The human hair follicle, a bistable organ?

Abstract

The hair cycle and its control remain today an object of debate. A number of factors, which can modulate this process, have been identified but its choreography remains elusive. For years, the hunt for the conductor has been on, but nobody ever caught him. Intuitively, the process being considered as cyclic, an automaton controlling this cycle should be looked for, by analogy with a clock. However, the putative hair follicle oscillator that would control hair cycle failed to be identified and characterized. In fact, we have revealed that human hair follicle has an autonomous behaviour and that the transitions from one phase to the next occur independently for each follicle, after time intervals given stochastically by a lognormal distribution characterized by a mean and a variance. From this analysis, one can conclude that instead of a cyclical behaviour with an intrinsic automaton, a bistable steady state controls human hair follicle behaviour, which under a stochastic way jumps from the dormant to the active steady state and vice versa.