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

  title={The arrector pili muscle, the bridge between the follicular stem cell niche and the interfollicular epidermis},
  author={Niloufar Torkamani and Nicholas Wolfgang Rufaut and Leslie Norman Jones and Rodney Daniel Sinclair},
  journal={Anatomical Science International},
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… 

Mechanical forces in skin disorders.

Adipose Infiltration of the Dermis, Involving the Arrector Pili Muscle, and Dermal Displacement of Eccrine Sweat Coils: New Histologic Observations in Frontal Fibrosing Alopecia.

New histologic findings in FFA involve the presence of adipose tissue in the dermis, and it is believed that the close interaction of the hair follicles and the APM with the adipose tissues may play a role in APM degeneration and in epithelial mesenchymal transition.

Hair follicle stem cells as a skin‐organizing signaling center during adult homeostasis

Taken together, the HFSCs emerge as a skin‐organizing center rich in signaling output for niche remodeling during various stages of adult skin homeostasis and adds important insight to skin biology that will inform clinical and bioengineering fields aiming to build complete and functional 3D organotypic cultures for skin replacement therapies.

Following historical “tracks” of hair follicle miniaturisation in patterned hair loss: Are elastin bodies the forgotten aetiology?

It is proposed that alterations in elastin architecture may contribute to the failure of vellus‐like hair reverting back to their terminal status and may indicate a new area for therapeutic intervention.

The Hair Follicle: An Underutilized Source of Cells and Materials for Regenerative Medicine.

The structure of a hair follicle is provided, the role of the follicle in regulating the microenvironment of skin and the impact on wound healing, individual cell types of interest for regenerative medicine are explored, and several applications of keratin-based biomaterials are covered.

Decreased expression of cytokeratin 15 and tropoelastin in men with androgenetic alopecia and its relationship with increased expression of p15/p16

The results suggest that patients with AGA suffer tissue damage that affects different components of hair follicle stem cells as well as the extracellular matrix itself.

Hair follicle stem cells promote cutaneous wound healing through the SDF-1α/CXCR4 axis: an animal model.

Based on the findings of this study, HFSC transplantation affects wound closure parameters and the expression of SDF-1α and CXCR4 in the injured area, the HFSCs contribute to wound repair through the SDF -1α/CX CR4 axis.

Histological and functional comparisons of four anatomical regions of porcine skin with human abdominal skin

Results showed that all four regions of porcine skin were similar to human skin, including the shapes of keratinocytes, structure of cell contacts and presence of Weibel Palade bodies in endothelial cells.



The microanatomy of the distal arrector pili: possible role for alpha1beta1 and alpha5beta1 integrins in mediating cell-cell adhesion and anchorage to the extracellular matrix.

Analysis of the relative density of immunoreactivity in digitized sections revealed increased alpha5 subunit expression at the extracellular matrix (ECM)-muscle interface, which suggests that anchorage of the AP muscle to the ECM is via alpha5beta1 integrin and alpha1beta1 Integrin functions in muscle cell-cell adhesion.

The Arrector Pili Muscle and the Follicular Unit of the Scalp: A Microscopic Anatomy Study

  • E. PobletF. OrtegaF. Jimenez
  • Biology
    Dermatologic surgery : official publication for American Society for Dermatologic Surgery [et al.]
  • 2002
At the isthmus level, above their follicular attachments, the arrector pili muscles that originate from their respective follicles join together, forming a single muscular structure that extends upward to its superior attachment zone.

A new model for the morphology of the arrector pili muscle in the follicular unit based on three‐dimensional reconstruction

The classic anatomy of the AP muscle must be modified with this new model, now confirmed by computer‐based 3D reconstruction of serially sectioned images.

Beyond Goosebumps: Does the Arrector Pili Muscle Have a Role in Hair Loss?

The arrector pili muscle (APM) consists of a small band of smooth muscle that connects the hair follicle to the connective tissue of the basement membrane, and the relationship between the follicular unit and the APM is discussed.

Immunofluorescent microscopic investigation of the distal arrector pili: a demonstration of the spatial relationship between alpha5beta1 integrin and fibronectin.

The anatomic co-localization between alpha5beta1 and fibronectin strengthens the hypothesis that interaction of these epitopes mediates the attachment of the distal AP to the ECM.

Merkel cells participate in the induction and alignment of epidermal ends of arrector pili muscles of human fetal skin

In vertical sections of the scalp skin of 16‐week‐old fetus, double immunoenzyme staining showed a close topographic correlation between the epidermal ends of the arrector pili muscles and the epidersmal and dermal Merkel cells, which allow speculation that fetal Merkel cells participate in the induction and alignment of arrecto-pili muscles.

Miniaturized Hairs Maintain Contact with the Arrector Pili Muscle in Alopecia Areata but not in Androgenetic Alopecia: A Model for Reversible Miniaturization and Potential for Hair Regrowth

Replacing contact between miniaturized follicles in AA could explain the complete hair regrowth while loss of contact between the APM and the bulge in MPHL and FPHL may explain why the hair loss is largely irreversible.

Detailed histological structure of human hair follicle bulge region at different ages: A visible niche for nesting adult stem cells

The results indicated that these cell-protrusions function as a niche house for the myriad stem cells and/or precursors to meet the needs of the development of hair follicles in an embryo.

Epidermal Cells Expressing Putative Cell Markers in Nonglabrous Skin Existing in Direct Proximity with the Distal End of the Arrector Pili Muscle

It is found that epidermal cells expressing stem cell markers in nonglabrous skin exist in direct connection with the distal end of the arrector pili muscle, which supports the hierarchical model of interfollicular epidersmal stem cell units of Fitzpatrick.

The ‘follicular trochanter’: an epithelial compartment of the human hair follicle bulge region in need of further characterization

The morphology and immunoreactivity patterns of a largely forgotten, peculiar epithelial protrusion of the outer root sheath, the ‘follicular trochanter’, are described.