Scientists have made smooth skin turn hairy using a new technique that might ultimately reverse baldness.
Baldness can occur as a consequence of ageing, disease, drugs and trauma. At the moment, the only way to reverse the effect is to transplant hair-producing follicles from one part of the skin to another. The result is a wider distribution of hair but without any net increase in the number of hairs.
Now, writing in PNAS, scientists in the US and the UK have discovered how to trigger the formation of new hair follicles in previously smooth, hairless skin.
The key to the process is a tiny knot of cells known as a dermal papilla, which sits in the skin beneath a hair follicle.
This structure contains cells capable of exerting a powerful influence over their surroundings, including inducing overlying skin cells to form hair follicles.
So, using small samples collected from the scalps of human volunteers, Columbia University researcher Claire Higgins and her colleagues dissected out the dermal papillae.
Transplanted into pieces of foreskin collected from newly-circumcised baby boys, the intact papillae triggered new hair follicle formation, proving that they retained their inductive powers when added to hairless skin.
Next, to see if the cells in the dermal papillae can be persuaded to divide, ultimately with the aim of making more dermal papillae to treat baldness, the team grew the cells in a culture dish.
In this environment, though, they rapidly altered their biochemistry and lost their hair-producing powers, which was reflected in their switching off a large number of previously-active genes.
Next, the team tried growing the cells in spherical "droplets" designed to mimic the three-dimensional structure of the dermal papilla in-situ.
Now, when balls of these cells were transplanted into foreskin tissue, hair follicles were triggered in the overlying skin up to 60% of the time. And grafted onto mice, the skin and hair follicles remained stable for 6 weeks.
Hirsutism is still some way off, however, because the follicles, whilst active, did not produce substantial hairs that could even break the skin surface, and the sebaceous glands that normally accompany a hair follicle were also absent, proving that there is some way to go yet.
Nevertheless, this is the first time that new hair follicles have been induced by cultured dermal papilla cells in human skin.