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| Archive : Winter 2006 |
THE NEW TOOLS OF RECONSTRUCTION:
Skin from a deceased donor's face // Fat // Milled bone chips // Resorbable tacks // Fibrin glue // Biodegradable scaffolding // And most critical, not expecting too much too soon.
Saving Faces [page 2]
 By Anita Slomski
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In the case of Maria, Howaldt shaved a small amount of bone from the girl's pelvis and, during the same procedure, took fat from her left buttock. Surgeons then removed scar tissue from around her skull and took an imprint of the skull surface, which was used to mold two macroporous sheets from a malleable polymer that the body will absorb over time.
Next, Howaldt and his colleagues milled the bone into chips, which they applied to the skull defects. Then they attached the protective sheets with resorbable tacks and soaked the milled grafts with stem cells injected through holes in the sheets. A fibrin glue, made from the girl's plasma, kept the cells in place. Howaldt hoped that adding stem cells to the small amount of bone from his young patient would stimulate bone regeneration. Three months later the girl's skull had healed.
Yet despite that and other early successes (physicians in Spain have used the cells to treat difficult-to-heal enterocutaneous fistulas, abnormal connections between an intestine and skin, and surgeons in Japan are using them to stimulate fatty tissue growth in and around the breast instead of implanting prostheses), how stem cells from fat promote healing is still mysterious. Marc Hedrick, president of Cytori Therapeutics, a biotechnology company conducting research on fat's reservoir of stem and regenerative cells, has one theory. "It may be," he says, "that when the body is revved up to heal—for instance, after a heart attack—it releases growth factors, proteins and other stimuli that could signal the stem cells to home in on the damaged area to repair or salvage it."
That theory is supported by animal studies in which Cytori researchers have found that stem cells from fat reduce damage to the heart after a heart attack by strengthening its ventricular function and laying down new vessels to produce greater blood flow. Similarly, in his work, Howaldt is convinced that bone fragments transplanted from the pelvis stimulate the stem cells to differentiate into bone tissue.
Whatever the underlying processes and however promising the work appears, Hedrick says it would be wrong to exaggerate the potential of the new therapy. "Stem cells aren't magical. Rather, think of them as a new class of pharmaceutical. Some diseases will be straightforward to treat with stem cells, others will be very hard, and some will be impossible." Still, he says, stem cells have the potential to change plastic surgery, giving surgeons a new approach for augmenting soft tissue after breast cancer surgery, healing wounds and treating bone defects.
Though in many ways a more radical procedure than the European experiments with stem cells, the face transplant that Siemionow hopes to perform breaks no new surgical ground. Plastic surgeons have long been able to transplant large skin flaps and their blood supplies from someone's own arm, leg or back. Even joining blood vessels a millimeter in diameter has become standard practice.
But it's difficult to harvest enough similar pieces of autologous skin to cover an entire face. And until recently, the problem with using skin from a deceased human donor has been rejection. Because skin is the first line of defense against infection, it triggers the strongest immune response and is the most difficult to transplant. It wasn't until 1998, when the first human hand was transplanted—by the same French surgeon who in November performed the partial face transplant—that doctors found the right combination of immunosuppressant drugs to enable recipients to even tolerate donated skin.
Siemionow and other surgeons point to the success of 24 hand transplants as evidence that a donated face should also take. Yet even now, a lifetime of immunotherapy to prevent the constant threat of rejection brings considerable risks, with side effects that may include life-threatening infections, malignancies, diabetes, and kidney and liver failure. The immunosuppressant drugs now in use, says Siemionow, could be expected to shave 10 to 15 years off a transplant recipient's normal life span.
Still, she says, immunosuppressant drugs may prove less toxic to otherwise healthy burn victims than they are to organ recipients whose bodies are already weakened by disease. And she predicts that, before long, a short course of immunosuppression may be enough to establish tolerance of the transplant. In her experiments, rats have accepted new faces, limbs and skin flaps after just a seven-day regimen of immunotherapy.
Even with immunosuppression, there is a 50% chance the face will fail, either during surgery or soon after.
Such odds, says Siemionow, are "reasonable for a procedure that has never been done." But the consequences of failure must be carefully considered, says Ira Papel, president of the American Academy of Facial Plastic and Reconstructive Surgery, who advises that such procedures be approached with extreme caution.
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Left to right: Photo by Erin Patrice O'Brien/Getty Images; Photo by Erik von Weber/Getty Images;
Photo by Erik von Weber/Getty Images; Photo by David Sacks/Getty Images
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