bims-ecemfi Biomed News
on ECM and fibroblasts
Issue of 2026–03–15
eight papers selected by
Badri Narayanan Narasimhan, University of California, San Diego



  1. Cell Biomater. 2025 May 27. pii: 100052. [Epub ahead of print]1(4):
      Fibroblast activation drives fibrotic disease; however, the complex interplay of how tissue mechanics and macrophage signaling combine to influence fibroblast activation remains unclear. Using hyaluronic acid hydrogels to mimic lung stiffness and viscoelasticity, we investigated macrophage influence on fibroblast activation. Fibroblasts cultured on stiff (50 kPa) hydrogels mimicking fibrotic tissue exhibit increased activation, as measured by cell spreading and type I collagen and cadherin-11 expression, compared to fibroblasts cultured on soft (1 kPa) viscoelastic hydrogels mimicking normal lung. Macrophage-conditioned media did not alter these trends, however co-culture with M2 macrophages increased fibroblast activation independent of direct macrophage contact, even on soft viscoelastic hydrogels. Blocking interleukin 6 (IL6) signaling mitigated this pro-fibrotic effect but did not affect fibroblast-only cultures. These findings demonstrate that M2 macrophages override hydrogel viscoelasticity to promote fibroblast activation independent of direct contact in an IL6-dependent manner and highlight the utility of hydrogels in deconstructing complex tissue microenvironments.
    Keywords:  fibrosis; hydrogels; macrophages; mechanotransduction
    DOI:  https://doi.org/10.1016/j.celbio.2025.100052
  2. Proc Natl Acad Sci U S A. 2026 Mar 17. 123(11): e2524427123
      To reach targets outside the bloodstream, immune cells can extravasate and migrate through connective tissue. During tissue infiltration, immune cells migrate in an amoeboid fashion, characterized by weak matrix adhesions and low traction forces, that allows them to achieve high migration speeds of up to 10 µm/min. How immune cells reconcile amoeboid migration with the need to overcome steric hindrance in dense matrices is currently not understood. Here we show that NK92 (natural killer) cells can switch from their default amoeboid migration mode to a contractile, mesenchymal-like migration mode when moving through fibrous human amniotic membrane (HAM) tissue. We subsequently study immune cell migration in reconstituted 3D collagen networks with known mechanical properties and pore sizes and apply time-lapse confocal reflection microscopy to obtain simultaneous measurements of migration speed, directional persistence, and cell contractility. We find that NK92 cells exert substantial acto-myosin driven, integrin-mediated contractile forces of up to 100 nN on the extracellular matrix during short contractile phases. This burst-like contractile behavior is also found in primary B, T, NK cells, neutrophils, and monocytes, and is tightly related to the fraction of cells that become stuck in narrow pores of the surrounding matrix. Our results demonstrate that steric hindrance guides the rapid regulation of integrin-mediated adhesion to the ECM in a large number of immune cell subtypes.
    Keywords:  cell migration; collagen matrices; immune cells; mechanosensitivity; traction forces
    DOI:  https://doi.org/10.1073/pnas.2524427123
  3. Nat Mater. 2026 Mar 10.
      Complex and robust tissue self-organization requires defined initial conditions and dynamic boundaries-neighbouring tissues and extracellular matrix that actively evolve to guide morphogenesis. A major challenge in tissue engineering is identifying material properties that are compatible with controlling initial culture conditions while mimicking dynamic tissue boundaries. Here we describe a highly tunable granular biomaterial, MAGIC matrix, that supports both long-term bioprinting and gold-standard tissue self-organization. We identify that significant stress relaxation at the long timescales and large deformation magnitudes relevant to self-organization is required for optimal morphogenesis. We apply optimized MAGIC matrices toward precise extrusion bioprinting of saturated cell suspensions directly into three-dimensional culture. Carefully controlling initial conditions for tissue growth yields dramatic increases in organoid reproducibility and complexity across multiple tissue types, enabling high-throughput generation of organoid arrays and perfusable three-dimensional microphysiological systems. Our results identify key biomaterial parameters for optimal organoid morphogenesis and lay the foundation for fabricating more complex and reproducible self-organized tissues.
