bims-ecemfi Biomed News
on ECM and fibroblasts
Issue of 2026–04–05
eight papers selected by
Badri Narayanan Narasimhan, University of California, San Diego



  1. Bioact Mater. 2026 Aug;62 480-494
      Hydrogels that recapitulate the dynamic mechanical cues of native extracellular matrix are powerful tools that can be leveraged for tissue engineering. Despite growing recognition that cues such as stress relaxation and plasticity modulate cell-matrix interactions, the influence of these properties on mesenchymal stromal cell (MSC) chondrogenesis has yet to be elucidated across a broad range of relaxation timescales and in the absence of confounding biochemical cues. Here, we report the adaptable sliding hydrogel (ASG) with tunable stress relaxation and plasticity as a novel MSC cell niche. By incorporating reversible hydrazone crosslinks into polyethylene glycol (PEG)-based sliding hydrogels (SG), ASG achieves a wide range of tunable stress relaxation and plasticity that are distinct from other dynamic hydrogels used for MSC chondrogenesis. Notably, increasing stress relaxation and plasticity in ASG promotes rapid and robust cartilage formation by human MSCs and supports long-term cell viability. Mechanistically, ASG facilitates local matrix remodeling and enables MSCs to form "pericellular pockets" in 3D that correlate with enhanced nascent extracellular matrix deposition and reorganization, integrin signaling, and nuclear dynamics. Overall, the ASG platform provides a tunable, synthetic microenvironment that helps probe the relationship between dynamic mechanical cues and stem cell fate and informs next-generation material design within the field of tissue engineering.
    Keywords:  Chondrogenesis; Dynamic; Hydrogels; Mechanotransduction; Viscoelasticity
    DOI:  https://doi.org/10.1016/j.bioactmat.2026.03.014
  2. Soft Matter. 2026 Apr 01.
      The mechanical properties of the extracellular matrix (ECM) regulate tumor growth and invasion in the tumor microenvironment. Models of biopolymer networks have been used to investigate the impact of elasticity and viscoelasticity of the ECM on tumor behavior. Under tumor compression, these networks also show poroelastic behavior that is governed by the resistance to water flow through their pores. This work investigates the hypothesis that stress-dependent transport properties of biopolymer networks regulate tumor growth. Here, alginate hydrogels are used as a model ECM system with tunable ionic and hybrid ionic/covalent crosslinking. Hydrogel stiffness, viscoelasticity, and stress relaxation behavior were characterized using stepwise axial compression. Among these properties, we find poroelastic fluid outflow dominates ECM stress relaxation, as the measured water flux was significantly affected under compression. Continuum mechanics-based modeling was developed to formulate and calculate the chemical potential gradients of water (solvent) in the hydrogels under compression. This framework was extended into an advection-diffusion framework to quantify growth factor (solute) distribution under varying strengths of stress and diffusion indexed by the relative strength of convective to diffusive transport, characterized by the Péclet number. An agent-based computational simulation showed that the Péclet numbers based on our experimental timescales strongly influenced tumor growth over longer, more physiologic timescales. Together, these results highlight the important role of water flux and transport in three-dimensional biopolymer networks.
    DOI:  https://doi.org/10.1039/d6sm00060f
  3. bioRxiv. 2026 Mar 28. pii: 2026.03.25.714233. [Epub ahead of print]
      Extracellular matrix (ECM) mechanical properties regulate tissue homeostasis and disease progression, with persistent ECM stiffening serving as a hallmark of fibrosis; yet, the early transition from healthy to diseased tissue remains poorly understood. Dynamic three-dimensional (3D) tissue models that capture early-stage stiffening are needed to investigate cellular responses during disease initiation. This work presents an innovative platform for studying cell responses in 3D environments undergoing active matrix stiffening. A bioinspired synthetic ECM incorporates collagen-mimetic peptides and employs sequential, non-terminal strain-promoted azide-alkyne cycloaddition (SPAAC) reactions to enable controlled increases in matrix stiffness over physiologically relevant timescales. Alternating polymer incubations produce a 2.5-fold increase in storage modulus over 72 hours, modeling the mechanical transition from healthy to early-stage fibrotic lung tissue. Live-cell reporter fibroblasts enable real-time monitoring of alpha-smooth muscle actin (αSMA) expression, revealing significant upregulation during matrix stiffening that remains transient and difficult to detect via traditional endpoint assays. Active stiffening also modulates fibroblast motility, transiently increasing migration speed while persistently enhancing directional persistence. Complementary computational reaction-diffusion modeling provides mechanistic insight into modulus gradient formation and reaction kinetics. This versatile toolbox enables investigation of early mechanobiological responses to matrix stiffening and may aid identification of markers of fibrotic disease onset.
