INTRODUCTION
Recent reports show a significant increase in the number of people with alopecia (Jang et al., 2013). In the skin of alopecia patients, many hair follicles overstay in their resting stage in which dermal papilla (DP) cells and keratinocytes, the two key players of hair cycle regulation, are inactive (Alonso & Fuchs, 2006; Botchkarev & Kishimoto, 2003; Sennett & Rendl, 2012). Inactivation of these cells is caused by various factors, and the inactivation leads to miniaturized hair follicles, resulting hair loss (Kligman, 1959; Price, 1999). Even though researchers have focused on developing drugs to cure alopecia, only two drugs, minoxidil (MNX) and finasteride, have been approved by the US Food and Drug Administration for clinical treatment of androgenic alopecia (Libecco & Bergfeld, 2004; Linas & Nies, 1981; Price, 1999). Although both drugs are effective in promoting hair growth, neither can initiate hair follicle neogenesis effectively due to complicated process of the hair regeneration (Paus, 2006).
Wnt/β-catenin signaling pathway plays an important role in hair morphogenesis, growth initiation, and regeneration (Andl, Reddy, Gaddapara, & Millar, 2002; Huelsken, Vogel, Erdmann, Cotsarelis, & Birchmeier, 2001; Iida, Ihara, & Matsuzaki, 2007; Ito et al., 2007; Kishimoto, Burgeson, & Morgan, 2000). The activated Wnt/β-catenin signaling pathway initiates embryonic hair formation in the epidermis and promotes the formation of dermal condensates (Andl et al., 2002; Huelsken et al., 2001). In addition, DP cells require activation of this pathway to initiate hair-inducing activity that prolongs the anagen phase (Kishimoto et al., 2000). The hair-inducing ability of DP cells can be confirmed by analyzing the expression of alkaline phosphatase (ALP) (Iida et al., 2007; S. H. Lee et al., 2012). Recent studies showed that the activation of Wnt/β-catenin signaling can recover ALP expression in long-term cultured primary DP cells (Yamauchi & Kurosaka, 2009).
Hair growth promoting drugs targeting Wnt/β-catenin signaling are not currently available. However small molecules are needed that, unlike MNX, can activate this pathway to enhance hair follicle neogenesis (S. H. Lee et al., 2017).
KY19382 is, one of the newly synthesized analogs of indirubin-3’-monoxime (I3O), a glycogen synthase kinase-3β (GSK-3β) inhibitor, and has a significant ability to activate the Wnt/β-catenin signaling. Indirubin is an active ingredient of the indigo plant, Danggui Longhui Wan, used as a traditional anti-leukemia medicine (Xiao, Hao, Liu, & Qian, 2002). I3O is known as a Wnt/β-catenin activator that stabilizes β-catenin via inhibition of GSK-3β, and has been shown to accelerate bone growth and inhibit adipogenesis (O. M. Choi et al., 2014; Zahoor, Cha, & Choi, 2014; Zahoor, Cha, Min do, & Choi, 2014). Furthermore, we recently found that KY19382 elongated tibial length by inactivating GSK-3β and blocking the binding of CXXC-type zinc finger protein 5 (CXXC5) and Dishevelled (Dvl) (S. Choi et al., 2019). Moreover, PTD-DBM, a peptide that interferes with CXXC5-Dvl interaction via binding to the PDZ domain of Dvl, stimulated wound-induced hair follicle neogenesis (WIHN) and hair regrowth (Lee et al., 2017). However, this peptide is limited for routine application due to its cost and stability.
In this study, we selected KY19382 as an optimal compound that can stimulate hair growth. KY19382 activated the Wnt/β-catenin signaling higher than I3O and showed low cytotoxicity in human DP cells. The KY19382 elongated vibrissa hair shaft and mouse dorsal hair. Moreover, KY19382 significantly induced the hair follicle neogenesis as shown in hairless mice injected with dermal cells and keratinocytes and wounded mice treated with KY19382. Overall, KY19382 is an effective Wnt/β-catenin signaling activator that can be used for treatment of alopecia with high efficacy and safety.
METHODS