Biology subjects

Janmey, P.

Publications and source records attributed to Janmey, P..

12 recordsLinked to original sources

bioRxiv2025

Plasma Gelsolin Prevents Organ-Specific Inflammation and Enhances Innate Immune Function in a Systemic Candida albicans Infection

Systemic Candida albicans infections (candidemia) remain a significant cause of morbidity and mortality in immunocompromised patients, mainly due to severe inflammation, organ damage, and delayed fungal clearance. Plasma gelsolin (pGSN), an actin-binding protein with immunomodulatory properties, has demonstrated protective effects in bacterial sepsis models, but its role in fungal infections remains unexplored. Here, we evaluated the impact of pGSN in a murine model of candidemia. Mice intravenously challenged with C. albicans exhibited strong inflammatory responses, particularly in the kidneys and lungs, as visualized by IRDye 800CW 2-deoxyglucose imaging and confirmed by histopathological examination. Subcutaneous injection of pGSN significantly reduced systemic and organ-specific inflammation, decreased blood fungal burden, and prevented microabscess formation in the kidneys. In parallel, pGSN suppressed inflammatory gene expression in whole blood and enhanced phagocytic activity of human monocytes. Additionally, pGSN modulated monocyte reactive radical production by increasing nitric oxide and reducing hydrogen sulfide and reactive oxygen species production. These results highlight the dual immunomodulatory and host-protective properties of pGSN, supporting its potential as an adjunctive therapy in fungal sepsis.

microbiology↗

bioRxiv2025

Role of nuclear ATPases in nuclear mechanics and cell migration through confined spaces: opposite effects of BRG1 and cohesin

Deformation of the nucleus often presents a barrier to cell migration through tight spaces, such as those encountered as cells move through tissues or across extracellular matrix barriers. Reorganization of the nucleus to allow its passage through spaces much smaller than its resting diameter requires forces generated by the cytoskeleton, as well as active reorganization within the nucleus driven by ATPases that crosslink or move chromatin. Here, we show that two different nuclear ATPases, the BRG1/SMARCA4 motor of the BAF or SWI/SNF complex and the bifunctional crosslinking and loop extruding complex, cohesin, have opposite effects on the stiffness of isolated nuclei. Inhibition of BRG1 stiffens the nucleus, and cohesin softens it in karyoplasts derived from multiple cell types, including four different cancer cells, fibroblasts, and mesenchymal stem cells. The effects on isolated nuclear stiffness coincide with the effects of these ATPases on the ability of cells to migrate through tight spaces. Stiffening the nucleus inhibits single cell migration through micron-sized pores and the outward migration of tumor cell spheroids into a surrounding collagen matrix. Softening the nucleus by inhibiting cohesin has the opposite effect: it enhances single-cell migration through pores, at least for some cell types, and facilitates the outgrowth of cells from a tumor cell spheroid into the surrounding matrix. These results emphasize the importance of active motions generated within the nucleus for the global mechanics of the nucleus and the way that it deforms in response to externally generated stresses. Statement of significanceCells often move through tight spaces within three-dimensional materials. This constricted motion requires deformation of the nucleus, which is often stiffer and less dynamic than the rest of the cell. Nuclear deformation is achieved in part by forces generated outside the nucleus, primarily by cytoskeletal motors, but nuclear deformation is also affected by intranuclear motor proteins that move and reorganize chromatin. Here we show that the activity of DNA binding chromatin remodeling ATPases affects not only the stiffness of the isolated nucleus but also the ability of cells to deform as they move through tight spaces. Inhibition of motors such as BRG1 that fluidize the nucleus prevents cell movement through tight spaces, whereas inactivation of the crosslinking ATPase cohesin tends to enhance it.

biophysics↗

bioRxiv2024

Extracellular Vimentin is a Damage-Associated Molecular Pattern Protein Serving as an Agonist of TLR4 in Human Neutrophils