    DOI:  https://doi.org/10.64898/2026.03.25.714233
  4. bioRxiv. 2026 Mar 26. pii: 2026.03.24.713716. [Epub ahead of print]
      Directed cell migration underlies many biological phenomena, from embryonic development to tumor metastasis and organ fibrosis. Most cells typically migrate toward stiffer regions of their extracellular matrix -a behavior known as positive durotaxis. Here we show that culture on rigid plastic reinforces this response, whereas preconditioning in soft 3D physiomimetic environments reprograms migration towards softer environments, a phenomenon known as negative durotaxis. Fetal rat lung fibroblasts preconditioned in 3D physiomimetic hydrogels exhibited negative durotaxis and accumulated near ∼5 kPa, corresponding to the physiological stiffness of the lung. In contrast, genetically identical cells maintained on conventional 2D plastic substrates migrated up stiffness gradients, toward stiffer regions. Although both populations displayed a biphasic force-stiffness relationship, they differed in force magnitude and cytoskeletal organization. Molecular-clutch modeling revealed that durotaxis reversal emerges from two distinct mechanical regimes: a mechanosensitive, high-motor-clutch state that stabilizes adhesions on stiff substrates and drives positive durotaxis, and a low-motor, weak-adhesion state in which clutch slippage on the stiff side causes negative durotaxis. Our results show that durotaxis direction is not an intrinsic cellular property. Rather, it emerges from the interplay between motor activity and adhesion dynamics and can be tuned by culture conditions.
    DOI:  https://doi.org/10.64898/2026.03.24.713716
  5. Math Biosci. 2026 Mar 28. pii: S0025-5564(26)00072-6. [Epub ahead of print] 109682
      We build a model of a general three-dimensional cell migrating across a flat substrate using an interconnected network of viscoelastic elements (damped springs). While the end goal is to use the model to investigate forces in migrating biological cells, the goal here is to demonstrate the model's validity, practical feasibility, and capability. We first show qualitative agreement with experiment including reasonable shape and speed, higher protrusive forces correlating with higher focal adhesion forces, and higher adhesive forces near the cell's front and back. We then show the model can produce estimates of deformation and stresses in migrating cells. We lastly perform a sensitivity analysis demonstrating that 1) cell length is increased by increasing driving force and focal adhesion attachment strength and by decreasing reference volume, 2) cell speed is increased by decreasing cell membrane-substrate interaction and increasing driving force, and 3) focal adhesion forces are increased by decreasing membrane elasticity and number of focal adhesions. Our results suggest that future model calibration will yield useful insights into how cell forces affect migration.
    Keywords:  cell migration; damped spring networks; focal adhesions; ode models
    DOI:  https://doi.org/10.1016/j.mbs.2026.109682
  6. Adv Sci (Weinh). 2026 Mar 31. e17631
      Transient activation of fibroblasts into contractile myofibroblasts is essential for extracellular matrix (ECM) production and remodeling during wound healing and tissue regeneration. While ECM-dependent mechanisms mediating transient activation is well studied, how fibroblasts switch from transient to a persistently activated state and drive fibrosis and aberrant tissue repair in diseases such as cancer is less understood. Here, we show that human cancer-associated fibroblasts (CAFs) switch from transient to persistently activated states upon prolonged exposure to stiff ECMs and stiffness-dependent secreted factors. This switch is accompanied by activation of ECM-stiffness-dependent mechanotransduction pathways and changes in the nuclear architecture and its association with chromatin. Mechanistically, we identify two pathways required for this switch- ECM ligand binding and activation of β1 integrins smoothens the nuclear lamina during prolonged exposure and reduces lamin-chromatin contacts while in parallel, exposure to the stiff ECM activates the formin mammalian Diaphanous-related formin 2 (mDia2) and independent of alterations in the nuclear architecture alters lamin-chromatin coupling, likely through its role in assembling nuclear actin. Importantly, we find that blocking either pathway prevents persistent myofibroblast activation, which is rescued by inhibition of histone deacetylases, indicating that dynamic chromatin modifications act downstream of these ECM-dependent pathways to maintain the persistently activated state. These findings link integrin-based ECM sensing to chromatin remodeling and fibroblast memory, with implications for stromal plasticity in the tumor microenvironment.
