bims-ecemfi Biomed News
on ECM and fibroblasts
Issue of 2024‒08‒25
nine papers selected by
Badri Narayanan Narasimhan, University of California, San Diego
  1. Cell-Material Interactions in Covalent Adaptable Thioester Hydrogels.
  2. Cellular stiffness sensing through talin 1 in tissue mechanical homeostasis.
  3. Hydrogel biomaterials that stiffen and soften on demand reveal that skeletal muscle stem cells harbor a mechanical memory.
  4. Nuclear deformation and dynamics of migrating cells in 3D confinement reveal adaptation of pulling and pushing forces.
  5. Compression-dependent microtubule reinforcement enables cells to navigate confined environments.
  6. Matrix stiffness aggravates osteoarthritis progression through H3K27me3 demethylation induced by mitochondrial damage.
  7. Biophysical characterization of synthetic adhesins for predicting and tuning engineered living material properties.
  8. Stem cells tightly regulate dead cell clearance to maintain tissue fitness.
  9. Dehydration drives damage in the freezing of brittle hydrogels.
  1. ACS Biomater Sci Eng. 2024 Aug 22.
    Cell-Material Interactions in Covalent Adaptable Thioester Hydrogels.
    Shivani Desai, Benjamin Carberry, Kristi S Anseth, Kelly M Schultz.
      Covalent adaptable networks (CANs) are polymeric networks with cross-links that can break and reform in response to external stimuli, including pH, shear, and temperature, making them potential materials for use as injectable cell delivery vehicles. In the native niche, cells rearrange the extracellular matrix (ECM) to undergo basic functions including migration, spreading, and proliferation. Bond rearrangement enables these hydrogels to mimic viscoelastic properties of the native ECM which promote migration and delivery from the material to the native tissue. In this work, we characterize thioester CANs to inform their design as effective cell delivery vehicles. Using bulk rheology, we characterize the rearrangement of these networks when they are subjected to strain, which mimics the strain applied by a syringe, and using multiple particle tracking microrheology (MPT) we measure cell-mediated remodeling of the pericellular region. Thioester networks are formed by photopolymerizing 8-arm poly(ethylene glycol) (PEG)-thiol and PEG-thioester norbornene. Bulk rheology measures scaffold properties during low and high strain and demonstrates that thioester scaffolds can recover rheological properties after high strain is applied. We then 3D encapsulated human mesenchymal stem cells (hMSCs) in thioester scaffolds. Using MPT, we characterize degradation in the pericellular region. Encapsulated hMSCs degrade these scaffolds within ≈4 days post-encapsulation. We hypothesize that this degradation is mainly due to cytoskeletal tension that cells apply to the matrix, causing adaptable thioester bonds to rearrange, leading to degradation. To verify this, we inhibited cytoskeletal tension using blebbistatin, a myosin-II inhibitor. Blebbistatin-treated cells can degrade these networks only by secreting enzymes including esterases. Esterases hydrolyze thioester bonds, which generate free thiols, leading to bond exchange. Around treated cells, we measure a decrease in the extent of pericellular degradation. We also compare cell area, eccentricity, and speed of untreated and treated cells. Inhibiting cytoskeletal tension results in significantly smaller cell area, more rounded cells, and lower cell speeds when compared to untreated cells. Overall, this work shows that cytoskeletal tension plays a major role in hMSC-mediated degradation of thioester networks. Cytoskeletal tension is also important for the spreading and motility of hMSCs in these networks. This work informs the design of thioester scaffolds for tissue regeneration and cell delivery.
    Keywords:  cell-mediated degradation; injectable scaffolds; multiple particle tracking microrheology; thioester networks
    DOI:  https://doi.org/10.1021/acsbiomaterials.4c00884
  2. Sci Adv. 2024 Aug 23. 10(34): eadi6286
    Cellular stiffness sensing through talin 1 in tissue mechanical homeostasis.
    Manasa Chanduri, Abhishek Kumar, Dar Weiss, Nir Emuna, Igor Barsukov, Miusi Shi, Keiichiro Tanaka, Xinzhe Wang, Amit Datye, Jean Kanyo, Florine Collin, TuKiet Lam, Udo D Schwarz, Suxia Bai, Timothy Nottoli, Benjamin T Goult, Jay D Humphrey, Martin A Schwartz.
