Response of cells and tissues to shear stress

Arrangement into layers and mechanobiology of multi-cell co-culture models of the uterine wall

STUDY QUESTION

Can a co-culture of three cell types mimic the in vivo layers of the uterine wall?

SUMMARY ANSWER

Three protocols tested for co-culture of endometrial epithelial cells (EEC), endometrial stromal cells (ESC), and myometrial smooth muscle cells (MSMC) led to formation of the distinct layers that are characteristic of the structure of the uterine wall in vivo.

WHAT IS KNOWN ALREADY

We previously showed that a layer-by-layer co-culture of EEC and MSMC responded to peristaltic wall shear stresses (WSS) by increasing the polymerization of F-actin in both layers. Other studies showed that WSS induced significant cellular alterations in epithelial and endothelial cells.

STUDY DESIGN, SIZE, DURATION

Human EEC and ESC cell lines and primary MSMC were co-cultured on a collagen-coated synthetic membrane in custom-designed wells. The co-culture model, created by seeding a mixture of all cells at once, was exposed to steady WSS of 0.5 dyne/cm2 for 10 and 30 min.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The co-culture of the three different cells was seeded either layer-by-layer or as a mixture of all cells at once. Validation of the models was by specific immunofluorescence staining and confocal microscopy. Alterations of the cytoskeletal F-actin in response to WSS were analyzed from the 2-dimensional confocal images through the Z-stacks following a previously published algorithm.

MAIN RESULTS AND THE ROLE OF CHANCE

We generated three multi-cell in vitro models of the uterine wall with distinct layers of EEC, ESC, and MSMC that mimic the in vivo morphology. Exposure of the mixed seeding model to WSS induced increased polymerization of F-actin in all the three layers relative to the unexposed controls. Moreover, the increased polymerization of F-actin was higher (P-value < 0.05) when the length of exposure was increased from 10 to 30 min. Furthermore, the inner layers of ESC and MSMC, which are not in direct contact with the applied shearing fluid, also increased their F-actin polymerization.

LARGE SCALE DATA

N/A.

LIMITATIONS, RESONS FOR CAUTION

The mixed seeding co-culture model was exposed to steady WSS of one magnitude, whereas the uterus is a dynamic organ with intra-uterine peristaltic fluid motions that vary in vivo with different time-dependent magnitude. Further in vitro studies may explore the response to peristaltic WSS or other physical and/or hormonal perturbations that may mimic the spectrum of pathophysiological aspects.

WIDER IMPLICATIONS OF THE FINDINGS

Numerous in vitro models were developed in order to mimic the human endometrium and endometrium-myometrium interface (EMI) region. The present co-culture models seem to be the first constructed from EEC, ESC, and MSMC on a collagen-coated synthetic membrane. These multi-cell in vitro models better represent the complex in vivo anatomy of the EMI region. The mixed seeding multi-cell in vitro model may easily be implemented in controlled studies of uterine function in reproduction and the pathogenesis of diseases.

STUDY FINDING/COMPETING INTEREST(S)

This study was supported in part by Tel Aviv University funds. All authors declare no conflict of interest.

Towards a better understanding of the effect of protein conditioning layers on microbial adhesion: a focused investigation of fibronectin and bovine serum albumin layers on SiO2 surfaces

The interaction of foreign implants with their surrounding environment is significantly influenced by the adsorption of proteins on the biomaterial surfaces, playing a role in microbial adhesion. Therefore, understanding protein adsorption on solid surfaces and its effect on microbial adhesion is essential to assess the associated risk of infection. The aim of this study is to evaluate the effect of conditioning by fibronectin (Fn) or bovine serum albumin (BSA) protein layers of silica (SiO2) surfaces on the adhesion and detachment of two pathogenic microorganisms: Pseudomonas aeruginosa PAO1-Tn7-gfp and Candida albicans CIP 48.72. Experiments are conducted under both static and hydrodynamic conditions using a shear stress flow chamber. Through the use of very low wall shear stresses, the study brings the link between the static and dynamic conditions of microbial adhesion. The results reveal that the microbial adhesion critically depends on: (i) the presence of a protein layer conditioning the SiO2 surface, (ii) the type of protein and (iii) the protein conformation and organization in the conditioning layer. In addition, a very distinct adhesion behaviour of P. aeruginosa is observed towards the two tested proteins, Fn and BSA. This effect is reinforced by the amount of proteins adsorbed on the surface and their organization in the layer. The results are discussed in the light of atomic force microscopy analysis of the organization and conformation of proteins in the layers after adsorption on the SiO2 surface, as well as the specificity in bacterial behaviour when interacting with these protein layers. The study also demonstrates the very distinctive behaviours of the prokaryote P. aeruginosa PAO1-Tn7-gfp compared to the eukaryote C. albicans CIP 48.72. This underscores the importance of considering species-specific interactions between the protein conditioning layer and different pathogenic microorganisms, which appear crucial in designing tailored anti-adhesive surfaces.

