bims-ecemfi Biomed News
on ECM and fibroblasts
Issue of 2025–06–15
eight papers selected by
Badri Narayanan Narasimhan, University of California, San Diego
  1. Tissue-like compression stiffening in biopolymer networks induced by aggregated and irregularly shaped inclusions.
  2. Fibroblast proximity to a tumor impacts fibroblast extracellular vesicles produced by 3D bioprinted stromal models.
  3. Tuning viscoelasticity and fine structure of living materials via synthetic adhesion logic and rheological perturbations.
  4. Instant fluorescence lifetime imaging microscopy reveals mechano-metabolic reprogramming of stromal cells in breast cancer peritumoral microenvironments.
  5. Direct Arp2/3-vinculin binding is required for pseudopod extension, but only on compliant substrates and in 3D.
  6. Macrophages migrate persistently and directionally upon entering 2D confinement in the presence of extracellular matrix.
  7. Charge microenvironment and bioactivity of in situ-formed PEG-RGD dual hydrogel dressings promote wound healing.
  8. A designer minimalistic model parallels the phase-separation-mediated assembly and biophysical cues of extracellular matrix.
  1. bioRxiv. 2025 Jun 06. pii: 2025.06.02.657447. [Epub ahead of print]
    Tissue-like compression stiffening in biopolymer networks induced by aggregated and irregularly shaped inclusions.
    Xuechen Shi, Jordan L Shivers, Fred C MacKintosh, Paul A Janmey.
      Biological tissues experience mechanical compression under various physiological and pathological conditions and often exhibit compression stiffening, in which their stiffness increases during compression, a phenomenon that plays a crucial role in regulating cell behavior and maintaining mechanical homeostasis. However, most isolated biopolymer networks, such as fibrin and collagen hydrogels that form the extracellular matrix and actin network that forms the internal cytoskeleton, undergo compression softening, raising questions about how tissues achieve compression stiffening despite the softening properties of their extracellular and intracellular matrix components. Previous studies have shown that spherical inclusions at large volume fractions can induce compression stiffening in biopolymer networks, but they do not account for the effects of aggregation and irregular morphologies of cellular assemblies or other components in tissues. Here, we demonstrate a novel mode of compression stiffening induced by aggregated or irregularly shaped inclusions that occurs at significantly lower volume fractions. Using carbonyl iron particles and coffee ground particles, we find that the morphological diversity of inclusions enables tissue-like compression stiffening at a low volume fraction of inclusions. Through a set of experiments and computational analyses, we demonstrate that these particles can percolate at low volume fractions. We further show that the percolation of stiff inclusions creates a stress-supporting network and enables tension-dominated stress propagation in fibrin fibers, both of which drive macroscopic stiffening during compression. These findings provide insights into the regulation of tissue stiffness and have implications for designing biomaterials with physiologically relevant mechanical properties for biomedical applications.
    Significance Statement: Biological tissues experience a variety of mechanical forces. Many tissues, such as brain, liver, fat, and blood clots, become stiffer under physiological compressive loads, a property known as compression stiffening. In contrast, most biopolymer networks, which are the primary structural components for tissues, soften under compression. Here, we show that incorporating a small amount of aggregated or irregularly shaped particles into biopolymer gels induces robust compression stiffening. These inclusions percolate through the gel and rearrange non-affinely under compression, stretching surrounding fibers and contributing to mechanical reinforcement. Together, these effects reproduce tissue-like compression stiffening. Our findings not only provide new physical models for understanding tissue mechanics but also offer insights for designing biomaterials to achieve physiologically relevant mechanical responses.
    DOI:  https://doi.org/10.1101/2025.06.02.657447
  2. Biomater Sci. 2025 Jun 10.
    Fibroblast proximity to a tumor impacts fibroblast extracellular vesicles produced by 3D bioprinted stromal models.
    Jensen N Amens, Jun Yang, Lauren Hawthorne, Pinar Zorlutuna.
