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 A study published on Wednesday involved pigs with a condition
called heart block that makes their hearts beat too slowly. By
injecting a human gene into a tiny region of the heart's pumping
chambers roughly the size of a peppercorn, the researchers
reprogrammed heart muscle cells into a type of cell that emits
electrical impulses to drive the beating heart.
In doing so, cardiologists at Cedars-Sinai Heart Institute in Los
Angeles created "biological pacemaker" cells that restored a normal
heart rate in the pigs. The procedure achieved the same result as
implanting an electronic pacemaker that sends electrical pulses to
the heart if it beats too slowly or skips a beat.
 "This development heralds a new era of gene therapy where genes are
used not only to correct a deficiency disorder but actually to
convert one type of cell into another to treat disease," Dr. Eduardo
Marbán, director of the Cedars-Sinai Heart Institute and leader of
the research team, told reporters.
The researchers noted that pig hearts are very similar to human
hearts. Dr. Eugenio Cingolani, director of the institute's
Cardiogenetics-Familial Arrhythmia Clinic, said "if all goes well"
in further animal studies examining the procedure's long-term
effectiveness and safety, "we hope to be able to begin trials in
humans within three years."
The researchers envision using the procedure initially to help
people with heart rhythm disorders who cannot use a pacemaker
because of device-related complications like an infection or in
fetuses in the womb with congenital heart block.
 Such fetuses cannot have a pacemaker implanted and risk severe heart
failure often resulting in stillbirth. The researchers hope to
develop an injection-based treatment to deliver the gene therapy to
these developing babies.
They said down the road the procedure might be used in a broader
patient population as a realistic alternative to the pacemaker.
Marbán said about 2 percent of pacemakers lead to an infection
requiring treatment. In the United States alone, about 300,000
people get pacemakers annually.
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"Rather than having to undergo implantation with a metallic device
that needs to be replaced regularly and can fail or become infected,
patients may someday be able to undergo a single gene injection and
be cured of the slow heart rhythm forever," Cingolani said.
Using a minimally invasive catheter procedure, the researchers
injected pigs that had complete heart block with a gene called TBX18
that is responsible for a protein that makes the heart keep the
right rhythm. On the second day after the gene was injected, the
pigs developed a faster, more normal heartbeat that lasted for the
rest of the 14-day experiment.
The researchers used a common type of virus called an adenovirus to
introduce the gene into the pigs but expressed confidence the virus
poses minimal risk.
The research appears in the journal Science Translational Medicine.
(Reporting by Will Dunham; Editing by Tom Brown)
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