Human Fat May Provide Stem Cells

URL: http://washingtonpost.com/wp-dyn/articles/A61404-2001Apr9.html

Date accessed: 10 April 2001

By Rick Weiss
Washington Post Staff Writer
Tuesday, April 10, 2001; Page A01

Scientists for the first time have transformed human fat into a variety of different tissue types, suggesting the much reviled substance may be an unexpected source of cells useful for the treatment of a wide range of ills.

Reporting in today's issue of the journal Tissue Engineering, researchers show that cells found in human fat can be made to grow into muscle cells in laboratory dishes. Working with quarts of the greasy yellow substance extracted by liposuction from patients' hips and thighs, the researchers also turned fat into healthy cartilage, muscle and bone cells.

The work is the latest in a recent series of advances suggesting that many parts of the adult body contain stem cells, which have the capacity to mature into many kinds of tissues. Those discoveries have begun to shatter a long-held belief that embryos and fetuses are the only significant source of stem cells -- a presumption that has put stem cell biology at the center of a politicized ethics debate and has slowed scientists' ability to harness the cells' regenerative potential.

Many abortion opponents object to embryonic stem cell research because human embryos must be destroyed to retrieve the cells. But the only places in the adult body where stem cells had been found are relatively inaccessible, such as deep within the brain or in bone marrow.

With the newest evidence that even cells in fat are capable of being transformed into tissue through the alchemy of biotechnology, some scientists said they are beginning to conclude they'll be able to grow with relative ease all sorts of replacement tissues without resorting to embryo and fetal cells.

Indeed, scientists said, given its abundance, accessibility and apparent versatility, human fat may someday gain respect as a premier biological building material, with uses ranging from wrinkle filling and breast augmentation to major bone, joint and muscle repairs.

"We usually think about fat as sort of worthless, something that everyone just wants to get rid of and throw away," said Marc H. Hedrick of the University of California-Los Angeles School of Medicine, who led the new research with Adam J. Katz of the University of Pittsburgh School of Medicine. "This work makes us think much differently about fat tissue."

Hedrick and Katz may even outdo the ancient alchemists by making gold not out of lead but out of people's fat. They plan to create a biotech startup that will grow a range of regenerated tissues from globs of fat that patients would just as happily say goodbye to anyway.

"It's highly provocative work and they're probably right," said Eric Olson, chairman of molecular biology at the University of Texas Southwestern Medical Center in Dallas, who said he has been awed by the ever-quickening pace of stem cell biology.

Like many biologists, Olson believes that adult, fetal and embryonic stem cell research all merit support. But he noted many scientists wishing to develop stem cell therapies have been hampered by ethics concerns over fetal cells and a ban on federal funding of embryo research, which the Bush administration is considering tightening further.

So it's heartening, he said, that almost "every other week there's another interesting finding of adult cells turning into neurons or blood cells or heart muscle cells. Apparently our traditional views need to be reevaluated."

Strictly speaking, the new work does not prove that human fat contains stem cells that can grow into many different tissues. To do so, the team would have to start with a single such cell from fat, allow it to make copies of itself in a laboratory dish, then show that those various identical offspring cells can, under the right conditions, become all kinds of cells.

What the team did instead was eliminate extraneous matter from fat, leaving behind a mixed population of cells that can multiply and replenish itself in the lab for at least a year and has the ability to produce muscle cells, cartilage cells, bone cells or more fat cells, depending on which chemicals are added. Further research may show that these cells can become virtually any kind of tissue, the researchers said.

The scientists don't show that all those cell types develop from the same precursor cell (though they claim to have done so in subsequent, unpublished work). So it's possible that each type emerged from its own precursor cell, not from a common primordial fat stem cell.

But ultimately, Hedrick and Katz said, it doesn't matter where the cells are coming from. The point is that fat from liposuction contains cells from which many useful tissues can be grown. And fat is a lot easier to remove than bone marrow.

Fat may have other advantages over marrow. Two or three quarts may provide all the cells needed to replace a layer of cartilage inside a damaged joint or to repair a traumatically fractured bone. By contrast, bone marrow aspirations produce just a few teaspoons of cells, necessitating a long period of cultivation in the lab until enough cells are present -- a period during which contamination or genetic mutations can foil the effort.

If fat cells do live up to their potential, the first applications will probably be for space-filling jobs, such as plumping up wrinkles or enlarging breasts with newborn fat cells, Hedrick said. Injections of young fat cells derived from stem cells should work better than today's transplants of mature fat, since old cells often die and collapse after transfer, creating imperfect cosmetic results.

Later, muscle and bone cells derived from fat may be used to rebuild gaps caused by cancer surgery or trauma. The idea would be to inject the cells near the injury -- perhaps on a biodegradable scaffold -- and allow them to naturally integrate themselves.

At least one company is already betting on fat's potential as a source of new tissues. Jeffrey Gimble of Artecel Sciences in Durham, N.C., said the company has also derived various tissues from human fat, though it has not yet published its work. Company scientists have been transplanting some of those tissues into animals, Gimble said, and will be meeting with Food and Drug Administration officials later this week to talk about how to work toward human clinical trials, perhaps within the next three years.

Despite fat's newfound ability to become muscle, Katz doubts the new research will transform the nation's couch potatoes into hunks. "I wouldn't want to whip up that frenzy in the public," he said. "It's not a potion to turn us all into muscle people."

Category: 31. Stem Cells