      Extracellular vesicles (EVs) are an important carrier of cellular communication that contain cargo such as cytokines, RNAs, or microRNAs (miRNA) and have been proven to play an important role in breast cancer tumorigenesis, progression, and metastasis. Although the role of cancer associated fibroblasts (CAFs), and EVs originated from them have been studied extensively, there is a lack in knowledge on the contribution of normal fibroblasts surrounding the tumor and their roles with respect to their proximity to the tumor. Here we investigate how the proximity of the tumor affects the EV production of the normal fibroblasts. We created stromal models by 3D bioprinting two different fibroblasts, normal human mammary fibroblasts (hMFs) and normal tumor adjacent fibroblasts (NTAF), within a collagen gel. We isolated EVs from both the effluent media and the 3D stromal model, which were then characterized and we found that EVs from each group were of consistent exosome size and displayed traditional exosome markers, however, the EVs from different groups also displayed different cytokine profiles of their cargo, with the NTAF media group showing an upregulation of cytokines associated with breast cancer progression. After this, we used the EVs to treat breast cancer cells to investigate the effects of the EV groups on the breast cancer cell behavior. The breast cancer cells treated with the NTAF groups had increased migration. Finally, we utilized a 3D breast tumor model to investigate the effects of the EVs on a tumor spheroid. Tumor spheroids treated with either NTAF EV groups showed increased proliferation, tumor diameter, and local invasion. This study is the first to investigate the effect of proximity to a breast tumor on EV production and the first to utilize 3D bioprinting of stromal models specifically to obtain EVs. Overall, our results show that EVs from normal fibroblasts closer to a tumor produce EVs that promote breast cancer progression, regardless of the secretion location of the EVs. These cells have a distinct EV secretome different from normal human mammary fibroblasts, showing that the proximity to a tumor influences the normal fibroblasts surrounding the tumor.
    DOI:  https://doi.org/10.1039/d4bm01569j
  3. bioRxiv. 2025 Jun 04. pii: 2025.06.04.657808. [Epub ahead of print]
    Tuning viscoelasticity and fine structure of living materials via synthetic adhesion logic and rheological perturbations.
    Stefana A Costan, Kira Hallerbach, Samuel Y Kim, Chris Camp, Minkyu Kim, Ingmar H Riedel-Kruse.
      Engineered living materials (ELMs) at the multicelluar level represent an innovation that promises programmable properties for biomedical, environmental, and consumer applications. However, the rational tuning of the mechanical properties of such ELMs from first principles remains a challenge. Here we use synthetic cell-cell adhesins to systematically characterize how rheological and viscoelastic properties of multicellular materials made from living bacteria can be tuned via adhesin strength, cell size and shape, and adhesion logic. We confirmed that the previous results obtained for non-living materials also apply to bacterial ELMs. Additionally, the incorporation of synthetic adhesins, combined with the adaptability of bacterial cells in modifying various cellular parameters, now enables novel and precise control over material properties. Furthermore, we demonstrate that rheology is a powerful tool for actively shaping the microscopic structure of ELMs, enabling control over cell aggregation and particle rearrangement, a key feature for complex material design. These results deepen our understanding of tuning the viscoelastic properties and fine structure of ELMs for applications like bioprinting and microbial consortia design including natural systems.
    DOI:  https://doi.org/10.1101/2025.06.04.657808
  4. bioRxiv. 2025 May 30. pii: 2025.05.28.656717. [Epub ahead of print]
    Instant fluorescence lifetime imaging microscopy reveals mechano-metabolic reprogramming of stromal cells in breast cancer peritumoral microenvironments.
    Julian Najera, Hao Chen, Bianca Batista, Frank Ketchum, Aktar Ali, Pinar Zorlutuna, Scott Howard, Meenal Datta.
