Aortic tissue stiffening during contractile stimulation is decreased by inhibition of Src, FAK, or MLCK.

(A) Tissue stiffness E measured in vitro during PE-induced contraction at optimum length L_O with small-amplitude (1%), high frequency (40Hz) sinusoidal stretches ΔL. Box height and width for magnified traces: 0.5 mN, 5 µm, and 0.02 s. Upper Inset: Stiffness calculation. Lower Inset: Fluorescent micrograph of aortic ring in cross-section, used to determine ring thickness for calculation of cross-sectional area A. Green: autofluorescent elastic laminae. Blue: cell nuclei. Scale bar, 100 µm. (B) PE-induced stress is significantly lower when pre-treated with MLCK inhibitor ML-9, confirming the importance of myosin activation and contraction to vascular stiffness (n = 4). PE-induced stress is also significantly reduced when pre-treated with Src inhibitor PP2 and FAK inhibitor 14. (C) PE-induced stiffening is significantly reduced when pre-treated with MLCK inhibitor ML-9, confirming the importance of myosin activation to aortic stiffness. Stiffening is also significantly lower when pre-treated with Src inhibitor PP2 and FAK inhibitor 14, indicating a role for Src, FAK, and FA proteins in aortic stiffness. n = 10 untreated, 6 ML-9, 4 PP2, 5 FI-14 rings. *p<0.05,**p<0.01, ***p<0.001, unpaired, two-tailed Student’s t-test.