Presence of amelanotic melanocytes within the outer root sheath in senile white hair.

In order to determine whether amelanotic melanocytes are present in senile white hair, we attempted to detect tyrosinase mRNA and its protein using in situ hybridization and immunohistochemical staining. Specifically stained cells containing tyrosinase mRNA or its protein were detected by each technique in 7/23 (30.4%) or 4/14 (28.6%) senile white hairs, respectively. These cells were located in the outer root sheath between the hair-bulb and the infundibulum. Silver staining was used to determine whether melanin was present within the outer root sheath of the senile white hair. Because none of the 21 white hairs tested showed specific staining within the outer root sheath, the absence of melanin was confirmed. Thus our results suggest the presence of amelanotic melanocytes within the outer root sheath of senile white hair.