Pro-inflammatory cytokine cascade in human plucked hair

Using reverse transcriptase polymerase chain reaction we showed that freshly plucked human anagen hair expressed both type 1 (80 kD) and type 2 (60 kD) interleukin (IL)-1 receptor mRNAs. The IL-1 receptor type 1 was functional since after in vitro stimulation of plucked hair with IL-1 alpha, we observed the induction of mRNA(s) for the inflammatory cytokines IL-1 beta, tumour necrosis factor alpha and IL-6 as well as for the chemokines monocyte chemotactic and activating factor and IL-8. In addition, the growth of dissected human anagen hairs in culture in vitro was significantly and dose-dependently inhibited by IL-1 alpha as a consequence of hair bulb degradation. These observations, together with those of other authors in IL-1 alpha transgenic mice evidence the inhibitory role of IL-1 on human hair growth. Therefore, in order to identify individuals with high inflammatory potential in their hair follicle environment, we designed a rapid and simple assay to detect variations in the level of IL-1 alpha production in the overnight supernatant of plucked hairs in culture. We observed that 32.7% of the specimens from the volunteers tested (n = 116) could be considered highly inflammatory in terms of IL-1 alpha production. Altogether, these results suggest that in alopecia androgenetica, hair growth might be negatively influenced by IL-1, directly produced by the outer root sheath keratinocytes. Consequently, identifying the "inflammatory alopecic individual' might be of clinical interest to discriminate among individuals for whom anti-IL-1 strategies might be of therapeutic relevance.