Taher Saif1

1, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States

Biological systems emerge through interactions between similar components. Individual components at a given hierarchy interact with one another, as well as with the ambient environment, to arrive at the next hierarchy with increased complexity and functionality. The precise nature of these interactions is yet to be resolved. We will discuss two examples where long range mechanical interactions between cells through extra cellular matrix or a compliant substrate lead to unusual collective behavior. First example involves primary cardiomyocytes cultured on soft gel substrate apart from each other. Here, contraction of any cell results in a stretch in the neighboring cells. This influences the beating of the neighbors as long as the stretch exceeds a threshold. They then behave as coupled oscillators. Stretch sensitive ion channels mediate this coupling. Over time, these cells beat in synchrony and the entire cell cluster beats as a single oscillator. The second example involves compaction of ECM by sparsely populated muscle cells (C2C12). Here, each cell remodels the matrix around itself. If the cells are far apart, their remodeled domains do not overlap, and they do not interact. If they are within a critical distance apart when their remodeled zones overlap, they interact and approach each other compacting the matrix. The critical gap appears to be around 100 µm. The cell-cell interaction lead to muscle formation in differentiation media. The interaction fails if the cell-cell gap is more than 100 µm, and gel compaction does not occur.