Rick Weiss
Washington Post
9/27/2004
 
The prospect of using human embryonic stem cells to treat disease appears a small step closer as the result of two new experiments with the cells, which are mired in political controversy because they are derived from human embryos.

In one report released yesterday, researchers showed that the versatile cells can serve as "biological pacemakers," correcting faulty heart rhythms when injected into the failing hearts of pigs. In another report, scientists demonstrated for the first time that stem cells can become a cell crucial to vision.

Many doctors believe that several vision-destroying diseases could be fought by transplanting these cells directly into the eyes. Human embryonic stem cells, derived from five-day-old embryos, have the biological potential to morph into virtually all of the 200 or so kinds of cells in the body.

Researchers are racing to learn how to direct them to develop into specific types of cells that can be transplanted into failing organs. It is an approach that could launch a new era of regenerative medicine -- but only if the cells prove capable of integrating into existing organs and functioning normally there.

Izhak Kehat and Lior Gepstein of the Technion-Israel Institute of Technology in Haifa and their colleagues sought to test that capacity with stem cells that were growing into heart muscle cells. The team started with masses of stem cells growing in laboratory dishes, from which they isolated those few that were spontaneously developing into heart cells. They were easy to spot: They were the ones that were pulsing in unison, as heart cells are apt to do. In one experiment, the scientists isolated small balls of the human cells -- each ball about the size of the head of a pin, or about 1 million cells -- and placed that little mass into a lab dish with rat heart cells. The cells of each species, rat and human, beat at different rates at first. Within 24 hours of living together, however, the combined masses of cells coordinated their pulsing into a single rhythm.