Engineering excitable cells
By altering the genetic makeup of normally “unexcitable” cells, bioengineers at Duke University have turned them into cells capable of generating and passing electrical current.
The researchers achieved this transformation by introducing genes into the cells that form ion channels. Ion channels allow the flow of electrically charged molecules, or ions, to exit or enter the cell thus enabling the transfer of electric current from one cell to its neighbor.
The Duke researchers hypothesized that a few key ion channels are sufficient to enable cell excitation, including those carrying potassium ions, sodium ions, and a gap junction channel, a highly specialized structure that enables cell-to-cell electrical communication.
In a key set of experiments, the researchers created an “S”-shaped pathway, with clusters of normal, living rat heart cells at either end. The space between the two clusters was filled with a population of either unexcitable cells (the control), or the genetically engineered cells. When an electrical stimulus was applied to a heart cell cluster at one end of the setup, an electrical impulse traveled throughout these heart cells but immediately stopped and disappeared at the entrance to the “S”-shaped path containing the unexcitable control cells.
However, when they used the genetically modified cells, the electrical impulse was rapidly regenerated and carried throughout the three-centimeter long pathway, eventually triggering the second cluster of cells to fire on the other side. Alternatively, if they applied the stimulus to the modified cells in the center of the pathway, the electrical impulse travelled outwardly in both directions toward the heart cells and electrically activated them.
The Duke scientists also said that their engineered excitable cells can be continuously and easily grown in the lab, are genetically and functionally identical to each other, and also have the capacity for further modifications to change their electrical or structural behavior.
These engineered excitable cells can be used in the laboratory as a platform for investigating the roles that specific ion channels have in tissue-level bioelectricity, and for testing the effectiveness of new drugs or therapies on bioelectrical activity, the researchers said.
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