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

• Published in: Journal of thrombosis and haemostasis Vol. 8; no. 8; pp. 1847 - 1854
• Main Authors: GARG, N., GOYAL, N., STRAWN, T. L., WU, J., MANN, K. M., LAWRENCE, D. A., FAY, W. P.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.08.2010; Wiley Subscription Services, Inc
• Subjects: Animals; Aorta - cytology; Cell Movement; Collagen; Collagen - chemistry; Gels - chemistry; Gene Expression Regulation; Humans; Low Density Lipoprotein Receptor-Related Protein-1 - metabolism; Mice; Mice, Inbred C57BL; Mice, Transgenic; Muscle, Smooth - cytology; Muscle, Smooth, Vascular - cytology; Muscular system; PAI‐1; Plasminogen Activator Inhibitor 1 - genetics; Plasminogen Activator Inhibitor 1 - metabolism; Smooth muscle; vascular smooth muscle cell; vitronectin; Vitronectin - genetics; Vitronectin - metabolism
• ISSN: 1538-7933; 1538-7836; 1538-7836
• DOI: 10.1111/j.1538-7836.2010.03907.x

Background:  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. Objective:  To determine the effects of PAI‐1 and vitronectin (VN) expressed by VSMC themselves on migration through physiological collagen matrices. Methods:  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. Results:  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. Conclusions:  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.