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Exp Dermatol. 2019 Jan 21. doi: 10.1111/exd.13889. [Epub ahead of print]

Anagen hair follicle repair: timely regenerative attempts from plastic extra-bulge epithelial cells.

Huang WY1, Lin ET1,2, Hsu YC3, Lin SJ1,2,4,5.

Author information

1
Department of Biomedical Engineering, National Taiwan University, Taipei, Taiwan.
2
Department of Dermatology, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan.
3
Department of Stem Cell and Regenerative Biology, Harvard University, and Harvard Stem Cell Institute, Cambridge, MA, 02138, USA.
4
Research Center for Developmental Biology and Regenerative Medicine, National Taiwan University, Taipei, Taiwan.
5
Graduate Institute of Clinical Medicine, College of Medicine, National Taiwan University, Taipei, Taiwan.

Abstract

Anagen hair follicle repair is the regenerative scheme activated to restore the structure and hair growth following injuries to anagen hair follicles. Compared with telogen-to-anagen regeneration and hair follicle neogenesis, anagen hair follicle repair is a clinically important, yet relatively unexplored regenerative feature of hair follicles. Due to their highly proliferative character, germinative cells and matrix cells within hair bulbs are highly susceptible to injuries, such as chemotherapy and radiotherapy. Clinical and experimental observations suggest that damaged anagen hair follicles are able to repair themselves to resume anagen growth, bypassing premature catagen/telogen entry. Mechanistically, extra-bulge epithelial cells in the outer root sheath and the lower proximal cup are quickly mobilized for regeneration. These cells acquire stem cell-like properties, exhibiting high plasticity by breaking lineage restriction to regenerate all cell types in the lower segment of anagen hair follicles. Facilitating extra-bulge epithelial cells' mobilization ameliorates hair loss from chemo- and radio-therapy. On the other hand, quiescent bulge stem cells can also be activated, but only after more severe injuries and with slower activation dynamics. They show limited plasticity and regenerate part of the outer root sheath only. The dysrhythmic activation might render bulge stem cells susceptible to concomitant injuries due to their exit from quiescence. This article is protected by copyright. All rights reserved.

KEYWORDS:

Hair follicle; chemotherapy; radiotherapy; regeneration; stem cell

PMID:
30664259
DOI:
10.1111/exd.13889

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