The neuroepithelial stem cell protein nestin is a marker of the companion cell layer of the adult and developing human hair follicle.
BACKGROUND
The interface between the inner root sheath (IRS) and the outer root sheath (ORS) represents a slippage plane for the hair shaft to evolve from the pilar canal to the skin surface. Interposed between the IRS and ORS is a single cell layer which is believed to represent the angle point of that slippage plane, termed the companion cell layer (CCL). The CCL is cited in most of the literature as part of the ORS.


OBJECTIVE
To describe the expression pattern of nestin, a neuroepithelial stem cell protein, in the adult and developing human hair follicle.


METHODS
Immunohistochemical evaluation with a monoclonal antibody against nestin was performed using standard techniques.


RESULTS
Nestin is selectively expressed in the CCL of the adult anagen and late stage fetal hair follicles. Early stages of hair follicle development are negative for nestin expression.


CONCLUSIONS
The selective demarcation of the CCL by nestin highlights the unique feature of this follicular cell layer and raises the question of whether the CCL should not be better conceptualized as a part of the IRS rather than the ORS. The results of the present study, together with published ultrastructural data, also suggest that the slippage plane for the evolving hair shaft may be located at the interface between the CCL and the ORS.
Institut für Dermatohistologie, Heidelberg, Germany.
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Krahl
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Sellheyer
D000328:Adult; D015415:Biomarkers / Q000378:metabolism; D064032:Calbindin 2; D018859:Hair Follicle / Q000166:cytology* / Q000254:growth & development / Q000378:metabolism*; D006801:Humans; D007381:Intermediate Filament Proteins / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D064231:Nestin; D064030:S100 Calcium Binding Protein G / Q000378:metabolism
D015415:Biomarkers; D064032:Calbindin 2; D007381:Intermediate Filament Proteins; C577484:NES protein, human; D009419:Nerve Tissue Proteins; D064231:Nestin; D064030:S100 Calcium Binding Protein G