Washington, Sep 9 (IANS): In a first, US researchers have addressed a major challenge in the quest to build replacement kidneys in the lab.

Working with human-sized pig kidneys, scientists at Wake Forest Baptist Medical Center in North Carolina have developed the most successful method to date to keep blood vessels in the new organs open and flowing with blood.

"Until now, lab-built kidneys have been rodent-sized and have functioned for only one or two hours after transplantation because blood clots developed," said Anthony Atala, director and professor at the Wake Forest Institute for Regenerative Medicine.

"In our proof-of-concept study, the vessels in a human-sized pig kidney remained open during a four-hour testing period," he added.

If proven successful, the new method - to more effectively coat the vessels that keep blood flowing smoothly - could potentially be applied to other complex organs that scientists are working to engineer, including the liver and pancreas.

The current research is part of a long-term project to use pig kidneys to make support structures known as "scaffolds" that could potentially be used to build replacement kidneys for human patients with end-stage renal disease.

Using pig kidneys as scaffolds for human patients has several advantages, including the fact that the organs are similar in size and pig heart valves - after their cells are removed - have safey been used in patients for more than three decades.

The study appeared in the journal Technology.