Study Offers New Look at Hair Follicle Mechanics

Newly published research from scientists at Queen Mary University of London and L’Oréal is pushing back on conventional thinking about hair growth.

The researchers say hair is not pushed out of the root. Instead, it is pulled upward by a force associated with a hidden network of moving cells.

Their work was published in a new issue of Nature Communications.

Researchers from L’Oréal Research & Innovation and the University used 3D live imaging to track individual cells within living human hair follicles kept alive in culture. It showed that cells in the outer root sheath move in a spiral downward path within the same region where the upward pulling force originates from.

For decades, it has been assumed that hair was pushed out by the dividing cells in the hair bulb. According to Dr. Inês Sequeira of Queen Mary University, instead it is actively being pulled upwards by surrounding tissue.

Dr. Sequeira, a reader in Oral and Skin Biology at the University, is one of the lead authors of the study.

The study’s first author is Dr. Nicolas Tissot of L’Oréal.

Expecting hair growth to stop, the researchers blocked cell division inside the follicle. But growth continued nearly unchanged. But when they interfered with actin, the hair growth rate dropped by more than 80%, according to a news post from the University. Computer models confirmed that the pulling force, correlated with coordinated motion in the follicle’s outer layers, was essential to match the observed speeds of hair movement.

Researchers used a novel imaging method allowing 3D time lapse microscopy in real-time to show the intricate, dynamic biological processes within the hair follicle. It revealed the “crucial cellular kinetics, migratory patterns, and rate of cell divisions” that are otherwise impossible to deduce from discrete observations, said Tissot.

L’Oréal’s Dr. Thomas Bornschlögl, the other lead author, said the outer root sheath actively pulls 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,” said Bornschlögl.

The research was carried out on human follicles in lab culture.