1.   And in a more preliminary but likewise promising study, researchers at Massachusetts General Hospital are reporting Tuesday that they have used gene therapy to revive failing heart cells.

2.   As the heart begins to fail, it changes shape in a process called remodeling, and heart cells change their structure and the kind of proteins they make.

3.   At Geron Corporation, scientists have already turned embryonic stem cells into heart muscle cells that spontaneously beat in the test tube.

4.   Biologists at Geron, of Menlo Park, Calif. have succeeded in making human embryonic cells develop into heart muscle cells.

5.   A group led by Greg Kovacs of Stanford University has built a handheld detector that responds to similar toxin-induced changes in mammalian heart cells.

6.   A skin cell does not turn into a heart cell.

7.   After that, the theory went, a brain cell stays a brain cell, a heart cell remains a heart cell.

8.   But Anversa wanted to learn where those new heart cells came from.

9.   But heart muscle cells have been grown from mouse embryonic stem cells and successfully integrated with the heart tissue of a living mouse.

10.   But new findings being provide strong evidence that human heart muscle cells do regenerate after a heart attack.