Cell behaviour on micropatterned substrata: limits of extracellular matrix geometry for spreading and adhesion

Cell adhesion, spreading and migration require the dynamic formation and dispersal of contacts with the extracellular matrix (ECM). In vivo, the number, availability and distribution of ECM binding sites dictate the shape of a cell and determine its mobility. To analyse the geometrical limits of ECM binding sites required for cell attachment and spreading, we used microcontact printing to produce regular patterns of ECM protein dots of defined size separated by nonadhesive regions. Cells cultured on these substrata adhere to and spread on ECM regions as small as 0.1 mum(2), when spacing between dots is less than 5 mum. Spacing of 5-25 mum induces a cell to adapt its shape to the ECM pattern. The ability to spread and migrate on dots greater than or equal to1 mum(2) ceases when the dot separation is greater than or equal to30 mum. The extent of cell spreading is directly correlated to the total substratum coverage with ECM-proteins, but irrespective of the geometrical pattern. An optimal spreading extent is reached at a surface coating above 15%. Knowledge of these geometrical limits is essential for an understanding of cell adhesion and migration, and for the design of artificial surfaces that optimally interact with cells in a living tissue.