LAUSR

Aims: Outer root sheath (ORS) is a highly proliferative component of a hair follicle. This study is performed to investigate whether hypoxia‐induced elevation of hypoxia‐inducible factor (HIF)‐1&agr;, a transcriptional activator, contributes to the outgrowth of ORS cells in vitro. Main methods: Hair follicles with intact ORS collected from 4‐month old male American minks were cultured in normoxic or hypoxic condition (3% oxygen) for 7 days. Primary ORS cells isolated from the mink hair follicles were exposed to hypoxia for 12, 24 or 48 h, and their proliferation was analyzed with immunofluorescence assay using anti‐proliferating cell nuclear antigen (PCNA) antibody. The migratory ability of ORS cells was detected via the transwell chamber. The endogenous HIF‐1&agr; was knocked down with its specific siRNA in ORS cells. Key findings: Hypoxic exposure induced an elevation of HIF‐1&agr; in ex vivo cultured hair follicles. The mRNA and protein levels of sonic hedgehog (Shh), Shh receptor Patched 1, Smoothened and glioma‐associated oncogene homologue 1 were upregulated. In vitro, hypoxia induced an increase in HIF‐1&agr; in ORS cells. Further, under hypoxic condition, the number of PCNA‐positive cells was increased, and more cells migrated towards high serum media. Hypoxia‐enhanced proliferation and migration of ORS cells were suppressed either by HIF‐1&agr; siRNA or by pharmacological inhibitors of Shh pathway, cyclopamine and GANT61. The activation of Shh pathway was attenuated in HIF‐1&agr;‐silenced ORS cells under hypoxic condition. Significance: Our work demonstrates a direct role of activated HIF‐1/Shh biological axis in sustaining the development of ORS in vitro.