INTRODUCTION: Hair follicles are skin appendages that undergo periods of growth (anagen), regression (catagen) and rest (telogen) enabled by the stem cell niche within the hair follicle bulge region, regulated by a mesenchymal component the dermal papilla (DP). It is known that the DP is central to hair follicle regulation, however signalling pathways in the DP are complex and not well understood. Expression array analyses of the DP and STAT5 knockout studies suggest that STAT5 may play an important role in the regulation of hair follicle cycling by the DP. We aimed to characterise STAT5 activation within the DP during hair follicle development and cycling.
METHODS: Backskin from Topflash transgenic mice using beta-catenin activity to monitor the hair cycle were obtained at each phase of the hair follicle cycle and stained with a phospho-STAT5 antibody.
RESULTS: Within the hair follicle development (P0-P19), the majority of phospho-STAT5 positive DP were present within the telogen phase, to a lesser extent within catagen and not at all during anagen. Adult skin showed phospho-STAT5 activation beginning in late catagen and persisting until late anagen, with minimal activation during late anagen and early catagen. Staining intensity increased from late catagen through to early anagen. Of note, Phospho-STAT5 could not be retrieved upon telogen to anagen transition induced by hair plucking. Finally, dermal spheroids able to induce hair regeneration displayed active STAT5.
CONCLUSION: Phospho-STAT5 activation may act as a switch to induce natural anagen entry following the first hair follicle cycle.