Northwestern study findings could help regenerate hair growth in aging follicles

12 Jun 2023 --- If a hair follicle’s stem cells are softened, they are more likely to produce hair, according to researchers at Northwestern University, US. Their latest research aims to combat hair follicle stem cell stiffness that increases with age, making it harder to grow hair, much like how joints get stiff as they age. 

In a study published in PNAS, the investigators report that they can soften the stem cells of mice by boosting the production of a tiny RNA, miR-205, that relaxes the hardness of the cells. When scientists genetically manipulated the stem cells to produce more miR-205, it promoted hair growth in young and old mice. 

“They started to grow hair in ten days. 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,” says corresponding author Rui Yi, the Paul E. Steiner research professor of pathology and professor of dermatology at Northwestern University Feinberg School of Medicine. 

Stimulating growth 
The scientists used advanced microscopy tools, including atomic force microscopy, to measure the stiffness and two-photon microscopy to monitor cell behaviors in live animals.

“Our study demonstrates the possibility of stimulating hair growth by regulating cell mechanics. 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,” explains Yi. 

Northwestern University researchers use mice to promote the growth of aging hair.The scientists genetically manipulated the stem cells to produce more miR-205 through genetically engineered mouse models. Hair follicle stem cells are stiff with high actomyosin contractility and resistant to size change, whereas hair germ (HG) progenitors are soft and periodically enlarge and contract during dormancy.

During activation of hair follicle growth, HGs reduce contraction and, more frequently, enlarge. This process is associated with weakening the actomyosin network, nuclear yes-associated protein accumulation and cell cycle reentry. 

The research finds that the induction of miR-205, a novel regulator of the actomyosin cytoskeleton, reduces actomyosin contractility and activates hair regeneration in young and old mice. 

It reveals the control of tissue stem cell size and activities by spatiotemporally compartmentalized mechanical properties and demonstrates the possibility of stimulating tissue regeneration by fine-tuning cell mechanics.

Human application
Future experiments will test if topically delivered miR-205 can promote hair growth in humans.

“If successful, we will design experiments to test whether this microRNA can promote hair growth potentially in humans,” adds Yi. 

In related studies, Chinese researchers used AI to predict compounds that could neutralize reactive oxygen species that cause balding on the scalp.

Edited by Sabine Waldeck