel, corrupting the reconstructed force map. The CFM architecture maintains a stable confining geometry over the timescales of live-cell imaging, from minutes to hours, so that force reconstructions remain quantitatively reliable. The precision of the confinement also allows single cells and multicellular aggregates alike to be studied under well-defined conditions, which is essential for comparing mechanical phenotypes across genetic backgrounds, drug treatments or differentiation states.

The applications span an unusually broad swath of biology. In cancer research, one of the central puzzles is how tumor cells invading through dense stiffer tissue generate and reorient forces in tight, crowded spaces. Conventional two-dimensional traction assays cannot reproduce this compressive regime, and invasion assays in organoids or tissue slices typically sacrifice quantitative force readouts for biological realism. CFM offers a bridge between the two: cells or small aggregates can be confined in tissue-like geometries while their complete traction signature is measured with subcellular resolution. Similar logic applies to immune cells squeezing through endothelial barriers, epithelial sheets closing wounds, and stem cells differentiating under the compressive loads of developing organs.

Cell aggregates add a further layer of biological complexity that the platform is specifically designed to handle. Multicellular clusters, such as spheroids used to model early tumors or embryonic tissues, generate forces collectively, coordinating contractility across many cells through junctions and extracellular matrix. Measuring aggregate-scale traction under confinement reveals how mechanical load is distributed across the cluster, where regions of high stress concentrate, and how the collective output changes as the group is compressed. These are questions that neither single-cell assays on flat gels nor bulk rheology of tissue can answer, positioning CFM as a tool for probing emergent mechanics in multicellular systems.

Technically, the method builds on the mature computational machinery of traction force microscopy while adding a second force channel from the confining interface. Displacements of fluorescent markers in the deformable substrate are converted into surface traction fields through regularized inverse algorithms, a process well established in the field. The confining element contributes complementary measurements of the forces transmitted vertically and laterally onto the cell. Combining these datasets requires careful mechanical calibration and modeling of the microconfiner’s own elasticity, but the payoff is a genuinely three-dimensional force balance for a living cell, something the field has pursued for years with more complex and less accessible systems.

The broader significance of the work lies in what it says about the maturation of mechanobiology as a discipline. The field has moved decisively from observing that cells are mechanical objects to quantifying precisely how they sense, generate and transmit force in contexts that resemble the body. Tools such as atomic force microscopy, micropillar arrays, optical tweezers and droplet microfluidics each probe one corner of the mechanical landscape, and CFM fills a conspicuous gap: the confined, compressive, three-dimensional regime that characterizes nearly every tissue. By making that regime dynamic and measurable, the platform opens experimental doors that were previously accessible only through indirect inference.

Looking ahead, the researchers and the field at large anticipate that confinement-resolved traction mapping will become a standard component of mechanobiological phenotyping, much as flow cytometry became standard for molecular phenotyping. Because the technique is compatible with live-cell imaging, it can be paired with fluorescent reporters of cytoskeletal dynamics, focal adhesion turnover and mechanosensitive signaling pathways, linking the force maps it produces directly to the molecular machinery that generates them. For cancer biologists, stem cell engineers and developmental biologists alike, the ability to watch and measure how cells push back against a crowded world represents a meaningful step toward understanding mechanics where it actually matters: inside tissue.

Subject of Research: A tunable microconfinement technique for measuring traction forces of single cells and aggregates under tissue-mimicking spatial confinement.

Article Title: CFM: confinement force microscopy—a dynamic, precise and stable microconfiner for traction force microscopy in spatial confinement

Article References: CFM: confinement force microscopy—a dynamic, precise and stable microconfiner for traction force microscopy in spatial confinement. (n.d.). https://doi.org/10.1038/s41592-026-03216-5

Image Credits: AI Generated

DOI: 10.1038/s41592-026-03216-5

Keywords: confinement force microscopy, traction force microscopy, mechanobiology, cell mechanics, spatial confinement, cell aggregates, 3D cell culture, traction stresses, microconfiner, Nature Methods, cellular forces, tissue mechanics

The findings, published in Science Advances, address a central question in cell biology: how do molecular structures operating at microscopic scales produce coordinated changes across an entire cell? Living cells contain thousands of interacting molecules, making it difficult to determine which processes are essential and which are secondary. To isolate the underlying mechanics, the researchers created cell-sized liposomes, spherical membrane compartments that resemble primitive cells but lack the complex internal machinery of biological organisms.

