VASCULAR SMOOTH MUSCLE CELLS IN CULTURES ON

2, passage 8) derived from the rat aorta by explantation method (2). Cells were incubated in Dulbecco-Modified Eagle Minimum Essential Medium with 10% of foetal calf serum for 1 to 7 days. We found that VSMC on MMP-13-treated collagen adhered at about 1.5 times lower initial number than those on unmodified collagen (p<0.01). The concentration of β 1-integrins (i.e., receptors for collagen) and β-actin in these cells was by 35% lower (p<0.05). The concentration of vinculin, talin and α -actin was unchanged. However, the clustering of vinculin and talin into focal adhesion plaques, as well as the assembly of α - and β-actin into microfilaments, were lower. VSMC on the modified collagen showed a slightly shorter cell population doubling time (by 7 ± 3 %, p<0.01), longer exponential phase of growth (at least by 2 days), a higher concentration of heat-shock protein 60 (by 20 ± 7 %, p<0.05), and were more prone to cell death (more than 3 times higher number of trypan-blue stained cells, p<0.01). These results suggest that cells on MMP-13degraded collagen could escape more easily the extracellular matrix-mediated growth control and could increase their turnover.