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.