Collagen I induces normal human lung fibroblast (NHLF) migration through collagen IV. NHLFs were grown on non-coated 8.0 μm polycarbonate inserts, or inserts coated with collagen IV (10 μg/cm2) or fibronectin (5 μg/cm2). Cells were serum-starved for 24 h and incubated with collagen I (25 μg/mL) or vehicle (acetic acid, 0.1 M) for 24 h. The bottom chamber was treated with cell dissociation buffer and acetomethoxycalcein (calcein AM) for 1 h at 37°C. Fluorescence of solution with detached cells was measured at 485 nm excitation and 520 nm emission. Results are representative of mean fold increase ± SD of two independent experiments performed in triplicate (n = 6, **P < 0.01).