2.3 Cellular and Molecular Biomechanics

Cellular and molecular biomechanics explores how cells respond to physical forces. It's all about understanding the tiny machinery inside cells that lets them sense and react to their environment. This field is crucial for figuring out how our bodies work at the smallest level.

Advanced biomechanics digs deeper into these cellular processes. It looks at how cells change shape, move around, and communicate using mechanical signals. This knowledge helps us develop new treatments and understand diseases better.

Cell Mechanics

Viscoelasticity and Cell Membrane Properties

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Top images from around the web for Viscoelasticity and Cell Membrane Properties

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• Viscoelasticity describes cellular materials exhibiting both viscous and elastic characteristics
  • Viscous component allows cells to flow and deform under stress
  • Elastic component enables cells to return to their original shape after deformation
• Cell membrane mechanics govern cellular response to mechanical stimuli
  • Lipid bilayer structure provides fluidity and flexibility
  • Membrane proteins contribute to mechanical properties and signal transduction
• Atomic force microscopy (AFM) measures mechanical properties of living cells
  • Uses a cantilever with a sharp tip to probe cell surface
  • Provides high-resolution topographical imaging and force measurements
• Micropipette aspiration technique assesses cellular deformability
  • Applies negative pressure to draw a portion of the cell into a glass micropipette
  • Measures cellular elasticity and viscosity based on aspiration length and time

Advanced Techniques for Cell Mechanics Analysis

• Optical tweezers manipulate microscopic objects using focused laser beams
  • Trap and move cellular components or whole cells with precision
  • Measure forces in the piconewton range
• Magnetic twisting cytometry applies controlled mechanical stress to cell surface receptors
  • Uses magnetic beads attached to specific cellular structures
  • Quantifies cellular stiffness and cytoskeletal remodeling
• Traction force microscopy measures forces exerted by cells on their substrate
  • Utilizes deformable substrates embedded with fluorescent markers
  • Calculates cellular traction forces based on substrate deformation

Mechanotransduction

Cellular Sensing of Mechanical Forces

• Mechanotransduction converts mechanical stimuli into biochemical signals
  • Enables cells to respond and adapt to their physical environment
  • Plays crucial roles in development, homeostasis, and disease
• Mechanosensitive ion channels open or close in response to mechanical forces
  • Allow rapid influx or efflux of specific ions (Na+, K+, Ca2+)
  • Trigger downstream signaling cascades and cellular responses
• Focal adhesions serve as mechanical linkages between cells and their environment
  • Consist of protein complexes that connect the extracellular matrix to the cytoskeleton
  • Act as mechanosensors and signal transduction hubs

Integrin-Mediated Mechanotransduction

• Integrins function as transmembrane receptors linking the extracellular matrix to the cytoskeleton
  • Composed of α and β subunits with extracellular and intracellular domains
  • Cluster and activate in response to mechanical forces
• Integrin activation initiates various signaling pathways
  • Triggers tyrosine phosphorylation cascades
  • Activates small GTPases (Rho, Rac, Cdc42) regulating cytoskeletal organization
• Mechanotransduction through integrins influences gene expression
  • Activates transcription factors (YAP/TAZ, NF-κB)
  • Regulates cell proliferation, differentiation, and survival

Cellular Structure

Cytoskeleton and Extracellular Matrix

• Cytoskeleton provides structural support and enables cellular movement
  • Consists of three main components: microfilaments, intermediate filaments, and microtubules
  • Microfilaments (actin filaments) contribute to cell shape and contractility
  • Intermediate filaments provide mechanical strength and stress resistance
  • Microtubules facilitate intracellular transport and cell division
• Extracellular matrix (ECM) forms the non-cellular component of tissues
  • Composed of proteins (collagen, elastin) and proteoglycans
  • Provides structural support and regulates cell behavior
  • ECM stiffness influences cell fate and function

Tensegrity and Mechanobiology

• Tensegrity model describes cellular architecture as a balance of tension and compression
  • Continuous tension elements (cytoskeleton) and discontinuous compression elements (ECM)
  • Explains how cells maintain shape and respond to mechanical forces
• Mechanobiology studies how mechanical forces influence biological processes
  • Investigates cellular responses to mechanical stimuli at molecular, cellular, and tissue levels
  • Applications in tissue engineering, regenerative medicine, and disease modeling
• Cellular mechanosensing involves multiple mechanisms
  • Stretch-activated ion channels respond to membrane deformation
  • Conformational changes in extracellular matrix proteins expose cryptic binding sites
  • Force-induced unfolding of proteins reveals new interaction domains