    Keywords:  integrin‐mediated mechanotransduction; nucleus‐actin coupling; persistent fibroblast activation; physical regulation of chromatin
    DOI:  https://doi.org/10.1002/advs.202517631
  7. PLoS Comput Biol. 2026 Mar 31. 22(3): e1014113
      Morphogenesis arises from biochemical and biomechanical interactions across multiple spatial and temporal scales. Experimental studies alone cannot fully resolve these dynamics, motivating computational models. Subcellular element modeling (SEM) is well suited for simulating emergent cellular and tissue morphologies, but traditional SEM frameworks do not explicitly include nuclear deformation or direct cell-extracellular matrix (ECM) interactions: capabilities typically associated with continuum approaches based on the finite-element method (FEM) approaches, FEM excels at modeling cell and tissue mechanics, but struggle to accommodate the large, non-linear deformations driven by local, geometry-changing events that define morphogenesis. Here, we introduce BIOPOINT, a particle-based framework that augments SEM with FEM-like mechanical capabilities by incorporating (1) a deformable, multi-particle nucleus capable of capturing nuclear stress and strain distributions and (2) an explicit ECM layer represented by structured static particles with tunable adhesive potentials. To ensure biological relevance, we calibrate BIOPOINT against single-cell indentation experiments (SKOV3). We then apply this calibrated parameter set, without additional refitting, to two independent scenarios: (i) cell (EC and hMSC) spreading on ECM micropatterns, capturing qualitative coupling between cell and nuclear shape; and (ii) confined migration (MDA-MB-231) through rigid constrictions, qualitatively reproducing the characteristic sequence of nuclear elongation and partial recovery. Differently from previous work, we present a full SEM model that uses heterogeneous particles to model nuclei, cells, and ECM via phase separation. By combining SEM's strength in modeling emergent cell and tissue geometry with a mechanically sound handling of nuclear and ECM interactions, BIOPOINT provides a versatile platform for studying cell behaviors, like shape acquisition and migration through confinement that are relevant to morphogenesis. Implemented within the widely used, open-source LAMMPS ecosystem, BIOPOINT offers an accessible and extensible tool for the community.
    DOI:  https://doi.org/10.1371/journal.pcbi.1014113
  8. Sci Adv. 2026 Apr 03. 12(14): eaea6734
      Pancreatic ductal adenocarcinoma (PDAC) is a lethal malignancy with a dense desmoplastic stroma and an immunosuppressive tumor microenvironment that contribute to therapeutic resistance. Here, we identify plasminogen activator inhibitor 1 (PAI1) as a stroma-derived mediator of immune evasion and tumor progression in PDAC. PAI1 is predominantly produced and secreted by cancer-associated fibroblasts, and its genetic ablation in the stromal compartment impairs tumor growth. Mechanistically, hypoxia induces PAI1 expression in fibroblasts, which in turn shifts macrophages toward immunosuppressive phenotypes and suppresses CD8+ T cell infiltration and function. We further show that tissue plasminogen activator (tPA), a direct PAI1 target, is also secreted by fibroblasts and supports antitumor CD8+ T cell responses. Notably, elimination of stromal tPA promotes immunosuppressive macrophage phenotypes, reduces CD8+ T cell infiltration, and accelerates PDAC progression. These findings define a previously unrecognized PAI1-tPA regulatory axis within the tumor stroma that modulates antitumor immunity. Targeting this pathway may provide a therapeutic opportunity to overcome stroma-driven immune suppression in PDAC.
    DOI:  https://doi.org/10.1126/sciadv.aea6734