bims-ecemfi 2025-10-26 papers

ACS Biomater Sci Eng. 2025 Oct 23.

Effects of Stiffness and Degradability on Cardiac Fibroblast Contractility and Extracellular Matrix Secretion in Three-Dimensional Hydrogel Scaffolds.

Kathleen N Halwachs, Alexander Hillsley, Alex Khang, Logan D Morton, Michael S Sacks, Janet Zoldan, Adrianne M Rosales.

Cardiac fibrosis results from persistent cardiac fibroblast activation and is heavily dependent on the interplay of extracellular matrix mechanics and proinflammatory cytokines. Studying this interplay using in vitro disease models is of interest for developing strategies to treat cardiac fibrosis. However, current metrics for quantifying myofibroblast activation rely heavily on the presence of α-SMA stress fibers, which works well for two-dimensional (2D) culture systems but not 3D cell scaffolds. Here, we investigate how contractility and extracellular matrix secretions, which are two phenotypic markers of cardiac myofibroblasts, correlate with 3D matrix stiffness and TGF-β concentration (a proinflammatory cytokine). Cardiac fibroblasts encapsulated in soft, degradable hydrogels were larger and more contractile and secreted more extracellular matrix than cells encapsulated in stiff, degradable hydrogels or nondegradable hydrogels. The addition of TGF-β to the soft, degradable hydrogels increased the volume, contractility, and extracellular matrix secretions, indicating myofibroblast activation. In addition, the presence of α-SMA increased, but α-SMA stress fibers were not detected. These results highlight the importance of local degradability in 3D hydrogels for cellular contractility and remodeling of the extracellular matrix. They also suggest the use of additional phenotypic markers to probe myofibroblast activation in 3D cellular scaffolds.

Keywords: cardiac fibroblast; contractility; extracellular matrix; hydrogel

DOI: https://doi.org/10.1021/acsbiomaterials.5c01093

Acta Biomater. 2025 Oct 21. pii: S1742-7061(25)00777-9. [Epub ahead of print]

Mechanical Maturation of Human Dermal Fibroblast-laden Microporous Annealed Particle Scaffolds During Long-term In Vitro Culture.

Claudia Daboin, Ethan Nicklow, Donald R Griffin.

The use of biomaterials to model diseases and tissues in vitro has updated our understandings of cellular processes through the inclusion of a 3D microenvironment that better mimics physiological conditions. A major limitation that remains is the ability to probe these cultures on longer timescales while maintaining a simple, reproducible 3D-structure. Microporous annealed particle (MAP) scaffolds demonstrate potential in circumventing some drawbacks of traditional bulk hydrogels, including lowered nutrient diffusivity and early inhibition of cell-to-cell interactions, that may limit efficacy over long timescales. Previous research explored impacts of degradation and cell-adhesion ligands on MAP's ability to promote creation of cell-mediated extracellular matrix (ECM) within its porous network over an 8-day period. This manuscript expands on this work by culturing a high density of human dermal fibroblasts in poly(ethylene glycol) (PEG) MAP scaffolds over 63 days. We evaluated mechanical maturation and viability over time between enzymatically insensitive (PEG-PEG) and sensitive (PEG-peptide) formulations of MAP. Mechanical modulus significantly increased in PEG-peptide scaffolds at 28 days, but viability was sustained for both conditions up to 63 days. Bulk RNAseq was performed on both conditions at equivalent timepoints, with many ECM-related genes highlighted as significant to the overall model and largest differences in gene profiles between conditions occurring at 28 days, corroborating mechanical data. Overall, this study demonstrates MAP's use for long-term in vitro cultures with sustained viability and begins to optimize scaffold formulation to promote material-tissue hybridization. Future work will further analyze mechanisms for the differential behaviors, including decoupling degradability from material composition. STATEMENT OF SIGNIFICANCE: Three-dimensional in vitro cultures better mimic the physiological environment compared to traditional 2D cultures, but extending their lifetime remains challenging. Microporous annealed particle (MAP) scaffolds address limitations of bulk hydrogels by providing a porous microenvironment that enables immediate cell migration and proliferation without extensive polymer breakdown. This study demonstrates sustained viability and mechanical maturation of human dermal fibroblasts in MAP scaffolds for over 63 days - significantly longer than previous reports. We demonstrate that protease-sensitive peptide crosslinkers, compared to protease-insensitive alternatives, lead to enhanced ECM deposition and mechanical maturation, supported by transcriptomic evidence. These findings establish MAP scaffolds as a platform for long-term in vitro modeling of tissue development and potential engineering of tissues for transplantation.