      Tissue mechanical properties are determined mainly by the extracellular matrix (ECM) and actively maintained by resident cells. Despite its broad importance to biology and medicine, tissue mechanical homeostasis remains poorly understood. To explore cell-mediated control of tissue stiffness, we developed mutations in the mechanosensitive protein talin 1 to alter cellular sensing of ECM. Mutation of a mechanosensitive site between talin 1 rod-domain helix bundles R1 and R2 increased cell spreading and tension exertion on compliant substrates. These mutations promote binding of the ARP2/3 complex subunit ARPC5L, which mediates the change in substrate stiffness sensing. Ascending aortas from mice bearing these mutations showed less fibrillar collagen, reduced axial stiffness, and lower rupture pressure. Together, these results demonstrate that cellular stiffness sensing contributes to ECM mechanics, directly supporting the mechanical homeostasis hypothesis and identifying a mechanosensitive interaction within talin that contributes to this mechanism.
    DOI:  https://doi.org/10.1126/sciadv.adi6286
  3. Proc Natl Acad Sci U S A. 2024 Aug 27. 121(35): e2406787121
    Hydrogel biomaterials that stiffen and soften on demand reveal that skeletal muscle stem cells harbor a mechanical memory.
    Christopher M Madl, Yu Xin Wang, Colin A Holbrook, Shiqi Su, Xuechen Shi, Fitzroy J Byfield, Gwendoline Wicki, Iris A Flaig, Helen M Blau.
      Muscle stem cells (MuSCs) are specialized cells that reside in adult skeletal muscle poised to repair muscle tissue. The ability of MuSCs to regenerate damaged tissues declines markedly with aging and in diseases such as Duchenne muscular dystrophy, but the underlying causes of MuSC dysfunction remain poorly understood. Both aging and disease result in dramatic increases in the stiffness of the muscle tissue microenvironment from fibrosis. MuSCs are known to lose their regenerative potential if cultured on stiff plastic substrates. We sought to determine whether MuSCs harbor a memory of their past microenvironment and if it can be overcome. We tested MuSCs in situ using dynamic hydrogel biomaterials that soften or stiffen on demand in response to light and found that freshly isolated MuSCs develop a persistent memory of substrate stiffness characterized by loss of proliferative progenitors within the first three days of culture on stiff substrates. MuSCs cultured on soft hydrogels had altered cytoskeletal organization and activity of Rho and Rac guanosine triphosphate hydrolase (GTPase) and Yes-associated protein mechanotransduction pathways compared to those on stiff hydrogels. Pharmacologic inhibition identified RhoA activation as responsible for the mechanical memory phenotype, and single-cell RNA sequencing revealed a molecular signature of the mechanical memory. These studies highlight that microenvironmental stiffness regulates MuSC fate and leads to MuSC dysfunction that is not readily reversed by changing stiffness. Our results suggest that stiffness can be circumvented by targeting downstream signaling pathways to overcome stem cell dysfunction in aged and disease states with aberrant fibrotic tissue mechanics.
    Keywords:  dynamic hydrogels; fibrosis; mechanical memory; mechanotransduction; muscle stem cells
    DOI:  https://doi.org/10.1073/pnas.2406787121
  4. Sci Adv. 2024 Aug 23. 10(34): eadm9195
    Nuclear deformation and dynamics of migrating cells in 3D confinement reveal adaptation of pulling and pushing forces.
    Stefan Stöberl, Johannes Flommersfeld, Maximilian M Kreft, Martin Benoit, Chase P Broedersz, Joachim O Rädler.