Inside these liposomes, the team introduced purified components of the actomyosin cytoskeleton. Actin is a protein that polymerizes into filaments, while myosin motor proteins use chemical energy to slide along those filaments and generate contractile forces. In living cells, actomyosin networks help control movement, division, adhesion, and mechanical organization. By reconstructing the network from selected components, the researchers could observe how molecular-scale forces deform a membrane without interference from signaling pathways, organelles, or other cellular systems.

The experiments focused on membrane blebbing, a process in which the cell membrane briefly detaches from the underlying cortex and expands outward as a rounded, bubble-like protrusion. Blebs are involved in several forms of cell movement and can appear at the front or rear of migrating cells. They are also associated with cell division, programmed cell death, and changes in tissue architecture. Although blebs are familiar features of living cells, their formation is governed by a complicated combination of membrane tension, cortical contractility, adhesion, and fluid movement.

When the artificial cells were subjected to a specific physical manipulation, the actomyosin network generated a bleb that expanded in a consistent direction. The liposomes consequently developed a distinct asymmetry, with one region behaving differently from the opposite side. This result indicates that front-rear polarity does not necessarily require a pre-existing biochemical signal or an internal molecular compass. Instead, mechanical stresses within the cytoskeletal network can be sufficient to break the symmetry of an initially uniform cell-like system.

The researchers combined microscopy with large-scale computer simulations and theoretical analysis to connect the behavior of individual actin filaments and myosin motors to changes occurring across the entire liposome. The simulations showed how local contractions can redistribute mechanical stress, alter membrane attachment, and create conditions favorable for bleb formation. Once a protrusion appeared, changes in membrane tension and cytoskeletal organization helped stabilize and enlarge it, allowing a local event to become a cell-scale transformation.

This distinction between local and global mechanisms is important because membrane blebs can arise through more than one physical route. In some cases, contraction of the actomyosin cortex increases internal pressure and forces the membrane outward. In others, a local weakening of the connection between the membrane and cortex allows the membrane to balloon into the surrounding space. By reconstructing the system with controlled ingredients, the researchers were able to distinguish these mechanisms and examine how they interact during bleb formation and symmetry breaking.

“By reconstructing membrane morphogenesis from purified proteins, we showed that local interactions within the actin cytoskeleton are sufficient to generate large-scale changes in cell shape,” Miyazaki said. The result does not mean that biochemical signaling is unimportant in living organisms. Rather, it reveals that signaling may act by regulating a physical system whose basic capacity for shape change is already embedded in the properties of the cytoskeleton, membrane, and surrounding fluid.

The artificial-cell platform could become a useful tool for investigating how cells move, divide, and organize themselves during development. Because the system is quantitatively controllable, researchers can vary protein concentrations, membrane composition, network architecture, and mechanical constraints one factor at a time. The same approach could help identify the minimal ingredients required for other cellular behaviors, including force sensing, directed movement, and dynamic remodeling of internal structures.

The work also contributes to the long-term goal of building autonomous artificial cells. Future versions could incorporate molecular sensors, energy-generating reactions, or programmable biochemical circuits, allowing them to respond to their surroundings or perform specific tasks. Potential applications include drug delivery, regenerative medicine, synthetic biology, and the manufacture of biological compounds. For now, the study provides a fundamental lesson: some of the complexity associated with living cells can emerge from the physics of interacting molecules, even before sophisticated biological signaling networks are added.

Subject of Research: Not applicable

Article Title: Reconstitution of actomyosin networks in cell-sized liposomes dissects distinct mechanisms of membrane blebbing and symmetry breaking

Web References: https://doi.org/10.1126/sciadv.aed8818

References: Science Advances, DOI: 10.1126/sciadv.aed8818

Image Credits: RIKEN

Keywords: artificial cells, actomyosin networks, actin cytoskeleton, myosin, membrane blebbing, cell morphogenesis, symmetry breaking, cell polarity, liposomes, synthetic biology, cellular mechanics, RIKEN