The researchers at the University of Wisconsin–Madison exposed liver cells to short electric pulses that caused the liver cells to take in over 40 times the amount of gene therapy material compared to cells that were not exposed to pulsed electric fields. The method could help reduce the dosage needed for these treatments, making them much safer and more affordable. The research is detailed in PLOS ONE.
Gene therapy replaces, alters or introduces new genetic material into a patient’s cells to cure or compensate for genetic diseases - including cystic fibrosis, sickle-cell disease, haemophilia and diabetes – but getting the right dose of genetic material into the target cells is a bottleneck in the process.
The UW–Madison research suggests that applying a moderate electric field, which left no lasting damage to the cells that received it, could help create more effective therapies.
The project began almost a decade ago with the late Hans Sollinger, who developed a gene therapy treatment for Type 1 diabetes.
Sollinger delivered the genetic code for insulin production into liver cells using an adreno-associated virus that assists in transporting the therapeutic genes across the cells’ membrane. This DNA can then take up residence in liver cells, producing insulin without being attacked by the immune system in the pancreas.
While Sollinger had a proof-of-concept that the therapy worked, he believed the future of the treatment hinged on delivery. He turned to Susan Hagness and John Booske, UW–Madison professors of electrical and computer engineering who have experience treating human cells with electrical pulses.
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“What we started talking about was local, targeted delivery and whether there was a way of getting the treatment DNA directly into the liver without passing it through the entire body and triggering the immune system,” Hagness said in a statement. “And whether we could use electric pulses in order to make this delivery process more efficient and dramatically reduce the dose needed.”
Researchers have previously found that exposing cells to electric fields can increase the ability of molecules to move through the cell membrane into the interior of a cell. In this latest study, PhD student Yizhou Yao sought to determine whether the technique would increase the penetration of virus particles into liver cells.
Using human hepatoma cells, a model system for studying the liver, Yao exposed batches of the cells to various concentrations of the gene therapy virus particles containing a fluorescent green protein. She used a pair of electrodes to deliver an 80-millisecond electric pulse to some samples and then incubated the cells for 12 hours.
When she examined the results 48 hours later under a fluorescence microscope, Yao found that a small percentage of the cells that had not received the electrical pulses glowed green. Cells that had received an electrical pulse accumulated about 40 times the amount of the fluorescent green proteins delivered by the virus.
While results provided evidence that the pulses helped facilitate the virus’s penetration of the cell walls, Booske said the team has yet to discover exactly how the process works at the molecular level.
“There’s enough known about electric pulsing that I think we could confidently state that it is opening nanopores through the cell membrane,” he said. “But then Yao got this remarkable result, and it dawned on us that virus particles are in general bigger and more complex than bare molecular particles and they already have their own way of getting inside cells. So, we don't really know if it's the pores opening that has anything to do with it directly or indirectly.”
The electrical engineering researchers are pursuing next steps with external funding and are optimistic that the technique will go on to clinical trials.
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