Eukaryotic initiation factor 6 regulates mechanical responses in endothelial cells

The repertoire of extratranslational functions of components of the protein synthesis apparatus is expanding to include control of key cell signaling networks. However, very little is known about noncanonical functions of members of the protein synthesis machinery in regulating cellular mechanics. We demonstrate that the eukaryotic initiation factor 6 (eIF6) modulates cellular mechanobiology. eIF6-depleted endothelial cells, under basal conditions, exhibit unchanged nascent protein synthesis, polysome profiles, and cytoskeleton protein expression, with minimal effects on ribosomal biogenesis. In contrast, using traction force and atomic force microscopy, we show that loss of eIF6 leads to reduced stiffness and force generation accompanied by cytoskeletal and focal adhesion defects. Mechanistically, we show that eIF6 is required for the correct spatial mechanoactivation of ERK1/2 via stabilization of an eIF6–RACK1–ERK1/2–FAK mechanocomplex, which is necessary for force-induced remodeling. These results reveal an extratranslational function for eIF6 and a novel paradigm for how mechanotransduction, the cellular cytoskeleton, and protein translation constituents are linked.

Immobilization of Polyethyleneimine (PEI) on Flat Surfaces and Nanoparticles Affects Its Ability to Disrupt Bacterial Membranes

Interactions between a widely used polycationic polymer, polyethyleneimine (PEI), and a Gram-negative bacteria, E. coli, are investigated using atomic force microscopy (AFM) quantitative imaging. The effect of PEI, a known membrane permeabilizer, is characterized by probing both the structure and elasticity of the bacterial cell envelope. At low concentrations, PEI induced nanoscale membrane perturbations all over the bacterial surface. Despite these structural changes, no change in cellular mechanics (Young’s modulus) was detected and the growth of E. coli is barely affected. However, at high PEI concentrations, dramatic changes in both structure and cell mechanics are observed. When immobilized on a flat surface, the ability of PEI to alter the membrane structure and reduce bacterial elasticity is diminished. We further probe this immobilization-induced effect by covalently attaching the polymer to the surface of polydopamine nanoparticles (PDNP). The nanoparticle-immobilized PEI (PDNP-PEI), though not able to induce major structural changes on the outer membrane of E. coli (in contrast to the flat surface), was able to bind to and reduce the Young’s modulus of the bacteria. Taken together, our data demonstrate that the state of polycationic polymers, whether bound or free—which greatly dictates their overall configuration—plays a major role on how they interact with and disrupt bacterial membranes.

The response of human induced pluripotent stem cells to cyclic temperature changes explored by BIO-AFM

Human induced pluripotent stem cells (hiPSCs) are highly sensitive to extrinsic physical and biochemical signals from their extracellular microenvironments. In this study, we analyzed the effect of cyclic temperature changes on hiPSCs behaviors, especially by means of scanning force microscopy (BIO-AFM). The alternation in cellular mechanics, as well as the secretion and pattern of deposition of extracellular matrix (ECM) protein in hiPSCs were evaluated. The arrangement of the actin cytoskeleton changed with the variation of the temperature. The rearranged cytoskeleton architecture led to the subsequent changes in cell mechanics (Young's modulus of hiPSCs). With the exposure to the cyclic cold stimuli, an increase in the average surface roughness (Ra) and roughness mean square (RMS) was detected. This observation might be at least in part due to the upregulated secretion of Laminin α5 during repeated temporary cooling. The expression of pluripotent markers, NANOG and SOX2, was not impaired in hiPSCs, when exposed to the cyclic cold stimuli for 24 h. Our findings provide an insight into the effect of temperature on the hiPSC behaviors, which may contribute to a better understanding of the application of locally controlled therapeutic hypothermia. Graphic abstract The cyclic temperature changes, from 37 to 10 °C, rapidly increased the mechanical strength of human-induced pluripotent stem cells (hiPSCs), which could be explained by the re-arrangement of cytoskeletons. The capacity of hiPSCs to remodel the extracellular matrix was also altered by the repeated temporary cooling, as they exhibit an enhanced ability to physically remodulate and secrete the ECM components.

How Mechanical Forces Change the Human Endometrium during the Menstrual Cycle in Preparation for Embryo Implantation

The human endometrium is characterized by exceptional plasticity, as evidenced by rapid growth and differentiation during the menstrual cycle and fast tissue remodeling during early pregnancy. Past work has rarely addressed the role of cellular mechanics in these processes. It is becoming increasingly clear that sensing and responding to mechanical forces are as significant for cell behavior as biochemical signaling. Here, we provide an overview of experimental evidence and concepts that illustrate how mechanical forces influence endometrial cell behavior during the hormone-driven menstrual cycle and prepare the endometrium for embryo implantation. Given the fundamental species differences during implantation, we restrict the review to the human situation. Novel technologies and devices such as 3D multifrequency magnetic resonance elastography, atomic force microscopy, organ-on-a-chip microfluidic systems, stem-cell-derived organoid formation, and complex 3D co-culture systems have propelled the understanding how endometrial receptivity and blastocyst implantation are regulated in the human uterus. Accumulating evidence has shown that junctional adhesion, cytoskeletal rearrangement, and extracellular matrix stiffness affect the local force balance that regulates endometrial differentiation and blastocyst invasion. A focus of this review is on the hormonal regulation of endometrial epithelial cell mechanics. We discuss potential implications for embryo implantation.

