Figure 1

Representation of the 3D culture model. A collagen gel layer was prepared by mixing 400 μl type I collagen at 2 mg/ml with 150 μl RPMI culture medium 5 fold concentrated, 15 μl NaOH 1 N and 100 μl DMEM with 10% fetal calf serum. To form the first layer of the microenvironment, 150 μl of this mixture was deposited on the membrane of a double compartment chamber (Transwell) and polymerized for 30 minutes at 37°C. A second collagen gel layer was formed by mixing 400 μl type I collagen at 2 mg/ml with 150 μl RPMI 5×, 15 μl NaOH 1N, 100 μl DMEM with 10% fetal calf serum and BZR cell suspension at 13 × 10⁴ cells/ml. 150 μl of this mixture was added over the first layer and 1.5 ml of DMEM was placed into the basal compartment of the chamber which was thereafter maintained for 24 hours at 37°C.