The study, published in the journal Nature Communications, was based on three-dimensional live imaging techniques of lab-grown hair follicles. These techniques showed that what happens under each hair is an integrated system of movement, precise forces, and harmonious cellular organization.
Hair Growth
The prevailing view previously was that hair grows as a result of cell proliferation at the bottom of the hair and pushing it upwards. However, the researchers noticed that the outer layers of the follicle slide downwards in helical movements, while the inner layers are pulled upwards with an active tensile force.
Dr. Ines Sequeira from Queen Mary University of London said:
“It has always been thought that hair is pushed out by cell division.”
“But we discovered that it is actually pulled upwards by the surrounding tissues.”
“It’s as if there is a tiny engine inside the follicle.”
The study also showed that internal cells rise at different speeds; cortical cells ascend at a steady pace, while parts of the inner sheath move much faster.
Experiments showed that the ascending movement continues even when cell division is pharmacologically disabled, confirming that growth does not depend solely on the pressure resulting from cellular proliferation.
The researchers identified a pivotal role for actin protein networks in generating tensile force; disrupting these networks resulted in a decrease in hair growth of more than 80%.
Dr. Nicolas Tissier from L’Oréal Research Laboratories said:
“Three-dimensional real-time imaging has enabled us to see cellular dynamics that cannot be observed with traditional images.”
Scientists confirm that this discovery opens new horizons in understanding hair loss disorders, developing drug treatments, and tissue engineering and regenerative medicine techniques, by targeting the pulling mechanism instead of merely stimulating cell division.
