108 Micrografts of human scalp onto nude mice: technical improvement of a human hair growth model in vivo.

D. Van Neste, MB. de Brouwer, T. Leroy, G. Shaker Skinterface sprl, Tournai, Belgium and Hair Technology®, Brussels, Belgium

Several sources of evidence support the use of human scalp grafts onto nude mice as a model for the study of human hair growth ex vivo. Grafted hair follicles showed slowing down of the linear growth rate to 2/3 of the initial value and reduction of the expected life span of the hair follicles (up to 8 months) even though some follicles may engage into a second cycle of hair production. Testosterone conditioning of such mice bearing samples from affected scalp sites (androgenetic alopecia) has been proposed for assessing the efficacy of compounds having anti-androgen activity. At this stage however, information on the % of success of graft take (in terms of grafts and in terms of follicular units) is lacking. In this study we performed micrografts (1 to 3 follicular units - unaffected androgen non sensitive donor site), aiming to document an eventual increase of the success rate usually obtained with the conventional punch grafts (10 to 15 follicles from affected scalp sites). These “micro” samples were implanted in mice and then monitored for hair growth during 7 months. Quantitative data were obtained from phototrichograms performed every month. The analysis of the phototrichograms showed 58.33% productive micrografts compared to the 31.1% ratio obtained from punch grafts. The number of productive follicular units in micrografts reaches 47.22 % of the initially active follicles while only 10.5% follicles remained active with the punch graft method. Our results suggest that the improved grafting method inspired from cosmetic scalp surgery protocols must be further investigated as a clinically relevant experimental model.