It's a decade from now, and an elderly man gets the grim news that his heart is rapidly decaying and that the left ventricle-the chamber that squeezes blood out to the body-needs to be replaced. His physician takes a biopsy of the heart cells that are still healthy and ships the tissue to a lab that is really an organ factory. There, workers use the patient's own cells and special polymers to fashion and grow a replacement part-certified by the original manufacturer. In three months, the new ventricle is frozen, packaged and sent to the hospital, where the patient undergoes a standard surgical procedure: the insertion of a living implant created from his own tissue. The surgery saves his life.

Not long ago, the notion of designing and growing living replacement body parts-a process now known as tissue engineering-seemed pure fantasy. But researchers in biotechnology are confident that the day will come when scenarios like the one above will be real and commonplace, thanks to advances made in the last decade in "biomaterials" that are compatible with living cells and the cultivation of new tissue, and to a far better understanding of how cells actually behave. The only question is, when? Some predict that within 20 years, possibly sooner, replacement ventricles, bladders, and the like will be readily available. For complex organs like lungs, though, it could take until mid-century.

A Run On Organs

For ill patients, breakthroughs in tissue-engineered organs can't come soon enough. The shortage of donor organs is infamous. In 1999 (the most recent year for which complete data are available) there were more than 72,000 people in the United States alone on transplant waiting lists, according to statistics from the United Network for Organ Sharing. By year's end, over 6,100 people had died waiting.