    DOI:  https://doi.org/10.1038/s41563-026-02519-4
  4. Biomater Sci. 2026 Mar 10.
      Gelatin methacryloyl (GelMA) hydrogels are widely used in tissue engineering because of their excellent biocompatibility, yet their dense network structure restricts substance transport and limits cell proliferation. Although the introduction of macroporous structures can alleviate this problem, most existing studies are limited to qualitative descriptions of permeability, lacking a quantitative framework to characterize the substance transport efficiency in such hydrogel networks and to study their impact on cell proliferation. In this work, we fabricated a series of GelMA macroporous hydrogels with tunable pore sizes through liquid-liquid phase separation (LLPS) combined with photopolymerization. The influence of pore size on the permeability of model solutes with different molecular weights was systematically investigated. Based on the classical analytical solution of Fick's second law, a quantitative diffusion model was established to determine the effective diffusion coefficient (Deff) of each solute in hydrogels with varying pore structures. A power-law relationship between the normalized diffusion coefficient and pore size was further constructed. The results indicated that for the same solute, its relative diffusion capacity exhibits a nonlinear increase with increasing pore size, indicating that larger pores significantly enhance permeability. Among different solutes, macromolecular solutes displayed significantly higher sensitivity to pore size variations compared to small molecules. In vitro studies with bone marrow mesenchymal stem cells (BMSCs) suggest that enhanced permeability facilitates glucose uptake and ATP production, consistent with the observed vigorous cell proliferation. This study offers insights into the quantitative correlation between pore architecture, substance transport, and cellular responses, providing a theoretical basis for designing hydrogel scaffolds with optimized microenvironments.
    DOI:  https://doi.org/10.1039/d5bm01628b
  5. Cancer Res. 2026 Mar 12.
      Cancer-associated fibroblasts (CAFs) exhibit phenotypic heterogeneity with each functional state playing critical roles in tumor progression. Notably, subtypes like inflammatory CAFs (iCAFs), characterized by increased chemokine/cytokine secretion, and myofibroblast-like CAFs (myCAFs), characterized by enhanced extracellular matrix (ECM) deposition and increased actomyosin contractility, can undergo phenotypic switching in response to cues from the tumor microenvironment (TME) and therapeutic interventions. Elucidation of the signaling pathways associated with the diverse phenotypes could enable development of strategies to therapeutically reprogram CAFs. Through the analysis of single-cell RNA sequencing data from colorectal cancer (CRC) patients, we identified that the PI3K/mTOR and MAPK/ERK signaling pathways, among other pathways, are linked to the formation of myCAF and iCAF subtypes, respectively. Unbiased pharmacological interference of 12 distinct signaling pathways using three-dimensional (3D) human CRC-derived CAF cultures, ex vivo patient-derived tumor fragments, and mouse models further revealed the significance of PI3K/mTOR and MAPK/ERK signaling in CAF plasticity and functional behavior. PI3K/mTOR inhibition drove iCAF formation through compensatory FGF-2 release and FGFR1-JAK2-STAT3 activation, leading to chemokine/cytokine secretion that promoted tumor spheroid growth and neutrophil infiltration. Conversely, MEK inhibition induced a myCAF phenotype via interferon-dependent ROCK and JAK1 signaling, resulting in ECM production that enhanced tumor colony formation. In summary, these findings reveal a functional significance of PI3K/mTOR and MAPK/ERK signaling pathways in CAF plasticity and underscore how standard-of-care targeted therapies can directly influence CAF phenotypes in CRC.
    DOI:  https://doi.org/10.1158/0008-5472.CAN-25-0766
  6. Sci Adv. 2026 Mar 13. 12(11): eaea1492
      Cell migration underlies immune surveillance, tissue repair, embryogenesis, and-when dysregulated-tumor metastasis. Yet unlike proliferation, which can be profiled at scale, migration studies remain limited by labor-intensive imaging and analysis. Existing assays often forfeit single-cell resolution, require phototoxic fluorescent labeling, or depend on tedious manual tracking, restricting the range of molecular perturbations and microenvironmental contexts that can be examined. We present Deep learning Brightfield Imaging and cell Tracking (DeepBIT), a high-throughput platform that captures live-cell behavior in multiwell plates and uses a convolutional neural network to detect and track individual cells in brightfield videos-without labels or user bias. Brightfield images are paired with nuclear fluorescence images to generate diverse ground-truth datasets, enabling automated training and eliminating manual annotation. This scalability supports a data-driven approach to systematically dissect the regulation of cell migration. Using breast cancer cells as a testbed, we tracked ~1500 cells per well across 840 conditions-including 96 FDA-approved drugs at multiple doses, a range of extracellular matrix and growth factor combinations, and CRISPR knockouts of cytoskeletal genes-yielding ~1.3 million trajectories in 30 hours (~2 minutes per condition). This dataset revealed previously unrecognized motility modulators among FDA-approved compounds and uncovered strong context dependence; for example, TNF-α and RhoA could either suppress or promote migration in the same cells depending on extracellular cues. Together, DeepBIT provides an unbiased, label-free platform for single-cell motility profiling at a scale compatible with modern drug libraries and genomic perturbation tools, enabling systematic exploration and therapeutic targeting of cell migration.
