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Turning Fat Cells Into Other Tissues

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Duke Health News 919-660-1306

DALLAS, TX -- 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.

The research team, which reported last year that they were
able to turn fat cells taken from liposuction procedures into
functional cartilage cells, 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," said M. Quinn Wickham, who presented the results of
the Duke research today (Feb. 10) at the annual meeting of the
Orthopedic Research Society. Wickham is a fourth-year medical
student working in the laboratory of Farshid Guilak, 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 continued. "We could
then grow cartilage custom-made for the individual to repair an
injury in the knee with the patient's own tissue."

The fat pad is a dense structure behind the patella, or
kneecap, that is unlike typical fat tissue found throughout the
body, the researchers said. While its function is not well
understood, researchers do know that it is metabolized much
more slowly than subcutaneous fat.

"This is another demonstration that adult stem cells are not
necessarily locked into their current fate, and furthermore, we
can reprogram them into becoming other cell types," Guilak
said. "It is unlikely that one source of stem cells can be used
to treat the wide variety of medical problems and diseases, but
different clinical problems could be addressed by using adult
cells taken from different spots throughout the body, without
the same ethical concerns associated with embryonic stem
cells."

In the current study, the researchers took the fat pads from
patients whose knee joints were removed during total joint
replacement surgery.

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. To grow cartilage, groups of cells
were infused into a matrix made of a substance known as
alginate, a complex carbohydrate that is often used as the
basis of bioabsorbable dressings.

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

"For example, fat tissue could be custom grown for use in
reconstructive or cosmetic cases performed by plastic
surgeons," Wickham said. "The bone tissue could be used to
repair bone defects caused by disease or trauma."

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.

"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," Guilak continued. "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."

Guilak 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 that this strategy has potential.

Collaborating with the Duke team was Dr. Jeff Gimble of
Durham, N.C.-based Artecel Sciences, who holds the patent for
the process of isolating these cells from fat. Guilak is a
consultant for Artecel Sciences.

Other members of the team, from Duke, were Geoffrey Erickson
and Dr. T. Parker Vail.

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