Graphene Oxide (GO)-Based Bioink with Enhanced 3D Printability and Mechanical Properties for Tissue Engineering Applications

Currently, a major challenge in material engineering is to develop a cell-safe biomaterial with significant utility in processing technology such as 3D bioprinting. The main goal of this work was to optimize the composition of a new graphene oxide (GO)-based bioink containing additional extracellular matrix (ECM) with unique properties that may find application in 3D bioprinting of biomimetic scaffolds. The experimental work evaluated functional properties such as viscosity and complex modulus, printability, mechanical strength, elasticity, degradation and absorbability, as well as biological properties such as cytotoxicity and cell response after exposure to a biomaterial. The findings demonstrated that the inclusion of GO had no substantial impact on the rheological properties and printability, but it did enhance the mechanical properties. This enhancement is crucial for the advancement of 3D scaffolds that are resilient to deformation and promote their utilization in tissue engineering investigations. Furthermore, GO-based hydrogels exhibited much greater swelling, absorbability and degradation compared to non-GO-based bioink. Additionally, these biomaterials showed lower cytotoxicity. Due to its properties, it is recommended to use bioink containing GO for bioprinting functional tissue models with the vascular system, e.g., for testing drugs or hard tissue models.

Role of viscoelasticity in the appearance of low-Reynolds turbulence: considerations for modelling

Inertial effects caused by perturbations of dynamical equilibrium during the flow of soft matter constitute a hallmark of turbulence. Such perturbations are attributable to an imbalance between energy storage and energy dissipation. During the flow of Newtonian fluids, kinetic energy can be both stored and dissipated, while the flow of viscoelastic soft matter systems, such as polymer fluids, induces the accumulation of both kinetic and elastic energies. The accumulation of elastic energy causes local stiffening of stretched polymer chains, which can destabilise the flow. Migrating multicellular systems are hugely complex and are capable of self-regulating their viscoelasticity and mechanical stress generation, as well as controlling their energy storage and energy dissipation. Since the flow perturbation of viscoelastic systems is caused by the inhomogeneous accumulation of elastic energy, rather than of kinetic energy, turbulence can occur at low Reynolds numbers.This theoretical review is focused on clarifying the role of viscoelasticity in the appearance of low-Reynolds turbulence. Three types of system are considered and compared: (1) high-Reynolds turbulent flow of Newtonian fluids, (2) low and moderate-Reynolds flow of polymer solutions, and (3) migration of epithelial collectives, discussed in terms of two model systems. The models considered involve the fusion of two epithelial aggregates, and the free expansion of epithelial monolayers on a substrate matrix.

Tuneable hydrogel patterns in pillarless microfluidic devices

Organ-on-chip (OOC) technology has recently emerged as a powerful tool to mimic physiological or pathophysiological conditions through cell culture in microfluidic devices. One of its main goals is bypassing animal testing and encouraging more personalized medicine. The recent incorporation of hydrogels as 3D scaffolds into microfluidic devices has changed biomedical research since they provide a biomimetic extracellular matrix to recreate tissue architectures. However, this technology presents some drawbacks such as the necessity for physical structures as pillars to confine these hydrogels, as well as the difficulty in reaching different shapes and patterns to create convoluted gradients or more realistic biological structures. In addition, pillars can also interfere with the fluid flow, altering the local shear forces and, therefore, modifying the mechanical environment in the OOC model. In this work, we present a methodology based on a plasma surface treatment that allows building cell culture chambers with abutment-free patterns capable of producing precise shear stress distributions. Therefore, pillarless devices with arbitrary geometries are needed to obtain more versatile, reliable, and biomimetic experimental models. Through computational simulation studies, these shear stress changes are demonstrated in different designed and fabricated geometries. To prove the versatility of this new technique, a blood-brain barrier model has been recreated, achieving an uninterrupted endothelial barrier that emulates part of the neurovascular network of the brain. Finally, we developed a new technology that could avoid the limitations mentioned above, allowing the development of biomimetic OOC models with complex and adaptable geometries, with cell-to-cell contact if required, and where fluid flow and shear stress conditions could be controlled.

