Anatomical Science International

, Volume 92, Issue 1, pp 151–158

The arrector pili muscle, the bridge between the follicular stem cell niche and the interfollicular epidermis

  • Niloufar Torkamani
  • Nicholas Rufaut
  • Leslie Jones
  • Rodney Sinclair
Method Paper

DOI: 10.1007/s12565-016-0359-5

Cite this article as:
Torkamani, N., Rufaut, N., Jones, L. et al. Anat Sci Int (2017) 92: 151. doi:10.1007/s12565-016-0359-5


Proximally, the arrector pili muscle (APM) attaches to the follicular stem cell niche in the bulge, but its distal properties are comparatively unclear. In this work, a novel method employing an F-actin probe, phalloidin, was employed to visualize the APM anatomy. Phalloidin staining of the APM was validated by comparison with conventional antibodies/stains and by generating three-dimensional reconstructions. The proximal attachment of the APM to the bulge in 8 patients with androgenic alopecia was studied using Masson’s trichrome stain. Phalloidin visualized extensive branching of the APM. The distal end of the human APM exhibits a unique “C”-shaped structure connecting to the dermal–epidermal junction. The proximal APM attachment was observed to be lost or extremely miniaturized in androgenic alopecia. The unique shape, location, and attachment sites of the APM suggest a significant role for this muscle in maintaining follicular integrity. Proximally, the APM encircles the follicular unit and only attaches to the primary hair follicle in the bulge; this attachment is lost in irreversible hair loss. The APM exhibits an arborized morphology as it ascends toward the epidermis, and anchors to the basement membrane.


Arrector pili muscle Phalloidin Stemcells 

List of abbreviations


Arrector pili muscle


Smooth muscle α-actin


Androgenic alopecia


Follicular unit




Phosphate-buffered saline


Outer root sheath keratinocytes

Copyright information

© Japanese Association of Anatomists 2016

Authors and Affiliations

  1. 1.Department of Dermatology, School of Medicine, Health and DentistryUniversity of MelbourneMelbourneAustralia
  2. 2.Epworth Hospital, Dermatology Research CentreMelbourneAustralia
  3. 3.Dermatology LabEpworth Research InstituteRichmondAustralia

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