Measuring SMC Contraction In Vitro: A Non-Invasive Method to Evaluate Smooth Muscle Cells Contraction using Electric Cell-Substrate Impedance Sensing

The aorta wall predominantly has smooth muscle cells, or SMCs, containing contractile protein machinery that contract and relax to regulate aortic blood flow.

To measure the contractile response of aortic SMCs in vitro, obtain a multi-well plate containing an electrical cell-substrate impedance sensing, or ECIS, sensor array. Each array contains gold film electrodes at the well bottom, delineated with an insulating film. Coat the wells with gelatin.

Seed primary human SMC suspension into the wells. Transfer the ECIS-containing well plate to a plate holder connected to an amplifier and data acquisition system while ensuring electrode contact with the holder. Apply small constant alternating current between the electrodes to measure the potential across them.

During incubation, SMCs adhere and spread onto the gelatin coating. The cells behave as insulators, limiting the current flow between the electrodes. As more cells attach to the surface, the current flow decreases further. As a result, the impedance, or opposition to the current flow, and potential increase. Eventually, the cells proliferate on the electrodes and form a monolayer.

Treat the SMCs with a calcium ionophore to facilitate calcium ion transport across the cell membranes. The extracellular calcium ion influx activates the contractile apparatus, inducing contraction.

Stimulated SMCs contract and lose cell-cell contact on the electrodes. The resulting reduction in electrode surface coverage decreases the impedance, facilitating real-time quantification of SMC contraction.