BackgroundVimentin is a type III intermediate filament protein, that plays an important role in cytoskeletal mechanics. It is now known that vimentin also plays important roles outside the cell. Recent studies show the controlled release of vimentin into the extracellular environment, where it functions as a signaling molecule. Such observations are expanding our current knowledge of vimentin as a structural cellular component towards additional roles as an active participant in cell signaling. MethodsOur study investigates the immunological roles of extracellular vimentin (eVim) and its citrullinated form (CitVim) as a damage-associated molecular pattern (DAMP) engaging the Toll-like receptor 4 (TLR4) of human neutrophils. We used in vitro assays to study neutrophil migration through endothelial cell monolayers and activation markers such as NADPH oxidase subunit 2 (NOX2/gp91phox). The comparison of eVim with CitVim and its effect on human neutrophils was extended to the induction of extracellular traps (NETs) and phagocytosis of pathogens. ResultsBoth eVim and CitVim interact with and trigger TLR4, leading to increased neutrophil migration and adhesion. CitVim stimulated the enhanced migratory ability of neutrophils, activation of NF-{kappa}B, and induction of NET formation mainly mediated through reactive oxygen species (ROS)-dependent and TLR4-dependent pathways. In contrast, neutrophils exposed to non-citrullinated vimentin exhibited higher efficiency in favoring pathogen phagocytosis, such as Escherichia coli and Candida albicans, compared to CitVim. ConclusionsOur study identifies new functions of eVim in its native and modified forms as an extracellular matrix DAMP and highlights its importance in the modulation of immune system functions. The differential effects of eVim and CitVim on neutrophil functions highlight their potential as new molecular targets for therapeutic strategies aimed at differential regulation of neutrophil activity in different pathological conditions. This, in turn, opens new windows of therapeutic intervention in inflammatory and immunological diseases characterized by immune system dysfunction, in which eVim and CitVim play a key role.

immunology↗

bioRxiv2024

Glomerular Elasticity and Gene Expression Patterns Define Two Phases of Alport Nephropathy

Alport syndrome (AS), caused by COL4A3,4,5 mutations, leads to progressive glomerular disease and eventual kidney failure. In Col43-/- mice (C57BL/6 background), we found that increased glomerular capillary deformability (reduced Youngs modulus, E) appears 2-3 months before detectable proteinuria or elevated serum creatinine. This early change indicates that podocyte injury precedes traditional clinical markers of disease and corresponds to reduced podocyte adhesion and loss. Bulk and podocyte-enriched RNA-seq data, obtained from deconvoluting bulk RNA sequencing data, showed that starting at 4 months, endoplasmic reticulum (ER) stress and the unfolded protein response (UPR) steadily rise while extracellular matrix remodeling, inflammation, epithelial-mesenchymal transition, and maladaptive repair begin. By 7 months, pathology shifts toward widespread parenchymal fibrosis, interleukin, cytokine, and chemokine signaling, cytoskeleton disruption, metabolic failure, and podocyte dedifferentiation. Notably, administration of the chemical chaperone Tauro-Urso-Deoxcycholic Acid (TUDCA) from weaning reduced ER stress, preserved glomerular stiffness, minimized podocyte detachment and loss, normalized inflammatory, injury, and fibrotic gene expression, and halved proteinuria and serum creatinine at 7 months, preserving kidney structure. Differentially expressed podocyte enriched genes from 4-month Col43-/- (vs WT) mice were mapped to human orthologs in the NEPTUNE cohort. Four genes (CRB2, GPC6, NKD1, STX11) were associated with End Stage Renal Disease or 40% loss of eGFR (ESRD40). Collectively, our results identify these four genes and ER stress/UPR as key and treatable drivers of podocyte injury and disease progression in Alport syndrome, well before overt proteinuria, and highlight UPR activation and several genes as promising targets for disease-modifying therapies.

cell biology↗

bioRxiv2023

Large polyacrylamide hydrogels for large-batch cell culture and mechanobiological studies

