Matrix Metalloproteinase 2 and 9 Dysfunction Underlie Vascular Stiffness in Circadian Clock Mutant Mice

Objective-To determine if elasticity in blood vessels is compromised in circadian clock-mutant mice (Bmal1-knockout [KO] and Per-triple KO) and if matrix metalloproteinases (MMPs) might confer these changes in compliance. Methods and Results-High-resolution ultrasonography in vivo revealed impaired remodeling and increased pulse-wave velocity in the arteries of Bmal1-KO and Per-triple KO mice. In addition, compliance of remodeled arteries and nave pressurized arterioles ex vivo from Bmal1-KO and Per-triple KO mice was reduced, consistent with stiffening of the vascular bed. The observed vascular stiffness was coincident with dysregulation of MMP-2 and MMP-9 in Bmal1-KO mice. Furthermore, inhibition of MMPs improved indexes of pathological remodeling in wild-type mice, but the effect was abolished in Bmal1-KO mice. Conclusion-Circadian clock dysfunction contributes to hardening of arteries, which may involve impaired control of the extracellular matrix composition. (Arterioscler Thromb Vasc Biol. 2010;30:2535-2543.)