['Regression of left ventricular hypertrophy (LVH) after surgical correction for aortic stenosis is not fully understood on the molecular level. The aim of this study was to examine whether there is an association between LVH regression and extracellular matrix (ECM) gene expression.', 'A standard model of controlled LVH induction by supracoronary banding (A=baseline) was applied in 44 growing sheep (age, 6 to 8 months). Surgical correction to release the pressure gradient was performed 8.3+/-1 months later (B). The animals were killed after another 10.1+/-2 months (C). At all time points, hemodynamic evaluations and quantitative analysis of mRNA and protein expression for matrix metalloproteinases (MMP) and their tissue inhibitors (TIMP) was performed. Left ventricular mass index was 82+/-21 (A) versus 150+/-33 (B), P<0.01, and 78+/-18 g/m(2) (C), P<0.01. Left ventricular function and cardiac index remained stable. Myocardial fiber diameter index was 9.1+/-1.2 (A) versus 12.3+/-1.4 (B), P<0.01, and 8.4+/-1.3 micrometer/m(2) (C), P<0.01. In parallel to the development of LVH at B, gene expression was increased significantly for MMP-1, MMP-2, MMP-3, and MMP-9 and for TIMP-1 and TIMP-2 and decreased significantly for TIMP-3. After surgical correction (C), there was a complete regression of gene expression to baseline measures.'] Is regression of left ventricular hypertrophy after surgical therapy for aortic stenosis associated with changes in extracellular matrix gene expression?