(337d) Extracellular Forces Tune Actomyosin Contractility to Regulate Fibroblast Migration and Persistence

Cell migration is essential to development, immune response, and cancer metastasis. During each of these processes, cells encounter external forces through mechanisms such as physical confinement, shear stress, and hydraulic pressure. Only a small portion of studies on cell migration consider the effects of external physical forces, leaving them poorly understood. Here we study how external forces control the behavior of primary dermal fibroblasts, which physiologically experience external forces due to the tensile and compressive forces of the extracellular matrix, as well as interstitial shear stress during vascular remodeling and repair.

Microfluidic devices were designed in order to control both cell confinement and external force produced by hydrostatically driven shear stress. Molds of the devices were created using lithography, and the patterns were replica molded in polydimethylsiloxane (PDMS). Cell behavior was observed using live-cell time-lapse microscopy, confocal microscopy, fluorescent dye-based calcium imaging, and genetic engineering to express fluorescently-tagged proteins.

Our results demonstrate that external forces act upon mechanosensitive ion channels to regulate cell migration. Activation of stretch-activated channels triggers the entry of extracellular calcium into the cell. There, calcium modulates actomyosin contractility to control cell migration phenotype, inducing a switch from protrusion-based migration to bleb-based. This switch in migration phenotype alters external signaling into the cell, and regulates cell localization by altering the effectiveness of cell migration. These effects are negated by the knockdown of specific transient receptor potential (TRP) channels. Furthermore, cell behavior responds to external force by regulating the direction of cell migration, even in confined spaces. Lastly, we demonstrate that cancer (fibrosarcoma) cells downregulate stretch-activated channels, reducing their sensitivity to external forces, and promoting their ability to navigate heterogeneous environments such as those encountered during metastasis.

Taken together, these results indicate that normal cells are highly sensitive to mechanical forces, which regulate their migration and thus their localization within the microenvironment. This sensation occurs through outside-in signaling mediated by stretch activated ion channels. In cancer, these channels are down-regulated to free cells from the constraints of external force.