Attenuation of Dickkopf 1-Induced Hair Growth Inhibition in Cultured Human Hair Follicles by Tianeptine

Perspectives on miRNAs Targeting DKK1 for Developing Hair Regeneration Therapy

Androgenetic alopecia (AGA) remains an unsolved problem for the well-being of humankind, although multiple important involvements in hair growth have been discovered. Up until now, there is no ideal therapy in clinical practice in terms of efficacy and safety. Ultimately, there is a strong need for developing a feasible remedy for preventing and treating AGA. The Wnt/β-catenin signaling pathway is critical in hair restoration. Thus, AGA treatment via modulating this pathway is rational, although challenging. Dickkopf-related protein 1 (DKK1) is distinctly identified as an inhibitor of canonical Wnt/β-catenin signaling. Thus, in order to stimulate the Wnt/β-catenin signaling pathway, inhibition of DKK1 is greatly demanding. Studying DKK1-targeting microRNAs (miRNAs) involved in the Wnt/β-catenin signaling pathway may lay the groundwork for the promotion of hair growth. Bearing in mind that DKK1 inhibition in the balding scalp of AGA certainly makes sense, this review sheds light on the perspectives of miRNA-mediated hair growth for treating AGA via regulating DKK1 and, eventually, modulating Wnt/β-catenin signaling. Consequently, certain miRNAs regulating the Wnt/β-catenin signaling pathway via DKK1 inhibition might represent attractive candidates for further studies focusing on promoting hair growth and AGA therapy.

Hair Growth Activity of Three Plants of the Polynesian Cosmetopoeia and Their Regulatory Effect on Dermal Papilla Cells

Hair loss is becoming increasingly prevalent as dietary and living habits change. The search for natural products to limit hair loss has led to tapping into traditional cosmetic knowledge. We studied three plants of the Polynesian cosmetopoeia, Bidens pilosa, Calophyllum inophyllum and Fagraea berteroana, to determine their ability to promote hair growth. Their chemical content was characterized by liquid chromatography coupled to mass spectrometry (LC-MS). Their proliferative activity on dermal papilla cells (DPCs) was assessed via MTT assay and molecular targets were evaluated by RT-qPCR analysis of seven factors involved in the modulation of the hair cycle, CCND1, LEF1, DKK1, WNT5A PPARD, TGFΒ1, PPARD and RSPO2. Our results show that our extracts significantly increased proliferation of dermal papilla cells. Furthermore, LC-MS/MS analysis revealed a diversity of molecules, flavonoids, iridoids and organic acids, some known for hair-inducing properties. Finally, specific extracts and fractions of all three plants either upregulated CCND1, LEF1 and PPARD involved in stimulating hair follicle proliferation and/or lowered the gene expression levels of hair growth inhibiting factors, DKK1 and TGFB1. Our findings suggest that extracts from B. pilosa, C. inophyllum and F. berteroana are interesting candidates to stimulate hair growth.

The Wnt/β-catenin signaling pathway is involved in regulating feather growth of embryonic chicks

Avian feathers have robust growth and regeneration capability and serve as a useful model for decoding hair morphogenesis and other developmental studies. However, the molecular signaling involved in regulating the development of feather follicles is unclear. The purpose of this study was to investigate the role of the Wnt/β-catenin pathway in regulating feather morphogenesis in embryonic chicks through in ovo injection of different doses of Dickkopf-1 (DKK1, a specific inhibitor of the target of the Wnt/β-catenin pathway). A total of 120 fertilized embryo eggs were randomly divided into 4 treatments, including a noninjection group (control group) and groups injected with 100 μL of phosphate-buffered saline (PBS)/egg (PBS control group), 100 μL of PBS/egg containing 600-ng DKK1/egg (600-ng DKK1 group), and 100-μL PBS/egg containing 1,200-ng DKK1/egg (1,200-ng DKK1 group). Feathers and skin tissues were sampled on embryonic (E) day 15 and the day of hatching to examine the feather mass, diameter and density of feather follicles, and the protein expression of the Wnt/β-catenin pathway. The results showed that, compared with CON and PBS treatment, the injection of DKK1 into the yolk sac of chick embryos had no significant effect on the hatching rate and embryo weight (P > 0.05), while it significantly decreased the relative mass of feathers in the whole body (P < 0.05). The high dose of DKK1 (1,200-ng DKK1/egg) decreased the relative mass of feathers on the back, chest, belly, neck, wings, head, and legs, which was more obvious than that in the 600-ng DKK1 group, which presented a dose-dependent effect. In addition, DKK1 injection significantly downregulated the protein expression levels of β-catenin, transcription factor 4, Cyclin D1, and c-Myc (P < 0.05). The immunofluorescence result of β-catenin was consistent with the Western blotting assay results. Altogether, these observations suggested that the Wnt/β-catenin signaling pathway is involved in regulating feather follicle development and feather growth during the embryonic development of chicks.

Macrophage-Derived Extracellular Vesicle Promotes Hair Growth

Hair loss is a common medical problem affecting both males and females. Dermal papilla (DP) cells are the ultimate reservoir of cells with the potential of hair regeneration in hair loss patients. Here, we analyzed the role of macrophage-derived Wnts (3a and 7b) and macrophage extracellular vesicles (MAC-EVs) in promoting hair growth. We studied the proliferation, migration, and expression of growth factors of human-DP cells in the presence or absence of MAC-EVs. Additionally, we tested the effect of MAC-EV treatment on hair growth in a mouse model and human hair follicles. Data from western blot and flow cytometry showed that MAC-EVs were enriched with Wnt3a and Wnt7b, and more than 95% were associated with their membrane. The results suggest that Wnt proteins in MAC-EVs activate the Wnt/β-catenin signaling pathways, which leads to activation of transcription factors (Axin2 and Lef1). The MAC-EVs significantly enhanced the proliferation, migration, and levels of hair-inductive markers of DP cells. Additionally, MAC-EVs phosphorylated AKT and increased the levels of the survival protein Bcl-2. The DP cells treated with MAC-EVs showed increased expression of vascular endothelial growth factor (VEGF) and keratinocyte growth factor (KGF). Treatment of Balb/c mice with MAC-EVs promoted hair follicle (HF) growth in vivo and also increased hair shaft size in a short period in human HFs. Our findings suggest that MAC-EV treatment could be clinically used as a promising novel anagen inducer in the treatment of hair loss.