MicroRNA promotes hair growth in mice

Hair growth has been stimulated in young and old mice using microRNA, with the potential for future trials in humans to treat baldness.

Researchers from Northwestern University, Illinois, have discovered that age-related stiffness in hair follicle stem cells inhibits hair growth. By expressing a microRNA, miR-205, in genetically modified mice, they softened these cells and stimulated hair growth.

'They started to grow hair in ten days' said Professor Rui Yi, from the Northwestern University Feinberg School of Medicine, who was a corresponding author on the study. 'These are not new stem cells being generated. We are stimulating the existing stem cells to grow hair. A lot of times we still have stem cells, but they may not be able to generate the hair. '

The paper, published in PNAS, describes how researchers observed the cell mechanics within hair follicle stem cells. They discovered that age-related stiffness and resistance to size change inhibits hair growth, whereas cells more likely to grow hair are softer and periodically change size.

The team then turned to miR-205 to modulate the stiffness. They used transgenic injections to induce miR-205 in mice and tracked the progression of hair growth compared with control mice, using two-photon microscopy. Hair growth was initiated in all miR-205-induced mice, regardless of age, within 14 days. The induction of miR-205 decreased the stiffness of the hair follicle stem cells and promoted hair growth.

In 2021, Professor Yi and his colleagues also found that stem cells migrating away from hair follicles contributed to hair whitening and loss in ageing mice. They discovered two genes that regulated this migration in younger hair follicles, that have the potential to be used as anti-hair loss treatment in human patients (see BioNews 1116).

The team aims to take the results from their preclinical research and translate it into future trials in humans.

'Our study demonstrates the possibility of stimulating hair growth by regulating cell mechanics' added Professor Yi. 'Because of the potential to deliver microRNA by nanoparticles directly into the skin, next we will test whether topically delivered miR-205 can stimulate hair growth first in mice. If successful, we will design experiments to test whether this microRNA can promote hair growth potentially in humans.'