Mice injected with the stem cells recovered better than untreated mice, showing improved heart function and less tissue damage.
The researchers say that, if similar cells can be identified in humans, the finding could lead to new treatments for heart failure.
'When we injected stem cells with this protein into damaged hearts, we saw a significant level of heart repair. Now that we know which stem cells to use, we want to find their equivalent in human hearts for more efficient heart repair and regeneration after heart attacks,' commented Professor Michael Schneider from Imperial College London, one of the study's lead authors.
The scientists isolated 'dormant' stem cells from the hearts of mice and categorised them into four groups according to their pattern of gene activity.
Then, by comparing these with cells taken from young heart muscle of newborn mice, they were able to identify which cells were most likely to have heart-repairing properties. This revealed cells that expressed a particular protein on their surface - PDGFR alpha - as the best candidates.
Following a simulated heart attack, the researchers injected the hearts of some of the mice with these cells. After 12 weeks, the areas of damaged tissue in their hearts were smaller and their hearts were also able to pump more blood compared with untreated mice.
The scientists found that only a few cells from the injection remained in the treated hearts but, of those that did, up to 50 percent showed the characteristic shape and protein contents of mature heart muscle cells.
Although the hearts of adult mammals contain some stem cells which show regeneration ability, they are not able to repair the large-scale effects of a heart attack.
It is now hoped that similar cell types to the ones identified by the researchers could be found in humans and have the same regenerative capabilities.
This could lead to treatments for conditions caused by damage to the heart, such as heart failure, where not enough blood is pumped to sustain the body's activity. Heart failure causes symptoms such as shortness of breath and tiredness, and affects about 900,000 people in the UK.
However, Professor Colin Berry, professor of cardiology and imaging at Glasgow University, told The Scotsman it would take time to see if the findings are relevant to patients: 'It is important science and cutting-edge stuff but there is so much more that needs to be done.'