The molecule studied is part of a complex signalling system called the Hedgehog pathway. The signalling system controls the development of many different organs.

- If we learn more about how the signalling system regulates stem cell behaviour, we will perhaps be able to develop new treatments for hair loss and cancer, says Amel Gritli-Linde, Reader in Oral Biochemistry at Sahlgrenska Academy.

Hair or breast is determined by signal activation
The study shows that the Hedgehog system is responsible for stem cells in skin getting the go-ahead to develop into a certain type of cell. The molecule that was studied is called Smoothened and is a link in the chain of information. Without it, no information can ever reach the cell´s nucleus.

Genetically mutated mice that lacked the molecule in part of the skin were used in the study.

- In normal cases, the stem cells in the hair follicles lie protected in special small niches in the skin, but the transgenic mice had no such protective niches. The stem cells that should have become hair instead developed into mammary gland cells, says Amel Gritli-Linde.

We already knew that excessive Hedgehog signalling can cause cancer. The new study shows that increased signalling also prevents the formation of mammary glands. Hedgehog signalling thus determines whether it is hair or breasts that are formed.

Hair stem cells can form new teeth
It is not unusual for researchers in odontology to study skin and hair follicles. The hair that is formed in the follicles develops in a similar way to teeth in tooth germs.

- It is very enlightening for us dentists to study the mechanisms underlying hair development. It is not wholly impossible that we will be able to make hair stem cells form new teeth some time in the future. Then, perhaps millions of people without teeth around the world may be able to have new real teeth, says Amel Gritli-Linde.

The study was carried out in collaboration with researchers in the USA and Great Britain.