Heart stem cells discovered that can make bone and muscle

Research in mice has shown the heart contains its own renewable source of stem cells which can differentiate into a variety of cell types. The research team in Australia hopes that one day the stem cells could be activated so a broken heart can be made to mend itself.

'If we are serious about organ regeneration we need to understand the biology', said Professor Richard Harvey, who co-authored the study, which was part of a seven-year collaboration between the Victor Chang Cardiac Research Institute in Sydney and University of New South Wales.

'In an injury situation where many of the vessels are killed and great slabs of tissue die, like in a heart attack, you need to replace muscle and vessels', Professor Harvey explained. 'We think these cells are intimately involved in the regeneration of the heart and replacement of the old heart tissue as the organism ages'.

The research describes a population of cells within the heart which are similar to the mesenchymal stem cells (MSCs) found in bone marrow. MSC-like cells have already been identified in other organs including the liver, lung and brain. The researchers showed that by isolating these cells from the heart and growing them in the laboratory they can reproduce over a long period of time and can be made to develop into a number of other cell types including bone, blood vessels and muscle.

The presence of MSC-like cells in the heart has been seen before, but it was unclear whether they were actually just bone marrow cells carried to heart by the blood stream, rather than from the heart itself. A number of experiments carried out using genetically modified mice allowed the scientists to label the bone marrow cells and show they do not enter the heart during development or in response to injury. They were also able to trace the lineage of the MSC-like cells to show that they originated from the heart. In adulthood, the team demonstrated they can be found in the heart's outer layer.

Coronary heart disease is the biggest killer in the UK and although in some cases the condition can be managed effectively, there is no cure except for a heart transplant.

A crucial next step for turning this research into therapy would be to show the existence of similar cells within the human heart. After that, as Professor Harvey told the Scientist, the real challenge is to find a way to 'wake' the stem cells up from their 'deep sleepy state' so that they can be made to repair the damaged heart. He believes harnessing these heart-resident MSCs will be more efficient than injecting bone marrow cells, which is already being trialled with some success in the treatment of heart attacks.

Professor Tim Kamp from the University of Wisconsin Stem Cell and Regenerative Medicine Center, who was not involved in the study, describes the findings as 'another fascinating twist' in the story of how the heart repairs itself. 'They make a strong case that these [cells] are resident within the heart, and are poised to do the maintenance of the structure of the heart' he says.

Dr Sean Wu, from the Harvard Stem Cell Institute, who was also not involved in the study, said: 'You could induce cell populations like this to be able to mediate heart repair'.