Transcript levels for cells grown on various collagen substrates as a function of substrate concentration. (A) Collagen (Col-1), (B) matrix metalloproteinase-1 (MMP-1), (C) matrix metalloproteinase-2 (MMP-2), (D) tissue inhibitor of matrix metalloproteinase-1 (TIMP-1), (E) tissue Inhibitor of matrix metalloproteinase-2 (TIMP-2), (F) heat shock protein-70 (HSP-70).