Electric stimulation alters intercellular stress within the epithelial monolayer

Abstract

IntroductionThe directed migration of cell plays a pivotal role in physiological processes such as development, wound healing, vasculogenesis, and cancer metastasis. Electric field (EF) is one of the prevailing guidance cues in vivo, which promotes directional migration in both single and collective cells. Numerous studies have studied the detailed biochemical mechanism of electrotaxis, directional guidance by EF, both in vivo and in vitro. However, these studies mainly focused on a single cell behavior. Since the collective cells are feeling severe confinement due to their neighboring cells, not only biochemical but also physical analysis is essential to understand the mechanism of coordinated cellular guidance by EF. Here, we aimed to investigate how the cellular physical forces are altered in response to externally applied direct current electric field (dcEF). We established the EF stimulating platform combined with polyacrylamide gel for the simultaneous measurement of Traction Force Microscopy (TFM) and Monolayer Stress Microscopy (MSM).Materials and MethodsIn this study, we developed cell observable platform, equipped with agar bridge and steinberg's solution to apply dcEF. To analyze cellular forces, we combined 0.5 μm fluorescence bead embedded poly‐acrylamide hydrogel within the chamber. We micropatterned HacaT cell‐line using PDMS stencil on the poly‐acrylamide gel before stimulating dcEF. After 1 day maturation of HacaT monolayer, we stimulated 0.5 V/cm dcEF continuously over the experiment. Traction field was calculated from the measured displacement field of fluorescent beads embedded within a hydrogel of 3 kPa stiffness. Gel displacement was quantified at each experimental time point, and a reference image was obtained after cell detachment. Traction was obtained by the numerical procedure from Fourier‐transform‐traction‐microscopy (FTTM). Based on the traction field, we calculated intercellular stress using monolayer stress microscopy (MSM).Results and discussionWe observed that the EF stimulation induced the rapid response of collective migration toward the anode. This guided migration was followed by the reorientation of individual cells to perpendicular axis against the EF direction. Interestingly, enhancement of intercellular stress component perpendicular to the EF preceded the coordinated alignment of cellular orientation within the epithelial monolayer. These results suggest that the EF‐induced formation of anisotropic intercellular stress leads the reorientation of individual epithelial cells within the bulk of collective monolayer.Support or Funding InformationThis work was supported by the National Research Foundation of Korea Grant funded by the Korean Government (NRF‐2013S1A2A2035518, NRF‐2016K2A9A2A08003761)This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.