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Hair Growth in Action

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Science Translational Medicine  11 Jul 2012:
Vol. 4, Issue 142, pp. 142ec124
DOI: 10.1126/scitranslmed.3004561

It’s easy to see when your hair has been growing and is in desperate need of a trim. But, what’s going on beneath the surface—in the hair follicle—is more of a mystery. To reveal the cellular mechanisms of hair growth, Rompolas and colleagues used two-photon microscopic imaging in the skin follicles of live mice. This microscopic technique allowed them to see individual stem cell contributions to hair regeneration in both space and time.

The authors used a type of mouse in which skin cell nuclei fluoresced, thus making them easy to see. A glass cover slip was placed between the head and the ear of the living mice in order to visualize proliferation and organization over the course of hours in distinct cell compartments of the follicle: stem cells (the “bulge”), their progeny, and the mesenchyme (also called the “dermal papilla”). Rompolas et al. discovered that the most proliferation occurred at the interface of the progeny and mesenchyme, at the bottom of the follicle, with the axis of cell division running parallel to the direction of hair growth. Progeny nuclei migrated downward during hair growth, and stem cells in the bulge showed a slight upward migration. This suggests that cells not only divide during hair growth but also rearrange and adjust their architecture, the temporal dynamics of which only live-imaging could capture. Lastly, the authors investigated the role of the mesenchyme by removing the dermal papilla with a laser. Follicles with disrupted dermal papilla appeared to be quiescent, or unable to grow, indicating the importance of epithelial-mesenchymal interactions for stem cell activation.

Being able to visualize hair growth in action has provided skin-deep insight into the organization and behavior of stem cells in the follicle. Albeit all in mice, these observations by Rompolas and coauthors could have implications for the use of stem cells in regenerative medicine in people.

P. Rompolas et al., Live imaging of stem cell and progeny behaviour in physiological hair-follicle regeneration. Nature, 1 July 2012 (10.1038/nature11218). [Abstract]

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