ICMCS Seminar - The Active Rim: Shaping Proliferative Dynamics

Proliferating cell collectives, from bacterial biofilms to epithelial tissues, can develop a peripheral growth layer where cells remain active while the crowded interior becomes arrested. In this talk, I will show that micromechanical feedback alone can generate such an active rim, whose size is set by the emergent mechanical length scale $\chi$, which governs the collective dynamics across scales. Using a particle-based model of proliferating cells with growth inhibited by compressive stress, I will show how $\chi$ (and therefore the size of the active rim) controls colony morphology and the onset of morphological instabilities, as well as the enhancement of collective growth through fingering, without introducing additional stabilizing mechanisms such as surface tension. I will also discuss the connection with nutrient-limited growth, showing that both descriptions lead to the same continuum mathematical structure. I will then discuss gene surfing during colony expansion by studying the evolution and competition of sectors carrying distinct strains or mutations, including the capture and evolution of remnant sectors. Finally, I will introduce a preliminary extension to deformable ellipsoidal cells, as a first step toward understanding how cell shape and deformability affect collective behavior.

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