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.
Dozens of groups in industry and academia are hoping to prevent those deaths, working on techniques for fashioning new organs out of cells from embryos, cadavers or patients themselves, combined with special biomaterials. Most current work in the commercial realm focuses on tissues, valves and other components of organs (see “Tissue Engineering in Industry” below). Already, there are a handful of tissue-engineered products on the market-skin, bone, and cartilage implants and patches-the first successes in a young field.
Michael Ehrenreich, president of Techvest, a New York-based investment company that closely follows the biotech sector, feels such achievements are only an indication of what’s to come, and he is blunt about where tissue engineering is now. “Skin. Big deal. It’s a proof of concept,” says Ehrenreich. “At the end of the day, many of us are going to die from some sort of organ failure. That’s what’s going to drive this market. And nobody’s really tackled a vascularized organ yet.”
Ehrenreich has touched on one of the more vexing problems facing tissue engineers: most organs need their own vasculature, or network of blood vessels, to get the nutrients they need to survive and to perform their intended functions. So before researchers can build a full-sized organ, such as a liver, say, or a set of lungs, they must learn to manufacture blood vessels.
Tissue Engineering in Industry
in the Pipeline
|Advanced Tissue Sciences||La Jolla, CA|| |
Skin (TransCyte, Dermagraft); cartilage, ligaments and tendons; blood vessels and heart valves
|Genzyme Biosurgery||Cambridge, MA||Cartilage cells (Carticel); cartilage graft (Carticel II)|
|CryoLife||Kennesaw, GA||Heart valves and blood vessels; ligaments|
|Curis||Cambridge, MA||Cartilage gel to prevent urinary reflux (Chondrogel); bladder|
|LifeCell||Branchburg, NJ||Skin (AlloDerm); blood vessels; ligaments and tendons|
|Organogenesis||Canton, MA||Skin (Apligraf, Vitrix); blood vessels|