GsMTx-4 venom toxin antagonizes biophysical modulation of metastatic traits in human osteosarcoma cells

Despite their genetic diversity, metastatic cells converge on similar physical constraints during tumor progression. At the nanoscale, these forces can induce substantial molecular deformations, altering the structure and behavior of cancer cells. To address the challenges of osteosarcoma (OS), a highly aggressive cancer, we explored the mechanobiology of OS cells, in vitro. Using uniaxial-stretching technology, we examined the biophysical modulation of metastatic traits in SAOS-2, U-2 OS, and non-tumorigenic hFOB cells. Changes in cell morphology were quantified using confocal and fluorescence microscopy. To elucidate the molecular mechanisms that translate biomechanical alterations into biochemical responses, we employed Western blotting, real-time quantitative RT-PCR, reactive oxygen species ROS assay, and the mechanosensitive channel blocker Grammostola MechanoToxin4 (GsMTx-4). Our study reveals that mechanical stimulation uniquely affects OS cells, increasing nuclear size and altering the N/C ratio. We found that mechanosensitive (MS) channels are activated, leading to ROS accumulation, Src protein modulation, and histone H3 acetylation. These changes influence OS cell motility and adhesion but not proliferation. Importantly, mechanical preconditioning differentially impacts doxorubicin resistance, correlating with the Src-H3 acetylation axis. This study underscores the critical role of MS channels in OS cells and highlights the importance of mechanobiology in identifying molecular pathways that traditional biochemical approaches may not reveal. Notably, the GsMTx-4 venom peptide effectively countered mechanically induced responses, particularly by inhibiting OS cell migration, without harming healthy cells. Thus, suggesting its potential as a promising therapeutic agent for targeting osteosarcoma metastasis.

Towards a more objective and high-throughput spheroid invasion assay quantification method

Multicellular spheroids embedded in 3D hydrogels are prominent in vitro models for 3D cell invasion. Yet, quantification methods for spheroid cell invasion that are high-throughput, objective and accessible are still lacking. Variations in spheroid sizes and the shapes of the cells within render it difficult to objectively assess invasion extent. The goal of this work is to develop a high-throughput quantification method of cell invasion into 3D matrices that minimizes sensitivity to initial spheroid size and cell spreading and provides precise integrative directionally-dependent metrics of invasion. By analyzing images of fluorescent cell nuclei, invasion metrics are automatically calculated at the pixel level. The initial spheroid boundary is segmented and automated calculations of the nuclear pixel distances from the initial boundary are used to compute common invasion metrics (i.e., the change in invasion area, mean distance) for the same spheroid at a later timepoint. We also introduce the area moment of inertia as an integrative metric of cell invasion that considers the invasion area as well as the pixel distances from the initial spheroid boundary. Further, we show that principal component analysis can be used to quantify the directional influence of a stimuli to invasion (e.g., due to a chemotactic gradient or contact guidance). To demonstrate the power of the analysis for cell types with different invasive potentials and the utility of this method for a variety of biological applications, the method is used to analyze the invasiveness of five different cell types. In all, implementation of this high-throughput quantification method results in consistent and objective analysis of 3D multicellular spheroid invasion. We provide the analysis code in both MATLAB and Python languages as well as a GUI for ease of use for researchers with a range of computer programming skills and for applications in a variety of biological research areas such as wound healing and cancer metastasis.

Biomechanical research using advanced micro-nano devices: In-Vitro cell Characterization focus

BACKGROUND

Cells in the body reside in a dynamic microenvironment subjected to various physical stimuli, where mechanical stimulation plays a crucial role in regulating cellular physiological behaviors and functions.

AIM OF REVIEW

Investigating the mechanisms and interactions of mechanical transmission is essential for understanding the physiological and functional interplay between cells and physical stimuli. Therefore, establishing an in vitro biomechanical stimulation cell culture system holds significant importance for research related to cellular biomechanics.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In this review, we primarily focused on various biomechanically relevant cell culture systems and highlighted the advancements and prospects in their preparation processes. Firstly, we discussed the types and characteristics of biomechanics present in the microenvironment within the human body. Subsequently, we introduced the research progress, working principles, preparation processes, potential advantages, applications, and challenges of various biomechanically relevant in vitro cell culture systems. Additionally, we summarized and categorized currently commercialized biomechanically relevant cell culture systems, offering a comprehensive reference for researchers in related fields.

