Duke University Medical Center researchers have "reprogrammed" adult stem cells taken from a small deposit of fat behind the kneecap into functioning cartilage, bone, or fat cells that could potentially be grown into replacement tissues for diseases such as osteoarthritis.

The research team has provided 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," said M. Quinn Wickham, who presented the results of the Duke research at the annual meeting of the Orthopedic Research Society.

"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 continued. "We could then grow cartilage custom-made for the individual to repair an injury in the knee with the patient's own tissue."

Since cartilage is a tissue type that is poorly supplied by blood vessels, nerves and the lymphatic system, it has a very limited capacity for repair when damaged. The researchers believe that this would be one of the earliest therapeutic uses of such tissue engineering techniques.

In the current study, the researchers took the fat pads from patients whose knee joints were removed during total joint replacement surgery. The fat pad is a dense structure behind the patella, or kneecap that is unlike typical fat tissue found throughout the body. While its function is not well understood, researchers do know that it is metabolized much more slowly than subcutaneous fat.

The researchers focused on specific cells within the samples known as adipose-derived stromal cells, which under normal situations would receive environmental cues to transform themselves into fat pad cells. After the samples were treated with a series of enzymes and centrifuged, the separated stromal cells were treated with a biochemical cocktail of different steroids and growth factors.

"By treating these stromal cells with different agents, we were able to induce them to commit to multiple lineages," Wickham said. "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."

In addition to controlling their biochemical environment, the researchers were able to grow different cell types from the adult stem cells by controlling their shape in a three-dimensional matrix, a crucial advance for using resulting tissues as human therapies.

The therapeutic potential for tissues grown from these adult stem cells is large and varied, Wickham said.

The researchers estimated that it might be more than five years before this approach becomes a clinical reality. However, based on the results of numerous prior animal studies, and the results of the current experiments, the researchers are confident of the strategy’s potential.