      The breast peritumor microenvironment (pTME) is increasingly recognized as a mediator of breast cancer progression and treatment resistance. However, if and how growth-induced tumor compressive forces (i.e., solid stresses) influence the breast pTME remains unclear. Here we show using instant fluorescence lifetime imaging microscopy (FLIM)-a frequency-domain FLIM system capable of simultaneous image acquisition and instantaneous data processing-that breast tumor-mimicking in vitro compression promotes metabolic changes in stromal cells found in the breast pTME. Namely, compression shifts NIH3T3 fibroblasts and differentiated 3T3-L1 (d3T3-L1) adipocytes toward a more glycolytic state, while it promotes increased oxidative phosphorylation in 3T3-L1 undifferentiated adipocytes. The gold-standard Seahorse extracellular flux assay fails to capture these changes, underscoring the superior sensitivity of instant FLIM in detecting metabolic shifts. We validate these phenotypic findings at the transcriptomic level via RNA sequencing, confirming that compressed fibroblasts downregulate oxidative phosphorylation and upregulate glycolysis compared to uncompressed controls. We further demonstrate that compression induces mitochondrial dysregulation in undifferentiated adipocytes, driven in part by upregulated mitophagy and disrupted fusion dynamics. Finally, we confirm that these stromal cell types recapitulate these distinct metabolic states in human breast cancer patient samples, consistent with our in vitro findings. By elucidating mechano-metabolic interactions occurring at the tumor-host interface, these results will inform the development of innovative mechano-metabolic reprogramming treatment strategies to improve breast cancer patient survival.
    DOI:  https://doi.org/10.1101/2025.05.28.656717
  5. iScience. 2025 Jun 20. 28(6): 112623
    Direct Arp2/3-vinculin binding is required for pseudopod extension, but only on compliant substrates and in 3D.
    Tadamoto Isogai, Kevin M Dean, Philippe Roudot, Evgenia V Azarova, Kushal Bhatt, Meghan K Driscoll, Shaina P Royer, Nikhil Mittal, Bo-Jui Chang, Sangyoon J Han, Reto Fiolka, Gaudenz Danuser.
      A critical step in cell morphogenesis is the extension of actin-dense pseudopods, controlled by actin-binding proteins (ABPs). While this process is well-understood on glass coverslips, it is less so in compliant three-dimensional environments. Here, we knocked out a series of ABPs in osteosarcoma cells and evaluated their effect on pseudopod extension on glass surfaces (2D) and in collagen gels (3D). Cells lacking the longest Arp3 gene variant, or with attenuated Arp2/3 activity, had the strongest reduction in pseudopod formation between 2D and 3D. This was largely due to reduced activity of the hybrid Arp2/3-vinculin complex, which was dispensable on glass. Our data suggests that concurrent formation of actin branches and nascent adhesions, supported by Arp2/3-vinculin interactions, is essential to form mechanically stable links between fibrous extracellular matrix and actin in 3D. This highlights how experiments on stiff, planar substrates may conceal actin architectural features that are essential for morphogenesis in 3D.
    Keywords:  Biological morphology; Cell biology; Molecular biology
    DOI:  https://doi.org/10.1016/j.isci.2025.112623
  6. Biol Open. 2025 Jun 10. pii: bio.061782. [Epub ahead of print]
    Macrophages migrate persistently and directionally upon entering 2D confinement in the presence of extracellular matrix.
    Matthew W Stinson, Summer G Paulson, Ethan M Carlile, Jeremy D Rotty.
      Cells sense and respond to their environment in a myriad of ways. In many instances they must integrate simultaneous cues ranging from the physical properties and composition of the extracellular matrix to guidance cues that stimulate chemotaxis or haptotaxis. How cells make sense of multiple simultaneous cues is an ongoing physiologically relevant question. The present study seeks to contribute to the understanding of multi-cue sensing by understanding how the transition to a confined setting with or without an added haptotactic gradient alters macrophage migration. We found that the transition to confinement is itself a directional cue capable of driving persistent migration hours after macrophages enter the confined environment. Next, we found that a haptotactic fibronectin gradient made cells even more directionally persistent under confinement. Finally, Arp2/3 complex deletion rendered macrophages unresponsive to the haptotactic gradient, but they retained directionally persistent migration due to their transition to confinement. These findings may be particularly relevant for cells that move from an adherent 2D environment into a confining 3D environment, like leukocytes and circulating tumor cells that extravasate into peripheral tissue.