Cell stretching devices integrated with live cell imaging: a powerful approach to study how cells react to mechanical cues

Mechanical stimuli have multiple effects on cell behavior, affecting a number of cellular processes including orientation, proliferation or apoptosis, migration and invasion, the production of extracellular matrix proteins, the activation and translocation of transcription factors, the expression of different genes such as those involved in inflammation and the reprogramming of cell fate. The recent development of cell stretching devices has paved the way for the study of cell reactions to stretching stimuliin-vitro, reproducing physiological situations that are experienced by cells in many tissues and related to functions such as breathing, heart beating and digestion. In this work, we review the highly-relevant contributions cell stretching devices can provide in the field of mechanobiology. We then provide the details for the in-house construction and operation of these devices, starting from the systems that we already developed and tested. We also review some examples where cell stretchers can supply meaningful insights into mechanobiology topics and we introduce new results from our exploitation of these devices.

A low-cost perfusion heating system for slice electrophysiology

Temperature-critical applications, such as patch-clamp electrophysiology, require constant perfusion at a fixed temperature. However, maintaining perfusate at a specific temperature throughout various applications requires heaters or coolers with integrated feedback systems, which has historically increased complexity and cost. This makes such systems prohibitively expensive in research environments with lower funding rates, particularly in developing countries. We developed a custom temperature control system that relies on off-the-shelf components and few custom parts, which can be easily produced with common tools. Our system can be built for less than $30 and maintains a set perfusate temperature within 0.4 °C while introducing negligible electrical interference. Using this system, we demonstrate that Striatal Medium Spiny Neurons exhibit increased membrane resistance, longer membrane time constants, lower firing rates, and increased rheobase current at room temperature compared to physiological temperature.

Towards a More Objective and High-throughput Spheroid Invasion Assay Quantification Method

Multicellular spheroids embedded in 3D hydrogels are prominent in vitro models for 3D cell invasion. Yet, quantification methods for spheroid cell invasion that are high throughput, objective and accessible are still lacking. Variations in spheroid sizes and the shapes of the cells within render it difficult to objectively assess invasion extent. The goal of this work is to develop a high-throughput quantification method of cell invasion into 3D matrices that minimizes sensitivity to initial spheroid size and cell spreading and provides precise integrative directionally-dependent metrics of invasion. By analyzing images of fluorescent cell nuclei, invasion metrics are automatically calculated at the pixel level. The initial spheroid boundary is segmented and automated calculations of the nuclear pixel distances from the initial boundary are used to compute common invasion metrics (i.e., the change in invasion area, mean distance) for the same spheroid at a later timepoint. We also introduce the area moment of inertia as an integrative metric of cell invasion that considers the invasion area as well as the pixel distances from the initial spheroid boundary. Further, we show that principal component analysis can be used to quantify the directional influence of a stimuli to invasion (e.g., due to a chemotactic gradient or contact guidance). To demonstrate the power of the analysis for cell types with different invasive potentials and the utility of this method for a variety of biological applications, the method is used to analyze the invasiveness of five different cell types. In all, implementation of this high throughput quantification method results in consistent and objective analysis of 3D multicellular spheroid invasion. We provide the analysis code in both MATLAB and Python languages as well as a GUI for ease of use for researchers with a range of computer programming skills and for applications in a variety of biological research areas such as wound healing and cancer metastasis.

