DKK1 and androgenetic alopecia: Responding to active androgen receptor signaling, hDPCs produce a variety of paracrine factors such as dkk1 and tgf β-1, impairing the proliferation and differentiation of hair follicle stem/progenitor cells, thus resulting in progressive HF miniaturization, a major characteristic of androgenetic alopecia (Kwack et al., 2008; Inui & Itami, 2011; Shin et al., 2013; Ceruti, Leirós & Balañá, 2017).