Adult Fat Turned into Stem Cells
With 30-40% of adults in the United States considered obese, their fat cells are a great source for stem cells. Scientists from Stanford have found fat cells removed during liposuction contain versatile cells that can be coaxed to become induced pluripotent stem cells, or iPS cells, easier than the skin cells most often used by researchers.
Ning Sun, PhD and colleagues from Stanford’s School of Medicine have published their research online Sept. 7 in the Proceedings of the National Academy of Sciences.
Mouse-derived feeder cells are often used when growing human skin cells outside the body, but there is worry that cross-species contamination could make them unsuitable for human use. The Stanford researchers where able to convert the fat cells without the need for “feeder cells.”
The liposuctioned fat contains multipotent cells called adipose, or fat, stem cells. Unlike highly specialized skin-cell fibroblasts, these adipose stem cells have a relatively wide portfolio of differentiation options. They can become fat, bone or muscle as needed. Ning Sun, PhD stated “They are more embryonic-like than fibroblasts, which take more effort to reprogram.”
Reprogrammed iPS cells are usually created by expressing four genes, called Yamanaka factors, normally unexpressed (or expressed at very low levels) in adult cells.
Sun found that the fat stem cells actually express higher starting levels of two of the four reprogramming genes than do adult skin cells—suggesting that these cells are already primed for change. When he added all four genes, about 0.01 percent of the skin-cell fibroblasts eventually became iPS cells but about 0.2 percent of the fat stem cells did so—a 20-fold improvement in efficiency.
The new iPS cells passed the standard tests for pluripotency: They formed tumors called teratomas when injected into immunocompromised mice. The iPS cells could also differentiate into cells from the three main tissue types in the body, including neurons, muscle and gut epithelium.
“Imagine if we could isolate fat cells from a patient with some type of congenital cardiac disease,” said Wu. “We could then differentiate them into cardiac cells, study how they respond to different drugs or stimuli and see how they compare to normal cells. This would be a great advance.”
"Feeder-free derivation of induced pluripotent stem cells from adult human adipose stem cells."; Ning Sun, Nicholas J. Panetta, Deepak M. Gupta, Kitchener D. Wilson, Andrew Lee, Fangjun Jia, Shijun Hu, Athena M. Cherry, Robert C. Robbins, Michael T. Longaker, and Joseph C. Wu.; PNAS, published online before print September 8, 2009.; DOI:10.1073/pnas.0908450106
Stanford University School of Medicine