Polycomb repressive complex 2 in adult hair follicle stem cells is dispensable for hair regeneration

Hair follicle stem cells (HFSCs) are multipotent cells that cycle through quiescence and activation to continuously fuel the production of hair follicles. Prior genome mapping studies had shown that tri-methylation of histone H3 at lysine 27 (H3K27me3), the chromatin mark mediated by Polycomb Repressive Complex 2 (PRC2), is dynamic between quiescent and activated HFSCs, suggesting that transcriptional changes associated with H3K27me3 might be critical for proper HFSC function. However, functional in vivo studies elucidating the role of PRC2 in adult HFSCs are lacking. In this study, by using in vivo loss-of-function studies we show that, surprisingly, PRC2 plays a non-instructive role in adult HFSCs and loss of PRC2 in HFSCs does not lead to loss of HFSC quiescence or changes in cell identity. Interestingly, RNA-seq and immunofluorescence analyses of PRC2-null quiescent HFSCs revealed upregulation of genes associated with activated state of HFSCs. Altogether, our findings show that transcriptional program under PRC2 regulation is dispensable for maintaining HFSC quiescence and hair regeneration.

Micro-Injury Induces Hair Regeneration and Vitiligo Repigmentation Through Wnt/ β-Catenin Pathway

Background: Extrinsic injury can evoke intrinsic stimulation subquently initiate physiological repair process. Several kinds of injury have been studied to promote hair growth and skin pigmentation. In this study, we ask if proper injury could be employed to create local stimuli subsquently to induce hair regeneration and vitiligo repigmentation.Methods: We firstly manufactured a novel designed device to precisely control all micro-injury parameters. Then the most appropriate micro-injury extent was evaluated without over-damage to skin. The effects of micro-injury on hair regeneration and vitiligo repigmentation were examined by macroscopical observation, histological staining, gene and protein expression analysis.Results: We discover that proper micro-injury effectively induces hair regeneration by activating the hair follicle stem cell proliferation and migration downwards to hair matrix, finally shifting the hair follicle stage from telogen into anagen. On vitiligo model mice, micro-injury also induces the hair follicle melanocyte stem cell migrate upwards to interfollicular epidermis, activate and give rise to melanocytes to repopulate vitiligo lesion. Mechanism analysis indicates that the canonical Wnt/b-catenin pathway plays a key role in the micro-injury induced regeneration process. Conclusions: The present study demonstrates that micro-injury has great potential in inducing hair regeneration and vitiligo repigmentation, laid a foundation to develop micro-injury based treatment method in alopecia and vitiligo.