A systematic summary of survival and death signalling during the life of hair follicle stem cells

Abstract

Hair follicle stem cells (HFSCs) are among the most widely available resources and most frequently approved model systems used for studying adult stem cells. HFSCs are particularly useful because of their self-renewal and differentiation properties. Additionally, the cyclic growth of hair follicles is driven by HFSCs. There are high expectations for the use of HFSCs as favourable systems for studying the molecular mechanisms that contribute to HFSC identification and can be applied to hair loss therapy, such as the activation or regeneration of hair follicles, and to the generation of hair using a tissue-engineering strategy. A variety of molecules are involved in the networks that critically regulate the fate of HFSCs, such as factors in hair follicle growth and development (in the Wnt pathway, Sonic hedgehog pathway, Notch pathway, and BMP pathway), and that suppress apoptotic cues (the apoptosis pathway). Here, we review the life cycle, biomarkers and functions of HFSCs, concluding with a summary of the signalling pathways involved in HFSC fate for promoting better understanding of the pathophysiological changes in the HFSC niche. Importantly, we highlight the potential mechanisms underlying the therapeutic targets involved in pathways associated with the treatment of hair loss and other disorders of skin and hair, including alopecia, skin cancer, skin inflammation, and skin wound healing.

Transcriptional Differences in Lipid-Metabolizing Enzymes in Murine Sebocytes Derived from Sebaceous Glands of the Skin and Preputial Glands

“…For a more detailed characterization, we subclustered SEB yielding five distinct SEB subpopulations in skin SGs and three in PGs ( Figure 2 A). Closer characterization of the subpopulations present in the skin showed high expression levels of the hair follicle (HF)-associated genes, such as Krt27 , Krt17 , Hoxc13 and Wnt5a in the major three subpopulations (HF/SEB1, HF/SEB2, HF/SEB3) ( Supplementary Figure S2 ) [ 55 , 56 , 57 , 58 , 59 , 60 , 61 ]. The two main clusters in PG were identified as early SEB and late SEB and were both also found in the skin, though at significantly smaller numbers.…”

Epithelial-Mesenchymal Interaction in Hair Regeneration and Skin Wound Healing

“…During the hair cycle, the hair matrix expresses Wnt3a and Wnt10b, and DP responds to Wnt pathway signals to activate HF epithelial cells ( 3 , 20 , 22 ). Matrix proliferation requires epithelial Wnt/β-catenin; inhibiting β-catenin or exogenously adding Dickkopf (Dkk) can inhibit matrix growth and anagen processing ( 23 ).…”

“…Simultaneously, Wnt signaling controls the activity of hair sheath-specific signals, showing its function in HFSC-specific differentiation ( 24 , 25 ). Furthermore, epithelial Wnt signaling is involved in DP-inducible properties, and experiments found that the addition of Wnt3a rebuilt the inducibility of DP that has been lost in vitro in both mice and human tissues ( 22 , 26 ).…”

Transcriptional differences of lipid-metabolizing enzymes in sebocytes derived from sebaceous glands of the skin and pre-putial glands

“…For a more detailed characterization, we subclustered SEB yielding five distinct SEB subpopulations in skin SGs and three in PGs (Figure 2A). Closer characterization of the subpopulations present in the skin showed high expression levels of hair follicle (HF)-associated genes, such as Krt27, Krt17, Hoxc13 and Wnt5a in the major three subpopulations (HF/SEB1, HF/SEB2, HF/SEB3) (Supplementary Figure 2) [55]- [61]. The two main clusters in PG were identified as early SEB and late SEB, and were both also found in the skin, though at significantly smaller numbers.…”