The discovery challenges a long-standing view of how hair grows and could lead researchers to rethink everything from hair loss treatments to regenerative medicine.

The findings come from researchers at L'Oréal Research & Innovation and Queen Mary University of London and were published in the journal Nature Communications.

Inside the Hair Follicle

A hair follicle is a complex structure embedded within the skin that produces and supports each strand of hair. At the base of the follicle is the hair bulb, where cells rapidly divide to create new hair. Scientists have traditionally believed that these newly formed cells acted like a conveyor belt, pushing older cells upward and causing hair to emerge from the scalp.

To investigate whether that explanation tells the whole story, researchers used advanced 3D live imaging technology to observe living human hair follicles maintained in laboratory culture. Unlike traditional microscopy, which captures only still images, this approach allowed scientists to watch individual cells move and interact in real time.

The team focused on the outer root sheath, a layer of tissue that surrounds the growing hair shaft. Surprisingly, they observed cells within this layer moving downward in a coordinated spiral pattern. Even more intriguing, this movement occurred in the same region where the force responsible for pulling hair upward appeared to originate.

A Hidden Cellular Motor

Dr. Inês Sequeira, Reader in Oral and Skin Biology at Queen Mary and one of the study's lead authors, said:

"Our results reveal a fascinating choreography inside the hair follicle. For decades, it was assumed that hair was pushed out by the dividing cells in the hair bulb. We found that instead that it's actively being pulled upwards by surrounding tissue acting almost like a tiny motor."

The discovery suggests that hair growth depends not only on creating new cells but also on mechanical forces generated by the coordinated movement of cells within the follicle itself.

Surprising Results Challenge Traditional Thinking

To test their theory, the researchers carried out a series of experiments designed to separate the effects of cell division from the effects of cell movement.

First, they blocked cell division inside the follicle. If the traditional explanation were entirely correct, hair growth should have slowed dramatically or stopped altogether. Instead, the follicles continued producing hair at nearly the same rate as before.

The team then turned its attention to actin, a protein found in cells throughout the body. Actin plays a critical role in allowing cells to move, change shape, and generate force.

When the researchers disrupted actin activity, the results were dramatic. Hair growth rates fell by more than 80 per cent, indicating that cellular movement and force generation are essential parts of the growth process.

Computer simulations reinforced these findings. The models showed that the coordinated motion of cells in the follicle's outer layers created pulling forces strong enough to explain the observed movement of the hair shaft.

Capturing Hair Growth in Real Time

Dr. Nicolas Tissot, the study's first author from L'Oréal's Advanced Research team, emphasized the importance of the new imaging approach:

"We use a novel imaging method allowing 3D time lapse microscopy in real-time. While static images provide mere isolated snapshots, 3D time-lapse microscopy is indispensable for truly unraveling the intricate, dynamic biological processes within the hair follicle, revealing crucial cellular kinetics, migratory patterns, and rate of cell divisions that are otherwise impossible to deduce from discrete observations. This approach made it possible to model the forces generated locally."

By tracking living cells over time, researchers were able to observe biological processes that would have remained hidden using conventional methods.

New Possibilities for Hair Loss Research

The study's findings could have important implications for understanding hair loss and developing new therapies.

Dr. Thomas Bornschlögl, another lead author from L'Oréal's Advanced Research team, explained:

"This reveals that hair growth is not driven only by cell division -- instead, outer root sheath actively pull the hair upwards. This new view of follicle mechanics opens fresh opportunities for studying hair disorders, testing drugs and advancing tissue engineering and regenerative medicine."

Scientists increasingly recognize that biological tissues are shaped not only by genes and chemical signals but also by physical forces. Understanding how these forces influence hair growth could help researchers design future treatments that target both the follicle's biochemical environment and its mechanical behavior.

Although the experiments were conducted on human hair follicles grown in laboratory culture rather than directly on people, the findings provide valuable new insights into how hair follicles function.

The researchers also believe their imaging technique could become a powerful tool for evaluating potential hair loss therapies, allowing scientists to observe how living follicles respond to different drugs and treatments in real time.

A New Role for Biophysics in Everyday Biology

Beyond hair research, the study highlights the growing importance of biophysics, a field that explores how physical forces influence living systems.

The results suggest that microscopic mechanical forces can play a major role in shaping organs and tissues throughout the body. In the case of hair growth, what once appeared to be a simple process may actually depend on a highly coordinated cellular machine working behind the scenes.

If confirmed by future research, this newly discovered mechanism could change how scientists understand one of the most familiar biological processes in everyday life.