TOKYO, April 11 (RIA Novosti) - A group of researchers on Japan's northernmost island of Hokkaido have broken new medical ground by developing a way to make human blood vessels using fish as a raw material, a leading Japanese newspaper said Wednesday.

According to the daily Mainichi Shimbun, the scientists devised a technology to produce artificial blood vessels with collagen obtained from salmon skin.

Until now, cows and pigs have mainly been used as donors, but that option carries with it the risk of transmitting mad cow disease and other infections to humans.

The main challenge with fish-sourced collagen has been to raise its heat resistance threshold, initially at plus 15 °C (59 °F), so that it could be used in transplant surgery, specifically to replace damaged vessels in patients with cardiovascular diseases.

Now the top limit has been extended to 55 °C (131 °F), well above the human body's average temperature of 36.6 °C (97.9 °F), Mainichi said.

Artificial blood vessels made with fish collagen have already proved viable in experiments with rats, but they are yet to undergo clinical trials involving humans.

Japan, which is rich in marine resources, will have no difficulty obtaining raw material for fish-sourced collagen if the new technology is endorsed for use in the public healthcare system.

On Hokkaido alone, about 2,000 metric tons of salmon skin is produced annually, an amount sufficient for the production of up to 600 tons of collagen, the paper said.