MMP-9 regulates both positively and negatively collagen gel contraction: a nonproteolytic function of MMP-9.
OBJECTIVE
Constrictive remodeling accounts for lumen loss in postangioplasty restenosis. Matrix metalloproteinase-9 (MMP-9) has been shown to prevent constrictive remodeling in vivo. To investigate potential mechanisms for this observation, we investigated the role of MMP-9 in smooth muscle cell (SMC)-mediated collagen gel contraction, an in vitro model of constrictive remodeling.


METHODS
Fischer rat SMCs were stably transfected with a construct-expressing rat-MMP-9 under the control of a tetracycline (Tet)-off promoter. SMCs were seeded in type I collagen gels (2.4 mg/ml) in the presence or not of tetracycline (1 microg/ml), and gel contraction was defined as the percentage of retraction of the collagen gel. The depletion of MMP-9 was obtained by using siRNA targeting MMP-9 mRNA or a blocking antibody.


RESULTS
Gel contraction was significantly reduced at all times when MMP-9 was overexpressed (Tet-) as compared with the control condition (Tet+). However, MMP-9 depletion of control (Tet+) SMCs (using siRNA or antibody) also inhibited gel contraction. To resolve the apparent discrepancy and determine if MMP-9 exerts a dose-dependent biphasic effect on gel contraction, conditioned medium and purified rat-MMP-9 were prepared. Gel contraction was significantly increased by addition of 0.8 ng/ml of MMP-9, while high concentrations of MMP-9 (> or =100 ng/ml) inhibited contraction. The addition of BB94 and TIMP-1 did not alter the inhibitory or stimulatory effect of MMP-9.


CONCLUSIONS
Our data suggest that MMP-9, independent of its proteolytic function, has a biphasic effect on SMC-mediated collagen gel contraction. Understanding the different roles of MMP-9 should allow the development of better therapeutic strategies for restenotic vascular disease.
Defawe
Olivier D
OD
Division of Vascular Surgery, Department of Surgery, University of Washington, Seattle, WA, USA. Olivier.Defawe@ulg.ac.be
Kenagy
Richard D
RD
Choi
Chun
C
Wan
Samuel Y C
SY
Deroanne
Christophe
C
Nusgens
Betty
B
Sakalihasan
Natzi
N
Colige
Alain
A
Clowes
Alexander W
AW
D000818:Animals; D001011:Aorta; D018929:Cell Culture Techniques; D049109:Cell Proliferation / Q000187:drug effects; D003094:Collagen; D004305:Dose-Response Relationship, Drug; D005782:Gels; D020780:Matrix Metalloproteinase 9 / Q000502:physiology*; D061965:Matrix Metalloproteinase Inhibitors; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D010649:Phenylalanine / Q000031:analogs & derivatives / Q000494:pharmacology; D051381:Rats; D011916:Rats, Inbred F344; D013876:Thiophenes / Q000494:pharmacology; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000494:pharmacology; D014661:Vasoconstriction / Q000187:drug effects
D005782:Gels; D061965:Matrix Metalloproteinase Inhibitors; D013876:Thiophenes; D019715:Tissue Inhibitor of Metalloproteinase-1; D010649:Phenylalanine; D003094:Collagen; C080985:batimastat; D020780:Matrix Metalloproteinase 9