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J Thromb Haemost. 2010 Aug;8(8):1847-54. doi: 10.1111/j.1538-7836.2010.03907.x. Epub 2010 May 12.

Plasminogen activator inhibitor-1 and vitronectin expression level and stoichiometry regulate vascular smooth muscle cell migration through physiological collagen matrices.

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Department of Internal Medicine, University of Missouri School of Medicine and Research Service, Harry S. Truman Memorial Veterans Affairs Hospital, Columbia, MO, USA.



Vascular smooth muscle cell (VSMC) migration is a critical process in arterial remodeling. Purified plasminogen activator inhibitor-1 (PAI-1) is reported to both promote and inhibit VSMC migration on two-dimensional (D) surfaces.


To determine the effects of PAI-1 and vitronectin (VN) expressed by VSMC themselves on migration through physiological collagen matrices.


We studied migration of wild-type (WT), PAI-1-deficient, VN-deficient, PAI-1/VN doubly-deficient (DKO) and PAI-1-transgenic (Tg) VSMC through three-D collagen gels.


WT VSMC migrated significantly slower than PAI-1- and VN-deficient VSMC, but significantly faster than DKO VSMC. Experiments with recombinant PAI-1 suggested that basal VSMC PAI-1 expression inhibits migration by binding VN, which is secreted by VSMC and binds collagen. However, PAI-1-over-expressing Tg VSMC migrated faster than WT VSMC. Reconstitution experiments with recombinant PAI-1 mutants suggested that the pro-migratory effect of PAI-1 over-expression required its anti-plasminogen activator (PA) and LDL receptor-related protein (LRP) binding functions, but not VN binding. While promoting VSMC migration in the absence of PAI-1, VN inhibited the pro-migratory effect of active PAI-1.


In isolation, VN and PAI-1 are each pro-migratory. However, via formation of a high-affinity, non-motogenic complex, PAI-1 and VN each buffers the other's pro-migratory effect. The level of PAI-1 expression by VSMC and the concentration of VN in extracellular matrix are critical determinants of whether PAI-1 and VN promote or inhibit migration. These findings help to rectify previously conflicting reports and suggest that PAI-1/VN stoichiometry plays an important role in VSMC migration and vascular remodeling.

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