While growing biological components in the lab such as a thymus gland, sperm cells, eye tissue and cartilage are becoming more and more commonplace, thus far, creating fully functioning lab-grown skin has eluded scientists. Previous attempts have produced epithelial cells only, which comprise the outer layer of skin. Now, researchers at Japan's RIKEN Center for Developmental Biology have created skin tissue complete with sebaceous glands as well as hair follicles. They started with mouse gums.

In particular, the researchers took cells from the gums of mice and chemically altered them so that they became induced pluripotent stem cells (iPS). These are adult cells that resemble embryonic stem cells. The iPS were then cultured to form something known as an embryoid body which, according to Riken, is "a three-dimensional clump of cells that partially resembles the developing embryo in an actual body."

Once the embryoid bodies had formed, the researchers implanted them into mice.

Just like with a growing embryo, the cells in these bodies began to differentiate themselves into different types of tissue. At that point, they were removed and implanted into the skin tissue of different mice. There they developed into what's known as integumentary tissue, which is like the "guts" of skin tissue, where hair and oil is produced. The tissue continued to grow, forming hair follicles and sebaceous glands and — most importantly — the tissue knitted itself into its surroundings, making critical connections with nerves and muscles so that it could thrive and function normally.

"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," says study leader Takashi Tsuji. "With this new technique, we have successfully grown skin that replicates the function of normal tissue. 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."

The work of Tsuji and his team, which included collaborators from the Tokyo University of Science, was published in the April 1 edition of the journal Science Advances.