A tiny black tuft of hair on a bald mouse’s head is evidence that stem-cell research in Japan could reverse hair loss in humans.

“The bioengineered hair follicle develops the correct structures (and) restored hair cycles,” Dr. Takashi Tsuji reports in the current issue of Nature Communications.

The strands of hair implanted themselves below the skin of the mice, showing it was not only possible to restore the hair follicle, but also to root it in the scalp, the study said.

Tsuji and his organ-regeneration team at Tokyo University Science have managed to “significantly advance the technological development of bioengineered hair follicle regenerative therapy.”

Restoring the nervous system is a critical issue in organ-regeneration work, Tsuji said. The study suggests that transplanting a “bioengineered hair follicle germ” can revive the muscles and nerve fibres associated with hair growth.

Painstaking research began with the bioengineering of various types of hair-follicle germs, which were grafted onto bald mice. The germs carried tiny nylon guides to nudge the growing hairs in the right direction.

Once that proved successful, the team moved on to bioengineering human hair-follicle germs and transplanting them in mice.

The human hairs grew in 21 days with the correct shafts, inner root sheaths and surrounding cells that normal human hair would, the study said.

Further tests proved the human hairs were, indeed, human.

The study is at the “proof-of-concept” stage, meaning the theory works. Scientists will have to do more research to see if it can turn into therapy for baldness.