Hormonal regulation of human hair follicle epithelial stem cell functions in situ and in vitro

  • Stephan Tiede, Department of Dermatology, University of Lübeck, Lübeck, Germany
  • Katrin Bohm, Department of Dermatology, University of Lübeck, Lübeck, Germany
  • Yuval Ramot, Department of Dermatology, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
  • Christian Plate, Department of Dermatology, University of Lübeck, Lübeck, Germany
  • Ralf Paus, Department of Dermatology, University of Lübeck, Lübeck and School of Translational Medicine, University of Manchester, Germany

Objective: The hormonal controls of adult epithelial stem cells in situ are largely unknown. Here, we investigated (neuro-)endocrine controls of normal adult human hair follicle epithelial stem cells (eHFSCs) as a model to characterize these controls in situ and in vitro.
Methods: Non-retroviral transfection of a human K15-promotor-GFP/geneticin-resistance expression system in microdissected, organ-cultured adult human scalp skin HFs generates specific K15-promoter-driven GFP expression in bulge eHFSCs in situ or in isolated K15-GFP+progenitors in vitro. This novel tool was used to investigate the influence of thyroid hormones (THs), thyrotropin (TSH), thyrotropin-releasing-hormone (TRH), calcitriol, and prolactin (PRL) on selected eHFSCs functions in situ and in vitro.
Results: THs up-regulate K15-promoter activity, K15 transcription and protein expression in eHFSCs in situ and in vitro. Moreover, THs reduce the colony forming efficiency (CFE), proliferation, viability and induce apoptosis in cultured K15-GFP+ progenitors. THs may also induce epithelial-mesenchymal-transition, indicated by fibroblastoid morphology and vimentin expression, and up-regulates expression of the immuno-inhibitory eHFSCs marker CD200 in situ and in vitro. THs accelerates TSH-beta-receptor expression, and become sensitive to TSH stimulation, which induces K15-GFP+progenitors to differentiate along the keratinocyte lineage and to express e.g. keratin-6. While TRH demonstrated no effects on eHFSCs in situ, influences, TRH induced proliferation and differentiation in isolated K15-GFP+progenitors. Calcitriol induced morphological changes, up-regulated vitamin-D-receptor and CD200 expression and impaired both CFE and proliferation. Finally, PRL up-regulated K15-promoter-driven GFP expression in the HF bulge region and extended the area K15-promoter activity beyond the bulge region, and stimulated K15 protein expression.
Conclusions: We document that human eHFSCs underlie prominent (neuro-)endocrine controls, not only by classical steroid hormones but also by peptide neurohomones. This encourages one to systematically explore the impact of these hormonal controls on human epithelial stem cells in situ and in vitro and to explore how these may be clinically exploited.