Cystatin C Deficiency Increases Elastic Lamina Degradation and Aortic Dilatation in Apolipoprotein E–Null Mice

Abstract

Abstract-The pathogenesis of atherosclerosis and abdominal aortic aneurysm involves substantial proteolysis of the arterial extracellular matrix. The lysosomal cysteine proteases can exert potent elastolytic and collagenolytic activity. Human atherosclerotic plaques have increased cysteine protease content and decreased levels of the endogenous inhibitor cystatin C, suggesting an imbalance that would favor matrix degradation in the arterial wall. This study tested directly the hypothesis that impaired expression of cystatin C alters arterial structure. Cystatin C-deficient mice (Cyst C Ϫ/Ϫ ) were crossbred with apolipoprotein E-deficient mice (ApoE Ϫ/Ϫ ) to generate cystatin C and apolipoprotein E-double deficient mice (Cyst C Ϫ/Ϫ ApoE Ϫ/Ϫ ). After 12 weeks on an atherogenic diet, cystatin C deficiency yielded significantly increased tunica media elastic lamina fragmentation, decreased medial size, and increased smooth muscle cell and collagen content in aortic lesions of ApoE Ϫ/Ϫ mice. Cyst C Ϫ/Ϫ ApoE Ϫ/Ϫ mice also showed dilated thoracic and abdominal aortae compared with control ApoE Ϫ/Ϫ mice, although atheroma lesion size, intimal macrophage accumulation, and lipid core size did not differ between these mice. These findings demonstrate directly the importance of cysteine protease/protease inhibitor balance in dysregulated arterial integrity and remodeling during experimental atherogenesis. (Circ Res. 2005;96:368-375.) Key Words: cystatin C Ⅲ apolipoprotein E Ⅲ cysteine protease Ⅲ atherosclerosis Ⅲ smooth muscle cells A therogenesis involves substantial remodeling of the arterial extracellular matrix. 1 Considerable evidence links degradation of elastic laminae and of interstitial collagen with migration of leukocytes and smooth muscle cells (SMCs), neointima formation, atherosclerotic plaque rupture, and to arterial ectasia and aneurysm formation.We previously proposed a role for cysteine proteases, in particular cathepsins S and K, in atherosclerosis. Human atheromata display substantially increased expression of cathepsins S and K compared with normal vessels, and cathepsin S-positive SMCs colocalize with sites of elastic lamina fragmentation in the tunica media. 2 Human vascular SMCs and endothelial cells express cathepsin S-dependent elastolytic and collagenolytic activity in response to proinflammatory cytokines or growth factors in vitro. 2,3 Our recent finding of attenuated atherosclerosis in cathepsin S-deficient mice provided direct evidence for cysteine protease involvement in atherogenesis. 4 Mice deficient in cathepsin S had 50% less atherosclerosis than controls at both 8 and 12 weeks of atherogenic diet.Importantly, we found a reciprocal relationship between the levels of cathepsins tested and their most abundant endogenous inhibitor cystatin C in diseased human arterial tissue. Both atherosclerotic and aneurysmal human lesions show reduction of cystatin C compared with normal arteries, 5 indicating an imbalance in cysteine proteases and their inhibitor in human arterial disease. 2 Eriksson et ...

Utility of Hyaluronan Oligomers and Transforming Growth Factor-Beta1 Factors for Elastic Matrix Regeneration by Aneurysmal Rat Aortic Smooth Muscle Cells

“…The predominant effect of TGF-b1 appears to be the stabilization of elastin mRNA, 39,40 although our own experiments and those of others suggest that TGF-b1 modestly enhances tropoelastin mRNA, 41 suppresses production of elastin-degrading metalloproteinases 42 and elastases, 43 enhances mRNA expression for the TIMP-1, 44 and augments LOX protein synthesis and activity critical to elastin=collagen crosslinking and fiber assembly. 45 In the present study, we studied the same per cell dose of TGF-b1 as that tested earlier on healthy RASMCs, on aneurysmal RASMCs.…”

Laminar shear stress inhibits cathepsin L activity in endothelial cells

“…26 Cystatin C deficiency in apoE-null mice resulted in increased elastic lamina fragmentation and collagen content, which could have contributed to the dilation of thoracic and abdominal aortas. 27 It remains controversial whether cystatin C deficiency affects atherosclerosis. 28,29 Increased cathepsin L expression and decreased cystatin C have been found in human atherosclerotic plaques and aortic aneurysms.…”

Cystatin C: current position and future prospects

“…CysC has been confirmed to play a protective role in situ in genetic models of arterial disease. Apolipoprotein E (ApoE)-/-mice in which the CysC gene has been incapacitated (Cyst-/-) develop aneurysmal lesions and rupture of the limiting internal elastic lamina compared to ApoE-/-, Cystq/q mice (212,213). These studies on animal models are supported by occasional human genetic data (214,215).…”