Multiscale Modeling in Systems Biology: Methods and Perspectives

In the last decades, mathematical and computational models have become ubiquitous to the field of systems biology. Specifically, the multiscale nature of biological processes makes the design and simulation of such models challenging. In this thesis we offer a perspective on available methods to study and simulate such models and how they can be combined to handle biological processes evolving at different scales. The contribution of this thesis is threefold. First, we introduce Orchestral, a multiscale modular framework to simulate multicellular models. By decoupling intracellular chemical kinetics, cell-cell signaling, and cellular mechanics by means of operator-splitting, it is able to combine existing software into one massively parallel simulation. Its modular structure makes it easy to replace its components, e.g. to adjust the level of modeling details. We demonstrate the scalability of our framework on both high performance clusters and in a cloud environment. We then explore how center-based models can be used to study cellular mechanics in biological tissues. We show how modeling and numerical choices can affect the results of the simulation and mislead modelers into incorrect biological conclusions if these errors are not monitored properly. We then propose CBMOS, a Python framework specifically designed for the numerical study of such models. Finally, we study how spatial details in intracellular chemical kinetics can be efficiently approximated in a multiscale compartment-based model. We evaluate how this model compares to two other alternatives in terms of accuracy and computational cost. We then propose a computational pipeline to study and compare such models in the context of Bayesian parameter inference and illustrate its usage in three case studies.

Nanotoxicity of multifunctional unlike cobalt nanoparticles (UCoNPs) with repercussions towards apoptosis and necrosis at nanobio-interfaces

: The development of multifunction nanoparticles proved their worth in the field of the discovery of drug/gene delivery, nanotheranostics (in-vivo imaging, coinciding diagnostics), in external healing intercessions, designing a nano-bio interface, and to do desired alterations in nanotherapeutic. Every so often, the cellular uptake of multifunctional unlike cobalt [Co, CoO, Co2(CO)8 and Co3O4] nanoparticles (UCoNPs) influenced cellular mechanics and initiated numerous repercussions (oxidative stress, tempted DNA damages, cyto-genotoxicity, and chromosomal damages), in pathways, routes and generate dysregulating factors in the biochemical transformations exceedingly. Unlike dimensions of UCoNPs-cell interfaces, their physical features (size, shape, shell structure, and surface chemistry), possessions on cell proliferation and differentiation are the vital whys and wherefores, which are hereby, specifically identified as the key causes responsible for nanotoxicity. In this review, the UCoNPs intricacies (cyto-genotoxicity, clastogenicity, and immunomodulatory), nanotoxicity, and associated repercussions have been highlighted and discussed. The interpretation of quantitative structure-activity relationships, chemical transformations, biological, and toxicological analysis are discussed. The concerns and influences of multifunctional UCoNPs on different cell mechanisms (mitochondria impermeability, hydrolysis of ATP, the concentration of Ca2+, impaired calcium clearance, defective autophagy, apoptosis, and necrosis), and interlinked properties (adhesion, motility, and internalisation dynamics, role in toxicity, surface hydrophilic and hydrophobicity, biokinetics and biomimetic behaviors of biochemical reactions) have been summarised. Various applications i.e. bio-imaging, cell labelling, gene delivery, enhanced chemical stability, and increased bio-compatibility are highlighted concerning apoptosis, necrosis, and nanobio-interfaces with suitable examples.

Hydrodynamics and Interfacial Surfactant Transport in Vascular Gas Embolism

Vascular gas embolism - bubble entry into the blood circulation - is pervasive in medicine, including over 340,000 cardiac surgery patients in the US annually. The gas-liquid interface interacts directly with constituents in blood, including cells and proteins, and with the endothelial cells lining blood vessels to provoke a variety of undesired biological reactions. Surfactant therapy, a potential preventative approach, is based in fluid dynamics and transport mechanics. Herein we review literature relevant to understanding of the key gas-liquid interface interactions inciting injury at the molecular, organelle, cellular and tissue levels, including clot formation, cellular activation, and adhesion events. We review the fluid physics and transport dynamics of surfactant-based interventions to reduce tissue injury from gas embolism. In particular, we focus on experimental research and computational and numerical approaches which demonstrate how surface-active chemical based intervention, based on competition with blood-borne or cell surface-borne macromolecules for surface occupancy of gas-liquid interfaces, alters cellular mechanics, mechanosensing and signaling coupled to fluid stress exposures occurring in gas embolism. We include a new analytical approach for which an asymptotic solution to the Navier-Stokes equations coupled to the convection-diffusion interaction for a soluble surfactant provides additional insight regarding surfactant transport with a bubble in a non-Newtonian fluid.