Liver damage can be reversed after all, scientists have announced, raising hopes of a potential cure for cirrhosis.

US researchers have overturned conventional medical opinion, by succeeding in reversing the excessive tissue scarring which is commonly linked to alcohol poisoning.

The breakthrough, made in mice, could lead to the first curative treatment for cirrhosis and other similar conditions caused by illness or injury.

Tissue scarring is also found in burn injuries and scleroderma - a chronic disease which causes hardening of the skin.

Livers affected by cirrhosis gradually have their healthy tissue replaced by tough, fibrous scar tissue, a process known as fibrosis.

As this transformation progresses, liver function begins to fail. Ultimately a liver transplant may be necessary to prevent complete liver failure and death.

Worldwide, almost 800,000 people die from cirrhosis each year. The condition can have a number of causes, but alcoholism and infection by the hepatitis C virus are the most common. Currently there is no treatment.

The mouse experiments conducted at the University of California in San Diego show that, contrary to popular belief, liver fibrosis can be reversed, with scar tissue returning to normal healthy liver tissue.

The researchers identified a weak link in the biochemical pathway that leads to overproduction of scar tissue and cirrhosis.

They found that when the liver is injured, for instance by alcohol, a protein called RSK was responsible for triggering the activation of a type of liver cells which orchestrate the scarring - known as HSCs.

However, RSK could be blocked by an inhibitory peptide, a small piece of a protein.

Dr Martina Buck, who led the research reported in the journal PLoS Online, said: "Remarkably, the death of HSCs may also allow recovery from liver injury and reversal of liver fibrosis."

The scientists discovered RSK to be similarly active in human patients with severe liver fibrosis, raising hopes that a similar blocking drug could reverse the scarring.