Differential expression of matrix metalloproteinases and tissue inhibitors and extracellular matrix remodeling in aortic regurgitant hearts.
OBJECTIVE
Myocardial fibrosis in experimental aortic regurgitation (AR) features abnormal fibronectin with normal collagen content, but the relevant degradative processes have not been assessed.


METHODS
To elucidate these degradative processes, mRNA (Northern) and protein levels (Western) of matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs), as well as MMP activity (zymography), were measured in cardiac fibroblasts (CF) from New Zealand white rabbits with experimental AR paired with normals (NL). Collagen and fibronectin were quantified by immunohistochemical staining.


RESULTS
In AR CF versus NL CF, MMP-2 and -14 mRNA and protein were increased (both p < 0.005), while TIMPs 1-3 were slightly decreased (p < 0.05-0.005; TIMP-4 undetectable). Gelatinase activity in AR CF was 1.7 times that in NL CF (p < 0.005); fibronectinase activity was unaffected. The Jun N-terminal kinase (JNK) inhibitor SP600125 suppressed MMP-2 protein (0.4-fold, p < 0.05) and mRNA (0.7-fold, p < 0.005) in AR CF; MMP-2 levels in NL CF were unaffected. AR MMP-9 mRNA, protein and activity were low and indistinguishable from NL. In left ventricular tissue, fibronectin was increased 1.9-fold (AR vs. NL, p < 0.05). Total AR collagen was indistinguishable from NL, but the collagen III to collagen I isoform ratio decreased (0.4-fold, p < 0.05).


CONCLUSIONS
Collagen is relatively deficient in AR fibrosis, due at least in part to upregulated MMPs and downregulated TIMPs; fibronectinase is unaltered. JNK-dependent regulation may stimulate both MMP-2 and fibronectin expression in AR, providing a potential therapeutic target.
Truter
Sharada L
SL
The Division of Cardiovascular Medicine and The Howard Gilman Institute for Heart Valve Disease, State University of New York Downstate Medical Center, 47 East 88th Street, New York, NY 10128, USA.
Catanzaro
Daniel F
DF
Supino
Phyllis G
PG
Gupta
Anuj
A
Carter
John
J
Herrold
Edmund M
EM
Dumlao
Themy F
TF
Borer
Jeffrey S
JS
D000818:Animals; D001022:Aortic Valve Insufficiency / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D002478:Cells, Cultured; D024042:Collagen Type I / Q000378:metabolism; D024061:Collagen Type III / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000378:metabolism; D005340:Fibrinogen / Q000378:metabolism; D005355:Fibrosis; D015870:Gene Expression / Q000502:physiology; D053511:Matrix Metalloproteinase 14 / Q000235:genetics / Q000378:metabolism; D020778:Matrix Metalloproteinase 2 / Q000235:genetics / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000235:genetics / Q000378:metabolism; D020782:Matrix Metalloproteinases / Q000235:genetics* / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000166:cytology / Q000502:physiology*; D011817:Rabbits; D015398:Signal Transduction / Q000502:physiology; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000235:genetics / Q000378:metabolism; D019716:Tissue Inhibitor of Metalloproteinase-2 / Q000235:genetics / Q000378:metabolism; D019717:Tissue Inhibitor of Metalloproteinase-3 / Q000235:genetics / Q000378:metabolism; D019714:Tissue Inhibitor of Metalloproteinases / Q000235:genetics* / Q000378:metabolism*
D024042:Collagen Type I; D024061:Collagen Type III; D016326:Extracellular Matrix Proteins; D019715:Tissue Inhibitor of Metalloproteinase-1; D019717:Tissue Inhibitor of Metalloproteinase-3; D019714:Tissue Inhibitor of Metalloproteinases; D019716:Tissue Inhibitor of Metalloproteinase-2; D005340:Fibrinogen; D020782:Matrix Metalloproteinases; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9; D053511:Matrix Metalloproteinase 14