Chiral Symmetry Breaking in Collective Dynamics of Multicellular System

Collective cell dynamics play a crucial role in many developmental and physiological contexts. While two-dimensional (2D) cell migration has been widely studied, how three-dimensional (3D) geometry and topology interplay with collective cell behavior to determine dynamics and functions remains an open question. In this talk, I will discuss our recent work on the biophysical mechanism underlying rotation in spherical tissues, a phenomenon widely reported both in vivo and in vitro. Using a 3D vertex model, I will demonstrate how the interplay between traction force and polarity alignment can account for the distinct rotational dynamics observed in pancreas organoids. Surprisingly, our analysis shows that the spherical tissue rotates as an active solid and exhibits spontaneous chiral symmetry breaking. Using a continuum model, we demonstrate how the types and location of topological defects in the polarity field underlie this symmetry breaking process. Altogether, our work shows that tissue chirality can arise via topological defects in the pattern of cell traction forces, with potential implications for left-right symmetry breaking processes in morphogenetic events and chiral rotation in marine embryos.