Textbooks Were Wrong: Human Hair Doesn't Grow the Way Scientists Thought
Arthur T Knackerbracket writes:
Scientists have discovered that human hair does not emerge because it is pushed upward from the root. Instead, it is pulled along by forces generated by a previously unseen network of moving cells. This finding overturns long held ideas in biology and may change how scientists approach hair loss and tissue regeneration.
Researchers from L'Oreal Research & Innovation and Queen Mary University of London used advanced 3D live imaging to observe individual cells inside human hair follicles that were kept alive in laboratory culture. Their study, published in Nature Communications, revealed that cells in the outer root sheath (the layer that surrounds the hair shaft) move in a downward spiral within the same region that produces the upward pulling force responsible for hair growth.
Dr Ines Sequeira, Reader in Oral and Skin Biology at Queen Mary and one of the 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."
[...] Dr. Thomas Bornschlogl, other lead author, from the same L'Oreal team adds: "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."
While the research was carried out on human follicles in lab culture, it offers new clues from hair science and regenerative medicine. The team believes that understanding these mechanical forces could help design treatments that target the follicles physical as well as biochemical environment. Furthermore, the imaging technique developed will allow live testing of different drugs and treatments.
The study also highlights the growing role of biophysics in biology, showing how mechanical forces at microscopic scale shape the organs we see every day.
Reference: "Mapping cell dynamics in human ex vivo hair follicles suggests pulling mechanism of hair growth" by Nicolas Tissot, Gaianne Genty, Roberto Santoprete, et. al., 21 November 2025, Nature Communications. DOI: 10.1038/s41467-025-65143-x
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