Fat May Be the Answer for Many Illnesses
Fat, the great American obsession, may provide a new source of replacement cells for a variety of medical treatments and eliminate the need for the controversial use of embryonic stem cells.
A team of researchers from UCLA and the University of Pittsburgh has isolated stem cells--primitive cells with the potential to become virtually any type of tissue--from fat collected by liposuction and converted them into bone, cartilage and muscle.
The researchers believe the cells could have many applications, from damaged knees to brain implants for Parkinson’s disease and strokes.
At a time when the Bush administration appears inclined to ban the use of embryonic stem cells from aborted tissues, the new research reported in today’s edition of Tissue Engineering offers an alternative source that could be much more plentiful and much less controversial.
“This could take the air right out of the debate about embryonic stem cells,” said Dr. Mark Hedrick of UCLA, the lead author. The newly identified cells have so many different potential applications, he added, that “it makes it hard to argue that we should use embryonic cells.”
“This is extremely significant in terms of its potential,” said Dr. Michael T. Longaker of Stanford University. “Unfortunately, fat is a substantial natural resource in the USA. This is a great way to do something with it.”
Another team at Duke University has produced similar results, turning stem cells from fat into cartilage. “It’s very important for different groups to reach the same conclusion with a study with this much potential impact,” said Dr. Farshid Guilak, who led the Duke study.
Both groups are performing tissue experiments in animals, and both suggested that it would be about five years before the first clinical trials could be conducted in humans.
Among the first applications might be cartilage implants for repairing knees and other joints, as well as noses and ears. Cartilage cells grown in the laboratory are already being used to repair damaged knees, but the use of stem cells would dramatically increase the supply of tissue available.
The repair of broken and defective bones that resist healing is also high on the agenda.
Further in the future, the cells might be used for a much broader variety of applications, including brain implants for Parkinson’s disease and strokes and in the repair of heart tissues.
“We don’t yet know the limits for stem cells found in fat,” said Dr. Adam J. Katz of the University of Pittsburgh, a co-author. “So far, we have seen promising results with all of the tissue types we have examined.”
Most cells in the adult human body are somatic cells. They have adopted an identity--skin, heart, muscle, whatever--from which there is no going back. Skin cells cannot be converted into brain tissue, or vice versa.
Embryos, in contrast, have a large percentage of cells that have not yet adopted a genetic program and that have the potential to become any kind of cell in the body. These stem cells--so-called because all other cells stem from them--are a prize for researchers and clinicians, but their use is highly controversial because the only way to obtain them is through an abortion.
Research that involves using any tissue obtained from abortion has been a hot-button political issue in recent years, pitting the scientific research community against anti-abortion forces.
Former President Ronald Reagan banned federal funding of research using fetal tissue, which involves the transplantation of more developed cells. That ban was continued by President Bush’s father, but reversed by former President Bill Clinton.
Federally funded fetal tissue research continues--researchers have already transplanted dopamine-producing fetal brain cells into Parkinson’s disease patients--but the fate of stem cell research is uncertain under the new Bush administration.
In 1993, Congress prohibited the executive branch from stopping fetal tissue transplantation research. But the Bush White House is reviewing the law involving stem cell research, and is believed to be leaning toward forbidding such research if the cells are obtained from embryos.
Any research that bolsters obtaining stem cells from adults is expected to solidify Bush’s position that it is unnecessary to use embryos to obtain stem cells.
Over the past decade, researchers have found that adults also have stem cells in a variety of locations, ranging from bone marrow to the brain. But they are present in small numbers, and recovering them can be difficult and painful.
They can be converted into specific tissues by exposing them to a complex mixture of growth hormones and other chemicals, which requires a different formula for each desired tissue. The trick is discovering what needs to be included in each cocktail.
The best source of such cells now is bone marrow, but recovering the cells requires drilling a hole directly into the bone, which remains painful for weeks after the procedure, Guilak said. And the yield is small, typically a few milliliters.
Liposuction, in contrast, is performed through an incision in the skin that is about 1 inch long and is relatively painless. Moreover, the procedure produces a thousand times as many stem cells as can be obtained from bone marrow.
In older adults, the percentage of stem cells is even higher in fat cells than in marrow, Guilak said.
And because each person would theoretically serve as his or her own fat donor, there would be no problem with rejection of implanted cells.
“This is extremely significant in terms of its potential,” said Longaker of Stanford.
You don’t even have to be fat to be a donor. “Even in skinny people, there is ample fat tissue in the buttocks and elsewhere,” said Hedrick of UCLA.
Both groups of researchers have grown human cartilage samples the size of a quarter to a half-dollar and implanted them in mice with no immune system, so that they are not rejected. So far, the implants have been very stable, with no signs of deleterious changes.
But they want to study them for much longer periods of time. “We wouldn’t want cartilage in the knee to turn into fat,” Guilak said. Guilak, for one, is optimistic, but he wants to make sure.
