The researchers used a treatment from Regulus Therapeutics - a joint venture between US biotech companies Alnylam Pharmaceuticals Inc and Isis Pharmaceuticals Inc - to block or 'silence' tiny strands of ribonucleic acid called microRNA.

These genetic fragments regulate the making of genes into proteins, and in this case the researchers discovered how a failing heart had three- to five-times more of a particular microRNA called miR-21.

'We view this new study as a landmark event in the advancement of microRNA therapeutics as a new class of innovative medicines,' Regulus Chief Executive Kleanthis Xanthopoulos, said in a statement.

'We believe that this is the first study to clearly demonstrate therapeutic efficacy for targeting microRNAs in an animal model of human disease.'

Heart failure, also known as congestive heart failure, is a condition in which the heart is unable to supply adequate blood flow to the body's organs. The condition affects 23 million people worldwide and kills 600,000 each year.

Significant or prolonged stress to the heart can cause the condition, which can occur following a heart attack, certain infections, high blood pressure and because of genetic causes.

In the study published in the journal Nature, researchers analysed hundreds of microRNAs within human and mouse heart samples to pinpoint miR-21 as a key cause of heart failure.

After identifying the genetic fragment, the researchers gave some mice an experimental compound called antagomir that blocked miR-21 and found that it prevented heart failure in these animals. Mice that did not get the drug developed the condition.

Animals with heart failure that later received the compound improved, compared with animals that did not get the treatment, said Dr Stefan Engelhardt, who led the research at the University of Wuerzburg in Germany, along with Dr Thomas Thum.

'We could both prevent cardiac disease and cure some aspects of cardiac disease,' Dr Engelhardt said in a telephone interview.

'Heart function and tissue damage improved in both cases.' The findings come after a US team earlier in November said it had shown how a different bit of RNA known as microRNA-101 may mean the difference between an easily treated tumour and an aggressive cancer.

They also underscore the promise of RNA technology, a hot area that has attracted big drugmakers like GlaxoSmithKline Plc in search of promising biotech assets.

In April, Glaxo signed a deal that could end up worth US$600 million (S$907 million) with Regulus Therapeutics to develop and market new microRNA-targeted treatments for conditions caused by chronic inflammation, such as rheumatoid arthritis and inflammatory bowel disease. -- REUTERS