Gray hair often shows up before anything else about you feels older. Your hair keeps growing just fine, but the color fades thanks to the cells in the hair follicles.
That switch doesn’t happen because your whole body suddenly “gets old.” It starts inside each follicle, where pigment stem cells are supposed to leave their safe zone, catch a cue, and become the color-making melanocytes that dye each new strand.
When those cells, known as melanocyte stem cells (McSCs) stop moving on schedule, the color step gets skipped – even though the hair still grows.
“Our study adds to our basic understanding of how melanocyte stem cells work to color hair,” said study lead investigator Qi Sun, PhD, a postdoctoral fellow at NYU Langone Health.
“The newfound mechanisms raise the possibility that the same fixed positioning of melanocyte stem cells may exist in humans. If so, it presents a potential pathway for reversing or preventing the graying of human hair by helping jammed cells to move again between developing hair follicle compartments.”
Follicle cells and gray hair
Inside a follicle, two neighborhoods matter most for color. The hair germ sends out strong chemical messages that tell pigment stem cells to mature into melanocytes. The bulge is a safer hangout with no “make color now” message.
In a healthy cycle, stem cells travel from the bulge into the hair germ right as a new hair begins. Next, they hear the signals from WNT proteins, then shift into McSCs, and load pigment into the growing shaft.
Later on, some of the cells that produce gray hairs will reset to a stem-like state for the next round.
How the study was done
Researchers watched this in action rather than guessing from snapshots.
Using long-term live imaging and single-cell RNA sequencing across multiple growth cycles in mouse follicles, they tracked where individual cells were and what instructions they were reading.
When regrowth was repeatedly forced, more pigment stem cells lingered in the bulge, missed the WNT-rich zone, matured less often, and gray hairs increased.
The location of the gray hair follicle cells led to a signal, the signal led to a decision, and that decision led to the hair’s color – or to gray when that chain broke.
Location, movement, and timing
That process completely reframes how we think about follicle cells and graying hair. Time matters, but not like a countdown clock that drains color. Movement and timing matter more.
Pigment stem cells have to make the trip at the right moment.
“It is the loss of chameleon-like function in melanocyte stem cells that may be responsible for graying and loss of hair color,” said study senior investigator Mayumi Ito, PhD, a professor in the Ronald O. Perelman Department of Dermatology and Department of Cell Biology at NYU Langone Health.
Lose that chameleon behavior – arriving in the right neighborhood when the cue is loud – and you can still grow healthy hair shafts that emerge silver because the dye step never happened.
Limitations on gray hair cell study
The scientists are careful to point out that there were limitations to what could be proven in this study. Stress isn’t a single switch that turns hair gray for good, and simply flipping stem cells “on” won’t fix it.
The gray hair follicle cells can be present and still fail if they never reach the signal.
Any future approach would need to help them move on time or make the hair germ more inviting, not just blast the whole follicle with a random growth command.
You might ask how this maps to people, since the experiments used mice. Human follicles share the same architecture and cell types.
Because of this fact, two separate paths make sense to explore in greater detail: restore the commute so pigment stem cells reach the hair germ right when a new hair starts.
Next, tune the local cues so that, once there, cells clearly hear the message to become McSCs.
Timing and restraint would be critical. Push too many cells to mature at once and you could drain the reserve; push too few and nothing changes.
Fixing gray hair cells in the real world
The goal isn’t a permanent “color” switch – it’s to keep the rhythm going so some cells color the hair now while others reset for later.
All of this fits a simple idea: cells read their surroundings before they act. DNA provides options; the neighborhood tells them which option to pick today.
In gray hair follicles, neighborhoods shift across time and space. When pigment stem cells reach the right spot at the right moment, they catch the message, become melanocytes, and color the strand.
When movement or timing fail, the message is lost and the hair grows in gray.
There’s no treatment yet – this is just a map, not a medicine. However, scientists do believe they’re getting very close to a real-world solution.
Next steps for scientists
If future studies in people confirm the same pattern, scientists can test gentle ways to ease the traffic – nudging cells out of the bulge or strengthening the hair germ’s signals – without derailing the rest of the system.
The challenge is to protect flexibility. They must mature enough cells to color the hair you’re growing now, and keep enough in reserve so the system still works years from now.
So the next time you spot a gray strand, remember that your hair didn’t forget how to grow. The factory is fine; it’s the commute inside the follicle that jammed. Fix the traffic and, in theory, color could return.
For now, gray doesn’t have to mean weak or unhealthy hair. It can mean the pigment team missed its cue – and that turns gray from a mystery into a timing problem science is learning how to read.
The full study was published in the journal Nature.
—–
Like what you read? Subscribe to our newsletter for engaging articles, exclusive content, and the latest updates.
Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.
—–
Source link
