Temporal expression and spatial distribution of the proteoglycan versican during cardiac fibrosis development.

Cardiac fibrosis is a central pathological feature in several cardiac diseases, but the underlying molecular players are insufficiently understood. The extracellular matrix proteoglycan versican is elevated in heart failure and suggested to be a target for treatment. However, the temporal expression and spatial distribution of versican and the versican cleavage fragment containing the neoepitope DPEAAE in cardiac fibrosis remains to be elucidated. In this study, we have examined versican during cardiac fibrosis development in a murine pressure overload model and in patients with cardiomyopathies. We found that versican, mainly the V1 isoform, was expressed immediately after induction of pressure overload, preceding collagen accumulation, and versican protein levels extended from the perivascular region into the cardiac interstitium. In addition, we found increased production of versican by collagen expressing fibroblasts, and that it was deposited extensively in the fibrotic extracellular matrix during pressure overload. In cardiac cell cultures, the expression of versican was induced by the pro-fibrotic transforming growth factor beta and mechanical stretch. Furthermore, we observed that the proteolytic cleavage of versican (DPEAAE fragment) increased in the late phase of fibrosis development during pressure overload. In patients with hypertrophic and dilated cardiomyopathies, we found elevated levels of versican and a positive correlation between versican and collagen mRNA in the heart, as well as increased cleavage of full-length protein. Taken together, the temporal expression profile and the spatial distribution of both the full-length versican and the DPEAAE fragment observed in this study indicates a role for versican in development of cardiac fibrosis.

Inhibition of the extracellular enzyme A disintegrin and metalloprotease with thrombospondin motif 4 prevents cardiac fibrosis and dysfunction.

AIMS: Heart failure is a condition with high mortality rates, and there is a lack of therapies that directly target maladaptive changes in the extracellular matrix (ECM), such as fibrosis. We investigated whether the ECM enzyme known as A disintegrin and metalloprotease with thrombospondin motif (ADAMTS) 4 might serve as a therapeutic target in treatment of heart failure and cardiac fibrosis. METHODS AND RESULTS: The effects of pharmacological ADAMTS4 inhibition on cardiac function and fibrosis were examined in rats exposed to cardiac pressure overload. Disease mechanisms affected by the treatment were identified based on changes in the myocardial transcriptome. Following aortic banding, rats receiving an ADAMTS inhibitor, with high inhibitory capacity for ADAMTS4, showed substantially better cardiac function than vehicle-treated rats, including ∼30% reduction in E/e' and left atrial diameter, indicating an improvement in diastolic function. ADAMTS inhibition also resulted in a marked reduction in myocardial collagen content and a down-regulation of transforming growth factor (TGF)-ß target genes. The mechanism for the beneficial effects of ADAMTS inhibition was further studied in cultured human cardiac fibroblasts producing mature ECM. ADAMTS4 caused a 50% increase in the TGF-ß levels in the medium. Simultaneously, ADAMTS4 elicited a not previously known cleavage of TGF-ß-binding proteins, i.e. latent-binding protein of TGF-ß and extra domain A-fibronectin. These effects were abolished by the ADAMTS inhibitor. In failing human hearts, we observed a marked increase in ADAMTS4 expression and cleavage activity. CONCLUSION: Inhibition of ADAMTS4 improves cardiac function and reduces collagen accumulation in rats with cardiac pressure overload, possibly through a not previously known cleavage of molecules that control TGF-ß availability. Targeting ADAMTS4 may serve as a novel strategy in heart failure treatment, in particular, in heart failure with fibrosis and diastolic dysfunction.