Hair Growth Study Suggests a Pulling Force Inside Human Follicles

A study of human hair follicles cultured outside the body suggests that hair growth involves a pulling force from surrounding cells, alongside cell division. The finding adds a mechanical explanation for how the hair fiber moves outward; it does not show that hair grows independently of producing new cells.

What the researchers observed

Researchers from L'Oréal Research & Innovation and Queen Mary University of London used three-dimensional live imaging to track cells in growing human hair-follicle segments. They observed spiral-like downward movement in cells of the outer root sheath, a layer around the inner follicle structures.

The team combined these observations with experiments affecting cell division and actin activity, plus fluid-dynamics modeling. Actin is involved in cellular movement and force generation. The results supported a model in which force from the outer root sheath contributes to the hair fiber's outward movement.

Why live imaging matters

A static microscope image shows where cells are at one moment. Tracking them over time helps reveal which layers move, their direction, and how those movements relate to growth. The study's contribution is this map of cell dynamics and a proposed mechanism supported by experiments, rather than a simple replacement of every previous explanation of hair biology.

The paper, Mapping cell dynamics in human ex vivo hair follicles suggests pulling mechanism of hair growth, was published in Nature Communications on November 21, 2025. Queen Mary also published a summary of the research.

What the study does not establish

The experiments used laboratory-cultured follicles, not a clinical trial of a hair-loss treatment. Cultured tissue cannot reproduce every aspect of a living scalp or the full hair cycle. The results may guide further research into follicle mechanics, but they do not prove that a product or procedure can regrow hair.

Hair movement and hair color are different questions. For related background, see why hair turns gray. A finding about movement within the follicle should not be treated as a treatment recommendation or a claim about pigmentation.