Collective durotaxis along a self-generated mobile stiffness gradient in vivo

A crucial aspect of tissue self-organization during morphogenesis, wound healing, and cancer invasion is directed migration of cell collectives. The majority of in vivo directed migration has been guided by chemotaxis, whereby cells follow a chemical gradient. In certain situations, migrating cell collectives can also self-generate the stiffness gradient in the surrounding tissue, which can have a feedback effect on the directionality of the migration. The phenomenon has been observed during collective durotaxis in vivo. Along the biointerface between neighbouring tissues, heterotypic cell-cell interactions are the main cause of this self-generated stiffness gradient. The physical processes in charge of tissue self-organization along the biointerface, which are related to the interplay between cell signalling and the formation of heterotypic cell-cell adhesion contacts, are less well-developed than the biological mechanisms of the cellular interactions. This complex phenomenon is discussed here in the model system, such as collective migration of neural crest cells between ectodermal placode and mesoderm subpopulations within Xenopus embryos by pointing to the role of the dynamics along the biointerface between adjacent cell subpopulations on the subpopulation stiffness.

Minimizing Shear Stress in Cell Signaling Studies

Cellular signal transduction comprises a complex series of biochemical reactions by which extracellular signals such as growth factors, hormones, cytokines, and neurotransmitters are translated into specific intracellular responses. Signal transduction is mediated by protein kinase phosphorylation cascades that culminate in the regulation of numerous cellular responses, including division, differentiation, migration, and survival. Importantly, signal relay pathways are dysregulated in human diseases, making the study of signal transduction important for both uncovering basic biology and understanding pathophysiology. Established laboratory cell culture models are useful for studying signal transduction mechanisms, but differences in sample handling procedures can introduce unwanted variability in experimental outcomes and conclusions. One such potential source of experimental variability is the introduction of fluid shear stress upon handling of tissue culture cells. Fluid shear stress triggers a wide range of cellular responses in adherent cell culture, including stimulating the production of cyclic AMP, potentiating the activation of extracellular signal-regulated kinases 1 and 2 (ERK1/2), and ultimately inducing changes in the gene expression of growth and remodeling factors. Further, mechanical stress on cells is physiologically relevant to the development of many pathologies. Here, we describe a detailed protocol for cell lysis and protein extraction that minimizes shear stress induced by classical cell harvest protocols. We also highlight the impact of fluid shear stress by using immunoblotting to assess ERK pathway activation as a readout for this protocol. © 2024 Wiley Periodicals LLC. Basic Protocol 1: Gentle cell lysis and protein extraction Basic Protocol 2: Immunoblotting for cell signaling readouts by SDS-PAGE.

Cancer Metastasis-on-a-Chip for Modeling Metastatic Cascade and Drug Screening

Microfluidic chips are valuable tools for studying intricate cellular and cell-microenvironment interactions. Traditional in vitro cancer models lack accuracy in mimicking the complexities of in vivo tumor microenvironment. However, cancer-metastasis-on-a-chip (CMoC) models combine the advantages of 3D cultures and microfluidic technology, serving as powerful platforms for exploring cancer mechanisms and facilitating drug screening. These chips are able to compartmentalize the metastatic cascade, deepening the understanding of its underlying mechanisms. This article provides an overview of current CMoC models, focusing on distinctive models that simulate invasion, intravasation, circulation, extravasation, and colonization, and their applications in drug screening. Furthermore, challenges faced by CMoC and microfluidic technologies are discussed, while exploring promising future directions in cancer research. The ongoing development and integration of these models into cancer studies are expected to drive transformative advancements in the field.