Transforming growth factor-β receptor II is preferentially expressed in the companion layer of the human anagen hair follicle

• Published in: British journal of dermatology (1951) Vol. 157; no. 1; pp. 161 - 164
• Main Authors: Sowden, H.M., Karoo, R.O.S., Tobin, D.J.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01-07-2007; Blackwell
• Subjects: Apoptosis - physiology; Biological and medical sciences; companion layer; Dermatology; Female; Fluorescent Antibody Technique - methods; hair follicle; Hair Follicle - metabolism; Humans; Male; Medical sciences; Protein-Serine-Threonine Kinases; Receptors, Transforming Growth Factor beta - metabolism; Scalp - metabolism; transforming growth factor-β receptors; Human; Anagen phase; companion layer; Dermatology; Transforming growth factor β; Hair follicle; Layer; transforming growth factor-β receptors
• ISSN: 0007-0963; 1365-2133
• DOI: 10.1111/j.1365-2133.2007.07925.x

Summary
Background  Transforming growth factor (TGF)‐β is a multifunctional growth factor with multiple roles in skin including hair follicle development and cycling, where it regulates cell proliferation, differentiation and apoptosis, as well as in wound healing. While TGF‐β receptor I (TGF‐β RI) and receptor II (TGF‐β RII) expression helps define early human hair follicle morphogenesis, expression in the adult human hair follicle remains to be established.
Objectives  To assess TGF‐β receptor expression in human scalp anagen hair follicles.
Methods  Immunohistochemical and double immunofluorescence analysis of TGF‐β RI and RII was conducted on frozen sections of haired human scalp obtained from 10 healthy individuals.
Results  TGF‐β RI expression was detected in the outer root sheath of anagen hair follicles while TGF‐β RII was expressed almost exclusively in the companion layer of inner root sheath and less so in premedulla keratinocytes. Both receptors were colocalized in the companion layer of the proximal and mid follicle.
Conclusions  The well‐described role of TGF‐β in keratinocyte apoptosis during catagen is likely to involve anagen‐specific hair follicle components including the companion layer, as this layer provides the slippage plane supporting the inner root sheath and hair shaft as they ascend to the skin surface. Results of this study suggest that the colocalization of TGF‐β RI/RII complexes at the companion layer would facilitate TGF‐β signalling at this site to regulate apoptosis of the companion layer keratinocytes, facilitating shrinkage/contraction of this cell layer during hair follicle regression/catagen.