• DNA fragments;
  • hair follicle;
  • MC-1R;
  • melanocyte;
  • tyrosinase

Abstract:  It was previously reported that telomere homologue oligonucleotides (T-oligos) can induce a variety of cellular responses in skin including increased melanogenesis. To assess the effects of T-oligos on hair pigmentation, we administered thymidine dinucleotide (pTT), one-third of the TTAGGG telomere repeat sequence, intradermally at distinct time points of the depilation-induced hair cycle in C3H/HeJ mice. Penetration of T-oligos into the hair follicle (HF) was monitored by using FITC-labelled pTT and confocal microscopy. pTT treatment on days 1–5 after depilation, during early anagen, did not significantly alter the number and proliferation of melanocytes (Trp-2-positive cells), compared with vehicle-treated controls. However, pTT treatment on days 5–12 after depilation, during mid- to late anagen, resulted in the formation of darker hairs, that showed a significantly increased eumelanin/total melanin ratio in their sub-apical agouti band region, compared with vehicle-treated controls (P < 0.05). By RT-PCR and western blot, full thickness skin of pTT-treated mice showed increases in Trp-1, Trp-2 and tyrosinase mRNA and protein levels, compared with control mice. Western blot analyses of two receptors that positively regulate eumelanogenesis, melanocortin type 1 receptor (MC-1R) and kit, showed increased expression of MC-1R protein in pTT-treated versus control skin, while the levels of c-kit receptor remained unchanged. These data demonstrate that pTT treatment increases eumelanogenesis in HFs, associated with increased tyrosinase, TRP-1 and MC-1R expression. These data also raise the possibility of using T-oligos to modulate hair pigmentation.