(607a) Feeling the Squeeze: How Motile Cells Respond to Confined Environments

Cell migration through tissues is a critical step during the metastatic spread of cancerous cells from the primary tumor to distal organs in the body. Although cell motility has primarily been studied using planar 2D surfaces or 3D collagen gels, tumor cells in vivo also travel through pre-existing longitudinal microchannels,which represent the “highways” that tumor cells take in order to migrate efficiently throughout the body. Intravital microscopy has revealed that in vivo, cells are dorsoventrally polarized as they migrate through these confined tracks. Therefore, these microchannels impose varying degrees of confinement in various directions on polarized migrating cells. As the largest, stiffest cellular component, the nucleus poses the biggest obstacle to confined cell migration. In the absence of matrix metalloproteinases, the nucleus must be deformed in various directions in order to pass through confined migration channels. In this study, we investigated how the cell and nucleus respond to compressive forces in various directions and the downstream effects on nuclear integrity and cell migration. To explore this phenomenon, we created a PDMS-based microfluidic model system in which polarized cells migrate through confined channels of equal cross sectional area (30µm²) but with opposite directions of primary confinement (3 µm width by 10 µm height, termed lateral confinement, or 10 µm width by 3 µm height, termed vertical confinement). We discovered that, while dorsoventrally polarized cells have the perinuclear actin machinery to effectively deform the nucleus laterally, compression on the top and bottom of the nucleus is inefficient and results in nuclear rupture. By employing a multi-disciplinary approach involving state-of-the-art bioengineering (Atomic Force Microscopy), high resolution imaging (confocal, FRET, FRAP) and molecular biology techniques, we explored the roles of contractility, nuclear influx/efflux, and nuclear volume expansion during confined cell migration and ultimately elucidated a novel mechanism for nuclear rupture. Collectively, our work enhances our understanding of the complex process of confined cell migration and provides a novel perspective on how the compressive forces applied in different directions affect cell migration and nuclear integrity.