It may sound like something out of Frankenstein,
but electric currents applied to the skin could
potentially speed up wound healing. Ironically,
though the phenomenon was reported 150 years ago
by the German physiologist Emil Du Bois-Reymond,
it has been ignored ever since.
Now Josef Penninger of the Austrian Institute
of Molecular Biotechnology in Vienna and Min Zhao
of the University of Aberdeen, UK, have demonstrated
that natural electric fields and currents in tissue
play a vital role in orchestrating the wound-healing
process by attracting repair cells to damaged
The researchers have also identified the genes
that control the process. "We were originally
sceptical, but then we realised it was a real
effect and looked for the genes responsible,"
Penninger says. "It's not homeopathy, it's biophysics."
Cells and tissues essentially function as chemical
batteries, with positively charged potassium ions
and negatively charged chloride ions flowing across
membranes. This creates electric field patterns
all over the body. When tissue is wounded this
disrupts the battery, effectively short-circuiting
it. Penninger and his colleagues realised that
it is the resulting altered fields that attract
and guide repair cells to the damaged area.
The researchers grew layers of mouse cells and
larger tissues, such as corneas, in the lab. After
"wounding" these tissues, they applied varying
electric fields to them, and found they could
accelerate or completely halt the healing process
depending on the orientation and strength of the
field (Nature, vol 442, p 457).
Next, they set about finding which genes were
involved. They looked at those already known to
make repair cells migrate under the influence
of chemical growth factors and attractants, and
found that their level of expression could be
influenced by electric fields. "We have not reinvented
the cells' genetic migration machinery," says
Penninger. "We have simply shown that electric
fields switch them on too." The gene expression
of several types of repair cells was affected,
including neutrophils and fibroblasts.
They then focused on one particular gene known
to prepare cells for migration, and another that
halts the process. When the team knocked out the
migration "promoter" gene, wounds exposed to electric
fields healed more slowly. They healed faster
when the migration "blocker" was knocked out.
The next stage is to investigate ways of manipulating
the phenomenon to accelerate healing, says Mark
Ferguson, a wound-healing specialist at the University
of Manchester, UK. "For many years there have
been anecdotal reports of the effects of electrical
currents on wound healing," he says. "This paper
not only demonstrates the effects of electrical
currents on cellular migration to wound defects,
it also provides a mechanistic understanding of
how such signals alter cell behaviour."
issue 2562 of New Scientist magazine, 26 July
2006, page 13