Scientists in Japan have designed artificial molecules which, when used in rats, successfully reversed liver cirrhosis.

Cirrhosis is the hardening or scarring of the liver, and is caused by factors such as heavy drinking and Hepatitis B and C. The disease is especially serious in parts of Asia, including China.

Cirrhosis occurs when a class of liver cells starts producing collagen, a fibrous material that toughens skin and tendons. Such damage cannot be reversed although steps can be taken to prevent further damage. In advanced cases, transplants are the only way out.

In the journal Nature Biotechnology, the researchers said they designed molecules that can block collagen production by liver "stellate cells", which are also known to absorb vitamin A.

The scientists then loaded the molecules into carriers that were coated with vitamin A, which tricked the stellate cells into absorbing the molecules.

"By packaging the (molecules) in carriers coated with vitamin A, they tricked the stellate cells into letting in the inhibitor, which shut down collagen secretion," the researchers wrote.

In the study, the researchers induced liver cirrhosis in rats and then injected them with the vitamin A-laced molecules.

"We were able to completely eradicate the fibrosis by injecting this agent ... we cured them of the cirrhosis," Yoshiro Niitsu at the Sapporo Medical University School of Medicine in Japan said.

"The liver is such an important organ, after you remove the fibrosis, the liver by itself starts to regenerate tissues. So liver damage is reversible."

Explaining how the damage reversal came about, Mr Niitsu said: "Liver is itself responsible for the production and deposition of collagen, it also secretes certain enzymes that dissolve collagen ... dissolve the fibrosis which has already been deposited in the tissues."

Mr Niitsu was hopeful that the molecules would provide a cure for cirrhosis patients in time.

"We hope it (a drug) will be ready for humans in a few years," he said.