The rigidity of a cells substrate or extracellular matrix plays a vital role in regulating cell and tissue functions. Polyacrylamide (PAAm) hydrogels are one of the most widely used cell culture substrates that provide a physiologically relevant range of stiffness. However, it is still arduous and time-consuming to prepare PAAm substrates in large batches for high-yield or multi-scale cell cultures. Here we present a simple method to prepare PAAm hydrogels with less time cost and easily accessible materials. The hydrogel is mechanically uniform and supports cell culture in a large batch. We further show that the stiffness of the hydrogel covers a large range of Youngs modulus and is sensed by cells, regulating various cell features including changes in cell morphology, proliferation, and contractility. This method improves reproducibility of mechanobiology studies and can be easily applied for mechanobiology research requiring large numbers of cells or experimental groups.

bioengineering↗

bioRxiv2022

Extracellular vimentin is sufficient to promote cell attachment, spreading, and motility by a mechanism involving N-acetyl glucosamine-containing structures

Vimentin intermediate filaments form part of the cytoskeleton of mesenchymal cells, but under pathological conditions often associated with inflammation, vimentin filaments depolymerize as the result of phosphorylation or citrullination, and vimentin oligomers are secreted or released into the extracellular environment. In the extracellular space, vimentin can bind surfaces of other cells and the extracellular matrix, and the interaction between extracellular vimentin and other cell types can trigger changes in cellular functions, such as activation of fibroblasts to a fibrotic phenotype. The mechanism by which extracellular vimentin binds external cell membranes and whether vimentin alone can act as an adhesive anchor for cells is largely uncharacterized. Here, we show that various cell types (normal and vimentin null fibroblasts, mesenchymal stem cells, A549 lung carcinoma cells) attach to and spread on polyacrylamide hydrogel substrates covalently linked to vimentin. Using traction force microscopy and spheroid expansion assays, we characterize how different cell types respond to extracellular vimentin. Cell attachment to and spreading on vimentin-coated surfaces is inhibited by hyaluronic acid (HA) degrading enzymes, HA synthase inhibitors, soluble heparin, or N-acetyl glucosamine, treatments that have little or no effect on the same cell types binding to collagen-coated hydrogels. These studies highlight the effectiveness of substrate-bound vimentin as a ligand for cells and suggest that carbohydrate structures, including the glycocalyx and glycosylated cell surface proteins that contain N-acetyl glucosamine, form a novel class of adhesion receptors for extracellular vimentin.

biophysics↗

bioRxiv2022

Electrical Stimulation Human Mesenchymal Stem Cells on Conductive Chitosan-Polyaniline Substrates Promotes Neural Priming

Electrical stimulation (ES) within conductive polymer substrates has been suggested to promote the differentiation of stem cells toward a neuronal phenotype. The use of conductive scaffolds in tissue regeneration provides a unique and attractive new option to control the amount and location of ES delivery. Scaffold stiffness has also been shown to be an important regulator of stem cells behavior and fate. Therefore, to improve stem cell-based regenerative therapies, it is essential to characterize the simultaneous effects of electroconductive substrate stiffness and electric field stimuli on stem cell fate processes. In this study, biodegradable electroconductive substrates based on chitosan-polyaniline (CS-g-PANI) were fabricated with different stiffnesses. Human mesenchymal stem cells (hMSCs) seeded on these scaffolds were electrically stimulated for 14 days with 100 mV/ cm (20 min every day). For hMSCs cultured on soft conductive scaffolds, a morphological change with significant filopodial elongation was observed after 2 weeks of electrically stimulated culture. Compared with stiff conductive CS-g-PANI scaffolds and non-conductive CS scaffolds, for soft conductive CS-g-PANI scaffolds microtubule-associated protein 2 (MAP2) and neurofilament (NF-H) expression increased after application of ES. At the same time, there was a decrease in the expression of the glial markers glial fibrillary acidic protein (GFAP) and vimentin after ES. Furthermore, the elevation of intracellular calcium [Ca2+] during spontaneous, cell-generated Ca2+ transients further suggested that electric field stimulation of hMSCs cultured on conductive CS-g-PANI substrates can promote a neural-like phenotype. Our findings propose that the combination of the soft conductive CS-g-PANI substrate and ES is a promising new tool for enhancing nerve tissue engineering outcomes.