Unveiling Mechanobiology: A Compact Device for Uniaxial Mechanical Stimulation on Nanofiber Substrates and Its Impact on Cellular Behavior and Nanoparticle Distribution

Biotechnology and its allied sectors, such as tissue culture, regenerative medicine, and personalized medicine, primarily rely upon extensive studies on cellular behavior and their molecular pathways for generating essential knowledge and innovative strategies for human survival. Most such studies are performed on flat, adherent, plastic-based surfaces and use nanofiber and hydrogel-like soft matrices from the past few decades. However, such static culture conditions cannot mimic the immediate cellular microenvironment, where they perceive or generate a myriad of different mechanical forces that substantially affect their downstream molecular pathways. Including such mechanical forces, still limited to specialized laboratories, using a few commercially available or noncommercial technologies are gathering increasing attention worldwide. However, large-scale consideration and adaptation by developing nations have yet to be achieved due to the lack of a cost-effective, reliable, and accessible solution. Moreover, investigations on cellular response upon uniaxial mechanical stretch cycles under more in vivo mimetic conditions are yet to be studied comprehensively. In order to tackle these obstacles, we have prepared a compact, 3D-printed device using a microcontroller, batteries, sensors, and a stepper motor assembly that operates wirelessly and provides cyclic mechanical attrition to any thin substrate. We have fabricated water-stable and stretchable nanofiber substrates with different fiber orientations by using the electrospinning technique to investigate the impact of mechanical stretch cycles on the morphology and orientation of C2C12 myoblast-like cells. Additionally, we have examined the uptake and distribution properties of BSA-epirubicin nanoparticles within cells under mechanical stimulation, which could act as fluorescently active drug-delivery agents for future therapeutic applications. Consequently, our research offers a comprehensive analysis of cellular behavior when cells are subjected to uniaxial stretching on various nanofiber mat architectures. Furthermore, we present a cost-effective alternative solution that addresses the long-standing requirement for a compact, user-friendly, and tunable device, enabling more insightful outcomes in mechanobiology.

Cell Stretcher Assay to Analyze Mechanoresponses to Cyclic Stretching

In their natural environment, most cells and tissues are continuously exposed to cyclic mechanical strain. Sensing these stimuli by mechanosensory proteins and subsequent conversion into a variety of biological responses (referred to as mechanotransduction) are key processes for tissue homeostasis, survival, and differentiation. Perturbations of underlying signaling pathways lead to severe diseases in vivo (Urciuoli E, Peruzzi B, Int J Mol Sci 21(24). https://doi.org/10.3390/ijms21249426, (2020)). In addition, cellular mechanoresponses to cyclic stretching of an isolated single cell differ from those of a cell monolayer, network, or even three-dimensional tissue. Since these processes depend on various physical and biological parameters, the development of a precise, well-characterized, and highly reproducible but also easily tunable stretcher assay is indispensable. Here, we describe the fabrication of defined elastic substrates and their application in cyclic stretching of cultured cells in a custom-made cell stretcher device. We focus on the detailed description of the system and provide a possibility for mechanoresponse characterization, using the analysis of actin stress fiber orientation as exemplary mechanoresponse to cyclic stretching of adherent cells.

The CaT stretcher: An open-source system for delivering uniaxial strain to cells and tissues (CaT)

Integration of mechanical cues in conventional 2D or 3D cell culture platforms is an important consideration for in vivo and ex vivo models of lung health and disease. Available commercial and published custom-made devices are frequently limited in breadth of applications, scalability, and customization. Herein we present a technical report on an open-source, cell and tissue (CaT) stretcher, with modularity for different in vitro and ex vivo systems, that includes the following features: 1) Programmability for modeling different breathing patterns, 2) scalability to support low to high-throughput experimentation, and 3) modularity for submerged cell culture, organ-on-chips, hydrogels, and live tissues. The strategy for connecting the experimental cell or tissue samples to the stretching device were designed to ensure that traditional biomedical outcome measurements including, but not limited to microscopy, soluble mediator measurement, and gene and protein expression remained possible. Lastly, to increase the uptake of the device within the community, the system was built with economically feasible and available components. To accommodate diverse in vitro and ex vivo model systems we developed a variety of chips made of compliant polydimethylsiloxane (PDMS) and optimized coating strategies to increase cell adherence and viability during stretch. The CaT stretcher was validated for studying mechanotransduction pathways in lung cells and tissues, with an increase in alpha smooth muscle actin protein following stretch for 24 h observed in independent submerged monolayer, 3D hydrogel, and live lung tissue experiments. We anticipate that the open-source CaT stretcher design will increase accessibility to studies of the dynamic lung microenvironment through direct implementation by other research groups or custom iterations on our designs.

