Scientists are testing drugs that could be used to treat hair loss after the medications successfully reversed baldness in mice.
In the mice experiments, scientists from The University of Columbia found that drugs that block the Janus kinase (JAK) family of enzymes promote "rapid and robust hair growth when applied to the skin".
The researchers tested two drugs known to inhibit JAK enzymes that have already been approved by the US Food and Drug Administration: Ruxolitinib, which is usually used to treat blood diseases, and Tofacitinib, which is usually used to treat rheumatoid arthritis.
Both drugs caused mice to regrow significant amounts of their hair within three weeks of treatment and "rapidly awakened resting follicles out of dormancy".
The researchers also tested the drugs on human hair follicles that had been developed in a lab, then skin grafted onto mice.
The drugs were shown to have a similar effect, with the human hair follicles growing in the same way the mice hair had.
"What we’ve found is promising, though we haven’t yet shown it’s a cure for pattern baldness," lead author Dr Angela M. Christiano commented.
"More work needs to be done to test if JAK inhibitors can induce hair growth in humans using formulations specially made for the scalp."
Mouse without treatment (left), mouse after receiving Tofacitinib (centre) and mouse after receiving Ruxolitinib (right)
All experiments with JAK inhibitors to date have been conducted with "average" mice and human hair follicles.
The scientists have yet to test whether the treatments will work on hair follicles that have been frozen in a resting state because of androgenetic alopecia (which causes male and female pattern baldness) or other forms of hair loss disorders.
Despite this, they are hopeful their findings could eventually lead to new treatments for such conditions.
"There aren’t many compounds that can push hair follicles into their growth cycle so quickly," Dr Christiano said.
"Some topical agents induce tufts of hair here and there after a few weeks, but very few compounds have this potent an effect so quickly."
According to the NHS, male-pattern baldness is the most common type of hair loss, affecting around half of all men by 50 years of age.
Although it is less common, women can be affected by female-pattern baldness.
There is currently no definitive cure for hair loss, although a range of treatments that may help are listed on the NHS website.