Role of Notch and Wnt Signaling in Differentiation of Human Hair Follicle Stem Cells

Stem cells of the hair follicle have significant therapeutic applications in regenerative medicine as a stem cell resource for transplantation. The differentiation pathway of hair follicle stem cells (HFSCs) is largely determined by local microenvironmental signals. In this study, human HFSCs were treated with Notch and Wnt signaling activator to explore an innovative approach in modulating human HFSC proliferation and differentiation in vitro. Human HFSCs were transduced with the constitutively active human Notch-1 intracellular domain (N1ICD) and Wnt10b vector to activate the Notch and Wnt signaling. The viability of the cells was investigated by clonogenic assays. The expression of stem cell markers, cell cycle, and cell apoptosis were analyzed by flow cytometry. Notch activation lead to inhibition of human HFSC proliferation on N1ICD transduction. Cells treated with Wnt10b had a high self-renewal ability and could form significantly more and larger colonies. Thus, Wnt10b treated cells underwent a significantly lower level of apoptosis compared to the N1ICD treated cells. Cell cycle analysis after Notch activation showed 7% of cells in the S-phase, while in Wnt10b transduced group, 39.92% of cells were in the S-phase. N1ICD transfection resulted in the upregulation of Hes1 and p21 levels. Wnt-10b had an opposite regulatory effect on Hes1 and p21 compared to the expression levels of the N1ICD transfection group. The activation of Notch and Wnt signaling had a regulatory effect on human HFSCs, and crosstalk between Notch and Wnt-inducing effects may be associated with p21.