The adhesion of MDCK II cells to porous and non-porous silicon substrates has been investigated by means of fluorescence and atomic force microscopy. The MDCK II cell density and the average height of the cells were increased on porous silicon substrates with regular 1.2 mu m pores as compared to flat, non-porous surfaces. In addition, we found a substantially reduced actin cytoskeleton within confluent cells cultured on the macroporous substrate compared to flat surfaces. The perturbation of the cytoskeleton relates to a significantly reduced expression of integrins on the porous area. The loss of stress fibers and cortical actin is accompanied by a dramatically reduced Young's modulus of 0.15 kPa compared to 6 kPa on flat surfaces as revealed by site-specific force-indentation experiments. (C) Koninklijke Brill NV, Leiden, 2010