Immunolocalization of telomerases in human hairs identifies proliferating cells in the bulb matrix and outer root...

Telomerase is present in cells with numerous or even un-limited replicative cycles, and some studies suggest it is a stemness marker. In order to determine whether this is the case for the human hair bulbs, an immunohistochemical and ultrastructural study has been carried out using antibodies against telomerase and PCNA (a cell proliferation marker). The observed labeling is similar for the two antibodies here utilized and is mainly nuclear. More frequent telomerase-positive cells are seen in the matrix epithelium of anagen hair bulbs but sparse labeled cells are also seen in the outer root sheath. In late catagen and also in telogen hair follicles only sparse labeled cells are present in the outer root sheath and few cells also in the secondary germinal epithelium formed at the base of the hair bulb in telogen. Electron microscopic immunogold shows a prevalent nuclear distribution and a lower cytoplasmic distribution in sparse cells of anagen bulb matrix that contain few keratin bundles. The nuclear localization is generally seen over the euchromatin or in areas occupied by more compact chromatin that may indicate an activity of telomerase in chromatin assemblage or dis-assemblage. The study concludes that the localization of telomerase is present in cells undergoing proliferation, namely transit amplifying cells of the outer root sheath that are sparsely detected in the lowermost secondary germinal hair bulb also in telogen.