Developments to Watch
THESE IMPLANTS `GROW' IN A LAMB'S HEART
EACH YEAR, ROUGHLY 60,000 Americans have an artificial heart valve implanted to replace one that fails to regulate blood flow properly. Constructed from plastic or extracted from the heart of a pig, such implants cannot make use of the body's mechanisms for growth and repair. They wear down over time and can cause blood clots. So scientists want to "grow" new heart valves from living cells.
This month, a collaboration of Advanced Tissue Sciences in La Jolla, Calif., and Boston Children's Hospital announced promising results with cells grown on a biodegradable scaffolding made of polyglycolic acid--the material used in dissolvable surgical sutures. Cells extracted from lamb blood vessels took about 10 weeks to grow around the scaffolding and form valves. Placed in the hearts of seven lambs, the valves have functioned normally for two weeks. Over time, the scaffolding dissolves and is absorbed by the lambs' bodies, leaving just the cells. Researchers, however, caution that a wide gulf separates sheep trials and human applications. Human tests are still years away.EDITED BY NEIL GROSS