bioengineering↗

bioRxiv2022

A study of hyperelastic continuum models for isotropic athermal fibrous networks

Many biological materials contain fibrous protein networks as their main structural components. Understanding the mechanical properties of such networks is important for creating biomimicking materials for cell and tissue engineering, and for developing novel tools for detecting and diagnosing disease. In this work, we develop continuum models for isotropic, athermal fibrous networks by combining a single-fiber model that describes the axial response of individual fibers, with network models that assemble individual fiber properties into overall network behavior. In particular, we consider four different network models, including the affine, three-chain, eight-chain, and micro-sphere models, which employ different assumptions about network structure and kinematics. We systematically investigate the ability of these models to describe the mechanical response of athermal collagen and fibrin networks by comparing model predictions with experimental data. We test how each model captures network behavior under three different loading conditions: uniaxial tension, simple shear, and combined tension and shear. We find that the affine and three-chain models can accurately describe both the axial and shear behavior, whereas the eight-chain and micro-sphere models fail to capture the shear response, leading to an unphysical zero shear moduli at infinitesimal strains. Our study is the first to systematically investigate the applicability of popular network models for describing the macroscopic behavior of athermal fibrous networks, offering insights for selecting efficient models that can be used for large-scale, finite-element simulations of athermal networks.

biophysics↗

bioRxiv2022

Vimentin Intermediate Filaments Can Enhance or Abate Active Cellular Forces in a Microenvironmental Stiffness-Dependent Manner

The mechanical properties of cells are largely determined by the cytoskeleton, which is a complex network of interconnected biopolymers consisting of actin filaments, microtubules, and intermediate filaments. While disruption of the actin filament and microtubule networks is known to decrease and increase cell-generated forces, respectively, the effect of intermediate filaments on cellular forces is not well understood. Using a combination of theoretical modeling and experiments, we show that disruption of vimentin intermediate filaments can either increase or decrease cell-generated forces, depending on microenvironment stiffness, reconciling seemingly opposite results in the literature. On the one hand, vimentin is involved in the transmission of actomyosin-based tensile forces to the matrix and therefore enhances traction forces. On the other hand, vimentin reinforces microtubules and their stability under compression, thus promoting the role of microtubules in suppressing cellular traction forces. We show that the competition between these two opposing effects of vimentin is regulated by the microenvironment stiffness. For low matrix stiffness, the force-transmitting role of vimentin dominates over their microtubule-reinforcing role and therefore vimentin increases traction forces. At high matrix stiffness, vimentin decreases traction forces as the microtubule-reinforcing role of vimentin becomes more important with increasing matrix stiffness. Our theory reconciles seemingly disparate experimental observations on the role of vimentin in active cellular forces and provides a unified description of stiffness-dependent chemo-mechanical regulation of cell contractility by vimentin. SignificanceVimentin is a marker of the epithelial to mesenchymal transition which takes place during important biological processes including embryogenesis, metastasis, tumorigenesis, fibrosis, and wound healing. While the roles of the actin and microtubule networks in the transmission of cellular forces to the extracellular matrix are known, it is not clear how vimentin intermediate filaments impact cellular forces. Here, we show that vimentin impacts cellular forces in a matrix stiffness-dependent manner. Disruption of vimentin in cells on soft matrices reduces cellular forces, while it increases cellular forces in cells on stiff matrices. Given that cellular forces are central to both physiological and pathological processes, our study has broad implications for understanding the effect of vimentin on cellular forces in different microenvironments.

biophysics↗

bioRxiv2021

The Correlation Between Cell and Nucleus Size is Explained by an Eukaryotic Cell Growth Model

