For the first time, stem cells purified from fat have been used to heal an injury in a living animal. Michael Longaker of Stanford University in California and his team showed in mouse experiments that so-called adipose derived adult stromal (ADAS) cells purified from a rodent’s belly fat could be coaxed to heal a skull fracture too large to mend by itself.The power of ADAS cells to transform into bone, cartilage and even neurons has been studied for years in test tubes. But Jeffrey Gimble, who studies human ADAS cells at Louisiana State University in Baton Rouge says Longaker’s report is an important step forward. "Actually repairing a defect in an animal model had never been done. This is an excellent study." If the same technique works in humans, these cells could be coaxed to mend broken bones and correct other defects in tens of thousands of surgical procedures each year in which bone grafts and prosthetics are now necessary.Longaker’s group tested the ability of ADAS cells to heal four-millimetre-long fractures surgically-induced in the skulls of mice. In 12 weeks, the cells filled 70 to 90 per cent of the defects, while untreated animals had only unorganized bone formation in less than 10 per cent of the fractures. No extreme genetic manipulation or treatment of the cells was necessary. ADAS cells began manufacturing bone when they were simply laid onto a biodegradable polymer that contained apatite, a compound that naturally occurs in bone. Furthermore, the ADAS cells performed as well as bone marrow stromal cells, which would seem to be more natural architects of bone. It remains to be seen whether human ADAS cells will build bone as effectively. But researchers are excited about the prospects. Human bone marrow stromal cells are already being used in clinical trials as sources of skeleton-building material, but the ADAS cells may have some significant advantages.Longaker reports that ADAS cells grow seven times faster than the bone marrow cells in the laboratory. And it is relatively easy to harvest more than a litre of fat tissue, even from patients who are not obese. Bone marrow is much less plentiful and must be removed in a painful surgical procedure. Of course, liposuction itself is not a pleasant operation. But according to the American Society of Plastic Surgeons, more than 300,000 people volunteered to have the procedure in 2003 simply for cosmetic reasons. "If the procedure was the first step to healing broken bones or replacing other tissue its popularity could only grow," says Gimble. "Just think of that.\ Gimble speaks highly of Longaker in that （）

A. his work made an unprecedented achievement in the field
B. he proved that ADAS cells contributed a lot to cell therapy
C. his work paved way for ADAS cell application in clinical trials
D. he cured an animal defect that had never been repaired before