Keywords: Enzymatic degradation; Extracellular matrix; Human dermal fibroblasts; Long-term 3D culture; Mechanical maturation; Microporous annealed particle (MAP) scaffold; Tissue engineering; Transcriptomics

DOI: https://doi.org/10.1016/j.actbio.2025.10.031

Soft Matter. 2025 Oct 22.

Loading causes molecular damage in fibrin fibers.

Sajjad Norouzi, Matthew J Lohr, Mayar T Ibrahim, Christian M Jennings, Daniel Wang, Pengyu Ren, Manuel K Rausch, Sapun H Parekh.

Blood clots are the body's natural biomaterials formed during wound healing, but they are also the cause of many pathologies, such as ischemic stroke. Fibrin, the main protein in clots, provides clots with mechanical strength through a network of fibrin fibers. These fibers exhibit high extensibility and primarily elastic properties under static loading conditions though little is known about single fiber mechanics under dynamic loading, as experienced in vivo. Indeed, many biological materials show distinct mechanical responses under repeated loading/unloading (cyclic loading), a prime example of which is clot embolization. Using lateral force microscopy, we show that fibrin fibers exhibit viscoelasticity and undergo irreversible molecular damage under cyclic loading. Cross-linking results in a more rigid structure with permanent damage occurring at larger strains - findings corroborated by computational modeling. Molecular spectroscopy analysis with broadband Raman scattering spectroscopy, combined with molecular dynamics simulations, allows identification of the damage source, unfolding pattern, and inter- and intramolecular changes in fibrin. The results reveal partial recovery of the protein's secondary and tertiary structures, providing a deeper understanding of fibrin's molecular wear under load and its behavior in wound healing and pathologies like stroke and embolism.

DOI: https://doi.org/10.1039/d5sm00681c

ACS Appl Mater Interfaces. 2025 Oct 21.

Emergence of a Cell-Guided Multivalent Ligand of Enzymes on Cancer Cells Triggered by Click Reaction between Hetero Nanoassemblies.

Rentaro Sakamoto, Yuki Koba, Masahiko Nakamoto, Tatsuya Fukuta, Kazunori Kadota, Michiya Matsusaki.

Stimuli-responsive nanomaterials with multivalent ligands have attracted significant attention in the context of cancer chemotherapy and imaging. However, challenges remain such as nonselective stimuli response and/or existence of triggers in healthy regions in addition to the intrinsic heterogeneity of cancer that causes insufficient target recognition. Inspired by the expression of precise and diverse functions of biological machineries triggered by specific protein-protein complexation and conformational change, we report an artificial system where a bio-orthogonal click reaction between hetero nanoassemblies triggers their complexation and conformational changes, resulting in the emergence of multivalent ligands for cancer-associated enzymes, namely, carbonic anhydrase IX (CAIX). We also demonstrated that the multivalent ligands selectively inhibited the proliferation of cancer cells overexpressing CAIX under hypoxic conditions. Additionally, the click reaction between nanoassemblies in the presence of target cells provided higher efficacy of the emerged multivalent ligands than that pre-formed in the absence of cells. Our study provides a basis for the development of multivalent ligands displaying adaptive binding interfaces for target cancer cells with high selectivity and affinity to thus potentially overcome tumor heterogeneity.

Keywords: bio-orthogonal chemistry; cancer; click reaction; multivalent ligand; nanoassembly

DOI: https://doi.org/10.1021/acsami.5c11290

Nat Biomed Eng. 2025 Oct 21.