Brick Strex: a robust device built of LEGO bricks for mechanical manipulation of cells

Cellular forces, mechanics and other physical factors are important co-regulators of normal cell and tissue physiology. These cues are often misregulated in diseases such as cancer, where altered tissue mechanics contribute to the disease progression. Furthermore, intercellular tensile and compressive force-related signaling is highlighted in collective cell behavior during development. However, the mechanistic understanding on the role of physical forces in regulation of cellular physiology, including gene expression and signaling, is still lacking. This is partly because studies on the molecular mechanisms of force transmission require easily controllable experimental designs. These approaches should enable both easy mechanical manipulation of cells and, importantly, readouts ranging from microscopy imaging to biochemical assays. To achieve a robust solution for mechanical manipulation of cells, we developed devices built of LEGO bricks allowing manual, motorized and/or cyclic cell stretching and compression studies. By using these devices, we show that [Formula: see text]-catenin responds differentially to epithelial monolayer stretching and lateral compression, either localizing more to the cell nuclei or cell-cell junctions, respectively. In addition, we show that epithelial compression drives cytoplasmic retention and phosphorylation of transcription coregulator YAP1. We provide a complete part listing and video assembly instructions, allowing other researchers to build and use the devices in cellular mechanics-related studies.

Integration of substrate- and flow-derived stresses in endothelial cell mechanobiology

Endothelial cells (ECs) lining all blood vessels are subjected to large mechanical stresses that regulate their structure and function in health and disease. Here, we review EC responses to substrate-derived biophysical cues, namely topography, curvature, and stiffness, as well as to flow-derived stresses, notably shear stress, pressure, and tensile stresses. Because these mechanical cues in vivo are coupled and are exerted simultaneously on ECs, we also review the effects of multiple cues and describe burgeoning in vitro approaches for elucidating how ECs integrate and interpret various mechanical stimuli. We conclude by highlighting key open questions and upcoming challenges in the field of EC mechanobiology.

Cyclic uniaxial cell stretching in tissue culture using a LEGO®-based mechanical stretcher and a polydimethylsiloxane stretchable vessel

Mechanical signals are essential for the regulation of many biological processes. Therefore, it has become paramount to account for these mechanical parameters when exploring biological processes. Here, we describe a protocol to apply cyclic uniaxial stretch on cells in culture using a LEGO®-based mechanical stretcher and a flexible custom-made polydimethylsiloxane culture vessel as well as validated downstream applications. While this system offers an out-of-the-box limited type of simulation, it provides a reliable and low-cost opportunity to perform cell stretching. For complete details on the use and execution of this protocol, please refer to Boulter et al. (2020).

A Fully Integrated Arduino-Based System for the Application of Stretching Stimuli to Living Cells and Their Time-Lapse Observation: A Do-It-Yourself Biology Approach

Mechanobiology has nowadays acquired the status of a topic of fundamental importance in a degree in Biological Sciences. It is inherently a multidisciplinary topic where biology, physics and engineering competences are required. A course in mechanobiology should include lab experiences where students can appreciate how mechanical stimuli from outside affect living cell behaviour. Here we describe all the steps to build a cell stretcher inside an on-stage cell incubator. This device allows exposing living cells to a periodic mechanical stimulus similar to what happens in physiological conditions such as, for example, in the vascular system or in the lungs. The reaction of the cells to the periodic mechanical stretching represents a prototype of a mechanobiological signal integrated by living cells. We also provide the theoretical and experimental aspects related to the calibration of the stretcher apparatus at a level accessible to researchers not used to dealing with topics like continuum mechanics and analysis of deformations. We tested our device by stretching cells of two different lines, U87-MG and Balb-3T3 cells, and we analysed and discussed the effect of the periodic stimulus on both cell reorientation and migration. We also discuss the basic aspects related to the quantitative analysis of the reorientation process and of cell migration. We think that the device we propose can be easily reproduced at low-cost within a project-oriented course in the fields of biology, biotechnology and medical engineering.

