DIFFERENTIAL GENE-EXPRESSION OF EXTRACELLULAR-MATRIX COMPONENTS IN DILATED CARDIOMYOPATHY

Extracellular matrix metalloproteinases (MMPs) are activated in dilate d cardiomyopathic (DCM) hearts [Tyagi et al. (1996): Mol Cell Biochem 155:13-21]. To examine whether the MMP activation is occurring at the gene expression level, we performed differential display mRNA analysis on tissue from six dilated cardiomyopathy (DCM) explanted and five no rmal human hearts. Specifically, we identified three genes to be induc ed and several other genes to be repressed following DCM. Southern blo t analysis of isolated cDNA using a collagenase cDNA probe indicated t hat one of the genes induced during DCM was interstitial collagenase ( MMP-1). Northern blot analysis using MMP-1 cDNA probe indicated that M MP-1 was induced three- to fourfold in the DCM heart as compared to no rmal tissue. To analyze posttranslational expression of MMP and tissue inhibitor of matrix metalloproteinase (TIMP) we performed immunoblot, immunoassay, and substrate zymographic assays. TIMP-1 and MMP-1 level s were 37 +/- 8 ng/mg and 9 +/- 2 ng/mg in normal tissue specimens (P < 0.01) and 2 +/- 1 ng/mg and 45 +/- 11 ng/mg in DCM tissue (P < 0.01) , respectively. Zymographic analysis demonstrated lytic bands at 66 kD a and 54 kDa in DCM tissue as compared to one band at 66 kDa in normal tissue. Incubation of zymographic gel with metal chelator (phenanthro line) abolished both bands suggesting activation of neutral MMP in DCM heart tissue. TIMP-1 was repressed approximately twentyfold in DCM he arts when compared with normal heart tissue. In situ immunolabeling of MMP-1 indicated phenotypic differences in the fibroblast cells isolat ed from the DCM heart as compared to normal heart. These results sugge st disruption in the balance of myopathic-fibroblast cell ECM-proteina se and antiproteinase in ECM remodeling which is followed by dilated c ardiomyopathy. (C) 1996 Wiley-Liss, Inc.