Expression of tissue‐type plasminogen activator and its inhibitor couples with development of capillary network by human microvascular endothelial cells on matrigel

Abstract

Human omental microvascular endothelial (HOME) cells seeded on Matrigel begin to migrate within 1 h, forming honeycomb-like structures and capillary-like networks within 18 h. Cross-sections of the capillary networks show them to be tube-like structures. Northern blot analysis showed that tissue-type plasminogen activator (t-PA) mRNA synthesis increased from the initial state at 0 h after seeding on Matrigel, reaching a steady state after 4 h. This elevated cellular t-PA mRNA level decreased markedly at 24 h. In contrast, the cellular plasminogen activator inhibitor-1 (PAI-1) mRNA level demonstrated biphasic curves during the 24 h after seeding on Matrigel: the PAI-1 mRNA level was increased eightfold initially at 4 h over that at 0 h, then declined, and again secondarily increased to greater than tenfold at 18 h. Cellular levels of both 72 kD type IV collagenase and tissue inhibitor of metalloproteinase (TIMP-2) mRNA were increased only a slightly within 2-4 h. These elevated mRNA levels were maintained for 18 h, while the TIMP-1 mRNA level increased up to 18 h, reaching around three times the level at 0 h. However, on collagen-coated dishes, cellular levels of t-PA, PAI-1, 72 kD type IV collagenase, TIMP-1, and TIMP-2 mRNA were not greatly changed during incubation for 24 h. On Matrigel, the cellular t-PA mRNA level at 18 h after seeding was greatly increased when treated with specific anti-transforming growth factor-beta (TGF-beta) antibody. In contrast, both PAI-1 and TIMP-1 mRNA levels at 18 h were reduced in the presence of anti-TGF-beta antibody. Development of the capillary network on Matrigel was inhibited in the presence of anti-t-PA antibody. Epidermal growth factor (EGF) enhanced t-PA gene expression and TGF-beta inhibited its expression in HOME cells cultured on collagen-coated dishes. On the other hand, TGF-beta enhanced cellular expression of the PAI-1 gene. The formation of a capillary network by HOME cells on Matrigel appears to be balanced by angiogenic EGF and anti-angiogenic TGF-beta through modulation of PA activity.