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Published in Splinter Robert, Illustrated Encyclopedia of Applied and Engineering Physics, 2017
[biomedical, chemical, general, thermodynamics] Operation of ion transport mediation in biological cells in response to external influences such as shear, stress, osmotic pressure, gravity, and acoustic mechanics. One function in particular, next to sensing of external influences, is the protection of the cell itself. Sensing the internal cell pressure will result in a pressure regulation mechanism that will ultimately prevent the cell from bursting. The mechanosensitive action of the cells is mediated by mechanosensitive ion channels (MSCs). These ion channels can currently be subdivided into two groups: (1) responding to fibrous protein and (2) responding to lipid bilayer stress. One measurable effect in response to applied shear and stress in the cell membrane is the change in diameter of what is known as the bacterial large mechanosensitive channels (MscL) in the range of 5–6 nm. The Gibbs free energy difference (ΔG) between the open and closed state of the channel (expressed by the cross-sectional area change ΔA) is defined by the lipid bilayer tension (T) as ΔG = TΔA. Apart from the change in area, there are also changes possible in the shape of the opening, without actual changes to the area. The shape change may provide a preferred vehicle for certain proteins to be transported through the membrane to act as signaling proteins.
Pneumatic piston hydrostatic bioreactor for cartilage tissue engineering
Published in Instrumentation Science & Technology, 2023
J. Hallas, A. J. Janvier, K. F. Hoettges, J. R. Henstock
Mechanical forces deriving from exercise are an essential stimulus for maintaining biological homeostasis in functional joint cartilage, whilst aberrant mechanical loading plays a role in degenerative conditions such as osteoarthritis.[1,2] The musculoskeletal system is composed of cells and tissues that are force responsive, and physical loading of bone, cartilage, muscle, and tendon results in adaptation of the tissue for increased resilience.[3] Stronger osteochondral tissues are formed in response to environmental demands due to an increase in cell activity that produces extracellular matrix molecules such as collagenous proteins and glycosaminoglycans.[4,5] In combination with other cues, including systemic (endocrine) and local biochemical signaling (e.g., growth factors and cytokines), mechanical forces play an important role in enabling the cell to sense its environment. Mechanical forces acting on a cell are converted into changes in intracellular signaling pathways by mechanotransduction events, including mechanosensitive ion channel activation, integrin-mediated signaling between the extracellular matrix and the cytoskeleton, and an array of other mechanically-linked processes. This connection between mechanical stimuli and changes in cell response is of interest to a range of disciplines including in biomedical tissue engineering strategies to create replacement graft tissues formed from hydrogel-encapsulated cells cultured in dynamic growth environments. [6–9]