Cell aggregation in monolayer culture: Clues to a universal kinetics

Aggregation of animal cells in culture comprises a series of motility, collision and adhesion processes of basic relevance for tissue engineering, bioseparations, oncology research and in vitro drug testing. In the present paper, we characterize the aggregation kinetics of normal and cancer cells in culture by determining their cluster size distribution functions. Our experiments reveal that the complementary cumulative distributions for eight cell lines from epithelial and mesenchymal origins are described by stretched exponential functions. Also, we find that as time evolves and the cell density increases, a dynamical phase transition occurs from an aggregation regime described by monotonically decreasing cluster size distributions to another one in which these distributions are nonmonotonic, exhibiting local maxima at large cluster sizes. Subtly, the universality of the stretched exponential distributions admits distinct cluster growth processes controlled by motility and adhesion traits of the cells.