Inflammatory regulation of extracellular matrix remodeling in calcific aortic valve stenosis.
BACKGROUND
Calcific aortic stenosis (AS), the most frequent heart valve disorder in developed countries, leads to the calcification and fibrous thickening of the valve. While several studies have addressed the process of valvular calcification, the molecular pathomechanisms of the extensive matrix remodeling remain unclear. Because inflammation is present in stenotic valves, we hypothesized that the proinflammatory cytokine tumor necrosis factor alpha (TNFalpha) might influence cell proliferation and regulate the expression and activation of matrix metalloproteinases (MMPs)--enzymes that are thought to be involved in calcific AS.


METHODS
Immunohistochemistry for leukocytes, TNFalpha, MMP-1, and the endogenous MMP inhibitor tissue inhibitor of metalloproteinase (TIMP)-1 was performed on human stenotic (n = 19) and control (n = 8) valves. Primary cultures of human aortic valve myofibroblasts were incubated with and without TNFalpha, and cell proliferation was assessed. The expression and activation of MMP-1 were detected by Western blotting and a specific MMP-1 activity assay.


RESULTS
Control valves showed scattered macrophages and low expression of TNFalpha, MMP-1, and TIMP-1. In stenotic valves, leukocyte infiltration and a strong, colocalized expression of TNFalpha and MMP-1 were present, while TIMP-1 remained unchanged. Double-label immunofluorescence localized TNFalpha mainly to macrophages. In cultured human aortic valve myofibroblasts, TNFalpha stimulated proliferation and induced a time-dependent increase in MMP-1 expression and activation, while TIMP-1 remained unchanged.


CONCLUSIONS
The results indicate that matrix remodeling in calcific AS involves the expression and activation of MMPs. Activated leukocytes, by the secretion of TNFalpha, may stimulate valvular myofibroblasts to proliferate and express MMPs, thus regulating actively the matrix remodeling in calcific AS.
Kaden
Jens J
JJ
1st Department of Medicine (Cardiology, Angiology, Pneumology), Faculty of Clinical Medicine Mannheim, University of Heidelberg, Mannheim, Germany. jens.kaden@med.ma.uni-heidelberg.de
Dempfle
Carl-Erik
CE
Grobholz
Rainer
R
Fischer
Carolin S
CS
Vocke
Daniela C
DC
Kiliç
Refika
R
Sarikoç
Aslihan
A
Piñol
Rafael
R
Hagl
Siegfried
S
Lang
Siegfried
S
Brueckmann
Martina
M
Borggrefe
Martin
M
D001024:Aortic Valve Stenosis / Q000378:metabolism / Q000473:pathology*; D002114:Calcinosis / Q000378:metabolism / Q000473:pathology*; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D005109:Extracellular Matrix / Q000378:metabolism*; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D008264:Macrophages / Q000378:metabolism* / Q000473:pathology; D020781:Matrix Metalloproteinase 1 / Q000378:metabolism; D013601:T-Lymphocytes / Q000378:metabolism* / Q000473:pathology; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000378:metabolism; D014261:Tricuspid Valve / Q000378:metabolism / Q000473:pathology*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism / Q000494:pharmacology
D019715:Tissue Inhibitor of Metalloproteinase-1; D014409:Tumor Necrosis Factor-alpha; D020781:Matrix Metalloproteinase 1