Human epithelial stem cell survival within their niche requires "tonic" cannabinoid receptor 1-signalling-Lessons from the hair follicle

Research output: Contribution to journalArticlepeer-review

  • External authors:
  • Koji Sugawara
  • Nóra Zákány
  • Stephan Tiede
  • Matthew Harries
  • Daisuke Tsuruta
  • Tamás Bíró


The endocannabinoid system (ECS) regulates multiple aspects of human epithelial physiology, including inhibition/stimulation of keratinocyte proliferation/apoptosis, respectively. Yet, how the ECS impacts on human adult epithelial stem cell (eSC) functions remains unknown. Scalp hair follicles (HFs) offer a clinically relevant, prototypic model system for studying this directly within the native human stem cell niche. Here, we show in organ-cultured human HFs that, unexpectedly, selective activation of cannabinoid receptor-1 (CB1)-mediated signalling via the MAPK (MEK/Erk 1/2) and Akt pathways significantly increases the number and proliferation of cytokeratin CK15+ or CK19+ human HF bulge eSCs in situ, and enhances CK15 promoter activity in situ. In striking contrast, CB1-stimulation promotes apoptosis in the differentiated progeny of these eSCs (CK6+ HF keratinocytes). Instead, intrafollicular CB1 gene knockdown or CB1 antagonist treatment significantly reduces human HF eSCs numbers and stimulates their apoptosis, while CB1 knockout mice exhibit a reduced bulge eSCs pool in vivo. This identifies "tonic" CB1 signalling as a required survival stimulus for adult human HF eSCs within their niche. This novel concept must be taken into account whenever the human ECS is targeted therapeutically.

Bibliographical metadata

Original languageEnglish
JournalExperimental Dermatology
Early online date1 Feb 2021
Publication statusPublished - 26 Feb 2021