Anybody can make skin cells—in fact, you’re doing it right now. But large, transplantable sheets of skin? That’s a bit harder. Still, it’s not impossible: Japanese scientists have successfully grown sophisticated artificial skin, including hair follicles and sweat glands. Their results were published last week in the journal Science Advances

These are heady days for lab-grown tissue. In the last decade, scientists have managed to create petri-dish tear ducts, kidneys, rat legs, muscle and bone, and even beef. All of this is good news, as transplantable organs and other body parts are in high demand, but some have been harder to cook up than others. Skin, for example. 

Your hide may look simple, but there’s actually a lot going on: there are three distinct layers (the epidermis, dermis, and hypodermis, which is composed of fat and connective tissue), sweat glands, and hair follicles. For skin to be skin, it’s got to be functional, lead author Takashi Tsuji said in a press statement. "Up until now, artificial skin development has been hampered by the fact that the skin lacked the important organs, such as hair follicles and exocrine glands, which allow the skin to play its important role in regulation.”

Tsuji and his colleagues decided to start at the very beginning, before skin cells are even skin cells. They used induced pluripotent stem cells (iPS), which are adult cells that have been reprogrammed with the stem-cell-like power to grow into anything.

The researchers used chemicals to activate a gene in the cells called Wnt10b, which is known for its role in skin growth. The iPS were cultured until they grew into little clumps called embryoid bodies (EBs), then transplanted into mice. Once inside the mice, the EBs continued to develop into skin tissue. To test the tissue’s medical potential, the researchers removed the new skin from the mice and transplanted it into other mice. They found that the artificial skin settled in and continued to develop normally as three-layered skin complete with glands and follicles. They also noticed that the new skin was able to connect with nearby nerves and muscles—an essential element in any transplanted tissue. 

Bioengineered skin with hair follicles. Image credit: © Takashi Tsuji, RIKEN

The researchers say their lab-grown skin is a step toward both important medical advances and a reduction in the use of lab animals in research (despite the study's reliance on mice subjects).

“With this new technique, we have successfully grown skin that replicates the function of normal tissue,” Tsuji said. “We are coming ever closer to the dream of being able to recreate actual organs in the lab for transplantation, and also believe that tissue grown through this method could be used as an alternative to animal testing of chemicals."