Relationship between type IV collagen degradation, metalloproteinase activity and smooth muscle cell migration and proliferation in cultured human saphenous vein.

The relationship between degradation of basement membranes, metalloproteinase (MMP) activity and smooth muscle cell (SMC) migration and proliferation has not been previously investigated in any intervention study. We used adenoviral overexpression of tissue inhibitors of metalloproteinases (TIMPs) in cultured human saphenous veins. By immunocytochemistry, the percentage of medial SMC surrounded by basement membrane type IV collagen (Coll-IV) decreased from 93+/-1 to 77+/-4% and 82+/-1% (n=18, both P<0.001) after 7 and 14 days of culture, respectively, while all SMC that migrated to the neointima lacked Coll-IV. Overexpression of TIMP-1 or TIMP-3 significantly increased the percentage of medial SMC surrounded by Coll-IV (94+/-2 or 98+/-2%, respectively, both P<0.01 vs. no treatment) and decreased the number of neointimal SMC. Some 44+/-18 and 30+/-6%, respectively, of BrdU or PCNA labeled medial SMC remained surrounded by type IV collagen and this was not affected by overexpression of TIMP-1 or TIMP-3. We conclude that MMPs mediate loss of basement membrane and this is closely related to SMC migration. SMC proliferation does not require complete basement membrane degradation, which itself does not require MMPs in proliferating SMC.