Originally Published MDDI March 2002

R&D DIGEST

Farshid Guilak, right, and M. Quinn Wickham are exploring methods for turning fat from behind the kneecap into joint tissue.

Researchers at Duke University Medical Center (Durham, NC) have developed a technique for "reprogramming" adult stem cells taken from small deposits of fat behind the kneecap to form functional cartilage, bone, or fat cells that can then be grown into replacement tissues. The group says they have previously demonstrated methods for turning fat cells taken from liposuction procedures into functional cartilage cells.

Their recent work, they suggest, provides further evidence that stem cells taken from different adult sources have the potential to be transformed into multiple specialized cell types. "In scientific terms, we have found a new source of adult stem cells that can be changed into different cells and tissues," says medical student M. Quinn Wickham, who works with Farshid Guilak, PhD, director of orthopedic research at Duke and senior member of the research team. "On the clinical side, for example, it would be relatively easy for a knee surgeon to obtain some of these fat cells using a minimally invasive approach," Wickham adds. "We could then grow cartilage custom made for the individual to repair an injury in the knee with the patient's own tissue."

In the study, fat cells were extracted from the dense, padlike structures behind the knee joints of patients who had undergone total joint replacement surgery. The researchers focused on the adipose-derived stromal cells that under normal situations would receive environmental cues to transform themselves into fat-pad cells. The samples were treated with a series of enzymes and centrifuged, and then the separated stromal cells were treated with combinations of steroids and growth factors.

Treating the stromal cells with different agents induced them to form multiple lineages, the researchers say. "These findings suggest that the fat pad, given its location and accessibility, may prove to be an excellent source of progenitor cells for tissue engineering or other cell-based therapies," Wickham adds.

The group found that different cell types could be grown from the adult stem cells by controlling their shape in a three-dimensional matrix, which they consider a critical advance for therapeutic use of the resulting tissues. To grow cartilage, groups of cells were infused into a matrix made of alginate.

Wickham suggests the therapeutic potential for tissues grown from these adult stem cells is quite promising. "For example, fat tissue could be custom grown for use in reconstructive or cosmetic cases performed by plastic surgeons," Wickham says. "The bone tissue could be used to repair bone defects caused by disease or trauma." Guilak adds that, "For patients with tissue damage, we envision being able to remove a small piece of fat and then growing customized, three-dimensional pieces of tissue which would then be surgically implanted where needed. One of the beauties of this system is that since the cells are from the same patients, there are no worries of adverse immune responses or disease transmission. However, we would still like to test whether cells from a person's fat tissue could be used to treat another patient without being rejected." The researchers expect it will be at least five years before the new technique is used in clinical applications.

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