Shear-related fibrillogenesis of fibronectin

Biomechanical forces can induce the transformation of fibronectin (Fn) from its compact structure to an extended fibrillar state. Adsorption of plasma proteins onto metallic surfaces may also influence their conformation. We used a cone-plate rheometer to investigate the effect of shear and stainless steel on conformational changes of Fn. In control experiments, cones grafted once or twice with polyethylene glycol were used. Plasma Fn was added at concentrations of 50 or 100 μg/ml to bovine serum albumin (BSA)- or Fn-coated plates and subsequently exposed to dynamic shear rates stepwise increasing from 50 to 5000 s-1 within 5 min and subsequently decreasing from 5000 to 50 s-1 within 5 min. The viscosity (mPa s) of Fn solutions was recorded over 10 min. Upon exposure to shear, the viscosity in the sample increased, suggesting conformational changes in Fn. Western blotting and densitometric analyses demonstrated that conformational changes of plasma Fn depended both on shear and protein concentration. However, there was no significant difference in fibril formation between BSA- or Fn-coated plates, suggesting that physical properties of stainless steel and biomechanical forces such as shear can affect the molecular structure of Fn. Our model may provide useful information of surface- and flow-induced alterations of plasma proteins.