US researchers have made albino mice grow a few coloured hairs. How? With a splash of gene therapy. A result that has lead the president of AntiCancer Inc, San Diego, California, Robert M Hoffman, to comment that, "the hair follicle stands as one of the most promising targets for effective, useful, safe and lucrative gene therapy."

Vitali Alexeev of the Thomas Jefferson University and Medical College, and colleagues, used a string of specially designed molecules known as an 'oligonucleotide' to replace the mutated DNA in pigment-producing hair follicle cells in albino mice. An oligonucleotide is made up of the same basic units as DNA, but is tailored either to stick to, and hence nullify, a stretch of genetic material, or, as in this case, to replace it altogether.

As the group explain in Nature Biotechnology1, they used their 'oligo' to correct the albino mutation in the 'melanocytes', cells found at the base of each hair follicle, that should produce the pigment melanin, but don't in albino mice. In this way they were able to induce coloured, rather than white hair to grow from several hair follicles in mice. Moreover the correction appeared to be passed on to progeny cells and thus gave rise to coloured hair for at least three months.

The researchers tried two delivery methods. Either, in keeping with hairdressing tradition, they rubbed a greasy goo -- containing the oligo -- into the mice' skin. Or they injected their gene therapy directly into the hair follicles. The second proved more efficient -- although neither was anywhere near as successful as would be necessary for the process to have cosmetic value. Firstly because melanocytes are deep under the skin and hence more difficult to access than other skin cells and secondly because hair pigmentation depends on the correction of many melanocytes per follicle -- to deposit enough melanin in the hair shaft.

Alexeev's team concludes that this strategy may be feasible for treating several hereditary skin diseases. But the high turnover in hair and skin cells means that the long-term success of skin gene therapy will depend on finding ways to correct skin stem cells -- the progenitor cells which give rise to all others.