The influence of the biophysical environment and cell-cell interactions on epithelial cell electrotaxis

Cell migration plays a pivotal role during tissue growth and development, wound repair, and progression of metastatic disease. Mechanical, chemical, and electrical cues all provide stimuli to direct cell migration. Electric fields as stimuli for directed cell migration, known as electrotaxis, have attracted attention in recent years due to their ability to override migratory cues from other types of stimuli. The use of electrotaxis has promising application in wound repair, where it is being utilized to treat chronic non-healing wounds such as ulcers. In this study, we sought to investigate the interactions between electric fields and intercellular connections on the electrotaxis of epithelial cells.;We found that the non-transformed mammary epithelial cell line, MCF-10A, cells migrate toward the anode of an applied electric field. Although cells in isolation will display electrotaxis, they require an electric field at or above a threshold of 0.26 V/cm in order to migrate toward the anode. Increasing the strength of the stimulating field increased the degree to which the cells migrate toward the anode. However, when adjacent to other cells in a cell cluster, they not only migrate toward the anode with more directed paths, but also require no threshold of electric field to begin migration. Analysis of these migration paths indicated that being in the clustered cell state inhibited reorientation for migration.;To investigate the non-geometric effects of cell clustering, expression of the cell adhesion protein, E-cadherin, was reduced in MCF-10A cells by 60%, since E-cadherin is a major player in epithelial intercellular interactions. Cells within clusters migrated toward the anode of an applied electric field even when E-cadherin expression was reduced. However, the degree to which movement was aligned with the electric field was reduced by 16% compared to non-transformed cells. Isolated cells with E-cadherin knockdown were also found to reorient to the electric field more quickly and, while they were equally aligned at 0.51 V/cm, they were significantly less directed at electric fields below this.;Since strong electrotaxis is often associated with metastatic potential of cancer cells, the electrotaxis of highly invasive MDA-MB-231 breast cancer cells was investigated. To spatially confine cells, the electrotactic chamber was first filled with a confluent layer of noninvasive breast epithelial cells. E-cadherin expression was perturbed in this system as well, with additional E-cadherin expression reducing overall electrotaxis of invasive cells. This is consistent with E-adherin being a tumor suppressor and prevent invasion of cells. In a modified transwell assay, invasion was lost with increased E-cadherin expression but rescued upon exposure to a weak electric field. These results indicate that both cell-cell interaction and spatial confinement associated with the tumor microenvironment play independent roles in modulating electrotaxis.;Overall, the data presented herein reveals how electric fields and the cellular environment interact with epithelial cells to generate a migratory response. Our work elucidates the operational space for tissue engineering applications using electric fields to spatially direct cells. We also show that the tumor microenvironment may act synergistically with bioelectric fields to promote metastasis. We present several new platforms that can be used to investigate molecular perturbations, which we expect will lead to the development of new chemical therapeutics which act upon electrotactic pathways.