Category Archives: Hair Follicle Stem Cells

Softening Stiff Hair Follicle Stem Cells to Regrow Hair

Update: July 12, 2024

In a pleasant surprise, we have an update on miR-205 for hair growth. Apparently, human clinical trials are set to commence “immediately” and “straight way” according to Trinity professor Luke O’Neill. It seems like the trials may test tablets as well as a cream or topical ointment.

June 6, 2023

MicroRNA-205 (miR-205) Promotes Hair Regeneration

Last month, an interesting new study was published in PNAS that was titled “MicroRNA-205 (miR-205) promotes hair regeneration by modulating mechanical properties of hair follicle stem cells”.

It seems like hair follicle stem cells become stiff with age, just like the rest of your body. MicroRNA (miRNA) can reverse the stiffness and regrow hair, at least in mice. Make sure to also read my past detailed post on MicroRNA and hair growth.

Softening Stiff Hair Follicles with MicroRNA.
Softening stiff hair follicle stem cells with microRNA (miR-205) regrows hair. Source: PNAS.

Softening Stiff Hair Follicle Stem Cells Regrows Hair

This latest study was led by scientists from Northwestern University School of Medicine (US), with significant contribution from Singapore’s A*Star) too. Neuroscience News has a succinct summary on the findings (h/t “curious”). In essence:

  1. Hair follicle stem cells become stiff and hardened with age, thus hindering hair growth.
  2. Northwestern scientists have discovered a way to soften these stem cells by increasing the production of miR-205. This in turn promotes hair regrowth in mice.
  3. Future experiments will investigate if humans see similar hair growth results after the topical application of miR-205 on scalp hair. The delivery will be done by nanoparticles.

MicroRNA-205 and Hair Regrowth

When the researchers genetically manipulated hair stem cells to produce more of a “tiny RNA” termed miR-205, it promoted hair regrowth in both young and old mice. It did this via mild and reversible downregulation of many genes. This in turn relaxed the hardened cells and promoted cell cycle reentry and hair regeneration.

Moreover, per a quote from the corresponding author Rui Yi:

“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.”

Interestingly, when people’s arteries get stiff with age, they get high blood pressure. Anti-hypertensive medications (such as oral Minoxidil) enable the relaxation of blood vessels. Topical Minoxidil also causes vasodilation (i.e., the widening of blood vessels).

Escaping Hair Follicle Stem Cells

Dr. Rui Yi and his team from Northwestern University’s YiLab just published a groundbreaking new paper explaining the reason for aging related hair loss. The current findings were shown in various mammals.

Escaped hair stem cells.
Escaped stem cells in aging hair follicles. Source: Nature Aging (2021). Zhang, C., Wang, D., Wang, J. et al.

The Great Stem Cell Escape

The findings in this paper suggest that hair loss is not caused by stem cell death, depletion and exhaustion as has long been postulated. Rather, the stem cells escape from the structures that house them (i.e., the hair follicle bulge). The New York Times has an in-depth summary of these very interesting findings. Also see another take from Futurism.

In order to flee, the cells change their shapes from round to amoeba-like structures. Then they squeeze out of tiny holes in the follicle. Finally, they recover their normal shapes and dart away!

Of note, the researchers (led by Dr. Yi and his PhD student Chi Zhang) discovered two genes (Foxc1 and Nfatc1) that were less active in older aging hair follicle cells. The role of these two genes is to to “imprison” stem cells in the bulge. Note that Foxc1 stands for Forkhead Box C1. Nfatc1 stands for Nuclear Factor of Activated T Cells 1.

This study found a “hitherto unknown activity” of epithelial cells escaping from their niche during the aging process. This escape subsequently leads to stem cell degradation.

“If I did not see it for myself I would not have believed it. It’s almost crazy in my mind.” — Dr. Yi.

Foxc1 and Hair Loss

Note that I have covered Foxc1 in two past posts. The first (“COL17A1 damage and hair turning into skin“) covered a 2016 study whose co-author was also Dr. Rui Yi. Key quote:

“In self-renewing stem cells (SCs), Foxc1 activates Nfatc1 and bone morphogenetic protein (BMP) signaling.”

The second post covered a 2016 article from Dr. Elaine Fuchs. In it, she found that Foxc1 plays a critical role in hair follicle and hair color (melanocyte cell) stem cell regenerative capabilities.

Stem cells residing in hair follicles are held in an inactive state for long periods of time. The new findings showed that these quiescent periods are essential for maintaining the stem cells’ rejuvenating potential.

On a somewhat related note, Dr. Yi and his team also published a new paper in September 2021 in relation to miRNA and hair loss. I have added it in that related post.