Simultaneous Analysis of Elastic and Nonspecific Adhesive Properties of Thin Sample and Biological Cell Considering Bottom Substrate Effect

Passive myocardial mechanical properties: meaning, measurement, models

Passive mechanical tissue properties are major determinants of myocardial contraction and relaxation and, thus, shape cardiac function. Tightly regulated, dynamically adapting throughout life, and affecting a host of cellular functions, passive tissue mechanics also contribute to cardiac dysfunction. Development of treatments and early identification of diseases requires better spatio-temporal characterisation of tissue mechanical properties and their underlying mechanisms. With this understanding, key regulators may be identified, providing pathways with potential to control and limit pathological development. Methodologies and models used to assess and mimic tissue mechanical properties are diverse, and available data are in part mutually contradictory. In this review, we define important concepts useful for characterising passive mechanical tissue properties, and compare a variety of in vitro and in vivo techniques that allow one to assess tissue mechanics. We give definitions of key terms, and summarise insight into determinants of myocardial stiffness in situ. We then provide an overview of common experimental models utilised to assess the role of environmental stiffness and composition, and its effects on cardiac cell and tissue function. Finally, promising future directions are outlined.

Comparing Migratory and Mechanical Properties of Human Bone Marrow-Derived Mesenchymal Stem Cells with Colon Cancer Cells In Vitro

BACKGROUND

Colon cancer cells can migrate and metastasize by undergoing epithelial-to-mesenchymal transition (EMT). Mesenchymal stem cells (MSCs) are non-cancerous, multipotent adult stem cells, which can also migrate. In this study, we wanted to compare the biological, physical, and functional properties of these migratory cells.

MATERIALS AND METHODS

HT-29 and HCT-116, two human colon carcinoma cell lines, represent less aggressive and more aggressive cancer cells, respectively. MSCs were isolated from human bone marrow. After confirming the identity of all the cell types, they were evaluated for E-cadherin, β1-integrin, Vimentin, ZEB-1, β-catenin, and 18S rRNA using Q-PCR. MMP-2 and MMP-9 activity were evaluated using gelatin zymography. Functional tests like wound healing assay, migration assay, and invasion assay were also done. Biomechanical properties like cell stiffness and non-specific adhesion (between indenter probe and cell membrane) were evaluated through nanoindentation using atomic force microscopy (AFM).

RESULTS

Expression of EMT and stem cell markers showed typical expression patterns for HT-29, HCT-116, and MSCs. Functional tests showed that MSCs migrated faster than malignant cells. MMP-2 and MMP-9 activity reinforced this behavior. Interestingly, the migration/invasion capacity of MSCs was comparable to aggressive HCT-116, and more than HT-29. MSCs also showed the maximum cell stiffness and non-specific cell-probe adhesions, followed by HCT116 and HT29 cells.

CONCLUSIONS

Our findings indicate that the migratory properties of MSCs is comparable or even greater than that of cancer cells and despite their high migration potential, they also have the maximum stiffness.

Determination of the Elastic Moduli of a Single Cell Cultured on a Rigid Support by Force Microscopy

The elastic response of a living cell is affected by its physiological state. This property provides mechanical fingerprints of a cell's dysfunctionality. The softness (kilopascal range) and thickness (2-15 μm) of mammalian cells imply that the force exerted by the probe might be affected by the stiffness of the solid support. This observation makes infinite sample thickness models unsuitable to describe quantitatively the forces and deformations on a cell. Here, we report a general theory to determine the true Young's moduli of a single cell from a force-indentation curve. Analytical expressions are deduced for common geometries such as flat punches, paraboloids, cones, needles, and nanowires. For a given cell and indentation, the influence of the solid support on the measurements is reduced by using sharp and high aspect ratio tips. The theory is validated by finite element simulations.