Effect of Flightless I Expression on Epidermal Stem Cell Niche During Wound Repair.

Activation of epidermal stem cells (EpSCs) from their quiescent niche is an integral component of wound reepithelialization and involves Wnt/β-catenin (β-Cat) signaling and remodeling of the actin cytoskeleton. The aim of this study was to investigate the effect of Flightless I (Flii), a cytoskeletal protein and inhibitor of wound healing, on EpSC activation during wound repair. Genetically modified Flii mice ( knockdown: , wild type: WT, overexpressing: ) received two incisional wounds along the lateral axis of the dorsal skin. Indicators of EpSC activation (epidermal growth factor receptor 1 [EGFR1], leucine-rich repeats and immunoglobulin-like domains-1 [Lrig1], K14), Wnt/β-Cat signaling (Lgr6, Flap2, β-Cat, and axis inhibition protein 2 [Axin2]), and cell proliferation (proliferating cell nuclear antigen [PCNA]) were assessed using immunohistochemistry. β-Cat stabilization was examined using western blotting with cell cycling and differentiation of isolated CD34ITGA6 EpSCs examined using real time-quantitative polymerase chain reaction after treatment with wound-conditioned media. led to increased numbers of activated EpSCs expressing PCNA, elevated EGFR1, and decreased Lrig1. EpSCs in hair follicle niches adjacent to the wounds also showed expression of Wnt-activation markers including increased β-Cat and Lgr6, and decreased Axin2. EpSCs (CD34ITGA6) isolated from unwounded skin showed elevated expression of cell-cycling genes including filaggrin () involucrin () cyclin D1 (), and cell-division cycle protein-20 (); and elevated and after treatment with wound-conditioned media compared with WT and counterparts. Flii was identified as an inhibitor of EpSC activation that may explain its negative effects on wound reepithelialization. Flii may inhibit EpSC activation by interrupting Wnt/β-Cat signaling. Strategies that reduce Flii may increase activation of EpSCs and promote reepithelialization of wounds.