Cell stretchers and the LINC complex in mechanotransduction

How cells respond to mechanical forces from the surrounding environment is critical for cell survival and function. The LINC complex is a central component in the mechanotransduction pathway that transmits mechanical information from the cell surface to the nucleus. Through LINC complex functionality, the nucleus is able to respond to mechanical stress by altering nuclear structure, chromatin organization, and gene expression. The use of specialized devices that apply mechanical strain to cells have been central to investigating how mechanotransduction occurs, how cells respond to mechanical stress, and the role of the LINC complexes in these processes. A large variety of designs have been reported for these devices, with the most common type being cell stretchers. Here we highlight some of the salient features of cell stretchers and suggest some key parameters that should be considered when using these devices. We provide a brief overview of how the LINC complexes contribute to the cellular responses to mechanical strain. And finally, we suggest that stretchers may be a useful tool to study aging.

Intranuclear strain in living cells subjected to substrate stretching: A combined experimental and computational study

Nuclear deformation caused by mechanical stimuli has been suggested to significantly impact various cellular activities, such as gene expression, protein synthesis and mechanotransduction. To understand how nuclear deformation regulates cellular behaviors, the details of intranuclear strain distribution caused by mechanical stimuli as well as intranuclear mechanical properties are required. Here, we examine local mechanical strains within the nucleus in a living cell subjected to substrate stretching and estimate the local nuclear mechanical properties. A HeLa cell in a PDMS chamber was subjected to a 10% step-strain by using a custom-made uni-axial stretching device. Local displacements and the distribution of the equivalent strain within the nucleus were obtained from fluorescence images of the nucleus before and after the application of stretching. The intranuclear strain showed heterogeneous distribution, and higher strain regions were observed not only at the center, but also periphery of the nucleus. We examined the role of the chromatin condensation level and actin cytoskeleton by treating cells with Trichostatin A and Cytochalasin D, respectively. Interestingly, these treatments did not cause significant changes in the intranuclear strain distribution. Referring to the experimental results, we reproduced the nuclear strain distribution in a finite element model to estimate relative distribution of Young's modulus within the nucleus, and observed substantially lower Young's modulus levels in the peripheral regions of the nucleus relative to those found in the central regions of the nucleus. We reveal heterogeneous strain distribution within the nucleus in a living cell subjected to substrate stretching, and the results provide insights into the importance of heterogeneity of intranuclear mechanical properties.

Design of a 3D printed, motorized, uniaxial cell stretcher for microscopic and biochemical analysis of mechanotransduction

Cells respond to mechanical cues from their environment through a process of mechanosensing and mechanotransduction. Cell stretching devices are important tools to study the molecular pathways responsible for cellular responses to mechanobiological processes. We describe the development and testing of a uniaxial cell stretcher that has applications for microscopic as well as biochemical analyses. By combining simple fabrication techniques with adjustable control parameters, the stretcher is designed to fit a variety of experimental needs. The stretcher can be used for static and cyclic stretching. As a proof of principle, we visualize stretch induced deformation of cell nuclei via incremental static stretch, and changes in IEX1 expression via cyclic stretching. This stretcher is easily modified to meet experimental needs, inexpensive to build, and should be readily accessible for most laboratories with access to 3D printing.

First person – Etienne Boulter

First Person is a series of interviews with the first authors of a selection of papers published in Journal of Cell Science, helping early-career researchers promote themselves alongside their papers. Etienne Boulter is first author on ‘Cyclic uniaxial mechanical stretching of cells using a LEGO® parts-based mechanical stretcher system’, published in JCS. Etienne is a Research Associate in the lab of Chloé Féral at the Institute for Research on Cancer and Aging (IRCAN), Nice, where he has a long-lasting interest in the study of cell adhesion and related signaling processes, which currently focuses on mechanical signaling.