Revealing Electromechanical Control of Tissue Homeostasis Using a Two-Layer Microfluidic Device

Cell behavior and cell fate are impacted by electric currents or fields that are endogenous or externally applied. Static electric signals can be applied in customized microfluidic devices to mimic the electric environment in slow physiological processes such as development, wound healing, and homeostasis. An important class of cellular electric studies is the control of cell migration by static in-plane galvanic currents in simple microfluidic channels mimicking wound currents, with current densities of ~0.1-1000 A/m². However, due to incompatible geometry, these devices are not appropriate to study electric effects in tissue homeostasis, where cells adopt apico-basal polarity and a transepithelial potential difference (TEPD). Here, we detail a unique microfluidic-based device that applies physiological ion currents perpendicular to the plane of confluent epithelial cell layers to perturb the TEPD and investigate electrical regulation of tissue steady states. The setup is made from a two-layer UV-curable polymer embedded with soft, polyacrylamide gel substrate coated with extracellular-matrix protein of choice. This microfluidic device provides the correct geometry and permeable substrate to induce a relatively uniform ion current across the cell layers of centimetric-scale. The setup is compatible with confocal live-cell imaging and Traction Force Microscopy to infer mechanical stresses induced by the transepithelial currents. Strikingly, the proliferation, extrusion and migration of cells are collectively influenced within the confluent epithelium depending on the direction of ion current, inducing a new tissue state characterized by different cell-cell interaction strengths, cell events (death and proliferation), and tissue structures. The electrically controlled cell behaviors can be understood as an electrically induced mechanical stress and cell response. This novel microfluidic device and protocol provide the tool and documentation required for the mechanobiology and bioengineering communities to study electric effects in tissue homeostasis and develop novel tissue engineering applications.