By David N. Leff
Liposuction is a fast-growing branch of plastic surgery that whisks unwanted fat out from under the skin, for purposes of cosmetic body contouring - removing unsightly bulges - or to pare down the grossly excess tissue of pathological obesity. Under local anesthetic, the surgeon cuts small slits a centimeter or so long into the epidermis, and inserts a tube called a cannula, impelled by a vacuum pump, that sucks up the fatty tissue.
So far, the suctioned-out subcutaneous fat is discarded as waste, but it's about to acquire unexpected value as an almost unlimited source of adult human stem cells.
An article in the April issue of the peer-reviewed journal Tissue Engineering bears the title: "Multilineage cells from human adipose tissue: Implications for cell-based therapies." Its senior author is plastic surgeon Marc Hedrick, at the University of California School of Medicine.
"Until now," Hedrick observed, "we have not identified a good source of stem cells, which can be thought of as the building blocks of tissue engineering. Fat," he added, "is perhaps the ideal source. There's plenty of it. It's easy and inexpensive to obtain. It even has a secondary cosmetic benefit."
Hedrick's serendipitous finding began, he narrated, when he liposuctioned fat to research lipodystrophy. This rare disorder features absence of fat tissue, rather than its overabundance. Insulin dystrophy plagues diabetics, whose daily injections of the hormone gouge fat-free hollows around the needle-entry sites. While investigating these fat-wasting disorders, he recalled, "looking at fat cells under a microscope, I noticed that some of them had characteristics resembling nerve or bone cells."
Fat: 'From Trash To Treasure'
"Our findings show that fat is not the tissue we once thought," Hedrick commented. "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." He made the point: "Its discovery could render the controversial use of human fetal tissue obsolete."
The UCLA co-authors are teamed with a similar division of plastic and reconstructive surgery at the University of Pittsburgh School of Medicine. Surgeon Adam Katz, a co-author of the paper, declared, "We do not 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." Their cross-country collaboration has harvested bone, muscle, nerve and blood vessel cell lines.
Today, human stem cells for clinical use and research come in two persuasions: embryonic, which have ethical problems and are under a U.S. federal ban, and highly experimental adult bone marrow stem cells. The byproduct stem cells salvaged from liposuction fat by the UCLA and Pittsburgh co-authors have potential differentiation potential for repairing and replacing bone (by osteogenesis), joint surfaces (chondrogenesis) and muscle (myogenesis).
Processing 300 cubic centimeters of liposuctioned material, the journal paper reported, "routinely yielded PLA (population of processed lipoaspirates) samples of 200 to 600 million cells."
"We're just figuring out the best ways," Hedrick allowed, "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. 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, on an outpatient basis. There is potential," he continued, "for regenerating a lot of different tissues, perhaps someday solid organs, glands, nerves or brain."
At Pittsburgh, Katz's epiphany came about the same time in the late 1990s.
"The very beginning of the story," he told BioWorld Today, "is that I was doing my general and plastic surgery training program. In 1996, I went into the lab and picked fat as my research project. My idea was that plastic surgeons attempt to move fat from one part of the body to the other all the time. In fact, autotransplantation of fat tissue has been attempted in the medical literature for over 100 years. In all that time, there has been minimal if any improvement in predictably and reproducibly making that fat survive.
"My goal," Katz continued, "was to try to lend some science at the cellular level that could improve fat transplantation for cosmetic and reconstructive surgery. As I was reading about bone marrow stem cells, I thought: 'If these people can turn bone marrow - which is just a fat tissue - into fat and bone and cartilage, and my cells look just like theirs, why don't I repeat some of their experiments?' So I did a little pilot study, trying to turn fat into bone, and it just went incrementally - first bone, then cartilage.
"About that time," Katz went on, "Hedrick was starting a tissue engineering lab. He chose to take what we had started and built upon it at UCLA".
Hedrick & Katz Incorporated
"He and I," Katz said, "are now co-founders of a tech transfer start-up company related to our work. Our company is incorporated as StemSource Inc., located in L.A. The intellectual property at this point is shared in some degree between Pitt and UCLA. We are in the process of licensing our intellectual properties from the two universities.
"At this stage," Katz pointed out, "it's predominantly an R&D operation, and we've moved ahead in one direction in hopes of rapidly identifying truly clonal or purified stem cell populations, and identifying markers that might allow one to rapidly identify cells as such. In vivo experiments are basically cooking as we speak, with Hedrick attempting to lay down new cartilage in the injured joint of a rat model.
"As a clinician potentially using this technology," Katz concluded, "I believe that liposuction will remain the most appealing and attractive way to harvest the fat cells for tissue engineering."