P#62  Detailed monitoring of hair cycle transitions in vivo using contrast enhanced phototrichogram

Dominique Van Neste and Yves Demortier. Skinterface, Tournai, Belgium

A technological feasibility study has been performed in order to test whether "capturing" subtle transitions of cycling hair was possible in vivo in the human subject with a non-invasive technique such as the contrast enhanced phototrichogram technique (CE - PTG). Based on monthly follow-up of 3 sites with incipient androgenetic alopecia during 12 consecutive months, it appears that the technique is reproducible with a general coefficient of variation <10% for hair density, anagen percentage. When comparing the averages of semester there was, in the absence of CE, a significant drop in visible hair density was noted in two sites (- 8 to - 3%). This relative change was much smaller in the CE technique (- 4 to - 1%) indicating that, depending on what limits are given to the detection technique, non visible hair does not always mean that hair has disappeared. One site was less sensitive to androgens as indicated by a less than 2% change whatever the photographic technique. Next to this statistical approach, a test-retest sequence with four repeat CE-PTGs at weekly intervals after the baseline PTG allowed us to monitor more than 100 individual hair fibres and to document transitions from anagen into catagen and telogen and finally shedding hair (exogen). These sequential changes are documented for the first time as well as the regrowth of the rapidly thickening fibre during the initial anagen 6 stage. Hence we demonstrate that the process of anagen termination and transition to hair shedding and/or its replacement can happen within a period of one month; during that time interval a thin re-growing hair may show significant thickening as it transits from incipient to mature anagen growth.