Strategic Targets in Acne: The Comedone Switch in Question.

The sequence of events and mechanisms leading to the development of the primary acne lesion, the comedone, is revisited. Recent knowledge obtained both from lineage tracing experiments in the mouse and the pilosebaceous response to xenobiotics in humans provides robust models for further understanding key biological events at the cellular roots of comedogenesis. The focus is set on the LRIG1+ sebaceous stem cells in the isthmus of the pilosebaceous duct. The master switch that transforms a normally functioning sebaceous gland into a microcomedone and the hierarchy of factors involved in this process are reviewed. The key strategic target in acne care appears to be the naïve pilosebaceous follicle that is not involved yet in the acne cycle. The prevention of the comedone switch implies that the key switching factors are adequately controlled in the long term.