Apparent elastic modulus and hysteresis of skeletal muscle cells throughout differentiation

Abstract

The effect of differentiation on the transverse mechanical properties of mammalian myocytes was determined by using atomic force microscopy. The apparent elastic modulus increased from 11.5 +/- 1.3 kPa for undifferentiated myoblasts to 45.3 +/- 4.0 kPa after 8 days of differentiation (P < 0.05). The relative contribution of viscosity, as determined from the normalized hysteresis area, ranged from 0.13 +/- 0.02 to 0.21 +/- 0.03 and did not change throughout differentiation. Myosin expression correlated with the apparent elastic modulus, but neither myosin nor beta-tubulin were associated with hysteresis. Microtubules did not affect mechanical properties because treatment with colchicine did not alter the apparent elastic modulus or hysteresis. Treatment with cytochalasin D or 2,3-butanedione 2-monoxime led to a significant reduction in the apparent elastic modulus but no change in hysteresis. In summary, skeletal muscle cells exhibited viscoelastic behavior that changed during differentiation, yielding an increase in the transverse elastic modulus. Major contributors to changes in the transverse elastic modulus during differentiation were actin and myosin.

Adhesion-contractile balance in myocyte differentiation

“…Although the upper cell sees only a soft cell below it, the lower cell always sees rigid substrate below it in spite of the soft cell above. The elastic modulus of earlystage myotubes has been determined previously by AFM indentation (Collinsworth et al, 2002) and proves remarkably similar to elastic moduli reported for the passive elasticity of skeletal muscle tissue. Separate studies of our own with C2C12 cells grown on collagen-coated polyacrylamide gels confirm that a tissue-like substrate modulus is indeed optimal for myotube differentiation (see Fig.…”

“…In addition, as these cells differentiate further with striation in classic culture conditions, they stiffen, as measured using atomic force microscopy (AFM) (Collinsworth et al, 2002). Stiffness of smooth muscle cells (measured by twisting magnetic beads) also increases linearly with contractile stress ).…”

Force measurements with the atomic force microscope: Technique, interpretation and applications

“…Experiments concerned changes in cell stiffness upon increasing Ca 2+ concentration [939,940] or the cellular contractility [941]. Also, the effect of cell differentiation [942], cell division [943], shear stress [917,944], culture time [307], and cell spreading [945] has been studied. Deformability of endothelial cell was found to increase after contact with monocytes (considered to play a major role in the early stage of atherosclerosis) [946].…”

Satellite Cells and the Muscle Stem Cell Niche

“…Recent studies reveal a previously unappreciated role for the stiffness of the ECM in regulating satellite cell proliferation and differentiation. Resting healthy skeletal muscles and cultured myotubes possess a similar elastic stiffness (elastic modulus ϳ12 kPa) (106,152), whereas aged (184,444) and dystrophic (152) skeletal muscles are apparently stiffer (elastic modulus ϳ418 kPa). These changes of stiffness are presumably due to increased extracellular matrix deposition, in particular collagen deposition by fibroblasts, a result of repeated muscle regeneration.…”