PHILADELPHIA - The pigmented cells called melanocytes aren't just for making freckles and tans. Melanocytes absorb ultraviolet light, protecting the skin from the harmful effects of the sun. They also are the cells that go haywire in melanoma, as well as in more common conditions as vitiligo and albinism.

Naturally, researchers would love to study melanocytes in the laboratory. There's just one problem -- melanocytes from adult skin don't grow very well in the lab. Now, researchers at the Perelman School of Medicine at the University of Pennsylvania have found a way to create melanocytes from mouse tail cells using embryonic stem cell-like intermediates called inducible pluripotent (iPS) cells.

Xiaowei Xu, MD, PhD, associate professor of Pathology and Laboratory Medicine, is senior author the study, which appears online in the Journal of Investigative Dermatology ahead of the December print issue. Xu and his team converted mouse tail-tip fibroblasts into iPS cells using four genes, which were first described by Shinya Yamanaka in 2006, producing pluripotent cells similar to embryonic stem cells, but without the concomitant ethical issues.

According to Xu, these lab-made melanocytes promise benefits in areas from tissue transplantation to drug discovery. "This method really has lots of clinical implications," says Xu. "We are not quite there yet, but this is an early step."

For example, by collecting a tissue sample from patients with, say, vitiligo, and converting it to iPS cells, researchers can study what goes wrong as those cells differentiate into melanocytes. Or, they can study the development and possible treatment of melanoma.

Xu's new study is the first to report creating melanocytes from iPS cells in mice, and builds on his previous work. Xu's lab was involved in the first study to work out the conditions for differentiating human embryonic stem cells to melanocytes in 2006. Earlier this year, a Japanese team became the first to differentiate human iPS cells to melanocytes.

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