New Study Triggers Hair Growth in Mice Within 20 Days by Stimulating Fat Cells

Skin injury and hair growth

New research offers encouraging evidence for efforts to reverse baldness. A study has shown that renewed hair growth can be induced in mice in as little as 20 days by activating fat cells surrounding the hair follicles in the skin.

Conducted by researchers at National Taiwan University, the work develops existing understanding that skin irritation and damage can frequently prompt hair growth. The researchers set out to establish why this occurs and whether the underlying processes might be used to address hair loss.

"The bodies of most mammals are covered by a dense hair coat, which serves as the first protective barrier," systems biologist Kang-Yu Tai and colleagues write in their published paper.

"Irritation or injury to the epidermal skin surface, the second body barrier in most mammals, should signal to regrow or reestablish the first protective barrier, the hair."

"Although humans have lost dense hair coverage on most of their bodies during evolution, clinical evidence that irritation or injury to skin surface can promote excessive hair growth (i.e., hypertrichosis) suggests that humans preserve this important regenerative capacity."

How fat cells reactivate hair follicles

For the experiments, the scientists shaved mice before causing mild skin damage with chemical irritants or heat. Using several forms of microscopic imaging, they compared hair growth in the injured skin with that in unaffected skin.

The team found that the irritation produced inflammation, bringing immune cells known as macrophages to the affected area. These macrophages then prompted adipocytes, or fat cells, to release fatty acids. Hair stem cells absorbed the fatty acids, receiving the signal needed to begin growing hair again.

"We demonstrate that in this context, adipocyte activation occurs downstream of immune cell-mediated local inflammation in the chain of skin injury-triggered cellular events," write the researchers in their published paper.

Hair regrowth in mice within 20 days

After identifying this sequence of events, the researchers applied a serum containing the same fatty acids directly to the skin of mice to determine whether injury could be avoided. This likewise initiated hair regrowth in around 20 days.

There is, however, an important limitation: the treatment works only on hair follicles in their resting phase, when they are awaiting a signal to resume growth. Baldness on the human scalp generally alters the duration of these stages from follicle to follicle, making it a more complicated situation than simply shaving mice, as in these experiments.

Reactivating hair stem cells could provide a safe, convenient and comparatively rapid method of treating hair loss, though restrictions remain on how broadly such a treatment might be used. The researchers are progressing towards clinical trials to determine whether the method translates to humans.

Further investigation is also needed into the processes triggered by skin irritation and the immune response, including precisely what causes macrophages to initiate the release of fatty acids.

"Their natural existence and established safety profile suggest considerable potential for treating hair loss conditions in the future," write the researchers.

The research was published in Cell Metabolism.