December 6, 2023

Using microRNA to genetically manipulate hair follicle stem cells, researchers have successfully stimulated hair growth in mice, suggesting that balding heads could one day grow a full head of hair.

Like the rest of our bodies, as we age, our hair follicle stem cells harden, making it harder for them to grow hair. Almost everyone experiences some degree of hair loss over time. All genders experience hair loss for a variety of reasons, including genetic traits, hormonal and thyroid disorders, and poor nutrition.

Hair follicles have a niche for mature stem cells called a “bulge” near the hair root. These stem cells help regenerate epidermal (skin) cells as well as the structure of hair follicles and sebaceous glands, the glands that produce oil (sebum). Hair follicle stem cells can remain in their niche and regenerate themselves, but they can also migrate to the base of the follicle to become hair germ progenitor cells that can differentiate to form the follicle and hair shaft.

Researchers at Northwestern University in Illinois first examined mice to determine what happened at the cellular level to hair follicle stem cells (HFSCs) and hair germ cells. They observed that HFSCs were stiffer compared to the relatively soft and mechanically dynamic hair germ progenitors.

They then determined whether the cells’ behavior correlated with gene expression and found that one specific microRNA, miR-205, was one of the most highly expressed microRNAs in hair germ progenitor cells and skin stem cells. MicroRNAs (miRNAs) are small, single-stranded, non-coding RNA molecules that play important roles in regulating gene expression. That is, whether a particular gene produces too much, too little, or just the right amount of protein at a particular time.

After genetically stimulating the stem cells of the mice to produce more miR-205, the germ cells of the softer hair became more sensitive and mobilized rapidly to initiate hair follicle regeneration, promoting hair growth in both young and old mice.

“They started growing hair within 10 days,” said Wray, the study’s corresponding author. “These are not new stem cells being made. We’re stimulating existing stem cells to grow hair. Many times we still have stem cells, but they may not be able to make hair.”

Now that they have shown that stimulating hair growth is possible, the researchers plan to expand their study.

“Our study demonstrates the possibility of stimulating hair growth by modulating cellular mechanics,” Yi said. “Since it is possible to deliver microRNA directly into the skin via nanoparticles, we will next test whether locally delivered miR-205 can stimulate hair growth in mice in the first place. If successful, we will design experiments to test whether this microRNA can Potentially promoting human hair growth.”

The study was published in the journal Member of the National Academy of Sciences.

source: Northwest University