      Eukaryotic cells show an astounding ability to remodel their shape and cytoskeleton and to migrate through pores and constrictions smaller than their nuclear diameter. However, the relation of nuclear deformation and migration dynamics in confinement remains unclear. Here, we study the mechanics and dynamics of mesenchymal cancer cell nuclei transitioning through three-dimensional compliant hydrogel channels. We find a biphasic dependence of migration speed and transition frequency on channel width, peaking at widths comparable to the nuclear diameter. Using confocal imaging and hydrogel bead displacement, we determine nuclear deformations and corresponding forces during confined migration. The nucleus deforms reversibly with a reduction in volume during confinement. With decreasing channel width, the nuclear shape during transmigration changes biphasically, concomitant with the transitioning dynamics. Our proposed physical model explains the observed nuclear shapes and transitioning dynamics in terms of the cytoskeletal force generation adapting from purely pulling-based to a combined pulling- and pushing-based mechanism with increasing nuclear confinement.
    DOI:  https://doi.org/10.1126/sciadv.adm9195
  5. Nat Cell Biol. 2024 Aug 19.
    Compression-dependent microtubule reinforcement enables cells to navigate confined environments.
    Robert J Ju, Alistair D Falconer, Christanny J Schmidt, Marco A Enriquez Martinez, Kevin M Dean, Reto P Fiolka, David P Sester, Max Nobis, Paul Timpson, Alexis J Lomakin, Gaudenz Danuser, Melanie D White, Nikolas K Haass, Dietmar B Oelz, Samantha J Stehbens.
      Cells migrating through complex three-dimensional environments experience considerable physical challenges, including tensile stress and compression. To move, cells need to resist these forces while also squeezing the large nucleus through confined spaces. This requires highly coordinated cortical contractility. Microtubules can both resist compressive forces and sequester key actomyosin regulators to ensure appropriate activation of contractile forces. Yet, how these two roles are integrated to achieve nuclear transmigration in three dimensions is largely unknown. Here, we demonstrate that compression triggers reinforcement of a dedicated microtubule structure at the rear of the nucleus by the mechanoresponsive recruitment of cytoplasmic linker-associated proteins, which dynamically strengthens and repairs the lattice. These reinforced microtubules form the mechanostat: an adaptive feedback mechanism that allows the cell to both withstand compressive force and spatiotemporally organize contractility signalling pathways. The microtubule mechanostat facilitates nuclear positioning and coordinates force production to enable the cell to pass through constrictions. Disruption of the mechanostat imbalances cortical contractility, stalling migration and ultimately resulting in catastrophic cell rupture. Our findings reveal a role for microtubules as cellular sensors that detect and respond to compressive forces, enabling movement and ensuring survival in mechanically demanding environments.
    DOI:  https://doi.org/10.1038/s41556-024-01476-x
  6. iScience. 2024 Aug 16. 27(8): 110507
    Matrix stiffness aggravates osteoarthritis progression through H3K27me3 demethylation induced by mitochondrial damage.
    Tianyou Kan, Hanjun Li, Lingli Hou, Junqi Cui, Yao Wang, Lin Sun, Liao Wang, Mengning Yan, Zhifeng Yu.
      Abnormal epigenetics is the initial factor of the occurrence and development of osteoarthritis (OA), and abnormal mechanical load is a key pathogenic factor of OA. However, how abnormal mechanical load affects chondrocyte epigenetics is unclear. Chondrocytes reportedly respond to mechanics through the extracellular matrix (ECM), which has a role in regulating epigenetics in various diseases, and mitochondria are potential mediators of communication between mechanics and epigenetics. Therefore, it is hypothesized that the matrix mechanics of cartilage regulates their epigenetics through mitochondria and leads to OA. The matrix stiffness of OA cartilage on the stress-concentrated side increases, mitochondrial damage of chondrocyte is severe, and the chondrocyte H3K27me3 is demethylated. Moreover, mitochondrial permeability transition pore (mPTP) opens to increase the translocation of plant homeodomain finger protein 8 (Phf8) into the nucleus to catalyze H3K27me3 demethylation. This provides a new perspective for us to understand the mechanism of OA based on mechanobiology.
    Keywords:  cell biology; epigenetics; mechanobiology
    DOI:  https://doi.org/10.1016/j.isci.2024.110507
  7. Matter. 2024 Jun 05. 7(6): 2125-2143
    Biophysical characterization of synthetic adhesins for predicting and tuning engineered living material properties.
    Stefana A Costan, Paul M Ryan, Honesty Kim, Charles W Wolgemuth, Ingmar H Riedel-Kruse.
