In situ [3H]thymidine labelling of human hair papilla: an in vitro autoradiographic study.

The labelling index (LI) and the location of labelled cells in the papilla of human anagen scalp hair have been studied after in vitro [3H]thymidine (3H-TdR) pulse labelling. Forty-three anagen stage VI papillae from 2 individuals (both females, 25 and 55 years) obtained by micropreparation from deep scalp biopsies were analysed. Labelled cells were found only paraaxially in the basal third of the papilla, i.e. below Auber's line. The 3H-TdR-LI of the papilla cells (0.13 and 0.16%) is about 200-times lower than that of the hair matrix cells below the line of Auber (25.5 and 29.5%). The biological significance of this low proliferation rate in the anagen stage VI hair papilla of healthy human should be defined.