Dynamic Mechanical Cue Facilitate Collective Responses of Crowded Cell Population

Collective cell behavior is essential for tissue growth, development and function, e.g. heartbeat 1 , immune responses 2 and cerebral consciousness 3 . In recent years, studies on population cells uncover that collective behavior emerges in both inter- and intra-cellular activities, e.g. synchronized signal cascade 4 , and collective migration 5 . As the movement and shape transition of cells within the crowded environment of biological tissue can generate mechanical cues at the cell-cell interface, which may affect the signaling cascade 6,7 , we suspect that the inter- and intra-cellular collective behavior interplay with one another and cooperatively regulate life machinery. To verify our hypothesis, we study the collective responses of fibroblasts in a confluent cell monolayer (CCM). Our results demonstrate that cells in CCM show distinctive behavior as compared to the stand-alone (SA) cells, suggesting effect of inter-cellular interactions. Upon periodic TNF-α stimulation, collective behavior emerges simultaneously in NF-κB signaling cascade and nuclear shape fluctuations in CCM but not SA cells. We then model the inter-cellular interactions in CCM using a customized microfluidic device, and discover a feedback loop intrinsic to CCM, in which dynamic mechanical cues and mechano-signaling act as link connecting the inter- and intra-cellular collective activities. We found that mechano-signaling triggered by the dynamic mechanical cues causes collective nuclear shape fluctuation (NSF), which subsequently facilitates the collective behavior in NF-κB dynamics. Furthermore, our studies reveal that regardless of the input TNF-α periodicity, cellular responses of single fibroblasts are elevated when the dynamic mechanical cues synergize with the chemical inputs, and inhibited when there is phase-mismatching. We, therefore, postulate that besides the biological significance of mechano-signaling in regulating collective cell responses, the induction of dynamic mechanical cues to human body may be a potential therapeutic approach, allowing us to regulate the action of single cells to achieve optimal tissue performance.