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The discovery of the first plentiful source of stem cells could make fetal tissue use unnecessary and accelerate procedures for joint repair. Ushering in a new era of tissue engineering research, scientists at UCLA and the University of Pittsburgh have isolated fat as the first practical, plentiful and economic source of stem cells used to grow a variety of human tissues in the laboratory.

The research team, which details the discovery in the April edition of the peer-reviewed journal Tissue Engineering, is the first to grow human tissue - bone, muscle, cartilage and fat - using stem cells harvested from fat. The team obtained the fat using liposuction.

Previously, stem cells for tissue engineering research had been harvested from bone marrow, brain and fetal tissue, limited sources that pose a variety of logistical and ethical challenges. The availability of the plentiful source of stem cells will accelerate development of new procedures for repairing and replacing damaged, dead or missing tissue in people. The finding is significant for researchers looking to repair the damaged joint and cartilage tissue that characterizes arthritic conditions.

"Until now, we had not identified a good source of stem cells, which can be thought of as the building blocks of tissue engineering," said Dr. Marc Hedrick of the UCLA School of Medicine's Division of Plastic and Reconstructive Surgery, the research team's primary investigator. "Fat is perhaps the ideal source. There's plenty of it. It's easy and inexpensive to obtain. It even has a secondary cosmetic benefit.

"Our findings show that fat is not the tissue we once thought. Just as the Industrial Revolution transformed oil from trash to treasure, our research shows that unwanted human fat actually is a vigorous tissue with a tremendous amount of potential for good." The researchers said the discovery could render the controversial use of fetal tissue obsolete.

"We don't yet know the limits for stem cells found in fat. So far, we have seen promising results with all of the tissue types we have examined," said Dr. Adam J. Katz, a member of the research team from the Division of Plastic and Reconstructive Surgery at the University of Pittsburgh School of Medicine. "This discovery potentially could obviate the need for using fetal tissue."

Immature and unspecified, stem cells are key contributors to the body's ability to renew and repair its own tissues. They are unique in their ability to mature into two or more different types of specific cells, depending on their environment. Researchers grow different tissues in the laboratory by manipulating stem cell environments.

"Stem cells are like little kids who, when they grow up, can enter a variety of professions," Hedrick said. "A child might become a fireman, a doctor or a plumber, depending on the influences in their life - or environment. In the same way, these stem cells can become many tissues by making certain changes in their environment."

Stem cells already are used as a treatment for leukemia and some joint repairs. With fat as a plentiful source of stem cells, researchers may be able to accelerate the pace of overcoming obstacles that prevent broader applications. These challenges include finding ways to supply blood to larger tissues, control growth and maturation, and eliminate scarring.

"We're just figuring out the best ways to apply this technology, but expect the first practical uses for laboratory-grown tissues to enter the medical marketplace within the next five years or so," Hedrick said. "We hope one day to be able to remove diseased tissue or organs, harvest stem cells and replace the lost tissues on the same day during the same operation. There is potential for regenerating a lot of different tissues, perhaps some day solid organs, glands, nerves or brain tissue."