The teeth grew and developed normally when transplanted into a mouse, said Takashi Tsuji of the Tokyo University of Science in Chiba, Japan and colleagues.

They said their method was the first to show an entire organ could be replaced using just a few cells. “To restore the partial loss of organ function, stem cell transplantation therapies have been developed” they wrote.

The ultimate goal of regenerative therapy, however, is to develop fully functioning bioengineered organs that can replace lost or damaged organs after disease, injury or aging.

The researchers went after the “organ germ”, the early cells made using partially differentiated cells known as epithelial and mesenchymal cells. In this case the cells were taken from what is known as the tooth germ, the little bud that appears before an animal grows a tooth.

“Our reconstituted tooth germ generates a complete and entirely bioengineered tooth”, they wrote. “This study thus provides the first evidence of a successful reconstitution of an entire organ via the transplantation of bioengineered material”, they added.

This finding should encourage the future development of organ replacement by regenerative therapy.