Interstitial fibrosis in the heart: differences in extracellular matrix proteins and matrix metalloproteinases in end-stage dilated, ischaemic and valvular cardiomyopathy

Aims: To investigate whether or not there are differences in the distribution of extracellular matrix (ECM) proteins and matrix metalloproteinases (MMPs) in end-stage heart failure underlying different cardiomyopathies. Methods and results: Thirty-nine explanted human hearts were investigated: 15 with dilated cardiomyopathy (DCM), 17 with ischaemic cardiomyopathy (ICM) and seven with valvular cardiomyopathy (VCM). Transmural samples from four different sites were investigated. Frozen sections were processed for immunohistochemistry for collagens type I, III, IV, laminin and fibronectin, as well as MMP-1, -2 and -9. Volume densities were determined. All ECM components were expressed more frequently in DCM than in ICM. Comparing ICM with VCM, all proteins were found more frequently in VCM than in ICM except for type III collagen, which was significantly more frequent in ICM. Comparing DCM and VCM, VCM showed significantly higher volume densities for type III collagen and laminin. MMPs showed only slight variations between the cardiomyopathies. Conclusion: The distribution of ECM proteins differs between DCM, ICM and VCM, which suggests that they can be morphologically discriminated by interstitial fibrosis, especially by their expression of matrix proteins.