bims-ecemfi 2025-07-06 papers

Mater Today Bio. 2025 Aug;33 101962

Virtual testing methodology to predict the mechanical behavior of collagen hydrogels from nanoarchitecture.

Elías Núñez-Ortega, Pablo Blázquez-Carmona, Raquel Ruiz-Mateos, José E Martín-Alfonso, José A Sanz-Herrera, Esther Reina-Romo.

Collagen-based hydrogels are three-dimensional, cross-linked structures capable of mimicking the extracellular fibered matrix of biological tissues, making them particularly well-suited for biomedical applications. These hydrogels typically exhibit highly non-linear mechanical behavior, which strongly depends on their internal nanostructural characteristics - an interconnection that remains poorly understood. The aim of this work is to combine high resolution imaging with a multiscale in silico structural model to virtually reproduce the mechanical behavior of a widely used collagen-based hydrogel, using solely its nanoarchitecture as input. The real fiber structure of the hydrogel was originally quantified at the nanometer scale using state-of-the-art microscopy, specifically, focused ion beam-scanning electron microscopy (FIB-SEM). In silico shear tests were then performed on the reconstructed collagen matrix to compute, through a multiscale approach, its homogenized mechanical response, including the energies and stresses developed by the fibers during the tests. Different samples of the hydrogel were also mechanically characterized by means of rheological tests to fit the model and show the feasibility of the methodology. The in silico simulations successfully captured the detailed mechanical interactions between fibers as well as the experimental non-linear mechanical behavior of the hydrogels. Results also highlight the relevant role of the bending energy throughout the entire range of deformation analyzed. This methodology provides a framework to elucidate the structure-mechanical behavior relationship of fiber network topologies, and can be applied to predict mechanical response of both native tissues and biomaterials based exclusively on their fibered nanostructures.

Keywords: Collagen-based hydrogels; FIB-SEM; Fiber structures; Homogenization; In silico model; Mechanobiology; Rheology

DOI: https://doi.org/10.1016/j.mtbio.2025.101962

Proc Natl Acad Sci U S A. 2025 Jul 08. 122(27): e2425452122

Clustered macrophages cooperate to eliminate tumors via coordinated intrudopodia.

Lawrence J Dooling, Alişya A Anlaş, Michael P Tobin, Nicholas M Ontko, Tristan Marchena, Maximilian Wang, Jason C Andrechak, Dennis E Discher.

Macrophages often pervade solid tumors, and clusters of macrophages sometimes associate with longer survival of patients. However, clustering mechanisms and impacts on key functions such as phagocytosis remain obscure. Here, under conditions that maximize cancer cell phagocytosis within cohesive tumors, we uncover pathways that favor dynamic clusters and find a colocalization of tumor-intrusive pseudopodia which we term "intrudopodia." Cluster formation over hours on low-adhesion substrates occurs after macrophage induction to a state colloquially referred to as M1 after exposure to interferons and T cell-derived cytokines. Clusters prove fluid on timescales of minutes and also sort from interleukin-4-treated, so-called M2 macrophages that tend to disperse. M1 macrophages upregulate specific cell-cell adhesion receptors but suppress actomyosin contractility, with both pathways contributing to cluster formation. Decreased cortical tension was not only reflected in a low level of nuclear lamin-A that downregulates cytoskeletal targets of serum response factor and tends to soften the nucleus but was also predicted to unleash pseudopodia. Macrophage neighbors in tumor spheroids indeed coextend intrudopodia between cancer cell junctions-at least when phagocytosis conditions are maximized. Intrudopodia from neighbors help detach and individualize cancer cells for rapid engulfment. Juxtaposition of a macrophage cluster with tumor cell nests defines a broad interface that minimizes cancer cell nearest neighbor interactions and maximizes coordination of macrophage intrudopodia. Cooperative phagocytosis thus overcomes solid tumor cohesion-and might explain why the macrophage clustering factor ITGAL associates with patient survival.

Keywords: cell–cell adhesion; macrophage; phagocytosis

DOI: https://doi.org/10.1073/pnas.2425452122

ACS Appl Mater Interfaces. 2025 Jul 03.

Nanofibrillar Cellulose Hydrogels with Anionic Surface Modifications for Modulating Macrophage Phenotype in 3D Culture.

Maria Heilala, Rita Turpin, Nikolaos Pahimanolis, Nonappa, Olli Ikkala, Juha Klefström, Pauliina M Munne.

Anti-inflammatory M2 macrophages are highly relevant in various physiological processes ranging from tissue regeneration to cancer progression. However, conventional two-dimensional (2D) in vitro cell cultures limit our understanding of macrophage phenotypes and how they can be modulated for immunotherapeutic approaches. Moreover, there is a growing demand for scalable, animal-free hydrogels to replace animal-derived materials in three-dimensional (3D) in vitro models. In this study, we explore hydrogels based on plant-derived nanofibrillar cellulose (NFC), also known as cellulose nanofibrils (CNFs) or microfibrillated cellulose (MFC), for generating 3D in vitro models of M2-like macrophages from human blood monocytes. Notably, flow cytometry analysis shows that cells cultured in 3D phosphorylated NFC hydrogels show enhanced expression of the M2 macrophage marker CD206 compared to cells cultured in other negatively charged hydrogels prepared from native NFC or NFCs with carboxylate or sulfate modifications. Furthermore, the upregulation of CD206 expression in 3D phosphorylated NFC is comparable to the induction of CD206 in interleukin 4 (IL-4)-differentiated M2a macrophages. In addition, the cells in the phosphorylated NFC hydrogel show a differential cytokine profile compared to 2D cultured cells, secreting similar levels of tumor necrosis factor α (TNF-α), but 2.6-fold higher amounts of IL-1β and 1.2-fold higher amounts of IL-10. The results suggest that the conversion of monocytes to M2-like macrophages can be controlled by the phosphorylation of NFC, a strategy which does not require the addition of polarization factors like growth factors and cytokines conventionally used to generate macrophages in vitro. The findings highlight the importance of surface chemistry in matrix-guided macrophage polarization, paving the way for xeno-free yet bioactive 3D macrophage culture scaffolds for immunological research.

Keywords: 3D cell culture; hydrogels; macrophage polarization; macrophages; nanocelluloses

DOI: https://doi.org/10.1021/acsami.5c06549