FDA-approved drugs promise new hair growth

When the researchers looked at normal mouse hair follicles, they found that JAK inhibitors rapidly awakened resting follicles out of dormancy.

Hair follicles do not produce hair constantly but rather by cycling between resting and growing phases.

JAK inhibitors trigger the follicles' normal reawakening process, the researchers found.

Mice treated for five days with one of two JAK inhibitors sprouted new hair within 10 days, greatly accelerating the hair follicle growth phase.

No hair grew on untreated control mice in the same time period.

The drugs also produce longer hair from human hair follicles grown in culture and on skin grafted onto mice.

"More work needs to be done to test if JAK inhibitors can induce hair growth in humans using formulations specially made for the scalp," Christiano said.

Both the drugs are being tested in clinical trials for the treatment of plaque psoriasis and alopecia areata, an autoimmune disease that causes hair loss, the study said.

The research was published online in the journal Science Advances.