Cortical stiffness measurement in VSMCs.

<p>(A) Controlled force pulses generated by magnetic tweezers displace aortic VSMC-adherent, RGD-coated superparamagnetic beads (2.8 µm) to measure the stiffness of the bead-focal adhesion-cortical cytoskeleton linkage (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0062461#s2" target="_blank">Methods</a>). The force <i>F</i> exerted on a bead depends on the induced magnetic moment in the bead <i>m</i> and the spatial gradient of the magnetic field <i>B</i>, which depends critically on the sharpness of the probe’s tip, characterized by its radius of curvature <i>R</i>. (B) Calibration curve relating the force exerted on a bead (d = 2.8 µm) to its distance from the MT tip (R = 40 µm) and the current through the electromagnet solenoid (I = 1.5 A). The gray box denotes the operating range used for the MT experiments, i.e. the distance that is set between the MT tip and a bead before pulling commences. (C) Mean cortical stiffness increases with LPA stimulation in a PP2-attenuated manner. Right: BSA beads, which do not bind integrins but adhere nonspecifically, do not register an increase in stiffness with LPA. *p<0.05, **p<0.01, n.s. – not significant, unpaired, two-tailed Student’s t-test, assuming unequal variances.</p>