Increased synthesis of matrix metalloproteinases by aortic smooth muscle cells is implicated in the etiopathogenesis of abdominal aortic aneurysms.
OBJECTIVE
The objective of this study was to identify the metalloproteinases elaborated by medial smooth muscle cells (SMCs) isolated from abdominal aortic aneurysm (AAA) and control arterial tissues and to ascertain if the levels produced by AAA SMCs were elevated.


METHODS
SMC monolayers cultured from the outgrowth cells of tunica media explants were established, and their identity was determined by fluorescent microscopy by using a fluorescein isothiocyanate conjugated anti-SMC alpha-actin antibody. Matrix metalloproteinases (MMPs) produced by SMC monolayers in serum-free culture were examined by gelatin zymography and Western blotting with monoclonal antibodies to MMP-2, 3, and 9.


RESULTS
Serum-free media from AAA SMCs contained metal-dependent elastolytic activity that cleaved the synthetic substrate succinyl trialanyl 4-nitroanilide (pH optima 7.2) and also 14C-insoluble elastin. The level of proteolytic activity found in these cultures was significantly greater than from control SMC media. Zymography established that AAA SMC media samples contained metal-dependent gelatinases of 50 to 64 and 92 kDa, which were identified respectively as MMP-2 and 9 by Western blotting by using monoclonal antibodies to these proteases.


CONCLUSIONS
Medial SMCs isolated from AAA tissue produce significantly higher levels of MMP-9 and 2 than SMCs from control arterial tissues. These proteinases have the capacity to degrade elastin and a range of extracellular matrix proteins. From these data, we suggest SMCs may be involved in the abnormal degradation of the aortic wall in AAA through the excessive metalloproteinase activity produced by SMCs.
Patel
M I
MI
Department of Vascular Surgery, Royal North Shore Hospital, Sydney, NSW, Australia.
Melrose
J
J
Ghosh
P
P
Appleberg
M
M
D000328:Adult; D000368:Aged; D001012:Aorta, Abdominal / Q000166:cytology / Q000201:enzymology; D017544:Aortic Aneurysm, Abdominal / Q000209:etiology* / Q000473:pathology; D001018:Aortic Diseases / Q000473:pathology; D001161:Arteriosclerosis / Q000473:pathology; D015153:Blotting, Western; D002478:Cells, Cultured; D017364:Collagenases / Q000096:biosynthesis*; D005260:Female; D018093:Gelatinases / Q000096:biosynthesis*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008297:Male; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9; D017537:Mesenteric Artery, Inferior / Q000166:cytology / Q000201:enzymology; D008666:Metalloendopeptidases / Q000096:biosynthesis*; D008875:Middle Aged; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000201:enzymology*; D017540:Tunica Media / Q000166:cytology / Q000201:enzymology
D017364:Collagenases; D018093:Gelatinases; D008666:Metalloendopeptidases; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9