Collective Motion of Cells Mediates Segregation and Pattern Formation in Co-Cultures

Abstract

Pattern formation by segregation of cell types is an important process during embryonic development. We show that an experimentally yet unexplored mechanism based on collective motility of segregating cells enhances the effects of known pattern formation mechanisms such as differential adhesion, mechanochemical interactions or cell migration directed by morphogens. To study in vitro cell segregation we use time-lapse videomicroscopy and quantitative analysis of the main features of the motion of individual cells or groups. Our observations have been extensive, typically involving the investigation of the development of patterns containing up to 200,000 cells. By either comparing keratocyte types with different collective motility characteristics or increasing cells' directional persistence by the inhibition of Rac1 GTP-ase we demonstrate that enhanced collective cell motility results in faster cell segregation leading to the formation of more extensive patterns. The growth of the characteristic scale of patterns generally follows an algebraic scaling law with exponent values up to 0.74 in the presence of collective motion, compared to significantly smaller exponents in case of diffusive motion.

A kinetic mechanism for cell sorting based on local variations in cell motility

“…This is qualitatively in agreement with the scaling reported from experiments. Méhes et al [7,43] studied the kinetics of cell sorting in mixtures of keratocytes from various species. For mixtures of primary fish keratocytes and EPC keratocytes, the interface index g and the growth of homotypic clusters were approximately linear on a log -log scale (over one decade of data).…”

“…Such cell sorting has also been observed for dissociated Hydra cells, co-cultures of cells not in contact during normal development and mixtures of cells extracted from different species [4][5][6][7].…”

“…The average of g i over all cells is the interface index g, which is a common measure for the degree of segregation in the system [7,14,15,26]. When g % 0 the two types of cells are completely segregated.…”

Co-culture systems and technologies: taking synthetic biology to the next level

“…For instance, culture volume and cell density can be important factors when establishing biomimetic in vitro models. In a study investigating the embryonic developmental processes segregation and pattern formation, cell number in the co-culture was chosen to be comparable in size to an embryo, so that it was relevant to the natural biological system [83]. In biotechnology, there are two opposing forces in the scaling of experimental volumes: efforts to scale up experiments to industrial volumes and yields, and efforts to scale down experiments to the microlitre scale to allow high-throughput testing of different systems or conditions and also for point-of-care or in-the-field applications [96].…”

Segregation mechanisms of tissue cells: from experimental data to models

“…In 2-dimensional co-cultures of adherent cells on a rigid substrate Méhes et al (2012) studied the dynamics of segregation of two initially mixed cell populations into distinct clusters by cell migration in an environment lacking pre-defined external cues. They have found that segregation into large multicellular clusters is facilitated by collective effects in cell motion such as an increase in the directional persistence of constituent cells.…”