In eukaryotes, the cell volume is observed to be strongly correlated with the nuclear volume. The slope of this correlation depends on the cell type, growth condition, and the physical environment of the cell. We develop a computational model of cell growth and proteome increase, incorporating the kinetics of amino acid import, protein/ribosome synthesis and degradation, and active transport of proteins between the cytoplasm and the nucleoplasm. We also include a simple model of ribosome biogenesis and assembly. Results show that the cell volume is tightly correlated with the nuclear volume, and the cytoplasm-nucleoplasm transport rates strongly influences the cell growth rate as well as the cytoplasm/nucleoplasm ratio. Ribosome assembly and the ratio of ribosomal proteins to mature ribosomes also influence the cell volume and the cell growth rate. We find that in order to regulate the cell growth rate and the cytoplasm/nucleoplasm ratio, the cell must optimally control groups of kinetic parameters together, which could explain the quantitative roles of canonical growth pathways. Finally, using an extension of our model and single cell RNAseq data, it is possible to construct a detailed proteome distribution, provided that a quantitative cell division mechanism is known. Author summaryWe develop computational model of cell proteome increase and cell growth to compute the cell volume to nuclear volume ratio. The model incorporates essential kinetics of protein and ribosome synthesis/degradation, and their transport across the nuclear envelope. The model also incorporates ribosome biogenesis and assembly. The model identifies the most important parameters in determining the cell growth rate and the nucleoplasm/cytoplasm ratio, and provides a computational starting point to construct the cell proteome based on the RNAseq data.

cell biology↗

bioRxiv2020

Synergistic effects of conductivity and cell-imprinted topography of chitosan-polyaniline based scaffolds for neural differentiation of adipose-derived stem cells

Smart nano-environments that mimic the stem cell niche can guide cell behavior to support functional repair and regeneration of tissues. The specific microenvironment of nervous tissue is composed of several physical signaling factors, including proper topography, flexibility, and electric conductance, to support the electrical conduction of neuronal communication. In this study, a cell-imprinting technique was used to obtain a hierarchical topographical conductive scaffold based on chitosan-polyaniline (PANI) hydrogels for directing the neural differentiation of rat adipose-derived stem cells (rADSCs). A chitosan-polyaniline hydrogel was synthesized, followed by characterization tests, such as Fourier transform infrared spectroscopy (FTIR), electrical conductivity, Young modulus, and contact angle measurements. A chitosan-PANI scaffold with a biomimetic topography was fabricated by molding it on a chemically fixed culture of PC12 cells. This substrate was used to test the hypothesis that the PC12 cell-imprinted chitosan-PANI hydrogel provides the required hierarchical topographical surface to induce neural differentiation. To test the importance of spatial imprinting, rADSCs were seeded on these conductive patterned substrates, and the resulting cultures were compared to those of the same cells grown on flat conductive chitosan-polyaniline, and flat pure chitosan substrates for evaluation of adhesion, cell viability, and expression of neural differentiation markers. The morphology of rADSCs grown on conductive patterned scaffolds noticeably was significantly different from that of stem cells cultivated on flat scaffolds. This difference suggests that the change in cell and nuclear shape imposed by the patterned conductive substrate leads to altered gene expression and neural differentiation of cultured cells. In addition, the percentage of rADSCs that differentiated into neural-like cells was almost 80 % on the imprinted chitosan-PANI scaffold. In summary, a conductive chitosan-polyaniline scaffold with biomimetic topography demonstrates a promising method for enhancing the neural differentiation of rADSCs for the treatment of neurodegenerative diseases.Competing Interest StatementThe authors have declared no competing interest.View Full Text

bioengineering↗

bioRxiv2019

Vimentin protects the structural integrity of the nucleus and suppresses nuclear damage caused by large deformations

Mammalian cells frequently migrate through tight spaces during normal embryogenesis, wound healing, diapedesis or in pathological situations such as metastasis. The nucleus has recently emerged as an important factor in regulating 3D cell migration. At the onset of migratory behavior, cells often initiate the expression of vimentin, an intermediate filament protein which forms networks extending from a juxtanuclear cage to the cell periphery. However, the role of vimentin intermediate filaments (VIFs) in regulating nuclear shape and mechanics remains unknown. Here, we used wild type and vimentin-null mouse embryonic fibroblasts to show that VIFs regulate nuclear shape, motility, and the ability of cells to resist large deformations. The results show that loss of VIFs alters nuclear shape, reduces perinuclear stiffness, and enhances motility in 3D. These changes increase nuclear rupture and activation of DNA damage repair mechanisms, which are rescued by exogenous re-expression of vimentin. Our findings show that VIFs provide mechanical support to protect the nucleus and genome during migration.

cell biology↗