Distinct structural and molecular features of the myocardial extracellular matrix remodeling in compensated and decompensated cardiac hypertrophy due to aortic stenosis

Objectives

We used immuhistochemistry and Western blot to study fibrillar and non-fibrillar collagens, collagen metabolism, matricellular proteins and regulatory factors of the ECM remodeling in left ventricular (LV) septum biopsies from 3 groups of patients with aortic valve stenosis (AS): (AS-1,n = 9): ejection fraction (EF) > 50%; AS-2,(n = 12): EF 30%–50%; AS-3,(n = 9): EF < 30%). Samples from 8 hearts with normal LV function served as controls.

Results

In comparison with controls, fibrillar collagens I and III were progressively upregulated from compensated (AS-1) toward decompensated hypertrophy (AS-3). The collagenIII/collagen I ratio decreased 2-fold in the AS-2 and AS-3 groups as compared with AS-1 and controls. Non-fibrillar collagen IV was upregulated only in AS-3 patients, whereas collagen VI progressively increased from AS-1 to AS-3 group. Collagen synthesis in AS-3 was shifted to collagen I, while the maturation/degradation level was shifted to collagen III. RECK was downregulated only in AS-3 patients. Matricellular proteins tenascin and osteopontin were increased in all AS patients. However, thrombospondin 1, 4 and CTGF were increased only in AS-3. Only AS-3 patients were characterized by increased levels of TGFβ1 and downregulation of TGFβ3, TGFβ-activated kinase1 and Smad7. In contrast, Smad3 gradually increased from AS-1 toward AS-3. Similar trend of changes was observed for TNFα-R1 and TNFα-R2, whereas TNFα was diminished only in AS-2 and AS-3.

Conclusions

Distinct changes in fibrillar collagen turnover, non-fibrillar collagens, matricellular proteins and the key regulatory profibrotic and anti-fibrotic factors of the myocardial ECM remodeling are involved in the transition from compensated to decompensated LV hypertrophy and HF in human patients with AS.