    Keywords:  Actin; Arp2/3 complex; Cell motility; Confined migration; Cytoskeleton; Haptotaxis; Macrophage
    DOI:  https://doi.org/10.1242/bio.061782
  7. J Mater Chem B. 2025 Jun 10.
    Charge microenvironment and bioactivity of in situ-formed PEG-RGD dual hydrogel dressings promote wound healing.
    Chuanjie He, Yulin Wang, Xinyu Fang, Wenkai Jiang, Sihan Liu, Xiaoli Yi, Kai Zhang, Hai Lin, Qin Zeng, Xiangdong Zhu, Ya Li, Xu Song, Xingdong Zhang.
      Healing of large skin wounds involves a complex biological process with overlapping phases, facing challenges from fibroblast proliferation, immune response, and extracellular matrix (ECM) remolding. Hydrogel dressings serve as temporary barriers protecting injured tissue from exogenous infections while providing an advantageous microenvironment for cellular regeneration. However, traditionally molded hydrogels through catalyzed or triggered crosslinking into fixed size and strength prior to treatment struggle to integrate tightly with irregular wound surfaces, leading to dressing detachment and wound exposure in areas with high curvature and mobility. Here, we designed CGRGDGC peptide enantiomers, incorporating with 4 arm-PEG-maleimide, to in situ form functional and morphologically matching dual-phasic hydrogel dressing. In situ elastic hydrogel dressing forms within 10 min after applying, with a storage modulus of 1300 Pa and internal porous networks. The peptide incorporation increased the surface potential to ∼370 mV, twice that of PEG hydrogels. The bioactive L-peptide hydrogel exhibited strongest immunomodulation and skin regeneration enhancement, while the non-bioactive D-peptide hydrogel also showed significant promotion compared to the PEG hydrogel. We demonstrated that both the charge microenvironment and bioactivity of hydrogel dressing regulate the immune response and promote wound healing after skin injury. This research provides novel insights and strategies showing that non-ligand peptide sequences achieve biological functions by modulating molecular potential and that adjusting the charge microenvironment and incorporating bioactive peptides through peptide phase introduction enhance skin regeneration.
    DOI:  https://doi.org/10.1039/d5tb00683j
  8. Nat Chem. 2025 Jun 09.
    A designer minimalistic model parallels the phase-separation-mediated assembly and biophysical cues of extracellular matrix.
    Xian Xie, Tianjie Li, Linjie Ma, Jiahao Wu, Yajing Qi, Boguang Yang, Zhuo Li, Zhinan Yang, Kunyu Zhang, Zhiqin Chu, To Ngai, Jiang Xia, Yi Wang, Pengchao Zhao, Liming Bian.
      The propensity for controlled liquid-liquid phase separation and subsequent directed phase transition are crucial for the coacervation-mediated assembly of extracellular matrix (ECM). This spatiotemporally controlled ECM assembly can be used to develop coacervate-based polymer assembly strategies to generate biomimetic materials that can emulate the complex structures and biophysical cues of the ECM. Inspired by the tropoelastin structure, here we develop a designer minimalistic model consisting of alternating hydrophobic moieties and covalent crosslinking domains. By increasing the valence and enhancing the interaction strength of the hydrophobic moieties, we can control the degree of the assembly to enhance the propensity for phase separation and thus emulate the extracellular coacervation process of tropoelastin, including droplet formation, coalescence and maturation. The subsequent covalent-bonding-triggered coacervate-hydrogel transition with enhanced assembly order stabilizes the phase-separated structure in the form of a heterogeneous hydrogel, thereby mimicking covalent crosslinking-derived elastin fibrillation. Furthermore, the heterogeneous hydrogel network establishes a biomimetic matrix that can effectively promote the mechanosensing of adherent stem cells.
    DOI:  https://doi.org/10.1038/s41557-025-01837-5
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