      Bacterial synthetic multicellular systems are promising platforms for engineered living materials (ELMs) for medical, biosynthesis, environmental, and smart materials applications. Recent advancements in genetically encoded adhesion toolkits have enabled precise manipulation of cell-cell adhesion and the design and patterning of self-assembled multicellular materials. However, in contrast to gene regulation in synthetic biology, the characterization and control of synthetic adhesins remains limited. Here, we demonstrate the quantitative characterization of a bacterial synthetic adhesion toolbox through various biophysical methods. We determine key parameters, including number of adhesins per cell, in-membrane diffusion constant, production and decay rates, and bond-breaking force between adhesins. With these parameters, we demonstrate the bottom-up prediction and quantitative tuning of macroscopic ELM properties (tensile strength) and, furthermore, that cells inside ELMs are connected only by a small fraction of available adhesins. These results enable the rational engineering, characterization, and modeling of other synthetic and natural adhesins and multicellular consortia.
    DOI:  https://doi.org/10.1016/j.matt.2024.03.019
  8. Nature. 2024 Aug 21.
    Stem cells tightly regulate dead cell clearance to maintain tissue fitness.
    Katherine S Stewart, Merve Deniz Abdusselamoglu, Matthew T Tierney, Anita Gola, Yun Ha Hur, Kevin A U Gonzales, Shaopeng Yuan, Alain R Bonny, Yihao Yang, Nicole R Infarinato, Christopher J Cowley, John M Levorse, Hilda Amalia Pasolli, Sourav Ghosh, Carla V Rothlin, Elaine Fuchs.
      Billions of cells are eliminated daily from our bodies1-4. Although macrophages and dendritic cells are dedicated to migrating and engulfing dying cells and debris, many epithelial and mesenchymal tissue cells can digest nearby apoptotic corpses1-4. How these non-motile, non-professional phagocytes sense and eliminate dying cells while maintaining their normal tissue functions is unclear. Here we explore the mechanisms that underlie their multifunctionality by exploiting the cyclical bouts of tissue regeneration and degeneration during hair cycling. We show that hair follicle stem cells transiently unleash phagocytosis at the correct time and place through local molecular triggers that depend on both lipids released by neighbouring apoptotic corpses and retinoids released by healthy counterparts. We trace the heart of this dual ligand requirement to RARγ-RXRα, whose activation enables tight regulation of apoptotic cell clearance genes and provides an effective, tunable mechanism to offset phagocytic duties against the primary stem cell function of preserving tissue integrity during homeostasis. Finally, we provide functional evidence that hair follicle stem cell-mediated phagocytosis is not simply redundant with professional phagocytes but rather has clear benefits to tissue fitness. Our findings have broad implications for other non-motile tissue stem or progenitor cells that encounter cell death in an immune-privileged niche.
    DOI:  https://doi.org/10.1038/s41586-024-07855-6
  9. Sci Adv. 2024 Aug 23. 10(34): eado7750
    Dehydration drives damage in the freezing of brittle hydrogels.
    Shaohua Yang, Dominic Gerber, Yanxia Feng, Nicolas Bain, Matthias Kuster, Laura de Lorenzis, Ye Xu, Eric R Dufresne, Robert W Style.
      It is widely known that freezing breaks soft, wet materials. However, the mechanism underlying this damage is still not clear. To understand this process, we freeze model, brittle hydrogel samples, while observing the growth of ice-filled cracks that break these apart. We show that damage is not caused by the expansion of water upon freezing or the growth of ice-filled cavities in the hydrogel that exert pressure on the surrounding material. Instead, local ice growth dehydrates the adjacent hydrogel, leading to drying-induced fracture. This dehydration is driven by the process of cryosuction, whereby undercooled ice sucks nearby water toward itself, feeding ice growth. Our results highlight the strong analogy between freezing damage and desiccation cracking, which we anticipate being useful for developing an understanding of both topics. Our results should also give useful insights into a wide range of freezing processes, including cryopreservation, food science, and frost heave.
    DOI:  https://doi.org/10.1126/sciadv.ado7750
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