Ageing and colony-forming efficiency of human hair follicle keratinocytes. 
The decline of tissue regenerative potential of skin and hair is a hallmark of physiological ageing and may be associated with age-related changes in tissue-specific stem cells and/or their environment.  Human hair follicles (hHF) contain keratinocytes having the property of stem cells such as clonogenic potential.  Growth capacity of hHF keratinocytes shows that most of the colony-forming cells are classified as holoclones, meroclones or paraclones when analysed in a clonal assay (Cell, Volume 76, page 1063).  Despite the well-known impact of ageing on human hair growth, little is known about changes in hHF keratinocyte clonogenic potential with age.  This study aimed at assessing the clone-forming efficiency (CFE) of hHF keratinocytes from three age groups of human donors.  It demonstrates that ageing affects hHF keratinocyte CFE.