Targeting circulating mechanoresponsive monocytes and macrophages to reduce fibrosis.

In response to injury, a variety of different cells are recruited to sites of injury to facilitate healing. Recent studies have examined the importance of the heterogeneity of tissue resident fibroblasts and mechanical signalling pathways in healing and fibrosis. However, tissue repair and the inflammatory response also involves blood cells that are recruited from the circulation. Here we identify mechanoresponsive myeloid subpopulations present in scar and unwounded skin. We then modulate these subpopulations by manipulating mechanical strain in vivo and in vitro and find that specifically targeting myeloid mechanical signalling is sufficient to reduce the pro-fibrotic myeloid subpopulations and restore the native, anti-inflammatory subpopulations. In addition, myeloid-specific mechanotransduction ablation also downregulates downstream pro-fibrotic fibroblast transcriptional profiles, reducing scar formation. As inflammatory cells circulate and home to injury sites during the initial healing phases in all organs, focusing on mechanoresponsive myeloid subpopulations may generate additional directions for systemic immunomodulatory therapies to target fibrosis and other diseases across other internal organ systems.

DOI: https://doi.org/10.1038/s41551-025-01479-5

Matrix Biol Plus. 2025 Dec;28 100182

Loss of fibronectin fiber tension is inherent to ECM remodeling in human myocarditis and post-inflammatory fibrosis.

Krishna Chander Sridhar, Julia Mehl, Karin Klingel, Mario Thiele, Sophie Van Linthout, Carsten Tschöpe, Georg N Duda, Viola Vogel.

Background: Viral myocarditis (MC) is associated with extracellular matrix (ECM) remodeling and involves excessive deposition of collagen and other ECM proteins by cardiac fibroblasts, potentially leading to scarring and ECM stiffening, which may subsequently contribute to impaired cardiac functions. Clarifying whether changes in ECM fiber tension are detectable during either the acute or scarring phase could provide a novel, mechanistically relevant mechanobiological signature.
Objectives: Our goal was to ask whether ECM mechano-markers can be identified in the myocardium, beyond excessive collagen fiber deposition, that are associated with the acute infection or the pathological scarring of the human heart, and how this might be associated with the infiltration of macrophages.
Methods: Left-ventricular (LV) endomyocardial biopsies were obtained from patients (N = 39) with acute myocarditis MC (N = 21) including COVID-19 (N = 4) patients suspected with myocarditis MC and/or impaired LV function, dilated cardiomyopathy (N = 6), inflammatory dilated cardiomyopathy (N = 12) to specify diagnosis and treatment options. Endomyocardial biopsies were analyzed for viral genomes, immune cells infiltration and ECM remodeling. Fibronectin fiber tension was assessed using the fibronectin-binding tension-sensor (FnBPA5), while collagen fiber deposits were visualized using second harmonic generation (SHG) microscopy.
Results: While fibronectin fibers were tensed in healthy hearts, histological staining with our novel tension probe FnBPA5 showed that fibronectin fibers had lost their tension in distinct loci in all patient groups. In the acute inflammatory phase (MC), loci with untensed fibronectin fibers were found in close proximity to infiltrated macrophages. In already dilated hearts, biopsies which presented low densities of infiltrated macrophages, thick collagen I/III fiber bundles as visualized by SHG were found in proximity to untensed fibronectin fibers and myofibroblasts, which together are indicative of fibrotic ECM niches where the inflammation has subsided. Comparison of clinical diagnostic and experimental histological data showed clear correlations between altered ECM niche properties and cardiac function deterioration.
Conclusions: Our data suggest that relaxed fibronectin fibers are a recurrent feature of myocarditis and associate with measures of cardiac dysfunction. These findings suggest that fibronectin fiber tension might be a mechanobiological signature that warrants validation in larger, longitudinal cohorts and evaluation of in-vivo measurability.

Keywords: Extracellular matrix fiber tension; Fibronectin-binding peptide FnBPA5; Inflammatory and fibrotic cell niches; Mechanobiological signature; Myocarditis

DOI: https://doi.org/10.1016/j.mbplus.2025.100182