Baldness could be beaten by an experimental drug originally designed to treat brittle bone disease, research suggests.
In lab experiments the osteoporosis drug had a dramatic effect on donated follicles, stimulating them to sprout growing hairs.
At a molecular level the compound, known as WAY-316606, targeted a protein that acts as a potent brake on hair growth and plays a key role in baldness.
The discovery, still to be tested in clinical trials, could open up a whole new approach to treating hair loss in both men and women, researchers believe.
Lead scientist Dr Nathan Hawkshaw, from the University of Manchester, said: “The fact this new agent, which had never even been considered in a hair loss context, promotes human hair growth is exciting because of its translational potential: It could one day make a real difference to people who suffer from hair loss.
“Clearly though, a clinical trial is required next to tell us whether this drug or similar compounds are both effective and safe in hair loss patients.”
Currently only two drugs, minoxidil and finasteride, are available for the treatment of male pattern baldness (androgenetic alopecia) - the classic type of receding hair-line hair loss in men.
Both have moderate side effects and often produce disappointing results.
The only other option open to patients losing their hair is transplantation surgery.
Scientific detective work led the Manchester team to test the osteoporosis drug’s ability to stimulate hair growth.
It began with a search for novel agents for treating male pattern baldness.
The researchers first latched onto an old immunosuppressive drug, cyclosporine A (CsA), used since the 1980s to prevent transplant organ rejection and reduce symptoms of autoimmune disease.
A well-known side effect of CsA is that it enhances unwanted hair growth. The scientists found that the drug reduced the activity of a protein called SFRP1, a key growth regulator that affects many tissues including hair follicles.
However, because of its side effects CsA would be quite unsuitable as a baldness treatment.
The team went on to look for another agent that targeted SFRP1 and found that WAY-316606 was even better at suppressing the protein.
In tests, follicles donated by more than 40 patients undergoing hair transplant surgery were treated with the osteoporosis drug for six days.
The follicles quickly went into the active “anagen” phase of hair growth, and began sprouting hair.
After two days, the measured rate of hair shaft production increased significantly in the treated follicles.
The research, published in the journal Public Library of Science Biology, is “clinically very relevant” since most previous similar studies have relied on cell cultures, said Dr Hawkshaw.