Human stem cells make mouse heart beat again

A mouse heart was able to
contract again after its own cells were removed and replaced with human stem cells, a study in Nature Communications reports.

This research
could pave the way for the regeneration of functional whole organs, which could
be used for transplantation or testing new drugs in the lab.

To make the engineered heart,
the team of scientists at University of Pittsburgh,
Pitt School of Medicine, USA, took a
heart from a mouse and removed all of its cells using detergents. The remaining
protein scaffold was then seeded with human heart precursor cells, which had
been produced by adding a combination of chemicals to human induced pluripotent
stem cells (iPS cells). Growth factors were then added to encourage the heart
precursor cells to differentiate into specialised heart cells such as
cardiomyocytes and smooth muscle cells.

After a few weeks the
engineered mouse heart had been rebuilt with human heart cells and began to
pulse at a rate of 40 to 50 beats per minute.

'Our engineered hearts
contain about 70 percent human heart precursor cells, which provide enough mechanical
force for contraction', study lead author Dr Lei Yang told New Scientist.

The researchers found that
the beating was not strong enough to pump blood effectively and the heart's
rhythm also differed from that of a normal mouse. The team's next steps will therefore
be to reconstruct the heart's electrical conduction network which could control
the rhythmic heart beats.

Heart disease is the UK's biggest killer, causing about 200 deaths
per day. Dr Yang noted that more than half of all heart disease patients do not
respond to existing therapies and there is a shortage of donor organs for
transplantation.

'Scientists have been
looking to regenerative medicine and tissue engineering approaches to find new
solutions for this important problem', said Yang. 'The ability to replace a
piece of tissue damaged by a heart attack, or perhaps an entire organ, could be
very helpful for these patients'.

In related news, a separate team of scientists at King's College
London have found that stem cells injected into rodents with heart failure
homed in on areas of damage and began to repair the tissue.

Both of the studies
illustrate the potential of stem cell technologies for the treatment of
cardiovascular disease. Dr Yang said that in the future it might be feasible to
take a skin biopsy from a patient and derive personalised stem cells, which
could then be used to regenerate a replacement organ for transplantation. 'We
hope to make a piece of human heart tissue soon but our dream is to regenerate
a human heart organ', he added.