Cellular organization of the human epidermal basal layer: Clues sustaining a hierarchical model

Abstract

Purpose: The basal layer of adult interfollicular epidermis is a highly dynamic cellular system, ensuring the continuous physiological renewal of this tissue, as well as regenerative processes in the context of wound healing. In human skin, despite its major importance for the maintenance of epidermal homeostasis and regenerative processes, the functional organization of basal keratinocytes is still debated today. Progress in this understanding is closely linked to the development of research models enabling investigations of the different coexisting basal keratinocyte subpopulations, to address their specific functional and molecular characteristics, particularly through clonal analyses. We review here different strategies that have led to significant advances in the knowledge of human basal keratinocyte properties, at both phenotypic and functional levels.

Conclusions: Convincing clues supporting a hierarchical organization of the keratinocyte basal layer in humans have emerged from the different functional studies. In particular, the hierarchical model constitutes a straight forward interpretation of the clearly non-equivalent potentialities observed when basal keratinocytes were studied individually in a cell culture context.

Keywords::

• Epidermis
• human
• stem cells
• hierarchy
• single-cell assay

Acknowledgements

The authors wish to thank AFM-Myobank (La Pitié-Salpêtrière Hospital, Paris) and Dr Hafez Serhal (Clinique de l’Essonne) for providing the biopsies of normal adult human skin necessary for their researches. The authors also thank Mr Stéphan Bouet from the ‘French National Institute for Agricultural Research’ (INRA), Jouy-en-Josas, for the preparation of histological tissue sections. Financial supports have been received from the French ‘National Research Agency’ (ANR) grant Lodora, CESA-024-04, and the ‘Association pour la Recherche sur le Cancer’ (ARC). Current financial supports are received from the French ‘Alternative Energies and Atomic Energy Commission’ (CEA), and French ‘Agency for Food, Environmental and Occupational Health & Safety’ (ANSES) [LOWRADSENSOR grand no. EST-2011/1/050].

Declaration of interest

The authors report no declaration of interest. The authors alone are responsible for the content and writing of the paper.