Nanoporosity Stimulates Cell Spreading and Focal Adhesion Formation in Cells with Mutated Paxillin

We have evaluated the response to nanotopography of CHO-K1 cells that express wild-type paxillin or paxillin with mutations at serine 273 that inhibit phosphorylation. Cells were grown on nanoporous and polished titanium surfaces. With all cell types, immunofluorescence showed that adhesion and spreading were minimally affected on the treated surface and that the actin filaments were more abundant and well-aligned. Scanning electron microscopy revealed changes in cell shape and abundant filopodia with lateral nanoprotrusions in response to nanoporosity. Gene expression of proteins associated with cellular adhesion and protrusions was significantly increased on the nanoporous surface regardless of the cell type. In particular, α-actinin, Rac1, Cdc42, and ITGα1 were upregulated in S273 cells with alanine substitutions, whereas FAK, Pxn, and Src were downregulated, leading to improved focal adhesion formation. These findings suggest that the surface nanoporosity can "compensate for" the genetic mutations that affect the biomechanical relationship of cells to surfaces.