While the majority of hair-related research has examined how best to grow new hair, the latest discovery focuses attention on how to stop existing hair from falling out.
A team at the Black Family Stem Cell Institute at the Icahn School of Medicine at Mount Sinai, in New York City, recently published the study, “Dermal sheath contraction powers stem cell niche relocation during hair cycle regression,” in the journal Science. Lead researcher Dr. Michael Rendl says the team zoomed in on the role played in the life cycle of a human hair follicle by the dermal sheath, the muscle that surrounds each follicle.
We’ve known for many years that dermal papilla cells are central in the creation of each new hair shaft. We previously posted the story, “Don’t Bank on Hair Follicle Banking,” about on one company’s efforts to isolate dermal papilla cells and then clone those cells. These specialized cells reside in the dermal papillae of the hair follicle and regulate hair follicle development and growth.
Rendl’s team observed that dermal papilla cells begin at the base of growing hair follicles, and slowly move up toward stem cells that are found at the follicle’s tip. In a news release from Mount Sinai, Rendl’s team explained that as the dermal papilla cells move up, they send signals to the stem cells “to start the next growth phase and make a new hair shaft, while the previous hair shaft is shed.”
If you aren’t already familiar with the three phases of hair growth, here is a quick overview:
- The anlagen phase is the active growth phase. It can last up to seven years!
- The catagen phase is a transition period when hair stops growing. It usually lasts two to four months.
- The telogen phase is a resting period. The old hair falls out and the process of creating a new hair begins. It usually takes three to four months.
What Rendl’s research team examined was what happened during the telogen phase and why new hair sometimes did not grow.
They found that there can be an interruption in the signaling, which causes the growth cycle to get out of whack. It might start with just a few hair follicles not receiving the signal, but over time it can lead to hundreds and then thousands of hair follicles naturally reaching the telogen phase but never being replaced by new hair.
Observing the growth cycle in mice in the lab, Rendl’s team successfully advanced our understanding of how this occurs at a microscopic level. They determined that the dermal sheath surrounding growing hair follicles is a smooth muscle. When it contracts it pushes up the hair shaft and pulls up the dermal papilla cells toward the stem cells.
They extended what they learned with experiments involving human hair and believe that our hair follicles behave in a similar way. The dermal sheath contracts to push up the hair shaft and pull up the dermal papilla cells. Years later, the sheath muscle contracts again, the existing hair falls out and the process begins all over again.
This is the first time that dermal sheath contraction has been highlighted as a key player in both hair growth and hair “destruction,” and Rendl believes this realization may point the way toward new ways of preventing hair loss. Basically, if we can stop the dermal sheath from contracting, the existing hair presumably would remain.
“Blocking contraction and arresting the destruction phase of the cycle has the potential to retain the existing hair shaft that is otherwise lost when a new hair shaft is produced,” Rendl said. “This type of muscle cannot be controlled voluntarily…but we can control it by drugs that can block contraction.”
Not everyone is super excited about this prospect. Among the reader comments of the story, “Blocking the contraction of the “dermal sheath” could halt hair loss,” by New Atlas was this quip from “paul314”:
“So instead of old hairs going away, they’d hang out on your scalp forever, getting more frayed and bleached and generally grungy over the months and years? Great idea.”
Our recommendation to paul314 and everyone else is to not jump to conclusions. At least some of the hairs on your head have been there for many years already and, assuming you care for it and don’t mistreat it, nobody can tell the difference between your old hairs and your newer hair. It all just looks like hair! Visit Hairguard.com for more information on hair loss.
If someday we are able to stop shedding and prevent hair loss completely, that would be very exciting. We at Arocha Hair Restoration congratulate Dr. Rendl and his team and wish them good luck as they continue this important research.