    DOI:  https://doi.org/10.1126/sciadv.aea1492
  7. Proc Natl Acad Sci U S A. 2026 Mar 17. 123(11): e2514484123
      Biochemical mechanisms of macrophage-driven tumor promotion are well documented, but the contribution of physical forces to early tumor development remains poorly understood. Here, we combine experimental analyses with physical modeling to investigate these forces in KrasG12D p53-/- (KP) lung tumor spheroids grown in 3D. Real-time microscopy showed that tissue-resident macrophages, but not monocytes, promote early tumor growth. Using quantitative measurements, we built a physical model that recapitulates cancer cell proliferation dynamics and macrophage-tumor interactions. KP tumor cells grown alone formed a single aggregate that contracted over time due to nutrient limitation, whereas macrophages induced the formation of multiple aggregates that grew, fused, and expanded nutrient access, thereby increasing proliferation. Similar macrophage-driven growth was observed when alveolar or bone-marrow-derived macrophages were cocultured with KP or pancreatic carcinoma cells. The model predicted a redistribution of macrophages toward the periphery of aggregates, a pattern confirmed in vitro and previously observed in vivo. It also identified adhesion forces between tumor cells and macrophages as a key driver of spheroid nucleation and growth. Among candidate integrins, CD11c was highly expressed by alveolar macrophages; CD11c blockade reduced adhesion forces, prevented macrophage-driven spheroid nucleation, and impaired tumor growth. Bone-marrow-derived macrophages required simultaneous CD11b and CD11c blockade for similar effects. Finally, CD11c inhibition in RAG-Knock Out (KO) mice reduced tumor survival probability and slowed the growth of ear-implanted tumors, indicating that CD11c-dependent interactions support tumor establishment beyond the lung. Together, these findings uncover a critical physical mechanism through which macrophages promote early tumor progression.
    Keywords:  macrophage; physical forces; tumor
    DOI:  https://doi.org/10.1073/pnas.2514484123
  8. Int J Cancer. 2026 Mar 07.
      Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest malignancies, due to its aggressive invasiveness and resistance to therapy. The dense, stiff extracellular matrix, composed primarily of collagen I and basement membrane components such as collagen IV and laminin, acts as a mechanical barrier that constrains PDAC invasion. We investigated whether the actin-related protein (Arp) 2/3 complex, a key actin nucleator, is essential for PDAC cells to overcome extracellular matrix stiffness and facilitate migration. CRISPR/Cas9 knockout of the Arpc4 gene in murine PDAC cell lines derived from KrasG12D-driven transgenic mice resulted in substantially downregulated all Arp2/3 complex members. Inactivation of Arp2/3 significantly impaired PDAC cell migration, disrupted branched tubular structure formation in collagen I, and inhibited invasive front formation in organoid culture together with tumor-associated macrophages and fibroblasts. Mechanistically, β1 integrin signaling emerged as a key regulator of Arp2/3-dependent migration through collagen-rich matrices. Clinically, elevated expression of Arp2/3 complex components correlates with poor patient survival and basal-like differentiation subtypes, underscoring its role in disease progression. This study identifies the Arp2/3 complex and β1 integrin signaling as critical mediators of PDAC invasiveness and suggests them as potential therapeutic targets for mitigating PDAC progression.
    Keywords:  Arp2/3; extracellular matrix; integrin; pancreatic cancer; type I collagen
    DOI:  https://doi.org/10.1002/ijc.70376