Donated hearts for lifesaving transplants are scarce, but now researchers may have hit upon a way to generate the blood-pumping organs in the lab--at least in rats. The approach, which involves transplanting cells from a newborn rat onto the framework of an adult heart, produced an organ that could beat and pump fluid. Further refinement will be necessary before the technique is ready for people, but it could also generate other organs.

Approximately 3000 patients in the United States are on the waiting list for a heart transplant, but only about 2000 donor organs become available each year. Stem cells, which can give rise to heart tissue, offer a potential solution. But to form an entire heart, the cells require a framework, or scaffolding, to grow on, and finding an adequate structure has proven difficult. Now, a team led by bioengineer Doris Taylor of the University of Minnesota, Minneapolis, has shown that old hearts stripped of their cells may provide a fix for the scaffolding problem.